Crystal and molecular structure of a racemic complex: µ-[1–3,6-η: 1,4–6-η-1,3,6-tris(trifluoromethyl)hexa-1,3,5-trien-1,6-diyl]-bis(dicarbonylcobalt)(Co–Co)

Abstract

The structure of the title compound (I) has been determined from three-dimensional photographic X-ray data. The complex crystallizes as a racemate in the orthorhombic space group Pna2₁(No 33) with a= 9·92, b= 11·97, c= 13·70 Å, Z= 4. The structure was refined by least-squares methods to R 0·097 for 757 independent observed reflections. The complex contains a six-carbon atom ligand bridging two [CO(CO)₂] moieties. Trifluoromethyl groups are attached to carbon atoms 1,3 and 6 within the six-carbon atom ligand. The bridging ligand is composed of two allylic functions joined by a C–C single bond; there is a dihedral angle of 60° between the two allylic planes. The allyl groups are each bonded to both cobalt atoms, which are separated by a normal bonding distance of 2·459(6)Å. The cobalt atoms are seven-co-ordinate if the allyl groups are regarded as tridentate ligands. The two cobalt atoms and the two terminal carbon atoms of the C₆-chain are coplanar: There is a symmetrical arrangement of these four atoms.