Photochemistry at adsorbate/metal interfaces

The low energy collision-induced dissociation (CID) of Cr(CO)6+ with Xe is investigated using a recently modified guided ion beam tandem mass spectrometer, in the energy range from 0 to 5 eV in the center-of-mass (CM) frame. The additions to the instrument, updated with a double octopole system, and the new experimental methods available are described in detail. Integral cross sections for product formation are presented and analyzed using our standard modeling procedure. A slightly revised value for the bond dissociation energy of (CO)5Cr+–CO of 1.43±0.09 eV is obtained, in very good agreement with literature values. Axial and radial velocity distributions for primary and product ions are measured at 1.3, 2.0, and 2.7 eV, in the threshold region for product formation. The resulting velocity scattering maps are presented and discussed. Evidence of efficient energy transfer is observed from angular scattering of CID products. Experimental distributions of residual kinetic energies are derived and extend to...

/pdf/guided-ion-beam-study-of-collision-induced-dissociation-1rr0toggw1.pdf

Guided ion beam study of collision-induced dissociation dynamics: integral and differential cross sections

Structure and Bonding of the Transition-Metal Carbonyl Complexes M(CO)5L (M = Cr, Mo, W) and M(CO)3L (M = Ni, Pd, Pt; L = CO, SiO, CS, N2, NO+, CN-, NC-, HCCH, CCH2, CH2, CF2, H2)1

Ab initio calculations have been carried out on the first- and second-row transition-metal mono- and dicarbonyl positive ions. The bonding in these systems is discussed in detail. Trends in the series of mono- and dicarbonyl ions and between the first- and second-row transition metals are explained in terms of a dominantly electrostatic bonding interaction and differences in metal ion state separations, ionization potentials, and s and d orbital sizes. Dissociation energies are presented and a detailed comparison is made with experimental data. Where reliable experimental data exists, agreement with the theoretical results is generally good.

Theoretical studies of the first- and second-row transition-metal mono- and dicarbonyl positive ions

Technetium Chemistry and Technetium Radiopharmaceuticals

Mass spectra, ionization energies, fragmentation energies, ionic and neutral dissociation energies, and heats of formation for the title compounds are measured and compared. Substitution of CS for CO in going from M(CO)/sub 6/ to M(CO)/sub 5/CS results in (a) a slight modification of the mass spectra, if only the M(CO)/sub n/CS/sup +/ and M/sup +/ ions are considered, (b) a lowering of the ionization energies by 0.1 to 0.4 eV, (c) a reduction of approximately 0.1 eV in the average M-CO bond energies in both the molecule and the molecular ion, and (d) a reduction of 3.0 +- 0.3 eV in the heats of formation of the molecules. Within each molecule or molecular ion the M-CS bond is stronger than the M-CO bonds by 1.5 to 2.0 eV. Both the M-CS and the M-CO bonds increase in strength in going from Cr to Mo to W. Comparison of calorimetric and mass spectrometric data for M(CO)/sub 6/ indicates that each neutral CO fragment leaves the ionization site in its first vibrationally excited state. 10 tables.

Gary D. Michels

Papers

Comparative mass spectrometry of the group 6B hexacarbonyls and pentacarbonyl thiocarbonyls

Characterization of decacarbonylmanganesetechnetium and decacarbonyltechnetiumrhenium