Experimental and Theoretical Studies of Nb₆C₇^0/+

Abstract

Nb6C7 + is studied using a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer coupled to a compact supersonic source. Its reactions with H2O, NH3, CH3OH, CH3CN, and C6H6 are reported. For each of these ligands, sequential attachment reactions occur leading to the initial truncation products Nb6C7L4 +. Minor amounts of Nb6C7L5 + and Nb6C7L6 + are observed for polar molecules, but they grow in slowly. A measurement of the relative rate constants for the sequential addition reactions of CH3OH, for example, demonstrates quantitatively that addition of the fifth CH3OH is very slow compared to the first four additions. Multiple excitation collisional activation (MECA) on Nb6C7 + yields Nb5C6 +, and MECA on Nb5C6 + yields Nb4C4 + as predominant products. Nb6C7 + undergoes iodine abstraction from one CH3I molecule to yield the truncation product, Nb6C7I+. Ab initio Hartree−Fock calculations of Nb6C7 suggest a structure consisting of two cubes with one carbon at the exact inversion center of the D 2h symmetry. This structure, in which four of the six niobium atoms are equivalent but different from the other two, is consistent with the experimental results. The structures of Nb4C4 and Nb5C6 are also optimized theoretically.

Onset of carbon–carbon bonding in the Nb5Cy(y = 0–6) clusters: a threshold photo-ionisation and density functional theory study

“…Several energetically competitive isomers are found for Nb The structure of Nb 5 C 6 has been examined previously by the seperate groups of Freiser and Dance. 33,35 Freiser and co-workers proposed a 2 Â 2 Â 3 nanocrystal fragment with a C atom removed from a corner position as the structure of Nb 5 C 6 . Harris and Dance considered two isomers; one where C atoms are bound to all six Nb faces of the trigonal bipyramid Nb 5 cluster and another where three C 2 units are each bound across two Nb faces of the same type of Nb 5 cluster.…”

The Geometric and Electronic Structures of Niobium Carbon Clusters

“…In the past decade, a variety of types and instances of metal carbon binary molecules have been uncovered experimentally, including (1) endohedral, exohedral, and networked metallofullerenes MC n , − (2) graphitic MC n , (3) metallocarbohedrenes M x C y with C 2 groups, and nanodimensional fragments of MC lattices containing C atoms. − These unprecedented and unpredictable systems raise many fundamental questions and intimate opportunities for further science and technology. All of this experimental work has involved the molecules or ions in the gas phase, and the principal experimental information on them involves their stabilities to dissociation 15,17,24,25,36,40 and their reactions with a range of molecules including oxygen, water, acetonitrile, ammonia, benzene, alkyl halides, alcohols, and acetone. − ,,,,− Bowers et al have determined their collisional cross-sections, measured as drift times through inert gas. − Wang, Li, and Wu have applied a photoelectron spectroscopy technique to measure electron affinities of a range of species. …”

Reactivities of Metallocarbohedrenes: Nb8C12+

“…22,41,47 If each ligand (acetonitrile and benzene) were to bond to two metal centers, truncation should be observed at Nb 4 C 4 L 2 + , Nb 4 C 5 L 2 + , Nb 6 C 7 L 3 + , and V 14 C 12-13 L 7 + . However, these product ions are intermediates, not initial or final truncation products.…”

“…Nb 4 C 4 + , Nb 6 C 7 + , and V 14 C 12 - 13 + 42 react in a sequential fashion with CH 3 CN and/or background water to yield the truncation products Nb 4 C 4 (CH 3 CN) 2 (OH) 2 + , Nb 6 C 7 (CH 3 CN) 4 + , V 14 C 12 - 13 (CH 3 CN) 7 (H 2 O) + , and V 14 C 12 - 13 (CH 3 CN) 8 + . In addition Nb 4 C 4 + , Nb 4 C 5 + , Nb 5 C 6 + , and Nb 6 C 7 + 47 all react with benzene (C 6 D 6 ) sequentially to yield a four ligand association truncation product.…”