ABSTRACT A series of tin(IV) derivatives of 1,6-bis (pyrimidin-2-ylthio)hexane (pth) have been investigated by Mössbauer spectroscopy to elucidate aspects concerning structure and bonding in solid state. The SnClPh 3 (1) and SnCl 2 Ph 2 (2) derivatives have 5- and 6-coordinate metal centres respectively. The phenyl groups of the diphenyltin(IV) derivative are in cis configuration as revealed by its isomer shift and quadrupole splitting as well as by the estimated C−Sn−C bond angle. The spectrum of the SnCl 3 Ph (3) derivative reveals three phases in solid state as a mixture of chemicals having tetrahedral and octahedral geometries. The magnitude of both isomer shift and quadrupole splitting of SnCl 3 Ph (3a) is smaller than the other two sites (3b and 3c) as a result of dephenylation of the metal precursor. The SnCl 4 (4) derivative has an octahedral geometry with the ligand bonded through the pyrimidyl moiety of pth. This polydentate compound is a weak σ-donor, in comparison to pyrazin, and it is acting as a bridging-bidentate as well as bridging- tetradentate ligand upon coordination. The ρ value (QS/IS ratio) of all organotin(IV) derivatives supports coordination number higher than four, except the compound from the 3c site. KEYWORDS: organotin(IV), 1,6-bis(pyrimidin-2- ylthio)hexane, Mössbauer spectroscopy, coordination chemistry Characterization of organotin(IV) derivatives of 1,6-bis(pyrimidin-2-ylthio)hexane by Mössbauer spectroscopy INTRODUCTION Mössbauer spectroscopy is an acknowledged technique for structural elucidation of organotin compounds in Coordination Chemistry. This methodology is significant because it gives information about the stereochemistry of substituent groups beyond the geometrical pattern surrounding the tin(IV) atom. Several organotin derivatives of N,S-bidentate ligands have been characterized by Mössbauer spectroscopy as well as by crystallography studies [1-5]. These compounds show a variety of structural arrangements with the metal bonded to either nitrogen or sulphur atom or both coordinate sites [1, 6-8]. Organotin(IV) derivatives of 2- mercaptobenzothiazole, 5-chloro-2-mercaptoben- zothiazole and 2-mercaptobenzoxazole have been characterized as having 5- and 6-coordinate metal centres [4]. These organotin(IV)-benzothiazole and benzoxazole derivatives are isomeric compounds having different Sn-N bond distances which are linked to the decreasing temperature at which the Mössbauer experiment was carried out. The polydentate character of 1,6-bis(pyrimidin-2-ylthio) hexane have given us motivation to work with this ligand in the Coordination Chemistry field [9]. Following our interest in tin chemistry, a series of organotin(IV) and SnCl 4 derivatives of 1,6-bis (pyrimidin-2-ylthio)alkanes was prepared in our laboratory and characterized by infrared and NMR spectroscopy [10]. However, a few of the tin(IV)- 1,6-bis(pyrimidin-2-ylthio)hexane derivatives were not described by 119 Sn NMR and have been chosen 1 Laboratório de Complexos Bioativos, Departamento de Química, CCE / UFV, Av. P. H Rolfs s/n, Viçosa - MG, 36570-000, Brasil, 2 Laboratório de Física Aplicada, CDTN / CNEN, Av. A. Carlos, 6627, Belo Horizonte - MG, 31270-901, Brasil Rafael César Russo Chagas 1 , José Roberto da Silveira Maia 1, * , José Domingos Ardisson 2 and Alexandre Gurgel 1 *Corresponding author jrsmaia@ufv.br Trends in Applied Spectroscopy Vol. 9, 2012