Experimental and theoretical probes of the structure of oxametallacycle intermediates derived from 1-epoxy-3-butene on Ag(110)

Near edge x-ray absorption fine structure (NEXAFS) and density functional t heory (DFT) calculations have been applied to study the interaction of 1-ep oxy-3-butene (EpB) with the Ag(110) surface. Three EpB adsorption states ha ve been identified: a multilayer state stable to 165 K, a chemisorbed EpB s tate stable to 215 K, and a highly stable oxametallacycle intermediate stab le to nearly 500 K. Carbon K-edge NEXAFS spectra for EpB multilayers are in excellent agreement with the time-dependent excitation spectrum calculated by DFT for the EpB molecule, permitting detailed analysis of the excited s tate orbital structure. This combined experimental/theoretical approach ind icates that chemisorbed EpB is weakly bonded to the surface with its vinyl group oriented at a small angle to the surface. NEXAFS spectra obtained at normal and glancing incidence for the oxametallacycle intermediate are full y consistent with the DFT-predicted geometry of this intermediate. These re sults demonstrate the importance of both theory and experiment in determini ng the identity, structure, and reactivity of complex surface intermediates such as these recently discovered oxametallacycles.