Rhenium applications

Temperature resistance, i.e. a combination of melting point and oxidation resistance, may be of prime importance. A general correlation exists between melting point and hardness since both reflect the bond strength of the atoms in the crystal lattice, and the preferred order of coating metals for use in high temperature applications as temperature is increased is silver, aluminium, nickel, rhenium, chromium, palladium, platinum and rhodium. 

Although the number of applications of olefin metathesis to transition metal complexes is small compared to the number of applications in organic synthesis, this field is becoming increasingly important. Spectacular examples are the double RCM reactions of copper phenanthroline complexes as a synthetic route to catenanes [113] or a recently reported approach to steric shielding of rhenium complex terminated sp-carbon chains [114]. 

Saladino R, Crestini C, Costanzo G, DiMauro E (2005) On the Prebiotic Synthesis of Nucle-obases, Nucleotides, Oligonucleotides, Pre-RNA and Pre-DNA Molecules. 259 29-68 Santos I, Paulo A, Correia JDG (2005) Rhenium and Technetium Complexes Anchored by Phosphines and Scorpionates for Radiopharmaceutical Applications. 252 45-84 Santos M, see Szathmdry E (2005) 259 167-211... 

Most published work has focused on the deposition of Ni, Co, and NiCo alloys from hypophosphite electrolytes [14], and this part of the review will deal primarily with these alloys. Other Co alloys studied include CoZnP [15, 16], the recording characteristics of which were described by Soraya [17] CoSnP [18], which is reported to have enhanced corrosion resistance and the rhenium and manganese alloys used for vertical recording, discussed below. Other reductants, such as hydrazine [19], dimethylamine borane [20-22], pyridine borane [23], and borohydride [24, 25], can be used for the chemical deposition of nickel and cobalt, but to date there has been no significant application of these to the technology of magnetic media. 

Only scare data is available in the literature on the application of rhenium containing mono- or bimetallic catalysts in the hydrogenolysis of esters to alcohols. Decades ago Broadbent and co-workers studied the hydrogenation of organic carbonyl compounds (aldehydes, ketones, esters, anhydrides, acids,... 

Bearing this situation in mind we wished to describe the present status of studies on chemistry and its applications of technetium and rhenium. A part of this book was planned before the "Topical Symposium on the Behavior and Utilization of Technetium 93" was held in Sendai, Japan in March 1993, but the planning of the book in this style was accelerated after the symposium by suggestions from our friends. The editors are grateful for the cooperation from the contributes and the publisher. 

Despite such problems many people are now interested in the radiopharmaceuticals of rhenium. We hope the coming decade will be characterized by more successful applications of this therapy. 

The development of chemistry itself has progressed significantly by analytical findings over several centuries. Fundamental knowledge of general chemistry is based on analytical studies, the laws of simple and multiple proportions as well as the law of mass action. Most of the chemical elements have been discovered by the application of analytical chemistry, at first by means of chemical methods, but in the last 150 years mainly by physical methods. Especially spectacular were the spectroscopic discoveries of rubidium and caesium by Bunsen and Kirchhoff, indium by Reich and Richter, helium by Janssen, Lockyer, and Frankland, and rhenium by Noddack and Tacke. Also, nuclear fission became evident as Hahn and Strassmann carefully analyzed the products of neutron-bombarded uranium. 

These metals form chalcogenolate complexes in several oxidation states, and from the application-oriented point of view manganese compounds have been synthesized as models for hydrodesulfurization processes and rhenium and technetium derivatives as models for radiopharmaceuticals. 

Despite a common perception that organometallic chemistry essentially belongs in the province of catalysis rather than in vivo applications because of high reactivity of metal carbon bonds, certain organometallic species have very high kinetic stability. Indeed, this point is highlighted by the present wide application of the isonitrile complex Tc(ses-tamibi), [Tc(2-methoxyisobutylisonitrile)6]+, in myocardial imaging. Rhenium tricarbonyl and cyclopentadienyl complexes offer further ex-... 

An interesting approach to rhenium bioconjugate formation that has been developed but apparently has yet to be fully evaluated from the standpoint of applicability and stability is the use of chelating and nonchelating phosphine imine and phosphine oxide ligands [110]. For... 

Various methods for incorporating radioactive rhenium into suitable particles have been introduced. The earliest example is the use of 186Re-labeled sulfur colloid for radiation synovectomy. Commercial preparations for this application have been available for many years (CIS, France, 1987 catalog). 186Re-sulfur colloid has been used for endocavi-tary irradiation of cystic craniopharyngiomas, where irradiation of surrounding tissue is a risk that must be avoided [155]. 

In catalyst preparation, one can use this knowledge to determine the relative contributions of various hydroxyl groups before and after application of the active phase onto the support. In this way Sibeijn etal. [31] established that rhenium oxide attached to acidic sites of the alumina support exhibits higher activity for the metathesis of olefins than rhenium oxide on neutral or basic sites. As, however, rhenium species preferentially exchange with basic hydroxyls, one needs to increase the loading above a certain value (6 wt% for an alumina of 200 m2/gram) before the catalyst exhibits appreciable activity [31]. 

Because of the importance of olefin metathesis in the industrial production of olefins and polymers, many different catalysts have been developed. Almost all of these are transition metal-derived, some rare exceptions being EtAlCl2 [758], Me4Sn/Al203 [759], and irradiated silica [760]. The majority of catalytic systems are based on tungsten, molybdenum, and rhenium, but titanium-, tantalum-, ruthenium-, osmium-, and iridium-based catalysts have also proven useful for many applications. 

The complex formation of technetium, rhenium, and molybdenum with toluene-3,4-dithiol and its analytical application have been studied by Koyama et al. . 

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