Synthesis, structrural characterization and biological studies of orgatin (iv) detervatives with carbohydrazone-bis(salicylaldehyde) (H,CBS) : x-ray crystal structure of 'Bu, Sn (H2CBS)

Abstract

An interesting series of new organotin (IV) complexes has been synthesized by the reaction of RnSnCl4-n (n = 1, 2) with carbohydrazone-bis(salicylaldehyde) (H4CBS) ligand in the presence of base and refluxing in 1:2:1 mole ratio (metal:base:ligand). All organotin(IV) complexes (2-7) have been characterized by the different physico-chemical techniques of molar conductivity measurements, elemental analysis, UV-visible, IR and 1H NMR spectral studies. All origanotin (IV) complexes (2-7) are non electrolytic in nature. Among them, di-tert-butyltin(IV) complex (4) is also characterized by X-ray crystallography diffraction analyses. In the solid state, the carbohydrazone ligand (1) exists as the keto tautomer but in solution in the presence of base and organotin(IV) chloride(s), it is converted to the enol tautomer and coordinated to the tin(IV) atom in its deprotonated enolate form. X-ray crystallographic analysis shows that the di-tert-butyltin(IV) complex tert-Bu2Sn(H2CBS) (4), is five-coordinated and has a distorted trigonal-bipyramidal geometry with the ligand coordinated to the tin(IV) as a tridentate dinegative fashion through its phenolic-O, enolic-O and imine-N atoms. The general bond length order is oxo < phenolato < enolato. The Sn-O (enolato) bond is longer than Sn-O (phenolato) bond by ca. 0.08 A and is identical with Sn-O (carboxylate) bond. The crystal structure of tert-Bu2Sn(H2CBS) (4) is monoclinic with space group C2/c with a = 34.365(8) A, b = 8.7304(19) A, c = 17.183(4) A, alpha = 90.011(4) degree, beta = 108.168(5) degree, gamma = 89.889(6) degree, V = 4898.2(19) A3, Z = 8 and Dcalc = 1.435 Mg/m3. The IR and 1H NMR data are consistent with all the organotin(IV) derivatives having similar geometry. The ligand [H4CBS, (1)] and its organotin(IV) complexes were tested against several bacteria and found to show a certain degree of biological activity.