Electron-Transfer-Catalyzed Rearrangement of Unsymmetrically Substituted Diiron Dithiolate Complexes Related to the Active Site of the [FeFe]-Hydrogenases

Novel asymmetrically substituted azadithiolate compounds [Fe2(CO)4(κ2-dppe){μ-SCH2N(R)CH2S}] (R = iPr, 1a;
CH2CH2OCH3, 1b; CH2C6H5, 1c) have been synthesized by treatment of [Fe2(CO)6(μ-adt)] [adt = SCH2N(R)CH2S,
with R = iPr, CH2CH2OCH3, CH2C6H5] with dppe (dppe = Ph2PCH2CH2PPh2) in refluxing toluene in the presence
of Me3NO. 1a−c have been characterized by single-crystal X-ray diffraction analyses. The electrochemical investigation
of 1a−c and of [Fe2(CO)4(κ2-dppe)(μ-pdt)] (1d) [pdt = S(CH2)3S] 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.