Linearbis‐Coordinate Silver(I) and Iodine(I) Complexes with R₃R₂R₁N Tertiary Amines

Abstract

Homoleptic [L–I–L]⁺ iodine(I) complexes (where L is a R3R2R1N tertiary amine) were synthesized via the [L–Ag–L]⁺ → [L–I–L]⁺ cation exchange reaction. In solution, the amines form [R3R2R1N‐Ag‐NR1R2R3]⁺ 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 kJmol‐1 and latter from ‐260 to ‐279 kJmol‐1. The X‐ray crystal structures revealed Ag+···Cπ 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.

Mono- and Bis-Carbonyl Hypoiodites of the Tertiary Amines Quinuclidine and DABCO

“…61,62 This level of theory has proved to excellently reproduce the molecular geometries obtained from the SCXRD studies of [N−I−N] + and R−C(O)O−I−N (hypoiodite) halogen-bonded iodine(I) complexes. 6,[17][18][19]26,27,33,38,40,45,50,57 The DFT structures generally showed excellent agreement with the experimentally determined structures, with most values falling within a ±0.01−0.03 Å range and a maximum discrepancy of 0.086 Å for the O−I bond length of 1e, though this discrepancy might have been exacerbated by the twinned data refinement of the solid-state structure of 1e (see Supporting Information). The calculated structures for 2c and 2d (2c_DFT and 2d_DFT, respectively), for which the SCXRD structures were not observed, indicated the same divergence from their quinuclidine analogues 1c_DFT and 1d_DFT, with noticeably shorter O−I and longer I−N bond lengths for the ditopic DABCO complexes, which in both cases predicted differences of ∼0.05 Å (for 1c_DFT vs 2c_DFT and 1d_DFT vs 2d_DFT).…”

“…36 On the other hand, hypoiodites of the form the RC(O)O−I−L are inherently heteroleptic in their substituents, offering a greater variety of options for modifying their substituents and ultimately tuning their properties, such as the first chiral hypoiodite complexes being recently reported based on chiral N-protected amino acids. 37 A handful of examples of [N−I−N] + iodine(I) complexes incorporating tertiary amines as the Lewis base have been synthesized, 38 though only the bicyclic tertiary amines quinuclidine (quin), 39−41 34,42 and hexamethylenetetramine (HMTA) 43 have been structurally characterized due to their relative stability in comparison to their acyclic counterparts. 40 To date, the solid-state examples of O−I−N hypoiodite complexes are limited to incorporating aromatic nitrogen-donor atom heterocycles and carboxylic acid derivatives.…”

“…A handful of examples of [N–I–N] + iodine­(I) complexes incorporating tertiary amines as the Lewis base have been synthesized, though only the bicyclic tertiary amines quinuclidine (quin), − 1,4-diazabicyclo[2.2.2]­octane (DABCO), , and hexamethylenetetramine (HMTA) have been structurally characterized due to their relative stability in comparison to their acyclic counterparts . To date, the solid-state examples of O–I–N hypoiodite complexes are limited to incorporating aromatic nitrogen-donor atom heterocycles and carboxylic acid derivatives. − With no prior examples of O–I–N hypoiodite complexes incorporating tertiary amines present in the literature, their synthesis and study are of great interest, given their potential to act as highly reactive iodination reagents.…”

Halogen Bonds of Halogen(I) Ions─Where Are We and Where to Go?

“…−15 ppm. 109 It is important to note that despite the halogen bonds of aliphatic amines being ∼50 kJ/mol stronger due to the larger Lewis basicity of these amines than those of the aromatic Lewis bases, their coordination shifts are significantly smaller. The large coordination shift of the pyridine complexes of halogen(I) ions is the consequence of paramagnetic ring currents (deshielding term), which are the result of the partial quaternary character of the nitrogen upon formation of the halogen bond.…”

“…The iodine­(I) complexes of tertiary amines show δ­( 15 N) coord of ca. −15 ppm . It is important to note that despite the halogen bonds of aliphatic amines being ∼50 kJ/mol stronger due to the larger Lewis basicity of these amines than those of the aromatic Lewis bases, their coordination shifts are significantly smaller.…”