Innocent anion

Since the discovery of the first organic conductors based on TTF, [TTF]C1 in 1972 [38] and TTF - TCNQ in 1973 [39], TTF has been the elementary building block of hundreds of conducting salts [40] (1) charge-transfer salts if an electron acceptor such as TCNQ is used, and (2) cation radical salts when an innocent anion is introduced by electrocrystallization [41]. In both cases, a mixed-valence state of the TTF is required to allow for a metallic conductivity (Scheme 5), as the fully oxidized salts of TTF+ cation radicals most often either behave as Mott insulators (weakly interacting spins) or associate into... 

Anions, too, are not always innocent. The borate anion B(C6F5)4 is very popular in early-transition-metal catalyzed polymerization, where it acts as a rather inert and non-coordinating anion. Examples of decomposition of the anion by, e.g., CeFs transfer exist but are not very common. In aluminium chemistry, transfer of CeFs groups from B(C6Fs)3, MeB(C6F5)3 and B(C6F5)4 to the metal appears to be rather easy [14, 15], and it may be that other, even more innocent anions will be required here. 

Perchlorate ion is usually considered to be an innocent anion and perchlorate salts are generally used in maintaining constant ionic strength in the studies of aqueous solutions... 

In general perchlorate is an innocent anion. However, complexes of the type La(HMPA)a (0104)3 have been isolated and their IR and Raman spectra gave evidence for the presence of both ionic and coordinated perchlorate [164], The Raman band at 436 cm 1 indicated perchlorate with C2V symmetry and as a bidentate ligand. 

Tetrafluoroboric acid is a very strong acid, and mixtures of HF and BF3 are extremely strong proton donors, although not quite as strong as those of HF and SbFs (see Section 9.7). Salts containing the [BF4] ion are frequently encountered in synthetic chemistry. The [BF4] ion (like [PFg] , structure 15.33) coordinates very weakly, if at all, to metal centres and is often used as an innocent anion to precipitate cations. For a discussion of the stability of KBF4 with respect to KF -b BF3, see Section 6.16. 

An important role is also played by the nature of the support electrolyte and, in particular, of the anion. As an example, tosylate greatly favors the electrodeposition of PP but is detrimental for PT for the latter, innocent anions, such as perchlorate, tetrafluoroborate, or hexafluorophosphate, are the best choice. 

Polythiophenes are generally electrogenerated in the presence of small innocent anions derived from strong acids (e.g., perchlorate, tetrafluoroborate, and hexafluophosphate) associated with lithium or tetraalkylammonium cations. The nature of the anion strongly affects the morphology and the electrochemical properties of the polymer. 

Depending on the coordinative properties of the anion and on the degree of the cation s reactivity, the ionic liquid can be regarded as an innocent solvent, as a ligand (or ligand precursor), as a co-catalyst, or as the catalyst itself... 

Ionic liquids with wealdy coordinating, inert anions (such as [(CF3S02)2N] , [BFJ , or [PFg] under anhydrous conditions) and inert cations (cations that do not coordinate to the catalyst themselves, nor form species that coordinate to the catalyst under the reaction conditions used) can be looked on as innocent solvents in transition metal catalysis. In these cases, the role of the ionic liquid is solely to provide a more or less polar, more or less weakly coordinating medium for the transition metal catalyst, but which additionally offers special solubility for feedstock and products. 

Thallium(i) salts have long been used in reactions with organic and organometallic halide complexes as a means of activating the halide by removal as insoluble T1X. However, the thallium ions proved not to be innocent bystanders, and numerous examples were reported in COMC (1995) where the metal-bound thallium complexes were formed. Deliberate reactions of thallium(i) and thallium(m) salts with metal carbonyl anions have yielded a variety of complexes of the form T1 MLJ3. In the past decade, new examples of metal carbonyl derivatives of thallium have been prepared (see Table 2). In addition, the propensity for Tl+ to form adducts with 16-electron noble metal complexes has been exploited. 

In this cluster system the enclosure of sulfite anions with a correct orientation transforms the anions from innocent structural templates to electronically reactive, functional units. These can now release electrons to the cluster shell upon activation by heat-the sulfite groups in type 2 clusters are activated whereas those in type 1 are not. 

In aqueous solutions the most common complex is aquo ion, [M(H20) ]3+ when the counter anion is an innocent or non-complexing anion. The value of n is known and is not constant in the lanthanide series. However a value of 9 for n for elements La to Nd and a value of 8 for elements Tb-Lu is proposed [90]. For ions from Nd3+ to Tb3+ steric factors play a critical role with an equilibrium mixture of 8-coordinated and 9-coordinated aquo... 

Anions which may be termed as innocent from the point of coordination readily coordinate in organic solvents like methanol and acetonitrile [28-30], Using 139La NMR,... 

Due to the good solubility of organometallic compounds, ionic liquids have been used as reaction media, replacing traditional molecular solvents, or as the catalyst-supporting phase in a biphasic system. Influences of the ionic liquid on the reaction rate and selectivity can mostly be explained by the reactivity of the anion, which can be noncoordinating or coordinating as well as Lewis-acidic, Lewis-basic or neutral. The cation, in contrast, is considered to be essentially noncoordinating and innocent. 

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