Alkylammonium salt complexation

The sulfate radical anion is formed by thermal, photochemical or redox decomposition of persulfate salts (41, sec 3.3.2.6.1). Consequently, it is usually used in aqueous solution. However, crown ether complexes or alkylammonium salts may be used to generate the sulfate radical anion in organic solution (see 3.3.2.6.1). 

In a similar manner, the diffusion of hexane into dichloromethane solutions containing mixtures of the alkylammonium salts of bromide and the olefinic acceptors o-CA and TCNE result in the formation of brown-red crystals [23]. X-ray analysis reveals the (1 1) complex of bromide with o-CA, in which the anion is located over the center of the C - C bond of the acceptor moiety (Fig. 15b) and Br - C contacts are shortened by as much as 0.6 A relative to the sum of van der Waals radii (Table 3). In bromide complexes with TCNE, the location of the anion relative to the acceptor is variable. In fact, a 2 1 complex [(Br )2,TCNE] is isolated in which both anions reside over the olefinic bond when the tetraethylammonium salt of bromide is used. In comparison, if the tetrapropyl- or tetrabutylammonium salts of the same anion are employed, the (1 1) complexes [Br ,TCNE] are formed in which the bromide donors are shifted toward the cyano substituents (Fig. 15a). In both cases however, the short intermolecular separations that are characteris-... 

Also of importance for analytical and structural studies are the complexes with alkylammonium salts, widely used under selective conditions of critical electrolyte concentrations (see Section III). 

Certain long-chain alkylammonium salts, notably tricaprylmethyl-ammonium chloride (Aliquat 336-S) and tri-Ao-octylamine hydrochloride (TIOA) are liquids, sometimes referred to as liquid anion exchangers, which can form extractable ion pairs or aggregates with anionic metal complexes in the... 

In the preceding section it was shown that the stability of crown-ether complexes with alkylammonium salts depends on the relationship between the structures of the crown ethers and the ammonium ions. How critically this relationship determines the complex stability will become clear in this section, which deals with the discrimination between the two enantiomers of racemic salts by chiral macrocyclic ligands. 

Many examples of the phase-transfer catalysed epoxidation of a,(3-unsaturated carbonyl compounds using sodium hypochlorite have been reported [e.g. 7-10]. The addition of transition metal complexes also aids the reaction [11], but advantages in reaction time or yields are relatively insignificant, whereas the use of hexaethyl-guanidinium chloride, instead of a tetra-alkylammonium salt, enhances the rate of epoxidation while retaining the high yields (>95%) [10]. Intermediate (3-haloalkanols are readily converted into the oxiranes under basic conditions in the presence of benzyltriethylammonium chloride [12]. 

Hydrogen peroxide may be efficiently employed for the epoxidation of unfunctionalized aikenes in the presence of polyoxo complexes of tungsten and molybdenum . Venturello and coworkers first developed a phosphotungstate catalyst , with particular emphasis on the tetrakis(diperoxotungsto)phosphate anion P04[W(0)(02)2]4 , 37 , that in conjunction with H2O2 and a lipophilic tetra-alkylammonium salt Q+X as phase transfer... 

BF3 reacts smoothly, in inert solvents, with alkali metal sulfates and phosphates to give stable 2 1 and 3 1 complexes (Table 9), whereas the intermediate complexes that form with NOT, SO and COl- decompose to [BF4] and B203.55 Brownstein et al. have established114 that BF3 reacts easily with alkylammonium salts in CH2C12 or liquid S02. [BF3A]- complex anions are formed with the salts of strong acids (equation 17) whereas complexes with salts of weak acids easily undergo disproportionation (equation 18) and/or conversion into a 2 1... 

The complex hydrate structure, 1.67 choline hydroxide-tetra-n-propyl-ammonium fluoride 30-33H2O (space group = R-3, a = 12.533, c = 90.525 A) was discovered by Udachin and Ripmeester (1999b). It should be noted that the tetra-n-propylammonium salt will not form a hydrate on its own (Dyadin et al., 1988), even though other tetra-alkylammonium salts will form a variety of hydrate structures. Similar to structures II, H, and IV, this complex structure consists of stacked sequences of layers, CABBCAABCCABBCAAB. That is,... 

The formation of complexes between aza derivatives of crown ethers and primary alkylammonium salts. Part 1. Monoaza derivatives, M. R. Johnson, I. O. Sutherland and R. F. Newton, J. Chem. Soc., Perkin Trans. 1, 1979, 357. 

The ability of crown polyethers to form complexes with ammonium and alkylammonium salts") gave rise to the development of Cram s concept of host-guest chemistry57). Asymmetric macrocyclic polyethers (host molecules) were designed and synthesized that distinguish between the enantiomers of chiral amine salts (guest molecules). For example, the (R,Reform of polyether (Fig. 66) which was obtained in pure state, forms complexes of different... 

Host-Guest Complexes of Crown Ethers and Cryptands. - The complexation of primary alkylammonium salts by macrocyclic multidentate compounds has been reviewed. ... 

Compound (4) reacts with halides, preferably their alkylammonium salts, in acetone or DME with exchange of one CO for a halide, giving anionic complexes of the type Co(CO)2(NO)X (X = Cl, Br, I, CN) (equation 29). Owing to the high charge density at the metal, these anions can act as sources for the hyponitrous ion, NO, which is transferred in nucleophilic substitutions at activated (benzyl) halides, giving aldoximes (e.g. PhCH=NOH from PhCH2Y) (equation 30). ... 

Non-aqueous solutions of the XWuM complexes may be prepared from tetra-alkylammonium salts or by using phase transfer agents. The coordination of the organic solvent to M, replacing the water molecule, usually takes place with donor solvents. Dehydration of some (but not all) of the XWnM(H20) anions occurs after phase transfer for solvents like toluene with formation of species with a free... 

Complexation experiments by Mock et al. [44, 45, 46] proved that Cucurbituril (53) forms 1 1 complexes with a number of alkylammonium salts where the guest is situated in the cavity of the host. The most stable host-guest complexes are observed with alkyldiammonium salts the dissociation constants are remarkably high to 10 moll . Binding results mainly from ion-dipole interactions... 

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