IN-SITU SPECTROSCOPY OF THE EARLY EVENTS IN THE RHODIUM MEDIATED PAUSON KHAND REACTION. AYMAN DAOUD ALLIAN NATIONAL UNIVERSITY OF SINGAPORE 2006 IN-SITU SPECTROSCOPY OF THE EARLY EVENTS IN THE RHODIUM MEDIATED PAUSON KHAND REACTION. AYMAN DAOUD ALLIAN (B. Eng. UIUC, M .Eng., NUS-UIUC JOINT MS. PROGRAM) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL & BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2006 ACKNOWLEDGEMENT The research carried out in this thesis was a multidisciplinary and required (1) designing and machining of flow through high/low pressure reactors and spectroscopic cells, (2) using various spectroscopic tools (IR and Raman and NMR) (3) carrying out blind deconvolution of the collected in-situ spectra, (4) a sound understanding of organometallic chemistry in particular coordination chemistry (5) the use of density functional theory to assist in geometrical assignments. Such an immense task can not be achieved by a single individual, therefore, I was very fortunate to be part of very competent team at the National University of Singapore and Institute of Chemical and Engineering Sciences (ICES) whom their constant support helped me tremendously overcome many of the obstacles faced while carrying out this diverse project. The first person I would like to thank is my supervisor Marc Garland for making sure that I acquired all the resources needed to carry out my research. In addition, I would like to thank him for all the good conversations on science, politics and life. I am very grateful to his understanding of my sense of curiosity which stretched me at times but it was very satisfying. I remember at some point I was working on (i) a thermodynamic project, (ii) analyzing spectra from a heterogeneous system and (iii) writing a MATLAB script to analyze Raman optical activity simultaneously. I would like to thank Prof. Mark Saeys and his research group in particular Xu Jing and Sun Wenjie for their help on DFT calculations. Our collaboration resulted in a successful project wherein the results were published in the journal of vibrational spectroscopy. DFT became an essential tool for the research conducted in this dissertation and I’ll always be grateful to Prof. Mark Saeys even for the DFT work carried out beyond the mentioned collaboration because he and his team were the one who got me started. In addition, I would like to thank the undergraduate students that I supervised while they were carrying out their final year project Teo Boon Wee and Wang Yezhong as both really made significant contribution to the development of the DFT calculations on Rhodium carbonyl species. I would like to thank Dr Li Chuanzhao, for training me on using in-situ high pressure spectroscopy and valuable remarks/feedback on my work throughout my PHD in particular issues related to organometallics chemistry and reactors design/use. I also would like to thank my friend and partner Martin Tjahjono. Martin’s expertise in thermodynamic i and my experience with chemistry/spectroscopy/DFT were an excellent combination that enabled us to complete four projects successfully. Results from two projects were published in good journals and were well received by the scientific community. Also, I would like to thank Martin for the wonderful conversation on life and religion. I like to thank Dr Effendi Widjaja, for his valuable support in using Raman spectroscopy and numerical aspects and Dr Chacko Jacob for carrying out the 13 C NMR experiment and his help in making sense of the resultant spectra. I would like to thank Dr Guo Liangfeng for his resourcefulness in using MATLAB. I also like to thank Dr Gao Feng and Mr Karl Irwin Krummel for enriching conversation on heterogeneous catalysis and rhodium phosphine chemistry. I also would like to thank Dr Chew Wee for many of stimulating discussions. I would like to express my thanks all of members in our research group including Ms Cheng Shuying and Mr Zhang Huajun my friends in NUS Jeremy Daniel Lease, N.V.S.N. Murthy Konda and Ng Yew Seng who made my graduate student life interesting. I would like to the technical staff at NUS, in particular Mr Ng Kim Poi and his employee at the workshop their help on machining my designed flow through spectroscopic cells. I would like to thank my family for their moral support through out my PHD. I also would like to thank God. While I did work hard in the past 10 years of my academic life, but the successful completion of my PHD was just beyond my wildest dreams as young boy growing up in east Jerusalem and would not be possible without his generosity. I always felt that I was in the right time and the right place and being part of the right team. Finally this thesis is dedicated to my parents Siham and Daoud Allian. ii TABLE OF CONTENTS ACKNOWLEDGEMENT ……………………………………………………… … i SUMMARY ………………………………………………………………………… x NOMENCLATURE ……………………………………………………………… . xii LIST OF FIGURES ……………………………………………………………… xv LIST OF TABLES ……………………………………………………………… …. xxiii INTRODUCTION ……… …………………………………………………… . 1.1 Problem Statement: Missing Links in the Early Events of Rh4(CO)12 PK Reaction …………………………………………… …. 1.2 Thesis Objective ………………………………………………………… 1.3 Thesis Organization …………………………………………………… … LITERATURE REVIEW ……… …………………………………………… . 2.1 Pauson Khand Reaction………….……………………………………… …. 2.1.1 Early Pauson Khand reactions……… .………… .………………… …. 2.1.2 Reaction Mechanism for the Pauson Khand Reaction…………… …. 10 2.1.3 Cobalt catalyzed Pauson Khand Reaction………….………………… . 12 2.1.4 Titanocene and Ruthenium catalyzed Pauson Khand Reaction………… 13 2.2 Rhodium Catalyzed Pauson Khand Reaction……………………………… . 14 2.2.1 Development of new protocols for the Rhodium catalyzed PK Reaction…………………………………………………………………… … 16 2.3 Terarhodium dodecacarbonyl……….……………………………………… . 18 2.3.1 Important transformation of Rh4(CO)12 ……………………………………. 21 2.3.2 FTIR spectroscopy to study rhodium carbonyl clusters …………………. 21 2.4 Unmodified Cobalt and Rhodium carbonyl cluster reaction with alkynes… . 22 2.4.1 Reaction of alkyne with homometallic cobalt carbonyl species …………. 23 2.4.2 Reaction of alkyne with hetrometallics carbonyl species…… .… …… 24 2.4.3 Reaction of alkyne with homometallic Rhodium carbonyl species….… 25 EXPERIMENTAL APPROACH AND METHODOLOGY…………… … 27 3.1 Homogenous Catalysis and in Situ Spectroscopy………………… .…… .… 27 3.2 Experimental Setups.…… .……………………………………………… . 29 3.2.1 General scheme of in-situ spectroscopy……………………………… … 29 iii 3.2.1.1 Advantages of the current in-situ spectroscopic approach ….…. 29 3.2.2 High Pressure in-situ FTIR apparatus……………………………… .… 30 3.2.3 Low Pressure in-situ FTIR apparatus……………………………… .… 32 3.2.4 Spectrometers and Flow through cells………………………………… . 33 3.3 General Experimental Procedure…………………………………………… . 34 3.3.1 Schlenk Techniques………………………… .……………………… . 34 3.3.2 Chemicals and Gases………………………………………………… . 35 3.3.3 Quantitative measurements ………………………………………… . 35 3.4 Chemometic tools for total algebraic system identification………………… 35 3.4.1 Experimental Procedure and Spectra collection ……… 37 3.4.1.1 Lambert-Beer-Bouguer law………………………………… 40 3.4.2 Singular Vale Decomposition (SVD) …………………………………… 41 3.4.3 Pure Component Spectra Reconstruction………………………………. 44 3.4.4 Solvent and background pure Component Spectra; Spectral Substraction…………………………………………………………… 48 3.4.5 Relative concentration……………………….………………………… . 49 3.4.6 Real Molar Concentration…………………………………………… . 52 3.4.6.1 Spectral Renormalization………………………………………. 52 3.4.6.2 Real spectral absorptivities and mole numbers………………… 56 TETRARHODIUM DODECACARBONYLS………………………………… 4.1 Experimental Section………………………………………… .………… . 59 59 4.1.1 Experimental design…………………………………………………… . 60 4.1.2 Experimental Procedure and Spectra collection…………………… …. 61 4.2 Spectral Analysis and preliminary results……………………… .………… . 65 4.2.1 Singular Value Decomposition and spectral reconstruction…………… . 65 4.2.2 Relative Concentration and Signal Ratio ………………………… …… 69 4.3 Discussion… .……………………… .…………………… ………… 71 4.3.1 Rhodium based Organometallics ……….… … ……………….…… . 71 4.3.2 Gas impurities Ni(CO)4 and Fe(CO)5…….… ……………….…… . 73 4.3.3 Species X………………………………………… …….……………… 74 4.4 Real molar concentration and thermodynamics .…… .…… ………… . 77 4.4.1Properly scaled pure component spectra……….… ……………….…… 78 iv 4.4.2 CO solubility …………………………………… … ……………….…… . 80 4.4.3 Thermodynamics…….………………………… … ……………….……… . 81 4.4.3.1 Fluxionally and the discovery of all-terminal Rh4(CO)12……… 81 4.4.3.2 The cluster fragmentation to Rh2(CO)6(μ-CO)8……………… . 83 4.5 Summary … .…… ………… 85 Density Functional Theory ………………………………………………… … . 86 5.1 Geometrical assignment based on vibrational spectroscopy…………………. 87 5.1.1 Traditional approaches for Vibrational assignment ….………… …… 87 5.1.2 DFT assisted structural determination………………………….……… . 87 5.2 Finding the appropriate density functional and basis set….………… …… 88 5.2.1 Widely applied DFT methods for Rhodium based Organometallics……. 89 5.2.2 The HRh(CO)4 Test……………… ………………………… …….… 90 5.2.2.1 Application to the cobalt hydride HCo(CO)4.…………… …. 93 5.3 Calculation of Metal Carbonyl Clusters……………….………………… 94 5.3.1 Dirhodium Octacarbonyl Rh2(CO)6(μ-CO)2…….……………… … 94 5.3.1.1 Different Geometries of Rh2(CO)8……… .…………… … 96 5.3.1.2 Cobalt dimer Co2(CO)6(μ-CO)2 ……… .…………… …… 97 5.3.2 Tetrarhodium Dodecacarbonyl Rh4(CO)9(μ-CO)3 ………………… … . 98 5.3.2.1 Solvent Effect on the Observed Vibrational Spectra .…… …. 101 5.3.2.2 All-terminal Geometries of Rh4(CO)12…………….…… … . 102 5.3.3 Hexarhodium Hexacarbonyl Rh6(CO)12(μ3-CO)4……………… .……. 103 5.3.4 Reliability of the Mid-infrared Predicted Vibrational Spectra…………. 105 5.3.4.1 Predicted terminal Carbonyl frequency…………….…… .… 105 5.3.4.2 Predicted Bridged Carbonyl frequency…………….…… …. 106 5.4 Calculation of modified Metal Carbonyl Species…… …………………… . 106 5.4.1 Acylrhodium tetracarbonyl………………………………………….… …… 106 5.4.2 Geometry of RCORh(CO)3(π-C2H4)…………………………………… 109 5.4.3 The Spectrum of Rh4(CO)11PPh3………………………………………… 111 5.5 Experimental Section…… ……………………………… ……………… 113 5.5.1 In-situ Cell For Liquid/Supercritical Gas Measurements………………… 113 5.5.2 Experimental Setup and Procedure………………………………………… 114 5.6 Summary…… ……………………………… …………… 115 The Homometallic Rhodium Butterfly Cluster……………………… …… …. 116 v 6.1 Preliminary Investigation…………………………………………… .…… . 116 6.1.1 Experimental Setup and Procedure ………………………………… 117 6.1.2 Spectra Analysis…………………………… ……………………… . 118 6.2 Mid-Infrared Characterization of the Butterfly Cluster……………………… 119 6.2.1 High resolution vibrational study of (μ4-η2-3-hexyne)Rh4(CO)8(μ-CO)2 120 6.2.1.1 Experimental Section and procedure…………….……… … . 120 6.2.1.2 Spectra Analysis and DFT Calculations ……….……… …. 121 6.2.2 Low resolution vibrational study of (μ4-η2-terminal)-Rh4(CO)8(μ-CO)2 125 6.2.3 Low resolution vibrational study of (μ4-η2-asymmetric alkyne)Rh4(CO)8(μ-CO)2……………………………… 127 6.2.4 Rates of Formation, Dependence on Substrate …………………… 128 6.2.5 Spectra of Various (μ4-η -alkyne)Rh4(CO)8(μ-CO)2 in d-benzene……… 129 6.2.5.1 Experimental Procedure and BTEM Results.…………… .…. 130 6.2.5.2 Spectra Analysis…………….…………………………… .…. 131 6.3 Raman spectra of (hexyne)Rh4(CO)8(μ-CO)2…….……… ……………….… 132 6.3.1 Experimental Section…….……… …………………………………… 133 6.3.1.1 Experimental Setup …………….……… ………………… . 133 6.3.1.2 Experimental Procedure …………….……… ……………… 134 6.3.2 Spectra Analysis.……… …………… .……… …………………… 135 6.3.2.1 Mid-Raman Vibrational Spectra …………….……… …… 135 6.3.2.2 Far-Raman Vibrational Spectra …………….……… ……… 140 6.3.2.3 Relative Concentrations…………….……… ………………. 145 6.4 NMR spectra of (3-hexyne)Rh4(CO)8(μ-CO)2……………………………… 146 6.4.1 Experimental Section- Rh4(CO)9(µ-CO)3 Enrichment…….……… . 146 6.4.2 Results and Discussion…….……… ……………………………….… 146 6.4.2.1 The 13C NMR Spectrum of Rh4(CO)9(µ-CO)3 ………… .…. 147 13 6.4.2.2 The C NMR Reaction Spectrum…………….……… .…. 148 6.4.2.3 The 13C NMR Reaction Spectrum of (μ4-η2-3hexyne)Rh4(CO)8(μ-CO)2…………… .….……… .…………… . 150 6.5 Kinetics of the formation of (C2H5C2C2H5)Rh4(CO)8(μ-CO)2… .…………… 152 6.5.1 Experimental Section……… .….……… .….……… .….……… . 152 6.5.1.1 Experimental Design……… .….……… .….……… .… 152 6.5.1.2 Experimental Procedure and Spectra Collection……… .…… 153 6.5.2 Spectra Analysis……… .….……… .….……… .….……… .… 155 vi 6.5.2.1 Relative Concentration…… .….……… .…… .….………. 155 6.5.2.2 Real Concentration…… .….……… .…… .….……… . 156 6.5.3 Alkyne and CO molar concentrations……… .…….……… .…….…… 157 6.5.4 Kinetic and Mechanism of the Reaction……… .…….……… .…….… 158 6.5.5 Thermodynamic and Apparent Eyring Activation……… .…….………. 163 6.6 Summary……… .…….……… .…….……… .…….……… .…….……… . 165 The Dirhodium Alkyne Species ……………………………………………… … 166 7.1 Preliminary Analysis …………………………………… ………………… . 167 7.1.1 Experimental Section ………………………………… ………… .… . 167 7.1.2 Spectra Analysis………………………………………………………… 168 7.2 High resolution vibrational study of the fragmentation of (μ4-η2C2H5C2C2H5)Rh4(CO)8(μ-CO)2……………… 169 7.2.1 Experimental Section ……………………………….………………… 169 7.2.1.1 Experimental Setup…………………………… ……… … 170 7.2.1.2 Experimental Procedure ………………………… …… …… 170 7.2.2 Spectral Analysis ……………………………………………………… . 171 7.2.2.1 Rh4(CO)9(μ-CO)3 and (μ4-η2- alkyne)Rh4(CO)8(μ-CO)2… .…. 172 7.2.2.2 Spectra and DFT Analysis of (3-hexyne)Rh2(CO)6 … .… .…. 172 7.2.2.3 Spectra and DFT Analysis of (3-hexyne)Rh2(CO)5 … .… .…. 176 7.2.3 Relative Concentration ……………………… .… .… .… .… .…… 179 7.3 Low resolution vibrational study of the fragmentation of (μ4-η2alkyne)Rh4(CO)8(μ-CO)2, Alkyne= 1-heptyne, Phenyl-1-hexyne…… ……… 180 7.3.1 Experimental Section……………………………………………… .… 181 7.3.3.1 Experimental Design ………………………………….… .…. 181 7.3.3.2 Experimental Procedure ……………………………….… .…. 181 7.3.2 Spectra Analysis……………………………………………………… 182 7.3.2.1 Pure Components of the Phenyl-1-hexyne Experiment ………. 182 7.3.2.2 Pure Components of the 1-heptyne Experiment …… .………. 185 7.4 Kinetics of the (1-heptyne)Rh4(CO)8(μ-CO)2 Fragmentation……………… . 187 7.4.1 Experimental Section……………………………………………… . 187 7.4.1.1 Experimental Design……………………………………… 188 7.4.1.2 Experimental Procedure and Spectra Collection……………… 188 7.4.2 Spectra Analysis………………….…………………………………… . 189 vii 7.4.2.1 Relative Concentration…………………………… . 191 7.4.2.2 Unknown species structural assignments…………… . 192 7.4.2.3 Organometallics Real Concentration…………… 195 7.4.2.4 CO and 1-heptyne molar Concentration.…………… . 195 7.4.3 Kinetic and Mechanism of the Reaction……………………………… . 196 7.4.4 Thermodynamic and Apparent Eyring Activation Parameters………… . 199 7.5 Summary…………………………………………………………………… 201 The Reaction of Rh4(CO)9(μ-CO)3 with Enyne…………………….…………… 202 8.1 Reaction of Catalytic Precursor Rh4(CO)9(μ-CO)3 with Equivalent amounts of Enyne………………………………………………………… ……… . 202 8.1.1 Experimental Section…….…………………………………………… 203 8.1.1.1 Experimental Design………………………………………… . 203 8.1.1.2 Experimental Procedure…………………………………… … 203 8.1.2 Spectra Analysis.……………………………… .………………… .… 204 8.1.3 Unknown Species X………………………… .……………………… . 207 8.2 Reaction of Catalytic Precursor Rh4(CO)9(μ-CO)3 with Excess Enyne.……… 209 8.2.1 Experimental Section………………………………………………… …… . 209 8.2.1.1 Experimental Design………………………………………… . 209 8.2.1.1 Experimental Procedure……………………………………… 209 8.2.2 Spectra Analysis……………………………………………………… …… . 209 8.3 On-line FTIR monitoring of the Effect of Ultrasonic Irradiation on Homogenous Liquids ………………………….……………………………. 212 8.3.1 Background……………….….…………………………………………… 213 8.3.2 Experimental Setup ……………………………………………….….…… 214 8.3.3 Preliminary Experimental Results .……………………………………. 215 8.3.3.1 Experimental Design ……………………………………….…. 215 8.3.3.2 Experimental Procedure……………………………………… 215 8.3.3.3 Spectra Analysis……………………………………………… 216 8.4 Summary ………………………….……………………………………… . 218 Conclusion and Future Work …………………………… ………… …………. 219 9.1 Results on the Early Event of Pauson Khand Reaction ………………… .… 219 9.1.1 Experimental Work and Findings …….………………………………… 220 9.1.2 Implication of the Results …….….…………………………………… . 221 viii REFERENCES Cariati, F., V. 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Rev., 91(5), pp. 651-67. 1991. 242 [...]... expertise in handling and analyzing the latter cluster and to the fact that it has been used to mediate PK reaction In particular, this study will focus on (i) understanding the catalytic precursor, (ii) the reaction of the precursor with various alkynes where the nature of the intermediates formed and their rate of formation will be investigated using in- situ spectroscopy For the Rh4(CO)12 mediated PK reaction, ... understanding of the reaction mechanism, which to date remains largely due unsupported, due to the absence of mechanistic studies on the reaction The main objective of the current dissertation is to study the pre-catalytic steps of the Rh4(CO)12 mediated Pauson Khand reaction which is an important step towards understanding the entire reaction mechanism and the catalytic cycle of the reaction Consequently,... improvement of the PK reaction conditions is needed in order to bring the idea of “Commercialized PK reaction closer to reality However, optimization of the reaction and the developing of adequate protocols † The main underlying assumption is that Rhodium chemistry is analogous to that of cobalt, which is a good starting point but not entirely correct 3 CHAPTER 1 INTRODUCTION requires a sound understanding of. .. certain obstacles have not been fully resolved by the introduction of the rhodium based catalytic precursors, in particular the high temperature requirements and the lengthy reaction times which can be as long as 60 hours (Kobayashi, et al., 2001) 1.1 Problem Statement: Missing Links in the Early Events of Rh4(CO)12 PK Reaction Although the detailed mechanism of the cobalt mediated PK reaction remains... O Scheme 1.1 The general form of (a) intramolecular and (b) intermolecular metal mediated Pauson Khand Reaction Despite the great economical potential the Pauson Khand (PK) reaction holds, to date it has not been commercialized largely due to harsh condition required or/and low yields obtained 1 CHAPTER 1 INTRODUCTION The early generation of PK reactions was mediated by cobalt and these reactions were... structure and (ii) spectroscopic assignments of its vibrational spectrum have been reported 2 CHAPTER 1 INTRODUCTION Unfortunately and to the best of the author’s knowledge, similar studies on the early events of the PK reaction mediated by rhodium based catalytic precursors have not been reported/attempted The current dissertation will investigate the early events of Rh4(CO)12 mediated PK reaction Rh4(CO)12... Kobs[(μ4-η2-1-heptyne)Rh4(CO)8(µ-CO)2][heptyne][CO]-1 In chapter 8, a study of the reaction of the catalytic precursor with enyne, C≡C-C-C-CC=C, resulted in the identification of a new class of butterfly clusters namely (1heptenyne)Rh4(CO)7(µ-CO)2 with both the alkyne and the alkene moiety from the same x substrate coordinating to rhodium Furthermore, the earlier observed intermediates namely the butterfly cluster and the dinuclear rhodium... are the specific targets that the current thesis will be addressing Target 1: Investigate the catalyst precursor Rh4(CO)12, in particular its geometry and fluxionality in solution along with studying its transformations under various gas partial pressures Target 2: Studying the reaction of the Rh4(CO)12 with alkynes in an attempt to characterize the intermediates involved and the mechanism of their... hand, the second dinuclear rhodium species (II) (alkyne)Rh2(CO)6 have not been observed yet despite the fact that its analogue (alkyne)Co2(CO)6 have been identified for more the 50 years (Sly, 1959) All of these missing links listed above were the main driving force in carrying out most of the research conducted in this thesis 1.2 Thesis Objectives From the discussion above, one can see that further... Entropy change of a reaction s Number of species T Temperature in Kelvin T1× z Transformation matrix U ∞ v CO V ν s×E Matrix of left singular vector Partial molar volume of the dissolved CO gas at infinite dilution Total volume of a reaction mixture Atomic matrix xiii VT Transposed matrix of the right singular vector xs mole fraction of chemical species s z Number of meaningful right singular vector . SUMMARY The current dissertation studied the pre-catalytic events involved in the Rh 4 (CO) 9 (µ- CO) 3 mediated Pauson Khand reaction using in- situ spectroscopy. In particular, the investigation. NATIONAL UNIVERSITY OF SINGAPORE 2006 IN- SITU SPECTROSCOPY OF THE EARLY EVENTS IN THE RHODIUM MEDIATED PAUSON KHAND REACTION. AYMAN. 2.1.1 Early Pauson Khand reactions……… ………… ………………… …. 9 2.1.2 Reaction Mechanism for the Pauson Khand Reaction ………… …. 10 2.1.3 Cobalt catalyzed Pauson Khand Reaction ……….…………………