| Chemical Properties | Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst. |
| Physical properties | White monoclinic crystal; sublimes at 317°C; melts at 432°C at 33 atm (triple point); critical temperature 452.5°C; critical pressure 53.49 atm; critical volume 314 cm3/mol.
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| Uses | Hafnium tetrachloride is an important intermediate in production of hafnium metal. It also is used to prepare many hafnium compounds. |
| Uses | Hafnium chloride tetrahydrofuran complex is an efficient catalyst for the Diels-Alder cycloadditions, Ziegler-Natta polymerization of alkenes. It is used as control rods in nuclear reactors and in manufacture of light bulb filaments. |
| Uses | Hafnium (IV) chloride can be used to catalyze the direct ester condensation of carboxylic acids with alcohols effectively. |
| Preparation |
Hafnium(IV) chloride can be prepared
(i) by chlorination of hafnium dioxide in the presence of carbon:
HfO2 + 2Cl2 + C → HfCl4 + 2CO
It also may be prepared by several other methods, such as
(ii) reaction of carbon tetrachloride with hafnium dioxide above 450°C;
(iii) heating a mixture of hafnium dioxide and carbon above 700°C;
and (iv) reaction of chlorine with hafnium at elevated temperatures.
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| Reactions |
Hafnium(IV) chloride hydrolyzes, evolving hydrogen chloride:
HfCl4 + H2O→ HfOCl2+ 2 HCl
Aged samples thus often are contaminated with oxychlorides, which are also colourless.
THF forms a monomeric 2:1 complex:
HfCl4+ 2 OC4H8→HfCl4(OC4H8)2
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| Flammability and Explosibility | Nonflammable |
| Solubility in organics | Soluble in methanol, acetone, reacts strongly with water, highly hygroscopic, hydrolyzes in water. |
| Structure and conformation | This group 4 halide contains hafnium in the +4 oxidation state. Solid Hafnium(IV) chloride is a polymer with octahedral Hf centers. Of the six chloride ligands surrounding each Hf centre, two chloride ligands are terminal and four bridge to another Hf centre.
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