Role of Intermolecular Interactions in Formation of Linear Polynuclear Platinum Complexes

The electronic and steric structures of cis- and trans-[Pt(NH₃)₂Hlg₂] were calculated by HF and DFT methods, and the differences between their thermodynamic functions H⁰298, S⁰298, G⁰298, and C_4p = f(T) were evaluated on the basis of DFT force fields. The differences between the stabilities of the cis and trans isomers are mainly due to features of molecular structure, namely, to the energy of interligand interaction. The nonvalent interactions Pt···Pt and NH₂-H···Hlg between the mononuclear fragments cis-[Pt(NH₃)₂· Hlg₂], weakening in the order Cl^- > Br^- > I^-, considerably enhance the stability of the cis isomers and provide conditions for formation of linear polynuclear complexes with Pt-Pt bonds.