Alkynyllithium compounds of the type RC≡CLi can be useful reagents in organic synthesis. The B≡N group is isosteric to the C≡C unit, but stable molecules of the types MB≡NR or RB≡NM (M = metal) are rare.

Liu Leo Liu, Southern University of Science and Technology, Shenzhen, China, Lingbing Kong, Shandong University, Jinan, China, and Nankai University, Tianjin, China, and colleagues have synthesized a boraiminolithium species of the type RB≡NLi (pictured). The team first synthesized the precursor DmpBBrNH₂ (Dmp = 2,6-bis(2,4,6-trimethylphenyl)phenyl) via a reaction of DmpBBr₂ and LiNH₂. This precursor was then reacted with lithium bis(trimethylsilyl)amide (LiHMDS) to give the desired product in a yield of 45 %.

The structure of the product was confirmed by X-ray crystallography, which showed that it consists of two [DmpBN]⁻ units held together by a cationic core composed of six lithium and four bromine atoms. The team found that the synthesized boraiminolithium species can be used to introduce B≡N units into organometallic and organic compunds, e.g., Mg, Sn, or Zn complexes as well as tetrazaboroles or other heterocycles.

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• Boraiminolithium: An Iminoborane-Transfer Reagent,
  Rui Guo, Tong Li, Rui Wei, Xin Zhang, Qianli Li, Liu Leo Liu, Chen-Ho Tung, Lingbing Kong,
  J. Am. Chem. Soc. 2021.
  https://doi.org/10.1021/jacs.1c06152