Metal complexes of meso-tetra-(p-chlorophenyl)porphyrin and meso-tetra-(p-bromophenyl)porphyrin: Tl[(p-Cl)4tpp](OAc) and In[(p-X)4tpp](OAc) [X = Cl, Br, tpp = 5,10,15,20-tetraphenylporphyrinate]

Article abstract of DOI:10.1016/S0277-5387(03)00330-9

The crystal structures of acetato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III) Tl[(p-Cl)₄tpp](OAc) (1), acetato-[mesotetra(p-chlorophenyl)porphyrinato]indium(III) In[(p-Cl)₄tpp](OAc) (2) and acetato-[meso-tetra(p-bromophenyl)porphyrinato]indium(III) In[(p-Br)₄tpp](OAc) (3) were determined. The coordination sphere around the Tl³⁺ ion in 1 is described as six-coordinate distorted square-based pyramid in which the apical site is occupied by a chelating bidentate OAc^- group, whereas for the In³⁺ ion in 2 and 3, it is a five-coordinate regular square-based pyramid in which the unidentate OAc^- ligand occupies the axial site. The plane of the four pyrrole nitrogen atoms [i.e. N(1)-N(4)] strongly bonded to Tl³⁺ (or In³⁺) is adopted as a reference plane 4N. The Tl³⁺ is moderately out of the 4N plane; its displacement of 0.69 ? is in the same direction as that of the acetate oxygen for 1. The In³⁺ are located at 0.57 ? from its 4N plane for 2 and 3. The free energy of activation at the coalescence temperature T_c for the intermolecular acetate exchange for 1 in CD₂Cl₂ is found to be ΔG₂₀₀^≠ = 42.54 kJ mol^-1 whereas the intermolecular OAc^- exchange for acetato-[meso-tetra(p-bromophenyl)porphyrinato]thallium(III) Tl[(p-Br)₄tpp](OAc) (4) in CD₂Cl₂ is determined to be ΔG₂₀₀^≠ = 42.46 kJ mol^-1 through ¹H NMR temperature-dependent measurements. Moreover, the two oxygen atoms of the acetato group for 2 and 3 are asymmetrically and chelating bidentately bound to the indium atom in CD₂Cl₂ (or CDCl₃) solvent.