Reactions of 1,2,4-trithiolanes with nonacarbonyldiiron:: Sulfurdithiolatodiiron and -tetrairon complexes as mimics for the active site of [Fe-only] hydrogenase

The reactions of 1,2,4-trithiolane (1a), 3,3,5,5-tetramethyl-1,2,4-trithiolane (1b), 3,3,5,5-tetraethyl-1,2,4-trithiolane (1c), 3,3,5,5-bis(pentamethylene)-1,2,4-trithiolane (1d) and dispiro{tricyclo[3.3.1.1]decane-2,3"-(1,2,4)-trithiolane-5',2'-tricyclo[3.3.1.1]decane} (1e) with nonacarbonyldiiron (2) have been investigated. The sulfurdithiolatodiiron complexes 3a-e, which can be considered as novel model complexes of the active site of the [Fe-only] hydrogenase, were isolated as the main products of these reactions. X-ray structure analyses were performed on compounds 3b-e. The carbon dithiolato (SCR2S)-bridged diiron side-products 4a-e and the tetranuclear clusters 6b-d were also obtained and characterised by X-ray diffraction analysis (4b-e and 6b-d). In contrast, the reaction of le with 2 affords the trinuclear complex 7, which contains a side-on bonded adamantanethione, besides 3e and 4e. Finally, the reaction of 3a with two equivalents of (Et4N)CN gives the monocyanide complex 8 in good yield. Density functional calculations have been performed to evaluate the bonding situation in the di- and tetranuclear clusters. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).