Trinuclear [NiFe] Clusters as Structural Models for [NiFe] Hydrogenase Active Sites

Abstract

Abstract[Fe(CH3COCH=CHPh)(CO)3] reacts with [Ni(‘S4’)]x (x = 1, 2) or [Ni(‘S4C3Me2’)] [‘S4’2− = 1,2‐bis(2‐mercaptophenylthio)ethane(2‐),‘S4C3Me2’2− = 1,3‐bis(2‐mercaptophenylthio)‐2,2‐dimethylpropane(2‐)] to afford trinuclear [NiFe] clusters [Ni(‘S4’){Fe(CO)3}2] (1) and [Ni(‘S4C3Me2’){Fe(CO)3}2] (2) and the dinuclear FeIIFe0 complex [Fe(CO)(‘S4C3Me2’)Fe(CO)3] (3). Clusters 1 and 2 have Ni−Fe bond lengths similar to those of active or reduced states of [NiFe] hydrogenases, a sulfur‐dominated coordination sphere of Ni and iron‐bound CO. Therefore, 1 and 2 may serve as structural model complexes for the [NiFe] hydrogenase active site. Combination of the ‘S4C3Me2’ ligand with FeCl2·4H2O yielded [Fe(‘S4C3Me2’)]2 (4), the dinuclearity of which suggests that the ‘S4C3Me2’ ligand is less flexible than its ethylene‐bridged derivative, which affords a tetrameric [Fe(‘S4’)]4 complex reported earlier. Compound 4 reacts with 2 equiv. of CO to give [Fe(CO)(‘S4C3Me2’)]2 (5), which like 4 is only sparingly soluble in all common organic solvents. Complex 5 easily loses CO even if stored in the solid state. [Fe(CH3COCH=CHPh)(CO)3] reacts with 5 to afford 3 as the only product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis of Diiron(I) Dithiolato Carbonyl Complexes

“…308,309 The complex Ni(pdt)-(dppe) reacts with iron(0) carbonyls to give Fe 2 ( μ -pdt)(CO) 6 . The conversion proceeds via the intermediacy of a NiFe intermediate according to eqs 17 and 18.…”

The Activation of Dihydrogen

“…Very recently, Tatsumi and coworkers developed the [(l-S(CH 2 ) 3 S)[Fe(CO) 2 (CN) 2 ][Ni(g 2 -S 2 CNR 2 )] 1-complex as excellent models of the composition of the [NiFe]H 2 ase active site [195]. The Sellmann laboratory has also published a series of trinuclear (FeNi 2 ) complexes which (ignoring the extra Ni center) serve as excellent models of the structural and compositional models of the [NiFe]H 2 ase active site [196,197].…”

Thiolate‐Bridged Iron–Nickel Models for the Active Site of [NiFe] Hydrogenase

“…[32] Similarly, Sellmann and co-workers used Ni('S 4 ') {21; 'S 4 ' = 1,2-bis(2-mercaptophenylthio)ethane} and Ni('S 4 C 3 Me 2 ') {22; 'S 4 C 3 Me 2 ' = 1,3-bis(2-mercaptophenylthio)-2,2-dimethylpropane} as precursors for the analogous Fe 2 Ni complexes [(CO) 6 Fe 2 ('S 4 ')Ni] (30) and [(CO) 6 Fe 2 ('S 4 C 3 Me 2 ')Ni] (31), respectively ( Figure 9). [33] The Ni-Fe [2.4789(9)-2.5038 (4) [25] Chemical reduction of 29 with Cp 2 Co (or electrochemical reduction of 29) leads to the formation of [29] -, which is EPR active and shows an interaction between the unpaired electron and the nickel nucleus upon 61 Ni (I = 3/2) enrichment.…”