Syntheses and characterizations of methylpalladium complexes bearing a biphenyl-based bulky phosphine ligand: Weak interactions suggested by NBO and QTAIM analyses

A methylpalladium chloride complex bearing a biphenyl-based bulky phosphine ligand, tBu2P(biphenyl-2-yl) (1), namely [Pd(1)(Me)Cl]2 (=8), was synthesized by the reaction of (cod)Pd(Me)Cl with 1. A following reaction of 8 with AgOTf gave the corresponding triflate complex, Pd(1)(Me)OTf (=9). These complexes were fully characterized by NMR spectroscopy and structurally characterized by X-ray crystallographic study. In the solid state of 8, biphenyl-based phosphine ligand 1 played a role of monodentate phosphine ligand with a possible weak η1-coordination from the phenyl ring at 2′-position of 1. On the other hand, phosphine ligand 1 in 9 showed a bidentate coordination mode consist of σ-donation of the phosphine and η2-coordination of the phenyl ring at 1′- and 2′-positions. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations also supported the existence of these weak interactions.

Graphical abstractTwo methylpalladium complexes [Pd(1)(Me)Cl]2 (=8) and Pd(1)(Me)OTf (=9) where 1 is tBu2P(biphenyl-2-yl) were synthesized and fully characterized by NMR and X-ray crystallography. In the solid state of 8, the terminal phenyl ring of ligand 1 coordinates to the palladium though a weak η1-coordination. On the other hand, in the case of 9, the terminal phenyl ring of 1 plays as η2-coordinating ligand. Theoretical calculations also supported the existence of these weak interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide