It was recently discovered that reduction of the tris(cyclopentadienyl) complexes, Cp′3Ln, 1, (Cp′ = C5H4SiMe3; Ln = Y, lanthanides), with potassium graphite forms molecular complexes with the formula [K(2.2.2-cryptand)][Cp′3Ln], 2, that contain yttrium and all the lanthanides (except Pm) in the +2 oxidation state. Although these complexes are isolable and crystallographically characterizable, they are so highly reactive that measurements of their physical properties are challenging. In search of more stable analogs of 2 that still utilize the features of the tris(cyclopentadienyl) ligand scaffold, which allows these +2 metal ions to be isolated, the reduction chemistry of Cpx3Ln complexes has been investigated where Cpx = C5H5, C5H4Me, C5H3(SiMe3)2-1,3, and C9H7. UV-Vis and EPR data indicate the formation of Y2+ and Gd2+ complexes with all of these tris(cyclopentadienyl) ligand sets except when Cpx = C9H7. The only isolable product obtained from reactions with the tris(indenyl) system was {K(2.2.2-cryptand)}{[(C9H7)2Dy(μ-η5:η1-C9H6)]2}, a complex containing the first example of the indenide dianion, (C9H6)2−, derived from C–H activation of the (C9H7)1− monoanion. The implications of this reductive chemistry in C–H bond activation will be discussed, and the stability of the Cpx3Ln reduction products will be compared with that of 2.

Ligand effects in the synthesis of Ln2+ complexes by reduction of tris(cyclopentadienyl) rare earth precursors including C–H bond activation of an indenyl ligand

249th National Meeting (2015)

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