Arene-alkali metal compounds

Most of the results published in this domain deal with the formation of arene-alkali metal compounds. The conventional preparations of their deep-colored solutions by dissolution of the metal by the hydrocarbon, generally in an ethereal solvent, are slow. The first purpose of sonochemists in this domain seems to be as simple as saving time. 

Most of the remaining examples of supramolecular alkali metal compounds involving r-coordination are alkoxides, siloxides, and thiolates. In polymeric sodium phenolate ( NaOC6H4Me-4 2]n, 79 [78], the / -arene interaction of the phenolate ligands with sodium plays a crucial role, because it restricts the structure of the resulting polymer to a one-dimensional stack of [NaOC6H4Me-4]2 dimers and prevents the formation of a fully extended three-dimensional network. 

Increasing the reducing agent/W ratio and using Na-naphthalenide led to the isolation of the two-electron-reduced, diamagnetic compound 19. The C2v symmetry of the h NMR spectrum and the X-ray analysis are in agreement with the cen-trosymmetric structure sketched in Scheme 2 for 19 [W = W, 2.614(1) A]. The six-coordination of the metal and the inclusion of the alkali metal cation removes the planarity ofthe 04 core and the cone conformation of the calix[4]arene. The sodium cation within the calix[4]arene cavity is r 3-bonded to two opposite arene rings. 

The stability of the polypyridyl rhenium(I) compounds mentioned above stimulated applications of this coordination chemistry. Thus, new heterotopic bis(calix[4]arene)rhenium(I) bipyridyl receptor molecules have been prepared and shown to bind a variety of anions at the upper rim and alkali metal cations at the lower rim. A cyclodextrin dimer, which was obtained by connecting two permethylated /3-cyclodextrins with a bipy ligand, was used for the preparation of a luminescent rhenium(I) complex. The system is discussed as a model conipound to study the energy transfer between active metal centers and a bound ditopic substrate. The fluorescence behavior of rhenium(I) complexes containing functionalized bipy ligands has been applied for the recognition of glucose. ... 

Photoirradiation of a tetrahydrofuran (THF) solution of calix[4]arene 386 having two anthryl groups produces 387 (Scheme 101). Encapsulation of alkali metal ions into the ionophoric cavities of 386-387 was investigated by Shinkai and co-workers [358], Compound 386 itself showed the poor ion affinity and the poor ion selectivity, whereas 387 showed the much improved ion affinity and the sharp Na+ selectivity. 

The recognition of different re-donating arene guests with a common re-accepting host has been subjected to control by metal ion crown ether recognition in the next case history to be described. The 18-crown-6 derivative 18, which bears a DNP ring system [12], is a ditopic compound that can act (Figure 11) as a host for alkali metal (e.g., K+) cations as well as as a... 

The use of macrocyclic compounds for extraction of various analyte cations in the presence of suitable anions is still growing. Extraction-spectrophotometric methods for the determination of alkali metals (with picrate counter ion) using 18-crown-6 and its derivatives [12-15] and calix[4]arene crown ethers [16] have recently been developed. The application of hexa-acetatocalix[6]arene for extraction of Fe [17] and Pb [18] have been described. 

Alkali metal arene radical anion complexes are useful sources of solvated electrons for reductive desulfonylation reactions.14 Aromatic compounds such... 

Although some cyclohexadienes are readily available, many can be obtained easily by Birch reduction, which involves reduction with solutions of alkali metals in liquid ammonia, a source of solvated electrons, in the presence of alcohol as a proton source.8-10 In previous years, the Bouveault-Blanc procedure, which uses sodium metal and alcohol in liquid ammonia, was frequently employed for direct reduction of aromatic esters however, it gave rise mainly to the corresponding substituted benzoic acid.11 Rabideau et al. reported a modified procedure 12 however, in our hands, this resulted in the reduction of the ester function to give benzoic acid. We have found that the Birch reduction of benzoic acid, followed by esterification, is an efficient procedure for the preparation of the corresponding 1,4-dihydro compound prior to the coordination of the arene to produce functionalized dimeric ruthenium-arene complexes.13... 

Very recently, the first genuine paramagnetic bis(arene)metal anions, namely [Cr(f/-C6H6 BRB)2] (R = SiMe3, n = 1-3), have been generated by alkali metal reduction of the neutral compounds (431). 

Arene compounds of V, Cr, and Ru are also formed by reactions of salts of these elements with radical anions of aromatic compounds of alkali metals. 

Other isocyanate syntheses that have recently been reported include several well-known reactions. One area which has attracted considerable attention is that of the direct production of isocyanates by the carbonylation of nitro-arenes. Both mono- and di-isocyanates are claimed to have been produced using various catalysts palladium, rhodium, and iron compounds often being cited. Other preparative reactions for isocyanates which have appeared in the literature include the acid catalysed hydrolysis of isocyanide dihalides and the reaction between alkyl halides and alkali-metal cyanates, although the latter has been given a modern flavour by the use of a polymer-supported reagent. ... 

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