A cationic mononuclear and a neutral trinuclear boron compound derived from boric acid and N2O2-type ligands of the Salan class

Four different ligands of the Salan class have been prepared and reacted with boric acid. Reaction of saleanH4 (saleanH4 = N,N′-bis(o-hydroxybenzyl)-1,2-diaminoethane) with three equivalents of boric acid gave a neutral trinuclear boron complex containing two four-coordinate and one three-coordinate boron atom involved in a system of four heterocyclic rings of the composition {C3BNO}, {C2B2N2O} and {B3O3}. The salceanH4 ligand (salceanH4 = N,N′-bis(o-hydroxybenzyl)-trans-1,2-diaminocyclohexane) gave a so far unknown mononuclear boronium complex of the general formula [(RO)2B(NR′R′′)2]+. Both compounds might have applications, the trinuclear species as Lewis acid catalyst and the borocation as positively charged counterion for voluminous anions. With salpanH4 (salpanH4 = N,N′-bis(o-hydroxybenzyl)-1,3-diaminopropane) and salophanH4 (salophanH4 = N,N′-bis(o-hydroxybenzyl)-1,2-diaminobenzene) only unseparable product mixtures of oligo- and/or polymeric boron complexes could be obtained.