B clusters in solids connections with molecular boranes

2 B clusters in solids connections with molecular boranes 

1 Octahedral B clusters in solids analogy with [B6H6]2 

Many other linked polyhedra similar to molecular boranes are found for B-rich solid compounds of alkali and alkaline-earth metals. There are octahedra in Li2B6, octahedra and pentagonal bipyramids in Na3B2o, dodecahedra and bicapped square antiprisms in U3B14 and icosahedra in Na2B29. The cluster connection is particularly clear for compounds of this type. 

2 Localized and delocalized bonding in B solid-stale chemistry the example of GdB4 

The first question posed by this structure concerns the formal charge distribution between the two Gd, B6 and B2 units. If we naively apply the Zintl-Klemm concept we arrive at [Gd3+]2[B6, B2]6. The [B6]2 cluster with six external bonds obeys the cluster electron-counting rules. Consequently, the B2 fragment must have a charge of —4. This corresponds to saturated eight-electron B centers, and requires non-planar (tetrahedral) B centers. This does not agree with the observed planar B centers. But we know the metal does not need to be fully oxidized. Consider sp2-hybridized B atoms which satisfy the octet rule. This would lead to [Gd2+]2[B62 ][B22 ] and suggests a B=B double bond. OK, but planar B is 

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