Palladium(II) coordination and cyclometallated complexes derived from 3- and 5-aryl-substituted pyrazoles
摘要:
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 [PdL2Cl2] 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-methyl-pyrazoles can be performed with palladium(II) acetate, and the resultant mu-acetate bridged dimers can be transformed into mu-chloro bridged dimers or acetylacetonate monomers. The structures of the complexes have been characterized by H-1- and C-13-NMR spectroscopy.
Cascade reaction to 1H-pyrazoles from hydrazones via sodium Ni-trite promoted dual C–C/C–N formation, annulation and aromatization with 1,2-dichloroethane