Carbon–carbon bond forming reactions on Cu(110) surfaces

Abstract

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.

Thermal chemistry of diiodomethane on Ni(110) surfaces II. Effect of coadsorbed oxygen

“…In contrast, the direct coupling of methylene surface species does not involve any hydrogenation-dehydrogenation steps. Coupling such as this is actually more typical of late transition metals [62], and has been reported for methylene on Cu(1 1 0) [63], Pd(1 0 0) [24], and Rh(1 1 1) [27], and for other alkyls on Cu(1 1 1) [64], Ag(1 1 1) [65], and Au(1 1 1) [66], among others.…”

The Chemistry of CH2I2 on MoAl Alloy Thin Films Formed on Dehydroxylated Alumina: Insight into Methylene Insertion Reactions

“…The surface chemistry of diiodomethane has been investigated previously on several transition-metal surfaces including Cu, 24,25 Ag, [26][27][28] Mo, 29,30 Pd, 31,32 Pt, 33 Rh, 34,35 Ru, 36 and Ni. 37,38 Studies have also been performed on Al surfaces.…”

Bond Forming Reactions Involving C1 Moieties: Late Versus Early Transition Metal Surfaces

“…Ethylene production via coupling of methylene is also seen in Fig. 1, which is somewhat surprising since this is a reaction more common on coinage metals [23,52]. When starting from diiodomethane, iodomethane is produced as well on this V(100) surface, an indication that hydrogenation reactions compete kinetically with carbon-halogen dissociation steps.…”

“…The growing alkyl chains can, at each stage of their growth, undergo disproportionation via b-hydride elimination to produce the corresponding alkene, and also reductive elimination with surface hydrogen to yield the appropriate alkane. In the UHV surface-science community this type of chain-growth reaction was first observed in experiments with coadsorbed methyl and methylene groups on copper surfaces [20,52]. In fact, we have reported that such carbon-carbon forming reactions are possible on Ni(110) even when starting with either diiodomethane [25] or iodomethane [42] alone: chain growth to up to C 4 products was observed on that surface (Fig.…”