Mono-o-semiquinonato mixed-halogenato tin(IV) complexes: EPR spectroscopic and X-ray investigations

A series of new mono-semiquinonato tin(IV) complexes of (3,6-DBSQ)SnHal3·THF type (3,6-DBSQ is radical-anion 3,6-di-tert-butyl-o-benzosemiquinone) were synthesized by the oxidation of catecholates (3,6-DBCat)SnHal2 (Hal = Cl (1), Br (2)) with halogens. The following complexes were prepared and characterized in details: (3,6-DBSQ)SnCl2Br·THF (3), (3,6-DBSQ)SnCl2I·THF (4), (3,6-DBSQ)SnBr3·THF (5), (3,6-DBSQ)SnBr2I·THF (6). The EPR spectroscopy studies have shown that complexes form geometric isomers with different halide ligand at the apical position. The reaction of complexes 3 and 5 with tetraethylammonium bromide yields new compounds [Et4N]+[(3,6-DBSQ)SnCl2Br2]− (7) and [Et4N]+[(3,6-DBSQ)SnBr4]− (8) containing complex radical-anion. In the case of complex 7, there are three isomers were found: with Cl,Cl (A), Cl,Br (B) and Br,Br (C) atoms in the apical sites. The molecular structures of 3 and 5 were confirmed by X-ray analysis.