MASS SPECTRA OF ORGANOMETALLIC COMPOUNDS .2. SOME CYCLOPENTADIENYLMETAL CARBONYL DERIVATIVES

Mass spectra of cyclopentadienylmetal carbonyl derivatives exhibit not only stepwise loss of their carbonyl groups but also extrusion of C2H2 from the C5H5M+ ions to give C3H3M + ions. Compounds of the type RFe(CO)2C5H5 also exhibit ions in their mass spectra arising from ferrocene and substituted ferrocene pyrolysis products. Sufficient metastable ions have been observed in the mass spectra of the iron compounds CH3COFe-(CO)2C5H5 and CH3OCOCH2Fe(CO)2C5H5 to establish degradation pathways from the molecular ion down to the bare metal ion Fe+. The mass spectra of the latter iron compound and of the related molybdenum compound C2H5OCOCH2Mo(CO)3C5H5 exhibit processes involving fragmentation of ketene (CH2CO, mass 42). This molybdenum compound as well as the iron compound C6H5COFe(CO)2C5H5 and the tungsten compound CH2=CHCOW-(CO)3C5H5 do not exhibit the parent ions in their mass spectra. Instead, the highest mass ion in their mass spectra occurs 28 mass units below the expected value for their parent ions, suggesting facile decarbonylation within the mass spectrometer. The mass spectrum of the π-allyl derivative C3H5Mo(CO)2C5H5 exhibits the carbonyl ions C3H5Mo(CO)nC5H5+ in = 1 or 2) but not the carbonyl-free allyl ion C3H5MoC5,H5+. Instead, the carbonyl-free cyclopropenyl ion C3H3MoC5H5+ is observed in high abundance. © 1968, American Chemical Society. All rights reserved.