Double HCl elimination and configuration change in the square-planar palladium complex trans-[{(Ph 2PC 6H 4CONH) 2C 6H 4}PdCl 2] under Suzuki conditions: Isolation and molecular structure of cis-[{(Ph 2PC 6H 4CON) 2C 6H 4}Pd

Abstract

The trans-configurated square-planar palladium complex trans-[{(Ph 2PC 6H 4CONH) 2C 6H 4}PdCl 2] ( 1), 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 cis-[{(Ph 2PC 6H 4CON) 2C 6H 4}Pd] ( 2). 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 1 into 2. Both complexes 1 and 2 show approximately the same catalytic performance for Suzuki reactions, suggesting 2 to be the catalytically active species.