Cluster reactivity in the gas phase has been probed extensively with clusters generated by using a variety of custombuilt sources. These include pulsed-laser vaporisation, continuous-operation ovens, fast-atom and secondary-ion sputtering, dc discharge, and pulsed-arc cluster-ion sources.[1] All generate an assortment of clusters of different nuclearities, and MS n techniques make selection of a particular sized cluster relatively straightforward. Both homo-and heteronuclear clusters are known.[2] All of these techniques employ a similar strategy to cluster synthesis; that is, the target is vaporised, the gas-phase metal atoms condensed, and the resulting clusters examined by mass spectrometry. We report herein an entirely different approach for the production of bare-metal gas-phase clusters, in which presynthesised transition-metal-carbonyl-cluster anions are delivered into the gas phase by a standard electrospray ionisation (ESI) source and stripped free of ligands by using collision-induced dissociation (CID) at the skimmer cone. The benefits of this approach are high yields of a specific cluster, no requirement for a special source, easy access to heteronuclear clusters and/ or those with interstitial atoms, and a vast library of known clusters to draw from.Because mixed-metal-carbonyl clusters are currently extensively used as precursors for metal nanoparticle catalysts (the clusters are absorbed inside mesoporous silica and calcined to remove the ligands), [3] examination of their gasphase reactivity may provide insight into their action as[*] Dr.
Yttrium- and lanthanum-carbide cluster cations YC(n)(+) and LaC(n)(+) (n = 2, 4, and 6) are generated by laser ablation of carbonaceous material containing Y(2)O(3) or La(2)O(3). YC(2)(+), YC(4)(+), LaC(2)(+), LaC(4)(+), and LaC(6)(+) are selected to undergo gas-phase ion-molecule reactions with benzene and cyclohexane. The FTICR mass spectrometry study shows that the reactions of YC(2)(+) and LaC(2)(+) with benzene produce three main series of cluster ions. They are in the form of M(C(6)H(4))(C(6)H(6))(n)(+), M(C(8)H(4))(C(6)H(6))(n)(+), and M(C(8)H(6))(C(6)H(6))(m)(+) (M = Y and La; n = 0-3; m = 0-2). For YC(4)(+), LaC(4)(+), and LaC(6)(+), benzene addition products in the form of MC(n)(C(6)H(6))(m)(+) (M = Y and La; n = 4, 6; m = 1, 2) are observed. In the reaction with cyclohexane, all the metal-carbide cluster ions are observed to form metal-benzene complexes M(C(6)H(6))(n)(+) (M = Y and La; n= 1-3). Collision-induced-dissociation experiments were performed on the major reaction product ions, and the different levels of energy required for the fragmentation suggest that both covalent bonding and weak electrostatic interaction exist in these organometallic complexes. Several major product ions were calculated using DFT theory, and their ground-state geometries and energies were obtained.
Cluster reactivity in the gas phase has been probed extensively with clusters generated by using a variety of custombuilt sources. These include pulsed-laser vaporisation, continuous-operation ovens, fast-atom and secondary-ion sputtering, dc discharge, and pulsed-arc cluster-ion sources.[1] All generate an assortment of clusters of different nuclearities, and MS n techniques make selection of a particular sized cluster relatively straightforward. Both homo-and heteronuclear clusters are known.[2] All of these techniques employ a similar strategy to cluster synthesis; that is, the target is vaporised, the gas-phase metal atoms condensed, and the resulting clusters examined by mass spectrometry. We report herein an entirely different approach for the production of bare-metal gas-phase clusters, in which presynthesised transition-metal-carbonyl-cluster anions are delivered into the gas phase by a standard electrospray ionisation (ESI) source and stripped free of ligands by using collision-induced dissociation (CID) at the skimmer cone. The benefits of this approach are high yields of a specific cluster, no requirement for a special source, easy access to heteronuclear clusters and/ or those with interstitial atoms, and a vast library of known clusters to draw from.Because mixed-metal-carbonyl clusters are currently extensively used as precursors for metal nanoparticle catalysts (the clusters are absorbed inside mesoporous silica and calcined to remove the ligands), [3] examination of their gasphase reactivity may provide insight into their action as[*] Dr.
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