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The synthesis of a series of 1,2‐diamino‐o‐carboranes (1–4) is reported. The molecular structures of these diamino‐o‐carboranes are remarkable as the inner‐cluster C−C bonds are all ultra‐long (162.7–193.1 pm) and vary substantially with small variations in the substituents. The results of quantum mechanical investigations suggest that the origin of the bond elongation is significant in‐plane negative hyperconjugation of lone pairs of the nitrogen substituents with the σ* orbitals of the C−C bonds in o‐carboranes. Breaking the law: A series of 1,2‐diamino‐o‐carboranes with exceptionally long C−C bonds (up to 193 pm) were synthesized. The origin of this bond elongation was attributed to the in‐plane negative hyperconjugation between the lone pairs of the nitrogen atoms and the σ*C−C orbital in the o‐carborane. [ABSTRACT FROM AUTHOR]

A fluorostannylenoid (Cs+[R2SnF]− ( 9), R2=(TMS)2CCH2CH2C(TMS)2) was prepared by reacting a stable dialkylstannylene (R2Sn ( 8), R2=(TMS)2CCH2CH2C(TMS)2) with cesium fluoride at room temperature in THF. While 9 is stable in THF and DME, removal of the solvent leads to the regeneration of stannylene 8. No reaction occurred when 8 was treated with CsF in a hydrocarbon solvent. Addition of dibenzo-21-crown-7 ether to the THF solution of stannylenoid 9 followed by usual workup affords the corresponding crystalline stannylenoid crown ether complex, the X-ray structural analysis of which revealed a fluorine-bridged contact ion-pair structure. The reaction of 9 with excess phenylacetylene gives the corresponding di(phenylethynyl)stannane. [ABSTRACT FROM AUTHOR]

A series of 1,2‐diamino‐o‐carboranes with exceptionally long C−C bonds (up to 193 pm) were synthesized. In their Communication on page 1397 ff., 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. In the artwork, two red‐crowned cranes are holding this molecule, stretching the C−C bond almost to breaking point (depicted by the "Broken Bridge", Hangzhou). [ABSTRACT FROM AUTHOR]