Collect. Czech. Chem. Commun. 2007, 72, 637-648

Synthesis and Reactivity of Pyrrolide-Diimine Complexes of Chromium

Brian A. Salisbury, John F. Young, Glenn P. A. Yap and Klaus H. Theopold*

Department of Chemistry and Biochemistry, Center for Catalytic Science and Technology, University of Delaware, Newark, Delaware 19716, U.S.A.


Lithium 2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ide (LiL) reacts with [CrCl3(thf)3] to yield the octahedral complex [(η2-L)CrCl2(thf)2] (1), in which only two of the three potential nitrogen donors are coordinated to chromium. In the presence of various alkyl aluminum cocatalysts, 1 catalyzes the polymerization of ethylene. Attempts to prepare alkyl derivatives of 1 were thwarted by an apparent disproportionation, yielding divalent [(η2-L)(η1-L)Cr(thf)] (2). The molecular structures of 1 and 2 have been determined by X-ray diffraction. The structure of 2 is unusual in that it features weak, but equivalent interactions of both imine groups of the η1-pyrrolide ligands with the chromium, giving rise to an approximately octahedral coordination geometry with two extremely long Cr-N distances.

Keywords: Chromium complexes; Pyrrolide-diimine ligands; Polymerization; Ethylene; Homogeneous catalysis; X-Ray diffraction.

References: 33 live references.