TFPB

Experience in PTC with cationic catalysts showed that, in general, the most suitable compounds have symmetrical structures, are lipophilic, and have the active cationic charge centrally located or sterically shielded by substituents. For anionic catalysis sodium tetraphenylborate fulfills these conditions, but it is not stable under acidic conditions. However, certain derivatives of this compound, namely sodium tetra-kis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB, 12.162) and sodium tetrakis[3,5-bis-(l,l,l,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]borate (HFPB) are sufficiently stable to be used as PTC catalysts for azo coupling reactions (Iwamoto et al., 1983b 1984 Nishida et al., 1984). These fluorinated tetraphenylborates were found to catalyze strongly azo coupling reactions, some of which were carried out with the corresponding diazotization in situ. 

An unprecedented carbene insertion reaction was observed on reaction of the cationic re-arene ruthenium amidinates with trimethylsilyldiazo-methane (Scheme 145, TFPB = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate). 

Though 1.84 X 10 moles of Na was transferred from NB to W, even in the absence of pyruvic acid, the transfer was not found in the absence of FMN or DMFC. In the absence of one of reagents among Na+TFPB , DMFC, FMN, and pyruvic acid, CO2 was scarcely generated (less than 5 x 10 moles). When N2 was bubbled into W instead of O2, Na transferred and CO2 formed were much less than those observed with O2 bubbling. 

NADH and DCE containing 10 M chloranil, CQ. As supporting electrolytes, 0.5 M 02804 and 0.05 M TPenA+TFPB were added in W and DCE, respectively. The buffer solution used was the same as that in Fig. 5. 

FIG. 11 Potential response of Na+-selective electrodes based on silicone-rubber membranes modified chemically by triethoxysilylated calix[4]arene (8) (O) without anion excluder ( ) with TFPB ( ) modified chemically by triethoxysilylated tetraphenylborate (9) as well. (From Ref. 44.)... 

In the field of stannylium ions, n-BusSn B (C6F5)3H , synthesized by the oxidation of stannyl hydride with B(CgF5)3 (Section 2.1.2.2, Scheme 2.2, D), was characterized by Lambert et al. as a tricoordinate stannyl cation becanse of its low-field Sn NMR resonance of 360ppm. The same n-BusSn cation, having a TPFPB connterion, exhibited a less deshielded valne of +263 ppm (at room temperature), which, however, was corrected in snbseqnent stndies to +434ppm (at -Bn3Sn+ TFPB, ... 

These rod-shaped ligands share a sterically efficient terminal N-donor and their divalent Co chemistry is well established. They will be discussed here only with selected examples. [Co (NCMe)6](TFPB)2 (TFPB- = tetrakis(3,5-bis(trifhioromethyl)phenyl)borate)) has been synthesized and characterized in the solid state along with a number of other divalent transition metal analogs.357 As a result of the extremely poor coordinating ability of the anion and facile loss of MeCN ligands from the cation, the salt is an excellent source of naked Co2+ ions. Thermolysis up to 100 °C leads to the loss of one MeCN and formation of a r -bound nitrile, whereas above 130 °C decomposition occurs with loss of MeCN and abstraction of fluoride from the anion to form CoF2. 

Cyclododecanone is reduced to a mixture of cis- and /ra .s -cyclododecenc in high yield with trimethylsilane and tetrakis-3,5-bis(trifluoromethylphenyl)borate (TFPB, 77) (Eq. 254).424... 

Figure 24 The n-A isotherms for mixtures of AA with AV2+ by a molar fraction of (a) 0.10, (b) 0.188, and (c) 0.50 at pH 63 and 18°C. The inset shows the schematic representation of surface monolayers during compression processes (C) -> (B) -> (A). Hie circle and rectangle in the inset represent TFPB" and 4,4 -bipyridinium group of AV2+, respectively.

Figure 27 Schematic representation of the orientation of 4,4 -bipyridinium radical cations in (a)HV2+/AA and (b) AV2+/AA LB films. Counter anions (TFPB ) and AA are not shown for simplicity.

Figure 28 Schematic representa- Figure 29 Changes in the OWG absorbance of PV2+(TFPB )2 tion of the OWG system for detect- thin films of various thickness during IPCT excitation ing photoinduced electrochromism (a) 10.0, (b) 40.4, (c) 64.9, (d) 955, and (e) 179.6 nm. of ultrathin films (S) in the evacuation chamber shown in an inset.

These results strongly suggested that PV2+(TFPB )2 thin films of various thickness are homogeneous and that 4>4 -bipyridinium groups are distributed randomly throughout the polymer films. 

The present author has developed a novel method called ion-association method. This is also a simple and versatile method for the preparation of ion-based organic dye nanoparticles in pure aqueous solution by the ion association approach [23]. It utilizes the control of hydrophilicity/hydrophobicity of the ionic material itself via ion-pair formation for example, addition of a cationic target dye solution into aqueous solution containing a certain kind of hydrophobic anions forms an electrically neutral ion-pair because of the strong electrostatic attraction, followed by aggregation of ion-pair species originated from van der Waals attractive interactions between them to produce nuclei and the subsequent nanoparticles (Fig. 3). In this case, hydrophobic but water-soluble anions, such as tetraphenyl-borate (TPB) or its derivatives (tetrakis(4-fluorophenyl)borate (TFPB), tetrakis [3,5-... 

The DASPE nanoparticles have been synthesized by the ion association reaction between the dye cation (note that the native compound is an iodide salt DASPE-I) and the hydrophobic borate anion (TPB or TFPB-) in the presence of neutral polymer stabilizer polyvinylpyrrolidone (PVP) in aqueous solution [38, 39]. In the absence of PVP, mixing of aqueous TPB- (or TFPB-) and DASPE+ solutions at the same molar fraction yielded the orange opaque solid dispersion composed of the anion-exchanged dye species, DASPE-TPB (or... 

DASPE-TFPB), respectively. The obtained solid precipitates were brightly emissive whereas that of the native DASPE-I were almost nonemissive (Fig. 7a the photo is taken under normal illumination and UV-light irradiation). This indicates that, in the solid of the ion-pair species between DASPE+ and TPB (or TFPB ), concentration quenching is effectively suppressed, and more importantly, these ion-pair complexes can generate fluorescent... 

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