Nickel-cysteine binding supported by phosphine chelates.

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)NiCysR(n+) and (triphos)NiCysR(n+) (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.

A stable monomeric nickel borohydride.

A stable discrete nickel borohydride complex (Tp*NiBH(4) or Tp*NiBD(4)) was prepared using the nitrogen-donor ligand hydrotris(3,5-dimethylpyrazolyl)borate (Tp*-). This complex represents one of the best characterized nickel(II) borohydrides to date. Tp*NiBH(4) and Tp*NiBD(4) are stable toward air, boiling water, and high temperatures (mp > 230 degrees C dec).