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 νsym(COO) and νasym(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.