Nickel thiolates

According to this model the iron-hydride bond is cleaved upon illumination and the hydride, together with the proton, leaves the complex. This would lead to re-establishment of the nickel thiolate bond which was weakened in the former state, explaining the changes in the EPR spectrum observed after illumination (Pig. 7.16-III). After a flip of the electronic z-axis the selenium could in this state interact with the unpaired electron in an orbital with d -y2 character. To get EPR-active, CO-treated... 

Structural models, which are synthesized to imitate features of the proposed structure of the active site. These may be used to demonstrate the chemical conditions, which allow such structures to exist, to investigate their chemical properties and to give a better understanding of the spectroscopic characteristics of the native proteins. Examples of these include the mixed carbonyl/cyano complexes of iron, used to verify the infrared spectra to the hydrogenases (Fig 7.4) (Lai et al. 1998) and the nickel-thiolate complexes which have low redox potentials like the hydrogenases (Franolic et al. 1992). 

The use of six equivalents of dihydrogen peroxide leads to a clean conversion of the dithiolate complex to the disulfonate compound. Earlier studies on oxidation of nickel thiolates showed that oxidations with dioxygen stop at monosulfinates. Our observation and the characterization of the first chelating bis-sulfonato nickel complex formed from the direct oxidation of a mononuclear nickel dithiolate, may also provide new insight into the chemistry of sulfur-rich nickel-containing enzymes in the presence of oxygen. 

Kockerling, M. and Henkel, G. (1993) Mononuclear nickel thiolate complexes containing nickel sites in different oxidation states - molecular definition of [Ni(SCgH40)2] and [Ni(SCgH40)2]-, Chem. Ber., 126, 951-3. 

Muller, A. and Henkel, G. (1995) [Ni2(SC4H9)g] , a novel binuclear nickel-thiolate complex with NiS4 tetrahedra sharing edges and [Ni(SC( H4SiMe3)4] , a structurally related mononuclear complex ion. Z. Naturforsch., B50, 1464-8. 

Sellmann, D., Geipel, F. and Moll, M. (2000) [Ni(NHPnPr3)(S3)], the first nickel thiolate complex modeling the nickel cysteinate site and reactivity of [NiFe] hydrogenase. Angew. Chem. Int. Ed. Engl., 39, 561-3. 

Silver, A. and Millar, M. (1992) Synthesis and structure of a unique nickel-thiolate dimer, [(RS)Ni(p.-2-SR)3Ni(SR)] - an example of face-sharing bitetrahedra. J. Chem. Sac. Chem. Commun., 1992, 948-9. 

Zhang W, Hong J, Zheng J, Huang Z, Zhou J., Xu R. Nickel-thiolate complex catalyst assembled in one step in water for solar H2 production. J Am Chem Soc. 2011 133 (51) 20680-3. 

The binuclear nickel-thiolate macrocyclic complex (101) displays noteworthy redox behavior, in which one-electron oxidation yields a Ni. Ni product with significant delocalization of the unpaired electron density onto the bridging thiolate ligands and not onto the second nickel ion. The charge delocalization consequently lies between the two redox extremes of nickel(III)-thiolate and nickel(II)-thiyl radical, thus mimicking the Ni-C state in [NiFeJhydrogenase (see 8ection 8). 

Studies on simple nickel-thiolate complexes are pertinent to discussions on the mechanisms of action of hydrogenases. Consider the pathway for reduction of protons. Initial protonation of metal-thiolate species will always occur at the lone pair of electrons on sulfur (most basic site). Protonation at the metal is thermodynamically less favourable, and usually kinetically slower than protonation of a stereochemical lone pair of electrons [48-50]. 

Datta, A., John, N. S., KuUcami, G. U., and Pati, S. K. 2005. Aromaticity in stable tiara nickel thiolates Computational and structural analysis. J. Phys. Chem. A 109 11647-11649. 

Stability of Tiara Nickel Thiolates Influence of Aromatic... 

STABILITY OF TIARA NICKEL THIOLATES INFLUENCE OF AROMATIC INTERACTIONS... 

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