Guest complexes salts

In this chapter we discuss host-guest complexes of arenediazonium salts with crown ethers and related compounds. Transition metal complexes of arenediazonium ions are treated together with those of dinitrogen and of diazoalkanes in our second book (Zollinger, 1995, Sec. 10.1). 

In addition to the influence of the complexation equilibrium constant K, the observed reaction rate of arenediazonium salts in the presence of guest complexing reagents is influenced by the intrinsic reaction rate of the complexed arenediazonium ion. This system of reactions can be rationalized as in Scheme 11-1. Here we are specifically interested in the numerical value of the intrinsic rate constant k3 of the complexed diazonium ion relative to the rate constant k2 of the free diazonium ion. 

Checking the literature of the second half of the 1980s for applications of crown complexes of arenediazonium salts for synthetic purposes, one gets the impression that these complexes are not widely used. The two comprehensive reviews by Izatt et al. (1985, 1991) show a definite decline of interest in host —guest complexation of arenediazonium ions in the second half of the 1980s. The subject of arenediazonium... 

Another related host-guest complex has been constructed from citric acid, boric acid, and a strontium salt in a 2 1 1 stoichiometry. In this complex the strontium cation is surrounded by four water molecules, two monodentate carboxyl groups and one oxygen atom of the BO4 unit [161]. 

Accepting) Guest Molecules Salt-type Associates and Ternary Complexes of 7 and Imidazole Clathrate of 13.89... 

The maximum observed free energy difference between two enantiomeric host-guest complexes in which one 1,1 -dinaphthyl element is the only source of chirality in the crown ether is about 0.3 kcal mol-1. Improvement of the free energy difference can be achieved by introduction of two such elements. Unfortunately crown ethers with three 1,1 -dinaphthyl groups did not form complexes with primary ammonium salts (de Jong et al., 1975). The dilocular chiral crown ether [294] forms complexes of different stability with R- and 5-cr-phenylethylammonium hexafluorophosphate. The (J )-J J -[284] complex was the more stable by 0.3 kcal mol-1 at 0°C (EDC value 1.77) (Kyba et al., 1973b). Crown ether [284] also discriminates between the two enantiomers of phenylglycine methyl ester hexafluorophosphate and valine methyl ester... 

Table 3.19 Free energy of complexation, (— AG° / kcal mol-1) of neutral and cationic guests (iodide salts) by chiral receptor 3.108 (20 °C, borate buffer, pD = 9, CDC13 solution).50...

Chao, Y., Weisman, G. R., Sogah, G. D. Y., Cram, D. J., Host-guest complexation. 21. Catalysis and chiral recognition through designed complexation of transition-states in transacylations of amino ester salts. J. Am. Chem. Soc. 1979, 101,... 

Actually, coordination complexes of different metal salts of DBTA with hydroxycarboxylic acid esters, hydroxycarboxylic acids and alcohols as well as host-guest complexes of DBTA with chiral phosphine oxides and racemic alcohols can be prepared and used for separation of optical isomers. In the next subchapters theoretical and practical aspects of these recent resolution processes are summarised. 

After we synthesized CB[10] we wanted to investigate its abilities as a host molecule. We found that CB[10] forms host-guest complexes with many of the guests typically used with the smaller members of the CB[n] family (e.g., ammonium salts of alkyl and arylamines, adamantanes, viologens, and ferrocene derivatives like 14-19). 

Host-guest complexes of azaaromatic quaternary salts 93H(36)1645. 

G. Dotsevi, Y. Sogah, and D. J. Cram, Host-guest complexation. 14. Host covalently bound to polystyrene resin for chromatographic resolution of enantiomers of amino acid and ester salts, / Am. Chem. Soc. 101 (1979), 3035. 

In 1967, Pedersen described the preparation and properties of crown ethers,3 which are macrocyclic polyethers capable of sequestering metal cations. These catalysts can enhance the solubility and reactivity of salts in nonpolar solvents. For example, 18-crown-6, i.e., yxo-anhydro-hexaethylene glycol, forms a host-guest complex with potassium cation (K+) (Equation (1)). This association enables ionic potassium fluoride (KF) to dissociate in nonpolar benzene. And since the nucleophilic F counterions are not complexed,4 the yield of the Finkelstein reaction,5 i.e., halide-halide exchange, is increased 6... 

The host (7.15) was found by combinatorial synthesis (from a library of 100 salts) It forms host-guest complexes with several alcohols, ketones, xylenes, and others (e.g., 2 3 with methanol, 1 1 with ethanol, 2 2 with acetone, and 2 1 with acetonitrile).76... 

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

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