Nine-atom clusters, reactivity

Wc will first examplify the above principles on a six atom and a seven atom cluster. These two clusters are the most striking examples of the differences beween nickel and cobalt clusters. These cobalt clusters are the two least reactive of all the cobalt clusters, whereas for nickel these two clusters are as reactive as clusters of other sizes. In the final subsection we will discuss also the four, five, eight, nine and ten atom clusters of which in particular the eight and nine atom clusters have a markedly lower reactivity for cobalt than for nickel. All calculations described in this section used a one- or two- electron ECP level description of the metal atoms. No all-electron atoms were included. 

Other Clusters. The cobalt clusters with six and seven atoms are the ones which differ most dramatically from the corresponding nickel clusters. The eight and nine atom clusters are also much less reactive for cobalt than for nickel, while the Co g cluster is as strongly reactive as the Ni.g cluster. The experimental result for the four and five atom cobalt clusters is not completely clear to us. For the five atom cluster it is on the one hand claimed that it has reacted almost completely but on the other hand the relative reactivity is given in a figure as smaller than for the unreactive COg cluster (1). For all these clusters we have obtained some preliminary results, which are described below. 

For the nine atom clusters it is first clear from the rules above, that the Ni cluster should be reactive, as found... 

Having a closer look at the reported solvate structures of homoatomic polyanions of group 14 elements, it becomes evident that only clusters and no rings or chains are stable in solid state as well as in solution (Fig. 13). Higher reduced polyanions with > 5, equivalent with a charge higher than —1 per atom, are not reported in solution so far. The nine-atom species is quite well established in solutions of ammonia and ethylenediamine. Their interesting reactivity is intensely studied and is discussed elsewhere [5, 125, 126]. The less-understood cluster... 

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