π-π stacking motifs in dialkylbis{5-[(E)-2-aryldiazen-1-yl]-2-hydroxybenzoato}tin(IV) complexes

The diorganotin(IV) complexes of 5-[(E)-2-aryldiazen-1-yl]-2-hydroxybenzoic acid are of interest because of their structural diversity in the crystalline state and their interesting biological activity. The structures of dimethylbis{2-hydroxy-5-[(E)-2-(4-methylphenyl)diazen-1-yl]benzoato}tin(IV), [Sn(CH3)2(C14H11N2O3)2], and di-n-butylbis{2-hydroxy-5-[(E)-2-(4-methylphenyl)diazen-1-yl]benzoato}tin(IV) benzene hemisolvate, [Sn(C4H9)2(C14H11N2O3)2]·0.5C6H6, exhibit the usual skew-trapezoidal bipyramidal coordination geometry observed for related complexes of this class. Each structure has two independent molecules of the Sn(IV) complex in the asymmetric unit. In the dimethyltin structure, intermolecular O-H...O hydrogen bonds and a very weak Sn...O interaction link the independent molecules into dimers. The planar carboxylate ligands lend themselves to π-π stacking interactions and the diversity of supramolecular structural motifs formed by these interactions has been examined in detail for these two structures and four closely related analogues. While there are some recurring basic motifs amongst the observed stacking arrangements, such as dimers and step-like chains, variations through longitudinal slipping and inversion of the direction of the overlay add complexity. The π-π stacking motifs in the two title complexes are combinations of some of those observed in the other structures and are the most complex of the structures examined.