Exceptionally Long C−C Single Bonds in Diamino‐o‐carborane as Induced by Negative Hyperconjugation

A series of 1,2‐diamino‐o‐carboranes with exceptionally long C−C bonds (up to 193 pm) were synthesized. In their Communication (DOI: 10.1002/anie.201812555), Z. Li, X.‐Q. Xiao et al. attribute this bond elongation to the in‐plane negative hyperconjugation between the lone pairs of the nitrogen atoms and the σ*_C−C orbital in the o‐carborane. Two red‐crowned cranes are holding this molecule, stretching the C−C bond almost to breaking point (depicted by the Broken Bridge, Hangzhou).

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