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.