Zirconium Monochloride and Monobromide

Submitted by RICHARD L. DAAKE and JOHN D. CORBETTt Checked by DONALD W. MURPHY t 

The two zirconium monohalides represent the first examples of metallic salts with double metal layers sandwiched between two halogen layers in a close-packed array.1,2,3 At the present time, they are also the most stable of these monohalides and the easiest to prepare in microcrystalline form. 

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 

Because of the relatively high intermediate pressures (20-40 atm) generated in the reactions, tantalum end caps with thickness 30-50% greater than that of the tubing itself are recommended. 

Thermal cycling will be lessened if the control (but not the measuring) thermocouple is placed between the liner and the furnace wall. It is highly advisable that the fused silica jacket about the welded container be sufficiently long to extend from the end of the furnace to permit condensation of the tetrahalide, should a leak develop. Unless a thermal gradient is required, the tantalum tube itself should be centered in the furnace. Although the explosion hazard is very slight if these procedures are followed, the open ends of the furnace should still be shielded from workers. 

Thermal cycling will be lessened if the control (but not the measuring) thermocouple is placed between the liner and the furnace wall. It is highly 

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Zirconium monochloride and monobromide are black powders or highly reflective microcrystals. Although the monohalides appear to be stable in air for days to weeks, they should be kept and handled under inert atmospheres if high purity is required, owing to a probable slow reduction of water vapor to form the hydrides (see below) and Zr02. These monohalides possess a rhombohedral (R3m), three-slab structure in which each slab consists of four tightly bound,... 

DAA/COR] Daake, R. L., Corbett, J. D., Zirconium monobromide, a second double metal sheet structure. Some physical and chemical properties of the metallic zirconium monochloride and monobromide, Inorg. Chem., 16, (1977), 2029-2033. Cited on pages 167, 173. 

Zirconium monochloride and zirconium monobromide [31483-18-8] are prepared in better purity by equiUbration of mixed lower haUdes with zirconium foil at 625°C (184—185) or by slowly heating zirconium tetrahaUde with zirconium turnings at 400—800°C over a period of two weeks and hoi ding at 800—850°C for a few additional days (186). Similar attempts to produce zirconium monoiodide [14728-76-8] were unsuccesshil it was, however, obtained from the reaction of hydrogen iodide with metallic zirconium above 2000 K (187). 

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