Halides polyhalides

Alkyl Halides, Polyhalides, a-Halo Ketones and Esters... 

Tables 11.8.11.9.11.10 and 11.11). energetic (Section 11.6. Table 11.12T chiral (Section 11.7) and multiply charged (Section 11.R. Table 11.13V The second class is ion type such as halide, polyhalide and pseudohalide (Section 11.9. Table 11.14T oxoanions and their esters (Section 11.10. Table 11.15T EX4 and related anions (Section 11.11. Table 11.161. 

Iodine Halides and Polyhalides. Iodine forms six weU-defined compounds with the other haUdes (115,116). These compounds are readily formed by direct reaction of the two halogens (117). 

Pure NI3 has not been isolated, but the structure of its well-known extremely shock-sensitive adduct with NH3 has been elucidated — a feat of considerable technical virtuosity.Unlike the volatile, soluble, molecular solid NCI3, the involatile, insoluble compound [Nl3.NH3] has a polymeric structure in which tetrahedral NI4 units are comer-linked into infinite chains of -N-I-N-I- (215 and 230 pm) which in turn are linked into sheets by I-I interactions (336 pm) in the c-direction in addition, one I of each NI4 unit is also loosely attached to an NH3 (253 pm) that projects into the space between the sheets of tetra-hedra. The stmcture resembles that of the linked Si04 units in chain metasilicates (p. 349). A further interesting feature is the presence of linear or almost linear N-I-N groupings which suggest the presence of 3-centre, 4-electron bonds (pp. 63, 64) characteristic of polyhalides and xenon halides (pp. 835-8, 897). 

At(0) reacts with halogens X2 to produce interhalogen species AtX, which can be extracted into CCI4, whereas halide ions X yield polyhalide ions AtX2 which are not extracted by CCLt but can be extracted into Pr O. The equilibrium formation constants of the various trihalide ions are intercompared in Table 17.28. 

The tendency of the halogens to form chain-like polyanions that are stabilized by delocalization of the negative charge [15,34] is a basic chemical principle. Donor-acceptor interactions between Lewis-acidic Br2 and halide anions, but also with polyhalides acting as Lewis bases, give rise to the formation of a variety of homo and heteroatomic adducts. The maximum number of atoms in these chains increases with the atomic weights... 

Dihalides are reduced by Cr(II) to the corresponding olefin ". Allylic and benzylic halides and polyhalides are reduced more readily than simple alkyl halides, but even the latter are readily reduced by an ethylenediamine complex ofCr(ri) . ... 

Much of the current research into halogen bonding involves organohalogen or inorganic halide acceptors. However, the dihalogens (X2) and inter halogens (XY) continue to attract attention. This review will focus specifically on structural and theoretical studies of such systems over the past decade. While polyhalide anions are closely related to the neutral donor-acceptor concepts that are the focus here, they will be discussed only when necessary to elaborate on the central theme of the review. 

Although 1, -elimination of o xylene polyhalides with sodium iodide, zinc, copper, or iron metal is a fundamental method for the formation of o-xylylene intermediates, it is difficult to carry out the reaction under mild conditions such as at room temperature. o Trimethylsilylmethyl)-benzyltrimethylammonium halides were devised for this purpose and were shown to generate the o-xylylene at room temperature. However, we have successfully generated o-xylylene at room temperature by the reaction of a, 0,-dibromo o-xylene with metallic nickel(51). The Diels-Alder reaction of... 

Iodine monobromide, like the other binary halogen compounds, has the faculty of forming polyhalides additively. They are obtained by the soln. of the halogen halide in a cone. soln. of the alkali halide salts. Thus, H. L. Wells and S. L. Pen-field 31 prepared KBr.IBr, CsCl.IBr, CsBr.IBr, RbBr.IBr, etc. Since CsBr2I is more stable than CsBrI2. it follows that it is the mutual affinity of the halogens themselves, rather than the volatility of the contained halogen, which determines the stability. 

When iodine is dissolved in hydriodic acid or a soln. of a metallic iodide, there is much evidence of chemical combination, with the formation of a periodide. A. Baudrimont objected to the polyiodide hypothesis of the increased solubility of iodine in soln. of potassium iodide, because he found that an extraction with carbon disulphide removed the iodine from the soln. but S. M. Jorgensen showed that this solvent failed to remove the iodine from an alcoholic soln. of potassium iodide and iodine in the proportion KI I2, and an alcoholic soln. of potassium iodide decolorized a soln. of iodine in carbon disulphide. The hypothesis seemed more probable when, in 1877, G. S. Johnson isolated cubic crystals of a substance with the empirical formula KI3 by the slow evaporation of an aqueous-alcoholic soln. of iodine and potassium iodide over sulphuric acid. There is also evidence of the formation of analogous compounds with the other halides. The perhalides or poly halides—usually polyiodides—are products of the additive combination of the metal halides, or the halides of other radicles with the halogen, so. that the positive acidic radicle consists of several halogen atoms. The polyiodides have been investigated more than the other polyhalides. The additive products have often a definite physical form, and definite physical properties. J. J. Berzelius appears to have made the first polyiodide—which he called ammonium bin-iodide A. Geuther called these compounds poly-iodides and S. M. Jorgensen, super-iodides. They have been classified 1 as... 

Polyhalide compounds are formed between iodine or iodine halides and other halide salts. The formulas of some of these compounds are Rbl3... 

The halides participate as terminal and bridge ligands and can be included in inner and external spheres of this kind of complex. A few examples of compounds with such terminal ligands are the boron ammines [BX3 NH3], [BX2(NH3)2]X, BX(NH3)3]X2, and [B(NH3)4]X3 (X = F, Cl, Br, I). Halides form part of many mixed-ligand carbonyl complexes, for example, Fe(CO)4I2 and polyhalide anions with various elements [4], In this respect, the structure of the anion [Re2Clx]2 provides important information the Re — Re bond is present and the chlorine atoms have a bridge function [4]. 

Carbonylmetalates will displace a halide from a metal halide complex to yield a metal-metal bonded species, Eq. (39). With di- and polyhalide... 

Interaction of Organic Halides or Polyhalides with Inorganic Fluorides... 

Vinyl halides are so inert that none has been converted to a fluoride by halogen exchange. Vinyl fluorides have been synthesized from saturated polyhalides by dehalogenation with zinc and by dehydrohalo- genation with alcoholic alkali, and from acetylene by addition of one molecule of hydrogen fluoride.12 18... 

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