Clathrochelates nonsymmetric

Ca-nonsymmetric iron(II) clathrochelates have been obtained by the cycloaddition of a-dioximes to initial square-planar macrocyclic iron (II) bis-dioximates by the Reaction 13 ... 

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). 

A C2-nonsymmetric FeNx3(BC6H5)(BF) complex was obtained via a "re-boronating" reaction from the initial FeNx3(BC6H5)2 clathrochelate attacked by triethyloxonium boron fluoride, and the complex obtained was chromatographically isolated (Scheme 10). 

The synthesis of C2-nonsymmetric clathrochelate iron(II) dioximates was realized through a stepwise assembling on the sorbent surface (Scheme 11). 

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... 

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... 

As described above, the C2-nonsymmetric boron- and boron-tin-capped clathrochelate compounds can be prepared by a solid-phase synthesis on the element oxide surface that serves as both a matrix... 

In all cases, except for 9-acetylanthracene, both Cs-symmetric amine clathrochelates with apical aromatic substituents and Ca-nonsymmetric imine sarcophaginates with substituents in the methylene units have been formed (Scheme 59). The reaction of 9-acetylanthracene under the same conditions led only to the aroyl-type sarcophaginate, since in this case a bulky substituent inhibits the condensation of a keto group with an amino group to give imine. 

The and i3C iH NMR spectra permitted one also to detect the isomers of nonsymmetric (HDEA)[CoMm3(SnHal3)2] clathrochelate, which is especially pronounced in the case of azomethine carbon atom signals. Either type of these atoms (methine or methyl-substituted type) manifests itself as four lines. Three of them correspond to the mer-isomer, whose dioximate fragments are magnetically nonequivalent. In the /oc-isomer, all of these three fragments are equivalent and demonstrate one line for each type of carbon atom in the spectra. 

The i/c=N values in IR spectra of the di- and hexachloride clathrochelate precursors are the lowest of all those known so far for clathrochelate iron(II) tris-dioximates. The vc=n bands of both types of dioximate fragments distinctly appeared in the case of partially substituted Cs-nonsymmetric complexes. Alongside the vm-o and vb-o bands of the macrobicyclic framework, the IR spectra of ribbed-functionalized clathrochelates also contained characteristic lines of the substituents in dioximate fragments [65, 68]. 

The UV-vis spectrum of the FeBd2Gm(BF)2 complex also proved to be quite unexpected since it contains only one band with an intermediate Vmax value ca 21 550cm-i, rather than two bands at 22 730 and 20 880 cm-i. With this complex, maximal tension in n-systems of different dioximate fragments has presumably been observed. Since UV-vis spectral characteristics of the FeDm3(BF)2 and FeGm3(BF)2 complexes are identical in the visible region, the CTB in the spectrum of the nonsymmetric FeDm2Gm(BF)2 clathrochelate is nearly the same as that of the first two complexes. To the contrary. 

The electrochemical properties of the clathrochelate Ca-nonsymmetric FeDnD 3-n(BX)2 and Ca-nonsymmetric FeD3(BX)(BY) tris-dioximates and their dependence on electronic characteristics of the substituents in the dioximate fragments and ones at capping atoms are discussed in Refs. 64 and 68. Table 36 lists the E1/2 and the Tomes criterion values for these complexes. As seen from this table, the oxidation process for most of the boron-capped iron(II) clathrochelates is reversible or quasi-reversible. 

The ability of encapsulated iron(II) ion to be oxidized to iron(III) ion drops in the series of capping atoms Ge > Sn > Sb > B. In C2-nonsymmetric clathrochelate complexes, the oxidation potentials are near average between the values for symmetric complexes with corresponding capping groups (Table 38). 

A still greater effect can be achieved if structural modifications, exhibiting more efficient central ion isolation and more efficient energy transfer from ligand to metal can be found (for example, as described in Ref. 380, the Cs-nonsymmetric clathrochelate [Eu(bpy.bpy.bpz)]5+ cation demonstrated substantial increases in both lifetime and quantum yield compared with other complexes of this type). 

Monoribbed-functionalized Ca-nonsymmetric diamino- and dithioclathrochelates can be prepared starting from the dichloride precursor by Scheme 130. The complexing capabilities of such clathrochelates as cis-ligands should first be studied with respect to Pt2+ and Pd2+ ions. In this case, both 1 1 and 2 1 complexes can be isolated (Scheme 130). 

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