Trihalides melt studies

As indicated by the data in table 32.2, unusual R2X3 compositions are observed for normally trivalent rare earths which have low stabilities of dipositive ions in their trihalide melts. A sesquihalide phase was first reported for the Gd-Cl system (Mee and Corbett, 1965) and subsequently for the Sc-Cl and Sc-Br systems (McCollum and Corbett, 1968 McCollum et al., 1973). In the Sc-1 system, a substantially higher composition, ScE.i , is the only phase observed. Initial data for the gadolinium phase, which forms long black-grey needles, showed it to be GdCli,5s o.o6 however, a more recent single crystal X-ray study... 

Thorough studies of solutions of xenon in boron trichloride and boron iribromide were undertaker. A phase study of the melting point of these systems sis a function of composition showed no evidence of compound formation. The Raman spectra of these mixtures are identical to those of pure BX, indicating no noble gas-boron trihalide interactions. 

I.r. and Raman studies have shown the formation of complexes between tributyl phosphate and both arsenic and antimony tribromides. Cryoscopy in fused arsenic tribromide is reported for a num r of inorganic and organic solutes, showing dTj X values lower than the ideal value, and with dioxan the compound 2AsBr3,3dioxan, melting at 64 °C, is formed. Arsenic and antimony trihalides give a-bonded transition-metal derivatives, such as X2E[Fe(CO)2(Cp)]J, where E = As or Sb and X = Cl or Br, on reaction with metal carbonyl anions or metal carbonyls with metal-metal bonds. ... 

As already mentioned in the case of samarium and europium trihalides (Chervonnyi and Chervonnaya, 2007a,g), these compoimds have low enthalpies of sublimation and tend to decompose at high temperatures. Hastie et al. (1968) made an effort to stabilize the trivalent europium state. These authors prepared a mixture of europium and lutetium trichlorides, which melt at different temperatures (T = 894 K for EuCla and 1198 K for LuCla), and studied the composition of the vapor over this mixture by mass spectrometry. Data from the mass spectrum recorded at T = 960 K are presented in Table 49. At this temperature, the EuCla melt is... 

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