Clusters metallocarborane

J. Tirouflet, P. Dixneuf, and P. Braunstein, Actual Chim., 1975, 3. Five typical families, metallocarbenes, metallocarbynes, ylides, clusters, metallocarboranes, and some applications. 

The structure of the bimetallic 10-vertex cluster was shown by X-ray diffraction to be (84). When the icosahedral carborane l,2-C2BioHi2 was used, the reaction led to the first supraicosahedral metallocarboranes with 13- and 14-vertex polyhedral structures (85)-(89). Facile isomerism of the 13-vertex monometallodicarbaboranes was observed as indicated in the scheme above (in which = CH and O = BH). 

To conclude, we shall mention some metal-atom reactions with boranes (172) and carboranes (173). When cobalt atoms reacted with pentaboraneO) and cyclopentadiene, a number of new metalloborane clusters were formed (172), two of which were 65115003(17-05115)3 and cyclopentyl-B5H40o2(i7-05H5)3. Possible structures for the former are shown in Fig. 42. The reaction of cyclopentadiene, pentaboraneO), and 2-butyne with cobalt atoms yielded the metallocarborane species illustrated in Fig. 43 (173). 

Metalloboranes, 4 172 exopolyhedral, 4 208-210 main group element, 4 207-208 transition element, 4 205-207 Metallo-carbohedrene clusters, 4 648 Metallocarboranes, 4 170 as catalysts, 4 217-218 economic aspects, 4 229 exopolyhedral, 4 215-216 f-block element, 4 225-226 host-guest chemistry-carborane anticrowns, 4 216-217 structural systematics, 4 176-179 transition metal, 4 210-215 Metallocene catalysis, MAO in, 16 92-93. 

Although most known metallocarboranes have only 1 metal atom per polyhedron, the existence of an increasing number of metallocarboranes with 2 or more metal atoms per cluster emphasizes the close relationship between metal clusters and borane clusters. Since they can be synthesized from cZoao-carboranes by replacing BH units by metal-carbonyl or metal-cyclopentadienyl residues, carborane clusters can effectively be used as disposable templates on which to fabricate... 

One particularly interesting category of metallocarborane is that in which a single metal atom is shared between two polyhedra that have a vertex in eommon. In effect, the metal is sandwiched between two nido-carborane residues. Examples are shown in Fig. 17. For such commo compounds, the metal can be assumed to contribute three AO s to the skeletal bonding of each polyhedron, when the (n + 1) rule for closo clusters is found to be obeyed. For example, the isoelectronic... 

The geometries of metal carbonyl and metallocarborane cluster compounds have been systematized recently by a set of simple rules described collectively as the polyhedral skeletal electron pair theory (153, 218, 232). This approach originated from a perceptive analogy between isostructural metal carbonyl and borane polyhedral cluster molecules (232), and its applications have been widely discussed and reviewed (147, 153, 210, 218, 233, 234, 235, 240). In this review,... 

Metalloboranes Their Relationship to Metal-Hydrocarbon Complexes and Clusters, 21, 57 Metallocarboranes, Ten Years of, 14,145 Methylene Bridge, 20,159... 

There are some interesting observations too concerning the structures of polyhedral molecules. Very often they are electron deficient in the sense that there are fewer than two electrons for each close contact. The heavy atoms forming the skeleton of the molecule may be either main group atoms (for example in the boranes and carboranes) or transition metal atoms (metal cluster compounds) or both (metallocarboranes). 50 shows the structures expected from Wade s rules for five atom polyhedral molecules with six, seven and eight pairs of skeletal electrons. There are a total of fifteen skeletal orbitals... 

The metal carbonyl clusters - They have been characterized by X-ray diffraction with nuclearities up to the range 30 to 40, by the pioneering work of Chini. They are neutral or, mono-, di-, or trianionic, and these anions can be protonated to give respectively mono-, di- or trihydrides. They have been much studied by organometallic chemists who have used them as models of the Fischer-Tropsch reaction and replaced some carbonyls by unsaturated hydrocarbon ligands. Wade has compared them to metalloboranes, which allowed him to propose a new, correct electron count. Metallocarboranes, derived from the latter, were introduced by Hawthorne. 

Waders rule polyboranes, carboranes, metallocarboranes AND transition-metal CLUSTERS... 

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