Efficient syntheses of 4 '-(2-thienyl)- and 4 '-(3-thienyl)-2,2 ': 6 ', 2 ''-terpyridine: preparation and characterization of Fe(II), Ru(II), Os(II) and Co(II) complexes

Efficient and convenient methods for the preparation of thienyl-substituted 2,2':6',2-terpyridines are reported. The formation and characterization of Fe(II), Ru(II), Os(II) and Co(II) complexes containing the isomeric ligands 4'-(2-thienyl)-2,2':6',2-terpyridine (1) and 4-(3-thienyl)-2,2':6',2-terpyridine (3) are described. The crystal structure of 3 is reported. During studies of possible routes to ligands 1 and 3, the reactions of thiophene-2-carbaldehyde or thiophene-3-carbaldehyde with 2-acetylpyridine under basic conditions led to 3-(2-thienyl)-1,5-bis(2-pyridyl)-2-(2-pyridylcarbonyl)cyclohexane-1,5-diol or 3-(3-thienyl)-1,5-bis(2-pyridyl)-2-(2-pyridylcarbonyl)cyclohexane-1,5-diol, respectively. These compounds have been fully characterized and their crystal structures have been determined. (C) 2003 Elsevier Ltd. All rights reserved.