The chloroiron(III) complex of alpha beta alpha beta-tetramethylchiroporphyrin : FeCl(TMCP), was prepared, and its structure was determined by X-ray crystallography. Black crystals of FeCl(TMCP). 0.72CH(2)Cl(2) form in the tetragonal space group P4(3)2(1)2 with a = b = 13.245(1) Angstrom and c = 26.355(5) Angstrom at 130 K with Z = 4. The structure shows an unusual five-coordinate high-spin iron(III) center in a strongly ruffled and domed porphyrin, with short equatorial bond distances (Fe-N(av) 2.034(9) Angstrom), and the iron 0.64 Angstrom out of the porphyrin mean plane toward the chlorine atom. The solid-state magnetic moment is 5.92 mu(B) at 20 K, slightly decreasing to 5.68 mu(B) at 300 K. In solution FeCl(TMCP) can be easily transformed to FeBr(TMCP) or FeOH(TMCP). The H-1 NMR spectra of the three species are consistent with their C-2 symmetry and S = (5)/(2) spin state. The pyrroIe proton resonances are shifted downfield to 80-100 ppm at 293 K, more than in the corresponding tetraaryl derivatives. The cyclopropyl protons on C-1, alpha to the porphyrin meso position, appear at ca. 160-200 ppm, in keeping with the nearly perpendicular orientation of the C-1-H bond with respect to the porphyrin mean plane. The temperature dependence of the IH NMR spectrum of FeCl(TMCP) suggests substantial zero-field splitting.