Strongly Electrophilic Borenium Ions for Small Molecule Activation
Inorganic Molecular Chemistry - Synthesis and Characterisation
Final Report Abstract
Hydride abstraction from N-heterocyclic carbene adducts of pentafluorophenylborane gave the [(NHC)BH(C6F5)]+ borenium cations, which served as the central compounds of our study. They gave stable borane carbonyls upon exposure to carbon monoxide. Insertion of elemental sulfur into the B-H bond followed by deprotonation gave NHC stabilized thioxoboranes. Thermolysis of the [(IPr)BH(C6F5)]+ borenium featuring isopropyl substituents at the NHC nitrogen atoms resulted in C-H activation with loss of dihydrogen. Subsequent deprotonation of the newly formed cyclic borenium system gave the respective acyclic boraalkene. Its reactions were intensively investigated. This included several examples of formal [2+2]cycloaddition reactions, but also chalcogena-borirane formation upon treatment with elemental sulfur or selenium, oxidation with dinitrogenmonoxide and nitroxide radical formation upon treatment with nitrosobenzene. Starting from our parent BH-borenium systems a short synthetic pathway led to the formation of the neutral acyclic NHC stabilized B=CH2 boraalkene examples, whose chemistry was characterized experimentally. Related C-substituted boraalkenes were obtained from a closely related preparation sequence that involved an initial alkene hydroboration reaction. A similar boraalkene example was prepared that contained the linear isothiocyanate substituent at boron instead of the ubiquitous fluorinated aryls. The acyclic boraalkene examples underwent an unusual reaction with carbon disulfide that resulted in the cleavage of the B=C linkage. Some of the newly formed acyclic boraalkenes were used as pi-ligands in metal coordination chemistry.
Publications
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A BH Borenium-Derived Thioxoborane, Its Persulfide, and Their Li+-Induced Reactions with Alkynes and with Carbon Dioxide. Journal of the American Chemical Society, 142(46), 19763-19771.
Chen, Chaohuang; Daniliuc, Constantin G.; Mück-Lichtenfeld, Christian; Kehr, Gerald & Erker, Gerhard
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The [(NHC)B(H)C6F5]+ Cations and Their [B](H)−CO Borane Carbonyls. Angewandte Chemie International Edition, 59(48), 21460-21464.
Chen, Chaohuang; Li, Jun; Daniliuc, Constantin G.; Mück‐Lichtenfeld, Christian; Kehr, Gerald & Erker, Gerhard
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Using the FpXylBH2•SMe2 reagent for the regioselective synthesis of cyclic bis(alkenyl)boranes. Chemical Communications, 56(81), 12178-12181.
Škoch, Karel; Daniliuc, Constantin G.; Kehr, Gerald & Erker, Gerhard
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Formation and Cycloaddition Reactions of a Reactive Boraalkene Stabilized Internally by N‐Heterocyclic Carbene. Angewandte Chemie International Edition, 60(36), 19905-19911.
Chen, Chaohuang; Daniliuc, Constantin G.; Kehr, Gerald & Erker, Gerhard
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A deprotonation pathway to reactive [B]CH2 boraalkenes. Dalton Transactions, 51(19), 7695-7704.
Škoch, Karel; Chen, Chaohuang; Daniliuc, Constantin G.; Kehr, Gerald & Erker, Gerhard
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Boraalkenes Made by a Hydroboration Route: Cycloaddition and B=C Bond Cleavage Reactions. Angewandte Chemie International Edition, 62(4).
Jie, Xiaoming; Chen, Chaohuang; Daniliuc, Constantin G.; Kehr, Gerald & Erker, Gerhard
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Generation of boryl-nitroxide radicals from a boraalkene via the nitroso ene reaction. Chemical Science, 13(36), 10891-10896.
Chen, Chaohuang; Daniliuc, Constantin G.; Klabunde, Sina; Hansen, Michael Ryan; Kehr, Gerald & Erker, Gerhard
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Bora‐alkenes: Metal Coordination and Reactions with BH‐boranes. Chemistry – A European Journal, 29(41).
Chen, Chaohuang; Daniliuc, Constantin G.; Kehr, Gerald & Erker, Gerhard
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The B=C bond: some recent developments. Organic Chemistry Frontiers, 10(16), 4161-4166.
Chen, Chaohuang; Kehr, Gerald & Erker, Gerhard
