Coordination of molecular oxygen by Co(II) β-diketonates

Mn-, Fe-, and Co-Catalyzed Radical Hydrofunctionalizations of Olefins

“…38 As noted in his later account, β -diketonate ligands have the advantage of easily modifiable electronic and steric properties; they were already known to regulate the stereochemical and/or electrochemical characteristics of coordinated complexes; and with the exception of the most simple metal complexes, were unexplored in this aerobic oxidation chemistry. 38 With respect to metals, cobalt was known to readily cycle between its +2 and +3 oxidation states and Co(acac) 2 was known to absorb oxygen in the presence of pyridine, 95,96 so the team at MPI began with exploration of Co(acac) 2 reactivity with molecular oxygen and later expanded to other transition metals. 38 …”

“…38 As noted in his later account, βdiketonate ligands have the advantage of easily modifiable electronic and steric properties, they were already known to regulate the stereochemical and/or electrochemical characteristics of coordinated complexes, and with the exception of the most simple metal complexes, they were unexplored in this aerobic oxidation chemistry. 38 With respect to metals, cobalt was known to readily cycle between its +2 and +3 oxidation states and Co(acac) 2 was known to absorb oxygen in the presence of pyridine, 95,96 so the team at MPI began with exploration of Co(acac) 2 reactivity with molecular oxygen and later expanded to other transition metals. 38 Subsequently in 1989, Isayama and Mukaiyama of the Basic Research Laboratories for Organic Synthesis with the Mitsui Petrochemical Industries in Japan published their first results: 97 an "oxidation−reduction hydration" reaction that used a Co II catalyst bearing acetylacetone (acac), with i-PrOH as both solvent and reductant (Figure 15).…”

Enantioselective Borohydride Reduction Catalyzed by Cobalt Complexes: Discovery, Analysis, and Design for a Halogen-Free System

“…It was reported that Schiff base-cobalt(II) complexes readily reacted with molecular oxygen to form the peroxy-cobalt radical species. 1 Based on this report, we started to examine the catalytic aerobic oxidation of 4phenylbut-1-ene in the presence of various bis(1,3-diketonato)cobalt(II) complexes. 2…”