DFT study of the role of intermolecular interactions in the formation of stable halogeno- and ammineaqua- platinum(II) coordination compounds

Autor: Svetlana A. Simanova, Mario Calligaris, Natalia S. Panina, Alexander N. Beljaev
Rok vydání: 2003
Předmět:
Zdroj: International Journal of Quantum Chemistry. 96:80-88
ISSN: 1097-461X
0020-7608
Popis: Density functional theory (DFT) and Hartree-Fock (HF) methods have been used to calculate the electronic and geometric structures of cis- and trans-[Pt(NH 3 ) 2 X 2 ] (X = Cl - , Br - , I - ), [cis-Pt(NH 3 ) 2 (H 2 O) 2 ] 2 + and its deprotonated forms. The thermodynamic parameters ΔH 0 298, ΔS 0 298, ΔG 0 298, and ΔC p = f(T) have been obtained from DFT force fields and normal mode frequencies. It is shown that the greater stability of the trans-isomers is due, at the molecular level, to different interligand interactions. The stability of the cis-isomers is significantly increased by intermolecular PtPt and NH 2 -HX nonvalence interactions between mononuclear [cis-Pt(NH 3 ) 2 X 2 ] moieties, the effect reducing in the row Cl - > Br - > I - . The thermodynamic parameters of possible phases of the hydrolysis of [cis-Pt(NH 3 ) 2 (H 2 O) 2 ] 2 + have been also derived. Solvent effects have been investigated calculating the equilibrium constants for the proton transfer reactions both in gas phase and water solution. It is shown that in aqueous medium the hydroxobridged platinum dimer [Pt(NH 3 ) 2 -(μ-OH)] 2 + 2, characterized by a PtPt distance of 3.119 A, is the preferred hydrolysis product. It is also shown that with short metal-metal interactions, such as those found in [cis-Pt(NH 3 ) 2 Cl 2 ] and [cis-Pt(NH 3 ) 2 (H 2 O) 2 ] 2 + , the conditions for the formation of linear polynuclear complexes with Pt-Pt bonds (the so-called "platinum blues") are created.
Databáze: OpenAIRE
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