The coupling of one-carbon (C]) fragments to form carbon-carbon bonds has been studied on a Cu(11O) surface. In these studies, methyl (CH 3 ) and methylene (CH 2 ) groups have been generated on Cu( 110) by the dissociative adsorption of CH3I and CH 2 I 2 , respectively. Formation of CH 3 (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 CH 2 I 2 to form CH 2 (a) is implicated based on the evolution of ethylene at 300 K in TPR studies. By studying the reactions of CD 3 (a) and CH 2 (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 -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.
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