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Group 13 Organometallic Chemistry: Sterically

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Group 13 Organometallic Chemistry: Sterically GROUP 13 ORGANOMETALLIC CHEMISTRY: STERICALLY DEMANDING LIGANDS, METAL-METAL BONDING, AND METALLOAROMATICY by BRANDON QUILLIAN (Under the Direction of Gregory H. Robinson) ABSTRACT The syntheses and molecular structures of several organometallic group 13 compounds and complexes are presented herein. The organometallic chemistry of RLi (R = 2,6-(4-t- BuC6H4)2C6H3-) and R´Li (R´ = 2,6-(4-Me-C6H4)2C6H3-) was examined on group 13 halides to yield a number of new compounds 1-8: RGaCl2(OEt2) (1), R2GaCl (2), RAlBr2(OEt2) (3), [RAlCl(OEt2)]2O (4), R3In (5), [RGaCl3][Li(OEt2)2] (6), [RInCl3][Li(OEt2)(THF)] (7), R3In. Compounds 5 and 8 are notable as the first tris-m-terphenyl-group 13 compounds, while 4 is an interesting oxo-bridged-di(m-terphenyl-aluminum chloride) complex with exceptionally long AlCl bonds. Sodium metal reduction of 1 provides a rare catenated tri-gallium complex, [R3Ga3][Na(OEt2)]3 (9). Additionally, the organometallic chemistry at the group 13group 4 interface was explored, wherein three new compounds were isolated: Cp2Hf(ER)2 (10, E = Ga; 11, E = In; R = 2,6-(2,4,6-i-Pr3C6H2)2C6H3-) and (C10H8)(ZrCp)2(μH)(μCl)(μGaR) (R = 2,6-(4-t- BuC6H4)2C6H3-) (12). Compounds 10 and 11 contain the first reported group 13Hf bonds, while compound 12 is the only compound with gallium engaged in bonding with two zirconium atoms. Extending the organometallic chemistry of m-terphenyl ligands to the group 4 metallocenes gave the first m-terphenyltitanium(III) radical Cp2TiR´ (13) and the first m- terphenylzirconocene(IV) compound, Cp2ZrR(Cl) (14) (R = 2,6-(4-t-BuC6H4)2C6H3-). This research project also involved the study of heterometallic aromaticity, which ultimately produced the first gallepin, bis(gallepin)2·TMEDA (18), by the reaction of 2,2- dilithio-Z-stilbene(TMEDA)2 (16) and GaCl3. The aromatic nature of the gallepin was evaluated using Nucleus-Independent Chemical Shifts (NICS) and compared to that of borepins. Additionally, the -donor properties of N-heterocyclic carbenes were evaluated on mesityl-group 13 dihalides, wherein several new carbene-mesityl-group 13 dihalide adducts were prepared: MesGaCl2(:L) (19), MesAlBr2(:L) (20), MesInBr2(:L) (21) (Mes = 2,4,6-Me3C6H2-; :L = :C 2). Potassium graphite reduction of 19 yielded a rare meso-digallane, [MesGaCl(:L)]2 (22), with four-coordinate gallium atoms, while reduction with potassium metal unexpectedly produced an unprecedented neutral Ga6-octahedron cluster, Mes4Ga6(:L)2 (23). NICS calculations were used to support its aromatic properties and compared with that of the -2 thoroughly studied dianionic hexaborate octahedron, [B6H6] . In conjunction with these studies a new detailed synthetic protocol to prepare Arduengo’s carbene (26) from adamantylammonium chloride was established and full single crystal X-ray structural analysis reported. INDEX WORDS: alkali metal reduction, aluminum, aromaticity, computations, cyclopentadienyl, gallepin, gallium, group 4, group 13, hafnium, indium, main group metals, mesityl, metallocene, metalloaromaticity, metalmetal bonds, m-terphenyl, N-heterocyclic carbene, Nucleus-Independent Chemical Shifts, organometallic, sterically demanding ligands, titanium, zirconium GROUP 13 ORGANOMETALLIC CHEMISTRY: STERICALLY DEMANDING LIGANDS, METAL-METAL BONDING, AND METALLOAROMATICY by BRANDON QUILLIAN B.S., Armstrong Atlantic State University, 2003 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2008 © 2008 Brandon Quillian All Rights Reserved GROUP 13 ORGANOMETALLIC CHEMISTRY: STERICALLY DEMANDING LIGANDS, METAL-METAL BONDING, AND METALLOAROMATICY by BRANDON QUILLIAN Major Professor: Gregory H. Robinson Committee: George F. Majetich Robert S. Phillips Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia December 2008 DEDICATION I dedicate this dissertation to my wife, Jennifer Quillian, whose loyalty and sacrifice gave me the strength to carry on in my desperate moments, and to my daughter, Kyleigh, whose smile and laughter consoled me. To those who were not able to witness my greatest accomplishment, my mother and father, Rosa Mae Rucker and Charles Edward Quillian, who gave me this precious life but left this world long before I ever knew them. To my Aunt Fannie whom raised me in my parents’ stead. iv ACKNOWLEDGEMENTS I owe great gratitude to my wife whose perseverance and patience never waned. It is with her support and understanding that I am able to complete The University of Georgia doctoral program in chemistry. Special thanks goes out to my committee members, Dr. George Majetich and Dr. Robert S. Phillips, for your guidance and support. I would also like to thank Dr. Yuzhong Wang. His ingenuity, knowledge, and guidance were invaluable assets. Last but not least, I would also like to thank Dr. Gregory H. Robinson for giving me the opportunity to become a better scientist and motivation and support throughout my years at UGA. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.........................................................................................................v LIST OF TABLES.................................................................................................................. viii LIST OF FIGURES ....................................................................................................................x CHAPTER 1 INTRODUCTION .....................................................................................................1 1.1 Purpose of Study..............................................................................................1 1.2 Organometallic Chemistry History and Origins................................................2 1.3 General Organometallic Synthetic Techniques.................................................5 1.4 Chemistry and Properties of the Group I, II, 13 Elements.................................6 1.5 Sterically Demanding m-Terphenyl Ligands ..................................................19 1.6 Main Group MetalMetal Multiple Bonding..................................................22 1.7 Metalloaromaticity.........................................................................................33 2 RESULTS AND DISCUSSIONS ............................................................................39 2.1 Less-sterically Demanding m-TerphenylGroup 13 Complexes.....................39 2.2 Organometallic Group 13Group 4 Complexes .............................................68 2.3 m-Terphenyl Group 4 Metallocenes ...............................................................81 2.4 Gallepins .......................................................................................................89 2.5 Examinations of Carbenes in Group 13 Chemistry.......................................104 2.6 A New Synthetic Procedure for Arduengo’s Carbene...................................126 vi 3 Conclusion.............................................................................................................133 3.1 Concluding Remarks....................................................................................133 4 EXPERIMENTAL.................................................................................................137 4.1 General Background ....................................................................................137 4.2 Preparation and Characterization of Starting Materials.................................139 4.3 Syntheses of m-TerphenylGroup 13 Complexes.........................................143 4.4 Syntheses of Organometallic Group 13Group 4 Complexes.......................147 4.5 Syntheses of m-Terphenyl Group 4 Metallocenes.........................................148 4.6 Syntheses of Gallepins and Precursor...........................................................149 4.7 Syntheses of CarbeneGroup 13 complexes.................................................151 4.8 Synthesis of Arduengo’s Carbene ................................................................153 REFERENCES .......................................................................................................................155 APPENDICES A CRYSTALLOGRAPHIC DATA...........................................................................172 B RESEARCH PUBLICATIONS .............................................................................284 vii LIST OF TABLES Page Table 2.1: Selected bond distances [Å] and angles [°] for RGaCl2(OEt2) (1)..............................45 Table 2.2: Selected bond distances [Å] and angles [°] for R2GaCl (2)........................................46 Table 2.3: Selected bond distances [Å] and angles [°] for RAlBr2(OEt2) (3)..............................48 Table 2.4: Selected bond distances [Å] and angles [°] for [RAlCl(OEt2)]2O (4).........................50 Table 2.5: Selected bond distances [Å] and angles [°] for R3In (5).............................................54 Table 2.6: Selected bond distances [Å] and angles [°] for [RGaCl3][Li(OEt2)2] (6)...................58 Table 2.7: Selected bond distances [Å] and angles [°] for [RInCl3][Li(OEt2)(THF)] (7)............61 Table 2.8: Selected bond distances [Å] and angles [°] for R3In (8)............................................62 Table 2.9: Selected bond distances [Å] and angles [°] for [R3Ga3][Na(OEt2)]3 (9) .....................66 Table 2.10: Selected bond distances [Å] and angles [°] for Cp2Hf(GaR)2 (10)...........................72 Table 2.11: Selected
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