Reactivity Study of Unsymmetrical β‑Diketiminato Copper(I) Complexes: Effect of the Chelating Ring

β-Diketiminato
copper­(I) complexes play important roles in bioinspired catalytic
chemistry and in applications to the materials industry. However,
it has been observed that these complexes are very susceptible to
disproportionation. Coordinating solvents or Lewis bases are typically
used to prevent disproportionation and to block the coordination sites
of the copper­(I) center from further decomposition. Here, we incorporate
this coordination protection directly into the molecule in order to
increase the stability and reactivity of these complexes and to discover
new copper­(I) binding motifs. Here we describe the synthesis, structural
characterization, and reactivity of a series of unsymmetrical N-aryl-N′-alkylpyridyl β-diketiminato
copper­(I) complexes and discuss the structures and reactivity of these
complexes with respect to the length of the pyridyl arm. All of the
aforementioned unsymmetrical ß-diketiminato copper­(I) complexes
bind CO reversibly and are stable to disproportionation. The binding
ability of CO and the rate of pyridyl ligand decoordination of these
copper­(I) complexes are directly related to the competition between
the degree of puckering of the chelate system and the steric demands
of the N-aryl substituent.