176104-76-0Relevant articles and documents
Synthesis of organosilicon macrocycles. Palladium-catalyzed ring-enlargement oligomerization of cyclic disilanes via Si-Si σ-bond metathesis
Suginome, Michinori,Oike, Hideaki,Shuff, Philippa H.,Ito, Yoshihiko
, p. 2170 - 2178 (2008/10/08)
Bis(tert-alkyl isocyanide)palladium(0) complexes catalyzed a ring-enlargement oligomerization of 1,1,2,2-tetramethyl-1,2-disilacyclopentane through Si-Si σ-bond metathesis to give cyclic oligomers up to the 40-membered octamer. The cyclic structure of the tetramer was established by the single-crystal X-ray diffraction method, which showed that the four Si-Si bonds of the tetramer were in a close to parallel arrangement. Reactivities of the dimer, trimer, and tetramer in the presence of bis(tert-butyl isocyanide)palladium(0) revealed that the present Si-Si σ-bond metathesis proceeded reversibly, in which the -Me2Si(CH2)3SiMe2-unit of the disilacyclopentane was successively inserted into the Si-Si bond of the oligomer to give higher oligomers. The intermediary 6-membered bis(organosilyl)bis(tert-alkyl isocyanide)palladium complex, which arose from oxidative addition of the disilacyclopentane onto bis(tert-alkyl isocyanide)palladium(0), was isolated and characterized by the single-crystal X-ray method. The insertion of the -Me2Si(CH2)3SiMe2- unit also occurred with linear disilanes and digermane to give linear oligomers. The cyclic trimer and tetramer reacted with 2,6-diisopropylphenyl isocyanide in the presence of Pd(OAc)2 to afford an 18-membered-ring triimine and 24-membered-ring tetraimine, respectively, in which the isocyanides were inserted into all the Si-Si linkages. Oxidation of the cyclic oligomers with trimethylamine oxide gave the corresponding cyclic oligo(disiloxane) species in quantitative yields. Unexpected polymerization of the disilacyclopentane occurred in the presence of the (η5-cyclopentadienyl)(η3-allyl)palladium(II) catalyst to give poly(Me2Si(CH2)3SiMe2) compounds with high molecular weights.
