TIME-RESOLVED INFRARED SPECTRAL STUDIES OF PHOTOCHEMICALLY INDUCED OXIDATIVE ADDITION OF BENZENE TO TRANS-RHCL(CO)(PME3)(2)

Time-resolved infrared and time-resolved optical spectroscopy were use d to examine the pathway(s) by which 355 nm photolysis of the rhodium( I) species trans-RhCl(CO)(PMe3)(2) (1) in benzene leads to the C-H oxi dative-addition product (Ph)(H)RhCl(CO)(PMe3)(2) (2). True reaction pa thways to the formation of 2 were found. One of these was the ''prompt '' formation (<150 ns) of 2, the apparent result of a direct reaction of the electronic excited state of the four-coordinate species 1 with the C6H6 solvent. The second route was more a convoluted stepwise proc ess, involving CO photodissociation to give the ''tricoordinate'' inte rmediate RhCl(PMe3)(2) followed by benzene oxidative addition then CO addition to give 2.