Theoretical studies of early-transition-metal alkyl and alkylidene complexes
by Zhi-Hui Peng
xv, 191 leaves : ill. ; 30 cm
This dissertation deals with the quantum mechanical studies of the reactions involving early-transition-metal alkyls and alkylidenes. The reactions of three different systems have been intensively investigated. 44344443323...[ Read more ]
This dissertation deals with the quantum mechanical studies of the reactions involving early-transition-metal alkyls and alkylidenes. The reactions of three different systems have been intensively investigated.
The decomposition mechanisms of Group IVB tetraalkyl complexes MR4 are described in Chapter 1. The unimolecular and bimolecular methane elimination through α-hydrogen abstraction for MMe4, unimolecular methane elimination through γ-hydrogen abstraction for M(n-Pr)Me3, unimolecular neopentane elimination through both [alpha-hydrogen abstraction and γ-hydrogen abstraction for MNp4 were studied. Several clear differences in geometry and reactivity between TiR4 and ZrR4 (HfR4) are predicted.
The mechanistic studies of the decomposition of alkyl silyl complexes R3M(SiH3) (R=Me, CH2CMe3; M=Ti, Zr) are presented in Chapter 2. Both the monomeric and dimeric mechanism for Me3M(SiH3) and the monomeric mechanism for Np3M(SiH3) were studied. The various decomposition pathways were investigated and their preferences were explained.
The mechanism and stereochemistry of molybdenum alkylidenes catalyzed ring-opening olefin metathesis polymerization are investigated with model systems in Chapter 3. Transition structures for different approaches of alkene to the catalyst were located. The effect of the electronic properties of the alkoxy ligands on the rotation barrier, stabilities, reactivities of the catalyst and stereo-preference of the transition structures were explored.