SYNTHESIS AND CHARACTERIZATION OF CIS-TETRACHLOROBIS(PYRIDINE)PLATINUM(IV) AND TRANS-TETRACHLOROBIS(PYRIDINE)PLATINUM(IV)

[Na(15-cr-5)](2)[PtCl6]. 2H(2)O reacts with pyridine in water as solve nt to give cb-[PtCl4(py)(2)] (1) and in MeCN, DMF or in CH2Cl2 to give trans-[PtCl4(py)(2)] (2). The substitution reaction can be accelerate d by irradiation with visible light. 1 isomerizes to give 2 in DMSO, D MF and MeCN as well as in solid state at 503 K. 1 and 2 were thoroughl y characterized IR and Raman spectroscopically. The molecular structur e of the trans isomer 2 was also established by X-ray structure analys is (monoclinic, C2/m, a = 14.143(5), b = 7.171(3), c = 7.199(3) Angstr om, beta = 116.42(4)degrees, Z = 2, R-1 = 0.0331, wR(2) = 0.0727). 2 h as nearly D-2h symmetry with two trans standing pyridine ligands lying in a plane. According to quantum chemical calculations, 2 (D-2h symme try) is more stable (48.28 kJ/mol) than 1(C-2v symmetry).