Comparative electronic analysis between hydrogen transfers in the CH_4/CH_3~+, CH_4/CH_3·, and CH_4/CH_3~- systems: on the electronic nature of the hydrogen (H~-, H~·, H~+)being transferred. II. Analysis of electron-pair interactions from intracule

摘要

The nature of the hydrogen transferred in theCH_3/CH_4~+, CH_3/CH_4~˙, and CH_3/CH_4~- systems isinvestigated by analyzing the topology of the contractedintracule and extracule electron-pair densities and theirrespective Laplacians. The CH_3/CH_4~+, CH_3/CH_4~˙,and CH3ICH4- systems are taken as simple models for the studyof hydride (H~-), hydrogen (H˙), and proton (H~+) transferreactions, respectively, under a constrained C-C distance. Thestudy is focused on the comparison of the intracule andextracule densities at the intermediate structures for the three H-transfer reactions, complementing a previous investigation ofthe same model reactions based on the analysis of one-electrondensities. The results obtained by analyzing the contractedelectron-pair densities are consistent with those obtained fromthe analysis of one-electron densities. The electronic nature ofthe H atom being transferred in the three systems can bedifferentiated by the topologies of the corresponding intraculeand extracule densities. However, the analysis underlies also thedifficulties to interpretation of the topologies of contractedelectron-pair densities, as different electron-electron interactionsmay contribute to the same point in the intracule or extraculespaces. In particular, for the systems studied, the contribution ofthe electron-electron interaction associated to the probability ofhaving two electrons on the H being transferred is not reflectedseparately neither in the intracule nor in the extraculedistributions. Nevertheless, the nature of the H being transferredcan still be studied by comparing the importance of the electron-electron interactions associated to the probability of having oneelectron in C and one in the transferring H. The effects ofinclusion of electron correlation are also discussed by means of(HF-CISD//HF) intracule and extracule density difference maps.