Siloxane-supported organometallic compounds and their catalytic activities for the hydrosilylation of vinylsilanes and dienes

Abstract

Two different classes of silicone-modified ligands were prepared: nitrile derivatives, 4′-[3-(organosilyl)propoxy]biphenyl-4-carbonitrile R′₃SiC₃H₆OC₆H₄C₆H₄CN 2 (R′₃Si– = a: Me₃SiOSiMe₂–, b: (Me₃SiO)₂SiMe–, c: Me₃SiO(Me₂SiO)₃SiMe₂–, d: Me₃SiO(Me₂SiO)₂₅SiMe₂–); and, pyridine derivatives, isonicotinic acid 2-methoxy-4-[3-(organosilyl)propyl]phenyl ester R′₃SiC₃H₆Ph(OMe)OC(O)C₅H₄N 6. Compounds 2 and 6 were bound to Pd and Pt using ligand substitution reactions with organometallic precursors to give (R₃SiC₃H₆OC₆H₄C₆H₄CN)₂PdCl₂3, (R₃SiC₃H₆OC₆H₄C₆H₄CN)₂PtCl₂4 and (R₃SiC₃H₆C₆H₃(OMe)OC(O)C₅H₄N)PtCl₂(η²-1-octene) 8. The polydimethylsiloxane (PDMS)-supported Pt and Pd compounds 3d and 4d had excellent solubility in both organic solvents and polysiloxanes. All the Pt compounds exhibited good catalytic activity for hydrosilylation of vinylsilanes. The PDMS-supported Pd compound 3d also was effective catalyst for hydrosilylation of a diene, isoprene, with 1,1,1,3,3-pentamethyldisiloxane MM^H to produce the 1,4-adduct Me₃SiOSiMe₂CH₂CHCMeCH₂–H as a major product.