• Actinide Stereochemistries show similarities with the Lanthanides
  • High coordination numbers

    e.g. [Th(NO₃)₆]^2- has distorted icosahedral (C.N. = 12) geometry

    e.g. C.N. = 8, 9 are very common UF₈^2-, Th(S₂CNEt₂)₄, Th(trop)₄(H₂O)

  • Distortions from idealised stereochemistries

    e.g. PuF₆^2- is not octahedral

  • but widest range of stereochemistries is for An(IV) rather than An(III)

    {possibly because chemistry of early actinides has received most attention!}

• Complexes
  • a wide range of complexes with monodentate and chelating ligands
  • complexing ability:- [M⁵⁺] > M⁴⁺ > MO₂²⁺ > M³⁺ > MO₂⁺

    uni-negative: F^- > NO₃^- > Cl^- > ClO₄^-

    bi-negative: CO₃^2- > C₂O₄^2- > SO₄^2-

  • geometry may be strongly influenced by covalent bonding effects

    e.g. MO₂²⁺ unit is always linear Þ UO₂(h²-NO₃)₂(H₂O)₂ is hexagonal bipyramidal

• Compounds Actinide Hydrides, Halides, Oxides, Oxyhalides,...
  • for a given oxidation state show similarly diverse C.N. to Lanthanides
  • different accessible oxidation states � even greater diversity of structure
• Wide variety of oxidation states of ligands & number of oxidation states

  Þ Extraordinary range of stereochemistry in actinide complexes and compounds

Stereochemistry of Actinides in Well-Defined Complexes and Crystalline Solids

Bibliography