Reductive Reactivity

The reduction potentials ofLn(III)/Ln(II) range from -0.35 V (Eu) to -2.6 V(Nd). Therefore all of the divalent organolanthanide complexes, except for Eu(II), have a strong reducing ability, and can be used as one-electron reducing agents. 

The non-classical divalent lanthanide complexes have stronger reducing power than divalent samarium complexes because of their higher reduction potentials. Dinitrogen is not an inert atmosphere for these non-classical divalent lanthanide complexes. Therefore, attempts to prepare non-classical divalent organolanthanide complexes by metathesis reactions in dinitrogen atmosphere have been unsuccessful, and the dinitrogen-activated products were isolated. A typical example is shown in Equation 8.36 [112]. 

It is worth noting that the sterically crowded tris(pentamethylcyclopentadienyl) lanthanide complexes (C5Mes)3Ln have similar reductive reactivity to the divalent samarium complex. This phenomenon has been termed sterically induced reduction (Section 8.2.1.2). 

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Nilekar AU, Mavrikakis M. 2008. Improved oxygen reduction reactivity of platinum mono-layers on transition metal surfaces. Surf Sci 602 L89-L94. 

Most biochemically relevant high-spin systems have such short 7j-relaxation times that their EPR is broadened beyond detection at ambient temperatures. An exception is the class of S = 5/2 Mn" systems with D hx. Also, S = 7/2 Gd"1-based MRI shift reagents exhibit readily detectable room-temperature EPR spectra. Otherwise, aqueous-solution transition ion bioEPR is limited to complexes of S = 1/2 metals, in particular Cu", and to a lesser extent VIV02+, NiIn, Ni1, Mov, and Wv. Cupric is the stable oxidation state of biological copper under aerobic conditions, however, the other metals are stable as Vv, Ni", MoVI, and WVI, and, therefore, the other oxidation states associated with S = 1/2 paramagnetism may exhibit oxidative or reductive reactivity and may thus require specific experimental precautions such as strict anaerobicity over the course of the EPR experiment. 

Deng B, Stone A (1996) Surface-catalyzed chromium(VI) reduction reactivity comparisons of different... 

The component waves in the voltammograms (a lower potential catalytic wave and a higher potential switch wave associated with the activation/inactivation of the enzyme) can be seen in Fig. 5.13. The positions of their inflection points were obtained as local extrema in the first derivative with respect to potential (Fig. 5.13, inset), switch corresponds to the potential of the reductive reactivation process. Figure 5.13 shows that as pH is increased Eswitch and both decrease. Furthermore, the pH dependence of Eswitch could be fitted to a 1H+ le stoichiometry with an apparent pK value of 7.7 and a potential at the alkaline limit of -166 mV. 

Complete reductive reactivation can be achieved (at 45°C) by a 2 min excursion to a reducing potential. 

CN(R)CH=CHN(CH2)2NBu in Ln " chemistry have been explored by P. L. Arnold, et A review by Trifonov, entitled Reactions of ytterbocenes with diimines steric manipulation of reductive reactivity , dealt with reduction of a-diimines and related compounds, which led to Ln " amides via electron transfer and/or C-H bond activation. 2"... 

Sensitivity to deactivation by oxygen and, in some cases, slow, reductive reactivation. 

Another type of ion pairing effect likely to influence the electron transfer reactivity of dianions is the so called triplet association (triplet being here taken in the sense of triple association between two cations and one dianion). When Coulombic interactions in such multiple ions are considered, the electrostatic stabilization is enhanced when the dianion charges are close together, an unexpected observation if the electrostatic repulsions within the dianion are considered [43]. Multiple association of this type probably affects the reductive reactivity of the anionic species. 

Cobalt accepts a methyl group from methyl-tetrahydrofolate, forming methyl Co +-cobalamin. Transfer of the methyl group onto homocysteine results in the formation of Co+-cobalamin, which can accept a methyl group from methyl-tetrahydrofolate to reform methyl Co +-cobalamin. However, except under strictly anaerobic conditions, demethylated Co+-cobalamin is susceptible to oxidation to Co +-cobalamin, which is catalyticaUy inactive. Reactivation of the enzyme requires reductive methylation, with S-adenosyl methionine as the methyl donor, and a flavoprotein linked to NADPH. For this reductive reactivation to occur, the dimethylbenzimidazole group of the coenzyme must be displaced from the cobalt atom by a histidine residue in the enzyme (Ludwig and Matthews, 1997). 

Evans, W.J. (2002) The expansion of divalent organolanthanide reduction chemistry via new molecular divalent complexes and sterically induced reduction reactivity of trivalent complexes. Journal of Organometallic Chemistry, 647, 2. 

Teliska, M. et al.. Correlation of water activation, surface properties, and oxygen reduction reactivity of supported Pt-M/C bimetallic electrocatalysts using XAS, J. Electro-chem. Soc., 152, A2159, 2005. 

Stamenkovic et al. used the adsorption energy of O on alloy surfaces as a catalytic activity indicator. They use this approach to develop a volcano model of activity for the oxygen reduction reactivity and compare their computed predictions of activity to experimental results. They showed that Pt-3d alloy surfaces are near the top of the volcano, but more significantly identified the chemical descriptor (d-band center or O adsorption energy) that could be used to identify new alloy surfaces that could have higher activity. 

To demonstrate characteristics of HTGRs under Reactivity insertion and Cooiant fiow reduction Reactivity insertion Test ... 

To summarize the aspects of one-electron reductant reactivity pattern, it is useful to examine a comparison of a similar reaction with two reductants, reduction of by Cr and Eu . In the former, the observed rate law ... 

An article published in 2011 explored the oxygen reduction reactivity of Co hangman corroles [153], Along with novel catalytic activity, this paper described some potentially useful synthetic procedures. For example, H3tpfc was obtained in... 

Scheme 2 Synthetic routes for the synthesis of high-valent organouranium-bis (imido) complexes and their reductive reactivity with dihydrogen...

Table 1 summarizes the temperature dependence of NO conversion with various reducing gases on H-Fe-silicate. The level of NO conversion markedly depended on the kind of reducing gases. CO and H2 were not effective for this reaction, and they were preferentially consumed by the reaction with O2. Reduction of NO proceeded when hydrocarbons were used as reductants, and the reduction reactivity decreased in the following order ... 

Grinstaff, M.W., M.G. Hill, E.R. Bimbaum, W.P. Schaefer, J.A. Labinger, and H.B. Gray (1995). Structures, electronic properties, and oxidation-reduction reactivity of halogenated iron porphyrins. Inorg. Chem. 34, 4896-4902. 

Mitochondria, as an energy metabolism regulator, play one of the basic roles in the organism response to the action of stressors. About 1 to 3% of oxygen consumed by mitochondria form, as a result of 1-electron reduction, reactive oxygen species (ROS), which participate in the cellular redox-signaling. 

McGuire R Jr, Dogutan DK, Teets TS, Suntivich J, Shao-Hom Y, Nocera DG. Oxygen reduction reactivity of cobalt(ll) hangman porphyrins. Chem Sd 2010 1 411—4. 

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