Mononuclear nickel(II) thiolates of square-planar geometry: syntheses, spectral and redox properties of [Ni(SCH 2CH 2S) 2] 2− and [Ni(SCH(CH 3)CH(CH 3)S) 2] 2− and the structure of (Ph 4P) 2[Ni(SCH 2CH 2S) 2]·4H 2O

Abstract

Reaction of NiCl 2·6H 2O with excess (> 10 equiv.) dithiolate ligands ethane-1,2-dithiolate (edt 2−) and butane-2,3-dithiolate (bdt 2−) in water or ethanol affords the mononuclear thiolato complexes [Ni(edt) 2] 2− and [Ni(bdt) 2] 2−, respectively. These homoleptic thiolates contain square-planar NiS 4 chromophores. The complex (Ph 4P) 2[Ni(edt) 2]·4H 2O ( 3) crystallizes in the monoclinic space group P2 1/ c with a=10.590(2), b=16.299(3), c=14.752(3) Å, β=100.20(2)°, V=2506.0(8) Å 3 and Z=2. The structure was refined to R=3.31% by using 2486 unique data ( F o 2>3σ( F o 2)). In DMF solution, [Ni(bdt) 2] 2− can be oxidized to the nickel(III) complex [Ni(bdt) 2] − at an extremely low potential of -0.75 V versus SCE. EPR parameters of [Ni(bdt) 2] − suggest a square-planar structure for this nickel (III) thiolate.