Bismuth halides

The trihalides are Lewis acids and form donor-acceptor complexes with a number of ethers, e.g. /ac-[BiCl3(THP)3], mer-[Bil3(py)3] (py = pyridine), cw-[Bil4(py)2], [BiCl3(py)4] 

In reaction 14.82, which species nndergo oxidation and which rednetion Confirm that the eqnation balances in terms of changes in oxidation states. 

AsBr3 + BrOTePj + As(OTep5)5 — [AsBr4]+[As(OTep5)6] Oxidation states AsBr3 As, 4-3 Br, — 1 

The redox chemistry involves As and Br. The As in AsBr3 is oxidized on going to [AsBr4]+, while Br in BrOTePs is reduced on going to [AsBr4]+. 

Therefore the equation balances in terms of oxidation state changes. 

and [Bi2l9] (15.45). Bismuth(III) also forms some higher nuclearity halide complexes, e.g. [Bi4Cli6] , as well as the polymeric species [ BiX4 ] and [ BiX5 ] . In each case, the Bi atoms are octahedrally sited. 

Worked example 15.8 Redox chemistry of group 15 metal halides 

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A number of complex bismuth halides are weU-known, eg, disodium bismuth pentachloride [66184-10-9] Na2BiCl sodium dibismuth heptachloride [66184-09-6J, NaBi Cl and trisodium bismuth hexachlotide [66114-82-7J, Na BiCl. The acid, hydrogen dibismuth heptachloride tnhydrate [66124-39-9] HBi Cl 3H20, is a crystalline substance, stable at room temperature, that maybe isolated by cooling a solution of BiCl in concentrated hydrochloric acid to 0°C. 

Partial substitution of halides on bismuth predictably gives alkoxy-bismuth halides, and salts of bismuth anions are obtained by reaction of the alkoxide with an ammonium or phosphonium halide (28). Two isostructural derivatives [Bi2Cl4(thf)2(ju,-OAr)2] (Ar = C6H3Me2-2,6 and C6H2Me3-2,4,6) are composed of dimeric units residing on a C2 axis 8. The bismuth is in a five-coordinate distorted square pyramidal geometry in each case. The apical sites are occupied by terminal... 

Initial investigations in the Mannich-type reaction of silyl enolates with benzal-dehyde and aniline employed a series of bismuth(III) salts (Scheme 9, Table 10). These results were promising because the corresponding (l-amino ketone could be obtained in moderate to good yield with bismuth halides, except bismuth fluoride (Table 10, entries 1 1). Bismuth nitrate smoothly afforded the expected product (Table 10, entry 5). While bismuth acetate gave no conversion, bismuth trifluor-oacetate provided the product in only moderate yield (Table 10, entries 6 and 7). Phenyl bismuth ditriflate and diphenyl bismuth triflate appeared to be more efficient catalysts than all those previously tested (Table 10, entries 8 and 9). Bismuth(III) triflate led to the expected product in a good yield and in a short reaction time, without any difference between the anhydrous and the hydrated form (Table 10, entries 10 and 11). 

The arsenic and the antimony halides, that have lone electron-pairs, too, form compounds similar to that of PC13, but less stable, and the bismuth halides do not react at all. The most probable explanation is that, in the series... 

Table 30 Some Crystal Structure Data for the Bismuth Halides...

Bismuth Halides. The bismuth trihalides are the best known. Bismuth does form a single pentahalide, BiF5, and subhalides that approximate the composition BiX, the best characterized of these being BiCl11(57. Vapors above solutions of a bismuth trihalide in molten bismuth contain the species BiX and/or (BiX)w, where X = Cl, Br, or I (9). At temperatures below 323°C, a black, diamagnetic, orthorhombic solid of the overall composition BiCl1 7 may be isolated from solutions of bismuth trichloride in molten bismuth (10). 

Direct halogenation of metallic bismuth yields bismuth pentafluoride in the case of fluorine, the corresponding bismuth trihalides for the other halogens. Reaction of bismuth trioxide with aqueous HF, HC1, or HBr yields the corresponding bismuth trihalide. Physical and thermochemical properties of the more important bismuth halides appear in Table 2. 

Bismuth Trifluoride. Bismuth(III) fluoride is a white to grey-white powder, density 8.3 g/mL, that is essentially isomorphous with orthorhombic YF3, requiring nine-coordination about the bismuth (11). It has been suggested that BiF3 is best considered an eight-coordinate structure with the deviation from the YF3 structure resulting from stereochemical activity of the bismuth lone-pair electrons. In accord with its structure, the compound is the most ionic of the bismuth halides. It is almost insoluble in water (5.03 0.05 x 10-3 M at pH 1.15) and dissolves only to the extent of 0.010 g per 100 g of anhydrous HF at 12.4°C. 

The M—M bonds in R3MMR3, R3M(R2M) MR3 or (R2M) for M = Sn, Pb are cleaved by water, alcoholic solution of AgN03, alkyl iodides, mercury and bismuth halides and are oxidized by air. In contrast, these compounds with M = Si, Ge are stable under similar reaction conditions. The stability of the highly reactive R2M=MR2, as well as the tendency of R2M to dimerize, diminish as the atomic number of M increases160-162. 

Bismuth Halides, Pseudohalides, and Complex Halo Ions... 

Ether bismuth halide adducts also exist. Structural work on bismuth chloride diethyl ether or THF complexes show that, at low temperature, polymeric chains of BiXs linked by hahde bridges exist and that the bismuth atoms may be coordinated by one or two ether molecules. Bismuth(ni) bromide coordinates three THF molecules. These solvent molecules are readily removed under vacuum. The polyethers diglyme and diethylcarbitol give dimeric adducts with Bids. In the presence of cyclic polyethers, simple coordination, or formation of polyether-coordinated bismuth cations... 

Simple amine adducts of the bismuth halides have been prepared, although many have not been structurally characterized. Adducts between amines and organobis-muth complexes have been better defined see Bismuth ... 

Cationic Naked Clusters of Bismuth Reduced Bismuth Halide Phases... 

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