S K-edge XAS and DFT calculations on square-planar NiII-thiolate complexes: effects of active and passive H-bonding.
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.
Dey
Abhishek
A
Department of Chemistry, Stanford University, Stanford, California 94305, USA.
Green
Kayla N
KN
Jenkins
Roxanne M
RM
Jeffrey
Stephen P
SP
Darensbourg
Marcetta
M
Hodgson
Keith O
KO
Hedman
Britt
B
Solomon
Edward I
EI
D006860:Hydrogen Bonding; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D013438:Sulfhydryl Compounds; D009532:Nickel