Cyclopalladation compounds of the 2-pyridylhydrazone derivatives of p-substituted acetophenones and acetylthiophenes

Cyclopalladation occurs for 2-pyridylhydrazones(HL) of p-methyl-, p-methoxy-, p-chloro-, and p-nitro-acetophenone, and 3-acetyl- and 2-acetyl-thiophene with lithium tetrahalopalladate to give the complexes PdXL] (X = Cl and Br) and some iodo complexes are prepared by metathesis of the chloro complexes with lithium iodide. These complexes are characterized spectroscopically. The hydrazones are coordinated to palladium through benzene or thiophene ortho-carbon, hydrazone-nitrogen, and pyridine ring-nitrogen atoms forming fused five-membered chelate rings.