Hydroboration of carbonyl compounds catalysed by a molybdenum germylyne complex: metal-ligand cooperative mechanism.

A molybdenum germylyne complex with a MoGe triple bond promotes the catalytic hydroboration of aldehydes and ketones with HBpin. Hydroboration of aldehydes proceeded efficiently at ambient temperature, affording the corresponding borate esters in 92-99% NMR yields, whereas hydroboration of ketones required a slight elevated temperature (70 °C), affording the products in 90-96% NMR yields. Mechanistic investigations, including KIE experiments, kinetic analyses and DFT calculations suggest a unique metal-ligand cooperative mechanism at the MoGe bond that promotes hydroboration of substrates through a six-membered-ring transition state during the rate-determining step.