47895-41-0Relevant academic research and scientific papers
Nickel-cysteine binding supported by phosphine chelates
Desrochers, Patrick J.,Duong, Davis S.,Marshall, Ariel S.,Lelievre, Stacey A.,Hong, Bonnie,Brown, Josh R.,Tarkka, Richard M.,Manion, Jerald M.,Holman, Garen,Merkert, Jon W.,Vicic, David A.
, p. 9221 - 9233 (2008/10/09)
The effect of chelating phosphines was tested on the structure and pH-dependent stability of nickel-cysteine binding. (1,2-Bis(diphenylphosphino) ethane (dppe) and 1,1,1-tris[(diphenylphosphino)methyl]ethane (triphos) were used with three different cysteine derivatives (L-cysteine, Cys; L-cysteine ethyl ester, CysEt; cystamine, CysAm) to prepare complexes of the form (dppe)NiCysRn+ and (triphos)NiCysRn+ (n = 0 for Cys; n = 1 for CysEt and CysAm). Similar 31P {1H} NMR spectra for all (dppe)NiCysRn+ confirmed their square-planar P2NiSN coordination spheres. The structure of [(dppe)NiCysAm]PF6 was also confirmed by single-crystal X-ray diffraction methods. The (triphos)- NiCysAm+ and (triphos)NiCysEt+ complexes were fluxional at room temperature by 31P NMR. Upon cooling to -80°C, all gave spectra consistent with a P2NiSN coordination sphere with the third phosphorus uncoordinated. Temperature-dependent 31P NMR spectra showed that a trans P-Ni-S π interaction controlled the scrambling of the coordinated triphos. In aqueous media, (dppe)NiCys was protonated at pH ～ 4-5, leading to possible formation of a nickel-cysteinethiol and eventual cysteine loss at pH - = hydrotris(3,5-dimethylpyrazolyl)borate. Importantly, results with these heterogeneous systems demonstrated the selectivity of these nickel centers for cysteine over methionine and serine and most specifically for N-terminus cysteine. The role of Ni-S π bonding in nickel-cysteine geometries will be discussed, including how these results suggest a mechanism for the movement of electron density from nickel onto the backbone of coordinated cysteine.
Unusual reaction pathways in the photolysis of diazidophosphane)nickelII) complexes: Nitrenes as intermediates in the formation of nickel0) complexes
Hennig,Hofbauer,Handke,Stich
, p. 408 - 410 (2008/10/09)
Insertions into C-H or C=C bonds and addition reactions with CO or CS2 confirm the formation of nitrenenickelII) complexes as intermediates in the photolysis of diazidophosphane)nickelII) complexes. Without reactive substrates the nitrene intermediates decay to coordinatively unsaturated phosphane nickel0) complexes, which may initiate the photocatalytic cyclization of alkynes to the corresponding benzene derivatives.
