Ammonium-centered ionic

The n values were high for all of the ionic liquids investigated (0.97-1.28) when compared to molecular solvents. The n values result from measuring the ability of the solvent to induce a dipole in a variety of solute species, and they will incorporate the Coulombic interactions from the ions as well as dipole-dipole and polarizability effects. This explains the consistently high values for all of the salts in the studies. The values for quaternary ammonium salts are lower than those for the monoalkylammonium salts. This probably arises from the ability of the charge center on the cation to approach the solute more closely for the monoalkylammonium salts. The values for the imidazolium salts are lower still, probably reflecting the delocalization of the charge in the cation. 

Upon dissolving the copolymer/catalyst mixture in ethylbutylamine (EtBuNH) the introduction of CO2 at atmospheric pressure results in formation of an equilibrium mixture of carbamic acid and the quaternary ammonium salt of carbamate. The carbamic acid serves to remove the copolymer from the metal center, at which time it precipitates in the ionic liquid and is isolated by filtration. The metal catalyst... 

To a greater or lesser degree the spectra of all C-6 ionic salts, whether they are substituted with a covalent group at C-2 or not, are comprised of a mixture of the spectra of C-6 ionic and C-6 covalent forms. Differences among the spectra of the compounds result from secondary effects on the structure of the bare anions such as hydrogen bonding and dimerization due to hydrophobic dye/dye molecular interactions. This is particularly obvious when the fluorescence spectra of the ammonium salts at room temperature of the C-2, C-6 bis trimethylammonium salt shows a triad of broad peaks centered at 583 nm. At reduced temperature the same compound shows three sharper peaks at 538, 583, and 605 nm. The shortest wavelength of these... 

This chapter will concentrate on the chemistry of metal-14-centered anions (Ge, Sn, Pb). These compounds and their silyl analogues are ionic or polarized alkaline and alkaline earth metal-14 compounds, as well as delocalized molecules such as metalloles. Ammonium metallates Mi4 R4N+ or metal-14-centered anion radicals are also considered. The subject was explored during the 1960s and 1970s and thoroughly reviewed in 1982 and 1995 in Comprehensive Organometallic Chemistry, Vols. I and and for silicon species in a previous volume of this series . By that time the main routes to metal-14 anions were known. Since then, the subject has been developed in the topics of particular syntheses, stabilization using steric hindrance, electronic effects and complexation, spectroscopic and structural analyses "... 

Stable zwitterions containing ammonium and carboxylate ionic centers have also been polymerized. The bulk zwitterionic polymerization of... 

New pyrazolyl ligands containing an aminomethyl group, in position 4, have been coordinated to rhodium(I) and show a good solubility in water, presumably because the ammonium group does not interact with the metal center. The resulting complexes have been characterized and, in our opinion, they are good candidates for biphasic catalysis [82], such as l,2,4-triazol-2-ium-5-ylidene complexes of Rh(I), Ir(I), Ni(0), Ni(II), Pd(II), and Hg(II) [83]. Due to their ionic character, these carbene complexes are extremely soluble in water. 

The zwitterion contains carboxlate and ammonium ionic centers but has a net charge of zero. a-Amino acids exist exclusively as zwitterions in the solid state. Even when drawn as the uncharged molecule, we must understand that the actual structure is that of the dipolar ion. Amino acids are referred to as amphoteric compounds because both acidic and basic groups are contained in the same molecule. 

---