Non-innocent bma ligand in a dissymetrically disubstituted diiron dithiolate related to the active site of the [FeFe] hydrogenases.

The purpose of the present study was to evaluate the use of a non-innocent ligand as a surrogate of the anchored [4Fe4S] cubane in a synthetic mimic of the [FeFe] hydrogenase active site. Reaction of 2,3-bis(diphenylphosphino) maleic anhydride (bma) with [Fe(2)(CO)(6)(mu-pdt)] (propanedithiolate, pdt=S(CH(2))(3)S) in the presence of Me(3)NO-2H(2)O afforded the monosubstituted derivative [Fe(2)(CO)(5)(Me(2)NCH(2)PPh(2))(mu-pdt)] (1). This results from the decomposition of the bma ligand and the apparent C-H bond cleavage in the released trimethylamine. Reaction under photolytic conditions afforded [Fe(2)(CO)(4)(bma)(mu-pdt)] (2). Compounds 1 and 2 were characterized by IR, NMR and X-ray diffraction. Voltammetric study indicated that the primary reduction of 2 is centered on the bma ligand.