The oxidation of a Ni(II) complex bearing a tetradentate phosphasalen ligand, which differs from salen by the presence of an iminophosphorane (PN) in place of an imine unit, was easily achieved by addition of a silver salt. The site of this oxidation was investigated with a combination of techniques (NMR, EPR, UV/Vis spectroscopy, X-ray diffraction, magnetic measurements) as well as DFT calculations. All data are in agreement with a high-valent Ni(III) center concentrating the spin density. This markedly differs from precedents in the salen series for which oxidation on the metal was only observed at low temperature or in the presence of additional ligands or anions. Therefore, thanks to the good electron-donating properties of the phosphasalen ligand, [Ni(Psalen)](+) represents a rare example of a tetracoordinated high-valent nickel complex in presence of a phenoxide ligand.

ChemInform Abstract The title compounds (III) are obtained according to the scheme and characterized by spectral (31P, 13C NMR, MS) data, and an X-ray structure analysis of the tetrasulfide (IV) of (IIIb) (space group P1, Z=2). These compounds are of interest as components of organic metals and superconductors.

n-Cyclopentadienyl-1,2-bis (diphenylphosphino)ethane iron bromide and magnesium in tetrahydrofuran (THF) afford the novel crystalline inorganic magnesium reagent (w-GH,) (diphos) FeMgBr, 3THF, containing a covalent iron-magnesium bond (Fe-Mg 2-59 A),

The oxidation of a Ni II complex bearing a tetradentate phosphasalen ligand, which differs from salen by the presence of an iminophosphorane (P = N) in place of an imine unit, was easily achieved by addition of a silver salt. The site of this oxidation was investigated with a combination of techniques (NMR, EPR, UV/Vis spectroscopy, X-ray diffraction, magnetic measurements) as well as DFT calculations. All data are in agreement with a high-valent Ni III center concentrating the spin density. This markedly differs from precedents in the salen series for which oxidation on the metal was only observed at low temperature or in the presence of additional ligands or anions. Therefore, thanks to the good electron-donating properties of the phosphasalen ligand, [Ni(Psalen)]+ represents a rare example of a tetracoordinated high-valent nickel complex in presence of a phenoxide ligand.N,N' -ethylenebis(salicylimine) (salen) derivatives constitute a very successful class of ligands that have found numerous applications in inorganic chemistry and catalysis. [1] Their extraordinary popularity comes from their easy synthesis, allowing a variety of skeleton variations, and their ability to coordinate to a great number of different metal ions. Moreover the presence of two phenoxide and imine functions is reminiscent of the coordination environment generated by two histidine and two tyrosine residues, encountered in several enzymes. Thus, in 1998, the one-electron oxidation of a (salen)copper(II) complex was described, and the resulting persistent phenoxy radical was established as a biomimetic functional model of galactose oxidase.[2] Since then, one-electron-oxidized metal salen complexes of firstrow transition metals have received considerable attention. [3] Depending on the nature of the redox-active orbitals, oxidation of salen complexes leads either to high-valent metal centers (metal-centered oxidation) or to species where the ligand is oxidized to a radical (ligand-centered oxidation). Therefore, various factors may affect the oxidation site, as it was nicely illustrated in the case of nickel salen complexes. In noncoordinating solvents, one-electron oxidation occurs on the ligand, and the unpaired electron is highly delocalized over the salen moiety with a small contribution of the nickel orbitals.[3b, 4] However, in coordinating solvents, or in the presence of exogenous ligands such as pyridine or coordinating anions, the geometry of the complex is modified and so is the site of the oxidation, allowing the formation of Ni III complexes.[4a,b, 5] Temperature-dependent behavior, that is, valence tautomerism, was also described in a few examples.[5b, 6] Moreover, the overall electronic distribution may be finely tuned by the substituents of the phenoxide rings. They influence not only the site of the oxidation (which takes place at the most electron-rich phenoxide ring) as evidenced with complexes featuring unsymmetrical salen, [3c, 7] but also the extent of radical delocalization. [3b, 8] The hybridization o...