Protonated Cyanogen Fluoride. Structure, Stability, and Reactivity of (FCN)H⁺ Ions

Abstract

Gaseous (FCN)H+ ions were obtained by protonation of cyanuric fluoride by strong Brønsted acids such as H3 + (D3 +) and C n H5 + (n = 1, 2), and their structure and reactivity were examined by FT-ICR mass spectrometry and computational methods at the G2 level of theory. The results show that FCNH+ is considerably more stable than the HFCN+ protomer, the gap amounting to 360 kJ mol-1 at the G2 level. The gas-phase basicity (GB) of FCN was estimated by “bracketing” experiments by measuring the efficiency of H+ transfer from FCNH+ to reference bases. Utilizing a general correlation between the rate and the ΔG° change of the proton-transfer we obtain GB(FCN) = 668.4 ± 10 kJ mol-1, to be compared with the G2 computed GB of 651.8 ± 8 kJ mol-1, both values being referred to N protonation. The reactions of FCNH+ with isolated (C2H4) and conjugated (C6H6) π systems were also investigated. The ion behaves as a FC+ = NH electrophile promoting aromatic cyanation, e.g., yielding C6H5CNH+ from benzene. Consideration is given to the reaction mechanism and its correlation with solution-chemistry cyanation.

The reaction HCl++CF4→HCF4++Cl: Implications for the heat of formation of CF3+

“…Therefore, contrary to the earlier report, reaction ͑1͒ is not relevant to the discussion of IE(CF 3 ) or AE(CF 3 ϩ /CF 4 ). The cation ͑protonated cyanogen fluoride͒ has the linear structure F-CwN-H, 22 while the anion has the linear structure F-H¯CwN according to the present calculations. Irikura pointed out several potential problems with a few of those experiments.…”

“…More importantly, the product identification was incorrect, i.e., the reaction was found to occur by proton transfer ͓reaction ͑5͔͒ and not by charge transfer ͓reaction ͑1͔͒. We note that both the cation 22 and the anion 23 of CHNF have been observed. While reaction ͑1͒ was a major part of the argument for the lower value of ionization energy of IE(CF 3 ), there were several other measurements that supported the low value for which new data are not presented here.…”

“…Irikura pointed out several potential problems with a few of those experiments. 22 The study of the reaction of HBr ϩ with CF 4 ͑yielding CF 3 ϩ ϩBrϩHF) was also used to put an upper limit on IE(CF 3 ). The reaction of HCN ϩ with CF 4 ͓reaction ͑2͔͒ was found to proceed slowly, and an endothermicity was derived from the expression kϭk col (exp(Ϫ⌬H/kT), where k col is the collision rate constant.…”

DFT studies on vibrational spectra, HOMO–LUMO, NBO and thermodynamic function analysis of cyanuric fluoride

“…It is used as a precursor for fiber-reactive dyes, and specific reagent for tyrosine residues in enzymes, and as a fluorinating agent in organic chemistry [1][2][3][4]. Cyanuric fluoride is a highly symmetrical molecule [5][6][7]. Cyanuric fluoride is synthesized by fluorinating cyanuric chloride [8][9][10][11].…”

Comment on “Destabilization of the halogen bond in complexes of protonated NCX (X = F, Cl, Br) molecules” [Chem. Phys. Lett. 603 (2014) 37–40]

“…A Letter in this journal [2] compared the structure and properties of a series of model halogen-bonded complexes NCX· · ·Y (X = F, Cl, Br: Y = F − , FH, OH 2 , NH 3 ) with their protonated analogues H + NCX· · ·Y, obtained by attaching the proton to the N end of the linear NCX molecule. As far as we are aware, the only reported experimental study of a protonated H + NCX species is an FT-ICR mass spectrometry study of the structure, stability and reactivity of protonated cyanogen fluoride (FCN)H + ions [3].…”