Crystal structures of [(IMe(2)SnOSnMe(2)OEt)(2)] and [{(PrCO2)Me(2)SnOSnMe(2)(O2CPr)(2)}(2)]

Centrosymmetric [(mu-Me(2)Sn)(2)(mu-IMe(2)Sn)(2)(mu-OEt)(2)(mu(3)-O-2)] (3), obtained from 1,2:5,6-di-O-isopropylidene-3-C-iododimethylstannyl-alpha-D- allofuranoside on solvolysis in aqueous EtOH, has a ladder structure, made up of three fused Sn2O2 rings. There are two pairs of distinct five-coordinate tin centres in 3. The ethoxide ligands bridge the two distinct Sn centres essentially symmetrically [Sn(1)-O(2) and Sn(2)-O(2) = 2.171(6) and 2.178(6) Angstrom]. In centrosymmetric, solid [mu-Me(2)Sn)(2){mu-PrCO2)Me(2)Sn}(2)(mu-PrCO2)(2) (mu(3)-O)(2)] (4) obtained from Me(2)SnCl(2) and CH3CH2CH2CO2H in H2O, there are also two distinct tin sites. The Sn(1) atoms are bonded to 2 C and 4 O atoms, with tin-oxygen bond lengths between 2.027(6) and 2.712(8) Angstrom. The immediate coordination sphere of Sn(2) consists of 2 C and 3 O [Sn(2)-O bond lengths between 2.020(5) and 2.216(11) Angstrom]; there are also intramolecular, Sn(2)-O(5) [2.990(12)], and intermolecular, Sn(2)-O(5(ii)) [3.109(11) Angstrom] contacts. The core of the structure of 4 is a five rung ladder, made up of Sn2O2 rings, with additionally two side rings, composed of Sn2O3C units. Copyright (C) 1996 Elsevier Science Ltd