X-Ray absorption spectroscopy (XAS) using synchrotron radiation has been used to probe the structure of copper(1) species in an aqueous ammonia solution that contains hydrazine to prevent any oxidation to copper(n) species. Combining a characteristic copper(1) pre-edge feature with the extended X-ray absorption fine structure (EXAFS) of the XAS enabled the stereochemistry and bond distances to be extracted for the predominant species, which is shown to be the diamminecopper(~) ion. The structure is linear with CU-N bond lengths of 1.88 f 0.02 A.Although, to a large extent, studies on the chemistry of copper have centred around the copper(11) valence state there is an increased awareness that the copper([) state also has important roles to play. Certainly, it has been known for some time that copper(1) has important functions in some life processes as exemplified in a number of metalloproteins.' In this context, studies on the inorganic chemistry of copper([) are particularly relevant, even for simple complexed species. Investigations on the XAS of copper(1) sites in simple species are especially useful because an understanding of the different spectral processes can, with advantage, be transferred to more complex systems.Copper(1) forms neutral, anionic, and cationic complexes. The strength of the copper(1)-ligand bonds increases in the order Cu-0, Cu-S, Cu-N, and whilst the highest coordination number attained is four, intermediate values of two and three are also k n o ~n . ~, ~In the older l i t e r a t ~r e , ~ twocoordination is attributed to complexes with ligands with oxygen-donor atoms and also for the acetonitrile (CH3CN) complex. However, we note that Persson et aL7 report that

MCM-48 mesoporous molecular sieves containing iron(III) were obtained using a direct sol−gel route followed by removal of the cetyltrimethylammonium hydroxide template before calcination. UV−visible, ESR, and XANES spectroscopies show that iron mostly occupies tetrahedral sites of the siliceous walls. The formation of oxide nanoclusters in the channels is favored in the presence of the organic template molecules during calcination.

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In situ XAFS spectroscopic studies have been carried out at 450 °C on the hydrogen reduction of a rhenium-promoted Co 3 O 4 /Al 2 O 3 catalyst. The results show that reduction at this temperature yields a highly dispersed system with small cobalt metal particles (<40 Å). In addition, a lower fraction of the cobalt content is randomly dispersed over the tetrahedral vacancies of the alumina support. This dispersion occurs during reduction and not calcination. The cobalt in these sites cannot be reduced at 450 °C, a temperature that is too low to permit formation of the spinel CoAl 2 O 4 . A particularly significant feature of the spectrum of the reduced material is that the energy of the K-edge is increased by 3-4 eV. This is attributed to the small size of the metal particles and consequently a deviation from bulk properties. The effect is a manifestation of changes in shielding of the 1s electrons by the valence orbitals relative to the situation pertaining to the bulk metal. The actual crystal form of the metal particles could not be determined, but the recently reported metastable non-close-packed body-centered cubic form cannot be excluded, especially since graphite was present and carbon is suggested to catalyze transformation to this structure.