Sarcophaginates synthesis

Monoimine, N-methylated, and semiclathrochelate complexes have been isolated and identified as by-products of sarcophaginate synthesis to gain a deeper insight into the reaction mechanism. The addition of sodium hydroxide to an aqueous solution of [Co(diNOsar)](0104)3 complex leads to a change in the colour of the solution from orange to violet. The violet crystals of the deprotonated [Co(diNOsar-H)] (0104)2 compound were isolated [101]. 

In some cases, a free clathrochelate ligand has been isolated after its template construction on the metal ion and demetallation of the resultant complexes. In particular, this has made it possible to synthesize sarcophaginates of many metals incapable of forming clathrochelates via direct template synthesis they are formed from... 

Application of the template encapsulation procedure to the rigid cyclohexanediaminate Ze(3-[Co(chxn)3] cation has yielded a high symmetric cage systems [107]. For the synthesis of the diaminocyclohexane sarcophaginates, the condensation procedure was modified (pH ll-rl2 and elevated temperatures) compared with that for ethylenediamine sarcophaginates. 

Cerium (III) or tin(II) ions were chosen as a reductant [5]. Application of redox processes is promising for the synthesis of novel sarcophaginates with higher stability and a small cavity size. The reactivity of sarcophaginate ligands may also be employed to prepare imine-, hydroxylamine-, and amide-containing systems not only with cyclohexanediamine derivatives, but with simpler clathrochelates as well. 

The reactivity of apical amino groups has been used in the synthesis of surface-active sarcophaginates (surfactants) [110] ... 

The synthesis of [Co(NOazasar)]3+ sarcophaginate was realized by two pathways starting from [Co(NOsen)]3+ and [Co(azasen)]3+ semiclathrochelates [119]. 

During the synthesis of the methyne-capped cobalt(II) sarcophaginate via reduction of the chlorosarcophaginate complex with zinc dust in water (Scheme 45), an alkylzinc clathrochelate stable even in 6 molar hydrochloric acid was isolated [120],... 

A more detailed synthesis of 4-nitrophenyl-, 2-naphthyl-, 2-phe-nanthryl-, 9-anthryl-, and 2-anthraquinonyl-substituted cobalt(III) sarcophaginates starting from the corresponding methylarylketones was reported in Ref. 137. 

The reactivity of aldehyde groups was also used for the synthesis of the long-chain cobalt (III) sarcophaginates, which display anthelmintic properties [110, 141]. 

The NaSa-containing analog of sarcophaginate 3 was obtained from 5,5 -bis-(4-amino-2-thiabutyl)-3,7-dithianonane-l,9-diamine by Scheme 63 [144], After reduction with zinc dust the resultant NaSa-sarcophaginate underwent demetallation with NaCN. Thus, the ligand obtained may be employed for the synthesis of other metal ion complexes. 

A caesium ion was used as the template in this synthesis. The resultant ligand easily formed a cobalt(II) complex in methanol-methylene dichloride mixture. The isolated [Co(diMEsar-S6)j (CF3S03)2 clathrochelate was readily oxidized by AgCFsSOa in aqueous solution to the cobalt (III) [Co(diMEsar-S6)](CF3S03)3 Se-sarcophaginate [146]. 

Condensation of [Co(tame)2]3+ cation with propanal is described in more detail in Ref. 152. The resultant [Co(/ ac-Me5tricosanesar)]3+ sarcophaginate was demetallated, and the free ligand was employed for the synthesis of a chromium(III) sarcophaginate with unusual spectral characteristics (Scheme 68) [153]. 

As mentioned above, a template synthesis is a very efficient approach to the preparation of sarcophaginates and sepulchrates of certain metals. For all other metal ions, this synthetic pathway is inapplicable or gives the desired products in low yields. For instance, the yields of nickel(II) and chromium(III) sepulchrates resulting from template condensation are only ca 1 and 10%, respectively. This problem can largely be overcome if the synthesis of a variety of metal... 

An analogous scheme has also been used for the synthesis of the nickel, copper, mercury, and zinc(II) diaminosarcophaginates [172-175], their N-methylated analogs [173], and simplest [Hg(sar)](C104)2 and [Ni(sar)](C104)2 sarcophaginates [174, 176],... 

Methods for the synthesis of sarcophaginates and sepulchrates based on redox and photochemical reactions are discussed in Chapter 5. 

Goedken and Peng s idea to employ the reaction between the amino groups, bound to the metal ion, and formaldehyde for the synthesis of clathrochelates proved to be beneficial. It has served as a basis for later studies of Sargeson and coworkers on the synthesis of sepulchrates and sarcophaginates. 

In all cases mentioned, the spectral and X-ray diffraction data on reaction intermediates and by-products have widely been used in considering kinetic and thermodynamic relationships. The identification of intermediates and by-products is still more important in determination of the mechanisms of sarcophaginate and sepulchrate synthesis because in this case kinetic approaches cannot be used. 

The fact that the synthesis of sarcophaginates and sepulchrates proceeds via the formation of an imine complex was also confirmed by isolation of the semiclathrochelate [Co(sen)]- + complex (as a by-... 

The reduction of apical nitro substituents to amino groups is a precursor to the synthesis of a large variety of sarcophaginate complexes. The redox behaviour of these nitro substituents is very diverse and complexes with nitro radical anions, nitroso, hydroxylamine and amine substituents were obtained as primary products from such reductions, depending on the t e of reductant, pH, solvent, and the amount of reductant supplied [414]. 

Another route to the synthesis of azacycloalkanes was inspired by Sargeson s template synthesis of Co(III) sepul-crate and sarcophagine complexes. Examples of this procedure are shown in Scheme 6. The bis-ethylenediamine complexes of Cu(II) or Ni(II) first undergo Schiff base condensation with four molecules of formaldehyde and then two molecules of a diprotic acid, such as CH3CH2NO2... 

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