Synthesis, Structure, and Reactivity of a Terminal Magnesium Hydride Compound with a Carbatrane Motif, [TismPriBenz]MgH: A Multifunctional Catalyst for Hydrosilylation and Hydroboration

The tris[(1-isopropylbenzimidazol-2-yl)-dimethylsilyl)]methyl ligand, [Tism(PriBenz)], has been employed to form the magnesium carbatrane compound, [Tism(PriBenz)]MgH, which possesses a terminal hydride ligand. Specifically, [Tism(PriBenz)]MgH is obtained via the reaction of [Tism(PriBenz)]MgMe with PhSiH3. The reactivity of [Tism(PriBenz)]MgMe and [Tism(PriBenz)]MgH allows access to a variety of other structurally characterized carbatrane derivatives, including [Tism(PriBenz)]MgX [X = F, Cl, Br, I, SH, N(H)Ph, CH(Me)Ph, O2CMe, S2CMe]. In addition, [Tism(PriBenz)]MgH is a catalyst for (i) hydrosilylation and hydroboration of styrene to afford the Markovnikov products, Ph(Me)C(H)SiH2Ph and Ph(Me)C(H)Bpin, and (ii) hydroboration of carbodiimides and pyridine to form N-boryl formamidines and N-boryl 1,4- and 1,2-dihydropyridines, respectively.