Macrobicycles

Concerning the efficacy of this approach, the authors state that compared with the methyl ester of 4 -carboxybenzo-15-crown-5, the macrobicyclic polyethers are considerably more effective in binding and NH4 cations . ... 

Alder and Sessions have reported that reductive cleavage of hydrazinium dications is a useful approach to macrobicyclic amines of the type developed by Park and Sim-mons , but the method does not appear to have been successfully applied to any cryptand syntheses. 

Shortly after their first report of all-oxygen bridged cryptands, Dietrich, Lehn and Sauvage reported incorporation of sulfur in the strands. The experimental methods used were essentially similar to those applied in the syntheses of the parent cryptands. As in previous cases, a diacyl chloride was condensed with a diamine under high dilution conditions. In this case, however, the diamine contained sulfur atoms rather than oxygen. The synthesis of compound 5 was accomplished in two stages as illustrated below in Eq. (8.3). The first cyclization step affords the macrocyclic amine in 55% yield. The macrobicyclic product (5) is formed in 25% yield from the monocyclic diamine and the acid chloride. 

There are essentially three methods which have been used for incorporation of the glycerol unit in macrobicyclic species. In all of these the pervasive problem is the tendency of glycerol to form five-membered acetals involving the primary and secondary hydroxyls rather than the two primary hydroxyls and the tendency of the glycerol equivalent 1,3-dichloro-2-propanol to form epichlorohydrin. 

The in-out bicyclic amines prepared by Simmons and Park bear a remarkable semblance to the cryptands but lack the binding sites in the bridges. As a result, these molecules interact with electrophiles in a fashion similar to other tertiary amines and generally do not exhibit strong interactions with alkali or alkaline earth metal ions. The in-out bicyclic amines are prepared by reaction of the appropriate acid chlorides and amines in two stages to yield the macrobicyclic amine after reduction of the amidic linkages. A typical amine is shown above as compound 18. 

Chapter 8 Macrobicyclic, macrotricyclic, or polycyclic compounds including crypt-ands, spherands, etc. 

Another group of very effective ligands that have recently been employed to coordinate alkali metal cations are the macrobicyclic polydentate ligands that J.-M. Lehn has termed... 

Recently considerable attention has been directed at anion binding ligands. Macrobicyclic 27 29) and macrotricyclic amines 30,31) were topologically designed to host anions such as spherical Cl-, linear Nf 32). These anion substrates are incorporated into macrocyclic cavities lined with appropriate anion-binding sites capable of forming hydrogen bonds like those of protonated amines (see /, below). 

Complexes containing encapsulated metal ions (clathrochelates ) with the formula [M(dioxime)3(BR)2] are known with iron(II) 135, cobalt(ll) 136, cobalt(III) 137, and ruthenium(ll) 138 (Fig. 37) [205-220]. Generally, these macrobicyclic complexes are prepared by template synthesis from a mixture of... 

The first three-dimensional macrobicyclic TTF derivatives have been obtained <96CC615> and work on TTF-containing crown ethers and thioethers has continued <96LA551, 96JCS(P1)1995> with structures of this type being used to obtain the first TTF-containing... 

An impressive achievement of this strategy has been the construction of three-dimensional structures. Utilizing branched phenylacetylene sequences, double cyclization yielded macrobicyclic arrays 54 and 55 [43]. The zenith of Moore s approach is macrotricycle 56, a freely hinged system with a sizable 36xl2xl2A molecular cavity [44]. 

The expression bimacrocycle (OT macrocycle or po/ymacrocycle) is used instead of macrobicycle (macrotricycle, etc.) because polymacrocycles can contain further, non-macrocyclic ring systems (e.g. aromatic rings). 

The remarkable physical properties exhibited by the divalent macrobicyclic cage complex [Co(sep)]2+ (29) are unparalleled in Co chemistry.219 The complex, characterized structurally, is inert to ligand substitution in its optically pure form and resists racemization in stark contrast to its [Co(en)3]2+ parent. The encapsulating nature of the sep ligand ensures outer sphere electron transfer in all redox reactions. For example, unlike most divalent Co amines, the aerial oxidation of (29) does not involve a peroxo-bound intermediate. 

Smaller macrobicycles and macrotricycles bearing less that six N-donors are also known. These ligands comprise tertiary or secondary amines and are derived from insertion of one or more straps between pairs of potentially bridgehead N-donors contained within a small ring macrocycle, and in this sense they may be considered analogs of the well-known azacryptands. The inability to offer six N-donors, and the presence of tertiary amines in these ligands leads to the preference for divalent over trivalent Co. 

Somewhat unanticipated applications can arise. For example, a process for the production of ultrapure hydrogen peroxide for the electronics industry has been patented recently,1425 which uses the macrobicyclic hexamine complex (29) supported on an inert material for dioxygen... 

The spectrum of the octahedral Ni11 complex (580) with a hexaaza macrobicyclic ligand is similar to that of [Ni(en)3]2+, but the ligand field strength of the complex is increased slightly by the capping of the [Ni(en)3]2+ moiety with two tris(methylene)amino groups.1461... 

Sargeson and co-workers have reported the use of [Pt(en)3]4+ in template reactions to produce the platinum(IV) complexes of the macrobicyclic ligands sep and (N02)2sar (170).477 These reactions are analogous to those that occur around cobalt(III). However, in contrast to the [Co((N02)2sar)]3+ system, reduction of the pendant dinitro groups did not yield amines, but hydroxyamine groups.478... 

Sargeson and co-workers have structurally characterized encapsulated zinc in hexaaza cryptands.742 743 Related cryptands (l-methyl-8-amino-3,13-dithia-6,10,16,19-tetraazabicyclo[6.6.6]-icosane and l-methyl-8-amino-3-thia-6,10,13,16,19-pentaazabicyclo[6.6.6]icosane) incorporating thioether donors also formed complexes with zinc which were structurally characterized. In both cases the zinc ion was encapsulated in the macrobicyclic cavity and the octahedral coordination geometry distorted to the mixed nitrogen and thioether donor atoms.744... 

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...

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