F. Scott Howell

One-pot and selective synthesis of a series of [RuCl6−2nLn] (L=bidentate ligand, n=0−3) types of complexes with polypyridyl ligands; another example of the synthetic utility of ‘ruthenium-blue’ solution

Abstract Convenient (one-pot) and selective syntheses of a series of ruthenium complexes with polypyridyl ligands, [RuL3]2+, cis-[RuCl2L2]+ and [RuCl4L]- (L=bpy, phen or Hdpa (di-2,2-dipyridylamine)), including [RuCl6]3−, have been reported as further examples of the synthetic utility of ‘ruthenium-blue’ solution. The methods developed here are also useful for synthesizing selectively such pair complexes as [RuIIICl3(terpy)]-[RuII(terpy)2]2+ and [RuIIICl4py2]−-[RuIICl2py4].

Preparation of various calcium-phosphate powders by ultrasonic spray freeze-drying technique

Abstract Various calcium–phosphate powders with Ca/P ratios ranging from 1.00 to 1.67 were prepared by an ultrasonic spray freeze-drying (USFD) technique: (i) 100 cm 3 of aqueous solution containing 0.500 mol·dm −3 of calcium acetate (Ca(CH 3 COO) 2 ), 0.300–0.500 mol·dm −3 of trimethyl phosphate (PO(OCH 3 ) 3 ) and 1.77 mol·dm −3 of acetic acid (CH 3 COOH) were refluxed at 80°C for 100 h; (ii) the droplets with diameters as small as 2–3 μm, which were formed by the ultrasonic spray of aqueous solution, were introduced into a chamber chilled by liquid nitrogen to freeze the droplets; (iii) the water ice in the frozen droplets was sublimed under reduced pressures; and (iv) the freeze-dried materials were heated at 900°C for 1 h to form calcium phosphates. The β-calcium orthophosphate (β-Ca 3 (PO 4 ) 2 ) and carbonate-containing hydroxyapatite powders with stoichiometric Ca/P ratios were prepared from the solutions with Ca/P ratio of 1.44 and 1.67, respectively.

Synthesis, properties and molecular structure of trans-hydroxobis(2, 2′-bipyridine)nitrosylruthenium(2+): influence of axial ligand on characteristics of nitrosyl moiety in trans-[Ru(NO)XL4]n+ (X=OH, Cl; L=py, 1/2(bpy)) type complexes

Abstract A new complex, trans -[Ru(NO)(OH)(bpy) 2 ] 2+ , was prepared and characterized. The trans form of the complex was confirmed by NMR spectra ( 1 H and 13 C) and X-ray structure determination: P 2 1 / n ; a =16.365(5), b =11.800(7), c =12.169(1) A, β=90.19(7)°; Z =4; D c =1.92, D m =1.92 g cm −3 ; formula weight=659.36; R =0.048 for 4825 observed reflections. Characteristics of the nitrosyl complex were compared with those of the corresponding complex, trans -[Ru(NO)Cl(bpy) 2 ] 2+ , which has a Cl ligand at the trans position of nitrosyl.

Effect of starting particle size on hot-pressing of magnesium oxide powder prepared by vapour-phase oxidation process

Effect of starting particle size on hot-pressing of magnesium oxide (MgO) powder was examined using seven kinds of MgO powders prepared by a vapour-phase oxidation process; the average primary particle sizes were 11, 25, 32, 44, 57, 107 and 261 nm. These compressed powders (compacts) were hot-pressed at a temperature between 900 and 1300°C. The densifications of these compacts during the hot-pressing proceeded via (i) the sintering of primary particles within secondary particles and the rearrangement of secondary particles/grains (900°C), (ii) the gradual grain growth controlled by the pore migration (900∼1100°C) and (iii) the rapid grain growth due to the active mass transfer (1300°C); the grain sizes of MgO compacts hot-pressed at and below 1100°C were <1 μm, while those at 1300°C attained 20∼30 μm. The transluscent compact with the relative density of 99.7% could be obtained when the compressed powder with the average primary particle size of 44 nm was hot-pressed at a temperature as low as 1100°C for 1 h.

Characterization and crystal structures of copper(II), cobalt(II), and nickel(II) complexes with two kinds of piperidine carboxylic acids

Abstract Copper(II) complex with dl -piperidine-3-carboxylic acid ( dl -Hpipe-3):[Cu( dl -pipe-3) 2 (H 2 O)] and cobalt(II) and nickel(II) complexes with piperidine-4-carboxylic acid (Hpipe-4):[M(Hpipe-4) 2 (H 2 O) 4 ]Cl 2 (M: Co, Ni) have been prepared and characterized by means of IR and powder diffuse reflection spectra, thermal analysis, and magnetic susceptibility. The crystal structures of these complexes have been determined by X-ray diffraction. The crystal of [Cu( dl -pipe-3) 2 (H 2 O)] is orthorhombic with the space group Pbcn. The copper atom is in a square pyramidal geometry, ligated by two carboxylato oxygen atoms, two nitrogen atoms, and a water molecule. One molecule of this complex consists of either d -piperidine-3-carboxylic acid or l -piperidine-3-carboxylic acid. The crystals of [M(Hpipe-4) 2 (H 2 O) 4 ]Cl 2 are monoclinic with space group P 2 1 / n . In these complexes the metal atom is in an octahedral geometry ligated by two carboxylato oxygen atoms and four water molecules.

Effect of metal-oxide addition on the sintering of β-calcium orthophosphate

The effect of metal-oxide addition (1∼10 mol %) on the sintering of β-calcium orthophosphate (β−Ca3(PO4)2) was examined by pressureless sintering at 1070 °C for 5 h. The metal-oxide additives used were as follows: (i) monovalent metal-oxides, Li2O, Na2O, and K2O; (ii) divalent metal-oxides, MgO, CaO, SrO, and BaO; (iii) trivalent metal-oxides, Al2O3 and Fe2O3; and (iv) tetravalent metal-oxides, SiO2, TiO2, and ZrO2. The relative densities of the sintered β−Ca3(PO4)2 compacts were reduced with increasing amounts of monovalent and divalent metal-oxide additions, except for the case of MgO addition when the relative density remained with increasing amount of MgO up to 4 mol %. In the case of trivalent metal-oxide additions, the relative density of sintered β−Ca3(PO4)2 compact was reduced with increasing amount of Al2O3 addition, whereas it was enhanced with increasing amount of Fe2O3 addition and reached 98.7% at 10 mol % Fe2O3 addition. In the case of tetravalent metal-oxide additions, relative densities of the sintered β−Ca3(PO4)2 compacts were slightly reduced with increasing amounts of SiO2 and ZrO2 additions, whereas no appreciable changes in the relative density were observed with increasing amount of TiO2 addition.

Sinterability of spinel (MgAl2O4)-Zirconia composite powder prepared by double nozzle ultrasonic spray pyrolysis

Abstract Two kinds of spinel (MgAl 2 O 4 )-zirconia (ZrO 2 ) composite powders were prepared by double nozzle ultrasonic spray pyrolysis; the aqueous solutions in the Mg(NO 3 ) 2 -Al(NO 3 ) 3 and ZrOCl 2 -YCl 3 systems were spray-pyrolysed in a hot zone of an electric furnace heated at 900 °C, using two ultrasonic vibrators. The compositions of the composite powders were as follows: (1) Sample No.1: MgAl 2 O 4 93.36 mol% and yttria-stabilized tetragonal ZrO 2 polycrystals (Y-TZP) 6.64 mol% and (2) Sample No. 2: MgAl 2 O 4 75.51 mol% and Y-TZP 24.49 mol%. While MgAl 2 O 4 and Y-TZP were present in both powders, MgO was additionally detected from Sample No. 2; such MgO disappeared when it was heated up to 1100 °C or higher. The composite powders contained spherical particles with diameters of below μm and, in part, acicular particles with long axis lengths of 1 to 2μm. The wet-milled powder of Sample No.1 showed an excellent sinterability; when the composite powder compact was fired at 1700 °C for h, the relative density attained 97.6%.

Syntheses and crystal structures of zinc(II) complexes with three kinds of piperidine carboxylic acids

Abstract Zinc(II) complexes with dl -piperidine-2-carboxylic acid (Hpipe-2), dl -piperidine 3-carboxylic acid (Hpipe-3), and piperidine-4-carboxylic acid (Hpipe-4):ZnCl2(Hpipe 2)2, ZnCl2(Hpipe-3)2(H2O)3, and ZnCl2(Hpipe-4) have been prepared and characterized by means of IR spectra and thermal analysis. The crystal structures of [ZnCl2(Hpipe-3)2]·3H2O and [ZnCl2(Hpipe-4)] have been determined by X-ray diffraction. The crystal of [ZnCl2(Hpipe-3)2]·3H2O is monoclinic with the space group P21/c. The zinc atom is in a tetrahedral geometry, ligated by two carboxylato oxygen atoms and two chlorine atoms. The crystal of [ZnCl2(Hpipe-4)] is triclinic with space group P1. This complex consists of a binuclear molecule bridged by two carboxylato oxygen atoms. The zinc atom is in a tetrahedral geometry ligated by two carboxylato oxygen atoms and two chlorine atoms.

Syntheses, characterization, structure and redox behavior of cis-[Ru(NO)X(bpy)(py)2]z (X=monodentate) type complexes of nitrosylruthenium(II) and their related complexes

Abstract Nitrosyl complexes which have both 2,2′-bipyridine and pyridine as co-existing ligands were synthesized and characterized as cis-[Ru(NO)(X)(pby)(py)2]z+ (X=OH, Cl, NO2 for z=2; X=py for z=3). Their characteristics were investigated under the condition of both chemical oxidation and electrochemical reduction. The molecular of cis-[Ru(NO)(OH)(pby)(py)2](PF6)2 was determined: Ru20N5H19O2P2F12,FW=752.40, orthorhombic, a=15.942(2), b=26.541(4), c=12.670(5) A , V=5360(1) A 3 , space group Pbca, Z=8, Dcalc=1.864 g cm−3, Dobs=1.857 g cm−3, μ (Mo Kα)=8.18 cm−1, no. of observations (I>3.00σ(I))=2232, R=0.050, Rw=0.042. The related nitro and oxo complexes which were obtained from the nitrosyl complexes are also reported.

Evidence for a new nitrosyl-to-nitro reaction and an acetamide formation in the {RuNO}6-type complex, cis-[Ru(NO)(CH3CN)(bpy)2]3+

Abstract The reaction between cis-[Ru(NO)(CH3CN)(bpy)2]3+ and a free NO2− gives an appreciable amount of the nitro species cis-[Ru(NO2)(CH3CN)(bpy)2]+. Although definitive evidence for the mechanistic illustration of the nitrosyl-to-nitro conversion is still unavailable, an oxide abstraction from NO2− to the nitrosyl ligand appears to be the key reaction. In addition, cis-[Ru(NO)(CH3C(O)NH)(bpy)2]2+ having an acetamide ligand is formed during the reaction. The structure of the complex, used as a starting material of the present reaction, was determined by single-crystal X-ray diffraction methods; for cis-[Ru(NO)(CH3CN)(bpy)2](ClO4)3·CH3CN: FW=823.91, monoclinic, P21/n, a=12.471(3), b=15.041(7), c=17.598(4) A, β=94.65(2)°, V=3289(1) A3, Z=4, R=0.081, Rw=0.050.