Crystal Structure of the Tetrakis(cyclopentadienyliron); Butterfly Cluster Compound of 1,3-Diyne, [Cp4Fe4(CO)2(C4Ph2)]

The structure of the title compound was determined by X-ray crystallography. A symmetry operation (1/2-x, 1/2+y, 1/2-z) generates the whole molecule. The compound crystallized in a monoclinic system, and was characterized as follows: P21/n: a = 12.8340(11)A, b = 17.8961(15)A, c = 12.5827(10)A, β = 90.333(7)°, z = 4, V = 2889.93(4)A3. The crystal structure was solved by direct methods and refined by full-matrix least-squares on F2 to final values of R1 = 0.0555 and wR2 = 0.1668. The structure consists of an iron four butterfly structure overbridged by 1,4-diphenyl-1,3-butadiyne. Carbon atoms in one alkyne group of 1,3-diyne bond to the wing-tip iron atoms by (η2:2π)-bonds with atomic distances of Fe3-C1 2.001(6), Fe3-C3 1.968(6), Fe4-C1 1.985(6), and Fe4-C3 2.022(6)A, and to the hinge iron atoms by (η1:2σ)-bonds with bond lengths of Fe2-C1 1.955(6) and Fe1-C3 1.989(6)A. However, the dihedral angle between the two Fe3-triangles is 108.65°, and two carbon mono-oxide are face-capped on the wings with an atomic distance of Fe-C 1.900(8) - 2.065(7)A.