A Preparative Method for Perfluoroalkyltrifluoroborates and Perfluoroalkyldifluoroboranes

Abstract

A convenient new preparative method for the unknown class of perfluoroalkyltrifluoroborates K[C n F 2n+1 BF 3 ] and perfluoroalkyldifluoroboranes C n F 2n+1 BF 2 (n > 1) is elaborated. The perfluoroalkyl group is introduced into the boric acid ester by using C n F 2n+1 MgBr. Treatment with K[HF 2 ] and HF aq results in K[C n F 2n+1 BF 3 ] which can be defluoridated by AsF 5 to the corresponding boranes C n F 2n+1 BF 2 .

Noncoordinating Anions—Fact or Fiction? A Survey of Likely Candidates

“…Additionally it should be nontoxic, hydrolytically stable, and be easily prepared from cheap starting materials. Likely candidates are mainly reported in the patent literature; some of the recent small but robust WCAs candidates are [F 4− x B(CF 3 ) x ] − ( x =2, 3, 4),27, 112 [F 6− x P(CF 3 ) x ] − ( x =3, 4, 5),113 [F 3 P(C 2 F 5 ) 3 ] − ,108 and [B(R′) 2 ] − (R′=OC(CF 3 ) 2 C(CF 3 ) 2 O) 114. However, contradicting the expectation, larger WCAs, such as [B(Ar F ) 4 ] − ,115 [M(OR F ) 4 ] − (M=B, Al; R F =C(H)(CF 3 ) 2 etc.…”

Perfluoroalkyltricyanoborate and Perfluoroalkylcyanofluoroborate Anions: Building Blocks for Low‐Viscosity Ionic Liquids

“…K[C n F 2 n +1 BF 3 ] ( n= 1–4) were obtained from M[C n F 2 n +1 B(OMe) 3 ] (M=Li, K; n= 1–4) and anhydrous HF as reported for K[C 2 F 5 BF 3 ] . M[C n F 2 n +1 B(OMe) 3 ] were synthesised according to known procedures starting from B(OMe) 3 with CF 3 SiMe 3 , n BuLi and C 2 F 5 H, t BuLi and C 3 F 7 H, or Mg and C 4 F 9 I respectively. K[B(CF 3 ) 4 ] was synthesised as described earlier .…”

“…The physicochemical properties of RTILs with perfluoroalkyltrifluoroborate anions like [C 2 F 5 BF 3 ] − ( 2 a , Figure ) have been reported, and some anions have been studied as component in Li‐ion electrolytes . Perfluoroalkyltrialkoxyborates are valuable starting materials for perfluoroalkyl transfer reactions in organic synthesis and for the preparation of the corresponding perfluoroalkyltrifluoroborates …”

Potassium Trifluoro(organo)borates: New Perspectives in Organic Chemistry

“…With the exception of this compound, no other trifluoro(perfluoroorgano)borates had been described until very recently. The synthesis of such compounds was studied in several papers by Frohn et al,37−39 who first elaborated a convenient route to potassium trifluoro(perfluoroalkyl)borates from the easily available perfluoroalkyl iodides37 (Scheme ).…”

“…Treatment with trimethoxyborane followed by KHF 2 gave incomplete formation of trifluoroborate salts but as mixtures with fluorinated boranes of formula K[R f BF n (OMe) 3− n ]. The remaining OMe ligand could, however, be replaced by fluorine by treatment with aqueous HF 37,38. The authors assumed38 that the replacement of the OMe substituent by fluorine, a highly electron‐withdrawing group, increases the Lewis acidity of the borane and hinders the elimination of the anion MeO − .…”