Heterobimetallic Cu-Ln complexes with sulfonyl-amido-phosphate and Schiff base ligands: synthesis and structure

The synthesis and structural characterization of two new heterobimetallic 3d-4f complexes is reported, namely, bis-[dimethyl (phenyl-sulfon-yl)amido-phosphato]-μ-nitrato-(μ-6,6'-{(1E,1'E)-[propane-1,3-diylbis(aza-nylyl-idene)]bis-(methanylyl-idene)}bis-(2-meth-oxy-phenolato))cerium(III)copper(II), [CeCu(C₁₉H₂₀N₂O₄)(C₈H₁₁NO₅PS)₂(NO₃)] or [Cu(Vanpen)Ce(μ-NO₃)(L)₂] (1), and [μ-dimethyl (phenyl-sulfon-yl)amido-phosphato][dimeth-yl(phenyl-sulfon-yl)amido-phosphato](nitrato)(μ-6,6'-{(1E,1'E)-[propane-1,3-diylbis(aza-nylyl-idene)]bis-(methanylyl-idene)}bis-(2-meth-oxy-phenolato))gadolinium(III)copper(II), [CuGd(C₁₉H₂₀N₂O₄)(C₈H₁₁NO₅PS)₂(NO₃)] or [Cu(Vanpen)Gd(μ-L)(L)(NO₃)] (2), obtained by combining the Schiff base (6,6'-{(1E,1'E)-[propane-1,3-diylbis(aza-nylyl-idene)]bis-(methanylyl-idene)}bis-(2-meth-oxy-phenol)) complex Cu(Vanpen) with the lanthanide(III) nitrates and sulfonyl-amido-phosphate (SAPh) ligand dimeth-yl(phenyl-sulfon-yl)amido-phosphate (L ^-). Single-crystal X-ray diffraction studies of Cu-Ce and Cu²⁺-Gd³⁺ complexes reveal that these species contain the Ln(L)₂NO₃ unit. The lanthanide centers adopt nine-coordinate, distorted muffin (Cs) geometries. The coordination modes of L ^- and NO^3- ligands change depending on the lanthanide. In the Cu²⁺-Ce³⁺ complex the NO₃ ^- group acts as a bridging ligand, whereas in the Cu²⁺-Gd³⁺ analogue the bridging function is assumed by SAPh, with NO₃ ^- binding only in a chelating fashion. The presence of a nitrate group can be explained by steric hindrance that prevents coordination of three SAPh ligands around the lanthanide center. Qualitative X-ray fluorescence analysis confirmed the presence of two different metal ions within each heterometallic species.