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.

以二当量烷基锂试剂对Cp*TiCl₂[N(i-Pr)C(Me)N(i-Pr)]（其中Cp* = η⁵-C₅Me₅，记为化合物1）进行烷基化反应，可高产率得到热稳定、结晶态的顺磁性钛(III)烷基配合物，其通式为Cp*Ti(R)[N(i-Pr)C(Me)N(i-Pr)]，其中R分别为乙基（Et，化合物2）、正丁基（n-Bu，化合物3）、异丁基（i-Bu，化合物4）、新戊基（化合物5）和正己基（n-hexyl，化合物6）。通过单晶X射线分析对化合物2~5进行固态结构表征，结果显示金属中心与烷基R之间不存在α-或β-氢的agostic相互作用。异氰化物（R′NC）可与化合物2~6的钛-碳烷基键发生定量的1,1-插入反应，高产率得到对应系列的结晶态顺磁性Ti(III) η²-亚胺酰基衍生物，通式为Cp*Ti[η²-N(R′)CR)][N(i-Pr)C(Me)N(i-Pr)]（分别对应化合物7~11）；其中化合物7和9~11的固态结构已通过X射线晶体学完成表征。最后，以氯化铅（PbCl₂）在乙醚中对化合物3~5进行氧化，可干净地得到相应的Ti(IV)单氯单烷基配合物Cp*Ti(R)(Cl)[N(i-Pr)C(Me)N(i-Pr)]（分别对应化合物12~14），其固态结构也通过单晶X射线分析完成测定。