Linear bis-Coordinate Silver(I) and Iodine(I) Complexes with R3 R2 R1 N Tertiary Amines

Abstract

Homoleptic [L-I-L]⁺ iodine(I) complexes (where L is a R₃ R₂ R₁ N tertiary amine) were synthesized via the [L-Ag-L]⁺ → [L-I-L]⁺ cation exchange reaction. In solution, the amines form [R₃ R₂ R₁ N-Ag-NR₁ R₂ R₃ ]⁺ silver(I) complexes, which crystallize out from solution as the meso-[L-Ag-L]⁺ complexes, as characterized by X-ray crystallography. The subsequent [L-I-L]⁺ iodine(I) analogues were extremely reactive and could not be isolated in the solid state. Density functional theory (DFT) calculations were performed to study the Ag⁺ -N and I⁺ -N interaction energies in silver(I) and iodine(I) complexes, with the former ranging from -80 to -100 kJ mol^-1 and latter from -260 to -279 kJ mol^-1 . The X-ray crystal structures revealed Ag⁺ ⋅⋅⋅C_π and Ag⁺ ⋅⋅⋅H-C short contacts between the silver(I) cation and flexible N-alkyl/N-aryl groups, which are the first of their kind in such precursor complexes.

Keywords: X-ray structure; coordination bonds; halogen bonds; meso; tertiary amines.