Trianionic Organoborate Triangles

The rigid, angular ligand 3,3,3',3'-tetramethyl-1,1'spirobisindane-5,5',6,6'-tetrol, LH 4, in the form of its tetra-anion, L 4- , affords crystalline compounds containing the triangular macrocyclic boron derivative [B 3 L 3 ] 3- with the counter cations, triethylammonium, imidazolium, tetraethylammonium, and protonated dabco (dabco = 1,4-diazabi-cyclo[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.