X-ray Crystal Structure and Ligand Binding to beta-tetralos (trifluorometyl)-meso-tetraphenylporphyrin cobalt(II)
Terazono, Y., Patrick, B.O., and David Dolphin
Inorg. Chimica Acta
[2,3,12,13-Tetrakis(trifluoromethyl)-5,10,15,20-tetraphenylporphyrinato]cobalt(II) (Co(TPP(CF3)4)) was prepared. The axial ligation of pyridine to the four co-ordinate Co(TPP(CF3)4) was examined by spectrophotometric titration in CH2Cl2. The binding constant for the first ligation was found to be higher than that of Co(TPP) due to the considerable electron deficiency of the macrocyclic ligand. Determination of the binding constant for the second ligation has been unsuccessful so far due to the extremely slow reaction from the five to the six co-ordinate species. An X-ray crystal structure of the five co-ordinate species revealed a severely saddle-distorted macrocycle due to the steric interactions among the peripheral substituents. The mode of distortion and the peripheral steric interactions may be a rationale for the slow second ligation.