Studies of some carbon compounds of the transition metals. I. The crystal structure of dicyclopentadienyldiiron tetracarbonyl

Dicyclopentadienyldi-iron tetracarbonyl, Fe2(CO)4(C5:Hs)2, is monoclinic with a = 7-07-4-0.03,b = 12.46~=0.05,c = 7.99+0.04A, fl = 108 ° 25'±25', Z = 2 and space group t)21/c.The structure has been determined from two-dimensional data estimated visually from Weissenberg photographs taken with Co Ka radiation.The molecule consists of two bridging and two non-bridging carbonyl groups with the cyclopentadienyl rings bonded to the iron atoms in a manner similar to, but with greater interatomie separation than, that in ferrocene, Fe(CsIts)2.The proximity of the iron atoms indicates an ironiron bond.The average bond lengths are Fe-Fe 2-49-4-0.02/~,Fe-C (ring) 2.11±0.03A, Fe-C (nonbridging) 1.75+0.03/~, Fe-C (bridging) 1.85+0.03/~, C-O (non-bridging) 1.12+0.04A, C--O (bridging) 1.21±0.04A, and C-C (ring) 1.41±0.04A, where the limits given are estimated standard deviations.The R factors for the Okl and hkO zones are 12.8 and 13.3% respectively.