Borate anions cations

Single-electron transfer from a borate anion particle to the excited polymethine cation generates a dye radical and an aLkylphenylbotanyl radical. The aLkylphenylbotanyl radical fragments to form an active alkyl radical. It is the alkyl radical particles that initiate the polymerization reactions (101). 

Figure 14.3 Examples of planar 3-coordinate O (a) the cation in [0(HgCl)3]Cl, (b) the central O atom in the discrete borate anion [OBeOeCOH) ] " in macallisterite — the three heterocycles are coplanar but...

Suitable electrolytes for the aqueous phase (w) comprise, for example, LiCl, HCl, MgCl2, MgS04, while suitable electrolytes for the organic phase (o) comprise salts of, for example, tetrabutylammonium, tetraphenylarsonium, or bis(triphenyl-phosphoranylidene)ammonium cations with tetraphenylborate, tertrakis(4-chloro-phenyl)borate, or tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion. 

The sensor layer consists of a selective ionophore (e.g. valinomycin for potassium), a lipophilic anionic site (borate) and the cationic PSD. Before interaction with potassium, a lipophilic ion pair between the cationic PSD and borate anion is formed in the polymer layer. When valinomycin (also contained in the layer) selectively extracts potassium into the layer, then the positively charged valinomycin-potassium complex forms an ion pair with... 

Hannant et al. also reported the synthesis (Scheme 44) of cationic zinc complexes bearing bulky diazabutadiene ligands.1 7 19F NMR spectroscopy showed that the borate anions of these compounds are non-coordinating in... 

Fig. 18a. 10. Chemical structures of ion exchangers used in polymeric membranes of ion-selective electrodes with preference toward ions as indicated, (a) Tetraphenyl borates anion exchanger, (b) tridodecyl methyl ammonium chloride cation exchanger and (c) newly introduced carborane cation exchanger.

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... 

The first landmark was the successful synthesis and structural characterization of the cyclotrigermylium cations 2 and 19 by Sekiguchi and co-workers. This was achieved by reaction of trityl cation with the cyclotrigermenes 20 in the presence of weakly coordinating borate anions (Scheme 8). The trityl cation acts here as a one-electron oxidizing reagent and the resulting radical cation of 20 decomposes to the... 

Many borates are known that contain non-metal cations. Examples include the ammonium borates [39], such as the commercial products ammonium pentaborate, NH4[B506(0H)4] 2 H2O, and ammonium tetraborate, (NH4)2 [6405(011)4] 2 H2O, both of which contain isolated borate anions shown above (Figs. 5a and 6a, respectively) [40]. Isolated borate anions containing more than six boron atoms are rare. However, the mineral ammonioborite [(NH4)3[Bi502o(OH)g] 4 H20 = (NH4)20 5 B2O3 2 2/3 H2O), which may be prepared synthetically by prolonged reflux of a saturated solution of ammonium pentaborate, contains the unusual isolated anion [Bi502o(OH)g] , shown in Fig. 10 [41]. This anion is not known to occur in any metal borate, its formation is apparently directed exclusively by the ammonium cations which can donate H-bonds to interstitial water and the borate structural unit. 

These examples illustrate not only how cations direct the structures of isolated borate anions and the spatial arrangements of extended borate polymers, but also how they determine chemical and physical properties of... 

Similar to their spontaneous 1,4-hydration in water, heterocycles 49a, 50a-e, and 50g all react simply upon dissolution in warm methanol to form his-addition products. The X-ray crystal structure of the bis-methanol adduct (51) derived from the diazaborine 50b clearly showed it to be a zwitterion comprised of tetrahedral borate anion and formamidinium cation fragments. Once again, 50f proved to be the only exception A weakly chelated dimethylborate ester (not shown) was found to be its structure in MeOH by B NMR. 

Some examples of correlations of electron transfer rate constants photo-induced from excited organic anions have been presented. In benzene solvent, intra ion pair electron transfer rates between borate anions and excited cyanine cation have been measured and correlated with the reaction free energy [93]. In a non polar medium such as benzene, the solvent reorganization energy is easily calculated to be nearly zero so that the 0.1 eV obtained from this correlation for dGo was attributed entirely to the inner contribution (dGo )v-... 

Historically, C-borylated pyrazoles were first described in 1962. A few years later, N-borylated species containing four-coordinate boron were prepared, i.e., the poly(l-pyrazolyl)borate anions and the (neutral) dimeric pyrazol-l-ylboranes = pyrazaboles. The first monomeric pyrazol-l-ylborane containing trigonal boron was reported in 1980. In addition, several cationic species in which two or more boron atoms or a boron and a carbon atom are bridged by pyrazolyl groups are known, but their chemistry has not yet been explored at all. 

Another type of ion pairs, called penetrated ion pairs [402], has been found by studying the conductivity of tetraalkylammonium tetrafluoroborates (with variable alkyl-chain lengths) [399, 403], and the UV/Vis spectroscopic behaviour of salts with a trimethinium cyanine cation and the tetrakis(phenylethynyl)borate anion [404], in nondissociating solvents of low relative permittivity. Clearly, in solutions of such low relative permittivity any ionic species will be highly associated. However, it has been found that the ion pairs formed can be smaller than the sum of the van der Waals radii of the components. Clearly, the ions of the ion pair interpenetrate each other depending on their molecular structure in the first case, the BF4 ion penetrates into the voids between the alkyl chains of the tetraalkylammonium ion, and in the second case the cyanine cation penetrates into the crevices of the borate ion. 

The structures of 4 and 5 are both constructed by isolated borate anion groups which are charge-balanced by the chiral M(en)3 (M = Zn, Co) cations. These borate... 

Ammonia, alkylamines, and other proton acceptor species can react with boric acid in aqueous or alcoholic solutions to form a wide range of crystalline nomnetal borate salts. Borate salts of aprotic nomnetal cations, such as quaternary ammonium cations, have also been characterized. The ammonium borates are significant commercial products, and the recognition that both protic and aprotic nonmetal cations can stabilize unusual borate anions has led to increased interest in the study of this area. 

Acac = acetyacetonate BArf = tetra(3,5-bis(trifluorome-thyl)phenyl)borate anion bridge = 1,3-diisocyanopropane COD = cycloocta-1,5-diene COE = cyclooctene DFT = Density Functional Theory dimen = 2,1,8-diisocyanoment-hane DMAD = dimethylacetylene dicarboxylate DMSO = dimethylsulfoxide dpmp = bis(diphenylphosphinomethyl) phenylphosphine DPPB = l,4-bis(diphenylphosphino)but-ane DPPE = l,2-bis(diphenylphosphino)ethane DPPM = bis(diphenylphosphino)methane en= 1,2-diaminoethane hfac = hexafluoroacetylacetonate HFB = hexafluorobut-2-yne HOTf = trifluoromethanesulfonic acid (triflic acid) MLCT = Metal Ligand Charge Transfer MO/MM = Molecular Orbital/Molecular Mechanics NBD = bicyclo[2. 2.1]heptadiene OTf = trifluoromethanesulfonate (triflate) ion OTs = p-toluenesulfonate (tosylate) ion /j-anis = /7-MeOC6H4 pip = piperidine pn = 1,2-diaminopropane PPN+ = bis(triphenylphosphine)iminium cation p-to = p-MeCeUt pz = pyrazolate QM/MM = Quantum Mechan-ics/Molecular Mechanics TFB = tetrafluorobenzobarrelene TM4 = 2,5-diisocyano-2,5-dimethyIhexane tn = 1,3-diami-nopropane. 

Cyanine borates exist as tight ion pairs certain of the salts have even been shown to form ion pairs in which the center-to-center distance between the ions is less than the sum of the individual radii [27-29]. Since the lifetime of the excited singlet state of cyanine dye is quite short, too short to allow an efficient encounter at an achievable concentration of borate in a situation in which diffusion is necessary, the self-association of the cyanine cation and borate anion is a prerequisite for efficient photoinduced reaction. 

Such electrochemical potentials are generally measured in a polar solvent such as acetonitrile. The electrochemical reduction of the cyanine cation (Figures 4B, 4C) in acetonitrile solution is reversible. Borate anions behave similarly (Figure 4A) ... 

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