QTAIM study of transition metal complexes with cyclophosphazene-based multisite ligands I: Zinc(II) and nickel(II) complexes

The metal–ligand bonds in [(ZnCl2)2L], [NiLCl]+ and two isomers of [NiLCl2] complexes with multimodal ligand L = hexakis(2-pyridyloxy)cyclotriphosphazene, cyclo-[NP(NC5H4O)2]3, are investigated at DFT level of theory using hybrid B3LYP functional. Electron density is evaluated in terms of QTAIM (quantum theory of atoms-in-molecule) topological analysis of electron density. The bonds of central transition metal atoms with phosphazene nitrogens are shorter, stronger and more polar than with the aromatic pyridine nitrogens. The atomic charges of phosphazene nitrogens are ca twice more negative than at the pyridine ones. The higher mechanical strain in the five-coordinate metal complexes than in the six-coordinate ones may be concluded.

Graphical abstractThe metal–ligand bonds in [(ZnCl2)2L], [NiLCl]+ and two isomers of [NiLCl2] complexes with multimodal ligand L = hexakis(2-pyridyloxy)cyclotriphosphazene are investigated at DFT level of theory. Electron density is evaluated in terms of QTAIM topological analysis of electron density.Figure optionsDownload full-size imageDownload as PowerPoint slide