Aliphatic C−H Bond Oxygenation by the CoIIOOX Species with the Hindered Hydrotris(pyrazolyl)borate Ligand (X = Co(II), Alkyl, H)

Aliphatic C−H bond oxygenation is achieved by Co(II)−peroxo species. The dinuclear Co(II)−μ-peroxo complex, {Co[HB(3,5-Pri2pz)3]}2(μ-O2) (2), is yielded by reaction of the bis(μ-hydroxo)−Co(II) complex, {Co(OH)[HB(3,5-Pri2pz)3]}2 (1), with an equimolar amount of H2O2. Spontaneous decomposition of the μ-peroxo complex 2 yields a mono-oxygenated μ-alkoxo-μ-hydroxo in which one of the six 3-isopropyl methine carbon atoms is oxygenated and the resulting alkoxo ligand bridges the two Co(II) centers. In contrast, decomposition of 2 in the presence of an excess amount of H2O2 results in further oxygenation to give a mixture of the dinuclear Co(II)−bis(μ-alkoxo) and the mononuclear Co(II)−hydroxo alcohol (6). In the bis(μ-alkoxo) complex 5, one of the three 3-isopropyl groups in each ligand is functionalized to give the alkoxide group, which bridges the two metal centers. In the mononuclear hydroxo alcohol complex 6, all of the three 3-isopropyl groups are oxygenated. The Co(II) center is coordinated by the resul...