Editing Vanadium (section)

=== Halide derivatives ===
Twelve binary [[halides]], compounds with the formula VX<sub>n</sub> (n=2..5), are known.<ref name="G&E989">{{Greenwood&Earnshaw2nd|page=989}}</ref> VI<sub>4</sub>, VCl<sub>5</sub>, VBr<sub>5</sub>, and VI<sub>5</sub> do not exist or are extremely unstable. In combination with other reagents, [[vanadium(IV) chloride|VCl<sub>4</sub>]] is used as a catalyst for the polymerization of [[diene]]s. Like all binary halides, those of vanadium are [[Lewis acid]]ic, especially those of V(IV) and V(V).<ref name="G&E989" /> Many of the halides form octahedral complexes with the formula VX<sub>''n''</sub>L<sub>6−''n''</sub> (X= halide; L= other ligand).

Many vanadium [[oxyhalide]]s (formula VO<sub>m</sub>X<sub>n</sub>) are known.<ref>{{Greenwood&Earnshaw|page=993}}</ref> The oxytrichloride and oxytrifluoride ([[vanadium oxytrichloride|VOCl<sub>3</sub>]] and [[Vanadium(V) oxytrifluoride|VOF<sub>3</sub>]]) are the most widely studied. Akin to POCl<sub>3</sub>, they are volatile,<ref>{{cite journal |last1=Flesch |first1=Gerald D. |last2=Svec |first2=Harry J. |date=1 August 1975 |title=Thermochemistry of vanadium oxytrichloride and vanadium oxytrifluoride by mass spectrometry |journal=Inorganic Chemistry |volume=14 |issue=8 |pages=1817–1822 |doi=10.1021/ic50150a015}}</ref> adopt tetrahedral structures in the gas phase, and are Lewis acidic.<ref>{{cite journal |last1=Iqbal |first1=Javed |last2=Bhatia |first2=Beena |last3=Nayyar |first3=Naresh K. |date=March 1994 |title=Transition Metal-Promoted Free-Radical Reactions in Organic Synthesis: The Formation of Carbon-Carbon Bonds |journal=Chemical Reviews |volume=94 |issue=2 |pages=519–564 |doi=10.1021/cr00026a008}}</ref>