Formamide as a precursor to cyanide in mixed-valence copper(I,II) cyanide complexes

Abstract

Copper(I) acetate reacts with acetic anhydride–formamide (1 : 1) in acetonitrile solution to give [Cu₂(O₂CMe)(CN)] or [Cu₂(CN)₂(NCMe)]. Anhydrous copper(II) acetate reacts with the same reagent to give [Cu(NCMe)₄][Cu₂(CN)₄] and [Cu(O₂CMe)₂(HCONH₂)]. The influence of various polar solvents on the products of the reaction is evaluated. The complex [Cu(NCMe)₄)][Cu₂(CN)₄] reacts with unidentate nitrogen-donor ligands, L, to form [CuL₄][Cu₂(CN)₄](L = pyridine or 4-methylpyridine) or [CuL₃][Cu₂(CN)₄](L = 2-methylpyridine or 2,6-dimethylpyridine). With bidentate nitrogen-donor ligands, L–L, substitution in [Cu(NCMe)₄][Cu₂(CN)₄] gives [Cu(L–L)₂(NCMe)][Cu₂(CN)₄](L–L = 1,2-diaminoethane or 2,2′-bipyridine). The insoluble complex products are obtained in good yield and characterized by microanalysis and spectroscopy (i.r. and visible reflectance). The role of copper ions in promoting the dehydration of formamide by acetic anhydride is assessed.