Mechanistic studies on activation of dioxygen using iridium and platinum triphenylphosphine complexes : protonation of coordinated peroxide, and oxygenation of coordinated hydride
department or school: Science, Faculty of
department or school: Chemistry, Department of
data provider: DSpace
degree campus: UBCV
creator: Sue, Chen-youn
issued: 2010-10-18T18:00:39Z
issued: 1988
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Kinetic and mechanistic studies on the activation of dioxygen using iridium and platinum triphenylphosphine complexes via oxygenation-protonation (i.e. protonation of coordinated peroxide) and protonation-oxygenation (i.e. oxygenation of coordinated hydride) processes are described. Dioxygen is activated in the form of a dioxygen (peroxide) metal complex, which upon protonation produces H₂O₂ stoichiometricaUy. Oxidation of the oxidizable ligands or substrates sometimes occurs when free H₂O₂ is present in the reaction systems. The reversible oxygenation of trans-IrCl(CO)(PPh₃)₂ (eq. 1) has been re-examined at 25 °C to obtain data in benzene (k₁ = (3.4 ± 0.3) x 10⁻² M⁻¹s⁻¹, k₋₁= ~1.5 x 10⁻⁵ s⁻¹) and in dichloromethane (k₁ = (6.6 ± 0.3) x 10⁻⁷s⁻¹mm Hg⁻¹, k₋₁= (1.6 ± 0.1) x 10⁻⁵ s⁻¹).[See Thesis for Equations] Complex II reacts stoichiometrically with trifluoroacetic acid to produce H₂O₂ which further oxidizes the CO and PPI13 ligands, but with HCl the oxidation of CO or PPH₃ ligand by H₂O₂ does not take place; II reacts with free PPh₃ to give I and OPPH₃. The reaction of IrHCl₂(CO)(PPh₃)₂, III, with O₂ follows the sequence of steps outlined in eqs. 2, 1, 3 and 4. [See Thesis for Equations] This reaction sequence is proposed based on kinetic studies and product analysis. At 25 °C in dichloromethane, the rate constant (k₂) of the reductive-elimination reaction is (3.1 ± 0.1) x 10⁻⁵ s⁻¹ and the rate constant (k₋₂) of the oxidative-addition reaction is (4.4 ± 0.2) x 10² M⁻¹s⁻¹. Within the reversible reactions (2) and (1), HCl and O₂ compete with the intermediate I. Reaction (1) is eventually favoured because of the rapid protonation reaction (3) that scavenges the free HCl and prevents the reverse of reaction (2). Reaction (3) is therefore the driving force of the overall reaction between III and O₂. However, the forward step of reaction (2) is rate-determining in the complex process. Removal of one chloride ligand from III leads to the elimination of HCl from III and the …
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/29301
note: M E C H A N I S T I C S T U D I E S O N A C T I V A T I O N O F D I O X Y G E N U S I N G I R I D I U M A N D P L A T I N U M T R I P H E N Y L P H O S P H I N E C O M P L E X E S : P R O T O N A T I O N O F C O O R D I N A T E D P E R O X I D E , A N D O X Y G E N A T I O N O F C O O R D I N A T E D H Y D R I D E B y C H E N - Y O U N S U E M . Sc. , U n i v e r s i t y o f W a t e r l o o , 1984 B . E n g . , T s i n g h u a U n i v e r s i t y , B e i j i n g , 1968 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F D O C T O R O F P H I L O S O P H Y i n T H E F A C U L T Y O F G R A D U A T E S T U D I E S D e p a r t m e n t o f C h e m i s t r y W e accept t h i s thes is as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A D e c e m b e r 1988 © C h e n - y o u n Sue , 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT Kinetic and mechanistic studies on the activation of dioxygen using iridium and platinum triphenylphosphine complexes via oxygenation-protonation (i.e. protonation of coordinated peroxide) and protonation-oxygenation (i.e. oxygenation of coordinated hydride) processes are described. Dioxygen is activated in the form of a dioxygen (peroxide) metal complex, which upon protonation produces H2O2 stoichiometricaUy. Oxidation of the oxidizable ligands or subs…
has type: Thesis/Dissertation
is shown at: 10.14288/1.0060262
language: eng
degree discipline: Chemistry
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/29301