Reactivity Study of Unsymmetrical ß-Diketiminato Copper(I) Complexes: Effect of the Chelating Ring.

ß-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 ß-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.

Extraction of cupric ions with ionic liquids containing polypyridine-type small molecules or peripherally pyridine-modified dendrimers.

The hydrophobic ionic liquid N-butyl-N-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (BMP-TFSA IL), which contains a series of flexible ionophores of polypyridine-type small molecules or two rigid ionophores of peripherally pyridine-modified PAMAM dendrimers, was used to extract cupric ions from aqueous solutions. The polypyridine-type ionophores show good selectivity toward cupric ions at pH 2. The selectivity is affected by the spacing between the two amino groups. However, the pyridine-modified dendrimers showed poor selectivity, although their extraction efficiency still depended on the pH of the aqueous solution. The ionic liquids that contained small molecular ionophores and their dendrimer analogs were reused after acid washing or electrochemical reduction. During acid washing, the nitrogen atoms of the ionophores were protonated to release the cupric ions into the aqueous phase, and the copper atoms were deposited onto the electrode surface during the electrochemical reduction accompanied by the regeneration of the ionophores.