Organometallic complexes. VII. The structure of the iron carbonyl phenylacetylene complex Fe2(CO)6(C6H5C2H)3

Abstract

The structure has been determined from visually estimated three-dimensional intensity data obtained using Co Ka radiation. The iron positions were found from a sharpened Patterson synthesis. Twenty-six of the light atoms were located by use of a minimum function and the remainder from two successive Fourier syntheses. Least-squares refinement led to a final R value of 15%. The three phenylacetylene residues and one carbonyl group form a seven-membered carbon chain with phenyl groups at the l, 3 and 6 positions and the carbonyl group in the 5 position. This chain is a-bonded from the 1, 4 and 7 positions to one iron atom to form two fused fivemembered rings with an iron and a carbon atom in common. This iron atom is also bonded to three carbonyl groups and is octahedrally coordinated. The second iron atom is linked to the remaining two carbonyl groups, to the three-electron donor system C1-C2-C a and to C6-C 7. Bond lengths are: Fe-Fe, 2.501 +0.003 (e.s.d.); Fe-C (carbonyl) 1.775_+0.012; Fe-C(a) 2.006, 2.097, 2.088; Fe-C (three-centre) 1.96-2.23 A. All other bond lengths are normal.