Although recent studies have demonstrated that all the lanthanides (except Pm) can be isolated in the +2 oxidation state as crystalline molecular compounds of the formula [K(2.2.2-cryptand)][Cp’3Ln], (Cp’ = C5H4SiMe3; Ln = Y, lanthanides), there are still many questions about the factors that affect the stability of divalent lanthanide ions in molecular compounds. For the larger metals, La and Ce, Lappert has shown that complexes with metals in the +2 oxidation state can be isolated using the more sterically encumbering ligand [C5H3(SiMe3)2]1- in molecular compounds of the formula [K(18-crown-6)(Et2O)x][Cp”3Ln], (x = 1, 2; Cp” = C5H3(SiMe3)2). However, for the smaller metal Y, the reduction product of Cp”3Y with potassium decomposes rapidly in solution perhaps because the (Cp”3)3- ligand system is too large for the smaller rare earths. To determine if a mixed ligand system could provide stable Ln2+ complexes, the effects on stability of replacing one of the Cp” ligands with Cp (C5H5) or CpMe (C5H4Me) in Cp”3Y and Cp”3Gd have been investigated. X-ray, EPR and UV-Vis data will be presented describing the formation and isolation of just the second crystallographically characterizable examples of Gd and Y in the +2 oxidation state using these heteroleptic tris(cyclopentadienyl) coordination environments. Comparisons with [K(2.2.2-cryptand)][Cp’3Ln] will be made.

Synthesis and structural characterization of Y2+ and Gd2+ in heteroleptic tris(cyclopentadienyl) rare earth complexes

249th National Meeting (2015)

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