Halide and Oxyhalide Complexes

Vedrine, J. P, Besse, and M. Capestan, J. Inorg. Nuclear Chem., 197Z 34, 2771. 

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

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. 

For general properties of the halides and oxyhalides of titanium, reference to the work by Clark is recommended.14 The chemistry of the complex halides will be treated here. 

Geoffroy, George, L., Photochemistry of Transition Metal Hydride Complexes George, J. W., Halides and Oxyhalides of the Elements of Groups Vb and VIb George, Philip and McClure, Donald S., The Effect of Inner Orbital Splitting on the Thermodynamic Properties of Transition Metal Compounds, and... 

Actinide halides and oxyhalides are known to form numerous complexes with oxygen and nitrogen donor ligands and the preparation and properties of such compounds have recently been reviewed (12, 13). Relatively few protactinium halide complexes are known, but this situation reflects the lack of research rather than a tendency not to form complexes. However, there is sufficient information available for certain ligands to permit a comparison with the behavior of other actinide halides, and to illustrate the similarities and differences observed with the tetrahalides of thorium to plutonium inclusive and, to a lesser extent, with the protactinium and uranium pentahalides. 

In his early study covering a large number of halides and oxyhalides of thorium and their hydrates, Chauvenet [1911CHA] reported a value of -293.67 kJ moT for the enthalpy of solution of ThBr4(cr) in ca. 16000 H2O, probably at 288 K. Use, as discussed in Appendix A, of the values adopted by this review (Table VII-15) for the hydrolysis of the thorium ion and of that for the formation of the first thorium bromide complex (Section VIII.2.2) leads to a dissolution reaction that can be written as ... 

It turned out, however, that it is impossible to stabilize the heaviest 6d elements in the atomic state, which would require temperatures much above 1000 °C. Therefore, volatile halides and oxyhalides had to be used. In this case, the influence of relativistic effects on AHads or Tads becomes more complicated, since those quantities are complex functions of many single parameters, with individual contributions often cancelling out. The only way to study relativistic effects in this case is to compare experimental behaviour with that predicted on the basis of relativistic versus nonrelativistic calculations. 

Zirconium(iii) and Ha ium(iii).— The complexes formed by the halides and oxyhalides of zirconium(iii) and hafnium(iii) have been reviewed. [ZrClj-(3,5-lutidine)2]2 has been prepared from its constituents and its structure is presumed to be a chloride-bridged dimer. 2,6-Lutidine does not react with ZrCl3 and 2,4-lutidine (L) affords [ZrCl3Lj (y ca. 1.1—1.33) together with a... 

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. 

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. 

Compounds of the formulas Re(CH3)6, ReO(CH3)4, Li e CH ] [60975-25-9], Re02(CH3)3 [56090-011-8], and Re03CH3 [70197-13-6] have been prepared. The first two compounds were obtained from reaction of rhenium halides or oxyhalides and methyllithium the last three were formed from the species by oxidation or reduction reactions. The use of these hydride and alkyl complexes as catalysts is under investigation. 

Monomeric complexes of W1 1 such as the halides, the oxyhalides and their derivatives have been known for quite some time. In most cases these are six-coordinate, but higher coordination numbers are also known. During the last two decades, new structural types have been reported. Of these, the most interesting are the dinuclear complexes containing W=W double bonds and the trinuclear dusters containing W—W single bonds. 

Several types of Werner complexes have been investigated over the last few years by TDDFT methods. They include metal oxide, metal halide, metal oxyhalide compounds, and transition metal complexes with bidentate ligands such as ethylenediamine and acetylacetonato. 

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