Polynuclear Palladium Complexes with 3,5-Dimethylpyrazolate Exhibiting Three Different Coordination Modes

The characterisation of dinuclear pyrazolato-bridged Pd(II) complexes, [(Pd(mu-dmpz)Cl(Hdmpz))2] (1) and [(Pd(mu-dmpz)(dmpz)(Hdmpz))2] (2) (Hdmpz=dimethylpyrazole), has been carried out. An X-ray study of compound 2 reveals the existence of intramolecular N-H...N hydrogen bonds between neighbouring dmpz groups. Compound 2 has been deprotonated and both acidic hydrogen atoms substituted by two metal atoms of Cu(I), Ag(I) or Au(I) to give the tetranuclear compounds [Pd2M2(mu(2)-dmpz-kappaN,N')6] (M=Cu, Ag, Au). The structure of these compounds resembles a box with a small cavity inside. There are also three pi-electron-rich clefts between each of the three pairs of azolato rings, capable of further complexation. The reactions of [Pd2M2(mu(2)-dmpz-kappaN,N')6] (M=Cu, Ag, Au) with AgClO4 render compounds of the type [(Pd2M2(mu(2)-dmpz-kappaN,N')2(-)(mu(3)-dmpz-kappaN,N',C4)4Ag2(mu(2)-O2ClO2))2] (M=Cu, Ag, Au). The X-ray structures of crystals obtained from a solution of compounds [(Pd2M2(mu(2)-dmpz-kappaN,N')2(mu(3)-dmpz-kappaN,N',C4)4Ag2(mu(2)-O(2)ClO2))2] (M=Ag, Au) in acetone reveals a [(Pd2M2(mu(2)-dmpz-kappaN,N')2(mu(3)-dmpz-kappaN,N',C4)4Ag(OCMe2)(OClO3)Ag(mu(2)-O2ClO2))2] stoichiometry, indicating that only two of the three pi-electron-rich clefts have been used to accommodate Ag+ ions. Each of the silver atoms are located in between two 3,5-dmpz rings and are eta(1)-bonded to the C4 atom of each group.