含十六族元素之異核金屬羰基團簇物：合成與電化學和電子吸收光譜以及理論計算探討

全文

(1)國立臺灣師範大學化學系博士論文. 指導教授：謝明惠博士. Bimetallic Carbonyl Chalcogenide Clusters: Synthesis, Electrochemistry, Optical Properties, and Computational Studies. 研究生：繆佳曄中華民國一百零一年三月.

(2) 謝誌取得化學領域之最高學位“哲學博士＂曾是我遙不可及的夢想，所謂「堅其志，苦其心，勤其力，事無大小，必有所成」，秉持此信念一步一腳印地求學問，而今日終能美夢成真。回憶研究所的日子中，在此我要特別感謝我的指導教授謝明惠博士，在專業領域之悉心指導、獨立思考之邏輯推演以及待人處事之應對進退，您的諄諄教誨以及嚴謹態度著實鞭策我不斷地努力精確求學、時時檢討自我以及勇於開創的胸襟，在此，獻上我最由衷的敬意與謝忱。本論文亦承蒙口試委員李國安博士、許文賢博士、張一知博士及陳輝龍博士給予寶貴意見與指正，使之更臻完備，僅在此致上誠摯的謝意。感謝師大貴儀中心郭頂審助教、何秋慧助教、郭依婷助教、林懿雯助教在 X-ray、NMR 及 Mass 的技術支援。而 EA、SQUID 及 ICP-AES 的測定則分別感謝台大貴儀中心陸靖蔚小姐與清大貴儀中心鄭武漢先生以及李采芸小姐的幫助。另外，感謝系上泰莉助教、彥慧助教、美玲助教、怡旬助教、玉珍助教、雅純助教、碧秀助教、靜芬助教以及姜大鵬先生和戴興堂先生在行政事務上的協助。回首 D405b 實驗室的生活，首先感謝緯廷學長在實驗上的啟蒙以及妙行、佳樺學姊們在我初期進到這間實驗室時，給予我許多指導與幫助，使我奠定良好的研究基礎。此外，感謝陳輝龍教授在理論計算方面的啟蒙與.

(3) 大力指導。另外，謝謝同窗佩琪、欣慧、宛珍在學業與研究上的互相切磋，晏頤、建男、宗毅、凱捷、立慈在實驗室事務上的協助，以及沛凡、柏綱、偉成、俊鋒、宇薪、超民、奕文、昌鴻、威名、彥銘、育緯、旻憲、思緯、蓉怡、佩瑄、韋綸、俞君、綺翰、詹昂、翔竣、志龍、舜柏的陪伴與幫助，也因為有你們這群可愛學弟妹的加入，讓我的研究生涯更增添了許多歡樂。最後非常感謝我的家人，由於你們無時無刻的支持和鼓勵，給予我無限的精神後盾，當面對排山倒海的困難及挫折，總是能排除萬難並勇往直前地攻讀我人生最高學歷的博士學位，此外也非常幸運能認識涵榮並感謝你以及你的家人給予我最美好的回憶。將此博士論文誠心地分享於我的家人以及關心我的摯友們，總而言之，此刻心情百感交集，無法一語道盡，即獻上我百分百的心以及最誠摯的祝福給予你們大家。. 繆佳曄謹致 2012 年 3 月于師大化學.

(4) § 中文摘要 § 1. E/Mn/Cr/CO (E = S, Se) 系統之研究當[PPN][E2Mn3(CO)9] (E = S, Se)、Cr(CO)6 和 PPNCl 以莫耳比 1：1：2 或 1：2：2 於混合乙腈及甲醇之鹼性溶液(4M)中反應，可得到含 hydride 之混合錳鉻化合物 [PPN]2[HE2Mn3Cr(CO)14] (E = S, [PPN]2[1a]; Se, [PPN]2[1b])。然而，起始物之陽離子來源為 TMBA 時，進而加入 Cr(CO)6 以莫耳比 1：1 於鹼性甲醇溶液(4M)中加熱迴流反應，可獲得八面體結構之混合錳鉻團簇物[TMBA]3[E2Mn3Cr(CO)12] (E = S, [TMBA]3[2a]; Se, [TMBA]3[2b])。化合物 1a 和 1b 亦可於鹼性甲醇溶液中加熱迴流並進行合環反應而轉變成化合物 2a 和 2b。此外，若化合物 1a 和 1b 加入一或兩當量 Cr(CO)6 於二氯甲烷溶液中加熱迴流反應，則可進行擴核反應而得到含 hydride 之混合錳鉻化合物 [HE2Mn3Cr2(CO)19]2─ (E = S, 3a; Se, 3b)。其化合物生成及相關性質、結構轉換以及電化學性質藉由理論計算進一步驗證。 2. E/Mn/Ru/CO (E = S, Se) 系統之研究當[PPN][E2Mn3(CO)9] (E = S, Se)與 Ru3(CO)12 以莫耳比 1：1 於混合乙腈及甲醇溶液中加熱迴流反應，可得到八面體結構之同核含釕團簇物[HE2Ru4(CO)10]− (E = S, 3a; Se, 3b)和異核含混合錳釕團簇物[E2Mn2Ru2(CO)11]2− (E = S, 4a; Se, 4b)。此外，化合物 4a 和 4b 相較於等電子的八面體結構之同核含錳團簇物[E2Mn4(CO)12]2− (E = S, 1a; Se, 1b)和異核含混合錳鉻團簇物[E2Mn3Cr(CO)12]3− (E = S, 2a; Se, 2b)具有良好電子傳遞行為，其氧化位置發生在雙錳金屬羰基片段。紫外可見光吸收光譜顯示此系列同核及異核化合物之電子躍遷為 MLCT (Mn→E or COs)或混合 MLCT 及 MMCT (Mn→Cr or Ru)特性，並藉由反射光譜得知此系列化合物其能隙介於 1.25 至 1.80 eV。其化合物生成及相關性質、電子吸收以及電化學性質藉由理論計算進一步驗證。. I.

(5) 3. Te/Ru/Cu/CO 系統之研究當[PPh4]2[TeRu5(CO)14]加入一當量[Cu(MeCN)4][BF4]於二氯甲烷溶液及低溫下反應，可得到三銅橋接之雙八面體結構的團簇物 [PPh4]2[{TeRu5(CO)14}2Cu3Cl] ([PPh4]2[1])。若將上述反應之[Cu(MeCN)4][BF4]提高至兩當量，可獲得四銅橋接之雙八面體結構團簇物[PPh4]2[{TeRu5(CO)14}2Cu4Cl2]·CH2Cl2 ([PPh4]2[2]·CH2Cl2)和雙銅蓋接之八面體結構團簇物[TeRu5(μ-CO)2(CO)12Cu2(MeCN)2] (3a)；然而，此反應若於室溫下進行，則可獲得化合物 2 以及化合物 3a 之結構異構物[TeRu5(μ-CO)3(CO)11Cu2(MeCN)2] (3b)。此外，化合物 1 和 2 的生成反應涉及二氯甲烷之碳氯鍵活化，而化合物 3a 和 3b 的生成是藉由反應溫度控制。化合物 1─3 的生成及相關性質、結構轉換、電子吸收以及電化學性質藉由理論計算進一步驗證。 4. Te/Fe/Cu/dipyridyl 系統之研究當[TeFe3(CO)9{Cu(MeCN)}2]與不同有機含氮配子依劑量莫耳比於四氫呋喃溶液中反應，可獲得一維或二維含有機配子之混合鐵銅羰基的有機金屬-有機混合之配位聚合物 1─4。此外，利用一鍋化方式將[TeFe3(CO)9]2─、[Cu(MeCN)4][BF4]與有機配子 H2bpe or tmdpy 於四氫呋喃溶液中反應，可得到聚合物 3 和 4 其結構中的陰離子之混合鐵銅團簇物[{TeFe3(CO)9Cu}2L]2─ (L = H2bpe, 5; tmdpy, 6)。化合物 1─6 之生成及相關性質、電子吸收以及導電性藉由理論計算進一步驗證。關鍵字：第十六族元素、異核金屬、團簇物、電化學、電子吸收光譜、理論計算. II.

(6) § Abstract § 1. E/Mn/Cr/CO (E = S, Se) System When trigonal-bipyramidal clusters, [PPN][E2Mn3(CO)9] (E = S, Se), were treated with Cr(CO)6 and PPNCl in a molar ratio of 1: 1: 2 or 1: 2: 2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)5-incorporated. HE2Mn3-complexes. [PPN]2[HE2Mn3Cr(CO)14]. (E. =. S,. [PPN]2[1a]; Se, [PPN]2[1b]), respectively, were formed. However, when the TMBA+ salts for [E2Mn3(CO)9]─ were mixed with Cr(CO)6 in a molar ratio of 1: 1 in 4 M KOH/MeOH solutions and refluxed at 60 oC, mono-Cr(CO)3-incorporated E2Mn3Cr octahedral clusters [TMBA]3[E2Mn3Cr(CO)12] (E = S, [TMBA]3[2a]; Se, [TMBA]3[2b]), respectively, were obtained. Clusters 1a and 1b (with [TMBA] salts) underwent metal core closure to form octahedral clusters 2a and 2b upon treatment with KOH/MeOH at 60 oC. In addition, 1a and 1b were found to undergo cluster expansion to form di-Cr(CO)5-incorporated HE2Mn3-clusters [HE2Mn3Cr2(CO)19]2─ (E = S, 3a; Se, 3b), respectively, upon the addition of 1 or 2 equiv of Cr(CO)6 heated in refluxing CH2Cl2. The nature, cluster transformation, and electrochemical properties of the mixed manganese─chromium carbonyl sulfides and selenides were systematically discussed in terms of the chalcogen elements, the introduced chromium carbonyl group, and the metal skeleton, with the aid of molecular calculations at the BP86 level of the density functional theory. 2. E/Mn/Ru/CO (E = S, Se) System Heating trinuclear E2Mn3-trigonal-bipyramidal clusters, [E2Mn3(CO)9]− (E = S, Se) with Ru3(CO)12 in a molar ratio of 1: 1 in MeCN/MeOH solutions afforded two tetranuclear products, E2Ru4-octahedral clusters [HE2Ru4(CO)10]− (E = S, 3a; Se, 3b) and mixed-metal E2Mn2Ru2-octahedral clusters [E2Mn2Ru2(CO)11]2− (E = S, 4a; Se, 4b). In addition, 4a and 4b exhibited intense electronic communication through the M4 square during oxidation of Mn2(CO)6 fragment, which were compared to the analogous homonuclear group 7 clusters, III.

(7) [E2Mn4(CO)12]2− (E = S, 1a; Se, 1b) and the heteronuclear mixed-group 6/7 clusters, [E2Mn3Cr(CO)12]3− (E = S, 2a; Se, 2b). The electronic absorptions of [E2Mn3(CO)9]− and 1 were assigned as the MLCT (Mn→E or COs) transitions while those of 2 and 4 were attributed to the MLCT (Mn→E or COs) and MMCT (Mn→Cr or Ru) transitions. Moreover, these clusters also showed optical transitions with band gaps of 1.25 to 1.80 eV. Furthermore, the formation and electronic properties as well as electrochemical and optical properties of these E2M4-octahedral carbonyl sulfides and selenides were studied and elucidated with the aid of molecular calculations at the BP86 level of the density functional theory. 3. Te/Ru/Cu/CO System When [PPh4]2[TeRu5(CO)14] was treated with 1 equiv. of [Cu(MeCN)4][BF4] in dichloromethane (CH2Cl2) at low temperature, the Cu3Cl-incorporated di-TeRu5 carbonyl cluster [PPh4]2[{TeRu5(CO)14}2Cu3Cl] ([PPh4]2[1]) was formed. When [PPh4]2[TeRu5(CO)14] reacted with 2 equiv. of [Cu(MeCN)4][BF4] in CH2Cl2 at low temperature, both Cu4Cl2-incorporated di-TeRu5 carbonyl clusters [PPh4]2[{TeRu5(CO)14}2Cu4Cl2]·CH2Cl2 ([PPh4]2[2]·CH2Cl2) and [TeRu5(μ-CO)2(CO)12Cu2(MeCN)2] (3a) were obtained. However, similar reaction of [PPh4]2[TeRu5(CO)14] with 2 equiv. of [Cu(MeCN)4][BF4] in CH2Cl2 at room temperature produced complexes 2 and [TeRu5(μ-CO)3(CO)11Cu2(MeCN)2] (3b). The formation of 1 and 2 involved the abstraction of chloride from dichloromethane while the formation of isomers 3a and 3b was governed by the reaction temperature. The nature, transformation, electrochemical, and optical properties of these CuX (X = MeCN or Cl)-incorporated mono- or di-TeRu5-based clusters were discussed in terms of the effects of copper, tellurium, temperature, and the size of the metal skeleton, which was elucidated in detail by DFT calculations at the MPW1PW91 level of the density function theory. 4. Te/Fe/Cu/dipyridyl System Four new mixed-metal cluster-based 1D or 2D organometallic-organic hybrid polymers IV.

(8) 1─4 were synthesized from the reactions of the neutral heterometallic cluster [TeFe3(CO)9{Cu(MeCN)}2]. with. 1,2-bis(4-pyridine)ethene. (bpe),. various. ditopic. organic. 1,2-bis(4-pyridine)ethane. linkers. such. (H2bpe),. as and. 4,4′-trimethylene-dipyridine (tmdpy) in the stoichiometric molar ratios in THF. Besides, the corresponding anionic clusters in 3 and 4, [{TeFe3(CO)9Cu}2L]2─ (L = H2bpe, 5; tmdpy, 6), could be isolated from a one-pot reaction of [TeFe3(CO)9]2─, [Cu(MeCN)4][BF4], and H2bpe or tmdpy. The ternary Te─Fe─Cu─dipyridyl complexes 1─6 were characterized spectroscopically and their nature, formation, and semiconducting properties were discussed systematically in terms of the nature of N-donor dipyridyl linkers, the dimensionalities, and the intermolecular hydrogen interactions with the aid of molecular calculations at the B3LYP level of the density functional theory. Keywords: group 16 elements, heteronuclear metals, clusters, electrochemistry, UV-vis spectra, computational studies.. V.

(9) Contents Abstract (Chinese)………………………………………………………………………..... I. Abstract (English)………………………………………………………………………..... III. Chapter 1 1.1. 1.2.. Introduction Background Objectives Reference. Chapter 2. Stepwise Construction of Manganese─Chromium Carbonyl Chalcogenide Complexes: Synthesis, Electrochemical Properties, and. 2.1. 2.2. 2.3. 2.4.. Chapter 3. Chapter 4. Chapter 5. Appendix A. 1 4 5. Computational Studies (Inorg. Chem. 2011, 50, 7735─7748.) Abstract Introduction Results and Discussion Conclusion Experimental Section References Supporting Information Insight to Mixed-Metal Chemistry of Mn─Ru Carbonyl Chalcogenide Clusters and Comparison of Their Corrosponding Homo- or Hetero-nuclear Octahedral Clusters: Synthesis, Electrochemistry, Optical Properties, and Computational Studies Abstract Reactivity of [TeRu5(CO)14]2− Toward Copper Salts: Synthesis, Transformations, Electrochemistry, Optical Properties, and Computational Studies Abstract. 7. 7 8 9 21 21 29 50 75. 75 77. 77. Semiconducting Te─Fe─Cu─Dipyridyl Carbonyl Polymers: Controlled Synthesis, Optical Properties, and Computational Studies Abstract. 79. Experimental Section References. 80 81. VI. 79.

(10) Appendix B. Publications. 82. VII.

(11) Chapter 1 Introduction. 1.1. Background In cluster chemistry, Cotton introduced the term ‘‘metal atom cluster’’ in 1964 to point. out ‘‘a finite group of metal atoms that are held together mainly, or at least to a significant extent, by bonds directly between the metal atoms, even through some nonmetal atoms may also be intimately associated with the cluster’’.1 After years of research in this area, several books have illustrated the developments of cluster chemistry, including new bonding modes, versatile reactivities, and diverse structures as well as the activation of small molecules and homo- and heterogeneous catalysis.2 One of many aspects of cluster chemistry that attracted much attention from chemists was to discover chemically different metals through direct metal─metal bonding, however, up to date many combinations still remain unknown. In metal carbonyl chemistry, carbonyls are the most common ligands for organometallic clusters and seem to stabilize the M─M bonds.2a,2b The reason is that the COs can effectively stabilize M(CO)n fragments which leads these fragments close to within the metal─metal bonding distance of each other. From 1930s through 1950s, Hieber first discovered a series of neutral and anionic carbonyl complexes containing more than one metal and/or main-group elements.3 Most studies in this field were mainly aimed at the neutral complexes whereas the chemistry of anionic complexes remained scarce. Recently, anionic metal carbonyl clusters have been reported to be utilized as synthetic synthons for further cluster-growth reactions to construct homo- or hetero-nuclear metal carbonyl clusters.4 In the group 7 (Mn) system, our group reported the stepwise growth from the smaller clusters, [E2Mn3(CO)9]− (E = S, Se), into larger E-rich or Mn-rich clusters (Figure. 1.

(12) 1.1),4 however, controlled-cluster expansion of [E2Mn3(CO)9]− with group 6 (Cr) and group 8 (Ru) to form mixed-metal carbonyl chalcogenide clusters were not explored.. Figure 1.1. Stepwise cluster-growth reactions from the trigonal-bipyramidal clusters [E2Mn3(CO)9]− (E = S, Se). For group 7 system (Ru), if we treated the octahedral cluster [TeRu5(CO)14]2− with various amounts of CuX (X = Cl, Br, I), a series of CuX-, Cu2X2-, and Cu4X2-linked monoor di-TeRu5-based and Cu2X2-incorporated Te2Ru4-based carbonyl clusters were formed, respectively (Figure 1.2).4. Figure 1.2. Stepwise cluster-growth reaction from the octahedral clusters [TeRu5(CO)14]2−. Apart from the development of fundamental chemistry among mixed-metal clusters, the exploration of the redox capacity of the high-nuclearity homo- or heterometal carbonyl clusters was even more important because of their potential uses as molecular capacitors.4,5 Besides, recent studies reported by Nishihara et al. showed that homo-nuclear M3 (M = Ru, 2.

(13) Co, Rh, Ir, Ni, and Pt) and hetero-nuclear Ir3Co6 and Co3Fe3 dithiolene carbonyl clusters exhibited interesting electron communication (Figure 1.3).6. Figure 1.3. Mixed-metal Ir3Co6 and Co3Fe3 dithiolene carbonyl clusters. On the other hand, coordination polymers (CPs) are currently one of the hottest topics in Inorganic and Supramolecular chemistry.7 Recent development of crystalline conducting materials8 has attracted much interest due to their applications on novel technologies such as porous electrodes for batteries, fuel cells, sensors, and nanomaterials.9 Nevertheless, the formation of organometallic-organic hybrid CPs involving metal carbonyl clusters was relatively scarce and their dimensionalities were restricted to one-dimensional (1D) frameworks, which were mainly reported by our group and others.4 Very recently, Scheer et al. first. discovered. a. two-dimensional. (2D). organometallic-organic. hybrid. material,. [{{Cp2Mo2(CO)4P2}2Cu2(H2bpe)}{BF4}2]n, by using a phosphorus-containing complex as a precursor with 1,2-bis(4-pyridine)ethane (H2bpe) (Figure 1.4).10. Figure 1.4. Structure of 2D CP [{{Cp2Mo2(CO)4P2}2Cu2(H2bpe)}{BF4}2]n and its portion of the crystal packing diagram. With these perspectives, we desired to explore the studies on new heterobimetallic Mn─Cr, Mn─Ru, and Ru─Cu carbonyl chalcogenide clusters as well as 2D 3.

(14) organometallic-organic Fe─Cu─dipyridyl CPs by the stepwise cluster-expansion reactions or self-assembly reactions. Furthermore, the nature, formation, and transformation as well as electrochemical and optical properties of these resultant mixed-metal carbonyl chalcogenide complexes will be systematically discussed and further rationalized by the density functional theory (DFT) calculations.. 1.2. Objectives Based on the unexplored and interesting issues above-mentioned, our objectives in this. work are set as follows: (1) In the E/Mn/Cr/CO (E = S, Se) system, the rational routes for the synthesis of different structures of mixed group 6 and group 7 carbonyl chalcogenide complexes will be studied by the introduction of Cr(CO)6 into trigonal-bipyramidal clusters [E2Mn3(CO)9]− (E = S, Se). The effect of the incoming Cr(CO)x fragment will be probed by the studies of the electrochemistry of the resultant complexes. (2) In the E/Mn/Ru/CO (E = S, Se) system, the extension to the facile synthesis of mixed-metal Mn─Ru carbonyl chalcogenide octahedral clusters from [E2Mn3(CO)9]− (E = S, Se) will be investigated. Besides, we will also systematically discuss the incorporation of manganese, chromium, and ruthenium carbonyl fragments into the E2M4 core in terms of their electrochemical and optical properties. (3) In the Te/Ru/Cu/CO system, we will investigate the reactivity of [TeRu5(CO)14]2− with [Cu(MeCN)4][BF4] and further explore electrochemical and optical properties of the resultant clusters. (4) In the Te/Fe/Cu/dipyridyl system, we desire to construct low- or high-dimensional Te─Fe─Cu─dipyridyl. organometallic-organic. CPs. from. the. reactions. of. [TeFe3(CO)9{Cu(MeCN)}2] with various N-donor ligands. Furthermore, their nature,. 4.

(15) formation, and optical properties will be discussed systematically in terms of the nature of N-donor linkers, the dimensionalities, and structural features.. References: (1) (a) Bertrand, J. A.; Cotton, F. A.; Dollase, W. A. J. Am. Chem. Soc. 1963, 85, 1349─1350. (b) Cotton, F. A. Inorg. Chem. 1964, 3, 1217─1220. (c) Cotton, F. A. Q. Rev. Chem. Soc. 1966, 20, 389─401. (2) (a) Shriver, D. F., Kaesz, H. D., Adams, R. D. The Chemistry of Metal Cluster Complexes; Wiley-VCH, Weinheim, 1990. (b) Braunstein, P., Rosé, J. Metal Clusters in Chemistry; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-VCH: Weinheim, 1999; Vol. 2, Chapter 2.2, pp 616─677. (c) Braunstein, P., Rosé, J. In Catalysis by Di- and Polynuclear Metal Cluster Complexes; Adams, R. D., Cotton, F. A., Eds.; Wiley-VCH: New York, 1998; Chapter 13. pp 443─508. (d) Schmid, G. Clusters and Colloids. From Theory to Applications; Wiley-VCH, Weinheim, 1964. (e) Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Heteronuclear Metal─Metal Bonds, Vol. 10; Adams, R. D., Ed.; Elsevier: Oxford, 1995. (f) Metal Clusters in Catalysis; Gates, B. C., Guczi, L., Knözinger, H., Eds.; Studies in Surface Science and Catalysis Series; Elsevier: Amsterdam, 1986; Vol. 29. (g) Hermans, S., Khimyak, T., Raja, R., Sankar, G., Thomas, J. M., Johnson, B. F. G. in Nanotechnology in Catalysis; Zhou, B., Hermans, S., Somorjai, G. A., Eds.; Kluwer Academic, Plenum Publishers: New York, 2004. (3) (a) Hieber, V. W.; Gruber, J. Z. Anorg. Allg. Chem. 1958, 296, 91─103. (b) Hieber, V. W.; Gruber, J.; Lux, F. Z. Anorg. Allg. Chem. 1959, 300, 275─287. (c) Hieber, V. W.; Beck, W. Z. Anorg. Allg. Chem. 1960, 305, 265─273. (d) Herrmann, W. A. J. Organomet. Chem. 1990, 383, 21─44.. 5.

(16) (4) Shieh, M.; Miu, C.-Y.; Chu, Y.-Y.; Lin, C.-N. Coord. Chem. Rev. 2012, 256, 637─694. (5) Femoni, C.; Iapalucci, M. C.; Kaswalder, F.; Longoni, G.; Zacchini, S. Coord. Chem. Rev. 2006, 250, 1580─1604. (6) (a) Kambe, T.; Tsukada, S.; Sakamoto, R.; Nishihara, H. Inorg. Chem. 2011, 50, 6856─6858. (b) Tsukada, S.; Shibata, Y.; Sakamoto, R.; Kambe, T.; Ozeki, T.; Nishihara, H. Inorg. Chem. 2012, 51, 1228─1230. (7) (a) Batten, S. R., Neville, S. M., Turner, D. R. Coordination Polymer: Design, Analysis and Application; RSC: Cambridge, U.K., 2009. (b) Steed, J. W., Atwood, J. L. Supramolecular Chemistry, 2nd ed.; Wiley: Chichester, U.K., 2009. (8) Givaja, G.; Amo-Ochoa, P.; Gómez-García, C. J.; Zamora, F. Chem. Soc. Rev. 2012, 41, 115─147. (9) (a) Carne, A.; Carbonell, C.; Imaz, I.; Maspoch, D. Chem. Soc. Rev. 2011, 40, 291─305. (b) Mas-Balleste, R.; Gomez-Herrero, J.; Zamora, F. Chem. Soc. Rev. 2010, 39, 4220─4233. (c) Mas-Balleste, R.; Gomez-Navarro, G.; Gomez-Herrero, J.; Zamora, F. Nanoscale, 2011, 3, 20─30. (10) Attenberger, B.; Welsch, S.; Zabel, M.; Peresypkina, E.; Scheer, M. Angew. Chem. Int. Ed. Engl. 2011, 50, 11516─11519.. 6.

(17) Chapter 2 Stepwise Construction of Manganese─Chromium Carbonyl Chalcogenide Complexes: Synthesis, Electrochemical Properties, and Computational Studiesa. Abstract When trigonal-bipyramidal clusters, [PPN][E2Mn3(CO)9] (E = S, Se), were treated with Cr(CO)6 and PPNCl in a molar ratio of 1: 1: 2 or 1: 2: 2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)5-incorporated. HE2Mn3-complexes. [PPN]2[HE2Mn3Cr(CO)14]. (E. =. S,. [PPN]2[1a]; Se, [PPN]2[1b]), respectively, were formed. X-ray crystallographic analysis showed that 1a and 1b were isostructural and each displayed an E2Mn3 square-pyramidal core with one of the two basal E atoms externally coordinated with one Cr(CO)5 group and one Mn─Mn bond bridged by one hydrogen atom. However, when the TMBA+ salts for [E2Mn3(CO)9]─ were mixed with Cr(CO)6 in a molar ratio of 1: 1 in 4 M KOH/MeOH solutions and refluxed at 60 oC, mono-Cr(CO)3-incorporated E2Mn3Cr octahedral clusters [TMBA]3[E2Mn3Cr(CO)12] (E = S, [TMBA]3[2a]; Se, [TMBA]3[2b]), respectively, were obtained. Clusters 2a and 2b were isostructural and each consisted of an octahedral E2Mn3Cr core, in which each Mn─Mn or Mn─Cr bond of the Mn3Cr plane was semi-bridged by one carbonyl ligand. Clusters 1a and 1b (with [TMBA] salts) underwent metal core closure to form octahedral clusters 2a and 2b upon treatment with KOH/MeOH at 60 oC. In addition, 1a and 1b were found to undergo cluster expansion to form di-Cr(CO)5-incorporated HE2Mn3-clusters [HE2Mn3Cr2(CO)19]2─ (E = S, 3a; Se, 3b), respectively, upon the addition of. a. This chapter has been published on Inorg. Chem. 2011, 50, 7735─7748. 7.

(18) 1 or 2 equiv of Cr(CO)6 heated in refluxing CH2Cl2. Clusters 3a and 3b were structurally related to clusters 1a and 1b, but with the other bare E atom (E = S, 3a; Se, 3b) further externally coordinated with one Cr(CO)5 group. The nature, cluster transformation, and electrochemical properties of the mixed manganese─chromium carbonyl sulfides and selenides were systematically discussed in terms of the chalcogen elements, the introduced chromium carbonyl group, and the metal skeleton, with the aid of molecular calculations at the BP86 level of the density functional theory.. 2.1. Introduction Heterometallic cluster complexes represent a challenging area of synthetic chemistry due to their numerous applications in catalysis,1,2 magnetism,3,4 nanoscience,5 and nanotechnology.6 Although systematic syntheses of heteronuclear cluster complexes have advanced significantly during the past few years,1c,7 rational stepwise cluster-growth processes, based on coupling reactions of suitable transition-metal species or the conversion of existing structural geometries to new ones, were few due to the lack of practical methodologies. In addition to the development of the fundamental chemistry among mixed-metal clusters, the exploration of the redox capacity of the high-nuclear homo- or hetero-metal carbonyl clusters is even more important, due to their potential uses as molecular capacitors.5b,8 Whereas homonuclear iron9─11 carbonyl chalcogenide clusters are well-developed, carbonylmanganese9a─9c,12─14 and carbonylchromium9a─9c,15─17 chalcogenide complexes have not been explored as much, and mixed manganese─chromium carbonyl chalcogenide complexes are even more rare.18,19 Very recently, our group reported two mixed chromium─manganese selenide carbonyl complexes from the reaction of the paramagnetic species [Se2Cr3(CO)10]2─ with Mn(CO)5Br in acetone.19c However, the question of how to. 8.

(19) search for suitable building blocks for step-by-step construction of mixed-metal ternary E─Mn─Cr complexes (E = chalcogen elements) is still a great challenge. Our previously reported trigonal-bipyramidal clusters, [E2Mn3(CO)9]─ (E = S, Se),14a were electron-precise anion clusters and could be viewed as potential candidates for incorporation with other nucleophilic or electrophilic transition metal fragments. To extend our studies of the chemistry of mixed Mn─Cr clusters, we have examined the interaction of [E2Mn3(CO)9]─ (E = S, Se) with group 6 chromium carbonyl species, Cr(CO)6, under carefully controlled conditions. This paper describes the full details of the syntheses and characterization of a new family of heterometallic Mn─Cr chalcogenide carbonyl cluster complexes, which included three different types of structures, mono- and di-Cr(CO)5-incorporated HE2Mn3 square-pyramidal. complexes. and. mono-Cr(CO)3-incorporated E2Mn3Cr. octahedral. complexes. In addition, the electrochemical properties of these mixed Mn─Cr clusters were systematically investigated to address and compare their redox capability in terms of the effect of the incoming chromium group that was either attached to the square-pyramidal E2Mn3 core or incorporated into the octahedral E2M4 core. Finally, the electronic properties, stepwise cluster-expansion reactions, and electrochemistry of these new Mn─Cr carbonyl sulfides and selenides were further elucidated and discussed on the basis of density functional theory (DFT) calculations.. 2.2. Results and Discussion 2.2.1. Synthesis of Complexes [HE2Mn3Cr(CO)14]2─ (E = S, 1a; Se, 1b). On the basis of the electron-counting rule, trigonal-bipyramidal complexes [E2Mn3(CO)9]─14a (E = S and Se) are electron-precise species (48 electrons). Although stepwise growth from smaller clusters, [E2Mn3(CO)9]─ (E = S, Se), into larger E-rich or Mn-rich clusters was found, providing facile routes to a series of nanosized manganese carbonyl chalcogenide. 9.

(20) clusters,14a,14d,14e until now, stepwise, controlled-cluster expansion of [E2Mn3(CO)9]─ (E = S, Se) with other transition metal fragments to form mixed-metal carbonyl chalcogenide clusters had not been explored. In the present study, when [PPN][E2Mn3(CO)9] was treated with Cr(CO)6 and PPNCl in a molar ratio of 1: 1: 2 or 1: 2: 2 in concentrated KOH/MeCN/MeOH solutions (4 M) in an ice-water. bath,. mono-Cr(CO)5-incorporated. HE2Mn3-based. complexes,. [PPN]2[HE2Mn3Cr(CO)14] (E = S, [PPN]2[1a]; Se, [PPN]2[1b]), were formed in moderate yields of 41 and 44%, respectively (see Scheme 2.1). Clusters 1a and 1b also can be isolated as the [TMBA]+ salts by similar procedures. They were both fully characterized by IR, NMR, ICP-AES, and elemental analysis, as well as single-crystal X-ray diffraction analysis. Oak Ridge thermal ellipsoid plot (ORTEP) diagrams of the structures of 1a and 1b were shown in Figures S2.1 and 2.1. Clusters 1a and 1b were isostructural species and each displayed an E2Mn3 square-pyramidal core (E = S, 1a; Se, 1b) with each Mn atom terminally coordinated with three COs, in which one Mn─Mn bond was bridged by one hydrogen atom and one of the two basal E atoms was externally coordinated with one Cr(CO)5 group. The 1H NMR study further confirmed the existence of the hydrides of 1a and 1b. For the dianionic 1a, 1H NMR gave the hydride resonance at −8.94 ppm. This value is close to the previously reported values for the hydride bridging the Mn─Mn bond in the neutral S2Mn2-based species [Mn2(CO)6(μ-H){μ-S(SC3H5)C=C(PPri3)S}]20a (−7.99 ppm) and [Mn2(CO)6(μ-H){μ-S(SR)C=C(PCy3)S}] (R = SnBu3, SnPh3, and CH2CH=CH2)20b (−8.59, −8.72, −8.42, respectively). However, it had a greater down-field shift than those in [Mn2(CO)6(μ-H)(μ-S2CPCy3)]−20c (−12.01 ppm) and [Mn2(CO)6(μ-H)(μ-R′SC(S)PR3)]20c (ranging from −13.43 to −13.77 ppm). On the other hand, the 1H NMR signal for the hydride of 1b (−7.78 ppm) was close to that of 1a (−8.94 ppm). There were no previous examples of hydride-bridged Mn─Mn bonds reported in the Se─Mn system, according to a search of the 10.

(21) Cambridge Crystallographic Data Centre. The formation of the anions 1 was proposed to occur via the [HCr(CO)5]─21 attack on the starting clusters [E2Mn3(CO)9]─ (E = S, Se),14a followed by the hydride transfer and CO2 loss, giving rise to complexes 1a and 1b. This hypothesis was supported by the independent experiments that [E2Mn3(CO)9]─ (E = S, Se) readily reacted with the isolated [HCr(CO)5]─ anion to give clusters 1a and 1b with the comparable yields, respectively. In addition, the formation of [HCr(CO)5]─ anion was detected by IR spectroscopy in the course of the reaction of [E2Mn3(CO)9]─ with Cr(CO)6 in KOH/MeOH/MeCN. Furthermore, the reaction of [E2Mn3(CO)9]─ with reductants such as KOH/MeOH or Na-Ketyl produced the known square-pyramidal clusters [E2Mn3(CO)9]2─.13a,14e Therefore, the source of the hydride in 1 was most likely from the hydride of [HCr(CO)5]─ which was produced from the nucleophilic attack of OH─ on CO of Cr(CO)6, followed by the beta-elimination and loss of CO2. Scheme 2.1 KOH/MeCN/MeOH ice r. t. E [X]. *Mn. Mn*. Mn* H [X]2. X = PPN E = S, 1: 1: 2 Se, 1: 2: 2. *Cr. △. E. E Mn *. *Mn. E = S, 1a; Se, 1b E. Mn*. Cr(CO)6/CH2Cl2. Mn *. X = PPN E = S, 1: 1 Se, 1: 2. H [X]2. *Cr. Mn *. E. E. Cr*. Mn * E = S, 3a; Se, 3b. KOH/MeOH 60 oC. +. X = TMBA E = S, Se. Cr(CO)6 + PPNCl. E. Mn* = Mn(CO)3 Mn# = Mn(CO)2 Cr* = Cr(CO)5 Cr# = Cr(CO)2 X = PPN or TMBA. KOH/MeOH 60 oC X = TMBA E = S, 1: 1: 0 Se, 1: 1: 0. OC [X]3. Mn# OC Mn#. Mn#. CO Cr# CO. E E = S, 2a; Se, 2b. 2.2.2. Synthesis of Octahedral Complexes [E2Mn3Cr(CO)12]3─ (E = S, 2a; Se, 2b). With careful control of the reaction conditions (the source of the cations and the temperature), the reaction of [TMBA][E2Mn3(CO)9] with Cr(CO)6 in a molar ratio of 1: 1 in 4 M KOH/MeOH at 60 oC led to the formation of mono-Cr(CO)3-incorporated octahedral complexes [TMBA]3[E2Mn3Cr(CO)12] (E = S, [TMBA]3[2a]; Se, [TMBA]3[2b]), 11.

(22) respectively (see Scheme 1.1.). The anionic 2a and 2b were extremely air- and moisture-sensitive and could only be isolated as the [TMBA]+ salt, but this was not feasible for other cationic salts such as [PPN]+ and [Et4N]+. The formation of octahedral clusters 2a and 2b from trigonal bipyramidal clusters [E2Mn3(CO)9]─14a (E = S and Se) was complicated by the Mn─Mn bond cleavage, E─Cr and Mn─Cr bond formation, and CO migration from the terminal to the bridging mode. Complexes 2a and 2b were also fully characterized using spectroscopic methods. As shown in Figures S2.2 and 2.2, 2a and 2b each displayed a bimetallic Mn3Cr square bicapped above and below by two quadruple-bridging chalcogenide atoms. 2.2.3. Synthesis of Complexes [HE2Mn3Cr2(CO)19]2─ (E = S, 3a; Se, 3b). To further investigate the nucleophilicity of the triply bridging μ3-E ligand of complexes 1a and 1b, the reaction of 1a or 1b with 1 or 2 equiv of Cr(CO)6 heated in refluxing CH2Cl2, respectively, were carried out. These reactions led to the formation of novel cluster-expansion products, di-Cr(CO)5-incorporated HE2Mn3-based complexes [HE2Mn3Cr2(CO)19]2─ (E = S, 3a; Se, 3b), with moderate yields (see Scheme 2.1). Clusters 3a and 3b are isomorphous and each was shown by X-ray analysis to have two asymmetric Cr(CO)5 groups connected by the square-pyramidal E2Mn3(CO)9 core with each Mn atom terminally coordinated with three COs, in which two basal E atoms were both externally coordinated with the Cr(CO)5 groups, with one of the two Mn─Mn bonds bridged by one hydrogen atom (Figures S2.3 and 2.3). The existence of the hydrides of complexes 3a and 3b was confirmed by an 1H NMR experiment, showing the 1H NMR singlet at −8.97 and −7.80 ppm, respectively. These values were close to the values of complexes 1a and 1b (−8.94, −7.78 ppm), indicative of the minimal effect of an additional Cr(CO)5 fragment. The infrared spectra of 3a and 3b showed the absorptions characteristic of terminal carbonyls, with a pattern similar to that of clusters 1a and 1b, but with the frequencies shifted to higher energies due to the electron-withdrawing 12.

(23) effect of the Cr(CO)5 fragment. This result seems to suggest, as might be expected, that 3a and 3b each consisted of an [H(μ3-E)(μ4-E)Mn3Cr(CO)14] core in which the bare μ3-E atom was further linked to the introduced Cr(CO)5 unit via the donor-acceptor bond. 2.2.4. Electron Counts of 1a, 1b, 2a, 2b, 3a, and 3b. As shown in Scheme 2.1, the dianionic clusters 1 (1a and 1b) and 3 (3a and 3b) were all electron-deficient E2Mn3-based square-pyramidal complexes with 70 and 86 electrons, respectively. Because the externally bound Cr(CO)5 moiety is thought to donate zero electrons to the metal skeleton, the dianionic clusters 1a, 1b, 3a, and 3b were found to possess seven skeletal electron pairs each, according to the Wade’s rule, in accord with the 7 skeletal electron pairs required for a square pyramidal structure. The octahedral complexes of 2 (2a and 2b) were electron-deficient 66 electron-species, and each possessed a closo-geometry with 7 skeletal electron pairs in terms of Wade’s rule. The nido-clusters 1 and 3 and closo-clusters 2 were all found to be diamagnetic species according to SQUID analysis. 2.2.5. Transformation of Complexes 1a and 1b to Octahedral Complexes 2a and 2b.. As described above, the reaction of [E2Mn3(CO)9]− with Cr(CO)6 in 4M. KOH/MeCN/MeOH. basic. solutions. in. an. ice-water. bath. produced. mono-Cr(CO)5-incroporated HE2Mn3-complexes [HE2Mn3Cr(CO)14]2− (E = S, 1a; Se, 1b), while a similar reaction refluxed at 60 oC led to the formation of mono-Cr(CO)3-incorporated octahedral clusters [E2Mn3Cr(CO)12]3− (E = S, 2a; Se, 2b). Therefore, clusters 1a and 1b were thought to act as the intermediate complexes for the formation of clusters 2a and 2b. This was indeed the case. By careful treatment with potassium hydroxide at 60 oC, cluster 1a or 1b could be successfully converted into the octahedral cluster 2a or 2b, which was accompanied by a remarkable color change from reddish-brown (complexes 1a and 1b) to purplish-black (complex 2a) or greenish-black (complex 2b). Simultaneously, the 1H NMR spectra showed that the hydride signals of 1a and 1b disappeared as they transformed into. 13.

(24) complexes 2a and 2b. In addition, the CO frequencies for closo-2a and 2b were quite similar, but shifted to low energies compared to those for nido-1a and 1b, due to the pronounced effect of the charge. In a previous study, it was postulated that the square pyramidal complex with a pendant metal fragment could be the key intermediate for the formation of an octahedral complex.22 However, there were no experimental examples to directly verify this assumption. The present study demonstrated a novel example of a facile conversion from a metal fragment-attached square pyramidal structure to the octahedral geometry. Moreover, the metal-core closure of clusters 1a and 1b to give octahedral clusters 2a and 2b upon treatment with KOH will be discussed later with the theoretical calculations. 2.2.6.. X-ray. Structural. Comparison. of. [Et4N]2[1a],. [PPh4]2[1b],. [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b]. As shown in Figures S2.1 and 2.1, complexes 1a and 1b each displayed a square-pyramidal E2Mn3 core with one E atom bonded to an additional Cr(CO)5 fragment, in which each cluster contained a nearly planar E2Mn2 base, with average distances of 0.090 and 0.073 Å, respectively, to the least-squares plane. The three Mn atoms of clusters 1a and 1b were six-, seven-, and eight-coordinated, respectively. The hydride of 1a or 1b across one Mn─Mn bond was refined with an isotropic temperature factor, in which the H─Mn distances in 1a or 1b were not equal (1.5929(9)/1.8362(8) Å, 1a; 1.69(4)/1.66(4) Å, 1b). Clusters 1a and 1b possessed four metal atoms: one chromium and three manganese. These four metal atoms were assembled in a cluster bridged by the chalcogen atoms with two different bonding modes: E(2) is a triply bridging atom that bridges three manganese atoms, but E(1) is a quadruple-bridging atom that bridges three manganese atoms and a pendant Cr(CO)5 group. To the best of our knowledge, the related mixed-metal carbonyl chalcogenide clusters containing both μ3- and μ4-E bonding modes are limited to the neutral complexes: [CpRe2Mo(CO)8(μ3-S)(μ4-S)CpMo(CO)3],23a. [Fe2Mn(CO)9(μ3-S)(μ4-S)Mn(CO)5],23b 14.

(25) [CpMoMn2(CO)9(μ3-S)(μ4-S)Mn(CO)4],23c. [Os3(CO)9(μ3-S)(μ4-S)W(CO)5],23d. [Fe3(CO)9(μ3-S)(μ4-S)W(CO)4PMe2Ph],23e [{P(CH2Ph)Ph2}2Ru3(CO)7(μ3-Se)(μ4-Se)W(CO)5],22. and. [Co3(CO)7(μ3-Te)(μ4-Te)Nb(C5Me4Et)2],23f and no examples of anionic mixed-metal carbonyl chalcogenides were ever reported prior to the present study. A search of the Cambridge Crystallographic Data failed to identify any structurally characterized E─Mn─Cr compound that contained both μ3- and μ4-E bonding modes. Clusters 1a and 1b represent the first examples of E─Mn─Cr clusters possessing both μ3- and μ4-E bonding modes. Clusters 2a and 2b were isostructural and each contained two structurally independent entities in the unit cell. As shown in Figures S2.2 and 2.2, clusters 2a and 2b each had a crystallographic center of symmetry at the center of the disordered E2M4 octahedral core (E = S, 2a; Se, 2b). The square heterometallic M4 unit in 2a or 2b, was supported by two Mn─Mn and two Mn─Cr bonds, with two μ4-E atoms capping above and below the M4 plane. In 2a, each M atom of the M4 square in the two independent forms was coordinated with two terminal COs and one semi-bridging CO, where Mn(1), Mn(2), Mn(3), and Mn(4) atoms and Cr(1), Cr(2), Cr(3), and Cr(4) atoms of the squares were disordered with 75 and 25% occupancy, respectively. In 2b, one independent square M4 plane showed the disordered M(1) and M(2) atoms where Mn and Cr are with 75 and 25% occupancy, and the other one showed the disordered M(3) atom with Mn and Cr present in a 50:50 ratio. According to a literature search, clusters 2a and 2b were structurally similar to the other neutral mixed-metal E2M4 octahedral complexes: [(μ4-S)2Ru3W(CO)11(PMe2Ph)],24a [(μ4-Se)2Fe3Ru(CO)10(μ-CO)],24b [(μ4-Se)2WRu3(μ-CO)4(CO)6(L)2] (L = phosphane),22 [(μ4-S)2PtRu3(CO)6(μ-CO)2(η2-P─P)] (P─P = dppf or dppr),24c and [(μ4-Se)2WRu3(μ-CO)4(CO)7(L)] (L = phosphine ligand).24d Clusters 2a and 2b represent the first examples of mixed group 7 and 6 carbonyl chalcogenide complexes in this octahedral E2M4 arrangement. 15.

(26) As shown in Figures S2.3 and 2.3, clusters 3a and 3b were isomorphous, and each contained five metal atoms: two chromium and three manganese. These five metal atoms are assembled in a cluster that is bridged by two quadruple μ4-E atoms (E = S, 3a; Se, 3b) with one hydride across one Mn─Mn bond. They could also be regarded as di-Cr(CO)5 groups sandwiching a HE2Mn3 metal core, or the μ3-E atom of complexes 1a and 1b further bonded to a secondary Cr(CO)5 group. X-ray analysis of complex 3a revealed that C(3), O(3); C(4), O(4); C(5), O(5); and C(17), O(17) atoms in the four terminal COs of the di-Cr(CO)5 fragments were disordered with 50, 55, 55, and 60% occupancy, respectively (See Figure S2.3). Similar to 1a and 1b, complexes 3a and 3b each contained a very slightly distorted E2Mn2 base of the E2Mn3 metal core, with average distances of 0.082 and 0.040 Å, respectively, to the least-squares planes, regardless of the effect of the two attached Cr(CO)5 groups. This novel type of structural feature containing both the H-bridged Mn─Mn bond and two μ4-E quadruple-bridging atoms is the only example reported in main group-containing manganese complexes. For further comparison, the distances of the E─Mn, Mn─Mn, E─Cr, H─Mn, and Mn─Cr bonds of [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], [PPN]2[3b], and related complexes are listed in Table 2.1. In general, the corresponding E─Mn, Mn─Mn, and E─Cr averaged bond distances in these new E─Mn─Cr clusters were similar to those reported for related complexes.12g,13a,14a,18b,19a,19c,25 The average Mn─Cr distances in 2a and 2b were 2.6(3) and 2.73(3) Å, which are comparatively shorter than. those. found. in. [Cp2Cr2(μ-SCMe3)(μ3-S)2Mn(CO)3]. (2.77(8). Å)18b. and. [CrMn2(CO)8(μ-CO)2(μ3-SN2C4H5)2] (2.849(1) Å)25, suggesting stronger Mn─Cr bonding due to the closo-octahedral skeleton. The corresponding average E─Mn, Mn─Mn, E─Cr, and H─Mn distances of 1a, 1b, 3a, and 3b were similar, due to the small effect of the secondary Cr(CO)5 group. In addition, the Mn─Mn and E─Cr bond lengths of 2a and 2b were slightly 16.

(27) shorter than those of 1a and 1b, while the E─Mn bond lengths of 2a and 2b were longer than those of 1a and 1b, probably due to the increased bonding character associated with the Cr atom. Moreover, in general, the distances of E─Mn, Mn─Mn, E─Cr, H─Mn, and Mn─Cr in the Se2-based Mn─Cr complexes were slightly longer than the S2-based Mn─Cr complexes, due to the larger atomic radius of the Se atom compared with the S atom. It is also interesting to note that the size of [E2Mn3(CO)9]− (E = S, Se), 1, 2, and 3 including COs were approximately 0.774(0.884), 0.976(1.004), 0.895(0.898), and 1.366(1.404) nm, respectively, indicative of controllable stepwise construction of these nanosized clusters. 1.2.7. DFT Calculations. The DFT method was employed to further describe the electronic structures of [E2Mn3(CO)9]− (E = S, Se) and 1─3 to rationalize their relevant reactions. All the calculations were carried out at the BP8626,27 and B3LYP28,29 functionals (Table S2.1). The TZVP30 basis set was applied for all atoms in each complex for these calculations. The geometries of [E2Mn3(CO)9]− (E = S, Se) and 1─3 were also fully optimized with the same level of theory. Basically similar results were obtained with the BP86 and B3LYP functionals. However, the former provided a better correlation with experimental parameters (Table S2.2) and was used for analysis of the frontier orbitals. The level of BP86 may be more reliable and work better than B3LYP for many organometallic systems.31─33 Therefore, the present study was focused on the analysis of the geometrical results provided by BP86/TZVP calculations. In addition, the Wiberg bond indices34 and natural population analyses (NPA)35 for these complexes were calculated, and the results are listed in Table S2.3. Formation of Clusters 1 and 3. The DFT calculations showed that the active sites of [E2Mn3(CO)9]− (E = S, Se) for the formation of clusters 1 (1a and 1b) could be related to the lowest unoccupied molecular orbitals (LUMO) and LUMO+1 of [E2Mn3(CO)9]−. As shown in Figure 2.4 and Table 2.2, the LUMO and LUMO+1 of the respective [E2Mn3(CO)9]− (E =. 17.

(28) S, Se) were degenerate and each had major contributions from the p orbital of the E atoms and d and p orbitals of the Mn atoms. It is reasonable to propose that the incoming chromium anions “[HCr(CO)5]−/[Cr(CO)5]2−”21 could interact with the “E” site of [E2Mn3(CO)9]−, presumably accompanied by the hydrogen atom bridging two Mn atoms, to form new E─Cr and H─Mn bonds accompanied by one Mn─Mn bond breakage, to give rise to complexes 1a and 1b. Hence, the formation of complexes 1a and 1b was not only dominated by the frontier orbitals, but also was induced by the Mn─Mn bond breakage of [E2Mn3(CO)9]− (E = S, Se), which reflected on their weaker Wiberg bond indices (0.279 and 0.285). As shown in Figure 2.4, the highest occupied molecular orbitals (HOMO) of 1a and 1b received major contributions from the p orbital of the E atoms (1a/1b, μ3-E, 10.24/19.01%; μ4-E, 4.04/0.14%) and d orbital of the Mn atoms (1a/1b, 62.41/59.94%). This suggests that the “μ3-E” atoms of 1a and 1b were reactive sites for the secondary chromium fragment Cr(CO)5 to form 3a and 3b, respectively, which was also supported by their space-filling models (see Figure 2.5). The Proposed Pathway from 1a(1b) to 2a(2b). The formation of cluster 2a(2b) is likely to occur via a nucleophilic attack of OH─ on CO of the pendant Cr(CO)5 fragment of complex 1a(1b), followed by loss of CO2, forming a “HCr(CO)4” fragment, followed by the Mn─Cr and E─Cr bond formation accompanied with H2 reductive elimination. This proposed pathway was supported by that the LUMO orbital of 1a or 1b was mainly contributed from the Cr(CO)5 fragment (59.31%, 1a; 51.65% 1b). Furthermore, the relative Gibb’s free energies ΔG(298 K), calculated by BP86 in MeOH, for the transformation of 1a or 1b into 2a or 2b ([HE2Mn3Cr(CO)14]2− (E = S, 1a; Se, 1b) + OH− → [E2Mn3Cr(CO)12]3− (E = S, 2a; Se, 2b) + CO2 + H2+ CO) were thermally favorable (ΔG: ─27.47 kcal/mol, E = S; ΔG: ─24.30 kcal/mol, E = Se). Electrochemistry. In view of the effect of the Cr(CO)x fragment on the E2Mn3 (E = S, Se) core and structural relationships among complexes 1a, 1b, 2a, 2b, 3a, and 3b, their 18.

(29) electrochemical properties were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in MeCN under N2, which was further compared with the related trigonal-pyramidal clusters [E2Mn3(CO)9]− (E = S, Se14e). The CVs of these clusters were somewhat broad and could not be assigned unambiguously. Therefore, DPV studies were carried out to explore the redox behavior of these clusters. The electrochemical data for each complex studied are listed in Tables 2.3 and S2.4, and the DPVs and CVs are shown in Figures 2.6 and S2.4 and S2.5, respectively. The scan range was set between ~ +1.00 to ~ −1.00 V, due to the interference of [PPN]+ and [TMBA]+. For the DPV measurements, the electron stoichiometry is determined by the measurement of the peak width at half-height (W1/2).36 As seen in Figures 2.6 and S2.4, the widths of the DPV peaks at half-height of [PPN][E2Mn3(CO)9] (E = S, Se) and clusters 1─3 (Table 2.3) were a bit greater than the value (W1/2 = 90 mV) expected for one-electron reversible redox reactions, indicating that these DPV responses were quasi-reversible.37 As listed in Table 2.3, mono-Cr(CO)5-incorporated 1a an 1b each had four one-electron quasi-reversible oxidations, at +0.032 to +0.756 V and +0.127 to +0.883 V, respectively. The DFT calculations showed that the HOMO and HOMO─1 of 1a and 1b were mainly localized on the E2Mn3 moieties, suggesting that the oxidation processes of 1a and 1b, mainly occurred in the E2Mn3 core (Table 2.2 and Figure 2.4), indicative of a small effect of the attached mono-Cr(CO)5 fragment. The rich quasi-reversible oxidation processes observed for the E2Mn3Cr-based complexes, 1a and 1b, were ascribed to the positive energy levels of the almost degenerate HOMO and HOMO─1 orbitals in each cluster (Figure 2.4). However, octahedral complexes, 2a and 2b, each exhibited two one-electron quasi-reversible oxidations at approximately +0.350 to +0.702 V and +0.370 to +0.538 V and three one-electron quasi-reversible reductions at −0.050 to −0.702 V and −0.044 to −0.684 V, respectively. The oxidative and reductive waves for 2a and 2b were tentatively assigned as the oxidations and. 19.

(30) reductions occurred in the square heterometallic M4 units, according to the HOMO and LUMO as well as LUMO+1 levels (Figure 2.4). In addition, the calculated components of Mn3Cr in the LUMO for 2a and 2b (61.87 and 61.22%) were significantly greater than those for 1a and 1b (36.80 and 41.15%) (Table 2.2), supportive of the ease and richness of the quasi-reversible reductions of 2a and 2b, implying their potential use as electron sponges.5b,8 On the other hand, the DPV of the di-Cr(CO)5-incorporatd complex 3a revealed five one-electron quasi-reversible redox oxidations at +0.323 to +0.867 V and one quasi-reversible redox reduction at −0.160 V, whereas 3b displayed five one-electron quasi-reversible redox oxidations at +0.325 to +0.849 V (see Figures 2.6 and S2.4). The rich quasi-reversible oxidations of 3a and 3b may be related to their narrow-spaced HOMO, HOMO─1, and HOMO─2 orbitals (Figure 2.4). Besides, these frontier orbitals for 3a and 3b mainly arose from the E2Mn3 metal core and di-Cr(CO)5 fragment, indicating that the oxidation and reduction processes both occurred mainly in the E2Mn3 metal core and the di-Cr(CO)5 fragments (Figure 2.4). In general, these quasi-reversible oxidation waves for complex 3a occurred at more positive potentials than those for complex 1a, which indicated that 3a was difficult to be oxidized because of the two electron-withdrawing Cr(CO)5 fragments (Figure 2.6). In particular, the first quasi-reversible oxidation wave of 3a (+0.323 V) displayed a pronounced anodic shift (291 mV) compared to that of 1a (+0.032 V), which was supported by the calculations that cluster 3a showed a lower HOMO energy level, decreasing components of HOMO, and decreased nature charges of the HS2Mn3(CO)9 core, as well as greater ionization energy, compared with those calculated for 1a (3a vs. 1a: −0.28 vs. 0.35 eV; 86.44 vs. 98.86%; −0.865 vs. −1.383 |e|; IE ≈ Eelec(N − 1) − Eelec(N), 36.59 vs. 19.93 kcal/mol, respectively).. 20.

(31) 2.3. Conclusions The present study demonstrated that the chalcogen elements of the E2Mn3 metal core (E = S, Se) played an important role in the controlled stepwise construction of a new series of mono-. or. di-Cr(CO)5-incorporated. HE2Mn3-based. complexes. 1. and. 3,. and. mono-Cr(CO)3-incorporated E2M4-based octahedral complexes 2, under different reaction conditions, and the subsequent transformation of 1 (1a and 1b) into octahedral complexes of 2 (2a and 2b) was also achieved. In addition, the electrochemical properties of these resultant E─Mn─Cr complexes displayed quasi-reversible redox waves over quite a large window (+0.883 ~ −0.702 V). These results can be summarized by the following conclusions. First, the unexpected electron-sponge behavior was observed for complexes 1a and 1b and octahedral complexes 2a and 2b, which can be readily fine-tuned by the control of electronic properties exhibited by the attached mono-Cr(CO)x fragment in different metal cores (HE2Mn3 vs. E2M4). Second, in the cases of 1a and 3a, significant anodic shifts were observed as a higher number of Cr(CO)5 groups incorporated into the HS2Mn3 metal core, due to the pronounced electron-withdrawing ability of the di-Cr(CO)5 groups. Furthermore, the stepwise cluster-growth processes, metal skeleton transformations, electronic properties, and electrochemistry of these E─Mn─Cr carbonyl clusters were rationalized by molecular orbital calculations at the BP86 level of the DFT.. 2.4. Experimental Section All reactions were performed under an atmosphere of pure nitrogen using standard Schlenk techniques.38 Solvents were purified, dried, and distilled under nitrogen prior to use. KOH (J. T. Baker), Cr(CO)6 (Strem), PPNCl (Strem), and TMBACl (ACROS) were used as received. [PPN][E2Mn3(CO)9], [TMBA][E2Mn3(CO)9] (E = S, Se), and [PPN][HCr(CO)5] were prepared according to published methods.14a,21e The 1H NMR spectra were taken on a. 21.

(32) Bruker AV 400 at 400.13 MHz. 1H chemical shifts are reported in ppm and were referenced internally with respect to the solvent resonances (1H, δ = 2.49 for DMSO-d5). Infrared spectra were recorded on a Perkin-Elmer Paragon 500 IR spectrometer as solutions in CaF2 cells. Elemental analyses of C, H, and N were performed on a Perkin-Elmer 2400 analyzer at the NSC Regional Instrumental Center at National Taiwan University, Taipei, Taiwan. The manganese and chromium contents of complexes 1, 2, and 3 were determined with an inductively coupled plasma-atomic emission (ICP-AES) spectrometer (Perkin Elmer Optima 3000DV) at the NSC Regional Instrumental Center at National Tsing Hua University, Hsinchu, Taiwan. 2.4.1. Synthesis of [PPN]2[HS2Mn3Cr(CO)14] ([PPN]2[1a]). Method A: MeOH (10 mL)/MeCN (5 mL) was added to a mixture of [PPN][S2Mn3(CO)9] (0.66 g, 0.65 mmol), Cr(CO)6 (0.14 g, 0.64 mmol), PPNCl (0.76 g, 1.32 mmol), and KOH (3.39 g, 60.4 mmol) in an ice-water bath. The mixture was stirred at room temperature for 3 h. The solid was collected by filtration, washed with deionized water and MeOH, and then extracted with CH2Cl2, which was recrystallized with CH2Cl2/MeOH/Et2O to give a reddish-brown sample of [PPN]2[HS2Mn3Cr(CO)14] ([PPN]2[1a]) (0.45 g, 0.26 mmol) (yield: 41% based on Cr(CO)6). IR (νCO, CH2Cl2): 2054 (w), 1967 (vs), 1963 (vs), 1928 (w), 1894 (m), 1869 (m) cm−1. 1H NMR (400 MHz, DMSO-d6, 300 K): δ −8.94 (s, hydride) (Chemical shifts not given for [PPN]+). Anal. Calcd for [PPN]2[1a]: C, 58.98; H, 3.51; N, 1.60. Found: C, 59.14; H, 3.52; N, 1.47. Crystals of [PPN]2[1a] suitable for X-ray diffraction were grown from CH2Cl2/MeOH/Et2O. ICP-AES: Mn: Cr = 3.18: 1. Similar procedures were applied for the preparation of [TMBA]2[HS2Mn3Cr(CO)14] by using [TMBA][S2Mn3(CO)9] (0.92 g, 1.46 mmol), Cr(CO)6 (0.33 g, 1.50 mmol), TMBACl (0.84 g, 4.57 mmol), and KOH (4.55 g, 81 mmol) in MeOH (15 mL)/MeCN (5 mL). The yield was 1.06 g (1.09 mmol) of ([TMBA]2[1a]) (75% based on [TMBA][S2Mn3(CO)9].). 22.

(33) Method B: MeOH (15 mL)/MeCN (5 mL) was added to a mixture of [PPN][S2Mn3(CO)9] (0.38 g, 0.37 mmol) and [PPN][HCr(CO)5] (0.28 g, 0.38 mmol) in an ice-water bath. The mixture was stirred at room temperature for 3 h. A methanol solution of PPNCl (0.49 g, 0.85 mmol) was added dropwise into the resulting solution, precipitating the solid. The solid was worked up as above-mentioned to give a reddish-brown sample of [PPN]2[1a] (0.38 g, 0.22 mmol) (yield: 59% based on [PPN][S2Mn3(CO)9]). 2.4.2. Synthesis of [PPN]2[HSe2Mn3Cr(CO)14] ([PPN]2[1b]). Method A: MeOH (15 mL)/MeCN (5 mL) was added to a mixture of [PPN][Se2Mn3(CO)9] (0.86 g, 0.77 mmol), Cr(CO)6 (0.34 g, 1.55 mmol), PPNCl (0.81 g, 1.41 mmol), and KOH (4.48 g, 80 mmol) in an ice-water bath. The mixture was stirred at room temperature for 17 h. The solid was collected by filtration, washed with deionized water and MeOH, and then extracted with CH2Cl2, which was recrystallized with CH2Cl2/MeOH/Et2O to give a reddish-brown sample of [PPN]2[HSe2Mn3Cr(CO)14] ([PPN]2[1b]) (0.63 g, 0.34 mmol) (yield: 44% based on [PPN][Se2Mn3(CO)9]). IR (νCO, CH2Cl2): 2050 (w), 1964 (vs), 1958 (vs), 1930 (w), 1891 (m), 1866 (m) cm−1. 1H NMR (400 MHz, DMSO-d6, 300 K): δ −7.78 (s, hydride) (chemical shifts not given for [PPN]+). Anal. Calcd for [PPh4]2[1b]: C, 51.48; H, 2.86. Found: C, 51.39; H, 2.89. Crystals of [PPh4]2[1b] suitable for X-ray diffraction were grown from CH2Cl2/MeOH/Et2O. ICP-AES: Mn: Cr = 3.06: 1. Similar procedures were applied for the preparation of [TMBA]2[HSe2Mn3Cr(CO)14] by using [TMBA][Se2Mn3(CO)9] (0.75 g, 1.04 mmol), Cr(CO)6 (0.50 g, 2.27 mmol), TMBACl (0.85 g, 4.63 mmol), and KOH (4.50 g, 80 mmol) in MeOH (15 mL)/MeCN (5 mL). The yield was 0.88 g (0.83 mmol) of [TMBA]2[HSe2Mn3Cr(CO)14] ([TMBA]2[1b]) (80% based on [TMBA][Se2Mn3(CO)9].). Method B: MeOH (15 mL)/MeCN (5 mL) was added to a mixture of [PPN][Se2Mn3(CO)9] (0.38 g, 0.34 mmol) and [PPN][HCr(CO)5] (0.50 g, 0.68 mmol) in an. 23.

(34) ice-water bath. The mixture was stirred at room temperature for 17 h. A methanol solution of PPNCl (0.49 g, 0.85 mmol) was added dropwise to the resulting solution, precipitating the solid. The solid was worked up as above-mentioned to give a reddish-brown sample of [PPN]2[1b] (0.19 g, 0.103 mmol) (yield: 30% based on [PPN][Se2Mn3(CO)9]). 2.4.3. Synthesis of [TMBA]3[S2Mn3Cr(CO)12] ([TMBA]3[2a]). MeOH (20 mL) was added to a mixture of [TMBA][S2Mn3(CO)9] (0.88 g, 1.40 mmol), Cr(CO)6 (0.31 g, 1.41 mmol), and KOH (4.51 g, 81 mmol). The mixture was stirred at 60 oC for 17 h. A methanol solution of TMBACl (0.91 g, 4.95 mmol) was added dropwise to the resulting solution, precipitating the solid. The solid was collected by filtration, washed with deionized water and MeOH several times, and then extracted with MeCN, which was recrystallized with MeCN/CH2Cl2 to give a purplish-black sample of [TMBA]3[S2Mn3Cr(CO)12] ([TMBA]3[2a]) (0.93 g, 0.88 mmol) (yield: 63% based on [TMBA][S2Mn3(CO)9]). IR (νCO, MeCN): 1983 (w), 1937 (w), 1904 (vs), 1893 (vs, sh), 1874 (m), 1849 (m), 1790 (vw) cm−1. Anal. Calcd for [TMBA]3[2a]·CH2Cl2: C, 45.04; H, 3.87; N, 3.66. Found: C, 45.12; H, 4.33; N, 3.62. Crystals of [TMBA]3[2a]·CH2Cl2 suitable for X-ray diffraction were grown from MeCN/CH2Cl2. ICP-AES: Mn: Cr = 2.89: 1. 2.4.4. Synthesis of [TMBA]3[Se2Mn3Cr(CO)12] ([TMBA]3[2b]). MeOH (20 mL) was added to a mixture of [TMBA][Se2Mn3(CO)9] (0.50 g, 0.69 mmol), Cr(CO)6 (0.16 g, 0.73 mmol), and KOH (4.57 g, 82 mmol). The mixture was stirred at 60 oC for 24 h. A methanol solution of TMBACl (0.95 g, 5.17 mmol) was added dropwise to the resulting solution, precipitating the solid. The solid was collected by filtration, washed with deionized water and MeOH several times, and then extracted with MeCN, which was recrystallized with MeCN/CH2Cl2. to. give. a. greenish-black. sample. of. [TMBA]3[Se2Mn3Cr(CO)12]. ([TMBA]3[2b]) (0.45 g, 0.39 mmol) (yield: 57% based on [TMBA][Se2Mn3(CO)9]). IR (νCO, MeCN): 1978 (w), 1948 (w), 1905 (vs), 1894 (vs, sh), 1866 (m), 1850 (m), 1782 (vw) cm−1. 24.

(35) Anal. Calcd for [TMBA]3[2b]·0.5 CH2Cl2: C, 42.40; H, 4.10; N, 3.49. Found: C, 42.21; H, 3.77; N, 3.49. Crystals of [TMBA]3[2b]·0.5 CH2Cl2 suitable for X-ray diffraction were grown from MeCN/CH2Cl2. ICP-AES: Mn: Cr = 2.95: 1. 2.4.5. Synthesis of [PPN]2[HS2Mn3Cr2(CO)19] ([PPN]2[3a]). CH2Cl2 (20 mL) was added to a mixture of [PPN]2[1a] (0.20 g, 0.11 mmol) and Cr(CO)6 (0.03 g, 0.14 mmol). The reaction mixture was heated in refluxing CH2Cl2 for 12 h. The resulting solution was filtered and the solvent removed under vacuum. The solid was washed with deionized water and MeOH and then extracted with CH2Cl2, which was recrystallized with CH2Cl2/MeOH/Et2O to give a reddish-orange sample of [PPN]2[HS2Mn3Cr2(CO)19] ([PPN]2[3a]) (0.12 g, 0.06 mmol) (yield: 55% based on [PPN]2[1a]). IR (νCO, CH2Cl2): 2054 (w), 1984 (vs), 1979 (vs), 1931 (m), 1905 (w), 1877 (m) cm−1. 1H NMR (400 MHz, DMSO-d6, 300 K): δ −8.97 (s, hydride) (chemical shifts not given for [PPN]+). Anal. Calcd for [PPN]2[3a]: C, 56.24; H, 3.16; N, 1.44. Found: C, 56.03; H, 3.04; N, 1.52. Crystals of [PPN]2[3a] suitable for X-ray diffraction were grown from CH2Cl2/MeOH/Et2O. ICP-AES: Mn: Cr = 1.51: 1. 2.4.6. Synthesis of [PPN]2[HSe2Mn3Cr2(CO)19] ([PPN]2[3b]). CH2Cl2 (20 mL) was added to a mixture of [PPN]2[1b] (0.20 g, 0.11 mmol) and Cr(CO)6 (0.05 g, 0.23 mmol). The reaction mixture was heated in refluxing CH2Cl2 for 18 h. The resulting solution was filtered and the solvent removed under vacuum. The solid was washed with deionized water and MeOH, and then extracted with CH2Cl2, which was recrystallized with CH2Cl2/MeOH/Et2O to give a reddish-orange sample of [PPN]2[HSe2Mn3Cr2(CO)19] ([PPN]2[3b]) (0.11 g, 0.05 mmol) (yield: 45% based on [PPN]2[1b]). IR (νCO, CH2Cl2): 2049 (w), 1982 (vs), 1972 (vs), 1931 (m), 1902 (w), 1871 (m) cm−1. 1H NMR (400 MHz, DMSO-d6, 300 K): δ −7.80 (s, hydride) (chemical shifts not given for [PPN]+). Anal. Calcd for [PPN]2[3b]·MeOH: C, 53.40; H, 3.17; N, 1.35. Found: C, 53.17; H, 3.45; N, 1.15. Crystals of [PPN]2[3b] suitable for X-ray diffraction were grown from CH2Cl2/MeOH/Et2O. ICP-AES: Mn: Cr = 1.68: 1. 25.

(36) 2.4.7. Conversion of [TMBA]2[1a] to [TMBA]3[2a]. MeOH (20 mL) was added to a mixture of [TMBA]2[1a] (1.06 g, 1.09 mmol) and KOH (2.25 g, 40 mmol). The mixture was stirred at 60 oC for 12 h. A methanol solution of TMBACl (0.82 g, 4.46 mmol) was added dropwise to the resulting solution, precipitating the solid. The solid was collected by filtration, washed with deionized water and MeOH several times, and then extracted with MeCN, which was recrystallized with MeCN/CH2Cl2 to give a purplish-black sample of [TMBA]3[2a] (0.64 g, 0.60 mmol) (yield: 55% based on [TMBA]2[1a]). 2.4.8. Conversion of [TMBA]2[1b] to [TMBA]3[2b]. MeOH (20 mL) was added to a mixture of [TMBA]2[1b] (0.88 g, 0.83 mmol) and KOH (2.25 g, 40 mmol). The mixture was stirred at 60 oC for 14 h. A methanol solution of TMBACl (0.92 g, 5.01 mmol) was added dropwise to the resulting solution, precipitating the solid. The solid was collected by filtration, washed with deionized water and MeOH several times, and then extracted with MeCN, which was recrystallized with MeCN/CH2Cl2 to give a greenish-black sample of [TMBA]3[2b] (0.40 g, 0.35 mmol) (yield: 42% based on [TMBA]2[1b]). 2.4.9.. X-ray. Structural. Characterization. of. [PPN]2[1a],. [PPh4]2[1b],. [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b]. Selected crystallographic data for [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b] are given in Table 2.4. All crystals were mounted on glass fibers with epoxy cement. Data collection for [PPN]2[1a], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b] was carried out on a Bruker Nonius Kappa CCD diffractometer using graphite-monochromated MoKα radiation, and an empirical absorption correction by multi-scan was applied.39 Data collection for [PPh4]2[1b] was carried out on a Siemens Smart Apex CCD diffractometer using graphite-monochromated MoKα radiation employing the θ–2θ scan mode, and an empirical absorption correction by multi-scan was applied.39 The structures of [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, 26.

(37) [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b] were solved by direct methods and were refined with SHELXL-97.40 The hydride atoms of [PPN]2[1a], [PPh4]2[1b], [PPN]2[3a], and [PPN]2[3b] were found in the bridging position across one Mn─Mn bond and were refined with isotropic temperature factors. For [TMBA]3[2a], the Mn(1), Mn(2), Mn(3), and Mn(4) atoms and the Cr(1), Cr(2), Cr(3), and Cr(4) atoms of the M4 square in the two independent forms were with 75 and 25% occupancy, respectively, and were refined with anisotropic temperature factors. For [TMBA]3[2b], one independent square M4 plane showed the disordered M(1) and M(2) atoms with Mn and Cr in 75 and 25% occupancy, and the other one showed the disordered M(3) atom with Mn and Cr present in a 50:50 ratio. All metal atoms were refined with anisotropic temperature factors. For [PPN]2[3a], the C(3), O(3); C(4), O(4); C(5), O(5); and C(17), O(17) atoms in the four terminal COs of the di-Cr(CO)5 group were disordered with 50, 55, 55, and 60% occupancy, respectively, and were refined with isotropic temperature factors. Except for the disordered C and O atoms on the di-Cr(CO)5 group of [PPN]2[3a], all of the non-hydrogen atoms for [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b] were refined with anisotropic temperature factors. The selected distances and angles for [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b] are listed in Table S2.5. Additional crystallographic data are available as CIF files in the Supporting Information. 2.4.10. Electrochemical Measurements. The cyclic voltammetry measurements were performed at room temperature under a nitrogen atmosphere and recorded using a BAS-100W and a CHI 621D electrochemical potentiostat. A platinum working electrode, a platinum wire auxiliary electrode, and a non-aqueous Ag/Ag+ electrode were used in a three-electrode configuration. Tetra-n-butylammonium perchlorate (TBAP) was used as the supporting electrolyte, and the solute concentration was ~10−3 -10−4 M. The redox potentials. 27.

(38) were calibrated with a ferrocenium/ferrocene (Fc+/Fc) couple in the working solution and referenced to SCE. 2.4.11. Computational Details. All calculations reported in the present study were performed via the density functional theory (DFT) with Becke’s 1988 exchange functional (B) and Perdew’s 1986 gradient correlation functional (BP86)26,27 or Becke’s three-parameter (B3) exchange functional and the Lee─Yang─Parr (LYP) correlation functional (B3LYP)28,29 with a larger basis set: TZVP30 (triple-zeta valence with one polarization function on each atom) using the Gaussian 03 series of packages.41 We focused our analyses on the pure DFT method (BP86) due to a better correlation with experimental structural parameters (Table S2.4). The geometries of [E2Mn3(CO)9]− (E = S, Se), 1a, 1b, 2a, 2b, 3a, and 3b were fully optimized using the BP86/TZVP method. Wiberg bond indices34 and natural charges35 were evaluated with Weinhold’s NBO method.42 Graphical representations of the molecular orbitals were obtained using CS Chem3D 5.0. For orbital contributions, the molecular orbital compositions were analyzed using the AOMIX program.43 2.4.12. Acknowledgements. This work was supported by the National Science Council of Taiwan (NSC Grant No. 98-2113-M-003-006-MY3 to M. Shieh). We are also grateful to the National Center for High-Performance Computing, which provided the Gaussian package and computer time. Our gratitude also goes to the Academic Paper Editing Clinic, NTNU. 2.4.13. Supporting Information Available: X-ray crystallographic files in CIF format for [PPN]2[1a], [PPh4]2[1b], [TMBA]3[2a]·CH2Cl2, [TMBA]3[2b]·0.5 CH2Cl2, [PPN]2[3a], and [PPN]2[3b], computational details for the optimized geometries of [E2Mn3(CO)9]− (E = S, Se), 1a, 1b, 2a, 2b, 3a, and 3b, ORTEPs for 1a─3a, and electrochemical data. This material is available free of charge via the Internet at http://pubs.acs.org.. 28.

(39) References: (1) (a) Braunstein, P., Rosé, J. In Catalysis by Di- and Polynuclear Metal Cluster Complexes; Adams, R. D., Cotton, F. A., Eds.; Wiley-VCH: New York, 1998; Chapter 13. pp 443─508. (b) Braunstein, P., Rosé, J. Metal Clusters in Chemistry; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-VCH: Weinheim, 1999; Vol. 2, Chapter 2.2, pp 616─677. (c) Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Heteronuclear Metal─Metal Bonds, Vol. 10; Adams, R. D., Ed.; Elsevier: Oxford, 1995. (d) Sinfelt, J. H. Bimetallic Catalysts. Discoveries, Concepts and Applications; Wiley: New York, 1983. (e) Metal Clusters in Catalysis; Gates, B. C., Guczi, L., Knözinger, H., Eds.; Studies in Surface Science and Catalysis Series; Elsevier: Amsterdam, 1986; Vol. 29. (f) Hermans, S., Khimyak, T., Raja, R., Sankar, G., Thomas, J. M., Johnson, B. F. G. in Nanotechnology in Catalysis; Zhou, B., Hermans, S., Somorjai, G. A., Eds.; Kluwer Academic, Plenum Publishers: New York, 2004. (2) (a) Thomas, J. M.; Johnson, B. F. G.; Raja, R.; Sankar, G.; Midgley, P. A. Acc. Chem. Res. 2003, 36, 20─30. (b) Sivaramakrishna, A.; Clayton, H. S.; Makhubela, B. C. E.; Moss, J. R. Coord. Chem. Rev. 2008, 252, 1460─1485. (c) Adams, R. D.; Captain, B. Acc. Chem. Res. 2009, 42, 409─418. (d) Adams, R. D.; Captain, B. Angew. Chem., Int. Ed. 2008, 47, 252─257. (e) Braunschweig, H.; Cogswell, P.; Schwab, K. Coord. Chem. Rev. 2011, 255, 101─117. (3) (a) Kahn, O. Molecular Magnetism; VCH: Weinheim, 1993. (b) Mathonière, C., Sutter, J.-P., Yakhmi, J. V. Bimetallic magnets: Present and perspectives. In Magnetism: molecules to materials; Miller, J. S., Drillon, M., Eds.; Wiley-VCH: Weinheim, 2002; Vol. 4. (4) (a) Robinson, I.; Zacchini, S.; Tung, L. D.; Maenosono, S.; Thanh, N. T. K. Chem. Mater. 2009, 21, 3021─3026. (b) Femoni, C.; Iapalucci, M. C.; Longoni, G.; Wolowska, J.; 29.

(40) Zacchini, S.; Zanello, P.; Fedi, S.; Riccò, M.; Pontiroli, D.; Mazzani, M. J. Am. Chem. Soc. 2010, 132, 2919─2927. (c) Riccò, M.; Shiroka, T.; Carretta, S.; Bolzoni, F.; Femoni, C.; Iapalucci, M. C.; Longoni, G. Chem.─Eur. J. 2005, 11, 2856─2861. (d) Eichhöfer, A.; Olkowska-Oetzel, J.; Fenske, D.; Fink, K.; Mereacre, V.; Powell, A. K.; Buth, G. Inorg. Chem. 2009, 48, 8977─8984. (e) Muratsugu, S.; Sodeyama, K.; Kitamura, F.; Sugimoto, M.; Tsuneyuki, S.; Miyashita, S.; Kato, T.; Nishihara, H. J. Am. Chem. Soc. 2009, 131, 1388─1389. (f) Costa, M.; Della Pergola, R.; Fumagalli, A.; Laschi, F.; Losi, S.; Macchi, P.; Sironi, A.; Zanello, P. Inorg. Chem. 2007, 46, 552─560. (g) Prinz, M.; Kuepper, K.; Taubitz, C.; Raekers, M.; Khanra, S.; Biswas, B.; Weyhermüller, T.; Uhlarz, M.; Wosnitza, J.; Schnack, J.; Postnikov, A. V.; Schröder, C.; George, S. J.; Neumann, M.; Chaudhuri, P. Inorg. Chem. 2010, 49, 2093─2102. (h) Bechlars, B.; Issac, I.; Feuerhake, R.; Clérac, R.; Fuhr, O.; Fenske, D. Eur. J. Inorg. Chem. 2008, 1632─1644. (i) Shieh, M.; Chung, R.-L.; Yu, C.-H.; Hsu, M.-H.; Ho, C.-H.; Peng, S.-M.; Liu, Y.-H. Inorg. Chem. 2003, 42, 5477─5479. (5) (a) Kong, X.-J.; Long, L.-S.; Zheng, Z.; Huang, R.-B.; Zheng, L.-S. Acc. Chem. Res. 2010, 43, 201─209. (b) Femoni, C.; Iapalucci, M. C.; Kaswalder, F.; Longoni, G.; Zacchini, S. Coord. Chem. Rev. 2006, 250, 1580─1604. (c) Welsch, S.; Gröger, C.; Sierka, M.; Scheer, M. Angew. Chem. Int. Ed. 2011, 50, 1435─1438. (d) de Silva, N.; Dahl, L. F. Inorg. Chem. 2006, 45, 8814─8816. (e) Scheer, M.; Schindler, A.; Merkle, R.; Johnson, B. P.; Linseis, M.; Winter, R.; Anson, C. E.; Virovets, A. V. J. Am. Chem. Soc. 2007, 129, 13386─13387. (f) Femoni, C.; Iapalucci, M. C.; Longoni, G.; Zacchini, S.; Zarra, S. J. Am. Chem. Soc. 2011, 133, 2406─2409. (6) (a) Ferrando, R.; Jellinek, J.; Johnston, R. L. Chem. Rev. 2008, 108, 845─910. (b) Femoni, C.; Iapalucci, M. C.; Longoni, G.; Tiozzo, C.; Zacchini, S. Angew. Chem. Int. Ed. 2008, 47, 6666─6669. (c) Naitabdi, A.; Toulemonde, O.; Bucher, J. P.; Rosé, J.; Braunstein, P. ;. 30.

(41) Welter, R.; Drillon, M. Chem.─Eur. J. 2008, 14, 2355─2362. (d) Schweyer-Tihay, F.; Estournès, C.; Braunstein, P.; Guille, J.; Paillaud, J.-L.; Richard-Plouet, M.; Rosé, J. Phys. Chem. Chem. Phys. 2006, 8, 4018─4028. (7) (a) Adams, R. D. In The Chemistry of Metal Cluster Complexes; Shriver, D. F., Kaesz, H. D.; Adams, R. D., Eds.; VCH: New York, 1990; Chapter 3, p 121. (b) Roberts, D. A., Geoffroy, G. L. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 6, Chapter 40, p 763. (8) (a) Wadepohl, H. Coord. Chem. Rev. 1999, 185─186, 551─568. (b) Cador, O.; Cattey, H.; Halet, J.-F.; Meier, W.; Mugnier, Y.; Wachter, J.; Saillard, J.-Y.; Zouchoune, B.; Zabel, M. Inorg. Chem. 2007, 46, 501─509. (9) (a) Whitmire, K. H. J. Coord. Chem. 1988, 17, 95─204. (b) Roof, L. C.; Kolis, J. W. Chem. Rev. 1993, 93, 1037─1080. (c) Mathur, P. Adv. Organomet. Chem. 1997, 41, 243─314. (d) Ogino, H.; Inomata, S.; Tobiya, H. Chem. Rev. 1988, 98, 2093─2021. (e) King, R. B.; Bitterwolf, T. E. Coord. Chem. Rev. 2000, 206─207, 563─579. (10) (a) Lesch, D. A.; Rauchfuss, T. B. Inorg. Chem. 1981, 20, 3583─3585. (b) Holliday, R. L.; Roof, L. C.; Hargus, B.; Smith, D. M.; Wood, P. T.; Pennington, W. T.; Kolis, J. W. Inorg. Chem. 1995, 34, 4392─4401. (c) Drake, G. W.; Schimek, G. L.; Kolis, J. W. Inorg. Chim. Acta 1995, 240, 63─69. (d) Calderoni, F.; Demartin, F.; Iapalucci, M. C.; Laschi, F.; Longoni, G.; Zanello, P. Inorg. Chem. 1996, 35, 898─905. (e) Hecht, C.; Herdtweck, E.; Rohrmann, J.; Hermann, W. A.; Beck, W.; Fritz, P. M. J. Organomet. Chem. 1987, 330, 389─396. (f) Imhof, W.; Huttner, G.; Eber, B.; Günauer, D. J. Organomet. Chem. 1992, 428, 379─400. (g) Bachman, R. E.; Whitmire, K. H. Organometallics 1993, 12, 1988─1992. (h) Bachman, R. E.; Whitmire, K. H. Inorg. Chem. 1994, 33, 2527─2533. (11) (a) Shieh, M. J. Cluster Sci. 1999, 10, 3─36. (b) Shieh, M.; Ho, C.-H. C. R. Chimie 2005, 8, 1838─1849. (c) Lai, Y.-W.; Cherng, J.-J.; Sheu, W.-S.; Lee, G.-A.; Shieh, M.. 31.

(42) Organometallics 2006, 25, 184─190. (12) (a) Adams, R. D.; Kwon, O.-S.; Miao, S. Acc. Chem. Res. 2005, 38, 183─190. (b) Adams, R. D.; Miao, S. J. Organomet. Chem. 2003, 665, 43─47. (c) Huang, S. D.; Lai, C. P.; Barnes, C. L. Angew. Chem. Int. Ed. Engl. 1997, 36, 1854─1856. (d) Fang, Z.-G.; Hor, T. S. A.; Mok, K. F.; Ng, S.-C.; Liu, L.-K.; Wen, Y.-S. Organometallics 1993, 12, 1009─1011. (e) Alper, H.; Sibtain, F.; Einstein, F. W. B.; Willis, A. C. Organometallics 1985, 4, 604─606. (f) Ruiz, J.; Ceroni, M.; Quinzani, O. V.; Riera, V.; Vivanco, M.; García-Granda, S.; Van der Maelen, F.; Lanfranchi, M.; Tiripicchio, A. Chem.─Eur. J. 2001, 7, 4422─4430. (g) Yao, W.-R.; Guo, D.-S.; Liu, Z.-H.; Zhang, Q.-F. J. Mol. Struct. 2003, 657, 165─175. (13) (a) Seidel, R.; Schnautz, B.; Henkel, G. Angew. Chem. Int. Ed. Engl. 1996, 35, 1710─1712. (b) Hermann, W. A.; Hecht, C.; Ziegler, M. L.; Balbach, B. J. Chem. Soc., Chem. Commun. 1984, 686─687. (c) Belletti, D.; Graiff, C.; Pattacini, R.; Predieri, G.; Tiripicchio, A. Eur. J. Inorg. Chem. 2004, 3564─3569. (d) Ruiz, J.; Araúz, R.; Ceroni, M.; Vivanco, M.; Van der Maelen, F.; García-Granda, S. Organometallics 2010, 29, 3058─3061. (14) (a) Huang, K.-C.; Tsai, Y.-C.; Lee, G.-H.; Peng, S.-M.; Shieh, M. Inorg. Chem. 1997, 36, 4421─4425. (b) Shieh, M.; Chen, H.-S.; Yang, H.-Y.; Ueng, C.-H. Angew. Chem., Int. Ed. 1999, 38, 1252─1254. (c) Shieh, M.; Chen, H.-S.; Yang, H.-Y.; Lin, S.-F.; Ueng, C.-H. Chem.−Eur. J. 2001, 7, 3152─3158. (d) Shieh, M.; Ho, C.-H.; Sheu, W.-S.; Chen, H.-W. J. Am. Chem. Soc. 2010, 131, 4032─4033. (e) Ho, C.-H.; Chu, Y.-Y.; Lin, C.-N.; Chen, H.-W.; Huang, C.-Y.; Shieh, M. Organometallics 2010, 29, 4396─4405. (15) (a) Hoefler, M.; Tebbe, K.-F.; Veit, H.; Weiler, N. E. J. Am. Chem. Soc. 1983, 105, 6338─6339. (b) Darensbourg, D. J.; Zalewski, D. J. Organometallics 1984, 3, 1598─1600. (c) Fischer, R. A.; Kneuper, H.-J.; Herrmann, W. A. J. Organomet. Chem.. 32.