Possible biotransformation reactions of polynuclear Pt(II) complexes.

The reactions of the two complexes BBR3464 [{trans-PtCl(NH3)2}2{mu-trans-Pt(NH3)2(NH2(CH2)6NH2)2}](4+) and BBR3610 [{trans-PtCl(NH3)2}2{mu-C2H4(NH2(CH2)6NH2)2}](4+) and the corresponding diaqua complexes with the nucleophiles thiourea (tu) and l-methionine (l-Met), were investigated under pseudo-first-order conditions as a function of concentration and temperature, using UV-vis spectrophotometric and stopped-flow techniques. 1H NMR spectroscopy was used to follow the stepwise substitution of the chloro ligands by guanosine-5'-monophosphate under second-order conditions. For the sulfur donor containing nucleophiles (tu and l-Met), a second reaction step, the displacement of the labilized amine chain linker, as a result of the strong trans-effect of tu and l-Met, was found. The activation parameters for all reactions studied suggest an associative substitution mechanism. The displacement of the chain linker by S-donor nucleophiles illustrates the limit of application of polynuclear complexes with monodentate aliphatic amine bridges and primary ammines, in agreement with previous studies reported in the literature.