Dehydrogenation, Methyl Elimination and Insertion Reactions of the Agostic Methyl-Bridged Complex [Mo Cp (μ-κ :η -CH )(μ-PtBu )(μ-CO)].

The high unsaturation of the title complex enabled it to react with a wide variety of molecules under mild conditions, whereby the agostic methyl ligand underwent unusual or unprecedented processes. Methane elimination occurred in the reactions with PPh H and SiPh H , this being followed in the latter case by Si-H bond oxidative addition to give the hydride silylene derivative [Mo Cp H(μ-PtBu )(μ-SiPh )(CO)]. Dehydrogenation, however, was the dominant process in the room temperature reaction with [Fe (CO) ], to give the unsaturated methylidyne cluster [Mo FeCp (μ -CH)(μ-PtBu )(CO) ] (Mo-Mo=2.6770(8) Å). In contrast, PMe elimination took place in the reaction with P , to give the unsaturated triphosphorus complex [Mo Cp (μ-η :η -P )(μ-PtBu )] (Mo-Mo=2.6221(3) Å). Yet a most remarkable reaction occurred with BH ⋅THF, involving insertion of two BH units and dehydrogenation to yield [Mo Cp (μ-B H Me)(μ-PtBu )(CO)], with the novel methyldiboranyl ligand acting as a 5-electron donor due to the presence of two 3-centre, 2-electron B-H-Mo interactions, according to spectroscopic data and DFT calculations (Mo-Mo ca. 2.65 Å).