Crystal structure of cis-Tetracarbonylbis(chloromercury)iron

The crystal structure of the title compound has been determined by direct methods from X-ray diffraction data and refined by least squares to a residual of 0.071 for 2647 ‘observed’ reflections. Crystals are monoclinic, C2/c, a = 36.81(1), b = 11.181(2), c = 20.369(5) Å, β = 95.28(3)^o, Z = 32. There are four independent molecules in the asymmetric unit, all with the cis disposition of ligands (<Fe-Hg), 2.49₈ Å, <Hg-Fe-Hg), 80.9^o); in one of the molecules one of the carbonyl sites is occupied by a more substantial moiety, possibly a result of partial occupancy of HgCl as a result of disorder or decomposition.