Sulfates tetraphenylphosphonium

Tetraphenylphosphonium tetraazidozincate, [(C6Hs)4P]2 [Zn(N3)4], results when an aqueous solution of 1 g zinc sulfate heptahydrate and 5 g sodium azide is precipitated with 0.5 g tetraphenylphosphonium chloride in water. The white precipitate is washed with water/alcohol 1 1 [139]. 

Quaternary onium salts. Quaternary ammonium salts include trioctymethylammo-nium chloride (Starks catalyst), Aliquat 336, tricaprylmethylammonium chloride, tetrabutylammo-nium hydrogen sulfate (Brandstrom s catalyst), and benzyltrimethylam-monium chloride (Mqkosza s catalyst) quaternary ammonium salts can also be generated in situ from trialkylamines, etc. Other quaternary onium salts include tetrabutylphospho-nium bromide, tetraphenylphosphonium bromide, triphenylbenzylphosphonium chloride, tetraphenylarsonium chloride, and triphenylsulfonium chloride, etc. Special quaternary salts are 4-aminopyridinium salts, bis-(quaternary ammonium) [R3N -(CH2) -NR3" R3N -(CH2) -0-(CH2) -NRj ] salts, 4,4 -dialkylbipyridinium salts, cluster quaternary ammonium [e.g., P(C6H4S03"NR4)3] salts, crown-quaternary salts [e.g. (18-crown-6)-(CH2)9PBuj Br ], and chiral V-(4-trifluoromethyl)benzylcinchonium bromide, etc. 

Table 2 lists the cooperativity parameter u and total stability constant K, which are calculated from the adsorption isotherm curves of a bulky surface active agent, tetraphenylphosphonium chloride (TPPC) and PAMPS gel [46]. For comparison, the data for the interaction between Ci2PyCl and PAMPS gel are also shown. When a low molecular weight salt is lacking, both cases show a small cooperativity parameter u and the effect of polymer networks. Since the polymer network effect diminishes under the presence of a large amount of sodium sulfate (lx 10 M), the... 

The best results so far have been with the tetraphenylphosphonium monoperoxy-sulfate system [89]. The standard conditions employed in epoxidation reactions catalysed by iminium salts involve the use of oxone as stoichiometric oxidant, a base (2 molar equivalents of Na COj per equivalent of oxone) and water/acetonitrile as solvent mixture (Scheme 1.43) the presence of water is essential for oxone solubility. Under the reaction conditions, there are separate aqueous and organic phases it is possible that the catalyst acts as a phase transfer agent in these reactions. 

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