Synthesis,Characterisation and Reactivity of Copper(I) Amide Complexes and Studies on Their Role in the Modified Ullmann Amination Reaction |
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Authors: | Simon Sung Dr D Christopher Braddock Prof Alan Armstrong Dr Colin Brennan Dr David Sale Dr Andrew J P White Dr Robert P Davies |
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Institution: | 1. Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ (UK);2. Process Studies Group, Syngenta, Jealott's Hill Research Centre, Bracknell, Berkshire RG42 6EY (UK) |
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Abstract: | A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide ( 1 ), copper(I) 2,2,6,6‐tetramethylpiperidide ( 2 ), copper(I) pyrrolidide ( 3 ), copper(I) piperidide ( 4 ), and copper(I) benzylamide ( 5 ). Their solid‐state structures and structures in D6]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1 , 2 and 4 are shown to exist as tetramers in the solid state by X‐ray crystallography. In D6]benzene solution, complexes 1 , 2 and 5 were found by using 1H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one‐dimensional 1H and 1H DOSY NMR spectroscopy. Complexes 3 – 5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10‐phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol. |
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Keywords: | amination copper homogeneous catalysis structure elucidation Ullmann reaction |
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