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