Halides and complex halides

The reverse reaction to give the gaseous species AlX(g) at high temperature accounts for the enhanced volatility of AIF3 when heated in the presence of A1 metal, and the ready volatilization of A1 metal in the presence of AICI3. Using calculations of the type outlined on p. 82 the standard heats of formation of the crystalline monohalides AIX and their heats of disproportionation have been estimated as  

Very recently the first All compound to be stable at room temperature, the tetrameric complex [ AlI(NEt3) 4], has been prepared and shown to feature a planar AI4 ring with Al-Al 265 pm, Al-I 265 pm and Al-N 207 pm.  

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Rhenium Halides and Halide Complexes. Rhenium reacts with chlorine at ca 600°C to produce rheniumpentachloride [39368-69-9], Re2Cl2Q, a volatile species that is dimeric via bridging hahde groups. Rhenium reacts with elemental bromine in a similar fashion, but the metal is unreactive toward iodine. The compounds ReCl, ReBr [36753-03-4], and Rel [59301-47-2] can be prepared by careful evaporation of a solution of HReO and HX. Substantiation in a modem laboratory would be desirable. Lower oxidation state hahdes (Re X ) are also prepared from the pentavalent or tetravalent compounds by thermal decomposition or chemical reduction. 

The succeeding actinides (Cm, Bk, Cf, Es, Em, Md, No, Lr) mark the point where the list of isolated compounds tends to involve binary compounds (oxides, halides and halide complexes, chalcogenides, and pnictides) rather than complexes. Those studies of complexes that have been made are usually carried out in solution and, from Em, onwards, have been tracer studies. 

The study of absorption spectra has demonstrated the unusual invariance of octahedral chromophores, Cr(III)X6, in glasses and minerals (4, 77). Empirical evidence from glass-making 124) has been extended, and one can study e.g. the equilibria between blue Co(II)04 and pink Co(II)06 or between purple Ni(II)04 and yellow-green Ni(II)06 in borate and silicate glasses 65). Similar observations can be made on molten chlorides 27) and sulfates 64). Relations between the crystal structure and absorption spectra of mixed oxides 61y 87, 90, 103, 104y 105) and fluorides 91) have been carefully evaluated. In this connection, Clark 11) discussed the invariance of the chromophores, M(II)Cl6 and M(III)Cl6, in solid halides and halide complexes. 

Complex halides of scandium and yttrium have been discussed in CCC (1987).1 Most halides and halide complexes reported are of Sc111 and Y111 but there are some reduced halide species such as the diiodide.229... 

J. H. Canterford and R. Colton, Halides of the Second and Third Row Transition Series, Intcrsciencc-Wilcy, 1968 (an exhaustive reference on halides and halide complexes) G. Thiele and K. Brodcrson, Fortschr. Chcin. Forsch., 1968,10,631 (structural chemistry of platinum halides). 

Germanium a)t 7V (ii), and Lead(ii) Halides and Halide Complexes. The crystal structures of hydrated tin(ii) chloride and bromide, and of anhydrous tin(ii) iodide, have been determined. That of SnQ2,2H20 is a more accurate redetermination and is shown in Figure 38. The tin atom is pyramidally... 

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