Functionalizations hexafluorophosphate

These compounds perform a dual function in synthesis procedures. The introduction of a complex anion assists in the stabilization of the desired product and the generation of unique intermediates by chloride displacement, eg, silver hexafluorophosphate, AgPF, forms adducts with neutral diamagnetic organometaHics which can act as controUed sources of highly reactive cations (29). Silver hexafluoroantimonate, AgSbF, is an electrophilic... 

Jahn combined the formation of the enolate 2-713 resulting from an intermolecu-lar Michael addition of 2-711 and 2-712 with a radical reaction (Scheme 2.157) [363]. The enolate 2-713 did not undergo any further transformations due to the lack of appropriate functionalities. However, after formation of a radical using a mixture of ferrocenium hexafluorophosphate (2-714) and TEMPO, a new reaction channel was opened which afforded the highly substituted cyclopentene 2-715a diastereoselec-tively. 

Inter- and intramolecular hetero-Diels-Alder cycloaddition reactions in a series of functionalized 2-(lH)-pyrazinones have been studied in detail by the groups of Van der Eycken and Kappe (Scheme 6.95) [195-197]. In the intramolecular series, cycloaddition of alkenyl-tethered 2-(lH)-pyrazinones required 1-2 days under conventional thermal conditions involving chlorobenzene as solvent under reflux conditions (132 °C). Switching to 1,2-dichloroethane doped with the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) and sealed-vessel microwave technology, the same transformations were completed within 8-18 min at a reaction temperature of 190 °C (Scheme 6.95 a) [195]. Without isolating the primary imidoyl chloride cycloadducts, rapid hydrolysis was achieved by the addition of small amounts of water and subjecting the reaction mixture to further microwave irradia-... 

Pyridine-functionalized N-heterocyclic carbene Rh and Ir complexes have also been described as active precatalysts for C=0 bond TH. For example, Peris and coworkers observed the formation of metal hydrides by C—H oxidative addition of a pyridine-N-substituted imidazolium salt such as N-"Bu-N -(2-pyridylmethyl-imidazolium) hexafluorophosphate in the reaction leading to M-pyNHC complexes, that is [lr(cod)H(pyNHC)Cl] (58) [54]. Transmetallation from silver carbene... 

Formation of 1,3-dioxanes was also effected by intramolecular cyclization of suitable precursors possessing a double bond either two or three carbons away from the oxygen functional group. For example, /3-trimethylsilylethoxymethyl (SEMI-protected allylic alcohols reacted with bromonium dicollidine hexafluorophosphate (BrDCH) to 5-bromo-l,3-dioxanes in acceptable yields and with a high preference for the 4,6-tfr-addition product (Equation 83) <2000JCX32797>. 

Polymer-bound active esters 26 were prepared from a 1-hydroxyben-zotriazole (HOBt) functionalized polymer and carboxylic acids in the presence of tripyrrolidinyl-bromophosphonium hexafluorophosphate (Py-... 

The possibility that metallocenes might function as Lewis acids in Diels-Alder reactions was probed with ferrocenium hexafluorophosphate [184]. The answer is affirmative the cycloadditions studied include methacrolein, crotonaldehyde, and methyl vinyl ketone as dienophiles and butadienes and cyclopentadienes as diene components. Yields are in the range 60-80 % with reaction times of 3-36 h at 0 to 20 °C. Fair to good yields were also obtained in reactions of isoprene and cyclopentadiene with acrolein and methyl vinyl ketone in the presence of 1 % [Pd(PPh3)2(MeCN)2](BF4)2 (in CH2CI2, room temperature). Methyl acrylate resulted in low yields, and chiral modification with (5)-BINAP is reported to give the cycloadducts with modest enantioselectivity [164]. 

Schrekker H S, Stracke M P, Schrekker C M L, et al. Ether-functionalized imidazolium hexafluorophosphate ionic liquids for improved water miscibilities. Ind. Eng. Chem. Res. 2007. 46, 7389-7392. 

Figure 4. The activation energy of ferrocenium-ferrocene (Cp2Pe+/°) self-exchange in acetone (e = 20.70) as the function of electrolyte concentration, (a and ) - experimental values for tetraethylammoniym perchlorate and tetraethylammoniym hexafluorophosphate correspondingly [42], (solid and dashed line)-theoretical prediction from the AMS A theory with parameters Rd = Rb. = L = 8 A, Ri = 6 A, and ft, = 8 A, respectively [41],...

Another example of dissolving metals in ILs is linking a complex to an IL. Tan et al. synthesized a series of salen Mn(III) complexes functionalized by l-propylamine-3-methylimidazolium tetrafluoroborate ILs [180], Iida et al. have reported an interesting set of Ag-based ILs, bis(/V-2-c(hylhcxylethylenediamine) silver nitrate, [Ag(eth-hex-en)2]N03, and bis(/V-hex yI et hyI enediamine)silvertl) hexafluorophosphate, [Ag(hex-en)2]PF6 [181], which are precursors for silver nanoparticles (Fig. 8). 

Fig. 1 Diagrams depicting a a layer of a cubic sodium chloride crystal b a monoclinic 1,3-dimethylimidazolium chloride ionic-liquid crystal c two radial distribution functions (RDFs) in liquid l-dodecyl-3-methylimidazolium hexafluorophosphate. Anions and cations are depicted in red and blue. In the cases of b and c the blue circles represent the centroid of the imidazolium rings of the cations. The alternating sequences of red and blue circles in a and b as well as the two curves in phase opposition in c clearly indicate the existence and nature of the polar networks in ionic condensed phases...

Bmim-PFg (l-butyl-3-methyl-lH-imidazolium hexafluorophosphate) was used as solvent and hydemim-PF (l-(2-hydroxyethyl)-3-methyl-l H-imidazolium hexafluorophosphate) was used as functionalized ionic liquid (so-called task-specific ionic liquid) (Scheme 16.5) [94],... 

Despite the utility of chloroaluminate systems as combinations of solvent and catalysts in electrophilic reactions, subsequent research on the development of newer ionic liquid compositions focused largely on the creation of liquid salts that were water-stable [4]. To this end, new ionic liquids that incorporated tetrafluoroborate, hexafluorophosphate, and bis(trifluoromethyl)sulfonamide anions were introduced. While these new anions generally imparted a high degree of water-stability to the ionic liquid, the functional capacity inherent in the IL due to the chloroaluminate anion was lost. Nevertheless, it is these water-stable ionic liquids that have become the de rigueur choices as solvents for contemporary studies of reactions and processes in these media [5]. 

---