Synthesis and vibrational spectra of copper(II) and erbium(III) complexes with 2-[2'-(oxymethyldiphenylphosphinyl)phenyldiazenyl]-4-tert-butylphenol (HL) [CuL2] • 2H2O and Er(NO3)2 • 2 HL • 2H2O. Crystal structure of [CuL2] • 2H2O

The syntheses of the complex copper salt CuL2 · 2H2O (I) and the erbium nitrate complex Er(NO3)3 · 2HL · 2H2O (II) (HL is 2-[2′-(oxymethyldiphenylphosphinyl)phenyldiazenyl]-4-tert-butylphenol) have been described. Basic vibrational frequencies in the IR spectra of I and II have been interpreted. The crystal structure of I has been determined by X-ray crystallography: the crystals are monoclinic, a = 15.157(3) Å, b = 17.080(2) Å, c = 22.451(9) Å, β = 106.09(3)°, V = 5584(3) Å3, Z = 4, space group C2/c, R = 0.0546 (for 1152 reflections with I > 2σ(I)). The coordination polyhedron of the copper atom (symmetry C2) can be described as a symmetrically elongated square bipyramid (4+2). The basic square of the Cu polyhedron is formed by the oxygen atom of the substituted phenol and one of the nitrogen atoms of the azo group of each of the two deprotonated ligands L− (Cu-N, 1.969(6) Å; Cu-O, 1.899(5) Å). The angles between the opposite O and N atoms are 157.6°, and the other equatorial angles are in the range 90.6°–95.9°. The axial positions are occupied by the anisole O(2) and O(2A) atoms (Cu-O, 2.737(6) Å, the O(2)Cu(1)O(2A) angle, 132.3°). In the crystal of I, complex molecules and water molecules of crystallization are combined by a system of hydrogen bonds. IR spectra show that, in complex II, as distinct from compound I, the HL ligand is coordinated to the erbium atom through the phosphoryl oxygen atom.