Influence of Ion Pairing in Inter-Ring Haptotropic Rearrangements in Cationic Cyclopentadienyl Complexes of Ruthenium with Naphthalene: A DFT Investigation

Abstract

DFT calculations have been performed on the naphthalene cationic complex η6-C10H8RuCp+ in the presence of different anions. In a first step, geometry optimization of the PF6 – salt carried out in the presence of 15 solvent molecules for 3 different solvents (methylene chloride, acetone, and water) indicated that ion pairing occurs in the less polar methylene chloride solvent, whereas the ions are separated in the more polar acetone and water. In a subsequent step, the inter-ring haptotropic rearrangement (IRHR) of η6-C10H8RuCp+ has been modeled both as an isolated cation (separated ion pairs (SIP)) and in the presence of a counterion (contact ion pair (CIP)). The IRHR activation barrier is found to be much lower in the CIP case due to the cation–anion interaction, which tends to reduce the metal unsaturation during the process. The size of the anion is also important. Small anions such as BF4 – favor lower barriers. These results should also hold for photochemically induced IRHR processes, since the SIP mechanism involves structurally similar intermediates and transition states.

DFT study of inter-ring haptotropic rearrangement in CpRu+ complexes of polycyclic aromatic ligands

“…PF 6 -). Such ion pairing facilitates the IRHR process, in contrast to what happens in polar solvents where separated ion pairs (SIPs) are formed [11]. Indeed, η 6 η 6 -IRHR is sufficiently rapid (hours) in CH 2 Cl 2 solvent, and extremely slow (weeks) in the much more polar acetone solvent.…”

Chromium Tricarbonyl and Chromium Benzene Complexes of Graphene, Their Properties, Stabilities, and Inter‐Ring Haptotropic Rearrangements – A DFT Investigation

“…[24] The influence of photochemical activation on the course of IRHRs has also been poorly studied, though many ther-96 mally induced reactions have photochemical analogues. It is possible to explain this by the fact that the mechanism for most of these processes might be quite complicated and may involve not just the lowest triplet state.…”

“…[25] Since the semi-empirical work of Albright et al, [26] 101 several quantum chemical investigations, mostly at the DFT level, of η n ,η n -IRHRs have been performed mainly for chromium tricarbonyl complexes of PALs [2,3,5,6,10] and to a considerably lesser extent for other transition metals. [7,8,18,[22][23][24]27,28] As such dynamic behavior could be 106 important for electronics, materials science, and catalysis, we have thoroughly investigated molecular models of chromium complexes of graphene to stimulate experimental investigations of transition-metal complexes of carbon allotropes such as fullerenes, graphites, nanotubes, or 111 graphenes.…”

Microwave‐Assisted Synthesis and Transformations of Cationic CpRu(II)(naphthalene) and CpRu(II)(naphthoquinone) Complexes

“…These observations are in keeping with precedent reports of high activation barriers for interring haptotropic migration in RuCp (polyarene) complexes. [42] Repeated partial dissolution of the [SbF 6 ] salt mixture with 1,2-dichloroethane afforded a sample highly enriched in 17[SbF 6 ] (95 : 5). This allowed crystals of 17[SbF 6 ] for X-ray analysis to be obtained ( Figures 5 and 6).…”