Imido-pyridine Ti(iv) compounds: synthesis of unusual imido–amido heterobimetallic derivatives

Abstract

The reaction of lithiated picolines and [TiCl₃(η⁵-C₅Me₅)] leads to several bridging or terminal imido compounds, each of which can be selectively formed by controlling the stoichiometry and temperature. Specifically, the dinuclear imido-bridged [TiCl(η⁵-C₅Me₅)(μ-NR)]₂ (1a, NR = 2-imido-3-picoline; 1b, NR = 2-imido-5-picoline) species and the unusual Ti–Li imido–amido heterobimetallic complex [{Li(THF)}{Ti(η⁵-C₅Me₅)(NR)(NHR)₂}] (2a, NR = 2-imido-3-picoline; 2b, NR = 2-imido-5-picoline) were isolated. Compounds 2 are in effect the first structurally characterized examples of titanium(IV) coordinated to terminal imido-pyridines. DFT-D calculations for 2a denote a multiple bond character between titanium and the imido ligand and a strong polarization of the electron density by the alkali cation in spite of the lack of intermetallic bonding.