CH bond activation of ethylene by bare neutral palladium and platinum atoms: a theoretical investigation

Abstract

The reactions of bare neutral palladium (Pd) and platinum (Pt) atoms with ethylene on both singlet and triplet surfaces were investigated at B3LYP and CCSD (T) levels of theory. The calculated potential energy profiles clearly show that Pt has higher reactivity than Pd toward ethylene. For both Pd and Pt, the reactions on singlet surfaces are energetically more favorable than those on triplet surfaces. However, notable barriers lie on the singlet and triplet surfaces for Pd +ethylene. This result rationalizes the experimental observation that Pd mainly forms π‐complex with ethylene. But under high‐energy condition, the reaction can proceed to yield dehydrogenation products, Pd‐CCH. and Pd (HCCH). For Pt, triplet‐singlet surface crossing was suggested to occur in the region where Pt forms π‐complex with ethylene to lead the reactions to the energetically more favorable singlet surfaces. For both the two metals, π‐complex and CH bond insertion species are the reaction intermediates and the H.‐elimination products are the final products. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of Supported Pd0 Nanoparticles from a Single-Site Pd2+ Surface Complex by Alkene Reduction

“…of acetylene and a Pd 0 species. [69][70] By calibrating the integrated area (see SI) of each gas-phase product using internal MS response factors, it can be seen that the molar ratio of 1,3-butadiene to H2 is ≈ 1, while the ratio of acetylene to H2 is >> 1, which supports the suggested reduction 80 °C under air in a batch reactor, using trifluorotoluene as the solvent. The conversion ratio is obtained from NMR analysis using an adamantane internal standard.…”

Spectroscopic Characterization of Lanthanum-Mediated Dehydrogenation and C–C Bond Coupling of Ethylene

“…Our predictions are consistent with previous computations for M(C 2 H 4 ) where M = Y, Zr, Nb, Pd, and Pt. 16,24,37,38 Because it exhibits only single electronic transition, the MATI spectrum of La(C 2 H 2 ) must be due to the ionization of one isomer, and this isomer is identified to be the most stable La[η 2 -(HCCH)], which is a metallacyclopropene. For this isomer, a 4 B 1 state is predicted at 11557 cm −1 above the 2 A 1 ground state for the neutral species; a 3 B 1 state is at 52773 cm −1 and a 1 A 1 state at 42018 cm −1 for the cation ion.…”

“…Reactions with neutral metal atoms are more difficult to study experimentally because the reaction products cannot be monitored directly by mass spectrometry. Instead, the reaction products have normally been monitored by laser photoionization detection or the depletion of the metal atoms monitored by laser fluorescence detection. − Like metal ions, reactions with early transition metal atoms normally produce dehydrogenated metal complexes MC 2 H 2 , where M is a transition metal atom, although metal inserted complexes H–M–C 2 H 3 have also been observed. , In spite of the previous experimental measurements on this class of reactions, the structures and electronic states of reaction intermediates and products have largely been from theoretical predictions. − However, a reliable prediction of the electronic states and molecular structures of organotransition metal radicals is complicated by the existence of multiple low-energy structural isomers of each complex and many low-energy states of each isomer. Therefore, a reliable identification of structural isomers and electronic states generally requires the confirmation by spectroscopic measurements, especially high-resolution spectroscopic techniques.…”

Ethylene C–H Bond Activation by Neutral Mn2O5 Clusters under Visible Light Irradiation

“…The calculation result suggests the binding energy (E b ) of Mn 2 O 5 with C 2 H 4 is 0.48 eV, which is smaller than the binding energy of C 2 H 4 with some bare metal atoms (Pd, 1.30 eV; Nb, 0.79 eV; and Pt, 0.74 eV). 49,50 Under 532 nm laser light irradiation, the signal intensity of Mn 2 O 5 (C 2 H 4 ) decreases to about one-half of its original (no radiation) value (see Figure 1c), while a new mass peak Mn 2 O 5 H 2 is observed. The intensity of Mn 2 O 5 H 2 does not increase when the light irradiation laser energy is higher than 25 2a), respectively.…”