Chemistry of proximal π-bond systems. Part IV. The structure of 5,6-dimethylenebicyclo[2,2,1]hept-2-ene molybdenum tricarbonyl

Abstract

Crystals of 5,6-dimethylenebicyclo[2,2,1]hept-2-ene molybdenum tricarbonyl 1 (M = Mo) are monoclinic, a = 7.4451(3) Å, b = 13.5783(7) Å, c = 11.2691(4) Å, β = 92.593(3)°, Z = 4, space group P2₁/c. The structure was solved by the 'heavy atom' method and was refined by full-matrix least square procedures to a final R = 0.031. The weighted R factor was 0.051. Experimental bond lengths and angles are close to other reported values for bicyclo[2,2,1]hept-2-ene systems except for three major distortions in the triene ligand namely: the closing of the angles C(2)—C(1)—C(6) and C(3)—C(4)—C(5) by about 5.3°, the bending of the butadiene fragment plane C(8)—C(5)—C(6)—C(9) toward the metal atom by about 20° and the twisting of the terminal methylene hydrogens H(8i) and H(9i) out of the butadiene fragment plane (0.44 and 0.53 Å respectively) away from the molybdenum atom.