C-X bond reactivity in the catalytic hydrodehalogenation of haloarenes over unsupported and silica supported Ni

Hydrodehalogenation over Ni/SiO2 follows the order fuorobenzene > chlorobenzene > bromobenzene > iodobenzene. Catalyst activation is monitored by on-line TG/MS (see representative profile) with pre-/post-reaction characterization that links loss of catalyst activity to disruption of H2/catalyst interactions. Debromination of 1,3-bromochlorobenzene exceeded dechlorination as a result of Cl/Br exchange.