Quantum Chemical Calculations of 31P NMR Chemical Shifts in Nickel Complexes: Scope and Limitations

The scope and limitations of a simple approach for the 31P NMR chemical shift calculations of phosphorus atoms directly involved in the formation of coordination bonds with Ni have been analyzed. A comparative analysis of calculated versus experimental 31P NMR shifts for the wide range of model nickel complexes based on small/-medium-sized organophosphorus ligands was carried out. Several functional–basis set combinations were tested. In general, for neutral singlet Ni complexes based on σ- and π-type ligands the 31P NMR shifts can be calculated quite well in the framework of the Kohn–Sham level of theory with hybrid functionals (PBE0, B3LYP, B97-2). In the case of charged complexes, the predictions are less accurate due to the inherent fluxionality of the systems. For complexes with triplet contamination this approach cannot be used. The most accurate results were reached with the PBE0/6-311G­(2d,2p)//PBE0/6-31+G­(d) combination (RMSE 31P NMR shifts of directly coordinated phosphorus. Moreover, the approach allows for the assignment of challenging structures with several coordination types.