Bulky cations

Extraction and flotation separation of POMs as ion-pair with a bulky cation of Astrazone Violet (AV) with different organic solvents is investigated. Conditions for separation of dye excess from ion-pair PMo TiO j with polymethine dye AV ai e found. 

The anionic complex K[Au(C6F5)(CN)] reacts with BzPh3PC104 to give the complex BzPh3P[Au(C6F5)(CN)] that is easily crystallizable thanks to the bulky cation [63]. This complex reacts with different substances such as [Au(C6F5)(tht)] that lead to the... 

These include the simplest ion-association systems in which bulky cations and anions are extracted as pairs or aggregates without further coordination by solvent molecules. An example of this type of system is the extraction of manganese or rhenium as permanganate or perrhenate into chloroform by association with the tetraphenylarsonium cation derived from a halide salt... 

One more difference between ionic liqnids and conventional organic solvents of the C-Cl cleavage should be mentioned. Normally, the intrinsic solvation of the developing halide ion disfavors the cleavage via the entropy term. Such a term cannot be significant in the ionic liquids composed of very bulky cations and anions. 

The reaction of [TcOCU] with various monodentate aromatic thiols in methanol produces complexes of the general formula [TcO(SAr)4] (89), which can be precipitated with bulky cations. The X-ray crystal structure of the complex with Ar = mesityl has been elucidated and has square-pyramidal geometry, with the Tc atom displaced from the basal plane by about 0.846 Direct... 

Silica and bonded phases decompose also in contact with aqueous solu lion of pH < 2. Therefore it is not advisable to use bulTci s Imviiig pH css than 2. Most commonly phosphoric acid buflTers are used in this pH range. Perhaps buffer made with glucose-l-phosphate (pJC, >= 1.1) and a bulky cation could make possible the bng-term use of columns with eluents of pH <2. 

The formation of crystalline fulleride salts at the electrode occurs when less polar solvents and bulky cations are used for the electrosynthesis. The first fulleride salt was synthesized by Wudl by bulk electrolysis of in o-dichlorobenzene with tetraphenylphosphonium chloride as supporting electrolyte [39, 80]. This black microcrystalline material with the composition (Ph4P )3(Cgg )(Cr)2 exhibits an ESR line with a g-value of 1.9991 and a line width of 45 G at room temperature. Single crystals of the slightly different salts (Ph4P )2(Cgg )(Cr) and (Ph4P )2(C50 )(Br ) could be obtained by electrocrystallization and their crystal structure was determined [82, 83]. Magnetic measurements showed the presence of unpaired spins. 

The complexes [AuX2]- are colourless when X = C1 or Br, but yellow when X = I. The complex ions with X = Cl or Br can be prepared by reduction of [AuX in absolute ethanol155 and, when X = I, by reaction of [AuBr2]- with excess iodide.155 They can be isolated as salts with bulky cations.155156... 

A preparation on less than 10 g scale was isolated by removal of solvent on a rotary evaporator. As the flask was raised from the water bath, but before any attempt was made to remove the flask from the evaporator or break the vacuum, the material detonated, causing permanent injury to the experimenter. This represents greater sensitivity then might be anticipated with the sandbagging given by the bulky cation. 

Different compounds which complex the fluoride anion were recently developed. Sapphyrine (1) is a porphyrin with 5 pyrrole rings, and when it is doubly protonated it can exclusively complex F in its cavity68. Similarly, Seppelt prepared the thermally stable salt 2 with a bulky cation where the fluoride can be completely desolvated, thus increasing its efficiency as a nucleophile and a base69. 

Basically, the final choice of the cation has to relate strictly to the application. The presence of cations such as Li+ or Na+ in solutions may lead to precipitation of insoluble surface films or noble metal electrodes and thus interfere with the basic electrochemical behavior of many redox couples on nonactive metal electrodes in polar aprotic solvents [9], The use of tetraalkyl ammonium salts eliminates this problem because the thermodynamics of insoluble salt precipitation on electrodes differs in the presence of these bulky cations from that developed in the presence of cations of alkaline or alkaline earth metals [6-9],... 

Reaction of P4S10 with KCN/FI2S yields the trithiometa-phosphate anion PSs, which has been stabilized using the bulky cation Plq As+ to stop dimerization to P2. The latter... 

Anion-selective liquid membranes can be made by using a bulky cationic species that will selectively extract anions into an organic solvent. Examples are substituted... 

---