Molecular orbitals framework, boranes

The reaction between a trinuclear metal carbonyl cluster and trimetbyl amine borane has been investigated (41) and here the cluster anion functions as a Lewis base toward the boron atom, forming a B—O covalent bond (see Carbonyls). Molecular orbital calculations, supported by stmctural characterization, show that coordination of the amine borane causes small changes in the trinuclear framework. 

Molecular orbital calculations have shown that closo boranes have 2n + 1 bonding molecular orbitals, including n B—Hct bonding orbitals and n + 1 bonding orbitals in the central core (described as framework or skeletal bonding orbitals). A useful example is which has Of, symmetry. In this ion, each boron has four va-... 

Molecular orbital calculations have shown that closo boranes have two types of molecular orbitals that are instrumental in holding the boron framework... 

Many rings and clusters, however, cannot be understood within the two-center two-electron bond framework. This is sometimes extended by assuming resonance, for example between the two Kekule-type structures for benzene (6). A more natural approach is to extend the molecular orbital (MO) approach (see Topic C6) to many atoms. The so-called Hiickel theory of ring systems makes important predictions relevant to inorganic molecules such as S2N2. Clusters such as boranes also... 

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