The University of Hull A Matrix Isolation Study of Transition Metal Halides and their Structure. being a Thesis submitted for the Degree of Doctor of Philosophy in the University of Hull by Antony Wilson, B.Sc. June 09 i This thesis is the result of my own work, except where due reference is given. No part of this work has been, or is currently being, submitted for a degree, diploma or other qualification at this or any other university or higher education establishment. This thesis does not exceed the 100,000 word limit, including tables, footnoted, bibliography and appendices. Antony Wilson ii Abstract The work within this thesis has concentrated on the formation and isolation of titanium, vanadium, palladium, and mercury halides, with emphasis on the fluorides. TiF, TiF2, TiF3, and TiF4 have all been isolated within an argon matrix and infrared spectra obtained. From the titanium isotope splitting pattern a bond angle has been determined for o TiF2 for the first time of 165 , or effectively linear. This work is also the first time that TiF has been isolated within an argon matrix. Work has also been conducted with vanadium which has lead to the isolation of VF5, VF4, VF3, and VF2, with VF4 undergoing Fermi Resonance. This is the first time that VF4 and VF2, consistent with a linear structure, have been isolated within a matrix. Work conducted upon palladium led to the isolation of numerous palladium fluorides, identified by the palladium isotope patterns in their IR spectra. Due to the similarity of the calculated stretching frequencies of PdF2, PdF3, PdF4, and PdF6 the assignment was challenging and so identification of these bands was conducted based photolysis and annealing behaviour in conjunction with computational calculations. This has allowed for the assignment of the bands present to PdF6, PdF4, PdF3, PdF2, and PdF. The bond length of molecular HgF2 has also been determined for the first time at 1.94(2) Å using the Hg L3-edge with EXAFS. Although the initial aim of this work was to isolate HgF4, using IR, UV/Vis, and XANES, no evidence could be found for oxidation states of II mercury higher that Hg . The work also developed a new clean way of making HgF2 in a matrix. The identification of a new Hg…X2 complex was also discovered which when photolysed forms the HgX2 compound, this has only been proven for HgF2. This was achieved by isolating mercury atoms in an argon matrix doped matrices, photolysis of this matrix the led to the formation of HgF2 in significant amounts. iii Acknowledgements. I would like to extend my deepest gratitude to my supervisor, Dr. Nigel Young, for offering me this opportunity and for his continued patience and guidance throughout the course of this work. I would also like to thank Dr. Adam Bridgeman for granting this studentship to me initially and his supervision in the initial year of my work, plus his computational contributions. Special thanks must go to project students over the years for their contributions to this work, and because I made a promise a mention also for Helen. I would also like to thank my parents for their unwavering support of my university studies and their continual emotional and financial support throughout my university life, without them this thesis would have never been produced and so this thesis is dedicated to them. I would like to thank the E.P.S.R.C. for a research studentship and to the University of Hull for funding, and all members of the Inorganic Chemistry department past and present for their input and support over the years. The mechanical workshop and the glass blowers must also get a thank you, without them this work would have stalled on many occasions. iv Contents Declaration ii Abstract iii Acknowledgements iv Chapter 1 Introduction 1.1 Introduction. 1 1.2 Matrix Isolation. 2 1.2.1 The History of Low Temperature Experiments. 2 1.2.2 Development of Matrix Isolation. 3 References. 4 Chapter 2 Matrix Isolation and Spectroscopic Techniques 2.1 Introduction. 6 2.2 Spectroscopic Methods. 8 2.3 Matrix Materials. 8 2.4 The Structure of the Matrix. 11 2.4.1 Close Packed Structure Under ‘Matrix Conditions’. 12 2.5 Matrix Effect. 13 2.5.1 Multiple Trapping Sites. 14 2.5.2 Molecular Rotation. 17 2.5.3 Matrix Shift. 18 2.5.4 Aggregation. 18 2.5.5 Coupling with Lattice Vibrations. 19 2.5.6 Phonon Bands. 19 2.6 Species Generation. 19 2.6.1 Direct Vaporisation. 20 v 2.6.2 Induction Heating and Pyrolysis. 20 2.5.3 Sputtering. 20 2.5.4 Electron Bombardment. 21 2.5.5 Laser Ablation. 21 References. 22 Chapter 3 Theory 3.1 Introduction. 24 3.2 Vibrational Theory. 26 3.2.1 Diatomic Molecules. 27 3.2.2 Polyatomic Molecules. 31 3.3 Group Theory. 32 3.4 Selection Rules. 40 3.5 SOTONVIB. 42 3.5.1 Wilson’s GF Method. 42 3.5.2 Determination of Bond Angles. 44 3.6 Electronic Spectroscopy (UV/Vis) 46 3.7 Effect of the Matrix on Spectroscopy. 48 3.8 Ultraviolet Photolysis of Precursor in the Matrix. 50 3.8.1 Results of Photolysis. 51 3.8.2 The Effects of Continued Photolysis. 53 3.9 X-Ray Absorption Spectroscopy. 54 3.9.1 EXAFS. 56 3.9.1.1 Data Analysis. 57 References. 59 Chapter 4 Experimental 4.1 Matrix Gases. 60 4.2 Mass Spectrometry. 62 vi 4.3 Fourier Transform Infrared (FTIR) Matrix Isolation Spectroscopy. 66 4.4 Matrix Isolation UV/Vis Spectroscopy. 72 4.5 Matrix Isolation EXAFS. 74 4.6 Experimental Considerations of Matrix Isolation. 77 4.7 Deposition Techniques. 79 4.7.1 Thermal Evaporation. 79 4.7.2 Furnace Evaporation. 80 4.7.3 RF Generator – Induction Heating. 82 4.8 Computational Calculations. 83 References. 84 Chapter 5 First Row Transition Metal Halides 5.1 Introduction. 86 5.1.1 History of Titanium and Vanadium. 87 5.1.1.1 Titanium. 87 5.1.1.1.1 Titanium Halides. 88 5.1.1.2 Vanadium. 89 5.1.1.2.1 Vanadium Halides. 90 5.2 Literature Review. 90 5.2.1 Theoretical/Calculations. 91 5.2.2 IR Data. 99 5.2.2.1 Titanium Fluorides in a Matrix. 100 5.2.3 ESR Studies on TiF3 and TiF2. 102 5.2.4 Conclusions from the Literature. 103 5.3 Experimental Results. 103 5.3.1 Introduction. 103 5.3.2 Titanium Results. 105 5.3.2.1 Ti in O2/Ar. 106 5.3.2.1.1 Ti in 10% O2/ Ar. 106 5.3.2.2 Ti in F2/Ar. 107 vii 5.3.2.2.1 Ti in 10% F2/Ar. 107 5.3.2.2.2 Ti in 0.63% F2/Ar. 108 5.3.2.2.3 Ti in 0.16% F2/Ar. 110 5.3.2.2.4 Ti in 0.3% and 0.2% F2/Ar. 112 5.3.2.2.5 Ti in 2% F2/Ar. 112 5.3.2.3 Ti in N2 and H2O in Ar. 113 5.3.2.4 Assignment of TiF4 and TiF3. 114 5.3.2.4.1 TiF4 in Ar. 114 5.3.2.4.2 TiF3 in Ar. 115 5.3.2.4.3 Mass Spectrometry Work with TiF3. 116 5.3.2.5 UV/Vis Spectroscopy. 116 5.3.2.6 Computational Work. 117 5.3.2.7 Discussion. 122 5.3.3 Vanadium Fluorides in a Matrix. 123 5.3.4 Conclusion from Literature. 125 5.3.5 Vanadium Isolated in F2/Ar 125 5.3.5.1 V in Ar. 127 5.3.5.2 V in 10%, 1%, 0.18% and 0.055% F2/Ar. 128 5.3.5.3 New Methods of Vanadium Evaporation. 132 5.3.5.3.1 V in a F2 and Ar ‘Sandwich’ Method. 132 5.2.5.3.2 V with Protective Ar and F2/Ar. 133 5.3.5.4 Discussion. 135 5.3.6 Conclusion. 137 5.3.7 CrF2 and CrCl2 Investigations. 138 5.3.8 Further Work. 140 References. 142 Chapter 6 Second Row Transition Metal Halides 6.1 Introduction. 149 6.1.1 History of Palladium. 149 viii 6.2 Palladium. 151 6.2.1 Literature Review. 151 6.2.2 Results . 157 6.2.2.1 Computational Studies. 159 6.2.2.1.1 DFT Study of PdFx. 159 6.2.2.2 Pd in 2% F2/Ar. 161 6.2.2.3 Pd in 0.5% F2/Ar. 163 6.2.2.4 Pd in 10% F2/Ar. 169 6.2.2.5 SOTONVIB Calculations. 171 6.2.3 Discussion. 175 6.2.4 Conclusion. 179 6.2.5 Further Work. 180 References. 181 Chapter 7 Third Row Transition Metal Halides 7.1 Introduction. 183 7.1.1 History of Mercury. 183 7.1.2 Mercury in these Experiments. 185 7.2 Literature Review. 188 7.3 Results - Hg and HgF2 in F2/Ar. 190 7.3.1 Early Mass Spectrometry Work. 191 7.3.2 Matrix Isolation IR Spectrometry. 192 7.3.2.1 HgF2 Vaporisation Experiments. 194 7.3.2.2 Mercury Vaporisation Experiments. 197 7.3.2.3 Noble Gas Discharge Lamps. 203 7.3.2.3 Conclusions From IR Experiments. 205 7.3.3 Matrix Isolation UV/Vis Spectroscopy. 207 7.3.3.1 Background and Introduction. 207 7.3.3.2 Experimental Results. 209 ix 7.3.3.2.1 HgF2 Experiments. 210 7.3.3.2.2 Hg Experiments.