Novel oligotopic poly(pyrazolyl)borate ligands

Poly(pyrazolyl)borates (“scorpionates“) are versatile ligands that are widely used in homogeneous catalysis as well as materials science. However, even though dinuclear transition metal complexes are of particular interest in many fields of research, only a surprisingly small number of ditopic scorpionate ligands have been described up to now. Starting from readily accessible bis(dibromoboryl)benzenes, our group has recently developed high-yield syntheses of ditopic meta- or para-phenylene bridged bis- and tris(pyrazolyl)borates (meta-1, para-1; R = 1-pyrazolyl, tBu, Ph, C₆F₅). Transition metal complexes of these ligands cover a broad range of structural variants from open-chain dinuclear compounds to coordination polymers and metallo-macrocycles. In order to further extend the application spectrum of scorpionate ligands, we are currently investigating the tritopic derivative 2 which shows promising potential for the preparation of solid materials featuring porous metal-containing frameworks.