Synthesis and Structures of Two New Types of Boronium Salts

Transamination of di(pyrid‐2‐yl)amine ( 1 ) with B(NMe 2 ) 3 leads to the isomeric heterocyclic bis(dimethylamino)boryl compound 4 and not to bis(dimethylamino)di(pyrid‐2‐yl)aminoborane ( 2 ). B(NMe 2 ) 3 reacts with aniline (1:2 ratio) to yield a 1:1 mixture of B(NHPh) 3 and (Me 2 N) 2 BNHPh. Transamination of this mixture with 1 yields the anilinodimethylamino analogue of 4 (compound 7 ). Compound 4 reacts with CHCl 3 to generate the boronium salt 5 by the abstraction of HCl from CHCl 3 and addition of HCl to one of the dimethylamino groups. Compound 5 crystallizes with 4 molecules of CHCl 3 . Compound 4 is attacked by AlCl 3 in toluene to give a mixture of unidentified products from which the tetrachloroaluminate of a new type of spirocyclic diboronium cation, 8 , was isolated and characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)