Yurii S. Nekrasov

Metastable ion study of substituted cyclopentadienylmanganese cations in the gas phase

The behavior of some substituted cyclopentadienylmanganese ions has been studied by tandem mass spectrometry. This metastable ion study showed that only C5H5Mn+ and (C5H4CN)Mn+ ions retain their nido-cluster structure (1), which is characterized by a simple metal-ligand bond cleavage. Other substituted ions, RXC5H4Mn+, rearrange to a different extent, depending on the nature of the substituent. The first rearrangement step is R radical migration to the central metal atom, leading to RMnC5H4X+-type ions (2). These ions decompose by elimination of X (for X=CO) or with formation of RMnX+, but further rearrangements can also occur. These are the reverse migration of R from the metal atom to the π-ligand (for R=H, Ph) and cyclopentadienyl ring expansion (for X=CH2). Collisional activation mass spectra contained an Mn+ ion peak, which can indicate the existence of stable type 1 structures for most cyclopentadienylmanganese ions. Carboxyl and hydroxymethyl derivatives exist, presumably as ions of type 2. The neutralization-reionization mass spectra of RXC5H4Mn+ ions are also discussed.

Fragmentation of μ4-oxohexa-μ-nitratotetraberyllium, Be4O(NO)3)6, under electron impact

Abstract The behaviour of Be4O(NO3)6 under electron impact is similar to that of its carboxylato analogues, Be4O(RCO2)6 where R is H, alkyl or halogenated alkyl. In all these systems, the dissociation of the molecular ions is dominated by steric interactions. The major fragmentations involve the elimination of N2O5 or (RCO)2O and Be(NO3)2 or Be(RCO2)2 from the ions [M-NO3]+ or [M-RCO2]+. The results obtained confirm the structural similarity of the nitrato complex to tetra-nuclear beryllium oxocarboxylates.

The structure of C5H5RFe+ (R = F, Cl, Br, I, O, OH, OCH3, C6H5, H) ions in the gas phase and the generation of their neutral counterparts by neutralization-reionization mass spectrometry

The structure of C5H5FeR+· ions was studied by tandem mass spectromerry that included the neutralization-reionization (NR) method. Halogen-containing species (R = F, Cl, Br, I) showed fragmentation that was consistent with a structure that has the cyclopentadienyl ring and R as separate ligands at the metal atom (structure A). This structure also was identified for C5H5FeO+ and CpFeOH+· ions, but these species also easily isomerized to metal-cyclopentadiene structure, RC5H5Fe+· (B), followed by hydrogen rearrangement(s) and CO loss. B was the dominant structure of C5H5FeH+· and C5H5FeC6H5+· ions. All ions that have structure A showed recovery signals in their NR mass spectra that indicated that their stable neutral counterparts were generated. The NR mass spectra also provided complementary information about the structure of ions before neutralization and after reionization.

Fragmentation of group IV metal tetranitrates and oxovanadium nitrate under electron impact

Abstract The mass spectra of TI(NO3)4, Zr(NO3)4, Hf(NO3)4, Sn(NO3)4 and VO(NO3)3 are reported. The heaviest ions in all the spectra are those formed by the loss of one NO3 group from the molecular ions. Further fragmentation involves change of metal or nitrogen valences. Splitting off of nitrogen reduction products is accompanied by the formation of fragment ions with peroxo structures.