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AN UNUSUAL SPECIES FROM THE REACTION OF THE UNSATURATED ANION {[RE3(MU-H)3(CO)9(MU-3-O ... H ... NME3)]-, AND CRYSTAL AND MOLECULAR-STRUCTURE OF ITS TETRAETHYLAMMONIUM SALT}
No full textThe reactions of the unsaturated cluster anion [Re3(μ-H)4(CO)10]- with Me3NO, in a solvent of low donor ability, such as acetone or tetrahydrofuran, give three products, in a ratio which depends on the reaction conditions: two of them, the unsaturated [Re3(μ-H)4(CO)9(NMe3)]- and [Re3(μ-H)4(CO)9(ONMe3)]- species, have been characterized spectroscopically. The third has been isolated and characterized by X-ray single crystal analysis as an adduct formed by hydrogen bonding between Me3N and the triangular cluster anion [Re3(μ-H)3(CO)9(μ3-OH)]-. The crystals are monoclinic, space group P21/m, with a 8.576(3), b 20.442(4), c 8.748(3) Å, β 108.08(4)°; Z = 2. The structure was solved by Patterson and Fourier methods by use of 2085 unique reflections and refined to a final R value of 0.026. The mean ReRe and ReO(OH) bond lengths are 2.979 and 2.126 Å, respectively. The O · H · N hydrogen bond is short and almost linear (O ⋯ N 2.502(10) Å). Various experiments have demonstrated that the triply bridging OH group can, according to the reaction conditions, come either from a water molecule (present in the commercial amine oxide) or by attack of a hydridic ligand on the oxygen of a coordinated amine oxide molecule. The same adduct has been obtained starting from the dianion [Re3(μ-H)3(CO)9(μ3-O)]2-, directly by reaction with Me3NHCl or in a two step sequence of protonation to [Re3(μ-H)3(CO)9(μ3-OH)]- and subsequent treatment with Me3N
Synthesis and Characterization of three Hydridocarbonyl Rhenium Cluster
No full textWe describe three new hydridocarbonylrhenium cluster anions, isolated as tetraethylammonium salts, viz. the triangular [H3Re3(CO)10]2-, the tetrahedral [H4Re4(CO)13]2- and the triangular [H3Re3(μ3-O)(CO)9]2-. These are obtained by decomposition of the hydride [H4Re4(CO)15][NEt4]2 in boiling ethanol under different conditions. The reactions also yield the known species [H2Re3(CO)12]- and [H6Re4(CO)12]2- as tetraethylammonium salts
Polynuclear Isocyanides Complexes of Rhenium
No full textThe kinetics of the decomposition of MeTl(OA)2 in C5D5N, and in the presence of equimolar amounts of C5D5N in CD3OD, have been studied by 1H NMR-spectroscopy. Products in pyridine are TlOAc and N-methylpyridinium acetate, as well as MeOac and decomposition products of N-methylpyridinium acetate; the reaction order changes during decomposition. In methanol MeTl(OAc)2 and pyridine give>90 mole-% N-methylpyridinium acetate and <10 mole-% MeOAc; the reaction follows in good approximation a second order law. On the basis of data calculated from the derived rate equation and experimental data, a bimolecular mechanism, and, as rate determining ste, an SN 2-attack of pyridine and OAc- at the Tl-bonded CH3-group of MeTlOAc+ is formulated. Because of the less nucleophilic character of OAc- in comparison with pyridine, MeOAc is formed only in minor amounts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A new metallic environment for carbon in a carbido metal cluster: X-ray crystal structure of the anion [Re4C(CO)15I]
No full textPartial fragmentation of [Re7C(CO)21]3-, by reaction with I2 in MeCN under CO atmosphere, affords the title compound, which contains a carbide atom at the centre of a tetrahedrally distorted square of rhenium atoms
SCALAR AND DIPOLAR CONTRIBUTIONS OF RHENIUM TO THE RELAXATION PROPERTIES OF COORDINATED LIGANDS
No full textThe longitudinal relaxation times (T1) of the hydridic ligands and of P-31 in [HRe(CO)4PPh3] (1), [HRe(CO)5] (2), and [Re2-(mu-H)2(CO)8] (3) have been measured as a function of the temperature and of the applied magnetic field. In 1 the relaxation of P-31 is dominated by the scalar interactions with the quadrupolar isotopes of rhenium up to 7 T. The field dependence of the relaxation rate of phosphorus has allowed the calculation of the coupling constant 1J(Re-P) (1260 +/- 20 Hz) and of the Re relaxation time (22 +/- 1 ns). For the hydridic ligand, dipolar interactions with rhenium account for more than 60% of the observed relaxation rate. 1J(H-Re) for 1 has been estimated as 440 Hz. The relaxation of the classical hydrides in 2 and 3 is completely determined by dipolar interactions with rhenium. 1J(H-Re) for 2 has been determined to be 385 Hz. The length of the Re-H bond (189 +/- 1 pm) in 3 has been calculated from the fitting of the temperature dependence of H-1 relaxation. Anisotropic reorientation was observed for compound 1. The relevance of the H-Re dipolar interaction in classical rhenium polyhydrides is discussed
High nuclearity carbido carbonyl clusters of rhenium. Synthesis, x-ray crystal structure, and 13C N.M.R. study of the anion [Re 8C(CO)24]2
No full textThe novel high nuclearity carbido carbonyl anion [Re8C(CO) 24]2-, isolated from the pyrolysis of [ReH 2(CO)4]-in n-tetradecane, has the metal atoms arranged as an octahedron capped on two opposite faces as shown by an X-ray crystal structure determination; 13C n.m.r. analysis has confirmed the nature of the interstitial atom and shown that the solid-state structure of the anion is maintained in solution
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