Zinc borylation and reduction by a diborane(4) species B-O bond formation.

We report a convenient synthesis of the zinc-boryl complex (Nacnac)ZnBpin under mild conditions formal disproportionation of bis(pinacolato)diboron(4), aided thermodynamically by B-O bond formation. This species can be isolated both base-free and as the DMAP adduct (Nacnac)Zn(DMAP)Bpin and crystallographically characterised in the latter form. Onward reactivity of the base free zinc boryl complex with CO occurs reductively, yielding further B-O bonds as well as CO gas. The strength of this driving force can then be harnessed in the reaction between (Nacnac)ZnBpin and a Zn-O bonded species (Nacnac)ZnOB{(NDippCH)}, which yields the metal-metal bonded dimer [(Nacnac)Zn], the overall formation of which utilizes a diboron(4) species as the stoichiometric reductant of Zn(ii) to Zn(i).