Halide vapor complexes

The Absorption Spectra and Excited State Relaxation Properties of Lanthanide and Actinide Halide Vapor Complexes. I. ErCl3(AlCl3L, W.T. Camall, J.P. Hessler, H.R. Hoekstra, and C.W. Williams, J. Chem. Phys. 68, 4304-4309 (1978). 

Vibrational Spectroscopy of High Temperature Metal-Halide Vapor Complexes... 

In most cases RXi Is a more volatile halide and Is present only as a vapor whereas GXy may be In a condensed or vapor phase depending on the temperature and total pressure of the system. Stoichiometric coefficients and thermodynamic quantities for reaction 1 have been measured using a variety of experimental techniques. Including mass-spectrometry, chemical transport and spectrophotometry. A large number of halide vapor complexes have been reported, and extensive reviews on their systematlcs and thermodynamics of formation are already available (4-9). 

Papatheodorou GN (1982) Spectroscopy, structure and bonding of metal halide vapor complexes. In E Kaldis (ed) Current topics in material sciences, vol 10. North Holland Amsterdam, chap 4, p 250... 

Rare-earth halide vapor complexes with monovalent and divalent metal halides 3.1. Knudsen effusion mass spectrometry... 

Rare-earth halide vapor complexes with... 

The systematics of high-temperature metal halide vapors and vapor complexes have earlier been summarized in a number of review articles or monographs. Worth mentioning are the books by Schafer (1964), Margrave (1967) and Hastie (1975) and a number of proceedings volumes, such as those edited by Hildenbrand and Cubicciotti (1978) and Hastie (1979). Schafer (1976, 1983) reviewed the thermodynamics of metal chloride vapor complexes. Papatheodorou (1982) and Brooker and Papatheodorou (1983) gave an extensive account on the electronic, vibrational, thermodynamic and structural properties of transition and rare-earth metal halide vapor complexes. Finally, Hilpert (1989, 1990)... 

Finally, the crystal structure of the rare-earth trihalides and the coordination of the rare-earth ion in the crystal lattice represents substantial interest and it will be addressed, since it has been argued (Papatheodorou 1982) that the coordination of the metal atom in a series of transition and rare-earth metal halide vapor complexes is most probably preserved on going from the solid halide to the vapor complex molecule. In each group... 

Hilpert (1989, 1990) has given extensive descriptions of the instrumentation involved in Knudsen effusion mass spectrometric investigations of high-temperature metal halide vapor complexes and has presented also the principles involved for identifying gaseous species and determining partial pressures and thermodynamic quantities. The reader should refer to the above articles and references cited therein in order to address descriptions of instrumental aspects and of particular types of Knudsen cells. 

Fig. 7. Molecular models for the MRX4-type rare-earth halide vapor complexes, (a) Cjv S5fmmetry (b) C2, symmetry (c) Cjv symmetry.

Table 14 summarizes the trivalent lanthanide halide vapor complexes which have been studied by means of spectrophotometry. Among the binary systems involving Group-IIIA trihalides, chlorides are by far the most extensively studied systems. The overall spectra of vapor complexes are similar to those observed in aqueous solutions (Carnall 1979) or in other (e.g. glass) media (Reisfeld 1975) in terms of transition energies but the hypersensitive transition intensities were foimd to vary. However, the hypersensitive intensity ( G5/2 <— 19/2) of Nd-Al-Cl vapor complexes compares well with the result... 

Regardless of the structure (i.e. R, K3 or S ) of the RX3 XAX3 complexes the A-X interaction will decrease the basicity of the ligand coordinated to R in the sequence In > Ga > Al, and thus the intensity of hypersensitive transitions are expected to decrease in the same sequence. The data presented in table 14 and the above discussion support this view, but no definite conclusions about the type of species and their structures can be made. In relation, however, to the proposed structures in fig. 11 the following statements can be made and might be helpful in choosing certain molecular structures for the lanthanide halide vapor complexes ... 

---