Cations antimony

Despite many synthetic efforts no P- or As-cluster cations have been characterized in condensed phases to date, although their existence in the gas phase is well established by mass spectrometry and photoionization in combination with quantum chemical calculations (see below). Only one antimony cation is claimed in con-... 

Another propylene ammoxidation catalyst that was used commercially was U-Sb-0. This catalyst system was discovered and patented by SOHIO in the mid-1960s (26,27). Optimum yield of acrylonitrile from propylene required sufficient antimony in the formulation in order to ensure the presence of the USbaOio phase rather than the alternative uranium antimonate compound USbOs (28-30). The need for high antimony content was understood to stem from the necessity to isolate the uranium cations on the surface, which were presumed to be the sites for partial oxidation of propylene. Isolation by the relatively inactive antimony cation prevented complete oxidation of propylene to CO2. Later publications and patents showed that the activity of the U-Sb-0 catalyst is increased by more than an order of magnitude by the substitution of a tetravalent cation, tin, titanium, and zirconium (31). Titanium was found to be especially effective. The promoting effect results in the formation of a solid solution by isomorphous substitution of the tetravalent cation for Sb + within the catalytically active USbaOio- phase. This substitution produces o gen vacancies in the lattice and thus increases the facility for diffusion of lattice o gen in the solid structure. As is discussed below, the enhanced diffusion of o gen is directly linked to increased activity of selective (amm)oxidation catalysts based on mixed metal oxides. 

The syntheses of cationic bismuth clusters were described in Section 9.12. The [Bis] ion may also be obtained by oxidation of Bi using GaCls in benzene, or using AsFs. Although [Bis], [Big] and [Bi9] have been known for many years, no well-characterized example of a homopolyatomic antimony cation was reported until 2004. 

Solutions of many antimony and bismuth salts hydrolyse when diluted the cationic species then present will usually form a precipitate with any anion present. Addition of the appropriate acid suppresses the hydrolysis, reverses the reaction and the precipitate dissolves. This reaction indicates the presence of a bismuth or an antimony salt. 

Tartaric acid is noteworthy for a) the excellent way in which the majority of its salts Crystallise, and h) the frequent occurrence of salts having mixed cations. Examples of the latter are sodium potassium tartrate (or Rochelle salt), C4H40 NaK, used for the preparation of Fehling s solution (p. 525), sodium ammonium tartrate, C4H OaNaNH4, used by Pasteur for his early optical resolution experiments, and potassium antimonyl tartrate (or Tartar Emetic), C4H404K(Sb0). The latter is prepared by boiling a solution of potassium hydrogen tartrate (or cream of tartar ) with antimony trioxide,... 

My work on long-lived (persistent) carbocations dates back to the late 1950s at Dow and resulted in the first direct observation of alkyl cations. Subsequently, a wide spectrum of carbocations as long-lived species was studied using antimony pentafluoride as an extremely strong Lewis acid and later using other highly acidic (superacidic) systems. 

Xeaoa difluoride behaves as a fluoride ioa doaor toward many metal pentafluorides to form complex salts containing the XeF" and Xe2F" 2 cations (10). In reactions with the pentafluorides of arsenic, antimony, and mthenium, for example, it forms the salts Xe2F" 2AsF(, [21308-45-2], XeF" AsF(, [26024-71-5], [12528-47-1], XeF+Sbp-g [36539-18-1], [17679-45-7], [15364-10-0], [36539-19-2], [26297-25-6],... 

The only example of xenon in a fractional oxidation state, +, is the bright emerald green paramagnetic dixenon cation, Xe [12185-20-5]. Mixtures of xenon and fluorine gases react spontaneously with tiquid antimony pentafluoride in the dark to form solutions of XeF+ Sb2 F, in which Xe is formed as an iatermediate product that is subsequently oxidized by fluorine to the XeF+ cation (83). Spectroscopic studies have shown that xenon is oxidized at room temperature by solutions of XeF+ ia SbF solvent to give the XE cation (84). 

Particular drawbacks of using alkylsiHcon and alkyltin haHdes with AlCl for the cationic polymerization of terpenes are low yields and the fact that they require rigorously dried feeds (<50 ppm H2O) to be effective. Increased water content results in lower yields and lower softening points (85). Catalyst systems comprised of AlCl with antimony haHdes in the presence or absence of a lower alkyl, alkenyl, or aralkyl haHde are particularly effective in systems containing up to 300 ppm H2O (89,90). Use of 2—12 wt % of a system composed of 2—3 parts AlCl, 0.7—0.9 parts SbCl, and 0—0.2 parts of an organic... 

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

Radical cations can be derived from aromatic hydrocarbons or alkenes by one-electron oxidation. Antimony trichloride and pentachloride are among the chemical oxidants that have been used. Photodissociation or y-radiation can generate radical cations from aromatic hydrocarbons. Most radical cations derived from hydrocarbons have limited stability, but EPR spectral parameters have permitted structural characterization. The radical cations can be generated electrochemically, and some oxidation potentials are included in Table 12.1. The potentials correlate with the HOMO levels of the hydrocarbons. The higher the HOMO, the more easily oxidized is the hydrocarbon. 

Addition of carbon and fluorine can also be initiated by elettraphilic attack on a/luorinated otefin under strongly acidic conditions [250, 251, 252,253 254 255] Best known are fluoroalkylations ot tetrafluoroethylene by tertiary or highly halogenated allylic or benzylic cations in the presence of antimony pentafluoride (equation 53)... 

Vinyl and phenyl mfluoromethyl groups are reactive in the presence of aluminum chloride [10] Replacement of fluorine by chlorine often occurs Polyfluori-nated trifluoromethylbenzenes form reactive a,a-difluorobenzyl cations in antimony pentafluoride [11] 1 Phenylperfluoropropene cyclizes in aluminum chloride to afford 1,1,3-trichloro 2 fluoroindene [10] (equation 10) The reaction IS hypothesized to proceed via an allylic carbocation, whose fluoride atoms undergo halogen exchange... 

The stabilized fluorinated allylic cation, generated from cis- or trans-l-(p-methoxyphenyl)pentafluoropropene and antimony pentafluoride in sulfur dioxide, is solvolyzed by methanol to methyl 2-(p-methoxyphenyl)difluoroacrylate [36] (equation 37)... 

Polyfluoropropenes alkylate fluormated ethylenes in the presence of antimony pentafluoride This condensation proceeds by initial formation of an allyl cation [175] (equation 150)... 

Strong acids or superacid systems generate stable fluorinated carbocations [40, 42] Treatment of tetrafluorobenzbarrelene with arenesulfonyl chlorides in nitro-methane-lithium perchlorate yields a crystalline salt with a rearranged benzo barrelene skeleton [43] Ionization of polycyclic adducts of difluorocarbene and derivatives of bornadiene with antimony pentafluonde in fluorosulfonyl chloride yields stable cations [44, 45]... 

Since both Bi3+ and Sb3+ cations belong to the same group of the periodic table, the formation of antimonyl ion from antimony(III) ion upon sonication seemed to be similar to that as suggested in case of bismuth earlier, following the similar sequences of steps as under ... 

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