Coordination chemistry of mixed pyridine-phenol ligands; mononuclear palladium(II) and dinuclear copper(II) complexes of derivatives of bidentate N, O-chelating ligands based on 2-(2-hydroxyphenyl)pyridine

• Published in: Polyhedron Vol. 17; no. 2; pp. 211 - 220
• Main Authors: Otter, Carl A., Bardwell, David A., Couchman, Samantha M., Jeffery, John C., Maher, John P., Ward, Michael D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1998
• Subjects: copper; crystal structures; palladium; copper; palladium; crystal structures
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(97)00384-7

The new ligands 2-(2-hydroxyphenyl)-4-
tbutyl-pyridine (HL
1), 2-(2-hydroxyphenyl)-6-methylpyridine (HL
2) and 2-(2-hydroxyphenyl)-6-[(2-phenyl)ethyl]pyridine (HL
3) were prepared. They are all substituted derivatives of the simple
N,
O-bidentate chelating ligand 2-(2-hydroxyphenyl)pyridine. HL
1 is solubilised derivative bearing a
tBu substituent in a position which will not sterically interfere with metal-ion coordination; HL
2 and HL
3 contain substituents at C
6 of the pyridyl ring, adjacent to the N atom, which will therefore sterically hinder metal-ion coordination. The complexes [PdL
2] (PdL
2] (L = L
1, L
2 and L
3) were prepared and structurally characterised to determine the effects (if any) of the substituents on the structures of the metal complexes. All are four-coordinate complexes with square planar coordination geometry about the Pd(II) ion, but the sterically hindered ligands L
2 and L
3 have to adopt a different conformation from L
1 to allow planar coordination, resulting in “bowl-like” structures. [Cu
2(L
1)
4] was also prepared and found to be a phenolate-bridged dinuclear complex in the solid state, both by X-ray crystallography and EPR measurements. In solution, however, it dissociates to give [Cu(L
1)
2] monomeric units. Cu(II) complexes of L
2 and L
3 could not be isolated.