Carbonyl complexes mass spectra

The mass spectrum of Fe2(CO)9, long assumed to be completely involatile, shows a parent ion, but the base peak is Fe2(CO) J, with a structure retaining the three bridging carbonyl groups [Fe(CO)3Fe]+ (70). Similar bridged ions containing iron have been postulated in the spectra of some phosphine and sulfide complexes (Section VI). 

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). 

Photolysis of Cp Mn(CO)3 in THF leads to the solvent complex Cp Mn-(CO)2(THF). Removal of solvent at -20°C followed by warming to room temperature while maintaining reduced pressure results in dimerization of solvent complex, decarbonylation, and solvent loss to form the air-sensitive 8 (17,51,88). While not isolated, the related Cp complex 8 has been observed in the gas phase. It is seen, in the electron-impact mass spectrum of the THF complex CpMn(CO)2(THF), which shows a molecular ion and cracking pattern assignable to 8 rather than the THF complex itself (51). The rhenium complex 9 is formed on photolysis of Cp Re-(CO)3 in THF (18) and in the carbonylation (15-20 atm, THF or toluene) of Cp 2Re2(0)2(ju.-0)2 (89,90). 

Complex 159 is unstable under mass spectrometric conditions. In addition to the molecular ion and ions corresponding to carbonyl ligands loss, its mass spectrum exhibits peaks due to the dimer ion, [LMn(CO)4.]2, where L = tetraphenylarsole. ... 

The appearance of an ion corresponding to AA-Na" in the mass spectrum was the first indication of ion-complexes of the cyclopeptide. An increase of carbonyl adsorption in the presence of Na in the infrared spectra, showed that the peptide interacts with cations through its amide carbonyl groups. The stability of AA-complexes with various cations was then determined, by various physical methods with the result that it exhibits the order of preference. 

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