Azido derivatives of low-valent group 14 elements:: Synthesis, characterization, and electronic structure of [(n-Pr)2ATI]GeN3 and [(n-Pr)2ATI]SnN3 featuring heterobicyclic 10-π-electron ring systems

Treatment of THF solutions of [(n-Pr)(2)ATI]MCl (where [(n-Pr)(2)ATI](-) = N-(n-propyl)-2-(n-propylamino)-troponiminate; M = Ge and Sn) with sodium azide affords the compounds [(n-Pr)(2)ATI]MN3 in excellent yield. X-ray analyses revealed that these Ge(II) and Sn(II) compounds feature linear azide moieties and planar heterobicyclic C7N2M ring systems. Germanium and tin atoms adopt a pyramidal geometry. IR spectra of [(n-Pr)(2)ATI]GeN3 and [(n-Pr)(2)ATI]SnN3 display a upsilon(asym)(N-3) band at 2048 and 2039 cm(-1), respectively. DFT. calculations on the corresponding methyl-substituted species demonstrate that the geometrical and electronic structure of these two species are very similar, and the dominant canonical form of the metal-azide moiety is M-N-N=N. The tin system is, as expected, slightly more ionic. A comparative CASSCF/DFT study on the model system H-Sn-N-3 illustrates that the DFT approach is viable for the calculation of the structures of these species.