UNIVERSITY OF CALIFORNIA IRVINE Ligand Exploration in the Synthesis and Reactivity of +2 Ion Rare-Earth Metal Complexes DISSERTATION submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Chemistry by David H. Woen Dissertation Committee: Distinguished Professor William J. Evans, Chair Professor A. S. Borovik Assistant Professor Jenny Y. Yang 2017 Portions of Chapter 1 © 2015 American Chemical Society Portions of Chapter 2 © 2016 The Royal Society of Chemistry Portions of Chapter 4 © 2017 Wiley-VCH Verlag GmbH & Co. KGaA Portions of Chapter 5 © 2017 American Chemical Society Portions of Chapter 6 © 2017 Wiley-VCH Verlag GmbH & Co. KGaA Portions of Chapter 7 © 2017 American Chemical Society All other materials © 2017 David H. Woen DEDICATION This dissertation is dedicated to my parents, Bambang and Sioengo, and to my sisters, Christine, Veronica, and Vicky, in recognition of their love, support, and inspiration. ii TABLE OF CONTENTS Page LIST OF FIGURES iv LIST OF TABLES xi ACKNOWLEDGEMENTS xii CURRICULUM VITAE xiv ABSTRACT OF THE DISSERTATION xviii INTRODUCTION 1 CHAPTER 1: Synthesis and Reactivity of +2 Ion Rare-Earth Metal Complexes with 10 1− 1− (C5H5) and (C5H4Me) as Ligands CHAPTER 2: Dinitrogen Reduction Reactivity of Rare-Earth Metal Complexes 38 1− with (C5H4Me) as Ligands CHAPTER 3: Synthesis and Reactivity of +2 Ion Rare-Earth Metal Complexes with 61 1− (C5Me4H) Ligands CHAPTER 4: Solution Synthesis, Structure, and Physical Properties of a Sc2+ 81 1− Complex, {Sc[N(SiMe3)2]3} CHAPTER 5: End-on Bridging Dinitrogen Complexes of Scandium 104 1− CHAPTER 6: Reactivity of {Sc[N(SiMe3)2]3} with Carbon Monoxide, Carbon 127 Dioxide, and Acetonitrile CHAPTER 7: Tris(pentamethylcyclopentadienyl) Complexes of the Late 147 Lanthanides, Tb, Dy, Ho, and Er: Solution and Mechanochemical Syntheses and Structural Comparisons EPILOGUE 176 APPENDIX A: Attempts to synthesize (C5Me5)3Ln complexes with Ln = Tm, Yb, Lu 180 3− APPENDIX B: A Bridging (N2) Radical Complex of Yttrium and Its Reactivity with 190 Nitric Oxide APPENDIX C: List of Crystal Structures, Cell Parameters, and UCI X-ray Codes 196 iii LIST OF FIGURES Page Me Figure 1.1 Thermal ellipsoid plot of Cp 3Y(THF) drawn at 50% probability level. 12 Hydrogen atoms are omitted for clarity. Me Figure 1.2 X-band EPR spectra of the reduction product of Cp 3Y(THF), 2-Y, 14 collected at 298 K and 77 K. Simulated spectra are shown as dotted lines. Me Figure 1.3 X-band EPR spectra of the reduction product of Cp 3Y(THF), 3-Y, 14 collected at 298 K and 77 K. Simulated spectra are shown as dotted lines. Figure 1.4 X-band EPR spectrum of an electride species formed from the reaction 15 of crypt and KC8 in THF collected at 298 K and 77 K. Figure 1.5 Expected trend in ligand electron donor ability based on substituent. 16 Me Figure 1.6 Thermal ellipsoid plot of [K(2.2.2-cryptand)][Cp 3Y(SiH2Ph)], 4. 19 Hydrogen atoms are omitted for clarity. Me Figure 1.7 Thermal ellipsoid plot of [K(2.2.2-cryptand)][(Cp 3Y)2(-H)], 5, drawn 20 at 50% probability level. No bridging moiety could be located. Hydrogen atoms are omitted for clarity. Me Figure 1.8 X-band EPR spectra of the reduction product of Cp 3La(THF), 3-La, 22 collected at 298 K and 77 K. Simulated spectra are shown as dotted lines if available. Me Figure 1.9 X-band EPR spectra of the reduction product of Cp 3Gd(THF), 3-Gd, 22 collected at 298 K and 77 K. Simulated spectra are shown as dotted lines if available. Figure 1.10 Thermal ellipsoid plot of one bimetallic anion of 23 Me [K(crypt)]2[(Cp 3La)2(-OCH2CH2CH2CH2)], 6-La, drawn at 50% probability level. Disorder, hydrogen atoms, two THF molecules, and two [K(crypt)]+ countercations are omitted for clarity. Me [K(crypt)]2[(Cp 3Pr)2(-OCH2CH2CH2CH2)], 6-Pr, is isomorphous. Figure 1.11 Thermal ellipsoid plot of one bimetallic anion of 24 Me [K(crypt)]2[(Cp 3La)2(-OCH2CH2CH2CH2)], 6-La, drawn at 50% probability level with disorder shown. Hydrogen atoms, two THF molecules, and two [K(crypt)]+ countercations are omitted for clarity. iv Me Figure 1.12 Thermal ellipsoid plots of [K(crypt)]2[(Cp 3La)2(-OCH2CH2CH2- 34 Me CH2)], 6-La, and [K(crypt)]2[(Cp 3Pr)2(-OCH2CH2CH2CH2)], 6-Pr, drawn at 50% probability level. Hydrogen atoms, disorder about one of the CpMe rings per metal and the THF molecules in the lattice are omitted for clarity. Me 2 2 Figure 2.1 Thermal ellipsoid plot of [Cp 2Y(THF)]2(μ-η :η -N2), 2-Y, drawn at the 40 50% probability level. Hydrogen atoms are omitted for clarity. Me 2 2 15 Figure 2.2 Raman spectra of [Cp 2Y(THF)]2(μ-η :η -N2), 2-Y, and its N 42 isotopologue with (N=N)2− Raman shifts at 1454 cm−1 and 1404 cm−1, respectively. Peak intensities are normalized to allow clearer comparison. Me 14 Figure 2.3 X-band EPR spectra of from the reduction of Cp Y(THF) under N2 45 15 and 5- N2 collected at 298 K. Simulated spectra are also shown. 14 15 Simulated parameters: giso = 2.005, Aiso( N) = 5.5 G, Aiso( N) = 8.0 G, 89 14 15 Aiso( Y) = 1.7 G (5- N2) and 1.9 G (5- N2). Figure 2.4 Diagram representations of the previously crystallographically- 46 2 2 characterized complexes, {K(THF)6}{[(R2N)2Y(THF)]2(μ-η :η -N2)}, 6- 2 2 K(THF)6, and {[(R2N)2Y(THF)]2(μ-η :η -N2)}, 6-K. Figure 2.5 Diagram representation of the postulated structure of the radical species 47 Me from the reduction of Cp 3Y(THF), 5. Figure 2.6 Diagram representation of the crystallographically-characterized 48 complex of a trimetallic titanium complex reported by Chirik and et. al. Me 2 2 Figure 2.7 Thermal ellipsoid plot of [Cp 2Dy(THF)]2(μ-η :η -N2), 2-Dy, drawn at 49 the 50% probability level. Hydrogen atoms are omitted for clarity. Me 2 2 2− Figure 2.8 Raman spectrum of [Cp 2Dy(THF)]2(μ-η :η -N2), 2-Dy with (N=N) 50 Raman shift at 1453 cm−1. Figure 2.9 X-band EPR spectrum of the brown solution from the exposure of 51 dinitrogen to a freshly generated solution of Y2+ species from the Me reduction of Cp 3Y(THF) with crypt using KC8 in THF under argon −45 °C, 7. The spectrum was collected at room temperature. Figure 2.10 X-band EPR spectrum of the yellow-orange species produced in the 52 reaction of [K(crown)][Cp'3Y], with dinitrogen in Et2O at −45 °C. tet Figure 3.1 Thermal ellipsoid plot of [K(crypt)][Cp 3Nd], 2-Nd, drawn at 50% 63 probability level. Hydrogen atoms are omitted for clarity. Mixed v solvents with 0.47 Et2O and 0.53 THF partial occupancies are shown with labelled oxygen atoms, O8 and O9. Figure 3.2 UV−visible−near-IR spectrum of a ~1 mM THF solution of 64 tet −1 −1 [K(crypt)][Cp 3Nd], 2-Nd, (λmax = 812 nm with ε = 5600 M cm ). The sample showed negligible decomposition after 10 minutes of exposure to direct sunlight at room temperature, which signified the high stability of 2-Nd. tet Figure 3.3 Thermal ellipsoid plot of [K(crypt)][Cp 3Pr], 2-Pr, drawn at 50% 65 probability level. Hydrogen atoms are omitted for clarity. The partial mixed solvents are shown with labelled oxygen atoms, O8 and O9. Figure 3.4 UV−visible−near-IR spectrum of a ~1 mM THF solution of 66 tet −1 −1 [K(crypt)][Cp 3Nd], 2-Nd, (λmax = 845 nm with ε = 5200 M cm ). tet Figure 3.5 X-band EPR spectra of the reduction product of Cp 3Y, 2-Y, collected 67 at 77 K and 298 K. The simulated spectra are also shown and were generated with the exclusion of the extra feature attributed to an electride species already described in Chapter 1. tet Figure 3.6 Thermal ellipsoid plot of [K(crypt)][Cp 3Nd(SiH2Ph)], 3-Nd, drawn at 71 50% probability level. Hydrogen atoms, except H1 and H2, are omitted for clarity. Figure 4.1 Thermal ellipsoid plot of [K(crypt)][Sc(NR2)3], 2-K(crypt), drawn at 81 50% probability. Hydrogen atoms are omitted for clarity. Figure 4.2 Experimental and simulated X-band EPR spectra of 85 [K(crypt)][Sc(NR2)3], 2-K(crypt), collected at room temperature and 77 K. Figure 4.3 Thermal ellipsoid plot of Sc(NR2)3 grown from solution, 1a drawn at 86 50% probability. Hydrogen atoms are omitted for clarity. Figure 4.4 Thermal ellipsoid plot of Sc(NR2)3 grown by sublimation, 1b, drawn at 86 50% probability. Hydrogen atoms are omitted for clarity. 1− Figure 4.5 (a) LUMO of Sc(NR2)3 and (b) HOMO of [Sc(NR2)3] with contour 87 value of 0.045. Hydrogen atoms are omitted for clarity. Figure 4.6 Experimental (solid) and simulated (dash) UV−visible spectra of 88 [K(crypt)][Sc(NR2)3], 2-K(crypt), in ~3 mM THF solution at room temperature. TDDFT excitations are shown as vertical lines. vi Figure 4.7 Decomposition plot of ~3 mM solution of [K(crypt)][Sc(NR2)3], 2- 89 K(crypt), in THF at room temperature. 1− Figure 4.8 25a2 α unoccupied orbital of [Sc(NR2)3] with a contour value of 0.045.