cis-β-Ruthenium Complexes with Sterically Bulky Salen Ligands: Enantioselective Intermolecular Carbene Insertion into Si–H Bonds and X-ray Crystal Structure of cis-β-[RuII(salen)(CO)(CPh2)] Complex

Abstract

The synthesis, spectroscopy, crystal structure, and electrochemical behavior of cis-β-RuII(CO)2, cis-β-RuII(CO)(H2O), and cis-β-RuII(CO)(carbene) complexes supported by sterically bulky salen ligands are described, along with the catalytic activity of chiral cis-β-[RuII(salen)(CO)2] complexes toward enantioselective carbene Si–H insertion using N2C(Ar)CO2R as the carbene source under light irradiation with product yields up to 96% and ee up to 84%. The cis-β-RuII(CO)(H2O) complex was isolated by using a binaphthyl salen ligand bearing bulky CPh3 substituents with the H2O molecule coordinated at the site trans to an Nimine atom of the salen ligand. Light irradiation of a cis-β-RuII(CO)2 complex, supported by a binaphthyl salen ligand with tBu substituents, followed by treatment with N2CAr2 (Ar = Ph, p-ClC6H4) gave cis-β-[RuII(salen)(CO)(CAr2)], which features a coordinated carbene ligand trans to a salen Nimine atom and undergoes carbene transfer to nitrosobenzene to give the corresponding nitrone product. These findings and related HR-ESI-MS studies provide evidence for the involvement of salen-supported cis-β-RuII(CO)(C(Ar)CO2R) active species in the intermolecular carbene Si–H insertion reaction catalyzed by cis-β-[RuII(salen)(CO)2] complexes.