Hexafluorophosphate salt

Addition of hexafluorophosphate salts reduces the dediazoniation rate of 4-me-thylbenzenediazonium tetrafluoroborate in TFE/H20 (1 1) (Maskill and McCrud-den, 1992). However, as the concentration of these salts (0.12 — 0.23 M) does not affect the rate, it is evident that these salts are intercepting one of the intermediates, i.e., either the ion-molecule pair or the aryl cation. 

B. l-Bromo-2-fluorobenzene. Cautionl This step should be carried outm a hood because the PFS evolved on thermal decomposition of the diazonium salt is poisonous. The apparatus consists of a 1-1., three-necked, round-bottomed flask equipped with a thermometer, a condenser, a magnetic stirrer (optional), and a 250-ml. Erlenmeyer flask that is attached by means of a short rubber Gooch connecting tube. The dry powdered hexafluorophosphate salt is placed in the Erlenmeyer flask, and 300 ml. of heavy mineral oil is placed in the round-bottomed flask. The mineral oil is heated to 165-170° by means of an oil bath or electric heating mantle and maintained at this temperature while the salt is added rapidly in portions over a period of 30 minutes. The flask is cooled rapidly to room temperature, the side flask is removed, and 400 ml. of 10% aqueous sodium carbonate is added slowly through the condenser. The mixture is steam-distilled until no more oil is visible in the distillate. 

Using a similar protocol, Loupy and coworkers have reported the synthesis of chiral ionic liquids based on (ll ,2S)-(-)-ephedrinium salts under microwave irradiation conditions (Scheme 4.21a) [75]. Importantly, the authors were also able to demonstrate that the desired hexafluorophosphate salts could be prepared in a one-pot protocol by in situ anion-exchange metathesis (Scheme 4.21b). The synthesis and transformation of so-called task-specific ionic liquids is discussed in more detail in Section 7.4. 

Materials. The radical-type photopolymerizable formulation consisted of a mixture of hexanediol diacrylate (HDDA from UCB) and a polyurethane-diacrylate (Actilane 20 from Arkros). A bis-acylphosphine oxide (BAPO from Ciba) was used as photoinitiator at a typical concentration of 1 wt %. The cationic type photopolymerizable resin consisted of a mixture of the divinylether of triethyleneglycol (RapiCure DVE-3 from ISP) and a divinylether derivative of bis-phenol A (DVE-BPA). The cationic photoinitiator (Cyracure UVI-6990 from Union Carbide) had a composition of 50 wt % of mixed triarylsulfonium hexafluorophosphate salts and 50 wt % of propylene carbonate. The BAPO initiator... 

Synthesis of the pyridine derivative, in which the nitrogen is closest to the A-ring was also described by Simoni et al. [60], is shown in Scheme 34 and was more productive than the synthesis described in Scheme 33. The keto-compound 134 was reacted with the vinamidinium hexafluorophosphate salt (CDT-phosphate) 135, ferf-BuOK, ammonium acetate, and an equimolar amount ofDABCO (l,4diazabicyclo[2.2.2]octane). Hydrogenation using 10%... 

Tetrahydrotetrazolo[l,5- ]pyridine 52 was reacted with dimethyl sulfate to give a mixture of quaternary salts 1-methyl 53 and 2-methyl compounds 54 from which the 1-alkyl compound was separated as a crystalline hexafluorophosphate salt 53 (A = PF6) in good yield. This salt when treated with potassium hydride in the presence of 18-crown-6 and KCN underwent deprotonation to give the saturated six-membered ring 55. 

Hexafluorophosphate derivatives, such as [M(Me2SO)n][PF6]3 (M = La, Lu, Y), have been synthesized (365), and infrared data show O-bonding of the sulfoxide with ionic hexafluorophosphate groups. Analytical data are incomplete for this series, as decomposition, postulated to be to lanthanide fluorides, occurs. The (CH2)4SO complexes [M( CH2 4SO)t.5][PF6]3 are reported (145), which are 3 1 electrolytes with uncoordinated anions, implying a possible semibridged structure, as previously mentioned. Complexes of other cyclic sulfoxides, including thioxane oxide (146) and trans-1,4-dithiane-1,4-dioxide (147) derivatives of hexafluorophosphate salts have also been prepared. 

The tri(azulenyl)methane derivative 24+ including a 6-azulenyl group was prepared by the reaction of azulene 6b with diethyl 6-formylazulene-l,3-dicarboxylate. Synthesis of 24+ was accomplished by hydride abstraction with DDQ. Cation 24+ was isolated as a hexafluorophosphate salt by treatment with aqueous HPF6. The new salt is a stable, deep-green colored crystals, that can be... 

Obtained by both cyclic (100 mV s-1) and square-wave (10 Hz, Osteryoung-type) voltammetry in acetonitrile solution containing 0.1 mol dm-3 BuJNBF4 as supporting electrolyte. Solutions were 1 x 10-3 mol dm-3 in compound with reference to an Ag/Ag+ electrode (330 10 mV vs SCE) at 21 1°G b Anodic shift of the reduction waves of [57] in the presence of 1.0 equiv of the respective cationic species added as their perchlorate or hexafluorophosphate salts. "Anodic shift in the presence of 2.0 equiv of the respective cations. The second reduction wave of [57] became obscure or disappeared in the presence of more than 1 equiv of the respective cations. 

There has been significantly less exploration of the corresponding ditellur-oethers. However, by analogy to diselenoether 112, 1,5-ditelluracyclooctane 118 was prepared, and converted to ditelluradication tetrafluoroborate salt 118a (Fig. 41) as well as to the hexafluorophosphate salt. " As expected, 118 was oxidized reversibly even more readily than 112 = —0.02 V) (Table 15) and... 

The rhodium-entrapped cage compound which is formed using a stoichiometric amount of [RhCl(CO)2]2 is a notable paradigm of the rhodium-catalyzed [2-I-2-I-1] al-kyne-alkyne and CO coupling [35]. Heating 57 in acetone at 50 °C for 8 h or irradiation by a tungsten or mercury lamp provided the cage compound in 50% yield based on NMR spectroscopy. However, due to mechanical losses it was isolated in only 16% yield from the reaction mixture, by crystallization as the hexafluorophosphate salt 58 (Eq. 13). 

Hexafluorophosphate salts behave similarly.101 The diazonium tetrafluoroborates can be prepared either by precipitation from an aqueous solution by fluoroboric acid102 or by anhydrous diazotization in ether, THF, or acetonitrile using /-butyl nitrite and boron trifluoride.103 104 Somewhat milder conditions can be achieved by reaction of aryldiazo sulfide adducts with pyridine-HF in the presence of AgF or AgN03. 

The melting points and enthalpies of the three isomeric l-butyl-3-methylimida-zolium hexafluorophosphate salts [BMIMJlPFg] [47] increase with the degree of chain branching, reflecting the changes in efficiency of the crystal packing as free-rotation volume decreases and atom density is increased. The same effects are also observed for the two isomers of l-propyl-3-methyHmidazoHum hexafluorophosphate [PMlM][PFd [24]. 

Cordon, C.M. et al., Ionic liquid crystals hexafluorophosphate salts, /. Mater. Chem., 8, 2627, 1998. 

Attempts to prepare fluorothiophenes from diazonium salts (the fluoro-borate and hexafluorophosphate salts) have met only variable success. Methyl 3-fluorothiophene-2-carboxylate (32) was obtained in 89% yield by this method (Scheme 12), but the 3-diazonium salt of the corresponding 4-ester could not be isolated. Furthermore, the methyl ester of 2-diazothiophene-3-carboxylic acid coupled before decomposition could be attempted [85H(23) 1431]. 

Figure 4. Complexation of the hexafluorophosphate salt 2 PF6 by the macrocyclic polyether, dibenzo-24-crown-8 (1). The insets show (i) the N NMR spectrum of a 1 1 mixture of 1 and 2 PF6 in CD3CN at room temperature and (ii) the solid-state structure of the pseudorotaxane [l-2]+.

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