Structure and dynamic behavior of CF3CO2− in solution with a previously unknown η2 chelation mode to silver(I) in [Ag2(2-NCH2C6H5NCTPP)2]2+·[Ag2(O2CCF3)4]2−

Reaction of N-confused porphyrin 2 (2-NCH2C6H5NCTPPH) with silver(I) trifluoroacetate in CH3CN gave a good yield of the related silver(III) complex [Ag2(2-NCH2C6H5NCTPP)2]2+·[Ag2(O2CCF3)4]2− (3). The oxidation state of the central metal in complex 3 was inferred from the diamagnetic NMR spectrum. The square-planar structure of this Ag(III) complex was elucidated by X-ray single-crystal analyses. X-ray diffraction analysis shows that the anion of complex 3, (3A; [Ag2(O2CCF3)4]2−), contains two different bonding modes of the fluorocarboxylate to the Ag atoms, including the first example of the terminal bidentate η2 mode. The free energy of activation at the coalescence temperature Tc and thermodynamic parameters for the isomerization process between the form I (windmill) isomer of 3A, I(3A), and the form II (paddlewheel) isomer of 3A, II(3A), in CD2Cl2 solvent of the disilver compound is found to be ΔG221≠=9.29kcal/mol and ΔH = −257 cal/mol, respectively, through 19F NMR temperature-dependent measurements.

Graphical abstractThis work reports the X-ray crystal structure of one new diamagnetic silver inverted complex, 3-Ag(III,I). Dynamic 19F NMR spectra of the trifluoroacetato group in the anion of 3 (i.e., 3A) reveals that this group undergoes an intermolecular and isomerization exchange for the I(3A) ⇋ II(3A) process in CD2Cl2 solvent.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The 3A contains two different bonding modes of the fluorocarboxylate to Ag atoms. ► Two isomeric forms (I, windmill; II, paddlewheel) exist for 3A complexes in solution. ► The isomerization between which is assisted by trifluorocarboxylate shift. ► ΔG221≠=9.29kcal/mol and ΔH = −257 cal/mol for the isomerization process are determined.