Organoaluminum Compounds as Catalysts for Monohydroboration of Carbodiimides

The effective catalytic activity of organoaluminum compounds for the monohydroboration of carbodiimides has been demonstrated. Two aluminum complexes, 2 and 3, were synthesized and characterized. The efficient catalytic performances of four aluminum hydride complexes L¹AlH₂ (L¹=HC(CMeNAr)₂, Ar=2,6-Et₂C₆H₃; 1), L²AlH₂(NMe₃) (L²=o-C₆H₄F(CH=N-Ar), Ar=2,6-Et₂C₆H₃; 2), L³AlH (L³=2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine; 3), and L⁴AlH(NMe₃) (L⁴=o-C₆H₄(N-Dipp)(CH=N-Dipp), Dipp=2,6-iPr₂C₆H₃; 4), and an aluminum alkyl complex L¹AlMe₂ (5) were used for the monohydroboration of carbodiimides investigated under solvent-free and mild conditions. Compounds 1–3 and 5 can produce monohydroborated N-borylformamidine, whereas 4 can afford the C-borylformamidine product. A suggested mechanism of this reaction was explored, and the aluminum formamidinate compound 6 was characterized by single-crystal X-ray, also a stoichiometric reaction was investigated.