Synthesis and structural characterization of polynuclear divalent ytterbium complexes supported by a bis(phenolate) cyclam ligand

A new [O2N2N'(2)] 1,4,8,11-tetraazacyclotetradecane-based bis(phenol) chelate, H-2((ArO)-Ar-Me2)(2)Me-2-cyclam (2), containing methyl groups in the phenolate rings, has been synthesized and fully characterized. The studies of the coordination chemistry of the hexadentate dianionic ligands, ((ArO)-Ar-R2)(2)Me-2-cyclam(2-) (R = Bu-t, Me), with [YbI2(thf)(2.5)] are reported. The reaction of K-2((ArO)-Ar-tBu2)(2)Me-2-cyclam with [YbI2(thf)(2.5)] in 1:1 ratio in thf led to the formation of a divalent ytterbium complex that is highly unstable and propitious to the formation of Yb(III) species, while the metathesis reaction of the less bulky ligand ((ArO)-Ar-Me2)(2)Me-2-cyclam(2-) with [YbI2(thf)(2.5)] showed a preference for the stabilization of polynuclear divalent ytterbium complexes. The reaction of the potassium salt of this ligand, K-2((ArO)-Ar-Me2)Me-2-cyclam with 1.5 and 2 equiv. of [YbI2(thf)(2.5)] in thf led to formation of [Yb-3(mu-{((ArO)-Ar-Me2)(2)Me-2-cyclam})(2)I]I (4) and [Yb-2(mu-{((ArO)-Ar-Me2)(2)Me-2-cyclam})I-2(thf)(2)] (5), respectively. The trimer (4) and dimer (5) were characterized by elemental analysis, UVVis and NMR spectroscopy and single-crystal X-ray diffraction. These are the first examples of ytterbium(II) complexes incorporating bis(phenolate) cyclam ligands. (C) 2016 Elsevier Ltd. All rights reserved.