Synthesis, Bonding and Reactivity of a Terminal Titanium Alkylidene Hydrazido Compound. Issue 13 (11th February 2013)

• Record Type: Journal Article
• Authors: Tiong, Pei Jen; Groom, Laura R.; Clot, Eric; Mountford, Philip
• Is Part Of: Chemistry. Volume 19:Issue 13(2013)
• Page Start: 4198
• Page End: 4216
• Publication Date: 2013-02-11
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201203905
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>We report a detailed study of the reactions of the TiNNCPh<sub>2</sub> alkylidene hydrazide functional group in [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}(NNCPh<sub>2</sub>)] (<bold>8</bold>) with a variety of unsaturated and saturated substrates. Compound <bold>8</bold> was prepared from [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}(N<italic>t</italic>Bu)] and Ph<sub>2</sub>CNNH<sub>2</sub>. DFT calculations were used to determine the nature of the bonding for the TiNNCPh<sub>2</sub> moiety in <bold>8</bold> and in the previously reported [Cp<sub>2</sub>Ti(NNCPh<sub>2</sub>)(PMe<sub>3</sub>)]. Reaction of <bold>8</bold> with CO<sub>2</sub> gave dimeric [(Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{μ‐OC(NNCPh<sub>2</sub>)O})<sub>2</sub>] and the "double‐insertion" dicarboxylate species [Cp*Ti‐{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{OC(O)N(NCPh<sub>2</sub>)C(O)O}] through an initial [2+2] cycloaddition product [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{N(NCPh<sub>2</sub>)C(O)O}], the congener of which could be isolated in the corresponding reaction with CS<sub>2</sub>. The reaction with isocyanates or isothiocyanates <italic>t</italic>BuNCO or ArNCE (Ar=Tol or 2, 6‐C<sub>6</sub>H<sub>3</sub><italic>i</italic>Pr<sub>2</sub>; E=O, S) gave either complete NNCPh<sub>2</sub> transfer, [2+2] cycloaddition to TiN<sub>α</sub> or single‐ or double‐substrate insertion into the TiN<sub>α</sub> bond. The treatment of <bold>8</bold> with isonitriles RNC (R=<italic>t</italic>Bu or Xyl) formed σ‐adducts [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}(NNCPh<sub>2</sub>)(CNR)]. With Ar<sup>F5</sup>CCH (Ar<sup>F5</sup>=C<sub>6</sub>F<sub>5</sub>) the [2+2] cycloaddition product [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{N(NCPh<sub>2</sub>)C(Ar<sup>F5</sup>)C(H)}] was formed, whereas with benzonitriles ArCN (Ar=Ph or Ar<sup>F5</sup>) two equivalents of substrate were coupled in a head‐to‐tail manner across the TiN<sub>α</sub> bond to form [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{N(NCPh<sub>2</sub>)C(Ar)NC(Ar)N}]. Treatment of <bold>8</bold> with RSiH<sub>3</sub> (R=aryl or Bu) or Ph<sub>2</sub>SiH<sub>2</sub> gave [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}{N(SiHRR′)N(CHPh<sub>2</sub>)}] (R′=H or Ph) through net 1, 3‐addition of SiH to the NNCPh<sub>2</sub> linkage of <bold>8</bold>, whereas reaction with PhSiH<sub>2</sub>X (X=Cl, Br) led to the TiN<sub>α</sub> 1, 2‐addition products [Cp*Ti{MeC(N<italic>i</italic>Pr)<sub>2</sub>}(X){N(NCPh<sub>2</sub>)SiH<sub>2</sub>Ph}].</p> </abstract>