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

摘要

Treatment of Cl_2Si(NH-t-Bu)_2 (6a) with t-BuNH_2 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 SiCl_4 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 Cl_2Si(NHAd)_2 (6b).Oxidation of the dimeric imidosilicates {Li_3[Si(NR)_3(NHR)] centre dot THF}_2 (3a,R = i-Pr;3b,R = f-Bu) with 1 mol of iodine produces the persistent radicals {Li_2[Si(NR)_3(NHR)] centre dot LiI centre dot 3THF}~(centre dot),which,on the basis of EPR spectra,exist as SiN_3Li_3I cubes in solution.The spirocyclic tetraimidosilicate monoanion radical {[(THF)_2Li(mu-Nnaph)_2Si(mu-Nnaph)_2Li(THF)_2]}~(- centre dot ) (10) is formed upon oxidation of the tetralithiated species {Li_4[Si(Nnaph)_4] centre dot 4Et_2O} (1) and {[Li(12-crown-4)]_2[(Et_2O)__2Li(mu-Nnaph)_2Si(mu-Nnaph)_2Li(Et_2O)_2]) (8) with iodine.The spectroscopic characterization of hexa(amino)disiloxane (t-BuNH)_3SiOSi(NH-t-Bu)_3 (14) formed from the reaction of Cl_3SiOSiCl_3 with 6 equiv.of LiNH-t-Bu is discussed.