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| ImageFile = Zirconium-tetrachloride-3D-balls-A.png |
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| ImageFile = Zirconium-tetrachloride-3D-balls-A.png |
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| Name = Hafnium(IV) chloride |
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| Name = Hafnium(IV) chloride |
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| IUPACName = Hafnium(IV) chloride<br/>Hafnium tetrachloride |
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| IUPACName = Hafnium(IV) chloride<br/>Hafnium tetrachloride |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 34591 |
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| ChemSpiderID = 34591 |
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| InChI = 1/4ClH.Hf/h4*1H;/q;;;;+4/p-4 |
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| InChI = 1/4ClH.Hf/h4*1H;/q;;;;+4/p-4 |
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| StdInChIKey = PDPJQWYGJJBYLF-UHFFFAOYSA-J |
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| StdInChIKey = PDPJQWYGJJBYLF-UHFFFAOYSA-J |
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| CASNo = 13499-05-3 |
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| CASNo = 13499-05-3 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = CNZ9V5JM5H |
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| PubChem = 37715 |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = HfCl<sub>4</sub> |
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| Formula = HfCl<sub>4</sub> |
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| MolarMass = 320.30 g/mol |
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| MolarMass = 320.302 g/mol |
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| Appearance = white crystalline solid |
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| Appearance = white crystalline solid |
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| Solubility = decomposes |
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| Solubility = decomposes<ref name=crc>{{RubberBible92nd|page=4.66}}</ref> |
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| Density = 3.89 g/cm<sup>3</sup><ref name=str/> |
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| MeltingPt = 432 °C (705 K) |
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| MeltingPtC = 432 |
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| VaporPressure = 1 mmHg at 190 °C |
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| MeltingPt_notes = |
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| VaporPressure = 1 mmHg at 190 °C |
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| Section3 = {{Chembox Structure |
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| Coordination = 4 |
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| Coordination = 4 |
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| CrystalStruct = ] |
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| CrystalStruct = ], ]<ref name=str>Niewa R., Jacobs H. (1995) ''Z. Kristallogr.'' '''210''': 687</ref> |
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| SpaceGroup = C2/c, No. 13 |
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| LattConst_a = 0.6327 nm |
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| LattConst_b= 0.7377 nm |
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| LattConst_c=0.62 nm |
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| Section7 = {{Chembox Hazards |
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| MainHazards = irritant and corrosive |
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| EUIndex = Not listed |
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| NFPA-H = |
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| MainHazards = irritant and corrosive |
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| FlashPt = Non-flammable |
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| NFPA-O = |
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| LD50 = 2362 mg/kg (rat, oral)<ref>{{IDLH|7440586|Hafnium compounds (as Hf)}}</ref> |
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| FlashPt = Non-flammable |
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| Section8 = {{Chembox Other |
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|Section8={{Chembox Related |
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| OtherAnions = ]<br/>]<br/>] |
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| OtherAnions = ]<br/>]<br/>] |
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| OtherCations = ]<br/>] |
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| OtherCations = ]<br/>] |
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'''Hafnium(IV) chloride''' is the ] with the ] HfCl<sub>4</sub>. This colourless solid is the precursor to most hafnium ] compounds. It functions as a ] and ] for certain ] and ] reactions. ] the metal center in the complex occurs in nature in small amounts associated with ] minerals such as zircon, cyrtolite and baddeleyite. Zircon contains 0.05 to 2.0 percent ] HfO<sub>2</sub>, cyrtolite with 5.5 to 17 percent HfO<sub>2</sub> and baddeleyite contains 1.0 to 1.8 percent HfO<sub>2</sub>.<ref name="IvanEdgar">Ivan Edgar Newnham. Purification of Hafnium Tetrachloride. U.S. patent 2,961,293 November 22, 1960.</ref> |
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'''Hafnium(IV) chloride''' is the ] with the ] HfCl<sub>4</sub>. This colourless solid is the ] to most hafnium ] compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst. |
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Hafnium and zirconium compounds are extracted from ores together because ] and ] have very similar chemical and physical properties. Therefore in the synthesis of Hafnium(IV) chloride which requires HfO<sub>2</sub>, the HfO<sub>2</sub> has to be purified from the mineral ore and this can be achieved through decomposition.<ref name="IvanEdgar" /> |
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==Preparation== |
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==Preparation== |
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HfCl<sub>4</sub> can be produced by several related procedures: |
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*The reaction of ] and ] at above 450 °C;<ref>{{cite book | title = Kirk-Othmer Encyclopedia of Chemical Technology | edition = 4th | year= 1991 | volume = 11}}</ref><ref>{{Cite book| doi = 10.1002/9780470132357.ch41| title= Zirconium and Hafnium Tetrachlorides| series= Inorganic Syntheses| volume = 4| pages = 121| year = 1953| last1 = Hummers | first1 = W. S.| last2 = Tyree, Jr. | first2 = S. Y.| last3 = Yolles | first3 = S. | isbn = 9780470132357}}</ref> |
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:HfO<sub>2</sub> + 2 CCl<sub>4</sub> → HfCl<sub>4</sub> + 2 COCl<sub>2</sub> |
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*Chlorination of a mixture of HfO<sub>2</sub> and ] above 600 °C using ] or ]:<ref>{{cite book | last1 = Hopkins | first1 = B. S. | title = Chapters in the chemistry of less familiar elements | year = 1939 | publisher = Stipes Publishing | page = 7 | chapter = 13 Hafnium}}</ref><ref>{{cite book | last1 = Hála | first1 = Jiri | title = Halides, oxyhalides and salts of halogen complexes of titanium, zirconium, hafnium, vanadium, niobium and tantalum | year = 1989 | publisher = Pergamon | location = Oxford | isbn = 978-0080362397 | pages = 176–177 | edition = 1st | volume = 40}}</ref> |
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:HfO<sub>2</sub> + 2 Cl<sub>2</sub> + C → HfCl<sub>4</sub> + CO<sub>2</sub> |
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*] of hafnium carbide above 250 °C.<ref>Elinson, S. V. and Petrov, K. I. (1969) ''Analytical Chemistry of the Elements: Zirconium and Hafnium.'' 11.</ref> |
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==Separation of Zr and Hf== |
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HfCl<sub>4</sub> is produced by several procedures: (1) the reaction of ] and ] at above 450 °C;<ref>''Encyclopedia of Chemical Technology.'' Kirk-Othermer. Vol.11, 4th Ed. ('''1991''')</ref> (2) chlorination of a mixture of HfO<sub>2</sub> and ] above 600 °C;<ref>Hala, J. ''Halides, Oxyhalides and Salts of Halogen Complexes of Titanium, Zirconium, Hafnium, Vanadium, Niobium and Tantalum.'' Vol. 40, 176-177, ('''1970''').</ref> and (3) ] of hafnium carbide above 250 °C.<ref>S.V. Elinson, K.I. Petrov. ''Analytical Chemistry of the Elements: Zirconium and Hafnium.'' 11, ('''1969''').</ref> |
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] and ] occur together in minerals such as zircon, cyrtolite and baddeleyite. Zircon contains 0.05% to 2.0% ] HfO<sub>2</sub>, cyrtolite with 5.5% to 17% HfO<sub>2</sub> and baddeleyite contains 1.0 to 1.8 percent HfO<sub>2</sub>.<ref name="IvanEdgar">Newnham, Ivan Edgar "Purification of Hafnium Tetrachloride". {{US Patent|2961293}} November 22, 1960.</ref> Hafnium and zirconium compounds are extracted from ores together and converted to a mixture of the tetrachlorides. |
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The separation of HfCl<sub>4</sub> and ZrCl<sub>4</sub> is difficult because the compounds of ] and ] have very similar chemical and ]. Their atomic radii are similar: the ] is 156.4 pm for hafnium, whereas that of Zr is 160 pm.<ref name=j1>{{Cite journal | doi = 10.1007/BF01151485| title = Electronographic investigation of the structure of zirconium and hafnium tetrachloride molecules in the gas phase| journal = Journal of Structural Chemistry| volume = 3| issue = 3| pages = 311| year = 1962| last1 = Spiridonov | first1 = V. P.| last2 = Akishin | first2 = P. A.| last3 = Tsirel'Nikov | first3 = V. I.| s2cid = 94835858}}</ref> These two metals undergo similar reactions and form similar coordination complexes. |
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Hafnium(IV) chloride is prepared by heating a mixture of HfO<sub>2</sub> and ] in a stream of ] or ] under hot temperatures as shown in the equation below.<ref>B.S Hopkins. Chapters in the chemistry of less familiar elements, Chapter 13 Hafnium; pp 7</ref> |
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A number of processes have been proposed to purify HfCl<sub>4</sub> from ZrCl<sub>4</sub> including ], fractional precipitation, fractional crystallization and ]. The log (base 10) of the vapor pressure of solid hafnium chloride (from 476 to 681 K) is given by the equation: log<sub>10</sub> ''P'' = −5197/''T'' + 11.712, where the pressure is measured in ]s and temperature in ]s. (The pressure at the melting point is 23,000 torrs.)<ref>{{Cite journal | doi = 10.1021/j150561a017| title = The Vapor Pressures of Zirconium Tetrachloride and Hafnium Tetrachloride| journal = The Journal of Physical Chemistry| volume = 62| issue = 3| pages = 319| year = 1958| last1 = Palko | first1 = A. A.| last2 = Ryon | first2 = A. D.| last3 = Kuhn | first3 = D. W.| hdl = 2027/mdp.39015086446302| hdl-access = free}}</ref> |
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::HfO<sub>2</sub> + 4Cl + C → HfCl<sub>4</sub> + CO<sub>2</sub> |
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One method is based on the difference in the reducibility between the two tetrahalides.<ref name="IvanEdgar" /> The tetrahalides can in be separated by selectively reducing the zirconium compound to one or more lower halides or even zirconium. The hafnium tetrachloride remains substantially unchanged during the reduction and may be recovered readily from the zirconium subhalides. Hafnium tetrachloride is volatile and can therefore easily be separated from the involatile zirconium trihalide. |
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HfCl<sub>4</sub> could also be prepared by reacting Hf(OH)<sub>4</sub> with HCl and then boiling the reactants until crystals are formed \. Since Hf mineral ores contain Zr compounds as well, some ZrCl<sub>4</sub> is also formed in the process of synthesizing HfCl<sub>4</sub> therefore the product has to be purified in order to obtain pure HfCl<sub>4</sub>. |
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==Structure and bonding== |
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==Purification== |
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This group 4 ] contains ] in the +4 ]. Solid HfCl<sub>4</sub> is a ] 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. In the gas phase, both ZrCl<sub>4</sub> and HfCl<sub>4</sub> adopt the monomeric tetrahedral structure seen for TiCl<sub>4</sub>.<ref>{{Greenwood&Earnshaw2nd|pages=964–966}}</ref> Electronographic investigations of HfCl<sub>4</sub> in gas phase showed that the Hf-Cl internuclear distance is 2.33 Å and the Cl...Cl internuclear distance is 3.80 Å. The ratio of intenuclear distances r(Me-Cl)/r(Cl...Cl) is 1.630 and this value agrees well with the value for the regular tetrahedron model (1.633).<ref name=j1/> |
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The purification of HfCl<sub>4</sub> tends to be a difficult endeavor because ] and ] have very similar chemical and physical properties. Both metals have the same number of d electrons and they have a small difference in atomic radii (hafnium atomic radius is 156.4 pm while that of Zr is 160 pm).<ref>V. P. Spiridonov, P. A. Akishin and V. I. Tsirel’nikov, M. V. Lomonosov. Electronographic Investigation of the structure of Zirconium and Hafnium Tetrachloride Molecules in Gas Phase. Journal of Structural Chemistry Vol. 3, 1962, pp 329-330</ref> This means that these two metals undergo similar reactions and form the similar coordination complexes which makes the separation of these so formed complexes difficult. |
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==Reactivity== |
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The Tetrahalides can also be separated by selectively reducing the Zirconium tetrahalide to one or more lower halides or even Zirconium. The Hafnium tetrachloride remains substantially unchanged during the reduction and may be recovered readily from the zirconium subhalides. Hafnium tetrachloride is volatile and can therefore easily be separated from the involatile zirconium trihalide. This is based on the difference in the reducibility between the two tetrahalides.<ref name="IvanEdgar" /> |
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] | year = 1990 | volume = C46 | pages = 890–2 | doi = 10.1107/S010827018901382X | last1 = Duraj | first1 = S. A. | last2 = Towns | last3 = Baker | last4 = Schupp | first4 = J. | issue = 5| doi-access = free }}</ref>]] |
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The compound hydrolyzes, evolving ]: |
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:HfCl<sub>4</sub> + H<sub>2</sub>O → HfOCl<sub>2</sub> + 2 HCl |
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Aged samples thus often are contaminated with oxychlorides, which are also colourless. |
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There have been a number of proposed processes that could be used to purify HfCl<sub>4</sub> from ZrCl<sub>4</sub> and some of the proposed methods include fractional distillation, fractional precicpitation, fractional crystallization and ion exchange.<ref>Misplaced Pages contributors. Misplaced Pages 💕. Hafnium (IV) Chloride, December 2009, pg version ID 331590363.</ref> |
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] forms a ] 2:1 complex:<ref>{{cite journal| title = Tetrahydrofuran Complexes of Selected Early Transition Metals | journal = ] | doi = 10.1002/9780470132524.ch31 | last1 = Manzer | first1 = L. E. | volume = 21 | pages = 135–140 | year = 1982 | isbn = 978-0-470-13252-4}}</ref> |
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==Structure and bonding== |
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:HfCl<sub>4</sub> + 2 OC<sub>4</sub>H<sub>8</sub> → HfCl<sub>4</sub>(OC<sub>4</sub>H<sub>8</sub>)<sub>2</sub> |
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This Group 4 ] contains ] in the +4 ]. Solid HfCl<sub>4</sub> is a ], each of the Hf centers are bridged by chloride ]s as found for ZrCl<sub>4</sub>. In the gas phase, both ZrCl<sub>4</sub> and HfCl<sub>4</sub> are expected to adopt the monomeric tetrahedral structure seen for TiCl<sub>4</sub>.<ref>Greenwood, N. N., Earnshaw, A. ''Chemistry of the Elements Second Ed.'' Butterworth-Heinemann, Boston, ('''1997''').</ref> |
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Electronographic investigations of HfCl4 in gas phase showed that the Hf-Cl internuclear distance is 2.33 Å and the Cl…Cl internuclear distance is 3.80 Å. The ratio of intenuclear distances r(Me-Cl)/r(Cl…Cl) is 1.630 and this value agrees well with the value for the regular tetrahedron model (1.633).<ref>V. P. Spiridonov, P. A. Akishin and V. I. Tsirel’nikov, M. V. Lomonosov. Electronographic Investigation of the structure of Zirconium and Hafnium Tetrachloride Molecules in Gas Phase. Journal of Structural Chemistry Vol. 3, 1962, pp 329-330.</ref> |
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Because this complex is soluble in organic solvents, it is a useful reagent for preparing other complexes of hafnium. |
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==Reactivity== |
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The compound is highly reactive toward water, evolving ]. Aged samples often are contaminated with the oxychloride, which is also colourless. The ] complex is ] and thus soluble in organic solvents, which allows this hafnium complex to react more easily.<ref>{{cite journal | title = Tetrahydrofuran Complexes of Selected Early Transition Metals | journal = ] | doi = 10.1002/9780470132524.ch31 | last1 = Manxzer | first1 = L. E. | volume = 21 | last2 = Deaton | year = 1982 | last3 = Sharp | last4 = Schrock | pages = 135 | first2 = Joe | first3 = Paul | first4 = R. R. | series = Inorganic Syntheses | isbn = 9780470132524}}</ref> |
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HfCl<sub>4</sub> undergoes ] with ]s. In this way, tetrabenzylhafnium can be prepared. |
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::HfCl<sub>4</sub> + 2 OC<sub>4</sub>H<sub>8</sub> → HfCl<sub>4</sub>(OC<sub>4</sub>H<sub>8</sub>)<sub>2</sub> |
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:{{chem2|4 C6H5CH2MgCl + HfCl4 -> (C6H5CH2)4Hf + 4 MgCl2}} |
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Similarly, salt metathesis with ] gives ]: |
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Little is known about Hf(III) compounds because HfCl<sub>4</sub> is especially difficult to reduce, but reduction can be effected with ]:<ref>{{cite journal | author = M. E. Riehl, S. R. Wilson, and G. S. Girolami | title = Synthesis, X-ray Crystal Structure, and Phosphine-Exchange Reactions of the Hafnium(III)-Hafnium(II1) Dimer Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> | journal = ] | volume = 32 | pages = 218–222 | year = 1993 | doi = 10.1021/ic00054a017 | issue = 2}}</ref> |
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:{{chem2|2 NaC5H5 + HfCl4 -> (C5H5)2HfCl2 + 2 NaCl}} |
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::2 HfCl<sub>4</sub> + 2 K + 4 P(C<sub>2</sub>H<sub>5</sub>)<sub>3</sub> → Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> + 2 KCl |
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Deep green Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> crystals form, which are ]. ] shows that Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> has an edge-shared bioctahedral structure, very similar to the Zr analogue. |
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With alcohols, alkoxides are formed. |
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HfCl<sub>4</sub> 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.<ref>Ian Westmoreland. Alkylation of hafnium tetrachloride with benzyl Grignard; Hafnium tetrabenzyl ; Group 4 tetrabenzyl, pp 211, 2003</ref> |
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:HfCl<sub>4</sub> + 4 ROH → Hf(OR)<sub>4</sub> + 4 HCl |
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These compounds adopt complicated structures. |
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===Reduction=== |
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Reduction of HfCl<sub>4</sub> is especially difficult. In the presence of ]s, reduction can be effected with ]:<ref>{{cite journal | author = Riehl, M. E. |author2=Wilson, S. R. |author3=Girolami, G. S. | title = Synthesis, X-ray Crystal Structure, and Phosphine-Exchange Reactions of the Hafnium(III)-Hafnium(III) Dimer Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> | journal = ] | volume = 32 | pages = 218–222 | year = 1993 | doi = 10.1021/ic00054a017 | issue = 2}}</ref> |
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:2 HfCl<sub>4</sub> + 2 K + 4 P(C<sub>2</sub>H<sub>5</sub>)<sub>3</sub> → Hf<sub>2</sub>Cl<sub>6</sub><sub>4</sub> + 2 KCl |
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The deep green dihafnium product is ]. ] shows that the complex adopts an edge-shared bioctahedral structure, very similar to the Zr analogue. |
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:: RMg-X + HfCl<sub>4</sub> → HfX<sub>4</sub> |
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==Uses== |
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==Uses== |
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Hafnium chloride is the precursor to highly active catalysts for the polymerization of ]s, especially ].<ref>{{cite news | author = Ron Dagani | title = Combinatorial Materials: Finding Catalysts Faster | url = http://pubs.acs.org/cen/topstory/8114/print/8114notw5.html | publisher = ] | date = 2003-04-07 | pages = 10}}</ref> Typical catalysts are derived from tetra]hafnium. |
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Hafnium tetrachloride is the precursor to highly active catalysts for the ] of ]s, especially ].<ref>{{cite news | author = Ron Dagani | title = Combinatorial Materials: Finding Catalysts Faster | url = http://pubs.acs.org/cen/topstory/8114/print/8114notw5.html | work = ] | date = 2003-04-07 | pages = 10}}</ref> Typical catalysts are derived from tetra]hafnium. |
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HfCl<sub>4</sub> is an effective Lewis acid for various applications in ]. For example, ] is alkylated with allyldimethylchlorosilane more efficiently using hafnium chloride relative to ]. The greater size of Hf may diminish HfCl<sub>4</sub>'s tendency to complex to ferrocene.<ref>{{cite journal | author = S. Ahn, Y. Song, B. Yoo, I. Jung | title = Lewis Acid-Catalyzed Friedel-Crafts Alkylation of Ferrocene with Allylchlorosilanes | journal = ] | volume = 19 | pages = 2777–2780 | year = 2000 | doi = 10.1021/om0000865 | issue = 14}}</ref> |
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HfCl<sub>4</sub> is an effective Lewis acid for various applications in ]. For example, ] is alkylated with allyldimethylchlorosilane more efficiently using hafnium chloride relative to ]. The greater size of Hf may diminish HfCl<sub>4</sub>'s tendency to complex to ferrocene.<ref>{{Cite journal | doi = 10.1021/om0000865| title = Lewis Acid-Catalyzed Friedel−Crafts Alkylation of Ferrocene with Allylchlorosilanes| journal = Organometallics| volume = 19| issue = 14| pages = 2777| year = 2000| last1 = Ahn | first1 = S. | last2 = Song | first2 = Y. S. | last3 = Yoo | first3 = B. R. | last4 = Jung | first4 = I. N. }}</ref> |
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HfCl<sub>4</sub> increases the rate and control of 1,3-dipolar cycloadditions.<ref>{{cite journal | author = P. Dunn, A. Graham, R. Grigg, P. Higginson | journal = ] | pages = 2035–2036 | year = 2000 | doi = 10.1039/b005389i | title = Tandem 1,3-azaprotiocyclotransfer–cycloaddition reactions between aldoximes and divinyl ketone. Remarkable rate enhancement and control of cycloaddition regiochemistry by hafnium(iv) chloride | issue = 20}}</ref> It was found to yield better results than other Lewis acids when used with ] and ] aldoximes, allowing specific ] formation. |
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HfCl<sub>4</sub> increases the rate and control of 1,3-dipolar cycloadditions.<ref>{{Cite journal | doi = 10.1039/b005389i| title = Tandem 1,3-azaprotiocyclotransfer–cycloaddition reactions between aldoximes and divinyl ketone. Remarkable rate enhancement and control of cycloaddition regiochemistry by hafnium(iv) chloride| journal = Chemical Communications| issue = 20| pages = 2035–2036| year = 2000| last1 = Graham | first1 = A. B. | last2 = Grigg | first2 = R. | last3 = Dunn | first3 = P. J. | last4 = Higginson | first4 = P. }}</ref> It was found to yield better results than other Lewis acids when used with ] and ] aldoximes, allowing specific ] formation. |
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===Microelectronics applications=== |
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Hafnium chloride is also the precursor to highly active catalysts for the polymerization of alkenes, especially propylene. Typical catalysts are derived from tetrabenzylhafnium. It was recently reported that MgCl2 supported HfCl<sub>4</sub> in combination with AlEt3 or Dimethyltitanocene specifically produces polypropylene.<ref>Francesco Masi, Francesco Menconi, Stefano Malquori, Renzo Invernizzi. Supported Hafnium Catalysts for Sterospecific polymerization of α-olefins, Dipartimento di Chimica e Chimica Industriale, Universita di Pisa, Pisa, Italy, 1989</ref> |
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HfCl<sub>4</sub> was considered as a precursor for ] and ] of ] and ], used as ]s in manufacture of modern high-density integrated circuits.<ref>{{Cite journal | doi = 10.1016/j.mser.2010.12.001| title = Development of hafnium based high-k materials—A review| journal = Materials Science and Engineering: R: Reports| volume = 72| issue = 6| pages = 97| year = 2011| last1 = Choi | first1 = J. H. | last2 = Mao | first2 = Y.| last3 = Chang | first3 = J. P. }}</ref> However, due to its relatively low ] and corrosive byproducts (namely, ]), HfCl<sub>4</sub> was phased out by metal-organic precursors, such as tetrakis ethylmethylamino hafnium (TEMAH).<ref>{{Cite journal | doi = 10.1088/0034-4885/69/2/R02| title = High dielectric constant gate oxides for metal oxide Si transistors| journal = ]| volume = 69| issue = 2| pages = 327–396| year = 2006| last1 = Robertson | first1 = John | authorlink=John_Robertson_(physicist) | bibcode = 2006RPPh...69..327R| s2cid = 122044323}}</ref> |
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===Materials science applications=== |
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HfCl<sub>4</sub> is the most common precursor for ] of ] and ], used as ]s in manufacture of modern high-density integrated circuits. |
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==References== |
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==References== |
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{{Reflist|30em}} |
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<references/> |
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==Further reading== |
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* {{cite journal | title = Structure of ''cis''-Tetrachlorobis(tetrahydrofuran)hafnium(IV) | journal = ] | year = 1990 | volume = C46 | pages = 890–2 | author1 = Duraj, S. A | author2 = Towns, R. L. R | author3 = Baker, R. J. and Schupp | doi = 10.1107/S010827018901382X | last1 = Duraj | first1 = S. A. | last2 = Towns | last3 = Baker | last4 = Schupp | first4 = J. | issue = 5}} |
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==External links== |
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{{Hafnium compounds}} |
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{{Hafnium compounds}} |
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{{Chlorides}} |
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{{DEFAULTSORT:Hafnium(Iv) Chloride}} |
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{{DEFAULTSORT:Hafnium(Iv) Chloride}} |
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