Transition metal compounds, chelated

These reactions, and in particular the ease of formation of the N(7)-0(6) chelate, may be relevant to the mechanism of action of the anticancer transition metal compounds such as m-[PtCl2(NH3)2].230... 

Neutral chelates derived from divalent transition-metal ions are prepared readily by metathetical reactions in water or, when the solubility of the ligand in water is low, in DMF-water mixtures. With the exception of some bidentate chelates of Mn(II) and Fe(II), which are air-sensitive, the transition-metal compounds are stable to air, and an inert atmosphere is not required during their synthesis or storage. The following procedures are applicable to the preparation of chelates derived from other transition-metal ions. 

This thinking applies, in particular, when planning the design of a chiral three-dimensional supramolecular host-guest system, since the mutual interaction of the two distinct complementary molecular units or coordination entities is necessary. Examples of this methodology include the above-described anionic, tris-chelated transition metal oxalato complexes [Mzl(ox)3/6 which form the host system together with the cationic, tris-chelated transition metal diimino complexes, e.g. [M(bpy)3]21/31, bpy = 2,2 -bipyridine, which play the role of the guest compounds. 

AO/FRS (LDL oxidation protectant, scavenge ROS, chelate transition metal ions) [UV-B protection colour, defensive compounds]... 

Due to the position of their free electron pairs in the colorless form, the 2-quinolylmethanes and -amines are able—in contrast to the 2,4 and 4,4 compounds—to form chelate complexes with suitable transition metal compounds. However, the formation of these complexes is dependent on sterical effects.10,11 While, for example,... 

On the other hand, transition metal compounds with chelating l,l -ferrocenylene, i.e., l-metalla-[l]ferrocenophanes, are rare, the best-known representatives being the group 4 metal complexes (Fig. 5-11) derived from the di(cyclopentadienyl) metal dichlorides, fc[MCp2] and fc[M(C5H4tBu)2] (M = Ti, Zr, Hf) [188, 212]. 

Fig. 4. Divalent organotin - transition metal compounds containing a C,Y-chelating ligand.

The process is initiated at terminal hydroxy groups and favoured by the spiral-like structure of polysiloxanes. Replacement of the hydroxy groups by methyl, or blocking them by chelation to copper, iron or zirconium acetylacetonates, considerably decreases the rate of decomposition of the polymer and increases its thermal stability (Table 9). However, pronounced crosslinking even at moderate temperatures was observed in the polymer stabilized by transition metal compounds. The effect of the metal additives during thermal ageing is associated with reactions leading... 

Some Ziegler-type catalysts have been used to polymerize terminal acetylenes (56, 57). Highly dispersed or soluble catalysts based on TiCl, Ti(OR), metal chelates (Co, Ni, V, Fe) plus AlEt have been most successful. Acetylenes, unlike a-olefins, polymerize with Group VIII transition metal compounds. With some acetylenes, trimerization reactions leading to the corresponding substituted benzene derivatives take place. 

Aromatic compounds with side chains containing coordinating atoms or groups of atoms react with transition-metal compounds to form chelated, ortho-substituted, [Pg.206]

As polyphenolic compounds, flavonoids have the ability to act as antioxidants by a free radical scavenging mechanism [140, 141, 142], This involves the formation of less reactive flavonoid phenoxyl radicals (Eq 1 and 2) on the other hand, through their known ability to chelate transition metals [143,144], these compounds may inactivate iron ions, and bivalent... 

There are many examples of sp sp or sp C—H bond cleavage in transition-metal compounds, especially if a five-membered chelate ring is formed. From the determined sites of metallation certain metals e.g. Pd and possibly Pt ) behave as electrophiles, while Mn, Ir, and Rh behave as nucleophiles. For example, 3-FC6H4CH2PR2 has been shown to give the product ratio (17) (18) = 80 20 with Ir or Rh but (18) is formed totally with Pd (Scheme 10). ... 

Diolefins, monoolefins, and transition metal compounds give l-a-alkyl-4, 5, 6-allyl chelated complexes during irradiation with ultraviolet light [equation (7.42)]. 

Contents Continuum Effects Indicated by Hard and Soft Antibases (Lewis Acids) and Bases. — Stereochemistry of the Reactions of Optically Active Organometallic Transition Metal Compounds. — Dynamics of Intramolecular- Metal-Centered Rearrangement Reactions of Tris-Chelate Complexes. — A Theoretical Approach to Heterogeneous Reactions in Non-Isothermal Low Pressure Plasma. 

Scheme 4 shows some optically active resolving agents used in the resolution of organometallic transition metal compounds of tetrahedral, octahedral, and square pyramidal geometry. Schemes 2 and 3 demonstrate the application of the menthoxide ion. The aminophosphine shown will be used in an example discussed later on. The pyridine imine chelate ligand has been the chiral auxiliary for the resolution of octahedral compounds [9,10], not described in detail here, and for the resolution of square pyramidal compounds to be discussed next [11]. 

What has been described for Norphos containing Rh catalysts is not unique but typical for the situation at present. A variety of optically active chelating phosphines developed in the last 20 years allows the synthesis of natural and unnatural amino acids by hydrogenation of the corresponding dehydroamino acid derivatives. The hydrogenation of dehydroamino acid derivatives is one of the most successful reaction types in enantioselective catalysis with transition metal compounds [5]. 

Triazasilatrane 195 behaves as a bidentate (PjF) or a tridentate (P, , ) ligand to form chelate complexes with transition metal compounds" On reaction with sulfur or methyl iodide, compound 195 is converted into the corresponding derivatives 196 and 197 (equations 183 and 184) ii. 

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