Niobium oxychloride
# Niobium oxychloride

Niobium oxychloride is the inorganic compound with the formula $NbOCl_3.$ It is a white, crystalline, diamagnetic solid. It is often found as an impurity in samples of niobium pentachloride, a common reagent in niobium chemistry.

## Structure

In the solid state the coordination sphere for niobium is a distorted octahedron. The Nb–O bonds and Nb–Cl bonds are unequal. This structure can be described as planar $Nb_2Cl_6$ core connected by O–Nb–O bridges. In this way, the compound is best described as a polymer, consisting of a double stranded chain.

In the gas phase above 320 °C the Raman spectrum is consistent with a pyramidal monomer containing a niobium–oxygen double bond.

## Synthesis

Niobium oxychloride is prepared by treating the pentachloride with oxygen:

    $NbCl_5$ + 1/2 $O_2$ → $NbOCl_3$ + $Cl_2$

This reaction is conducted at about 200 °C. $NbOCl_3$ also forms as a major side-product in the reaction of niobium pentoxide with various chlorinating agents such as carbon tetrachloride and thionyl chloride.

    2 $Nb_2O_5$ + 6 $CCl_4$ → 4 $NbOCl_3$ + 6 $COCl_2$
