Hafnium(IV) Chloride - Reactivity

Reactivity

The compound is highly reactive toward water, evolving hydrogen chloride. Aged samples often are contaminated with the oxychloride, which is also colourless. The THF complex is monomeric and thus soluble in organic solvents, which allows this hafnium complex to react more easily.

HfCl₄ + 2 OC₄H₈ → HfCl₄(OC₄H₈)₂

Little is known about Hf(III) compounds because HfCl₄ is especially difficult to reduce, but reduction can be effected with potassium-sodium alloy:

2 HfCl₄ + 2 K + 4 P(C₂H₅)₃ → Hf₂Cl₆₄ + 2 KCl

Deep green Hf₂Cl₆₄ crystals form, which are diamagnetic. X-ray crystallography shows that Hf₂Cl₆₄ has an edge-shared bioctahedral structure, very similar to the Zr analogue.

HfCl₄ can undergo the Grignard reaction for the substitution of chloride ligands. This can be achieved by reacting HfCl4 with a Grignard reagent of general formula R-Mg-X in dry diethyl ether solvent.

RMg-X + HfCl₄ → HfX₄