Polynuclear palladium complexes with 3,5-dimethylpyrazolate exhibiting three different coordination modes

Abstract

The characterisation of dinuclear pyrazolato-bridged PdII complexes, [{Pd(μ-dmpz)Cl(Hdmpz)}2] (1) and [{Pd(μ-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 CuI, AgI or AuI to give the tetranuclear compounds [Pd2M2(μ2-dmpz-κN,N′)6] (M=Cu, Ag, Au). The structure of these compounds resembles a box with a small cavity inside. There are also three π-electron-rich clefts between each of the three pairs of azolato rings, capable of further complexation. The reactions of [Pd2M2(μ2-dmpz-κN,N′)6] (M=Cu, Ag, Au) with AgClO4 render compounds of the type [{Pd2M2(μ2-dmpz-κN,N′)2(μ3-dmpz-κN,N′,C4)4Ag2(μ2-O2ClO2)}2] (M=Cu, Ag, Au). The X-ray structures of crystals obtained from a solution of compounds [{Pd2M2(μ2-dmpz-κN,N′)2(μ3-dmpz-κN,N′,C4)4Ag2(μ2-O2ClO2)}2] (M=Ag, Au) in acetone reveals a [{Pd2M2(μ2-dmpz-κN,N′)2(μ3-dmpz-κN,N′,C4)4Ag(OCMe2)(OClO3)Ag(μ2-O2ClO2)}2] stoichiometry, indicating that only two of the three π-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 η1-bonded to the C4 atom of each group.