Direct Transformation of SiH 4 to a Molecular L(H) 2 Co═Si═Co(H) 2 L Silicide Complex.

The synthesis of bimetallic molecular silicide complexes is reported, based on the use of multiple Si-H bond activations in SiH 4 at the metal centers of 14-electron LCo I fragments (L = Tp″, HB(3,5-diisopropylpyrazolyl) 3 - ; [BP 2 t Bu Pz], PhB(CH 2 P t Bu 2 ) 2 (pyrazolyl)). Upon exposure of (Tp″Co) 2 (μ-N 2 ) ( 1 ) to SiH 4 , a mixture of (Tp″Co) 2 (μ-H) ( 2 ) and (Tp″Co) 2 (μ-H) 2 ( 3 ) was formed and no evidence for Si-H oxidative addition products was observed. In contrast, [BP 2 t Bu Pz]-supported Co complexes led to Si-H oxidative additions with the generation of silylene and silicide complexes as products. Notably, the reaction of ([BP 2 t Bu Pz]Co) 2 (μ-N 2 ) ( 5 ) with SiH 4 gave the dicobalt silicide complex [BP 2 t Bu Pz](H) 2 Co═Si═Co(H) 2 [BP 2 t Bu Pz] ( 8 ) in high yield, representing the first direct route to a symmetrical bimetallic silicide. The effect of the [BP 2 t Bu Pz] ligand on Co-Si bonding in 7 and 8 was explored by analysis of solid-state molecular structures and density functional theory (DFT) investigations. Upon exposure to CO or DMAP (DMAP = 4-dimethylaminopyridine), 8 converted to the corresponding [BP 2 t Bu Pz]Co(L) x adducts (L = CO, x = 2; L = DMAP, x = 1) with concomitant loss of SiH 4 , despite the lack of significant Si-H interactions in the starting complex. On heating to 60 °C, 8 underwent reaction with MeCl to produce small quantities of Me x SiH 4- x ( x = 1-3), demonstrating functionalization of the μ-silicon atom in a molecular silicide to form organosilanes.