(η 4 -Tetraphenylcyclobutadiene)-(η 5 -pentaphenylcyclopentadienyl)-cobalt

A one-pot reaction starting with C 5 Ph 5 Br, n -BuLi and [CoCl(PPh 3 ) 3 ] followed by the addition of diphenylethyne produces the title compound with 12% yield. Spectroscopic characterization involved 1 H, 13 C-NMR, UV-Vis and mass spectrometry. A crystal structure determination showed that the central aromatic rings are exactly parallel with the cyclobutadiene ring further apart from the metal as usual. The pentaphenyl–cyclopentadienyl ligand shows an usual paddlewheel orientation, whereas in the tetraphenyl–cyclobutadiene ligand, two of the phenyl groups are nearly coplanar with the four-membered ring. There are also numerous C–H…C(π) interactions between the phenyl groups on the same ring, as well as between rings.