Gas-phase reactions of Nb sup + and Ta sup + with alkanes and alkenes. C-H bond activation and ligand-coupling mechanisms

Journal Article · Wed Sep 06 04:00:00 EDT 1989 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00317a024· OSTI ID:7108197

Buckner, S W; MacMahon, T J; Byrd, G D; Freiser, B S ^[1]

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1. Purdue Univ., West Lafayette, IN (USA)

The gas-phase reactions of Nb{sup +} with small alkanes and alkenes are reported. Nb{sup +} sequentially activates C-H bonds in ethene six times to produce NbC{sub 2n}H{sub 2n}{sup +} (n = 1-6). The C{sub 2}H{sub 2} ligands in this reaction couple via migratory insertion of the acetylene units. Ethane sequentially reacts with Nb{sup +} five times. Ligand coupling is proposed for these reactions as well. Comparison of NbC{sub 4}H{sub 6}{sup +} produced from isobutane, n-butane, and ethane indicates the presence of at least two isomeric forms. NbC{sub 4}H{sub 4}{sup +} ions produced from ethene, cyclobutane, and 1-butene produced similar CID spectra, supporting the presence of one structure. Excited Nb{sup +} produced by direct laser desorption reacts with methane to produce NbCH{sub 2}{sup +} and NbCH{sub 3}{sup +}, but collisional cooling with argon quenches the reaction. Primary reactions indicate a strong preference for C-H insertion, and reaction products indicate 1,3-hydrogen migration when {beta}-hydrogens are not present. The reactions with alkanes are compared to those with Ta{sup +}, which reacts with CH{sub 4} four times to produce TaC{sub 4}H{sub 8}{sup +}. Ta{sup +} and Nb{sup +}, which react similarly, are by far the most reactive metal ions toward C-H bond activation reported to date. CID spectra of the products form the Nb{sup +} reactions indicate that the extensive dehydrogenation reactions occur via ligand coupling and, for larger alkanes (C{sub 5} and C{sub 6}), dehydrocyclization. For example, Nb{sup +} undergoes a novel dehydrocyclization reaction with pentane to generate Nb(Cp){sup +} (Cp = cyclopentadienyl). Nb{sup +} reacts with cyclopentane to generate Nb(Cp){sub 2}{sup +} as a second product. 34 refs., 3 figs., 2 tabs.

• DOE Contract Number: FG02-87ER13776
• OSTI ID: 7108197
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 28:18; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
ALKENES
CATIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
DATA
EXPERIMENTAL DATA
FLUIDS
GASES
HYDROCARBONS
INFORMATION
IONS
NIOBIUM COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
REFRACTORY METAL COMPOUNDS
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS