Palladium-Catalyzed Insertion of 1,2- and 1,4-Quinones into Si−Si Bonds and Its Application to the Modification of Si−Si-Bond-Containing Polymers

Me 3 SiSiMe 3 reacted with 1,2- and 1,4-quinones ( p -benzoquinone ( 2a ), its derivatives, 1,2- and 1,4-naphthoquinone, 9,10-phenanthraquinone ( 2f ), 9,10-anthraquinone) in the presence of palladium catalysts to give the corresponding bis(trimethylsiloxy) aromatics in excellent to moderate yields. Active palladium catalysts were PdCl 2 L 2 (L = tertiary phosphine) and Pd(dibenzylideneacetone) 2 −2P(OCH 2 ) 3 CEt, among which PdCl 2 (PEt 3 ) 2 was in general the most efficient. A 1,2-disilacyclohexane cleanly underwent the reaction with 2f to form a 10-membered cyclic adduct. The reaction of Me 3 SiSiMe 2 SiMe 3 with 2a also afforded p -(Me 3 SiO) 2 C 6 H 4, via formal extrusion of a silylene unit. Treatment of cis -(PhMe 2 Si) 2 Pt(PMe 2 Ph) 2 with 2a gave p -(PhMe 2 SiO) 2 C 6 H 4, indicative of the involvement of bis(silyl)palladium species in the catalysis. Quinones 2a, f smoothly underwent the palladium-catalyzed insertion into the Si−Si bonds of (SiMePhSiMePh- p -C 6 H 4 ) n ( 9a ), (SiMe 2 SiMe 2 CH 2 CH 2 ) n, and (SiMe 2 SiMe 2 O) n to give partially or exhaustively modified polymers with arylenedioxy units incorporated in the backbones. A polysilane, (SiMe 2 ) n, also reacted with 2a to provide a polymer with −SiMe 2 −O− p -C 6 H 4 −O− linkages. Upon UV irradiation, a partially modified polymer obtained from 9a and 2f showed a smaller extent of decrease in molecular weight than did the original polymer. Modification with 2f improved the thermal stability of 9a in thermogravimetric analysis.