Metal complexes—continued kinetic studies

The catalytic activity of Hg in elimination and substitution reactions of transition-metal complexes continues to be the subject of study. Kinetic studies on the Hg" catalysed aquation of both cis-[Co(en)2(CN)Cl], cis-[(chloro)(aniline)CO(en)2], and [PdLX] (L = tetramethyldiethylenetriamine X = Cl, Br, or I) are consistent with intermediate adduct formation at the halide substituent. Mercury(ii) reacts reversibly with the [Co(NH3)5SCN] ion to yield [Co(NH3)5(SCN)Hg] which irreversibly undergoes either aquation to yield [Co(NH3)sH20] or isomerization to yield [Co(NH3)5(NCS)Hg] at approximately equal rates. The kinetics of the reaction... 

Bipyridyl (continued) as ligand, 12 135-1% catalysis, 12 157-159 electron-transfer reactions, 12 153-157 formation, dissociation, and racemization of complexes, 12 149-152 kinetic studies, 12 149-159 metal complexes with, in normal oxidation states, 12 175-189 nonmetal complexes with, 12 173-175 oxidation-reduction potentials, 12 144-147... 

Continuing a long series of kinetic and mechanistic studies on transition metal complexes, rischer et al have published a detailed account of the reaction between... 

Kinetic studies of molybdenum complexes have continued, and a picture is now available for the relative labilities of molybdenum complexes with the metal ion in oxidation states +3, +4 92,33 +5 34 +5. The nature of molybdenum(iv)... 

Although cobalt(m) and chromimn(m) continue to be kinetically the most widely investigated inert metal ions, some progress has been made in recent years towards our understanding of the rarer metals. The continuing efforts of Taube and his associates are particularly noteworthy in the field of ruthenium chemistry, and several interesting publications from them dealing with aspects of ruthenium(n) and ruthenium(in) complexes have appeared recently. - The photochemical studies of... 

The first reported controlled polymerization based on the OMRP-RT principle appears to have been presented by Minoura in a series of articles starting in 1978, where the redox initiating system BPO/Cr was used for the polymerization of vinyl monomers.Not only were the kinetics different than in free-radical polymerization (very low reaction orders in Cif and BPO), but also the polymerization was observed to continue after all Cr had been converted by the peroxide to Cr and the degree of polymerization was found to increase with monomer conversion at low temperatures (<30 0). These studies included the report of a block copolymer (PMMA-b-PAN). Polydispersity indexes were not reported for these studies. Minoura formulated the mechanistic hypothesis of the formation of a metal complex with the free radical and stated that "the recombination of free radicals formed by the dissociation of the complexed radicals competes with a disproportionation of free radicals". However, these studies did not have a great impact in the polymer community, being cited only a handful of times before 1994. A few subsequent contributions reported the application of similar conditions to other metals but well-controlled polymerizations were not found."- " ... 

The coverage in this chapter is not comprehensive and no tabulation of rate data has been attempted. A more extensive account of the material will appear in Volume 9 of the series the presentation of the material also differs slightly from previous volumes. There have been many important developments in this general area. A comprehensive review of one-electron reduction potentials for nonmetallic substrates has appeared. Detailed kinetic studies have been reported for several important reactions where metal ions serve as catalysts in the transformation of organic substrates.Catalytic oxidation reactions involving metal complexes and macrocyclic metal complexes have been reviewed. Continued interest centers on catalysis by metalloporphyrins, and the role of metal complexes in electrocatalytic reductions has been reviewed. ... 

The different types of coordination modes of carbonate in metal carbonato complexes offer challenges to investigate intimate mechanisms of their formation. The study of the kinetics and mechanisms of the formation and decomposition of such complexes, therefore, continue to be an interesting area of activity as it has a direct bearing on... 

The methodology for studying M-Ng complexes in the gas phase is essentially the same as the TRIR method for liquified noble gases a pump pulse photolyzes a metal carbonyl ion and the fragment is detected with the aid of a continuous IR laser. In these experiments helium is utilized as the standard buffer gas. A xenon complex may be detected by alteration in the spectrum and kinetics on addition of xenon. Since the spectra are free of solvent effects, the effect of coordination should be more easily discerned than in the liquid phase. This method has been used to study M(CO)sXe (M = Cr, Mo, W) and W(CO)sKr. Metal-xenon bond energies of ca. 35 kJmol are deduced from the kinetics of reaction with CO. The variation between metals in comparable to the error bars, about 4 kJ mol . The W-Kr bond energy is estimated to be less than 25 kJmol . ... 

Oxidation of aqueous phenol solutions was studied over various catalysts in a semibatch slurry and continuous-flow fixed-bed reactors at temperatures up to 463 K and pressures slightly above atmospheric. The results show that due to a complex consecutive-parallel reaction pathway and a heterogeneous-homogeneous free-radical mechanism both kinetics and reaction selectivity are strongly dependent on the type of reactor used. Although the catalysts employed were found to be active in converting aqueous phenol solutions to nontoxic compounds, neither metal oxides nor zeolites were stable at the reaction conditions. 

The redox properties of thallium are important in preparative organic and organometallic/inorganic chemistry. For this reason, studies of redox behavior and the thermodynamics and kinetics of complexing processes are likely to remain relevant. The employment of the TF ion as a probe for in biological systems will no doubt continue, because of the easy detection of the former. For the same reason, thallium(III) can be used as a representative for several other metal ions in solution. 

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