Reactions of neutral palladium atoms in the gas phase: formation of stable palladium(alkane) complexes at 300 K

Abstract

The authors and others are surveying the gas-phase reactivity of bare neutral transition metal atoms with alkanes and alkenes. In the 3d series, none of the neutral atoms reacts with alkanes at 300 K, and only Sc, Ti, V, and Ni react with alkenes. Here the authors report state-specific kinetics data for the 4d series. The 4d[sup 10] ([sup 1]S[sub 0]) ground state of the Pd atom reacts rapidly with ethylene, propylene, cyclopropane, and 1-butene and moderately rapidly with ethane, propane, and n-butane at 300 [+-] 5 K in 0.5-0.8 Torr of He. The latter are apparently the first clear-cut examples of gas-phase chemistry between a neutral ground-state transition metal atom and an alkane. Earlier gas-phase studies of Pd reactivity with CH[sub 4] found no reaction of the Pd atom and very slow reaction of the clusters Pd[sub x], x [le] 2. CH[sub 4] is inert to Rh atoms and to Fe atoms. The ground-state Pt atom might react with CH[sub 4], n-hexane, and cyclohexane, but interpretation was complicated by the possible presence of excited-state atoms or of multiphoton ionization and fragmentation. 20 refs., 1 fig., 1 tab.