Synthesis and characterization of organotin complexes with 2-mercaptopyridine derivatives

By reaction of diphenyltin(IV) chloride and triphenyltin(IV) hydroxide with esters of the 2-mercaptopyridine-5-carboxylic acid (OVERBAR)NH(CS)CHCHC(COOR)(/OVERBAR)CH (HTNME, R = methyl; HTNEE, R = ethyl; HTNIPE, R = isopropyl) the complexes Ph3Sn(L), Ph2SnCI(L) (L = TNME, TNEE and TNIPE) and Ph2Sn(TNEE)2 have been prepared and characterized by IR, NMR and Mossbauer spectroscopies. Moreover, the Ph2SnCl2/2-mercaptopyridine (HMP) system has been found to yield either the Ph2SnCl2(HMP)2 adduct or the Ph2SnCl(MP) complex. The structures of Ph2SnCl(TNEE) and Ph2SnCl(MP) have been determined by X-ray single-crystal diffraction studies. The two structures are similar. Both ligands behave as bidentate chelating groups forming a four-membered ring with an identical small N(SINGLE BOND)Sn(SINGLE BOND)S bite angle of 63.7°. The tin atom is pentacoordinated, presenting a severely distorted trigonal bipyramidal geometry with apical Cl(SINGLE BOND)Sn(SINGLE BOND)N angles of 155.0(2)° [Ph2SnCl(TNEE)] and 155.7(7)° [Ph2SnCl(MP)] and equatorial C(SINGLE BOND)Sn(SINGLE BOND)C angles of 114.9(2)° and 125.0(3)° respectively. On the basis of 119Sn Mossbauer data, all the complexes should present analogous structures except Ph2Sn(TNEE)2 and Ph2SnCl2(HMP)2, for which an octahedral coordination geometry with a trans arrangement of the phenyl groups can be proposed. The effect of dimethyl sulphoxide on Ph2SnCl(L) and Ph2SnCl2(HMP)2 is also discussed.