Transition metal complexes rhenium

Carbonyl Complexes of the Transition Metals Electronic Sfructme of Organometalhc Compounds Hydride Complexes of the Transition Metals Ligand Field Theory Spectra Manganese Organometalhc Chemistry Photochemistry of Transition Metal Complexes Rhenium Organometalhc Chemistry Rutheiuum Organometalhc Chemistry. 

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]. 

The photochemistry of rhenium complexes occupies a prominent position in the photochemistry of transition metal complexes. Along with early preparative studies on photosubstitution of carbonyl species like Re(CO)sX, the preparation of the remarkably stable yellow complex /ac-Re(CO)3(phen)Cl foreshadowed the discovery of the a large class of related luminescent materials by Wrighton and co-workers in the 1970s [ 1 ]. As pointed out by Vogler and Kunkley, the current photochemistry of rhenium complexes is rich, spanning eight oxidation states from formal Re(0) (for example, Re2(CO)io) to formal Re(VII) (for example MeReOs) [2],... 

Another class of metal-employing anion receptors is represented by structure 24 [23]. Its function is based on the incorporation of positively charged transition metal complexes directly into the calixarene skeleton. Such calixarenes with enhanced electron deficiency of the aromatic walls provide well-preor-ganised cavities suitable for anion inclusion. The corresponding rhenium [24], ruthenium, rhodium or iridium complexes of this type were prepared and studied for anion recognition [25,26]. 

Different strategies have been used to attach transition metal complexes to proteins for example, the imidazole moiety of histidine can be coordinated to metal centres such as ruthenium(II), osmium(II) and rhenium(I). Many studies have utilised the imidazole of a histidine residue as a ligand for... 

The optoelectronic properties of conjugated polymers containing the rhenium diimine unit [Re(CO)3(phen)Cl] have been studied. Charge-carrier mobility measurements showed that the presence of metal complexes could facilitate the charge-transport process, and the enhancement in carrier mobility was dependent on the metal content in the polymer. The use of transition metal complexes for both photovoltaic and electroluminescence applications was demonstrated. 

Knowledge of polynuclear transition-metal complexes has been obtained largely by x-ray structure determinations, but the systematic exploration of the chemistry of these compounds is only beginning. Convenient syntheses of some polynuclear carbonylchloronitrosylrhenium compounds are reported here, starting from commercially available Re2(CO)io. Some of these compounds are valuable intermediates in the synthesis of other mononitrosyl rhenium complexes. - ... 

The prototypical photochemical system for CO2 reduction contains a photosensitizer (or photocatalyst) to capture the photon energy, an electron relay catalyst (that might be the same species as the photosensitizer) to couple the photon energy to the chemical reduction, an oxidizable species to complete the redox cycle and CO2 as the substrate. Figure 1 shows a cartoon of the photochemical CO2 reduction system. An effective photocatalyst must absorb a significant part of the solar spectrum, have a long-lived excited state and promote the activation of small molecules. Both organic dyes and transition metal complexes have been used as photocatalysts for CO2 reduction. In this chapter, CO2 reduction systems mediated by cobalt and nickel macrocycles and rhenium complexes will be discussed. 

In conclusion, it can be noted that high valent transition metals seem perfectly capable of serving as effective Lewis acids. Many of the systems discussed here exhibit exceptional robusmess, stability and a propensity to form crystalline complexes. This would facilitate the task of crystallization and structural analysis, and one can imagine that transition metal complexes can be used as structural probes of Lewis acid-carbonyl interactions. In this vein, the first glimpse of the origins of Cram selectivity in a-chiral aldehydes may have been obtained from the crystal structure of a rhenium aldehyde complex. Lastly, the... 

Several types of transition metal complexes have been used as photocatalysts for C02 reduction,63,67 but the ones most studied are ruthenium (II) and rhenium (I) complexes with polypyridine ligands. Thus, Ru(bpy)32+ can be both photosensitizer and catalyst or another metal complex may serve as catalyst. Alternatively, Re(bpy)(CO)3X-type complexes may serve as... 

In order to illustrate the complexity of excited states reactivity in transition metal complexes two selected examples are reported in the next section dedicated to the ab initio (CASSCF/MR-CI or MS-CASPT2) study of the photodissociation of M(R)(CO)3(H-DAB) (M=Mn, R=H M=Re, R=H, Ethyl) complexes. Despite the apparent complexity and richness of the electronic spectroscopy, invaluable information regarding the photodissociation dynamics can be obtained on the basis of wave packet propagations on selected 1-Dim or 2-Dim cuts in the PES, restricting the dimensionality to the bonds broken upon visible irradiation (Metal-CO or Metal-R). The importance of the intersystem crossing processes in the photoreactivity of this class of molecules will be illustrated by the theoretical study of the rhenium compound. 

The enolates (48) and (49) of the transition metals tungsten, rhenium and molybdenum can be successfully prepared by the nucleophilic displacement of a-chloro ketones and a-chloro esters with the appropriate transition metal anion (Scheme 6). They are isolated as C-bound enolate derivatives and, except for the rhenium enolate (49), do not undergo thermal aldol additions to benzaldehyde. However, Bergman and Heathcock et al. have found that an aldol reaction of complex (48) with benzaldehyde can occur on irradiation via the rearranged q -oxaallyl derivative (50), where the metal aldolate (51) can then be... 

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