Seven-Coordinate Ruthenium Complex with an SiNN-Pincer Ligand as a Catalyst for Vinyl C─H Deuteration of Olefins

Seven-coordinate ruthenium complexes 1a and 1b, featuring silyl-2,2´-bipyridine SiNN-pincer ligands with i-Pr and t-Bu groups on Si, respectively, were synthesized. Their capped octahedral structures were revealed by single-crystal X-ray diffraction study. The stoichiometric reactions of 1a and 1b with styrene in THF afforded η²-silylalkene chelate complexes. In contrast, performing the same reaction using 1a in C₆D₆ resulted in the liberation of deuterated styrene (PhDC═CD₂), alongside the formation of a deuterated η²-silylalkene complex. Complex 1a exhibited efficient catalytic activity for the triple deuteration of vinyl hydrogens in mono-substituted olefins with C₆D₆ to afford RDC═CD₂ (R = Ph, C₆H₄-4-OMe, t-Bu) with high deuterium incorporation (92%-99%D).