Reinvestigation of Reactions of HgPh(2) with Eu and Yb Metal and the Synthesis of a Europium(II) Bis(tetraphenylborate) †

Europium bis(tetraphenylborate) [Eu(thf)(7)][BPh(4)](2)⋅thf containing a fully solvated [Eu(thf)(7)](2+) cation, was synthesized by protolysis of “EuPh(2)” (from Eu and HgPh(2)) with Et(3)NHBPh(4), and the structure was determined by single-crystal X-ray diffraction. Efforts to characterize the putative “Ph(2)Ln” (Ln = Eu, Yb) reagents led to the synthesis of a mixed-valence complex, [(thf)(3)Yb(II)(μ-Ph)(3)Yb(III)(Ph)(2)(thf)]⋅2thf, resulting from the reaction of Yb metal with HgPh(2) at a low temperature. This mixed-valence Yb(II)/Yb(III) compound was studied by (171)Yb-NMR spectroscopy and single-crystal X-ray diffraction, and the oxidation states of the Yb atoms were assigned.