Complexes between cyclopentene and cyclopentyne derivatives with HCu and FCu: The importance of cyclization effects

Abstract

B3LYP/6-3111G(3df,2p)//B3LYP/6-311G(d,p) density functional theory calculations show that cyclopentene and cyclopentyne derivatives yield very strong p-type complexes with HCu and FCu molecules. This interaction is so strong in the case of cyclopentyne derivatives that the complexes formed can be considered as a new kind of metallocycles. These complexes resemble those reported before in the literature for ethylene and acetylene, though whereas the interaction energies between cyclopentene and HCu and FCu are smaller than those reported for ethylene, those involving cyclopentyne are larger than the ones calculated for acetylene. This very different behavior is due to the dramatic change in the local environment of the two carbon atoms of cyclopentyne with respect to acetylene, which does not occur on going from ethylene to cyclopentene.The introduction of heteroatoms in the five-membered rings opens the possibility of forming other isomers in which the CuX (X 5 H, F) is attached to the heteroatom rather than to the unsaturated CC bond. This arrangement is precisely the most favorable one for cyclopentene derivatives, though for cyclopentyne ones the p-type complexes are still the global minima. K E Y W O R D S cyclopentene, cyclopentyne, DFT calculations, homogeneous catalysis, metallocycles with FCu | I N TR ODU C TI ONThe huge development experienced by chemistry all along the twentieth century and the first decades on the present century is in part due to the progress in our ability to explore and to design new and more efficient catalysts, for both homogeneous [1,2] and heterogeneous [3,4] catalysis. Our knowledge about the intrinsic mechanisms behind the catalytic phenomena has increased significantly along the years, and theoretical modeling has contributed in a significant way, among other things because it is cheaper and more efficient to model a possible catalyst to explore its efficiency [5][6][7][8][9] than to do its synthesis and to investigate its performance from an experimental viewpoint. In this line, the contributions of N. Russo have been significant. [10][11][12][13][14][15] Nowadays, it seems clear that the effect of a catalyst is to alter the bonding pattern of the reactants, so that the bond cleavages normally occurring along a chemical reaction are facilitated, what leads to a decrease in the activation barriers, which is in the basis of catalysis.In our group, we have devoted specific attention to the bonding distortions associated with non-covalent interactions, which play also a role in catalytic effects, mainly in the realm of homogeneous catalysis. We have shown for instance that the formation of beryllium bonds, defined by the first time back in 2009, [16] in which BeXY derivatives act as strong Lewis acids, lead to a dramatic perturbation of the electron density of the Lewis base interacting with the beryllium derivative. More importantly, these electron density perturbations may lead to cooperative effects when associated with other non-covalent interactions, as the ones stabilizing...

On the nature of the interaction of copper hydride and halide with substituted ethylene and acetylene

“…Density Functional Theory (DFT) was chosen for geometry optimization and vibrational frequencies calculations of the molecules, since previous theoretical works show a good performance for this kind of systems. [14] The geometry of the monomers and complexes under survey has been fully optimized using B3LYP [16,17] functional combined with 6-311G(d,p) basis set. The same level of theory was used to calculate the harmonic vibrational frequencies to confirm that the stationary points found correspond to local minima of the potential energy surface.…”

“…Taking that as antecedent and based on the recent study on fluorinate ethylene and acetylene compounds towards CuF, [14,15] the present study will focus on the study of 2substituted prop-1-ene and prop-1-yne derivatives towards CuX (X=H, F, Cl). The main aim is to explore the impact of substituting of position 2 of the ethylene and acetylene on the interaction between the double/triple bonds and halide/hydride copper.…”