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Dehydrotropylium–Co 2 (CO) 6 Ion: Generation, Reactivity and Evaluation of Cation Stability
Author(s) -
Amiralaei Sheida,
Gauld James,
Green James R.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002685
Subject(s) - nucleophile , chemistry , reactivity (psychology) , ion , aromaticity , reactive intermediate , medicinal chemistry , computational chemistry , inorganic chemistry , organic chemistry , molecule , catalysis , medicine , alternative medicine , pathology
Abstract The dehydrotropylium–Co 2 (CO) 6 ion was generated by the action of HBF 4 or BF 3 ⋅ OEt 2 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–Co 2 (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–Co 2 (CO) 6 ion over an acyclic cation. DFT studies on the dehydrotropylium–Co 2 (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–Co 2 (CO) 6 ion is weakly aromatic.