Bromide complex

Step 1 The bromine-iron(III) bromide complex is the active electrophile that attacks benzene... 

EFFECT OF QUATERNARY AMMONIUM SAET EXCHANGE CENTER STERIC ACCESSIBILITY ON EXTRACTION OF CADMIUM BROMIDE COMPLEXES... 

Thus, the QASes of the asymmetrical stmcture with improved steric accessibility of the exchange centre show the high selectivity to double-charged cadmium bromide complex ions relative to single-charged ions. 

Ethereal methyl1ithiurn (as the lithium bromide complex) was obtained by the submitters from Aldrich Chemical Company Inc. The checkers used 1.19 M methyl1ithiurn-lithium bromide complex in ether supplied by Alfa Products, Morton/Thiokol, Inc. The concentration of the methyllithium was determined by titration with 1.0 M tert-butyl alcohol in benzene using 1,10-phenanthroline as indicator. The submitters report that ethereal methyllithium of low halide content purchased from Alfa Products, Morton/Thiokol, Inc., gave similar results. 

Moreover, calculations on the evaporation rate of bromine from the complex phase were carried out assuming a worst-case scenario, namely a complete spill age of the total bromine inventory (as poly bromide complex) of a fully charge (100% SOC) 15 kWh module which means -32.5 kg of available Br2, forming a 10 m2... 

The addition reactions of alkyllithium-lithium bromide complexes to a-trimethylsilyl vinyl sulfones that have as a chiral auxiliary a y-mono-thioacetal moiety derived from ( + )-camphor are highly diastereoselective. A transition state that involves chelation of the organolithium reagent to the oxygen of the thioacetal moiety has been invoked. The adducts are readily converted via hydrolysis, to chiral a-substituted aldehydes22. 

Another hydro-de-diazoniation method in which the solvent is the reagent is that of dediazoniation in hexamethylphosphoric acid triamide (HMPT) it was discovered by Newman and Hung (1974). The mechanism is discussed in some detail in Section 8.9. We do not recommend it for synthetic purposes, however, as (solid) arenediazonium mercuric bromide complexes are used in all but one case. The authors mention only briefly that 4-toluenediazonium tetrafluorophosphate can also be used. 

In fact, Eq. (1-32) is not a direct conversion at all. The bromide complex is first converted to one with a water molecule. The product is formed when Co(NH3)5H203+, an intermediate in this system, reacts with the nucleophile. 

However, with bromide and iodide ions the five-coordinate adducts [Pt(PPh3)2(CNCH3)2X]+ are isolated the bromide complex loses isocyanide slowly but the iodide complex is stable. The analogous reactions with [Pt(diphos)(CNCH3)2] give disubstitution. 

The initial work in this field appeared as a communication in 1969 8), and this work was later expanded to a full paper (9). Badley et al. described the synthesis of m-Pt(PEt3)(CNCjH5)Cl2 from Pt2(PEt3)2Cl4 and the isocyanide the bromide complex could be obtained from this complex by addition of bromide ion. These complexes were then observed to react with various substances [Eq. (16)]. A crystal structure study on the complex... 

Quantitative analysis of the absorption intensity affords values of the formation constants (Kda) and extinction coefficients (act) listed in Table 1 for comparison with the corresponding characteristics of the bromide complexes with tetrabromomethane. 

Fig. 9 Solid-state spectra of bromide complexes with TCP (solid lines) 1 Pr4N+[Br", (TCP)4], 2 (Et4N+)2[(Br )2,(TCP)3], 3 Bu4N+ [Br, (TCP)4]. Note spectra of the corresponding complexes in solution are shown as gray dashed line [23]...

Fig. 11 Fragment of the crystal structures of tetracyanobenzene/bromide complex showing different modes of anion coordination to the acceptor moieties (coordinates from [24])...

In a similar manner, the diffusion of hexane into dichloromethane solutions containing mixtures of the alkylammonium salts of bromide and the olefinic acceptors o-CA and TCNE result in the formation of brown-red crystals [23]. X-ray analysis reveals the (1 1) complex of bromide with o-CA, in which the anion is located over the center of the C - C bond of the acceptor moiety (Fig. 15b) and Br - C contacts are shortened by as much as 0.6 A relative to the sum of van der Waals radii (Table 3). In bromide complexes with TCNE, the location of the anion relative to the acceptor is variable. In fact, a 2 1 complex [(Br )2,TCNE] is isolated in which both anions reside over the olefinic bond when the tetraethylammonium salt of bromide is used. In comparison, if the tetrapropyl- or tetrabutylammonium salts of the same anion are employed, the (1 1) complexes [Br ,TCNE] are formed in which the bromide donors are shifted toward the cyano substituents (Fig. 15a). In both cases however, the short intermolecular separations that are characteris-... 

Fig. 15 Molecular structures of bromide complexes with TCNE (a) and o-CA (b) acceptors...

Miscellaneous Reactions of Phosphines.- The role of chiral phosphines as ligands in the catalysis of reactions leading to the formation of chiral products has been reviewed.1111 A procedure for the determination of the enantiomeric excess in chiral phosphines has been developed, based on 13C n.m.r. studies of the diastereoisomeric complexes formed by phosphines with the chiral pinenyl nickel bromide complex. 111 Studies of the sulphonation of triphenylphosphine and of chiral arylphosphines have been reported in attempts to prepare water soluble ligands which aid... 

As already mentioned, larger ring size triazamacrocyclic ligand complexes have also been characterized. The zinc bromide complex of 1,5,9-triazacyclododecane has been characterized as a mononuclear complex with a tetrahedral zinc center.672 Kimura and co-workers have extensively studied zinc complex formation with 1,5,9-triazacyclododecane-based ligands.445,673-676 1,6,11-triazacyclopentadecane forms a zinc complex of the composition Zn3L2Cl6. NMR studies... 

Methyllithium - lithium bromide complex Lithium, methyl- (8,9) (917-54-4)... 

Methyliithium-iithium bromide complex was purchased from the Aldrich Chemical Company, Inc., and was titrated prior to use. 

The extent of the ionization produced by a Lewis acid is dependent on the nature of the more inert solvent component as well as on the Lewis acid. A trityl bromide-stannic bromide complex of one to one stoichiometry exists in the form of orange-red crystals, obviously ionic. But as is. always the case with crystalline substances, lattice energy is a very important factor in determining the stability and no quantitative predictions can be made about the behaviour of the same substance in solution. Thus the trityl bromide-stannic bromide system dilute in benzene solution seems to consist largely of free trityl bromide, free stannic bromide, and only a small amount of ion pairs.187 There is not even any very considerable fraction of covalent tfityl bromide-stannic bromide complex in solution. The extent of ion pair and ion formation roughly parallels the dielectric constant of the solvents used (Table V). The more polar solvent either provides a... 

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