Reactivity toward Neutral N- and P-Donor Ligands of Eight-Membered Palladacycles Arising from Monoinsertion of Alkynes into the Pd–C Bond of Orthopalladated Homoveratrylamine and Phentermine. A New Example of the Transphobia Effect

Abstract

Eight-membered palladacycles arising from the insertion of one molecule of alkyne into the Pd–C bond of the palladacycles derived from homoveratrylamine and phentermine react with neutral N- and P-donor ligands to give mononuclear or unusual dinuclear complexes, containing a vinylarylethylamino bridge, depending on the size of the ligand and the substituents of the palladacycle. Diffusion-ordered nuclear magnetic resonance spectroscopy experiments are used to measure the diffusion coefficients and propose the nuclearity of these complexes in solution. Density functional theory calculations show that steric and electronic (transphobia) effects are responsible for the unprecedented observed reactivity differences. A mechanism for the formation of the unusual dinuclear complexes is proposed.