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Fe L-Edge XAS Studies of K 4 [Fe(CN) 6 ] and K 3 [Fe(CN) 6 ]: A Direct Probe of Back-Bonding

2006; American Chemical Society; Volume: 128; Issue: 32 Linguagem: Inglês

10.1021/ja061802i

1943-2984

Rosalie K. Hocking, Erik C. Wasinger, Frank M. F. de Groot, Keith O. Hodgson, Britt Hedman, Edward I. Solomon,

Metal complexes synthesis and properties

Distinct spectral features at the Fe L-edge of the two compounds K3[Fe(CN)6] and K4[Fe(CN)6] have been identified and characterized as arising from contributions of the ligand π* orbitals due to metal-to-ligand back-bonding. In addition, the L-edge energy shifts and total intensities allow changes in the ligand field and effective nuclear charge to be determined. It is found that the ligand field term dominates the edge energy shift. The results of the experimental analysis were compared to BP86 DFT calculations. The overall agreement between the calculations and experiment is good; however, a larger difference in the amount of π back-donation between Fe(II) and Fe(III) is found experimentally. The analysis of L-edge spectral shape, energy shift, and total intensity demonstrates that Fe L-edge X-ray absorption spectroscopy provides a direct probe of metal-to-ligand back-bonding.