- Oligomeric Rare-Earth-Metal Halide Clusters. Three Structures Built of (Y16Z4)Br36 Units (Z = Ru, Ir)
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Suitable reactions in sealed Nb tubing at 850-950 °C gave good yields of a family of oligomeric cluster phases that were characterized by single-crystal X-ray diffraction means. The basic Y16Z4 units (?4? symmetry) can be derived from 2+2 condensation of centered Y6Br12Z-type clusters or as tetracapped truncated tetrahedra Y16 that are centered by a large tetrahedral Z4. These are surrounded by 36 bromine atoms which bridge edges or cap faces of the Y16Z4 nuclei and, in part, bridge to metal atoms in other clusters. The principal bonding appears to be Y-Z and Y-Br, with weaker Y-Y (d ? 3.70 A?) and negligible Z-Z interactions. The phase Y16Br20Ru4 (P42/nnm, Z = 2; a = 11.662(1) A?, c = 16.992 (2) A?) is isostructural with Y16I20Ru4 and with the new Sc16-Br20Z4 (Z = Fe, Os). Syntheses only in the presence of Ir and ABr-YBr3 fluxes (A = K-Cs) produce Y16-Br24Ir4 (Fddd, Z = 8; a = 11.718(3) A?, b = 22.361(7) A?, c = 44.702(2) A?), in which the electron-richer Ir interstitials are compensated by four additional bromine atoms and altered bridging between macroclusters. Larger amounts of YBr3 yield a third example, Y20Br36Ir4 (Y16Br24Ir4·4YBr3, I41; a, Z = 4; a = 12.699(1) A?, c = 45.11-(1) A?). Here infinite zigzag chains of YBr6/2 octahedra that share cis edges lie between and bridge to the Y16Ir4 clusters. All of these phases contain 60-electron, closed-shell macroclusters. Y16Br20Ru4 and Y20Br36Ir4 were found to exhibit temperature-independent (Van Vleck) paramagnetism with values typical of those found for other rare-earth-metal, zirconium, niobium, and tantalum cluster halides.
- Steinwand, Sharon J.,Corbett, John D.
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- Structural characterization of methanol substituted lanthanum halides
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The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
- Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
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p. 1784 - 1795
(2010/07/03)
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- Systematics and anomalies in rare earth/aluminum bromide vapor complexes: Thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu
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Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor compl
- Wang, Zhi-Chang,Yu, Jin
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p. 4248 - 4255
(2008/10/09)
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