Influence of Coordination to Silver(I) Centers on the Activity of Heterocyclic Iodonium Salts Serving as Halogen‐Bond‐Donating Catalysts

Abstract

Kinetic data based on the 1H NMR monitoring and computational studies indicate that in a solution pyrazole‐containing iodonium triflates and silver(I) triflate bind each other, and such an interplay results in the decrease of the total catalytic activity of the mixture of these Lewis acids compared to the separate catalysis of the Schiff condensation, the imine–isocyanide coupling, or the nucleophilic attack on a triple carbon–carbon bond. Moreover, the kinetic data indicate that such a cooperation with the silver(I) triflate results in prevention of decomposition of the iodonium salts during the reaction progress. XRD study confirms that the pyrazole‐containing iodonium triflate coordinates to the silver(I) center via the pyrazole N atom to produce a rare example of a pentacoordinated trigonal bipyramidal dinuclear silver(I) complex featuring cationic ligands.

Halogen bonded associates of iodonium salts with 18-crown-6: does structural flexibility or structural rigidity of the σ-hole donor provide efficient substrate ligation?

“…Although both cyclic and acyclic iodonium salts previously exhibited excellent titration curves during the study of their binding with a series of simple nucleophiles in protic and aprotic solvents, 4,5,7,8 the titration of 18-crown-6 with 1 OTf or 2 OTf exhibited some peculiarities. Thus, in CD 3 CN, the titration of 18-crown-6 with cyclic 2 OTf showed points excellently fitted by the approximation curve (Fig.…”

“…Diaryliodonium salts play an important role in modern organic chemistry due to their useful applications in synthetic organic chemistry as reactive arylating agents and noncovalent electrophilic organocatalysts. 1 In particular, iodonium salts effectively catalyze important transformations such as Mannich, 2 Michael, 3 and Groebke–Blackburn–Bienaymé 4–6 reactions, as well as Knoevenagel, 7 Knorr-type 8 and Schiff condensations, 9 Ritter-type solvolysis, 10,11 the Diels–Alder reaction, 3,11,12 living cationic polymerization, 13 and other reactions. 14–16 Such catalytic activity is provided via the availability of a region with a positive electrostatic potential (σ-hole) in the iodine( iii ) center, which serves as a labile coordination vacancy capable of ligating reaction substrates.…”

Chalcogen- and Halogen-Bond-Donating Cyanoborohydrides Provide Imine Hydrogenation

“…Although, in early works, some catalytic effect was observed for noncharged XB and ChB donors, , the cationic σ-hole donors exhibit a significantly higher catalytic activity (Figure ). For XB donors, it has been demonstrated that iodoazoliums − and iodopyridiniums featuring an exocyclic iodine­(I) center effectively catalyze an extensive series of organic transformations, whereas hypervalent iodine­(III) species (iodonium salts) possess even a greater catalytic activity than the iodine­(I) derivatives. − For ChB donors, recent publications unambiguously indicate that telluronium salts (R 3 Ch + X – , Ch = Te IV ) exhibit a significantly higher Lewis acidity compared to the tellurium­(II) derivatives and lighter chalcogen­(IV)-derived species, − whereas selenonium salts (Ch = Se IV ) have a higher , or comparable catalytic activity than their sulfonium analogues (Ch = S IV ), which, in turn, exhibit a sufficient catalytic activity toward a series of model organic transformations. , …”

4,5-Diiodo-1-H-imidazole-derived linker ligand and Cu(i) and Co(ii) coordination polymers based thereupon

“…While keen interest in this area is mostly driven by fundamental considerations, there are also many examples demonstrating that XBs can be utilized as a tool for “fine tuning” of certain useful properties. These include (but not limited to) their application in sensors, 4–6 luminescence, 7–11 catalysis, 12–17 magnets, 18,19 etc.…”