Zirconium halides

Within the family of interstitially centered cluster phases the zirconium halides comprise a special field of materials, because it has been developed solely by J. D. Corbett and coworkers. This is truly Corbetts chemistry . 

Of course, the chemistry of zirconium cluster phases has been well described and reviewed in the literature [1-4]. Apart from a very few examples, mostly in the binary halides, almost all reduced zirconium halides contain octahedra of zirconium atoms centred on an interstitial atom Z. Several possible and experimentally realized Z include H, Be-N, K, Al-P, and the transition metals Mn-Ni. All these compounds have the general formula Ax"[(Zr6Z)Xi2X[J], with a " = alkali or alkaline earth metal cation, X=C1 Br or I, X =inner edge-bridging halide [5], X =outer exo-bonded halide, and 0[Pg.61]

Fig. 5.1 [(Zr6Z)XTg] cluster unit in reduced zirconium halides.

Reaction products of a zirconium halide with sorbitol and citric, malic, or lactic acids [1495]... 

GZO films were electrodeposited from an electrodeposition bath containing 0.29-g gadolinium halide and 0.1-g zirconium halide dissolved in a 150-mL electrolyte solution. Electrodeposition was performed at a current density of 1 mA/cm2 and under constant stirring in a vertical two-electrode cell configuration. The average rate of deposition was about 25 nm/min. 

Excision reactions are sometimes accompanied by redox chemistry. For example, dissolution of the 2D solid Na4Zr6BeCli6 in acetonitrile in the presence of an alkylammonium chloride salt results in simultaneous reduction of the cluster cores (144). Here, the oxidation product remains unidentified, but is presumably the solvent itself. As a means of preventing such redox activity, Hughbanks (6) developed the use of some room temperature molten salts as excision media, specifically with application to centered zirconium-halide cluster phases. A number of these solids have been shown to dissolve in l-ethyl-2-methylimidazolium chloride-aluminum chloride ionic liquids, providing an efficient route to molecular clusters with a full compliments of terminal chloride ligands. Such molten salts are also well suited for electrochemical studies. 

Rahlfs, O., and Fischer, W. Thermal properties of halides. VI. Vapor pressures and vapor densities of beryllium and zirconium halides. Z. Anorg. AUgem. Chem. 211, 349-367 (1933). 

Heat capacity estimated by comparison to the other zirconium halides and titanium halides. Entropy estimated from additive constants. 

The decomposition products of zirconium halides heated under ammonia arc a blue nitride with the rocksalt structure 6-Zi N (yellow at perfect stoichiometry) and a brown compound of composition Zr,N4 both are diamagnetic, but 6-ZrN is a metallic conductor (superconducting Tc -- 10 K). whereas Zr, N4 is an insulator [286, 287], Band structure calculations suggest ZrN Zr, N4 would form a good Josephson junction [288],... 

The electroreduction of zirconium halides in alkali halide melts has led to the measurement of reversible potentials (Table XXV) in the temperature range 670°-750°C (550). Phase rule studies of the mixed systems preceded the cell studies and revealed that the phase diagrams of the KCl-ZrCl2 and NaCl-ZrCl2 systems were of the simple eutectic type. The liquidus curves of these binary systems were established by freezing point measurements. The melting point of pure zirconium dichloride was found to be 722° 1°C. In the potassium chloride-zirconium dichloride system, the eutectic is found at 698° 1°C at... 

Because zirconium halides are air- and moisture-sensitive, handling of these compounds must be done in an inert atmosphere dry box equipped to maintain both... 

This value is in good agreement with the value calculated by van der Vis et al. [97VIS/COR] -(759.4 3.0) kJ-mol", from the earlier work of Efimov et al. [87EFI/PRO], in their recent review of the thermochemistry of the zirconium halides. 

There have been no studies of the enthalpies of formation of the lower gaseous zirconium bromides. Values for these parameters have been estimated by [97V1S/COR] from the bond energies of the other zirconium halides. The values estimated by [97V1S/COR] are, Af//° (ZrBr, g, 298.15 K) = (366 25) kJ-mol, Af//° (ZrBrj, g,... 

The preparation of a phosphinocyclopentadiene containing an intervening silane bridge has been reported by Schore/ This wqrk has involved not only the preparation of the usual ferrocenyl derivatives and their subsequent complexation, but a novel zirconium(IV)-iron(0) complex (Figure 7.21). Since cyclopentadienyl zirconium halides represent precursors to useful synthetic reagents, this work represents a significant step towards the assembly of heterobimetallic complexes which contain two reactive metal ions. 

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