Zirconium compounds properties

Many of the most important achievements in organic chemistry in the last 20—25 years have been associated in some way with the use of transition metal complexes. Among these complexes, an increasingly important place is occupied by zirconium compounds, which have a number of unique properties enabling them to be used as highly reactive reagents in organic synthesis [1—9]. 

Zirconium can be a shiny grayish crystal-Uke hard metal that is strong, ductile, and malleable, or it can be produced as an undifferentiated powder. It is reactive in its pure form. Therefore, it is only found in compounds combined with other elements—mosdy oxygen. Zirconium-40 has many of the same properties and characteristics as does hafhium-72, which is located just below zirconium in group 4 of the periodic table. In fact, they are more similar than any other pairs of elements in that their ions have the same charge (+4) and are of the same general size. Because zirconium is more abundant and its chemistry is better known than hafnium s, scientists extrapolate zirconium s properties for information about hafnium. This also means that one twin contaminates the other, and this makes them difficult to separate. 

Zirconyl chloride is used to make pigment toners and improve properties of color lakes of acid and basic dyes. Also, it is used to prepare body deodorants and antiperspirant, water repellant, dye precipitant, catalysts, and many zirconium compounds. 

The similarity in size causes a very close similarity in chemical properties hafnium and zirconium compounds occur together in nature and are very difficult to distinguish from each other, and other pairs of elements following zirconium and hafnium resemble each other more closely than is usual for two successive members of a family. 

There are several complete compilations of the literature concerning zirconium and hafnium that take the reader up to about 1960 62, 344, 420, 558). Since then several reviews of more limited scope have been published, one on the structural aspects of zirconium chemistry 116), and others on the separation of zirconium and hafnium 578), aqueous chemistry 234, 533), and ion-exchange properties of zirconium compounds 29). In general, the data in the present review are drawn from publications since 1960, although references to earlier work are included where necessary to complete the picture. 

Alcock et al. [76ALC/JAC] reviewed the thermochemical properties of zirconium metal and a range of zirconium compounds and presented a considerable amount of data with assigned uncertainties. However, a number of important parameters were not determined and studies that post-date [76ALC/JAC] indicate that alternative interpretations of the data may be more realistic. 

CHEMICAL PROPERTIES most zirconium compounds are considered inert zirconium metal can react with hydrofluoric acid, aqua regia, and hot phosphoric acid attacked hy fused potassium hydroxide or potassium nitrate not attacked by cold, concentrated sulfuric or hydrochloric acid resistant to attack by nitric acid very resistant to corrosion oxidizes rapidly at 6°C nitrided slowly at 700°C compact form combines with oxygen, nitrogen, carbon, and the halogens on prolonged heating FP (NA) LFLAJFL (NA) AT (NA) HF (0.0 kJ/mol crystal at 25 C) Hf (21.0 kJ/mol at 2127.85K). 

Aiken B, Hsu WP, Matijevic E (1990) Preparation and properties of uniform mixed and coated colloidal particles, 5. Zirconium compounds. J Mater Sci 25 1886-1894... 

The ion exchange properties of the a-zirconium compound can be used for the separation of some radioactive elements. Full ion exchange capacity is developed at pH 9-10, but the best separations are achieved at pH 3. These include Cs+ from Rb+ and Ra + from Ba +. The cerium salt Ce(HP04)2 riW-f) can be fabricated in fibrous form which is an effective ion exchanger for Sr + (Table 5.31). 

The titanium, hafnium and other analogues of the above zirconium compounds have been less extensively investigated than the latter, but they all have some ion-exchange properties and appear to form similar intercalation compounds, for example, M(HP04)2 2C H2 +i NH2 H2O. (M = Ti, Hf). 

Previously we reported the preparation of all members of zirconium compounds of (Mef,-C5H5 j )2ZrCl2 and their use in propylene polymerizations. The number and the position of methyl groups on cyclopentadienyl(Cp) rings were confirmed to exert great influence on the physical properties of atactic polypropylene. ... 

M.M. Opeka, l.G. Talmy, E.J. Wuchina, J.A. Zaykoski and S.J. Causey Mechanical, Thermal, and Oxidation Properties of Refractory Hafnium and zirconium Compounds. Journal of the European Ceramic Society 19, 2405-2414(1999). 

Lead zirconate [12060-01 -4] PbZrO, mol wt 346.41, has two colorless crystal stmctures a cubic perovskite form above 230°C (Curie point) and a pseudotetragonal or orthorhombic form below 230°C. It is insoluble in water and aqueous alkaUes, but soluble in strong mineral acids. Lead zirconate is usually prepared by heating together the oxides of lead and zirconium in the proper proportion. It readily forms soHd solutions with other compounds with the ABO stmcture, such as barium zirconate or lead titanate. Mixed lead titanate-zirconates have particularly high piezoelectric properties. They are used in high power acoustic-radiating transducers, hydrophones, and specialty instmments (146). 

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Zirconium and hafnium have very similar chemical properties, exhibit the same valences, and have similar ionic radii, ie, 0.074 mm for, 0.075 mm for (see Hafniumand hafnium compounds). Because of these similarities, their separation was difficult (37—40). Today, the separation of zirconium and hafnium by multistage counter-current Hquid—Hquid extraction is routine (41) (see Extraction, liquid—liquid). 

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