(π-Cyclopentenyl)(π-cyclopentadienyl)nickel: A novel catalyst for the conversion of ethylene to 1-butene and n-hexenes

Abstract

(π-Cyclopentenyl)(π-cyclopentadienyl)nickel, ( h 5-C 5H 5)Ni( h 3-C 5H 7), is a novel, highly active, unicomponent catalyst for the conversion of ethylene to n-butenes and n-hexenes at 145–150° C. At high conversions of ethylene (70–90%), the dimeric product (80–86% yield) contains a high percentage (90–82%) of 1-butene. Experimental evidence is presented which strongly indicates that the cyclopentadienyl group remains bonded to the nickel during catalysis while the cyclopentenyl group is labile. A possible mode of activation is the reversible elimination of cyclopentadiene from ( h 5-C 5H 5)N 1( h 3-C 5H 7) to generate π-cyclo pentadienylnickel hydride as a catalytically active intermediate. An improved synthesis of the title compound (70% yield) by direct hydrogenation of nickelocene is also reported.