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Can weakly coordinating anions stabilize mercury in its oxidation state +IV?
Sebastian Riedel1, Michal Straka, Martin Kaupp
1Universität Würzburg, Institut für Anorganische Chemie, Am Hubland, 97074 Würzburg, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 1, 2005
Summary
Researchers explored mercury(IV) chemistry in condensed phases using density functional calculations. While most mercury(IV) complexes are unstable, some show potential for synthesis, particularly those with arsenic hexafluoride ligands.
Area of Science:
- Inorganic Chemistry
- Computational Chemistry
- Quantum Chemistry
Background:
- Experimental verification of mercury(IV) chemistry is lacking despite theoretical predictions of gas-phase HgF4 stability.
- Density functional calculations are employed to investigate novel condensed-phase mercury(IV) species.
Purpose of the Study:
- To explore alternative species for accessing condensed-phase mercury(IV) chemistry.
- To assess the structures and thermochemical stabilities of various Hg(IV) complexes.
- To compare the stability of these complexes with known related compounds.
Main Methods:
- Detailed density functional calculations were used to model Hg(IV)X4 and Hg(IV)F2X2 complexes.
- Thermochemical stabilities were assessed for ligands including AlF4-, Al2F7-, AsF6-, SbF6-, As2F11-, Sb2F11-, OSeF5-, and OTeF5-.
- Comparisons were made with smaller gas-phase HgX4 complexes and noble gas compounds.
Main Results:
- Most investigated Hg(IV) complexes exhibit exothermic F2 elimination, with energies ranging from -60 to -180 kJ mol(-1).
- Complexes with AsF6 ligands are more promising than SbF6 analogues due to aggregation effects.
- HgF2X2 complexes with OSeF5- or OTeF5- ligands show endothermic F2 elimination but exothermic pathways via ligand coupling products.
Conclusions:
- All studied complexes possess at least one exothermic decomposition pathway.
- The stability of these condensed-phase complexes is lower than gas-phase HgF4 due to product stabilization.
- Potential synthetic routes for promising condensed-phase Hg(IV) complexes are proposed.