Cyclische diazastannylene : XIV. Das tetramere eines 1-oxa-2-sila-3-aza-4λ2-stannetidins mit S4-symmetrie

1,3-Di-t-butyl-2,2-dimethyl-1,3,2,4λ²-diazasilastannetidine (II) reacts with 3,4,5-trimethoxybenzaldehyde to yield 3,4,5-trimethoxybenzaldehyde-t-butylimine (IV) and the title compound 2,2-dimethyl-3-t-butyl-1,2,3,4λ²-oxasilazastannetidine (III). III combines four different Main Group elements in one ring and is tetrameric in solvents as well as in the tetragonal crystalline state. An X-ray structure determination (R-value: 0.037) reveals the tetramer to have crystallographic S₄-symmetry, and that the molecules of III interact via oxygen-tin bonds, which are perpendicular to the plane of the ring. The oxygen atoms thus adopt trigonal-planar coordination, while the tin atoms have grigonal-pyramidal environments. The tin atoms are substituted by three different ligands: one nitrogen and two chemically non-equivalent oxygen atoms (SnN: 209.5(9), SnO: 218.8(6), SnO′: 213.7(6) pm). Each tin atom thus represents a center of chirality, which due to symmetry must be divided into two R- and two S-enantiomers. As a consequence the whole tetrameric molecule belongs to the optically inactive “meso”-form.