Effect of hydrogen bonding on the coordination: Part 2. Semi-coordination in trans-di(salicylato)bis(1,3-diaminopropane- N, N’)copper(II)

• Published in: Inorganica Chimica Acta Vol. 324; no. 1; pp. 212 - 217
• Main Authors: Sundberg, Markku R, Kivekäs, Raikko, Huovilainen, Pertti, Uggla, Rolf
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 12-11-2001
• Subjects: Carboxylate Complexes; Copper Complexes; Crystal structures; Hydrogen bonding; Natural bond order; Semi-coordination; Crystal structures; Semi-coordination; Copper Complexes; Hydrogen bonding; Carboxylate Complexes; Natural bond order
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(01)00605-3

The crystal and molecular structure of
trans-di(
ortho-hydroxobenzoato
-O)bis(1,3-diaminopropane-
N,
N′)copper(II) [
ortho-hydroxobenzoate=salicylate hereafter] determined by single crystal X-ray diffraction methods at
T=193(2) K. The structure is composed of monomeric complex units with the central copper(II) ion occupying a centre of symmetry. The coordination polyhedron can be described as axially elongated distorted octahedron with the axial Cu–O bond length of 2.559(3) Å indicating semi-coordination. There is notable asymmetry in the coordinated 1,3-diaminopropane molecule, which forms a six-membered chelate ring displaying Cu–N1–C1 and Cu–N2–C3 angles of 121.5(2) and 117.4(2)°, respectively. This deviation may be correlated to differences in hydrogen bonding between the amino groups and the non-coordinated oxygen atoms of the salicylate anions. The coordinated salicylate anion shows considerable declination of 28.9°, which may be correlated to intramolecular hydrogen bonding. The electronic properties of benzoate anions were studied by Natural Bond Order (NBO) analyses for optimised model compounds at the MP2/6-311+G*//MP2/6-311+G* level of theory. The results suggest that semi-coordination is mainly characterised by concomitant electrostatic attraction of the charges at the central copper(II) cation and repulsion between an electron lone pair of a ligand atom and the electron lone pair at the copper(II) 3d
z
2
atomic orbital.
Detailed analysis of the structural parameters of the complex unit of
trans-di(salicylato)bis(1,3-diaminopropane-
N,
N′)copper(II) and comparison with related complexes as well as NBO analysis of optimized benzoates (MP2/6-3-311+G* level of theory) suggest that hydrogen bonding plays marked role in semi-coordination of Werner-type copper(II) complexes.