Higher order speciation effects on plutonium L(3) X-ray absorption near edge spectra.

Pu L(3) X-ray near edge absorption spectra for Pu(0-VII) are reported for more than 60 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides, and other compounds both as solids and in solution, and substituted in zirconolite, perovskite, and borosilicate glass. This large database extends the known correlations between the energy and shape of these spectra from the usual association of the XANES with valence and site symmetry to higher order chemical effects. Because of the large number of compounds of these different types, a number of novel and unexpected behaviors are observed, such as effects resulting from the medium and disorder that can be as large as those from valence.

Low-temperature synthesis of uranium tetraboride by solid-state metathesis reactions.

A novel synthesis of uranium tetraboride (UB(4)) by solid-state metathesis reaction is demonstrated. This approach significantly lowers the temperature required to synthesize this material to < or = 850 degrees C. When UCl(4) is reacted with 2 equiv of MgB(2) at 850 degrees C, crystalline UB(4) is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl(4) to UCl(3) as the initial step in the reaction. The UB(4) product is purified by washing with water.

Nonclassical Metal Carbonyls: Appropriate Definitions with a Theoretical Justification.

MP2 calculations show that the D∞h isoelectronic dicarbonyl complexes [M(CO)2 ]n (Mn =Rh- , Pd0 , Cu+ , Ag+ , Au+ , Zn2+ , Cd2+ , Hg2+ ) depicted in structure 1 can be classified as classical or nonclassical depending on whether the metal-carbon bond lengths decrease or increase when weak, anionic ligands approach the metal centers.