Structure and bonding in the d4/d3 alkyne redox pairs [WX(CO)(MeCCMe)Tp′]z (X = F, Cl, Br and I; z = 0 and 1): halide stabilisation of electron deficient metal alkyne complexes

Abstract

X-Ray structural and EPR spectroscopic studies of the redox-related pairs [WX(CO)(MeCCMe)Tp′]^z (X = F, Cl, Br and I; z = 0 and 1) [Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate] are consistent with the HOMO of the d⁴ (z = 0) species being π-bonding with respect to the W–CO bond, π-antibonding with respect to the W–X bond, and δ-bonding with respect to the W–alkyne bond.