Photoinduced Isomerization of Potassium Polyfluoroalk‐1‐enyltrifluoroborates

The UV irradition of K [RCF=CFBF₃] [R = C₄F₉ (trans), C₂F₅ (cis), C₆F₁₃ (cis), Cl (cis/trans 1 : 1)] in acetone led to cis/trans‐isomerization with a final cis/trans composition 7 : 3. In the case of R = C₄H₉ (trans) or C₃F₇O (cis/trans 25 : 75) the photoisomerization was accompanied by a partial decomposition.     

(Fluoroorgano)fluoroboranes and ‐borates. 7 [1] The Reaction of RFBF2 and K [RFBF3] (RF = perfluorophenyl‐, perfluoroalk‐1‐enyl‐ and perfluoroalkyl) with Xenon Difluoride in Anhydrous HF

The dissolution of (perfluoroorgano)difluoroboranes R_FBF₂ in anhydrous HF (aHF) resulted in equilibrium mixtures of the starting borane and different kinds of acid‐base products: [H₂F] [R_FBF₂(F · HF)] (R_F = C₆F₅, cis‐C₂F₅CF=CF, trans‐C₄F₉CF=CF) or [H₂F] [R_FBF₃] (R_F = C₆F₁₃). In aHF the aryl compounds C₆F₅BF₂ and K [C₆F₅BF₃] showed two parallel reactivities with XeF₂: xenodeborylation (formation of the [C₆F₅Xe]⁺ cation) and fluorine addition to the aryl group. In aHF perfluoroalk‐1‐enyldifluoroboranes R_FBF₂ as well as potassium perfluoroalk‐1‐enyltrifluoroborates K [R_FBF₃] (R_F = cis‐C₂F₅CF=CF, trans‐C₄F₉CF=CF) underwent only fluorine addition across the carbon‐carbon double bond under the action of XeF₂. Potassium perfluorohexyltrifluoroborate K [C₆F₁₃BF₃] did not react with XeF₂ in aHF.     

The unusual reactivity of C3F7OCFCF2 with PBu3 and the complex hydrides M[EH4] (M: Li, Na; E: B, Al); preparation of potassium perfluoro-2-propoxyeth-1-enyltrifluoroborate K[C3F7OCFCFBF3]

The nucleophilic hydrodefluorination of C₃F₇OCFCF₂ with the complex hydrides Li[AlH₄], Li[BH₄] or Na[BH₄] proceeded non-stereoselectively and was accompanied by the formation of either cis- and trans-C₃F₇OCHCFH and/or C₃F₇OCHFCF₂H. The reaction of C₃F₇OCFCF₂ with PBu₃ followed by treatment with BF₃·OMe₂ or BF₃·OEt₂ yielded [C₃F₇OCFCFPBu₃] [BF₄] (cis and trans) and, probably, [trans-Bu₃PCFCFPBu₃] [BF₄]₂. The hydrolysis of the latter with pure water proceeded quickly while the former isomeric mixture formed the isomeric olefins C₃F₇OCFCFH slowly. The usage of aqueous NaOH instead of water produced mainly trans-CHFCHF. The metallation of C₃F₇OCFCFH (cis:trans=45:55) to C₃F₇OCFCFLi and its subsequent reaction with B(OMe)₃ and K[HF₂] gave the salt K[C₃F₇OCFCFBF₃] in a different cis to trans ratio (25:75) with satisfactory yield.     

Polyfluoroorganotrifluoroborates and -difluoroboranes: interesting materials in fluoroorgano and fluoroorgano-element chemistry

The aimed introduction of the polyfluoroorgano groups (4-C₅F₄N), C₆F₁₃C₂H₄, and C₂F₅ into methoxy group-containing boron electrophiles is reported. The new compounds obtained after transformations K[(4-C₅F₄N)BF₃], (4-C₅F₄N)BF₂, K[C₆F₁₃C₂H₄BF₃], C₆F₁₃C₂H₄BF₂, K[(C₂F₅)₂B(OMe)₂], and K[(C₂F₅)₂BF₂] were isolated and characterised. Additionally some of their precursors as there are Li(4-C₅F₄N), Li[(4-C₅F₄N)B(OMe)₃], (4-C₅F₄N)B(OH)₂ and the by-products Li[(4-C₅F₄N)₂B(OMe)₂], (4-C₅F₄N)₂BOH, and K[(4-C₅F₄N)₂BF₂] are described. The usefulness of polyfluoroorganodifluoroboranes for introducing polyfluoroorgano groups into hypervalent FEF bonds is demonstrated by the synthesis of [C₆F₅(4-C₅F₄N)I][BF₄] and [p-FC₆H₄(trans-CF₃CFCF)I][BF₄].     

A well feasible and general route to (organoethynyl)difluoroboranes, RHCCBF2, and their perfluorinated analogues, RFCCBF2

A representative series of (organoethynyl)difluoroboranes RCCBF₂ (RC₄H₉, (CH₃)₃C, CF₃, C₃F₇, (CF₃)₂CF, CF₃CFCF, C₄F₉CFCF, C₆F₅) was prepared by abstraction of fluoride from the corresponding K[RCCBF₃] salts with BF₃ in appropriate solvents (1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, or dichloromethane).     

The Reactivity of Potassium Polyfluoroaryl‐, Polyfluoroalkenyl‐, and Perfluoroalkyltrifluoroborates and their Hydrocarbon Analogues towards Acids of Different Strength: A Systematic Study of the Hydrodeboration

The hydrodeboration of the (fluoroorgano)trifluoroborates K [R_FBF₃] [R_F = C₆F₅, XCF=CF (X = F, cis‐ and trans‐Cl, C₃F₇O, cis‐C₂F₅, trans‐C₄F₉, ‐C₄H₉) and C₆F₁₃] and of the organotrifluoroborates K [RBF₃] (R = C₆H₅, cis‐ and trans‐C₄H₉CH=CH, C₄H₉ and C₈H₁₇) with CH₃CO₂H (100 %), CF₃CO₂H (100 %), aqueous HF and anhydrous HF was investigated. In the alkenyltrifluoroborates K [R'CF=CFBF₃] the formal replacement of BF₃ by a proton occurred stereospecifically under retention of the configuration. The ¹⁹F NMR spectra of K [R_FBF₃] in acids indicate strong interactions of the BF₃ group with protons or acid molecules.