Contain Iron, Rhenium Metal Organic Compounds Involved In The Reaction Mechanism Of Theoretical Research

In this work, the reaction mechanisms of two different types of reactions havebeen studied with the aid of density functional theory （DFT） calculations at thetheory of B3LYP, and the selectivity for forming different products has also beenexplored and analyzed.1. In the first part, for the reaction between the aryl complex [CpFe（CO）₂Ar]and styrene, the reaction mechanisms have been studied. The selectivity forforming different products has also been discussed by means of DFT method.1)The reaction completes mainly by four steps. The first step is dissociation of COfrom [CpFe（CO）₂Ar], giving a16e intermediate [CpFe（CO）Ar]. The second step isinsertion of olefin into Fe-Ph bond, affording an alkyl complex intermediate. Thethird step is an isomerization process giving a Fe···H-C agnostic-type intermediate.The last step undergoes β-H elimination, producing the product stilbene.2)Possible formation for the three isomeric products has been analyzed and explored,finding that the product trans-stilbene is preferred over the other two productskinetically and thermodynamically.3) Our study shows that the reaction becomesmore favorable kinetically when a strong electron-withdrawing group is attached tothe olefin.4) The reactivity for such reactions with different metal centers in thesame group has the following order: Fe> Ru> Os.2) In the second part, the mechanisms have been studied for the catalyticreaction between acetylene benzene and acetic acid in the presence of [Re（CO）₅Br].The selectivity for forming different products has also been discussed by means ofDFT method.1) The reaction completes according to the following steps. The firststep is dissociation of CO from [Re（CO）₅Br], giving a16e catalytically activespecies [Re（CO）₄Br]. The second step is insertion of terminal alkyne into theRe-Br bond, generating an alkenyl complex intermediate. The third step iscoordination of acetic acid to Re, accompanying cleavage of the Re←Brcoordination bond. In the fourth step, the hydroxyl hydrogen atom in acetic acidmigrates to the α-C of the alkenyl group, affording a complex of vinyl bromide.The fifth step is a coordination isomerism that C=C coordination is replaced bybromide coordination. The last process is related to formation of new C-O bondand re-formation of the Re-Br bond, obtaining the product and regenerating thecatalytically active species [Re（CO）₄Br].2) Possible formation for two of theisomeric products （E-3a and4a，see Figure4-3-1） has been analyzed and explored,finding that the product4a is preferred kinetically over the other one, while both of the products are similar in thermodynamics.