A monoclinic polymorph of 1-(chloridomercurio)ferrocene

A monoclinic modification of chlorido­mercurioferrocene, [FeHgCl(C5H4)(C5H5)], was found on its crystallization from acetonitrile. A triclinic form of the title compound [Sunkel & Kiessling (2001). J. Organomet. Chem. 637, 796–799] was crystallized from chloro­form. Both forms have two molecules per asymmetric unit. In the monoclinic form, both mol­ecules have an eclipsed conformation, while in the triclinic form one of them has an eclipsed and the other a staggered conformation. In the monoclinic crystals, mol­ecules form infinite ribbons due to inter­molecular secondary coordination between Hg and Cl atoms, while in the triclinic form mol­ecules are arranged in tetra­mers.