Vanadium oxytrichloride
Vanadium oxytrichloride is the inorganic compound with the formula VOCl. This yellow distillable liquid hydrolyzes readily in air. It is an oxidizing agent. It is used as a reagent in organic synthesis. Samples often appear red or orange owing to an impurity of vanadium tetrachloride. Properties. VOCl is a vanadium compound with vanadium in the +5 oxidation state and as such is diamagnetic. It is tetrahedral with O-V-Cl bond angles of 111° and Cl-V-Cl bond angles of 108°. The V-O and V-Cl bond lengths are 157 and 214 pm, respectively . VOCl is highly reactive toward water and evolves HCl upon standing. It is soluble in nonpolar solvents such as benzene, CHCl, and hexane. In some aspects, the chemical properties of VOCl and POCl are similar. One distinction is that VOCl is a strong oxidizing agent, whereas the phosphorus compound is not. Neat VOCl is the usual chemical shift standard for V NMR spectroscopy. Preparation. VOCl arises by the chlorination of VO. The reaction proceeds near 600 °C: Heating an intimate (well-blended with tiny particles) mixture of VO, chlorine, and carbon at 200–400 °C also gives VOCl. In  this case the carbon serves as a deoxygenation agent akin to its use in the chloride process for the manufacturing of TiCl from TiO. Vanadium(III) oxide can also be used as a precursor: A more typical laboratory synthesis involves the chlorination of VO using SOCl. Reactions. Hydrolysis and alcoholysis. VOCl quickly hydrolyzes resulting in vanadium pentoxide and hydrochloric acid. In the picture, orange VO can be seen forming on the walls of the beaker. An intermediate in this process is VOCl: VOCl reacts with alcohols especially in the presence of a proton-acceptor to give alkoxides, as illustrated by this  synthesis of vanadyl isopropoxide: Interconversions to other V-O-Cl compounds. VOCl is also used in the synthesis of vanadium oxydichloride. VOCl can be prepared by an unusual reaction involving ClO. At >180 °C, VOCl decomposes to VO and VOCl. Similarly, VOCl also decomposes to give VOCl, together with VOCl. Adduct formation. VOCl is strongly Lewis acidic, as demonstrated by its tendency to form adducts with various bases such as acetonitrile and amines. In forming the adducts, vanadium changes from four-coordinate tetrahedral geometry to six-coordinate octahedral geometry: VOCl in alkene polymerization. VOCl is used as a  catalyst or precatalyst in production of ethylene-propylene rubbers (EPDM).