Exploration of Transition Metal-Containing Catalytic Cycles via Computational Methods

PDF Version Also Available for Download.

Description

Styrene production by a (FlDAB)PdII(TFA)(η2-C2H4) complex was modeled using density functional theory (DFT). Benzene C-H activation by this complex was studied via five mechanisms: oxidative addition/reductive elimination, sigma-bond metathesis, concerted metalation deprotonation (CMD), CMD activation of ethylene, and benzene substitution of ethylene followed by CMD of the ligated benzene. Calculations provided evidence that conversion of benzene and ethylene to styrene was initiated by the fifth pathway, arylation via CMD of coordinated benzene, followed by ethylene insertion into the Ru-Ph bond, and then β-hydrogen elimination. Also, monomer (active species)/dimer equilibrium concentrations were analyzed. The results obtained from present study were compared ... continued below

Creation Information

Ceylan, Yavuz Selim May 2019.

Context

This dissertation is part of the collection entitled: UNT Theses and Dissertations and was provided by UNT Libraries to Digital Library, a digital repository hosted by the UNT Libraries. More information about this dissertation can be viewed below.

Who

People and organizations associated with either the creation of this dissertation or its content.

Publisher

Rights Holder

For guidance see Citations, Rights, Re-Use.

  • Ceylan, Yavuz Selim

Provided By

UNT Libraries

The UNT Libraries serve the university and community by providing access to physical and online collections, fostering information literacy, supporting academic research, and much, much more.

Contact Us

What

Descriptive information to help identify this dissertation. Follow the links below to find similar items on the Digital Library.

Degree Information

Description

Styrene production by a (FlDAB)PdII(TFA)(η2-C2H4) complex was modeled using density functional theory (DFT). Benzene C-H activation by this complex was studied via five mechanisms: oxidative addition/reductive elimination, sigma-bond metathesis, concerted metalation deprotonation (CMD), CMD activation of ethylene, and benzene substitution of ethylene followed by CMD of the ligated benzene. Calculations provided evidence that conversion of benzene and ethylene to styrene was initiated by the fifth pathway, arylation via CMD of coordinated benzene, followed by ethylene insertion into the Ru-Ph bond, and then β-hydrogen elimination. Also, monomer (active species)/dimer equilibrium concentrations were analyzed. The results obtained from present study were compared with that of a recently reported RhI complex to help identify more suitable catalysts for the direct production of styrene from ethylene and benzene.

Second, theoretical studies of heterobimetallic {Ag–Fe(CO)5}+ fragments were performed in conjunction with experiments. The computational models suggested that for this first example of a heterodinuclear, metal-only FeAg Lewis pair (MOLP) that Fe(CO)5 acts as a Lewis base and AgI as a Lewis acid. The ῡCO bands of the studied molecules showed a blue shift relative to those measured for free Fe(CO)5, which indicated a reduction in Fe→CO backbonding upon coordination to silver(I). Electrostatic interaction is predicted via DFT as the dominant mode of Fe—Ag bonding augmented by a modest amount of charge transfer between Ag+ and Fe(CO)5.

Third, computational analyses of hypothetical transition metal-terminal boride [MB(PNPR)] complexes were reported. DFT, natural orbital analysis (NBO), and multiconfiguration self-consistent field (MCSCF) calculations were employed to investigate the structure and bonding of terminal boride complexes, in particular the extent of metal dπ - boron pπ bonding. Comparison of metal-boride, -borylene and –boryl bond lengths confirms the presence of metal-boron π bonds, albeit the modest shortening (~ 3%) of the metal-boron bond suggests that the π-bonding is weak. Their instabilities, as measured by free energies of H2 addition to make the corresponding boryl complexes, indicate terminal boride complexes to be thermodynamically weak. It is concluded that for the boride complexes studied, covering a range of 4d and 5d metals, that the metal-boride bond consisted of a reasonably covalent σ and two very polarized π metal-boron bonds. High polarization of the boron to metal π-bonds indicated that a terminal boride is an acceptor or Z type ligand.

Finally, anti-Markovnikov addition of water to olefins has been a long-standing goal in catalysis. The [Rh(COD)(DPEphos)]+ complex was found as a general and regioselective group 9 catalyst for intermolecular hydroamination of alkenes. The reaction mechanism was adapted for intermolecular hydration of alkenes catalyzed by a [Rh(DPEphos)]+ catalyst and studied by DFT calculations. Olefin hydration pathways were analyzed for anti-Markovnikov and Markovnikov regioselectivity. On the basis of the DFT results, the operating mechanism can be summarized as follows: styrene activation through nucleophilic attack by OHδ− of water to alkene with simultaneous Hδ+ transfer to the Rh; this is then followed by formation of primary alcohol via reductive elimination. The competitive formation of phenylethane was studied via a β-elimination pathway followed by hydrogenation. The origin of the regioselectivity (Markovnikov vs anti-Markovnikov) was analyzed by means of studying the molecular orbitals, plus natural atomic charges, and shown to be primarily orbital-driven rather than charge-driven.

Language

Identifier

Unique identifying numbers for this dissertation in the Digital Library or other systems.

Collections

This dissertation is part of the following collection of related materials.

UNT Theses and Dissertations

Theses and dissertations represent a wealth of scholarly and artistic content created by masters and doctoral students in the degree-seeking process. Some ETDs in this collection are restricted to use by the UNT community.

What responsibilities do I have when using this dissertation?

When

Dates and time periods associated with this dissertation.

Creation Date

  • May 2019

Added to The UNT Digital Library

  • June 10, 2019, 9:31 a.m.

Usage Statistics

When was this dissertation last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 10

Interact With This Dissertation

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

International Image Interoperability Framework

IIF Logo

We support the IIIF Presentation API

Ceylan, Yavuz Selim. Exploration of Transition Metal-Containing Catalytic Cycles via Computational Methods, dissertation, May 2019; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc1505287/: accessed August 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; .