Complexes of carbon suboxides with silver: new chemistry of silver

Abstract

Reaction of silver^I acetate with acetic anhydride at reflux under argon gives an explosive silver complex of empirical formula Ag₃C₃O₂(I). Pyrolysis of complex (I) gives carbon suboxide as the major gaseous product. Decomposition of (I) by aqueous alkali, followed by acidification, gives some malonic acid. The complex (I) isolated under strictly anhydrous conditions is diamagnetic, but treatment with dilute acetic acid gives a complex (II) of the same empirical formula which exhibits an unusual type of strong field-dependent antiferromagnetism. Complexes (I) and (II) are oxidized by oxygen at 20° in daylight, but not in the dark, to complexes of empirical formula Ag₃C₃O₃. Oxygen is taken up (reversibly) in the dark at –78°. Molecular nitrogen is taken up photochemically at 20°, even in presence of oxygen. There is evidence that these complexes contain silver atom clusters. Certain of the silver complexes undergo ligand exchange with iodide and bromide ions to form silver halides of empirical formula AgHal which exhibit field-dependent antiferromagnetism both as solids and in solution. These new forms of silver halides are thought to contain silver atom clusters inherited from their precursors. Complexes akin to complex (I), but which differ in certain properties, are obtained at room temperature from many silver^I salts and acetic anhydride in the presence of tertiary amines such as pyridine or triethylamine. These may be complexes with C₂O (ketenides), and complexes (I) and (II) may contain elements of a ketenide structure.