Theoretical Study On The Rare Gas Compounds Of Insertion Type

In 1962,British chemist Neil Bartlett successfully synthesized Xe⁺[Pt F₆]^-,the first Xe compound,breaking the traditional understanding that rare gas elements cannot form bonds.In 2000,Khriachtchev and his colleagues successfully synthesized the first Ar compound HAr F,which set off a wave to the research of rare gas elements.In recent decades,more and more rare gas compounds have been predicted and detected through theoretical calculation or experiment.At present,the rare gas compounds of insertion type have become a hot topic and attracted much attention.In this paper,we used the ab initio method and density functional method of quantum chemistry to study theoretically several Rg inserted compounds containing boron(B)or transition metals(Cu,Ag,Au,Fe),and analyzes their geometry structure,stability and bonding nature.The main contents of the study are as follows:(1)Ab initio and DFT calculations were performed to investigate the geometric structure,stability,and chemical bonding nature of the noble gas inserted compounds F-Rg-BR₂(Rg=Ar,Kr,Xe and Rn).The equilibrium geometries and the transition state structures were optimized on the ground state potential energy surface using the B3LYP-D3 and MP2 methods.It was found that the F-Rg-B portion of the F-Rg-BR₂ species is linear in the local energy minima but curved in the saddle points.The NBO,AIM,ELF and EDA analyses suggest that these compounds can be expressed as F^-(Rg-BR₂)⁺due to the covalent Rg-B bond and the ionic interaction between F and Rg.The single point energy and activation energy barrier were calculated by CCSD(T)/aug-cc-pVTZ(-PP)method.Thermodynamic data assert the metastable behavior of the F-Rg-BR₂ molecules.The transition state structure and IRC of the spontaneous dissociation into BFR₂+Rg for F-Rg-BR₂ affirms the kinetic stability of the F-Rg-BR₂ molecules.The effects of the various substituents R=F,OH,CN and CCH on the structural parameters and the bond nature have been systematically studied.It is found that the substituent CN can lead to form the shortest and strongest FRg and Rg B bonds.(2)The structural optimization and frequency calculation were carried out for the stable and transition states of the inserted rare gas compounds FMBRg F(Rg=Ar,Kr,Xe,Rn;M=Cu,Ag,Au),using B3LYP-D3 and MP2 methods combined with aug-cc-pVTZ(-PP)basis sets.Three dissociation pathways of FRg BMF molecules are discussed,and the single-point energy of the molecule is calculated by CCSD(T)/aug-cc-pVTZ(-PP)level.The metastable properties of the molecule were proved from two aspects of thermodynamic stability and kinetic stability.Meanwhile,the bonding properties of the chemical bonds in FRg BMF molecules were analyzed.It was found that the F-M bond and the Rg-F bond in the molecule are ionic bonds,and the M-B bond and the B-Rg bond have strong covalent characteristics.In addition,the insertion of Rg atoms plays a certain role in stabilizing the chemical bonds in BMF₂.(3)The equilibrium geometries were optimized for the Fe Rg(Rg=He?Rn)molecules and Rg-inserting compounds Fe Rg F^+/-and HRg Fe^+/-(Rg=Kr,Xe,Rn)using the B3LYP,MP2 and MP4(SDQ)methods combined with aug-cc-pVTZ(-PP)basis sets,and the frequency and dissociation energy were also calculated.In addition,we also used the CCSD(T)/aug-cc-pVTZ(-PP)method to refine the energy.It was found that the Fe Rg F^+/-and HRg Fe^+/-species are linear in the local energy minima.The dissociation processes of the Rg compounds are generally endergonic,endothermic and nonspontaneous,thus these compounds are thermodynamically stable.The NBO and AIM analyses and the electron localization function(ELF)were employed to study the bonding nature of rare gases with iron.In these compounds the rare gas atoms are found to be positively charged and lost electron density more or less.In the diatomic molecules Fe Rg there is only small charge transferred from Rg to Fe,the bond orders are also very small,and the topological properties at the BCP between Rg and Fe imply a noncovalent interaction between Rg and Fe.The ELF distribution of the diatomic molecules for He?Kr is divided into two disjunct parts of Fe and Rg;in Fe Xe the ELF distributions of Fe and Xe link upinto a single stretch enclosing in a fluorescent light blue profile;in the ELF of Fe Rn the two parts of Fe and Rn also adheres with each other.There are many new special characters of chemical bonding between Rg and transition metals.