Organometal electron donors

Organometals and metal hydrides as electron donors in addition reactions 245 Oxidative cleavage of carbon-carbon and carbon-hydrogen bonds 253 Electron-transfer activation in cycloaddition reactions 264 Osmylation of arene donors 270... 

ORGANOMETALS AND METAL HYDRIDES AS ELECTRON DONORS IN ADDITION REACTIONS... 

Traditionally, electron transfer processes in solution and at surfaces have been classified into outer-sphere and inner-sphere mechanisms (1). However, the experimental basis for the quantitative distinction between these mechanisms is not completely clear, especially when electron transfer is not accompanied by either atom or ligand transfer (i.e., the bridged activated complex). We wish to describe how the advantage of using organometals and alkyl radicals as electron donors accrues from the wide structural variations in their donor abilities and steric properties which can be achieved as a result of branching the alkyl moiety at either the a- or g-carbon centers. 

Homogeneous Processes with Tris-phenanthroline Metal(III) Oxidants. The rates of electron transfer for the oxidation of these organometal and alkyl radical donors (hereafter designated generically as RM and R, respectively, for convenience) by a series of tris-phenanthroline complexes ML33+ of iron(III), ruthe-nium(III), and osmium(III) will be considered initially, since they have been previously established by Sutin and others as outer-sphere oxidants (5). 

The intermediate states Crv and CrIV have a somewhat restricted chemistry. The very low formal oxidation states are found largely in carbonyl- and organometal-lic-type compounds. With ligands such as aryl isocyanides, bipy, terpy, and phen, which are better donors and somewhat less obligatory back-acceptors than CO, it is possible to generate stable Cr1 compounds. With the isocyanides Cr(CNR)6, electrochemical or Ag+ oxidation may be used to obtain the +1 and +2 ions [Cr(CNR)6]"+, with one and two unpaired electrons, respectively. With the chelating... 

Kminek et al. [154-156] established that the electron transfer ability of donors decreases in the order N, N, N , V -tetramethylethylenediamine > THF > 1, 2-dimethoxyethane > triethylamine and the electron accepting ability of organometals in the order BuLi > oligostyryllithium > oligoiso-prenyllithium. 

Grogger C, Fallmann H, Fiirpass G, Stiiger H, Kickelbick G (2003) The [Cp(CO)2Fe] (Fp) group as a donor in donor/acceptor substituted disilanes synthesis, structure and electronic properties of Fp-Si2Me4-CgH4CH C(CN)2. J Organomet Chem 665 186... 

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