Synthesis and spectral properties of group V heteroatom-permethylcyclopolysilanes, MeN(SiMe 2) n and MeP(SiMe 2) n

Abstract

The permethylazacyclopolysilanes (MeN(SiMe 2) n , n =4, 5) and permethylphosphacyclopolysilanes (MeP(SiMe 2) n , n =4, 5, 6) were prepared by ring closure reactions of dichloropermethylsilanes (Cl(Me 2Si) n Cl, n =4–6) with monomethylamine and dilithium methylphosphide respectively. The permethylazacyclopolysilane MeN(SiMe 2) 6 was prepared by pyrolysis of Me(H)N(SiMe 2) 6-N(H)Me which was the initial product from the reaction of 1,6-dichlorododecamethylhexasilane with monomethylamine. Ultraviolet spectra were obtained for the nitrogen and phosphorus heterocyclic compounds and the results are compared with the data for linear and cyclic permethylpolysilanes. The 1H, 13C, 31P and 29Si NMR parameters for the permethylphosphacyclopolysilanes are reported and discussed in terms of electronic and molecular structure variations with ring size.