Vanadium complexes effect

It was discovered nearly 20 years ago that V(V) as vanadate and V(IV) as vanadyl can mimic some of the effects of insulin (stimulate glucose uptake and oxidation and glycogen synthesis) (512, 513). Vanadate is an effective insulin mimetic in the diabetic rat (514), but has proved to be too toxic for human use. Vanadyl, as VOS04, is also unsuitable because high doses are needed on account of its poor oral absorption. Vanadium complexes with organic ligands have proved to be less toxic and can have improved aqueous solubility and lipophil-icity. 

Shul pin and coworkers have demonstrated, in several papers, that other peroxo vanadium complexes closely related to 36, containing in the coordination sphere amino acids, nitrogen-containing bases or weak carboxylic acids, are effective oxidants of satnrated and aromatic hydrocarbons. An accnrate account containing this work, together with results related to the use of other transition metals, has appeared and aU the relevant literature can be found there. 

Highly oxygenated VO(V) complexes can be electrosynthesized. K2[V0(02)2P], K[V0(02)2(X)] (X = H2O, O2, bipyridine, 1,10-phenanthroline), and similar species have been generated by the dissolution of vanadium anodes in the presence of H2O2, HF and various ligands [113, 114[. Such complexes effect unusual oxidations of substrates such as cresols. Vanadium... 

W. Wang and K. Nomura, Remarkable effects of aluminum cocatalyst and comonomer in ethylene copolymerizations catalyzed by (arylim-ido)(aryloxo) vanadium complexes efficient synthesis of high molecular weight ethylene/norbomene copolymer, Macromolecules, 38(14) 5905-5913, July 2005. 

Acetic acid is formed when methane reacts with CO or C02 in aqueous solution in the presence of 02 or H202 catalyzed by vanadium complexes.327 A Rh-based FeP04 catalyst applied in a fixed-bed reactor operating at atmospheric pressure at 300-400° C was effective in producing methyl acetate in the presence of nitrous oxide.328 The high dispersion of Rh at sites surrounded by iron sites was suggested to be a key factor for the carbonylation reaction. 

Comparison of V(IV,V) hydroxamic acid complexes showed the V(V) complex induced a stronger insulin-enhancing effect than the V(IV) complex, and both complexes were better than either of the salts, vanadyl sulfate or sodium vanadate, in relieving the symptoms of mice with STZ-induced diabetes. The distribution of vanadium in tissues was the same irrespective of the complex administered however, the tissue distribution of vanadium when the salts were administered was different from that seen after vanadium complex administration [146], These results suggest that the difference in the antidiabetic activity of the hydroxaminic acid V complexes is related to the different oxidation state, although there was no difference in the final tissue distribution of these complexes. 

Not all vanadium chelates have antidiabetic properties in animals. For instance, four mixed 0,S binding bidentate ligand precursors were derived from maltol to yield four new complexes, two pyranthiones and two pyridinethiones. These complexes are hydrolytically stable and had no observable insulin-enhancing properties [147], The ultimate effectiveness of a vanadium-complex as an antidiabetic drug... 

Lampronti, I., N. Bianchi, M. Borgatti, E. Fabbri, L. Vizzielo, M.T.H. Khan, A. Ather, D. Brezena, M.M. Tahir, and R. Gambari. 2005. Effects of vanadium complexes on cell growth of human leukemia cells and protein-DNA interactions. Oncol. Rep. 14 9-15. 

Epoxidation of allylic alcohols with peracids or hydroperoxide such as f-BuOaH in the presence of a transition metal catalyst is a useful procedure for the synthesis of epoxides, particularly stereoselective synthesis [587-590]. As the transition metal catalyst, molybdenum and vanadium complexes are well studied and, accordingly, are the most popular [587-590], (Achiral) titanium compounds are also known to effect this transformation, and result in stereoselectivity different from that of the aforementioned Mo- and V-derived catalysts. The stereochemistry of epoxidation by these methods has been compared for representative examples, including simple [591] and more complex trcMs-disubstituted, rrans-trisubstituted, and cis-trisubstituted allyl alcohols (Eqs (253) [592], (254) [592-594], and (255) [593]). In particular the epoxidation of trisubstituted allyl alcohols shown in Eqs (254) and (255) highlights the complementary use of the titanium-based method and other methods. More results from titanium-catalyzed diastereoselective epoxidation are summarized in Table 25. 

Early transition metal catalysts such as vanadium complexes and zirconocenes effectively copolymerize ethene with norbornene [81]. This capabihty eventually led to the commercial development of the APEL and TOPAS line of cyclic olefin copolymers by Mitsui and Ticona (formerly Hoechst), respectively [82]. Interest in this class of polymers is due to its high glass transition temperatures and transparency that is imparted by the norbornene component. 

W. Zhang, A. Basak, Y. Kosugi, Y. Hoshino, H. Yamamoto, Enantioselective epoxidation of allylic alcohols by a chiral complex of vanadium An effective controller system and a rational mechanistic model, Atigfiw. Chem. Int. Ed. Engl. 44 (2005) 4389. 

Table 5.1 Insulin-like effects of selected vanadium complexes with organic ligands.

Lapina et al. [58] observed by H MAS NMR that V2O5 on Si02/Ti02 interacts both with Si02 and Ti02. From data obtained from NMR it was found that the structure of vanadium complexes at the surface depends on the sequence of V and Ti deposition. However, the effect of the preparation technique on the SCR reaction... 

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