The formation of carbon-carbon bonds mediated by metal surfaces and nanoparticles continues to attract considerable attention. [1,2] Recent work on the interaction of allyl halides (C 3 H 5 X) with a range of metal surfaces revealed different reactivity that depends on both the metal as well as the halide. [3, 4] Of all the metal surfaces examined, silver surfaces appear to be the most effective at mediating carbon-carbon bond coupling of allyl halides to give 1,5-hexadiene. Two distinct pathways have been observed: [4a] 1) dissociative adsorption of C 3 H 5 X to give surface-bound allyl groups, which then undergo coupling, and 2) a coupling reaction between C 3 H 5 X and a surface-bound allyl group. Surface defects play a significant role in the selectivity of 1,5hexadiene formation which increases from 20 % to greater than 60 % when chlorine atoms are preadsorbed on silver surfaces. [4b] Also of interest are the largely forgotten results of Tamura and Kochi, [5] who synthesized silver nanoparticles over 30 years ago and showed that they reacted with allyl bromide to give 1,5-hexadiene and silver bromide [Eq. ( 1)].
Here we describe the gas-phase assembly of the subvalent silver hydride cluster [Ag 4 H] + [6] and its subsequent ionmolecule reactions with allyl bromide.