Mono-, Di-, and Tricarbonylic Species in Copper(I)-Exchanged Zeolite ZSM-5: Comparison with Homogeneous Copper(I) Carbonylic Structures

Abstract

The structural and spectroscopic similarities between homogeneous and heterogeneous [CuI(CO)n]+A- (n = 1−3; A- = [AsF6]- or zeolite anion Z-) carbonyls are evidenced and discussed. While [CuI(CO)2]+ and [CuI(CO)3]+ have linear and planar structures in [CuI(CO)n]+[AsF6]- solid compounds, they are bent in the zeolite channels. The [AsF6]- anion has a base strength lower than that of the zeolite anion; consequently, the [CuI(CO)n]+ moieties have a more positive character in the solid compounds than in the intrazeolitic ones. The CuI−framework distance is influenced by the formation of the [CuI(CO)n]+ complexes: this is demonstrated by both EXAFS and IR results concerning the effect of CO complexation on the CuI−framework distance and on the CuI-sensitive skeletal modes, respectively. The role of basic ligands in increasing the π-character of the Cu−CO bond (with simultaneous decrease of the electrostatic and σ contributions) has been studied on [CuI(CO)n(NH3)]+Z- (n = 1, 2) and [CuI(CO)(H2O)n]+Z- (n = 1, 2) complexes synthesized in situ in the zeolite channels.