Macrocycle sulfur-donor

Other donor systems. Although not as common as all-nitrogen donor rings, macrocycles incorporating sulfur donor atoms have been widely reported. Structures (42)-(45) illustrate four representative examples of this type. 

Ligand (119) yields nickel complexes of type [Ni2L](BF4)4 (low spin) and [Ni2L(NCS)4].2H20 (high spin). For each of these complexes, physical studies indicate that the macrocycle circumscribes the two nickel ions such that each ion is surrounded by four sulfur donors in a planar array. 

Crown polyethers. Macrocyclic effects involving complexes of crown polyethers have been well-recognized. As for the all-sulfur donor systems, the study of the macrocyclic effect tends to be more straightforward for complexes of cyclic polyethers especially when simple alkali and alkaline earth cations are involved (Haymore, Lamb, Izatt Christensen, 1982). The advantages include (i) the cyclic polyethers are weak, uncharged bases and metal complexation is not pH dependent (ii) these ligands readily form complexes with the alkali and alkaline earth cations... 

It has been recognized that sulfur donors aid the stabilization of Cu(i) in aqueous solution (Patterson Holm, 1975). In a substantial study, the Cu(ii)/Cu(i) potentials and self-exchange electron transfer rate constants have been investigated for a number of copper complexes of cyclic poly-thioether ligands (Rorabacher et al., 1983). In all cases, these macrocycles produced the expected stabilization of the Cu(i) ion in aqueous solution. For a range of macrocyclic S4-donor complexes of type... 

Macrocycles with 2 nitrogen and 3 sulfur donors have been prepared (14) by a template synthesis in which the dialdehyde (XCI) is condensed with primary diamines, e.g., ethylenediamine gives XCII in boiling acetonitrile containing Fe(II) perchlorate. The reaction is typical of template condensation between carbonyl compounds and primary amines. An unusual monanionic macrocyclic ligand was produced (2) when formaldehyde was condensed with the hydrazine (XCIII) instead of a primary amine in the presence of Ni(II) salts, and complexes XCIV have been characterized. 

D. Waknine, M. J. Heeg, J. F. Endicott, and L. A. Ochrymowyzc, Inorg. Chem., 30, 3691 (1991). Tetradentate Macrocyclic Complexes of Platinum. X-Ray Crystal Structures and Redox Behavior of Complexes Containing Nitrogen or Sulfur Donor Atoms. 

Mixed nitrogen-sulfur donor macrocycles show relatively low affinities for lead(II) despite assumptions based upon hard-soft arguments. The ligands (187) and (188) complex lead with moderate efficiency. " " ... 

Bernardo etal. [51] subsequently determined the potentials of a series of copper(II/I) complexes formed with 14-membered macrocyclic quadridentate ligands involving amine nitrogen and thioether sulfur donor atoms and found that the substitution of each sulfur donor atom by an amine nitrogen resulted in an average decrease of 0.3 V in the Cu(II/I) potential. Since the Afcu L values had been determined previously for these systems [99], Bernardo et al. were able to calculate the A (jji values using Eq. (9). The latter values proved to be nearly constant, indicating that Cu(I) does not discriminate... 

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