Synthesis, Bonding and Reactivity of a Terminal Titanium Alkylidene Hydrazido Compound

Authors

  • Dr. Pei Jen Tiong,

    1. Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (UK)
    2. Current address: Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak (Malaysia)
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  • Laura R. Groom,

    1. Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (UK)
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  • Dr. Eric Clot,

    Corresponding author
    1. Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, cc 1501, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France)
    • Eric Clot, Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, cc 1501, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France)

      Philip Mountford, Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (UK)

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  • Prof. Dr. Philip Mountford

    Corresponding author
    1. Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (UK)
    • Eric Clot, Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, cc 1501, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France)

      Philip Mountford, Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (UK)

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Abstract

We report a detailed study of the reactions of the Ti[DOUBLE BOND]NNCPh2 alkylidene hydrazide functional group in [Cp*Ti{MeC(NiPr)2}(NNCPh2)] (8) with a variety of unsaturated and saturated substrates. Compound 8 was prepared from [Cp*Ti{MeC(NiPr)2}(NtBu)] and Ph2CNNH2. DFT calculations were used to determine the nature of the bonding for the Ti[DOUBLE BOND]NNCPh2 moiety in 8 and in the previously reported [Cp2Ti(NNCPh2)(PMe3)]. Reaction of 8 with CO2 gave dimeric [(Cp*Ti{MeC(NiPr)2}{μ-OC(NNCPh2)O})2] and the “double-insertion” dicarboxylate species [Cp*Ti-{MeC(NiPr)2}{OC(O)N(NCPh2)C(O)O}] through an initial [2+2] cycloaddition product [Cp*Ti{MeC(NiPr)2}{N(NCPh2)C(O)O}], the congener of which could be isolated in the corresponding reaction with CS2. The reaction with isocyanates or isothiocyanates tBuNCO or ArNCE (Ar=Tol or 2,6-C6H3iPr2; E=O, S) gave either complete NNCPh2 transfer, [2+2] cycloaddition to Ti[DOUBLE BOND]Nα or single- or double-substrate insertion into the Ti[DOUBLE BOND]Nα bond. The treatment of 8 with isonitriles RNC (R=tBu or Xyl) formed σ-adducts [Cp*Ti{MeC(NiPr)2}(NNCPh2)(CNR)]. With ArF5CCH (ArF5=C6F5) the [2+2] cycloaddition product [Cp*Ti{MeC(NiPr)2}{N(NCPh2)C(ArF5)C(H)}] was formed, whereas with benzonitriles ArCN (Ar=Ph or ArF5) two equivalents of substrate were coupled in a head-to-tail manner across the Ti[DOUBLE BOND]Nα bond to form [Cp*Ti{MeC(NiPr)2}{N(NCPh2)C(Ar)NC(Ar)N}]. Treatment of 8 with RSiH3 (R=aryl or Bu) or Ph2SiH2 gave [Cp*Ti{MeC(NiPr)2}{N(SiHRR′)N(CHPh2)}] (R′=H or Ph) through net 1,3-addition of Si[BOND]H to the N[BOND]N[DOUBLE BOND]CPh2 linkage of 8, whereas reaction with PhSiH2X (X=Cl, Br) led to the Ti[DOUBLE BOND]Nα 1,2-addition products [Cp*Ti{MeC(NiPr)2}(X){N(NCPh2)SiH2Ph}].

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