Actinides hydrogen

Lin and Marks have considered olefin insertion into the actinide-hydrogen bonds of Cp2An(H)(OR) complexes [Cp = ti -(CH3)5C5 An = Th, U R = achiral or chiral group].Calculations included molecular mechanics analysis of the interaction of Cp U(H) [l(S)-entfo]-bornoxide with norbor-nene. The DREIDING and MMP2 force fields were used to calculate the relative energetics of olefin approach trajectories toward the U center. Three reaction pathways were considered. The authors note that whereas this method is approximate, the energetically favored pathway corresponds to the stereo-chemically favored course of the reaction. 

A combined review of the rare-earth and actinide hydrides is appropriate. A reasonable literature on actinide-hydrogen systems now exists with an attendant realization that the 5f metals form fully rare-earth-like hydrides as well as totally unique hydride phases. This chapter concentrates on correlating the 4f and 5f metal-hydrogen systems and relies heavily on the most recent interpretations of the solid-state physics and chemistry. 

Work on actinide-hydrogen systems through 1984 are assessed in detail by Ward (1985a). Additional relevant work has been published for the rare-earth-like transuranium systems of interest here. Ward et al. (1987) describe a new study on Np + H from 0.0005 to 70 bar pressure using doubly electrorelined Np metal. The P-C-Tdata are discussed above and are shown in fig 6. This experimental study resolved serious differences between two earlier reports, as reviewed by Ward (1985a) and by Flotow et al. (1984). For the reaction 0.94 Np + Hj = 0.94 NPH2.13, the data are described by the equation... 

ORCANOACTINIDE CHEMISTRY PROPERTIES OF COMPOUNDS WITH ACTINIDE-CARBON, ACTINIDE-HYDROGEN, AND ACTINIDE-TRANSITION-METAL a BONDS... 

The reduction potentials for the actinide elements ate shown in Figure 5 (12—14,17,20). These ate formal potentials, defined as the measured potentials corrected to unit concentration of the substances entering into the reactions they ate based on the hydrogen-ion-hydrogen couple taken as zero volts no corrections ate made for activity coefficients. The measured potentials were estabhshed by cell, equihbrium, and heat of reaction determinations. The potentials for acid solution were generally measured in 1 Af perchloric acid and for alkaline solution in 1 Af sodium hydroxide. Estimated values ate given in parentheses. 

Potential fusion appHcations other than electricity production have received some study. For example, radiation and high temperature heat from a fusion reactor could be used to produce hydrogen by the electrolysis or radiolysis of water, which could be employed in the synthesis of portable chemical fuels for transportation or industrial use. The transmutation of radioactive actinide wastes from fission reactors may also be feasible. This idea would utilize the neutrons from a fusion reactor to convert hazardous isotopes into more benign and easier-to-handle species. The practicaUty of these concepts requires further analysis. 

Actinide Peroxides. Many peroxo compounds of thorium, protactinium, uranium, neptunium, plutonium, and americium are known (82,89). The crystal stmctures of a number of these have been deterrnined. Perhaps the best known are uranium peroxide dihydrate [1344-60-1/, UO 2H20, and, the uranium peroxide tetrahydrate [15737-4-5] UO 4H2O, which are formed when hydrogen peroxide is added to an acid solution of a uranyl salt. 

Step (2.3), and AS, are 1.52 kcal.mole and —37.3 cal.deg . mole , respectively. It is noteworthy that the following reduction reactions of the analogous M02 actinide ions show a similar first-order hydrogen-ion dependence (NpOi- +Fe + ) , (Np02-"- -Np + ) , (Pu02++Pu02 ") and (U02 "-l-In Table 1 the activation parameters of the V(V)-t-Fe(II) reaction are... 

As already noted, the carbonylation of bis(pentamethyl-cyclopentadienyl) actinide hydrocarbyls is irreversible in the cases studied thus far. Thus, thermolysis does not result in CO loss, but rather in interesting chemical reactions. Thermolysis of 1 ( 5) in toluene solution results in hydrogen atom migration to yield an enolate (eq.(5)). NMR studies establish that eq.(5) is essentially quantitative, and that the stereochemical course... 

Metal hydrides and acyl-like CO insertion products are two types of species likely to be present in any homogeneous or heterogeneous process for the catalytic reduction of carbon monoxide. The discovery and understanding of new types of reactivity patterns between such species are of fundamental interest. As discussed elsewhere (11,22,54-57), bis(pentamethylcyclo-pentadienyl) actinide hydrides (58) are highly active catalysts for olefin hydrogenation as well as H-H and C-H activation. 

Hydrogenation with Early Transition Metal, Lanthanide and Actinide Complexes... 

In hydrogenation, early transition-metal catalysts are mainly based on metallocene complexes, and particularly the Group IV metallocenes. Nonetheless, Group III, lanthanide and even actinide complexes as well as later metals (Groups V-VII) have also been used. The active species can be stabilized by other bulky ligands such as those derived from 2,6-disubstituted phenols (aryl-oxy) or silica (siloxy) (vide infra). Moreover, the catalytic activity of these systems is not limited to the hydrogenation of alkenes, but can be used for the hydrogenation of aromatics, alkynes and imines. These systems have also been developed very successfully into their enantioselective versions. 

Hydrogenation Catalysts Based on Group III, Lanthanide, and Actinide Complexes I 131... 

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