D 4 Transition Metal Complexes Of Alkynyl And Vinyl Fork Ligand Isomerization Mechanism Of Inquiry

Quantum chemistry is a ramose subject of theoretical chemistry.Basal theories and methods of quantum mechanics are applied to research questions of chemistry.It is an basal science.Now, quantum chemistry was developed as an universal means to predict and explain molecular structures in chemistry or other subjects related to it.Quantum chemistry has been rapidly developed to be a powerful tool to explore the structures,bonding,stability,reactive properties, reaction mechanisms,and catalysis of organometallic compounds.The applications of quantum chemistry are clearly demonstrated to be significanly inportant in helping and guiding experimental chemists to design and synthesize new compounds and catalysts.In this paper,we made a simple introduction to the development of quantum chemistry,its applications in the organometallie chemistry and the selection of the calculational methods. Osmium and ruthenium compounds were used as study object in our work.All molecular geometries were optimized at the Becke 3LYP(B3LYP)level of density functional theory(DFT). Frequency calculations at the same level of theory have also been performed to identify all stationary points as minima(zero imaginary frequencies)or transition states(one imaginary frequency).The transition states involved were checked by IRC(Intrinsic Reaction Coordinate) analysis.The molecular structure,bonding and the isomerization mechanism are explained by the orbital interactions in chemistry.The isomerization mechanism of CpCl(PH₃)Os(HC=CH)system is studied at first.There are four possible rearrangement pathways:In pathâ… ,the reactant undergoes firstly 1,2-hydrogen migration to afford aη²-bound vinylidene metal intermediate,followed by cleavage of the M-(β-C)bond to give product.Pathâ…¡starts with the slide of the liagand to afford a transition state containingη²-(C-H)metal interaction,leading to the formation of alkynyl(hydrido)metal intermediate.Following this step,three possible paths are proposed.Pathâ…¡a undergoes 1, 3-hydrogen transfer from the metal center to theβ-carbon to yield the intermediate,followed by formation of product.In pathâ…¡b,reactant is directly formed via a 1,3-hydrogen transfer,but this transition state is structurally different from the transition state inâ…¡a.All the proposed mechanisms above are considered to be only the intramolecular hydrogen transfer.Pathâ…¡c considers an intermolecular hydrogen transfer in which a dinuclear transition state is involved. The CpCl(PH₃)Ru(HC=CH)and[Cp(PH₃)₂Ru(HC=CH)]⁺systems are studied subsequently. The investigation indicates the intermolecular hydrogen transfer is the most reasonable pathway for all the model system.For original experimental compounds having bulky substituents,steric hindrance should be taken into account and further investigations are needed.