Syntheses involving co-ordinatively unsaturated cyclopentadienyl-molybdenum and -tungsten complexes. Molecular and crystal structure of [Mo·C(CF₃):C(CF₃)·C₅H ₅(CF₃C₂CF₃) (η⁵-C₅H₅)]

The 16-electron chloro-complexes [MCl(CF₃C₂CF₃)₂(η ⁵-C₅H₅)] (M = MO or W) react with TISC₆F₅ to give compounds [M(SC₆F₅) (CF₃C₂CF₃]₂(η⁵-C ₅H₅)]; the related species [M(SC₆F₅)(CO)(PhC₂Ph)(η⁵-C ₅H₅)] were similarly obtained from [MCl(CO)(PhC₂Ph)(η⁵-C₅H₅)]. Cyclopentadienylthallium reacts with the compounds [MCl(CF₃C₂CF₃)₂(η ₅-C₅H₅)] to afford insertion products [MC(CF₃)C(CF₃)C₅H₅(CF ₃C₂CF₃)(η⁵-C₅H ₅)], the molybdenum compound being characterised by a single-crystal X-ray diffraction study. It crystallises in the centrosymmetric monoclinic space-group P2₁/n, with lattice parameters a = 12.904(6), b = 9.641 (3), c = 15.302(6) Å, β = 103.34(4)°. The structure was elucidated via analysis of 2 148 independent diffracted data, and refined to R 0.39, R′ 0.044.

The molybdenum compound [MoCl(CF₃C₂CF₃)₂(η ⁵-C₅H₅)] undergoes an unusual reaction with the tris-(pyrazolyl)borate anion to give a complex containing no boron but an η³-allyl group, linking two pyrazole ligands and formed by condensation of the two hexafluorobut-2-yne ligands originally co-ordinated to the metal. Buta-1,3-diene reacts with [MoCl(CF₃C₂CF₃)₂(η ⁵-C₅H₅)] to give [MoCl₂(η⁴-C₄H₆(η ⁵-C₅H₅)] and with [MoCl(CO)-(PhC₂Ph)(η⁵-C₅H₅)] to yield the same compound or [MoCl(CO) (η⁴-C₄H₆)(η⁵-C ₅H₅], depending on the solvent. The tungsten compound [WCl(CO)(η⁴-C₄H₆) (η⁵-C₅H₅)] was also prepared. Reactions of bicyclo[2.2.1]-heptadiene with the compounds [MCl(CF₃C₂CF₃)₂(η ⁵-C₅H₅)] were also studied.