He S-G, Xie Y, Dong F, Bernstein E R
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA.
J Chem Phys. 2006 Oct 28;125(16):164306. doi: 10.1063/1.2360278.
Neutral niobium and tantalum clusters (Nbn and Tan) are generated by laser ablation and supersonic expansion into a vacuum and are reacted in a pickup cell with various low pressure (approximately 1 mTorr) unsaturated hydrocarbons (acetylene, ethylene, propylene, 1-butene, 1,3-butadiene, benzene, and toluene) under nearly single collision conditions. The bare metal clusters and their reaction products are ionized by a 193 nm laser and detected by a time of flight mass spectrometer. Partially and fully dehydrogenated products are observed for small (n<or=m) and large (n>or=m) neutral metal clusters, respectively, with m ranging from 2 to 5 depending on the particular hydrocarbon. In addition to primary, single collision products, sequential addition products that are usually fully dehydrogenated are also observed. With toluene used as the reactant gas, carbon loss products are observed, among which Nb8C12 and Ta8C12 are particularly abundant, indicating that the Met-Car molecule M8C12 can be formed from the neutral metal cluster upon two collisions with toluene molecules. The dehydrogenation results for low pressure reactions are compared with those available from previous studies employing flow tube (high pressure) reactors. Low pressure and high pressure cluster ion reactions are also compared with the present neutral metal cluster reactions. Reactions of unsaturated hydrocarbons and metal surfaces are discussed in terms of the present neutral cluster results.
中性铌和钽团簇（Nbn和Tan）通过激光烧蚀并超声膨胀进入真空产生，然后在捕集池中于近单碰撞条件下与各种低压（约1毫托）不饱和烃（乙炔、乙烯、丙烯、1-丁烯、1,3-丁二烯、苯和甲苯）发生反应。裸金属团簇及其反应产物通过193纳米激光电离，并由飞行时间质谱仪检测。对于小（n≤m）和大（n＞m）中性金属团簇，分别观察到部分脱氢产物和完全脱氢产物，其中m根据特定烃类在2到5之间变化。除了初级单碰撞产物外，还观察到通常完全脱氢的连续加成产物。以甲苯作为反应气体时，观察到碳损失产物，其中Nb8C12和Ta8C12特别丰富，这表明Met-Car分子M8C12可由中性金属团簇与甲苯分子发生两次碰撞形成。将低压反应的脱氢结果与先前使用流动管（高压）反应器的研究结果进行了比较。还将低压和高压团簇离子反应与当前的中性金属团簇反应进行了比较。根据当前的中性团簇结果讨论了不饱和烃与金属表面的反应。
