212 Battistuzzi et al. Transition Met. Chem., 20, 212 219 (1995) Synthesis, spectroscopic, magnetic, conductometric and electro- chemical investigations of nickel(II)-l-phenyl-4,6-dimethylpyri- midine-2-thione complexes Gianantonio Battistuzzi, Marco Borsari, Daniela Dallari and Raffaele Battistuzzi* Department of Chemistry, University of Modena, 41100 Modena, Italy Summary Tris-, bis- and mono-ligand complexes of Ni n with 1- phenyl-4,6-dimethylpyrimidine-2-thione (L) having the general formulae NiL3X2.2H20 (X=C1Og, BF2), NiL2X 2 (X = CI-, Br-, SCN- or NO3), NiL2X 2.EtOAc (X = Br- or I-), NiL2X2.HzO.EtOH (X = I- or NO3) and NiLC12.3H20, were synthesized and their structures deduced from i.r. and electronic spectra, and magnetic properties. The combined evidence is consistent with an octahedral coordination for the Ni n ion in all the com- plexes, with the ligand acting as a bidentate N,S-chelating agent. Spectral evidence, conductivity data and electro- chemical results in DMF solution show that the complexes undergo solvolysis readily. Polarographic and c.v. data for the [NiL3I(C10,)z.2H20 complex and for the [Ni- (DMF)6](C1Og)2-L systems, at increasing ligand con- centrations, have shown that in DMF solution the [Ni(DMF)6] 2§ cation prevails and that the thiopyri- midine-containing species, [NiL(DMF)5] z§ (L =N- monodentate ligand) (fl = 2.42 x 106), can be formed only in the presence of a large excess of free ligand. Introduction Among pyrimidine derivatives, thiopyrimidines have been the subject of extensive chemical and physico-chemical investigations~l.2) due to their close relationship to sulphur analogues of the DNA bases and their application as inhibitors ~3), anti-metabolites <4) and bacteriostatic <5'6) agents. Since metal complex formation ~7) is likely to be impli- cated in the biological activity of these molecules, the coordination chemistry of thiopyrimidines is currently attracting a wide interest. As neutral ligands, these heterocyclic thiones are potentially ambidentate or multifunctional donors with either the exocyclic sulphur and heterocyclic non-substi- tuted nitrogen atoms available for coordination. Typical bonding modes, including N- and S-donation, and N,S- chelation or bridging, have been spectroscopically inferred and sometimes structurally established (8-24). Being particularly interested in the coordinating ability of these ligands, this paper reports on the synthesis and physico-chemical characterization of nickel(II) complexes with 1-phenyl-4,6-dimethylpyrimidine-2-thione. All the complexes have been characterized by elemental analysis, magnetic susceptibility, electronic and i.r. spectroscopy, and conductivity; the perchlorato-derivative has also been investigated by electrochemical measurements. Experimental The 1-phenyl-4,6-dimethylpyrimidine-2-thione (L) was prepared by a previously reported method ~25). The [Ni- * Author to whom all correspondenceshould be directed. (DMF)6 ] (C104) 2 compound used for electrochemical and spectral electronic measurements was obtained by dis- solving 6 mmol of Ni(C104) 2.6H20 in 4 cm 3 of DMF and 8 cm 3 of HC(OEt)3 (TEOF) as dehydrating agent. On cooling at 0 ~ the solution afforded [-Ni(DMF)6 ] (C104) 2 as green crystals. (Found: C, 30.9; H, 6.1; N, 12.0; Ni, 8.4; [Ni(DMF)6](C104) 2 calcd.: C, 31.0; H, 6.1; N, 12.1; Ni, 8.4%.) Preparation of NiL3X2"2H20 (X = ClO 4 or BF2, ) The compounds were obtained by dissolving, with stirring at 40-50~ the solid ligand (4.5mmol) in an EtOH solution (25cm 3) of the corresponding hydrated salt (1.5mmol). After two days the solid compounds were filtered and washed with EtOH and Et20. Preparation of NiL2(N03) 2 The compound was obtained as a green-yellow solid dissolving under stirring at room temperature, solid L (4 mmol) in a EtOH (5 cm 3) and TEOF (6cm 3) solution containing Ni(NO3) 2.6H20 (2 mmol). Preparation of NiL2(NO3)2"H20"EtOH This complex was prepared in EtOH as the above perchlorato and fluoroborato complexes using a 1:2 metal:ligand molar ratio. With a low concentration at room temperature the dark green solution gave a pale green product. Preparation of NiL2C12, NiL2X2"EtOAc ( X = Br- or I- ) The appropriate hydrated nickel(II),salt (2mmol) was dissolved in an absolute EtOH (10cm 3) and EtOAc (20 cm 3) solution containing 2 cm 3 of TEOF as dehydrating agent. The solutions were allowed to stand at room temperature for one day in stoppered flasks. By adding solid L (4 mmol) with stirring (3 h) at room temperature, the complexes began to precipitate. After standing over- night the compounds were filtered, and then washed with EtOAc and Et20. Preparation of NiLCI2"3H20, NiLzBr 2 and NiL212"H20"EtOH Solid L (4mmol) was added slowly with stirring to a solution (20cm 3) of the corresponding hydrated salt (4 mmol) in EtOH-EtOAc (1:3 v/v), the resulting mixtures, after heating under reflux for 4 h, were kept at room temperature for two days. After filtration the products were washed with EtOAc and Et20. 0340-4285 9 1995 Chapman& Hall