Nine-coordinate rare earth metal complexes with aminopolycarboxylic acids: Mononuclear (NH4)3[TbIII(ttha)]·5H2O and binuclear (NH4)4[Tb 2 III (dtpa)2]·9H2O

The two title coordination compounds, (NH4)3[TbIII(ttha)]·5H2O (ttha = triethylenetetramine-N,N,N′,N″,N‴,N‴-hexaacetic acid) and (NH4)4[Tb 2 III (ttha)]·9H2O (dtpa = diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid), have been prepared and characterized by FT-IR, elemental analyses, TG-DTA and single crystal X-ray diffraction techniques. The (NH4)3[TbIII(ttha)]·5H2O compound is monoclinic, P21/c; a = 10.398(1) A, b = 12.791(1) A, c = 23.199(2) A; β = 90.914(2)°; V = 3084.9(5) A3; Z = 4; D calc = 1.704 g/cm3; µ(MoK α ) = 2.376 mm™; R = 0.023 and wR 2 = 0.049 for 5429 observed reflections with I ≥ 2σ(I). The [TbIII(ttha)]3− complex anion in the crystal has a nine-coordinate mononuclear molecular structure with pseudo-monocapped square-antiprismatic configuration. The (NH4)4[Tb 2 III (dtpa)2]·9H2O compound is triclinic, P-1; a = 9.739(1) A, b = 10.010(1) A, c = 12.968(2) A; α= 85.890(2)°, β = 77.338(2)°, γ = 77.587(2)°; V = 1204.2(2) A3; Z = 1; D calc = 1.832 g/cm3; µ(MoK α ) = 3.015 mm™; R = 0.024 and wR 2 = 0.060 for 4750 observed reflections with I ≥ 2σ(I). The [Tb 2 III (dtpa)2]4− complex anion has a binuclear structure in the crystal; the two TbIII centers are equivalent and have a nine-coordinate environment with the same pseudo-tricapped trigonal-prismatic configuration. The thermal analysis revealed that the coordination cores of the (NH4)3[TbIII(ttha)]·5H2O and (NH4)4[Tb 2 III (dtpa)2]·9H2O compounds are stable up to 221°C and 252°C, respectively.