Asymmetric [N–I–N]⁺ halonium complexes

Abstract

The first examples of unrestrained asymmetric silver(i) and halonium complexes have been prepared and characterised.

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

“…It should be noted that, while halonium ions usually bind two identical XB acceptor moieties to form a linear and homoleptic halonium complexes, [28][29][30][31][32][33][34][35] the first heteroleptic (and therefore asymmetric) halonium solid-state complexes were also recently reported by us, 37 further increasing the potential scope of halonium ions as supramolecular synthons.…”

Iodonium complexes of the tertiary amines quinuclidine and 1-ethylpiperidine

“…Upon complexation from uncoordinated quinuclidine to [1]PF6, the three peaks in the 1 H NMR spectra were observed to shift to higher values by 0.46 ppm (α-H), 0.25 ppm (β-H), and 0.23 ppm (γ-H) (Figure 1), a consistent trend with reported NMR data from aromatic iodonium complexes. 18 However, the 15 26,27 it would indicate that the pendant ethyl substituent is not solely the cause of the observed reactivity. Complex [2]NO3 was observed to have the longest lifetime of the [2] + complexes, with observation of the iodonium complex in the 1 H- 15 N HMBC experiment being possible, and will therefore be discussed as a representative of the series.…”

“…As a consequence, these tertiary amine iodonium complexes have never been comprehensively studied in detail by modern analytical techniques. Given the recent of slew of revelations in halonium chemistry with the first unrestrained heteroleptic, [17][18][19] supramolecular, 15,[20][21][22][23] and nucleophilic interactions of iodonium complexes being reported, 1,24,25 a renewed interest in halonium ions comprised of tertiary amines is warranted. The tetrafluoroborate bromonium (Br + ) and iodonium (I + ; [1]BF4) solid-state structures of quinuclidine (quin) were reported in the 1980's, 12,13 however, no solution state data was included in either instance.…”

“…This gives reliability to the level of theory, that has been already used by us for the analysis of similar systems. 1,24,25 The natural population analysis (NPA) charges at the I-atom are given in red in Figures 4 and 5 (see also Table 1) and show that the iodine's positive charge is greater in the [I(DMAP)2] + cation than in [1] + and [2] + . This is counterintuitive taking into consideration that the I-N distance is shorter in [I(DMAP)2] + .…”

Halogen Bonds of Iodonium Ions: A World Dissimilar to Silver Coordination

“…Deviation of computational and experimental observations have previously been reported for analogous [N•••X•••N] + complexes. 30,31 Here, it is most likely the consequence of the counterions not being involved into the computations.…”