摘要:
Di(amine)di(chloro)platinum(II) complexes react in aqueous acid solution to form an equilibrium mixture L2PtCl2 k-1 reversible kj L2PtCl(OH2)+ + Cl-. Values of k1, K-1 and the equilibrium constant K(T) (-k1/k-1) have been measured for the systems L2 = cis(NH3)2, trans(NH3)2, cis(py)2, en, RR-chxn, tn and Me2tn, with varying temperature and ionic strength (cis(NH3)2 only). At 25-degrees-C and I = 0.1 M, data for cis-PtCl2(NH3)2 are k1 = 5.18 x 10(-5) s-1 (DELTA-H# = 86.7 kJ mol-1, DELTA-S# = -36 J K mol-1), k1 = 7.68 x 10(-3) M-1 s-1 (DELTA-H# - 72.7, DELTA-S# = - 41) and K1 = 6.74 x 10(-3). Corresponding data for trans-PtCl2(NH3)2 are k1 = 1.90 x 10(-5) s-1 (DELTA-H# = 92.2, DELTA-S# = - 26), k-1 - 3.05 x 10(-2) M-1 s-1 (DELTA-H# = 85.7, DELTA-S# = + 14) and K1 = 6.22 x 10(-4). These data provide a kinetic explanation for the inactivity of the trans-isomer as an anti-cancer drug.