Cyclams, cross-bridged

Wei L, Butcher C, Miao Y, Gallazzi E, Quinn TP, Welch MJ, Lewis JS. Synthesis and biologic evaluation of 64Cu-labeled rhenium-cyclized alpha-MSH peptide analog using a cross-bridged cyclam chelator. J. Nucl. Med. 2007 48 64-72. 

The group of Busch also presented evidence that the Mn(n) complex of a cross-bridged cyclam ligand, 4,ll-dimethyl-l,4,8,ll-tetraazabicyclo[6.6.2]hexadecanc, denoted as Mn"(Me2EBC)CL, forms a Mn(IV) adduct with lodosylbenzene which is a new active intermediate in epoxidation reactions [600,609,610]. These examples with Mn, and in the previous section with Fe, are instances of late transition metals catalyzing epoxidation reactions by both the redox and the Lewis acid mechanisms (see Chapter 3). 

Key Words Lewis acid adducts, Radical oxidations, Epoxidation, Hydrogen peroxide, Bond dissociation energy, Catalyst durability, Methyltrioxorhenium, Cross-bridged cyclam, Mn(IV), Late transition metal. Propylene oxide. Titanium silicalite (TS-1) catalyst, Ethylanthrahydroquinone/H2 process, Polyoxometallates, Mn(IV) catalyst. Hydrogen abstraction. Rebound mechanism, Isotopic label, t-BuOOH, Peroxide adduct. 2008 Elsevier B.v. 

G. Yin, A. M. Danby, D. Kitko, J. D. Carter, W. M. Scheper, D. H. Busch, Olefin epoxidation by alkyl hydroperoxide with a novel cross-bridged cyclam manganese complex Demonstration of oxygenation by two distinct reactive intermediates. [Erratum to document cited in CA146 316400], Inorg. Chem. 46 (2007) 2173. 

Metal-oxo complexes abstract hydrogen atom from substrates faster than their protonated metal-hydroxo counterparts, as was shown for Mn(IV) compounds with crossed-bridged cyclam.136 Hydrogen atom abstraction is characterized by a fairly large H/D kinetic isotope effects KIE usually exceeds 3, and sometimes reaches values as high as 30 -0.58 In contrast, a modest kinetic isotope effect of about 1.3-1.5 is usually observed for proton-coupled electron transfer reactions.137,138... 

H2CBC cross-bridged cyclam N,N -bis(5-bromo-3-methoxysalicylidene)pheny-lene-1,2-diamine... 

The reaction of the cross-bridged cyclam ligand H2CBC with divalent ytterbium precursors, YbR2 (solvent)2 (solvent = THF or Et20) produced a trinuclear, cationic 3-imido Yb(III) cluster (O Connor et al., 2006). The edifice is made up of three Yb(III)(CBC) units, arranged into a triangular... 

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