Reactions of 1,1- and 1,2-bis-boranes with a protic diamine and hydrazine

Abstract

The reactions of 1,1- and 1,2-bis-boranes, PhCH₂CH(B(C₆F₅)₂)₂1 and Me₃SiCH(B(C₆F₅)₂)CH₂B(C₆F₅)₂2, with o-phenylenediamine and hydrazine are reported. The coordination of o-phenylenediamine gives the expected adducts, PhCH₂CH(B(C₆F₅)₂(H₂N))₂C₆H₄4 and Me₃SiCH(B(C₆F₅)₂)CH₂B(C₆F₅)₂((H₂N)₂C₆H₄) 6. Under thermal duress, 4 undergoes retrohydroboration, resulting in the reaction of the diamine with HB(C₆F₅)₂ to give (C₆F₅)₂B(NH)(NH₂)C₆H₄5. In contrast, 6 undergoes protolytic loss of C₆F₅H, affording Me₃SiCH(B(C₆F₅)₂)CH₂(B(C₆F₅)(NH₂)(NH)C₆H₄) 7. In a related fashion, the bis-boranes react with hydrazine. In the case of bis-borane 1, the isolated adduct PhCH₂CH(B(C₆F₅)₂(NH₂))₂·THF 8 can be deprotonated to give species 9. In contrast, the reaction of 2 proceeds with rapid protonolysis, leading to the formation of Me₃SiCH(B(C₆F₅)₂)CHB(C₆F₅)(N₂H₃)·THF 10. This study illustrates both the reaction pathways accessible from the adducts of bis-boranes and the impact of coordination to boron on the acidity of NH groups.