Synthesis,Bonding and Reactivity of a Terminal Titanium Alkylidene Hydrazido Compound |
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| Authors: | Dr Pei Jen Tiong Laura R Groom Dr Eric Clot Prof Dr Philip Mountford |
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| Institution: | 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);3. Institut Charles Gerhardt, Université Montpellier 2, CNRS 5253, cc 1501, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France) |
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| Abstract: | We report a detailed study of the reactions of the Ti?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?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?Nα or single‐ or double‐substrate insertion into the Ti?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?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? H to the N? N?CPh2 linkage of 8 , whereas reaction with PhSiH2X (X=Cl, Br) led to the Ti?Nα 1,2‐addition products Cp*Ti{MeC(NiPr)2}(X){N(NCPh2)SiH2Ph}]. |
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| Keywords: | alkynes carbon dioxide density functional calculations isocyanates nitriles silanes |
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