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Small Cycloalkane (CN) 2 CC(CN) 2 Structures Are Highly Directional Non‐covalent Carbon‐Bond Donors
Author(s) -
Bauzá Antonio,
Mooibroek Tiddo J.,
Frontera Antonio
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403680
Subject(s) - cyclopropane , cycloalkane , cyclobutane , synthon , covalent bond , supramolecular chemistry , crystallography , chemistry , ring (chemistry) , electrophile , carbon fibers , stereochemistry , crystal structure , materials science , organic chemistry , composite number , composite material , catalysis
High‐level calculations (RI‐MP2/def2‐TZVP) disclosed that the σ‐hole in between two C atoms of cycloalkane X 2 CCX 2 structures (X=F, CN) is increasingly exposed with decreasing ring size. The interacting energy of complexes of F − , HO − , N≡C − , and H 2 CO with cyclopropane and cyclobutane X 2 CCX 2 derivatives was calculated. For X=F, these energies are small to positive, while for X=CN they are all negative, ranging from −6.8 to −42.3 kcal mol −1 . These finding are corroborated by a thorough statistical survey of the Cambridge Structural Database (CSD). No clear evidence could be found in support of non‐covalent carbon bonding between electron‐rich atoms (El.R.) and F 2 CCF 2 structures. In marked contrast, El.R.⋅⋅⋅(CN) 2 CC(CN) 2 interactions are abundant and highly directional. Based on these findings, the hydrophobic electrophilic bowl formed by 1,1′,2,2′‐tetracyano cyclopropane or cyclobutane derivatives is proposed as a new and synthetically accessible supramolecular synthon.