Koshiro Toriumi

Competition between electron correlation of NiIII states and electron-phonon interaction of PdII-PdIV mixed-valence states in quasi-one-dimensional halogen-bridged mixed-metal complexes, Ni1-xPdX(chxn)2Br3

A series of single crystals of quasi-one-dimensional halogen-bridged Ni-Pd mixed-metal compounds, Ni1-xPdx(chxn)2Br3 (chxn equals 1R, 2R- cyclohexanediamine) have been obtained by electrochemical oxidation methods. In order to investigate the competition between the electron-correlation in the NiIII states (SDW states) and the electron-phonon interaction in the PdII-PdIV mixed-valence states (CDW states) in the Ni-Pd mixed-metal compounds, the single-crystal electrical conductivities, IR, resonance Raman spectra, ESR, magnetic susceptibilities, and XPS, have been measured. The electrical conductivities of these compounds show semiconducting behavior with the conductivities maximized and the activation energies minimized at x equals ca. 0.5. The IR, resonance Raman spectra, and XPS show that the PdII- PdIV mixed-valence states are influenced and approaching to the PdIII states with the increase of the NiIII components.

X-Ray Structural Study of a Zinc(II) Inclusion Complex of a Phenolate-pendant Cyclam

The molecular structure of phenol-pendant cyclam-zinc(II) complex,4a, has been determined by X-ray structure analysis. Crystals of4a · ClO4 · CH3OH (C16H27N4OZn · ClO4 · CH3OH) are monoclinic, space groupP21/nn, with four molecules in the unit cell of dimensionsa=31.198(2) Å,b=8.426(1) Å,c=8.214(1) Å, andβ=93.96(1)°. The structure was solved by the heavy atom method and refined anisotropically toR=0.044,Rw=0.062 for 1551 independent reflections. The complex assumes a five-coordinate, square pyramidal geometry, where zinc(II) is surrounded by the cyclam moiety in a planar fashion with the pendant phenolate anion occupying an axial position. An extremely short Zn-O(phenolate) bond distance of 1.983(5) Å, in conjunction with the 0.288 Å displacement of Zn(II) above the cyclam N4 plane toward the phenolate, accounts for the extremely low pKa value of 5.8 for the pendant phenol. These facts about4a, in comparison with the previous findings for the Ni(II) (4b) and Cu(II) complexes (4c) with the same ligand, illustrate well the characteristics of zinc(II) ion coordination properties.

Stereochemistry of sugar units in glycosylamine ligands of octahedral complexes derived from tris(trimethylenediamine)-nickel(II) and natural aldohexoses

Some natural aldohexoses reacted with [Ni(tn)3]2+(tn = trimethylenediamine) to yield octahedral nickel(II) complexes containing glycosylamine ligands. The complexes were characterized by elemental analyses, magnetic moments, electronic and CD spectra. The molecular structure of [Ni(L-Rha-tn)2]Br2·2H2O·MeOH [L-Rha-tn = 1-(3-aminopropylamino)-1,6-dideoxy-L-mannose]1 has been determined by single-crystal X-ray techniques: orthorhombic, space group P212121, a= 12.373(1), b= 21.614(2), c= 11.272(1)A, least-squares refinement led to a final R factor of 0.044 using 2657 reflections having Fo > 3σ(Fo). From X-ray crystallographic studies of glycosylamine complexes, two typical co-ordination structures of the aldose unit have been found in 1 and [Ni(D-GlcN-en)2]2+[D-GlcN-en = 2-amino-1-(2-aminoethylamino)-1,2-dideoxy-D-glucose], which can be discriminated by the two geometrical isomeric forms arising from the two substituents on C1 and C2 of the pyranoside ring, namely cis and trans. The sugar unit of 1 has cis geometry containing equatorial and axial substituents on C1 and C2 of the pyranoside ring. In contrast, the sugar unit of the D-GlcN-en complex has trans geometry at these positions, which are both equatorial. Assuming the 4C1(chair) conformers to be the most stable and based on some stereochemical considerations of both the sugars and the chelate rings, the structures of the sugar units in the glycosylamine complexes from all natural aldohexoses can be classified into either of the above two types, the only difference being the relative absolute configuration at C2 and C5. This classification is well correlated with the CD spectral patterns obtained in methanolic solutions.