Theoretical studies of structures and energetics of benzene complexes with Nb{sup +} and Nb{sub 2}{sup +} cations

Journal Article · Thu Jul 22 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp9907950· OSTI ID:682156

Roszak, S ^[1]; Majumdara, D; Balasubramaniana, K ^[1]

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1. Arizona State Univ., Tempe, AZ (United States). Dept. of Chemistry and Biochemistry

A primary reason for the increased interest in the reactivity of transition metal clusters with hydrocarbons is that such reactivity studies could provide valuable insight into heterogeneous catalysts. Many industrially important reactions rely on catalysis, although the catalytic processes are still far from being understood at the microscopic level. Transition metals are the most widely employed catalysts. The initial process in heterogeneous catalysis if the adsorption of the reactant molecules on the catalyst surface, and consequently, the study of the interaction between the reactant and the transition metal surface could provide vital insight into heterogeneous catalysis. Ab initio calculations of the ground and excited states have been carried out for the Nb{sub n}{sup +}-benzene (n = 1, 2) complexes and for the reaction products Nb{sub n}C{sub 6}H{sub 4}{sup +} and NbC{sub 6}{sup +} using state-of-the-art computational techniques. It is found that the chemical bonds in Nb{sub n}C{sub 6}H{sub 6}{sup +} complexes are formed as a consequence of electronic density transfer from the {pi} electrons of benzene to the Nb metal. This process has significant impact on the benzene ring and leads to the destruction of aromaticity for the Nb{sub 2}C{sub 6}H{sub 6}{sup +} complex. The reaction products that contain dehydrogenated benzene exhibit {sigma} bonds that are formed at the sites where the metal replaces hydrogens. The formation of the physisorbed Nb{sub n}C{sub 6}H{sub 6}{sup +} complex has been found as a preferable channel for the Nb{sub n}{sup +} reactions with benzene for small values of n considered here. The computed energetics for the physisorbed and chemisorbed species are extensively compared with the Fourier transform ion cyclotron resonance mass spectrometric study of Bondybey and co-workers. Their theoretical results support the experimental observations on the cooling of the reaction products through the evaporation of H{sub 2} from the surface of the cluster and also the relative stabilities of chemisorbed and physisorbed species.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 682156
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 29 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
BENZENE
CHEMICAL REACTION KINETICS
ELECTRONIC STRUCTURE
HETEROGENEOUS CATALYSIS
MOLECULAR STRUCTURE
NIOBIUM COMPLEXES