Re-evaluating the Cu K pre-edge XAS transition in complexes with covalent metal–ligand interactions

Three [Me2NN]Cu(h2 -L2) complexes (Me2NN ¼ HC[C(Me)NAr]2; L2 ¼ PhNO (2), ArF 2N2 (3), PhCH]CH2 (4); Ar ¼ 2,6-Me2-C6H3; ArF ¼ 3,5-(CF3)2-C6H3) have been studied by Cu K-edge X-ray absorption spectroscopy, as well as single- and multi-reference computational methods (DFT, TD-DFT, CASSCF, MRCI, and OVB). The study was extended to a range of both known and theoretical compounds bearing 2p-element donors as a means of deriving a consistent view of how the pre-edge transition energy responds in systems with significant ground state covalency. The ground state electronic structures of many of the compounds under investigation were found to be strongly influenced by correlation effects, resulting in ground state descriptions with majority contributions from a configuration comprised of a Cu(II) metal center anti-ferromagentically coupled to radical anion O2, PhNO, and ArF 2N2 ligands. In contrast, the styrene complex 4, which displays a Cu K pre-edge transition despite its formal d10 electron configuration, exhibits what can best be described as a Cu(I):(styrene)0 ground state with strong pbackbonding. The Cu K pre-edge features for these complexes increase in energy from 1 to 4, a trend that was tracked to the percent Cu(II)-character in the ground state. The unexpected shift to higher preedge transition energies with decreasing charge on copper (QCu) contributed to an assignment of the pre-edge features for these species as arising from metal-to-ligand charge transfer instead of the traditional Cu1s / Cu3d designation

El Diario de Pontevedra : periódico liberal: Ano XXVII Número 7742 - 1910 marzo 1

Copper­(II) aryl species are proposed key intermediates in Cu-catalyzed cross-coupling reactions. Novel three-coordinate copper­(II) aryls [Cu^II]-C₆F₅ supported by ancillary β-diketiminate ligands form in reactions between copper­(II) alkoxides [Cu^II]-O^<i>t</i>Bu and B­(C₆F₅)₃. Crystallographic, spectroscopic, and DFT studies reveal geometric and electronic structures of these Cu­(II) organometallic complexes. Reaction of [Cu^II]-C₆F₅ with the free radical NO_(g) results in C-N bond formation to give [Cu]­(η²-ONC₆F₅). Remarkably, addition of the phenolate anion PhO^– to [Cu^II]-C₆F₅ directly affords diaryl ether PhO-C₆F₅ with concomitant generation of the copper­(I) species [Cu^I]­(solvent) and {[Cu^I]-C₆F₅}⁻. Experimental and computational analysis supports redox disproportionation between [Cu^II]-C₆F₅ and {[Cu^II]­(C₆F₅)­(OPh)}⁻ to give {[Cu^I]-C₆F₅}⁻ and [Cu^III]­(C₆F₅)­(OPh) unstable toward reductive elimination to [Cu^I]­(solvent) and PhO-C₆F₅

A Copper(II) Thiolate from Reductive Cleavage of an <i>S</i>‑Nitrosothiol

<i>S</i>-Nitrosothiols RSNO represent circulating reservoirs of nitric oxide activity in the plasma and play intricate roles in protein function control in health and disease. While nitric oxide has been shown to reductively nitrosylate copper­(II) centers to form copper­(I) complexes and ENO species (E = R₂N, RO), well-characterized examples of the reverse reaction are rare. Employing the copper­(I) β-diketiminate [Me₂NN]­Cu, we illustrate a clear example in which an RS–NO bond is cleaved to release NO_gas with formation of a discrete copper­(II) thiolate. The addition of Ph₃CSNO to [Me₂NN]Cu generates the three-coordinate copper­(II) thiolate [Me₂NN]­CuSCPh₃, which is unstable toward free NO

A Copper(II) Thiolate from Reductive Cleavage of an <i>S</i>‑Nitrosothiol

<i>S</i>-Nitrosothiols RSNO represent circulating reservoirs of nitric oxide activity in the plasma and play intricate roles in protein function control in health and disease. While nitric oxide has been shown to reductively nitrosylate copper­(II) centers to form copper­(I) complexes and ENO species (E = R₂N, RO), well-characterized examples of the reverse reaction are rare. Employing the copper­(I) β-diketiminate [Me₂NN]­Cu, we illustrate a clear example in which an RS–NO bond is cleaved to release NO_gas with formation of a discrete copper­(II) thiolate. The addition of Ph₃CSNO to [Me₂NN]Cu generates the three-coordinate copper­(II) thiolate [Me₂NN]­CuSCPh₃, which is unstable toward free NO