Showing papers by "Zhen Hua Li published in 2012"

Bonding in homoleptic iron carbonyl cluster cations: a combined infrared photodissociation spectroscopic and theoretical study

Abstract: Infrared spectra of mass-selected homoleptic iron carbonyl cluster cations including mononuclear Fe(CO)5+ and Fe(CO)6+, dinuclear Fe2(CO)8+ and Fe2(CO)9+, and trinuclear Fe3(CO)12+ are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. Only one IR band is observed for the Fe(CO)5+ cation, which is predicted to have a C4v structure. The Fe(CO)6+ cation is determined to be a weakly bound complex involving a Fe(CO)5+ core ion. In contrast to neutral clusters which have symmetric structures with two and three bridging carbonyl ligands, the dinuclear Fe2(CO)8+ and Fe2(CO)9+ cations are characterized to have unbridged asymmetric (OC)5Fe–Fe(CO)n+ (n = 3 and 4) structures. The trinuclear Fe3(CO)12+ cluster cation is determined to have an open chain like (OC)5Fe–Fe(CO)2–Fe(CO)5 structure instead of the triangular structure with two bridging CO groups for the Fe3(CO)12 neutral. The di- and trinuclear cluster cations all involve a square pyramid like Fe(CO)5 building block that satisfies the 18-electron configuration of this iron center. The Fe(CO)5 building block is isolobal to the CH3 fragment in hydrocarbon chemistry, the Fe2(CO)9+ and Fe3(CO)12+ cluster cations may be considered through isolobality to be metal carbonyl analogues of the ethyl and isopropyl cations.

Deep Oxidations in the Oxidative Dehydrogenation Reaction of Propane over V2O5(001): Periodic Density Functional Theory Study

Abstract: The oxidative dehydrogenation (ODH) of propane to propene over a vanadium-based catalyst suffers from side reactions of further and complete oxidations of propene and other intermediates, which lim...

Infrared photodissociation spectra of mass selected homoleptic dinuclear iron carbonyl cluster anions in the gas phase

Abstract: Infrared spectra of mass-selected homoleptic dinuclear iron carbonyl cluster anions Fe2(CO)n− (n = 4–9) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The cluster anions are produced via a laser vaporization supersonic cluster source. Density functional calculations have been performed and the calculated vibrational spectra are compared to the experimental data to identify the gas-phase structures of the cluster anions. The experimentally observed Fe2(CO)n− (n = 4–7) cluster anions are characterized to have unusual asymmetric (OC)4Fe–Fe(CO)n−4 structures, which also correspond to the computed lowest energy structures. The experimentally observed Fe2(CO)8− cluster anion is determined to have an unbridged structure instead of the previously reported dibridged structure. The Fe2(CO)9− cluster anion is determined to involve a Fe2(CO)8− core anion that is solvated by an external CO molecule. Bonding analysis indicates that these anions each have a Fe–Fe single bond to satisfy the 18-electron configuration of one iron center. The results provide important new insight into the structure and bonding mechanisms of transition-metal carbonyl clusters.

Infrared photodissociation spectroscopic and theoretical study of homoleptic dinuclear chromium carbonyl cluster cations with a linear bridging carbonyl group.

Abstract: Infrared spectra of mass-selected homoleptic dinuclear chromium carbonyl cluster cations Cr2(CO)n+ with n = 7–9 are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. The Cr2(CO)n+ cluster cations are characterized to have the (OC)5Cr–C–O–Cr(CO)n−6+ structures with a linear bridging carbonyl group bonded to one chromium atom through its carbon atom and to the other chromium atom through its oxygen atom. The cluster cations all have a sextet ground state with the positive charge and the unpaired electrons located on the Cr(CO)n−6 moiety. The formation of the linear bridging structures without Cr–Cr bonding can be rationalized that chromium forms strong Cr–CO bonds but weak Cr–Cr bonds.

Matrix isolation spectroscopic and theoretical study of carbon dioxide activation by titanium oxide molecules.

Abstract: The reactions of titanium monoxide and dioxide molecules with carbon dioxide were investigated by matrix isolation infrared spectroscopy. It was found that the titanium monoxide molecule is able to activate carbon dioxide to form the titanium dioxide–carbon monoxide complex upon visible light excitation via a weakly bound TiO(η1-OCO) intermediate in solid neon. In contrast, the titanium dioxide molecule reacted with carbon dioxide to form the titanium monoxide–carbonate complex spontaneously on annealing. Theoretical calculations predicted that both activation processes are thermodynamically exothermic and kinetically facile.