Halides and Oxyhalides

Koyama and Y. Hashimoto, Nippon Kagaku Kaishi, 1973,195 Chem. Abs., 1973, 78, 91916c). 

Although halides of titanium in the +2, +3, and +4 states are known, only TiCU has important uses. High-temperature reactions by which TiCl4 can be produced include the following  

One of the reasons for the importance of TiCl4 is that it reacts with [A1(C2H5)3]2 to generate the effective catalyst that is used in the Ziegler-Natta process for the polymerization of ethylene (see Chapter 21). Halides such as TiCU hydrolyze in water as do most covalent halides  

Vanadium forms halides in the +2, +3, +4, and +5 oxidation states. For the +2 and +3 states, all of the halides are known, but only the fluoride is well characterized for the +5 state. Both VC14 and VBr4 are rather rare compounds. Some of the vanadium halides can be prepared by the direct reaction of the elements as illustrated by the reaction 

The halides of vanadium(IV) are unstable with respect to disproportionation so VF4 reacts to give VF5 and VF3  

Chromium halides that have the formulas CrX2 and CrX3 (where X = F, Cl, Br, or I) are all known. The CrX3 compounds in particular can behave as Lewis acids toward a variety of electron pair donors. The following reactions can be used to prepare CrCl3  

Asbrink, S. Asbrink, A. Magneli, H. Okinaka, K. Kosuge, and S. Kachi, Acta Chem. Scand.. 

Binary Compounds and Related Systems—Halides and Oxyhalides. The heat capacity of Tip4 has been determined.The peculiar temperature dependence of the magnetic susceptibility of P-TiClj is attributed to the presence of two kinds of chain-end site. The kinetics of disproportionation of TiClj have been measured over the temperature range 873—1373 K.  

Molecular force constants for TiCl4 have been calculated from i.r. data on the isotopic species TiCU and Ti Cl, in argon matrices, and in the gas phase. 

Binary Compounds and Related Systems.—Halides and Oxyhalides. At 1100—1450 °C TiCl4 reacts with metallic Ti to give lower Ti chlorides with a Cl Ti ratio in the gas phase of 2.00—2.50. An increase in temperature does not affect the degree of reaction of TiCl4. Reduction of the partial pressure of TiCl4 vapour in the original mixture with Ar reduces the Cl Ti ratio from 2.60 to 2.00.18 The fraction of Ti2+ ions in a NaCl melt at a concentration of Ti of 0.83—0.4 wt. % and at 950—1100°C is close to unity (0.80—0.97). The amount of Ti2+ increases with decreasing temperature. At 

An electron diffraction study of TiBr4 and Til4 has shown them to have regular tetrahedral structures.26 Pure TiF4 has been obtained in high yield (91 %) by treating preoxidized ilmenite with FeF3 at 850°C.27 

During the past few years numerous new penta- and tetravalent protactinium halides and oxyhalides have been characterized, but of the. possible trivalent compounds only Pal3 has been reported. The presently known halides and oxyhalides are compared with those of the other actinide elements in Tables I and II, respectively. It is immediately 

Fluorides AcFs — — XJFs NpFs PuFs AmFs CmFs BkFs  

Chlorides AoCls — — UCI3 NpCls PuCls AmCls CmCls BkCls CfCls EsCls — — — — 

Bromides AcBrs — — UBrs NpBrs PuBrs AmBrs CmBrs BkBrs —  

The only fluorides known at present are PaFs, Pa20F8, PagFg (or Pa Fiv), and PaF.  

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Niobium Halides and Oxyhalides. AH possible haUdes of pentavalent niobium are known and preparations of lower valent haUdes generally start with the pentahaUde. Ease of reduction decreases from iodide to fluoride. 

Vanadium Halides and Oxyhalides. Known haUdes and oxyhahdes of vanadium, their valences, and their colors are Hsted in Table 3. 

Halides and Oxyhalides. Vanadium(V) oxytrichloride is prepared by chloriaation of V20 mixed with charcoal at red heat. The tetrachloride (VCl is prepared by chlorinating cmde metal at 300°C and freeing the Hquid from dissolved chlorine by repeated freezing and evacuation. It now is made by chlorinating V20 or VOCl ia the presence of carbon at ca 800°C. Vanadium trichloride (VCl ) can be prepared by heating VCl ia a stream of CO2 or by reaction of vanadium metal with HCl. 

Antimony trioxide (SbaOj). It is produced from stibnite (antimony sulphide). Some typical properties are density 5.2-5.67 g/cm- pH of water suspension 2-6.5 particle size 0.2-3 p,m specific surface area 2-13 m-/g. Antimony trioxide has been the oxide universally employed as flame retardant, but recently antimony pentoxide (SbaOs) has also been used. Antimony oxides require the presence of a halogen compound to exert their fire-retardant effect. The flame-retarding action is produced in the vapour phase above the burning surface. The halogen and the antimony oxide in a vapour phase (above 315 C) react to form halides and oxyhalides which act as extinguishing moieties. Combination with zinc borate, zinc stannate and ammonium octamolybdate enhances the flame-retarding properties of antimony trioxide. 

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. 

Halides and oxyhalides of the early transition series and their stability and reactivity in non-aqueous media. R. A. Walton, Prog. Inorg. Chem., 1972,16, 1-226 (65). 

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

Reacts with many metals to give hydrogen, sometimes violently. With non-metals pyrophoric hydrides may result. Frequently initiates explosive reactions between other substances. Violent reactions with many non-metal and some metal halides and oxyhalides, also with many organometallic compounds. Many metal nonmetal-lides produce toxic, flammable or pyrophoric gases on contact with diprotium monoxide. 

George, J. W., Halides and Oxyhalides of the Elements of Groups Vb and Vlb George, Philip and McClure, Donald S., The Effect of Inner Orbital Splitting on the Thermodynamic Properties of Transition Metal Compounds, and 2 33... 

Resonance Walder, L., see Gerfin, T Wallbridge, M. G. H., see James, B. D. Walton, R., Halides and Oxyhalides of the Early Transition Series and Their 14 1... 

Halides and Oxyhalides. Molecules of VCI2, prepared by Knudsen cell techniques, have been isolated in solid inert-gas matrices and their i.r. spectra indicate a linear structure. However, similar studies suggested that VF2 molecules are non-linear. The d d spectrum of gaseous VCI2 has been discussed in terms of ligand field theory, and the Tanabe-Sugano matrix for a linear d system presented. ... 

Halides and Oxyhalides. Thermodynamic data have been presented for MF compounds (M = Nb or Ta, n = 1—5). ° The equilibrium pressure of dissociation of NbBr4 into the penta- and tri-bromides, as... 

Table 5-9 Bond Distances in Transition-Metal Oxides, Halides and Oxyhalides... 

There are many liquids capable of rapidly generating a solid product, when their droplets dispersed in an inert gas are contacted with a vapor coreactant. Such compounds include metal alkoxides, halides, and oxyhalides that react with water, hydrogen sulfide, etc., and organic monomers that can undergo either addition or condensation polymerization in the presence of appropriate initiators. The resulting powders consist of spherical particles, the size distribution of which depends on the method and conditions of droplet generation. 

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. 

This chapter has been devoted to the coordination chemistry of titanium and has made no attempt to describe the more basic chemistry of this element. References to alloys, to the simple halides and oxyhalides, the oxides, sulfides, selenides, tellurides, nitrides, azides, phosphides, arsenides and antimonides are well reviewed by Clark,14 and the recent text by Greenwood and Earnshaw180 contains a good section on titanium. 

Halides and Oxyhalides op Sulphur —Fluorides, Chlorides, Sulphur Bromide, Sulphur and lodino, Oxyfluorides, Oxychlorides, Thionyl Bromide. 

The variable valency of vanadium is well displayed in its halides and oxyhalides. These are set out in the following table —... 

The pentavalent halides and oxyhalides, as in the case of other niobium compounds, are the most stable. It is remarkable that the pentavalency is maintained with increase in the atomic weight of the halogen. All the halogen compounds are characterised by their ready tendency to undergo hydrolysis on the addition of water or even in damp air with precipitation of niobie acid and formation of the hydrogen halide. Their preparation can, therefore, be effected only in the dry way (a) synthetically, or (b) by the action of chlorine, carbon tetrachloride, or sulphur monochloride on the oxide or sulphide. They do not possess saline properties, and cannot be prepared by the action of the halogen acids on the oxide. 

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