Several Iridium, Tungsten Metal Organic Compounds Involved In The Theoretical Study Of Reaction Mechanism

Density functional theory (DFT)calculations at the B3LYP level of theory are carried out to study and analyze the following three projects. Our major purpose is to investigate the molecular structures, bonding, and mechanisms of the reactions in the three different projects in which most of the species are organometallic compounds.1. The detailed catalytic mechanisms on transfer hydrogenation of ketones are explored by employing the representative reaction of 3-pentanone and 2-propanol catalyzed by the model complex IrH₃[(Me₂PC₂H₄)₂NH], derived from the catalyst IrH₃[(ⁱPr₂PC₂H₄)₂NH], with the aid of the density functional theory calculations. The geometrical transformation from an octahedron to a Y-type involved in the catalytic cycle is also elucidated in terms of molecular theory of transition metal complexes. The trend for the variation of Ir-N bond distance is also analyzed. In addition, transfer hydrogenation between butanone and 2-propanol catalyzed by the model complex IrH₃[(Me₂PC₂H₄)₂NH] is also studied sequently as a supplement, and the result is very similar to case of the 3-pentanone.2. By the aid of density functional theory (DFT) calculations we studied the formation mechanism of two complexes Cp^*(CO)₂W{κ²(Si,N)-Me₂N-(o-C₆H₄SiMe₂)} and Cp^*(CO)₂W{κ²(Si,C)- SiMe₂NMe₂(o-C₆H₄)} developed by Hiromi Tobita group in 2003. Our calculations indicate that the reaction mechanism involves dissociation of one carbonyl ligand of Cp^*(CO)₃WMe, oxidative addition of the Si-H bond , release of methane, and then ligating of the intramolecular nitrogen atom to the metal center to give the first complex mentioned above that has been demonstrated to be existent experimentally. This intermediate is theoretically predicted to be favored kinetically. Then 1,2-aryl migration from Si atom to the metal center occurs accompanying coordination of the N atom to Si, to give the final product. The final product is found to be most thermodynamically favorable. Some experimental observations were explained on the basis of our results of calculations. The structural features and relative stability involved in the reaction mechanisms were also discussed.3. In recent years, more and more scientists considerably concerned about transition-metal-mediated transformation of nitriles, such as nitrile insertion, coupling, C-N or C-C bond formation, and cyclo-addition, because all of these typical reactions mentioned above are of potential applications for synthesis of nitrogen-containing organic compounds. The organometallic compounds containing nitrile have been investigated experimentally in recent years. Hiromi Tobita and co-workers obtained N-silylatedη²-ininoacyl tungsten complexes Cp^*(CO)₂W{κ²(C,N)-C(Me)=N(SiR₃)(R = Et or p-Tol) having a three-membered metallacycle, by treatment of Cp^*(CO)₂W(NCMe)Me with tertiary silanes in 2007. In this paper, with the aid of density functional theory (DFT) calculations, we attempt to theoretically investigate the detailed reaction mechanisms for this reaction on the basis of the experimental observations and the experimentally proposed reaction mechanism by using the model reaction of Cp(CO)₂W(NCMe)Me with HSiMe₃.