We describe the synthesis and characterization of a Cu- (I) complex, Q3Sb- (o-chlor) -Cu- (OTf) (Q = 8-quinolinyl; OTf = trifluoromethanesulfonate; o-chlor = o-choranil), supported by the Sb- (V) ligand Q3Sb- (o-chlor). The complex Q3Sb- (o-chlor) -Cu- (OTf) was experimentally characterized via 1H, 13C-1H, and 19F-1H NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) as well as examined computationally with density functional theory (DFT) calculations. Variable temperature 1H NMR spectroscopy (20 to -110 °C) indicates temperature-dependent fluxional processes for Q3Sb- (o-chlor) -Cu- (OTf) and uncoordinated Q3Sb- (o-chlor). The electron density of Cu for Q3Sb- (o-chlor) -Cu- (OTf) was probed by comparing CuII/CuI redox potential and Cu 2p electron binding energies, using XPS, with a related non-Sb-containing complex, (TMQA) -Cu- (OTf) (TMQA = tris- (quinolin-2-ylmethyl) -amine). The E 1/2 of the CuII/CuI redox of Q3Sb- (o-chlor) -Cu- (OTf) is shifted 670 mV more positive than that of (TMQA) -Cu- (OTf). XPS spectra of Q3Sb- (o-chlor) -Cu- (OTf) and (TMQA) -Cu- (OTf) indicate a 0. 8 eV higher Cu 2p binding energy for Q3Sb- (o-chlor) -Cu- (OTf). Computational studies of the molecular orbitals and localized natural bonding orbitals (NBOs) are consistent with a weak Cu- (I) → Sb- (V) interaction for Q3Sb- (o-chlor) -Cu- (OTf), for which Sb- (V) acts as a Z-type ligand.
Webber et al. (Thu,) studied this question.