N‑Heterocyclic Carbene-Ag(I)-Phosphine Complexes: Comprehensive Synthesis, Characterization, and Bonding Analysis via...

The substitution of a chloro ligand in (IPr)-Ag-Cl with aliphatic and aromatic phosphine ligands, PPh₃, PCy₃, PPh₂Py, dppf, dppm, and dppe, was investigated. Unlike gold-(I) complexes, the heteroleptic complexes, [(IPr)-Ag-PR₃]⁺, are less stable in the solution phase. The order of mixing reactants, solvent type, and reaction time plays crucial roles in obtaining the desired product. In a methanolic solution, the generated [(IPr)-Ag-(I)]⁺ ions from (IPr)-Ag-Cl are less stable compared with [(IPr)-Au-(I)]⁺ and only PCy₃ and PPh₂Py stabilize this cationic fragment in solution. In the single-crystal X-ray diffraction analysis of complexes 1 and 2, the Ag-(I) centers exhibited a linear geometry. Other forms of silver-(I) complexes containing only phosphine ligands were also formed in a solution containing the (IPr)-Ag-Cl precursor. Computational analysis of the complexes using density functional methods provided insights into the nature of electronic transitions, noncovalent interactions, and fragmental bonding contributions.