cis–trans Isomerism in some octahedral diaryltin(IV) dichloride complexes with bidentate ligands

A series of 24 octahedral organotin complexes (including 16 new compounds) of general formula Sn(C6H4Z-4)2Cl2.L2(Z = OMe,Me,But,H,F,or CF3;L = dimethyl sulphoxide or L2= 2,2′-bipyridyl, 4,4′-dimethyl-2,2′-bipyridyl, 1,10-phenanthroline, or 3,4,7,8-tetramethylphenanthroline) has been prepared under a variety of experimental conditions. The optimum conditions for obtaining either cis or trans isomeric forms are indicated. The 119Sn Mössbauer parameters for all the complexes have been determined and used in each case to assign either cis or trans configurations. The isolation of pure cis and trans isomeric pairs has been achieved in four cases where Z = OMe, CF3, or H and L2= 4,4′-dimethyl-2,2′-bipyridyl and Z = OMe and L2= 2,2′-bipyridyl. The effects of both structure and solvent on relative cis–trans stabilities are discussed. Infrared spectra have been recorded for the cis–trans isomeric pairs and substantial differences in the aromatic substitution pattern are indicated.