PREPARATION, SPECTROSCOPIC, MAGNETIC, CONDUCTOMETRIC AND POLAROGRAPHIC CHARACTERIZATION OF OBALT(II)-1-PHENYL-4,6-DIMETHYLPYRIMIDINE-2-THIONE COMPLEXES

The following coordination compounds of cobalt(II) with 1-phenyl-4,6-d imethylpyrimidine-2-thione: CoLX2 . n H2O (X = Cl-, n = 1; X = Br-, n = 2; X = SCN-, n = 0; X = NO3-, n = 4), Co2L3Cl4 . H2O, CoL2X2 (X = Br -, I-, SCN-, NO3-), CoL2X2 . n H2O . p Me2CO (X = I-, ClO4-, p = 2; X = NO-, n = 1, p = 0), CoL3(ClO4)2 . 0.5 Me2CO, Co2L5(NO3)4 and Co2L7X4 (X = Cl-, Br-, I-) have been isolated and characterized by chemical a nalyses, visible and IR spectra, paramagnetic susceptibility, conducti vity and polarographic measurements. Solid phase IR spectra suggest th at the heterocyclic ligand is almost always bonded through non-substit uted ring nitrogen and exocyclic sulfur atoms. The solid compounds wit h the exception of the [CoL(SCN)2]2, [CoL2(H2O)2][CoCl4] and [CoL3][Co Cl4] . H2O have originally a distorted octahedral geometry. By grindin g the solid [CoL2(SCN)2], Co2L7Cl4 and all the bromide complexes the c obalt(II) coordination undergo octahedral --> tetrahedral geometry cha nge. Spectral evidences and polarographic results in DMF solution have shown that for these and [CoL(SCN)2]2, [CoL2(H2O)2][CoCl4] and [CoL3] [CoCl4] . H2O complexes, the solvolysis gives rise to equilibria betwe en tetrahedral anionic [CoX4]2- (X = SCN-, Cl-), [COX3(DMF)]- (X = SCN -, Cl-, Br-) and some possible [Co(DMF)6]2+, [CoX(DMF)5]+. [CoXL(DMF)4 ]+, [CoL(DMF)5]2+ (L = N-monodentate ligand) cationic octahedral speci es. Polarographic data for perchlorate complexes and for [Co(DMF)6](Cl O4)2-L system at increasing ligand concentration have shown that in DM F solution the solvated ions (Co(DMF)6]2+ are the prevailing species a nd that the thiopyrimidine-containing species [CoL(DMF)5]2+ (beta = 3. 78 . 10(5)) and (CoL2(DMF)4]2+ (beta = 9.59 . 10(7)) can be formed onl y in presence or a large excess of the free ligand.