Fluorinated counterions

Coefficients for the metal complexes and their fluorinated counterions were determined from and diffusion experiments respectively and the hydrodynamic radii calculated from these values assuming solution viscosities matched those of die pure solvents. 

When the chain length of the fluorinated counterion is increased further, the counterion assumes surfactant characteristics in its own right. The cationic surfactant then becomes a mixed surfactant consisting of a fluorinated surfactant anion and a hydrocarbon surfactant cation (see Section 7.2). 

A novel route to 2-fluoropyridines involved the base-induced decomposition of substituted N-fluoropyridinium salts. Abstraction of the 2-H produces a singlet carbene (11) that removes F from a counterion. This is in contrast to the reaction with C nucleophiles, which are fluorinated, and is attributed to the high stability of C—F compared to O—F and N—F (89JOC1726). 

It appears that Te is more flexible in the possible arrangements (Figure 18) 72,73 it should be noted though that the counterions of these Te cations are more basic than the fluorinated anions used for S and Se cations. Thus, it may well be that the structural flexibility of the Te cations is a result of the increased cation-anion interactions in these salts. 

The Lewis acidity and reactivity of these alkyl aluminum cocatalysts and activators with Lewis basic polar monomers such as acrylates make them impractical components in the copolymerization of ethylene with acrylates. To address this shortcoming, Brookhart et al. developed well-defined cationic species such as that shown in Fig. 2, in which the counterion (not illustrated) was the now-ubiquitous fluorinated arylborate family [34] such as tetrakis(pentaflurophenyl)borate. At very low methyl acrylate levels the nickel catalysts gave linear copolymers but with near-zero levels of acrylate incorporation. 

The Na-Na distances of 3.076(3) (Nal-Na2) and 3.202(3) A (Nal-Nal ) reflect Na-Na bonds (3.82 A in elemental Na), whereas the Nal-Na2 distance of 3.530(3) A suggested less attractive interactions. The Na4-dication cluster is embedded between two silyl(fluoro-silyl)phosphanide counterions. The relatively low-coordinated Na centers are remarkably stabilized by the -fluorine atoms and by... 

These reactions are carried out in a polar solvent (Solv-H, Fig. 45), such as a 1 1 mixture of fluorotrichloromethane and chloroform, which not only encourages polarisation of the fluorine molecule and makes it more susceptable to nucleophilic attack, but more importantly, acts as an acceptor for the counterion (fluoride ion) in the transition state (Fig. 45). It has been suggested that the... 

Takenaka et al. 595) used XPS to study deterioration of a thin polythiophene film on an ITO electrode, such as might be used in a display device. After 105 dopingundoping cycles at 0.5 Hz with BF4" counter-ions there was evidence of extensive fluorination of the polymer, probably due to decomposition of the counter-ion or its hydrolysis by traces of water in the electrolyte. Corradini et al. 596) carried out a similar study of polypyrrole, polythiophene and their analogues with C104 counterions and concluded that all of the polymers are unstable to cycling or to standing in contact with the electrolyte, although polypyrrole performed best. 

Fluorination and methylation have been used to synthesize975 related fluorinated nitronium ions [Eq. (4.231)]. The trifluoromethyl(methyl)nitronium ion ON(Me) CF3 + exits in the keto form in solution, but X-ray crystal structure data indicate that the enol form HON(CH2)CF3+ exists in the solid state stabilized by a hydrogen bond between the enolic OH group and one of the fluorines of the counterion. 

The case of Srcl8C6(PFO)2 complexes differs, as the PFO" counterions are amphiphilic in nature and their carboxylate head coordinates to strontium, while their perfluoroalkyl chain cannot and do not attract each other, thus preventing selfaggregation of the complexes. The affinity of these fluorinated chains for C02 contributes to solubilize the strontium complexes. As a result, the Srcl8C6(PFO)2 complexes sitting at the interface are "diluted", while the others migrated from the interface to SC-C02 40 % are found at more than 8 A from the interface, and can thus be considered as "extracted" at 305 K. 

Diazotization procedures. Widely used for the production of aromatic fluorine is the Balz-Schiemann reaction. The approach involves diazotization of the aniline and isolation of the insoluble tetrafluoroborate salt, followed by decomposition under heating conditions (Fig. 32). Initially introduced in 1927 [137,138], it did not achieve commercial utility until the mid-1980s. A modification of the Balz-Schie-mann reaction involves replacing the tetrafluoroborate with other counterions such as a fluorine anion [139],... 

Further evidence for the existence of cationic centers is given by the activation of metallocene catalysts for olefin polymerization by the use of anionic counterions such as tetraphenylborate (CeFIs B-, carborane (C2B9H12), or fluorinated borate. The use of (CgF5)4B counterions by Hlatky et al. (83), Sishta et al. (84), and Zambelli et al. (85) leads to highly active metallocene catalysts, which are formed by the reaction of a dealkylated zirconocene with dimethylaniliniumtetra(/us,-perfluorophenyl)borate ... 

It is actually possible to observe this cationic intermediate. The trick is to pick a nonnucleophilic and nonbasic counterion X , such as antimony hexafluoride SbFg. In this octahedral anion, the central antimony atom is surrounded by the fluorine atoms and the negative charge is spread over all seven atoms. The protonation is carried out using FSO3H and SbFs at -120 °C. 

Kadirov MK, Bosnjakovic A, Schlick S (2005) Membrane-derived fluorinated radicals detected by electron spin resonance in UV-irradiated Nation and Dow ionomers effect of counterions and H202. J Phys Chem B 109(16) 7664-70... 

The crystal structure for pentamethylcyclopentadienyltin(II) tetra-fluoroborate has been determined (23) and is shown in Fig. 4. The Sn—C bonds are all equal and quite short at 2.462 A. Apparently, the Sn—Cp bonding is stronger in the +1 ion than in the neutral SnCp2 species. Each tin atom is associated to two fluorine atoms of the BF4 counterion at distances of 2.97 and 2.99 A. 

The same silyl ion also was examined in condensed phases by Lambert with his perfluorinated tetraphenylborate counterion [41]. While the solid state structure of this complex is not known, its Si shift is 107.6 ppm, close to the Reed s value. As the silicon atom might be coordinated to one or to two fluorine atoms [42], we calculated model complexes of SiMe3 with methyl fluoride and with cis-difluorethene. The smaller fluorine atoms are able to approach closer to silicon than bromine (Fig. 16), but the shift in electron density towards the cationic moiety is negligible. 

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