Complexes of copper(II) formate with 2-(phenylamino)pyridine and 2-(methylamino)pyridine: New copper formato paddle-wheel compounds

Abstract

The derivatives of Cu(HCOO) 2 · 4H 2O with 2-(phenylamino)pyridine and 2-(methylamino)pyridine, [Cu 2(μ-HCOO) 4(PhNHpy) 2] ( 1), [Cu 2(μ-HCOO) 4(MeNHpy) 2] ( 2) and Cu(HCOO) 2(MeNHpy) 2 ( 3), have been synthesized and characterized. Compounds 1 and 2 show the paddle-wheel structure of [Cu 2(μ-HCOO) 4L 2], with four syn–syn bridging formato groups and two molecules of PhNHpy or MeNHpy coordinated to the axial positions, respectively. Intramolecular hydrogen bonds are formed in both cases: two in each dimer of 1 and four in the dimer of compound 2. The dimer units are oriented in two different directions. Dimers with the same orientation form rows along the “ c” and the “ a” axis in compounds 1 and 2, respectively, with a π–π stacking of the pyridine rings. In compound 1, an intercalation of the phenyl rings of contiguous rows of dimers gives rise to a succession of phenyl rings at a distance of 4.38 Å and an angle of 30.44° between alternate rings. They are antiferromagnetic. Signals of the triplet state are observed in their EPR spectra and the zero-field splitting parameter has been determined. Compound 3 obeys the Curie–Weiss law and the magnetic results indicate the absence of magnetic interaction between Cu(II) atoms.