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Relative stabilities of weakly coordinating anions: a computational study
1Universität Karlsruhe, Institut für Anorganische Chemie, Engesserstr. Geb. 30.45, 76128 Karlsruhe. krossing@chemie.uni-karlsruhe.de <krossing@chemie.uni-karlsruhe.de>
Chemistry (Weinheim an Der Bergstrasse, Germany)
|September 17, 2004
Summary
This study used DFT calculations to assess the stability and coordinating abilities of weakly coordinating anions (WCAs). Results provide a reliable relative ordering for selecting appropriate WCAs and Lewis acids for chemical applications.
Area of Science:
- Computational Chemistry
- Inorganic Chemistry
- Quantum Chemistry
Background:
- Weakly coordinating anions (WCAs) are crucial in stabilizing reactive cationic species.
- Understanding WCA stability and coordinating ability is essential for designing advanced chemical systems.
- Previous studies have explored various WCA structures, but a systematic comparison of their properties is needed.
Purpose of the Study:
- To systematically evaluate the relative stabilities and coordinating abilities of a diverse set of weakly coordinating anions (WCAs).
- To establish reliable metrics for predicting WCA performance in various chemical applications.
- To provide a computational framework for selecting optimal WCAs and Lewis acids.
Main Methods:
- Density Functional Theory (DFT) calculations using the BP86/SV(P) level of theory.
- Auxiliary calculations employing MP2/TZVPP, G2, and CBS-Q methods for enhanced accuracy.
- Isodesmic reactions were utilized to ensure the reliability of calculated quantities.
- COSMO solvation model was applied to investigate media effects on WCA stability.
Main Results:
- Relative stabilities and coordinating abilities of various WCAs were determined based on fluoride ion affinities (FIA) and ligand affinities (LA).
- Decomposition pathways (proton and copper decomposition) were analyzed to assess WCA reactivity.
- Electronic properties, including HOMO position and HOMO-LUMO gap, were correlated with WCA stability.
- Gas-phase and solution calculations showed comparable results for anion stability, indicating the robustness of the findings.
Conclusions:
- The study provides a reliable relative ordering of WCA stabilities, aiding in the selection of appropriate anions for specific applications.
- The calculated metrics (FIA, LA, decomposition energies) serve as valuable guides for thermodynamic-based WCA selection.
- Computational methods employed offer a robust approach for future WCA design and characterization.