Trianionic Organoborate Triangles

Abstract

The rigid, angular ligand 3,3,3',3'-tetramethyl-1,1'spirobisindane-5,5',6,6'-tetrol, LH4, in the form of its tetra-anion, L(4-), affords crystalline compounds containing the triangular macrocyclic boron derivative [B3L3](3-) with the counter cations, triethylammonium, imidazolium, tetraethylammonium, and protonated dabco (dabco = 1,4-diazabicyclo[2,2,2]octane). Within a triangular unit all three chiral L(4-) ligands have the same hand although the crystal does contain a racemic mixture of macrocycles. In all four compounds, one out of the three counter-cations per macrocycle is bound inside the macrocycle.