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

Abstract

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

Activation of H2 and CO by Sulfur‐Rich Nickel Model Complexes for [NiFe] Hydrogenases and CO Dehydrogenases

“…[20] The high ν(CO) frequencies of these complexes are rationalized by a subtle interplay of σ-donor, π-acceptor and semipolar contributions in the MϪCO bonds. [21] In accordance with this rationalization, the results obtained here show that binding CO to [Ni(L)( R S 3 )] complexes not only enhances the polarity of the CO bond but also increases the susceptibility of CO towards attack by nucleophiles. This may be a reason why coordination of CO to the [NiS 4 ] core of CO dehydrogenase centers can enable the CO/CO 2 conversion according to Equation (2) (vide infra).…”

Vibrational Spectroscopy of Zeolites

“…The stretching frequencies of the copper-carbonyls are very similar to those observed in homogeneous conditions 109 and demonstrate that bonding between Cu C and CO involves considerable overlap forces. This result differentiates the intracavity chemistry of Cu C from that of the other monovalent cations.…”

“…In conclusion, in both cases (CO and NO) true intrazeolitic complexes, showing strong spectroscopic and structural similarities with homoleptic or nonclassical complexes synthesized in homogenous acidic solutions, 109 are formed. We also recall that Cu C ions in ZSM-5 are also able to form Cu C (N 2 ) complexes stable at room temperature.…”

Spectroscopic and structural characterization of Cr(II)/SiO2 active site precursors in model Phillips polymerization catalysts

“…The interaction of CO with grafted Cr(II) involves electrostatic, covalent r-bonding and p-back-bonding contributions. The first two induce a blue shift in the CAO stretching frequency, while the last causes a red shift [49,50].…”