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GAS-PHASE REACTIONS OF IRON(I) AND OLEFINS: MECHANISM AND ANALYTICAL APPLICATIONS (TRANSITION-METAL IONS, MASS SPECTROMETRY, DOUBLE BOND LOCATION)
Abstract
The reactions of gas-phase transition-metal ions with neutral olefins are the subject of this thesis. Activation of the allylic C-C bonds is observed for reactions of Fe('+), Ni('+), Co('+) and Cu('+) and alkenes. Upon complexation with Fe('+), olefins ranging from pentene to tetradecene rearrange to a bis(olefin) complex. These rearrangements are general, and are consistent with a mechanism that begins with addition of an allylic C-C bond to the metal ion. This is followed by abstraction of a (beta)-H atom from the resulting alkyl ligand to form a hydrido (pi)-allyl intermediate. Transfer of the H atom to the allylic fragment produces a bis(olefin) complex. The mechanism was verified by examining the structures of the alkene complexes formed by reaction of ionized Fe(CO)(,5) with olefins in a high-pressure ion source of a tandem mass spectrometer. The structures of the Fe(olefin)('+) adducts were determined by collisionally activating the ion and analyzing the decomposition products. Additional support for the mechanism was obtained by studying the structures of the decomposition products. These studies involved comparisons with reference spectra of the collisionally activated decomposition (CAD) spectra of decomposition products formed either in the ion source by bimolecular reactions or by collisional activation of stable Fe(olefin)('+) adducts, (an MS/MS/MS experiment). Rearrangements of Fe(alkyne)('+) adducts were also investigated. The reaction of Fe('+) and alkynes proceeds via oxidative addition of the propargylic C-C bond. The terminus of the (beta)-H atom was determined to be primarily the third carbon of the propargylic fragment. In contrast, for Fe(alkene)('+) adducts the (beta)-H is transferred primarily to the first carbon of the (pi)-allyl fragment. The use of transition-metal ions as chemical ionization reagents for locating multiple bonds in olefins was explored. For mixture analysis, iron(I) chemical ionization was combined with either tandem mass spectrometry or Fourier transform mass spectrometry (FTMS). Mixtures of isomers and congeners were analyzed by using multicomponent analysis of MS/MS data or by combining capillary gas chromatography and FTMS.
Subject Area
Analytical chemistry
Recommended Citation
PEAKE, DAVID ANDREW, "GAS-PHASE REACTIONS OF IRON(I) AND OLEFINS: MECHANISM AND ANALYTICAL APPLICATIONS (TRANSITION-METAL IONS, MASS SPECTROMETRY, DOUBLE BOND LOCATION)" (1986). ETD collection for University of Nebraska-Lincoln. AAI8624610.
https://digitalcommons.unl.edu/dissertations/AAI8624610