Theoretical Studies On The Bonding Properties Of Group 13 Compounds-Monovalent Metal Ions（or N₂）

Group 13 compounds have attracted much attention due to their special electron-deficient properties and their application value in the fields of synthesis,medicine,and optoelectronic materials.In recent years,the nature of the metal-metal multiple bond in Group 13 metal alkyne compounds and the activation of small organic molecules by boron compounds have been continuously discussed.Exploring the nature of bonding in Group 13compounds can help us understand the structure and properties of Group 13 compounds,enrich the theory of chemical bonds,and provide theoretical basis for chemical synthesis.In this work,quantum chemical calculation methods are used to discuss the bonding properties of Group 13 compounds with monovalent metal ions and N₂.The work of this thesis is divided into the following two parts:1.The multiple bonding between group 13 elements is still the challenging frontiers in modern chemistry.And there are several ways for metals（M）to bind to multiple bonded diatomic center（XX）.To explore the side-on and end-on bond modes between metals cations M⁺and dialuminyne,a theoretical study of the interactions between alkali metal cations Li⁺,Na⁺,K⁺or transition metal cations Cu⁺,Ag⁺,Au⁺and（NHC）Al≡Al（NHC）has been carried out.The bent geometry and the negative electrostatic potential region at the end of the Al-Al bond make it possible to bind M⁺.The calculated results show that only side-on bond mode has been found in alkali metal cations complexes while the transition metal cations complexes prefer end-on bond mode.The interactions between alkali metal cation and（NHC）Al≡Al（NHC）follows the order of Li⁺>Na⁺>K⁺while,for the end-on transition metal cations complexes,the interactions increase in order of Au⁺>Cu⁺>Ag⁺.There is obvious covalent character for end-on transition metal cations complexes by BLW-ED and QTAIM analyses.2.The binding of transition metal（TM）to dinitrogen is critical to the industrial Haber-Bosch process and the natural fixation of nitrogen by nitrogenase enzymes.However,due to the scarcity,high cost,toxicity,and environmental issues associated with transition metals,the exploration of main-group compounds that behave and react similarly to transition metal complexes has attracted significant interest in recent years.Recently,Braunschweig and coworkers found that borylene（CAAC）DurB,where CAAC is a cyclic alkyl（amino）carbene and dur refers to 2,3,5,6-tetramethylphenyl,can bind and notably activate N₂,and the resulting[（CAAC）DurB]₂N₂ is of a bent B-N-N-B core.Since the dinitrogen ligand in transition metal complexes is generally linear,here we probed the bonding characteristics of both terminal end-on and end-on bridging borylene-N₂ complexes from a novel theoretical perspective.While the activation of N₂ in the terminal end-on（CAAC）HBN₂ follows a similar mechanism in transition metals and can be explained with aσdonation from theσorbital（lone pair）of N₂ and aπback-donation from theπorbitals of（CAAC）HB,computations reveal a different bonding scheme for the end-on bridging borylene-N₂ complex where theσdonation mainly comes from theπorbitals of N₂ and thus there are two opposite push-pull channels.It is the push-pull interaction that governs the enhanced activation of N₂ and the B-N-N-B bent geometry as the N-N bond length would be shortened（less activated）and the B-N-N-B core would be linear when the push-pull effect were deactivated.Further studies show that replacing the substituents bonded to the boron atom can modulate the strength of the push-pull interaction and lead to different geometries of end-on bridging borylene-N₂ complexes.