Kinetic control of the transmetalation of labile metalloporphyrins in individual and mixed solvents

Abstract

Transmetalation reactions of cadmium complexes of tetraphenylporphine (CdTPP, I) and tetra benzoporphine (CdTBP, II) in individual and mixed solvents have been investigated. For individual solvents, provided that the reaction proceeds via the same mechanism, its rate generally increases as the donor number increases in the order DMSO < DMF < PrOH 1 < MeCN (CdTPP-Zn(OAc) 2 -Solv system). On passing to the CdTPP-Cu(OAc) 2 -Solv system, the reaction rate order changes to DMSO < PrOH 1 < MeCN < DMF because the transmetalation mechanism changes from mixed to associative, as follows from the reaction order with respect to the salt being zero. The effect of the DMSO-DMF mixed solvent on the transmetalation reac tion is limited to changing the reaction rate through alteration of the stability of the [CuX 2 (Solv 1 ) n -m -2 (Solv 2 ) m ] solvated salts. The trans effect of the ligands in the solvated salts does not increase the transmetala tion rate.

Post-synthetic modifications of cadmium-based knots and links

“…Thus, we inferred that the greater stability of the Zn complexes would provide enough thermodynamic driving force for the replacement of Cd(II) by Zn(II) in the solution, and would occur if the Cd(II) complexes were not kinetically inert. 19,20 Initially, Cd-TK was mixed with different The 1 H NMR spectra corresponding to the additions of one and two equivalents of Zn(OAc) 2 reveal that the high symmetry Cd-TK complex is converted to lower symmetry species with the gradual addition of the zinc(II) salt. New peaks appear with additions of up to three equivalents of Zn(OAc) 2 .…”