X-ray structural analysis and thermal decomposition of 1-Aza-2-silacyclobutanes: A new route to silanimine species

Article abstract of DOI:10.1021/ja00027a028

X-ray structural analysis of a 1-aza-2-silacyclobutane derivative, trans-1-(tert-butyldimethylsilyl)-2,2,4-triphenyl-3-isopropyl-1-aza-2- silacyclobutane (1), has been carried out for the first time. The 1-aza-2-silacyclobutane skeleton is of small angle strain, being nonplanar in relation to the nearly planar nitrogen atom, and has normal bond lengths, aside from the considerably long C-N bond. 1-Aza-2-silacyclobutanes undergo thermal decomposition around 200 °C in toluene to form a silanimine species, R₂S=NR, and an olefin. The formation of silanimine has been confirmed by quantitative formation of the dimer and a 1:1 adduct with Me₃SiOEt in the copyrolysis. The 3,4-trans and -cis isomers form trans and cis olefins, respectively. The decomposition rates obey the first-order rate law and decrease in the order 3,4-trans > 3,4-cis > 3,3,4-trisubstituted derivatives. The results are analyzed by the concerted [2_s + 2_a] cycloreversion mechanisms.