Review article

Intramolecular Cyclization Reactions in Haloalkyl-Cobalt Complexes with Macrocyclic Equatorial Ligands

Renata Dreos orcid.org/0000-0001-6469-4126 ; Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, 34127, Trieste, Italy
Lucio Randaccio ; Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, 34127, Trieste, Italy
Patrizia Siega orcid.org/0000-0003-1700-6380 ; Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, 34127, Trieste, Italy
Višnja Vrdoljak orcid.org/0000-0002-8422-1075 ; Laboratory of General and Inorganic Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia

Abstract

Organocobalt complexes containing axial haloalkyl groups afford metallacycles of different size by N or O alkylation of the macrocyclic equatorial ligands. The reaction mechanism involves the intra-molecular nucleophilic attack of a negatively charged atom of the equatorial ligand on the axial XCH₂ haloalkyl group with simultaneous detachment of a halide ion, X−. In imino/oxime and amino/oxime derivatives, the generation of the negatively charged nitrogen requires the abstraction of a proton and the reaction occurs only in alkaline medium. In bis(dimethylglioximato) and Schiff base complexes, a negatively charged oxygen is present in the equatorial ligand and the reaction occurs even in neutral medium. Three-, six- and seven- membered metallacycles are obtained, with the common feature that the Co–C bond is shorter and more resistant toward homolysis than in parent complexes or in closely related derivatives.
Keywords:

Keywords

intramolecular metallacyclization; haloalkyl-cobalt; reaction mechanism; X-ray structures

Hrčak ID:

39692

URI

https://hrcak.srce.hr/39692

Publication date:

15.7.2009.

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