Metathetical reaction

The alkali metal tetrahydridoborates are salts those of sodium and potassium are stable in aqueous solution, but yield hydrogen in the presence of a catalyst. They are excellent reducing agents, reducing for example ion(III) to iron(II). and silver ions to the metal their reducing power is used in organic chemistry, for example to reduce aldehydes to alcohols. They can undergo metathetic reactions to produce other borohydrides, for example... 

Potassium Sulfate. Potassium sulfate is a preferred form of potash for crops that have a low tolerance for chloride. Tobacco and potatoes ate two such crops. K2SO4 is produced most often from langbeinite by metathetical reaction in aqueous solution ... 

The monofluorophosphates can be prepared by neutralization of monofluorophosphoric acid (1). Sodium monofluorophosphate [7631 -97-2] is prepared commercially (57) by fusion of sodium fluoride and sodium metaphosphate, and the potassium monofluorophosphate [14104-28-0] can be prepared similarly. Insoluble monofluorophosphates can be readily prepared from reaction of nitrate or chloride solutions with sodium monofluorophosphate. Some salts are prepared by metathetical reactions between silver monofluorophosphate [66904-72-1] and metal chlorides. 

In those cases where hydrolysis is not required, the metathetical reaction leads directiy to the product (plus magnesium hahde) in the solvent. 

In commercial manufactuie of ammonium peichloiate, sodium peichloiate can be the starting material. The ammonium ion can be contributed by such materials as ammonium chloride, sulfate, and nitrate, eg, the metathetical reaction of sodium perchlorate and ammonium chloride ... 

RM can be a traditional Grignard reagent or an organolithium, 2inc, aluminum, or mercury compound. The Grignard route is employed commercially for production of tertiary phosphines, even though these reactions are subject to side reactions. Yields are often low, eg, 40—50% for (C4H )2P prepared via a Grignard reaction (18). A phosphoms—carbon bond can form from the metathetical reaction of a phosphoms haUde and a pseudohaUde salt. 

The salts in turn may be decomposed by a metathetical reaction involving a stronger base than (+)B or stronger acid than (+)A. 

Other. Insoluble alkaline-earth metal and heavy metal stannates are prepared by the metathetic reaction of a soluble salt of the metal with a soluble alkah—metal stannate. They are used as additives to ceramic dielectric bodies (32). The use of bismuth stannate [12777-45-6] Bi2(Sn02)3 5H20, with barium titanate produces a ceramic capacitor body of uniform dielectric constant over a substantial temperature range (33). Ceramic and dielectric properties of individual stannates are given in Reference 34. Other typical commercially available stannates are barium stannate [12009-18-6] BaSnO calcium stannate [12013 6-6] CaSnO magnesium stannate [12032-29-0], MgSnO and strontium stannate [12143-34-9], SrSnO. ... 

Diaryhodostibines are usually obtained by the metathetical reaction of the chlorostibines with sodium iodide (111,112). Diphenylfluorostibine [6651-55-4] Ci2HioFSb, can be prepared from an organosiUcon species (113) ... 

Other halo- and dihaloarsines can also be prepared by suitable metathetical reactions (82). 

Metathetical reactions of pyrimidines have been studied widely over the last hundred years. Indeed, probably 90% of all known pyrimidines have been made from a relatively few pyrimidine substrates available by primary synthesis. 

This method is particularly applicable to the more reactive benzyl halides which are easily hydrolyzed in the aqueous media usually employed for the metathetical reaction with alkali cyanides. For example, anisyl chloride treated with sodium cyanide in aqueous dioxane gives, as a by-product, 5-10% of anisyl alcohol as determined by infrared analysis. The use of anhydrous acetone not only prevents hydrolysis to the alcohol but also decreases the formation of isonitriles. This method was also applied successfully by the submitters to the preparation of -chlo-rophenylacetonitrile in 74% yield. 

This method is an adaptation of that of Dengel. -Methoxy-phenylacetonitrile can also be prepared by the metathetical reaction of anisyl chloride with alkali cyanides in a variety of aqueous solvent mixtures by the nitration of phenylaceto-nitrile, followed by reduction, diazotization, hydrolysis, and methylation 1 by the reduction of ct-benzoxy- -methoxy-phenylacetonitrile (prepared from anisaldehyde, sodium cyanide, and benzoyl chloride) and by the reaction of acetic anhydride with the oxime of -methoxyphenylpyruvic acid. ... 

Although the structure of [SsN] has not been established by X-ray crystallography, the vibrational spectra of 30% N-enriched [SsN] suggest an unbranched [SNSS] (5.22) arrangement of atoms in contrast to the branched structure (Dsh) of the isoelectronic [CSs] and the isovalent [NOs] ion (Section 1.2). Mass spectrometric experiments also support the SNSS connectivity in the gas phase.Many metal complexes are known in which the [SsN] ion is chelated to the metal by two sulfur atoms (Section 7.3.3). Indeed the first such complex, Ni(S3N)2, was reported more than twenty years before the discovery of the anion. It was isolated as a very minor product from the reaction of NiCl2 and S4N4 in methanol. However, some of these complexes, e.g., Cu and Ag complexes, may be obtained by metathetical reactions between the [S3N] ion and metal halides. 

A variety of complexes of the thionyl imide anion [NSO] with both early and late transition-metal complexes have been prepared and structurally characterized. Since both ionic and covalent derivatives of this anion are readily prepared, e.g., K[NSO], McsMNSO (M = Si, Sn) or Hg(NSO)2, metathetical reactions of these reagents with transition-metal halide complexes represent the most general synthetic method for the preparation of these complexes (Eq. 7.10 and 7.11). ... 

Complexes in which two metal centres are linked by one or two [NSN] ligands, e.g., [Na(15-crown-5)]2[F5Mo( -NSN)MoF5] and Cp2Zr( -NSN)2ZrCp2, are known. The cyclic zirconium system is prepared by a metathetical reaction (Eq. 7.14). However, the formation of polymers in which metal centres are linked by NSN units has not been achieved. 

Salts of the [NSO] anion can be used for the synthesis of both transition-metal and main group element thionyl imides by metathetical reactions, e.g., Cp2Ti(NSO)2 and Ph3, .As(NSO)x (x = 1,2), respectively (Section 7.6). 

In view of the facile oxidation of 10.13a-c it is not surprising that some metathetical reactions with metal halides result in redox behaviour. Interestingly, lithium halides disrupt the dimeric structures of 10.13a or 10.13c to give distorted cubes of the type 10.14, in which a molecule of the lithium halide is entrapped by a Ei2[E(N Bu)3] monomer. Similar structures are found for the MeEi, EiN3 and EiOCH=CH2 adducts of 10.13a. In the EiN3 adduct, the terminal... 

Although redox processes are sometimes observed in metathetical reactions with metal halides, the pyramidal dianion [Te(NtBu)3] has a rich coordination chemistry (Scheme 10.8). For example, the reaction... 

Sulfinyl azides have higher thermal stability than their divalent counterparts. For example, benzenesulfmyl azides ArS(0)N3 (Ar = Ph, 4-MeCelFt, 4-NO2C6H4), which are obtained by the metathetical reaction of the sulfinyl chloride and sodium azide in acetonitrile, can be stored in the solid state at low temperatures. ... 

Conducting polymers with p-phenylene groups in the backbone can be generated by the metathetical reaction shown in Eq. 14.1. Doping of these polymers with acceptors such as h. Bra, or AsFs increases the conductivity to ca. lO " cm. ... 

Many other anions can then be introduced by metathetical reactions with the appropriate silver salt ... 

First, mention should be made of the metathetical reaction, replacing an anion of a pyrylium salt by another-, when the solubility of the latter salt is lower than that of the former, the conversion is easy. In the opposite case, one has to find a solvent in which the solubilities are reversed (perchlorates are less soluble in water than chloroferrates or iodides, but in concentrated hydrochloric or hydroidic acids, respectively, the situation is reversed For preparing chlorides which are usually readily soluble salts, one can treat the less soluble chloroferrates with hydrogen sulfide or hydroxylamine. Another method is to obtain the pseudo base in an organic solvent and to treat it with an anhydrous acid. 

The metathetic reaction occurs in the gas phase at relatively high temperatures (150°-350°C) with molybdenum or tungsten supported catalysts or at low temperature (=50°C) with rhenium-based catalyst in either liquid or gas-phase. The liquid-phase process gives a better conversion. Equilibrium conversion in the range of 55-65% could be realized, depending on the reaction temperature. ... 

The major synthetic route leading to homoleptic lanthanide tris(amidinates) and guanidinates, however, is the metathetical reaction between anhydrous lanthanide trichlorides and preformed lithium amidinates or guanidinates, respectively, in a molar ratio of 1 3. This is outlined in Scheme 69, showing a samarium(lll) guanidinate as a typical example. ... 

Titanium imido complexes supported by amidinate ligands form an interesting and well-investigated class of early transition metal amidinato complexes. Metathetical reactions between the readily accessible titanium imide precursors Ti( = NR)Cl2(py)3 with lithium amidinates according to Scheme 84 afforded either terminal or bridging imido complexes depending on the steiic bulk of the amidinate anion. In solution, the mononuclear bis(pyridine) adducts exist in temperature-dependent, dynamic equilibrium with their mono(pyiidine) homologs and free pyridine. 

Metathetical reactions between NbCl4(THF)2, NbCls, TaCls, [(Et2N)2TaCl3]2, or (R2N)3Ta(=NBu (R = Me, Et) with various amounts of lithium amidinates have been employed to synthesize the corresponding heteroleptic niobium and tantalum amidinate complexes. The products were investigated as potential precursors to metal nitrides (cf. Section VI) Carbodiimide insertion routes... 

Ionic interactions have been used to prepare lanthanide-core dendrimers. This has been achieved using a convergent synthesis, in which polyether den-drons with a carboxylic acid group at the focal point were assembled around a lanathanide cation. This involved a metathetical reaction with compounds such as Er(OAc)3, Tb(OAc)3 or Eu(OAc)3 to introduce the appropriate lanthanide ion. 

When 5ym.-ethylphenylurea is heated alone at 160°, ethylamine escapes and the phenylisocyanate and aniline combine to form 5ym.-diphenylurea. The imea dearrangement then provides the true explanation of the apparently metathetical reaction in which the ethyl groups of 5ym.-diethylurea are successively replaced by phenyl. ... 

The complexes [Cu(NHC)(MeCN)][BF ], NHC = IPr, SIPr, IMes, catalyse the diboration of styrene with (Bcat) in high conversions (5 mol%, THF, rt or reflux). The (BcaO /styrene ratio has also an important effect on chemoselectivity (mono-versus di-substituted borylated species). Use of equimolecular ratios or excess of BCcat) results in the diborylated product, while higher alkene B(cat)j ratios lead selectively to mono-borylated species. Alkynes (phenylacetylene, diphenylacety-lene) are converted selectively (90-95%) to the c/x-di-borylated products under the same conditions. The mechanism of the reaction possibly involves a-bond metathetical reactions, but no oxidative addition at the copper. This mechanistic model was supported by DFT calculations [68]. 

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