PHOTOGENERATED CATALYSIS BY TRANSITION-METAL COMPLEXES. PHOTOACCELERATION OF THE VALENCE ISOMERIZATION OF QUADRICYCLENE TO NORBORNADIENE IN THE PRESENCE OF PdCl2( eta 4-NORBORNADIENE).

Article abstract of DOI:10.1021/ja00329a030

Light accelerates the rate at which PdCl//2( eta **4-NBD) (1) catalyzes the valence isomerization of quadricyclene (Q) to norbornadiene (NBD). The observed quantum yield, defined as (mol of NBD produced/mol of photons absorbed), can exceed 10**2 and is dependent upon Q concentration, light intensity, and solvent. Several lines of evidence are consistent with the intermediacy of radical species in the isomerization process. The results are discussed in terms of a redox-chain mechanism in which the initiation step involves reductive quenching of a Pd-to-NBD charge-transfer excited state of 1 by Q.