Electron-counting scheme for macropolyhedral boranes mno rule

6 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. 

Some examples illustrating the application of the mno rule are given in Table 13.4.4, which makes reference to the structures of compounds shown in Fig. 13.4.10. 

B20H16 is composed of two polyhedra sharing four atoms. The (m + n) electron pair count is 2 + 20 = 22, which is appropriate for a closo stmcture stabilized by 22 skeletal electron pairs (16 from 16 BH groups and 6 from four B 

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