Robert E. Winters

Ions produced in the mass spectrometer from cyclopentadienylmetal carbonyl compounds of cobalt, manganese and vanadium

Abstract The positive and negative ions formed from (C 3 H 3 )Co(CO) 2 , (C 3 H 3 Mn(CO) 3 and (C 3 H 3 )V(CO) 4 upon electron impact in the mass spectrometer have been investigated. Separation of the carbonyl groups in preference to the cyclopentadienyl ring system from the remainder of the molecular ion was found to occur. Ionization potentials of 8.3 ≠ 0.2, 8.3 ≠ 0.4 and 8.2 ≠ 0.3 eV were determined for cyclopentadienylcobalt dicarbonyl, cyclopentadienylmanganese tricarbonyl and cyclopentadienylvanadium tetracarbonyl, respectively. A discussion of the probable processes of ionization and dissociation, consistent with the observed energetics, is presented and the thermochemical data for D [(C 3 H 3 )-M + ] and D [(C 3 H 3 )-M + ] are considered.

Unimolecular Decomposition of Negative Ions Formed from the Transition‐Metal Carbonyls of Ni, Fe, Cr, Mo, and W

Negative‐ion mass spectra and dissociative electron‐capture energetics for the principal metal‐containing ions have been determined for nickel tetracarbonyl, iron pentacarbonyl, chromium hexacarbonyl, molybdenum hexacarbonyl, and tungsten hexacarbonyl. These data are utilized in the first application of the statistical theory of mass spectra to describe the unimolecular decompositions of negative ions. The mechanism proposed for the formation of the various M(CO)x− ions is an ion‐pair production process followed by a series of consecutive ionic‐unimolecular decomposition reactions involving the elimination of CO groups.

Ionization and fragmentation of dimethylzinc, trimethylaluminum, and trimethylantimony☆

Ionization and appearance potentials determined with a time-of-flight mass spectrometer are reported for the principal positive ions in the mass spectra of dimethylzinc, trimethylaluminum, and trimethylantimony. The heats of formation, deduced by the application of the experimentally determined energetics and additional thermochemical data, have been listed for the principal positive ions of the three metal alkyls. The observed ionization potentials for Zn(CH3)2 (8.86±0.15 eV), Al(CH3)3 (9.09±0.26 eV), and Sb(CH3)3 (8.04±0.16 eV) are compared to the ionization potentials reported previously for methyl-substituted metal compounds. Additionally, the ionization potentials of the following radicals have been estimated: Zn(CH3) ⋍ 9.2 eV; Al(CH3)2 ⋍ 6.6 eV; AlCH3 ⋍ 7.8 eV; Sb(CH3)2 ⋍ 7.7 eV; and SbCH3 ⋍ 9.4 eV.