Reversible metalation

Markovich G, Collier C P and Heath J R 1998 Reversible metal-insulator in ordered metal nanocrystal... 

Study of instantaneous corrosion rates. Sathyanarayana and Srinivasan114,115 have extended faradaic rectification studies to the determination of instantaneous corrosion rates of partially reversible metal ion/metal interfaces. They emphasized the practical utility of the method in the fast monitoring of the corrosion of a battery. 

P, mendocina, P. aeruginosa, B. subtilis, and B. cereus adsorbed more Cd, Co, and Pb after exposure to acidic solutions than the corresponding unexposed cells. The increase in sorption following acid treatment was attributed to the irreversible displacement of structurally bound Mg and Ca by protons. The protonated sites can participate in reversible metal sorption reactions. 

Hydride Compressors using reversible metal hydride alloys offer an economical alternative to traditional mechanical compressors for GH2. The simplicity and passive operation of the hydride compression process offers many advantages over mechanical compressors. Hydride compressors are compact, silent, do not have dynamic seals, require very little maintenance, and can operate unattended for long periods. However, they are a very new and may be difficult to be built at the scale required for GH2 transmission pipeline service. 

Metals can combine with hydrogen to form metal hydrides by three different bond types (1) ionic, (2) covalent, and (3) metallic. Based on the strength of the bonds, metal hydrides are broadly classified into two categories (1) reversible and (2) irreversible. Examples of reversible metal hydrides are as follows ... 

The reversible metal hydrides can undergo a reversible equilibrium reaction as follows ... 

Zaluska, A., L. Zaluski, and J.O. Strom-Olsen, Lithium-beryllium hydrides The lightest reversible metal hydrides,. Alloys Compd., 307,157,2000. 

Of interest is the metal ion selectivity of bifunctional exchangers having both sulfonic and phosphonic acid groups, since phosphonic acid resins prefer Pb(II) to Ba(II) but sulfonic acid resins show the reversed metal ion selectivity. 

The three generic classifications of hydrogen storage materials are reversible metal hydrides, non-reversible chemical hydrides, and adsorbent materials. Reversible metal hydride materials and adsorbents can be recharged with hydrogen without removing them from the vehicle, while non-reversible chemical hydride materials must be removed from the vehicle in order to be recharged. 

Reversible metal hydrides On-board refueling High volumetric densities Lowering desorption temperatures Improving kinetic response Heat management during refill... 

The CVs of alkynylbipyridyl-ruthenium complexes, such as [Ru(bpy)2(5-HC= C-bpy)] " and the related terpy complex, [Ru(terpy)(4-HC=C-terpy)] +, contain reversible metal-centered oxidation waves and several ligand-dependent reduction... 

For Ni2Cp2 2(M 7 -A PhC2C2Ph), two well-resolved, reversible metal-centered reductions are found at —1.26 and —1.93 V (vs. The sepa-... 

One can in principle combine different exchange reactions in the same system in order to further increase the structural diversity accessed by the library. However, as this compounds the problem of selectivity (i.e., one now has two or more reactions that must exclusively involve one pair of functional groups), there are very few examples thus far of the practical implementation of this concept. An early, highly intriguing example was described by Lehn and coworkers in 2001 [68]. In this system, imine exchange (acyl hydrazone formation) and reversible metal coordination were employed in library generation. 

Sasaki and coworkers have examined reversible metal coordination as a mechanism for DCL generation in the presence of lectin biomolecules [49,50]. The use of metal ions in reversible processes is canonical to supramolecular chemistry, and has been explicitly demonstrated for doublelevel orthogonal DCLs by Lehn and Eliseev [51]. Sasaki s system is designed around octahedral Fe(II) bipyridine complexes. The bipyridine-modified A-acetylgalactosamine (bipy-GalNAc) (78) was found to trimer-ize in the presence of Fe(II) to afford a 3 1 mixture of the fac (79) and mer (80) diastereoisomers, each as a racemic mixture (A+A) (Scheme 2.12). 

Li and Wang described a convenient linear plotting protocol that permits one to evaluate stability constants for the formation of reversible metal hgand complexes. Added accuracy is achieved over classical approaches, because their generalized equations quantitatively account for side-reactions of metal ion and/or ligand as well as the difference between the total and free ligand concentration. 

While metallation of 625 with a LiCKOR reagent such as BuLi—KOBu-f again leads to orthometallation and 626, reversible metallation of 625 by LDA-KOBu-f generates the more stable benzylically metallated species 627. Carboxylation and alkylation (2 equiv. LDA-KOBu-f then Mel) of 627 gives flurbiprofen 622. 

Although the fundamental properties of metal hydride systems are still under intensive study, increased emphasis is being placed on developing the known applications for reversible metal hydrides, while the search for new applications continues. In this paper, we will summarize the current development status of a few selected applications. 

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