10466-65-6Relevant academic research and scientific papers
Temperatures and enthalpies of melting of alkali-metal perrhenates
Lukas, W.,Gaune-Escard, M.
, p. 593 - 598 (1982)
Melting temperatures and enthalpies of melting were determined for alkali-metal perrhenates by differential enthalpic analysis using a high-temperature Calvet microcalorimeter.The following values were obtained: for LiReO4: 692 K and 24.9 kJ/mol; for NaReO4: 693 K and 33 kJ/mol; for KReO4: 828 K and 36 kJ/mol; for RbReO4: 878 K and 34 kJ/mol; for CsReO4: 893 K and 34 kJ/mol.
Reduction pathways in lateral and diagonal (η5-C5Me5)Re(CO)2Br2. Synthesis, structure, and reactivity of [(η5-C5Me5)Re(CO)2Br -]
Nunn, Christine M.,Cowley, Alan H.,Lee, Sang Woo,Richmond, Michael G.
, p. 2105 - 2112 (2008/10/08)
The rhenium anion [(η5-C5Me5)Re(CO)2Br -] (2-) has been prepared in high yield from the reaction of lateral or diagonal (η5-C5Me5)Re(CO)2Br2 (1) with alkyl/aryllithium and Grignard reagents, trialkylborohydrides, and one-electron reducing agents. The molecular structure of 2- (as the [PPP+] salt) was established by X-ray crystallography. [(η5-C5Me5)Re(CO)2Br][PPP] crystallizes in the orthorhombic space group Pbca with a = 20.646 (5) A?, b = 17.690 (5) A?, c = 17.555 (3) A?, V = 6412 A?3, and Z = 8. Solution FT-IR studies of 2- (in THF) reveal the presence of only solvent-separated ion pairs when the gegencation is [Li+], [K+], or [PPP+] from-70°C to room temperature. [2][Na] at room temperature displays a 39:61 mixture of carbonyl oxygen-sodium and solvent-separated ion pairs, respectively. Variable-temperature FT-IR examination of [2][Na] reveals a reversible temperature-dependent equilibrium involving both anionic species. The equilibrium constant for these ion pairs has been determined by IR band-shape analysis over the temperature range -70°C to room temperature, and values of ΔH and ΔS are reported. The reactivity and stability of 2- are described.
Reactivity of 2-(2-hydroxyphenyl)benzothiazoline with the oxotetrahalometalate(V) complexes [MOX4]- (M = Tc, Re; X = Cl, Br). Synthesis and characterization of new oxo-M(V) complexes containing 2-(2-hydroxyphenyl)benzothiazole. Crystal structure of tetraphenylarsonium oxotrichloro[2-(2-hydroxyphenyl)benzothiazolato]technetate(V)
Duatti, Adriano,Marchi, Andrea,Rossi, Roberte,Magon, Luciano,Deutsch, Edward,Bertolasi, Valerio,Bellucci, Fabrizio
, p. 4208 - 4213 (2008/10/08)
2-(2-Hydroxyphenyl)benzothiazoline (hbtH) is converted into its oxidized form, 2-(2-hydroxyphenyl)benzothiazole (hbt), by interaction with the five-coordinate tetrahalooxometalate(V) complexes [MOX4]- (M = Tc, Re; X = Cl, Br). The reaction proceeds very rapidly at room temperature, and only a small amount of metal complex is necessary to obtain conversion of a large excess of hbtH to hbt. When this conversion is conducted in acetone, the formation of isopropyl alcohol is detected within a few minutes after mixing the reagents. When M = Re, an intermediate in the reaction sequence can be isolated; this intermediate contains one ligand comprised of the hbt product and one ligand comprised of the Schiff base tautomeric form of the hbtH starting material [i.e., N-(2-mercaptophenyl)salicylideneamine, S-phsalH2] and is formulated as the six-coordinate Re(V) complex [ReO(S-phsal)(hbt)]. A general scheme accounting for these and other results is given. The hbt ligand also reacts directly with [MOX4]- to yield [MOX3(hbt)]- anions and [MOX(hbt)2] complexes, which have been characterized by elemental analyses and IR, 1H NMR, and mass spectral analyses. The [TcOCl3(hbt)]- anion is characterized by single-crystal X-ray structural analysis refined to a conventional R factor of 0.045 for 3041 observed reflections with I > 2σ(I). Red-orange crystals of the tetraphenylarsonium salt crystallize in the orthorhombic space group P212121 with a = 12.104 (2) A?, b = 13.772 (3) A?, c = 20.539 (4) A?, and V = 3424 (1) A?3 with Z = 4. The Tc(V) center is in a distorted-octahedral configuration with the three chlorine atoms and the neutral nitrogen atom of the hbt ligand in the plane normal to the Tc=O linkage and the anionic phenolate oxygen atom of the hbt ligand situated trans to the Tc=O linkage.
The heat capacity and thermodynamic properties of potassium perrhenate and ammonium perrhenate from 8 to 304 K
Weir, R. D.,Staveley, L. A. K.
, p. 1386 - 1392 (2007/10/02)
The heat capacities of KReO4 and NH4ReO4 from 8 to 304 K have been measured.The data show no obvious order-disorder phase transition but the curve for NH4ReO4 has a broad bump extending from about 100 to 250 K with a maximum around 200 K.This bump is absent from KReO4.For each salt, however, there is a tiny reproducible peak between 265-275 K, which is the result of impurity, probably water.An attempt has been made to calculate the normal curves of heat capacity against temperature for each salt, making use of spectroscopic information available for these crystals about the librational frequencies.For KReO4, the maximum difference between the experimantal and calculated Cp values below 265 K is less than 0.8percent.This excellent agreement is taken as evidence of an absence of any anomaly below 265 K.The case of NH4ReO4 is very different.Because the librational frequency ν6 of the NH4+ disappears from the spectrum at T>180 K, the difference between the experimental and calculated Cp values was expressed as ΔCp=Clib NH4++Cextra, where the Cextra refers to any other unaccounted contribution.When plotted against temperature, ΔCp rises steeply from 100 K to a sharp peak at 190 K (ΔCp= 45 JK-1mol-1) and then drops to 3 R (24.9 JK-1mol-1) as 260 K is reached.Various models of restricted rotation of the ammonium ion are tested including that of a tetrahedron in a tetrahedral environment.All models tested so far fail to produce the peak in ΔCp.Our data are consistent with recent x-ray measurements suggesting that the hydrogen bonding present at 135 K disappears at room temperature and with NMR data showing a large amount of rotational motion of the NH4+ ion about 100 K.
