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Advances in Carborane-based Ionic Liquids for Olefin Polymerization and Catalysis

This study explores the synthesis and reactivity of carborane-based ionic liquids, highlighting their potential in catalysis and electrochemical applications. With exceptional inertness and unique properties, carboranes are characterized by their weakly coordinating anions and low nucleophilicity. The investigation includes various cations and their effect on the properties of these ionic liquids, providing insights into their applications in protonation, alcohol oxidation, and the stability of reactive intermediates. Findings also cover the reactivity of carborane anions in olefin polymerization.

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Advances in Carborane-based Ionic Liquids for Olefin Polymerization and Catalysis

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  1. Ag O N [H(OEt2)2]+ [C(Ph)3]+ - - C C C B B B H H H 1 1 1 1 1 1 1 1 1 2 2 2 (CH ) + Ru Ru CH-OH + (CH3)2C=O Ru 3 2 OTf N O N OTf O R u Parent carborane R R R u u u M e M M M e e e N O N N N O O O 1-Et carborane C l M M e e 1-Me carborane catalyst: + Ru - BAr THF f N CH O 3 BAr = B((3,5-(CF ) C H ) f 3 2 6 2 4 Hexabromo carborane 1-Bu carborane CsCB11H12 /ether + HCl(gas) - H [H(Et2O)2]+ CB11H12 - - H Carborane anion 1H NMR, CD3CN Known reactivity: Cations and anions olefin polymerization catalysis observed Carborane Acid H+ alcohol oxidation: CB11H12- • Extremely inert • Weakly coordinating • Low nucleophilicity • Large, charge-diffused • Synthesized in 3 steps • Derivatizable • Stabilizes “hot” cations THF oxidation catalysis: R u 1H NMR, CD3CN reaction in progress L N O [Ru]-cat. O L ' starting Cp* O new Cp* 2 starting Me product Me • References • Larsen, A. S., Holbrey J.D., Tham F.S., Reed C.A. J. Am. Chem. Soc.2000, 122, 7264--7272. • Jelíneck, T.; Baldwin, P.; Scheidt, R.W.; Reed, C.A. Inorg. Chem., 1993, 32, 1982--1990. • Jeljnek, T et al. Coll. Czech. Chem. Comm.1984, 49, ,p. 1559. • Chang, J.; Bergman, R. G. J. Am. Chem. Soc. 1987, 109, 4298-4304. • Chang, J.; Seidler, M. D.; Bergman, R. G. J. Am. Chem. Soc. 1989, 111, 3258-3271. • Brookhart, M.; Grant, B.; Volpe, A. F. Jr. Organometallics1992, 11, 3920-3922. • Rifat, A.; Kociok-Kohn, G.; Steed, J. W.; Weller, A. S. Organometallics2004, 23, 428-432 • Hlatky, G. G.; Eckman, R. R.; Turner, H. W. Organometallics 1992, 11, 1413-1416. • Hubbard, J. L.; Morneau, A.; Burns, R. M.; Zoch, C. R. J. Am. Chem. Soc. 1991, 113, 9176-9180. • Xie, Z; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994, 116, 1907-1913. • Acknowledgements • We are grateful to Dr. John D. Holbrey for a donation of imidazolium halides, to professor Christopher A. Reed for a donation of decaborane, to professor Geoff Coats for helpful suggestions. • Funding for summer internships to J.K, M.S, J.M., start-up funds and Faculty Development Award to A.L. were provided by Ithaca College and are gratefully acknowledged. carborane acid m.p. data Cp*Ru(NO)Me2 Effect of Anion on Melting Point protonation product n-HexPy hexabromo-CB -> solution IR (CD3CN) 1 NO region m.p. (°C) 2 3 (works!) R=H X=H R=Me X=H R=H X=Br *Super-cooling effects Effect of Cation on Melting Point <- n-butyl pyridinium carborane m.p. (°C) O O Derivatization: Carborane synthesis: R H - - C C 1 . n - B u L i ( > > 2 e q ' s ) B H B H H B B H H B B H N M e • H C l 2 . R - X ( X = C l , B r ) 3 B H B H + B H B H N M e H L i + 3 B H B H B H B H H O 2 H B B H H B B H B H B H B B H H Jesse Kleingardner, Matthew Pearsall, Joshua Masland, Anna S. Larsen Department of Chemistry, Ithaca College, Ithaca, NY 14850 Low-melting salts with carborane anion Electrophilic Cp*Ru(NO) paired with carborane • Ionic liquids (IL): • possess wide liquid temperature range • have virtually no vapor pressure • dissolve covalent and ionic compounds • can serve both as catalyst and solvent • advantageous for electrochemistry • Carborane-based IL: • need for non-reactive anion (instead of AlCl4-, PF6-, BF4-) • factors for low m.p. studies systematically through • varied derivatized anion and cation combinations • employ alkyl-pyridinium cations to compare to our earlier study • bis-alkyl-imidazolium carboaren salts • Cp*Ru(NO) piano-stool complexes • Accessible synthetically • NMR marker (Cp*) • IR marker (NO) • Electrophilic metal center Preliminary X-ray data From the X-ray facilities of the university of Alabama and University of Wisconsin n-BuPyCB m.p. 134 oC alkyne reactivity n-HexPy 1-MeCB m.p. 70oC Clean Protonation of [Ru]Me2 : Differential Scanning Calorimetery • Problems with reported systems: • OTf binds tightly to metal center, hampers • catalytic reactivity towards substrate • BAr4F disintegrates • Carborane analogs are not known Undergraduate Projects at Ithaca College: Carboranes for [RuCp*(NO)] Chemistry and Low-melting Ionics carried out the at the facilities of the Cornell University ether from carborane acid gas formation observed upon mixing (CH4) Synthetic routes to CB complex • Immediate and future plans: • Isolation and characterization • Reactivity studies with • Olefins • Alkynes • ROH • CO2 • H2O • On-going studies and plans: • Electrochemical studies in melts: ion mobility • X-ray studies • EPR studies for conductivity/viscosity • Synthesis of unsymmetrically halogenated CB • Synthesis of hydrophilic salts of derivatized CB

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