The crystal structure of a catalytic intermediate, dichloro(dodeca-2,6,10-triene-1,12-diyl)ruthenium(IV)

Abstract

The crystal structure of RuCl₂C₁₂H₁₈, an intermediate in the catalytic trimerisation of butadiene, has been determined by three-dimensional X-ray crystal-structure analysis. In a monoclinic unit cell having a= 13·98, b= 8·62, c= 11·75 Å, β= 63°, at 120°K, and space group P2₁/a, there are four formula units. From 1607 visually estimated intensities the structure was established by Patterson and Fourier methods. Refinement by least squares, including hydrogen atoms with isotropic vibration parameters and other atoms with anisotropic vibration parameters, gave an R value of 0·081.

The molecule consists of a nearly linear Cl–Ru–Cl group (Ru–Cl = 2·46 Å) surrounded equatorially by an unbranched chain of twelve carbon atoms; of these the first three and the last three from antiparallel allyl groups (average C–C, 1·405 Å) and the middle two form a trans double-bond, CC, 1·44 Å. The ruthenium atom has the formal oxidation state IV and approximately pentagonal bipyramidal co-ordination, if the allyl groups are assumed to occupy two positions each and the double bond to occupy one position. The Cl–Ru–Cl angle is 168° corresponding to a displacement of the chlorine atoms towards the centre of the gap, which is 2·84 Å, between the first and last carbon atoms of the chain.