Speciation of [Cp*2M2O5] in Polar and Donor Solvents

Authors

  • Dr. Pelin Sözen-Aktaş,

    1. CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4 (France), Fax: (+33) 561553003
    2. Université de Toulouse, UPS, INPT, 31077 Toulouse Cedex 4 (France)
    3. Celal Bayar University, Faculty of Sciences & Liberal Arts, Department of Chemistry, 45030 Muradiye-Manisa (Turkey)
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  • Dr. Iker Del Rosal,

    1. Universitat Autónoma de Barcelona, Departament de Química, Edifici Cn, 08193 Cerdanyola del Vallès (Spain)
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  • Dr. Eric Manoury,

    1. CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4 (France), Fax: (+33) 561553003
    2. Université de Toulouse, UPS, INPT, 31077 Toulouse Cedex 4 (France)
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  • Prof. Funda Demirhan,

    1. Celal Bayar University, Faculty of Sciences & Liberal Arts, Department of Chemistry, 45030 Muradiye-Manisa (Turkey)
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  • Prof. Agustí Lledós,

    Corresponding author
    1. Universitat Autónoma de Barcelona, Departament de Química, Edifici Cn, 08193 Cerdanyola del Vallès (Spain)
    • Universitat Autónoma de Barcelona, Departament de Química, Edifici Cn, 08193 Cerdanyola del Vallès (Spain)
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  • Prof. Rinaldo Poli

    Corresponding author
    1. CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4 (France), Fax: (+33) 561553003
    2. Université de Toulouse, UPS, INPT, 31077 Toulouse Cedex 4 (France)
    3. Institut Universitaire de France, 103, bd Saint-Michel, 75005 Paris (France)
    • CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4 (France), Fax: (+33) 561553003
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  • M=Mo, W; Cp*=pentamethylcyclopentadienyl.

Abstract

The speciation of compounds [Cp*2M2O5] (M=Mo, W; Cp*=pentamethylcyclopentadienyl) in different protic and aprotic polar solvents (methanol, dimethyl sulfoxide, acetone, acetonitrile), in the presence of variable amounts of water or acid/base, has been investigated by 1H NMR spectrometry and electrical conductivity. Specific hypotheses suggested by the experimental results have been further probed by DFT calculations. The solvent (S)-assisted ionic dissociation to generate [Cp*MO2(S)]+ and [Cp*MO3] takes place extensively for both metals only in water/methanol mixtures. Equilibrium amounts of the neutral hydroxido species [Cp*MO2(OH)] are generated in the presence of water, with the relative amount increasing in the order MeCN≈acetone<MeOH<DMSO. Addition of a base (Et3N) converts [Cp*2M2O5] into [Et3NH]+[Cp*MO3], for which the presence of a N[BOND]H⋅⋅⋅O[DOUBLE BOND]M interaction is revealed by 1H NMR spectroscopy in comparison with the sodium salts, Na+[Cp*MO3]. These are fully dissociated in DMSO and MeOH, but display a slow equilibrium between free ions and the ion pair in MeCN and acetone. Only one resonance is observed for mixtures of [Cp*MO3] and [Cp*MO2(OH)] because of a rapid self-exchange. In the presence of extensive ionic dissociation, only one resonance is observed for mixtures of the cationic [Cp*MO2(S)]+ product and the residual undissociated [Cp*2M2O5] because of a rapid associative exchange via the trinuclear [Cp*3M3O7]+ intermediate. In neat methanol, complex [Cp*2W2O5] reacts to yield extensive amounts of a new species, formulated as the mononuclear methoxido complex [Cp*WO2(OMe)] on the basis of the DFT study. An equivalent product is not observed for the Mo system. The addition of increasing amounts of water results in the rapid decrease of this product in favor of [Cp*2W2O5] and [Cp*WO2(OH)].

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