Tetraglyme complex

Compounds which produce a complex with Li+ ions have been investigated. The compounds examined were N,N,N, N tetramethylethylenediamine (TMEDA), eth-ylenediamine, crown ethers, cryptand [211], diglyme, triglyme, tetraglyme, eth-ylenediamine tetraacetic acid (EDTA) and EDTA-Li+ (n=l, 2, 3) complexes [59]. The cycling efficiency was improved by adding TMEDA, but the other additives did not show distinct effects. 

Rhodium losses can also be reduced by using a two-phase system to separate the polyol products from the catalyst solution (64). In this modification the reaction is carried out in a production solvent (e.g., tetraglyme). In order to separate the products, water and an essentially water-immiscible organic extraction solvent (e.g., dichloromethane or chloroform) are added. The resulting two-phase system then consists of a water phase containing the alcohol products and an organic phase containing essentially all the rhodium complex. 

The log K value for the formation of the Na+-fluorenyl complex with tetraglyme, CHs(OCH2CH2)40CH3, is reported to be over 3 log units lower than that of the corresponding complex with 4 -methylbenzo-15-crown-5 in tetrahydrofuran (18, 36). 

The solvents used in these rhodium-catalyzed reactions may also act as complexing agents for counterions of the anionic rhodium complexes. For example, tetraglyme is known to coordinate alkali metal cations. Such solvation decreases the possibility of the cation interacting with the anionic rhodium catalyst and lowering its activity or solubility. The crown ethers, such as [18]-crown-6... 

Since the crown ethers are very effective complexing agents, the amount of free M+ in solution, as in (33)—(36), is expected to be small the crown ether competes very well with Rh and X for M +. Indeed, it is found that the addition of excess salt causes a much lower degree of rate inhibition in [18]-crown-6 as compared to some other solvents. For example, Fig. 10 illustrates the differences between [18]-crown-6 and tetraglyme as the level of salt promoter is increased. The capability of using an excess of salt reduces the criticality of precisely controlling the salt concentration and is beneficial for the stability of the catalyst (92). 

For complex III, the Na+ Is probably as accessible to solva-tlon by solvent molecules as is the Na In the tight Fl-,Na+ Ion pair. Hence, no externally bound solvent molecules need to be removed. This may be different In other systems. For example, the formation constant of a loose Ion pair complex between FI", Na+ and tetraglyme (tetraethylene glycol dimethyl ether) Is nearly four times lower In dloxane than In THF (10). This may be caused by specific solvent effects rather than by the difference In solvent dielectric constant. The flexible glyme ligand wraps Itself around the Na+ Ion, and this may make It more difficult for solvent molecules to remain bound to Na+ In the glyme-separated Ion pair. 

Fig. 52. Molecular structures of the disodium perylene Na[C2oH,2] complexes with mono-, di-, and tetraglyme showing the change from solvent-shared to solvent-separated ion pairs. (Reprinted with permission from H. Bock ei at, J. Am. Chem. Soc. 1995,117, 3869. Copyright 1995 American Chemical Society.)...

It was later realized by the same authors that the complex formed between vanadium(III), tetraglyme (teg) and bromine [V(teg)(Br)2]+Br is the actual catalyst in the oxybromination process258. 

In the cation portion of the complex two Sm environments are nearly tetrahedral and the remaining Cp Sm unit is bound to three oxygen atoms of the tetraglyme molecule. The anion part is [Cp ClSm((/z-Cl)SmClCp ]. ... 

Recent interest in cobalt films has been driven by the importance of cobalt oxides as cathode materials in hthium batteries. Many different precursors have been employed for the MOCVD growth of cobalt-containing thin films. Diketonate-based precursors include Co(acac)2, Co(tmhd)2, Co(tmhd)3, Co(hfac)2, Co(tmhd)2(tmeda), Co(hfac)2(H20)2, and Co(hfac)2(H20)2 tetraglyme. Carbonyl-based precnrsors (see Carbonyl Complexes of the Transition Metals) inclnde Co2(CO)g, Co(C5H5)(CO)2, various cobalt carbonyl clnsters, Co(CO)3(NO), and Co(CO)2(NO)L (L = PEts, TeMc2, TeEt2). Other cobalt precursors include CoH(P(OnPr)(OMe)2)4, Co(N03)3, and Co(rBu NC(CH3)NtBu)2. ... 

Tetraglyme (2,5,8,11,14-pentaoxapentadecane) has been used in the hy-droxymethylation of aldehydes via addition of benzyl chloromethyl ether in the presence of Sml2. Addition of tetraglyme suppresses the competitive pinacol formation, presumably by a complex formation with Sml2 as evidenced by a purple color [25]. Tetraglyme has also been used as a cosolvent in an intramolecular Barbier reaction involving an iodoaldehyde and a THF solution of diiodosamar-ium [26]. 

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