Ruthenium ions

Ru(II)-Ru(III) valence distribution, but that there is complete delocalization with formal ruthenium valence 2.5. The ruthenium ions are crystallographically indistinguishable. The intervalence (MMCT) absorption band is at 6400 cm (fimax = 5500M" cm ). 

Figure 28.20 The structure of Ru(II)pby32+ a chelated ruthenium ion coordinated with three bipyridine groups.

Transition-metal catalysts are, in general, more active than the MPVO catalysts in the reduction of ketones via hydrogen transfer. Especially, upon the introduction of a small amount of base into the reaction mixture, TOFs of transition-metal catalysts are typically five- to 10-fold higher than those of MPVO catalysts (see Table 20.7, MPVO catalysts entries 1-20, transition-metal catalysts entries 21-53). The transition-metal catalysts are less sensitive to moisture than MPVO catalysts. Transition metal-catalyzed reactions are frequently carried out in 2-propanol/water mixtures. Successful transition-metal catalysts for transfer hydrogenations are based not only on iridium, rhodium or ruthenium ions but also on nickel [93], rhenium [94] and osmium [95]. It has been reported that... 

The Ru(IV)/Ru(III) redox potential is 0.78 V, so that Ru(III) or even Ru(II) species may be present in vivo. Indeed, the related Ru(III) complex 32 is also active (171), and the pendant arms in these octahedral polyaminocarboxylate complexes increase the rate of substitution reactions. Complex 32 binds rapidly to the blood proteins albumin and transferrin (172), and the ruthenium ion appears to remain in the... 

Like other peroxides, also dioxetanes are sensitive to the presence of metal ions and their complexes, which catalyze the decomposition of the dioxetane molecule. In most cases, this decomposition is dark, i.e. no chemiluminesce is generated in such a catalytic cleavage42. An informative exception, for instance, constitutes the chemiluminescent decomposition of the dioxetane 19 in Scheme 13, initiated by the ruthenium complex Ru(bipy)3Cl243. It has been shown that this chemiexcitation derives from the valence change of the ruthenium ion in the process Ru3+ I e — Ru2+, for which the efficiency of the excited-state generation may be as much as 40%44. Hence, when the radical anion of the carbonyl cleavage fragment from the dioxetane and the Ru3+ ion are formed in... 

In fact, equilibria between ruthenium ions in different oxidation states in aqueous solution add complexity to the mechanistic analysis of these oxidations. Thus, Burke and Healy presented mechanistic evidences9 suggesting that putative oxidations of alcohols with ruthenate ion are in fact produced by perruthenate originated by dismutation of ruthenate. 

Clarke MJ, Bitler S, Rennert D, Buchbinder M, Kelman AD (1980) Reduction and subsequent binding of ruthenium ions catalyzed by subcellular components. J Inorg Biochem 12 79-87... 

The geometries of Mn(3-TRPyP) and Mn(4-TRPyP) species already investigated by density function theory (DPT) and molecular mechanics calculations (270, 271). They are consistent with a planar configuration for the porphyrin ring in both systems. However, while the peripheral ruthenium ions are in the same plane in the Mn(4-TRPyP) species, they are located above and below the porphyrin plane in the Mn(3-TRPyP) complex (Fig. 27), so that the stereochemical positioning of these groups provides local picket fences, or pockets, capable of influencing the accommodation of the substrates near the catalytic site. 

For the preparation of the required 1 2 [Ru ligand 47] intermediate, a pro-tection-deprotection strategy was employed. This involved reaction of 47 with trimethyloxonium tetrafluoroborate to block one metal co-ordination site in 47 to yield 48. After co-ordination of one ruthenium ion, the remaining site was unblocked by reaction with DABCO in refluxing acetonitrile. Reaction of this 1 2 (metal ligand) product with a second metal ion was then carried out. 

Platinum and palladium complexes of thietane and 3,3-dimethylthietane have been prepared as illustrated for 90. The platinum complexes exist in cis and trans configurations, but no cis-trans isomerization of the palladium complexes in the solid state was observed. Stability constants of thietane with Mn(ll), Co(II), and Ni(II) chelates have been determined. Proton nmr studies show that the absorption of the a-methylene protons, which are syn to the metal, is shifted downfield (about 0.7 ppm) more than the absorption of the protons anti to the metal (about 0.4 ppm downfield). Energies of activation for pyramidal inversion were determined. Bis-ruthenium complexes of di-, tri- and tetraspirothietanes (e.g., 90a) show rapid electron transfer between the ruthenium ions long-range electron tunneling was proposed. ... 

Uniform impregnation of ruthenium can be obtained with ruthenium chloride in the presence of citric acid the acid is competitive with the very strongly adsorbed complex ruthenium ion although as we saw earlier citric acid will completely displace the chloroplatinate anion. 

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