title: X-ray absorption spectroscopic and computational investigation of a possible S···S interaction in the [Cu3S2]3+ core.
abstract: The electronic structure of the [Cu(3)S(2)](3+) core of [(LCu)(3)(S)(2)](3+) (L = N,N,N',N'-tetramethyl-2R,3R-cyclohexanediamine) is investigated using a combination of Cu and S K-edge X-ray absorption spectroscopy and calculations at the density functional and multireference second-order perturbation levels of theory. The results show that the [Cu(3)S(2)](3+) core is best described as having all copper centers close to but more oxidized than Cu(2+), while the charge on the S(2) fragment is between that of a sulfide (S(2-)) and a subsulfide (S(2)(3-)) species. The [Cu(3)S(2)](3+) core thus is different from a previously described, analogous [Cu(3)O(2)](3+) core, which has a localized [(Cu(3+)Cu(2+)Cu(2+))(O(2-))(2)](3+) electronic structure. The difference in electronic structure between the two analogues is attributed to increased covalent overlap between the Cu 3d and S 3p orbitals and the increased radial distribution function of the S 3p orbital (relative to O 2p). These features result in donation of electron density from the S-S σ* to the Cu and result in some bonding interaction between the two S atoms at ~2.69 Å in [Cu(3)S(2)](3+), stabilizing a delocalized S = 1 ground state.
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA. ritis@slac.stanford.edu
authors.forename: Ritimukta
authors.initials: R
authors.lastname: Sarangi
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Winikoff
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
authors.forename: William B
authors.initials: WB
authors.lastname: Tolman
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
mesh_terms: D003300:Copper / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013455:Sulfur / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D009942:Organometallic Compounds; D013455:Sulfur; D003300:Copper