Subhalides

Figure 16.11 Structural relations between tellurium and its subhalides (a) tellurium, (b) Te3Cl2, (c) Te2Br and Te2l, (d) /3-TeI, and (e) a-Tel.

Figure 16.12 Structures of some selenium subhalide cations.

It is also convenient to mention here several cationic subhalide species that have recently been synthesized. Reaction of 8e with [NO][8bCl6] in liquid 8O2 yields lustrous dark red crystals of [8e9Cl]+[8bCl6]" which is the first example of a 7-membered 8e ring, [cyclo-8e7-8e8eCl]+ (Fig. 16.12a).Again, reaction of stoichiometric amounts of 8e (or 8), Br2... 

The cleavage of the isoxazole ring by organomagnesium compounds may proceed by either one or both of two alternative mechanisms. Magnesium subhalides produced during the associated reaction may act as reducing agents as proved in specific cases.Another possibility is that the reduction involves a six-membered cyclic complex (171). 

Among one-component polymerization catalysts subhalides of the transition metals are most similar in composition to the traditional Ziegler-Natta catalysts. In this connection, the study of the simplest one-component catalyst of this type (especially TiCl2) is of great importance for the clarification of still disputable problems of the mechanism of polymerization by two-component catalysts. 

Single-crystal LaBg in well-formed parallelipipeds (0.15 X 0.15 X 2 m) grows when LaBrj is used as transport agent in an Ar atmosphere with T in the source and crystallization zones of 1150 and 900°C, respectively. The transport probably proceeds through the subhalide. The amount of transported LaB is increased by a factor of 10 when oxygen is replacing Ar, and LaClj is substituted for LaBrj. The more efficient transport in this case is due to the formation of LaOCl. 

Metallic Sr can be prepared by methods similar to those used for Ca manufacture (sec 7.2.3.3.1). Thus thermal reduction of SrO using A1 and electrolysis of anhyd SrCU both yield pure Sr. Reduction of SrO by CH4 is also successful on a pilot scale. Metallic Ba is produced by thermal reduction of BaO by Al alternative reducing agents arc Na, Mg, Si and FeSi. Electrolysis of fused anhydrous halides (c.g., BaCK) is not applicable since the reaction yields a subhalide rather than the pure metal. 

M. Ruck, From metals to molecules - ternary subhalides of bismuth. Angew. Chem. Int. Ed. 40 (2001) 1182. 

Figure 7 Structural units of tellurium and the tellurium subhalides Te3Cl2, Te2X, fi-Tel, and a-Tel with bond lengths and bond angles. The upper numbers in Te2X refer to X — Br, the numbers below refer to X — I...

Bismuth salts, 4 25 Bismuth sesquisulfide, 4 24 Bismuth subcarbonate, 4 36 Bismuth subgallate, 4 36 Bismuth subhalides, 4 19 Bismuth subnitrate, 4 36 Bismuth subsalicylate, 4 1, 36 medical applications of, 22 11-12 Bismuth(III) sulfate, 4 25 Bismuth(III) sulfide, 4 24 Bismuth sulfides, 4 24-25 Bismuth thiolates, 4 25 Bismuth-tin alloy waterfowl shot, 4 15 Bismuth triacetate, 4 25 Bismuth tribromide, 4 21 physical properties of, 4 20t Bismuth trichloride, 4 19-20 physical properties of, 4 20t Bismuth trifluoride, 4 19 physical properties of, 4 20t Bismuth trihalides, 4 19 Bismuth triiodide, 4 21-22 physical properties of, 4 20t Bismuth trinitrate pentahydrate, 4 25 Bismuth trioxide, 4 23-24 physical properties of, 4 20t Bismuth triperchlorate pentahydrate, 4 25... 

See also Borates Boric acid Sodium borates boron oxides, 4 246-249 boron oxides table,4 242t environmental concerns, 4 284—285 health and safety factors, 4 285-288 occurrence, 4 245—246 Boron perchlorates, 18 278 Boron phosphate, 4 242t, 283 Boron removal, from water, 14 418 Boron-stabilized carbanions, 13 660-661 Boron subhalides, 4 141 Boron suboxide, 4 242t Boron tribromide, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t, 325 reactions, 4 141 specifications, 4 147t uses of, 4 149 Boron trichloride, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t reactions, 4 141... 

Figure 28 Structures of organometal subhalides as obtained from insertion reactions of tetrahedral M(l) clusters with halogen donors.

The clusters described so far have in common, that the number of metal atoms is less or equal than the number of substituents. However, there is a still growing number of both neutral and anionic clusters in which the number of metal atoms is larger than the number of substituents. As a consequence, these metal-rich clusters contain naked metal centers which are only bonded to other metal centers. Schnockel referred these ones to as metalloid clusters. Several metalloid A1 and Ga clusters were prepared by standard salt elimination reactions using metastable solutions of metal subhalides MX (M = Al, Ga X = Cl, Br) as well as solutions of Gal. Since the metal subhalides were found to play the key role for the successful synthesis of this particular class of compounds, they will be discussed first. (For excellent review articles see Refs 273 and 274.)... 

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