Catalytic hydroboration of carbon dioxide and cyclohexyl isocyanate with diimine zinc hydrides

Reactions of generated in situ zinc hydride complexes [(dpp-bian)Zn(mu-H)]2(1) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and [(ArBIG-bian)ZnH] (ArBIG-bian is 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with carbon dioxide in tetrahydrofuran resulted in formates [(dpp-bian)Zn(mu-OCHO)]2(2) and [(ArBIG-bian)Zn(mu-OCHO)]2(3), respectively. Paramagnetic complexes 2 and 3 were characterized by ESR spectroscopy, the molecular structure of complex 2 was determined by X-ray diffraction analysis. The reduction of carbon dioxide by pinacolborane HBpin (pin is O2C2Me4) in the presence of compound 1 (10 mol.%) at 80 degrees C for 3 h quantitatively gave pinBOBpin and pinBOMe. Hydroboration of cyclohexyl isocyanate with pinacolborane at a 1:1 molar ratio in the presence of complex 1 (1 mol.%) at room temperature proceeded with the rate equal to the mixing rate of the reagents to afford selectively N-boryl formamide.