ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Structural and electronic effects involving pyridine rings in 4-methylpyridine Cu₄OX₆L₄ complexes. II. Correlations based on molecular structure of the Cu₄OCl₆(4-Mepy)₄ complex

Gregor Ondrejovič, Marian Koman, and Adela Kotočová

Department of Inorganic Chemistry, Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia

E-mail: gregor.ondrejovic@stuba.sk

Received: 5 December 2007  Revised: 27 March 2008  Accepted: 28 March 2008

Abstract: Correlations involving bond lengths and bond angles in the molecular structure of the Cu₄OCl₆(4-Mepy)₄ complex (4-Mepy = 4-methylpyridine) with four symmetrically independent molecules present in the unit cell showed that the donor-acceptor behavior involving the π-back donation into the pyridine rings of the 4-Mepy ligands is most effectively stimulated by a suitable orientation of the pyridine rings in the trigonal bipyramidal geometry. The pyridine ring planes are almost in parallel orientation with one of the three Cu-Cl bonds. The bond lengths of these Cu-Cl bonds are in a significant linear correlation with the Cu-N bond lengths and the bonds lengths of the pyridine rings. The pyridine rings orientation is affected by distortion of the trigonal bipyramidal geometry to tetragonal pyramidal coordination, by out-of plane pyridine rings deviation and in-plane pyridine rings tilting, by puckering of the pyridine rings and by the effects of the methyl groups. The pyridine rings in at least seven of the sixteen trigonal bipyramidal coordinations exhibit an orientation supporting the π-back bonding between the Cu(II) atoms and the pyridine rings.

Keywords: tetranuclear Cu₄OCl₆(4-Mepy)₄ complex - scatter graph correlations -  π-back bonding

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-008-0067-2

Chemical Papers 62 (6) 566–574 (2008)