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)

The crystal structures of diamagnetic (cis-acetato) (N-o-chlorobenzamido-meso-tetraphenylporphyrinato)thallium(III)·0.5 water solvate [cis-Tl(N-NCO(o-Cl)C6H4-tpp)(OAc)·0.5 H2O; 3·0.5 H2O] and diamagnetic (trans-acetato) (N-o-chlorobenzamido-meso-tetraphenylporphyrinato)cadmium(II) methylene chloride solvate [trans-Cd(N-NHCO(o-Cl)C6H4-tpp)(OAc)·CH2Cl2; 4·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 Å from it 3N plane, but in 4, Cd2+ and N(5) are located on different sides at 1.06 and −1.55 Å from it 3N plane. The free energy of activation at the coalescence temperature Tc for the intermolecular acetate exchange process in 3 in CD2Cl2 solvent is found to be ΔG198≠=42.1 kJ/mol through 1H NMR temperature-dependent measurements. Likewise, the free energy of activation ΔG293≠=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 (1H and 13C) 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 δ −0.09 ppm with Δν1/2 = 13 Hz at 20 °C indicating that the NH protons undergo intermediate intermolecular proton exchange with water at this temperature.

This work reports X-ray crystals of two new diamagnetic porphyrin complexes, namely, mononuclear thallium(III) complex of cis-Tl(N-NCO(o-Cl)C6H4-tpp)(OAc) (3) and mononuclear cadmium(II) complex of trans-Cd(N-NHCO(o-Cl)C6H4-tpp)(OAc) (4).Figure optionsDownload as PowerPoint slide