Decarbonylation of aryl ketones mediated by bulky cyclopentadienylrhodium bis(ethylene) complexes

The cleavage of C-C bonds of diaryl ketones and aryl alkyl ketones mediated by bulky (1,2,4-triisopropyl-3,5-dimethylcyclopentadienyl)rhodium bis(ethylene) (1) and (1,2,4-tri-tertbutylcyclopentadienyl)rhodium bis(ethylene) (2) is reported. The reactions using 2 proceed at 120-150 degreesC, and the products of the decarbonylation are the (tri-tert-butylcyclopentadienyl)rhodium carbonyl dimer 4, the carbonyl ethylene complex 7, biphenyls (from benzophenones), and toluenes (from acetophenones). Use of beta-phenylpropiophenone as substrate results initially in dehydrogenation to form the eta(4)-enone complex 13, followed by decarbonylation at higher temperatures to yield stilbene.