Electron-transfer-catalyzed rearrangement of unsymmetrically substituted diiron dithiolate complexes related to-the active site of the [FeFe]-Hydrogenases

Novel asymmetrically substituted azadithiolate compounds [Fe-2(CO)(4)(kappa(2)-dppe){mu-SCH2N(R)CH2S}] (R = Pr-i, 1a; CH2CH2OCH3, 1b; CH2C6H5, 1c) have been synthesized by treatment of [Fe-2(CO)(6)(mu-adt)] [adt = SCH2N(R)CH2S, with R = Pr-i, CH2CH2OCH3, CH2C6H5] with dppe (dppe = Ph2PCH2CH2PPh2) in refluxing toluene in the presence of Me3NO. la-c have been characterized by single-crystal X-ray diffraction analyses. The electrochemical investigation of 1a-c and of [Fe-2(CO)(4)(kappa(2)-dppe)(mu-pdt)] (1d) [pdt = S(CH2)(3)S] in MeCN- and THF-[NBu4][PF6] has demonstrated that the electrochemical reduction of 1a-d gives rise to an Electron-transfer-catalyzed (ETC) isomerization to the symmetrical isomers 2a-d where the dppe ligand bridges the iron centers. Compounds 2a-d were characterized by IR and NMR spectroscopy, elemental analysis, and X-ray crystallography for 2a.