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-CCH2)(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)A] and one longer side [2.602(1)A], 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)A, 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 CS 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)A; 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].