CARBON CARBON BOND FORMING REACTIONS ON CU(110) SURFACES

The coupling of one-carbon (C1) fragments to form carbon-carbon bonds has been studied on a Cu(110) surface. In these studies, methyl (CH3) and methylene (CH2) groups have been generated on Cu(110) by the dissociative adsorption of CH3I and CH2I2, respectively. Formation of CH3(a) below 200 K on this surface is inferred from the lack of molecular desorption as well as the lack of recombinative hydrogen desorption in temperature-programmed reaction (TPR) experiments. Similar low temperature C-I bond dissociation in CH2I2 to form CH2(a) is implicated based on the evolution of ethylene at 300 K in TPR studies. By studying the reactions of CD3(a) and CH2(a) coadsorbed and adsorbed separately on Cu (110), three C-C bond forming reactions have been identified: methyl coupling above 400 K to form ethane, methylene coupling at approximately 300 K to form ethylene, and methyl/methylene coupling (methylene insertion) at 300-350 K to produce ethyl groups. To our knowledge, this is the first time that methylene insertion, a potentially important chain growth step in hydrocarbon syntheses, has been definitively established on metal surfaces.