Reactions of allyl- and propadienyl-rhodium(III) and -iridium(III) complexes with polyhalogenomethanes. Rhodium(II) and iridium(II) species as reactive intermediates

Abstract

Die Allyl‐Komplexe (I) reagieren mit CBrCl3 zu den Trihalogenokomplexen (III) und den Butenen (II).

Insertion of Molecular Oxygen into a Palladium(II) Methyl Bond: A Radical Chain Mechanism Involving Palladium(III) Intermediates

“…Homolytic substitutions at the carbon of transition metal alkyls that involve simple alkyl groups (e.g., M−R with R = Me, benzyl), for which a concerted displacement (S H 2) is expected, have thus far been limited to Co(III) complexes of macrocyclic nitrogen ligands . This reactivity is likely related to the facility with which these types of complexes generate alkyl radicals by homolysis of Co III −R bonds. , Rare examples of radical substitutions at the alkyl group of complexes of other metals like Fe, Rh, and Ir involve unsaturated groups of the type M−CR 2 −CR=CR 2 (e.g., M−(η 1 -allyl), M−(η 1 -cyclopentadienyl)). For these, and for many Co complexes, , mechanistic studies suggest that the homolytic displacement most likely does not involve direct attack at the carbon bound to the metal (α position) but rather an initial attack at the γ carbon of the allyl system, with an overall transposition of the allyl moiety.…”

The Organometallic Chemistry of Rh‐, Ir‐, Pd‐, and Pt‐Based Radicals: Higher Valent Species

“…Paramagnetic Rh(II) species have been suggested to play an important role as intermediates mediating chemical transformations of diamagnetic Rh III -allyl species in reactions with CCl 3 Br (196). The Rh(II) intermediates, or Rh III -superoxo complexes, have also been reported to mediate the catalytic isomerization of 1-nonene to 2-nonene (in the presence of oxygen) (197).…”

Oxidative Addition of Propargyl Halides, Chloroacetonitrile, and Ethyl Chloroacetate to a Dimethylplatinum(II) Complex: Kinetic and DFT Studies

“…[M]CHCCH 2 . The related chemistry is of importance, as it may help in understanding the more complex structures. − As mentioned by Wojcicki, although the standard enthalpies of formation of MeCCH and CH 2 CCH 2 reflect a slightly higher stability of the propargyl species, a stronger metal–allenyl bond in comparison to a metal–propargyl bond favors the allenyl tautomer . Typically, two pathways have generally been considered for the oxidative addition reaction of propargyl halides, including 1,3-hydrogen and 1,3-metal (involving η 3 -allenyl and propargyl intermediates) migration.…”