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Electron counts for face-bridged octahedral transition metal clusters.
Peng-Dong Fan1, Peter Deglmann, Reinhart Ahlrichs
1Theoretical Chemistry, Institute of Physical Chemistry, University of Karlsruhe, 76128 Karlsruhe, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 14, 2002
Summary
Valence electron counts predict stable octahedral clusters. Electron counts of 80, 84, or 98 are favored for pi-accepting ligands, while 84 is favored for pi-donating ligands like chloride.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Octahedral clusters with the formula [M(6)E(8)L(6)] are common in inorganic chemistry.
- Understanding the factors that govern their stability is crucial for designing new materials.
Purpose of the Study:
- To rationalize valence electron counts for stable face-capped octahedral clusters.
- To establish general counting rules for these clusters based on ligand properties.
Main Methods:
- Utilized Kohn-Sham orbital energy patterns to analyze electron counts.
- Investigated clusters with various metal (M) and ligand (L) combinations, including E=S, Se, Te, Cl and L=CO, PMe(3), Cl(-).
Main Results:
- Stable closed-shell clusters were found for 80, 84, and 98 electrons when L is a pi acceptor (CO, PMe(3)).
- For pi-electron donor L=Cl(-), only 84 electrons were favorable, as seen in [Mo(6)Cl(14)](2-).
- Fivefold coordination of M becomes unstable above 98 electrons, favoring tetrahedral coordination and altered cluster structures for elements like Nickel.
Conclusions:
- Kohn-Sham orbital energy patterns provide a reliable method for predicting cluster stability.
- Ligand electronic properties (pi-acceptor vs. pi-donor) significantly influence favorable electron counts.
- Electron counting rules are essential for understanding and predicting the structures of M(6) clusters.