Polymeric boron-nitrogen compounds formation

Generally, during hydroboration polymerization of dicyano compounds, the formation of the borazine structures that have a six-membered boron-nitrogen ring (scheme 19a) and dihydroborated end groups (scheme 19b) as a structural defect is unavoidable. The borazine cross-linked structures often cause the gelation, and dehydroboration causes a decrease in molecular weight. 

Cyclic species of equal numbers of alternating boron and nitrogen atoms may be considered as condensation products of monomeric B—N units and recent work by Paetzold 8-11> gives some credence to Wiberg s view that boronimides, XB=NR, are possible intermediates in the formation of cyclic B—N compounds. Boronimides may polymerize or may be trapped by 1,3-dipolar agents 8 11>. In similar fashion, the formation of the cyclotetrazenoborane ring system 1... 

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