Development of heterogeneous metal oxide catalytic system with selective redox transition and highly recyclic feature is of challenging research in synthetic organic chemistry. In consideration with stability and reusability, very limited attention has been given so for. Nafion® is a rigid perfluropolymer backbone containing polymer bearing ion-exchangeable sulfonic acid terminal group (-SO3-.H+), extensively used as a solid-state protonic conductor in fuel cell applications and seldom used for chemical modification and in synthetic organic chemistry. In this thesis, we are presenting nano ruthenium oxide pyrochlore (Ru2Pb2O7, Pyc) modified Nafion® membrane (designated as |NPyc|) catalyst for selective organic functional group transformations including oxidation of alcohols to aldehyde and ketone, amine to nitriles under ambient conditions. We are covering preparation, characterization by XRD, SEM, SECM, AFM, TGA, XAS and catalytic organic synthesis in triphasic medium with cooxidants such as H2O2, NaOCl and O2. Under optimal working condition, the membrane catalyst showed very good selectivity and good turnover for wide range of organic compounds. The |NPyc| catalyst can be recycled over >100 times without any catalytic degradation. As to the mechanism, a high valent-oxo ruthenium redox species, perruthenate/ruthenate redox couple (Pyc-RuO4-/Pyc-RuO42-) exists in the |NPyc| believed to participate in the oxidation reaction with the co-oxidants.
In continuation to the above studies, a novel ruthenium functionalized nickel hydroxide (designated as Ru/Ni(OH)2) catalyst containing specific Ru-Ru and Ru-OHhydroxo bondings was prepared by simple solution phase procedures and characterized by XRD, IR, TGA, SEM, XPS and XAS (EXAFS and XANES). By using this as a new catalyst, series of alcohols were cleanly oxidized to corresponding aldehydes and ketones with higher turnover factors (~132 h-1) than that of the literature reports, which were based on the monomeric Ru and Ru-Ru bonded catalysts. The Ru/Ni(OH)2 can be recycled and reused without any leaching of metals. As to the mechanism, a low valent-hydroxo ruthenium species (Ru-OH) exists on the surface of the Ru/Ni(OH)2 believed to participate in the aerobic alcohol oxidation reaction via a hydridometal pathway.Chapter1:GeneralIntroduction………………………………… 1
1.1. Abstract…………………………………………………… 1
1.2. Introduction……………………………………………… 2
1.3. Traditional methods……………………………………… 2
1.4. Homogeneous catalysis…………………………………… 13
1.4.1. Copper complexes……………………………………… 14
1.4.2. Cobalt complexes………………………………………. 18
1.4.3. Vanadium complexes…………………………………… 21
1.4.4. Iron……………………………………………………… 24
1.4.5. Ruthenium complexes…………………………………… 25
1.4.6. Palladium complexes…………………………………… 29
1.4.7. Gold complexes………………………………………… 34
1.4.8. Bimetallic systems………………………………………36
1.5. Heterogeneous catalysis………………………… 37
1.5.1. Pt and Pd Supported catalysts…………………… 37
1.5.2. Gold (Au) Supported catalysts……………………… 43
1.5.3. Ruthenium (Ru) Supported catalysts……………… 47
1.5.4. Other metal supported catalysts…………………… 55
1.5.5. Polyoxometalate catalysts………………… 55
1.5.6. Silica and polymer supported TEMPO……………… 57
1.5.7. Oxidation of alcohols with hydrogen peroxide… 59
1.5.8. Oxidation of alcohols with sodium hypo chlorite (NaOCl…………………………………………………… 66
1.5.9. Oxidation of alcohols under anaerobic conditions68
1.6. Aim and Scope of the present work………………… 70
1.7. References………………………………………………… 71
Chapter 2: Synthesis, characterization and catalysis of nano crystalline Ruthenium oxide pyrochlore in an ionic clusters of nafion polymer……………………………………86
2.1. Abstract…………………………………………………. 86
2.2. Introduction…………………………………………….. 87
2.3. Experimental……………………………………………… 88
2.3.1. Materials and reagents……………………………… 88
2.3.2. Apparatus and measurementsc……………… 89
2.3.3. In situ precipitation of Pyc into Nafion® 417 membrane ……………………………………………………………90
2.3.4. General procedure for selective benzyl alcohol oxidation reaction……………………………………………… 90
2.4. Results and discussion…………………………………. 92
2.4.1. Physico-chemical characteristics of the |NPyc| catalyst………………………………………………………… 92
2.4.1.1. X-ray diffraction measurements………………… 92
2.4.1.2. Scaning electron microscopy (SEM) …………… 94
2.4.1.3. Atomic force microscopic analysis (AFM) …… 95
2.4.1.4. Scaning electrochemical microscopy (SECM) … 96
2.4.1.5 Thermo gravimetric analysis (TGA) ……………… 97
2.4.1.6 Cation exchange property (CEP) ……………………99
2.4.1.7. X-ray absorption spectroscopy analysis (XAS) 100
2.4.1.7.1. Extended X-ray absorption near edge structure
(XANES)………………………………………………………………100
2.4.1.7.2. Extended X-ray absorption spectroscopy (EXAFS)100
2.4.1.8. Selective benzyl alcohol oxidation reaction… 103
2.5. Conclusions………………………………………………… 107
2.6. References…………………………………………………. 107
Chapter 3: A nano crystalline ruthenium oxide pyrochlore - nafion polymer composite for highly selective oxidation of alcohols………………………………………………………………111
3.1. Abstract ………………………………………………………111
3.2. Introduction…………………………………………………112
3.3. Experimental……………………………………………… 113
3.3.1. Chemicals………………………………………………… 113
3.3.2. Apparatus and measurements……………… 114
3.3.3. Catalyst preparation and oxidation procedure 115
3.3.4. Preparation of the NPycCME……………………… 115
3.4. Results and discussion………………………………… 116
3.4.1. Catalytic performance………………………………… 116
3.4.2. |NPyc|-catalyzed alcohol oxidation reactions… 119
3.4.3. Catalytic mechanism …………………………………. 121
3.4.4. Kinetics of 2-pyridine methanol oxidation reactions.... 123
3.4.4.1. Effect of stirring speed……………………………125
3.4.4.2. Effect of catalyst amount……………………... 126
3.4.4.3. Effect of [substrate] …………………………… 127
3.4.4.4. Effect of amount of NaOCl……………………… 128
3.4.4.5. Effect of the amount of solvent (CH2Cl2) … 129
3.4.4.6. Effect of temperature………………………….. 129
3.4.4.7. Mechanism……………………………………………. 131
3.4.5. |NPyc| stability ……………………………………….132
3.5. Conclusions……………………………………………... 133
3.6. References…………………………………………………. 134
Chapter 4 : Oxidation of alcohols with molecular oxygen promoted by nano ruthenium oxide pyrochlore composite at room temperature……………………………………………………136
4.1. Abstract…………………………………………………. 136
4.2. Introduction………………………………….......... 137
4.3. Experimental Section…………………………………... 138
4.3.1. Chemicals and Reagents…………………………... 138
4.3.2. Apparatus and Measurements……………………….. 138
4.3.3. Catalyst Preparation…………………………...... 138
4.3.4. Adsorbed Alcohol Oxidation Reaction……………. 139
4.3.5. Typical alcohol oxidation reactions…………….. 139
4.3.6. Membrane Catalyst Regeneration……………………. 139
4.4. Results and Discussion………………………………. 140
4.5. Conclusion…………………………………………………. 147
4.6. References………………………………………………. 147
Chapter 5: Nano ruthenium oxide pyrochlore-nafion composite assisted aerobic oxidation of amine at room temperature…………………………………………………………149
5.1. Abstract……………………………………………………. 149
5.2. Introduction…………………………………………….. 150
5.3. Experimental Section…………………………………………………... 151
5.3.1. Chemicals and Reagents……………………………………………... 151
5.3.2. Apparatus and Measurements………………………………………... 152
5.3.3. Catalyst Preparation…………………............. 152
5.3.4. Adsorbed Amine Oxidation ………………………….. 152
5.3.5. Typical amine oxidation reactions……………… 153
5.3.6. Membrane Catalyst Regeneration…………………… 153
5.4. Results and discussion…………………………………. 153
5.5. Conclusion ………………………………………………… 159
5.6. References…………………………………………………. 160
Chapter 6: Ruthenium Functionalized Nickel Hydroxide Catalyst Containing Ru-Ru and Ru-Ohydroxo Bondings for Highly Efficient Alcohol Oxidations ………………………163
6.1. Abstract …………………………………………………… 163
6.2. Introduction ……………………………………………. 164
6.3. Experimental …………………………………………... 165
6.3.1. Chemicals ………………………………………………. 165
6.3.2. X-ray absorption spectroscopic analysis (XAS) …………………………………………………………… 165
6.3.3. Apparatus and measurements………………………… 166
6.3.4. Product analysis……………………………………………………… 166
6.3.5. Preparation of βbc-Ni(OH)2 powder…………….. 166
6.3.6. Preparation of Ru/Ni(OH)2 powder………………… 168
6.3.7. Typical procedures for the aerobic oxidation of alcohols…………………………………………………… 168
6.4. Result and discussion ……………………………….. 168
6.4.1. X -ray diffraction (XRD) ………………………. 168
6.4.2. IR spectroscopy………………………………………. 169
6.4.3. TGA analysis……………………………………………. 170
6.4.4. SEM and SEM-EDAX analysis…………………………… 171
6.4.5. XPS analysis……………………………………..... 173
6.4.6. X-ray absorption spectroscopy analysis (EXAFS & XANES) ………………………………………………………… 174
6.5. Conclusions………………………………………………. 184
6.6. References…………………………………………………. 18
