SEARCH

SEARCH BY CITATION

Keywords:

  • Macrocyclic ligands;
  • Polymers;
  • Rare earths;
  • Hydrides

Abstract

Hydrogenation of the neutral bis(allyl) complexes of the early lanthanides [Ln(Me3TACD)(η3-C3H5)2] [(Me3TACD)H = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, Me3[12]aneN4] with phenylsilane gave the tetranuclear octahydrido complexes [Ln(Me3TACD)(μ-H)2]4 [Ln = Ce (1-Ce), Pr (2-Pr)] or the dinuclear allyl/hydrido complexes [Ln(Me3TACD)(η3-C3H5)(μ-H)]2 [Ln = Nd (3-Nd), Sm (4-Sm)], which were isolated and characterized. The structures of 1-Ce and 2-Pr are constructed of a tetrahedral Ln4H8 core. Single-crystal X-ray diffraction analyses of 3-Nd and 4-Sm revealed a C2 symmetric planar Ln2H2 core. The experimental structures agreed with the results of DFT calculations, which predict that the nuclearity of the dihydrido complexes depend on the ionic radius of the metal. Compounds 1-Ce, 2-Pr, 3-Nd and 4-Sm were tested as catalysts in the copolymerization of cyclohexene oxide with CO2 to give highly carbonate-linked copolymers with moderate activities.