A Flexible and Modular Approach to [2]Ferrocenophanes with Nitrogen in Bridging

A Flexible and Modular Approach to [2]Ferrocenophanes with Nitrogen in Bridging Position A Thesis Submitted to the College of Graduate Studies and Research in Partial Fulfilment of the Requirements for the Degree of Doctor of Philosophy in the Department of Chemistry University of Saskatchewan Saskatoon Canada by Subhayan Dey © Copyright Subhayan Dey, September, 2016. All rights reserved. PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor who supervised my thesis work or, in his absence, by the Head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis. Requests for permission to copy or to make other uses of materials in this thesis in whole or part should be addressed to: Head of the Department Department of Chemistry University of Saskatchewan Saskatoon, Saskatchewan, S7N 5C9, Canada i ABSTRACT [n]Ferrocenophanes are interesting because these strained sandwich compounds can be polymerized to metallopolymers by ring-opening polymerization reactions. Although there are many strained [n]ferrocenophanes known, only few of them can be polymerized with controlled molecular weight and molecular weight distribution. Among them, the Me2Si-bridged [1]ferrocenophane is the mostly explored species. To expand the possibility of accessible monomers we synthesized a new class of strained [2]ferrocenophanes. Although there are plenty of examples of symmetrically bridged [2]ferrocenophanes known, similar species with two different bridging elements are comparatively rare. In order to induce a difference in polarity over the diatomic bridge, nitrogen was introduced in the bridging position. Via a known synthetic methodology, one bromine of 1,1'-dibromoferrocene was selectively replaced by an amino group. The resulting compound was then modified into a class of easily synthesizable starting materials which were cleanly lithiated under optimized condition and in-situ reacted with different elemental dihalides to produce unsymmetrically bridged aza[2]ferrocenophanes. This is the first reported development of a modular synthetic approach towards this class of strained sandwich compounds. Aza[2]ferrocenophanes with boron, gallium, silicon, tin, and phosphorus as the second bridging element were prepared and characterized. Among these strained compounds, only the silicon- and tin-bridged species have been investigated for ring-opening polymerizations. However, no polymeric materials were obtained from these reactions. The preparation of azaphospha[2]ferrocenophanes was surprisingly difficult and led to unexpected products like 1,1'-disubstituted ferrocenes and azacarbaphospha[3]ferrocenophane. ii ACKNOWLEDGEMENTS I am grateful to my supervisor Prof. Dr. Jens Müller for his support, guidance and encouragement during my studies as a Ph.D. student. I would like to thank the University of Saskatchewan and Department of Chemistry for providing me with the opportunity to study here; the members of my advisory committee for their support, and the stuffs at the Saskatchewan Structural Science Centre. In particular, I am grateful to Ken Thoms for his help with mass measurements and Dr. Keith C. Brown for his help with NMR measurements. I would like to acknowledge all present and past members of the Müller group for their help and support. In particular, I would like to acknowledge Dr. Bidraha Bagh, Hridaynath Bhattacharjee and Cao Phan Thuy My for their support and inspiration. I am grateful to my parents Nemai Tirtha and Minu De, and wife Soumi Dutta for their love, moral support and encouragement for such a long time. I would like to convey my special thanks to Prof. Dr. Jaydip Biswas (MS, Calcutta) and Dr. Santosh M. Kumar (MS, Calcutta) for giving me a new life. iii TABLE OF CONTENTS Pages PERMISSION TO USE.................................................................................................................i ABSTRACT...................................................................................................................................ii ACKNOWLEDGEMENTS.........................................................................................................iii TABLE OF CONTENTS.............................................................................................................iv LIST OF ABBREVIATIONS....................................................................................................viii LIST OF FIGURES........................................................................................................................x LIST OF SCHEMES..................................................................................................................xiii LIST OF TABLES......................................................................................................................xix CHAPTER 1. INTRODUCTION.................................................................................................1 1.1. Ferrocenophanes...........................................................................................................2 1.2. [2]Metallocenophanes with Iron, Ruthenium and Osmium in the center.......................6 1.2.1. Symmetrically Bridged [2]Ferrocenophanes..................................................6 1.2.1.1. Carbon-bridged [2]Ferrocenophanes...............................................7 1.2.1.2. Boron-bridged [2]Ferrocenophanes................................................9 1.2.1.3. Heavier Group-14-bridged [2]Ferrocenophanes............................12 1.2.1.4. Phosphorus-bridged [2]Ferrocenophanes......................................14 1.2.2. Symmetrically Bridged [2]Ruthenocenophanes and Osmocenophanes.......................................................................................16 1.2.3. Unsymmetrically Bridged [2]Ferrocenophanes............................................18 1.3. Polymers with Ferrocene.............................................................................................21 1.4. Polymers from [2]Metallocenophanes.........................................................................31 1.5. Objectives....................................................................................................................39 CHAPTER 2. RESULTS AND DISCUSSIONS........................................................................41 2.1. Synthesis of 1-Amino-1'-bromoferrocene (114).........................................................41 iv 2.1.1. Synthesis of 1-Bromo-1'-(ethoxycarbonyl)ferrocene (129).........................45 2.1.2. Synthesis of 1-Bromo-1'-carboxyferrocene (128)........................................47 2.1.3. Synthesis of 1-Azidocarbonyl-1'-bromoferrocene (132)..............................47 2.1.4. Synthesis of Benzyl N-(1'-bromoferrocen-1-yl)carbamate (139).................48 2.1.5. Synthesis of 1-Amino-1'-bromoferrocene (114)...........................................50 2.2. N-substituted Aminobromoferrocenes........................................................................52 2.2.1. Lithiation of 1-Amino-1'-bromoferrocene (114)..........................................52 2.2.2. Synthesis of Silyl-Substituted Aminobromoferrocene (142).......................53 2.2.3. Syntheses of Alkyl Substituted Aminobromoferrocenes (147 and 149).....54 2.2.4. Lithiation of 1-Bromo-1'-(trimethylsilyl)aminoferrocene (142)...................57 2.2.5. Dilithiation of Alkyl-Substituted Aminobromoferrocenes (147 and 149)....60 2.3. Aza[2]Ferrocenophanes with Group 14 Elements in the Bridging Position...............61 2.3.1. Azasila[2]ferrocenophane (161)...................................................................62 2.3.2. Azastanna[2]ferrocenophane (162)..............................................................65 2.3.3. Azastanna[2]ferrocenophane with Increased Bulk on Tin (165)...................69 2.3.4. Attempted Ring-Opening Polymerization of Compounds 161 and 165........74 2.3.5. Azastanna[2]ferrocenophane with Reduced Bulk on Nitrogen (174)...........79 2.3.6. Investigation of Anionic ROP on compound 174.........................................80 2.4. Aza[2]ferrocenophanes with Phosphorus in the Bridging Position..............................81 2.4.1. Azaphospha[2]ferrocenophane (176)...........................................................81 2.4.2. Sulfurization of Azaphospha[2]ferrocenophane (176).................................83 2.4.3. An Azaphospha[2]ferrocenophane with Reduced Bulk on Phosphorus (179)...........................................................................................................87 2.4.4. Attempts to Synthesize Azaphospha[2]ferrocenophanes with Reduced Bulk on Nitrogen (181).......................................................................................90 2.4.5. Characterization and Relative Configuration of Azacarbaphospha[3]ferrocenophane (183)................................................96

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