Macrocyclic ligand effect

Non-leaving ligand effects, for a series of 13-, 14- and 15-membered tetraaza-macrocycles with amine or carboxylate pendant groups, have... 

The Macrocyclic Ligand Effect. A few very recent studies have demonstrated that simple tra/rs-Cc (S )X2 complexes (N4 a macrocyclic amine ligand, X " NH3 or CN ) have exceptionally long lifetimes in fluid solution at room temperature (8, 18,... 

Many of these complexes are more stable than those formed with the corresponding open-chain ligands. This macrocyclic effect is determined by enthalpic as well as by entropic contributions. Still higher stability constants are obtained when side chains with additional donor groups are attached to the macrocycle thus, tetraacetic acid 22 forms complexes with most metal ions, including alkaline earth ions and transition metal ions these complexes show stabilities among the highest known. 

Interaction of [Ni(OH2)6] with 9S3 in ethanol affords the octahedral brick red [Ni(9S3)2] cation (Eq. 4a) [62], Nickel-sulfur distances (Table 1) [62] fall well short (0.06 A) of the sum of ionic radii [2, 104]. Such short Ni-S distances (compared to Ni(II) complexes of acyclic thioethers) [109,110] stem from compression induced by the macrocyclic nature of the ligand (the macrocyclic constriction effect) [16, 17, 18]. 

The template effects of potassium and lithium ions are responsible for the efficiency of the synthesis of macrocyclic ligands in 18-CROWN-6 and2,2.7,7,12,12,17,l 7-OCTAMETHYL-21,22,23,24-TETRAOXAPER-HYDROQUATERENE. 

Macrocyclic effect and specific character of complex formation with rigid macrocyclic ligands such as porphyrins and phthalocyanins 97MI8. 

Electronic effects on the reactions of [Rh(Por)h dimers and hydrides were probed by varying the porphyrin macrocycle. OEP and TPP vary considerably in their properties, with OEP being one of the strongest and TPP one of the weakest (7-donors among porphyrin derivatives. However. Rh(Por)]2, Rh(Por)H, and Rh(Por)r showed the same reactivity in a variety of reactions for both OEP and TPP, indicating that electronic effects relating to the porphyrin ligand have... 

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