Synthesis,characterization, and electrochemistry of phosphine-substituted diiron butane-1,2-dithiolate complexes

Abstract

The reactions of the starting complex, [Fe₂(CO)₆{μ-SCH₂CH (CH₂CH₃)S}] (1), with the phosphine ligands tris(4-methylphenyl)phosphine, diphenyl-2-pyridylphosphine, tris(4-fluorophenyl)phosphine, 2-(diphenylphosphino)benzaldehyde, or benzyldiphenylphosphine in the presence of the decarbonylating agent Me₃NO·2H₂O yielded the corresponding phosphine-substituted diiron butane-1,2-dithiolate complexes [Fe₂(CO)₅(L){μ-SCH₂CH(CH₂CH₃)S}] (L?=?P(4-C₆H₄CH₃)₃, 2; Ph₂P(2-C₅H₄N), 3; P(4-C₆H₄F)₃, 4; Ph₂P(2-C₆H₄CHO), 5; Ph₂PCH₂Ph, 6) in 75%–87% yields. The complexes have been characterized by elemental analysis, IR, ¹H, and ³¹P{¹H} NMR spectroscopy, as well as by single-crystal X-ray diffraction analysis. Moreover, the electrochemistry of 2–4 was studied by cyclic voltammetry, suggesting that they can catalyze the reduction of protons to H₂ in the presence of HOAc.     

Synthesis,characterization, and electrochemistry of diiron ethane-1,2-dithiolate complexes with monosubstituted ethyldiphenylphosphine or dicyclohexylphenylphosphine

Abstract

In this contribution, two diiron ethane-1,2-dithiolate complexes with one ethyldiphenylphosphine or dicyclohexylphenylphosphine ligand have been synthesized and characterized as mimics for the active site of [FeFe]-hydrogenases. Treatment of complex [Fe₂(CO)₆(μ-SCH₂CH₂S)] (1) with ethyldiphenylphosphine or dicyclohexylphenylphosphine and Me₃NO · 2?H₂O as decarbonylating agent gave complexes [Fe₂(CO)₅(Ph₂PCH₂CH₃)(μ-SCH₂CH₂S)] (2) and [Fe₂(CO)₅{PhP(C₆H₁₁)₂}(μ-SCH₂CH₂S)] (3) in 93% and 86% yields, respectively. Complexes 2 and 3 were characterized by elemental analysis, IR, and NMR spectroscopy. X-ray crystallographic studies confirmed the molecular structures of complexes 2 and 3, indicating that they contain a butterfly diiron ethane-1,2-dithiolate cluster with five terminal carbonyl ligands and an apically-coordinated phosphine ligand. Additionally, the electrochemical properties of these complexes were investigated by cyclic voltammetry, suggesting that they can be regarded as electrocatalysts for the reduction of protons to H₂ in the presence of HOAc. A possible mechanism for the proton reduction was proposed.     

2-(Diphenylphosphino)benzoate-functionalized diiron ethane-1,2-dithiolate complexes with uncoordinated or coordinated phosphine ligand

Abstract

Treatment of the starting complex [Fe₂(CO)₆{μ-SCH₂CH(CH₂OH)S}] (1) with 2-(diphenylphosphino)benzoic acid in the presence of N,N’-dicyclohexylcarbodiimide and 4-dimethylaminopyridine gave the corresponding ester derivative [Fe₂(CO)₆{μ-SCH₂CH(CH₂O₂CC₆H₄PPh₂-2)S}] (2) in 92% yield. Further treatment of complex 2 with one equivalent of Me₃NO · 2?H₂O as the decarbonylating agent yielded diphenylphosphino-substituted complex [Fe₂(CO)₅{μ-SCH₂CH(CH₂O₂CC₆H₄PPh₂-2)S}] (3) in 79% yield. Both complexes were characterized by elemental analysis, spectroscopy, as well as by X-ray crystallography. Additionally, the electrochemical properties of these complexes were studied by cyclic voltammetry.     

Phosphine-substituted diiron 1,2-dithiolate complexes as the models for the active site of [FeFe]-hydrogenases

Abstract

In this article, five diiron 1,2-dithiolate complexes containing phosphine ligands are reported. Treatment of complex [Fe₂(CO)₆(μ-SCH₂CH₂S)] (1) with the phosphine ligands tris(4-methylphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(3-chlorophenyl)phosphine, tris(3-methylphenyl)phosphine, or 2-(diphenylphosphino)biphenyl in the presence of Me₃NO·2H₂O as the decarbonylating agent afforded the target products [Fe₂(CO)₅(L)(μ-SCH₂CH₂S)] [L?=?P(4-C₆H₄CH₃)₃, 2; P(4-C₆H₄OCH₃)₃, 3; P(3-C₆H₄Cl)₃, 4; P(3-C₆H₄CH₃)₃, 5; Ph₂P(2-C₆H₄Ph), 6] in 80–93% yields. Complexes 2–6 have been characterized by elemental analysis, spectroscopy, and X-ray crystallography. Additionally, the electrochemical properties were studied by cyclic voltammetry.     

Synthesis and characterization of diiron ethanedithiolate complexes with monosubstituted phosphine ligands

Reactions of (μ-edt)Fe₂(CO)₆ (edt = SCH₂CH₂S) (1) with the monophosphine ligands Ph₂PCH₂Ph, Ph₂PC₆H₁₁, Ph₂PCH₂CH₂CH₃, or P(2-C₄H₃O)₃ in the presence of Me₃NO?2H₂O afforded (μ-edt)Fe₂(CO)₅L [L = Ph₂PCH₂Ph, 2; Ph₂PC₆H₁₁, 3; Ph₂PCH₂CH₂CH₃, 4; P(2-C₄H₃O)₃, 5] in 70–88% yields. Complexes 2–5 were characterized by spectroscopy and single crystal X-ray diffraction analysis. The phosphorus of 2–5 is in an apical position of the distorted octahedral geometry of iron.     

Synthetic and structural studies of the diiron toluenedithiolate carbonyl complexes with monophosphine ligands

Four diiron toluenedithiolate complexes 2–5 with monophosphine ligands are reported. Treatment of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₆ (1) with tris(3-chlorophenyl)phosphine, tris(4-chlorophenyl)phosphine, tris(4-methylphenyl)phosphine or 2-(diphenylphosphino)benzaldehyde, and Me₃NO?2H₂O in MeCN resulted in the formation of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(3-C₆H₄Cl)₃] (2), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (3), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄CH₃)₃] (4), and [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[Ph₂P(2-C₆H₄CHO)] (5) in 64–82% yields. Complexes 2–5 have been characterized by elemental analysis, IR, ¹H NMR, ³¹P{¹H} NMR, ¹³C{¹H} NMR and further confirmed by single crystal X-ray diffraction analysis. The molecular structures show that 2–5 contain a butterfly diiron toluenedithiolate cluster coordinated by five terminal carbonyls and an apical monophosphine.     

Synthesis and characterization of diiron(I) 1,2-dimethylethanedithiolate complexes with bridging or chelating 1,2-bis(diphenylphosphino)ethylene

The reaction of complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₆ (1) with trans-1,2-bis(diphenylphosphino)ethylene (trans-dppv) in the presence of Me₃NO?2H₂O in CH₂Cl₂/CH₃CN afforded complex {[μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₅}₂(trans-dppv) (2) with a bridging dppv. Complex [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₄(cis-dppv) (3) was prepared by the reaction of 1 with cis-dppv and Me₃NO?2H₂O. The new complexes 2 and 3 were characterized by elemental analysis, spectroscopy, and X-ray diffraction analysis.     

Synthesis,structures, and electrochemistry of diiron toluene-3,4-dithiolate complexes containing phosphine ligands

Transition Metal Chemistry - In this paper, four diiron toluene-3,4-dithiolate complexes with phosphine ligands were synthesized and characterized. Treatment of complex...     

Reaction of the diiron toluenedithiolate hexacarbonyl complex with 1,1-bis(diphenylphosphino)methane

Reaction of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₆ (1) with 1.5 equivalents of 1,1-bis(diphenylphosphino)methane (dppm) in toluene at reflux gave monosubstituted [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅(dppm) (2) and disubstituted [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₄(dppm)₂ (3) in 27 and 37% yields, respectively. Complexes 2 and 3 were characterized by elemental analysis, IR, NMR spectroscopy, and single crystal X-ray diffraction analysis.     

Synthesis,characterization, and electrochemistry of monophosphine‐containing diiron propane‐1,2‐dithiolate complexes related to the active site of [FeFe]‐hydrogenases

Five monophosphine‐substituted diiron propane‐1,2‐dithiolate complexes as the active site models of [FeFe]‐hydrogenases have been synthesized and characterized. Reactions of complex [Fe₂(CO)₆{μ‐SCH₂CH(CH₃)S}] ( 1 ) with a monophosphine ligand tris(4‐methylphenyl)phosphine, diphenyl‐2‐pyridylphosphine, tris(4‐chlorophenyl)phosphine, triphenylphosphine, or tris(4‐fluorophenyl)phosphine in the presence of the oxidative agent Me₃NO·2H₂O gave the monophosphine‐substituted diiron complexes [Fe₂(CO)₅(L){μ‐SCH₂CH(CH₃)S}] [L = P(4‐C₆H₄CH₃)₃, 2 ; Ph₂P(2‐C₅H₄N), 3 ; P(4‐C₆H₄Cl)₃, 4 ; PPh₃, 5 ; P(4‐C₆H₄F)₃, 6 ] in 81%–94% yields. Complexes 2 – 6 have been characterized by elemental analysis, spectroscopy, and X‐ray crystallography. In addition, electrochemical studies revealed that these complexes can catalyze the reduction of protons to H₂ in the presence of HOAc.     

Synthesis and characterization of diiron ethane-1,2-dithiolate complexes with tricyclohexylphosphine,methyl diphenylphosphinite,or tris(2-thienyl)phosphine coligands

Transition Metal Chemistry - We have prepared three diiron ethane-1,2-dithiolate complexes [Fe2(CO)5L(µ-SCH2CH2S)] [L?=?P(C6H11)3, 2; Ph2POCH3, 3; P(2-C4H3S)3, 4] by CO exchange of...     

Synthesis,crystal structures and electrocatalytic properties of bridgehead-C-functionalized diiron dithiolate complexes

To investigate the influence of bridgehead-C functionality in diiron dithiolate complexes on the molecular structure and electrocatalytic properties of [FeFe]-hydrogenase models, three new bridgehead-C-functionalized model complexes 1–3 have been synthesized and structurally characterized. Treatments of parent complex [(μ-SCH₂)₂CHCO₂H][Fe₂(CO)₆] (A) with the esterification agents o-MeC₆H₄OH, p-ClC₆H₄OH, or p-HOC₆H₄CHO in the presence of 4-dimethylaminopyridine and dicyclohexylcarbodiimide in CH₂Cl₂ at room temperature resulted in formation of [(μ-SCH₂)₂CHCO₂R][Fe₂(CO)₆] (R = o-MeC₆H₄–, 1; p-ClC₆H₄–, 2; p-OHCC₆H₄–, 3) in 53–55% yields. The new complexes 1–3 were characterized by elemental analysis, IR and NMR spectroscopy, and especially determined by X-ray crystallography. The electrochemical properties of 1–3 and the electrocatalytic H₂ evolution catalyzed by 1 have been investigated by cyclic voltammetry, where 1 is a catalyst for HOAc proton reduction to H₂ under electrochemical conditions.     

膦配体取代的乙基乙撑双铁配合物的合成、晶体结构及电化学催化性能

以母体配合物[Fe₂(CO)₆(μ-SCH₂CH(CH₂CH₃)S)](1)分别与三(2-呋喃基)膦、二苯基丙基膦、双(二苯基膦)乙炔、1,2-双(二苯基膦基)苯和脱羰试剂Me₃NO·2H₂O反应,制备了单取代配合物[Fe₂(CO)₅(L)(μ-SCH₂CH(CH₂CH₃)S)](L=P(2-C₄H₃O)₃,2;Ph₂PCH₂CH₂CH₃,3)、桥联配合物{[Fe₂(CO)₅(μ-SCH₂CH(CH₂CH₃)S)]2(Ph₂PC≡CPPh₂)}(4)和螯合配合物[Fe₂(CO)₄(κ²-(Ph₂P)₂(1,2-C₆H₄))(μ-SCH₂CH(CH₂CH₃)S)](5)。配合物2~5经元素分析、红外光谱、核磁共振氢谱和磷谱表征,并进一步得到单晶X射线衍射的确证。电化学研究表明,在弱酸HOAc作为质子源存在的情况下,这些配合物可以实现催化质子还原产生氢气的功能。     

Structural studies of diiron complexes with monophosphine ligands tris(4-chlorophenyl)phosphine or diphenyl-2-pyridylphosphine

Four diiron dithiolate complexes with monophosphine ligands have been prepared and structurally characterized. Reactions of (μ-SCH₂CH₂S-μ)Fe₂(CO)₆ or [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₆ with tris(4-chlorophenyl)phosphine or diphenyl-2-pyridylphosphine in the presence of Me₃NO·2H₂O afforded diiron pentacarbonyl complexes with monophosphine ligands (μ-SCH₂CH₂S-μ)Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (1), (μ-SCH₂CH₂S-μ)Fe₂(CO)₅[Ph₂P(2-C₅H₄N)] (2), [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (3), and [μ-SCH(CH₃)CH(CH₃)S-μ]Fe₂(CO)₅[Ph₂P(2-C₅H₄N)] (4) in good yields. Complexes 1–4 were characterized by elemental analysis, ¹H NMR, ³¹P{¹H} NMR and ¹³C{¹H} NMR spectroscopy. Furthermore, the molecular structures of 1–4 were confirmed by X-ray crystallography.     

4-硝基邻苯二硫酚金属镍配合物的合成、结构和性质

合成了4-硝基邻苯二硫酚配体及相应金属镍配合物，(Bu₄N)₂[Ni(nbdt)₂] (1)和(Bu₄N)[Ni(nbdt)₂] (2)(nbdt=4-硝基邻苯二硫酚阴离子), 并通过X-射线单晶结构测定、循环伏安、ESR谱、紫外可见吸收光谱和变温磁化率实验对其结构和性质进行了表征。这两个化合物均为略有变形的平面四方型配合物。配合物2是由配合物1通过I₂氧化制备。配合物2含有一个未成对电子，磁性研究表明由于分子间的自旋耦合使它表现为反铁磁性。     

Synthesis,characterization, and crystal structures of N-functionalized diiron azadithiolate complexes related to the active site of [FeFe]-hydrogenases

A series of N-functionalized diiron azadithiolate complexes, [(µ-SCH₂)₂NCH₂CO₂Me]Fe₂(CO)_5?L [L?=?CO (1); PPh₃ (2); Ph₂PCH₂PPh₂ (3)], as active site models of [FeFe]-hydrogenases has been prepared and characterized. While 1 was prepared by a sequential reaction of (µ-HS)₂Fe₂(CO)₆ with two equiv. of aqueous HCHO, followed by treatment of (µ-HOCH₂S)₂Fe₂(CO)₆ with one equiv. of H₂NCH₂CO₂Me in 46% yield; 2 and 3 were prepared by a carbonyl substitution reaction of 1 with PPh₃ or Ph₂PCH₂PPh₂ in the presence of Me₃NO?·?2H₂O in 90% and 85% yields, respectively. The crystal structures of 1 and 2 revealed that the substituent attached to the bridgehead nitrogen occupies an equatorial position and the PPh₃ ligand resides in an axial position of the square pyramid of Fe2.     

膦配体取代的乙基乙撑双铁配合物的合成、晶体结构及电化学催化性能

以母体配合物[Fe₂(CO)₆(μ-SCH₂CH (CH₂CH₃) S)](1)分别与三(2-呋喃基)膦、二苯基丙基膦、双(二苯基膦)乙炔、1,2-双(二苯基膦基)苯和脱羰试剂Me₃NO · 2H₂O反应,制备了单取代配合物[Fe₂(CO)₅(L)(μ-SCH₂CH (CH₂CH₃) S](L=P (2-C₄H₃O)₃,2;Ph₂PCH₂CH₂CH₃,3)、桥联配合物{[Fe₂(CO)₅(μ-SCH₂CH (CH₂CH₃) S)]₂(Ph₂PC≡CPPh₂)}(4)和螯合配合物[Fe₂(CO)₄(κ₂-(Ph₂P)₂(1,2-C₆H₄))(μ-SCH₂CH (CH₂CH₃) S)](5)。配合物2~5经元素分析、红外光谱、核磁共振氢谱和磷谱表征,并进一步得到单晶X射线衍射的确证。电化学研究表明,在弱酸HOAc作为质子源存在的情况下,这些配合物可以实现催化质子还原产生氢气的功能。     

Synthesis,structures and electrochemical properties of hydroxyl- and pyridyl-functionalized diiron azadithiolate complexes

The hydroxyl- and pyridyl-functionalized diiron azadithiolate complexes [{(μ-SCH₂)₂N(CH₂CH₂OH)}Fe₂(CO)₆] (1) and [{(μ-SCH₂)₂N(CH₂CH₂OOCPy)}Fe₂(CO)₆] (Py = pyridyl) (2) were prepared as biomimetic models of the active site of Fe-only hydrogenases. Both complexes were characterized by MS, IR, ¹H NMR spectra and elemental analysis. The molecular structures of 1 and 2 were determined by single crystal X-ray analysis. A network is constructed by intermolecular H-bonds in the crystals of 1. An S?O intermolecular contact was found in the crystals of 2, which is scarcely found for organometallic complexes. Cyclic voltammograms of 1 and 2 were studied to evaluate their redox properties.     

Synthesis and structural characterization of diiron azadithiolate complexes relevant to the active site of [FeFe] hydrogenases

Two N-functionally substituted diiron azadithiolate complexes, [(µ-SCH₂)₂NCH₂CH₂OC(O)C₆H₄I-p]Fe₂(CO)₆ (1) and {[(µ-SCH₂)₂NCH₂CH₂OC(O)C₆H₄I-p]Fe₂(CO)₅Ph₂PCH}₂ (2) as models for the active site of [FeFe] hydrogenases, have been prepared and fully characterized. Complex 1 was prepared by the reaction of [(µ-SCH₂)₂NCH₂CH₂OH]Fe₂(CO)₆ with p-iodobenzoic acid in the presence of 4-dimethylaminopyridine (DMAP) and N,N′-dicyclohexylcarbodiimide (DCC) in 78% yield. Further treatment of 1 with 1 equiv. of Me₃NO?·?2H₂O followed by 0.5 equiv. of trans-1,2-bis(diphenylphosphino)ethylene (dppe) affords 2 in 60% yield. The new complexes 1 and 2 were characterized by IR and ¹H (¹³C, ³¹P) NMR spectroscopic techniques and their molecular structures were confirmed by X-ray diffraction analysis. The molecular structure of 1 has two conformational isomers, in one isomer its N-functional substituent is axial to its bridged nitrogen and in the other isomer its N-functional substituent is equatorial. The crystal structure of 2 revealed that its N-functional substituents are equatorial to its nitrogens and dppe occupies the two apical positions of the square-pyramidal irons.     

The effect of a pendant amine in phosphine ligand on the structure and electrochemical property of diiron dithiolate complexes

Abstract

In order to explore the effect of a pendant amine on a phosphine ligand on the structure and electrochemical properties of diiron dithiolate complexes, this work reports the crystallographic and electrocatalytic comparisons of three diiron monophosphine complexes Fe₂(μ-pdt)(CO)₅{Ph₂P(NHR)} [pdt?=?propanedithiolate (SCH₂CH₂CH₂S); R?=?para-methoxycarbonylphenyl (C₆H₄CO₂Me-p) (1), para-methoxyphenyl (C₆H₄OMe-p) (2) and phenyl (Ph) (3)] with a pendant amine and one reference analogue Fe₂(μ-pdt)(CO)₅{Ph₂P(CH₂Ph)} (4). While the new complex 4 has been characterized by elemental analysis and various spectroscopic techniques, the molecular structures of 3 and 4 were further determined by X-ray crystallography. In addition, the electrochemical properties of 1–4 were studied in acetonitrile (MeCN) in the absence and presence of acetic acid (HOAc) as a mild proton source using cyclic voltammetry (CV). This may demonstrate that they are found to be active electrocatalysts for proton reduction to hydrogen (H₂).