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Volumn 112, Issue 19, 2008, Pages 7477-7485

Reactivity of binuclear tantalum clusters on silica: Characterization by transient time-resolved spectroscopy

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EID: 44449164098     PISSN: 19327447     EISSN: 19327455     Source Type: Journal    
DOI: 10.1021/jp074910f     Document Type: Article
Times cited : (8)

References (47)
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    • 2 treatment.
    • 2 treatment.
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    • Wyckoff, R. W. G, Ed, 2nd ed, Wiley: New York
    • Wyckoff, R. W. G., Ed. Crystal Structures, 2nd ed.; Wiley: New York, 1963; Vol. 1, p 16.
    • (1963) Crystal Structures , vol.1 , pp. 16
  • 19
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    • The Ta, Ta bond distance determined by EXAFS spectroscopy for this sample under vacuum is 2.94 Å, which is substantially longer than the Ta, Ta bond length of 2.74 Åobserved for the sample at steady state in the presence of H2. The bond length contraction of 0.2 Åwith respect to the sample under vacuum is attributed to the presence of H 2. Contact of H2 with a closely related sample, SiO 2-supported clusters that were, on average, tritantalum, also causes a Ta, Ta bond length contraction; the change in the bond length is attributed to an increase in the number electrons in metal- metal bonding orbitais of the clusters. The Ta, Ta bond length contraction observed for the binuclear clusters in this work also suggests an increase in the number of electrons in the metal, metal bonding orbitais and further supports our inference that the bond characterized by a distance of 2.74 Å is representative of a Ta=Ta double bon
    • 2-supported tantalum clusters is a reaction involving two electrons associated with metal - metal bonding. This pattern differs from what is observed for group 7 and group 8 metals, for which the metal - metal bond length relaxes in the presence of hydrogen.
  • 20
    • 53649092271 scopus 로고    scopus 로고
    • The lack of confidence in the Ta, Si contribution is not associated primarily with the error generated by the scatter in me data, but is associated instead primarily with the difficulty in choosing an appropriate fitting reference. The lack of an appropriate reference compound that closely approximates the interface between silica and a tantalum cluster gives rise to the lack of confidence in the results for this contribution
    • The lack of confidence in the Ta - Si contribution is not associated primarily with the error generated by the scatter in me data, but is associated instead primarily with the difficulty in choosing an appropriate fitting reference. The lack of an appropriate reference compound that closely approximates the interface between silica and a tantalum cluster gives rise to the lack of confidence in the results for this contribution.
  • 28
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    • Negligible H2 spillover occurs on blank SiO2
    • 24
    • , vol.24
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    • The position of this band was identified in a blank experiment as the spectrum of gas-phase ethylene
    • The position of this band was identified in a blank experiment as the spectrum of gas-phase ethylene.
  • 32
    • 53649083484 scopus 로고    scopus 로고
    • The EXAFS data were not sufficient to detect both the decrease of the Ta, Ta coordination number and the increase in the Ta, C coordination number simultaneously, because inclusion of both shells in the data analysis exceeds the statistically justified number variables that can be used in the fitting process
    • The EXAFS data were not sufficient to detect both the decrease of the Ta - Ta coordination number and the increase in the Ta - C coordination number simultaneously, because inclusion of both shells in the data analysis exceeds the statistically justified number variables that can be used in the fitting process.
  • 33
    • 53649084545 scopus 로고    scopus 로고
    • 32 Our data are not sufficient to resolve the influences on the observed changes in the intensity of the white line.
    • 32 Our data are not sufficient to resolve the influences on the observed changes in the intensity of the white line.
  • 36
    • 53649103430 scopus 로고    scopus 로고
    • If large amounts of alkene intermediates would accumulate during alkane disproportionation, we would expect cluster fragmentation to occur; a key parameter that determines whether fragmentation occurs is the ratio of alkene to tantalum during catalysis
    • If large amounts of alkene intermediates would accumulate during alkane disproportionation, we would expect cluster fragmentation to occur; a key parameter that determines whether fragmentation occurs is the ratio of alkene to tantalum during catalysis.
  • 43
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    • Villars, P, Calvert, L. D, Eds, 2nd ed, ASM International: Metals Park, OH
    • Villars, P., Calvert, L. D., Eds. Pearson's Handbook of Crystallographic Data for Intermetallic Phases, 2nd ed.; ASM International: Metals Park, OH, 1991; Vol. 4, p 5253.
    • (1991) Pearson's Handbook of Crystallographic Data for Intermetallic Phases , vol.4 , pp. 5253
  • 45
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    • Wyckoff, R. W. G, Ed, 2nd ed, Wiley: New York
    • Wyckoff, R. W. G., Ed. Crystal Structures, 2nd ed.; Wiley: New York, 1963; Vol. 1, p 90.
    • (1963) Crystal Structures , vol.1 , pp. 90
  • 47
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    • Error Reporting Recommendations: A Report of the Standards and Criteria Committee, Adopted by the International XAFS Society, Standards and Criteria Committee, July 26, 2000, Ako, Japan (http://ixs.iit.edu/subcommittee_reports/ sc/err-rep.pdf). Accessed February 16, 2006.
    • Error Reporting Recommendations: A Report of the Standards and Criteria Committee, Adopted by the International XAFS Society, Standards and Criteria Committee, July 26, 2000, Ako, Japan (http://ixs.iit.edu/subcommittee_reports/ sc/err-rep.pdf). Accessed February 16, 2006.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.