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.

Structure and properties of tricarbonyl(2-5:9,10-.eta.-9-methylenebicyclo[4.2.1]nona-2,4,7-triene)chromium(0). New chromium-olefin stereochemistry

“…We also note a recent counter example to this where it was not until data with 29 > 40°(X-1 sin 9 > 0.4822 A*1) were included that a recognizable solution appeared, despite, in this case, the input of considerable (correct) molecular information for the calculation of E values.34 All hydrogen atoms were easily located in a penultimate difference Fourier map. Least-squares refinements converged at values for R and ftw on F of 0.040 and 0.048 for a model comprising 17 nonhydrogen atoms with anisotropic thermal parameters, 10 hydrogen atoms with isotropic thermal parameters, and a parameter for secondary extinction-a total of 195 variable parameters. The final value for the error in an observation of unit weight was 1.36 e.…”