Metal complexes of N-o-chlorobenzamido-meso-tetraphenylporphyrin: cis-Tl(N-NCO(o-Cl)C6H4-tpp)(OAc) and trans-Cd(N-NHCO(o-Cl)C6H4-tpp)(OAc) (tpp=5, 10, 15, 20-tetraphenylporphyrinate)

Abstract

The crystal structures of diamagnetic (cis-acetato) (N-o-chlorobenzamido-meso-tetraphenylporphyrinato)thallium(III)center dot 0.5 water solvate [cis-Tl(N-NCO(o-Cl)C6H4-tpp)(OAc)center dot 0.5 H2O; 3 center dot 0.5 H2O] and diamagnetic (trans-acetato) (N-o-chlorobenzamido-meso-tetraphenylporphyrinato)cadmium(II) methylene chloride solvate [trans-Cd(N-NHCO(o-Cl)C(6)H(4)APP)(OAc)center dot CH2Cl2; 4 center dot CH2Cl2] were determined. The coordination sphere around the Tl3+ (or Cd2+) in 3 (or 4) is a distorted square-based pyramid in which the apical site is occupied by a chelating bidentate OAc- group. In 3, Tl3+ and N(5) are located on the same side at 1.18 and 1.26 angstrom from it 3N plane, but in 4, Cd2+ and N(5) are located on different sides at 1.06 and -1.55 angstrom from it 3N plane. The free energy of activation at the coalescence temperature T-c for the intermolecular acetate exchange process in 3 in CD2Cl2 solvent is found to be Delta G(198)(not equal) = 42.1 kJ/mol through H-1 NMR temperature-dependent measurements. Likewise, the free energy of activation = 55.94 kJ/mol is determined for the intramolecular exchange of the ortho protons between o'-H (34, 40) and o'-H (38, 44) in 3 in CD2Cl2. VT NMR (H-1 and C-13) studies of 4 show that the acetate acts as a bidentate ligand and the OAc- exchange does not occur in CD2Cl2. Moreover, the NH proton [i.e., H(5)] of 4 in CD2Cl2 is observed as a singlet at delta -0.09 ppm with Delta v(1/2) = 13 Hz at 20 degrees C indicating that the NH protons undergo intermediate intermolecular proton exchange with water at this temperature. (c) 2010 Elsevier B.V. All rights reserved.