Transition metal complexes of substituted alkynes. VII. Some cyclopentadienone complexes of cobalt and rhodium

Abstract

π-Cyclopentadienone-π-cyclopentadienyloobalt complexes have been prepared from reactions of π-oyclopentadienyldicarbonylcobalt and the alkynes bis(pentafluorophenyl)acetylene and 2,3,4,5,6-pentafluorodiphenylacetylene. Spectroscopic data indicate that the complex derived from the latter alkyne has an unsymmetrical arrangement of the substituents in the cyclopentadienone ring. It is formulated as 2,4-bis(pentafluorophenyl)-3,5-diphenylcyclopentadienone-π-cyclopentadienyl-cobalt. A related cyclopentadienone complex, π-tetrakis(pentafluorophenyl)cyclopenta-dienone-π-cyclopentadienylrhodium has been prepared from π-cyclopentadienyl-dicarbonylrhodium and bis(pentafluorophenyl)acetylene. Similar organorhodium complexes could not be isolated from reactions of π-C₅H₅Rh(CO)₂ with diphenylacetylene and 2,3,4,5,6-pentafluorodiphenylacetylene. These compounds could, however, be prepared indirectly by the in situ treatment with thallous cyclopentadienide of the cyclopentadienone complexes formed in reactions of [Rh(CO)₂Cl]₂ with RC=CR' (R = phenyl, R' = phenyl or pentafluorophenyl). Like its cobalt analogue, π-bis(pentafluorophenyl)diphenylcyclopentadienone-.π-cyclopentadienyl- rhodium has an unsymmetrical arrangement of the substituents in the ring.