Crystal and molecular structure of tricarbonyl(8,8-dibromobicyclo-[5.1.0]octa-2,4-diene)iron

Abstract

Single crystal X-ray analysis of the title compound (1) has established it as the precurson in an unusual rearrangement. Crystals are monoclinic, space group P2₁/c, with Z= 4 in a cell of dimensions a= 14·827(6), b= 6·816(3), c= 12·693(8)Å, β= 94·26(4)°. The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares calculations to R 0·05 for 1533 observed data measured by diffractometer. The molecule shows evidence of strain due to intramolecular repulsive interactions of the endo-bromine atom with carbon atoms of the seven-membered ring. A possible reaction mechanism is suggested involving a spirocyclopropene intermediate.