Stibonium, cations

R3Sb or stibonium, R4Sb+ compounds. Example for a dimetalla stibine is [PhSb(Fe(CO)2Cp)2l97 (Fig. 23a) and for trimetalla stibonium cations (type 27) [PhSb Fe(CO)2Cp 3]2[FeCl4]91. ... 

Electrophilic aromatic substitution is the mechanism suggested in both cases the initial step being attack of the cation radical on the aromatic compound (ArH) (reaction 101), followed by deprotonation of the intermediate (reaction 102) and further oxidation of the radical to the resulting arsonium or stibonium ion (reaction 103). 

Summary Bissilylated onium ions of the elements N -> Sb are formed by intramolecular addition of transient silylium ions to EPh2 groups (E = N, P, As, Sb). Solutions of the onium salts in aromatic hydrocarbons are stable at room temperature for days, with the exception of the stibonium ion, which decomposes slowly. The cations were isolated as their [B(C6F5)4] salts and were characterized by NMR spectroscopy supported by quantum mechanical calculations. 

The cations are prepared from 2,5-disilaheptanes, 3, by hydride transfer reactions. The transient silylium ion 4 undergoes an intramolecular reaction to the more stable cyclic onium ion 2. The precursor silanes, 3, are synthesized by salt metathesis reaction from compounds of the type Ph2ELi, where E is the relevant Group 15 element, and the silylchloride 5. The salts 2 [B(C6Fs)4]" are isolated after washing with pentane as white to yellow microcrystalline powders in nearly quantitative yield. Solutions of the cations 2a-c in aromatic solvents are stable at room temperature. The stibonium ion 2d decomposes in solution slowly, yielding unidentified products. 

Arsonium and stibonium salts have properties consistent with their ionic constitution. The hydroxides are strong alkalis like quaternary ammonium hydroxides. The tetrahedral structures of their cations have been confirmed in some instances by X-ray analysis. Of the few bismuthonium salts known, the tetraphenylborate Ph4Bi BPh4 (from Ph5Bi+Ph3B) is among the more stable. The halides readily lose halobenzene, e.g. 

Several efforts have been reported to synthesize new organoclays to improve organoclay thermal stability, while enhancing the interaction between polystyrene and the modified clay. Organoclays prepared from phosphonium, stibonium or imidazolium cations have been employed in such studies [3-5]. Although evidences suggests that clay dispersion and the improvement in nanocomposite properties depend on the surface... 

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