Pyrophosphoryl chloride is the inorganic compound with the formula . Its structure is . It is a colorless syrup. In terms of its chemical structure, the compound consists of two tetrahedral phosphorus sites that share an oxo bridge. The name implies that the compound is a derivative of pyrophosphoric acid, .
The compound is obtained by treating phosphoryl chloride with half an equivalent of methanol, as described in the following chemical equation:
Pyrophosphoryl chloride is proposed as an intermediate in the chlorination of alcohols by phosphoryl chloride. It is also a reagent for Vilsmeier-Haack formylations.