Purification, general procedures salts

Alkynylphenyl tellurides from arylteUurolates and alkynyliodonium salts (general procedure) To a stirred solution of PhLi in Et20/cyclohexane at room temperature under N2, tellurium powder was added and the solution was stirred for 1 h. The appropriate iodonium triflate was added and the solution was stirred for 2 h. The product was eluted through a small portion of silica gel with CHjCN and the volume was reduced in vacuo followed by purification via radial chromatography. 

In general, the H2B(pzx)2 ligands are prepared from reaction, in refluxing anhydrous DMF, of substituted pyrazole and MBH4 (M = Li, Na or K) in a 2.3 1.0 mole ratio. When the reaction is complete, DMF is distilled out at reduced pressure. The residue is boiled with toluene, which should dissolve most of the un-reacted pyrazole, and the mixture is filtered. The crude M[H2B(pzx)2] is contaminated by only small amounts of Hpzx and is usually suitable for complex formation. Additional purification can be achieved by converting the crude K salt to the T1 salt which shows no tendency to retain Hpzx. Specific procedures for synthesizing diversely substituted scorpionates are given in the references in Table 1. 

The ammonia is removed by distillation with steam, most of the byproduct hydroxy compounds going into solution as the sodium salt during this operation. The aminoanthraquinone is then filtered hot and washed with hot dilute alkaline solutions. Generally, no purification operation is required. The results obtained by the foregoing/procedure are set forth in Table 8-15. 

Some nitronium salts with complex fluoride anions are commercially available or can be readily prepared in the laboratory by the procedure of Olah et ai from nitric acid [54]. As nitric acid always contains some nitrous acid, the commerical salt generally needs to be purified from nitrosonium ion impurities. This according to Ridd can be readily achieved in case of NOJPFe by recrystallization using nitromethane [61]. In the case of NO2 BFJ, because of its limited solubility, such purification is difficult. To obtain pure NO2BF4 free of NO BFJ starting from nitric acid, it is necessary to purify it from nitrous acid by treatment with urea and immediately convert it into the nitronium ion [62]. Alternatively, alkyl nitrates that can be prepared in piue form can be converted into nitronium salts free of NO [57]. 

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