Reactions of diboratetrahalides(4) with boriranylideneboranes - Formation,reactivity, and structures of cyclic tetraborylmethanes and isomeric diborylmethyleneborane derivatives

Reaction of the boriranylideneboranes 1a,b,e with tetrahalogenodiboranes(4) leads to two types of products. In the case of la the cyclic tetraborylmet hane derivatives 2a,a' are formed in high yield, whereas Ib,e yield the iso meric linear diborylmethyleneboranes 3b,c. Compound 2a reacts with di-ethyl amine, (dimethylamino)trimethylsilane, and lithium pyrrolidinide to give th e 1,3-diboretanes 4a,b,c. The composition of the products was determined fr om spectroscopic data and X-ray structure analyses of 2a, 3c, 4a, and 4c.