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transition appears at progressively lower energy as n increases. An interesting additional case is Rh"("+2,+ with n odd, in particular, the Rh35+ unit characterized by Balch and Olmstead12 in the complex [(C6H5CH2NC)12Rh3I2]3+. The MO diagram for Rh35+ is shown in Figure 9, where the orbitals are energetically ranked according to the number of nodes (just as for Rh46+). The Rh-Rh bond order is 1 /V2 (neglecting overlap), which is consistent with the observed12 ¿(Rh-Rh) = 2.796 Á. The only allowed -* transition is a2u -*• 2a lg, a nonbonding-to-antibonding transition that can also be described as outerinner rhodium charge transfer. The observed wavelength (525 nm)12 for the

The oxidation rate of methanol and the subsequent production and destruction of the primary intermediate, formaldehyde, were investigated using Raman spectroscopy as an in situ analytical method. Experiments were conducted in supercritical water over temperatures ranging from 440 to 500 °C at 24.1 MPa and at a nominal feed concentration of 0.05 mol/L (1.5 wt %). Effluent samples were also examined using gas chromatography. In these experiments, feed concentrations ranging from 0.011 to 1.2 wt % and temperatures from 430 to 500 °C were examined and showed that the effective first-order reaction rate for the oxidation of methanol is dependent on the initial feed concentration. Raman measurements reveal a temperature-dependent induction period of less than 1 s over the range of conditions investigated. In addition, quantitative measurements of the production of formaldehyde indicate it is a key metastable intermediate. An elementary reaction mechanism, which reproduces accurately the quantitative features of methanol oxidation and formaldehyde production, is used to identify key rate controlling reactions during the induction period and the transition to the primary oxidation path.

The electronic structure of the calcium monohalides is addressed using a ligand field model which approximates the halide as a polarizable negative charge perturbing the one electron valence structure of the Ca+ ion. A simple, zero-free-parameter model is shown to predict accurately electronic energies, transition moments, permanent dipole moments, and several other molecular constants that have been experimentally determined. The molecular properties and electronic wave functions are interpreted in terms of the polarization (s/p/d/f mixing) and radial expansion (nl/n+1l mixing) of the low lying, free ion, basis functions caused by the electric field of the ligand.