Tailoring Ru(II) pyridine/triazole oxygenation catalysts and using photoreactivity to probe their electronic properties

Tuning of ligand properties is at the heart of influencing chemical reactivity and generating tailor-made catalysts. Herein, three series of complexes [Ru(L)(Cl)(X)]PF6 (X=DMSO, PPh3 , or CD3 CN) with tripodal ligands (L1-L5) containing pyridine and triazole arms are presented. Triazole-for-pyridine substitution and the substituent at the triazole systematically influence the redox behavior and photoreactivity of the complexes. The mechanism of the light-driven ligand exchange of the DMSO complexes in CD3 CN could be elucidated, and two seven-coordinate intermediates were identified. Finally, tuning of the ligand framework was applied to the catalytic oxygenation of alkanes, for which the DMSO complexes were the best catalysts and the yield improved with increasing number of triazole arms. These results thus show how click-derived ligands can be tuned on demand for catalytic processes.