Synthesis of Partially Fluorinated Alkyl Triflates by Electrochemical Fluorination (Simons Process)

A scalable straightforward synthesis of monofluoro- and difluoromethyl triflate CF3 SO2 OCH2 F (MH2F ) and CF3 SO2 OCHF2 (MHF2 ) through electrochemical fluorination (ECF, Simons process) of methyl triflate MH3 in anhydrous hydrogen fluoride at nickel anodes is presented. The ECF method is also feasible for the preparation of the deuterated analogues CF3 SO2 OCD2 F (MD2F ) and CF3 SO2 OCDF2 (MD2F ). Surprisingly, no H/D exchange occurs during ECF of CF3 SO2 OCD3 (MD3 ); this provides further evidence for a NiF3 /NiF4 -mediated ECF mechanism. The ECF of selected partially fluorinated ethyl triflates is described, and electrochemical fluorination of CF3 SO2 OCH2 CF3 (EH2F3 ) leads to the until now unknown chiral CF3 SO2 OCHFCF3 (EHFF3 ). The analogous fluoromethyl and fluoroethyl nonaflates are also accessible by ECF. This study contains detailed spectroscopic, structural, and thermal data on (fluoro)methyl and fluoro(ethyl) triflates.

Monitoring dynamic pre-crystallization aggregation processes in solution by VT-DOSY-NMR spectroscopy

Equimolar mixtures of pyridine (Py) with para-halotetrafluoropyridine (BrTFP and ITFP) were investigated by VT-diffusion NMR experiments. The formation of a halogen-bond-stabilized ITFP·Py complex was detected upon cooling a solution in methylcyclohexane-d₁₄ to 260 K; this allows monitoring a halogen-bond-driven aggregation process preceding crystallization in solution.

Very close I⋯As and I⋯Sb interactions in trimethylpnictogen-pentafluoroiodobenzene cocrystals

The unusually short, for any experimentally characterized molecular (co)crystal, directional C–I⋯As and C–I⋯Sb halogen bonds have been engineered in the supramolecular reactions of the in situ cocrystallized (CH3)3E (E = As or Sb) with C6F5I.

Two-dimensional halogen-bonded organic frameworks based on the tetrabromobenzene-1,4-dicarboxylic acid building molecule

2D halogen-bonded organic frameworks were readily engineered by strong and directional effects of the primary Br⋯O and the secondary Br⋯π halogen bonding interactions from the tetrabromobenzene-1,4-dicarboxylic acid building molecule involving 100% supramolecular yields.

Four-Center Nodes: Supramolecular Synthons Based on Cyclic Halogen Bonding

The isocyanide trans-[PdBr₂ (CNC₆ H₄ -4-X')₂ ] (X'=Br, I) and nitrile trans-[PtX₂ (NCC₆ H₄ -4-X')₂ ] (X/X'=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four-center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C-X'⋅⋅⋅X-M halogen-bonding contacts and include one Type I M-X⋅⋅⋅X-M interaction, thus giving the rhombic-like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6-2.9 kcal mol^-1 .