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Published July 23, 2012 | Published + Supplemental Material
Journal Article Open

Mechanistic Studies of Ethylene and α-Olefin Co-Oligomerization Catalyzed by Chromium−PNP Complexes


To explore the possibility of producing a narrow distribution of mid- to long-chain hydrocarbons from ethylene as a chemical feedstock, co-oligomerization of ethylene and linear α-olefins (LAOs) was investigated, using a previously reported chromium complex, [CrCl_3(PNP^(OMe))] (1, where PNP^(OMe) = N,N-bis(bis(o-methoxyphenyl)- phosphino)methylamine). Activation of 1 by treatment with modified methylaluminoxane (MMAO) in the presence of ethylene and 1-hexene afforded mostly C_6 and C_(10) alkene products. The identities of the C_(10) isomers, assigned by detailed gas chromatographic and mass spectrometric analyses, strongly support a mechanism that involves five- and seven-membered metallacyclic intermediates comprised of ethylene and LAO units. Using 1-heptene as a mechanistic probe, it was established that 1-hexene formation from ethylene is competitive with formation of ethylene/LAO cotrimers and that cotrimers derived from one ethylene and two LAO molecules are also generated. Complex 1/MMAO is also capable of converting 1-hexene to C_(12) dimers and C_(18) trimers, albeit with poor efficiency. The mechanistic implications of these studies are discussed and compared to previous reports of olefin cotrimerization.

Additional Information

© 2012 American Chemical Society. Received: June 1, 2012; Published: July 10, 2012. This work was supported by BP. L.H.D. acknowledges the National Institute of General Medical Sciences for a postdoctoral fellowship (F32 GM099189-02). We thank Dr. Emmanuelle Despagnet-Ayoub, Matt Winston, and Rachel Klet for helpful comments on this paper. The authors declare no competing financial interest.

Attached Files

Published - Do2012p19257Organometallics.pdf

Supplemental Material - om300492r_si_001.pdf


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