Synthesis of (2,6-Diadamantyl Aryloxide) Ln(II) Complexes of Samarium, Europium, and Ytterbium and Their Ln(III) Precursors.

The syntheses of Ln(II) (aryloxide) complexes of Sm, Eu, and Yb have been examined with the bulky aryloxide ligand (OCH-2,6-Ad-4-Bu) [(OAr*); Ad = 1-adamantyl]. These Ln(OAr*)(THF) complexes were pursued for comparison with the (aryloxide) Ln(II) complexes [Ln(OAr*)] (Ln = La, Ce, Nd, Gd, Dy, and Lu), which have 4f5d electron configurations, and with 4f [Yb(OAr*)]. Although the Ln(II) chemistry of Sm, Eu, and Yb is often similar since they all adopt 4f electron configurations, their chemistry is surprisingly diverse with (OAr*). Reactions of LnI(THF) with KOAr* in THF form the (aryloxide) Ln(II) complexes Ln(OAr*)(THF), , that were characterized by X-ray diffraction for and , but crystals of have been elusive. Reduction of the (aryloxide) Sm(III) complex, Sm(OAr*), , prepared from Sm(NR) (R = SiMe) and HOAr* in refluxing toluene, generated the (aryloxide) complex, , and KOAr* rather than a Sm analogue of [Yb(OAr*)]. Reduction of Eu(OAr*), , prepared from EuCl with KOAr* in THF, caused an immediate dark blue-purple to bright red-orange color change, but crystals of the product were elusive. Neither reduction of Tm(OAr*), , nor the reaction of TmI(DME) with KOAr* provided crystalline Tm(II) complexes.