In summary, complex A was demonstrated to be an efficient pre-catalyst for the hydroboration of both nitriles and Nheteroarenes using HBpin as the terminal reductant. Stoichiometric studies of complex A with pyridine and benzonitrile furnish new paramagnetic species 6 and 7 respectively, which have been spectroscopically and crystallographically characterized. Combined computational and experimental mechanistic studies of the hydroboration of benzonitrile reveal a first-order dependency in complex A, a first-order dependency at low HBpin concentration changing to near zero-order at higher HBpin concentration and an inverse first-order dependency in nitrile, suggesting inhibition. An inverse kinetic isotope effect (kH/kD = 0.3) reveals that B-H bond activation is not the rate-limiting step and that this value can be attributed to an equilibrium isotope effect, as supported by DFT calculations, suggestive of the C-H bond in the boryl imine intermediate ( ) being more prone to undergoing the reversible C-H oxidative addition back to complex 8 compared to the corresponding C-D addition.