- Electrochemical, Electron Spin Resonance and Nuclear Magnetic Resonance Investigations of Tertiary Phosphine Complexes of Nickel. Part 1. Mono- and Di-nuclear Nickel Dithiolene and Nickel Dihalide Species
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The synthesis, characterisation and 31P NMR parameters of (PR3)2> (PR3 = PMePh2 or PBunPh2) and of n> complexes (L-L = ditertiary phosphine containing vinylene or ortho-phenylene interphosphorus linkages, n = 1 or 2, R = CN or Ph) are reported.The 31P NMR data for the n> complexes show that the ring contribution to the chemical shift is large an positive for the mononuclear species (n = 1) and near zero or negative for the dinuclear species (n = 2).Electrochemical studies of the complexes and ESR studies of their electrogenerated products have shown variations in electrochemical and ESR parameters due to variations in (i) co-ordination ring size, (ii) interphosphorus linkage and (iii) substituent at phosphorus.The ESR spectrum of the redox product identified as >8(+) exhibited two chemically inequivalent 31P nuclei.The dinuclear complexes (n = 2) exhibited multiple redox proceses.The ESR spectra show that the reduction products involve metal-based electron addition to yield the corresponding nickel(I) species, while the oxidation products involve removal of a primarily ligand-based electron.The one-electron reduction product of the complex > shows a spectrum characteristic of a nickel(I) monomer (S = 1/2) at ca. 298 K, but is ESR inactive at ca. 90 K.This is attributed to the reversible formation of a diamagnetic dimer (S = 0) upon freezing.The reduction products of the complexes 2> (X = Cl, Br, I or SCN) exhibit no solution ESR spectra at ca. 298 K, but for X = I a triplet state (S = 1) spectrum at ca. 90 K is observed, characteristic of a dinuclear Ni(I)-Ni(I) species.
- Bowmaker, Graham A.,Williams, Julian P.
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p. 3593 - 3600
(2007/10/02)
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