Gas-Phase Ion-Molecule Reactions of Copper Hydride Anions [CuH2](-) and [Cu2H3]().

Author(s) Zavras, A.; Ghari, H.; Ariafard, A.; Canty, A.J.; O'Hair, R.A.J.
Journal Inorg Chem
Date Published 2017 Feb 10
Abstract

Gas-phase reactivity of the copper hydride anions [CuH2](-) and [Cu2H3](-) toward a range of neutral reagents has been examined via multistage mass spectrometry experiments in a linear ion trap mass spectrometer in conjunction with isotope labeling studies and Density Functional Theory (DFT) calculations. [CuH2](-) is more reactive than [Cu2H3](-), consistent with DFT calculations, which show it has a higher energy HOMO. Experimentally, [CuH2](-) was found to react with CS2 via hydride transfer to give thioformate (HCS2(-)) in competition with the formation of the organometallic [CuCS2](-) ion via liberation of hydrogen; CO2 via insertion to produce [HCuO2CH](-); methyl iodide and allyl iodide to give I(-) and [CuHI](-); and 2,2,2-trifluoroethanol and 1-butanethiol via protonation to give hydrogen and the product anions [CuH(OCH2CF3)](-) and [CuH(SBu)](-). In contrast, the weaker acid methanol was found to be unreactive. DFT calculations reveal that the differences in reactivity between CS2 and CO2 are due to the lower lying π* orbital of the former, which allows it to accept electron density from the Cu center to form the initial three-membered ring complex intermediate, [H2Cu(η(2)-CS2)](-). In contrast, CO2 undergoes the barrierless side-on hydride transfer promoted by the high electronegativity of the oxygen atoms. Side-on SN2 mechanisms for reactions of [CuH2](-) with methyl iodide and allyl iodide are favored on the basis of DFT calculations. Finally, the DFT calculated barriers for protonation of [CuH2](-) by methanol, 2,2,2-trifluoroethanol, and 1-butanethiol correlate with their gas-phase acidities, suggesting that reactivity is mainly controlled by the acidity of the substrate.

DOI 10.1021/acs.inorgchem.6b02145
ISSN 1520-510X
Citation Inorg Chem. 2017.

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