Hydrothermal Synthesis and Characterization of Four Oxalatotitanates with Ti4O4(C2O4)8 Tetramers as Basic Building Blocks

Abstract

Four oxalatotitanates have been prepared hydrothermally in the presence of organic amine and their structures solved by means of single-crystal X-ray diffraction. The compound Ti4O4(C2O4)8·4C2N2H10·4H2O 1 crystallizes in the triclinic space group P1 with a=10.7587(7) Å, b=11.3180(7) Å, c=11.5940(8) Å, α=114.8650(10)°, β=109.2980(10)°, γ=95.7160(10)°, V=1161.07(13) Å3, Z=1, R=0.0357, wR=0.1019. The compound Ti4O4(C2O4)8·4C4N2H12·8H2O 2 crystallizes in the tetragonal space group I4(1)/a with a=13.2270(10) Å, b=13.2270(10) Å, c=32.799(4) Å, V=5738.2(9) Å3, Z=4, R=0.0529, wR=0.1496. The compound Ti4O4(C2O4)8·4C6N2H14·10H2O 3 crystallizes in the monoclinic space group P2(1)/c with a=13.1613(7) Å, b=18.2394(11) Å, c=13.8579(7) Å, α=90°, β=104.8600(10)°, γ=90°, V=3215.4(3) Å3, Z=2, R=0.0445, wR=0.1188. These compounds are all composed of Ti4O4(C2O4)8 tetramer anions and protonated organic amine cations. The fourth compound Ti4O4(C2O4)7·3C4N2H12·2H2O 4 crystallizes in the triclinic space group P1 (No. 2) with a=9.5187(13) Å, b=11.4926(15) Å, c=11.6349(15) Å, α=67.405(3)°, β=81.407(3)°, γ=66.906(3)°, V=1080.9(2) Å3, Z=1, R=0.0356, wR=0.0932. For 4, the Ti4O4(C2O4)8 tetramers are connected by sharing the oxalates as bridging ligands and form a one-dimensional chain with negative charges which are neutralized by protonated piperazine cations. The as-synthesized products are characterized by X-ray powder diffraction, IR spectroscopy, inductively coupled plasma analysis, thermogravimetric analysis, and differential thermal analysis.