Iron compounds mass spectrum

A second application of DI-MS was in the analysis of archaeological adhesive of a blackish amorphous residue present on the chape of a bronze sword, discovered in a tomb from the Iron Age (ca. 800 700 BC) at the archaeological site of Argancy (Moselle, France). In the mass spectrum (Figure 3.13) the ion fragment at mlz 189, which is characteristic of triterpenoid compounds, is evident and represents the base peak. 

The pentanuclear carbido species Ms(CO)lsC (M = Fe, Ru, Os) have been prepared. The iron compound has been known for some considerable time (209), but the ruthenium and osmium complexes were prepared recently by pyrolysis reactions (210). The ruthenium adduct was only isolated in low yield (—1%), while the osmium complex was obtained in higher yield (—40%). The infrared spectrum and mass spectral breakdown pattern indicate a common structure to these compounds. The molecular structure of the iron complex is shown in Fig. 46. 

Figure 9 Anion photoelectron spectroscopy. Its unique features are (I) Intrinsic mass selectivity and (ii) neutrals as final states. Here, as an example the results for compounds of iron, carbon and hydrogen are shown which exist in catalytic processes, high-temperature terrestrial or low-temperature astrophysical chemistry. Bottom spectrum a primary anion mass spectrum containing anions of the complexes of interest. Top spectra anion photoelectron spectra obtained by electron kinetic energy analysis after laser-induced photodetachment. They reveal the change of molecular structure and electronic energies for increasing numbers of hydrogen atoms in the complex.

Recording the mass of the moleeular ion as accurately as possible can be invaluable in proving the identity of a compound. Consider a carbonyl complex of iron that gives a molecular ion at 504 Da. As iron has a mass of 56 Da, that total mass can be fitted equally well by the formulae [Fe(CO)ie] (admittedly somewhat unlikely ), [Fe2(CO)i4], [Fe3(CO)i2], [Fe4(CO)io], [Fe5(CO)g] and so on. But with high-resolution instruments it is possible to determine the masses of ions to within 0.0001 Da, and as atomic masses are not exact integers, it is usually possible to distinguish between the various options. In our iron carbonyl example, the exact masses are 503.85366,503.79876,503.74386,503.68896, and 503.63406 Da, respectively, so it is easy to decide which formula is correct. It is always a good idea to measure the mass of the parent ion in a spectrum accurately, to check that the proposed formula is correct. 

Substituted iron carbonyl complexes ineluding Fe(C0)3 As(C6H40Me-/>)3)2 and Fe(C0)4 As(C6H40Me-/>)3) were examined by electrospray mass spectrometry (ESMS). Whereas the related compound Fe(CO>3(AsPh3)2 did not give an ESMS spectrum, the methoxy-substituted compounds did. This was attributed to the presence of protonatable methoxy groups. Both the monosubstituted and disubstituted compounds were observed in a crude... 

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