Ligand exchange processes in some iron-sulphur-carbonyl and -nitrosyl complexes

Abstract

The complex [Fe 2(SMe) 2(CO) 6] undergoes stepwise exchange with Et 2S 2 to yield successively [Fe 2(SMe)(SEt)(CO) 6] and [Fe 2(SEt) 2(CO) 6]. Carbonyl complexes [Fe 2(SR) 2(CO) 6] are efficiently converted to the nitrosyls [Fe 2(SR) 2(NO) 4] by the action either of NO gas or of methanolic sodium nitrite: the analogous species [Fe 2S 2(CO) 6], [Fe 2S 2(CO) 6] 2−, and [Fe 3S 2(CO) 9] all, with methanolic nitrite, yield [Fe 4S 3(NO) 7] −. This anion, [Fe 4S 3(NO) 7] −, reacts with sulphur to give the cubane-like [Fe 4S 4(NO) 4]: the synthesis of its selenium analogue, [Fe 4Se 3(NO) 7] − is described. The complexes [Fe 2(SR) 2(NO) 4] (R = Me, Et, Pr n, Pr i, Bu t, PhCH 2) all consist of two isomers in solution, presumed to have structures of C 2h and C 2v, symmetry: activation parameters for the C 2h⇌C 2v reaction are reported.