行政院國家科學委員會專題研究計畫 成果報告

行政院國家科學委員會專題研究計畫 成果報告

雙亞硝醯基鐵化合物之合成，反應性研究及其電子結構與 作為一氧化氮傳遞劑效率探討

研究成果報告(精簡版)

計 畫 類 別 ： 個別型

計 畫 編 號 ： NSC 99-2119-M-040-001-

執 行 期 間 ： 99 年 08 月 01 日至 100 年 07 月 31 日 執 行 單 位 ： 中山醫學大學應用化學系（所）

計 畫 主 持 人 ： 陳建宏

計畫參與人員： 碩士級-專任助理人員：何怡潔 碩士級-專任助理人員：洪士軒

碩士班研究生-兼任助理人員：何怡潔 碩士班研究生-兼任助理人員：王正弘

處 理 方 式 ： 本計畫涉及專利或其他智慧財產權，2 年後可公開查詢

中 華 民 國 100 年 08 月 25 日

New Members of the {Fe(NO)

}

Dinitrosyl Iron Complexes (DNICs) Bound with [Thiolate, Thiolate]

and [Amide, Amide] Ligations

Introduction

Interest in nitric oxide (NO) derives from its physiological and biological functions in living organisms. ¹ In vivo, nitric oxide can be stabilized and stored in the two forms, protein-bound thionitrosyls (Rprotein-SNO) and protein-bound dinitrosyl iron complexes (protein-bound DNICs).² The displacement of protein-bound DNICs with free thiols/thiolates yielding low-molecular-weight DNICs (LMW-DNICs) has been suggested.³ In vitro/in vivo, both protein-bound DNICs and LMW DNICs are possibly identified and characterized by their distinctive electron paramagnetic resonance (EPR) signals at g = 2.03.⁴ In spite of the major thiol components of cellular DNICs composed of cysteine and glutathione in vivo,⁵ DNICs ligated by phenoxide, thiolate, imidazole, and deprotonated imidazole were proposed in enzymology based on EPR spectra.^3a,6 Recently, the protein-bound DNIC with [S,O] ligation has been well characterized by X-ray diffraction study via the addition of a dinitrosyldiglutathionyl iron complex into human glutathione transferase P1-1 in vitro/ in vivo.^6c In biomimetic complexes, varieties of DNICs containing S/O/N-donor ligands were synthesized to serve as the spectroscopic references.^7,8 Based on the Enemark-Fetham notation,⁹ these synthesized LMW DNICs can be classified as the EPR-active {Fe(NO)2}⁹ DNICs and the EPR-silent {Fe(NO)2}¹⁰ DNICs. In spite of a large number of the neutral {Fe(NO)2}¹⁰ DNICs with nitrogen or phosphorous liagnds, the dianionic {Fe(NO)2}¹⁰ DNICs are limited.⁸ Recently, we report the monoanionic

sulfur-containing {Fe(NO)2}¹⁰ DNIC

[K-18-crown-6-ether][Fe(SC6H4-o-NMe2)(NO)2].¹⁰ In addition to the classical four-coordinate DNICs, the non-classical DNICs, including the five-coordinate DNICs [(6-Me3-TPA)Fe(NO)2]⁺, [(TMEDA)Fe(NO)2I],^11,12 and the six-coordinate DNIC [(1-Melm)2(η²-ONO)Fe(NO)2],¹³ are also structurally characterized. In this contribution, the dianionic {Fe(NO)2}¹⁰ DNICs with [thiolate,thiolate] and [amide,amide] ligation, [Fe(SC7H4SN)2(NO)2]²⁻ (1) and [Fe(OC7H4SN)2(NO)2]²⁻ (2) (cation = Na-18-crown-6-ether (1-Na/2-Na), PPh4

(1-PPh4/2-PPh4)) were delineated. The reversible interconversion among the dianionic {Fe(NO)2}¹⁰ DNICs 1/2 and the anionic {Fe(NO)2}⁹ DNICs [Fe(SC7H4SN)2(NO)2] ⁻ (3)/[Fe(OC7H4SN)2(NO)2]⁻ (4) (cation =

Na-18-crown-6-ether (3-Na/4-Na), PPh4+ (3-PPh4/4-PPh4)) were demonstrated. In particular, the different binding affinity of [OC7H4SN]⁻ vs [SC7H4SN]⁻ toward {Fe(NO)2}⁹/{Fe(NO)2}¹⁰ motif was studied.

Experimental Details

General Procedures. Manipulations, reactions, and transfers were conducted under nitrogen according to Schlenk techniques or in a glovebox (nitrogen gas).

Solvents were distilled under nitrogen from appropriate drying agents (methylene chloride from CaH2; acetonitrile from CaH2-P2O5; diethyl ether, hexane and tetrahydrofuran(THF) from sodium benzophenone ) and stored in dried, N2-filled flasks over 4Å molecular sieves. Nitrogen was purged through these solvents before use. Solvent was transferred to the reaction vessel via stainless cannula under positive pressure of N2. The reagents, iron pentacarbonyl (Strem), tetraphenylphosphonium bromide ([PPh4][Br]), 18-crown-6-ether, nitrosonium tetrafluoroborate (Alfa Aesar), 2-mercaptobenzothiazole sodium salt,2-hydroxybenzothiazole (TCI), ferrocenium hexafluorophosphate (Sigma-Aldrich) were used as received. Fe(TMEDA)(NO)2 has been prepared according to the literature procedure.¹

Physical Measurements. Infrared spectra of the nitrosyl ν(NO) stretching frequencies were recorded on Jasco FT/IR-4100 spectrophotometer/Bruker Alpha spectrophotometer with sealed solution cells (0.1 mm) and KBr windows. UV/vis spectra were recorded on a GBC Cintra 101. X-band EPR spectrum was recorded on a Bruker EMX spectrometer equipped with a Hewlett-Packard 5246 L electronic counter. Cyclic voltammetry (CV) was carried out with a CH Instruments

electrochemical analyzer 611C. A three-electrode system consisted of a glassy carbon working electrode, a platinum wire auxiliary electrode, and a 0.1 M Ag/Ag⁺ reference electrode. All CV data were recorded with the scan rate of 1 V s^-1 in

CH3CN with tetrabutylammonium hexafluorophosphate as the supporting electrolyte.

All potential values are reported verse ferrocene/ferrocenium ion. Analyses of carbon, hydrogen, and nitrogen were obtained with a CHN analyzer (Heraeus).

Crystallography. Crystallographic data and structure refinements parameters of complexes 1-PPh4, 2-PPh4 and 4-PPh4 are summarized in the Supplementary Material (Tables S1, S2 and S3). The crystals of complexes 1-PPh4, 2-PPh4 and 4-PPh4 chosen for X-ray diffraction studies are measured in size 0.38 x 0.25 x 0.07 mm, 0.58 × 0.40 × 0.32 mm, and 0.40 × 0.25 × 0.25 mm, respectively. Each crystal was mounted on a glass fiber and quickly coated in epoxy resin. Unit-cell

parameters were obtained by least-squares refinement. Diffraction measurements for complexes 1-PPh4, 2-PPh4 and 4-PPh4 were carried out on a Nonius Kappa CCD and Bruker SMART Apex CCD diffractometers using graphite-monochromated Mo

Kα radiation (λ = 0.7107 Å) and between 2.22 and 25.06° for complex 1-PPh⁴, 2.26 and 25.04° for complex 2-PPh4, between 1.94 and 27.50° for complex 4-PPh4. Least-squares refinement of the positional and anisotropic thermal parameters for the contribution of all non-hydrogen atoms and fixed hydrogen atoms was based on F2. A SADABS absorption correction was made. The SHELXTL structure

refinement program was employed.

Preparation of [cation]2[Fe(SC7H4SN)2(NO)2] (1) (cation = Na-18-crown-6-ether (1-Na), PPh4+

(1-PPh4)). 1-Na: The compounds Fe(TMEDA)(NO)2 (0.232 g, 1 mmol), [Na][SC7H4SN] (0.398 g, 2 mmol) and 18-crown-6-ether (0.528 g, 2 mmol) were loaded into a Schlenk tube, and then 20 mL of THF was added under positive N2 at ambient temperature. The reaction solution was stirred overnight and then the light green precipitates were afforded.

When the upper solution was discarded via cannula under a positive pressure of N2, the residual light green solid was washed with 15 mL of THF. After drying the light green solid under vacuum, the light green solid of

[Na-18-crown-6-ether]2[Fe(SC7H4SN)2(NO)2] (1-Na) (yield: 0.95 g, 92.9 %) was afforded. IR: 1684 (s)，1633 (s) cm^-1 (CH3CN); 1654 (s), 1609 (s) (νNO) cm^-1 (KBr).

Absorption spectrum (THF) [λmax, nm (ε, M^–1 cm^–1)]: 670 (307), 488 (781). 1-PPh4: To the CH3CN solution (10 mL) of (TMEDA)Fe(NO)2 (0.232 g, 1 mmol) was added the CH3CN solution (20 mL) of [PPh4][SC7H4SN] (1.012 g, 2 mmol) dropwise under N2 at ambient temperature. After storing the reaction solution without stirring for 5 days under nitrogen atmosphere at -15°C, the upper solution was discarded by cannula under positive N2 pressure and then the brown crystals suitable for

single-crystal X-ray diffraction was dried under vacuum to afford

[PPh4]2[Fe(SC7H4SN)2(NO)2] (1-PPh4) (yield: 0.878 g, 77.9%). IR: 1661 (s), 1613 (s) cm^-1 (νNO) (KBr). Anal. Calcd for C62H48FeN4O2P2S4: C, 66.07; H, 4.29; N, 4.97.

Found: C, 66.51; H, 3.88; O, 4.63.

Preparation of [cation]2[Fe(OC7H4SN)2(NO)2] (2) (cation = Na-18-crown-6-ether (2-Na), PPh4 (2-PPh4)). 2-Na: The compounds

Fe(TMEDA)(NO)2 (0.232 g, 1 mmol), [Na][OC7H4SN] (0.346 g, 2 mmol) and 18-crown-6-ether (0.528 g, 2 mmol) were loaded into a Schlenk flask, and then 10 mL of THF was added under positive N2 at ambient temperature. The reaction solution was stirred overnight and then 40 mL of diethyl ether was added to the reaction solution. After the reaction mixture was stirred for 1 h, the light green precipitates were afforded. The upper solution was discarded via cannula under a positive pressure of N2 and the residual light green solid was washed with 20 mL of diethyl ether. After drying the light green solid under vacuum, the light green solid of [Na-18-crown-6-ether]2[Fe(OC7H4SN)2(NO)2] (2-Na) (yield: 0.65 g, 65.7%) was

afforded. IR: 1665 (m)，1609 (sh) (νNO), 1627 (s) (νCO) cm^-1 (CH3CN); 1664 (s), 1606 (s) (νNO), 1623 (s) (νCO) cm^-1 (KBr). Absorption spectrum (THF) [λmax, nm (ε, M^–1 cm^–1)]: 712 (125), 390 (858). 2-PPh4: To the CH3CN solution (10 mL) of (TMEDA)Fe(NO)2 (0.162 g, 0.7 mmol) was added the CH3CN solution (20 mL) of [PPh4][OC7H4SN] (0.685 g, 1.4 mmol) dropwise under N2 at ambient temperature.

After storing the reaction solution without stirring for 5 days under nitrogen

atmosphere at -15°C, the upper solution was discarded by cannula under positive N2

pressure and then the brown crystals suitable for single-crystal X-ray diffraction was dried under vacuum to afford [PPh4]2[Fe(OC7H4SN)2(NO)2] (2-PPh4) (yield: 0.457 g, 59.6 %). IR: 1662 (s), 1637 (s) (νNO) cm^-1 (KBr). Anal. Calcd for

C62H48FeN4O4P2S2: C, 68.01; H, 4.42; N, 5.12. Found: C, 67.73; H, 4.05; N, 5.50.

Reaction of [cation]2[Fe(SC7H4SN)2(NO)2] (1) with [Cp2Fe][PF6] (cation = Na-18-crown-6-ether (1-Na), PPh4+

(1-PPh4)). 1-Na: The 10 mL CH3CN solution of [Cp2Fe][PF6] (0.497 g, 1.5 mmol) was added dropwise into the 50 mL Schlenk flask containing CH3CN solution of complex 1-Na (1.534 g, 1.5 mmol) via a cannula under positive N2 pressure at 0℃. After being stirred for 5 h, the reaction solution was dried under vacuum to afford the brown solid. 30 mL of THF was added to dissolve the brown solid and the resulting THF solution was monitored with FTIR. The IR spectrum showing νNO stretching frequencies at 1767 (s), 1716(s) cm^-1 (THF) was assigned to the formation of

[Na-18-crown-6-ether][Fe(SC7H4SN)2(NO)2] (3-Na).² The THF solution was

filtered through Celite to separate insoluble [Na-18-crown-6-ether][PF6]. The brown filtrate was concentrated to 5 mL and 40 mL hexane was added to precipitate the brown solid. The brown solid was washed with 20 mL of diethyl ether twice and dried under vacuum to yield complex 3-Na (yield: 1.03 g, 93.6 %). IR: 1773 (s), 1721 (s) (νNO) cm^-1 (CH3CN); 1768 (s), 1729 (s) (νNO) cm^-1 (KBr). Absorption spectrum (THF) [λmax, nm (ε, M^–1 cm^–1)]: 788 (491), 457 (2918). 1-PPh4: The 5 mL CH3CN solution of [Cp2Fe][PF6] (0.099 g, 0.3 mmol) was added dropwise into the 50 mL Schlenk flask containing CH3CN solution of complex 1-PPh4 (0.338 g, 0.3 mmol) via a cannula under positive N2 pressure at 0℃. After being stirred for 5 h, the reaction solution was dried under vacuum to afford the brown solid. 10 mL of THF was added to dissolve the brown solid and the resulting THF solution was monitored with FTIR. The IR spectrum showing νNO stretching frequencies at 1767 (s), 1716(s) cm^-1 (THF) was assigned to the formation of

[PPh4][Fe(SC7H4SN)2(NO)2] (3-PPh4).³ The THF solution was filtered through Celite to separate insoluble [PPh4][PF6]. The brown filtrate was concentrated to 5 mL and 25 mL diethyl ether was added to precipitate the brown solid. The brown solid was washed with 20 mL of diethyl ether twice and dried under vacuum to yield

complex 3-PPh₄ (yield: 0.182 g, 76.7 %). IR: 1774 (s), 1721 (s) (νNO) cm^-1 (CH3CN); 1781 (s), 1739 (s) (νNO) cm^-1 (KBr).

Reaction of [cation]2[Fe(OC7H4SN)2(NO)2] (2) with [Cp2Fe][PF6] (cation = Na-18-crown-6-ether (2-Na), PPh4+

(2-PPh4)). 2-Na: The 8 mL CH3CN solution of [Cp2Fe][PF6] (0.331 g, 1 mmol) was added dropwise into the 50 mL Schlenk flask containing CH3CN solution of complex 2-Na ((0.991 g, 1 mmol) via a cannula under positive N2 pressure at 0℃. After being stirred for 5 h, the reaction solution was dried under vacuum to afford the brown solid. 20 mL of THF was added to dissolve the brown solid and the resulting THF solution was monitored with FTIR.

The IR spectrum showing νNO stretching frequencies at 1786 (m), 1714(s) cm^-1 (THF) was assigned to the formation of

[Na-18-crown-6-ether][Fe(OC7H4SN)2(NO)2] (4-Na). The THF solution was filtered through Celite to separate insoluble [Na-18-crown-6-ether][PF6]. The brown filtrate was concentrated to 5 mL and 40 mL diethyl ether was added to precipitate the brown solid. The brown solid was washed with 20 mL of diethyl ether twice and dried under vacuum to yield complex 4-Na (yield 0.585 g, 83.1 %). IR: 1791 (m), 1723 (s) (νNO), 1634 (s) (νCO) cm^-1 (CH3CN); 1786 (s), 1696 (s) (νNO), 1626 (s) (νCO) cm^-1 (KBr). Absorption spectrum (THF) [λmax, nm (ε, M^–1 cm^–1)]: Absorption

spectrum (THF) [λmax, nm (ε, M^–1 cm^–1)]: 721 (281), 440 (1719). 2-PPh4: The 5 mL CH3CN solution of [Cp2Fe][PF6] (0.099 g, 0.3 mmol) was added dropwise into the 50 mL Schlenk flask containing CH3CN solution of complex 2-PPh4 (0.329 g, 0.3 mmol) via a cannula under positive N2 pressure at 0℃. After being stirred for 5 h, the reaction solution was dried under vacuum to afford the brown solid. 10 mL of THF was added to dissolve the brown solid and the resulting THF solution was monitored with FTIR. The IR spectrum showing νNO stretching frequencies at 1786 (m), 1718(s) cm^-1 (THF) was assigned to the formation of

[PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4). The THF solution was filtered through Celite to separate insoluble [PPh4][PF6]. The brown filtrate was concentrated to 5 mL and 25 mL diethyl ether was added to precipitate the red-brown solid. The red-brown solid was washed with 20 mL of diethyl ether twice and dried under vacuum to yield complex 4-PPh4 (yield: 0.141 g, 61.9 %). Diffusion of diethyl ether into the THF solution of complex 4-PPh4 at -15 ℃ led to red-brown crystals suitable for single-crystal X-ray diffraction. IR: 1791 (m), 1723 (s) (νNO), 1636 (m) (νCO) cm^-1 (CH3CN); 1785 (s), 1718 (s) (νNO), 1636 (m), 1623 (s) (νCO) cm^-1 (KBr). EPR (THF) at 298 K: g = 2.031. Anal. Calcd for C38H28FeN4O4PS2: C, 60.40; H, 3.74; N, 7.41. Found: C, 60.71; H, 3.54; N, 7.72.

Reaction of complex 3-PPh4 with [PPh4][OC7H4SN]. The compounds, complex 3-PPh4 (0.157 g, 0.2 mmol) and [PPh4][OC7H4SN] (0.197 g, 0.4 mmol)

were loaded into a Schlenk tube, and then 10 mL of THF was added under positive N2 at ambient temperature. After being stirred overnight, the solution was monitored with FTIR. The IR spectrum showing νNO stretching frequencies at 1786 (m), 1718(s) cm^-1 (THF) was assigned to the formation of complex 4-PPh4. The THF solution was filtered through Celite to separate insoluble [PPh4][SC7H4SN]. The brown filtrate was concentrated to 5 mL and 25 mL diethyl ether was added to precipitate the brown solid. The brown solid was washed with 20 mL of diethyl ether twice and dried under vacuum to yield complex 4-PPh4 (yield: 0.134 g, 88.7 %).

Reaction of complex 2-Na with [Na][SC7H4SN] and 18-crown-6-ether. The compounds, complex 2-Na (0.495 g, 0.5 mmol), [Na][SC7H4SN] (0.189 g, 1 mmol) and 18-crown-6-ether (0.264 g, 1 mmol) were loaded into a Schlenk flask, and then 10 mL of THF was added under positive N2 at ambient temperature. After being stirred overnight, the light green precipitates were afforded. When the upper solution was discarded via cannula under a positive pressure of N2, the residual light green solid was washed with 10 mL of THF. After drying the light green solid under vacuum and identifying by FTIR (IR: 1654 (s), 1609 (s) cm^-1 (νNO) (KBr)), the light green solid of [Na-18-crown-6-ether]2[Fe(SC7H4SN)2(NO)2] (1-Na) (yield: 0.44 g, 86.3 %) was afforded.

Reaction of complex 3-PPh4 with CoCp2 (or Reaction of 4-PPh4 with CoCp2). Complex 3-PPh4 (0.236 g, 0.3 mmol) (or complex 4-PPh4 (0.227 g, 0.3 mmol))and CoCp2 (0.057 g, 0.3 mmol) were dissolved in THF (8 mL) and stirred overnight under nitrogen at ambient temperature. After being stirred overnight, the upper solution was discarded via cannula under a positive pressure of N2, and the residual light green solids (or light brown solids) were washed with 15 mL of diethyl ether. The IR spectrum of the light brown solids showed the νNO stretching

frequencies at 1652 (s), 1602(s) cm^-1 (KBr) was assigned to the formation of [PPh4][CoCp2] [Fe(SC7H4SN)2(NO)2] (The IR spectrum of the light green solids showed the νNO stretching frequencies at 1663 (s), 1636(s) cm^-1 (KBr) was assigned to the formation of [PPh4][CoCp2] [Fe(OC7H4SN)2(NO)2]. After drying the light green solids under vacuum, light green solids of [PPh4][CoCp2]

[Fe(SC7H4SN)2(NO)2] (yield: 0.18 g, 61.4 %) (or brown solid of [PPh4][CoCp2] [Fe(OC7H4SN)2(NO)2] (yield: 0.23 g, 81.2 %)) were afforded.

Reaction of complex 3-PPh4 with complex 2-PPh4. Complex 3-PPh4 (0.157 g, 0.2 mmol) and complex 2-PPh4 (0.218 g, 0.2 mmol) were loaded into a Schlenk flask, and then 6 mL of THF and 2 mL of CH3CN were added under positive N2 at ambient temperature. After being stirred for 3 days, 15 mL of hexane was added to the reaction mixture. When the reaction mixture was stand for several minutes, the upper red solution was transferred to the other flask via cannula under a positive

pressure of N2. The residual solid was washed with 10 mL of THF and the THF solution was transferred to the above flask via cannula under a positive pressure of N2. After drying the light green solid under vacuum and identifying by FTIR (IR:

1661 (s), 1613 (s) cm^-1 (νNO) (KBr)), the light green solid of complex 1-PPh₄ (yield:

0.158 g, 70.2 %) was afforded. In addition, the solution of the other flask was concentrated to 5 mL and 35 mL diethyl diether was added to precipitate the red solid. The IR spectrum of the red solids showed the νNO stretching frequencies at 1785 (s), 1718(s) cm^-1 (KBr) was assigned to the formation of complex 4-PPh4 and the yield was 92.7 % (0.140 g).

Results and Discussion

Reaction of Fe(TMEDA)(NO)2 with 2 equiv of [SC7H4SN]⁻ and [OC7H4SN]⁻ yielded DNICs 1 and 2 characterized by single-crystal X-ray diffraction, IR and UV/vis spectra, respectively (Scheme 1a and 1b). DNICs 1 and 2 display the EPR-silent {Fe(NO)2}¹⁰ electronic structures with [thiolate, thiolate]/[amide, amide]

ligation mode. Compared to the other {Fe(NO)2}¹⁰ DNICs, 1-PPh4 is the first example of the dianionic mononuclear {Fe(NO)2}¹⁰ DNICs coordinated with two thiolate ligands.

Upon the addition of Cp2FePF6 into the CH3CN solution of DNICs 1 and 2 in a 1:1 stoichiometry, respectively (Scheme 1c and 1d), oxidation ensued over the course of 5 h to yield the {Fe(NO)2}⁹ DNICs 3 and 4, respectively, identified by EPR and IR spectra. In contrast to the ligand-centered oxidation of the thiolate-containing {Fe(NO)2}⁹ DNICs resulting in dimeric {Fe(NO)2}⁹-{Fe(NO)2}⁹ RREs,^7c,7f the isolation of DNIC 3 may reveal that the oxidation of thiolate-containing {Fe(NO)2}¹⁰ DNICs is a metal-centered process.

In cyclic voltammograms of 3-PPh4 and 4-PPh4, the quasi-reversible one-electron reduction at -0.94 and -1.17 V (E1/2 vs Fc⁺/Fc), respectively, in CH3CN are observed and assigned to the {Fe(NO)2}⁹-{Fe(NO)2}¹⁰ couple (Figure S1 in the Supporting Information). The slightly negative reduction potential of 4-PPh4 than that of 3-PPh₄ indicates that [OC7H4SN]⁻ performs the stronger electron-donating ability than [SC7H4SN]⁻. Chemical reduction of 3-PPh₄ and 4-PPh₄ with CoCp2 (Scheme 1c’ and 1d’) afforded {[PPh4][CoCp2]}{[Fe(SC7H4SN)2(NO)2]} and {[PPh4][CoCp2]}{[Fe(OC7H4SN)2(NO)2]}, respectively, characterized by FTIR. The reduction process is also consistent with the {Fe(NO)2}⁹-{Fe(NO)2}¹⁰ couple in the cyclic voltammogram of 3-PPh4/4-PPh4. In contrast to the reduction of the thiolate-containing {Fe(NO)2}⁹ DNICs leading to the dissociation of thiolate of DNICs reported previously,^7b the redox reaction of DNICs 3 and 1 displays the

reversible interconversion between the thiolate-containing {Fe(NO)2}⁹ and {Fe(NO)2}¹⁰ DNICs.

Scheme 1.

The relative affinity of the different ligands toward the {Fe(NO)2}⁹ motif has been studied by Liaw et al. via the ligand-exchange experiments.^7b,7g,7j Similarly, the coordinated ligands [SC7H4SN]⁻ of {Fe(NO)2}⁹ 3-PPh4 could be replaced by the stronger donor [OC7H4SN]⁻ to yield the more stable 4-PPh4 (Scheme 1f).

Interestingly, the addition of 2 equiv of [SC7H4SN]⁻ to the THF solution of {Fe(NO)2}¹⁰ 2-Na led to the light green precipitates of the more stable 1-Na, characterized by IR spectra (Scheme 1e). The different binding affinity of [OC7H4SN]⁻ and [SC7H4SN]⁻ toward the {Fe(NO)2} core of DNICs reveals that the electron-rich {Fe(NO)2}¹⁰ motif prefers the binding of the less electron-donating ligand [SC7H4SN]⁻. In contrast, the stronger electron-donating ligand [OC7H4SN]⁻ favors to coordinate to the electron-deficient {Fe(NO)2}⁹ motif. This rationalization may support that reaction of {Fe(NO)2}¹⁰ 2-PPh4 and {Fe(NO)2}⁹ 3-PPh4 afforded the relatively stable {Fe(NO)2}⁹ 4-PPh4 and {Fe(NO)2}¹⁰ 1-PPh4 via intermolecular electron transfer in THF (Scheme 2).

Fe O N O N

Me2 N NMe₂

Fe ON ON S

Fe ON

ON

S

2- 2-

(c) Cp2FePF6 (d) Cp2FePF6

N S

N S

O S N

N O S

Fe O N ON

O S N

N O S S

Fe O N

O N

S N

S

N S

2[OC7H4SN]^- 2[SC7H4SN]^-

(c') CoCp₂ (d') CoCp2

(e) 2[SC₇H₄SN]^-

(f) 2[O C7H4SN]^-

(1) (2)

(3) (4)

1-Na, 2-Na, 3-Na, 4-Na : cation = Na-18-crown-6-ether 1-PPh₄, 2-PPh₄, 3-PPh₄, 4-PPh₄: cation = PPh₄

(a) (b)

Scheme 2.

Figure 1. Structure of anion of 1-PPh4 displaying 50% thermal ellipsoids for all non-hydrogen atoms. Selected bond distances (Å) and angles (deg): Fe(1)−N(1), 1.645(4); Fe(1)−N(2), 1.642(4); Fe(1)−S(1), 2.3679(13); Fe(1)−S(3), 2.3240(13);

N(1)−O(1), 1.193(4); N(2)−O(2), 1.205(4); Fe(1)−N(1)−O(1), 168.3(4);

Fe(1)−N(2)−O(2), 167.6(4); N(1)−Fe(1)−N(2), 115.34(19); S(1)−Fe(1)−S(3), 84.48(5).

Fe ON ON

2-

O S N

N O S (2)

S Fe ON

ON

S N

S

N S

(3)

S Fe ON

ON

S

2-

N S

N S

(1) Fe

ON ON

O S N

N O S (4)

Figure 2. Structure of anion of 2-PPh₄ displaying 50% thermal ellipsoids for all non-hydrogen atoms. Selected bond distances (Å) and angles (deg): Fe(1)−N(1), 1.638(3); Fe(1)−N(2), 2.094(2); N(1)−O(1), 1.203(3); N(1)−Fe(1)−N(1A), 110.45(19); N(2)−Fe(1)−N(2A), 88.80(13); Fe(1)−N(1)−O(1), 164.6(3).

Figures 1 and 2 display the thermal ellipsoid plots of the dianionic 1-PPh4 and 2-PPh₄, respectively, and the selected bond angles and bond lengths are given in the figure captions, respectively. The structures of 1-PPh4 and 2-PPh4 contain a four-coordinate iron center in a distorted tetrahedral geometry. The comparisons of mean Fe-S bond distances (2.2941(18) Å in [PPN][Fe(SC7H4SN)2(NO)2]^7b vs 2.3460(13) Å in 1-PPh4) and Fe-N bond distances (1.993(2) Å in 4-PPh4 (Figure S2 in the Supporting Information) vs 2.094(2) Å in 2-PPh4) reveal that reduction of {Fe(NO)2}⁹ core to {Fe(NO)2}¹⁰ core lead to the elongation of Fe−N and Fe−S distances. Meanwhile, the shorter Fe−N(O) bond distances of 1.644(4) Å and 1.638(3) Å and the longer N−O bond distances of 1.199(4) Å and 1.203(3) Å found in 1-PPh4 and 2-PPh4, respectively, compared to the Fe−N(O) bond distances of 1.684(6) Å and 1.687(2) Å and the N−O bond distances of 1.174(6) Å and 1.175(3) found in [PPN][Fe(SC7H4SN)2(NO)2] and 4-PPh4, respectively, are consistent with a relatively considerable degree of π-backbonding in the {Fe(NO)2}¹⁰ core. In contrast to the distinct bond distances in [PPN][Fe(SC7H4SN)2(NO)2] and 1-PPh₄/4-PPh4 and 2-PPh4, the comparable Fe−N−O bond angles (169.9(5)∘in [PPN][Fe(SC7H4SN)2(NO)2] vs 168.0(4)∘in 1-PPh4 and 163.6(2) ∘in 4-PPh4 vs 164.6(3) ∘in 2-PPh4) are observed when the {Fe(NO)2}⁹ DNICs are reduced to the structurally analogous {Fe(NO)2}¹⁰ DNICs.

In summary, the dianionic {Fe(NO)2}¹⁰ DNICs containing [thiolate,thiolate]/[amide/amide] ligation were isolated and structurally characterized.

The synthetic methodology reveals that Fe(TMEDA)(NO)2 acts as an {Fe(NO)2}¹⁰ motif-donor reagent in the presence of thiolates and amides. Redox reaction between DNICs 1/2 and DNICs 3/4 successfully demonstrate the reversible interconversion with no dissociation of the coordinated ligands of the structurally analogous {Fe(NO)2}⁹/{Fe(NO)2}¹⁰ DNICs. The ligand substitution reactions of DNICs 2 and 3 to form the relatively stable DNICs 1 and 4, respectively, have demonstrated that the {Fe(NO)2}⁹ motif shows strong preference for the stronger electron-donating ligands over the weaker electron-donating ligands; however, the {Fe(NO)2}¹⁰ motif shows the stronger binding affinity toward the weaker electron-donating ligands. In addition to the ligand-exchange reactions yielding the more stable DNICs,^7b,7g,7j the reaction of {Fe(NO)2}¹⁰ 2-PPh4 and {Fe(NO)2}⁹ 3-PPh4 yielding the relatively stable {Fe(NO)2}⁹ 4-PPh4 and {Fe(NO)2}¹⁰ 1-PPh4 may signify that the intermolecular electron transfer between {Fe(NO)2}¹⁰ and {Fe(NO)2}⁹ DNICs is the alternative mechanism to afford the more stable DNICs for transport and storage of NO in biology. Studies on the electronic structure (NO/Fe oxidation states) of the series of {Fe(NO)2}⁹/{Fe(NO)2}¹⁰ DNICs by X-ray absorption spectroscopy and DFT calculations are ongoing. Also, the binding preference of a series of ligands toward {Fe(NO)2}⁹/{Fe(NO)2}¹⁰ motifs are currently being investigated in our laboratory.

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Supplementary Material

Contents:

Figures

Figure S1. Cyclic voltammograms of [PPh4][Fe(SC7H4SN)2(NO)2] (3-PPh4) and [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4).

Figure S2. Fully labeled thermal ellipsoid (50%) drawing of [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4).

Figure S3. X-band EPR spectrum of [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4).

Tables

Table S1. Crystal data and structure refinement for [PPh4]2[Fe(SC7H4SN)2(NO)2] (1-PPh4).

Table S2. Crystal data and structure refinement for [PPh4]2[Fe(OC7H4SN)2(NO)2] (2-PPh4).

Table S3. Crystal data and structure refinement for [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4).

Figures

Potential vs. Fc⁺/Fc (V)

-2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0

Current (μA)

-80 -60 -40 -20 0 20 40 60 80 100

complex 4-PPh4 complex 3-PPh4

  Figure S1. Cyclic voltammograms of 2.5 mM CH3CN solution of

[PPh4][Fe(SC7H4SN)2(NO)2] (3-PPh4) (solid line) and [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4) (dashed line) in 0.1 M [TBA][PF6] with a glassy carbon working electrode at a scan rate of 1 V s^-1.

Figure S2. ORTEP diagram of the anion of [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4) showing 50% thermal ellipsoids for all non-hydrogen atoms. Selected bond distances (Å) and angles (deg): Fe−N(1), 1.685(2); Fe−N(2), 1.688(2); Fe−N(3), 1.992(2);

Fe−N(4), 1.994(2); N(1)−O(1), 1.178(3); N(2)−O(2), 1.172(3); N(1)−Fe−N(2), 111.23(11); N(3)−Fe−N(4), 101.84(9); N(1)−Fe−N(3), 111.04(10); N(2)−Fe−N(3), 112.12(10); Fe−N(1)−O(1), 162.8(2); Fe−N(2)−O(2), 164.3(2).

2.20 2.15 2.10 2.05 2.00 1.95 1.90 -1.0x10⁴

-8.0x10³ -6.0x10³ -4.0x10³ -2.0x10³ 0.0 2.0x10³ 4.0x10³ 6.0x10³ 8.0x10³ 1.0x10⁴

Intensity

g factor

g = 2.031

Figure S3. X-band EPR spectrum of [PPh4][Fe(OC7H4SN)2(NO)2] (4-PPh4) in THF at 298 K.

Tables

Table S1. Crystal data and structure refinement for complex 1-PPh4. Empirical formula C62 H48 Fe N4 O2 P2 S4

Formula weight 1127.07

Temperature 200(2) K

Wavelength 0.71073 Å

Crystal system Monoclinic

Space group P 21/n

Unit cell dimensions a = 10.6617(2) Å α= 90°.

b = 36.6398(6) Å β= 96.0940(10)°.

c = 14.0069(3) Å γ = 90°.

Volume 5440.77(18) Å3

Z 4 Density (calculated) 1.376 Mg/m3

Absorption coefficient 0.538 mm-1

F(000) 2336 Crystal size 0.38 x 0.25 x 0.07 mm3

Theta range for data collection 2.22 to 25.06°.

Index ranges -12<=h<=12, -38<=k<=43, -16<=l<=12 Reflections collected 17171

Independent reflections 9448 [R(int) = 0.0631]

Completeness to theta = 24.86° 96.6 %

Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.9648 and 0.8397

Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 9448 / 0 / 676

Goodness-of-fit on F2 1.034

Final R indices [I>2sigma(I)] R1 = 0.0522, wR2 = 0.1127 R indices (all data) R1 = 0.0974, wR2 = 0.1354 Largest diff. peak and hole 0.280 and -0.381 e.Å-3

Table S2. Crystal data and structure refinement for complex 2-PPh4. Empirical formula C62 H48 Fe N4 O4 P2 S2 Formula weight 1094.95

Temperature 293(2) K

Wavelength 0.71073 Å

Crystal system Monoclinic

Space group C 2/c

Unit cell dimensions a = 23.4730(5) Å α= 90°.

b = 13.4520(3) Å β= 119.0330(10)°.

c = 19.3090(5) Å γ = 90°.

Volume 5330.8(2) Å3

Z 4 Density (calculated) 1.364 Mg/m3

Absorption coefficient 0.475 mm-1

F(000) 2272 Crystal size 0.58 x 0.4 x 0.32 mm3

Theta range for data collection 2.26 to 25.04°.

Index ranges -23<=h<=26, -15<=k<=15, -13<=l<=22 Reflections collected 12513

Independent reflections 4446 [R(int) = 0.0486]

Completeness to theta = 25.04° 94.4 %

Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.7552 and 0.596

Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 4446 / 0 / 339

Goodness-of-fit on F2 1.011

Final R indices [I>2sigma(I)] R1 = 0.0463, wR2 = 0.1232 R indices (all data) R1 = 0.0608, wR2 = 0.1344 Largest diff. peak and hole 0.681 and -0.558 e.Å-3

Table S3. Crystal data and structure refinement for complex 4-PPh4. Empirical formula C38 H28 Fe N4 O4 P S2

Formula weight 755.58

Temperature 150(2) K

Wavelength 0.71073 Å

Crystal system Orthorhombic

Space group Pbca

Unit cell dimensions a = 15.5535(8) Å α= 90°.

b = 16.8415(8) Å β= 90°.

c = 26.5880(12) Å γ = 90°.

Volume 6964.6(6) Å3

Z 8 Density (calculated) 1.441 Mg/m3

Absorption coefficient 0.646 mm-1

F(000) 3112 Crystal size 0.40 x 0.25 x 0.25 mm3

Theta range for data collection 1.94 to 27.50°.

Index ranges -20<=h<=20, -21<=k<=16, -34<=l<=18 Reflections collected 34619

Independent reflections 7993 [R(int) = 0.0674]

Completeness to theta = 27.50° 100.0 %

Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8551 and 0.7821

Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 7993 / 0 / 451

Goodness-of-fit on F2 1.042 Final R indices [I>2sigma(I)] R1 = 0.0506, wR2 = 0.1063 R indices (all data) R1 = 0.0769, wR2 = 0.1172 Largest diff. peak and hole 0.632 and -0.375 e.Å-3

國科會補助計畫衍生研發成果推廣資料表

日期:2011/08/15

國科會補助計畫

計畫名稱: 雙亞硝醯基鐵化合物之合成，反應性研究及其電子結構與作為一氧化氮傳遞 劑效率探討

計畫主持人: 陳建宏

計畫編號: 99-2119-M-040-001- 學門領域: 無機化學

無研發成果推廣資料

99 年度專題研究計畫研究成果彙整表

計畫主持人：陳建宏 計畫編號：99-2119-M-040-001-

計畫名稱：雙亞硝醯基鐵化合物之合成，反應性研究及其電子結構與作為一氧化氮傳遞劑效率探討 量化

成果項目 ^{實際已達成}

數（被接受 或已發表）

預期總達成 數(含實際已

達成數)

本計畫實 際貢獻百

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參與計畫人力

（本國籍）

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期刊論文 1 1 100%

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技術移轉

權利金 0 0 100% 千元

碩士生 0 0 100%

博士生 0 0 100%

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國外

參與計畫人力

（外國籍）

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人次

其他成果

(

果如辦理學術活動、獲 得獎項、重要國際合 作、研究成果國際影響 力及其他協助產業技 術發展之具體效益事 項等，請以文字敘述填 列。)

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經由 Fe(TMEDA)(NO)2 與分別與兩當量[SC7H4SN] and [OC7H4SN]反應可以得到第一 個含[硫基,硫基]及[胺基,胺基]的負二價雙亞硝醯基鐵化合物([Fe(SC7H4SN)2(NO)2]2  (1) [Fe(OC7H4SN)2(NO)2]2  (2))。負二價雙亞硝醯基鐵化合物(DNICs 1/2)與負一價雙 亞硝醯基鐵化合物([Fe(SC7H4SN)2(NO)2] (3) [Fe(OC7H4SN)2(NO)2] (4) (DNICs 3/4)) 之 間的相互轉換也成功的被證實。利用這四個化合物的反應比較，我們發現 [SC7H4SN]對雙亞硝醯基鐵化合物中{Fe(NO)2}10 的單元親和力較好，而[OC7H4SN] 則 對雙亞硝醯基鐵化合物中{Fe(NO)2}9 的單元親和力較好。另外我們也發現要得到相對穩定 的雙亞硝醯基鐵化合物，除了以交換配位子的方式來進行之外，直接進行分子間的電子轉 移亦可能是另外的一個途徑。