Complex formation reactions of two sterically hindered platinum(II) complexes with some N-bonding ligands

The kinetics of the complex formation reactions of two [(TL (tBu))PtCl](+) and [Pt(tpdm)Cl](+) complexes (TL (tBu) = 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine and tpdm = terpyridinedimethane) with N-donor ligands, l-histidine (L-His), inosine (Ino), inosine-5'-monophosphate (5'-IMP) and guanosine-5'-monophosphate (5'-GMP), were studied. All reactions were studied under pseudo-first-order conditions as a function of nucleophile concentration and temperature in aqueous 0.1 M NaClO4 solution in the presence of 10 mM NaCl using variable-temperature Uv-Vis spectrophotometry. The order of reactivity of the studied ligands is L-His > Ino > 5'-GMP > 5'-IMP. This order of reactivity is in relation to their electronic properties and structures. The mechanism of the substitution reactions is associative in nature as supported by the negative entropy of activation.