NONMACROCYCLIC COMPLEXES

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]. 

Since the resultant cobalt(II) complex undergoes two types of conversions, one of which (Reaction 143) results in the initial product, the quantum yield of the photocatalytic reaction is lower than those of nonmacrocyclic complexes. The quantum yields of the irradiated [Co(sep)]3+ cation in 50% methanol and the irradiated [Co(diAMsar)]3+ cation in water and 33% methanol are of the same order of magnitude as that for the [Co(sep)]3+...I ion pair in water. The quantum yields of the complexes examined markedly change. The [Co(diNOsar)]3+, [Co(diAMHsar)], and [Co(diNOsar-H)]2+ cations proved to be the... 

Morf W.E. Ammann, D. Bissig. R. Pretsch. E. Simon. W. Cation selectivity of neutral macrocyclic and nonmacrocyclic complexing agents in membranes. Prog. Macrocyclic Chem. 1979, 1, 1-61. 

Morf, W. E. et al. Cation Selectivity of Neutral Macrocyclic and Nonmacrocyclic Complexing Agents in Membranes, in Progr. Macrocyclic Chem., Vol. 1 (R. M. Izatt and J. J. Christensen (Eds.)), John Wiley and Sons, New York, 1979, p. 1... 

Complexes with Nonmacrocyclic Nitrogen Donor Ligands 284... 

Complexes with nonmacrocyclic nitrogen donor ligands 486... 

Complexes with Nonmacrocyclic Nitrogen Donor Ligands 63.4.4.1 Complexes with monodentate amino, amido, and imido ligands... 

Since most Ni1 species with simple N-donor ligands are prone to disproportionation into Ni° and Ni11, relatively few Ni1 complexes with nonmacrocyclic N-donor ligands have been reported. Formation of Ni1 species is in most cases proposed on the basis of electrochemical data, although ligand-centered redox processes have to be considered. The ligands usually contain imine donor atoms or aromatic N-heterocycles, which because of their 7r-acceptor ability favor stabilization of lower oxidation states. 

Macrocyclic and maeropolycyclic (cryptate) effects designate the greater thermodynamic stability of macrocyclic ligand complexes compared to nonmacrocyclic analogs. 

N4-M catalysts can also be made from nonmacrocyclic precursors. - In the presence of a nitrogen source, they can be prepared by pyrolyzing transition metal salts or complexes adsorbed on a carbon support. Examples of salts/complexes include acetate,Ee(OH)2 (derived from EeS04), " and phenanthroline complexes. The nitrogen sources may come from an external supply such as or... 

The first route proved to be the most universal one. Owing to a shift in the equilibrium brought about by the formation of a clathrochelate complex, it permits one to prepare a number of compounds in relatively high summary yields. The second pathway, which is carried out in aprotic media, offers higher yields than the first one. However, a low yield of the nonmacrocyclic tris-complex at the first stage imposes restrictions on the scope of this method. 

The preparation of the [CoDm3(BF)2](BF4) complex was described in detail [39]. Its disadvantage is a low (13%) yield of an intermediate KaCoDma product. A more facile and efficient Reaction 5 requires no isolation of an intermediate nonmacrocyclic tris-dioximate [40] ... 

Clathrochelate (HAm)2[FeD3(SnCl3)2] complexes were also formed by cross-linking of the initial nonmacrocyclic iron(II) tris-dioximates with tin(IV) tetrachloride either in acetone or in an acetone-benzene mixture with subsequent addition of amine [71] ... 

Direct Reaction 16 is likely to proceed via an intermediate step, i.e, the formation of a protonated tris-complex. Although the product yield of Reaction 17 is higher, Reaction 16 is preferred because of the difficulties encountered in the isolation of nonmacrocyclic iron(II) tris-dioximates. Tin-capped complexes also arise from the interaction of the Tchugaev type Fe(HD)2Am2 bis-dioximates with tin(IV) tetrachloride, and from the labile boron-capped FeD3(BOR)2 complexes with a great excess of SnCh. 

The nonmacrocyclic iron(II) tris-complex (an intermediate product in the synthesis of clathrochelates, see Chapter 4) have readily reacted with two molecules of IGe(CF3)3 in aqueous solution. In this case IGe(CF3)3 formed dianionic octahedral capping groups. The ions released in the course of the reaction were neutralized by calcium carbonate. The resultant clathrochelate [FeNx3(Ge(CF3)3)2] dianion was isolated as a salt with a bulky organic (n.-C4H9)4hT cation [73]. 

Polynuclear iron(II) and cobalt(III) oximehydrazonates have arisen from the template macrocyclization of the initial nonmacrocyclic tris-complexes with polydentate ligands resulting from the condensation of the corresponding diketones and their monooximes with hydrazine [193]. The tris-complexes formed have... 

Macrobicyclic binuclear iron(II) oximehydrazonates were synthesized by encapsulation of initial nonmacrocyclic tris-complexes with boron- and tin-containing Lewis acids and by direct template reactions on the Fe + ion (Scheme 89). 

X-ray diffraction studies were performed for all the complexes of this type [248-251] to gain unambiguous information on the structure of phosphorus-containing d-metal clathrochelates. A detailed analysis of the geometry of macrohicyclic phosphorus-containing d-metal tris-diiminates and a number of d-metal complexes with nonmacrocyclic hexadentate ligands, shown in Fig. 9, was reported in Ref. 93. Some structural parameters of these complexes with geometry intermediate between a TP and a TAP are listed in Table 9. 

Co-N distance that is characteristic of low-spin cobalt(II) and cobalt(III) complexes. But the difference in Co-N distance (0.08 A) for these clathrochelates is twice as large as normal for a cobalt(II)/(III) pair with a given nonmacrocyclic ligand. 

The calculated ligand field parameters are close to the values obtained for low-spin macrocyclic polyamines and clathrochelate boron-capped cobalt(III) tris-dioximates (see above). The ligand field strength in trichlorotin-capped cobalt(III) tris-dioximates is substantially higher than that in nonmacrocyclic and tribromotin-capped complexes and slightly exceeds that in their boron-capped analogs [44],... 

The CTB molar absorption coefficient values for macrobicyclic complexes are much (1.5-2 time) higher than that of their nonmacrocyclic analogs. To the contrary, the band half-widths for the latter are markedly higher (Fig. 20) (i.e., when macrobicyclic... 

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