New class of trianionic constrained geometry ligands: Representative complexes of zirconium

Abstract

Acid-catalyzed condensation of fluorenylacetaldehyde diethylacetal (1) or indenylacetaldehyde diethylacetal (2) with 3-methylindole yields fluorenylbis(3-methylindolyl)ethane (3) or indenylbis(3-methylindolyl)ethane (4), respectively. Compounds 3 and 4 were used to demonstrate the coordination modes of this new class of ligands to zirconium. Transamination of Zr(NEt2)4 with 3 (H3L) yields (HL)Zr(NEt2)2(THF) (5) in which doubly deprotonated 3 chelates zirconium via two N-indolide moieties. The fluorenyl group remains protonated and uncoordinated. Transamination of Zr(NEt2)4 with 4 (H3L´) yields L´Zr(NEt2) (6) in which triply deprotonated 4 coordinates to zirconium via an η5-indenyl and both N-indolide moieties in a constrained geometry fashion. The molecular structures of 3·THF, 5·3THF, and 6·0.5C7H8 were confirmed by X-ray crystallography.