Bonds arsenic-halogen

Table 9 Arsenic-Halogen Bond Lengths and Angles...

Compounds of Pentacoordinated Arsenic(V) Containing Arsenic-Halogen Bonds... 

Relatively little is known of the chemistry of antimony rings compared to arsenic rings. The reactions of arsenic homocycles have been reviewed several times " . They include cleavage of the As—As bonds with halogens and insertion of chalcogens or unsaturated hydrocarbons and reductive cleavage with potassium metal. Representative examples are given in equations 15-18. 

Many of the methods described in Section II, A for the preparation of compounds with As—C bonds also result in compounds with, arsenic-halogen bonds. These bonds are also produced by disproportionation and cleavage reactions (Section II, B). Previously mentioned reactions will not be discussed further in this section. 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

Table 3 Geometric parameters for halogen bonded complexes with arsenic and selenium electron donors... 

The 8-N rule states that the number of bonds (or local coordination, x) equals 8 minus the number of the periodic group. This rule is illustrated in Fig. 1.2 where we see that for N — 7 the halogens take dimeric structure types with x = 1, for N = 6 the chalcogenides selenium and tellurium take helical chain structures with x = 2, for N = 5 the pnictides arsenic, antimony, and bismuth take a puckered layer structure with x = 3, and for N = 4 the semiconductors... 

The chemistry of antimony and nitrogen is not as rich as that of arsenic and nitrogen. The N—Sb bond mainly exists in compounds where N is but one of a number of donor atoms. These compounds, where significant, will be dealt with under various other headings (mainly oxo and halogen ligands). Some Sb—N bond data are assembled in Table 12. 

POLYACETYLENE. A linear polymer of acetylene having alternate single and double bonds, developed in 1978. It is electrically conductive, but this property can be varied in either direction by appropriate doping either with electron acceptors (arsenic pentaflnoride or a halogen) or with electron donors (lithium, sodium). Thus, it can be made to have a wide range of conductivity from insulators to n- or >-type semiconductors to strongly conductive forms, Polyacetylene can be made in both cis and trans modifications in the form of fibers and thin films, the conductivity... 

Compounds of pentacoordinated arsenic(V) containing As—halogen bonds are summarized in Table VI. Compounds containing As—Br and As—I bonds are generally ionic and hence are not included in the table. For the same reason, compounds of type R4ASX have been excluded. 

Several organoarsenic(III) compounds containing arsenic(III)-transition metal bonds have been oxidized by halogen-based electrophiles or by elemental sulfur to give the corresponding dihalides or sulfides (equations 365 , 366 and 367 - ). 

The addition of a carbon atom to the 0=N double bond has been reported using sulfur (equation 35)133 and arsenic ylides, halogen-stabilized carbenes, and diazo compounds.i i-i The best substrates are imines in which the nitrogen is substituted with an aromatic ring, substituted oximes, and hydrazones. 

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