Cluster compounds expansion reactions

In 222, the Mo atom occupies the common apical site of two distorted square-pyramidal cores, in each of which the two Fe atoms, one Se atom, and one Te atom occupy the basal sites. The formation of 222 demonstrates the contrast in the influence of the chalcogens in cluster-expansion reactions. Although 77 readily reacts with [M(CO)s(THF)] (M = W, Mo) to form [Fe2M(CO)io(/i3-Se)2] (M = W (217), Mo (218)), 110 reacts with the tungsten compound only to form 216 formation of [Fe2Mo(CO)io((u.3-Te)2] is not observed. An intermediate situation arises when the mixed-chalcogenide compound 114 is used for reacting with [Mo(CO)5(THF)]. The formation... 

Through this study we suggest a useful synthetic procedure for good candidate compounds of a new cage-cluster. The ort/io-carboranes are very stable chemicals in this research. Carboranyl acetic ester can be easily introduced to the ortho- carborane skeleton and then many types of cyclisation of carboranyl cluster can be made to occur. The reactivity and reaction mechanism for cyclisation of carborane cluster have been discussed. The mechanisms for boron cluster expansion reaction and cyclisation at carboranyl edge are summarized as follows. 

The boron cluster expansion reaction which occurs through the reaction of decaborane with alkynyl pyrimidine is in accord with two path ways of forming c/oso-compounds and m do-compounds. Acetonitrile accelerates decaborane to react and to take the role of a good nucleophile. 

The material reviewed in this Chapter hitherto has focused on metallacarboranes in which the metal atom is a vertex in an icosahedral cage framework. Until recently, monocarbollide metal compounds with core structures other than 12 vertexes were very rare since suitable carborane precursors were not readily available." However, Brellochs recent development of the reaction of decaborane with aldehydes to give 10-vertex monocarboranes permits a considerable expansion in this area of boron cluster chemistry. As a consequence, several intermediate-sized monocarboranes are now easily accessible and we have recently begun to exploit the opportunities that these present. In particular, we have focused thus far on complexes derived from the C-phenyl-substituted species [6-Ph- zJo-6-CBgHii] It is clear from these initial studies that a wealth of new chemistry remains to be discovered in this area, not only from among the metal derivatives of PhCBg car-boranes such as those discussed in this section, but also in the metal complexes of other newly available carboranes. 

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