Cleavage of the N≡N Triple Bond and Unpredicted Formation of the Cyclic 1,3‐Diaza‐2,4‐Diborete (FB) 2 N 2 from N 2 and Fluoroborylene BF

A complete cleavage of the triple bond of N 2 by fluoroborylene (:BF) was achieved in a low‐temperature N 2 matrix by the formation of the four‐membered heterocycle FB( μ ‐N) 2 BF, which lacks a trans ‐annular N−N bond. Additionally, the linear complex FB=N−N=BF and cyclic FB( η 2 ‐N 2 ) were formed. These novel species were characterized by their matrix infrared spectra and quantum‐chemical calculations. The puckered four‐membered‐ring B 2 N 2 complex shows a delocalized aromatic two‐electron π‐system in conjugation with the exo ‐cyclic fluorine π lone pairs. This work may contribute to a rational design of catalysts based on borylene for artificial dinitrogen activation.