Selective C–C bond formation at diiron µ-aminocarbyne complexes†
Abstract
The reactions of [Fe2{µ-CN(Me)R}(µ-CO)(CO)2(Cp)2]SO3CF3 (Cp = η-C5H5, R = Me 2a or CH2Ph 2b) with a variety of carbon nucleophiles result in C–C bond formation at different sites of the molecules depending on the nature of the carbanions: (i) R′Li (R′ = Me, Bun or Ph) and R′MgCl (R′ = Me, CH2Ph or Pri) added at the Cp ligand giving η4-cyclopentadiene complexes [Fe2{µ-CN(Me)R}(µ-CO)(CO)2(η4-C5H5R′)(Cp)] 3; (ii) Li2Cu(CN)R′2 (R′ = Me or Bun) and LiCCR′ (R′ = Ph or p-tolyl) afforded the stable acyl complexes [Fe2{µ-CN(Me)R}(µ-CO)(CO){C(O)R′}(Cp)2] 4 and [Fe2{µ-CN(Me)R}(µ-CO)(CO){C(O)CCR′}(Cp)2] 5, respectively. With R ≠ Me the NMR spectra of type 3–5 derivatives show the presence of two isomers arising from the double-bond character of the µ-CN group ascertained from the crystal structure of [Fe2(µ-CNMe2)(µ-CO)(CO){C(O)Bun}(Cp)2] 4b. The structural study reveals the presence of interligand interactions involving the acyl oxygen and the µ-CNMe2 moiety which is also in accord with an extended-Hückel calculation of the charge distribution.