Gas Phase Activation of Methane Molecule with Lead Benzene Dication Complex Ion, [Pb(Benzene)₂]²⁺

Abstract

Motivated by the search for ways of a more efficient usage of the ubiquitous, and unexploited resources of methane, recent progress in the gas-phase activation of methane by metal dication complex ion is discussed. The gas phase theoretical and experimental analysis on [Pb(Benzene) 2 ] 2+ was conducted. The [Pb(Benzene) 2 ] 2+ complex ions were prepared using a combination of the pick-up technique and high energy electron impact, and then held in a cold ion trap. Excitation with tuneable UV radiation resulted in the formation of [Pb(Benzene) 2 (H 2 O)] 2+ , [Pb(Benzene) 2 (H 2 O) 2 ] 2+ , [Pb(Benzene)] + , Pb + and Benzene + ions when the experimental results were analysed. The two optimised geometries of [Pb(Benzene) 2 ] 2+ namely the C 2V eclipse and C 2 staggered were observed. Methane activation of [Pb(Benzene) 2 ] 2+ complex ion yielded [Pb(Benzene) 2 (Me)] 2+ . [Pb(Benzene) 2 (H 2 O)(Me) 2 ] 2+ , [Pb(Benzene) 2 (H 2 O)(Me)] 2+ , [PbBenzene(Me) 3 ] 2+ and [Pb(Benzene)(Me)] 2+ . The PEC calculated binding energy of methane to lead benzene dication complex ion was approximately 25.45% higher than the value recorded on DFT calculation. This difference was due to the charge differences on the lead metal centre. While the actual calculated charge on the Pb metal in the optimised geometry was 1.68 the charge of +2 on the Pb metal was considered in the PEC calculation.