Document Type

Article

Publication Date

4-4-2011

Publication Title

Chemistry - A European Journal

Volume

17

Issue

15

First Page

4157

Last Page

4165

DOI

10.1002/chem.201002685

Keywords

aromatic compounds, carbocations, cobalt, cycloalkynes, organometallic compounds

Abstract

The dehydrotropylium–Co2(CO)6 ion was generated by the action of HBF4 or BF3OEt2 on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The reaction of the cycloheptadienynol complex via the dehydrotropylium–Co2(CO)6 ion with several nucleophiles results in substitution reactions with reactive nucleophiles (N>1) under normal conditions, and a radical dimerisation reaction in the presence of less reactive nucleophiles. Competitive reactions of the cycloheptadienynol complex with an acyclic trienynol complex show no preference for generation of the dehydrotropylium–Co2(CO)6 ion over an acyclic cation. DFT studies on the dehydrotropylium–Co2(CO)6 ion, specifically evaluation of its harmonic oscillator model of aromaticity (HOMA) value (+0.95), its homodesmotic-reaction-based stabilisation energy (≈2.8 kcal mol−1) and its NICS(1) value (−2.9), taken together with the experimental studies suggest that the dehydrotropylium–Co2(CO)6 ion is weakly aromatic.

Funding Reference Number

NSERC

Comments

This is the accepted version of the following article: Amiralaei, S.; Gauld, J.; Green, J. R. (2011) “Dehydrotropylium-Co2(CO)6 Ion. Generation, Reactivity and Evaluation of Cation Stability”, Chemistry A European Journal, 17, 4157-4165. DOI: 10.1002/chem.201002685., which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/chem.201002685/abstract. View publisher’s website at http://www.interscience.wiley.com/.

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