Crystal structures of binuclear complexes of gadolinium(III) and dysprosium(III) with oxalate bridges and chelating N,N′-bis­(2-oxido­benz­yl)-N,N′-bis­(pyridin-2-ylmeth­yl)ethyl­enedi­amine (bbpen(2−))

The reaction between mononuclear [Ln(bbpen)Cl] [Ln = Gd or Dy; H(2)bbpen = N,N′-bis­(2-hy­droxy­benz­yl)-N,N′-bis­(pyridin-2-ylmeth­yl)ethyl­enedi­amine, C(28)H(30)N(4)O(2)] and potassium oxalate monohydrate in water/methanol produced the solvated centrosymmetric isostructural binuclear (μ-oxalato)bis­{[N,N′-bis­(2-oxidobenzyl-κO)-N,N′-bis­(pyridin-2-ylmethyl-κN)ethyl­enedi­amine-κ(2) N,N′]dilanthanide(III)}–methanol–water (1/4/4) complexes, [Ln (2)(C(28)H(28)N(4)O(2))(2)(C(2)O(4))]·4CH(3)OH·4H(2)O, with lanthanide(III) = gadolinium(III) (Ln = Gd) and dysprosium(III) (Ln = Dy), in high yields (ca 70%) directly from the reaction mixtures. In both complexes, the lanthanide ion is eight-coordinate and adopts a distorted square-anti­prismatic coordination environment. The triclinic (P [Image: see text]) unit cell contains one dimeric unit together with four water and four methanol mol­ecules; in the final structural model, two of each type of solvating mol­ecule refine well. In each lanthanide(III) dimeric mol­ecule, the medium-strength O⋯H—O hydrogen-bonding pattern involves four oxygen atoms, two of them from the phenolate groups that are ‘bridged’ by one water and one methanol mol­ecule. These inter­actions seem to contribute to the stabilization of the relatively compact shape of the dimer. Electron densities associated with an additional water and methanol mol­ecule were removed with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9–18]. These two new compounds are of inter­est with respect to magnetic properties.