Some General Features of Diboron Chemistry

Synthesis of specific diboron compounds may involve either (1) reductive coupling reactions of monoboron derivatives to form materials containing the boron-boron bond, or (2) reactions of compounds possessing preformed B2 fragments. Since the formation of the boron-boron bond is in a sense the central synthetic difficulty in diboron chemistry, it is of interest to consider in some detail the approaches of various workers to this problem. 

Timms has also reported another high-temperature approach to the formation of B—B bonds by the insertion of BF (formed at 2000° C from boron and BF3) into the B—F bond (98)  

The coupling procedure appears to be well suited to the formation of dialkylamino- and mixed alkyl-dialkylaminodiboron derivatives. It is less satisfactory for the formation of diboron esters of low molecular weight alcohols. 

Formation of more extended boron chains by the coupling reaction has been reported 48)  

It is reported that the trimethylamine complex of tetramethyldiborane(4) was obtained from the reduction of bromodimethylborane with sodium or silver in trimethylamine (92). 

---