Synthesis and reactivity of η3-butadienyl molybdenum complexes formed by deprotonation or desilylation of 1,3-diene cations; structure of [Mo(CO)2(η3-CH2CHCCH2)(η-C5Me5)]

Abstract

Reaction of [Mo(CO)₂(η⁴-CH₂CH–CHCH₂)(η-C₅Me₅)][BF₄](4) with Li[N(SiMe₃)₂] in tetrahydrofuran (THF) at –78 °C results in an unusual deprotonation reaction affording, in low yield, the novel η³-butadienyl complex [Mo(CO)₂(η³-CH₂CHCCH₂)(η-C₅Me₅)](5), which has been characterised by X-ray crystallography; the fluoride anion-induced desilylation of [Mo(CO)₂(η⁴-CH₂CH–C–{SiEt₃}CH₂)(η-C₅Me₅)][BF₄](6), using Bu₄NF affords (5) in quantitative yield, facilitating a rational strategy for the synthesis of these complexes, which on protonation access cationic species containing η³-vinylcarbene ligands.