Ruthenium macrocycles bearing pyridine bis(carboxamide): synthesis, structure, and catalytic activity for hydrosilylation

Abstract

Ruthenium complexes Ru(MC33)(CO)_n(L)_2−n (L = H₂O, PPh₃, P(OEt)₃; n = 1, 2) with a pincer-type macrocyclic ligand MC33 with a cavity were synthesized and characterized. Ru(MC33)(CO)₂(H₂O) was obtained in yields of up to 97% using a pincer-type ligand containing the bis(carboxamide) moiety and ruthenium(0) carbonyl precursor. Ru(AC)(CO)₂(H₂O) having a pincer-type acyclic ligand AC was also synthesized in a similar manner to Ru(MC33)(CO)₂(H₂O). Mono(phosphine) and bis(phosphite) complexes were formed via the selective thermal ligand exchange of CO with phosphorus ligands. The structure of the complexes was studied by nuclear magnetic resonance spectroscopy, infrared spectroscopy, electrospray ionization–high-resolution mass spectroscopy, and X-ray analyses. In addition, their catalytic activity for hydrosilylation was demonstrated.