Cyclische Diazastannylene. XV [1]. Charakterisierung einer instabilen Zwischenstufe: 1,3-Di-tert-butyl-2,2-dimethyl-4-tert-butylammonium-1,3,2,4λ3-diazasilastannatetidin

Cyclic Diazastannylenes. XV. Characterization of an Unstable Intermediate: 1,3-Di-tert-butyl-2,2-dimethyl-4-tert-butyl-ammonium-1,3,2,4λ³-diazasilastannatetidine The primary step in the reaction of 1, 3-di-tert-butyl-2,2-dimethyl-1,3,2,4λ²-diazasilastannetidine ( 1 ) with tert-butylamine is the formation of the Lewis-acid-base adduct 5 . In 5 the electrophilic tin atom of 1 is coordinated by the nucleophilic nitrogen atom of the tert-butylamine. 5 crystallizes below ?110°C in a triclinic cell with dimensions (conventional cell see Table 2): a = 1034(4), b = 1492(5), c = 654(3) pm, α= 89.9(3), β = 96.8(3), γ = 91.6(3)°, Z = 2. Above ?110°C the triclinic phase of 5 can be transformed to a monoclinic one (space group P2₁/m) with cell dimensions a = 1048(3), b = 1513(4), c = 654(2) pm, β = 96.9(3)°, Z = 2. An X-ray structural investigation of the latter phase reveals the adduct 5 to have C_S(m)-point symmetry. Important molecular dimensions are the rather long donor bond Sn→N of 242(3) pm, the Sn? N distances within the ring of 211(2) pm and the trigonal pyramidal coordination of the tin atom with mean N? Sn? N angles of 82.3°. The nitrogen atoms of the ring are pyramidal disturbing the planarity of the ring by a bending of 12°. This geometry is due to intramolecular N? H contacts (～290 pm) of the amino-hydrogen atoms with the nitrogen atoms of the ring. Some conclusions for the reaction path can be drawn from the structure of 5 .