New bis-o-benzosemiquinonato tin(IV) complexes

New bis-o-benzosemiquinonato tin(IV) complexes (3,6-SQ)2SnCl2, (3,6-SQ)2SnBr2 and (3,6-SQ)2SnPh2 (3,6-SQ is radical-anion 3,6-di-tert-butyl-o-benzosemiquinone) were synthesized by different methods. The reaction of tin(IV) catecholates (3,6-Cat)SnX2·2THF (Х = Cl, Br) with nitrogen(IV) oxide leads to EPR-active six-coordinated mono-o-benzosemiquinonato complexes of (3,6-SQ)SnX2(NO2)·THF type which undergo symmetrization to the corresponding diradical bis-o-benzosemiquinonato species (3,6-SQ)2SnX2. Diphenyltin(IV) catecholate (3,6-Cat)SnPh2·THF reacts with Br2, I2 and NO2 to give five-coordinated species (3,6-SQ)SnPh2X (X = Br, I, NO2) which transform to bis-(o-benzosemiquinonato)diphenyltin(IV) (3,6-SQ)2SnPh2. The molecular structures of (3,6-SQ)2SnBr2 and (3,6-SQ)2SnPh2 were determined by X-ray analysis.

New bis-o-benzosemiquinonato tin(IV) complexes (3,6-SQ)2SnCl2, (3,6-SQ)2SnBr2 and (3,6-SQ)2SnPh2 were synthesized by different methods such as the substitution reaction between tin(IV) halide and alkali metal o-semiquinonate (1:2); the oxidative addition of o-quinone to SnX2 in acetonitrile; oxidation of bis-catecholato tin(IV) with bromine; and disproportionation of mono-o-semiquinonato tin(IV) complexes of SQSnX3 type. It is shown that the solvent plays a crucial role in the possibility to synthesize such complexes. Molecular structures of (3,6-SQ)2SnBr2 and (3,6-SQ)2SnPh2 were determined by X-ray analysis.Figure optionsDownload as PowerPoint slideHighlights
► A series of new diradical bis-o-semiquinonato tin(IV) complexes were synthesized.
► Intermediate paramagnetic SQSnX3 were detected by EPR.
► Disproportionation of SQSnX3 complexes to SQ2SnX2 was applied for the first time.
► Molecular structures of complexes SQ2SnX2 were confirmed by X-ray analysis.