Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

Oxidation of Cobalt(ii) Bispidine Complexes with Dioxygen*

Peter Comba A B , Bianca Pokrandt A and Hubert Wadepohl A
+ Author Affiliations
- Author Affiliations

A Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 270, D-69121 Heidelberg, Germany.

B Corresponding author. Email: peter.comba@aci.uni-heidelberg.de

Australian Journal of Chemistry 70(5) 576-580 https://doi.org/10.1071/CH16674
Submitted: 30 November 2016  Accepted: 4 January 2017   Published: 10 February 2017

Abstract

Bispidine (3,7-diazabicyclo[3.3.1]nonane) ligands, derivatives of diazaadamantane, possess a very rigid backbone and have a high degree of pre-organization for cis-octahedral coordination geometries. Despite their rigidity, they exert a flexible coordination sphere, resulting in stable complexes with a variety of metal ions in various oxidation states. Due to the known high III/II redox potentials of their cobalt complexes, the CoII bispidine complexes are generally resistant to oxidation by dioxygen. Discussed in the present study are various CoII bispidine complexes with tetra- and pentadentate bispidines, with one of these complexes shown to be unstable under aerobic conditions. The decay process has been identified as an oxidative elimination of the 2-methylene pyridine substituent at one of the tertiary amine donors, resulting in picolinate, which is found coordinated to a CoIII product, where the dealkylated N-donor remains unprotonated. The mechanism of this interesting reaction has been studied, and details of the resulting structure of the product complex are discussed.


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