Double HCl elimination and configuration change in the square-planar palladium complex <i>trans</i>-[{(Ph₂PC₆H₄CONH) ₂C₆H₄}PdCl₂] under Suzuki conditions: Isolation and molecular structure of <i>cis</i>-[{(Ph₂PC₆H₄CON)₂C₆H₄}Pd]

The trans-configurated square-planar palladium complex <i>trans</i>-[{(Ph₂PC₆H₄CONH) ₂C₆H₄}PdCl₂] (<b>1</b>), which catalyzes the Suzuki cross coupling of 4-bromotoluene with phenylboronic acid, was found to react with potassium carbonate in toluene at 90 °C (Suzuki conditions) to give <i>cis</i>-[{(Ph₂PC₆H₄CON)₂C₆H₄}Pd] (<b>2</b>). The single-crystal X-ray structure analysis of 2 reveals the square-planar palladium center to be in a cis configuration. The trans–cis configuration change at palladium is possible because of the elimination of two HCl equivalents in the conversion of <b>1</b> into <b>2</b>. Both complexes <b>1</b> and <b>2</b> show approximately the same catalytic performance for Suzuki reactions, suggesting <b>2</b> to be the catalytically active species.