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Quantum chemical calculations using BP86 with TZ2P basis sets were carried out to elucidate the structures and the bond-bond dissociation energies of the donor-acceptor complexes [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] with X = H, F, Cl, Br, I; E = B, Al, Ga, In, Tl; and M = Ni, Pd, Pt. The nature of the metal-ligand bond was investigated with an energy decomposition analysis. The geometry optimizations gave for most compounds T-shaped structures with nearly linear P-M-P angles where the [EX.sub.3] ligand has either a staggered or eclipsed conformation with respect to the PMP plane. The energy differences between the conformations are very small which means that there is nearly free rotation about the [M-EX.sub.3] axis. The equilibrium structures of eight nickel compounds have a distorted geometry where one E-X bond is engaged in attractive interactions with the metal atom which yields a distorted square-planar arrangement of the metal atom. The complex [[(P[Me.sub.3]).sub.2]Ni-Tl[I.sub.3]] exhibits two attractive interactions between Tl-I bonds and the metal which features a five-coordinated metal atom. The calculated bond dissociation energies show that the boron complexes exhibit a different trend for the [D.sub.e] values than the heavier group-13 homologues. The results for the Pd and Pt complexes suggest that the [[(P[Me.sub.3]).sub.2][M-BX.sub.3]] bond strength increases with F < Cl < Br < I < H which means that the [BH.sub.3] ligands are the most strongly bonded Lewis acids and [BF.sub.3] is the most weakly bonded species . The trend for the heavier group-13 complexes [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] where E = Al, Ga, In, Tl follows the opposite order F > Cl > Br > I > H. The energy decomposition analysis of the [M-EX.sub.3] bonds indicates a substantial π contribution of between 12.7% and 30.3% to the total orbital interactions. There is no direct correlation between the strength of the orbital interactions or any of the other energy terms Δ[E.sub.elstat] or Δ[E.sub.Pauli] which correlates with the total interaction energy. The bond dissociation energy of the [EX.sub.3] ligands after breaking the [M-EX.sub.3] bonds is quite large. It is shown that the intrinsic strength of the [M-EX.sub.3] bonds is much larger than the BDEs and that the trends of Δ[E.sub.int] and [D.sub.e] are not always the same. The [EX.sub.3] ligands in [[(P[Me.sub.3]).sub.2][M-BX.sub.3]] always carry a large negative charge. Key words: density functional calculations, bonding analysis, Lewis acids, transition metal complexes, reversed DCD model. On a effectue des calculs de mecanique quantique BP86 a l'aide d'ensembles de base TZ2P dans le but d'elucider les structures et les energies de dissociation de liaison des complexes donneur-accepteur [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] dans lesquels X = H, F, Cl, Br, et I; E = B, Al, et Ga, In, Tl; et M = Ni, Pd, et Pt. On a etudie la nature de la liaison metal-ligand par le biais d'une analyse de l'energie de decomposition. Les optimisations de la geometrie conduisent, pour la plupart des composes, a des structures en forme de T avec des angles P-M-P pratiquement lineaires, dans lesquels le ligand [EX.sub.3] se trouve dans une conformation decalee ou eclipsee par rapport au plan PMP. Les differences d'energie entre les conformations sont tres faibles, ce qui implique qu'il existe une rotation pratiquement libre autour de l'axe [M-EX.sub.3]. Les structures a l'equilibre dans les neuf composes du nickel comportent toutes une geometrie deformee dans laquelle une liaison E-X est engagee dans des interactions attractives avec l'atome metallique ce qui conduit a un arrangement plan carre deforme de l'atome metallique. Le complexe [[(P[Me.sub.3]).sub.2]Ni-Tl[I.sub.3]] presente meme deux interactions attractives entre les liaisons Tl-I et le metal qui comporte un atome de metal pentacoordonne. Les energies de dissociation de liaison calculees montrent que les complexes de bore presentent une tendance differente pour les valeurs [D.sub.e] que les homologues plus lourds du groupe 13. Les resultats pour les complexes du Pd et du Pt suggerent que la force de la liaison [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] augmente avec F < Cl < Br < I < H, ce qui signifie que les ligands [BH.sub.3] sont les acides de Lewis les plus fortement lies et que les especes [BF.sub.3] participent aux liaisons les plus faibles. La tendance pour les complexes plus lourds du groupe 13 [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] dans lesquels E = Al, Ga, In et Tl conduit a l'ordre inverse F > Cl > Br > I > H. L'analyse de l'energie de decomposition des liaisons [M-EX.sub.3] met en evidence la presence d'une contribution π importante, allant de 12,7 % a 30,3 % des interactions or bitalaires totales. Il n'existe aucune correlation directe entre la force des interactions orbitalaires ou l'un des autres termes d'energie, tel Δ[E.sub.elstat] ou Δ[E.sub.Pauli] et l'energie totale d'interaction. L'energie de dissociation de la liaison des ligands [EX.sub.3] apres le bris des liaisons [M-EX.sub.3] est tres elevee. On a demontre que la force intrinseque des liaisons [M-EX.sub.3] est beaucoup plus elevee que les BDE et que les tendances des Δ[E.sub.int] et [D.sub.e] ne sont pas toujours les memes. Les ligands [EX.sub.3] dans les complexes [[(P[Me.sub.3]).sub.2][M-EX.sub.3]] portent toujours une forte charge negative. Mots-cles : calculs de la fonctionnellle de la densite, analyse de liaison, acides de Lewis, complexes de metaux de transition, modele DCD inverse. [Traduit par la Redaction], Introduction The chemical bonds in donor-acceptor complexes of transition metals with main-group ligands are usually described using the Dewar-Chatt-Duncanson (DCD) model (1) where the ligand, being a Lewis base, serves [...]

The self-reaction of state-selected HCl+ (DCl+) ions with HCl has been investigated in a guided ion beam setup. The absolute cross sections for proton transfer and deuteron transfer decrease with increasing center of mass collision energy, Ec.m.. The cross section for charge transfer (DCl+ + HCl) exhibits a maximum at Ec.m. = 0.5 eV. The cross section for PT and DT decrease significantly with increasing rotational angular momentum in the molecular ion, for the PT the cross section increases again for the highest angular momentum investigated. The rotational dependence of the cross section is rationalized by a simple model in which both the collision energy and part of the rotational energy are available for the reaction. The contribution of the rotation to the total energy available itself depends on the collision energy. [ABSTRACT FROM AUTHOR]

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