Solar hydrogen production offers a clean and environmentally friendly alternative energy source. Bis(diphosphine) nickel catalysts are promising catalysts for production of molecular hydrogen and CO2 reduction. These Ni(P2RN2R’)2 catalysts contain an inexpensive first row transition metal but, depending on the ligands, display dramatically different hydrogen production rates and selectivity. The goal of the current work is to better understand how geometric changes due to ligand variations affect the electronic properties. Based on the X-ray diffraction analysis of the catalyst structure in its paramagnetic Ni(I) state, a comprehensive set of density functional theory (DFT) calculations with varied side groups (R, R') was performed. Comparison of calculated magnetic resonance parameters using the EPRII/Wachters basis with the B3LYP functional for the “key” magnetic parameters like g-tensor and hyperfine coupling constants show good agreement with experimental values. The systematic variation of the residues (R, R') in the DFT calculations allows subtle geometric/electronic changes to be related to changes in the magnetic resonance parameters. Furthermore, DFT calculations on model systems with different side groups confirm the absence of a stable structure with a small solvent molecule like acetonitrile bound to the Ni(I). The data presented here are vital for understanding electronic structure and catalytic activity of bis(diphosphine) nickel catalysts.

Influence of ligand substitution on electronic properties in bis(diphosphine) nickel (I) catalysts used in hydrogen catalysis

249th National Meeting (2015)

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