25640-47-5

Upstream product

• 67969-82-8 tetrafluoroboric acid diethyl ether 
• 15628-25-8 Ni⁽⁰⁾(1,2-bis(diphenylphosphino)ethane)2 
• 56213-47-9 Ni(1,2-ethanedithiolate)(1,2-bis(diphenylphosphino)ethane) 
• 1663-45-2 1,2-bis-(diphenylphosphino)ethane 
• 61703-81-9 [nickel(II)(1,3-propanedithiolate)(1,2-bis(diphenylphosphino)ethane)] 

Relevant academic research and scientific papers

Dihydrogen Evolution by Protonation Reactions of Nickel(I)

Nickel-mediated formation of H2 by protonation of Ni(I) has been established and the kinetics of the process investigated. The diamagnetic complex [NiII(psnet)](BF4)2 was prepared and reduced to [NiI(psnet)](BF4) with NaBH4 in THF (psnet = bis(5-(diphenylphosphino)-3-thiapentanyl)amine). Both complexes were structurally characterized by X-ray diffraction. [Ni(psnet)]I+ was demonstrated to be an authentic Ni(I) complex with a ...(dz2)I ground state. Under appropriate conditions, [Ni(psnet)]+ reacts with acids in nonaqueous media to give near-quantitative yields of H2 according to the stoichiometry NiI + H+ → NiII + 1/2H2. Dihydrogen production was demonstrated to be directly related to Ni(I) oxidation. The reaction system [Ni(psnet)]+/HCl/DMF, which gives H2 yields of ≥90%, was subjected to a kinetics analysis. The overall reaction [Ni(psnet)]+ + HCl → [Ni(psnet)Cl]+ + 1/2H2 proceeds by two parallel pathways dependent on chloride concentration. Addition of Bu4NCl accelerates the reaction, whereas (Bu4N)(PF6) decreases the rate. A two-term rate law is presented which includes contributions from both pathways, whose common initial step is protonation of Ni(I). Path A (low chloride concentration) involves the formation and collapse of nickel hydride chloride ion pairs; the rate-determining step is the minimal reaction 2NiIII-H- → H2 + 2NiII. Path B (high chloride concentration) includes as the rate-limiting step collapse of a nickel hydride dichloride ion pair followed by the bimolecular reaction of two NiIII-H- intermediates or reduction to NiII-H- by NiI followed by protonation of the hydride. The relation of these results to the reactions of hydrogenase enzymes is considered.

Studies of structural effects on the half-wave potentials of mononuclear and dinuclear nickel(II) diphosphine/dithiolate complexes

Two series of mononuclear Ni(II) complexes of the formula (PNP)Ni(dithiolate) where PNP = R2PCH2N(CH 3)CH2-PR2, R = Et and Ph, have been synthesized containing dithiolate ligands that vary from five- to seven-membered chelate rings. Two series of dinuclear Ni(II) complexes of the formula {[(diphosphine)Ni]2(dithiolate)}(X)2 (X = BF4 or PF6) have been synthesized in which the chelate ring size of the dithiolate and diphosphine ligands have been systematically varied. The structures of the alkylated mononuclear complex, [(PNPEt)Ni(SC 2H4SMe)]OTf, and the dinuclear complex, [(dppeNi) 2(SC3H6S)](BF4)2, have been determined by X-ray diffraction studies. The complexes have been studied by cyclic voltammetry to determine how the half-wave potentials of the Ni(II/I) couples vary with chelate ring size of the ligands. For the mononuclear complexes, this potential becomes more positive as the natural bite angle of the dithiolate ligand increases. However, the potentials of the Ni(II/I) couples of the dinuclear complexes do not show a dependence on the chelate ring size of the ligands. Other aspects of the reduction chemistry of these complexes have been explored.