Hexafluoroantimonate complexes

It was indeed found necessary to have excess antimony pentafluoride present in order to obtain stable alkylcarbonium hexafluoroantimonate complexes. Antimony pentafluoride is a liquid Lewis acid fluoride (b.p. 148-150°) of low dielectric constant (e 3), which has been shown by fluorine N.M.R. studies in the pure liquid state and in solution to exist in both cyclic and acyclic polymeric forms involving fluorine bridges. The antimony is in approximately octahedral co-ordination with predominant bridging by coordinating fluorines (Gillespie and Rothenbury, 1963). As fluorine generally does not show bridging properties, the structure of antimony pentafluoride itself indicates the very... 

Infra-red Fundamental Frequencies of Alkylcarbonium Hexafluoroantimonate Complexes and their Assignment... 

Ene Reactions. Bis(triflate) complex 2 catalyzes the ene reaction of glyoxylate esters (eq 15). Catalyst turnover was not observed at low temperature. As is the case with Diels-Alder reactions, the related bis(hexafluoroantimonate) complex is a more efficient catalyst for this transformation. 

Friedel-Crafts Alkylation Reactions. The activation of glyoxylate esters,trifluoromethyl pyruvate esters, and unsaturated a-ketoesters by catalyst 2 converts these materials into effective electrophiles for asymmetric Friedel-Crafts alkylation reactions with activated arenes (eqs 16 and 17). In fact, bis(triflate) (2) is far superior to tbe bis(hexafluoroantimonate) complex at catalyzing the enantioselective alkylation of benzene derivatives. Aniline and anisole derivatives both give the reaction, as do heterocyclic aromatic compounds such as indole and furan. 

Synthesis of isotopically labelled cationic hexafluoroantimonate complexes... 

Deuterium and carbon-13 labelled cationic hexafluoroantimonate complexes in a study of the catalytic carbonylation of methanol to acetic acid... 

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... 

The nature of the counterion has had a profound impact on catalysis, as will be seen. Structurally, it was of considerable interest to delineate the factors that influence selectivity and to examine whether the counterion plays a role in the solid-state geometry of these catalysts. While the hexafluoroantimonate copper complexes of bis(oxazoline) 55c are completely dissociated in the solid state, analogous triflate complexes exhibit weak bonding to one counterion in the apical position (2.62 A from the metal), Fig. 23. Association of the triflates in the solid state was also noted for Complex 266d. The water molecules are distorted toward the phenyl substituents, similar to the SbF6 complex 265d. 

Hexafluoroantimonate catalysts are formed from the corresponding chloride complexes. LigandCuCl2 complexes are formed by stirring the two reagents in di-chloromethane until the largely insoluble CuCl2 is completely dissolved (typically... 

The hydrated complexes 266c and 265c offer the distinct advantage of stability and ease of use. Their effectiveness as catalyst precursors in the Diels-Alder reaction has been addressed (200). A comparison of the behavior of these catalysts in the presence and absence of sieves in the reaction of acryloylimide and piperylene has revealed that the hydrated catalysts are effective precursors for this reaction. The triflate-derived catalyst 266c is ineffective unless the reaction is conducted in the presence of molecular sieves, Table IV. On the other hand, hydration does not adversely impact the performance of the hexafluoroantimonate catalyst 265c. The presence of sieves has a deleterious effect on this catalyst, leading to greatly reduced reactivity for reasons that are unclear. 

In 2000 Xumu Zhang and co-workers reported a bisphosphine complex of rhodium, [RhCl(dppb)]2, which, when used with silver hexafluoroantimonate, in some cases offers a rate advantage over the Wilkinson s catalyst/silver triflate system [28], allowing the reaction to be conducted at room temperature (Tab. 13.5). Scott Gilbertson and coworkers reported a related example, employing [Rh(dppe)(CH2Cl2)2] SbFg as a catalyst for the [5+2] reaction (Tab. 13.5, entry 5) [29]. 

The production of 1-alkenes from ethylene oligomerization was carried out with high selectivity in ionic liquids in the presence of a cationic nickel complex catalyst (ri -methallyl)-[bis(diphenylphosphino)methane-monoxide-K -P,0]nickel(II) hexafluoroantimonate, [(mall)-Ni(dppmo)]Sbp6 (240). The overall reaction rate of... 

At low temperatures in inert solvents (such as methylene dichloride) a controlled polymerization can be effected using various acids and alkylating agents. These initiators include boron trifluoride etherate, triethylaluminum, trityl hexachloroantimonate, triethylam-monium hexachloroantimonate, diethyloxonium hexafluoroantimonate, p-toluenesulfonic acid and diethylzinc or cadmium-1,2-dioI complexes. Crystalline, high molecular weight... 

The pentazolate anion. Ns (11.2), is estimated to have a half-life of 2.2 days, whereas that of the parent pentazole HN5 is predicted to be only ca 10 min in methanol at 0 Although HN5 is unknown, the cyclic anion N5 has been detected by tandem mass spectrometric studies of 4-hydroxyphenylpentazole. Similarly to its congener P5 (Section 11.2), N5 (isoelectronic with cyclopenta-dienide [C5H5] ) has the potential to form metallocene-like complexes. The acyclic (V-shaped) cation Ns has been isolated as a hexafluoroantimonate salt, which decomposes at ca 70 °C. The estimated energy density of [N5] [N5] is approximately twice that of hydrazine, a well-known rocket propellant, suggesting that this ionic polynitrogen allotrope would be an excellent monopropellant... 

Silver hexafluoroantimonate (3.4 mg) was placed in another flask under nitrogen and to this flask was added the above palladium complex solution. After being stirred for 1 h at room temperature, the mixture was Altered through a short pad of Celite under nitrogen. 

The reactions of chlorosilicon and chlorogermanium transition metal complexes with silver hexafluoroantimonate, as well as with silver tetrafluoroborate or silver hexafluorophosphate. 

The hexafluoroantimonate and hexafluoroarsenate complexes were found to be particularly stable.91 645,646 Deno et al.648 investigated solutions of carboxylic acids in sulfuric acid and oleum. They observed protonation at lower acid concentrations and dehydration, giving acyl cations, at higher acidities [Eq. (3.95)]. 

The caged species may escape geminate recombination and produce various species that can initiate cationic polymerization. Solvent (RH) often participates in these reactions producing protonic acids. As shown in Eq. (44), protonic acids are also formed by reaction of radical cations with aryl radicals or by Friedel-Crafts arylation. Up to 70% of the protonic acid is formed upon photolysis of diaryliodonium salts [205]. In addition to initiation by protons, arenium cations and haloarene radical cations can react directly with monomer. The efficiency of these salts as cationic initiators depends strongly on the counterions. Those with complex anions such as hexafluoroantimonate, hexafluorophosphate, and triflate are the most efficient. 

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