The `super acid' BF₃H₂O stabilized by 1,4-dioxane: new preparative aspects and the crystal structure of BF₃H₂O·C₄H₈O₂

Abstract

The crystal structure of BF3H2O·C4H8O2 – the dioxane adduct of the ’super acid’ BF3H2O – is reported along with new preparative aspects and results of 1H, 11B and 13C and 19F spectroscopic investigations. The pronounced thermal stability of the solid adduct (m.p. 128–130 °C) in com­parison to the liquid com­ponents is attributed to the chain structure established by O—H⋯O hydrogen bonds of exceptional strength taking into account the mol­ecular (non-ionic) character of the structural moieties.

Aquatrifluoridoboron–1,3-dioxolan-2-one (1/2)

“…1). The two OC(OCH 2 ) 2 molecules have an essentially identical molecular shape (slightly twisted), which also agrees well with the crystal structure determination of 1,3-dioxolan-2-one (Atterberry & Bond, 2019) (Barthen & Frank, 2019), or adducts of BF 3 and organic carbonates (Bodin et al, 2023). The F-B-F angles [110.75 (12)-112.57 (12) ] are larger than the O-B-F angles, with the angle involving F1 [109.23 (11) ] being significantly larger than the other two angles [105.47 (11) and 106.41 (12) ].…”

“…Aquatrifluoridoboron is stabilized in the solid state by hydrogen-bonding interactions with oxygen hydrogen-bond acceptors, such as 1,4-dioxane (Barthen & Frank, 2019) or crown ethers (Bott et al, 1991;Simonov et al, 1996;Fonari et al, 1997;Gelmboldt et al, 2012). In the present case, the BF 3 H 2 O molecule is hydrogen-bonded to the carbonyl oxygen atoms of the two ethylene carbonate molecules, forming a C OÁ Á ÁH-O-HÁ Á ÁO C fragment with a D 2 2 (5) graph-set motif (Etter, 1990) and OÁ Á ÁO distances of 2.5637 (15) A ˚and 2.5985 (15) A ˚(Table 1, Figs.…”

Experimental and computational study of BF3-catalyzed transformations of ortho-(pivaloylaminomethyl)benzaldehydes: an unexpected difference from TFA catalysis

“…It cannot be explained by the Brønsted acid vs. Lewis acid character of TFA and BF 3 •OEt 2 , because the transformation of the latter to boron trifluoride monohydrate (BF 3 •H 2 O) can be expected due to the water elimination in the introductory reaction steps leading to products 14 and 15 [11][12][13] and that species is considered as a strong Brønsted acid. [14][15][16][17] Similarly to the reaction sequence shown in Scheme 2, the formation of compound 14 can be rationalized by the primary formation of cation 11B (hydroxyfluoroborate salts are designated with "B" after the compound number). This cation isomerizes then via intermediate 16 to its more stable isomer 17B (contrary to the analogous reaction with TFA, where this isomerization does not occur).…”