Stability and Solution Behavior of [(dpp-Bian)Ln] and [(dpp-Bian)LnX] (Ln = Yb, Tm, or Dy; X = I, F, or N₃)

Abstract

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– Yb 2+ (DME) 2 ] ( 1 ) along with [YbI 2 (DME) 2 ] 2 and an over-reduced byproduct [(dpp-Bian) 3– Yb 2+ I(DME)Yb 2+ (DME) 2 ] ( 2 ). Oxidation of 1 with iodine is accompanied by electron transfer from the ligand to the metal atom to give [(dpp-Bian) − Yb 2+ I(THF) 2 ] 2 ( 3 ). Azide complexes [(dpp-Bian) 2– Yb 3+ N 3 (DME)] 6 ( 4 ) and [(dpp-Bian) 2– Yb 3+ N 3 (THF) 2 ] 2 ( 5 ) were obtained by either oxidation of 1 with TMSN 3 or salt metathesis reaction of 3 with NaN 3 . Fluorine complexes [(dpp-Bian) 2– Yb 3+ F(DME)] 2 ( 7 ) and [(dpp-Bian) 2– Yb 3+ F(THF) 1.5 ] 2 ( 8 ) were obtained by oxidation of 1 with F 2 C═CF 2 . Complex 3 in solution revealed reversible thermally induced intramolecular electron transfer {[(dpp-Bian) − Yb 2– ] ⇄ [(dpp-Bian) 2– Yb 3+ ]}. 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)K 2 ] with DyI 2 or TmI 2 . These solutions treated with TMSN 3 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.