The first neutral homoleptic lanthanoid pyrazolates, including the mixed oxidation state species [Yb2(But2pz)5] (But2pz = 3,5-di-tert-butylpyrazolate), from a simple new synthesis of pyrazolate complexes

Reaction of 3,5-di-tert-butylpyrazole (But2pzH) with lanthanoid metals and mercury at 220 °C in the absence of an added solvent yields [Ln(But2pz)3] (Ln = Nd, Sm), [Eu(But2pz)2] and [Yb2(But2pz)5], which is a mixed oxidation state complex with the structural arrangement [(η2-But2- pz)YbII(µ-η2∶η2-But2pz)2YbIII(η2-But2pz)2].