title: Description of the ground state wave functions of Ni dithiolenes using sulfur K-edge X-ray absorption spectroscopy.
abstract: The pterin-dithiolene cofactor is an essential component of the catalytic sites of all molybdoenzymes except nitrogenase. Understanding its bonding to transition metals allows for development of electronic structure/function correlations in catalysis. The electronic structure description for a series of bis(dithiolene) complexes ([NiL(2)](Z)(), L = 1,2-Me(2)C(2)S(2); Z = 2-, 1-, 0) using sulfur XAS provides the basis for extension to the biologically relevant metal-containing dithiolenes. The transition dipole integral has been developed for the dithiolene sulfur through correlation of XAS pre-edge energy positions of sulfide-, thiolate-, and enedithiolate-S. The ground state wave functions of all three NiL(2) complexes have more than 50% S character experimentally demonstrating the noninnocent behavior of the dithiolene ligand. The S K-edge experimental results are correlated with spin-unrestricted, broken-symmetry density functional calculations. These show only limited spin polarization in the neutral complex and delocalized, ligand based ground states for the mono- and dianionic complexes. These XAS and DFT results are correlated with other spectroscopic features and provide insight into reactivity.
authors.affiliation: Contribution from the Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Szilagyi
authors.forename: Booyong S
authors.initials: BS
authors.lastname: Lim
authors.forename: Thorsten
authors.initials: T
authors.lastname: Glaser
authors.forename: Richard H
authors.initials: RH
authors.lastname: Holm
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
mesh_terms: D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013455:Sulfur / Q000737:chemistry; D014050:Toluene / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D014050:Toluene; D013455:Sulfur; D009532:Nickel; C004848:dithiol