Platinum thiolate complexes supported by PBP and POCOP pincer ligands as efficient catalysts for the hydrosilylation of carbonyl compounds

Abstract

Diphosphino-boryl-based PBP pincer platinum thiolate complexes, [Pt(SR){B(NCH₂P^tBu₂)₂-1,2-C₆H₄}] (R = H, 1a; Ph, 1b), and benzene-based bisphosphinite POCOP pincer platinum thiolate complexes, [Pt(SR)(^tBu₂PO)₂-1,3-C₆H₃] (R = H, 2a; Ph, 2b), were prepared and fully characterized by multinuclear NMR, X-ray crystallography, HRMS and elemental analyses. The application of these complexes in the catalytic hydrosilylation of aldehydes and ketones was investigated. It was found that these platinum thiolate complexes are efficient catalysts for the hydrosilylation of aldehydes and ketones at 65–75 °C. Comparatively, the PBP complexes are more active than the corresponding POCOP complexes. Both phenylsilane and polymethylhydrosiloxane (PMHS) can be used as silyl reagents. The expected alcohols were obtained in good to excellent yields after the basic hydrolysis of the hydrosilylation products and many functional groups were not affected. With turnover frequencies (TOFs) of up to 67 000 h⁻¹, the present catalytic system represents the most effective platinum catalytic system for the hydrosilylation of carbonyl compounds. The reactions were likely catalysed by the in situ generated platinum hydride species.