A hemilabile diphosphine pyridine pincer ligand: σ- and π-binding in molybdenum coordination complexes

Abstract

A series of molybdenum compounds supported by a hemilabile pyridine diphosphine pincer ligand have been synthesized. The ligand demonstrates variable binding modes, adapting to the electronic and geometric requirements of the metal center. In Mo0 and MoII polycarbonyl complexes, coordination through the σ-donating pyridine nitrogen lone pair is observed. Upon oxidative group transfer with anionic azide, a MoIV nitride compound is formed, accompanied by a change in the ancillary ligand binding mode to the pyridine π-system. The σ-coordination was restored by subsequent functionalization of the nitride moiety with either silyl electrophiles or protons. Protonation results in redox disproportionation with concomitant nitride functionalization. Characterization by single crystal X-ray diffraction, nuclear magnetic resonance, and infrared spectroscopy is discussed.