| Abstract: | Mass spectra of alkylferrocenes and biferrocenyls have molecular ion peaks which are also base peaks. The predominant fragment ions are formed by beta-cleavage of the alkyl group. Gamma-and alpha-cleavages are the only other significant modes of alkyl side-chain fragmentation. The cleavage of the alkyl group is often accompanied or followed by the cleavage of either one or both of the cyclopentadienyl-iron bonds. Weak m/e 121 (C5H5]+) mass peaks are found in the spectra of 1,1′-dialkyl- and 1,1′-disilyl-ferrocenes. Therefore, the m/e 121 peak may not be used as a sensitive criterion to determine the presence of unsubstituted cyclopentadienyl rings. The relative intensity of the peak may, however, serve as an indicator. Expansion of the cyclopentadienyl ring to six- and seven-carbon rings in the fragmentation of alkylferrocenes, diethylbiferrocenyl and deuterated ethylferrocenes is indicated. The spectra of benzylferrocene and benzylferrocene-alpha-d2 do not show a beta-cleavage but suggest a pentalene ring formation. Methyl and phenyl groups in the beta-position of substituted ferrocenes were found to migrate to the iron atom. |
