The synthesis and molecular structure of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I)

Abstract

The reaction of π-cyclopentadienyl-π-1,5-cyclooctadienerhodium(I) and diphenylacetylene gives hexaphenylbenzene as the principal product with a low yield of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I). The crystal structure of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I) was determined by X-ray diffraction techniques using diffractometer data. The crystals are monoclinic with unit cell dimensions of a=13.416(3), b=19.534(6), c=13.411(2) Å and β=135.01 (1)°. The space group is P2 1/ c and, with four molecules per unit cell, no molecular symmetry is required ( D m=1.40 g/cm 3 and D c=1.411 g/cm 3). The structure was solved by the heavy atom method and refined by least-squares methods to a final R of 0.043 for the 3675 observed reflections used in the analysis. The rhodium atom is coordinated to both the cyclopentadienyl group (Rh-ring distance is 1.868 Å) and the tetraphenylcyclobutadiene group (Rh-ring distance is 1.828 Å). The phenyl groups are twisted relative to the C 4 ring and bent away from the rhodium atom.