Bimetallic catalysis

Keywords Bifunctional catalysis Bimetallic complexes Cooperative catalysis Dual catalysis Early-late heterobimetallic complexes... 

ViUa A, Wang D, Su DS, Prati L. New challenges in gold catalysis bimetallic systems. Catal Sci Technol. 2015 5 55-68. 

In contrast to oxidation in water, it has been found that 1-alkenes are directly oxidized with molecular oxygen in anhydrous, aprotic solvents, when a catalyst system of PdCl2(MeCN)2 and CuCl is used together with HMPA. In the absence of HMPA, no reaction takes place(100]. In the oxidation of 1-decene, the Oj uptake correlates with the amount of 2-decanone formed, and up to 0.5 mol of O2 is consumed for the production of 1 mol of the ketone. This result shows that both O atoms of molecular oxygen are incorporated into the product, and a bimetallic Pd(II) hydroperoxide coupled with a Cu salt is involved in oxidation of this type, and that the well known redox catalysis of PdXi and CuX is not always operalive[10 ]. The oxidation under anhydrous conditions is unique in terms of the regioselective formation of aldehyde 59 from X-allyl-A -methylbenzamide (58), whereas the use of aqueous DME results in the predominant formation of the methyl ketone 60. Similar results are obtained with allylic acetates and allylic carbonates[102]. The complete reversal of the regioselectivity in PdCli-catalyzed oxidation of alkenes is remarkable. 

Bimetallic catalysis by binuclear complexes of Cu, Fe, Mn, Ni, Pd, and Rh with heterocyclic ligands 98T12985. 

Cyclodiphosphazanes(III) 27 shown in Scheme 16 undergo oxidation reactions to give the cyclodiphosphazanes(V) of type 28. These are prospective ligands in catalysis since these ligands due to lack of phosphorus lone-pairs are less susceptible to the destructive cycloreversion of the ligands. Hence they could prevent catalyst deactivation in the process. When treated with trimethyl aluminum the cyclodiphosphazanes form symmetrically substituted bimetallic species of type 29 [90]. Characterization by single-crystal X-ray studies show... 

Heterogeneous catalysis by metals has been of long-standing interest, with bimetallic catalysts a particular focus.Transition metal carbonyls have... 

The HKR reactions follow the cooperative bimetallic catalysis where epoxide and nucleophile activate simultaneously by two different (salen)Co-AlX3 catalyst molecules. The linking of two (salen)Co unit through the A1 induces the cooperative mechanism, albeit through a far less enantio-discriminating transition state than that attained with the catalyst la and la (Scheme2). 

Kinetic, spectroscopic, and enantioselectivity data provided strong evidence for a mechanism involving bimetallic catalysis. The configurational outcome depends upon the face selectivity of the enol approaching the Michael acceptor in 59 (Fig. 32). To differentiate between the enantiotopic faces, the catalyst has thus... 

Jautze S, Peters R (2008) Enantioselective bimetallic catalysis of Michael additions forming quaternary stereocenters. Angew Chem Int Ed 47 9284-9288... 

Surface Chemistry and Catalysis on Some Platinum-Bimetallic Catalysts... 

Since 1976 until present time Toshima-t5q)e nanocolloids always had a major impact on catalysis and electrocatalysis at nanoparticle surfaces [47,210-213,398-407]. The main advantages of these products lie in the efficient control of the inner structure and morphology especially of bimetallic and even multimetallic catalyst systems. 

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... 

Bimetallic nanoparticles (including monometallic ones) have attracted a great interest in scientific research and industrial applications, owing to their unique large sur-face-to-volume ratios and quantum-size effects [1,2,5,182]. Since industrial catalysts usually work on the surface of metals, the metal nanoparticles, which possess much larger surface area per unit volume or weight of metal than the bulk metal, have been considered as promising materials for catalysis. 

Markovic NM, Radmilovic V, Ross PN. 2003. Physical and electrochemical characterization of bimetallic nanoparticle electrocatalysts. In Wieckowski A, Savinova E, Vayenas C, eds. Catalysis and Electrocatalysis at Nanoparticle Surfaces. New York Marcel Dekker, pp. 311-342. 

Collman et al., 2007b]. However, when the electron delivery was slow, only the bimetallic forms manifested ORR catalysis (it was presumed that the monometallic Cu-free (Fe-only) catalysts degraded rapidly under these conditions) [Collman and Boulatov, 2002 Collman et al., 2007b]. 

Bimetallic surfaces are well known for showing radically different chemistry from the individual components and the catalysis industry frequently makes use of these properties to tune catalysts, a recent example is the alloying of... 

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