Theoretical Studies On Chemical Bonds In Group 13 Dimetal Sandwich Complexes And Dicopper Cluster Compounds

Organometallic clusters have attracted much attention due to their unique redox, electron transport, electrical, catalytic, optical, andmagnetic properties. The sandwich complexes have been appied into Olefin polymerization catalysis reaction, C-H activation reaction and biochemicalreaction processes due to their interesting electronic structure and bonding properties. Studies on organometallic clusters have great contributions to the development of chemistry, especially for catalytic and materials science. In this thesis, the electron structure and nature of chemical bond in copper(I) complexes with NHC/NHCP ligands and in low valence state Group 13 sandwich metal compounds were studied. All of the works have been studied within the framework of the ‘atoms in molecules’(AIM) theory and by using ‘electron localization functions’(ELF) analysis. All calculations are carried out by using the Gaussian program package. The topological analysis of electron density of molecules has been studied by using AIMALL, AIM2000, Multiwfn and TOPMOD programs. The main contents are the following aspects: 1. Factors which affecting the Cu···Cu distance in copper(I) complexes with the N-heterocyclic carbene(NHC), Bis-NHC and N-phosphinomethyl-functionalized NHC(NHCP) ligands have been investigated. The calculated results show that the ligands, ring size and shape, substitution pattern of NHC/NHCP, and overall charge of the system are factors that affect the Cu···Cu distance. The NHC ligand and an overall positive charge of the system lead to short Cu···Cu distance. Topological analysis shows that there are attractions between the two Cu atoms. And the Cu···Cu attractions in the eight-membered systems and in the 10-membered cation systems are moderately strong and belong to closed-shell type, which have partially covalent shared-closed interactions. Whereas the same interactions in the 12-membered cation system and in the neutral system with Br are weak and belong to closed-closed interactions. 2. It has been found in experiment that the geometries of Cp*4Al4(Cp*=C5Me5) and Cp4Al4(Cp=C5H5) are similar, while Cp*4Al4 is more stable than Cp4Al4. In this part, the different stabilities of Cp*4Al4 and Cp4Al4(Cp=C5H5) have been expained for the view of theoretical study. The influences of X atom on the nature of M-M bond in Cp2M2X2(M=B, Al, and Ga) have been analyzed and compared within the framework of AIM and ELF. The calculated results show the more stability of Cp*4Al4 is due to the H···H interaction between the methyl on the same and different Cp ring; In Cp2M2X2, the B-B bond belongs to covalent bond while Al-Al and Ga-Ga bonds belong to metallic bond. The strengths of M-M bond in Cp2M2X2(M=B, Al, and Ga) decrease in the sequence of B-B > Al-Al> Ga-Ga. The inflences of X atoms on the B-B bond are different from those on Al-Al and Ga-Ga bonds. The B-B bonds of Cp2B2X2 become stronger in the following of X=F, Cl, Br, and I. While the strength of the Al-Al and Ga-Ga bonds decrease in the following of X=F, Cl, Br, and I. 3. In the third part, the nature of M-M bonding in Cp2M1M2I2(M =B, Al, Ga, In, Tl, Cp=C5H5) have been analyzed and compared within the framework of AIM, ELF and NBO. The calculated results show that except Cp2 BAl I2 and Cp2 BGa I2, the M-M bond lengths of Cp2M1-M2I2(M=B, Al, Ga, In, Tl; Cp=C5H5) increased in the sequences of M=B, Al, Ga, In and Tl, which is the same as the atom radius sequences. Both the strength and the covalent character of the M-M bond are decrasing in the order of M= Al, Ga, In, Tl. The metallic character of the M-M bonds has the reverse trending. The innovations in the thesis: 1. The regulatory factors, which affected the Cu···Cu distances in copper(I) complexes with Bis-NHC/NHCP ligands, have been determined assessed by theoretical approaches. This can provide useful information for chemical syntheses and applications of these complexes. 2. The geometries of Cp*4Al4(Cp*=C5Me5) and Cp4Al4(Cp=C5H5) are similar, while their stabities are different. The more stability of Cp*4Al4 are explained form the view of topological analysis of electron density. 3. The existence of Non-nuclear attractor(NNA) in binuclear main-group metal metallocenes have been found and explained.