Clathrochelates formation

The reactions described here represent a significant amount of organization in that up to eight separate ions and molecules eventually come together to make the final product. In view of the relatively high yields it must be assumed that the clathrochelate formation is highly favored thermodynamically and/or kinetically. It is anticipated that clathrochelates as a class of compounds will be particularly well suited to studies pertaining to stereochemistry,1,3 limited-pathway intramolecular isomerizations, analysis of metal ions, and ion transport phenomena.6... 

The iron(II) clathrochelate formation schemes are also confirmed by investigations on the kinetics of their decomposition in solution. In aqueous solution of FeD3(BOH)2 complexes, it is equilibrium... 

The second type of reaction of a monocarbonyl compound to yield a macrocyclic product is represented by the condensation of [Ni(en)2]2+ or [Cu(en)2]2+ with formaldehyde in the presence of a suitable nucleophile (Scheme 4).15-16 This reaction is related to the condensations of [Co(en)3]3+ with formaldehyde plus nucleophiles to form clathrochelate compounds (Chapter 21.3), and also to the formation of the Coin[14]aneN4(02) complex (8) by reaction of a bis(ethanediamine)cobalt(III) complex with formaldehyde.17... 

Certain iron(II) complexes, on treatment with strong base, undergo an interesting tautomerism which results in a change of ligand geometry and formation of clathrochelate structures (equation 24).133... 

The first route proved to be the most universal one. Owing to a shift in the equilibrium brought about by the formation of a clathrochelate complex, it permits one to prepare a number of compounds in relatively high summary yields. The second pathway, which is carried out in aprotic media, offers higher yields than the first one. However, a low yield of the nonmacrocyclic tris-complex at the first stage imposes restrictions on the scope of this method. 

The cycloaddition reaction proceeds under more rigid conditions and takes more time than a direct template condensation on the iron(II) ion. This can be explained by the fact that the overall mechanism of clathrochelate synthesis involves an intermediate tris-complex formation step. It is evident that macrocyclic square-planar iron(II) bis-dioximates are relatively kinetically stable, and the... 

A direct synthesis of C2-nonsymmetric tris-dioximate iron (II) clathrochelates via the formation of semiclathrochelate complex 2 cannot be realized even with a great excess of complex 1, since compound 2 readily disproportionates to give 1 and 3 (Scheme 9). 

The reaction with an excess of methylmercaptan in the presence of potassium carbonate at room temperature led to the formation of partially substituted products only, mainly trisubstituted clathrochelates. Therefore, a more active potassium methylmercaptanate was used in the synthesis of the hexasubstituted product, and the reaction readily proceeded in a high yield [65]. 

The reaction of a n-butylboronic precursor with potassium phenolate led to the formation of hexaphenol Fe((C6H50)2Gm)3(Bre-C4H9)2 complex (Scheme 13). Attempts to obtain of the n- and t-butoxy-containing clathrochelates met with failure because of the destruction of precursors. 

The well-known synthetic procedures for crown ethers and their analogs allowed one to synthesize clathrochelates with dioximate fragments of the 0x0- and thioether crown type (Scheme 13). The interaction of phenylboronic and re-butylboronic precursors with 3 mols of the sodium salt of bis-(2-(o-oxyphenoxy))diethyl ether for 5 h in THF at 50-60° led largely to the formation of Ca-nonsymmetric tworibbed-substituted products (Scheme 13). The reactions of n-butylboronic precursor were studied in more detail. The use of a 30% excess of the sodium salt of bis-(2-(o-oxyphenoxy))diethyl ether and an increase in the reaction time up to 30 h permits one to isolate a tricrown ether clathrochelate (Scheme 13). Tetrabutylammonium salt ((re-C4H9)4N)Cl was used as an interphase catalyst for the... 

The reaction of a phenylboronic precursor with an excess of n-butylamine unexpectedly led to the preferential formation of the tetrasubstituted clathrochelate by the modification of two of the three dichloroglyoximate fragments (Scheme 13). A similar product was also obtained in the case of cyclohexylamine. Attempts to obtain a hexa-M-butylamine clathrochelate were not successful. The interaction of precursors with aniline and its derivatives has resulted in the formation of a mixture of di- and trisubstituted products, which failed to be isolated as individual compounds [65]. 

Clathrochelate ribbed-functionalized tris-dioximates have attracted interest because they offer scope for the synthesis of polynuclear complexes with targeted structural parameters and physicochemical properties (see above). In most instances, it is not necessary to functionalize all a-dioximate fragments, and it appears to be sufficient to modify only one of the three ribs in the clathrochelate framework to alter the properties significantly. Several feasible synthetic routes to clathrochelate monoribbed-functionalized tris-dioximates have been proposed in Ref. 68. A direct template condensation of the mixture of a-dioximes with Lewis acids on a metal ion (Scheme 15, Route I) leads to the formation of a poorly separable mixture of nonsymmetric and symmetric products, in which the latter predominate. Halogenation of the initial clathrochelate... 

The reactions of phenyl-, i-butyl- and fluoroboron-capped hexachloride iron(II) precursors with aliphatic amines proceeded under steady-state conditions of the solvent, temperature, and reaction time to produce clathrochelates of only one type irrespective of the nature of the substituent at the boron atom (Scheme 18). Therefore, the reactions of the phenylboronic Fe(Cl2Gm)3(BC6H5)2 precursor were studied. The reaction of precursor with n.-butylamine in DMF, benzene, THF, and /i-butylamine as the solvent led to the formation of only tetrasubstituted clathrochelate, whereas the reaction in chloroform unexpectedly resulted in trisubstituted clathrochelate, which underwent further functionalization in DMF with re-butylamine and cyclohexylamine but did not react with diethylamine (Scheme 18). 

The reaction of phenylboronic precursor with primary alicyclic cyclohexylamine in DMF and CHCI3 also led to the formation of tetra-and trisubstituted clathrochelates, respectively (Scheme 19). Trisubstituted clathrochelate underwent further functionalization in DMF with an excess of re-butylamine and aliphatic diamine (cadaverine). Thus, the overall reaction pathway in the previously mentioned reactions with primary sterically unhindered aliphatic amines involved a stepwise substitution in two of the three dichloroglyoximate fragments of hexachloride clathrochelates [69]. 

The reactions of nucleophilic substitution with participation of reactive clathrochelates are very sensitive to the donor properties of an attacking amine. With aromatic amines, as well as secondary and primary sterically hindered amines in acceptor solvents, and hexachloride precursors, the reaction stops with the formation of disubstituted products. When secondary and sterically hindered primary aliphatic amines are used in donor solvents and sterically unhindered primary aliphatic amines in acceptor solvents, the reaction terminates at trisubstituted products. In the case of sterically unhindered aliphatic amines, tetrasubstituted clathrochelates are formed. With dichloride precursor FeBd2(C12Gm)(BF)2, the primary aliphatic amines in donor solvents form diamine clathrochelates, whereas the secondary amines (diethylamine or piperazine) give only monoamine complexes both in acceptor and donor solvents. 

In the case of primary aliphatic amines, the reaction products are dramatically affected by the solvent employed. For instance, in the presence of solvents apt to produce a specific solvation of amines (chloroform, and an amine chlorohydrate solution in methylene dichloride), the reaction with hexachloride precursors terminates to yield the trisubstituted product DD D" formed via route A. At the same time, the use of some other solvents (such as benzene, 1,4-dioxane, THF, methylene dichloride, DMF, and alcohols, or the corresponding amine media) led to the formation of the sole tetrasubstituted product (DD"D"). In addition, in the case of sterically unhindered primary amines an alternative isomer (D D D") is not isolated, which indicates reaction route A and a specific control of the tie reaction in the transition state by solvation interactions and intramolecular hydrogen bonds. In the case of the dichloride FeBd2(C12Gm)(BF)2 precursor, with both primary (cyclohexylamine) and secondary (diethylamine and piperazine) aliphatic amines, only a monosubstituted product of the Bd2D type is formed in chloroform, whereas in some other solvents, a diamine clathrochelate of the Bd2D" type is obtained with both sterically hindered and unhindered primary aliphatic amines. 

The known analytical reaction for a qualitative determination of microamounts of iron with dioximes after reduction with tin(II) chloride responsible for the intense coloring of the solution is, in our opinion, caused by the formation of such clathrochelate complexes. 

Cross-linking of [Co(sen)]Cl3 semisarcophaginate with nitro-methane and formaldehyde led to the formation of the [Co(NOMEsar)]Cl3 complex readily reducible to [Co(AMMEsar)]Cl3 sarcophaginate. A detailed procedure for the preparation of [Co(NOMEsar)]Cl3 complex was reported in Refs. 101 and 118. Nitrosation of [Co(AMMEsar)]Cl3 clathrochelate accompanied by reduction with zinc dust resulted in the [Co(MEsar)]Cl3 complex [94] ... 

Co(diAMsar)]3+ cation, nitrosation of the [Co(AMMEsar)]3+ cation led to the formation of "orange" and "yellow" fractions separated by lEC. The orange fraction contained the products of nucleophilic addition to carbanion without rearrangement (expected [Co(ClMEsar)]Cl3 (ca 70%) and [Co(HOMEsar)]Cl3 (ca 20%)sarcophaginates). The yellow fraction contained the product of nucleophilic addition to carbocation with rearrangement - [Co((ClME)MEabsar)]Cl3 clathrochelate (ca 10%) [101],... 

The interaction of the free ligand with cobalt(II) perchlorate in the presence of AgC104 as a precipitant in the nitromethane-methanol mixture made it possible to isolate the [Co(diME l,3pnsar-S6)](C104)3 clathrochelate. The reduction of this clathrochelate with sodium dithionate led to the formation of a cobalt (II) complex that readily produced a free sarcophagine [147],... 

The interaction of tamox ligand with Co + ions in the presence of air oxygen led to the formation of [Co(tamox)]Cl(C104)2 H20 and [Co(tamox-H)]Cl2 3H20 complexes. These compounds appear to be promising for the synthesis of the corresponding clathrochelate complexes. 

The condensation of butanedione-2,3-dihydrazone with formaldehyde on a metal ion (Fe-, Co-" and Ni +) matrix (Scheme 74), performed by Goedken and Peng, led to the formation of clathrochelate [M(thz)](BFi)2 complexes. Direct reaction between the three components proved to be efficient only with iron(II) ion [183]. Therefore, nickel, cobalt, and iron(II) tris-dihydrazonates were preliminarily synthesized. It was noted that even when the reaction was carried out under nitrogen and cobalt(II) tris-dihydrazonate was used as the starting material, only cobalt(III) clathrochelate could be isolated from the reaction mixture. Its reduction with anhydrous hydrazine yielded cobalt(II) clathrochelate [95, 183]. 

The binuclear germanium-capped clathrochelate [Fe2DA03(Ge(CF3)3)2] oximehydrazonate was obtained by a template condensation of the tetradentate H2DAO ligand with IGe(CF3)3 in an aqueous solution in the presence of CaCOs (Reaction 52). The resulting intramolecular macrobicyclic compound precipitated from the reaction mixture, and the equilibrium shift due to the formation of the solid allowed one to isolate this complex in a relatively high yield [73]. 

The interaction of tranbpy ligand with an excess of [CUAN4KBF4) and AgBF4 led to the formation of a binuclear [Cu2(tranbpy)](BF4)2 (2) and a trinuclear clathrochelate [Ag3(tranbpy)](BF4)3 (3) compounds, as well as allowed one to isolate the heteroronuclear Cu -Ag -Cu complex. 

The reduction of imBT ligand with NaBH4 in methanol led to the formation of a saturated octaazamacrocyclic amBT ligand that forms binuclear complexes with zinc(II) and copper(II) [199] and mononuclear clathrochelates with manganese, iron, cobalt, nickel, and zinc (II) [203] by treatment of the free ligand with the corresponding metal ion salts. 

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