The co-ordination chemistry of divalent cobalt, nickel, and copper. Part 13. Characterization and stability constants of copper(II) species isolated from mixed-ligand solutions; crystal structure of the complex (pyridine-2,6-dicarboxylato)(N,N,N′,N′-tetramethyl-1,3-diaminopropane)copper(II)

Abstract

Six-co-ordinate complexes [Cu(pydca)(L)(H₂O)]·H₂O and five-co-ordinate complexes [Cu(pydca)(L)], where pydca = pyridine-2,6-dicarboxylate, L = en (1,2-diaminoethane), tmen (N,N,N′,N′-tetramethyl-1,2-diaminoethane), pn (1,3-diaminopropane), or pen [1,2-di(pyrrolidin-1-yl)ethane], were isolated and characterized by thermogravimetric, calorimetric, spectrophotometric, magnetic, and stability constant measurements. A structure determination on [Cu(pydca)(tmpn)](tmpn =N,N,N′,N′-tetramethyl-1,3-diaminopropane), which was monoclinic, with space group P2₁/c, a= 14.970(2), b= 7.290(1), c= 14.822(2)Å, β= 106.64(2)°, Z= 4, indicated a distorted square-pyramidal co-ordination sphere with considerable steric interaction between the tertiary amine groups and the two carboxylate groups. The splitting of the ν_sym(COO) and ν_asym(COO) i.r. bands of all the above complexes having tertiary amine ligands was ascribed to the distortions resulting from this steric interaction. Stability constants for some complexes are reported.