Density Functional Study On The Geometries And Electronic Properties Of Bcod Transition Metal Complexes

Compared with the rigid planar pentagonal cyclopentadiene?C₅H₅?ligands,the bis?bicyclo[3.2.1]octa-2,6-dien-4-yl??bcod?ligands are more flexible in providing electrons to the transition metal atoms with different coordination modes.In this thesis,several density functional methods,such as M06-L,B3PW91,and OPBE are used to systematically study the geometric structure and electronic properties of transition metal sandwich complexes?bcod?₂M?M=Ti to Cu?and the iron carbonyl complexes?bcod?₂Fe₂?CO?_n?n=4,3,2,1?.The main research results are as follows:?1?A theoretical study of the geometries,electronic structures,and the thermal stabilities for the bis?bicyclo[3.2.1]octa-2,6-dien-4-yl?complexes of the first row transition metals,?bcod?₂M?M=Ti to Cu?,including the experimentally known chromium and iron derivatives,are performed.For the early first row traisiton metals?Ti,V,Cr?complexes,each bcod ligand will denote all the five electrons to the central metal atom for filling the valence obitals.However,for the late transition metal complexes,the electrons from the C=C double bond and the allyl part of the bcod ligands only provide portion of the five electrons to the metals due to rich electron characters of these metals.In some predicted structure,the C-H bond from the bcod ligand can form three-center two-electron M-H-C bond to the central metal atoms for flexibly providing electrons with unique mode.?2?Study of the binuclear iron carbonyl complexes?bcod?₂Fe₂?CO?_n?n=4,3,2,1?,compared with the?C₅H₅?₂Fe₂?CO?_n system,shows that the bcod ligand can regulate the electronic structure of the central metal atoms in the bcod metal carbonyl derivatives more flexibly by forming the C-H—M multi-center agostic bonds of the the bcod ligand.Except the Fe₂C two-electron three-center bonding styles,the partially bonding mode of the C=C double bond of the bcod ligand and bridging four-electron donor carbonyl group?²-?-CO were also found in the investigated compounds.The research also suggests that multicentric interactions can reduce the effective direct interactions between the metal atoms,the iron-iron bond WBI values for the structures containing double bridged carbonyl groups are lower than those without the bridged carbonyl groups.It also indicates that the triplet spin state structure has a lower WBI value than a similar singlet structure.This thesis is divided into the following four chapters to elaborate.Chapter 1 and chapter2 are the introduction section and theoretical methods section.In chapter 3,the calculated results for the?bcod?₂M?M=Ti to Cu?and?bcod?₂Fe₂?CO?_n?n=4,3,2,1?compounds are discussed in detall.Finally,in chapter 4 the research work of the whole thesis is summarized.