Palladium(II) coordination and cyclometallated complexes derived from 3- and 5-aryl-substituted pyrazoles

Article abstract of DOI:10.1016/0022-328X(92)83269-N

Palladium(II) coordination complexes of nine 3- or 5-arylpyrazoles (phenyl, 2-bromophenyl, or 3-methoxyphenyl), as well as of 3,5-diphenylpyrazole, are reported.A cis-trans mixture of isomers is found in the case of 3-aryl-1-methylpyrazoles, the cis-isomers being transformed into trans by heating.Only trans isomers are isolated with the other ligands.Cyclopalladation of 3-aryl-1-methylpyrazoles can be performed with palladium(II) acetate, and the resultant μ-acetate bridged dimers can be transformed into μ-chloro bridged dimers or acetylacetonate monomers.The structures of the complexes have been characterized by 1H- and 13C-NMR spectroscopy.