An imidazolin-2-iminato ligand organozinc complex as a catalyst for hydroboration of organic nitriles

Abstract

The reaction of diethylzinc with imidazolin-2-imines (ImRNH, R = Dipp (2,6-diisopropylphenyl)), Mes (2,4,6-trimethylphenyl), and tBu (tert-butyl) afforded the corresponding dimeric zinc(II) imidazolin-2-iminato complexes [{(ImRN)Zn(CH2CH3)}2] (R = Dipp, 1a; R = Mes, 1b; R = tBu, 1c). The zinc complexes were characterised using spectroscopic techniques and the molecular structure of complex 1b was established by single-crystal X-ray diffraction analysis. Complex 1c was used as a catalyst for the chemo-selective hydroboration of organic nitriles with pinacolborane (HBpin) at ambient temperature to obtain diborylamines of a broad substrate scope in high yield. Zinc complex 1c exhibits a versatile substrate scope and good functional group tolerance for catalytic hydroboration reactions. A most plausible mechanism is proposed on the basis of the kinetic study.