Products of the reaction of Ru₃(CO)₁₂ with 1,3-cyclohexadiene. X-ray structure of (η-benzene)nonacarbonyl-1-cyclohexen-1,2-ylenetetraruthenium, Ru₄(CO)₉(C₆H₆)(C₆H₈)

The reaction between Ru₃(C0)₁₂ and 1,3-cyclohexadiene has been carried on under different conditions: contrary to previous findings Ru₃(CO)₁₂ does not catalyze the cleavage and the hydrogenation of 1,3-cyclohexediene. The products of the reaction have been characterized by i.r., n.m.r. and mass spectrometry. The crystal structure of the novel complex Ru₄(CO)₉(C₆H₆)(C₆H₈) has been determined by X-ray methods. Crystals are monoclinic, space group P2₁/2c with Z = 4 in a unit cell of'dimensions: a = 15.167(15), b = 10.114(9), c = 15.517(12) Å, β = 87.1(1)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.058 for 3828 observed reflections. A four metal atom cluster, in a "butterfly" arrangement, is coordinated by nine terminal CO groups, by a benzene molecule and a 1-cyelohexen-1,2-ylene unit obtained, respectively, by dehydrogenation and isomerization of two diene molecules.