Antimony cage compounds

In spite of the more metallic properties of arsenic and antimony compared to those of phosphor, known homonuclear compounds of these elements do not differ very much from equivalent phosphor derivatives. The most stable arsenic and antimony cage compounds are indeed those isoelectronic with the anion P7" described above. 

Table 9 List of structurally characterized cage compounds of antimony and bismuth...

Treatment of 37 with 1 equiv of SbCh furnished the bicyclic compound 117 featuring the structural motif of a phosphastibirane. Removal of the chloride anion by a Lewis acid (e.g., AICI3) or exchange of chloride by reaction with Ag[Al OC(CF3)3 4] yielded the cage compound 118 with the antimony atom located in the apex of the square-based pyramidal structure (Scheme 43) <2006CC1375>. 

Sonochemical rearrangements are rare. The first case reported consists of the rearrangement of polycyclic hydrocarbons to ada-, dia-, and triamantane cage compounds (Eq. 75).223 The catalysts are usually superacids, such as trifluoro-methylsulfonic acid-antimony pentafluoride. 

A previously synthesized cage compound containing phosphorus and antimony, P4Sb2C4 Bu4, was reacted with Fe2(CO)9. " The intermediate complex depicted in Scheme 41 was proposed, but no evidence for it was observed by NMR. The authors propose the insertion of an Fe(CO)4 moiety into the Sb-P bond with loss of a carbonyl to form the final product. 

In addition to iodonium, sulfonium and selenonium compounds, onium salts of bromine, chlorine, arsenic, and phosphoras are also stable and can act as sources of cation radicals as well as Bronsted acids, when irradiated with light. Performance of diaryl chloronium and diaryl bromonium salts was studied by Nickers and Abu. Also, aryl ammonium and aryl phosphonium, and an alkyl aryl sulfonium salt were investigated. It appears that the general behavior of these materials is similar to diphenyl iodonium and triphenyl sulfonium salts. These are formations of singlet and triplet states followed by cleavages of the carbon-onium atom bonds and in-cage and out of cage-escape reactivity. The anions of choice appear to be boron tetrafluoride, phosphorus hexafluoride, arsenic hexafluoride, and antimony hexafluoride. 

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