SYNTHESIS AND REACTIVITY OF PYRROLIDE-DIIMINE COMPLEXES OF CHROMIUM

Lithium 2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ide (LiL) reacts with [CrCl 3 (thf) 3 ] to yield the octahedral complex [(η 2 -L)CrCl 2 (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 [(η 2 -L)(η 1 -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 η 1 -pyrrolide ligands with the chromium, giving rise to an approximately octahedral coordination geometry with two extremely long Cr-N distances.

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