Preparation, spectroscopic characterization, and deprotonation reactions of Si(NHR)(4) (R = i-Pr, t-Bu, p-tolyl) - EPR identification of persistent radicals formed by oxidation of polyimidosilicates

Treatment of Cl2Si(NH-t-Bu)(2) (6a) with t-BuNH2 in boiling toluene yields trisamino(chloro)silane ClSi(NH-t-Bu)(3) (7); formation of the tetraaminosilane Si(NH-t-Bu)(4) is not observed. The reaction of SiCl4 with 4 equiv. of LiNHR produces the corresponding tetraaminosilanes Si(NHR)(4) (2a, R = i-Pr; 2b, R = t-Bu; 2c, R = p-tol) in good yields. When the sterically demanding adamantyl derivative LiHNAd is employed, only disubstitution occurs to form Cl2Si(NHAd)(2) (6b). Oxidation of the dimeric imidosilicates {Li-3[Si(NR)(3)(NHR)]center dot THF}(2) (3a, R = i-Pr; 3b, R = t-Bu) with 1 mol of iodine produces the persistent radicals {Li-2[Si(NR)(3)(NHR)]center dot LiI center dot 3THF}(.), which, on the basis of EPR spectra, exist as SiN3Li3I cubes in solution. The spirocyclic tetraimidosilicate monoanion radical {[(THF)(2)Li(mu-Nnaph)(2)Si(mu-Nnaph)(2)Li(THF)(2)]} - (10) is formed upon oxidation of the tetralithiated species {Li-4[Si(Nnaph)(4)]center dot 4Et(2)O} (1) and {[Li(12-crown-4)](2)[(Et2O)(2)Li(mu-Nnaph)(2)Si(mu-Nnaph)(2)Li(Et2O)(2)]} (8) with iodine. The spectroscopic characterization of hexa(amino)disiloxane (t-BuNH)(3)SiOSi(NH-t-Bu)(3) (14) formed from the reaction of Cl3SiOSiCl3 with 6 equiv. of LiNH-t-Bu is discussed.