Ligand acyclic

Two- or three-carbon backboned bi- and tridentates can also bridge adjacent metal centres, e.g. with Cu(I), Ag(I), Sb(III) and Bi(III), giving rise to one-, two- or three-dimensional polymers.130-133 

A specific feature of the coordinated (heavier) chalcogenoethers is their ability to undergo E-C bond cleavage under certain conditions. For sulfur this process (S-dealkylation) has been known for many years,1 however, Se/Te-dealkylation also occurs.134,140 Relatively few systems have been characterized 

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In this review, recent development of active transport of ions accross the liquid membranes using the synthetic ionophores such as crown ethers and other acyclic ligands, which selectively complex with cations based on the ion-dipole interaction, was surveyed,... 

Inspired by the results of aromatic-ring hydroxylation from the laboratory of Karlin and co-workers, a few groups provided further examples of such reactivity, including some structurally characterized complexes of modified m-xylyl-based pyridine-donor ligands (Schiff base and non-Schiff base acyclic ligands), as well as aliphatic amine donor ligands (179) (Cu-Cu 2.990 A),169 (180) (Cu-Cu 3.015 A),170 and (181) (Cu-Cu 2.999 A).171 172 A m-xylyl-based ligand system that was used by Mukherjee and co-workers in the formation of complex (181) also resulted in the isolation of a bis(/i-hydroxo)dicopper(II) complex (182) (Cu-Cu 3.004 A).171,172 Casella and co-workers demonstrated that when their dicopper(I) complex... 

Other complexes with tetraaza macrocycles have been prepared by reaction of [Au(en)2]Cl3, ethylenediamine, or nitroethane and formaldehyde, although with nitroethane an acyclic ligand was also obtained (293).1715,1716 A gold(III) complex with a hexaaza macrocycle (1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) has been obtained by a transmetallation reaction from the nickel compound [NiL]2+ by reaction with [AuC14], 1717 The chemistry of tetraazamacrocycles in aqueous solution has been reported.1718... 

Markies et al. have studied the coordination of zinc to cyclic and acyclic polyether ligands. In some cases the zinc is not coordinated within the ligand cavity but only through two of the ether donors in the macrocyclic ring.360 The bis(methoxyethyl)ether complex of zinc diphenyl (41) is five-coordinate with three ether oxygens coordinating from the acyclic ligand.361... 

Lee, S. S. Yoon, I. Park, K.-M. Jung, J. H. Lindoy, L. F. Nezhadali, A. Rounaghi, G. Competitive bulk membrane transport and solvent extraction of transition and post transition metal ions using mixed-donor acyclic ligands as ionophores. J. Chem. Soc.-Dalton Trans. 2002, 2180-2184. 

The closed structure of the cyclophane ligand also induces dramatic changes in the polymer microstructure. Polyethylene from the cyclophane catalyst 1.53a is considerably more branched than with catalysts bearing acyclic ligands, which suggests... 

Twelve out of 15 ligands show good to excellent yields. The only unreactive one is the indanol amin ligand 54 with only 3% conversion. Regarding enantioselectivities the best results were obtained with the acyclic ligands 49 and 51. It was therefore decided to investigate aliphatic ketones. 

Acyclic ligands Attached substituents are generally indicated by a prefix followed by a series of numbers representing the sequential number of carbon atoms connecting the donor atoms followed by the sequential identities of the donor atoms. 

As noted by Patterson and Holm, a sharp decrease in potential was also observed by Dockal etal. when amine nitrogens were substituted for thioether sulfurs in the acyclic ligand series. 

Only three PBP complexes of Fe(III) with acyclic ligands from the class of bis(acylhydrazone) of dap have been structurally characterized at present (41,49,53) and this prompted studies in that direction. Both direct and template synthesis afforded the complex [Fe(Hdapsox) Cl2] - 1/2H20 (9) with a monoanionic H2dapsox ligand (7). Protonation of the coordinated ligand was unsuccessful even upon addition of HC1 to the reaction mixture (Scheme 5). In spite of asymmetrical mono-deprotonation, the ligand was symmetrically pentadentately... 

A number of other acyclic ligand systems have been developed that use tris(aminoethyl)amine (tren) as a central unit (for macrobicycles... 

A number of non-podand (i.e., those without an apical atom or group) acyclic ligand systems have been developed for lanthanide luminescence applications. Many of these are designed as helicating ligands such that the lanthanide ion is well encapsulated despite the linearity of the ligand. 

The bipyridyl chromophore has been extensively used in lanthanide coordination chemistry. In addition to those based on the Lehn cryptand (see Section IV.B.4), a number of acyclic ligands have also employed this group. One such ligand is L17, which binds to lanthanide ions such that one face of the ligand is left open (Scheme 3) (60). As expected, luminescence is extremely weak in water and methanol, but stronger in acetonitrile ( = 0.30, 0.14 for europium and terbium, respectively). In addition, the nature of the counter ion can... 

The interaction of oxygen-containing acyclic ligands with alkali and alkaline earth metal cations has provided a burgeoning area of interest. In historic terms, this was preceded by the advent of crown ethers and the accompanying almost retrospective look at their acyclic precedents. This section is sub-divided into five parts simple chelates, metal complexes as ligands, podands, polypodands and sugars. 

The usefulness of such a series is twofold (I) If two different unsaturated ligands are found in the same complex, one can predict which ligand will react, and (2) it is possible to eslimaie how activating a metal fragment must be in order to cause a reaction to occur. Notice that hydrocarbons of even hapticity are more reactive than those with odd hapticity. In addition, acyclic ligands are more reactive than cyclic ones. 

Although some scattered examples of binding of alkali cations (AC) were known (see [2.13,2.14]) and earlier observations had suggested that polyethers interact with them [2.15], the coordination chemistry of alkali cations developed only in the last 30 years with the discovery of several types of more or less powerful and selective cyclic or acyclic ligands. Three main classes may be distinguished 1) natural macrocycles displaying antibiotic properties such as valinomycin or the enniatins [1.21-1.23] 2) synthetic macrocyclic polyethers, the crown ethers, and their numerous derivatives [1.24,1.25, 2.16, A.l, A.13, A.21], followed by the spherands [2.9, 2.10] 3) synthetic macropolycyclic ligands, the cryptands [1.26, 1.27, 2.17, A.l, A.13], followed by other types such as the cryptospherands [2.9, 2.10]. 

Light-driven (electron, cation) symport occurs when combining this system with the (nickel complex, macrocycle) process described above [6.62]. Photocontrol of ion extraction and transport has been realized with macrocyclic or acyclic ligands (containing, for instance, azo or spirobenzopyran groups) that undergo a reversible... 

FIGURE 5.10 Assessment of stability constant (log K) values of the complexes of crown ethers and their acyclic analogs with K+in methanol.25-77 Linear correlations between predicted and experimental log K values for the test set (a) of crown ethers and for the set of acyclic ligands (b) in Figure 5.6a. As QSPR models were built on the training set containing exclusively crown ethers, it is not surprising that predictions for the test set (a) are more reliable. 

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