The crystallography and electron distribution of octafluorocyclohexa-1, 3-dieneiron tricarbonyl

Abstract

Octafluorocyclohexa-1, 3-dieneiron tricarbonyl crystallizes in the orthorhombic system with a = 13.49 Å, b = 6.92 Å, c = 11.89 Å, Z = 4, M = 364, space group Pcam . The molecule has exact m(C s ) symmetry in the crystal, the metal-carbon bond lengths being reported with e. s. d. of 0.007 to 0.013 Å, the average standard deviations of the carbon–carbon, carbon–fluorine and carbon–oxygen bonds being 0.013 Å. The conformation of the cyclohexadiene ligand suggests the value of a σ – π description of the metal-ligand bonding although a molecular orbital scheme allows a more quantitative discussion of the molecular geometry. The carbonyl groups are distorted from exact C 3 v symmetry, their precise arrangement, correlated with the stereochemistry of other molecules, allowing a re-examination of the probable bonding in butadieneiron tricarbonyl. The atomic thermal motions and crystal structure are also discussed.