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

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