title: S K-edge XAS and DFT calculations on square-planar NiII-thiolate complexes: effects of active and passive H-bonding.
abstract: S K-edge XAS for a low-spin NiII-thiolate complex shows a 0.2 eV shift to higher pre-edge energy but no change in Ni-S bond covalency upon H-bonding. This is different from the H-bonding effect we observed in high-spin FeIII-thiolate complexes where there is a significant decrease in Fe-S bond covalency but no change in energy due to H-bonding (Dey, A.; Okamura, T.-A.; Ueyama, N.; Hedman, B.; Hodgson, K. O.; Solomon, E. I. J. Am. Chem. Soc. 2005, 127, 12046-12053). These differences were analyzed using DFT calculations, and the results indicate that two different types of H-bonding interactions are possible in metal-thiolate systems. In the high-spin FeIII-thiolate case, the H-bonding involves a thiolate donor orbital which is also involved in bonding with the metal (active), while in the low-spin NiII-thiolate, the orbital involved in H-bonding is nonbonding with respect to the M-S bonding (passive). The contributions of active and passive H-bonds to the reduction potential and Lewis acid properties of a metal center are evaluated.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305, USA.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dey
authors.forename: Kayla N
authors.initials: KN
authors.lastname: Green
authors.forename: Roxanne M
authors.initials: RM
authors.lastname: Jenkins
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Jeffrey
authors.forename: Marcetta
authors.initials: M
authors.lastname: Darensbourg
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
mesh_terms: D006860:Hydrogen Bonding; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D013438:Sulfhydryl Compounds; D009532:Nickel