Polyhedron Polyhedral skeletal electron pair theory

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molecular-orbital (mo) diagram of b2h6. atoms , corresponding orbitals colored same. green mos symbolize bonding, while red symbolize anti-bonding.



the bonding in diborane best described treating each b sp-hybridized. 2 sp-hybrid orbitals on each boron form bonds terminal hydrogens. remaining sp-orbitals create bonds bridging hydrogens. because angles in diborane structure not tetrahedral orbitals contain sp character.



closo-b

6h2−

6


mo diagram of b

6h2−

6 showing orbitals responsible forming cluster. pictorial representations of orbitals shown; mo sets of t , e symmetry each have 2 or 1 additional pictorial representation, respectively, not shown here.



the boron atoms lie on each vertex of octahedron , sp hybridized. 1 sp-hybrid radiates away structure forming bond hydrogen atom. other sp-hybrid radiates center of structure forming large bonding molecular orbital @ center of cluster. remaining 2 unhybridized orbitals lie along tangent of sphere structure creating more bonding , antibonding orbitals between boron vertices. orbital diagram breaks down follows:




the 18 framework molecular orbitals, (mos), derived 18 boron atomic orbitals are:

1 bonding mo @ center of cluster , 5 antibonding mos 6 sp-radial hybrid orbitals
6 bonding mos , 6 antibonding mos 12 tangential p-orbitals.




the total skeletal bonding orbitals therefore 7, i.e. n + 1.



main group atom clusters
the bonding in other main group cluster compounds follow similar rules described boron cluster bonding. atoms @ vertex hybridize in way allows lowest energy structure form.


the 18 framework molecular orbitals, (mos), derived 18 boron atomic orbitals are:

1 bonding mo @ center of cluster , 5 antibonding mos 6 sp-radial hybrid orbitals
6 bonding mos , 6 antibonding mos 12 tangential p-orbitals.


the total skeletal bonding orbitals therefore 7, i.e. n + 1.




^ cite error: named reference cotton3 invoked never defined (see page).
^ cite error: named reference mnorules invoked never defined (see page).






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