Synthesis, X-ray Structure, and Catalytic Activity in the Hydrosilylation Process of Platinum Complexes Bearing Buchwald Ligands

The controlled reaction between [Pt 2 (DVTMS) 3 ], where DVTMS represents 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, and dialkylbiaryl phosphines (Buchwald ligands) 2-(di- tert -butylphosphino)biphenyl (JohnPhos, 1 ), 2-(dicyclohexylphosphino)biphenyl (CyJohnPhos, 2 ), 2-di- tert -butylphosphino-2′,4′,6′-triisopropylbiphenyl ( t BuXPhos, 3 ), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 4 ), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (SPhos, 5 ), 2-dicyclohexylphosphino-2′-( N,N -dimethylamino)biphenyl (DavePhos, 6 ), and 2-dicyclohexylphosphino-2′,4′,6′-trimethoxybiphenyl (MeOSPhos, 7 ) generates an efficient platinum catalyst of type [Pt(DVTMS)(L)] ( 1a – 7a ), where L represents the Buchwald ligand, applied for hydrosilylation of phenylacetylene by diphenylsilane. The X-ray crystal structure analysis of the obtained Pt catalysts showed the presence of specific Pt-aryl interactions with the phenyl group of the dialkylbiarylphosphine ligand in complex 1a, while the same effect was not observed for the related 2′,4′,6′-triisopropyl substituted aromatic ring in 3a . The evaluation of the steric parameters from X-ray diffraction analysis (XRD) showed the increase of the steric hindrances around the platinum atom improves the selectivity and the yield of the β(E) -product.