The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(II) and Co(II) complexes with oxalate, oxamidate and dithiooxamidate bridges. - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Dalton Transactions Année : 2012

The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(II) and Co(II) complexes with oxalate, oxamidate and dithiooxamidate bridges.

Elena A Mikhalyova
  • Fonction : Auteur
Sergey V Kolotilov
  • Fonction : Auteur
Olivier Cador
Swiatoslaw Trofimenko
  • Fonction : Auteur
Lahcène Ouahab
  • Fonction : Auteur
  • PersonId : 943424
Anthony W Addison
  • Fonction : Auteur
Vitaly V Pavlishchuk
  • Fonction : Auteur
Allen D Hunter
  • Fonction : Auteur

Résumé

Six homodinuclear and two heteronuclear complexes Tp(Np)Co-C(2)O(4)-CoTp(Np) (1), Tp(Np)Co-C(2)O(4)-NiTp(Cy) (2), Tp(Cy)Ni-C(2)O(4)-NiTp(Cy) (3), Tp(Np)Co-C(2)O(2)(NH)(2)-CoTp(Np) (4), Tp(Cy)Ni-C(2)O(2)(NH)(2)-NiTp(Cy) (5), Tp(Np)Co-C(2)S(2)(NH)(2)-CoTp(Np) (6), Tp(Np)Co-C(2)S(2)(NH)(2)-NiTp(Cy) (7), Tp(Cy)Ni-C(2)S(2)(NH)(2)-NiTp(Cy) (8) (Tp(Np) = tris(3-neopentylpyrazolyl)borate, Tp(Cy) = tris(3-cyclohexylpyrazolyl)borate), were synthesized and characterized by mass spectrometry, electronic spectroscopy and X-ray crystallography. These compounds possess similar molecular structures, with the metal ions linked by bridging oxalate (1-3), oxamidate (4 and 5) or dithiooxamidate (6-8) ions. The heteronuclear nature of compounds 2 and 7 was additionally confirmed by high-resolution mass spectrometry. The magnetic properties of the Co(2+) complexes were modelled taking into account zero-field splitting of this ion, yielding D-values for Co(2+) in the range -17(1) to -50(1) cm(-1). All the metal ion pairs in compounds 1-8 are antiferromagnetically-coupled, with J values between -10.0(1) and -45.0(2) cm(-1) (via the exchange Hamiltonian Ĥ(ex.) = -2JŜ(1)Ŝ(2)) and |J| increasing in the order oxalate < oxamidate < dithiooxamidate. This tendency can be attributed to greater M-S bond covalency compared to M-N or M-O bonds (M = Co(2+) and Ni(2+)). It was found that this antiferromagnetic coupling of Co(2+) and Ni(2+) ions through oxalate is more efficient for these tris(pyrazolyl)borate complexes than for similar oxalate-bridged systems with neutral aliphatic amine ligands.
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Dates et versions

hal-00847132 , version 1 (22-07-2013)

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Elena A Mikhalyova, Sergey V Kolotilov, Olivier Cador, Matthias Zeller, Swiatoslaw Trofimenko, et al.. The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(II) and Co(II) complexes with oxalate, oxamidate and dithiooxamidate bridges.. Dalton Transactions, 2012, 41 (37), pp.11319-29. ⟨10.1039/c2dt31121f⟩. ⟨hal-00847132⟩
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