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

Abstract A new [O 2 N 2 N′ 2 ] 1,4,8,11-tetraazacyclotetradecane-based bis(phenol) chelate, H 2 ( Me2 ArO) 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, ( R2 ArO) 2 Me 2 -cyclam 2− (R =  t Bu, Me), with [YbI 2 (thf) 2.5 ] are reported. The reaction of K 2 ( tBu2 ArO) 2 Me 2 -cyclam with [YbI 2 (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 ( Me2 ArO) 2 Me 2 -cyclam 2− with [YbI 2 (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 ( Me2 ArO)Me 2 -cyclam, with 1.5 and 2 equiv. of [YbI 2 (thf) 2.5 ] in thf led to formation of [Yb 3 (μ-{( Me2 ArO) 2 Me 2 -cyclam}) 2 I]I ( 4 ) and [Yb 2 (μ-{( Me2 ArO) 2 Me 2 -cyclam})I 2 (thf) 2 ] ( 5 ), respectively. The trimer ( 4 ) and dimer ( 5 ) were characterized by elemental analysis, UV–Vis and NMR spectroscopy and single-crystal X-ray diffraction. These are the first examples of ytterbium(II) complexes incorporating bis(phenolate) cyclam ligands.