Anionic stability increasing

This last reaction is typical of many in which F3CIO can act as a Lewis base by fluoride ion donation to acceptors such as MF5 (M = P, As, Sb, Bi, V, Nb, Ta, Pt, U), M0F4O, Sip4, BF3, etc. These products are all white, stable, crystalline solids (except the canary yellow PtFe ) and contain the [F2CIO] cation (see Fig. 17.26h) which is isostructural with the isoelectronic F2SO. Chlorine trifluoride oxide can also act as a Lewis acid (fluoride ion acceptor) and is therefore to be considered as amphoteric (p. 225). For example KF, RbF and CsF yield M [F4C10] as white solids whose stabilities increase with increasing size of M+. Vibration spectroscopy establishes the C4 structure of the anion (Fig. 17.29g). 

The most stabilized anion is PO3 which has three equivalent charge delocalizing oxygens. The other three anions have only two such oxygens. The stability differences for these three anions are due to the electron-withdrawing effect of the OH group. The stability increases as the number of OH group increases from zero to two. 

As we have recently shown [3], the stability of GIC with Bronstcd acids is governed by ionization potential of the intercalated anion. Solvation of the anion substantially increases ionization potential and hence stabilizes GIC. Such a possibility was predicted by Inagaki [4] who proposed to use organic molecules as additional cointercalants for the purpose of stabilization. Afterwards, we successfully used glacial acetic acid and water to synthesize stable products [5],... 

An extensive study132 has been presented on the polarizability effects of alkyl groups in RX moieties (R = Me, Et, i-Pr and i-Bu X = CH2, S, SO2, O and N) in families of weak acids and on the stabilities of adjacent anions and radicals in DMSO solution. Some of the results related to the 9-(dialkylamino)fluorenes are given in Table 12. The increases in acidity are believed to be caused by the progressive increases in anion stabilizing... 

Handa et al. reported the synthesis of a phosphorus equivalent of Barthel s salts in which the hexavalent phosphorus(V) was coordinated by three bidentate ligands. 1.2-benzenediolato-O.C7. Its thermal stability is similar to that of its boron counterparts, and moderate ion conductivity was achieved in nonaqueous media. The authors attributed the less-than-satisfactory ion conduction to the large size of the anions, which increased the viscosity of the resultant electrolyte solutions. The anodic stability limit, as measured by voltammetry on a Ni electrode, was below 3.7 V. A preliminary test of this salt in EC/ THF was conducted in a lithium cell using the low potential cathode. V2O5. and the authors believed that this salt could be a superior electrolyte solute, judging from the utilized cell capacity that was close to the theoretical value. 

In organic chemistry this stabilizing effect is well known the stability of carbanions is known to be enhanced by nitro groups. The stability of the cyclopentadienide anion is increased by complexing with a typical Lewis acid so that it becomes less reactive. For example, ferrocene is not ionized in nitromethane solution. Addition of a Lewis acid such as aluminum chloride facilitates the occurrence of intramolecular race-mization (75) a process which is believed to involve ionic intermediates [16). This belief is supported by kinetic evidence and the failure of the reaction to occur in nearly inert solvents like methylene chloride and in those of high donidty. Whereas the former do not support the solvation of the cation formed in the process of ionization, the latter will react preferentially with the Lewis acid, which is then no longer available for the stabilization of the carbanion. 

Pu(IV) forms polyatomic complexes with inorganic and organic ligands. As the number of anionic ligands increases, cationic, neutral, and anionic complexes form and the sequential stability constants, Kn> typically decrease. For the following reaction, where M is Pux+ and L is a ligand,... 

We can be confident that substituent groups that stabilize the anion will increase the acidity. Thus 4-nitrobenzenol is about 500 times stronger as an acid than benzenol, because of the increased delocalization of charge to the nitro group ... 

Increased electronegativity of an atom allows it to cany negative charge more readily, and the stability of die anion is increased. It is for tins reason that the order of acidity of first-row hydrides is C-H < NH < -OH < FH. Transfer of a proton from these substances to water yields a series of anions whose stabilities are ordered according to die electronegativity of die negatively charged atom. 

An ab initio study of the effect of a-substituents on the acidity of cyclopropaben-zene has shown that a-substituents stabilize the cyclopropabenzenyl anion (5) less efficiently than the cyclopropenyl anion (6).2 The attachment of induedvely/field acting substituents attached to the carbanionic site predominantly stabilize the cyclopropenyl anion by increasing the, v character of the lone pair, diminishing the antiaromatic character of the three-membered ring at the same time. 

Reversible step transfer of up to 6 electrons per one molecule to form anion radicals is observed in the cathodic polarization of C6o fullerene solutions [6], Anion particles are stable in aprotic media, however in the general case anion stability decreases with increasing charge [7]. The number of observed steps depends on the medium and experimental conditions. The literature analysis [8-10] has revealed that the use of different solvent systems, base electrolytes and electrodes results in considerable variations in redox potentials for the most extensively studied pairs of C(JC , C(,fC(f2, C(,fCeo"3. 

Scheme 2.11 Electron-withdrawing groups increase acidity by increasing anionic stability.

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