Vanadium oxyhalides

The electrical conductivities of arsenic, antimony, bismuth, vanadium, selenium and tellurium oxides and of antimony, bismuth and vanadium oxyhalides have been determined in chlorosulfonic acid. Arsenic, antimony and bismuth oxides in chlorosulfonic acid yield the corresponding oxychlorosulfonates as shown (Equation 9). 

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. 

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

The equilibria among the species are dependent on the pH of the solution in much the same way as the equilibria among the various phosphate species (see Chapter 14). Not only is the formation of polyvanadates reminiscent of phosphorus chemistry, so is the fact that vanadium forms oxyhalides such as OVX3 and V02X. 

As mentioned in the previous section, transition metals in high oxidation states exhibit behavior that is similar to that of some nonmetals. Vanadium(V) does this with the formation of oxyhalides having the formulas VOX3 and V02X. 

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

Since fluorine is difficult to prepare and manipulate, the anhydrous fluorides and oxyfluorides are prepared by the action of anhydrous hydrogen fluoride on other halides or oxyhalides of vanadium.1... 

Hala, J. Halides, Oxyhalides and Salts of Halogen Complexes of Titanium, Zirconium, Hafnium, Vanadium, Niobium and Tantalum, Vol, 40, Elsevier Science, New York, NY, 1989. 

Vanadium hi).—Halides and Oxyhalides. Solid-state reactions275 in the systems VF3-M1F and VF3-M2F2 (M1 = Tl1, M2 = Ca, Sr, Ba, or Pb) have yielded 17 double fluorides of five different structural types depending on the VF3 MF ratio. The chief structural type is the cryolite-like M3VF6. 

In reporting a Ziegler-Natta catalyst, the kind of transition metal compound should not be omitted. Group 4-8 transition metal compounds, such as halides, oxyhalides, alkoxides, acetylacetonates, etc., have been used as catalyst precursors with activators such as alkyl derivatives or hydrides of group 1-4 metals. Titanium chlorides and triethylaluminium are most commonly applied for the preparation of heterogeneous catalysts in an aliphatic hydrocarbon medium. Also, vanadium oxychloride or acetylacetonate and dialkyaluminium chloride are often used for the preparation of homogeneous catalysts in an aliphatic hydrocarbon or an aromatic hydrocarbon medium. 

Ziegler-Natta Catalysts (Heterogeneous). These systems consist of a combination of a transition metal compound from groups IV to VIII and an organometallic compound of a group I—III metal.23 The transition metal compound is called the catalyst and the organometallic compound the cocatalyst. Typically the catalyst is a halide or oxyhalide of titanium, chromium, vanadium, zirconium, or molybdenum. The cocatalyst is often an alkyl, aryl, or halide of aluminum, lithium, zinc, tin, cadmium, magnesium, or beryllium.24 One of the most important catalyst systems is the titanium trihalides or tetra-halides combined with a trialkylaluminum compound. 

Vanadium(ill).—Halides and Oxyhalides. Magnetic susceptibilities have been obtained for MVF4, M2VF5, M2VFj,H20, and MVF4(H202) (M = NH4, K, Rb, or Cs) over the temperature range 78.5—290 and also for p-K VFj (0.45 < x <... 

Most commonly, the catalyst component consists of halides or oxyhalides of titanium, vanadium, chromium, molybdenum, or zirconium, and the cocatalyst component often consists of an alkyl, aryl, or hydride of metals such as aluminum, lithium, zinc, tin, cadmium, beryllium, and magnesium. The catalyst systems may be heterogeneous (some titanium-based systems) or soluble (most vanadium-containing species). Perhaps the best known systems are those derived from TiCl4 or TiCls and an aluminum trialkyl. 

Vanadium(iv).—Halides and Oxyhalides. The formation constant of [VOF ]" has been determined by an ion-exchange method. ... 

Vanadium(v).—Halides and Oxyhalides. The vapour-phase Raman spectra of VOF3 and VOCI3 have been obtained and compared with the corresponding... 

Palladium complexes with an heterocyclic N-containing ligand have been used in the carbonylation of aromatic nitro compounds with cocatalysts such as cyclopentadienyl halides or oxyhalides of transition metals belonging to group V e.g. CP2VCI) [168], a cyclopentadienyl halide or oxyhalide together with phosphorus oxytrichloride [169], or a 1,3-diketone derivative of vanadium [170], even also in the presenee of phosphorus oxychloride [171]. 

Another group of initiator systems are metal halides (e.g., ZrC, TiCl4, etc.) and metallic oxyhalides (e.g., vanadium oxychloride) prepared on silica gel such as Cab-O-Sil (with a surface OH content of ca. 1.5mEq/g) or on a carbon black such as channel black or furnace black [492,513]. NVP and i-BusAl are added to a toluene slurry of this material. The reaction mixture is heated up to 80°C to yield 25% of PVP [513]. The polymerization initiated by carbon black at room temperature was totally inhibited by pyridine and DMF, which indicates the cationic nature of the reaction [514]. The polymerization rate is first order in carbon black [492]. The activation energy of the polymerization was determined to be 85 kJ/mol from an Arrhenius plot [514]. 

---