Synthesis, Structural Characterization, and Preliminary Reactivity Profile of a Series of Monocyclopentadienyl, Monoacetamidinate Titanium(III) Alkyl Complexes Bearing β-Hydrogens

Alkylation of Cp*TiCl2[N(i-Pr)C(Me)N(i-Pr)] (Cp* = η5-C5Me5) (1) with two equivalents of an alkyllithium reagent provided high yields of the thermally stable, crystalline, paramagnetic titanium(III) alkyl complexes of general structure Cp*Ti(R)[N(i-Pr)C(Me)N(i-Pr)] where R = Et (2), n-Bu (3), i-Bu (4), neopentyl (5), and n-hexyl (6). Solid-state structural characterization of compounds 2−5 by single-crystal X-ray analysis revealed the absence of α- or β-hydrogen agostic interactions between the metal center and the alkyl group R. Isocyanides (R′NC) undergo quantitative 1,1-insertion into the titanium−carbon bond of the alkyl group of 2−6 to provide high yields of the corresponding series of crystalline, paramagnetic Ti(III) η2-iminoacyl derivatives, Cp*Ti[η2-N(R′)CR)][N(i-Pr)C(Me)N(i-Pr)] (7−11, respectively), which were also structurally characterized by X-ray crystallography for compounds 7 and 9−11. Finally, compounds 3−5 were oxidized with PbCl2 in diethyl ether to cleanly generate the respective Ti(IV) monochloro, monoalkyl complexes Cp*Ti(R)(Cl)[N(i-Pr)C(Me)N(i-Pr)] (12−14, respectively), the solid-state structures of which were also determined by single-crystal X-ray analyses.