Surface organometallic chemistry on metals applied to the environment: Hydrogenolysis of AsPh₃ with nickel supported on alumina

The reaction of AsPh₃ with Ni/Al₂O₃ at 100 to 200°C under 6 to 30 bars of hydrogen has been followed by kinetic analysis of both the consumption of AsPh₃ and the evolution of benzene and cyclohexane as well as magnetic and XRD measurements of the metallic and intermetallic phase(s). The reaction proceeds via complete hydrogenolysis of the As-Ph bonds, with final formation of a well-characterized NiAs alloy (XRD). The mechanism of alloy formation is complex: at low coverage of the nickel surface, stepwise hydrogenolysis of the As-Ph bonds leads to the formation of the surface organometallic fragments Ni_s[AsPh_x]_y (kinetic studies and analytical data). Further hydrogenolysis of these fragments progressively leads to the formation of arsenic "adatoms" which quickly migrate inside the nickel particles to form NiAs_0.45 amorphous intermetallic phases (XRD and magnetic measurements). The reaction then proceeds slowly up to the As/Ni ratio of unity with formation of the crystalline NiAs "nickeline" phase (XRD).