Catalytic hydrogenolysis of alkyl halides by sulfido-bridged molybdenum clusters: A density functional study

Density functional theory has been used to explore the mechanism of cleavage of H2 at a sulfido-bridged molybdenum cluster, CpMo(μ-SH)(μ-S)(μ-S2CH2)MoCp. The addition occurs across a single Mo–S bond, and the disruption of the strong Mo–S π bonding in the ground state leads to a very high-lying transition state (+43 kcal mol−1). Once formed, the adsorbed hydrogen migrates over the cluster via a series of hops from metal to sulphur, formally corresponding to a switch from hydridic to protic character. The low barrier (+15 kcal mol−1) for migration leads to facile hydrogenolysis of coordinated substrates.