Isomerization Dynamics and Control of the η²/N Equilibrium for Pyridine Complexes

A series of pyridine complexes are prepared of the general form TpW(NO)(PMe3)(pyr) where pyr is either pyridine or a substituted pyridine. Depending on substitution pattern, the pyridine can be either N- or η2-coordinated, and the role of the pyridine substituents and metal oxidation state in determining this equilibrium is explored. For η2-pyridine complexes, the substituent pattern and solubility characteristics also determine the ratio of coordination diastereomers. Rates of both intra- and interfacial linkage isomerizations are explored along with the pyridine rotational barrier. This study is supported by DFT calculations and X-ray data and includes characterization of both η2-pyridine and η2-pyridinium complexes.