Copper(I) and silver(I) carbonyls. To be or not to be nonclassical

摘要: The traditional, or classical, picture of M–CO bonding is not a good model for more than 200 metal carbonyl species with average ν(CO) values greater 2143 cm−1. These “nonclassical” complexes, exemplified in this Perspective by the cations Cu(CO)n+ and Ag(CO)n+ (n = 1–4), possess interactions that are best described as M←CO σ bonds having significant electrostatic component. There relatively little M→CO π backbonding. However, despite similarity values, homologous complexes behave differently when subjected to perturbations such stretching metal–carbon adding pair weak ligands center.