Magnesium complex formation

Figure 2, The effect of magnesium complex formation for the diradical 3...

These can be prepared by electrolytic oxidation of chlorates(V) or by neutralisation of the acid with metals. Many chlorates(VII) are very soluble in water and indeed barium and magnesium chlorates-(VII) form hydrates of such low vapour pressure that they can be used as desiccants. The chlorate(VII) ion shows the least tendency of any negative ion to behave as a ligand, i.e. to form complexes with cations, and hence solutions of chlorates (VII) are used when it is desired to avoid complex formation in solution. 

The proportion of hydrochloric acid in the mobile phase was not to exceed 20%, so that complex formation did not occur and zone structure was not adversely affected. An excess of accompanying alkaline earth metal ions did not interfere with the separation but alkali metal cations did. The hthium cation fluoresced blue and lay at the same height as the magnesium cation, ammonium ions interfered with the calcium zone. 

The 1 l)5-hydroxyl group in the A -3-ketone (33) favors attack towards the j -face of the molecule, possibly due to complex formation with the methyl-magnesium halide. Thus, the )5-methyl isomer (34), is obtained as the major product in 22% yield after reacetylation. 

What effect does the solvent have on the structure, charges and reactivity of Grignards Compare geometries, atomic charges and electrostatic potential maps of the diethyl ether complex to that of methylmagnesium chloride itself. How does solvent-magnesium bond formation affect the reactivity of the methyl group Explain. 

In contrast to the ionic complexes of sodium, potassium, calcium, magnesium, barium, and cadmium, the ease with which transition metal complexes are formed (high constant of complex formation) can partly be attributed to the suitably sized atomic radii of the corresponding metals. Incorporated into the space provided by the comparatively rigid phthalocyanine ring, these metals fit best. An unfavorable volume ratio between the space within the phthalocyanine ring and the inserted metal, as is the case with the manganese complex, results in a low complex stability. 

Hybrid scorpionate/cyclopentadienyl-Mg (63) and -Zn (64,65) complexes were structurally characterized and reported to catalyze the formation of PLAs with medium molecular weights and narrow polydispersities [85]. Among them, the magnesium complex 63 is much more active than the others, giving a polymerization of L-lactide in toluene at 90 °C with 97% conversion in 2.5 h. However, it takes 30 h for zinc complexes 64 and 65 to reach similar results under the same conditions. Some representative structures of magnesium and zinc complexes are summarized in Table 2 as they display closely related ROP activity of lactide, and often stmcrnrally similar ligand systems are employed to construct these initiators. 

Lunestad B.T. and J. Gokspyr (1990). Relaxation in the antibacterial effect of ox)4etracycline in sea water by complex formation with magnesium and calcium. Diseases of Aquatic... 

The first effective enantioselective 1,3-dipolar cycloaddition of diazoalkanes catalyzed by chiral Lewis acids was reported in the year 20(X) (139). Under catalysis using zinc or magnesium complexes and the chiral ligand (R,/ )-DBFOX/Ph, the reaction of diazo(trimethylsilyl)methane with 3-alkenoyl-2-oxazolidin-2-one 75 (R = H) gave the desilylated A -pyrazolines (4S,5R)-76 (R =Me 87% yield, 99% ee at 40 °C) (Scheme 8.18). Simple replacement of the oxazohdinone with the 4,4-dimethyloxazolidinone ring resulted in the formation of (4R,5S)-77 (R = Me 75% yield, 97% ee at -78 °C). 

Chlorins (2) are undoubtedly the most important dihydroporphyrins, since the chlorin chromophore is found in chlorophylls and some bacteriochlorophylls and, as the magnesium complex, is the catalyst in photosynthesis. The method of choice for formation of trans-chlorins involves reduction of iron porphyrins with sodium in boiling isopentyl alcohol (57JCS3461), but methods involving photochemical reduction of tin(IV) porphyrins, isomerization of phlorins, reduction of metalloporphyrins with sodium anthracenide followed by protonolysis, heating with sodium ethoxide, and photoreductions of zinc(II) porphyrins in the presence of ascorbic acid have also been employed. The best method for formation of c/s-chlorins (note that all natural chlorophylls possess the trans arrangement) appears to... 

When an aminoacyl-tRNA synthetase catalyzes the esterification of tRNA with an amino acid, the amino acid is activated by formation of an enzyme-bound mixed anhydride with AMP (equation 2.67) in the same way that an organic chemist activates a carboxylic acid by forming an acyl chloride or a mixed anhydride. (Note that in equation 2.67 the substrate is the magnesium complex of ATP, with the metal ion acting as an electrophilic catalyst. The Mg2+ binds primarily to the /3,y-phosphates.50 51)... 

The role of ATP and S-adenosylmethionine in the reaction remains an intriguing but as yet unresolved question. Recently Yuan and Meselson have reported that in the presence of magnesium ion, ATP and S-adenosylmethionine the R-K endonuclease forms a specific complex with its DNA substrate (55). Complex formation is, however, observed at ATP concentrations (4 X 10-8 M) at which nucleolytic activity is not detectable. This result suggests that ATP may be involved in at least two steps (1) formation of a nonhydrolytic complex at low ATP levels and (2) formation of more stable (or more numerous) complexes and nucleolytic action at higher concentrations of ATP. The S-adenosylmethionine requirement for complex formation is in the same concentration range as observed for restriction. 

Similarly some degree (5-10% of the reported concentrations) of complex formation might be expected for such metal ions as magnesium or cobalt (II), but apparently there are no examples of extensive sulfato entities. 

In spite of much information available for the interactions of various metal ions with small oxoanions of phosphorus, relatively little information has been obtained for the complex formation of long-chain polyphosphate ion. This may be due to the fact that the conventional methods useful for the study of the complex formation of a relatively small ligand are not always applicable to the polyanion complex formation system. Since a gel chromatographic method based on the same principle as the equilibrium dialysis method has been proved to be applicable in the field of inorganic complex chemistry (1), this method has been applied to the study of the binding of long-chain polyphosphate ions to magnesium ion. 

The binding ability of each magnesium ion to one site is not affected by the complex formation at other sites of the same chain. 

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