Reactivity of chromium(II) bimetallocycles and their role in ethylene trimerization

INOR 554

John Francis Young, youngjo@udel.edu, Glen P. A. Yap, and Klaus H. Theopold. Department of Chemistry and Biochemistry, Center for Catalytic Science and Technology, University of Delaware, Newark, DE 19716
There are a number of chromium catalysts that selectively trimerise ethylene to 1-hexene. It is commonly suggested that the mechanism of this reaction involves metallocycle intermediates; however, to our knowledge the role of bimetallocycles as plausible intermediates has not been investigated. Several Cr(II) bimetallocycles of varying ring sizes have been synthesized using dilithioalkyl reagents. It was found that these bimetallocycles do not insert ethylene, but presumably decompose to Cr(I) fragments which then give butene, 1-hexene, and 1-octene. Decomposition of the four carbon bimetallocycle gives several products. One of these products was determined to be a Cr(I) butadiene adduct, which in turn serves as a model of binding of two ethylene molecules to Cr(I).
 

Organometallic Catalysts
1:30 PM-5:20 PM, Tuesday, August 21, 2007 BCEC -- 211, Oral

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007