The reductive coupling of dinitrogen

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Science  22 Mar 2019:
Vol. 363, Issue 6433, pp. 1329-1332
DOI: 10.1126/science.aav9593

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Boron brings nitrogen together

Whereas carbon is prone to making chains, nitrogen usually sticks to itself just once in the particularly stable form of N2. Légaré et al. now show that boron can coax two N2 molecules together under reductive conditions below room temperature. Two borylene units sandwiched the resulting N4 chain between them.

Science, this issue p. 1329


The coupling of two or more molecules of dinitrogen (N2) occurs naturally under the radiative conditions present in the ionosphere and may be achieved synthetically under ultrahigh pressure or plasma conditions. However, the comparatively low N–N single-bond enthalpy generally renders the catenation of the strongly triple-bonded N2 diatomic unfavorable and the decomposition of nitrogen chains a common reaction motif. Here, we report the surprising organoboron-mediated catenation of two N2 molecules under near-ambient conditions to form a complex in which a [N4]2– chain bridges two boron centers. The reaction entails reductive coupling of two hypovalent-boron-bound N2 units in a single step. Both this complex and a derivative protonated at both ends of the chain were characterized crystallographically.

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