A family of pincer-ligated cobalt complexes has been synthesized and are active for the catalytic C-H borylation of heterocycles and arenes. The cobalt catalysts operate with high activity and under mild conditions and do not require excess borane reagents. Up to 5000 turnovers for methyl furan-2-carboxylate have been observed at ambient temperature with 0.02 mol % catalyst loadings. A catalytic cycle that relies on a cobalt(I)-(III) redox couple is proposed.
Investigating the Nature of the Active Species in Bis(imino)pyridine Cobalt Ethylene Polymerization Catalysts
作者:Igor E. Soshnikov、Nina V. Semikolenova、Alexey N. Bushmelev、Konstantin P. Bryliakov、Oleg Y. Lyakin、Carl Redshaw、Vladimir A. Zakharov、Evgenii P. Talsi
DOI:10.1021/om900490b
日期:2009.10.26
The activation of bis(imino)pyridine cobalt-based catalysts of ethylene polymerization with methylalumoxane (MAO), AlMe3, and AlMe3/[CPh3][B(C6F5)(4)] has been studied by H-1, H-2, and F-19 NMR and EPR spectroscopy. The nature of the active sites of polymerization is discussed. The polymerization kinetics and the polymer properties for the different catalyst/activator systems were correlated with spectroscopic data.