Macropolyhedral boranes

From the reaction of -butyl nitrite with the macropolyhedral borane [ //-B18H22], an 18-vertex azaborane anti-[9-NB17H2q] was isolated and characterized on the basis of NMR spectroscopy data.119... 

Reacting the two isomers of the macropolyhedral borane B18H22 [anti-B18H22l or [syn-BlgH22] with elemental sulfur, two dithiaboranes were isolated in 48% yield each and structurally characterized [S2B, 711,H 41 from the anti-... 

Metal atoms have fewer valence electrons than orbitals available for bonding and in this they resemble boron. The consequences of this idea are examined and it is shown that many metals with electronegativities in the range 1.6-2.4 (B = 2.0) can subrogate boron atoms as vertices in polyhedral clusters. Such metalloboranes are often much more stable than the parent boranes or borane anions. Not only can metals mimic boron in known cluster geometries but the flexibility thus introduced can lead to novel and previously unsuspected cluster geometries. The construction of macropolyhedral clusters containing 17-20 vertices is also described. 

Figure 6b. An outline diagram of the macropolyhedral borane ligand geometry and its interaction with the Pt center C8j.

Electron-counting scheme for macropolyhedral boranes mno rule... 

A generalized electron-counting scheme, known as the mno rule, is applicable to a wide range of polycondensed polyhedral boranes and heteroboranes, metal -laboranes, metallocenes, and any of their combinations. According to this mno rule, the number of electron pairs N necessary for a macropolyhedral system to be stable is... 

For a closo macropolyhedral borane cluster, the rule giving the required number of electron pairs is N = m + n. 

We reported to the previous IMEBORON meeting on a variety of macropolyhedral thia-boranes and their rearrangements (e.g. structures I to V).1 This work is still on-going.2 3 A new finding here is the isomerism of S2BI6H16, which exhibits both structures V and VI, Extensive isomerism will be a fascinating feature of future macropolyhedral chemistry. 

Jemmis, E. D. and D. L. V. K. Prasad. 2006. Icosahedral B12 macropolyhedral boranes, P-rhombohedral boron and boron-rich solids. J. Solid State Chem. 179 2768-2774. 

Shameema, O. and Jemmis, E.D. (2009) Relative stability of closo-closo, closo-nido, and nido-nido macropolyhedral boranes the role of orbital compatibility. Chem. Asian J., 4 (8), 1346-1353. 

Macropolyhedral Condensed Boranes and Supra-icosahedral Clusters... 

Half-sandwich complexes have also been reported with macropolyhedral boranes, but the Ni-borane bonding in these complexes does not involve 7r-interactions. For instance, reacting nickelocene with anti- > zz results in the elimination of CpH and formation of the 19-vertex conjuncto- xxwQXm anions [Bi8H2oNiCp] , 231 subtle differences in the reaction conditions lead to the oxidation of 231 to give 232. Structural studies of these compounds have shown that their overall structures consist of two edge-fused cluster subunits (a 10-vertex and a ////To-10-vertex)... 

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