Ring-expanded N-heterocyclic copper(I) boryl complexes : the structures of [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex]

Babula, Dawid J. and Charman, Rex S. C. and Jerome, Thomas H. and Horsley Downie, Thomas M. and Mahon, Mary F. and Liptrot, David J. (2023) Ring-expanded N-heterocyclic copper(I) boryl complexes : the structures of [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex]. European Journal of Inorganic Chemistry, 26 (13). e202300043. ISSN 1434-1948 (https://doi.org/10.1002/ejic.202300043)

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Abstract

Abstract σ-Bond metathesis reactions between [(6-Dipp)CuOtBu] (6-Dipp=:C({Dipp}NCH2)2CH2, Dipp=2,6-iPr2?C6H3) and three diboranes gave access to three new copper(I) boryl complexes [(6-Dipp)CuBcat], [(6-Dipp)CuBneop], and [(6-Dipp)CuBhex] (cat=1,2-O2C6H4; neop=(OCH2)2C(CH3)2; hex=OC(CH3)HCH2C(CH3)2O). Whilst [(6-Dipp)CuBcat] and [(6-Dipp)CuBneop] formed rapidly in toluene, access to [(6-Dipp)CuBhex] required heating to 60?°C for days. The complexes were characterised by single-crystal X-ray crystallography which showed in all three cases that the systems were monomers and distorted-linear at the copper atom. The stability of [(6-Dipp)CuBneop] was found to be comparable to that of [(IPr*)Cu-Bneop] (IPr*=1,3-bis(2,6-(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene); it persisted in solution for days with no sign of decomposition. [(6-Dipp)CuBhex] is a rare crystallographically characterised example of a complex containing a boryl anion supported by the hexylene glycolato ligand.

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