Longest C–C Single Bond among Neutral Hydrocarbons with a Bond Length beyond 1.8 Å

Abstract

Compounds with an ultralong CC single bond have been successfully constructed in three steps from commercially available dihalo aromatics. The intramolecular ''core-shell strategy'' is a key tactic for stabilizing compounds with an ultralong CC bond. Using this concept could lead to an even longer CC bond (''hyper covalent bonds'' with a bond length of 1.8-2.0 Å) because the covalently bonded state and non-bonded state are seamlessly connected in terms of the interatomic distance.

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

“…However,t he measured C À Cb ond lengths in the nitrogensubstituted o-carboranes 1-4 significantly exceed this value. [14,17] This CÀCdistance is also longer than the 1,2-dithiolato-, 1,2diphosphono-, and mono-amino o-carborane derivatives (180.3 pm, [35] 172.2 pm, [36] and 185.2 pm, [21] respectively). This value exceeds that of the bis-diamondoids,and those of the dispiro(acridan)-substituted acenaphthenes.…”

“…This value exceeds that of the bis-diamondoids,and those of the dispiro(acridan)-substituted acenaphthenes. [14,17] This CÀCdistance is also longer than the 1,2-dithiolato-, 1,2diphosphono-, and mono-amino o-carborane derivatives (180.3 pm, [35] 172.2 pm, [36] and 185.2 pm, [21] respectively). In this comparison it is notable that the primary diamine 1 already shows am arked bond length elongation (by 13 %), but that the C À Cb ond in diimine 2b is much less stressed (only 6% elongation).…”

“…[5] Larger deviations from the standard value have been found in compounds having extraordinary ring strain, extreme steric congestion, or electronic perturbations. [15][16][17][18] Also for closo-1,2dicarbadodecaboranes,w ith formally hexa-coordinated carbon atoms and am ulticenter bonding situation, many experimental results reveal CÀCb onds that are longer than 174.8 pm. Recently,F okin, Schreiner, and co-workers reported the synthesis of hydrocarbons with extremely long CÀCbonds,stabilized by attractive London dispersion forces between two large diamondoid substituents [12][13][14] (Figure 1).…”

“…Ishigaki, Suzuki, and co-workers obtained aseries of dispiro-(acridan)-substituted pyracene and acenaphthenes with C À C bond lengths of up to 180.6 pm. [15][16][17][18] Also for closo-1,2dicarbadodecaboranes,w ith formally hexa-coordinated carbon atoms and am ulticenter bonding situation, many experimental results reveal CÀCb onds that are longer than 174.8 pm. [19][20][21] Previous density-functional theory (DFT) computations indicated that 1,2-(NH 2 ) 2 -o-carboranes could have strikingly long C À Cb onds.…”

O(−)⋯C interactions and bond formation in 1-naphtholate anions with peri-located electrophilic carbon centres

“…11 O---C interactions occur too when oxygen lone pairs stabilise an electron-deficient alkene or a carbocation, with 4 and 5 being particular examples 12 and have been reported between an ether and a ketone 13 and between an ester carbonyl and a nitrile. 14 The peri-naphthalene scaffold's unique structure has been used considerably for studying molecular interactions especially those involving nitrogen, [15][16][17][18][19] and has provided an effective molecular environment for the observation of C-C bonds as long as 1.75 Å) in 7 20 and for the study of rare sulfur functionalities such as vic-disulfoxides and bis(sulfonyl)nitroxide radicals and for preparation of a source of S=O 21 as well as S---C interactions. 22 We recently reported two types of interaction between carboxylate and aldehyde groups in the anion 6 for a range of salts of naphthaldehydic acid (Fig.…”