MoO-04


GAS PHASE REACTIONS OF SMALL LANTHANUM-CARBON CLUSTER IONS LaC2n+ ( n<5 )

Gary Willett, Rui Zhang, Femia G. Hopwood, Keith J. Fisher, Derek R. Smith, Ian G. Dance and Gerry E. Gadd*

School of Chemistry, University of New South Wales, Sydney, NSW 2052
*Australian Nuclear Science and Technology Organisation


Small positive lanthanum-carbon cluster ions LaC2n+ (n<5) and La2C2n+ (n<5) were observed during laser ablation mass spectrometry studies of lanthanide metallo-fullerenes. These ions were generated by a 8 ns laser pulse from a Q-switched Nd-YAG laser (1064 nm) which was focussed onto a target consisting of a mixture of La2O3 and various carbon-based materials. We are exploring the possibility that these ions are involved in the formation of metallo-fullerenes during the laser ablation process. Collision induced dissociation experiments on these ions reveals that LaC2n clusters progressively lose C2 units. Gas phase reactions of these lanthanide-carbon cluster cations with methanol, H2S, benzene and benzenethiol on a Fourier transform/ICR mass spectrometer are also presented. These experiments reveal that LaC2n+ reacts with the above reagent gases by replacing C2 units with different ligands and that the carbon is only weakly bonded to the lanthanum.

Gaussian-94 and DMOL ab initio calculations are used to examine the potential energy surface for the reactions. Results will be presented on the thermochemistry and optimised ionic structures with a discussion on the reaction pathways and reaction mechanisms.

Figure

Positive-ion laser ablation mass spectrum of a mixture of La2O3 and Koppers coal tar pitch residue