Bifurcated Halogen Bonding Involving Diaryliodonium Cations as Iodine(III)-Based Double-σ-Hole Donors

Abstract

Three diaryliodonium tetrachloroaurates­(III), [Ar1IAr2]­[AuCl4] (Ar1/Ar2 = Ph/Ph (1), Ph/Mes (2), o-(C6H4)2 (3)), were obtained as solids (62–80%) by the metathetical reaction of [Ar1IAr2]­(CF3CO2) and H­[AuCl4]. In particular, the single-crystal X-ray diffraction studies of 1–3 revealed three-center bifurcated C–I···(Cl–Au–Cl) halogen bond (XB) and the more conventional interionic two-center C–I···Cl–Au XB. An XB with the iodine­(III) center of a diaryliodonium cation can be formed even when ∠(C–I···X) is much less than 180° (decrease by 55° in our experiments). A Cambridge Structural Database search and processing revealed other examples of bifurcated XBs involving diaryliodonium species. All recognized bifurcated XBs with diaryliodonium cations were classified and divided into two categories: “bifurcated plus two-center” and “double-bifurcated” structural types. The nature and energies of the XB interactions were studied by density functional theory (DFT) calculations and a topological analysis of the electron density distribution in the framework of the quantum theory of atoms in molecules (QTAIM) at the ωB97XD/DZP-DKH level of theory. The nature of all XB contacts is purely noncovalent, and the total energy of bifurcated XBs is generally ca. 50% higher than the energy of two-center XBs.

Orbital analysis of bonding in diarylhalonium salts and relevance to periodic trends in structure and reactivity

“…The C–Cl–C bond angle observed for 18 is almost identical to that obtained previously for phenyl(mesityl)chloronium salts containing a different tetraaryl borate counter anion (107°). 1 f However, the C–I–C bond angle obtained for 16 is larger than that obtained previously for phenyl(mesityl)iodonium tetrachloroaurate salt, 22 and may be the largest C–I–C bond angle recorded to date for a diaryliodonium salt ( cf. , 102.3° vs. 98.3°).…”

Preparation and Synthetic Applicability of Imidazole-Containing Cyclic Iodonium Salts

“…Additionally, the iodine atoms form close contacts with neighboring O4 atoms of sulfates (I1−O4 (2.552 Å)), which can be considered as yet another example of bifurcated twocentered halogen bonds. 18 The first coordination sphere of hypervalent iodine centers in 3c is close to square planar geometry, as attested to by the CCOO torsion angle, i.e., O(3)− O(4)−C(1)−C(7), of 4.35°. Generally, the crystal structure of 3c is in a good agreement with those published previously, such as carbocyclic iodonium salts.…”

Photo-sensitive hybrids constructed from diphenyliodonium and metal-thiocyanates: photo-induced structure and property transformations

“…1b). 42 The dihedral angles defined by the phenyl rings in three DPI + are 88.922 (14), 89.422 (12) and 88.142( 16)°, which are much larger than that of free DPI + in DPI•I3 (76.892°). 22 Based on the C-H⋯π interactions between DPI + cations, a DPI + dimer chain is given (Fig.…”

“…10 Additionally, the diphenyliodonium cation has an adjustable torsion angle between two benzene rings, which can play a steric template role in manipulating the structures of molecular assemblies; this is particularly significant for establishing structure-property relationships in these charge transfer complexes. [11][12][13][14][15][16] To date, DPI + -based composites are still rare, and the reported compounds involve the combination of DPI + with organic molecules, 17-20 X 3− (X = I − , Br − , Cl − ) [21][22][23][24][25][26] and halobismuthate. 11 Its co-crystallization with transition metal pseudohalides has never been reported.…”