Copper(II) complexes with acetone picolinoyl hydrazones: Crystallographic insight into metalloligand formation

• Metalloligand formation from CuII salts and picolinoyl hydrazones is assessed.
• Nicotinic and isonicotinic acid hydrazides are ligand precursors.
• Two new copper(II) complexes are isolated and characterized.
• SC-XRD reveals mononuclear and extended (2D) structures of the compounds.
• Copper salt acidity and the hydrazide influence the formation of pure products.

Complexes with free donor atoms, termed metalloligands, are important building blocks in the stepwise approach towards mixed-metal organic frameworks. In this work, the possibility of a metalloligand formation from nicotinic or isonicotinic acid hydrazides and copper(II) centers, is assessed. Syntheses, X-ray crystal structures and spectroscopic properties of two new copper(II) compounds with acetone 3- and 4-picolinoyl hydrazones are reported. The structural studies reveal the formation of a mononuclear cationic metalloligand in [Cu(Hisn)2](NO3)2 (1) with a zwitterionic acetone isonicotinoyl hydrazone (Hisn), as well as a neutral, layered (2D) coordination polymer, [Cu(μ-nic)2]n (2), with a deprotonated acetone nicotinoyl hydrazone (Hnic). Heteroatom position in the hydrazide precursor and copper salt acidity influence the formation of pure products.

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