Macrobicyclic tris-dioximates

Several macrobicyclic ruthenium, nickel, zinc, manganese, copper, chromium, magnesium, and lithium complexes, as well as two free macrobicyclic tris-dioximate ligands, have also been synthesized. 

The proposed schemes for the synthesis of macrobicyclic tris-dioximates have most readily been realized in high yields for alicyclic dioximes, having a cis-conformation both in crystals and in solutions. The change of the acyclic dioxime conformation from trans to cis during complexation decreases the stability of the compounds formed. 

Transesterification of alkoxy-groups in macrobicyclic tris-dioximates is a modification reaction whereby the compounds that cannot be readily prepared by conventional methods may be... 

Hexadentate trioximetriamine compounds proved to possess properties intermediate between those of macrobicyclic tris-dioximates and sarcophaginates. The hexadentate tamox ligand arises from the reaction of the corresponding polyamine with 2-chlor-2-methyl-3-nitrosobutane [182] ... 

The main X-ray data for l,4,7-trimethyl-l,4,7-triazacyclononane-ended macrobicyclic tris-dioximates... 

Since the main bands in the UV-vis spectra of the macrobicyclic tris-dioximates are stipulated by intraligand n-ii transitions in the dioximate fragments (UV range) and the charge transfer... 

A) is somewhat higher than those in the corresponding macrobicyclic tris-dioximates, which is indicative of a larger ligand cavity size. All chelate rings have skew conformations with the... 

The fell values for most macrobicyclic tris-dioximates and Ne-nSn-sarcophaginates (n = 2, 3) increase with decreasing E values. The cobalt Se-sarcophaginates and boron-capped tris-benzyldioximates drop out of linear correlation for both low-spin cobalt(II) and cobalt(III) complexes. The lack of this correlation in the first case may be attributed to the absence of structural changes in passing from the cobalt(III) complex to the cobalt(II) complex. In the second case, an increased fen value may be attributed to the special rigidity of hexaphenyl-substituted cobalt clathrochelates. 

In the majority of cases, the formation of macrobicyclic metal tris-dioximates is stipulated by the interaction of the reactive oxime groups in tris-dioximate complexes with Lewis acids. The most efficient capping agents have proved to be trigonal organic and inorganic boron compounds. 

Cobalt(III) tris-dioximates were also cross-linked with other Lewis acids, such as SnCL and SiCL [39]. Reaction of KaCoDma in methylene chloride with anhydrous SnCL resulted in the macrobicyclic [CoDma(SnCla)2] anion, which was isolated as an ionic associate with a bulky (/i-CaH7)4N+ cation [39]. 

For the first time, a macrobicyclic ruthenium (II) tris-dioximate was obtained by refluxing of RuCl3-3H20 and nioxime in dry ethanol under argon with subsequent cooling to room temperature and treatment with phenylboronic acid [76]. 

Drago and Elias s idea [46] to employ tridentate amines for protection of one of the two triangular bases of hexacoordinate d-metal ions coordination polyhedron (in case the latter act as capping agents) from polymerization has successfully been developed by P. Chaudhuri and K. Wieghardt for the synthesis of linear homo-and heterotrinuclear macrobicyclic complexes with tris-dioximate bridging ligands. 

Binuclear clathrochelate iron(II) oximehydrazonates may be synthesized by the main methods used for the synthesis of macrobicycles of this type proposed for clathrochelate tris-dioximates by a direct template reaction on a metal ion the cross-linking of initial nonmacrocyclic complexes a cross-linking group exchange reaction and a ligand modification reaction. The template condensation of a mononuclear complex to a binuclear one followed by the encapsulation of another metal ion and capping reaction may be also used for the preparation of these compounds. The main methods for the synthesis of these complexes are shown in Scheme 88 [193]. 

For macrobicyclic d-metal tris-dioximates, the X-ray crystallography analysis is performed least often. This is because the charge of the central metal atom in the majority of such compounds is balanced by that of the clathrochelate ligand, and crystals of the resulting intramolecular complexes are purely molecular. Alongside the structural peculiarities in the structure of such complexes, this... 

The IR spectra of macrobicyclic cobalt tris-dioximates confirmed their clathrochelate nature and contained characteristic bands of... 

The main structural characteristics of the macrobicyclic cobalt(III) tris-dioximates. 

The shielding of protons and carbon atoms of the dioxime fragments is determined by the superimposition of the central ion and macrobicyclic ligand contributions. Both these types of atoms are maximally deshielded in the fluoroboron-capped cobalt (III) tris-dioximates [44]. 

The main bond lengths and angles for the monoamine Fe((/i-C4H9NH)Cl)(C12Gm)2(BC6H5)2 molecule are also typical for macrobicyclic iron(II) tris-dioximates the distortion angle is equal to 17° the distance between polyhedron bases h is 2.35 A, and the average Fe-N distance is 1.91 A [69],... 

Thus, in spite of a significant change in the distortion angle (p of the coordination polyhedron in the TP- TAP range, the Fe-N distance in all X-ray crystallographically studied macrobicyclic p-element-capped iron(II) tris-dioximates is within very narrow limits, namely,... 

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]. 

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