A discrete {Co sub(4)( mu sub(3)-OH) sub(4)} super(4+) cluster with an oxygen-rich coordination environment as a catalyst for the epoxidation of various olefins

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 45; no. 4; pp. 1727 - 1736
• Main Authors: Lee, Sun Young, Kim, Namseok, Lee, Myoung Mi, Jo, Young Dan, Bae, Jeong Mi, Hyun, Min Young, Yoon, Sungho, Kim, Cheal
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Asymmetry; Catalysts; Clusters; Cuba; Epoxidation; Olefins; Spectroscopy; Terminals
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt03422a

Using the sterically hindered terphenyl-based carboxylate, the tetrameric Co(ii) complex [Co sub(4)( mu sub(3)-OH) sub(4)( mu -O sub(2)CAr super(4F-Ph)) sub(2)( mu -OTf) sub(2)( Py) sub(4)] (1) with an asymmetric cubane-type core has been synthesized and fully characterized by X-ray diffraction, UV-vis spectroscopy, and electron paramagnetic resonance spectroscopy. Interestingly, the cubane-type cobalt cluster 1 with 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins, including terminal olefins which are more challenging targeting substrates. Moreover, this catalytic system showed a fast reaction rate and high epoxide yields under mild conditions. Based on product analysis and Hammett studies, the use of peroxyphenylacetic acid as a mechanistic probe, H sub(2) super(18)O-exchange experiments, and EPR studies, it has been proposed that multiple reactive cobalt-oxo species Co super(V)&z.dbd; O and Co super(IV)&z.dbd; O were involved in the olefin epoxidation.