Cationic complexes studied

Interestingly Gokel has demonstrated the existence of a direct coordination coupling pathway between this ferrocene cryptand and a silver cation. Complexation studies were carried out with [24] and [25] (as well as other ferrocene cryptand-type species) by X-ray crystallography, FAB mass spectral analysis, nmr and UV/Vis spectroscopy. 

Fages. F. Desvergne, J.-P. Bouas-Laurent. H. Lehn, J.-M. Barrans. Y. Marsau, P. Meyer. M. Albrecht-Gary, A.-M. Synthesis, stmctural. spectroscopic, and alkali-metal cations complexation studies of a bis-anthracenediyl macrotricyclic ditopic receptor. J. Org. Chem. 1994. 59. 5264-5271. 

Figure 7.1 Cationic complexes studied as antibacterial and antifungal agents.

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

The conductivity of a number of bromine containing complexes with different quaternary ammonium cations was studied by Gerold (see Ref. 156]) with respect to the dependence on temperature and bromine... 

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

X-ray crystallography and variable temperature H NMR studies show that the conformation of the coordinated imidazolidin-2-ylidene, in both the neutral and cationic complexes 70, is anti, anti with respect to the Ph of the backbone of the NHC, exclusively in the solid state and predominantly in solution at lower temperatures (-75°C). At room temperature in solution, possible conformer interconversion by the rotation around the phenyl-N bond of the NHC substituent is apparent from the broadness of the peaks in the NMR spectra. Hydrosilylation of acetophenone by Ph SiH catalysed by 70 at room temperature or at -20°C results in maximum ee of 58%. However, at lower temperatures the reaction rates are much slower [55]. 

Iron(III) complexes of 2-acetylpyridine Af-oxide iV-methyl- and 3-azabicyclo[3.2.2.]nonylthiosemicarbazone, 24 and 25, respectively, have been isolated from both iron(III) perchlorate and chloride [117], The perchlorate salt yields low spin, octahedral, monovalent, cationic complexes involving two deprotonated, tridentate thiosemicarbazone ligands coordinated via the N-oxide oxygen, azomethine nitrogen and thiol sulfur based on infrared spectral studies. Their powder ESR g-values are included in Table 1 and indicate that bonding is less covalent than for the analogous thiosemicarbazones prepared from 2-acetylpyridine, 3a and 4. Starting with iron (III) chloride, compounds with the same cations, but with tetrachloroferrate(III) anions, were isolated. 

Complexation studies with bidentate phosphine ligands showed that stable cationic complexes of Tc(V), Tc(III), and Tc(I) are easily accessible. The influence of reaction conditions on reaction route and products is well demonstrated by the reaction of pertechnetate with the prototype 1,2-bis(dimethylphosphino)-ethane (dmpe) (Fig. 16). Careful control of reduction conditions allows the synthesis of [Tc02(dmpe)2]+, [TCl2(dmpe)2]+, and [Tc(dmpe)3]+, with the metal in the oxidation states V, III, and I [120,121]. This series illustrates the variety of oxidation states available to technetium and their successive generation by the action of a 2-electron reducing agent. 

The mechanism of uptake and retention of the mono-cationic 99mTc complexes in the myocardium - or other tissues - has not been fully resolved. Most of the mechanistic studies have been conducted with 99mTc (MIBI)6f and "mTc-diphosphine complexes. It has been shown that these mono-cationic complexes are not taken up in myocytes via the Na+/K+-ATPase pump as is 201T1+ [41]. Instead, these cationic tracers are localized and retained in cellular membranes, including mitochondrial membranes [41]. 

Studies of the base-hydrolysis mechanism for hydrolysis of technetium complexes have further been expanded to an octahedral tris(acetylacetonato)techne-tium(III) [30], Although a large number of studies dealing with base hydrolysis of octahedral metal(III) complexes have been published [31], the mechanism of the tris(acetylacetonato)metal complex is still unclear. The second-order base hydrolysis of the cationic complex tris(acetylacetonato)silicon(IV) takes place by nucleophilic attack of hydroxide ion at carbonyl groups, followed by acetylacetone liberation, and finally silicon dioxide production [32], The kinetic runs were followed spectrophotometrically by the disappearance of the absorbance at 505 nm for Tc(acac)3. The rate law has the following equation ... 

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