Treatment of an excess of ytterbium metal with dpp-Bian
{dpp-Bian
= 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene} in the presence
of 0.5 equiv of iodine resulted in a mixture of [(dpp-Bian)2–Yb2+(DME)2] (1) along with [YbI2(DME)2]2 and an over-reduced byproduct
[(dpp-Bian)3–Yb2+I(DME)Yb2+(DME)2] (2). Oxidation of 1 with
iodine is accompanied by electron transfer from the ligand to the
metal atom to give [(dpp-Bian)−Yb2+I(THF)2]2 (3). Azide complexes [(dpp-Bian)2–Yb3+N3(DME)]6 (4) and [(dpp-Bian)2–Yb3+N3(THF)2]2 (5) were obtained
by either oxidation of 1 with TMSN3 or salt
metathesis reaction of 3 with NaN3. Fluorine
complexes [(dpp-Bian)2–Yb3+F(DME)]2 (7) and [(dpp-Bian)2–Yb3+F(THF)1.5]2 (8) were obtained
by oxidation of 1 with F2CCF2. Complex 3 in solution revealed reversible thermally
induced intramolecular electron transfer {[(dpp-Bian)−Yb2–] ⇄ [(dpp-Bian)2–Yb3+]}. Unstable solutions of [(dpp-Bian)Dy(DME)2]
(11) and [(dpp-Bian)Tm(DME)2] (12) were obtained by salt metathesis reaction of [(dpp-Bian)K2] with DyI2 or TmI2. These solutions treated
with TMSN3 result in [(dpp-Bian)Dy(N)3(DME)]6 (13) and [(dpp-Bian)Tm(N)3(DME)]6 (14). The crystalline structure of azide and
fluorine compounds depended on the crystallization solvent. New compounds
are characterized by nuclear magnetic resonance, infrared spectroscopy,
magnetic moment and differential scanning calorimetry measurements,
and elemental and X-ray diffraction analysis. Solution transitions
were probed by absorption spectroscopy.