Ru Cations Research Articles

Electrochemical behaviour of spin-coated films of vanadium pentoxide xerogel in aqueous electrolyte. Electron transfer between vanadium centres in the gel layers and intercalated tris (2,2′-bipyridyl) metal cations

The cyclic voltammogram of spin-coated films of vanadium pentoxide xerogel (V 2O 5 · nH 2O) in aqueous electrolyte was found to depend on the potential range. When a freshly prepared film was cycled between 1.5 and 0.1 V vs. SCE a large broad oxidation peak at 0.55 V was observed. When the potential was swept down to −0.6 V irreversible reduction of the film occurred. After a few cycles a new voltammogram consisting of two much smaller waves at 0.1 and −0.3 V was obtained. The UV-visible spectra monitored in situ during the voltammogram showed a decrease in two absorption bands at 254 and 380 nm. These spectral changes were reversible when the potential was swept between 1.5 and 0.1 V. They became irreversible when the potential was swept down to −0.6 V. Aging the films in air or in vacuum affected the reversibility of the initial voltammetric wave at 0.55 V. The basal spacings of a fresh electrode decreased from 13.5 to 11.2 Å when the film was oxidized at 1.2 V. Films reduced at −0.5 V gave a much smaller reflection at 9.5 Å, indicating the loss of much of the layered structure of the gel. [M(bpy) 3] 2+ (M is Fe, Ru or Os) cations intercalated in the xerogel films were found to be electrochemically active. When the potential was swept low enough to reduce vanadium atoms in the gel, large enhancements of the cation anodic peaks were observed. They are attributed to electron transfer between the V 4+ sites in the V 2O 5 layers and the electrochemically oxidized intercalated cations.

Crystal structure ofcis-[Ru(bpy)2(PPh3)Cl+][ClO 4 − ]·(toluene)·∼0.5(CH2Cl2), a species with two different disordered solvent molecules of crystallization

The complexcis-[Ru(bpy)2(PPh3)Cl+][ClO4−] (where bpy=2,2′-bipyridyl) crystallizes from a solution in toluene/dichloromethane as the toluene-hemi(dichloromethane) solvate in the centrosymmetric space group\(P\bar 1\) witha=10.343(2)A,b=11.823(3)A,c=18.469(4)A, α=98.90(2)o, β=93.32(2)o, γ=101.46(2)o,V=2177.8(8)A3 andZ=2. The structure was refined toR(F)=4.6% for those 4248 reflections above 6σ(Fo). The octahedral Ru(II) cation is associated with the bond lengths Ru−Cl=2.424(2)A, Ru−PPh3=2.328(1) A and Ru−N=2.045(5)–2.109(4)A. Both the cation and the perchlorate anion are ordered. However, the unit cell also contains two disordered toluene molecules (centered about inversion centers at 1, 1/2, 0 and 1/2, 0, 1/2), and a disordered dichloromethane molecule of a partial occupancy (centered about 1/2, 0, 1).

Crystal structure ofcis-[Ru(bpy)2{PPh2(o-tol)}Cl][ClO4]·1.5(CH2Cl2), a structure containing both ordered and disordered dichloromethane molecules of crystallization

The complexcis-[Ru(bpy)2 {PPh2(o-tol)}Cl][ClO4] crystallizes from dichloromethane as the sesqui-dichloromethane solvate. The complex crystallizes in the monoclinic space group P21/n with Z=4. The structure was refined toR=5.50% for those 2552 independent reflections with |F0|>6σ(|F0|) The octahedral Ru(II) cation is associated with the following bond lengths: Ru-PPh2(o-tol)=2.360(3)A. Ru−Cl=2.433(2)A and Ru−N(bpy)=2.041(8)–2.095(8)A. Both the perchlorate anion and the dichloromethane molecules of solvation exhibit large amplitudes of vibration. One dichloromethane molecule lies in a general position, the other lies about an inversion center and suffers from disorder.

A hydrogen-bonded dichloromethane-perchlorate-water channel in the crystal structure ofcis-[Ru(bpy)2{PPh-(o-tolyl)2}Cl+][ClO4 −]·CH2Cl2·H2O

The complexcis-[Ru(bpy)2{PPh(o-tolyl)2}Cl+][ClO4−] crystallized from a solution in dichloromethane as the dichloromethane-water solvate. The structure was refined toR=4.5% for those 2433 reflections with |Fo|>6σ(|Fo|). The octahedral Ru(II) cation is associated with metal-ligand distances as follows: Ru−Cl=2.434(3)A, Ru-PPh(o-tol)2=2.382(2)A, and Ru−N=2.037(7)–2.088(7)A. The structure is stabilized by a hydrogen-bonded CH2Cl2...ClO4−...H2O channel which incorporates adventitious water of crystallization.

Structural and Electronic Properties of the Mixed Co/Ru Perovskites AA′CoRuO 6 ( A, A′ = Sr, Ba, La)

The compounds Sr 2CoRuO 6, SrLaCoRuO 6, Ba 2CoRuO 6, and BaLaCoRuO 6 have been prepared and characterized by X ray powder diffraction and SQUID magnetometry. All but Ba 2CoRuO 6 crystallize as pseudo-cubic perovskites with a disordered arrangement of Co and Ru cations over the six-coordinate sites. Ba 2CoRuO 6 adopts the hexagonal 6H perovskite structure with Co in the vertex-sharing octahedra and a random arrangement of Co and Ru in the M 2O 9 dimers. Frustration is apparent in the magnetic properties of each of these compounds at low temperatures, in contrast to the 6H perovskite Ba 3CoRu 2O 9, which shows no structural disorder and orders antiferromagnetically at 106 K.

Magnetic properties of La2CuTi1–xRuxO6and La2ZnRuO6

The compound La2CuRuO6 has been prepared by standard ceramic techniques and characterized by X-ray powder diffraction and magnetometry. The Cu2+ and Ru4+ cations are partially (≈80%) ordered over the six-coordinate (B) sites of a monoclinic perovskite structure [a= 5.5897(2)A, b= 5.7550(2)A, c= 7.7584(2)A, β= 90.15°]. The material shows a transition to a weakly ferromagnetic phase at 12 K. Substitution of Ti4+ for 20% of the Ru cations leads to the loss of both the cation ordering and the spontaneous magnetization, although there is some evidence for the formation of superparamagnetic spin clusters and, below 10 K, a freezing of frustrated spins. The magnetically dilute but structurally ordered compound La2ZnRuO6 is paramagnetic down to a temperature of 6 K.

Oxidation of Fe25Cr4AlPd and Fe25Cr4AlRu alloys

Fe25Cr4Al alloys containing Pd and Ru additions were oxidized in air at 1090°C. Scanning electron microscopy, dispersive x-ray analyses, and x-ray mapping were used to characterize the morphologies of the scales formed on these alloys. The results showed that Pd tended to segregate at the oxide-alloy interface as discrete and platelike particles during elevated temperature oxidation of the Pd-containing FeCrAl alloys. These Pd particles appeared to improve the adherence of the alumina scale. However, no improvement of the scale adherence of Ru-containing FeCrAl alloys was observed as outward diffusion of Ru cations to the external alumina scale led to the formation of RuO 2 within this scale.

Synthesis and NMR study of the cations C 5Me 5MC 5Me 4CHAr + (M = Ru, Os). A comparison with Fe-containing analogues

The novel secondary carbinols C 5Me 5MC 5Me 4CH(OH)Ar have been prepared by reaction of C 5Me 5MC 5Me 4CHO (M = Ru, Os) with an excess of ArLi. Protonation of the carbinols by the strong acids, CF 3COOH, HBF 4 and HPF 6 (HA), leads to the corresponding stable carbocations C 5Me 5MC 5Me 4CHArA −, and the salts with A = BF 4 and PF 6 have been isolated as solids. Comparison of the behaviour of the various Fe-subgroup metal cations C 5Me 5MC 5Me 4CHAr + has shown that Ru and Os cations are more stable than the Fe derivatives and do not undergo the C 5Me 5FeC 5Me 5 C + HAr⇄C 5Me 5Fe C 5Me 5 C HAr singlet-triplet transition. Comparison of the ruthenium and osmium cations C 5Me 5MC 5Me 4CHAr + of the 1H and 13C NMR data with the corresponding data for iron complexes [1] indicates that the shielding of 1H and 13C nuclei by the carbenium centre CH +-increases on going from Fe to Ru and then to Os compounds. For the metal cations the shielding of the same nucleus ( 1H and 13C) increases in the series Me 3C 6H 2 < Ph < C 6F 5, i.e. with increasing electron withdrawing ability of the aryl substituent adjacent to the carbenium centre. A change in the properties of the Fe subgroup cations C 5Me 5MC 5Me 4CHAr + implies that direct participation by the metal atom in the stabilization of the carbenium centre increases from Fe to Os.