Trans ligand effects on 195Pt NMR shielding constants of square planar Pt(II) complexes

Abstract

The trans ligand effects on the isotropic σiso 195Pt NMR shielding constants, described by the unified term of trans-philicity, for a broad series of square planar trans-Pt(PMe3)2(X)L (X = H, CO, CH3, NH2, OH2, Cl) complexes, were investigated by DFT computational protocols at the 2-component spin–orbit zero-order approximation (2c-SO-ZORA) level of theory. The established trans-philicity sequences are almost identical for all series of complexes. The relative strength of trans-philicity is defined as the difference between the calculated σiso(SO) 195Pt NMR shielding constants for the complete set of ligands and the σiso(SO) 195Pt NMR shielding constant of the complex containing the ligand with the weakest trans-philicity. Noteworthily, the 195Pt NMR trans-philicity sequences retrieve the experimental trans-orienting series. The linear correlations between the σiso(SO) 195Pt NMR shielding constants and the σiso(SO) X NMR shielding constants shows that upon increase in the upfield shift of the σiso(SO) 195Pt NMR increase the downfield shift of the σiso(SO) X NMR shielding constants. The linear σiso(SO) 195Pt versus QPt correlations show that the increase in the negative natural atomic charge QPt increases the downfield shift of the σiso(SO) 195Pt shielding constants.