Metal-acetylene binding in gaseous WC2H2+

The binding energy between W+ and C2H2 in gaseous WC2H2+ has been investiga ted by photodissociation in the cell of a Fourier transform ion cyclotron r esonance spectrometer, and by quantum-chemical calculations. It is found th at the only low-energy structure of WC2H2+ is a metallacyclopropene, which dissociates only to bare W+ and C2H2 under visible irradiation. The binding energy determined both experimentally and theoretically is 3.3 +/- 0.4 eV, significantly larger than any of the previously determined metal-acetylene bond energies in the gas phase. The experimental value is determined from both single- and two-photon dissociation thresholds. No absorption is detec ted below 1.5 eV of photon energy, in reasonable agreement with the first a llowed transitions being calculated at 1.1 and 1.5 eV. (C) 1998 Elsevier Sc ience B.V. All rights reserved.