On the dissociation energy of Ti(OH₂)⁺. An MCSCF, CCSD(T), and DFT study

Abstract

The dissociation energy of the Ti(OH,)+ ion-molecule complex was calculated by the multiconfigurational selfconsistent field theory, coupled cluster theory, and two density functional theory based methods, using both all-electron basis sets and effective core potentials. The calculations show that approximate density functional theory gives results in better agreement with experiment than either the multiconfigurational self-consistent field theory or the coupled cluster theory, with both allelectron basis sets and effective core potentials. Nevertheless, the optimized geometries and harmonic vibration frequencies are very similar, irrespective of the level of theory used. The interconfigurational energy ordering of the two valence electronic configurations dn-'s and dn-'s' of the 4~ electronic state of the titanium cation were also calculated and are discussed.Key words: ab initio, dissociation energy, ion-molecule complex, effective core potentials, transition metals.Resume : On a calculC l'knergie de dissociation du complexe ion-molCcule, Ti(OH,)+, a I'aide de la thCorie de champ autocohCrent rnulticonfigurationnel, de la thCorie de I'agrCgat couplt et de deux mCthodes basCes sur la thCorie de la densite fonctionnelle, utilisant des ensembles de base de tous les Clectrons ainsi que tous les potentiels effectifs des noyaux. Les calculs montrent que la theorie approximative de la densit6 fonctionnelle conduit h des rksultats qui sont en meilleur accord avec les donnCes expkrimentales que ceux obtenus a I'aide tant de la thCorie du champ autocohkrent multiconfigurationnel que de la thCorie de l'agrCgat coup16 incorporant les ensembles de base de tous les Clectrons ainsi que tous les potentiels effectifs des noyaux. NCanmoins, les gComCtries optimisCes et les frCquences de vibration harmonique sont trks semblables, quel que soit le niveau de la thCorie utilist. On a aussi calculC l'ordre des Cnergies interconfigurationnelles des deux configurations Clectroniques de valence dn-'s et dn-,s' de 176tat Clectronique 4~ des cations du titane et on en discute.

Two State Reactivity Paradigm in Catalysis. The Example of XH (X = O, N, C) and CC Bonds Activation Mediated by Transition Metal Compounds

“…This conclusion is slightly different from that made by the Calabria [58,[72][73][74][75][76] and Donostia [59,[61][62][63][64] groups upon investigating the reaction of first-row transition metal cations with XaH (X ¼ O, N, C) prototypical bonds. The most relevant difference appears to be the energy gap between quintet and septet states of the HaMn þ aNH 2 intermediate that are almost degenerate at the CCSD(T)// B3LYP level, whereas the gap is 12 kcal mol À1 at the B3LYP/DZVP level.…”

“…Detailed PES calculations for the reaction of water with the entire series of first-row transition metal ions have been performed by Ugalde and coworkers [59,[61][62][63][64]. They have reported similar PESs for all first-row transition metal atoms.…”

Noncovalent metal-ligand bond energies as studied by threshold collision-induced dissociation

“…However, strong variations in the bond energies across the row indicate that other effects are also in¯uential. These variations can be understood by considering the electronic con®guration of each of the metal ions (Rosi & Bauschlicher, 1989Armentrout, 1995;Irigoras et al, 1996Irigoras et al, , 2000Irigoras, Fowler & Ugalde, 1998, 1999a.…”

Concepts of metal-mediated methane functionalization. An intersection of experiment and theory

“…The peculiarities of the reactions of FeO + with CH 4 , and also with H 2 , as well as the strikingly different product distribution for different binary metal-oxide cations (see Table 2) has initiated an "explosion" of computational activities [69,[71][72][73][74][75][76][77][78][79][80][81][82] that eventually resulted in a new paradigm for the metal-mediated oxygenation of hydrocarbons: the two-state reactivity (TSR) concept [77,83,84]. The essence of a TSR scenario is depicted in a simplified manner [85] in Scheme 4 for the reaction of an alkane (RH) with bare FeO + , and the following features are worth mentioning in the present context.…”