Knowledge Bank

“In diborane $(B2H6)$, a maximum of four hydrogen may be replaced by alkyl groups, leaving the unique ; bridge intact. Thus, there exist five types of alkyldiboranes: mono-, 1,2-di-1,1-di-1,tri-, and tetra-alkyldiborances. (Cis and trans isomers of 1,2-dialkylboranes cannot be separated.) For the present study, the infrared spectra of $B10$-enriched and boron-, carbon-, and per-deuterated methyl-and ethyl-diboranes (40 of a possible 50 such variants) were $analyzed.1,2$ The effect of alkyl substitution on the stretching and bending frequencies of the remaining B-H bonds is examined and compared with similar effects in ethylenes. Coupling across the bridge is investigated, and changes in the stretching frequencies of the bridge itself are explored. It has been possible to verify earlier $assignments8$ for stretching frequencies in partially deuterated bridges, B(HD)B.”