Computational studies on the hydride transfer barrier for the catalytic hydrogenation of CO2 by different Ni(II) complexes.

Hydride transfer is the most crucial step for the catalytic hydrogenation of CO2 in homogeneous condition. Here, we perform state-of-the-art calculations to show the effect of geometry and spin states of Ni-hydride complexes containing different types of multidentate phosphine ligands on their hydride transfer barrier. For doing this, we first choose Ni-bis(diphosphine) complexes of the type NiP4, which have been synthesized recently and then by extrapolating the idea we propose a new type of NiP2N2 complex showing much lower hydride transfer barrier. We also compute the hydricities of the Ni-hydride complexes in aqueous medium and try to correlate these thermodynamic quantities with the kinetic barrier of hydride transfer. Graphical Abstract NiP2N2 complex can efficiently hydrogenage CO2 with a quite low hydride transfer barrier.