Acetylene complexes, mass spectra

In the mass spectrum of the cycloheptadienol complex (CXIII), dehydrogenation, dehydration, and elimination of acetylene occur and compete with stepwise loss of carbonyl groups from the molecular ion (119). 

The mass spectrum of cyclooctatetraeneiron tricarbonyl shows stepwise loss of the three carbonyl groups from the molecular ion, followed by elimination of acetylene giving C6H6Fe+, and further breakdown gives Fe+ (119). The mass spectra of two substituted cyclooctatetraene complexes (see Table VIII) show the molecular ion and stepwise loss of the carbonyl groups (83). 

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