Pyrolysis of trimethylborane. Part 2. Formation of carbaboranes and other boron-containing compounds

Abstract

The pyrolysis of BMe₃ has been studied by gas chromatography and mass spectrometry; effects of varying the pyrolysis time and temperature have been investigated. Compounds formed include BMe₂Et, Me₂BCH₂BMe₂, carbaboranes Me₃B₃C₂H₂, Me₅B₅C₂H₂, and 2,4,6,8,9,10-hexamethyl-2,4,6,8,9,10-hexabora-adamantane (Me₆B₆C₄H₄). The pyrolysis of BMe₃–H₂ mixtures, in marked contrast to that of pure BMe₃, gives a mixture of carbaboranes of formulae Me_xH_{(5 –x)}B₅C₂H₂(x= 2–5) in high overall yield (60–66%). Pyrolyses of BMe₃ in the presence of D₂, C₂H₆, and HgMe₂ provide evidence for the involvement of methyl radicals in the reaction.