Periodic Trends in Reactions of Benzene Clusters of Transition Metal Cations, M(C₆H₆)_1,2⁺, with Molecular Oxygen

Abstract

Mono- and bis-adducts of benzene of the type M(C6H6)1,2 + have been generated in the gas phase with first-, second-, and third-row transition metal cations, and their reactivities toward molecular oxygen have been measured using an inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Trends in reactivity were identified for the metal cation adducts across and down the periodic table. The intrinsic effect of the benzene ligand(s) on the reactivity of the bare metal cations was determined through comparisons with earlier results obtained for the bare metal ions. Molecular oxygen activation by early transition metal cations is preserved in the presence of one benzene ligand but almost disappears in the presence of two benzene molecules. The rate coefficients for O2 addition to late transition metal−benzene adducts are enhanced by up to 4 orders of magnitude in the presence of benzene. Thermochemical information is derived from the occurrence or absence of ligand-switching or metal-abstraction reactions. Oxidation of the benzene ligand itself was observed to be mediated by the transition metal cations V+, Cr+, Fe+, Co+, and Re+ and appeared to result from simultaneous activation of C−H, C−C, and O−O bonds. Catalytic oxidation of the benzene ring observed in the presence of Fe+, Cr+, and Co+ is postulated to result in the production of catechol.

Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity

“…These distributions have been derived from available optical spectra 35,36 and reported by us previously for the two electronic spin states with the highest population at 5500 K. 4 Energy levels as high as 3.7 eV (3 × 10 4 cm -1 ) were included in the calculations. The calculations show that excited states of the main-group elemental cations except Ba + are high in energy and contribute little (never more than 10%) to the total ion population at 5500 K. The ground 2 The ions emerging from ICP are injected through a differentially pumped sampling interface into a quadrupole mass spectrometer and, after mass analysis, introduced through an aspirator-like interface into flowing helium carrier gas at 0.35 ( 0.01 Torr and 295 ( 2 K. The ions are allowed to react with added D 2 O a few milliseconds downstream of the flow tube.…”

“…Our multi-collision induced dissociation technique, 48 which involves simply raising the potential of the sampling nose cone, did not yield bond cleavage for MO 2 + and so did not provide bond connectivity information. But, based on the elemental composition, three different bonding isomers are possible: the end-on metal dioxygen complex I, MOO + , the side-on complex II, c-MO 2 + , and the inserted metal dioxide complex III, OMO + .…”

“…Reactions of heavy water, D 2 O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca.…”

Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations

“…Consequently, a late transition state should be expected for these processes. Through transition structure TS2, the intermediate C 1 transforms into intermediate C 2 . This complex has C s symmetry, except for the Mg + + CH 3 X reactions where the C 2 complex shows C 3v symmetry.…”

Reactions of Laser Ablated Metal Plasma with Molecular Alcohol Beams: Dependence of the Produced Cluster Ion Species on the Beam Condition

“…The probable pathways for the formation of the protonated water-methanol clusters are the combination of methanol with protonated water to arise from the multi-collision of the metal plasma and the methanol, and the intra-cluster elimination of a neutral dimethyl ether CH 3 …”