The reaction of [{Co(η5-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CS)] and related complexes with carbon disulfide. Synthesis, structure and reactivity of [{Co(η5-C5H5)}2{Fe(CO)(L)}(μ3-S)(μ3-C2S3)] derivatives (L = PR3 and CNR)

Abstract

[{Co(η⁵-C₅H₅)}₂{Fe(CO)(L)₂}(μ₃-S)(μ₃-CS)] complexes 1 where (L)₂ = (a) (CO)(PPh₃), (b) (CO){P(OPh)₃}, (c) (CO)(PBuⁿ₃), (d) (CNMe)₂ and (e) (CNMes)₂ (Mes = 2,4,6-Me₃C₆H₂), but not (CO)(CNMes), react with CS₂ under reflux to give [{Co(η⁵-C₅H₅)}₂{Fe(L)₂}(μ₃-S)(μ₃-C₂S₃)], 2, in which a CS₂ molecule has been incorporated into a FeSC(S*)SC heterocycle with a trithiocarbonate moiety bridging the Fe–C cluster edge. Clusters 2 react with incoming ligands either by simple ligand substitution, or by displacement of CS₂ to form clusters of type 1. The exocyclic sulfur atom S* is nucleophilic and with electrophiles E forms [{Co(η⁵-C₅H₅)}₂{Fe(L)₂}(μ₃-S)(μ₃-C₂S₃E] adducts which contain S*→E bonds where E = Me⁺ [3]⁺, Et⁺ [4]⁺, HgCl₂ [5], and I₄ (or I⁺) [6]. The clusters 2a–c and the [3]⁺ and [4]⁺ derived from them are chiral as indicated by their NMR spectra, and do not racemize on the NMR timescale. The structures of 2a·2C₆H₆ and [3a]I·C₆H₆·CHCl₃ are reported. Cluster 2a contains a very short Fe–C_μ bond as compared with 1a, and it is suggested that in many respects the FeSC(S)SC_μ ring is best regarded as a metallo-1,3-dithiole-2-thione (or metallovinyl trithiocarbonate) with a Fe–C_μ double bond which, on alkylation at the exocyclic S*, adopts a more delocalised electronic structure with a longer Fe–C_μ bond. Spectroscopic and electrochemical data for the new compounds are discussed.