PI,PI-ALLYL, AND TRIMETHYLENEMETHANE COMPLEXES DERIVED FROM ISOBUTYLENE ADSORPTION ON OXYGEN-ACTIVATED AG(110)

In this work the use of atomic oxygen on Ag(110) to synthesize two unusual intermediates, pi-2-methylallyl CH3C(CH2)2(a) and trimethylenemethane C(CH2)3(a), was investigated. Isobutylene (2-methylpropene) (CH3)2C = CH2 adsorbs weakly, without reaction, on clean Ag(110) held at 115 K, desorbing from two overlapping states with binding energies of 9.0 kcal mol-1 (37.9 kJ mol-1) and 11.5 kcal mol-1 (48.1 kJ mol-1), respectively. No multilayer formation is observed at surface temperatures of greater-than-or-equal-to 115 K. Co-adsorption of isobutylene and atomic oxygen on Ag(110) results in C-H bond activation via an acid-base mechanism, a reaction pathway which has been observed previously for acidic alkenes. Surface hydroxyl groups are formed at temperatures as low as 115 K. Although the major products are CO2(g) and H2O(g), a small amount of (CH3)2C = CH2(g) evolves near 310 K. Evidence for the formation of co-adsorbed pi-2-methylallyl CH3C(CH2)2(a) and trimethylenemethane C(CH2)3(a) was obtained by the combined use of temperature-programmed reaction spectroscopy (TPRS) and electron energy loss spectroscopy (EELS).