[Pd(HL)Cl₂] and [PdL₂], where HL is 2-(3-Pyrazolyl)pyridine

The complexes cis-[Pd(HL)Cl₂] {dichloro[2-(3-pyrazolyl-N²)pyridine-N]palladium(II), [PdCl₂(C₈H₇N₃)]} and trans-[PdL₂] {bis[2-(3-pyrazolyl-N²)pyridinato-N]palladium(II), [Pd(C₈H₆N₃)₂]} were isolated as by-products from preparations of palladium(II) complexes with the podand ligand tris[3-(2-pyridyl)pyrazol-1-yl]hydroborate, [HBL₃]^-. Both have square-planar coordination geometries. In cis-[Pd(HL)Cl₂], the ligand HL acts as a neutral bidentate chelate. In [PdL₂], which has a trans geometry, the pyrazole N¹ position is deprotonated. This has two consequences: (a) steric interference with the pyridyl H⁶ proton of the alternate ligand is removed, and (b) inter-ligand intramolecular hydrogen-bonding occurs between the pyridyl H⁶ proton and the deprotonated pyrazolyl N¹ atom.

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