Electron and proton transfers at diiron dithiolate sites relevant to the catalysis of proton reduction by the [FeFe]-hydrogenases

The complexes [Fe2(CO)6{μ-SCH2N(R)CH2S}] (R = CH2CH2OCH3, 1a; R = iPr, 1b) and [Fe2(CO)6(μ-pdt)] 2 (pdt = S(CH2)3S) are structural analogues of the [2Fe]H subsite of [FeFe]H2ases. Electrochemical investigation of 1 and 2 in MeCN–[NBu4][PF6] under Ar and under CO has demonstrated that the reduction can be resolved into two one-electron transfer steps by using fast scan cyclic voltammetry. At slow scan rates the reduction of 1 tends towards a two-electron process owing to the fast disproportionation of the anion, while the two-electron reduction of 2 is clearly favoured in the presence of CO. Substitution of a CO ligand in 2 by a N-heterocyclic carbene results in the destabilisation of the anion. Thus, in MeCN–, thf- or CH2Cl2–[NBu4][PF6], the electrochemical reduction of Fe2(CO)5LNHC(μ-pdt)] 3 (LNHC = 1,3-bis(methyl)-imidazol-2-ylidene, 3a; 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene, 3b) occurs in a single-step, two-electron process at moderate scan rates; under appropriate conditions this process can be separated into two one-electron steps. Density Functional Theory calculations successfully rationalize the effects of the S-to-S linkage on the electrochemistry of the complexes.

Electrochemical and theoretical investigations of the reduction of [Fe2(CO)5L{μ-SCH2XCH2S}] complexes related to [FeFe] hydrogenase

Dinuclear molybdenum thiolato-bridged compounds: syntheses, reactivities and electrochemical studies of site–substrate interactions

Chemistry of highly electrophilic binuclear cations. 1. oxidation reactions of m2(eta 5-c5h5)2(co)4(mu -ph2pch2pph2) (m = mo, w) with fecp2x (x = bf4, pf6)

The first examples of stable, mononuclear 17-electron carbonyl complexes of Mo(III) have been synthesized, isolated, and characterized by IR and EPR spectroscopy. Oxidation of Cp*MoCl(CO)(PMe3)2 (1; E1/2 = −0.48 V vs Fc/Fc+), Cp*MoCl(CO)(dppe) (2; E1/2 = −0.44 V), and CpMoCl(CO)(dppe) (3; E1/2 = −0.25 V) with Fc+PF6- yields [1]PF6, [2]PF6, and [3]PF6, respectively. The IR stretching vibration of the 17-electron oxidation products are 136−153 cm-1 blue-shifted with respect to the corresponding stretching vibrations of the parent Mo(II) compounds. The room temperature EPR spectra show observable coupling to the Mo and P nuclei and indicate a trans geometry for 1+ and a cis geometry for 2+ and 3+. The four-legged piano stool geometry of 2+ with the phosphines atoms in relative cis positions has been confirmed by a single-crystal X-ray analysis. The X-ray data for [2]PF6·THF are the following:  monoclinic, P21/n, a = 13.7394(14) A, b = 20.421(2) A, c = 14.857(2) A, β = 99.119(8)°, V = 4115.8(8) A3, Z = 4, Dx ...

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl- Addition Reactions

Electrochemically-induced isomerization of {(η5-C5H5)Mo(CO)2(μ-SR)}2 (R Me, t-Bu, Ph) complexes. 1H NMR and electrochemical studies. Sythesis and X-ray crystal structure of {(η5-C5H5)Mo(CO)2(μ-S-t-Bu)}2(BF4)2

Electrochemistry of Dinuclear, Thiolato-Bridged Transition-Metal Compounds. Part 1. Electrochemical Behaviour of ((η5-C5H5)(CO)3M(μ-SR)W(CO)5) (R: Me, M: Mo or W; R: Ph, M: W) Complexes in Non-aqueous Media.

Electrochemistry of Dinuclear, Thiolato-Bridged Transition-Metal Compounds. Part 2. Reductive Electrochemistry of Metal-Metal Bonded Complexes Cyclic ((η5-C5H5)(CO)2Mo(μ-SMe)W(CO)4L) (L: CO or P(OMe)3).

J. Courtot-Coupez

Papers

Electrochemically-induced isomerization of {(η5-C5H5)Mo(CO)2(μ-SR)}2 (R Me, t-Bu, Ph) complexes. 1H NMR and electrochemical studies. Sythesis and X-ray crystal structure of {(η5-C5H5)Mo(CO)2(μ-S-t-Bu)}2(BF4)2

Electrochemistry of Dinuclear, Thiolato-Bridged Transition-Metal Compounds. Part 1. Electrochemical Behaviour of ((η5-C5H5)(CO)3M(μ-SR)W(CO)5) (R: Me, M: Mo or W; R: Ph, M: W) Complexes in Non-aqueous Media.

Electrochemistry of Dinuclear, Thiolato-Bridged Transition-Metal Compounds. Part 2. Reductive Electrochemistry of Metal-Metal Bonded Complexes Cyclic ((η5-C5H5)(CO)2Mo(μ-SMe)W(CO)4L) (L: CO or P(OMe)3).