Coordination Compounds of Copper(II) Nitrate with Products of Aminotris(hydroxymethyl)methane Condensation with Salicyl- and 5-Nitrosalicylaldehydes: Synthesis and Crystal Structures

Abstract

The crystal structures of copper(II) nitrate complexes with 2-(2-hydroxybenzylideneamino)-2-hydroxymethylpropane-1,3-diol (HL) and 2-hydroxymethyl-2-(2-hydroxy-5-nitrobenzylideneamino)propane-1,3-diol (HL¹) were determined. The resulting complexes were formulated as [Cu₃OL₃(H₂O₂]NO₃ · 3H₂O (I) and [Cu(H₂O)L¹]NO₃ (II). The crystals of I are monoclinic, a = 17.809(4) Å, b = 30.549(6) Å, c = 18.962(4) Å, β = 115.36(3)°, space group Cc, Z = 8, R = 0.0482. Complex I is composed of two independent three-dimensional µ₃-oxo complexes; the coordination polyhedron of the copper atoms in both compounds is an elongated tetragonal bipyramid. The coordination polyhedron of the third Cu atom is a tetragonal pyramid. The bases of the pyramids are composed of the oxygen atoms of the phenol and alcohol OH groups, the imine N atom of ligand L, and µ ₃-oxo atoms. The phenol and water O atoms serve as the apices in both the tetragonal bipyramids. The crystals of II are triclinic, a = 6.062(1) Å, b = 7.701(2) Å, c = 16.162(3) Å, α = 88.15(3)°, β = 84.94(3)°, γ = 78.13(3)°, space group P1¯, Z = 2, R = 0.0272. Complex II is composed of polymer chains formed by coordination bonds between the copper atom and two O atoms of the amino alcohol in the azomethine of the neighboring complex connected to the initial one by translation along the x axis. These chains are linked through hydrogen bonds involving the oxygen atoms of the NO₂ groups. The benzene rings of the azomethine ligands of the adjoining complexes from different chains are antiparallel to each other. The coordination polyhedron of the central atom is an elongated tetragonal bipyramid. Its equatorial plane is formed by the phenol O atom, one of the alcohol O atoms, the N atom of ligand L¹, and the O atom of the amino alcohol in the neighboring complex. The apices are the O atom of the water molecule and the O atom of the amino alcohol in the neighboring azomethine molecule. In complexes I and II, the outer-sphere nitrato group mainly serves to unite trimers and polymers in the crystal by means of hydrogen bonds.