Alkoxistannate, II [1] Tri(tert-butoxi)alkalistannate(II): Darstellung und Strukturen / Alkoxistannate, II [1] Tri(tert-butoxi)alkalistannates(II): Synthesis and Structures

Abstract

Tri(tert-butoxi)alkalistannates (M(O'Bu)₃Sn, M = Li, Na, K, Rb, Cs) are obtained by reaction of alkali-fert-butanolates with tindi-tert-butoxide. If M equals Li or Na (1, 2) molecular com pounds are formed, which consist of two formula units. 1 crystallizes in a m onoclinic cell (space group P2₁/c; a = 966.5(3), b = 1819(1), c = 1014(1) pm. β = 107.1(1)°, Z = 4); 2 is triclinic (space group P1̄; a = 1041(1), b = 2046(1), c = 1033(1) pm. a = 92.3(2), β = 118.6(1), y = 108.3(3)° and Z = 4). The molecules 1 and 2 are closely related structurally despite their different space groups. The common structural feature is a Sn₂O₆M₂ cage, which is built of two seco-norcubane Sn₂M₂O , units, sharing a M₂O₂ four-membered ring. Characteristic distances are: 1: Sn-O = 209.3, L i-O = 193.0 and 211.6 pm, 2: Sn-O = 210.5, Na-O = 227.4 and 240.7 pm. The tert/-butoxistannates of K, Rb and Cs (3, 4, 5) all crystallize in the orthorhombic crystal system, space group P2₁2₁2₁ (cell constants of 3: a = 1907(1), b - 1060(1), c - 896(1) pm, Z = 4). Contrary to the lithium- and sodium derivates 3, 4 and 5 have a polymeric structure. The one dimensional polymer consists of distorted trigonal bipyramidal SnO₃M “cages” (substituted at the oxygen atoms by tertbutyl groups), which align in a way to allow the metal atom to have a five-fold oxygen coordination. The tin atoms have trigonal pyramidal coordination. While the tin-oxygen bond lengths are essentially invariant (average value 206.7 pm ), the potassium-oxygen distances range from 256.4(5) pm to 318.8(6) pm