Experiments have shown * that the ruthenium red cation is [Ru,O,(NH,), J6+ in which there are two oxo-bridges and the average oxidation number of ruthenium is + 10/3. The cation is oxidised reversibly by a one-electron change to the more paramagnetic brown cation [Ru,O,(NH,), J7+. The relation to other polynuclear complexes is discussed. JOLY formulated ruthenium red as Ru,Cl4(OH),,7NH3,3H,O, and Morgan and Burstall,2 who prepared from it supposed mononuclear complexes of ruthenium, as [Ru11x(OH)Cl(NH,),]C1,H20. The latter structure was rejected by Gleu and Breuel3 because [RuIrl(OH)C1(NH,),] + is paramagnetic whereas ruthenium red is diamagnetic.It has been suggested that the highly coloured cation is polynuclear, but further evidence on its structure has not been advanced.Our interest in ruthenium red arose from a view that the diamagnetism and intense colour of many complexes of ruthenium are due to their being polynuclear. In particular, the occurrence in solution of an aquochloro-* and an aquonitrato-complex 5 3 6 as transient violet species with unusually high molar extinction coefficients (cRU -20,000 at A , , -550 mp) suggested a chromatic group similar to that in ruthenium red for which we find that cRu is 21,000 at A, , , 532 mv. It has now been shown that this cation, here called ruthenium red, has no complexed halogen groups, and behaves as a trinuclear complex in which, associated with three ruthenium atoms, there are 14 nitrogen atoms which can be liberated as ammonia. This suggests that the red cation has two oxo-bridges, as in (I), to satisfy hexa-co-ordination of the ruthenium atoms. This cation is oxidised, reversibly, [(NH3),R~-O-R~(NH,)4-O-Ru(NH3)5]6+ [( N H 3)5 Ru-O-Ru (N H3I4-O-Ru (N HJJ ' + (I) Red (11) Brown in acid solution to a brown cation (11). in the respective cations are 10/3 and 1113. red cation points to a linear configuration of the Ru-O-Ru-O-Ru group.
The magnetic behaviour of ruthenium dioxide up to 1000°K is interpreted in terms of J being ca. -3000 cm.-l in dioxo-bridged chains of ruthenium atoms. The high electrical conductivity as well as certain structural features imply that the average oxidation state of the ruthenium atoms is substantially greater than +4.The oxide hydrate has a high surface area ; it is formulated as Ru02+,, yH,O since there can be an excess (chemisorbed) of oxygen particularly after removal of some of the water. Values of x up to 0.1 2 have been found whereas y is often 1 to 1.3. The susceptibility, though generally similar to that of RuO,, varies from sample to sample: its behaviour is discussed in relation both to the influence of adsorbed groups and also to some terminal ruthenium atoms behaving as mononuclear Ru(V), i.e., being in the d3 state. Expected spectral bands in the infrared have not been detected owing to the presence of electronic conductance bands. Solid State Physics Divisions, A.E.R.E., Harwell. Berkshire IN a recent note,l Cotton and Mague conclude that ruthenium dioxide has the rutile structure ; however, they point out that the closest Ru-Ru distance (3.107 A) excludes metal-metal coupling as the cause of the very of this second term and certain other properties to strong super-exchange, via the dioxo-bridges, in the chains (A) which exist in the c direction. Strong bondlow magnetic susceptibility. In this paper we report \RU/O\ /OARL,/ magnetic susceptibility measurements from 1.3 to from 298-673"~ together with other properties of the / \o/Ru\o/ \ 1033"~, supplementing previously available values (A) dioxide. The susceptibility per g.-atom of ruthenium, defined as XA-Xdia, has a temperature independent term ( N a ) which is relatively large, about 185 x lo* e.m.u. ; the temperature dependent term is small, about 20 x e.m.u. at room temperature and about 85x lo4 e.m.u. at 1000"~. We attribute the smallness ing within the chains is also indicated by the contraction along the c axis with increase of temperature that we have observed.The shape of the susceptibility-temperature curve is completely different from that predicted3 for a mononuclear 4d4 svstem in an octahedral environment but 1 F.
UK Nirex Ltd are seeking to develop a deep underground repository for the disposal of solid ILW and LLW in the UK. The formation of water-soluble complexants from the degradation of the solid organic polymers and cellulosic materials present in such wastes may influence the solubility and sorption properties of a number of radioelements. A number of materials have been chemically degraded under alkaline, anaerobic conditions representative of the near field of the repository. Measurements of plutonium solubility in the leachates obtained show that the degradation of cellulose is of particular concern; the effects on the solubility can be several orders of magnitude greater than those of other organic materials. Products formed from the degradation of ion-exchange resins were found to have little effect. Solubilities of a number of other radioelements in aerobically degraded cellulose leachates are also given. The effect of reducing the ratio of celluloseto cement in the degradation experiments results in a decrease in plutonium solubility in the corresponding leachate. Several of the likely degradation products of cellulose have been individually synthesised including isosaccharinic acid, a key degradation product of cellulose. Enhanced plutonium solubilities have been measured in 10-3M solutions of these compounds. Sorption of plutonium onto cement from leachates obtained by the degradation of 10% cellulose in cement is reduced by about two orders of magnitude. Interaction with cement removes significant concentrations of complexants from solution. Thermodynamic modelling studies show that hydroxyl groups present in the compounds which result from the alkaline degradation of cellulose can strongly complex with plutonium.
Solubility / Radionuclides / Technetium / Uranium / Plutonium / Americium / ComplexationSummary A range of commercial products can be added to cements and concretes in order to modify their properties. These admixtures may be used in cementitious materials employed in the construction and backfilling of a radioactive waste repository vault. Many admixtures contain organic materials and it is known that some organic compounds can alter the solubility and sorption behaviour of radionuclides in a repository. In this work, the effects of two Japanese cement additives on the solubilities of technetium, uranium, plutonium and americium at pH 12 have been studied. In some cases, radionuclide solubility enhancements in excess of two orders of magnitude were observed in the presence of additives. This can be interpreted in terms of the formation of radionuclide/hydroxy/additive complexes.
Nirex is seeking to develop a deep underground repository for the disposal of solid intermediate-level and low-level radioactive wastes (ILW and LLW) in the UK. One possible influence on the behaviour of radionuclides is the formation of water-soluble complexants by the degradation of the solid organic polymers that will be present in the wastes. The degradation products of cellulose have been shown to increase the solubility of plutonium and other radionuclides and to reduce sorption onto near-field and far-field materials. Degradation of cellulose under anaerobic alkaline conditions produces a range of organic acids. In this paper 2-C-(hydroxymethyl)-3-deoxy-D-pentonic acid (isosaccharinic acid, ISA) is identified by High Performance Liquid Chromatography as a significant component of cellulose leachates. A combination of fractionation of cellulose leachates and plutonium solubility determinations shows that ISA is responsible for the majority of the enhancement of plutonium solubility observed in such leachates. Further degradation of ISA by chemical or microbial action may lessen the effect of degraded cellulose leachates. Experimental studies on the chemical degradation of this compound under alkaline conditions suggest that the presence of oxygen is required. Microbial degradation studies show that the plutonium solubility in solutions of ISA is reduced by their exposure to microbial action.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.