Ligand Effects in the Synthesis of Ln2+ Complexes by Reduction of Tris(cyclopentadienyl) Precursors Including C-H Bond Activation of an Indenyl Anion

Jordan F. Corbey, David H. Woen, Chad T. Palumbo, Megan E. Fieser, Joseph W. Ziller, Filipp Furche, William J. Evans

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Abstract

The tris(cyclopentadienyl) yttrium complexes Cp3Y(THF), CpMe3Y(THF), Cp″3Y, Cp″2YCp, and Cp″2YCpMe [Cp = C5H5, CpMe = C5H4Me, Cp″ = C5H3(SiMe3)2] have been treated with potassium graphite in the presence of 2.2.2-cryptand to search for more stable examples of complexes featuring the recently discovered Y2+ ion first isolated in [K(18-crown-6)][Cp′3Y] and [K(2.2.2-cryptand)][Cp′3Y], 1-Y (Cp′ = C5H4SiMe3). Reduction of the tris(cyclopentadienyl) complexes generates dark solutions like that of 1-Y, and the EPR spectra contain doublets with g values between 1.990 and 1.991 and hyperfine coupling constants of 34-47 gauss that are consistent with the presence of Y2+. [K(2.2.2-cryptand)][Cp″2YCp], 2-Y, was characterizable by X-ray crystallography. Reduction of the Cp″3Gd, Cp″2GdCp, and Cp″2GdCpMe complexes containing the larger metal gadolinium were also examined. In each case, dark solutions and EPR spectra like that of [K(2.2.2-cryptand)][Cp′3Gd], 1-Gd, were obtained, and [K(2.2.2-cryptand)][Cp″2GdCp], 2-Gd, was crystallographically characterizable. None of the new yttrium and gadolinium complexes displayed greater stability than 1-Y and 1-Gd. Exploration of this reduction chemistry with indenyl ligands did not give evidence for +2 complexes. The only definitive information obtained from reductions of the CpIn3Ln (CpIn = C9H7, Ln = Y, Ho, Dy) complexes was the X-ray crystal structure of {K(2.2.2-cryptand)}2{[(C9H7)2Dy(μ-η51-C9H6)]2}, a complex containing the first example of the indenyl dianion, (C9H6)2-, derived from C-H bond activation of the (C9H7)1- monoanion. Density functional theory analysis of these results provides an explanation for the observed hyperfine coupling constants in the yttrium complexes and for the C-H bond activation observed for the indenyl complex. (Figure Presented).

Original languageEnglish (US)
Pages (from-to)3909-3921
Number of pages13
JournalOrganometallics
Volume34
Issue number15
DOIs
StatePublished - Aug 10 2015

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