Zwitterionic Nickel Catalyst for Carbonylative Polymerizations A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements of the Degree Master of Science Bradley M. Schmidt December, 2011 Zwitterionic Nickel Catalyst for Carbonylative Polymerizations Bradley M. Schmidt Thesis Approved: Accepted: ______________________________ ______________________________ Advisor Dean of the College Dr. Li Jia Dr. Stephen Z. D. Cheng ______________________________ ______________________________ Faculty Reader Dean of the Graduate School Dr. Colleen Pugh Dr. George R. Newkome ______________________________ ______________________________ Department Chair Date Dr. Ali Dhinojwala ii ABSTRACT The goal of this research project was to develop a catalyst for the copolymerization of carbon monoxide (CO) and epoxides and/or aldehydes. Zwitterionic palladium and nickel complexes were synthesized that contained bidentate phosphine-borate ligands. Under the assumption that a polymerization mechanism similar to the established cobalt-catalyzed copolymerization of CO and aziridines is applicable, the zwitterionic nature of the complexes were expected to posses the high activity of cationic metal-acyl bonds, while maintaining the anionic nature required for ion pairing during the polymerization. Characterization of the nickel complex was completed through NMR spectroscopy, FTIR spectroscopy, and X-ray crystallography. Upon completion of the metal complex syntheses a variety of polymerization conditions were screened, and the products were characterized by NMR and IR spectroscopy. Although the spectroscopic methods showed the system had activity, a pure polymer product was not obtained. iii ACKNOWLEDGMENTS I would like to thank Dr. Li Jia for his guidance and financial support to make this project possible. I would also like to thank my group members Nishant Kumar, Joseph Scavuzzo, Chao Wang, Sarang Bhawalkar, and Ilknur Babahan for their assistance with my research, and Jim Engle for his help with X-ray crystallography. Finally, I would like to thank my friends and family, especially my parents, who always support me in my endeavors. iv TABLE OF CONTENTS Page List of Figures ………………………………………………………………………………………………………………………….. ix List of Tables …………………………………………………………………………………………………………………………… xi List of Schemes ………………………………………………………………………………………………………………………. xii Chapter I. Introduction ……………………………………………………………………………………………………………… 1 II. Historical Background 2.1 Origins of Carbonylation Chemistry ………………………………………………………….… 3 2.2 Polyamides via Carbonylative Polymerizations …………………………………………... 4 2.3 Polyesters via Carbonylative Polymerizations ………………………………………...… 15 2.4 Bidentate Phosphine Ligands in CO/Ethylene Polymerization …………………... 22 III. Experimental 3.1 Handling of Air Sensitive Materials …………………………………………………………... 28 3.2 Polymerization Procedure ……………………………………………………………………...… 29 v 3.3 Characterization ………………………………………………………………………………....…… 29 3.3.1 Nuclear Magnetic Resonance Spectroscopy (NMR) ………………….... 29 3.3.2 Fourier Transform Infrared Spectroscopy (FTIR) ……………………...... 30 3.3.3 X-ray Crystallography …………………………………………………………...…... 30 3.4 Anhydrous Solvents, Deuterated Solvents, Reagents, and Monomers …...... 31 3.5 Monodentate Phosphine-Borane Ligand Synthesis ……………………………........ 32 3.5.1 Synthesis of BrC6H4-2-(CH2PPh2) …………………………………………......... 32 3.5.2 Synthesis of bromodiphenylborane ……………………………………......... 33 3.5.3 Synthesis of Ph2PCH2C6H4-2-(BPh2) …………………………………….......... 33 3.5.4 Attempted Cobalt Catalyst Synthesis ………………………………….......... 34 3.6 Bidentate Pyridine-Borane Ligand Synthesis ………………………………………........ 34 3.6.1 Synthesis of Hydrogen diphenyldi(2-pyridyl)borate ………………...... 34 3.6.2 Synthesis of Trityl diphenyldi(2-pyridyl)borate ……………………........ 35 3.7 Bidentate Phosphine-Borane Ligand Synthesis …………………………………......... 36 3.7.1 Synthesis of Ph2PCH2Li(TMEDA) …………………………………………......... 36 3.7.2 Synthesis of [BPh2(CH2PPh2)2][Li(TMEDA)2] ………………………........... 36 vi 3.7.3 Synthesis of 5-azonia-spiro[4.4]nonane bromide (ASNBr) ……....... 37 3.7.4 Synthesis of [Ph2B(CH2PPh2)2][ASN] ………………………………….......... 37 3.8 Palladium Complex Synthesis ……………………………………………………………....... 38 3.8.1 Synthesis of [Ph2B(CH2PPh2)2PdMe2][ASN] …………………………....... 38 3.8.2 Synthesis of [(iPr)2EtNH][BPh4] ……………………………………………...... 38 3.8.3 Synthesis of Ph2B(CH2PPh2)2PdMe(THF) ……………………………......... 38 3.9 Attempted Polymerizations with Palladium Complex …………………………..... 39 3.9.1 Propylene Oxide Attempted Polymerization ………………………....... 39 3.9.2 Benzaldehyde Attempted Polymerization ……………………………...... 39 3.10 Synthesis of Nickel Complex ……………………………………………………………....... 39 3.10.1 Synthesis of (TMEDA)Ni(acac)2 .…………………………………………....... 39 3.10.2 Synthesis of Dimethylaluminumethoxide (Me2AlOEt) …………...... 40 3.10.3 Synthesis of (TMEDA)NiMe2 …………………………………………………..... 40 3.10.4 Synthesis of [Ph2B(CH2PPh2)2NiMe2][ASN] …………………………........ 41 3.10.5 Synthesis of Ph2B(CH2PPh2)2NiMe(CH3CN) ……………………………..... 41 3.10.6 Synthesis of Ph2B(CH2PPh2)2NiCOMe(CO) ……………………………...... 42 vii 3.11 Attempted Polymerizations with Nickel Complex ....................................... 42 3.11.1 Propylene oxide (run 1) ................................................................ 42 3.11.2 Propylene oxide (run 2) ................................................................ 42 3.11.3 THF (run 3) .................................................................................... 43 3.11.4 Butyl Aziridine (run 4) ................................................................... 43 3.11.5 Butyl Aziridine (run 5) ................................................................... 43 3.11.6 N-benzylidenemethylamine (run 8) ............................................. 43 3.11.7 Butyl Aziridine (run 6) ................................................................... 44 3.11.8 Butyl Aziridine (run 7) ................................................................... 44 3.11.9 Aziridine (run 9) ............................................................................ 44 3.11.10 Ethyl Aziridine (run 10) ............................................................... 44 3.11.11 Ethyl Aziridine (run 11) ............................................................... 45 3.11.12 Ethyl Aziridine (run 12) ............................................................... 45 IV. Results and Discussion 4.1 Investigation of monodentate phosphine-borane ligand ………………………….. 47 4.2 Investigation of the Bidentate Pyridine-Borate Ligand ……………………………... 51 viii 4.3 Synthesis and Characterization of Bidentate Phosphine-Borate Ligand ….... 52 4.4 Synthesis and Attempted Polymerizations with Palladium Complex ………... 55 4.5 Synthesis and Characterization of Nickel Complex ………………………………...... 58 4.6 Attempted Polymerizations with Nickel Complex …………………………………..... 68 V. Conclusion ………………………………………………………………………………………………………........ 75 VI. References ................................................................................................................. 76 ix LIST OF FIGURES Figure Page 2.1 GPC trace of polymer from cobalt-catalyzed copolymerization of CO and aziridine …..... 9 2.2 (○) Mn by GPC; (+) Mn by end-group analysis; (∆) PDI by GPC for the copolymerization of n-ehtylaziridine and CO ….…........................................................................................ 10 2.3 FTIR spectrum of CO/N-butylaziridine copolymerization employing CH3COCo(CO)3PPh3 (-) or CH3COCo(CO)3P(o-tolyl)3 (-) ……………………………………..…………. 11 2.4 Microstructures of CO / propylene oxide copolymerization …………………………………....... 16 2.5 Examples of the variety of bidentate phosphine ligands synthesized ……………………...... 22 2.6 Variety of bis(phosphino)borates synthesized by the Peters group ………………………...... 26 4.1 (a) 1H NMR spectrum of monodentate phosphine-borane ligand ………………………………...... 48 4.1 (b) 31P NMR spectrum of monodentate phosphine-borane ………………………………………........ 49 4.1 (c) 11B NMR spectrum of monodentate phosphine-borane ligand ………………………………….. 49 4.2 (a) 1H NMR spectrum of trityl-coordinated pyridine-borate ligand ……………………………….... 52 4.2 (b) 13C NMR spectrum of bidentate pyridine-borate ligand …………………………………………..... 53 4.3 1H NMR spectrum of bidentate phosphine borate ligand ………………………………………...... 54 4.4 1H NMR of palladium complex ………………………………………………………………………………...... 58 4.5 1H NMR spectrum of palladium catalyzed CO/propylene oxide copolymerization …...... 59 4.6 (a) 1H NMR spectrum of ligand-coordinated dimethyl nickel complex …………………………..... 61 x 4.6 (b) 31P NMR spectrum of ligand-coordinated dimethyl nickel complex ………………………….... 62 4.7 1H NMR spectrum of acetonitrile-coordinated nickel complex ………………………………..... 63 4.8 1H NMR spectrum of 5-coordinate nickel complex …………………………………………………..... 65 4.9 (a) 1H NMR spectrum of final zwitterionic nickel catalyst ……………………………………………..... 65 4.9 (b) 31P NMR of final zwitterionic nickel catalyst …………………………………………………………….... 66 4.10 Crystal structure of zwitterionic nickel complex ………………………………………………………... 67 4.11 1H NMR spectrum of product from CO/THF copolymerization trial ………………………….... 70 4.12 1H NMR spectrum of product from CO/butyl aziridine copolymerization in THF ……..... 71 4.13 1H NMR spectrum of product from CO/aziridine copolymerization trail …………………..... 72 4.14 1H NMR spectrum of product from CO/ethyl aziridine copolymerization in THF ……...... 73 4.15 1H NMR spectrum of CO / 1-hexene copolymerization in THF ......................................