Synthesis of (diphosphine)Ni-bridged double-butterfly Fe/S cluster complexes and isolation of the reactive μ-CO-containing anionic Fe/S cluster intermediates

A new series of (diphosphine)Ni-bridged double-butterfly Fe/S clusters [(μ-RS)(μ-Sdouble bond; length as m-dashCS)Fe2(CO)6]2[Ni(diphosphine)] (1–6, R = p-MeC6H4, Ph, n-Bu; diphosphine = dppe, dppv, dppb, dppf) was prepared by a new type of sequential reactions of the μ-CO-containing anions [(μ-RS)(μ-CO)Fe2(CO)6]− (type A anions, generated in situ from Fe3(CO)12, RSH, and Et3N) with excess CS2, followed by treatment of the resulting μ-CS2-containing anions [(μ-RS)(μ-Sdouble bond; length as m-dashCS)Fe2(CO)6]− (type B anions) with various (diphosphine)NiCl2 complexes. In addition, two of the type A anions, namely [(μ-p-MeC6H4S)(μ-CO)Fe2(CO)6]− (A1) and [(μ-PhS)(μ-CO)Fe2(CO)6]− (A2) were successfully isolated as their [Et3NH]+ and [Ph4P]+ salts, respectively. Products 1–6 as well as the two isolated complex salts A1·[Et3NH] and A2·[Ph4P] were fully characterized by elemental analysis and spectroscopy, and particularly for 4, 6, A1·[Et3NH], and A2·[Ph4P] by X-ray crystallography.