Complex oxyhalides

In addition to finite oxyhalide ions there are infinite oxyhalide ions in some complex oxyhalides. Examples include the anion in K2(Nb03F), which has the K2Nip4 (layer) structure (see Table 10.11), and the cis octahedral AX5 chain ion in K2(V02F3), F atoms forming the bridges. 

All the elements Al, Ga, La, Ti, V, and the 4f and 5f metals form an oxychloride MOCl and most of them also form MOBr and MOI. Antimony and bismuth also form more complex oxyhalides, which are described in Chapter 20, and Bi forms BiOF which belongs in this group. Other oxyfluorides MOF of the above elements were included in group (a), ionic oxyfluorides. 

Other oxyhalides, mostly oxychlorides and oxybromides, result from the controlled hydrolysis of the trihalides, and are of interest for two main reasons. First, they are quite unrelated to the oxyhalides of bismuth. Although both antimony and bismuth form compounds MOX the structures of the antimony compounds are quite different from those of the compounds BiOX, which have been described on p. 408. The more complex oxyhalides of Sb have no analogues among Bi compounds. Second, a feature of the published structures of the antimony oxyhalides is the coordination of Sb by either three or four O atoms. It should perhaps be remarked here that the investigation of the structures of these complex compounds is difficult, and the precise positions of the O atoms are by no means certain. However, it appears that a feature of these compounds is the formation of extended Sb—O systems, generally layers, interleaved with halogen... 

In the two more complex oxyhalides the characteristic structural feature is apparently a double chain, in which all the Sb atoms are 4-coordinated, which is joined through OH groups to form infinite layers [Sb808(0H)4] in the first compound and complex cylindrical chain ions [Sb40s(0H)] in the second. 

The only significant difference between halide melts and oxyhalide melts is that oxyfluoride complexes have a tendency to dissociate at relatively high concentrations yielding polyanion groups. This phenomenon is related with the need to achieve coordination saturation. 

No complexes have at present been authenticated in oxidation states greater than +6, whereas oxyhalide complexes exist where the +8 state is known this parallels trends in the halides and oxyhalides. 

Halide and oxyhalide complexes of elements of the titanium, vanadium and chromium sub-groups. 

Data from this laboratory and others8,9,10 indicate that the general procedure outlined for the synthesis of F2PX compounds may be extended to the synthesis of the oxy derivatives of pentavalent phosphorus such as F2C1P0 and Cl2FPO, but the detailed directions are not given here. The mixed oxyhalides of phosphorus, like the corresponding mixed halophosphines, have not been obtained easily in pure form from complex reaction mixtures.11,12... 

Chromium(vi) Complexes.—These studies have been virtually confined to oxyhalide and oxide systems. 

Oxyhalide Complexes. (Ph4A)[Cr03X] (A = P or As and X = F or Cl) have been precipitated from a solution of the corresponding potassium salt in dilute HF or HCl and their unit cells, i.r., and electronic spectra reported.The interactions of Cr02Cl2 with aromatic hydrocarbons and fluorocarbons have been examined and the intermolecular charge-transfer transitions recorded. 

In these oxyhalide complexes, the inter-halide distances between layers are smaller than the sum of the ionic radii of the halides (Table 11). In the oxybromides and ox5dodide series the M—Br (next layer) and M—I (next layer) distances increase (Table 11) with increase in parameter c (Table 10) as these distances depend solely on the dimensions of the c-axis. In the oxychloride series the M—Cl (next layer) distance, however, show a decrease along the lanthanide series. So does the parameter c (Table 10). This is the reason why the oxychlorides of Tm, Yb and Lu cannot maintain the PbFCl type structure. 

Boric acid forms complexes with a number of inorganic ions and organic molecules. Ammonia, hydrazine, hydroxides and oxyhalides from complexes with boric acid. The organics include diols, thiols, dioxane, pyridine and many other solvents in which boric acid dissolves. 

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