Theoretical investigation of organotin(IV) complexes of substituted benzohydroxamic acids

Abstract

The complexing abilities of para-substituted benzohydroxamates to the tin metal center of organotin(IV) ions have been investigated using DFT, since organotin(IV) compounds have been touted as promising anti-cancer agents. We have studied the coordination structures of Sn(IV) complexes (R2SnL2) with organoligands (R = Me, Et, n-Bu) and para-substituted benzohydroxamate ligands (L) so as to study the effect of electron withdrawing (Cl, F, NO2) and electron donating substituents (OCH3, NH2) in the ligand as well as in the alkyl group of the organotin compound. The structures of all the complexes are found to be intermediate between distorted octahedron and bicapped tetrahedron, in agreement with experiment. We have analyzed all the complexes in detail, using their Mayer bond orders, ESP charges, HOMO-LUMO plots and Fukui indices. Of all the complexes, the one having methyl as the alkyl group and the para-amino benzohydroxamate ligand is found to be the most stable. This is owing to the stronger ionic and covalent interaction of Sn(IV) with the para-amino benzohydroxamate ligand and methyl group, respectively.