Defense Date

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Scott Gronert

Abstract

Gas phase studies of organometallic systems have provided deep insight into reaction mechanisms and reaction intermediates. In this thesis, several metal/ligand systems were examined in an effort to form metal carbenes in the gas phase. With cobalt and iron porphyrins, the carbene undergoes metal-ligand insertion. With copper bis-oxazolines, metal carbenes tend to undergo metal-ligand insertion and a Wolff rearrangement. To avoid insertions, we turned to a rigid ligand, 1, 10-phenanthroline. Under ESI conditions, a copper (I) complex with phenanthroline can be formed. When treated with diazoacetate esters, the dominant product results from addition with loss of nitrogen followed by loss of CO. This appears to be the result of a Wolff rearrangement of the metal carbene to give a metal ketene complex that spontaneously loses CO. There is no evidence of any stable metal carbenes in this reaction system. Trimethylsilyldiazomethane was also used as a carbene precursor, and its reaction with the copper phenanthroline complex gives addition with loss of nitrogen; but the product exhibits no carbene reactivity with alkenes. Here computational modeling suggests that the metal carbene undergoes a 1, 2 methyl migration, giving an exceptionally stable sila-alkene complex with the copper. As an alternative path to a metal carbene, we have used ESI to form a complex between the copper (I) phenanthroline and betaine (N, N, N-trimethylglycine). Under CID, this complex wills decarboxylates to give a copper ylide complex. Further CID leads to loss of trimethylamine and the formation of a complex between methylene and the copper phenanthroline. Depending on the CID conditions, two isobaric products are formed. One exhibits no carbene reactivity and the other readily gives carbene behavior with alkenes. The former is likely a metal-ligand insertion product, and the latter is the true metal carbene species. We explored the reactions of the carbene with electron-rich alkenes, such as ethyl vinyl ether and 3, 4-dihydro-2H-pyran, and electron-deficient alkenes, such as trichloroethylene.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2014

Included in

Chemistry Commons

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