Zirconocene-Mediated Radical Hydrophosphination

Hydrophosphination activity has been solicited from the parent and decamethyl zirconocene dichloride compounds, Cp2ZrCl2 and Cp*2ZrCl2. Given recent reports of photocatalytic hydrophosphination, these compounds were irradiated in the near ultraviolet (UV) as precatalysts resulting in the successful hydrophosphination of styrene substrates and activated alkenes. Irradiation appears to induce homolysis of the Cp or Cp* ligand, resulting in radical hydrophosphination. Successful detection of this radical reactivity was achieved by monitoring for EPR signals with in situ irradiation, a methodology proving to be general for the determination of radical versus closed-shell reactivity in transition-metal photocatalysis.