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Ternary Complexes Stabilized by Chalcogen and Alkaline‐Earth Bonds: Crucial Role of Cooperativity and Secondary Noncovalent Interactions
Author(s) -
Mó Otilia,
MonteroCampillo M. Merced,
Alkorta Ibon,
Elguero José,
Yáñez Manuel
Publication year - 2019
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.201901641
Subject(s) - chalcogen , chemistry , crystallography , ternary operation , cooperativity , hydrogen bond , non covalent interactions , base (topology) , atom (system on chip) , molecule , organic chemistry , mathematical analysis , biochemistry , mathematics , computer science , embedded system , programming language
High‐level G4 calculations show that the strength of chalcogen interactions is enhanced dramatically if chalcogen compounds simultaneously form alkaline‐earth bonds. This phenomenon is studied by exploring binary YX 2 ⋅⋅⋅ N ‐Base complexes and two types of ternary MCl 2 ⋅⋅⋅YX 2 ⋅⋅⋅ N ‐Base, YX 2 ⋅⋅⋅ N ‐Base⋅⋅⋅MCl 2 complexes, in which YX 2 is a chalcogen compound (Y=S, Se; X=F, Cl), the N ‐Bases are sp , sp 2 , and sp 3 bases (NCH, HN=CH 2 , NH 3 ), and MCl 2 are alkaline‐earth BeCl 2 or MgCl 2 derivatives. Starting from the chalcogen‐bonded complexes YX 2 ⋅⋅⋅NH 3 and YX 2 ⋅⋅⋅HN=CH 2 , the binding site of a new incoming alkaline‐earth bond is found, surprisingly, to depend on the nature of the halogen atom attached to the chalcogen. For the YF 2 binary complexes the association site is the F atom of the YF 2 subunit, whereas for YCl 2 it is the N atom of the nitrogen base. Regarding YX 2 ⋅⋅⋅NCH complexes, N is the most favorable site for an alkaline‐earth interaction in ternary complexes, regardless of which YX 2 derivative is used. The explanation relies on the interplay of all the noncovalent interactions involved: the strong cooperativity between chalcogen and alkaline‐earth bonds, and the appearance of secondary noncovalent interactions in the form of hydrogen bonds.