Chemistry of Selected nido- and closo-Polyborane Anions

Chemistry of Selected nido- and cfoso-Polyborane Anions 

Amongst the cioso-hydroborate anions the closo-dodecaborate B 2H 22 is the best known because many derivatives can be made by maintaining its icosahedral structure in substitution reactions. Thus the replacement of its hydrogen atoms 

Amongst the hydro-closo-polyborates B H 2- members with n = 6 to 12 are known. All hydro-closo- but also hydro-nido-polyborates act as bases they are, however, not typical Lewis-bases as they miss free electron pairs. However, the negative charge at the hydrogen atoms allows for an interaction with Lewis acids A by formation of hydride bridge bonds (3c2e bonds)  

In most cases the Lewis add A is a transition metal or main group element fragment. Because the hydrogen atoms bear a negative charge, the hydropolyborates are reduting agents. 

The cioso-B H 2 anions can all be considered as three dimensional aromatic systems [74, 75], all of them being characterized by an n I 1 electron pair count. Amongst these the is the smallest unit, and, therefore, the partial negative 

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