Density functional study of the tetraoxometallates of Cr VI , Mn VI and Fe VI
- 1 January 1993
- journal article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 89 (20) , 3745-3749
- https://doi.org/10.1039/ft9938903745
Abstract
Local density approximation (LDA) density functional theory (DFT) calculations are reported for the tetrahedral anions [CrO4]2–, [MnO4]2– and [FeO4]2–. A range of STO basis sets is considered to determine the sensitivity of the optimised MO bond lengths and charge-density distributions. For a given complex, the computed bond lengths decrease smoothly as the basis set increases. The overall spread of predicted values is 0.04 Å, with experiment reproduced to within 0.02 Å for bases which include polarisation functions. The charge-density analysis across the series describes increasing covalence from [CrO4]2– to [FeO4]2–, while the computed relative bond strengths decrease. The latter correlate well with the observed increase in reactivity along this series. The computed values for the ligand-field parameter, Δtet, are about 2000 cm–1 too high for d0[CrO4]2– and d1[MnO4]2–, and 600 cm–1 too low for [FeO4]2–. In conjunction with theoretical estimates of the Racah parameters from spin-unrestricted LDA calculations, the computed d–d spectrum of [FeO4]2– is in reasonable agreement with experiment.Keywords
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