Structural Systematics of Rare Earth Complexes. XVIII (Hydrated) Mononuclear 1 : 1 Adducts of Lanthanoid(III) Chlorides with 2,2′-Bipyridine

Abstract

Room-temperature single-crystal X-ray structure determinations are recorded for a number of adducts of hydrated lanthanoid(III) chlorides with 2,2′-bipyridine, ‘bpy’, crystallized from water/ethanol solutions, which contain mononuclear arrays with 1 : 1 Ln/bpy stoichiometry. Extended isomorphous series have been defined pertinent to the heavy end of the Ln series: crystals of LnCl₃/bpy/H₂O (1 : 1 : 6) ([(bpy)Ln(OH₂)₆]Cl₃), seemingly inclusive of (at least) the range Ln = Ho(-)Lu and Y, are monoclinic, P 2₁/n, a ≈ 14·2, b ≈ 7·7, c ≈ 17·4 Å, β ≈ 91°, Z = 4, with an eight-coordinate LnN₂O₆ array; conventional R values on |F| were 0·043, 0·029, 0·057 for N_o 2435, 3120, 1846 independent ‘observed’ (I > 3σ(I)) diffractometer reflections (Ln = Ho, Lu, Y). Crystals of LnCl₃/bpy/H₂O (1 : 1·5 : 8) ([(bpy)Ln(OH₂)₆]Cl₃.½bpy.2H₂O), seemingly encompassing (at least) the range Ln = Er(-)Lu and Y, are triclinic, P 1, a ≈ 11·7, b ≈ 11·0, c ≈ 10·1 Å, α ≈ 85·8, β ≈ 74·7, γ ≈ 79·5°, Z = 2, R 0·038, 0·033, 0·048 for N_o 3897, 4377, 3130, and contain similar [(bpy)Ln(OH₂)6]³⁺ cations as does HoCl₃/bpy/H₂O (1 : 2 : 7), [(bpy)Ho(OH₂)₆]Cl₃.bpy.H₂O, orthorhombic, Pbca, a 18·02(2), b 20·06(2), c 15·051(9) Å, Z = 8, R 0·057 for N_o 3009. By contrast, only sporadic, diverse and unrelated forms are thus far defined among the lighter Ln: EuCl₃/bpy/H₂O(1 : 1 : 5) ([(bpy)Eu(OH₂)₄Cl₂]Cl.H₂O), triclinic, P 1, a 11·506(7), b 11·098(5), c 6·974(8) Å, α 77·35(7), b 85·1(1), γ 89·54(4)°, Z = 2, R 0·063 for N_o 4633, also contains a mononuclear [(N,N′-bidentate)Ln(unidentate)₆] array. PrCl₃/bpy/H₂O(1 : 1 : 3)(× 4) is a remarkable compound, being 2[(bpy)Pr(OH₂)₃Cl₃] [(bpy)(H₂O)₂Cl₂Pr(µ-Cl)₂PrCl₂(OH₂)₂(bpy)].2H₂O, triclinic, P 1, a 13·490(4), b 11·121(2), c 10·162(1) Å, α 96·06(1), β 90·08(2), γ 96·43(2)°, Z = 2 f.u., R 0·045 for N_o 4127, with a mononuclear species of PrCl₃/bpy/H₂O (1 : 1 : 3) stoichiometry and a binuclear species of 1 : 1 : 2 stoichiometry. A binuclear ethanol solvated array has been characterized for LaCl₃/bpy/EtOH (1 : 1 : 2) [(bpy)(EtOH)₂Cl₂La(µ-Cl)2LaCl₂(HOEt)₂(bpy)], with eight-coordinate lanthanum; this complex is triclinic, P 1, a 11·426(8), b 10·673(7), c 10·453(7) Å, α 109·60(5), β 113·10(5), γ 105·80(5)°, Z = 1 dimer, R 0·046 for N_o 2786.