Molecular Co(III)/Fe(II) cyano-bridged mixed-valence compounds with high nuclearities and diversity of Co(III) coordination environments: Preparative and mechanistic aspects

Bernhardt, Paul V., Martínez, Manuel and Rodríguez, Carlos (2009) Molecular Co(III)/Fe(II) cyano-bridged mixed-valence compounds with high nuclearities and diversity of Co(III) coordination environments: Preparative and mechanistic aspects. Inorganic Chemistry, 48 11: 4787-4797. doi:10.1021/ic802198s


Author Bernhardt, Paul V.
Martínez, Manuel
Rodríguez, Carlos
Title Molecular Co(III)/Fe(II) cyano-bridged mixed-valence compounds with high nuclearities and diversity of Co(III) coordination environments: Preparative and mechanistic aspects
Formatted title
Molecular CoIII/FeII cyano-bridged mixed-valence compounds with high nuclearities and diversity of CoIII coordination environments: Preparative and mechanistic aspects
Journal name Inorganic Chemistry   Check publisher's open access policy
ISSN 0020-1669
1520-510X
Publication date 2009-06-01
Sub-type Article (original research)
DOI 10.1021/ic802198s
Volume 48
Issue 11
Start page 4787
End page 4797
Total pages 11
Editor Arlene Bristol
Richard Eisenberg
Place of publication Washington, DC, U.S.A.
Publisher American Chemical Society
Collection year 2010
Language eng
Subject C1
030207 Transition Metal Chemistry
970103 Expanding Knowledge in the Chemical Sciences
Formatted abstract
The kinetico-mechanistic study of the formation of discrete tri- and tetranuclear mixed-valence cyano-bridged (CoIII)2/FeII and (CoIII)3/FeII complexes has been carried out from their already described parent dinuclear CoIII/FeII and mononuclear CoIII complexes. Different CoIII encapsulating units have been used in order to tune both the redox potential on the mono- and dinuclear complexes and the lability of the mononuclear building blocks. The importance of outer-sphere precursor complex formation involving the oppositely charged reactants has been established by experiments conducted at high ionic strength where electrostatic effects are nullified. The influence of the pH is also crucial, and this has been linked to the pH dependence of the precursor CoIII/II redox potentials in terms of enabling a redox-assisted association (at low pH) between the ferricyanide analogue and the labile CoII partner. A new asymmetric CoIIIL/FeII/CoIIIL′ complex has been fully characterized, and a series of putative (CoIIIL)2/FeII/CoIIIL′ and (CoIIIL)3/FeII forms have been spectroscopically detected. A comparison with the mechanistic reaction pathways established for the formation of the parent dinuclear CoIII/FeII complexes indicates that an important tuning of the direct substitution and redox-catalyzed mechanism is applicable. For the formation of the trinuclear complexes, only in the most favorable conditions is a redox-assisted sequence observed. The rate and activation parameters for the reactions have been determined and are indicative of an essential outer-sphere precursor formation. Similarly, for reactions where redox-assisted mechanisms are unfavorable, only direct substitution processes have been found to be applicable, with their rate coefficients and activation parameters also agreeing with the expectations, once an outer-sphere precursor complex is formed. Formation of the tetranuclear (CoIIIL)3/FeII complexes has only been detected on decomposition of the parent trinuclear (CoIIIL)2/FeII complexes following reduction to their CoII form. The overall processes seem to be based on the outer-sphere association between the respective building blocks in such a way that both unfavorable redox potentials and Lewis basicities are overcome.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
ERA 2012 Admin Only
School of Chemistry and Molecular Biosciences
 
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Created: Thu, 03 Sep 2009, 18:02:21 EST by Mr Andrew Martlew on behalf of School of Chemistry & Molecular Biosciences