Stability of Ag^III towards Halides in Organosilver(III) Complexes

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Coordination Chemistry

Background:

• The emerging role of silver in two-electron oxidation states (Ag^I/Ag^III) necessitates understanding the stability of uncommon Ag^III species.
• The stability of Ag^III across the halide series in organosilver(III) complexes was previously unknown.

Purpose of the Study:

• To theoretically analyze the stability of Ag^III with a comprehensive range of halide ligands (F, Cl, Br, I, At) within the [(CF₃ )₃ AgX]^- complex framework.
• To experimentally validate theoretical predictions and characterize novel silver(III) halide and pseudohalide complexes.
• To investigate the decomposition pathways and thermal stability of these Ag^III complexes.

Main Methods:

• Theoretical analysis of Ag^III-halide bond stability.
• Experimental synthesis and isolation of halide and pseudohalide complexes: [PPh₄ ][(CF₃ )₃ AgX] (X=F, Cl, Br, I), [PPh₄ ][(CF₃ )₃ AgCN], and [PPh₄ ][(CF₃ )₃ Ag(N₃ )].
• Single-crystal X-ray diffraction for structural determination.
• Multistage mass spectrometry (MSⁿ) for gas-phase decomposition analysis.
• Thermolysis studies of bulk samples to assess thermal stability.

Main Results:

• Theoretical analysis revealed that even soft, less electronegative halides like iodide (I) and astatine (At) form stable Ag^III-X bonds.
• A series of novel halide complexes [PPh₄ ][(CF₃ )₃ AgX] (X=F, Cl, Br, I) and pseudohalide complexes were successfully synthesized and isolated, including the first silver(III) azido complex.
• Gas-phase studies confirmed the robustness of the Ag-X bond, evidenced by the formation of mixed complexes.
• Thermal stability in the solid state decreases gradually from X=F (145 °C) to X=I (78 °C).

Conclusions:

• The stability of Ag^III is compatible with a wide range of halide ligands, including heavier ones.
• The Ag-X bond in these organosilver(III) complexes is remarkably robust.
• The findings have significant implications for the development of silver-mediated and silver-catalyzed processes.