Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate |
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| Authors: | Anurag Noonikara-Poyil Alvaro Muoz-Castro H V Rasika Dias |
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| Institution: | 1.Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 76019, USA;2.Grupo de Química Inorgánica y Materiales Moleculares, Facultad de Ingenieria, Universidad Autonoma de Chile, El Llano Subercaseaux 2801, Santiago 8910060, Chile |
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| Abstract: | Copper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HC≡CSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in C≡C stretch of H2B(3,5-(CF3)2Pz)2]Cu(HC≡CH) and H2B(3,5-(CF3)2Pz)2]Cu(HC≡CSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2(μ-3,5-(CF3)2Pz])2(HC≡CH)2 display similar Cu-alkyne bonding features. The mononuclear H2B(3,5-(CF3)2Pz)2]Cu(NCMe) complex catalyzes 3 + 2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates. |
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| Keywords: | copper acetylene alkyne click chemistry pyrazolyl borate |
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