A “nucleophilic” iodine in a halogen-bonded iodonium complex manifests an unprecedented I+···Ag+ interaction

Nucleophilic iodonium interactions (NIIs) in 2-coordinate iodine(i) and silver(i) complexes

“…Three of the NII-complexes (3c-4c, 6c) gave Dd N shifts greater than both those reported for the only two known examples of NIIs (cf. À2.9 and 2.2 ppm), 9,10 which could be interpreted as those three NII-complexes exhibiting stronger NIIs in solution.…”

“…1). 9,10 Computational studies on the I + Á Á ÁAg + interaction indicated that it is different from an argentophilic interaction, as it is comprised of electron donation from the I + to the Ag + and notably lacks a retro-donation component, with the I + acting as a nucleophile.…”

“…1 The only two known examples of nucleophilic iodonium interactions (NIIs, indicated with a dashed red line; PF 6 anions omitted for clarity). 9,10 of ligand scrambling that was demonstrated to be a possible complication when the first examples of heteroleptic iodonium complexes were reported. 15,16 For this work, a series of silver(I) (1a-6a), iodonium (1b-6b), and 1 : 1 I + : Ag + NII-complexes (1c-6c) were synthesised from common substituted pyridines : pyridine (py; 1), 4-methylpyridine (4-Mepy; 2), 4-ethylpyridine (4-Etpy; 3), 4-isopropylpyridine (4-i Prpy; 4), N, N-dimethylaminopyridin-4-amine (4-DMAP; 5), and 2-ethylpyridine (2-Etpy; 6).…”

“…3b), and to further corroborate the recent explanation given by us for this counterintuitive I + Á Á ÁAg + noncovalent contact where the iodonium acts as electron donor in spite of bearing a formal positive charge. 9 The quantum theory of ''atoms-in-molecules'' QTAIM and the NCIplot index surface analyses were performed in both 2a and 2c dimers (for 2c the motif with the shortest Ag + Á Á ÁI + distance of 3.5184(7) Å was selected, see Fig. 3 (right)).…”

Electrophilic Aromatic Substitution: theoretical insight into halonium ion self-existence in catalytic system

“…Using semiempirical PM7 methods, we were able to discover a type of noncovalent interaction that appears to control the outcome of the experimental procedure in these systems. In the studies carried out with PM7 functionality, we have succeeded in finding and localizing interactions that were not known in the chemical community since the recently published work on the topic of the bimetallic catalytic process between the interactions between transition and main group metals [42,49]. Based on the same mechanistic principles, we have solved for the first time a stabilizing interaction between transition metal -halogen ion pair where the halogen serves as the electrophilic species, which is different from the textbook predictions at the theoretical level for this type of complexes/ catalytic species.…”