SYNTHESIS AND STEREOCHEMISTRY OF HOMOLEPTIC COBALT(III) COMPLEXES CONTAINING PYRIMIDINE-2-THIONATE AND ITS DERIVATIVES

A room-temperature reaction of Co(CH3CO2)(2) .4H2O with pyrimidine-2-t hione (Hpymt), or eight kinds of their derivatives (mole ratio=1:2.8-3 .0) in methanol, was carried out in air. It was found that the substit uent group at a 4-position in the pymt skeleton governs the product. T he pymt and its derivatives, having an alkyl or an amino group as the 4-substituent, gave tris-type cobalt(III) complexes mer-[Co(N-S)(3)] i n good yields. On the other hand, the 2-thiouracil derivatives, having an oxygen or a sulfur atom as the 4-substituent, produced only bis-ty pe cobalt(II) complexes [Co(N-S)(2)]. Such different ligand behavior c oncerns the different electronic structures of the pyrimidine rings. T he presence of three linkage isomers in mer- [Co(4-methyl-pymt)(3)] ha s been confirmed by Co-59 NMR spectroscopy, and an important role of t he CH rr attractive interaction has been found.