Synthesis and characterisation of [tris(1,3-dithiole-2-thione-4,5-dithiolato)stannate]2-, [Q]2[Sn(dmit)3], [tris(1,3-dithiole-2-one-4,5-dithiolato)stannate]2-, [Q]2[Sn(dmio)3] and [tris(1,3-dithiole-2-thione-4,5-selenolato)stannate]2-, [Q]2[Sn(dsit)3], complexes -: Analysis of the structural variations of the [Sn(dmit)3]2- and [Sn(dmio)3]2- dianions

[Tris(1,3-dithiole-2-thione-4,5-dithiolato)stannate](2-), [Q](2)[Sn(C3S5)(3)], [tris(1,3-dithiole-2-one-4,5-dithiolato)stannate](2-), [Q](2)[Sn(C3S4O)(3)], and [tris(1,3-dithiole-2-thione-4,5-diselenolato)stannate](2-) [Q](2)[Sn(C3S3Se2)(3)], complexes, have been synthesised and characterised. Crystal structure determinations of [Q](2)[Sn(C3S5)(3)] (Q = 1,4-dimethylpyridinium, monoclinic and orthorhombic forms; NMe4, NEt4, and PPh4) and [NEt4](2)[Sn(C3S4O)(3)] revealed variations in the overall dianion structures. The geometry about tin in each case is essentially octahedral with the chelate bite angles in the range 80.7(5)-87.45(4)degrees: the range of Sn-S distances is 2.5207(18)-2.571(17) Angstrom. A statistical analysis, carried out on the crystal structure data for the six complexes, indicated that the most critical factors in controlling the overall shape of the dianion were the distances of the Sn atom from the dithiolate ligand planes [Sn-OOP]. Interanionic S ... S interactions, within the sum of the van der Waals' radii for two S atoms, are affected by the size of the cation, Q; the secondary connectivity is 3-dimensional for the smallest cations, Q = 1,4-dimethylpyridinium and NMe4, in chains for the somewhat larger cation, NEt4 and is absent for the still larger, PPh4 cation. (C) 1999 Elsevier Science Ltd. All rights reserved.