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1 2020

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Wiązanie trielowe, tetrelowe, pnikogenowe, chalkogenowe, halogenowe, aerogenowe : oddziaływania niekowalencyjne pierwiastków bloku P

Zierkiewicz Wiktor, Michalczyk Mariusz

Wiadomości Chemiczne

2020

[Z] 74, 9-10

587--607

It is widely accepted that hydrogen bonds contribute into a variety of meaningful processes in nature and human body which has reflection in the share of the scientific community attention over the last decades. Recent years have seen a veritable explosion of research into noncovalent interactions that are analogous to the commonly acknowledged H-bonds. It became obvious that detailed investigation of these types of short contacts should be extensively considered as the main target for theoretical chemistry. In 2007 the article described the σ-hole concept enlightened the phenomena of the halogen bond. Later extensions of this concept into the other elements in periodic table provided the necessary knowledge about the origin of these interactions and gave arise for introducing the other members of the σ-hole bonds family as the chalcogen, pnicogen, tetrel and triel bonds or even those involving noble gases. The foundation of the σ-hole theory is the presence of the region of thinned electronic density caused by the anisotropic accumulation of the negative charge on the covalent R-X bond (where X=halogen) what causes the rising of positive electrostatic potential on the outer side of X atom. This particular location becomes the binding site for the approaching nucleophile. As the σ-hole is located in plane of molecule on an extension of covalent bond, some molecules also contain a σ-hole region situated above and below the plane of the molecular framework. In current work the representative examples of complexes bonded through the σ- or π-holes and their most important features have been briefly given. The main goal was to show the diversity of this type of interaction which covers nearly all the elements of the block p of periodic table. Triel bonds are produced mainly by -hole interaction with Lewis bases and can be characterized by different nature for different elements (boron complexes are stabilized by electrostatics and charge transfer, while Al and Ga ones mostly by electrostatics). In tetrel, pnicogen and chalcogen bonded complexes it has been shown that during the process of dimerization the substantial geometric distortion is observed on the π-hole donor molecules. It causes the creation of the second complexation path through newly created π-hole. In chalcogen bonded complexes the alternative dimer is stabilized by π-hole and something like - due to presence of lone electron pair of chalcogen. Within the halogen bonds one can highlight the issue of weakening the negative hyperconjugation on the molecules of methylated derivatives of ammonia (like methylamine). It is caused by the appearing of σ-hole donor (FCCl3) which takes control of the majority part of intramolecular charge transfer and in this way enhances the link between subunits at the price of hampering the internal conjugation. Finally, the short report of aerogen bonds in literature is inserted in the last chapter of current paper. Some molecules with noble gases connected with highly electron-withdrawing constituents are able to generate both: σ- and π-hole on their surfaces and in consequences the stable complexes with Lewis bases (for example, diazines). The presence of the latter proves that the discussed types of interaction are very common for massive amount of atoms, even for those which are considered as less reactive.