Edwin F van der Eide

Pacific Northwest National Laboratory, Ричленд, Washington, United States

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Publications (7)47.42 Total impact

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    ABSTRACT: The synthesis of the 1,5-diphenyl-3,7-diisopropyl-1,5-diaza-3,7-diphosphacyclooctane ligand, PiPr2NPh2, is reported. Two equivalents of the ligand react with [Ni(CH3CN)6](BF4)2 to form the bis(diphosphine)–NiII complex [Ni(PiPr2NPh2)2](BF4)2, which acts as a proton reduction electrocatalyst. In addition to [Ni(PiPr2NPh2)2]2+, we report the synthesis and structural characterization of the Ni0 complex Ni(PiPr2NPh2)2 and the NiII–hydride complex [HNi(PiPr2NPh2)2]BF4. The [HNi(PiPr2NPh2)2]BF4 complex represents the first NiII–hydride in the [Ni(PR2NR′2)2]2+ family of compounds to be structurally characterized. In addition to the experimental data, the mechanism of electrocatalysis facilitated by [Ni(PiPr2NPh2)2]2+ is analyzed by using linear free energy relationships recently established for the [Ni(PR2NR′2)2]2+ family.
    Berichte der deutschen chemischen Gesellschaft 09/2014; 2014(27). DOI:10.1002/ejic.201402250
  • Edwin F van der Eide, Ping Yang, R Morris Bullock
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    ABSTRACT: Two of a kind: Two agostic isomers of [CpMo(CO)2 (PiPr3 )](+) B(C6 F5 )4 (-) have been isolated. Both were characterized in the solid state by X-ray crystallography and spectroscopic techniques, and also by DFT calculations. Significantly different LUMO energies cause the difference in color (blue versus orange, see picture) of these isomers.
    Angewandte Chemie International Edition 09/2013; 52(39). DOI:10.1002/anie.201305032 · 11.34 Impact Factor
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    ABSTRACT: Despite the importance of group 6 metal-centered 17-electron radicals CpM(CO)(3)(center dot) (M = Cr, Mo, W) in establishing many of the fundamental reactions now known for metal-centered radicals, spectroscopic characterization of their electronic properties and structures has been very challenging, due to their high reactivity. Here we report a gas-phase study of these species by photodetachment photoelectron spectroscopy (PES) of their corresponding 18-electron anions and by theoretical electronic structure calculations. Three well-separated spectral features are observed by PES for each anionic species. Electron affinities (EAs) of CpM(CO)(3)(center dot) were experimentally measured from the threshold of each spectrum and were found to be 2.38 +/- 0.02 (M = Cr), 2.63 +/- 0.02 (Mo), and 2.63 +/- 0.01 eV (W). These experimental values correlate well with the reported redox potentials measured in solution. Theoretical calculations for all anionic and neutral (radical) species gave calculated EAs and band gaps that are in good agreement with the experimental data. Molecular orbital (MO) analyses for each anion indicate that the top three occupied MOs are mainly metal-based and contribute to the first spectral feature, whereas the next two MOs are associated with Cp-M pi bonding and contribute to the second spectral feature. The calculations further exhibit appreciable anion-to-neutral structural changes for all three species, with the change for the W species being the smallest.
    Organometallics 03/2013; 32(7-7):2084-2091. DOI:10.1021/om3011454 · 4.25 Impact Factor
  • Edwin F van der Eide, Monte L Helm, Eric D Walter, R Morris Bullock
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    ABSTRACT: The 17-electron radical CpCr(CO)(2)(IMe)(•) (IMe = 1,3-dimethylimidazol-2-ylidene) was synthesized by the reaction of IMe with [CpCr(CO)(3)](2), and characterized by single crystal X-ray diffraction and by electron paramagnetic resonance (EPR), IR, and variable temperature (1)H NMR spectroscopy. The metal-centered radical is monomeric under all conditions and exhibits Curie paramagnetic behavior in solution. An electrochemically reversible reduction to 18-electron CpCr(CO)(2)(IMe)(-) takes place at E(1/2) = -1.89(1) V vs Cp(2)Fe(+•/0) in MeCN, and was accomplished chemically with KC(8) in tetrahydrofuran (THF). The salts K(+)(18-crown-6)[CpCr(CO)(2)(IMe)](-)·(1)/(2)THF and K(+)[CpCr(CO)(2)(IMe)](-)·(3)/(4)THF were crystallographically characterized. Monomeric ion pairs are found in the former, whereas the latter has a polymeric structure because of a network of K···O((CO)) interactions. Protonation of K(+)(18-crown-6)[CpCr(CO)(2)(IMe)](-)·(1)/(2)THF gives the hydride CpCr(CO)(2)(IMe)H, which could not be isolated, but was characterized in solution; a pK(a) of 27.2(4) was determined in MeCN. A thermochemical analysis provides the Cr-H bond dissociation free energy (BDFE) for CpCr(CO)(2)(IMe)H in MeCN solution as 47.3(6) kcal mol(-1). This value is exceptionally low for a transition metal hydride, and implies that the reaction 2 [Cr-H] → 2 [Cr(•)] + H(2) is exergonic (ΔG = -9.0(8) kcal mol(-1)). This analysis explains the experimental observation that generated solutions of the hydride produce CpCr(CO)(2)(IMe)(•) (typically on the time scale of days). By contrast, CpCr(CO)(2)(PCy(3))H has a higher Cr-H BDFE (52.9(4) kcal mol(-1)), is more stable with respect to H(2) loss, and is isolable.
    Inorganic Chemistry 01/2013; 52(3). DOI:10.1021/ic302460y · 4.79 Impact Factor
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    ABSTRACT: No support required: Unlike the unobservable radical cations [{CpM(CO)(3) }(2) ](.+) (M=W, Mo), derivatives [{CpM(CO)(2) (PMe(3) )}(2) ](.+) are stable enough to be isolated and characterized. Experimental and theoretical studies show that the shortened MM bonds are of order 1${{ 1/2 }}$, and that they are not supported by bridging ligands. The unpaired electron is delocalized over the MM cores, with a spin density of about 45 % on each metal atom.
    Angewandte Chemie International Edition 08/2012; 51(33):8361-4. DOI:10.1002/anie.201203531 · 11.34 Impact Factor
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    ABSTRACT: The thermal W-W bond homolysis in [CpW(CO)2(IMe)]2 (IMe = 1,3-dimethylimidazol-2-ylidene) was investigated and was found to occur to a large extent compared to other tungsten dimers such as [CpW(CO)3]2. CpW(CO)2(IMe)H was prepared by heating a solution of [IMeH]+[CpW(CO)2(PMe3)]â, and exists in solution as a mixture of interconverting cis and trans isomers. The carbene rotation in CpW(CO)2(IMe)H was explored by DFT calculations, and low enthalpic barriers (< 3.5 kcal molâ1) are predicted. CpW(CO)2(IMe)H has pKaMeCN = 31.5(3) and deprotonation with KH gives K+[CpW(CO)2(IMe)]â (⢠MeCN). Hydride abstraction from CpW(CO)2(IMe)H with Ph3C+PF6â in the presence of a coordinating ligand L (MeCN or THF) gives [CpW(CO)2(IMe)(L)]+PF6â. Electrochemical measurements on the anion [CpW(CO)2(IMe)]â in MeCN, together with digital simulations, give an E1/2 of â1.54(2) V vs Cp2Fe+/0 for the [CpW(CO)2(IMe)]â¢/â couple. A thermochemical cycle provides the solution bond dissociation free energy of the W-H bond of CpW(CO)2(IMe)H as 61.3(6) kcal molâ1. In the electrochemical oxidation of [CpW(CO)2(IMe)]â, reversible dimerization of the electrogenerated radical CpW(CO)2(IMe)⢠occurs, and digital simulation provides kinetic and thermodynamic parameters for the monomer-dimer equilibrium: kdimerization ~ 2.5 ï´ 104 Mâ1 sâ1, khomolysis ~ 0.5 sâ1 (i.e., Kdim ~ 5 ï´ 104 Mâ1). Reduction of [CpW(CO)2(IMe)(MeCN)]+PF6â with cobaltocene gives the dimer [CpW(CO)2(IMe)]2, which in solution exists as a mixture of anti and gauche rotomers. As expected from the electrochemical experiments, the dimer is in equilibrium with detectable amounts of CpW(CO)2(IMe)â¢. This species was observed by IR spectroscopy, and its presence in solution is also in accordance with the observed reactivity toward 2,6-di-tert-butyl-1,4-benzoquinone, chloroform and dihydrogen. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated for DOE by Battelle. The EPR studies were performed at EMSL, a national scientific user facility sponsored by the Department of Energyâs Office of Biological and Environmental Research located at Pacific Northwest National Laboratory.
    Organometallics 03/2012; 31(5):1775-1789. DOI:10.1021/om201162g · 4.25 Impact Factor
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    ABSTRACT: A series consisting of a tungsten anion, radical, and cation, supported by the N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and spanning formal oxidation states W(0), W(I), and W(II), has been synthesized, isolated, and characterized. Reaction of the hydride CpW(CO)(2)(IMes)H with KH and 18-crown-6 gives the tungsten anion [CpW(CO)(2)(IMes)](-)[K(18-crown-6)](+). Electrochemical oxidation of [CpW(CO)(2)(IMes)](-) in MeCN (0.2 M (n)Bu(4)N(+)PF(6)(-)) is fully reversible (E(1/2) = -1.65 V vs Cp(2)Fe(+•/0)) at all scan rates, indicating that CpW(CO)(2)(IMes)(•) is a persistent radical. Hydride transfer from CpW(CO)(2)(IMes)H to Ph(3)C(+)PF(6)(-) in MeCN affords [cis-CpW(CO)(2)(IMes)(MeCN)](+)PF(6)(-). Comproportionation of [CpW(CO)(2)(IMes)](-) with [CpW(CO)(2)(IMes)(MeCN)](+) gives the 17-electron tungsten radical CpW(CO)(2)(IMes)(•). This complex shows paramagnetically shifted resonances in the (1)H NMR spectrum and has been characterized by IR spectroscopy, low-temperature EPR spectroscopy, and X-ray diffraction. CpW(CO)(2)(IMes)(•) is stable with respect to disproportionation and dimerization. NMR studies of degenerate electron transfer between CpW(CO)(2)(IMes)(•) and [CpW(CO)(2)(IMes)](-) are reported. DFT calculations were carried out on CpW(CO)(2)(IMes)H, as well as on related complexes bearing NHC ligands with N,N' substituents Me (CpW(CO)(2)(IMe)H) or H (CpW(CO)(2)(IH)H) to compare to the experimentally studied IMes complexes with mesityl substituents. These calculations reveal that W-H homolytic bond dissociation energies (BDEs) decrease with increasing steric bulk of the NHC ligand, from 67 to 64 to 63 kcal mol(-1) for CpW(CO)(2)(IH)H, CpW(CO)(2)(IMe)H, and CpW(CO)(2)(IMes)H, respectively. The calculated spin density at W for CpW(CO)(2)(IMes)(•) is 0.63. The W radicals CpW(CO)(2)(IMe)(•) and CpW(CO)(2)(IH)(•) are calculated to form weak W-W bonds. The weakly bonded complexes [CpW(CO)(2)(IMe)](2) and [CpW(CO)(2)(IH)](2) are predicted to have W-W BDEs of 6 and 18 kcal mol(-1), respectively, and to dissociate readily to the W-centered radicals CpW(CO)(2)(IMe)(•) and CpW(CO)(2)(IH)(•).
    Journal of the American Chemical Society 07/2011; 133(37):14593-603. DOI:10.1021/ja202754e · 11.44 Impact Factor