Macrobicyclic boron-capped

The high selectivity of macrobicyclic boron-capped iron(II) dioximate formation and the stability of these compounds may be attributed to a favourable action of the main factors that govern the metal ion capability to form macrobicyclic clathrochelate compounds ... 

Fragmentation of the molecules of macrobicyclic boron-capped iron(II) tris-dioximates in the gas phase occurs mainly by an alternative scheme compared with the reactions in solution [292]. Excited molecules of the complexes that gained from a cascade of reactions sufficient energy for rupture of bonds with fragmentation occurred by similar routes for all complexes considered (Table 28). 

The results of FAB-MS study of the macrobicyclic boron-capped iron(II) dioximates indicated that in the gas phase the energetics of bond rupture in their molecular complexes changes compared with... 

Redox characteristics (mV) of macrobicyclic boron-capped MD3(BR)2 tris-dioximates in nonaqueous solutions. 

The boron-capped transition metals macrobicyclic clathrochelates also belong to the family of compounds containing a ring-junction boron atom. Their main types 177a-d are shown in Figure 18 and the corresponding references are presented in Table 12. 

Table 12 Literature on boron-capped transition metals macrobicyclic clathrochelates...

Thus, QS in boron-capped macrobicyclic iron(II) dioximates has a positive sign that follows from large values of QS, and in some cases the sign of QS was confirmed by direct measurements [272]. 

The spectral characteristics for tin-, germanium-, and antimony-capped macrobicyclic iron(II) dioximates differ greatly from those of the corresponding boron-capped complexes discussed above. 

Different configurations of boron- and tin-capped complexes are accounted for by essential differences in their structures the geometry of the former approaches a TP, whereas that of the latter is close to a TAP. The distortion angle q> values for macrobicyclic iron(II) oximehydrazonates were predicted from QS values in their Fe Mdssbauer spectra [188], The predicted

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Considerable discrepancies in the geometry of macrobicyclic boron- and tin-capped oximehydrazonates were observed in their UV-vis spectra the intense Md->Ln CTBs in the spectra of the boron-capped clathrochelates are UV-shifted compared with the spectra of the tin-capped ones. The shape of the spectra is also somewhat changed an asymmetric singlet band is characteristic of the boron-capped compounds, whereas the spectra of the tin-capped ones in the visible region consist of two overlapping bands of nearly the same intensity. Similar differences have also been detected for clathrochelate iron(II) tris-dioximates (see Section 3.3) [188]. 

The electrochemical behaviour of the macrobicyclic boron-, germanium-, antimony-, and tin-capped iron, cobalt, and ruthenium dioximates has been studied by cyclic voltammetry, polarography, and electrolytic experiments [41, 52, 64, 65, 68, 73, 74, 77, 78, 328-330]. For every metal ion, the dependence of the redox potentials on the electronic characteristics of the substituents in the dioximate... 

The electrochemical characteristics of macrobicyclic ferrocenyl-boron-capped iron(II) tris-dioximates are listed in Table 35. ... 

Cyclic voltammetric data (mV) for macrobicyclic boron-, tin-, antimony- and germanium-capped iron(II) oximehydrazonates and a-dioximates [73, 74, 188],... 

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. 

An extremely selective synthesis reaction of the boron-capped macrobicyclic iron dioximates was proposed for the analysis and purification of extra-pure materials [54], The extraction-photometric procedure reported for iron determination enables one to detect iron at a concentration down to 10- % and, additionally, to purify these materials. The extraction-photometric procedure is unaffected by the presence of other metal ions even in great amounts (from 10- to 100-fold excess). 

Complexes with type I.II ligands are usually referred to as boron (tin, germanium, silicon, antimony)-capped macrobicyclic dioximates (oximehydrazonates, azineoximates). Their abbreviated... 

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. 

An apical functionalization of clathrochelates enables one to obtain complexes with improved chemical, physicochemical, biomimetic, and bioactive properties and characteristics that are primary governed by functionalized groups [65]. The possibility of an apical modification of macrobicyclic a-dioximates and oximehydrazonates is indicated by the relative availability of functionalized boron-containing Lewis acids as efficient capping agents. 

The redox properties of macrobicyclic iron(II) mono- and binuclear oximehydrazonates and a-dioximates formed by capping with antimony(V) and germanium(IV) triorganyles were studied by cyclic voltammetry [73, 74]. The electrochemical behaviour of these compounds is similar to that of analogous boron- and tin-capped clathrochelates. Oxidation of all mononuclear complexes involves a one-electron process, assigned to the oxidation of encapsulated iron(II) ion to iron(III) ion. This process is electrochemically... 

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