Trianionic Organoborate Triangles

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, L4−, 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 L4− 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.