Theoretical Modeling of Water Exchange on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)]

Area of Science:

• Computational chemistry
• Inorganic chemistry
• Physical chemistry

Background:

• Water exchange mechanisms on metal complexes are crucial in various chemical and biological processes.
• Understanding these mechanisms provides insights into reactivity and coordination chemistry.
• Density functional theory (DFT) offers a powerful computational tool for studying such systems.

Purpose of the Study:

• To model the water exchange mechanism on [Pd(H2O)4]2+, [Pt(H2O)4]2+, and trans-[PtCl2(H2O)2] using DFT.
• To investigate the role of relativistic effects on the electronic structure and energetics of platinum complexes.
• To correlate computed activation enthalpies with experimental data and explain observed trends.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Optimized ground state and transition state geometries were determined.
• Local density approximation (LDA) and nonlocal gradient corrections were utilized.
• Relativistic corrections were applied to platinum complexes.

Main Results:

• Calculated geometries for ground states agree well with experimental data.
• Trigonal bipyramidal transition state models show small energy differences from actual transition states.
• Equatorial M-OH2 bond expansion in transition states explains observed activation volumes.
• Relativistic corrections account for higher activation enthalpies in platinum complexes.
• Computed activation enthalpies closely match experimental values for all studied complexes.

Conclusions:

• DFT, including relativistic effects, accurately models water exchange on Pd and Pt complexes.
• The associative mechanism is supported by geometric and energetic findings.
• The study provides a theoretical framework for understanding water exchange kinetics and thermodynamics in these systems.