om8b00443_si_002.pdf (20.63 MB)
Dicopper Alkyl Complexes: Synthesis, Structure, and Unexpected Persistence
journal contribution
posted on 2018-08-08, 18:48 authored by Micah S. Ziegler, Nicole A. Torquato, Daniel S. Levine, Amélie Nicolay, Hasan Celik, T. Don TilleyCationic
μ-alkyl dicopper complexes [Cu2(μ-η1:η1-R)DPFN]NTf2 (R = CH3, CH2CH3, CH2C(CH3)3; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine
NTf2– = N(SO2CF3)2–) were synthesized by treatment of
the acetonitrile-bridged dicopper complex [Cu2(μ-η1:η1-NCCH3)DPFN](NTf2)2 with LiR or MgR2. Structural characterization
by X-ray crystallography and NMR spectroscopy revealed that the alkyl
ligands symmetrically bridge the two copper centers, and the complexes
persist in room-temperature solution. Notably, the μ-methyl
complex showed less than 20% decomposition after 34 days in room-temperature
THF solution. Treatment of the μ-methyl complex with acids allows
installation of a range of monoanionic bridging ligands. However,
surprisingly insertion into the dicopper–carbon bond was not
observed upon addition of a variety of reagents, suggesting that these
complexes exhibit a fundamentally new reactivity profile for alkylcopper
species. Electrochemical characterization revealed oxidation–reduction
events that evidence putative mixed-valence dicopper alkyl complexes.
Computational studies suggest that the dicopper–carbon bonds
are highly covalent, possibly explaining their remarkable stability.