2736.     POWELL, H. M., AND EWENS, R. V. G.  Crystal Structure of Iron Enneacarbonyl.  Jour. Chem. Soc., vol. 61, 1939, pp. 286-292; Chem. Absw., vol. 33, 1939, p. 3651.

        Crystal structure of Fe enneacarbonyl, Fe₂(CO)₉, prepared by the method of Dewar and Jones (abs. 700) was derived by a Patterson and fournier analysis differing from that of Brill (abs. 354) and of Sidgwick and Bailey (abs. 3184).  Each Fe atom is linked to 3 terminal carbonyl groups and the 2 Fe atoms are joined by 3>C=O bridges.  Data are based on single crystal oscillation and zero-layer-line Weissenberg photographs about the a and c axes of thin, hexagonal, crystal plates.  The unit cell contains 2 mol., a=6.45, c=15.98 Å., density=2.08.  The space group is C 6₃/m.  The interatomic distances are:  Fe-Fe, 2.46, Fe-C (in C=O), 1.9; Fe-C (in C=O), is 1.8; C=O is 1.15; and C=O is 1.3 Å.  Angle between (OC)-Fe bond is 94°; between Fe-C bonds, 78°; and between bonds of >C=O, 87°.  The structure simultaneously fixes the molecular formula of the compound as Fe₂ (CO)₉, as no direct molecular-weight determination is available.  Its magnetic properties are discussed.