Construction Of Multilayer Sandwich Compounds From Half-metal-sandwich: Theoretical Assessments

The chemistry of sandwich complexes continues to attract a great deal of attention, due to their successful applications in many areas of chemistry such as olefin polymerization catalysis, asymmetric catalysis, C-H bond activation, and bioorganometallic chemistry.In this thesis, we studied the probability of constructing double(Cp2M) and triple decker(Cp3M2) sandwich compounds from half-sandwich(Cp M, Cp = C5H5; M = Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Cu, and Zn) and Pn10 M from Pn5- and Pn5M(Pn = N, P, As, Sb, Bi; M = Li, Na, K, Be, Mg, Ca, Fe, Co and Ni). The nature of chemical bonds has been studied within the framework of the ‘atoms in molecules’(AIM) theory and by using ‘electron localization function’(ELF) analysis. All of the quantum chemistry calculations are carried out by using the Gaussian program package. The topological analysis of electron density has been studied using AIMALL program, AIM2000 program, TOPMOD program and MULTIWFN program. The main contents include three parts:1. The probability and property of constructing double(Cp2M) and triple decker(Cp3M2) sandwich compounds from half-sandwich(Cp M, Cp = C5H5; M = Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Cu, and Zn) are discussed based on the geometry, energy and topological properties at B3LYP/6-311++G(d, p) level. The calculated results show that the alkali metals and transitional metals(Fe, Co, Ni) with more unpaired electron are more inclined to form the high-symmetry sandwich complexes than alkaline earth metals do. The symmetries of Cp2 M and Cp3M2(M = Cu and Zn) are low. In Cp2 M and Cp3M2 sandwich complexes, the electrostatic character and π orbital interaction are dominant. For Cp3M2, the proportion of both orbital interaction in the total M-C interaction and the σ interaction in the orbital interaction are larger than those in Cp2 M. The nature of the M-C bond and the aromaticity of Cp ring are well correlated to the bond length of M-C bond. The shorter M-C bond, the more covalent character it has. For s-blocked main group metal, the shorter bond length corresponds to the larger NICS(1), while corresponds to the smaller NICS(1) for the d-blocked transition metal.2. The geometries and property of Pn10 M, which constructed by Pn5- and Pn5M(Pn = N, P, As, Sb, Bi; M = Li, Na, K, Be, Mg, Ca, Fe, Co, Ni), are discussed at M062 X level. The 6-311++G(d) basis set were used for Li, Na, K, Be, Mg, Ca, Fe, Co and Ni and cc-pvdz basis set for N, P and As and the cc-pvdz-PP basis set for Sb and Bi. The calculated results show that the alkali(Li, Na, K) and transitional metal with more unpaired electron(Fe, Co, Ni) are more inclined to form the sandwich complexes with high-symmetry. For the same metals, π-type interactions in the Pn10 M are bigger than those in Pn5 M. The half-sandwich and sandwich complexes with alkali metals and the alkaline earth metals are aromaticity, while those complexes with transition metals are antiaromaticity.3. The properties of a new delocalized E···E bonding(E = VA, VIA elements) in peri-1,8-disubstituted naphthalene derivatives are studied at the B3LYP/aug-cc-pvdz level. The calculated results predict the existence of the delocalized bonding, E···E bond for E=O, S, Se, N, P and As in the peri-1,8-disubstituted naphthalene derivatives. In total, chalcogen···chalcogen bonding is stronger than nitrogen···nitrogen bonding. Topological analysis show that this kind of E···E bonding belongs to weak interaction. The strength of the E···E bonding decreased in the sequence of O, S, Se or N, P, As. The E···E bonding are electrostatic interactions for E = O, S, Se, N, and P, while the As···As bonding has partly covalent interaction.The innovations in the thesis:1. The alkali metals and transitional metals with more unpaired electron are more inclinedto form the high-symmetry sandwich complexes than alkaline earth metals do.2. The natures between metal-Cp- and metal-Pn5- are different:π orbital interactions aredominant between metal-Cp-, while between metal and Pn5-, σ-type interaction aredominant.3. The influences of transition metals and main group metals on the aromaticity aredifferent, due to d electron of transition metals.