Towards the formation of dimeric and trimeric lithium benzamidinates: characterization of intermediate structures

Abstract

p-Toluonitrile reacts with LiN(TMS)₂ in diethyl ether (1 ∶ 1) to yield a dimeric complex 1 containing a lithium benzamidinate unit, a molecule of p-toluonitrile attached to the lithium atom and a molecule of lithium bis(trimethylsilyl)amide coordinated to a lithium–nitrogen bond, of the benzamidinate unit, forming a four-membered ring. The crystal structure of 1 shows the molecularity, the stereochemistry and the manner of activation of nitriles by lithium amido salts in the formation of amidinates. When the same reaction is carried out in hexane, the trimeric complex 2 is formed, containing lithium atoms simultaneously π- and σ-bonded to amidine moieties. When the ratio of p-toluonitrile and LiN(TMS)₂ in diethyl ether–hexane is 2 ∶ 1, complex 1 is obtained, which can be treated with two equivalents of LiN(TMS)₂ to produce 3.