Reinvestigation of Reactions of HgPh2 with Eu and Yb Metal and the Synthesis of a Europium(II) Bis(tetraphenylborate).

Europium bis(tetraphenylborate) [Eu(thf)7][BPh4]2⋅thf containing a fully solvated [Eu(thf)7]2+ cation, was synthesized by protolysis of "EuPh2" (from Eu and HgPh2) with Et3NHBPh4, and the structure was determined by single-crystal X-ray diffraction. Efforts to characterize the putative "Ph2Ln" (Ln = Eu, Yb) reagents led to the synthesis of a mixed-valence complex, [(thf)3YbII(μ-Ph)3YbIII(Ph)2(thf)]⋅2thf, resulting from the reaction of Yb metal with HgPh2 at a low temperature. This mixed-valence YbII/YbIII compound was studied by 171Yb-NMR spectroscopy and single-crystal X-ray diffraction, and the oxidation states of the Yb atoms were assigned.