An Electron Transfer Chain Mechanism for Photoinduced Oxidative Addition of Alkyl Iodide to a Dimeric Rhodium(I) Complex under Low Energy Irradiation (553 nm)

Article abstract of DOI:10.1246/bcsj.56.709

A dimeric Rh^I complex, ²⁺ (dicp = 1,3-diisocyanopropane) was found to undergo a photoinduced oxidative addition with butyl iodide and isopropyl iodide in MeCN by 553 nm irradiation in high quantum yields, Φ = 25.2 and 22.6, respectively.Electron acceptors (p-dinitrobenzene, p-benzoquinone, and chloranil) and radical scavengers (oxygen and isopentyl nitrite) act as inhibitors for the photoinduced oxidative addition, providing unambiguous evidence for a chain character of this reaction.The fluorescence quenching of ²⁺ by the electron acceptors as well as butyl iodide has also been examined.Based on the kinetics of the photochemical reactions in the absence or the presence of electron acceptors and radical scavengers, an electron transfer chain mechanism has been proposed.The formation of butyl radicals in the photoinitiation step was confirmed by the trap with oxygen to yield equimolar amounts of 1-butanol and butyraldehyde.The nature of the excited state of ^2+*(¹A_2u or ³A_2u) involved in the photoinitiation step has also been discussed.