Steric Effects in Lanthanide Sandwich Complexes Containing Bulky Cyclooctatetraenyl Ligands

Abstract

This paper gives a full account of the complex reaction system LnCl3/(COT″)2– (COT″ = 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion). Four different series of organolanthanide complexes of this bulky COT ligand have been reported: (1) anionic sandwich complexes containing [Ln(COT″)2]− anions, (2) dimeric chloro-bridged mono(COT″) complexes, (3) cluster-centered multidecker-sandwich complexes, and (4) linear triple-decker sandwich complexes. In order to get a more complete picture of the reaction system LnCl3/(COT″)2– and to examine possible steric effects exerted by the COT″ ligand, four new rare-earth-metal COT″ complexes have been prepared: [Li(DME)3][Ce(COT″)2] (1), [Li(THF)4][Nd(COT″)2] (2), [(COT″)Nd(μ-Cl)(THF)]2 (4), and (COT″)Yb(DIPPForm)(THF) (5,; DIPPForm = [HC(NAr)2]−, Ar = 2,6-diisopropylphenyl). For comparison, the COTTBS derivative [Li(DME)3][Ce(COTTBS)2] (3; COTTBS = 1,4-bis(tert-butyldimethylsilyl)cyclooctatetraenyl dianion) has also been synthesized. It was found that the steric effect...