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 Cl 2 Si(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 2 Si(NHAd) 2 (6b). Oxidation of the dimeric imidosilicates {Li 3 [Si(NR) 3 (NHR)]·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)]·LiI·3THF} · , which, on the basis of EPR spectra, exist as SiN 3 Li 3 I cubes in solution. The spirocyclic tetraimidosilicate monoanion radical {[(THF) 2 Li(µ-Nnaph) 2 Si(µ-Nnaph) 2 Li(THF) 2 ]} –· (10) is formed upon oxidation of the tetralithiated species {Li 4 [Si(Nnaph) 4 ]·4Et 2 O} (1) and {[Li(12-crown-4)] 2 [(Et 2 O) 2 Li(µ-Nnaph) 2 Si(µ-Nnaph) 2 Li(Et 2 O) 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 Cl 3 SiOSiCl 3 with 6 equiv. of LiNH-t-Bu is discussed. Key words: imido ligands, silicate, radicals, EPR spectra, lithium.