Coordination of bis-(pyrazol-1-yl)amine to palladium(II): influence of the co-ligands and counter-ions on the mol-ecular and crystal structures.

The structures of a series of complexes with general formula n[Pd(pza)X]Y·mH2O (n = 1, 2; X = Cl, Br, I, N3, NCS; Y = NO3, I, N3, [Pd(SCN)4]; m = 0, 0.5, 1) have been determined, where pza is the tridentate ligand bis-[2-(3,5-di-methyl-pyrazol-1-yl)eth-yl]amine, C14H23N5. In all complexes, {bis-[2-(3,5-di-methyl-pyrazol-1-yl-κN (2))eth-yl]amine-κN}chlorido-palladium nitrate, [Pd(pza)Cl]NO3, (1), {bis-[2-(3,5-di-methyl-pyrazol-1-yl-κN (2))eth-yl]amine-κN}bromido-palladium nitrate, [Pd(pza)Br]NO3, (2), {bis-[2-(3,5-di-methyl-pyrazol-1-yl-κN (2))eth-yl]amine-κN}iodido-palladium iodide hemihydrate, [Pd(pza)I]I·0.5H2O, (3), azido{bis-[2-(3,5-di-methyl-pyrazol-1-yl-κN (2))eth-yl]amine-κN}palladium azide monohydrate, [Pd(pza)N3]N3·H2O, (4), and bis-[{bis-[2-(3,5-di-methyl-pyrazol-1-yl-κN (2))eth-yl]amine-κN}(thio-cyanato-κN)palladium] tetra-kis-(thio-cyanato-κS)palladate, [Pd(pza)NCS]2[Pd(SCN)4], (5), the Pd(pza)X complex cation displays a square-planar coordination geometry, and the pza ligand is twisted, approximating twofold rotation symmetry. Although the pza ligand is found with the same conformation along the series, the dihedral angle between pyrazole rings depends on the co-ligand X. This angle span the range 79.0 (3)-88.6 (1)° for the studied complexes. In (3), two complex cations, two I(-) anions and one water mol-ecule of crystallization are present in the asymmetric unit. In (5), the central amine group of pza is disordered over two positions [occupancy ratio 0.770 (18):0.230 (18)]. The complex Pd(SCN)4 anion of this compound exhibits inversion symmetry and shows the Pd(2+) transition metal cation likewise in a square-planar coordination environment. Compound (5) is also a rare occurrence of a non-polymeric compound in which the pseudohalide ligand NCS(-) behaves both as thio-cyanate and iso-thio-cyanate, i.e. is coordinating either through the N atom (in the cation) or the S atom (in the anion).