Complexes with Chelating Ligands

The second-order NLO response of various bipyridine and phenanthroUne ligands increases upon coordination to a metal center, as in the case of pyridines and stilbazoles (see Sect. 3.1.2), the EF of the quadratic hyperpolarizabUity stiU depending on the electronic configuration of the metal, its oxidation state, and its sphere of ancillary ligands [10, 16]. 

An investigation was carried out on powders of Re, Pd, and Pt complexes with 2,2 -bipyridine, which exhibit modest second-order NLO activities as evidenced by the Kurtz technique [67]. A more extended investigation on the second-order NLO response of various Re Zn and Hg complexes with donor-substituted vinyl bipyridines (for examples, 6 and 7) was done by the EFISH technique, working at 1.34 pm incident wavelength [10, 68, 69]. 

In the related complexes 8, for a given donor group, a slight increase of the value of / i5i.34(EFISH) occurs by replacing CH with N. However, the significant increase of the NLO response seems to be mainly controlled by resonant enhancement [70]. 

Very recently, the efficient photoswitching of the second-order NLO responses of some dipolar photochromic Zn° complexes (9) was reported [71]. The NLO activity for the open forms is very small, as expected for the absence of 7i-conjuga-tion between the two thiophene rings. Upon conversion to the closed form in the photo-stationary state, the NLO activity increases dramatically (/i)So(EFISH) from 

75-160 X 10 to 1,020-1,800 x 10 esu). This substantial enhancement reflects a more efficient delocalization of the 7i-electron system in the closed forms favoring an efficient on/off switching of the NLO responses [71]. 

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Actinide complexes with chelating ligands containing sulfur and amidic nitrogen donor atoms. U. Casellato, M. Vidali and P. A. Vigato, Coord. Chem. Rev., 1979, 28, 231-277 (181). 

Complexes with chelating ligands incorporating N-heterocycles 294... 

The latest developments in the mechanistic understanding of platinum catalyzed alkane oxidation have involved Pt complexes with chelating ligands having mainly - but not exclusively - nitrogen donors. This review will focus on recent studies of these chelated Pt systems. The selection of the literature is somewhat subjective and will not be comprehensive. However, it should provide a true flavor of the current state of progress in the field. 

Metal ions, especially transition metal ions, form coloured complexes with chelating ligands that are the basis of the analytical methods and indicators for these ions that have been used for many decades. " The term metallochromism has been apphed to this phenomenon, and hence metallochromic indicators. Typical bidentate ligands are dimethylglyoxime, 1,2-dihydoxybenzenes and 1-hydroxyanthraquinones, 8-... 

An alternative pathway when soluble alkoxide or silylamido bases are used, involves reaction of a palladium amido aryl complex with the alkoxide or silylamide to form an intermediate alkoxide or amide. These complexes can react with amines to form the required amido aryl intermediate. This pathway seems to occur for aryl halide animations catalyzed by complexes with chelating ligands. The inorganic... 

Mechanism for Amination Catalyzed by Palladium Complexes with Chelating Ligands... 

The larger ions form complexes with chelating ligands such as EDTA. Complexes with ammonia such as [Mg(NH3)6]2+ can be Inorganic Chemistry... 

In the case of Fem complexes with chelating ligands, generation of ligand radicals is observed. Thus, in the case of the Fem complexes with aminopolycarboxylic acids, eg [Femedta] , photoreduction of Fem - Fe11 is accompanied by decarboxylation and formation of the respective organic radical [11,20-22. ... 

Regeneration of Fem forms from Fe11 products is rather a simple task in alkaline media it is readily done by molecular oxygen Fe11 complexes with chelating ligands behave similarly in acidic media, eg oxidation of [FenL] complexes (L = EDTA, diethylenetriaminepentaacetate, and N- (hydroxyethyl) ethylenediaminetriacetate) by 02 was reported to proceed in three steps ... 

Similar distorted Cu11 is found in some Schiff base complexes with bulky substituents on N and in some dipyrromethane species. With these few exceptions neutral 4-coordinate Cu11 complexes with chelate ligands have planar coordination. 

As relatively hard acids, Ln + ions would not be expected to complex readily with soft donor atoms like sulfur. Apart from the thiolates discussed in (see Section Polypyrazolylbo-rates ), several types of complex with chelating ligands such as dithiophosphates and dithiocarbamates have been synthesized by reaction in nonpolar solvents. These fall into two main classes, Ln(S2Q)3 and [Ln(S2Q)4] (Q = R2NC (dithiocar-bamate) or R2P (dithiophosphate)). Several crystal structures... 

Iron(III) Complexes with Chelating Ligands Fe(acac)3 and Related Complexes... 

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