Synthesis and molecular structures of hydrotris(dimethylpyrazolyl)borate complexes of the lanthanides

The reaction of lanthanide triflates with 2 equiv of potassium hydrotris(dimethylpyrazolyl)borate (Tp(Me2)) gives good yields of complexes of composition Ln(Tp(Me2))(2)OTf. For La (2), Ce (3), Pr (4), and Nd (5) the complexes ate seven-coordinate in the solid state with the triflate group coordinated to the metal in unidentate fashion. Complex 5 crystallizes in the monoclinic space group P2(1)/c with a = 17.629(3) Angstrom, b = 12.740(2) Angstrom, c = 18.163(3) Angstrom, beta = 107.35(1)degrees, V = 3893(1) Angstrom(3), Z = 4, and R(w) = 0.0458. For the complexes of Y (1), Sm (6), Eu (7), Gd (8), Dy (9), Ho (10), and Yb (11), the smaller size of the metal ion leads to ejection of the triflate from the coordination sphere and the complexes are ionic in the solid state with a six-coordinate metal center. Complex 11 crystallizes in the monoclinic space group C2/m with a = 16.593(7) Angstrom, b = 13.671(5) Angstrom, beta = 91.66(3)degrees, V = 1983(1) Angstrom(3), Z = 2, and R(w) = 0.0416. In solution, however, complex 6 adopts a seven-coordinate molecular structure with the triflate ion within the first coordination sphere.