Bimolecular Reactions of the Chromium-Benzyne Ion Cr⁺-C₆H₄ in the Gas Phase

An FT-ICR Study

authored by

Doris Wittneben, Hans Friedrich Grützmacher, Holger Butenschön, Hans Günther Wey

Abstract

The chromium-benzyne ion Cr⁺-C₆H₄ was generated in the gas phase by electron-impact-induced loss of 5 CO from (η⁶-1,2-dioxocyclobutabenzene)tricarbonylchromium(0). The gas-phase reactions of the Cr⁺-C₆H₄ ions with methanol, ammonia, several alkanes, alkadienes, and aromatic species were studied by Fourier transform ion cyclotron resonance spectrometry (FT-ICR) using an external ion source. The results show that the bimolecular reactivity of the Cr⁺-C₆H₄ cations is determined by the C₆H₄ ligand, exhibiting the high reactivity of benzyne. No reactions due to a primary reaction at Cr⁺ are discovered. In most of the reactions, the main product observed for the bimolecular reaction is Cr⁺ released from the complex by the great exothermicity of the reaction at the C₆H₄ ligand. However, in the case of less exothermic reactions and if the excess energy is removed from the reaction complex by “evaporating” a neutral leaving group, Cr⁺ complexes are observed whose ligands arise from addition reactions of the reactants to C₆H₄. This is the case for cycloadditions of benzene-d₅ and naphthalene-d₈ to Cr⁺-C₆H₄, where the adducts still containing Cr⁺ as well as ions formed by loss of acetylene-d₂ from the adducts are observed. Thus, in the family of transition-metal-cation-benzyne complexes, the Cr⁺-C₆H₄ cation is extraordinary in exhibiting reactivity exclusively at the benzyne ligand.

External Organisation(s)

Max-Planck-Institut für Kohlenforschung
Bielefeld University

Type

Article

Journal

ORGANOMETALLICS

Volume

11

Pages

3111-3116

No. of pages

6

ISSN

0276-7333

Publication date

01.09.1992

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physical and Theoretical Chemistry, Organic Chemistry, Inorganic Chemistry

Electronic version(s)

https://doi.org/10.1021/om00045a028 (Access: Unknown)