N-confused tetraphenylporphyrin-silver(III) complex

The synthesis, characterization, and X-ray structure of the first example of an air-stable silver(III) complex of an N-confused tetraphenylporphyrin (5,10,15,20-tetraphenyl-2-aza-21-carbaporphyrin argentate(III) or Ag(III)NCTPP, 7) is reported. Crystals of Ag(III)NCTPP·CH₂Cl₂ belong to the monoclinic space group P2₁/c (No. 14), with a = 9.038(4) Å, b = 15.097(3) Å, c = 25.578(8) Å, β = 91.32(3)°, and Z = 4. The lengths (Å) of the three silver-nitrogen and one silver-carbon bonds are inequivalent [Ag-N(1), 2.06(2); Ag-N(2), 2.08(2); Ag-N(3), 2.03(2); and Ag-C(17), 2.04(2)], reflecting the asymmetric structure of the NCTPP ligand. The very small distortion from a square planar geometry is shown in N-Ag-N and N-Ag-C angles (degrees): N(1)-Ag-N(2), 89.7(8); N(1)-Ag-N(3), 179(1); N(1)-Ag-C(17), 90.3(9); N(2)-Ag-N(3), 89.6(9); N(2)-Ag-C(17), 179(1); and N(3)-Ag-C(17), 90.9(1). The diamagnetic nature of Ag(III)NCTPP was confirmed by ¹H and ¹³C NMR and magnetic susceptibility measurements. Electrochemical and spectrochemical studies revealed that ring reduction and oxidation occur at -0.72, 1.21, and 1.50 V vs SHE, respectively. The potential role of NCTPP ligand for stabilization of higher oxidation states of metal ion is discussed.