Application of DFT Methods on the Mechanistic Studies of Selected Organometallic Reactions

• Main Authors: Chia-Ming Weng, 翁嘉明
• Other Authors: Fung-E Hong
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/75239446852566990190

博士 === 國立中興大學 === 化學系所 === 100 === Part 1 The transmetallation processes of di-substituted diimine (PhN=CH-CH=NPh) chelated palladium complexes catalyzed Suzuki-Miyaura cross-coupling reactions of phenyl chloride (PhCl) and phenylboronic acid [B(OH)2Ph] in the presence of diverse Lewis bases (OH-, F-, OtBu-, CO32- and PO43-) were studied by DFT methods with the B3LYP functional. The flexibility of diimine as either mono- or bi-dentate ligand in the mechanism provides a valuable channel for lowering the energy barriers of this process. The energy barriers for the process with multi-valent bases are smaller than that of uni-valent cases. Besides, high valent oxoanions such as CO32- and PO43- provide more versatile bonding modes in the processes. Activation Strain Model has also been employed to investigate the extent of deformation of the reactants including the catalyst in the transition state. Part 2 Several adiabatic potential energy surfaces (PES) were employed for probing the processes of the formations of cobaltacycles (η5-C5H5)(PMe3-κP)Co(1,4-C4(PPh2)2R2-1κC,4κC’) (3P1) and their conversions to CpCo-cyclobutadienes (η5-C5H5)Co(η4-1,2-C4(PPh2)2R2) (41). Various substituents of alkynes, RC≡CPPh2 (R = H, F, CF3, CH3, Ph, iPr), are taken into account. The results show that the reaction leads to the formation of cobaltacycle derivative with electron-withdrawing or less steric effect substituent (R = F, H) and to the formation of CpCoCb derivative with bulky group (R = iPr). Part 3 A new method for the direct preparation of H-phosphinates, O=P(H)(R)(OC4H8X) (R=Ph, tBu; X=Cl, Br, I), has been explored. It is through unprecedented ring-opening reactions of cyclic ethers with magnesium halides in the presence of PRCl2 or PCl3. The process is straightforward and all the reagents are cheap and readily available. Two distinct reaction pathways were examined by DFT methods. For one pathway, the phosphine ensures the product(s) is/are stable thermodynamically. Another pathway demonstrated that the participation of phosphine reduces the activation energy.