81097-97-4Relevant academic research and scientific papers
Syntheses of photoactive complexes. Electronic spectra, electrochemistry, and SCF-Xα-DV calculations for bis(phosphine)palladium oxalate and dithiooxalate complexes. Crystal and molecular structures of (dithiooxalato-S,S′)bis(trimethylphosphine)palladium(II) and (1,1-dithiooxalato-S,S′)bis(μ 3-sulfido)-2,2,3,3-tetrakis(trimethylphosphine)-triangulo- tripalladium(II)
Cowan, Robert L.,Pourreau, Daniel B.,Rheingold, Arnold L.,Geib, Steven J.,Trogler, William C.
, p. 259 - 265 (2008/10/08)
The compounds M(S2C2O2)L2 (M = Ni, Pd, Pt; L = P(CH3)3 (PMe3) or L2 = [P(C6H5)2CH2]2 (dppe), [P(C2H5)2CH2]2 (depe)) were prepared from the reaction between K2S2C2O2 and MCl2L2 (M = Ni, Pd, Pt; L = depe, dppe), except for NiCl2(PMe3)2, which was prepared from NiCl2(1,2-dimethoxyethane), K2S2C2O2, and PMe3. In all complexes the dithiooxalate ligand chelates through both sulfur atoms as evidenced by vC-O =1632-1640 cm-1 for the uncomplexed carbonyl groups in the solution IR spectra. Crystals of Pd(S2C2O2)(PMe3)2 belong to the space group Pbca with a = 13.479 (2) ?, b = 12.488 (2) ?, c = 17.542 (2) ?, Z = 8, and V = 2952.7 (7) ?3. Solution of the structure by direct methods led to final values of RF = 2.63 and RwF = 3.23 with 137 least-squares parameters for 2159 unique reflections with Fo > 5σ(Fo). The structure confirmed the square-planar structure about Pd with Pd-P = 2.294 (1) and 2.307 (1) ? and Pd-S = 2.324 (1) and 2.344 (1) ?. All dithiooxalate complexes were photoactive and liberated carbonyl sulfide and products derived from ML2 on photolysis. Thermolysis of Pd(S2C2O2)(PMe3)2 in DMF produced crystals of Pd3(μ3-S)2(S2C2O 2)(PMe3)4 on cooling that belong to the space group P21 with a = 9.580 (2) ?, b = 11.578 (2) ?, c = 13.400 (4) ?, β = 96.93 (2)°, Z = 2, and V = 1475.4 (4) ?3. Solution of the structure by direct methods led to final values of RF = 2.50 and RwF = 2.82 with 245 least-squares parameters for 2523 unique reflections with Fo > 5σ(Fo). The molecular structure consists of a triangle of palladium atoms with Pd(1)-Pd(2) = 3.174 (1) ?, Pd(1)-Pd(3) = 3.038 (1) ?, and Pd(2)-Pd(3) = 3.141 (1) ? capped above and below the plane by sulfurs Pd(1)-S(1) = 2.364 (2) ?, Pd(1)-S(2) = 2.374 (2) ?, Pd(2)-S(1) = 2.356 (2) ?, Pd(2)-S(2) = 2.353 (2) ?, Pd(3)-S(1) = 2.333 (2) ?, and Pd(3)-S(2) = 2.339(2) ?. The coordination geometry, including the capping sulfides, about each palladium is pseudo square planar with Pd(1) and Pd(2) each binding two PMe3 ligands and Pd(3) binding to a dithiooxalate-S,S′ ligand. SCF-Xα-DV calculations for the model complexes Pd(C2O4)(PH3)2 and Pd(S2C2O2)(PH3)2 show a similar orbital energy scheme. The lowest energy and presumably photoactive electronic transitions are to empty C2O42- and S2C2O22- π* orbitals rather than to a ligand to metal charge-transfer transition. Several of the dithiooxalate complexes prepared showed chemically reversible reductions at -1.5 to -1.6 V in CH3CN vs. Ag/AgCl, while all analogous oxalate complexes showed irreversible reductions at -1.5 to -2.1 V.
Spectroelectrochemistry of nickel complexes. Voltammetric and ESR studies of the redox reactions of phosphine-dithiolate and phosphine-catecholate complexes of nickel
Bowmaker,Boyd,Campbell
, p. 2403 - 2412 (2008/10/08)
The redox properties of nickel(II) complexes of the type [Ni(PPh3)2L]n+ (L = dithiolate (n = 0) or dithiocarbamate (n = 1)) and Ni(dpe)L (dpe = bis(diphenylphosphino)ethane, L = dithiolate or catecholate) have been studied by cyclic voltammetry at a platinum electrode, and the products of the redox reactions have been identified by electron spin resonance spectroscopy. All of these complexes show reversible or quasi-reversible one-electron reduction processes, and the reduction potentials for the PPh3 complexes are about 0.5 V higher than those of the corresponding dpe complexes. In the case of triphenylphosphine complexes such as Ni(PPh3)2((CN)2C2S2), the voltammetry shows evidence of a dissociation equilibrium involving loss of triphenylphosphine from the nickel species present after the electron-transfer process. The frozen-solution ESR spectra of the reduction products show large, anisotropic hyperfine coupling to two equivalent 31P nuclei and anisotropic g values characteristic of d9 nickel(I) species. The PPh3 complexes have smaller 31P hyperfine coupling constants than the corresponding dpe complexes. The 31P hyperfine coupling parameters have been analyzed for some representative complexes, and the amount of spin density transferred from the metal to the phosphine ligands has been estimated. In addition to the reduction process, the catecholate complexes undergo a reversible one-electron oxidation. The ESR spectra of the products of such oxidations show only a small 31P hyperfine coupling, hyperfine coupling to nuclei in the catecholate ligand, and almost isotropic g values. These species are therefore formulated as nickel(II) complexes containing coordinated semiquinone radical anions.
