Surface Chemistry and Decarbonylation of Molybdenum Hexacarbonyl on Thin Alumina Films

Kaltchev, M.

doi:10.1006/jcat.2000.2880

Cited by 31 publications

(17 citation statements)

References 43 publications

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“…15,16 Reflection-absorption infrared spectroscopy (RAIRS) spectra were collected from a Pd(111) singlecrystal sample mounted in a modified 2 3 / 4 in. six-way cross equipped with infrared-transparent, KBr windows.…”

Section: Methodsmentioning

confidence: 99%

Requirements for the Formation of a Chiral Template

et al. 2004

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The chemisorptive enantioselectivity of propylene oxide is examined on Pd(111) surfaces templated by chiral 2-methylbutanoate and 2-aminobutanoate species. It has been found previously that chiral propylene oxide is chemisorbed enantiospecifically onto Pd(111) surfaces modified by either (R)-or (S)-2-butoxide. The enantiomeric excess (ee) varied with template coverage, reaching a maximum of ∼31%. Templating the surface using 2-methylbutanoate, where the chiral center is identical to that in the 2-butoxide species, but is now anchored to the surface by a carboxylate rather than an alkoxide linkage, shows no enantiospecificity. The enantioselectivity is restored when the methyl group is replaced by an amine group, where a maximum ee value of ∼27% is found. DFT calculations and infrared measurements suggest that the structures of the butyl group on the surface are similar for both 2-butoxide and 2-methylbutanoate species, implying that gross conformational changes are not responsible for differences in chemisorptive enantioselectivity. There is no clear correlation between the location of the chiral center and enantioselectivity, suggesting that differences in the template adsorption site are also not responsible for the lack of enantioselectivity. It is proposed that the 2-butyl group in 2-methylbutanoate species is less rigidly bonded to the surface than that in 2-butoxides, allowing the chiral center to rotate azimuthally. It is postulated that the role of the amino group in 2-aminobutanoate species is to anchor the chiral group to the surface to inhibit azimuthal rotation.

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Section: Methodsmentioning

confidence: 99%

Requirements for the Formation of a Chiral Template

et al. 2004

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“…The CO from the strongly bound surface species desorbs in two states in temperature-programmed desorption (TPD) with a profile that is very similar to that found on high-surface-area substrates. This strongly bound species has been identified on aluminas with various degrees of hydroxylation as an oxalate species, which decomposes by desorbing CO at ∼320 and 430 K [28,30,31]. Unfortunately, because of the kinetic competition between carbonyl desorption at ∼250 K and decomposition to form the surface species, only relatively small molybdenum coverages (a few percent of a monolayer) can be achieved in ultrahigh vacuum.…”

Section: Introductionmentioning

confidence: 98%

“…The interaction between molybdenum hexacarbonyl and alumina thin films has been studied in ultrahigh vacuum (UHV) by us [28][29][30][31] and others [32]. Mo(CO) 6 desorbs molecularly from the surface below ∼250 K and also reacts to form strongly bound species, where these reaction pathways compete [28,30]. The CO from the strongly bound surface species desorbs in two states in temperature-programmed desorption (TPD) with a profile that is very similar to that found on high-surface-area substrates.…”

Section: Introductionmentioning

confidence: 99%

“…Second, it potentially allows the formation of novel surface structures that would not otherwise be accessible by evaporating a metal onto the surface. The interaction between molybdenum hexacarbonyl and alumina thin films has been studied in ultrahigh vacuum (UHV) by us [28][29][30][31] and others [32]. Mo(CO) 6 desorbs molecularly from the surface below ∼250 K and also reacts to form strongly bound species, where these reaction pathways compete [28,30].…”

Section: Introductionmentioning

confidence: 99%

“…The resulting surface species are relatively inactive in UHV. Complete decarbonylation of the carbonyl typically occurs at or below ∼600 K [28][29][30][31]37]. It is therefore possible to deposit pure Mo particles on the surface at a substrate temperature higher than 600 K. However, since the resulting molybdenum easily dissociates CO, pure metal deposition is generally difficult.…”

Section: Introductionmentioning

confidence: 99%

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Interaction of molybdenum hexacarbonyl with metallic aluminum at high temperatures: Carbide and alloy formation

Wang

Gao

2005

Journal of Molecular Catalysis A: Chemical

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Supported Organotransition Metal Compounds

Hanson¹

2005

Encyclopedia of Inorganic Chemistry

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Supported transition metal complexes were first prepared in the 1960s as a potential method for the immobilization of homogeneous catalysts. Although this goal is yet to be commercially realized, the chemistry of supported complexes has given insight to the preparation of heterogeneous catalysts as, for example, in the use of discrete metal complexes as precursors to heterogeneous polymerization catalysts. The purpose of this article is to review the general methods for the immobilization of transition metals with examples of each type of immobilization technique.

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Surface Chemistry and Decarbonylation of Molybdenum Hexacarbonyl on Thin Alumina Films

Cited by 31 publications

References 43 publications

Requirements for the Formation of a Chiral Template

Requirements for the Formation of a Chiral Template

Interaction of molybdenum hexacarbonyl with metallic aluminum at high temperatures: Carbide and alloy formation

Supported Organotransition Metal Compounds

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