Nephelauxetic effects

Racah parameters The parameters used to express quantitatively the inter-electronic repulsion between the various energy levels of an atom. Generally expressed as B and C. The ratios between B in a compound and B in the free ion give a measure of the nephelauxetic effect. ... 

The nephelauxetic effect calculation and accuracy of the interelectronic repulsion parameters /, cubic high spin d1, d3, d7 and d systems. E. Konig, Struct. Bonding (Berlin), 1971, 9, 175-212 (64). 

Optical electronegativity and nephelauxetic effect in oxide systems. J. A. Duffy, Struct. Bonding (Berlin), 1977, 32,148-166 (33). 

Filling out observation b), it is found that for a series of complexes with a common metal, the nephelauxetic effect increases in the order given in Eq. (6.2)... 

The magnitude of Dq in any given complex is clearly a direct measure of the interaction between the spectral metal d electrons and their molecular environment. As for the nephelauxetic effect, values of Dq have been collated for a large number of species and found to fit, very approximately, another multiplicative relationship of metal and ligand functions (Eq. 6.5). 

The central point, then, is that tiny ligand-field splittings and normal sized nephelauxetic effects in lanthanoid spectra are not at all contradictory. The one reveals the isolation of the/shell, the other attests to the normality of the metal-ligand bonding. 

Drillon M, Darriet J (1992) Progress in Polymetallic Exchange-Coupled Systems, some Examples in Inorganic Chemistry. 79 55-100 Duffy JA (1977) Optical Electronegativity and Nephelauxetic Effect in Oxide Systems. 32 147-166... 

Calls for an explanation were answered by Jorgensen and elaborated by Nugent [26]. When a lanthanide ion moves from the aqueous to the organic phase, the nephelauxetic effect leads to a small decrease in inter-electronic repulsion within the 4f shell. This decrease varies irregularly with atomic number and is responsible for the irregularities in Fig. 1.3. 

Table 1.3 contains values for two 3d cases. At KsCuFg, ATreplirreg) contributes about 40% of the total stabilization, but at Ni (aq) only 15%. This is because in the first transition series, the nephelauxetic effect increases substantially when the oxidation state increases from -i-2 to -e3. The relatively small contribution for the M (aq) ion explains why text books use this example to explain the double bowl shapes AErep(irreg) is almost exactly cancelled by the sum of AEso and ATrix, so the total stabilization is nearly equal to the orbital stabilization energy. In most other cases, A rep(irreg) is much more important and may play an important role in sustaining the Irving-WilUams rule in complex-ing reactions [32, 33]. 

C6H50)3P. The decrease in rate parallels an increase in basicity (a-donation) and/or a decrease in nephelauxetic effect (n-acceptance) with the exception, that is, of the phosphite, which appears an anomalously stable compound on both counts. 

Konig, E. The Nephelauxetic Effect. Calculation and Accuracy of the Interelectronic Repulsion Parameters I. Cubic High-Spin d, d, and d Systems. Vol. 9, pp. 175-212. 

Duffy, J.A. Optical Electronegativity and Nephelauxetic Effect in Oxide Systems. Vol. 32, pp. 147—166. 

Table 25. Interpretations of the nephelauxetic effect for hexachloro anions...

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