Kläui ligand
The Kläui ligand is the anion −. The ligand, popularized by Wolfgang Kläui, binds metals and metalloids via a facial O3 donor set. Related tridentate and tripodal anionic ligands include trispyrazolylborates.
The ligand is derived from the cationic complex of trimethylphosphite 2+ via an Arbuzov reaction. Using other phosphites and other cyclopentadienyl ligands, a large variety of derivatives are possible. The parent acid H is highly soluble in water. Its pKa is about 2. Many complexes have been described, including bis complexes of the type
