Dehydrogenation, Methyl Elimination and Insertion Reactions of the Agostic Methyl-Bridged Complex [Mo 2 Cp 2 (μ-κ 1 :η 2 -CH 3 )(μ-PtBu 2 )(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 PPh2 H and SiPh2 H2 , this being followed in the latter case by Si-H bond oxidative addition to give the hydride silylene derivative [Mo2 Cp2 H(μ-PtBu2 )(μ-SiPh2 )(CO)]. Dehydrogenation, however, was the dominant process in the room temperature reaction with [Fe2 (CO)9 ], to give the unsaturated methylidyne cluster [Mo2 FeCp2 (μ3 -CH)(μ-PtBu2 )(CO)5 ] (Mo-Mo=2.6770(8) Å). In contrast, PMe elimination took place in the reaction with P4 , to give the unsaturated triphosphorus complex [Mo2 Cp2 (μ-η3 :η3 -P3 )(μ-PtBu2 )] (Mo-Mo=2.6221(3) Å). Yet a most remarkable reaction occurred with BH3 ⋅THF, involving insertion of two BH3 units and dehydrogenation to yield [Mo2 Cp2 (μ-B2 H4 Me)(μ-PtBu2 )(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).