Two New Examples for the Unusual R12I17Z2-Structure Type: La12I17Fe2and Ce12I17Mn2

Lulei, M.; Martin, James D.; Corbett, John D.

doi:10.1006/jssc.1996.0293

Cited by 17 publications

(23 citation statements)

References 11 publications

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“…Comparison with the c- axis view of NaGaSn 2 in Figure shows a clear distortion of the network in NaInSn 2 and different positions for the (unsplit) cations within the channels. Similar observations have been made in other systems, in CsNa[La 9 I 16 N 4 ] where changes in either the cation or framework result in a shift of the cation positions within a structurally unchanged channel, or in the recent report on the microporous catalyst HSAPO-34 19 in which two separate channel coordination sites were identified for hydrogen-bound water and hydronium ions. In the case of the two NaTrSn 2 microporous Zintl phases (Tr = Ga, In), the sodium cation adopts a position nearer to the center of the channel in NaGaSn 2 where it can maximize its framework coordination (judging from bond distances), while in NaInSn 2 , the cation bonding is optimized (again, judging by distances) when the cation is closer to one framework wall.…”

Section: Resultssupporting

confidence: 82%

Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Vaughey

Corbett

1996

J. Am. Chem. Soc.

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A new Zintl phase NaGaSn2 is obtained pure from stoichiometric reactions of the elements in sealed Ta at ∼450 °C. Its orthorhombic framework structure (space group C2221, 6.309(3) × 10.986(4) × 6.162(4) Å) contains one-dimensional helical pores ∼6 Å in diameter along c⃗ (6 atoms/turn) that bind relatively well-ordered sodium countercations at 50% occupancy. The structure can also be described in terms of interlinked puckered double layers normal to b⃗ and parallel to the channels. Gallium is disordered over both tetrahedral framework sites, the gallium-richer and more negative site having closer sodium neighbors. The potassium compound cannot be made. Among analogous phases reported by others, NaInSn2 has a lower symmetry and ordered cations, while NaGaSn5 cannot be reproduced.

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Section: Resultssupporting

confidence: 82%

Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Vaughey

Corbett

1996

J. Am. Chem. Soc.

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“…The focus of the magnetic investigations is of course the moments, which range from about 0.8 to 1.1 μ B per dimer at 3 T (Table ). These lie below the ideal spin-only value of 1.73 μ B for one unpaired electron, but they are comparable to those for both the 17-electron monoclusters in La 12 I 17 Fe 2 , 1.11 μ B , and the magnetically less well behaved CsLa 6 I 10 Fe, ca. 1.4 μ B …”

Section: Resultsmentioning

confidence: 52%

Two Closely Related Structure Types with Unprecedented Bioctahedral Rare-Earth-Metal Clusters Centered by Transition Metals: A₂R₁₀I₁₇Z₂(A = Rb, Cs; R = La, Ce, Pr; Z = Co, Ni, Ru, Os) and La₁₀I₁₅Os₂

et al. 1997

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A family of compounds has been discovered in which pairs of octahedral rare-earth-metal clusters, each centered by a late transition metal Z, share a common edge. These R10Z2 units, sheathed and interbridged by iodine atoms, occur in the quaternary phases Rb2La10I17Co2, Cs2La10I17Z2 (Z = Co, Ni, Ru, Os), Cs2Ce10I17Os2, and Cs2Pr10I17Z2 (Z = Co, Ru, Os) and in the ternary La10I15Os2. All are obtained as black, air-sensitive crystals from reactions of RI3, R, Z, and RbI or CsI as appropriate in welded Nb containers at 800−850 °C. The structure of Cs2Ce10I17Os2 has been refined by single-crystal X-ray diffraction methods for comparison with the isotypic Cs2La10I17Co2 (monoclinic, C2/m, Z = 2, R(F)/R w = 4.0/4.4%), and the structure of a unique ternary La10I15Os2 has been defined (triclinic, P1̄, Z = 1, R/R w = 5.0/5.1%). These new bioctahedral clusters may be regarded as the missing links between discrete clusters and infinite chains of condensed octahedral clusters among rare-earth-metal cluster halides that are stabilized by interstitial transition metals. The biclusters in both structures are extensively interconnected into three-dimensional arrays through bridging iodine atoms. The structural interconversion between Cs2La10I17Os2 and La10I15Os2 + 2CsI may be easily visualized in terms of changes in iodide bridging modes and accommodation of cesium cations. All the biclusters contain an odd number of cluster-bonding electrons, and this feature has been confirmed by magnetic susceptibility studies. EHMO cluster and band calculations on biclusters and their structures are in agreement with the localized bonding properties and ranges of electron counts.

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“…Eighteen electrons is well-known to be optimal for octahedral 6−12 clusters centered by transition elements, corresponding to the R−Z bonding a 1g 2 t 2g 6 , the nonbonding e g 4 on Z, and the R−R bonding HOMO t 1u 6 . Accordingly, many 16-electron clusters with potential t 1u 4 HOMOs have been found to exhibit appreciable tetragonal distortions, namely Y 6 I 10 Ru (by 0.21 Å in Δ d (Y−Ru), 50% of the compression), K 2 La 6 I 12 Os (0.25 Å), and Pr 6 Br 10 Ru (0.28 Å), as well as 0.16 Å for eight of nine independent clusters in the related superstructure of La 48 Br 81 Os 6 (0.16 Å) . A few other compounds with 16-e - clusters show relatively smaller distortions, e.g.…”

Section: Resultsmentioning

confidence: 99%

α-K₄R₆I₁₄Os (R = La, Pr): A Novel Iodine-Rich Structure with a Layered Network of Electron-Poor Clusters. An Incipient Delocalized System with Metal-like Conductivity

1999

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The title compounds are obtained from reactions of KI, RI3, R, and Os at 750−850 °C in sealed Nb or Ta containers. The structure was established by single-crystal X-ray diffraction studies (tetragonal, P4/mnc, Z = 2; a = 10.044(4), 9.879(3) Å and c = 21.825(4), 21.86(1) Å for La, Pr, respectively) for three samples, La and Pr at 23 °C and La at −100 °C. This particular combination of large R, interstitial Z, and halogen results in the highest X:R ratio known among rare-earth-metal cluster halides and an unprecedented structure type. The cluster units are interconnected according to the pattern [(R6Os)Ii 8Ii-a 4/2Ia-i 4/2Ia 2]4- in which four R in the waist of each cluster, the Os, and four bridging Ii-a,a-i pairs generate a planar 2D network of geometrically nearly ideal, 16-electron R6Os octahedra. This contrasts with the tetragonal compression found for many other 16-e- examples with the parallel disappearance of Curie−Weiss paramagnetism. Powdered α-K4La6I14Os exhibits an exceptionally low resistivity for a cluster halide (∼120 μΩ·cm) over 110−280 K and a small paramagnetism over about 35 to ∼250 K associated with a probable Mott−Hubbard state that changes to a temperature-independent (presumably Pauli) paramagnetism above about 300 K. EHTB band calculations show that a significant broadening of the HOMO (∼t1u) states takes place in the plane of the intercluster bridging. The unique structure, properties, and band picture for the compound indicate a transition to a delocalized (band) state.

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Two New Examples for the Unusual R12I17Z2-Structure Type: La12I17Fe2and Ce12I17Mn2

Cited by 17 publications

References 11 publications

Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Two Closely Related Structure Types with Unprecedented Bioctahedral Rare-Earth-Metal Clusters Centered by Transition Metals: A₂R₁₀I₁₇Z₂(A = Rb, Cs; R = La, Ce, Pr; Z = Co, Ni, Ru, Os) and La₁₀I₁₅Os₂

α-K₄R₆I₁₄Os (R = La, Pr): A Novel Iodine-Rich Structure with a Layered Network of Electron-Poor Clusters. An Incipient Delocalized System with Metal-like Conductivity

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Two New Examples for the Unusual R12I17Z2-Structure Type: La12I17Fe2and Ce12I17Mn2

Cited by 17 publications

References 11 publications

Synthesis and Structure of NaGaSn2. A Zintl Phase with a Helical Framework Structure

Synthesis and Structure of NaGaSn2. A Zintl Phase with a Helical Framework Structure

Two Closely Related Structure Types with Unprecedented Bioctahedral Rare-Earth-Metal Clusters Centered by Transition Metals: A2R10I17Z2(A = Rb, Cs; R = La, Ce, Pr; Z = Co, Ni, Ru, Os) and La10I15Os2

α-K4R6I14Os (R = La, Pr): A Novel Iodine-Rich Structure with a Layered Network of Electron-Poor Clusters. An Incipient Delocalized System with Metal-like Conductivity

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Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Synthesis and Structure of NaGaSn₂. A Zintl Phase with a Helical Framework Structure

Two Closely Related Structure Types with Unprecedented Bioctahedral Rare-Earth-Metal Clusters Centered by Transition Metals: A₂R₁₀I₁₇Z₂(A = Rb, Cs; R = La, Ce, Pr; Z = Co, Ni, Ru, Os) and La₁₀I₁₅Os₂

α-K₄R₆I₁₄Os (R = La, Pr): A Novel Iodine-Rich Structure with a Layered Network of Electron-Poor Clusters. An Incipient Delocalized System with Metal-like Conductivity