Triiodides

Johnson A E and Myers ABA 1996 A comparison of time- and frequency-domain resonance Raman spectroscopy in triiodide J. Cham. Phys. 104 2497-507... 

The hydrolysis of phosphorus tribromide or triiodide is used in the preparation of hydrogen bromide and hydrogen iodide respectively ... 

The best known polyhalide is the triiodide ion, Ij", found when iodine dissolves in the aqueous solution of the iodide of a large unipositive cation (usually K ) ... 

Nitrogen triiodide Acids, bromine, chlorine, hydrogen sulflde, ozone... 

Galhum triiodide [13450-914], Gal, is obtained by direct reaction of the elements or by reaction of iodine solution in carbon disulfide on galhum. 

The hberated iodine, as the complex triiodide ion, may be titrated with standard thiosulfate solution. A general iodometric assay method for organic peroxides has been pubUshed (253). Some peroxyesters may be determined by ferric ion-catalyzed iodometric analysis or by cupric ion catalysis. The latter has become an ASTM Standard procedure (254). Other reducing agents are ferrous, titanous, chromous, staimous, and arsenite ions triphenylphosphine diphenyl sulfide and triphenjiarsine (255,256). 

The tnhahdes of phosphoms usually are obtained by direct halogenation under controlled conditions, eg, in carbon disulfide solution in the case of the triiodide. Phosphoms trifluoride [7647-19-0] is best made by transhalogenation of PCl using AsF or Cap2. AH of the phosphoms tnhahdes are both Lewis bases and acids. The phosphoms tnhahdes rapidly hydroly2e in water and are volatile. Examination by electron diffraction has confirmed pyramidal stmctures for the gaseous tnhahde molecules (36). Physical properties and heat of formation of some phosphoms hahdes are hsted in Table 7. 

Plutonium tribromide [15752-46-2] PuBr3, and plutonium triiodide [13455-01 -17, PUI3, both bright green soflds, have no practical appHcations. Comprehensive reviews of the binary and ternary haHdes are available (147,154,155). 

Thallium (ITT) fluoride has been prepared by the action of fluorine or bromine trifluoride on thaUium(III) oxide at 300°C. It is stable to ca 500°C but is extremely sensitive to moisture. Thallium (ITT) chloride can be obtained readily as the tetrahydrate [13453-33-3] by passing chlorine through a boiling suspension of HCl in water. It can be dehydrated with thionyl chloride. Thallium (ITT) bromide tetrahydrate [13453-29-7] is prepared similarly, whereas the iodide prepared in this manner is thaUium(I) triiodide [13453-37-7] H" F2-... 

Titanium Triiodlde. Titanium triiodide is a violet crystalline soHd having a hexagonal unit cell (146). The crystals oxidize rapidly in air but are stable under vacuum up to 300°C above that temperature, disproportionation to the diiodide and tetraiodide begins (147). 

Titanium triiodide can be made by direct combination of the elements or by reducing the tetraiodide with aluminum at 280°C in a sealed tube. Til reacts with nitrogen, oxygen, and sulfur donor ligands to give the corresponding adducts (148). 

Tungsten triiodide [15513-69-6] prepared by the action of iodine on tungsten hexacarbonyl in a sealed tube at 120°C (18). 

Zirconium tetraiodide [13986-26-0], Zrl, is prepared directly from the elements, by the reaction of iodine on zirconium carbide, or by halogen exchange with aluminum triiodide. The reaction of iodine with zirconium oxide and carbon does not proceed. The physical properties are given in Table 7. 

Lower Valent Halides. Zirconium trichloride [10241-03-9], ZrCl, tribromide [24621 -18-9], ZrBr, and triiodide [13779-87-8], Zrl, are... 

Antimony Tribromide and Triiodide. Antimony(III) bromide [7789-61-9] SbBr, is a colorless, crystalline soHd having a pyramidal dimorphic molecular stmcture and an acicular (a-SbBr ) and a bipyramidal (P-SbBr ) habit. 

Boron Triiodide. Boron ttiiodide is not manufactured on a large scale. Small-scale production of BI from boron and iodine is possible in the temperature range 700—900°C (70—72). Excess I2 can be removed as Snl by reaction with Sn, followed by distillation (71). The reaction of metal tetrahydroborates and I2 is convenient for laboratory preparation of BI (73,74). BI can also by synthesized from B2H and HI in a furnace at 250°C (75), or by the reaction of B with excess Agl or Cul between 450—700°C, under vacuum (76). High purity BI has been prepared by the reaction of I2 with mixtures of boron carbide and calcium carbide at elevated temperatures. 

Boron Triiodide. There are no large-scale commercial uses of boron ttiiodide. It can cleave ethers without affecting aldehyde groups and thus finds use in the synthesis of the antibiotic fmstulosin (115,116). BI is used to prepare Snl, Sbl, and Til (117) in 99—100% yield. It is used to clean equipment for handling UE (118) and in the manufacture of lithium batteries (119). 

In biological materials, various nonspecific precipitants have been used in the gravimetric deterrnination of choline, including potassium triiodide, platinum chloride, gold chloride, and phosphotungstic acid (28). Choline may also be determined spectrophotometricaHy and by microbiological, enzymatic, and physiological assay methods. 

Iodine. Iodine has been important for many years, primarily as an antiseptic (see Iodine and iodine compounds). In the American Civil War physicians used it to treat battie wounds. Elemental iodine is not very soluble in water, but dissolves readily when sodium iodide is added, forming triiodide + I I Iodine may thus be used as an aqueous solution but it has generally been used as a tincture of 2% iodine in 70% alcohol. Tests on... 

Boron triiodide rapidly cleaves methyl ethers of ortho-, meta-, or para-suhsti-tuted aromatic aldehydes (0°, 25° 0.5-5 min 40-86% yield). 

Arsenic triiodide [7784-45-4] M 455.6, m 146°, b 400°/atm. Crystd from acetone, sublimes below 100°. POISONOUS... 

Phosphorus triiodide [ 13455-01-1 ] M 411.7, m 61 . Decomposes in moist air and must be kept in a desiccator over CaCl2. It is crystallised from sulfur-free CS2 otherwise the m decreases to ca 55°. It is best prepared freshly. [J Am Chem Soc 49 307 7927 Handbook of Preparative Inorganic Chemistry (Ed. Brauer) vol I 541 7965.] HARMFUL VAPOURS. 

Figure 4 Free energy surfaces of triiodide ion in various solutions. Contours correspond to isoenergy lines of IkgT, Ik T, and 3kgT, respectively.

Computed free energy surfaces of the triiodide ion in its ground state in acetonitrile, methanol, and aqueous solution are presented in Figure 4, in which the two I—I bond... 

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