Synthesis, Characterization, Thermodynamic and Kinetic Properties of a New Series of Dinuclear Pt^II Complexes

Abstract

The dinuclear PtII complexes bis{[(1R,2R)‐(–)‐1,2‐diaminocyclohexane]chloroplatinum(II)}(μ‐1,8‐octanediamine), bis{[(1R,2R)‐(–)‐1,2‐diaminocyclohexane]chloroplatinum(II)}(μ‐1,10‐decanediamine) and bis{[(1R,2R)‐(–)‐1,2‐diaminocyclohexane]chloroplatin(II)}[μ‐1,4‐bis(3‐pyridyl)buta‐1,3‐diyne] were synthesized. Acid‐base titrations and concentration and temperature dependent measurements of the reactions with chloride and thiourea were performed to study the influence of the nature of the bridging ligand on the thermodynamic and kinetic properties of the complexes. The reactions with chloride and thiourea were followed under pseudo‐first‐order conditions by stopped‐flow and UV/Vis spectrophotometry. The results indicate that the bridging ligand has an influence on the reactivity and stability of the complexes towards nucleophiles as well as on possible electronic interactions between the two PtII centres. The experimental results are discussed in reference to structures obtained by DFT (BP86/LACVP*) calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A kinetic study of aqua ligand substitution in dinuclear Pt(II) complexes containing four non-coplanar pyridine ligands

“…This is ascribed to reduction of the overall charge from ?4 to ?3 following deprotonation of the first aqua ligand, causing a decrease in acidity and electrophilicity of the second Pt(II) centre. This increase in pK a value due to the change in overall charge of the complex has also been observed in previous studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…This observation was ascribed to the decrease in charge addition of the Pt atoms caused by a combination of increased electrostatic interactions with a concomitant increase in the r-donor capacity towards each Pt atom [1,2]. A similar trend in reactivity was observed by van Eldik et al [1,[9][10][11][12] when anionic and biologically relevant nucleophiles were used to study the ligand substitution reactions in alkanediamine-bridged Pt(II) complexes with a bis(2-pyridylmethyl)amine chelate framework around each Pt atom. The trend in reactivity is the same in all known cases as that reported in the study by Jaganyi et al [8] for dinuclear complexes with monodentate amine ligands around the Pt(II) centres.…”

“…Kinetic studies of the ligand substitution of dinuclear Pt(II) complexes with flexible and rigid linkers have been reported [1][2][3][4][5][6][7][8][9][10][11][12]. The reactivity of the metal centres has been shown to depend on the length and nature of the bridging ligand [1][2][3][4][5][6][7][8][9][10][11][12].…”

“…The reactivity of the metal centres has been shown to depend on the length and nature of the bridging ligand [1][2][3][4][5][6][7][8][9][10][11][12]. For example, when a straight aliphatic chain is used in dinuclear complexes with monodentate ammine [8] and bis (2-pyridylmethyl)amine [1,[9][10][11][12] carrier ligands around the Pt centres, the reactivity increases with the increase in chain length until it reaches the point where it is independent of the chain length. This observation was ascribed to the decrease in charge addition of the Pt atoms caused by a combination of increased electrostatic interactions with a concomitant increase in the r-donor capacity towards each Pt atom [1,2].…”

Kinetics and mechanism of substitution reactions of the new bimetallic [{PdCl(bipy)}{μ-(NH2(CH2)6H2N)}{PtCl(bipy)}]Cl(ClO4) complex with important bio-molecules

“…Similarly, the published results show that the substitution of both labile ligands was carried out before cleavage of the strong Pt-N bond and in the case of reaction between Tu and some mononuclear complexes which contain diamine chelate as inert ligand [26]. The same results were observed for substitution reactions of some dinuclear Pt(II) complexes with Tu [41].…”