Cobalt(II) Dioxygen Carriers Based on Simple Diamino Ligands: Kinetic and ab Initio Studies

Abstract

The kinetics of the oxygenation reaction of CoL2(2+) complexes (L=ethylenediamine (en), N,N'-dimethylethylenediamnine (dmen)) have been investigated in dimethyl sulfoxide (dmso) at 298 K and in a medium adjusted to 0.1 mol dm(-3) with Et4NClO4 by means of a UV-vis spectrophotometric technique. The reaction mechanisms are consistent with the fast formation of superoxo 1:1 initial CoL2-O2 species (L=en, dmen), whereas the dimeric mu-peroxo (CoL2)2O2 adduct is formed only when L=en, in the rate determining step. The kinetic results are discussed taking into account the effects of ligand/solvent substitution. EPR results give information on the electronic structure and the coordination geometry of the Co(II) complexes and further confirm the stoichiometry of the species formed. Ab initio calculations provide insights on the geometrical parameters of all the complexes investigated and allow us to draw some hypotheses about the influence of H.H nonbonded interactions in the eventual formation of the dimeric mu-peroxo (CoL2)2O2 complexes. Solvational effects are also considered. The formation of the (CoL3)2O2 adduct is also proved when L=en by means of O2 volumetric absorption.

Aerobic Epoxidation of Olefins Catalyzed by the Cobalt‐Based Metal–Organic Framework STA‐12(Co)

“…Note that Co III -peroxo species, which might also form from reaction of Co II with O 2 , are not EPR active. [51] Co-epoxidation of styrene and (E)-stilbene: Driven by the observation that styrene epoxidation not only proceeds faster but also features a shorter induction period, the coepoxidation of styrene and (E)-stilbene was investigated, thus doubling the substrate/catalyst ratio (Figure 11 a). Although the catalyst amount was not increased, the presence of styrene induced much faster conversion of (E)-stilbene.…”

Ethylenediamine-modified oriented MCM-41 at the electrode surface, cobalt adsorption ability and electrochemical performance

“…1 and 2 clearly demonstrate adduct formation between the cobaltammine complex and molecular oxygen as reported previously in the literature. 14 The appearance of the reductive peak (C 2 ) in the negative going scan demonstrated the cobalt nucleolus of this adduct has a higher oxidative state (Co 3+ ). This is likely due to the charge transfer causing oxidation of Co 2+ with concomitant reduction of dioxygen during the adduct formation.…”

“…13 Moreover, cobaltammine complexes are of interest for their reversible adduct formation with molecular oxygen and the importance of their desired adducts. 14 …”

The interaction between sulfathiazole and cobalt(II): potentiometric studies

“…In this sense, the Co(II) complexes with N donor ligands are known for their ability to bind dioxygen more or less reversibly and therefore frequently studied for their importance in industrial processes and as model compounds [16][17][18] .…”