Silylene-Nickel Promoted Cleavage of B-O Bonds: From Catechol Borane to the Hydroborylene Ligand.

The first 16 valence electron [bis(NHC)](silylene)Ni0 complex 1, [(TMS L)ClSi:→Ni(NHC)2 ], bearing the acyclic amido-chlorosilylene (TMS L)ClSi: (TMS L=N(SiMe3 )Dipp; Dipp=2,6-Pri2 C6 H4 ) and two NHC ligands (N-heterocyclic carbene=:C[(Pri )NC(Me)]2 ) was synthesized in high yield and structurally characterized. Compound 1 is capable of facile dihydrogen activation under ambient conditions to give the corresponding HSi-NiH complex 2. Most notably, 1 reacts with catechol borane to afford the unprecedented hydroborylene-coordinated (chloro)(silyl)nickel(II) complex 3, {[cat(TMS L)Si](Cl)Ni←:BH(NHC)2 }, via the cleavage of two B-O bonds and simultaneous formation of two Si-O bonds. The mechanism for the formation of 3 was rationalized by means of DFT calculations, which highlight the powerful synergistic effects of the Si:→Ni moiety in the breaking of incredibly strong B-O bonds.