Hexahalide complexes

Other series of mixed hexahalide complexes have been made. Thus from K2OsI6 and concentrated HBr ... 

Table 6. Wavenumbers in kK of prominent electron transfer bands of hexahalide complexes, the corrected wavenumber acorr of 7r- 42g when spin-pairing energy is taken into account (in the de-systems, the corrected wavenumber of 7r- -eg has been diminuished by ) and the optical electronegativities.

Empirical correlation of intensities of absorption bands with the structure of complexes in solutions have been made for lanthanide complexes. It has been recognized that forced electric-dipole transitions of low intensities, in some cases lower in intensity than those of magnetic-dipole transitions, may indicate that the ligand field has point group symmetry with a center of inversion. This criterion has been used in the determination of the ligand field by symmetry of Eu3+ aquo ion [202], The absorption band intensity ratios have been used to show the octahedral structure [49] of lanthanide hexahalide complexes, LnXg. ... 

Further studies of the spectra of the trivalent actinide hexahalide complexes are being carried out and will be presented in greater detail later. 

Unfortunately, a way has not been found to exploit hexahalide complexes of Fe2+ for this purpose. The divalent ion is unstable towards oxidation in aqueous solution it aquates too rapidly for successful incorporation as the desired hexachloride complex and it forms strong coordination complexes with gelatin, the peptizer of choice for practical applications. Such reactions prevent its incorporation into emulsion grains in a controlled manner. Despite the recent contention that the lower valence states of many transition-metal ions could fulfill the functions of Fe2+ [193], similar problems with incorporation have also frustrated their commercial application. This is especially true of Pt2+ and Pd2+, which showed much promise in single crystal studies [177,208]. 

Table 6.S.A Exchange rates K and activation energies of chloride and bromide isotopic e.xchangc in 1 c(IV) and Re(IV) hexahalide complexes 57).

Wave-number /iVj, of first electron transfer band of octahedral samarium(lll), europium(III), thulium(III) and ytterbium(III) hexahalide complexes (Ryan and Jorgensen 1966, Ryan 1969). The parameter M of the refined spin-pairing treatment (table 1, last column) is added to liVj, in the corrected values. 

Among the linear combinations of orbitals from the ligands of an octahedral complex, the two sets odd y are unique in allowing a mixture of a and n character. This will be shown later to be of great importance for the absorption spectra of certcdn hexahalide complexes. 

At the present, the M.O. configuration description of polyatomic molecules and ions containing transition group elements has been most elaborated for octahedral complexes, especially hexahalide complexes MXg with X = F--, Cl, Br, and 1 and... 

TABLE VII. Values of ffp From Eq. (34) For Hexahalide Complexes in Units of 1000 cm. Some of the A Values (Marked ext.) are Extrapolated... 

As a Chatt-Ahrland type A or Pearson hard cation, association of Am with inorganic ligands proceeds initially through electrostatic interactions to form outer-sphere complexes. However, in some cases (e.g. F", SO "), there is evidence that the ligand displaces the water of hydration, at least to some extent, to form inner-sphere complexes. Spectrophotometric results of Marcus and Shiloh [124] also provide evidence for inner-sphere complexation of chloride and nitrate ions to Am in concentrated LiCl and UNO3 solutions, respectively. Preparation of the solid compound [(CeHslsPHjsAmQg, containing the octahedral hexahalide complex AmCl, has been described by Ryan [107]. 

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