Polynuclear pyrazolato complexes. Synthesis, chemical reactivity and crystal structures of [{Pd(dmpz)2(Hdmpz)2}2] and [{PdAg2(dmpz)4}2] (Hdmpz = 3,5-dimethylpyrazole)

The dinuclear complex [{Pd(dmpz)2(Hdmpz)2}2] (Hdmpz = 3,5-dimethylpyrazole) has been synthesized and its solid-state structure determined by X-ray methods. Each dimeric molecule, of idealized 422 symmetry, possesses four strong intramolecular hydrogen bonds, equalizing the Hdmpz and dmpz ligands. The complex has been treated with AgNO3 and [Cu(MeCN)4]BF4, in search of heterobimetallic derivatives; [{PdCu2(dmpz)4}2] and [{PdAg2(dmpz)4}2] species have been isolated. The latter, characterized by X-ray methods, is a non-bonded octahedral cluster (trans Pd2Ag4) bridged by eight dihapto dmpz ligands, thus formally deriving from its precursor by substitution of four H+ by Ag+ ions. This increases the Pd⋯Pd distance from 3.746(1) to 5.160(1) Å, and slightly changes the ligand conformation.