Synthesis and structural studies of heteroleptic complexes of ytterbium(III) involving aryloxy- or alkoxy- and cyclopentadienyl ligands

Treatment of tris-cyclopentadienyl-ytterbium in thf with one equivalent of 2,6-di(tert-butyl)phenol, N,N-dimethyl-2-aminoethanol or N,N-diethyl-2-aminoethanol resulted in substitution of one cyclopentadienyl ligand and formation of [YbCp2(O-C6H3tBu-2,6)(thf)] (1), [{YbCp2(μ-OCH2CH2NMe2)}2] (2) or [{YbCp2(μ-OCH2CH2NEt2)}2] · (thf)2 (3), respectively. All compounds were characterised by spectroscopic and X-ray crystallographic techniques, the latter two also being studied by variable temperature 1H NMR spectroscopy. Compound (1) is mononuclear with the Yb centre bound by two η5-cyclopentadienyl ligands one O-bound thf and an O-bound phenoxy ligand. Compounds (2) and (3) are centrosymmetric dimers with the Yb centre bound by two η5-cyclopentadienyl ligands, while the bidentate ligands chelate the metal centre and also bridge to the adjacent Yb through the alkoxy oxygen atom. Variable temperature 1H NMR studies on compounds (2) and (3) show a solution-state equilibrium between the dimeric solid-state structure and one with the nitrogen atoms non-bound to Yb.