A mononuclear nonheme cobalt(III) complex of a tetradentate ligand containing two deprotonated amide moieties, [Co(bpc)Cl2][Et4N] (1  ), were prepared and then characterized by IR, elemental analysis, UV-vis and electron paramagnetic resonance spectroscopy. Complex 1  was also characterized by X-ray crystallography. This nonheme CoIII complex catalyzes olefin epoxidation upon treatment with meta-chloroperbenzoic acid. It is proposed that complex 1  shows partitioning between the heterolytic and homolytic cleavage of an O-O bond to afford CoV=O and CoIV=O intermediates, proposed to be responsible for the stereospecific olefin epoxidation and radical-type oxidations, respectively. Moreover, under extreme conditions, where the concentration of an active substrate is very high, the Co-OOC(O)R (2  ) might be a possible reactive species for epoxidation. Evidence for these multiple active oxidants was derived from product analysis, the use of peroxyphenylacetic acid as peracid and EPR measurements. Our results suggest that a less accessible CoV=O moiety can form in a system wherein the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors.

Amide-based nonheme cobalt(III) olefin epoxidation catalyst: Partition of multiple active oxidants CoV=O , CoIV=O, and CoIII-OO(O)CR species

243rd National Meeting (2012)

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