Benzylic Complexes of Palladium(II): Bonding modes and Penta- coordination for Steric Relief

Abstract

A large variety of α-(pentafluorophenylmethyl)benzylic palladium complexes with different ligands have been synthesized and char- acterized. Multinuclear NMR spectroscopic data allow to determine the σ-or η3-benzylic nature of the complexes in solution. The adoption of either coordination mode is a function of the number of ligands coordinated to palladium and, remarkably, the presence of bulky phosphines favors the adoption of a bidentate η3-benzylic mode and palladium pentacoordinated complexes. Experimental data and DFT calculations indicate that this five- coordination could alleviate the steric hindrance of two cis bulky phosphines. The benzylic complexes show a rich fluxional behavior that involves both ligand exchange and σ- to η3-benzylic interconversion.