Intermediates in the formation of N-methylaminoborane trimer and N,N-dimethylaminoborane dimer

Article abstract of DOI:10.1021/ic50051a004

Experimental evidence for the intermediates in the formation of N-methylaminoborane trimer, (H₂BNHCH₃)₃, and N,N-dimethylaminoborane dimer, (H₂BN(CH₂)₂)₂, has been obtained by synthetic methods and trapping procedures. The pyrolysis of methylamine borane, H₃BNH₂CH₃, yields the six-membered ring of (H₂BNHCH₃)₃ by initially forming H₂B(NH₂CH₃)₂⁺BH ₄^-, then [H₂CH₃NBH₂NHCH₃BH₂NH ₂CH₃]⁺BH₄^- through a series of successive dehydrogenation condensation reactions. The final step of the proposed mechanism is ring closure by dehydrogenation. The new compound, [H₂CH₃NBH₂NHCH₃BH₂NH ₂CH₃]⁺Cl^-, was prepared by heating a mixture of H₂B(NH₂CH₃)₂⁺Cl ^- and H₃BNH₂CH₃ and was characterized by elemental analysis, its reactions with FeCl₃ and NaBH₄, and its pmr spectrum. The experimental evidence for the intermediates during the pyrolysis of dimethylamine borane to form (H₂BN(CH₃)₂)₂ is consistent with monomeric H₂BN(CH₃)₂ species which then associate to give the dimer.