Tetraalkylammonium metals

Reduction in aprotic media of ammonium compounds having four aliphatic substituents at mercury or some other metals yields tetraalkylammonium amalgam or tetraalkylammonium metals. This phenomenon is discussed in Chapter 28. 

TAA ions may make interstitial compounds with graphite [23,24] that have reducing properties similar to those of the tetraalkylammonium metals. 

More interestingly, acyloxycarbene- chromium complexes, which are generated in situ by acylation of the corresponding tetraalkylammonium metal acylates, transfer their carbene ligand to silyl enol ethers under very mild conditions and with excellent simple diastereoselectivity to provide 2-(/m-butyldimethylsilyloxy)cyclopropyl acetates. When R2 is hydrogen the cu-iso-mers predominate, whereas formation of the trans-product is favored when R2 is phenyl18. 

The Hg/dimethyl formamide (DMF) interface has been studied by capacitance measurements10,120,294,301,310 in the presence of various tetraalkylammonium and alkali metal perchlorates in the range of temperatures -15 to 40°C. The specific adsorption of (C2H5)4NC104 was found to be negligible.108,109 The properties of the inner layer were analyzed on the basis of a three-state model. The temperature coefficient of the inner-layer potential drop has been found to be negative at Easo, with a minimum at -5.5 fiC cm-2. Thus the entropy of formation of the interface has a maximum at this charge. These data cannot be described... 

In the Koenigs-Knorr method and in the Helferich or Zemplen modifications thereof, a glycosyl halide (bromide or chloride iodides can be produced in situ by the addition of tetraalkylammonium iodide) is allowed to react with a hydrox-ylic compound in the presence of a heavy-metal promoter such as silver oxide, carbonate, perchlorate, or mercuric bromide and/or oxide,19-21 or by silver triflu-oromethanesulfonate22 (AgOTf). Related to this is the use of glycosyl fluoride donors,23 which normally are prepared from thioglycosides.24... 

Group-IIIB element-transition-metal compounds have been synthesized by means of anionic metal bases and halide-free group-IIIB compounds. The carbonylate anions of Mn and Re interact with BHj to give [HjBMfCOlj]", which are best isolated as the tetraalkylammonium or phosphonium salts ... 

Water. The pH range that can reasonably be used extends from 0 to 14, with the neutral point at pH 7. A solution with pH <7 is acidic and with PH >7 is basic. The commonest strong acids are HC104, H2S04, HC1 and HN03 strong bases include alkali metal and tetraalkylammonium hydroxides. 

The crystals of (V) and (VI) (Table 1) are built from tetraalkylammonium cations and cluster anions [Tc6(/i-Br)6Br6]Br2] " , where n = 2 for (V) and n = 3 for (VI). The metal core of the cluster anions [Tc6(ju-Br)6Br6]Br2] 3-(Fig. Id) is a regular trigonal prism formed from technetium atoms. The vertical... 

The first catalysts reported for the electroreduction of C02 were metallophthalocyanines (M-Pc).126 In aqueous solutions of tetraalkylammonium salts, current-potential curves at a cobalt phthalocyanine (Co-Pc)-coated graphite electrode showed a reduction current peak whose height was proportional to the C02 concentration and to the square root of the potential sweep rate at a given C02 concentration. On electrolysis, oxalic acid and glycolic acid were detected, but formic acid was not. Mn and Pd phthalocyanines were inactive, while Cu and Fe phthalocyanines were slightly active. At the potentials used for C02 reduction, M-Pc catalysts would be in their dinegative state, and the occupied dz2 orbital of the metal ion in the metallophthalocyanine was suggested to play an important role in the catalytic activity. 

Tetraalkylammonium fluorides or metal fluorides are also effective as catalysts for the Michael addition of nitroalkanes (see, Table 4.2).143-145... 

One possible strategy in the development of low-overpotential methods for the electroreduction of C02 is to employ a catalyst in solution in the electrochemical cell, A few systems are known that employ homogeneous catalysts and these are based primarily on transition metal complexes. A particularly efficient catalyst is (Bipy)Re[CO]3Cl, where Bipy is 2,2 bipyridine, which was first reported as such by Hawecker et al. in 1983. In fact, this first report concerned the photochemical reduction of C02 to CO. However, they reasoned correctly that the complex should also be capable of catalysing the electrochemical reduction reaction. In 1984, the same authors reported that (Bipy)Re[C013CI catalysed the reduction of C02 to CO in DMF/water/ tetraalkylammonium chloride or perchlorate with an average current efficiency of >90% at —1.25 V vs. NHE (c. —1.5V vs. SCE). The product analysis was performed by gas chromatography and 13C nmr and showed no other products. 

Anionic metal complexes such as ZnC14 > GaCl4 and Co(CN 6 can extracte(j w(th tetraalkylammonium salts, e.g. 

Ammonium salts are commonly used to stabilize aqueous colloidal suspensions of nanoparticles. The first such example was reported in 1983-84 by Januszkie-wicz and Alper [96, 97], who described the hydrogenation of several benzene derivatives under 1 bar H2 and biphasic conditions starting with [RhCl(l,5-hexa-diene)]2 as the metal source and with tetraalkylammonium bromide as a stabilizing agent Some ten years later, Lemaire and coworkers investigated the cis/... 

The polymerization catalysts that are preferred because of their selectivity are the alkali metal (especially cesium) carbonates, tetraalkylammonium and bis(triphenylphosphoranylidene)ammonium (PPN) chlorides and bicarbonates (Table 4.2). Undesired side reactions are minimized by using relatively low (< 5% by weight) catalyst levels. Under these conditions, the fraction of cyclic oligomer was usually 5% or less and was easily removed from the desired polymer by Kugelrohr distillation. Conversions of 5 were essentially quantitative as judged by product weights and lack of detectable amounts of unreacted monomer by GPC. 

Interesting results have been obtained from polarographic studies in various donor solvents. Measurements have been made of various metal perchlorates in solutions of donor solvents containing tetraalkylammonium perchlorate as supporting electrolyte against an aqueous saturated calomel electrode 113. In order to eliminate differences in liquid-liquid junction potentials bisbiphenylchromium (I) has been used as a reference ion 114 118). 

Tetrailkylammonium hydroxide, 736 Tetraalkylammonium ozonide, 736 Tetraalkylammonium salts, transition metal peroxides, 1082... 

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