Formation of Re

EXAFS analysis for the sample after the fifth pulse reaction of benzene and O2 revealed the formation of Re monomers with Re=0 bonds (CN = 3.7 0.2) at 0.173 O.OOlnm and Re-O bond (CN = 1.3 0.6) at 0.211 0.002nm (Table 10.7). The monomeric structure (vi) in Table 10.7 was similar to that after the steady state reaction (i). The Re monomers (vi) were transformed into the Rejo clusters again by NH3 treatment for 2h. NH3 has two roles, N supplier and reduc-tant, in producing the catalytically active N-interstitial Re cluster, which converts benzene and O2 into phenol with a selectivity of 93.9%, accompanied with oxidation of the cluster to the inactive Re monomer (Scheme 10.4). Thus, the formation of the N-interstitial Rejo clusters and the decomposition of the Rejo clusters to the Re monomers are balanced under the steady-state reaction conditions [73]. 

Homoleptic phenoxido complexes of the composition [Re(L)4] where L = 2,6-diisopropylphenoxide or 2,6-dimethylphenoxide have been prepared by the reaction of [ReCl4(THF)2] with the lithium salts of the ligands. The molecular geometry is square planar and the metal center is well protected from above and below the Re04 plane by the isopropyl groups and protects the complex from reactions with alkynes, whereas such a reaction and the formation of [Re(OC6H3-2,6-Me2)4(RC=CR)] adducts (R = Me, Eth, Ph) has been observed for the dimethyl derivative of the phenoxide. ... 

The formation of RES and their evolution into post-solitons have been observed in three-dimensional simulations as well [14], The EM structure of the three-dimensional soliton is such that the electric field is poloidal and the magnetic field is toroidal. Therefore it is named a TM-soliton. The soliton core is characterized by an overall positive charge, resulting in its Coulomb explosion and in the acceleration of the ion. On the long time-scale, the quasi-neutral plasma cavity is subject to a slow continuous radial expansion, while the soliton amplitude decreases and the ion temperature increases. 

A hot fluid model would be highly desirable for applications in astrophysics. As we have already mentioned, the formation of RES in the primordial plasma could be an important source of large-scale nonuniformities in density and temperature, which seeded the formation of galaxies and clusters of galaxies [4], In particular, it is conjectured that in the early universe matter was present in the form of a mixture of electrons, positrons and photons in thermal equilibrium at a temperature above me2. It is evident that the propagation of relativistic EM waves in such peculiar environment should be addressed in the framework of a hot-plasma model. 

On the basis of the strong photo-oxidising behaviour of [Re(phen)(CO)3(imidazole)]+ (9) (Re(I) /Re(0) = ca. +1.3 V vs. NHE in CH3CN), Gray and co-workers reacted [Re(phen)(C0)3(H20)]+ with azurin, resulting in the formation of [Re(phen) (CO)3(His83)]+-AzCu+, and studied the electron-transfer in this mutant [28], Excitation of the rhenium(I) complex leads to direct oxidation of the copper centre of the protein to copper(II). Using the flash-quench technique with... 

The reactions between Re3X9 (X = Cl or Br) and the more basic heterocyclic tertiary amines (L) that result in the reduction of the cluster and the formation of [Re Lj], (Section 43.4.3) are known to proceed via the intermediacy of Re3X9L3, since purple Re3Cl9py3 can first be isolated by careful control of the reaction conditions.79 The less basic amines such as pyrazine, 2,6-dimethylpyrazine and 3-chloropyridine give unreduced Re3X9L3. Similar 1 3 adducts have also been prepared by the reactions of Re3Cl9 with acetonitrile and benzonitrile.5... 

A. von Keudell, C. Hopf, T. Schwarz-Selinger, W. Jacob Surface loss probabilities of hydrocarbon radicals on amorphous hydrogenated carbon film surfaces Consequences for the formation of re-deposited layers in fusion experiments. Nuclear Fusion 39, 1451 (1999)... 

The complex [Mn(CO)3(terpy)Br] has been isolated, and is thought to contain a bidentate terpy ligand, on the basis of the similarity of its infrared spectrum to that of [Mn(CO)3(bipy)Br] (205). The reaction of [Re(C0)5(N03)] with terpy leads to the formation of [Re(C0)3(terpy)(N03)] this complex is a nonelectrolyte in nitromethane, and is also thought to contain a bidentate terpy ligand (4). 

For example, [Re (CN)(CO)3(bpy)] in strictly aprotic solvents at low temperature is reduced in two chemically reversible one-electron steps at —1.77 and —2.42 V, which correspond to formation of [Re (CN)(CO)3(bpy)] z = 1— and 2—, respectively [130]. The first reduction of [Re(CO)4(bpy)]+ or [Re(P(OEt3))(CO)3(bpy)]+ is chemically reversible even at room temperature [133, 135]. Halide complexes [Re (X)(CO)3(bpy)] (X = Cl, Br) have a complicated reduction pattern because of further reactions of the reduced products. Several reaction intermediates and products have been characterized spectroelectrochemically [131, 135-137] and rate constants of the main steps have been determined [130] by low-temperature cyclic voltammetry. 

IR spectral changes during the further reduction of Re(bpy)(CO)3Cl indicate rapid loss of a Cl ligand with formation of [Re(bpy)(CO)3] . The further reduction of either [Re(bpy)(CO)3(solvent)] or [Re(bpy)(CO)3]2 also yields [Re(bpy)(CO)3]. This illustrates the instability of non-Ti-backbonding ligands coordinated to the formally Re center. 

Both electrochemical and photochemical reduction of Re(bpy)(CO)3X (X = halide), yield [Re(bpy)(CO)3X] [54]. It has been suggested that [Re(bpy) (CO)3X]- reacts directly with CO2 after loss of a CO [56] however, electrochemical results [54, 61] indicate that CO2 attachment only takes place after loss of X". The labilization of X produces either a five-coordinate [Re(bpy)(CO)3] or the six-coordinate [Re(bpy)(CO)3S]. The five-coordinate species can dimerize but under photolysis conditions their low concentration makes this reaction slow. The intermediates may react with CO2 or pick up a second electron and a proton to give Re(bpy)(CO)3H. The formation of Re(bpy)(CO)3H and Re(bpy)(C0)3(02CH) has been reported for Re(bpy)(CO)3X (X = Cl and Br) systems [38, 54, 55, 57, 58, 66]. 

Formation of 7i-bonds between carbon atoms compared with the formation of re-bonds between heteroatoms... 

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