Acknowledgement
Firstly, I would like to thank both of my supervisors and mentors, Assoc. Prof.
Ang Siau Gek and Assoc. Prof. Fan Wai Yip for their patience, dedication and
guidance from the initial to the final stages of my project. Without their guidance,
it would not be possible for me to be able to understand and develop this project. I
am grateful for their constant encouragements and patience which they have given
me through the years.
My research experience in NUS would not have been as enjoyable and fulfilling
without my fellow group members; Tan Sze Tat, Kee Jun Wei, Tan Kheng Yee
Desmond, Fong Wai Kit, Chong Che Chang, Sum Yin Ngai, Lim Ching Si, Sim
Bai Ting, Lim Xiao Zhi, Tan Yong Yao and Goh Wei Bin. It is a pleasure to be
able to work in the same lab as them, and I sincerely thank them for their help and
support through these years.
I would also like to thank Mdm Han Yanhui from the Chemistry Department
NMR Laboratory, Mdm Patricia Tan from the Physical Chemistry Laboratory, and
also to the various staffs of the Chemistry Department who have helped me in one
way or another.
Most importantly, I would like to acknowledge the continuous support that my
family has given me. Of which without their persistent encouragements, I would
not be able to persevere through this course of study.
Lastly, I wish to thank the National University of Singapore for awarding me a
research scholarship and granting me the opportunity to pursue my degree.
i
Thesis Declaration
The work in this thesis is the original work of Toh Chun Keong, performed
independently under the supervision of A/P Fan Wai Yip, (in the IR and Laser
Research Laboratory), Chemistry Department, National University of Singapore,
between 3 August 2009 and 2 August 2012.
Toh Chun Keong
Name
Signature
Date
ii
Table of Contents
Acknowledgement
i
Table of Contents
ii
Summary
iii
CHAPTER 1 Introduction
1
1.1 Organometallic Compounds in Catalysis
2
1.1.1 Organometallics
2
1.1.2 Organo-Rhenium Complexes
3
1.1.3 Organo-Ruthenium Complexes
6
1.2 Organosilane Chemistry
9
1.3 Main Objectives
12
1.3.1 Catalytic Hydrosilylation of Carbonyls via Re(CO)5Cl Photolysis
12
1.3.2 Ruthenium Carbonyl-Catalyzed Si-X Coupling (X = S, O, N)
13
1.4 References
15
iii
CHAPTER 2 Catalytic Hydrosilylation of Carbonyls via
19
Re(CO)5Cl Photolysis
2.1 Introduction
19
2.2 Results and Discussion
21
2.2.1 Hydrosilylation of Silanes with Aldehydes and Ketones
21
2.2.2 Hydrosilylation of Esters and Carbonates
24
2.2.3 Comparison of Hydrosilylation Rates for Different Carbonyls
26
2.2.4 Mechanism
27
2.2.5 Calculations
33
2.3 Conclusion
40
2.4 Experimental Section
40
2.5 References
43
CHAPTER 3 Ruthenium Carbonyl-Catalyzed Si-X Coupling (X
45
= S, O, N)
3.1 Introduction
45
3.2 Results and Discussion
47
3.2.1 Reactive Intermediates and Mechanism
51
iv
3.2.2 Calculations
56
3.3 Conclusion
60
3.4 Experimental Section
61
3.5 References
63
v
Summary
The hydrosilylation reaction between silanes and various carbonyl substrates has
been catalysed by Re(CO)5Cl uv-photolysis. Kinetic studies have shown that the
reaction is favoured for the least sterically-hinderd silanes with aldehydes. The IR
spectrum of a rhenium carbonyl dimer HRe2(CO)9(SiR3) has been recorded in the
reaction mixture and is believed to be the resting state of the active catalyst
Re(CO)4SiR3.
A catalytic mechanism has been proposed and supported by
computational studies, which can also be used to explain relative hydrosilylation
rates among various carbonyl substrates.
Ru3(CO)12 has been shown to catalyze the coupling of silanes with thiols,
alcohols and amines with turnover number and turnover frequency of up to 200 and
50 hr-1 at 80oC. IR, NMR and mass spectroscopic studies have identified a
ruthenium dimer complex, [Ru(CO)4(SiEt3)]2 as a likely resting state of the catalyst.
A mechanism involving this complex has been proposed for the silicon-thiol
coupling process with supporting evidence from computational studies.
vi
... Introduction 1. 1 Organometallic Compounds in Catalysis 1. 1 .1 Organometallics 1. 1.2 Organo -Rhenium Complexes 1. 1.3 Organo -Ruthenium Complexes 1. 2 Organosilane Chemistry 1. 3 Main Objectives 12 1. 3 .1 Catalytic... Photolysis 12 1. 3.2 Ruthenium Carbonyl -Catalyzed Si-X Coupling (X = S, O, N) 13 1. 4 References 15 iii CHAPTER Catalytic Hydrosilylation of Carbonyls via 19 Re(CO)5Cl Photolysis 2 .1 Introduction 19 2.2... References 43 CHAPTER Ruthenium Carbonyl -Catalyzed Si-X Coupling (X 45 = S, O, N) 3 .1 Introduction 45 3.2 Results and Discussion 47 3.2 .1 Reactive Intermediates and Mechanism 51 iv 3.2.2 Calculations