Studies of Structural Effects on the Half-Wave Potentials of Mononuclear and Dinuclear Nickel(II) Diphosphine/Dithiolate Complexes

Abstract

Two series of mononuclear Ni(II) complexes of the formula (PNP)Ni(dithiolate) where PNP = R2PCH2N(CH3)CH2PR2, 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(SC2H4SMe)]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.

Mixed-Valence Nickel–Iron Dithiolate Models of the [NiFe]-Hydrogenase Active Site

“…These are comparable to the average Ni-P (2.176 Å) and Ni-S (2.222 Å) distances in the related dinickel( ii ) complex {(pdt)[Ni(dppe)] 2 }(BF 4 ) 2 . 35 The product resembles [(dppe)Ni(pdt)Fe(CO) 2 (CN) 2 ], 17 and might be compared to the 34e - Ni( ii )Fe( ii ) core present in the Ni-SCO state of [NiFe]-H 2 ase.…”

Phosphine and N-heterocyclic carbene ligands on Pt(II) shift selectivity from ethylene hydrophenylation toward benzene vinylation

“…All other reagents were used as received from commercial sources. The synthesis of (N-pyrrolyl) 2 P(CH 2 ) 2 P(Npyrrolyl) 2 (bppe), 38 (bis-(diphenylphosphino)methyl)methylamine (bma), 39 8-(diisopropylphosphino)quinolone (diq), 40 1,1'methylene-3,3'-di-tert-butylimidazol-2,2'-diylidine (D t BuC), 41 (dmpe)Pt(Ph) 2 (dmpe = 1,2-bis(dimethylphosphino)ethane), 42 (dppp)Pt(Ph) 2 (dppp = 1,3-bis(diphenylphosphino)propane), 43 (dppe)Pt(Ph) 2 (dppe = 1,2-bis(diphenylphosphino)ethane), 44 and (dppf)PtPh 2 (dppf = 1,1ˈ-bis(diphenylphosphino)ferrocene) 45 were previously reported.…”

Supramolecular assembly and DNA cleavage activity of a nickel(II) complex

“…1 The perspective view of the complex. Ellipsoids are drawn at 30% probability level -0.14, 0.16 [22]. The value of i pc /m 1/2 remained almost constant when the scan rate was varied between 50 and 150 mVÁ s -1 , indicating that this process is controlled by diffusion [23].…”