Structural Characterization of Novel ortho ‐Lithiated Imines

ortho ‐Metallated imines are commonly used as ligands for late transition metals. Unfortunately, not all metals, such as titanium, zirconium, and niobium, can undergo the necessary oxidative addition reactions to form the desired ortho ‐metallated complexes directly. Therefore, a synthetic methodology allowing easy access to this binding mode from simple early transition metal halides via an ortho ‐lithiated imine precursor is desirable. ortho ‐Lithiation of benzylamines and othersystems has been well studied; in contrast, that of imines is poorly developed. However, inclusion of a 3,4‐methylenedioxy group on phenyl imines allows for straightforward lithiation and simple isolation of the ortho ‐lithiated imines. NMR spectroscopy and single‐crystal X‐ray diffraction allowed for the structural elucidation of the clustering in these lithium complexes. It has been determined that the nature of the imine nitrogen substituent has a profound effect on the clustering of the lithiated imines. Alkyl (Cy, t Bu) substituents clustered in a tetrameric form, whereas aryl (2,6‐R 2 C 6 H 3 ; R = Me, Et, i Pr) substituents formed dimers that exhibited long‐range ordering in the solid state as coordination polymers. The introduction of coordinating solvent, such as dimethoxyethane and diethyl ether, changed the long‐range order of the coordination polymer and in some cases, forced the formation of discrete dimeric lithium complexes. Lithium NMR spectroscopy indicates that in solution the coordination polymer breaks up to form discrete dimers. These complexes also display a pronounced decrease in the ring bond angle of the aromatic carbon atom directly attached to the lithium atom, which indicates an increase in the p‐character of the carbon–lithium bond.