Synthesis of Aminoiminophosphoranate Complexes of Palladium and Platinum and X-ray Diffractional Investigation of the Weak C−H···Pd Interactions Affecting the Geometry of the PdNPN Metallacycles

Abstract

New aminoiminophosphoranate (κ2-(N,N)-(NC6H4i-Pr-p)2PPh2, NPN) complexes (NPN)Pd(PPh3)Cl, (NPN)2Pd, (NPN)Pt(η2-C2H4)Cl, and (NPN)Pt(PPh3)Cl were prepared in high yields from anionic [NPN]Li and the corresponding transition metal chloride precursors. Reaction of (PhCN)2PdCl2 with aminoiminophosphorane [NPN]H afforded bis-imino complex Pd{[NPN]H}2Cl2 in 82% yield. X-ray structures of all palladium complexes were reported, and the specific weak interactions C−H···Pd were detected in the crystals of both (NPN)Pd(PPh3)Cl (intramolecular) and (NPN)2Pd (intermolecular). The topological analysis of electron density function ρ(r) within the AIM theory performed for (NPN)2Pd allowed us to analyze the peculiarities of the chemical bonding of the NPN ligand and to estimate the energy of the intermolecular C−H···Pd interaction as 0.8 kcal/mol. The plausible influence of these weak interactions on the bending of the PdNPN metallacycle was discussed.