Synthesis and Characterization of a Copper Complex Supported by a Z‑type SbV Ligand: XPS and DFT Study of Electronic Structure

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 E1/2 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.