Di-cation

The 20e complex Fe(C6Me6)2, easily synthesized in high yield by Na/Hg reduction of the dry di-cationic precursor in THF at 20 °C [28], is also very useful for functionalization. Its reaction with electrophiles RX directly gives functional cyclohexadienyl iron cations, which saves one step with respect to the route using hydride protection/deprotection [47] Scheme V ... 

Although the o-xylylene complex is thermally unstable, it was characterized at — 50 °C by its 1H- and 13C-NMR spectra showing the exocyclic methylene at 5 = 5.04,4.42 ppm (JH) and 5 = 144.8 ppm (13C) using C6D5CD3 as the solvent. Its reaction with benzoyl chloride on the exocyclic carbon leaves a very acidic methylene group which transfers a proton onto the adjacent methylene unit. The double bond is benzoylated again in in situ and a di-cation of the [bis(arene)Fe]2+ type is obtained [47] Scheme VIII. 

DOPED PA MODELS. We selected two criteria to characterize the structure of the mono- and di-cations. The wavefunctions of the cations at their respective optimized geometries were used to determine Mayer s bond indices which reflect the strength of the interatomic bonds. The differences in the cations and also the neutral molecule emerge very clearly from Table III. 

A close analysis of the chlorine-centered ClA6.nMn octahedral SBU (secondary building unit) has revealed that the acentricity of the bulk lattice may be introduced via cation substitution. The di-cation substitution (n=2) in ClNas... 

Chlorhexidine base is not readily soluble in water therefore the freely soluble salts, acetate, gluconate and hydrochloride, are used in formulation. Chlorhexidine exhibits the greatest antibacterial activity at pH 7-8 where it exists exclusively as a di-cation. The cationic nature of the compound results in activity being reduced by anionic compounds including soap and many anions due to the formation of insoluble salts. Anions to be wary of include bicarbonate, borate, carbonate, chloride, citrate and phosphate with due attention being paid to the presence of hard water. Deionized or distilled water should preferably be used for dilution purposes. Reduction in activity will also occur in the presence of blood, pus and other organic matter. 

The interactions of (212) and related species with monovalent and divalent metal cations have been studied by nmr spectroscopy (Lehn Simon, 1977). The study indicated that sequential formation of mono-and di-cation complexes occurs (see [4.7]). These studies, and especially a 13C nmr study of the 1 1 complex of (212) with barium nitrate, suggest that the 1 1 species are unsymmetrical with the metal ion being contained in one of the azacrown cavities. Nevertheless, the nmr data also indicate that these 1 1 species undergo internal cation exchange between the respective azacrown sites. This intramolecular dynamic behaviour serves... 

The porphyrin complexes of manganese exist in a range of formal oxidation states of which the +3 state is most stable. Mn(m) porphyrins may be electrochemically oxidized in non-aqueous media to yield products which are probably Mn(m) cation radicals or di-cations (Kelly Kadish, 1982). The potentials at which these reactions occur are sensitive... 

One of the simplest ways to tell at a glance if our tap water contains much Ca2+ - we say it is hard - is to look at the bath after letting out the water. Surfactants form micelles with the calcium di-cation at temperatures above 7k, i.e. in a hot bath. But after cooling to a temperature of about 20 °C, the micelles precipitate to yield hydrated crystals - which we observe as a ring of scum along the waterline. 

Some benzylic mono- and di-cations have been studied by the NMR/DFT/IGLO technique. Of the stable dications, the trimethyl species (76 R = Me) was found to be the major resonance contributor to the structure of (75), and the same was found to be true for the trimethoxy derivative. In the related monocations, for (77) the major resonance contributor was (78), and this was also the case for the pentamethyl and 2,5-dimethyl-4-r-butyl compounds. The dication (79) and the trication (80),... 

The formation of the bimetallic complexes 118-123 involves combination of di-cationic transition metal fragments with the dianion of compound 14. A further possibility exists, scarcely studied for 12-vertex 0/050-2,l-ReCBjo species but more extensively exploited in the analogous 11-vertex c/o5o-l,2-MCBg system (M = Mn, Re) discussed in Section IV. Treatment of the dianion of 14 with two... 

As a result of a high intensity band (e 70 000-100 000) at wavelengths between 600-700 nm, chlorins have a characteristic green color, with a typical type of spectrum as shown in Figure 3b chlorin mono- and di-cations have spectra which are similar to those of the neutral compounds. The Soret band in chlorins occasionally shows a tendency to be split. 

During the dissolution of the irradiated fuel in nitric acid the acidity of the solution will fall from 7-8 M HN03 to 3-5 M HN03. The metals present will be dissolved as their nitrate salts and under these conditions the Group I and II metals, principally cesium, strontium and barium, will then be present as solvated mono- or di-cations respectively. These do not form extractable... 

The details of protonation of several alkyl-substituted phenanthrenes by superacids have been reported.73 The observed mono- and di-cations are usually in agreement with those predicted by AMI MO calculations. Molecular modelling studies have suggested a multi-step pathway for the sulfonation of toluene widi sulfur trioxide.74 Intermediate 71-complcx. Wheland intermediate and pyrosulfonate species (34) are suggested, the product (p-toluenesulfonic acid) arising from an exothermic reaction between toluene and the acid (35) fonned by a facile prototropic rearrangement of (34). The sulfur trioxide monosulfonation of isopyrene and some derivatives leads usually to sulfonated... 

The mesomeric stabilisation in this system (A) is comparable to the di-cationic system (G) [see reaction (5)] and the anionic system (B), which my be obtained according to (11). 

Scheme 4 Possible intramolecular stabilisation of mono-cation or di-cation...

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