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

The controlled reaction between [Pt2(DVTMS)3], where DVTMS represents 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, and dialkylbiaryl phosphines (Buchwald ligands) 2-(di-tertb u t y l p h o s p h i n o ) b i p h e n y l (John P h o s, 1), 2(dicyclohexylphosphino)biphenyl (CyJohnPhos, 2), 2-di-tert-butylphosphino-2 ',4 ',6 '-triisopropylbiphenyl (tBuXPhos, 3), 2-dicyclohexylphosphino-2 ',4 ',6 '-triisopropylbiphenyl (XPhos, 4), 2dicyclohexylphosphino-2 ',6 '-dimethoxybiphenyl (SPhos, 5), 2dicyclohexylphosphino-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 beta(E)-product.