Reactions of metal carbonyl derivatives. Part 22. The crystal and molecular structures of dicarbonyl(η-cyclopentadienyl)(ethylthio)iron and µ-ethylthio-bis[dicarbonyl(η-cyclopentadienyl)iron] tetrafluoro-borate, and a comparison of their molecular parameters

Abstract

The solid-state structures of [Fe(cp)(CO)₂(SEt)](1) and [{Fe(cp)(CO)₂}₂SEt][BF₄]{[BF₄]^– salt of (2)}(cp =η-C₅H₅) have been determined by single-crystal X-ray analyses. Compound (1) crystallises in the orthorhombic space group Pnma with cell parameters a= 14.118(5), b= 9.822(5), c= 7.443(5)Å, and Z= 4 while the [BF₄]^– salt of (2) crystallises in the triclinic space group P with a= 9.41 (1), b= 11.36(1), c= 10.04(l)Å. α= 99.77(l), β= 104.40(l)γ= 67.83(1)°, and Z= 2. The structures have been solved by conventional Patterson and Fourier techniques and refined to R= 0.049 and 0.030 for 885 and 2 197 independent reflections respectively. Molecule (1) lies on a mirror plane of symmetry with the cyclopentadienyl group being disordered. The cation (2) has symmetry C₁ and contains the two cyclopentadienyl groups cis disposed with respect to the Fe(1)SFe(2) plane. The ct(cp)–Fe(1)–Fe(2)–ct(cp)[ct(cp)= centroid of the cyclopentadienyl group] torsional angle τ′ is 58.2 °. The Fe–S bond distance and the Fe–S–C bond angle remain essentially unaltered on co-ordination of (1) to [Fe(cp)(CO)₂]⁺ to give (2). The n.m.r. data for the salt of (2) are interpreted in terms of fluxional behaviour in solution.