Hydrotris(indazolyl)borate, Tp4Bo, a surprisingly effective Tp ligand for supramolecular assembly

The assembly of TlTp4Bo and M(Tp4Bo)2 (M e.g. Co, Ni) in the crystal is dictated by aromatic π–π and C–H⋯π interactions. This leads to the formation of chiral C2-symmetrical pairs (for Tl) or solvent-filled, about 30%-porous, non-covalent framework structures (for Co and Ni). The potassium salt KTp4Bo features a κN,η-C–C,η2-C–N cation-π coordination mode — curious for a Tp-type ligand.