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Note
Reactions of the cationic diruthenium carbonyl complex
[Ru
2(
m-dppm)
2(CO)
4(
m,h
2-O
2
CMe)]
+with bidentate ligands;
intramolecularly assisted stereospecific synthesis via the
second-sphere face-to-face
p–p stacking interactions
Kom-Bei Shiu
a,*, Shih-Wei Jean
a, Yu Wang
b, Gene-Hsiang Lee
baDepartment of Chemistry, National Cheng Kung Uni6ersity, Tainan701, Taiwan, ROC bInstrument Center, National Taiwan Uni6ersity, Taipei106, Taiwan, ROC
Received 19 November 2001; received in revised form 21 January 2002; accepted 24 January 2002
Abstract
The reactions of the diruthenium carbonyl complexes [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]X (X = BF4−(1a) or PF6−(1b)) with
neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru2(m-dppm)2
(m-CO)2(h2-(L,L))2]Xn ((L,L) = acetate (O2CMe), 2,2%-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2).
Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]+either
migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru2(m-dppm)2(CO)4(m,h2
-O2CMe)]+ (1) with 2,2%-bipyridine produces [Ru2(m-dppm)2(m-CO)2(h2-O2CMe)2] (2), [Ru2(m-dppm)2(m-CO)2(h2-O2CMe)(h2
-bpy)]+(3), and [Ru
2(m-dppm)2(m-CO)2(h2-bpy)2]2 +(4). Alternatively compound 2 can be prepared from the reaction of 1a with
MeCO2H – Et3N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone – Et3N
produces [Ru2(m-dppm)2(m-CO)2(h2-O2CMe)(h2-acac)] (5) and [Ru2(m-dppm)2(m-CO)2(h2-acac)2] (6). Compound 2 can also react
with acetylacetone – Et3N to produce 6. Surprisingly [Ru2(m-dppm)2(m-CO)2(h2-quin)2] (7) was obtained stereospecifically as the
only one product from the reaction of 1b with 8-quinolinol – Et3N. The structure of 7 has been established by X-ray
crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere p–p face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV – vis spectrum. © 2002 Published by Elsevier Science B.V.
Keywords:Ruthenium; Carbonyl; Acetate; 2,2%-Bipyridine; Acetylacetonate; 8-Quinolinolate
1. Introduction
Our recent interest in exploring the novel reactions and structures of diruthenium carbonyl complexes [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]X (X−= BF4− (1a), PF6− (1b)) has led us to find that a uni-negative anion (Y−) such as I− or N
3
− can convert 1a into neutral complexes with the acetate ligand removed, [Ru2 (m-dppm)2(CO)2(m-Y)(m-CO)Y], while a neutral PR3 con-verts 1a into the CH2Pbond cleaved products with the acetate ligand intact, [Ru2(m-dppm)(m-PPh2)(m,h2 -O2CMe)(h2-CH
2PPh2)(PR3)(CO)2]X and [Ru2(
m-dppm)(m-PPh2)(m,h2-O2CMe)(PR3)2(CO)2]X [1,2]. However, we wish to present here that the reactions of the cation [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]+ (1) with various anionic or neutral bidentate ligands (L,L) afford a series of diruthenium bridging carbonyl com-plexes [Ru2(m-dppm)2(m-CO)2(h2-(L,L))2]n + ((L,L) = acetate (O2CMe), 2,2%-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n = 0, 1, 2). Apparently with coordination of the bidentate ligands, the acetate ligand of 1 either migrates intra- or intermolecularly, or is simply replaced to form the observed products. Sur-prisingly we observed a stereospecific reaction between
1 and 8-quinolate to form [Ru2(m-dppm)2(m-CO)2(h2 -quin)2] in the cis- rather than trans-geometry. Both spectral and structural evidences accumulated for this * Corresponding author. Fax: + 886-6-274-0552.
E-mail address:kbshiu@mail.ncku.edu.tw(K.-B. Shiu).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V. PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 1 9 8 - 1
reaction product indicate obviously that the specific reaction is assisted by the intramolecular second-sphere effect [3].
2. Experimental
The compounds [Ru2(CO)4(m-dppm)2(m,h2-O2 CMe)]-X (CMe)]-X−= BF
4
−(1a), PF 6
−(1b)) [4] were prepared accord-ing to the literature method. All reactions were per-formed under prepurified nitrogen using freshly distilled solvents.1H- and31P-NMR spectra were recorded on a Bruker AMC400 spectrometer (1H, 400 MHz;31P, 162 MHz) calibrated against internal deuterated solvents (1H) or external 85% H
3PO4 (31P). IR spectra were recorded on a Bio-Rad FTS 175 instrument. UV – vis spectra were carried out on a Hewlett – Packard HP8452A instrument. Microanalyses were carried out by the staff of the Microanalytical Service of the De-partment of Chemistry, National Cheng Kung Univer-sity.
2.1. Reaction between [Ru2(v-dppm)2 -(CO)4(v,p2-O2CMe)]X and 2,2%-bipyridine
2.1.1. Method A
In a 100 ml Schlenk flask were added 0.696 g of 1a (0.566 mmol), 0.132 g of bpy (0.837 mmol), and 20 ml of MeCN at room temperature. The mixture was then heated at 82 °C for 8.5 h forming yellow precipitate and orange – red solution. The precipitate was collected on a medium frit, washed six times with 5 ml of MeCN, and dried under vacuum to afford 0.042 g of [Ru2 (m-dppm)2(m-CO)2(h2-O2CMe)2] (2). Yield 6%. The filtrate was combined and the solvent was removed under vacuum forming a solid residue. Recrystallization from CH2Cl2– MeOH gave 0.635 g of [Ru2(m-dppm)2( m-CO)2(h2-O
2CMe)(h2-bpy)][BF4] (3a). Yield 84%. 2, Anal. Calc. for C56H50O6P4Ru2: C, 58.74; H, 4.40. Found: C, 58.68; H, 4.41%.1H-NMR (CD
2Cl2):l 0.70 (s, 6H, Me), 2.66 (s, 4H, Ph2PCH2PPh2), 7.17 – 7.47 (m, 40H, Ph2PCH2PPh2).31P{1H}-NMR (CD2Cl2):l 35.62 (s, 4 P). IR (CH2Cl2):w(CO), 1669 (s) cm− 1. 3a, Anal. Calc. for C64H55BF4N2O4P4Ru2: C, 57.84; H, 4.17; N, 2.11. Found: C, 57.47; H, 4.19; N, 2.08%. 1H-NMR (CD2Cl2): l 0.64 (s, 3H, Me), 2.61 (s, 4H, Ph2PCH2PPh2), 6.68 – 7.43 (m, 40H, Ph2PCH2PPh2), and bpy signals at l 7.06 (m, 2H), 7.53 (m, 2H), 7,63 (d, 2H, 3J H,H= 7.9 Hz), 9.95 (d, 2H, 3JH,H= 5.2 Hz). 31P{1H}-NMR (CD 2Cl2): l 28.71 (m, 2 P), 31.19 (m, 2 P). IR (CH2Cl2):w(CO), 1659 (s) cm− 1. 2.1.2. Method B
In a 100 ml Schlenk flask were added 0.389 g of 1b (0.302 mmol), 0.064 g of bpy (0.406 mmol), and 24 ml of MeCN at room temperature. The mixture was then
heated at 82 °C for 13 h forming yellow precipitate and orange – red solution. The precipitate was collected on a medium frit, washed twice with 5 ml of MeCN, and dried under vacuum to afford 0.011 g of [Ru2 (m-dppm)2(m-CO)2(h2-O2CMe)2] (2). Yield 3%. The filtrate was combined and 0.112 g of NH4PF6(ca. 0.69 mmol)) was added. The solvent was then removed from the mixture under vacuum forming a solid residue. Recrys-tallization from CH2Cl2– MeOH gave 0.342 g of impure [Ru2(m-dppm)2(m-CO)2(h2-bpy)(h2-O
2CMe)][PF6] (3b), contaminated with [Ru2(m-dppm)2(m-CO)2(h2 -bpy)2][PF6]2(4b) in a ratio of 3b/4b = 18/1 based on the 1H-NMR signals.
2.2. Preparation of
[Ru2(v-dppm)2(v-CO)2(p2-O2CMe)2] (2)
In a 100 ml Schlenk flask were added 0.202 g of 1b (0.157 mmol), 1.5 ml of acetic acid (ca. 26 mmol), 1.5 ml of Et3N (ca. 11 mmol), and 24 ml of MeCN at room temperature. The mixture was then heated at 82 °C for 7 h forming yellow precipitate. The precipitate was collected on a medium frit, washed twice with 10 ml of MeCN, and dried under vacuum to afford 0.120 g of [Ru2(m-dppm)2(m-CO)2(h2-O
2CMe)2] (2). Yield 67%.
2.3. Preparation of
[Ru2(v-dppm)2(v-CO)2(p2-bpy)2][PF6]2 (4b)
In a 100 ml Schlenk flask were added 0.202 g of impure 3b described above, 0.073 g of bpy (0.463 mmol), and 20 ml of MeCN at room temperature. The mixture was then heated at 82 °C for 90 h. 0.237 g of NH4PF6 (ca. 1.381 mmol) was added, and the volume of the solution was then reduced to ca. 1 ml. 10 ml of MeOH was added and the resulting suspension was filtered through a medium frit. The orange – yellow solid was washed with 5 ml of MeOH, and 5 ml of CH2Cl2, and dried under vacuum to give 0.122 g of [Ru2( m-dppm)2(m-CO)2(h2-bpy)2][PF6]2 (4b). Anal. Calc. for C72H60F12N4O2P6Ru2: C, 53.08; H, 3.71; N, 3.44. Found: C, 52.85; H, 3.69; N, 3.37%. 1H-NMR (CD2Cl2):l 3.29 (s, 4H, Ph2PCH2PPh2), 7.22 – 8.99 (m, 40H for Ph2PCH2PPh2 and 8H for bpy), and bpy signals atl 9.32 (d, 4H, 3J H,H= 5.1 Hz), 10.93 (d, 2H, 3J H,H= 5.3 Hz). 31P{1H}-NMR (CD3CN):l 23.00 (s, 4 P). IR (CH2Cl2): w(CO), 1655 (s) cm− 1. 2.4. Reaction between[Ru2(v-dppm)2 -(CO)4(v,p2-O
2CMe)][PF6] (1b)and acetylacetone – Et3N In a 100 ml Schlenk flask were added 0.149 g of 1b (0.116 mmol), 0.6 ml of acetylacetone (ca. 5.84 mmol), 2 ml of Et3N (ca. 14.3 mmol) and 20 ml of CH2Cl2 at room temperature. The mixture was then heated at 40 °C for 24.5 h. The volatiles were removed under
vac-uum. Recrystallization from CH2Cl2– MeOH gave 0.089 g of a pink solid. The volume of the filtrate obtained from recrystallization was reduced to ca. 2 ml, forming 0.006 g of an orange – yellow solid. This solid was collected and found to be [Ru2(m-dppm)2( m-CO)2(h2-O2CMe)(h2-acac)] (5). Yield 4%. The pink solid was found to be [Ru2(m-dppm)2(m-CO)2(h2-acac)2] (6). Yield 63%. 5, Anal. Calc. for C59H54O6P4Ru2: C, 59.80; H, 4.59. Found: C, 59.47; H, 4.89. 1H-NMR (CDCl3): l 0.85 (s, 3 H, MeCO2), 0.91 (s, 6 H, Me of acac), 2.56 (s, 4 H, Ph2PCH2PPh2), 4.11 (s, 1 H, H of acac), 7.12 – 7.56 (m, 40 H, Ph2PCH2PPh2). 31P{1 H}-NMR (CDCl3): l 31.77 (m, 2 P), 33.00 (m, 2 P). IR (CH2Cl2): w(CO), 1690 (s) cm− 1. 6, Anal. Calc. for C62H58O6P4Ru2: C, 60.78; H, 4.77. Found: C, 60.53; H, 4.95%.1H-NMR (CD 2Cl2):l 0.94 (s, 12H, Me of acac), 2.48 (s, 4H, Ph2PCH2PPh2), 4.12 (s, 2H, H of acac), 7.07 – 7.48 (m, 40H, Ph2PCH2PPh2). 31P{1H}-NMR (CD2Cl2):l 30.71 (s, 4 P). IR (CH2Cl2):w(CO), 1656 (s) cm− 1. UV – vis (CH 2Cl2): 232 (m=850), 256 (710), 308 (240) nm.
2.5. Preparation of[Ru2(v-dppm)2(v-CO)2(p2-acac)2]
(6)
In a 100 ml Schlenk flask were added 0.103 g of 2 (0.090 mmol), 2 ml of acetylacetone (ca. 19.5 mmol), 2 ml of Et3N (ca. 14.3 mmol) and 20 ml of CH2Cl2 at room temperature. The mixture was then stirred for 16 h. The volatiles were removed under vacuum. Recrys-tallization from CH2Cl2– MeOH gave 0.091 g of a pink solid, 6. Yield 82%.
2.6. Preparation of
[Ru2(v-dppm)2(v-CO)2(p2-quin)2][PF6]2 (7)
In a 100 ml Schlenk flask were added 0.198 g of 1b (0.154 mmol), 0.069 g of 8-quinolinol (0.471 mmol), 2 ml of Et3N (ca. 14.3 mmol), and 21 ml of CH2Cl2 at room temperature. The mixture was then heated at 40 °C for 22 h. The solvent was removed under vacuum. Recrystallization from CH2Cl2– MeOH gave 0.150 g of orange – yellow [Ru2(m-dppm)2(m-CO)2(h2-quin)2] (7). Yield 74%. Anal. Calc. for C70H56N2O4P4Ru2: C, 63.92; H, 4.29; N, 2.13. Found: C, 63.76; H, 4.28; N, 2.11%. 1H-NMR (CD 2Cl2): l 2.51 (m, Ph2PCH2PPh2, 2H), 2.20 (m, Ph2PCH2PPh2, 2H), 6.10 – 9.10 (m, Ph and quin, 52H). 31P{1H}-NMR (CD 2Cl2): l 25.06 (s, 4 P). IR (CH2Cl2): w(CO), 1734s cm− 1. UV – vis (CH2Cl2): 234 (m=1100), 260 (1100), 356 (140), 458 (120) nm.
2.7. X-ray data collection, solution and refinement Data were collected at 150 K on a Siemens SMART-CCD instrument, equipped with a normal focus and 3 kW sealed-tube X-ray source. The structures of 7 were solved by heavy-atom methods and refined by a full-matrix least-squares procedure using NRCVAX [5]. All the non-hydrogen atoms were refined anisotropically. The other essential details of single-crystal data mea-surement and refinement are given in Table 1. Three CH2Cl2molecules were found in the asymmetric unit of the crystal of 7. There is a residual peak with 2.427 e A, − 3 in a distance of 1.037 A, close to the Ru(2) atom on the last difference Fourier map.
3. Results and discussion
The reaction of [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]+ (1) with 2,2%-bipyridine (bpy) in a slightly excess amount, relative to that of 1, produces [Ru2( m-dppm)2(m-CO)2(h2-O
2CMe)2] (2), [Ru2(m-dppm)2( m-CO)2(h2-bpy)(h2-O
2CMe)]+ (3), and [Ru2(m-dppm)2 -(m-CO)2(h2-bpy)
2]2 + (4). Compound 3 is the major product. The neutral compound, 2, is insoluble in the reaction solvent, MeCN, and can be separated from other products, 3 and 4. However, we had difficulty Table 1 Crystal data 7·3CH2Cl2 Compound Empirical formula C73H62Cl6IN2O4P4Ru2 1569.97 Formula weight Triclinic, P1( Space group a (A, ) 14.2282(2) b (A, ) 14.6067(2) c (A, ) 18.8527(2) h (°) 79.716(1) i (°) 87.126(1) k (°) 62.927(1) 3506.6(6) V (A,3) Z 2 Dcalc(g cm−3) 1.520 1592 F(000)
Unit cell detn
2–53 2q range (°) 917, 918, 923 h, k, l range 0.818 v(Mo–Ka) (mm−1) Transmission factors 0.8621–0.6547 0.71073 u (Mo–Ka) (A, ) 0.20×0.14×0.12 Crystal size (mm) 150(1) Temperature (K) 29 516 Number of measured reflections
Number of observed reflections (No) 13586 (\2|)
0.0675, 0.1714
Ra, R w
a
Goodness-of-fita 1.070
Refinement program NRCVAX
Number of refined parameters (Np) 816
Weighting scheme [|2(F o)+0.0013Fo2]−1 2.427 (Dz)max (e A,3) (Dz)min(e A,3) −1.275 aR = [S F o − Fc /S Fo ]. Rw= [S ( Fo − Fc )2/S Fo 2]1/2. GOF = [S ( Fo − Fc )2/No−Np]]1/2.
Scheme 1.
separating the mixture of [Ru2(m-dppm)2(m-CO)2(h2 -bpy)(h2-O
2CMe)][PF6] (3b) and [Ru2(m-dppm)2 (m-CO)2(h2-bpy)2][PF6]2 (4b), when [Ru2(m-dppm)2 -(CO)4(m,h2-O2CMe)][PF6] (1b) was used as the reactant. Fortunately we soon found that [Ru2(m-dppm)2( m-CO)2(h2-bpy)2][BF4]2 (4a) is slightly soluble in MeOH but not in CH2Cl2. Hence, we start the reaction using [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)][BF4] (1a) as the re-actant, and then with a simple recrystallization from CH2Cl2– MeOH, we can obtain [Ru2(m-dppm)2 (m-CO)2(h2-bpy)(h2-O2CMe)][BF4] (3a) as a pure solid.
Alternatively, compound 2 can be prepared from the reaction of 1a with MeCO2H – Et3N, while the pure compound, 4b, can be obtained from the reaction of the impure 3b, contaminated with 4b in a ratio of 3b/4b = 18/1 based on the 1H-NMR signals. Thus, it appears that with the coordination of a neutral bidentate ligand such as bpy, the bound acetate ligand in 1 can migrate intramolecularly to form 3 first, then replaced subse-quently by a second bpy to form 4. The replaced acetate finds 1 in the reaction solvent, MeCN, and reacts to form the insoluble precipitate, 2 (Scheme 1). The reaction of 1b with acetylacetonate (acac), via acetylacetone – Et3N, in CH2Cl2 produces [Ru2 (m-dppm)2(m-CO)2(h2-O2CMe)(h2-acac)] (5) and [Ru2( m-dppm)2(m-CO)2 (h2-acac)2] (6). The solubility of both compounds is different in two organic solvents used. Compound 6 is insoluble in MeOH but slightly soluble in CH2Cl2. Compound 5 is very soluble in this solvent
but slightly soluble in MeOH. Hence, compounds 5 and
6 can be separated easily. Compound 6 obtained from
the reaction is the major product, while compound 5 is the minor one. When the reaction time is lengthened from 24.5 h to more than 30 h, compound 6 can be obtained as a pure product. Compound 6 can also be prepared via an alternative way from the reaction of 2 with acetylacetone – Et3N. Apparently the reaction of 1b with an anionic bidentate ligand such as acetylaceto-nate follows a similar pathway to that of 1 with bpy. It forms 5 first, and then 6. The neutral product, 2, if obtained as one of the products, is soluble in the reaction solvent, CH2Cl2, and reacts further with acety-lacetonate to form 6 as the final product. Likewise the reaction of 1b with 8-quinolinolate (quin) via 8-quinoli-nol/Et3N may form [Ru2(m-dppm)2(m-CO)2(h2-O2 CMe)-(h2-quin)] first, and then [Ru
2(m-dppm)2(m-CO)2 (h2 -quin)2] (7) (Scheme 1).
The four P atoms resonate in the 31P{1H}-NMR spectra as one singlet at l 35.62 for [Ru2(m-dppm)2( m-CO)2(h2-O2CMe)2] (2), 23.00 for [Ru2(m-dppm)2 (m-CO)2(h2-bpy)
2]2 + (4), and 30.71 for [Ru2(m-dppm)2 -(m-CO)2(h2-acac)2] (6), indicating that the molecule may adopt a geometry with a D2h symmetry. Since 8-qunio-late is an anionic (O, N) bidentate ligand, we expected to obtain a mixture of both cis- and trans-[Ru2 (m-dppm)2(m-CO)2(h2-quin)2] with the former in a C26 symmetry and the latter in a C2h symmetry before the experiment. To our surprise, the reaction appears quite
stereospecific to produce only one product 7, showing only one31P{1H} singlet atl 25.06. In order to find out the specific geometry and the possible cause, the solid-state structure of 7 was determined by X-ray crystallog-raphy. The two (O, N) ligands were found to adopt the
cis rather than trans geometry (Fig. 1). In a projection
view with overlapping P(1) and P(3) atoms (and over-lapping P(2) and P(4) atoms) (Fig. 2), we found that some sort of p–p face-to-face stacking interactions probably exist between the phenyl rings of dppm above
or below the electron-deficient six-membered ring moi-ety of the quinolinate (i.e. the N-included six-membered ring plane). The distances and angles formed between two such nearly parallel planes are (3.531 A, , 15.90°) between plane 1 and plane 2, (3.569 A, , 20.69°) between plane 2 and plane 3, (3.599 A, , 19.8°) between plane 4 and plane 5, and (3.636 A, , 22.62°) between plane 5 and plane 6, where plane 1 contains C23, C24, C25, C26, C27, and C28; plane 2 contains N1, C3, C4, C5, C6, and C11; plane 3 contains C53, C54, C55, C56, C57, and C58; plane 4 contains C41, C42, C43, C44, C45, and C46; plane 5 contains N2, C12, C13, C14, C15, and C20; and plane 6 contains C65, C66, C67, C68, C69, and C70. This ‘‘second-sphere coordination’’ via the p–p interactions may help to drive a stereospecific reaction between 1b and 8-quinolate [3,6]. Indeed, the presence of such interactions is supported by an ob-served charge-transfer band at 458 nm in a UV – vis spectrum measured in CH2Cl2. (Compound 7 also dis-plays three other bands at 234, 260, and 356 nm, but compound 6 displays only three bands at 232, 256, and 308 nm.) This feature reflects apparently that (1) the parallel arrangement and close contact (3.53 – 3.64 A, ) between the phenyl planes of dppm and the N-included six-membered ring planes of quinolate ligands observed in the solid state are also retained in solution, and (2) the quinolate ligand can act as an electron acceptor (a p acid), except for the common role it plays as an electron donor (a s base) [7]. The p-acid character is probably more important than thes-base character, for the relatively shorter Ru – Ru distance of 2.7672(6) found in 7, compared with that of 2.841(1) A, observed in 1b [3], and for the very highw(CO) frequency of 1734 cm− 1displayed by 7, compared with that of 1699 in 2, 1659 in 3, 1655 in 4, 1690 in 5, and 1656 cm− 1 in 6.
4. Conclusion
The reactions of the diruthenium carbonyl cation [Ru2(m-dppm)2(CO)4(m,h2-O2CMe)]+ (1) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru2 (m-dppm)2(m-CO)2(h2-(L,L))2]n + ((L,L) = acetate (O2 -CMe), 2,2%-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n = 0, 1, 2). Apparently with the coordination of a bidentate ligand, the bound acetate ligand in 1 can migrate intramolecularly to form [Ru2(m-dppm)2(m-CO)2(h2-O2CMe)(h2-(L,L))]n + (n = 0, (L,L) = acac (5), quin; n = 1, (L,L) = bpy (3)) first, then replaced subsequently by a second (L,L) to form [Ru2(m-dppm)2(m-CO)2(h2-(L,L))
2]n + (n = 0, (L,L) = acac (6), quin (7); n = 2, (L,L) = bpy (4)). The replaced acetate can react with 1 to form [Ru2(m-dppm)2( m-CO)2(h2-O2CMe)2] (2) as an insoluble precipitate in MeCN. However, if the reaction solvent is CH2Cl2, 2 Fig. 1. ORTEPplot of 7 with 50% thermal ellipsoids. Part of phenyl
groups containing C(30)C(34), C(36)C(40), C(48)C(52), and C(60)C(64) atoms are omitted for clarity. Selected bond lengths: Ru(1)Ru(2)=2.7676(2), Ru(1)C(1)=2.034(6), Ru(1)C(2)= 1.998(6), Ru(1)N(1)=2.182(5), Ru(1)O(3)=2.183(4), Ru(1) P(1) = 2.379(2), Ru(1)P(3)=2.367(2), Ru(2)C(1)=2.033(6), Ru(2)C(2)=1.994(6), Ru(2)N(2)=2.188(5), Ru(2)O(4)= 2.186(4), Ru(2)P(2)=2.378(2), Ru(2)P(4)=2.367(2), C(1)O(1)= 1.187(7), C(2)O(2)=1.236(7) A, . Selected bond angles: Ru(1)Ru(2)C(1)=47.1(2), Ru(1)Ru(2)C(2)=46.2(2), Ru(2) Ru(1)C(1)=47.1(2), Ru(2)Ru(1)C(2)=46.0(2), Ru(1)C(1) Ru(2) = 85.7(2), Ru(1)C(2)Ru(2)=87.8(2), Ru(1)C(1)O(1)= 138.0(4), Ru(1)C(2)O(2)=136.3(4), Ru(2)C(1)O(1)=136.3(4), Ru(2)C(2)O(2)=135.7(4), C(1)Ru(1)O(3)=94.4(2), O(3)Ru(1) N(1) = 76.1(2), N(1)Ru(1)C(2)=96.5(2), C(2)Ru(1)C(1)= 93.1(2), C(1)Ru(2)O(4)=93.6(2), O(4)Ru(2)N(2)=75.7(2), N(2)Ru(2)C(2)=97.5(2), C(2)Ru(2)C(1)=93.3(2), P(1)Ru(1) P(3) = 173.74(5), P(2)Ru(2)P(4)=174.66(5)°.
Fig. 2. A projection view of 7 along P(1)P(3) and P(2)P(4) vectors. Phenyl groups containing C(29)C(34), C(35)C(40), C(47)C(52), and C(59)C(64) are omitted for clarity.
remains soluble and can react further with two equiva-lents of (L,L) to produce the substituted product such as 6 (Scheme 1). The crystal structure of 7 was deter-mined by X-ray crystallography to reveal a stereospe-cific reaction between 1 and quin, forming a
cis-{Ru2(h2-quin)2} arrangement (Fig. 1). The possible cause is due to the intramolecular p–p face-to-face stacking interactions between the phenyl rings of dppm above and below the p-electron-deficient N-included six-membered ring plane of the bound quinolinate (Fig. 2). The presence of such interactions is further sup-ported by an observed charge-transfer band in a UV – vis spectrum.
5. Supplementary material
Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC no. 173958 for compound 7. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: + 44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www: http:// www.ccdc.cam.ac.uk).
Acknowledgements
The authors thank the National Science Council of the Republic of China for financial support of this research (Contract No. NSC90-2113-M006-021).
References
[1] K.-B. Shiu, W.-N. Guo, T.-J. Chan, J.-C. Wang, L.-S. Liou, S.-M. Peng, M.-C. Cheng, Organometallics 14 (1995) 1732. [2] K.-B. Shiu, S.-W. Jean, H.-J. Wang, S.-L. Wang, F.-L. Liao, J.-C.
Wang, L.-S. Liou, Organometallics 16 (1997) 114.
[3] (a) H.M. Colquhoun, J.F. Stoddart, D.J. Williams, Angew. Chem. Int. Ed. Engl. 25 (1986) 487;
(b) F.M. Raymon, J.F. Stoddart, Chem. Ber. 129 (1996) 981. [4] S.J. Sherlock, M. Cowie, E. Singleton, M.M.d.V. Steyn,
Organometallics 7 (1988) 1663.
[5] E.J. Gabe, Y. Le page, J.-P. Charland, F.L. Lee, P.S. Lee, J. Appl. Crystallogr. 22 (1989) 384.
[6] (a) C.A. Hunter, J.K.M. Sanders, J. Am. Chem. Soc. 112 (1990) 5525;
(b) C.A. Hunter, Angew. Chem. Int. Ed. Engl. 32 (1993) 1584; (c) C.A. Hunter, Chem. Soc. Rev. 23 (1994) 101;
(d) P.R. Ashton, S. Menzer, F.M. Raymo, G.K.H. Shimizu, J.F. Stoddart, D.J. Williams, J. Chem. Soc. Chem. Commun. (1996) 487.
[7] R.H. Crabtree (Ed.), The Organometallic Chemistry of the Tran-sition Metals, 3rd ed., Wiley, New York, 2001, p. 43.
