The Counterion Effect on the Assembly of Coordination Networks of Cationic (η3-Allyl)palladium Complexes Containing 3,5-Dimethyl-4-nitro-1H-pyrazole

Abstract

Two new (η3-allyl)palladium complexes containing the ligand 3,5-dimethyl-4-nitro-1H-pyrazole (Hdmnpz) were synthesized and characterized as [Pd(η3-C3H5)(Hdmnpz)2]BF 4 (1) and [Pd(η3-C3H 5)(Hdmnpz)2]NO3 (2). The structures of these compounds were determined by single-crystal X-ray diffraction to evaluate the intermolecular assembly. Each complex exhibits similar coordination behavior consistent with cationic entities comprised of two pyrazole ligands coordinated with the [Pd(η3-C3H5)]+ fragment in an almost square-planar coordination geometry. In 1, the cationic entities are propagated through strong intermolecular H-bonds formed between the pyrazole NH groups and BF4- ions in one-dimensional polymer chains along the a axis. These chains are extended into two-dimensional sheet networks via bifurcated H-bonds. New intermolecular interactions established between NO2 and Me substituents at the pyrazole ligand of neighboring sheets give rise to a three-dimensional network. By contrast, compound 2 presents molecular cyclic dimers formed through N-H⋯O H-bonds between two NO3- counterions and the pyrazole NH groups of two cationic entities. The dimers are also connected to each other through C-H⋯O H-bonds between the remaining O-atom of each NO3 - ion and the allyl CH2 H-atom. Those interactions expand in a layer which lies parallel to the face (101).