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Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD Me )Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions **
Author(s) -
Passos Gomes Gabriel,
Xu Guangcan,
Zhu Xiaolei,
Chamoreau LiseMarie,
Zhang Yongmin,
BistriAslanoff Olivia,
Roland Sylvain,
Alabugin Igor V.,
Sollogoub Matthieu
Publication year - 2021
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.202100263
Subject(s) - covalent bond , electrostatics , chemistry , crystallography , electrostatic interaction , metal , natural bond orbital , atomic orbital , interaction energy , unpaired electron , electron , computational chemistry , chemical physics , molecule , density functional theory , physics , organic chemistry , quantum mechanics
What happens when a C−H bond is forced to interact with unpaired pairs of electrons at a positively charged metal? Such interactions can be considered as “contra‐electrostatic” H‐bonds, which combine the familiar orbital interaction pattern characteristic for the covalent contribution to the conventional H‐bonding with an unusual contra‐electrostatic component. While electrostatics is strongly stabilizing component in the conventional C−H⋅⋅⋅X bonds where X is an electronegative main group element, it is destabilizing in the C−H⋅⋅⋅M contacts when M is Au(I), Ag(I), or Cu(I) of NHC−M−Cl systems. Such remarkable C−H⋅⋅⋅M interaction became experimentally accessible within (α‐ICyD Me )MCl, NHC‐Metal complexes embedded into cyclodextrins. Computational analysis of the model systems suggests that the overall interaction energies are relatively insensitive to moderate variations in the directionality of interaction between a C−H bond and the metal center, indicating stereoelectronic promiscuity of fully filled set of d ‐orbitals. A combination of experimental and computational data demonstrates that metal encapsulation inside the cyclodextrin cavity forces the C−H bond to point toward the metal, and reveals a still attractive “contra‐electrostatic” H‐bonding interaction.