Synthesis and Characterization of the First Dinuclear Europium (II) Complex Supported by Carbon-Bridged Biphenolate Ligand

Anhydrous EuCl3 reacted with sodium carbon-bridged biphenolate LNa2[L = 2,2′-methylene bis(6-tert-butyl-4-methyl-phenoxo] in a 1:1 molar ratio in THF in the presence of HMPA (HMPA = hexamethylphosphoric triamide), then the product formed in situ was reduced by Na-K alloy to generate the divalent carbon-bridged biphenolate europium complex [LEu(HMPA)2]2(THF)4(1) in a good isolated yield. Complex 1 was fully characterized by elemental analysis, NMR and IR spectra, and X-ray structural determination. The crystal data of complex 1 are monoclinic, P21/c space group, a = 1.6521(3) nm, b = 2.8274(3) nm, c = 1.2074(2) nm, β = 111.723(6)°, V = 5.2393(14) nm3, Z = 2, Dc = 1.259 mg·m−3, μ = 1.304 mm−1, F(000) = 2092, R = 0.0815, wR = 0.1723. Complex 1 is a dimer with two Eu - 0 bridges. The coordination geometry of each europium atom can be best described as a distorted trigonal bipyramid.