Direct observation of beta-aryl eliminations from Rh(I) alkoxides.

beta-Aryl eliminations from a series of rhodium(I) alkoxides to form rhodium aryl complexes and free ketones are reported. Tertiary phenylmethoxide complexes [Rh(PEt3)n(OCPhRR')] (n = 2, 3) were prepared via alcoholysis of {Rh(PEt3)2[N(SiMe3)2} by the corresponding alcohols HOCPhRR' in the presence and absence of added PEt3. Heating of these complexes in the presence of added PEt3 generated the rhodium phenyl complex, (PEt3)3RhPh, and the corresponding ketones in good to high yields. Kinetic results are most consistent with irreversible beta-phenyl elimination from a bisphosphine-ligated rhodium alkoxide complex. Such bisphosphine complexes result from ligand dissociation from the trisphosphine complexes and have been isolated in some cases. The bisphosphine complexes are stabilized by Rh-Cphenyl interactions, as evidenced by an X-ray structure, and this structure with a metal-aryl interaction likely illustrates the pathway for C-C bond cleavage.