52057-73-5Relevant academic research and scientific papers
Copper(II) and Nickel(II) alkylxanthate complexes (R = C2H 5, i-C3H7, i-C4H9, s-C4H9, and C5H11): EPR and solid-state 13C CP/MAS NMR s
Ivanov,Bredyuk,Antzutkin,Forsling
, p. 480 - 485 (2004)
Alkylxanthate complexes of the general formula [MS(S)COR2] (M = Ni, 63Cu, and 65Cu; R = C2H5, i-C3H7, i-C4H9, s-C 4H9, and C5/su
Nickel(III)-sulfur binding. Chemistry of the tris(xanthate) family
Choudhury, Suranjan Bhanja,Ray, Debashis,Chakravorty, Animesh
, p. 4603 - 4611 (2008/10/08)
Tris(xanthates) of trivalent nickel, Ni(Rx)3 (2, R = Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, s-Bu), are quantitatively generated in acetonitrile solution by electrooxidation of Ni(Rx)3- (1). The nickel(III)-nickel(II) formal potentials are in the range 0.1-0.16 V vs SCE (298 K). The X-ray structure of one nickel(II) precursor complex, [Et4N][Ni(Etx)3], is reported: space group P21/n, Z = 8, a = 18.842 (7) ?, b = 16.448 (4) ?, c = 18.987 (7) ?, β = 115.65 (3)°, V = 5304 (3) ?3, R = 0.0484, Rw = 0.0578. The anionic NiS6 coordination sphere has approximate 3-fold symmetry with an average Ni-S distance of 2.439 (2) ?. Solutions of Ni(Rx)3 undergo facile disproportionation: 2Ni(Rx)3 ? 2Ni(Rx)2 + R2x2. For R = Et the equilibrium constant is 391 L mol-1 at 298 K. The forward reaction is first order (k = 1.0 × 10-3 s-1 at 253 K; ΔS? ～ -40 eu) and is believed to proceed via the transition state Ni(Etx)2(Etx+). Significant concentrations of Ni(Etx)3 can be generated in solution via oxidative addition of Et2x2 (excess) to Ni(Etx)2. By crystallization of Co(Rx)3 from such solutions, 1 mole % of Ni(Rx)3 has been substitutionally incorporated into the cobalt(III) lattice. The nickel(III) EPR spectrum of the polycrystalline doped lattice at 77 K is axial due to the dictates of crystal symmetry: g⊥ = 2.099, g∥ = 2.082. The expected Jahn-Teller distortion (low spin d7) becomes observable in glassy solutions (77 K): g1 = 2.141, g2 = 2.124, g3 = 2.035. A free energy cycle (298 K) has been constructed, incorporating the disproportionation reaction along with the following processes: Ni(Etx)2 + Etx- ? Ni(Etx)3- (K = 105 L mol-1); Etx+ + e ? Etx- (Eo = 0.23 V); 2Etx+ ? Et2x2 (K = 4.56 × 1016 L mol-1); Ni(Etx)3 + e ? Ni(Etx)3- (Eo = 0.11 V). The corresponding cycle for cognate dithiocarbamate species is also given for comparison. The analysis reveals that, in fluid media containing sulfur in oxidation states -2 (as in Rx-) and 0 (as in R2x2), the bivalent and trivalent states of nickel appear as natural thermodynamic entities. The factors that favor the NiIIIS- species are noted. Disproportionation is effectively hindered by lowering the nickel(III)-nickel(II) reduction potential. The significance of these results in relation to nickel-containing hydrogenases is noted. It is proposed that nickel-sulfur systems containing the metal in the formally trivalent state can be described as resonance hybrids of the canonical forms NiIII-S-and NiII-S+-, the latter approximating the transition state of disproportionation.
