Copper(I) Coordination Chemistry of (Pyridylmethyl)amide Ligands

Copper(I) chloro complexes were synthesized with a family of ligands, HL^R [HL^R = N-(2-pyridylmethyl)acetamide, R = null; 2-phenyl-N-(2-pyridylmethyl)acetamide, R = Ph; 2,2-dimethyl-N-(2-pyridylmethyl)propionamide, R = Me₃; 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph₃)]. Five complexes were synthesized from the respective ligand and cuprous chloride:  [Cu(HL)Cl]_n (1), [Cu₂(HL)₄Cl₂] (2), [Cu₂(HL^Ph)₂(CH₃CN)₂Cl₂] (3), [Cu₂(HL^Ph₃)₂Cl₂] (4), and [Cu(HL^Me₃)₂Cl] (5). X-ray crystal structures reveal that for all complexes the ligands coordinate to the Cu in a monodentate fashion, and inter- or intramolecular hydrogen-bonding interactions formed between the amide NH group and either amide CO or chloro groups stabilize these complexes in the solid state and strongly influence the structures formed. Complexes 1−5 display a range of structural motifs, depending on the size of the ligand substituent groups, hydrogen bonding, and the stoichiometry of the starting materials, including a one-dimensional coordination polymer chain (1) and binuclear (2−4) or mononuclear (5) structures.