ZrCl4

Zirconium tetrachloride (ZrCl4) is an inorganic compound widely used as a Lewis acid and as a precursor in zirconium chemistry. It appears as a white to pale yellow solid that is highly moisture sensitive and can fume in air. In the absence of water, ZrCl4 readily forms adducts with donor ligands such as tetrahydrofuran (THF) or diethyl ether, giving ZrCl4(L)2-type complexes that are useful for handling and reaction in solution.

ZrCl4 undergoes hydrolysis in the presence of water, producing zirconium oxychloride and hydrochloric acid: ZrCl4 + 2 H2O → ZrOCl2 + 2 HCl. Further hydrolysis and calcination lead to zirconia (ZrO2). The solid-state structure of ZrCl4 is polymeric, while in the gas phase it can exist as discrete tetrahedral molecules. ZrCl4 readily forms adducts with donor ligands, which facilitates its use in synthesis and catalysis.

Preparation methods typically involve direct chlorination of zirconium metal or zirconium oxide with chlorine gas at elevated temperatures, followed by purification. ZrCl4 can also be prepared or generated in situ from related zirconium chlorides under appropriate conditions.

Applications include use as a versatile Lewis acid catalyst and as a foundational precursor for various zirconium-containing materials and catalysts. It is employed in olefin polymerization chemistry when used with co-catalysts such as alkylaluminium compounds and other activators, contributing to the production of Ziegler–Natta and metallocene-type systems. ZrCl4 is also a starting material for preparing zirconium alkoxides, zirconium oxides, and a range of Zr-containing inorganic and organometallic compounds.

Safety considerations are significant: ZrCl4 is corrosive and reacts violently with water, releasing hydrochloric acid. It should be handled under strictly dry, inert conditions and stored in tightly closed containers away from moisture.