A Dissertation entitled The Study of Lanthanides for Organometallic and Separations Chemistry by Andrew Charles Behrle Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemistry _____________________________________ Dr. Joseph A. R. Schmidt, Committee Chair ____________________________________ Dr. Mark R. Mason, Committee Member ____________________________________ Dr. Steven J. Sucheck, Committee Member ____________________________________ Dr. Constance A. Schall, Committee Member ____________________________________ Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo December 2012 Copyright 2012, Andrew Charles Behrle This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of The Study of Lanthanides for Organometallic and Separations Chemistry by Andrew Charles Behrle Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemistry The University of Toledo December 2012 Part 1. The effective use of f-element complexes as catalysts for reactions such as hydroamination and hydrophosphination has been demonstrated in many recent reports. Unfortunately, the homoleptic starting materials underpinning this chemistry are generally derived from only a handful of ligands. That is, of the homoleptic lanthanide complexes that exist, the majority make use of alkylsilane (-CH2SiMe3), silylamide (- N(SiMe3)2), or benzyl (-CH2C6H5) derivatives. The paucity of tri-alkyl lanthanide complexes can be attributed to the required extended coordination sphere and high Lewis acidity or electrophilicity of these metals. While these properties make lanthanum alkyl complexes very reactive, in turn they also make their synthesis and manipulation quite challenging. Our efforts have focused on the development of unexplored homoleptic tri-alkyl rare-earth metal complexes utilizing simple ligands that fulfill both the electronic and steric requirements of these metal iii centers. Herein, we report our findings of a new class of homoleptic tri-alkyl rare-earth metal complexes using alpha-metallated N,N-dimethylbenzylamine ligands as stable benzyl ligand derivatives to form lanthanide complexes free of coordinating solvent. We have also expanded the reactivity scope of these homoleptic lanthanide complexes to include stoichiometric insertion and catalytic hydrophosphination reactions involving heterocumulenes. The tris alpha-metallated N,N-dimethylbenzylamine lanthanum and yttrium complexes [α-La(DMBA)3, α-Y(DMBA)3] have proven to be capable starting materials that undergo triple insertion reactions with a variety of carbodiimide ligands. In addition α-La(DMBA)3 demonstrated excellent catalytic activity for the room temperature hydrophosphination of a wide array of heterocumulenes. Part 2. Another current focus of the Schmidt group involves development of a class of lower rim functionalized calix[4]arenes containing ligands that have been previously shown to selectively separate lanthanides. These calix[4]arenes will be attached to a solid support through an alkyl linker at the methylene position and separation will be based primarily on the ionic radius of the metal cation. In summary, we report the synthesis and derivatization of a series of 2-(ω- (alkyl))tetramethoxy-p-tert-butylcalix[4]arenes. These calix[4]arenes represent intermediates in a multi-step synthesis for the design of lower rim modified iv calix[4]arenes that will be evaluated for the separation of lanthanide ions with the future goal of attachment to a solid support. v Acknowledgements First and foremost I want to acknowledge my family. I have been blessed and fortunate to have parents who stressed the importance of an education throughout my life. I cannot find the words to fully express my gratitude for my parents loving and caring support throughout my life and their help with the endeavors I have overcome. I also want to thank my sisters, Catherine and Kristen. I would like to acknowledge three people who were instrumental in my decision to pursue chemistry: Fr. John Ebenhoeh, O.S.F.S, Dr. Hongcai Zhou, and Dr. Joseph A. R. Schmidt. Joe not only pushed me to be the best synthetic chemist I can be, but encouraged me to always remember to try new reactions. I thank Joe for his seemingly bottomless chasm of chemistry knowledge, help and his willingness to always give advice. I want to acknowledge and thank my committee members for their input and suggestions throughout my graduate career. I also acknowledge my co-workers over the past five years. I want to thank Dr. Andrew R. Shaffer, Dr. John F. Beck, Dr. Tamam Baiz, Matt Hertel, Danielle Samblanet, Nick Zingales, and Sreejit Menon for all their help in and outside the lab. Finally I want to thank my wife Natalie for all her love, support, and patience. I am very blessed to have you in my life. You have been with me since I began this journey and continue to remain at my side. I love you more than words can describe. vi Contents Abstract iii Acknowledgements vi Contents vii List of Tables ix List of Figures x List of Schemes xii Chapter 1 An Introduction to Lanthanides and Their Chemistry 1.1 General Properties 1 1.2 Inorganic Complexes 5 1.3 Organometallic Chemistry of the Lanthanides 9 1.4 Catalysis 24 Chapter 2 Synthesis and Protonolysis Reactivity of Homoleptic Alpha- Metallated N,N- Dimethylbenzylamine Rare-Earth Metal Complexes 2.1 Introduction 27 2.2 Results and Discussion 29 2.3 Conclusion 41 2.4 Experimental 42 vii 2.4.1 General Considerations and Instrumentation 42 2.5 Crystallography 54 Chapter 3 Insertion Reactions and Catalytic Hydrophosphination of Heterocumulenes using Alpha-Metallated N,N- Dimethylbenzylamine Rare-Earth Metal Complexes 3.1 Introduction 60 3.2 Results and Discussion 62 3.3 Conclusion 73 3.4 Experimental 74 3.4.1 General Considerations and Instrumentation 74 3.4.2 General Procedures for the Hydrophosphination of 79 Heterocumulenes 3.4.2.1 Method A 79 3.4.2.2 Method B 80 3.4.2.3 Method C 80 3.5 Crystallography 87 Chapter 4 Modification and Synthesis of 2-(ω-Chloroalkyl)- 91 Tetramethoxy-p-tert-Butylcalix[4]arenes 4.1 Introduction 91 4.2 Results and Discussion 96 4.3 Conclusions 102 4.4 Experimental Details 103 References 113 viii List of Tables 1.1 Abundance of Lanthanides 2 1.2 Selected Properties of Lanthanides and Their Ions 3 1.3 Colors and Electronic Ground States of M3+ Ions 5 2.1 Selected Bond Distances and Angles for (2-1)-(2-8) 33 2.2 Crystal Data and Collection Parameters (2-1)-(2-5) 58 2.3 Crystal Data and Collection Parameters (2-6)-(2-9) 59 3.1 Catalytic Addition of Phosphines to Heterocumulenes 69 3.2 Crystal Data and Collection Parameters (3-3) and (3-5) 90 ix List of Figures 1.1 Multiple coordination modes of carbonates to rare-earth metals 7 1.2 Coordination mode of phosphates to rare-earth metals 7 1.3 Coordination mode of sulfate to lanthanum ions 8 1.4 Bidentate secondary phosphine ligands 21 2.1 1H NMR spectrum of 2-1 30 2.2 1H NMR spectrum of 2-8 31 2.3 ORTEP diagram of 2-1 32 2.4 ORTEP diagram of 2-8 33 2.5 ORTEP diagram of 2-2 35 2.6 ORTEP diagram of 2-3 35 2.7 ORTEP diagram of 2-4 36 2.8 ORTEP diagram of 2-5 36 2.9 ORTEP diagram of 2-6 37 2.10 ORTEP diagram of 2-7 37 2.11 ORTEP diagram of 2-9 40 2.12 ChemDraw figure of 2-1 44 2.13 ChemDraw figure of 2-8 48 3.1 ORTEP diagram of 3-3 65 x 3.2 ORTEP diagram of 3-5 72 4.1 The four conformations of p-tert-butylcalix[4]arene 92 4.2 Location of the three possible positions for modification of calix[4]arene 93 4.3 1H NMR spectrum of 4-3 98 4.4 1H NMR spectrum of 4-5 100 4.5 1H NMR spectrum of 4-9 102 xi List of Schemes 1.1 Synthesis of rare-earth metal borates 9 1.2 Synthesis of (trimethylsilyl)methyl rare-earth metal complexes 11 1.3 Synthesis of Ln(CH2SiMe3)3 11 1.4 Synthesis of rare-earth metal cationic complexes 12 1.5 Synthesis of heteroleptic rare-earth alkyl complexes 12 1.6 Synthesis of homoleptic lanthanide tribenzyl complexes 14 1.7 Synthesis of donor functionalized benzyl divalent lanthanide complexes 14 1.8 Synthesis of Ln(II) phenyl substituted complexes 16 1.9 Synthesis of organometallic triphenyl lanthanide complexes 16 1.10 Formation of anionic and neutral rare-earth phenyl complexes 17 1.11 Synthesis of cationic, dicationic, and tris(cyclopentadienyl) rare-earth metal complexes 18 1.12 Synthesis of N-methylimidazole samarium complexes 19 1.13 Synthesis of salen yttrium(III) complex 20 1.14 Synthesis of rare-earth metal phosphide complexes 20 1.15 Salt metathesis reactions to generate rare-earth metal hydrides 22 1.16 β-Hydride elimination to form rare-earth metal hydrides in situ 23 1.17 Hydride transfer reactions to yield lanthanide hydrides 23 xii 1.18 Hydrogenolysis of lanthanide alkyls to yield hydrides 23 1.19 Catalytic cycles of hydroamination and hydrosilylation 25 1.20 Proposed hydrophosphination mechanism 26 2.1 Synthesis of α-Ln(DMBA) [(2-1)-(2-8)] 3 29 2.2 Protonolysis reactions of α-Ln(DMBA) [(2-9)-(2-18)] 3 39 3.1 Stoichiometric insertion of carbodiimides [(3-1)-(3-3)] 63 3.2 Synthesis of N,N-dimethylbenzylamine amidinate (3-4) 64 3.3 Synthesis of homoleptic lanthanum phosphaguanidinate (3-5) 70 3.4 Proposed catalytic cycle for the hydrophosphination of N,N- diisopropylcarbodiimide 73 4.1 Synthesis of p-tert-butylcalix[4]arene 92 4.2 Fragment condensation reaction to form a methylene-substituted calix[4]arene 94 4.3 Addition of chloro-alkyl