83691-33-2Relevant academic research and scientific papers
Electrochemical, EPR and computational results on [Fe2Cp 2(CO)2-based complexes with a bridging hydrocarbyl ligand
Boni, Adriano,Funaioli, Tiziana,Marchetti, Fabio,Pampaloni, Guido,Pinzino, Calogero,Zacchini, Stefano
, p. 3551 - 3556 (2011)
The dimetallacyclopentenone complexes [Fe2Cp2(CO) (μ-CO){μ-η1:η3-CαHC β(R)C(O)} (R = CH2OH, 1a; R = CMe2OH, 1b; R = Ph, 1c) were prepared by photolytic reaction of [Fe2Cp 2(CO)4 with alkyne according to the literature procedure. The X-ray and the electrochemical characterization of 1c are presented. The μ-allenyl compound [Fe2Cp2(CO)2(μ-CO) {μ-η1:η2α,β-C αHCβCMe2[BF4 ([2[BF 4), obtained by reaction of 1b with HBF4, underwent monoelectron reduction to give a radical species which was detected by EPR at room temperature. The EPR signal has been assigned to [Fe2Cp 2(CO)2(μ-CO){μ-η1: η2α,β-CαHC βCMe2}, [2?. The molecular structures of [2+ and [2? were optimized by DFT calculations. The unpaired electron in [2? is localized mainly at the metal centers and, coherently, [2? does not undergo carbon-carbon dimerization, by contrast with what previously observed for the μ-vinyl radical complex [Fe2Cp2(CO)2(μ-CO){μ- η1:η2-CHCH(Ph)}?, [3 ?. Electron spin density distributions similar to the one of [2? were found for the μ-allenyl radical complexes [Fe 2Cp2(CO)2(μ-CO){μ-η1: η2α,β-CαHC βC(R1)(R2)}? (R 1 = R2 = H, [4?; R1 = H, R 2 = Ph, [5?; R1 = R2 = Ph, [6?).
Organic Chemistry of Dinuclear Metal Centres. Part 1. Combination of Alkynes with Carbon Monoxide at Di-iron and Diruthenium Centres: Crystal Structure of 3-C(O)C2Ph2>(η-C5H5)2>
Dyke, Andrew F.,Knox, Selby, A. R.,Naish, Pamela J.,Taylor, Graham E.
, p. 1297 - 1308 (2007/10/02)
Under u.v. radiation a variety of alkynes (HC2H, MeC2Me, PhC2Ph, MeO2CC2CO2Me, MeC2H, PhC2H, and PhC2Me) reacts with to form complexes 3-C(O)C2R2>(η-C5H5)2> in 10-90percent yields.Only PhC2Ph produces an analogous complex with , but 3-C(O)C2Ph2>(η-C5H5)2> undergoes alkyne exchange on heating in toluene with HC2H, MeC2Me, MeC2H, PhC2H, or PhC2Me to afford the appropriate 3-C(O)C2R2>(η-C5H5)2> in near quantitative yield.The linking of alkyne and CO to produce a dimetallacyclopentenone ring was established through an X-ray diffraction study of the title compound.Crystals are orthorombic, space group Pbca, with Z=8 in a unit cell of dimensions a=14.797(3), b=17.805(8), and c=16.739(8) Angstroem.The structure was solved by heavy-atom methods and refined by least squares to R0.033 for 3 726 diffractometer-measured reflection intensities.The molecule contains a dimetallacyclopentenone ring in which the ethylenic bond is η2-bound to ruthenium, so that the bridging C(O)C(Ph)C(Ph) ligand is ?-co-ordinated to one ruthenium and η3-co-ordinated to the other.Compounds 3-C(O)C(R1)C(R2)>(η-C5H5)2> (M=Fe or Ru) in which R1R2 exist as isomers as a result of linking of either end of the alkyne with CO.Steric factors appear to determine the relative stability of the isomers when one of R is H, but electronic factors are influential when neither is H.The dimetallacyclopentenones are fluxional, undergoing synchronous carbonyl 'insertion' into, and elimination from, the dimetallacycle.Free energies of activation appear dependent upon the size of the 'alkyne' substituents.In boiling toluene, carbonyl elimination from the dimetallacycle in 3-C(O)C2(CO2Me)2>-(η-C5H5)2> becomes irreversible, and the dimetallacyclobutene complex -(η-C5H5)2> is formed quantitatively as cis and trans isomers.Only cis-(η-C5H5)2> is generated when 3-C(O)C2Ph2>(η-C5H5)2> is heated with MeO2CC2CO2Me.The ease with which carbon-carbon bond-making and -breaking occurs at the di-iron and diruthenium centres is recognised.
