Crossed beams studies of Mo(a 7S3) and Mo*(a 5S2) collisions with CH4 and C2H6

Abstract

The interactions of Mo(a 7S3) and Mo*(a 5S2) with methane, CH4, and ethane, C2H6, were studied under single collision conditions using the crossed molecular beams technique. Ground state Mo(a 7S3) atoms were found to be unreactive at all collision energies studied up to 〈Ecoll〉=35.4 kcal/mol. Nonreactive scattering of Mo(a 7S3) with methane and ethane was studied and compared to collisions with Ne and Ar. A forward peaking center-of-mass angular distribution, T(Θ), was necessary to simulate the elastic collisions with inert gases as well as inelastic collisions with the alkanes. At a collision energy of 14.4 kcal/mol with CH4 and 21.0 kcal/mol with C2H6, inelastic collisions were found to transfer ∼10% and ∼19% of the initial kinetic energy into alkane internal energy, respectively. For collisions of Mo*(a 5S2)+CH4, the dehydrogenation product, MoCH2, was observed at all collision energies studied down to 2.1 kcal/mol. The reaction Mo*(a 5S2)+C2H6→MoC2H4+H2 was observed down to 〈Ecoll〉=4.5 kcal/mol. For a given total energy (electronic+translational), it was found that electronic energy is highly effective in promoting this reaction whereas translational energy is ineffective.

C–C versus C–H bond activation of propyne by Y: A DFT study

“…Experimental studies indicate that the reactions of ground state Y( 2 D), Zr( 3 F), Nb( 6 D) and Mo * with hydrocarbons generally yield the C-H insertion products or dehydrogenation products [7][8][9][10], whereas C-C bond activation has only been observed in select cases, such as the reactions of Y with cyclopropane and propene [3,13,15]. The factors which lead to strong preference for C-H insertion have elucidated [13].…”

“…In the past decade, crossed molecular beam (CMBs), kinetic techniques and theoretical calculations have been carried out to study the reactions of transition metal atoms with small hydrocarbons in gas phase [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Experimental studies indicate that the reactions of ground state Y( 2 D), Zr( 3 F), Nb( 6 D) and Mo * with hydrocarbons generally yield the C-H insertion products or dehydrogenation products [7][8][9][10], whereas C-C bond activation has only been observed in select cases, such as the reactions of Y with cyclopropane and propene [3,13,15].…”

A DFT study on the mechanism of the gas phase reaction of ground-state Y (4d15s2,2D) with 2-butyne

“…In these studies, the groundstate Y ( 2 D), Zr( 3 F), Nb ( 6 D) and Mo ( 7 S) were found to be able to activate CAH bonds in hydrocarbons containing three or less carbon atoms, generally yielding dehydrogenation products [7][8][9][10], whereas CAC bond activation products were only observed in selected cases, such as the reactions of propene and cyclopropene [3,13,15]. Previous theoretical studies [13,16,17] on the reactions of Y and Zr with ethene and ethyne proposed that the formation of the dehydrogenation products involves initial insertion of metal atom into a CAH bond, followed by concerted or stepwise H-migration, leading to elimination of H 2 .…”

“…In the past decade, a number of experimental and theoretical studies have been carried out to investigate the reactivity of neutral transition metal atoms, such as Y, Zr, Nb and Mo, toward small hydrocarbons in gas phase [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In these studies, the groundstate Y ( 2 D), Zr( 3 F), Nb ( 6 D) and Mo ( 7 S) were found to be able to activate CAH bonds in hydrocarbons containing three or less carbon atoms, generally yielding dehydrogenation products [7][8][9][10], whereas CAC bond activation products were only observed in selected cases, such as the reactions of propene and cyclopropene [3,13,15].…”

Reactions of Neutral Gas-Phase Yttrium Atoms with Two Cyclohexadiene Isomers

“…7−11 We have studied reactions of ethylene, 11 acetylene, 11 cyclopropane, 12 propene, 12 four butene isomers, 13 propyne, 14 and 2-butyne. 14 In our studies of the methane and ethane reactions, only products from cleavage of C−H bonds were observed, 5,6 while reactions with the larger hydrocarbons also yielded product channels resulting from cleavage of C−C bonds. 12−14 Experimentally measured branching ratios for these reactions have, in some cases, shown the C−C bond cleavage products to be dominant.…”