The reaction of a bridged vinylidenedi-iron complex with cobalt, iron, and manganese carbonyl species; X-ray crystal structures of the complexes [Fe3(µ3-CMe)(µ-CO)2(CO)6(η-C5H5)] and [Co3Fe(µ4-CCH2)(µ-CO)2(CO)7(η-C5H5)]

Abstract

Treatment of trans-[Fe₂(µ-CCH₂)(µ-CO)(CO)₂(η-C₅H₅)2] with [Fe₂(CO)₉] in diethyl ether affords [Fe₃(µ₃-CMe)(µ-CO)₂(CO)₆(η-C₅H₅)](1), which was characterised by X-ray crystallography, and shown to contain a tetrahedral CFe₃ core which has near, but not exact, mirror symmetry. The Fe₃ triangle has two nearly equal sides [2.519(1) and 2.509(1)Å] and one longer side [2.602(1)Å], the two former being bridged approximately symmetrically by carbonyl ligands. The Fe₃ triangle is triply bridged by the µ₃-CMe ligand, but with the C atom significantly closer to the unique iron atom, which also carries the cyclopentadienyl ligand. The C-Me vector is perpendicular to the Fe₃ plane, and the terminal carbonyl ligands form two mutually orthogonal sets of three on each of the ‘basal’ iron atoms. Crystals of (1) are monoclinic, space group P2₁/c with four molecules in a unit cell of dimensions a= 8.943(4), b= 12.156(4), c= 15.904(8)Å, and β= 103.57(4)°; R= 0.026 for 2 771 intensities [I 3.0σ(I)]. Reaction of compound (1) with C₅H₆ in toluene, or thermolysis of the complex trans-[Fe₂(µ-CCH₂)(µ-CO)(CO)₂(η-C₅H₅)₂], gives [Fe₃(µ₃-CMe)(µ-CO)₃(η-C₅H₅)₃]. Treatment of trans-[Fe₂(µ-CCH₂)(µ-CO)(CO)₂(η-C₅H₅)₂] with [Co₂(CO)₈] in diethyl ether yields as the principal product [Co₃Fe(µ₄-CCH₂)(µ-CO)₂(CO)₇(η-C₅H₅)](3). The latter complex was shown by X-ray crystallography to have a Co₃Fe core arranged as a ‘butterfly’(interplanar angle 124°) with the iron atom occupying one of the ‘wingtips’ and carrying the cyclopentadienyl ligand. The molecule has overall C_S symmetry (required crystallographically), the mirror being defined as the perpendicular bisector of the body of the butterfly. The µ₄-C atom bridges the four metal atoms on the concave side, and the –CCH₂ moiety is η²-bonded to the wingtip cobalt atom. Two of the nine carbonyl ligands bridge the Co–Fe edges, approximately symmetrically; the other seven are terminal and form orthogonal sets (2 + 2 + 3). Crystals of (3) are orthorhombic, space group Pcam, with four molecules in a unit cell of dimensions a= 18.135(16), b= 8.194(9), and c= 12.711(10)Å; R= 0.054 for 1 772 intensities [I 2.0σ(/)]. The trimanganese complex [Mn₃(µ-H)₃(CO)₁₂] reacts with trans-[Fe₂(µ-CCH₂)(µ-CO)(CO)₂(η-C₅H₅)₂] in benzene to form the mixed-metal cluster [Fe₂Mn(µ₃-CMe)(µ-CO)₃(CO)₃(η-C₅H₅)₂].