Applications transition metal cations

Amey, M. D. H. and Bridle, D. H., Application and development of ion chromatography for the analysis of transition metal cations in the primary coolants of light water reactors, /. Chromatogr., 640, 323, 1993. 

Solvated transition metal cations containing weakly bonded organic ligands are potentially useful as intermediates in preparative coordination chemistry. The coordinated solvent molecules provide solubility of the compounds in various organic solvents, and they can be replaced readily by other ligands with better donor properties.1, 2 The preparation of mononuclear transition metal complexes with weakly bonded anions has been described previously3 and preparative applications of such complexes have been reviewed.4... 

Several simple models exist5 that approximately describe the temperature dependence of x for transition metal cations that do not represent spin-only centers. As one example that is applicable to coordination complexes at low temperatures, the Kotani theory6 incorporates the effects of spin-orbit coupling into the Van Vleck equation and describes y(T) as a function of the spin-orbit coupling energy C,. 

Efforts have also been made to improve the methodology used to prepare various mixed donor macrocycles especially applicable to binding transition metal cations <2006POL599>. Various approaches were tried including amide formation followed by reduction (see Figure 4). Activated leaving groups such as tosylate were employed and... 

The investigation of thia crown ethers, e.g. trithiacyclononane (64, 9S3 ). wh< complexation properties towards transition metal cations were of interest [61,62], was complicated for a long time by the low yields obtained from the corresponding cyclization reactions [63]. The combined application of the cesium effect and of the high dilution principle [1] in the reaction of 1,2-dichloroethane and the dithiol 63 led to an increase of the yield of 64 from 4.1 % (tetraalkylammonimn methano-late as the base) [64] to 50% [65, 66]. 

Transition metal oxides exhibit a number of properties that are conducive to catalytic applications, including thermal and mechanical stability needed to survive severe reaction conditions. More importantly, transition metal cations can typically exist in several different valence states. Titanium dioxide has a bulk band gap energy of about 3.2 eV, but electrons can be placed in (3d) gap states... 

Since the incorporation of transition metals into the frameworks of zeolites or micro-porous ahiminophosphates to form heteroatom-containing molecular sieves with important application values, the synthesis, structure, and characterization of microporous transition metal phosphates have been extensively studied in the last decade. In particular, because transition metal cations possess redox and coordination features, they are a kind of catalytic material with useful applications, and promise potential... 

Metal cations are essential in many biological processes. The functioning of the nervous system depends on the control of Na and ions, while transition metal cations are present in the active site of many enzymes often playing catalytic roles. Furthermore, the selective extraction of metal salts from aqueous systems is important for both industrial and environmental reasons. Receptors that are able to extract precious metal ions from aqueous solution or detect/remove toxic and polluting cations (such as Cs and Pb ) are highly desirable. In response to these diverse applications, the study of synthetic receptors for cationic guest species has become a well-established field with many organometallic examples to draw upon. 

Transition metal cations solvated by weakly coordinating solvents are useful precursors for a variety of nonaqueous synthetic applications. The dissociation of acetonitrile ligands opens up vacant coordination sites for catalysis, and allows transition metals to be introduced into extended arrays formed by condensation reactions with polydentate ligandsAlthough salts of homoleptic acetonitrile metal cations with tetrafluoroborate anions have been known since the 1960s, there has been no detailed description of the syntheses and characterization of these compounds. Likewise, there have been general descriptions of the syntheses of trifluoromethanesulfonate salts, but no specific outline for individual metals has been published. In this report, the syntheses of [M (CH3CN)x][BF4]2 (M = Cr,Mn,Fe,Co,Ni,Cu) and [M CHaCNlJlSOsCFsla (M = Mn,Fe,Co,Ni) are described. Two different methods are used to prepare tetrafluoroborate salts (1) the oxidation of metals with nitrosonium tetrafluoroborate, first described by Hathaway et al. and (2) the dehydration of aqueous tetrafluoroborate salts in a Soxhlet extractor with molecular sieves. The oxidation reaction is rapid, anhydrous, and recommended for smaller-scale preparations because of the relatively... 

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