Two new three-dimensional chromium(III) dicarboxylate, MIL-105 or Cr-III(OH)center dot{O2C-C-6(CH3)(4)-CO2}center dot nH(2)O, have been obtained under hydrothermal conditions, and their structures solved using X-ray powder diffraction data. Both solids are structural analogs of the known Cr benzenedicarboxylate compound (MIL-53). Both contain trans corner-sharing CrO4(OH)(2) octahedral chains connected by tetramethylterephthalate di-anions. Each chain is linked by the ligands to four other chains to form a three-dimensional framework with an array of 1D pores channels. The pores of the high temperature form of the solid, MIL-105ht, are empty. However, MIL-105ht re-hydrates at room temperature to finally give MIL-1051t with pores channels filled with free water molecules (It: low temperature form; ht: high temperature form). The thermal behaviour of the two solids has been investigated using TGA. Crystal data for MIL-105ht: monoclinic space group C2/c with a = 19.653(1) angstrom, b = 9.984(1) angstrom, c = 6.970(1) angstrom, beta = 110.67(1)degrees and Z = 4. Crystal data for MIL-1051t: orthorhombic space group Pnam with a = 17.892(1) angstrom, b = 11. 165(1) angstrom, c = 6.916(1) angstrom and Z = 4. (C) 2006 Elsevier Ltd. All rights reserved.