inorganic compounds
Dibarium tricadmium bismuthide(-I,-III) oxide, Ba2Cd3−δBi3O
aDepartment of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA, and bState Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100, People's Republic of China
*Correspondence e-mail: sbobev@mail.chem.udel.edu
Ba2Cd2.13Bi3O, a new bismuthide(-I,-III) oxide, crystallizes with a novel body-centered tetragonal structure (Pearson code tI36). The contains eight crystallographically unique sites in the all on special positions. Two Ba, one Cd and two Bi atoms have 4mm, the third Bi atom has mmm. and the O atom has m2 symmetry; the second Cd site (2mm. symmetry) is not fully occupied. The layered structure is complex and can be considered as an intergrowth of two types of slabs, viz. BaCdBiO with the ZrCuSiAs type and BaCd2Bi2 with the CeMg2Si2 type.
Related literature
Isotypic compounds are not known; however, there are several compounds whose structures are based on fused CdBi4 tetrahedral fragments, including BaCdBi2 (Brechtel et al., 1981), Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008). Condensed trigonal CdBi5 bi-pyramids and distorted CdBi6 octahedra are known for Ba2Cd3Bi4 (Cordier et al., 1982; Xia & Bobev, 2006b). The serendipitous discovery of the title compound was the result of a systematic study of the Ba—Cd—Bi system, inspired from the identification of Ba3Cd2Sb4 (Saparov et al., 2008). The compound BaCdSbF (Saparov & Bobev, 2010) is an example of a structure that epitomizes the BaCdBiO slabs. Recently, the idea that intermetallic oxide-pnictides and fluoride-pnictides could be a widespread class of quaternary solids has been discussed on the examples of Ba5Cd2Sb5Ox (0.5<x<0.7) and Ba5Cd2Sb5F (Saparov & Bobev, 2010). Theoretical considerations of non-classical electron-rich networks of the pnictogen elements is proved by Papoian & Hoffmann (2000). For standardization of the atomic coordinates, the program STRUCTURE-TIDY was used (Gelato & Parthé, 1987). For further information on structure types among intermetallic phases, we refer to Pearson's Handbook (Villars & Calvert, 1991).
Experimental
Crystal data
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Data collection: SMART (Bruker, 2002); cell SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: XP in SHELXTL and CrystalMaker (CrystalMaker, 2009); software used to prepare material for publication: SHELXTL.
Supporting information
https://doi.org/10.1107/S1600536810046283/wm2421sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810046283/wm2421Isup2.hkl
Handling of the reagents was done in an argon-filled
or under vacuum. All metals were with a stated purity higher than 99.9% (metal basis). They were purchased from Alfa, kept in a and were used as received.The
reaction was carried out in a 2 cm3 alumina crucible, using a mixture of elemental Ba and Cd in a molar ratio 3 : 2 and ca 2.1 grams of Bi. The reaction was aimed at growing crystals of Ba3Cd2Bi4, a hitherto unknown phase with the Ba3Cd2Sb4 structure (Saparov et al., 2008), using excess of bismuth as a metal The crucible was subsequently enclosed and flame-sealed in an evacuated fused silica ampoule, and then was heated at 200Kh-1 to 973 K, homogenized at 973 K for 20 h, cooled at a rate of -5Kh-1 to 723 K, where the excess Bi was removed by decanting it, leaving behind some irregularly shaped silver pieces and a few dark-to-black plates. The former were confirmed (via single-crystal and powder X-ray diffraction) to be Ba2Cd3Bi4 (Xia & Bobev, 2006b) and the latter turned out to be the title compound.After the structure of the new compound was solved from single-crystal X-ray diffraction data, it was realized that an unadventurous exposure of the starting materials to air has led to the formation of Ba2Cd2.13Bi3O (minor product), alongside the intermetallic phase (major product). Subsequent attempts to produce Ba2Cd2.13Bi3O in quantitative yields from reactions of Ba, Cd, Bi and BaO2 (Acros, 95%) were not successful, suggesting it might be a metastable phase.
The observed reflections satisfied the systematic extinction conditions for a body-centered cell, and the centrosymmetric
I4/mmm (No. 139) was chosen based on intensity statistics. The structure was successfully solved by which located six atomic positions – the two alkaline-earth metals, the three Bi atoms and one Cd atom. Subsequent structure refinements by full matrix least-squares methods on F2 showed the location of the oxygen atom in a tetrahedral void of Ba atoms with Ba–O distances of 2.6736 (14) Å. The difference Fourier map, however, also showed a residual peak of about 15 e- Å-3, located ca. 2.7 Å away from Bi. At first, we attempted to refine this as oxygen, however, there were serious problems with this model: 1) the electron density was much higher than a fully occupied O2-; 2) such coordination is inconsistent with the bonding requirements of oxygen; 3) the electron count was clearly implausible, viz. (Ba2+)2(Cd2+)2(Bi3-)2(Bi1-)(O2-)2. Here, the polyanionic networks features bismuth in two different coordination modes, which require different formal charges. The Bi atoms in the square-net are hypervalent, thus formally Bi1-, as analyzed computationally elsewhere (Papoian & Hoffmann, 2000). Therefore, this additional site was modeled as a partially occupied Cd atom (Cd2). The formal electron count taking into account the ca. 1/8 occupied Cd2 site is then (Ba2+)2(Cd2+)2.13(Bi3-)2(Bi1-)(O2-), rendering this model much more reasonable (despite the shortcoming of the shorter Cd2–Bi distances, vide supra)The occupancy of Cd2 was fixed at 12.5%. After including the partially occupied Cd2 site, the
converged at low residuals, accompanied with a flat final difference Fourier map - the maximum residual electron density lies 0.74 Å from Bi1, and the minimum residual electron density lies 2.33 Å from O.In the final ε, 1987).
cycles, all atoms were refined with anisotropic displacement parameters and with coordinates standardized using the software STRUCTURE-TIDY (Gelato & ParthOur previous work in the A–Cd–Bi systems, where the symbol 'A' is used to denote Ca, Sr, Ba, Eu, and Yb, led to the identification of several novel compounds such as Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008), among others. During these exploratory investigations, a new phase was serendipitously discovered. Upon subsequent structural work by means of single-crystal X-ray diffraction, it turned out to be the quaternary bismuthide(-I,-III) oxide Ba2Cd2.13Bi3O. It crystallizes in
I4/mmm in what appears to be a structure with a previously unreported structure type.The
of the title compound is shown schematically in Figure 1. In this representation, the layered nature of the structure and the basic building blocks are emphasized. As seen from the plot, it can be readily described as consisting of PbO-type layers of fused [CdBi4] tetrahedra, running parallel to the ab plane and which are alternately stacked along the c axis with BaO slabs and Bi square-nets (Figure 1). The actual structure is more complicated due to the partially occupied Cd2 site. The Cd2 atoms cap the Bi square-nets from above and below and link these fragments to the CdBi slabs. Figure 2 shows a representation with anisotropic displacement ellipsoids.The observed Cd–Bi (from 2.9688 (14) to 3.0565 (14) Å) and Bi–Bi distances (3.3514 (3) Å) are comparable to those reported for other cadmium-bismuthides such as BaCdBi2 (Brechtel et al., 1981), Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008), Ba2Cd3Bi4 (Cordier et al., 1982; Xia & Bobev, 2006b). The Cd–Bi distances involving the Cd2 atoms are shorter, but due to the very low occupancy of the Cd site (close to 1/8 occupied), the physical significance of such contacts is hard to be rationalized. The Ba–O contacts (2.6736 (14) Å) match well the recently reported Ba–O distances for Ba5Cd2Sb5Ox (0.5<x<0.7) (Saparov & Bobev, 2010).
Being a new structure type, it is important to relate the structure of the title compound to the structure(s) of previously reported phases with known structure types (Villars & Calvert, 1991). A good starting point for a discussion is BaCdBi2 (Brechtel et al., 1981), reported with the ZrAl3 type (Villars & Calvert, 1991). Coincidentally, BaCdBi2 also crystallizes in
I4/mmm and with cell parameters a = 4.77 Å and c = 23.6 Å. This structure features the very same PbO-type CdBi layers, stacked along the c-axis in alternating order with Bi square-nets. Not considering the partially occupied Cd2 site (for simplicity), one can then immediately reason that replacing every other BaBi slab in BaCdBi2 with a BaO slab will yield a hypothetical Ba2Cd2Bi3O compound. The latter can be considered as a super-structure of BaCdBi2 with doubled periodicity along the stacking detection, i.e., the c axis. Another way to relate the structure under consideration to other structure types is to consider the Cd2 site fully occupied and rationalize the structure of such an ordered Ba2Cd3Bi3O compound as an intergrowth of two types of slabs – BaCdBiO with the ZrCuSiAs type and BaCd2Bi2 with the CeMg2Si2 type, respectively. This line of thinking is schematically illustrated in Figure 1.Isotypic compounds are not known; however, there are several compounds whose structures are based on fused CdBi4 tetrahedral fragments, including BaCdBi2 (Brechtel et al., 1981), Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008). Condensed trigonal CdBi5 bi-pyramids and distorted CdBi6 octahedra are known for Ba2Cd3Bi4 (Cordier et al., 1982; Xia & Bobev, 2006b). The serendipitous discovery of the title compound was the result of a systematic study of the Ba—Cd—Bi system, inspired from the identification of Ba3Cd2Sb4 (Saparov et al., 2008). The compound BaCdSbF (Saparov & Bobev, 2010) is an example of a structure that epitomizes the BaCdBiO slabs. Recently, the idea that intermetallic oxide-pnictides and fluoride-pnictides could be a widespread class of quaternary solids has been discussed on the examples of Ba5Cd2Sb5Ox (0.5<x<0.7) and Ba5Cd2Sb5F (Saparov & Bobev, 2010). Theoretical considerations of non-classical electron-rich networks of the pnictigen elements is proved by Papoian & Hoffmann (2000). For standardization of the atomic coordinates, the program STRUCTURE-TIDY was used (Gelato & Parthé, 1987). For further information on structure types among intermetallic phases, we refer to Pearson's Handbook (Villars & Calvert, 1991).
Data collection: SMART (Bruker, 2002); cell
SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and CrystalMaker (CrystalMaker, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Ba2Cd2.13Bi3O | Dx = 7.788 Mg m−3 |
Mr = 1148.47 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, I4/mmm | Cell parameters from 938 reflections |
Hall symbol: -I 4 2 | θ = 4.7–26.7° |
a = 4.7396 (4) Å | µ = 66.05 mm−1 |
c = 43.601 (7) Å | T = 120 K |
V = 979.5 (2) Å3 | Plate, black |
Z = 4 | 0.05 × 0.05 × 0.02 mm |
F(000) = 1890 |
Bruker SMART APEX diffractometer | 433 independent reflections |
Radiation source: fine-focus sealed tube | 386 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.066 |
ω scans | θmax = 28.2°, θmin = 0.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2002) | h = −6→6 |
Tmin = 0.137, Tmax = 0.352 | k = −6→6 |
5274 measured reflections | l = −56→56 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.032 | Secondary atom site location: difference Fourier map |
wR(F2) = 0.073 | w = 1/[σ2(Fo2) + (0.0055P)2 + 124.164P] where P = (Fo2 + 2Fc2)/3 |
S = 1.22 | (Δ/σ)max < 0.001 |
433 reflections | Δρmax = 4.75 e Å−3 |
25 parameters | Δρmin = −1.93 e Å−3 |
Ba2Cd2.13Bi3O | Z = 4 |
Mr = 1148.47 | Mo Kα radiation |
Tetragonal, I4/mmm | µ = 66.05 mm−1 |
a = 4.7396 (4) Å | T = 120 K |
c = 43.601 (7) Å | 0.05 × 0.05 × 0.02 mm |
V = 979.5 (2) Å3 |
Bruker SMART APEX diffractometer | 433 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2002) | 386 reflections with I > 2σ(I) |
Tmin = 0.137, Tmax = 0.352 | Rint = 0.066 |
5274 measured reflections |
R[F2 > 2σ(F2)] = 0.032 | 0 restraints |
wR(F2) = 0.073 | w = 1/[σ2(Fo2) + (0.0055P)2 + 124.164P] where P = (Fo2 + 2Fc2)/3 |
S = 1.22 | Δρmax = 4.75 e Å−3 |
433 reflections | Δρmin = −1.93 e Å−3 |
25 parameters |
Experimental. Selected in the glove box, crystals were put in a Paratone N oil and cut to the desired dimensions. The chosen crystal was mounted on a tip of a glass fiber and quickly transferred onto the goniometer. The crystal was kept under a cold nitrogen stream to protect from the ambient air and moisture. Data collection is performed with four batch runs at φ = 0.00 ° (607 frames), at φ = 90.00 ° (607 frames), at φ = 180.00 ° (607 frames), and at φ = 270.00 (607 frames). Frame width = 0.30 ° in ω. Data are merged and treated with multi-scan absorption corrections. |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ba1 | 0.0000 | 0.0000 | 0.22161 (7) | 0.0529 (9) | |
Ba2 | 0.0000 | 0.0000 | 0.43606 (5) | 0.0129 (4) | |
Cd1 | 0.0000 | 0.5000 | 0.13679 (4) | 0.0181 (4) | |
Cd2 | 0.0000 | 0.0000 | 0.0330 (6) | 0.020 (4) | 0.13 |
Bi1 | 0.0000 | 0.0000 | 0.09251 (3) | 0.0165 (3) | |
Bi2 | 0.0000 | 0.0000 | 0.32220 (3) | 0.0145 (3) | |
Bi3 | 0.0000 | 0.5000 | 0.0000 | 0.0237 (4) | |
O | 0.0000 | 0.5000 | 0.2500 | 0.037 (7) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ba1 | 0.0665 (15) | 0.0665 (15) | 0.0257 (14) | 0.000 | 0.000 | 0.000 |
Ba2 | 0.0120 (6) | 0.0120 (6) | 0.0148 (10) | 0.000 | 0.000 | 0.000 |
Cd1 | 0.0133 (9) | 0.0217 (10) | 0.0193 (9) | 0.000 | 0.000 | 0.000 |
Cd2 | 0.014 (6) | 0.014 (6) | 0.032 (12) | 0.000 | 0.000 | 0.000 |
Bi1 | 0.0109 (4) | 0.0109 (4) | 0.0278 (7) | 0.000 | 0.000 | 0.000 |
Bi2 | 0.0137 (4) | 0.0137 (4) | 0.0161 (6) | 0.000 | 0.000 | 0.000 |
Bi3 | 0.0123 (7) | 0.0415 (9) | 0.0173 (7) | 0.000 | 0.000 | 0.000 |
O | 0.029 (10) | 0.029 (10) | 0.052 (19) | 0.000 | 0.000 | 0.000 |
Ba1—Oi | 2.6736 (14) | Cd2—Cd2xv | 2.87 (5) |
Ba1—O | 2.6736 (14) | Cd2—Ba2i | 3.613 (9) |
Ba1—Oii | 2.6736 (14) | Cd2—Ba2iv | 3.613 (9) |
Ba1—Oiii | 2.6736 (14) | Cd2—Ba2v | 3.613 (9) |
Ba1—Bi2iv | 3.8575 (16) | Cd2—Ba2ii | 3.613 (9) |
Ba1—Bi2i | 3.8575 (16) | Bi1—Cd1xiii | 3.0565 (14) |
Ba1—Bi2ii | 3.8575 (16) | Bi1—Cd1xi | 3.0565 (14) |
Ba1—Bi2v | 3.8575 (16) | Bi1—Cd1iii | 3.0565 (14) |
Ba2—Bi1iv | 3.5756 (9) | Bi1—Ba2iv | 3.5756 (9) |
Ba2—Bi1i | 3.5756 (9) | Bi1—Ba2i | 3.5756 (9) |
Ba2—Bi1ii | 3.5756 (9) | Bi1—Ba2ii | 3.5756 (9) |
Ba2—Bi1v | 3.5756 (9) | Bi1—Ba2v | 3.5756 (9) |
Ba2—Cd2i | 3.613 (9) | Bi2—Cd1xvi | 2.9688 (14) |
Ba2—Cd2iv | 3.613 (9) | Bi2—Cd1i | 2.9688 (14) |
Ba2—Cd2ii | 3.613 (9) | Bi2—Cd1xvii | 2.9688 (14) |
Ba2—Cd2v | 3.613 (9) | Bi2—Cd1ii | 2.9688 (14) |
Ba2—Bi3vi | 3.6588 (16) | Bi2—Ba1iv | 3.8575 (16) |
Ba2—Bi3vii | 3.6588 (16) | Bi2—Ba1i | 3.8575 (16) |
Ba2—Bi3viii | 3.6588 (16) | Bi2—Ba1v | 3.8575 (16) |
Ba2—Bi3ix | 3.6588 (16) | Bi2—Ba1ii | 3.8575 (16) |
Cd1—Bi2i | 2.9689 (14) | Bi3—Cd2xv | 2.771 (13) |
Cd1—Bi2ii | 2.9689 (14) | Bi3—Cd2x | 2.771 (13) |
Cd1—Bi1 | 3.0565 (14) | Bi3—Cd2xviii | 2.771 (13) |
Cd1—Bi1x | 3.0565 (14) | Bi3—Bi3xii | 3.3514 (3) |
Cd1—Cd1xi | 3.3514 (3) | Bi3—Bi3xi | 3.3514 (3) |
Cd1—Cd1xii | 3.3514 (3) | Bi3—Bi3xiv | 3.3514 (3) |
Cd1—Cd1xiii | 3.3514 (3) | Bi3—Bi3xiii | 3.3514 (3) |
Cd1—Cd1xiv | 3.3514 (3) | Bi3—Ba2i | 3.6588 (16) |
Cd1—Ba2ii | 3.963 (2) | Bi3—Ba2xix | 3.6588 (16) |
Cd1—Ba2i | 3.963 (2) | Bi3—Ba2xx | 3.6588 (16) |
Cd2—Bi1 | 2.60 (2) | Bi3—Ba2ii | 3.6588 (16) |
Cd2—Bi3xi | 2.771 (13) | O—Ba1i | 2.6736 (14) |
Cd2—Bi3iii | 2.771 (13) | O—Ba1x | 2.6736 (14) |
Cd2—Bi3xiii | 2.771 (13) | O—Ba1ii | 2.6736 (14) |
Cd2—Bi3 | 2.771 (13) | ||
Oi—Ba1—O | 77.62 (5) | Bi3xi—Cd2—Bi3iii | 74.4 (4) |
Oi—Ba1—Oii | 124.84 (12) | Bi1—Cd2—Bi3xiii | 121.2 (4) |
O—Ba1—Oii | 77.62 (5) | Bi3xi—Cd2—Bi3xiii | 117.5 (9) |
Oi—Ba1—Oiii | 77.62 (5) | Bi3iii—Cd2—Bi3xiii | 74.4 (4) |
O—Ba1—Oiii | 124.84 (12) | Bi1—Cd2—Bi3 | 121.2 (4) |
Oii—Ba1—Oiii | 77.62 (5) | Bi3xi—Cd2—Bi3 | 74.4 (4) |
Oi—Ba1—Bi2iv | 140.694 (10) | Bi3iii—Cd2—Bi3 | 117.5 (9) |
O—Ba1—Bi2iv | 140.694 (10) | Bi3xiii—Cd2—Bi3 | 74.4 (4) |
Oii—Ba1—Bi2iv | 71.62 (2) | Bi1—Cd2—Cd2xv | 180.0 |
Oiii—Ba1—Bi2iv | 71.62 (2) | Bi3xi—Cd2—Cd2xv | 58.8 (4) |
Oi—Ba1—Bi2i | 71.62 (2) | Bi3iii—Cd2—Cd2xv | 58.8 (4) |
O—Ba1—Bi2i | 71.62 (2) | Bi3xiii—Cd2—Cd2xv | 58.8 (4) |
Oii—Ba1—Bi2i | 140.694 (10) | Bi3—Cd2—Cd2xv | 58.8 (4) |
Oiii—Ba1—Bi2i | 140.694 (10) | Bi1—Cd2—Ba2i | 68.0 (4) |
Bi2iv—Ba1—Bi2i | 120.64 (8) | Bi3xi—Cd2—Ba2i | 138.99 (16) |
Oi—Ba1—Bi2ii | 140.694 (9) | Bi3iii—Cd2—Ba2i | 138.99 (16) |
O—Ba1—Bi2ii | 71.62 (2) | Bi3xiii—Cd2—Ba2i | 68.47 (4) |
Oii—Ba1—Bi2ii | 71.62 (2) | Bi3—Cd2—Ba2i | 68.47 (4) |
Oiii—Ba1—Bi2ii | 140.694 (9) | Cd2xv—Cd2—Ba2i | 112.0 (4) |
Bi2iv—Ba1—Bi2ii | 75.81 (4) | Bi1—Cd2—Ba2iv | 68.0 (4) |
Bi2i—Ba1—Bi2ii | 75.81 (4) | Bi3xi—Cd2—Ba2iv | 68.47 (4) |
Oi—Ba1—Bi2v | 71.62 (2) | Bi3iii—Cd2—Ba2iv | 68.47 (4) |
O—Ba1—Bi2v | 140.694 (9) | Bi3xiii—Cd2—Ba2iv | 138.99 (16) |
Oii—Ba1—Bi2v | 140.694 (9) | Bi3—Cd2—Ba2iv | 138.99 (16) |
Oiii—Ba1—Bi2v | 71.62 (2) | Cd2xv—Cd2—Ba2iv | 112.0 (4) |
Bi2iv—Ba1—Bi2v | 75.81 (4) | Ba2i—Cd2—Ba2iv | 136.1 (7) |
Bi2i—Ba1—Bi2v | 75.81 (4) | Bi1—Cd2—Ba2v | 68.0 (4) |
Bi2ii—Ba1—Bi2v | 120.64 (8) | Bi3xi—Cd2—Ba2v | 138.99 (16) |
Oi—Ba1—Ba1i | 38.81 (2) | Bi3iii—Cd2—Ba2v | 68.47 (4) |
O—Ba1—Ba1i | 38.81 (2) | Bi3xiii—Cd2—Ba2v | 68.47 (4) |
Oii—Ba1—Ba1i | 103.24 (10) | Bi3—Cd2—Ba2v | 138.99 (16) |
Oiii—Ba1—Ba1i | 103.24 (10) | Cd2xv—Cd2—Ba2v | 112.0 (4) |
Bi2iv—Ba1—Ba1i | 173.23 (11) | Ba2i—Cd2—Ba2v | 82.0 (3) |
Bi2i—Ba1—Ba1i | 66.13 (4) | Ba2iv—Cd2—Ba2v | 82.0 (3) |
Bi2ii—Ba1—Ba1i | 107.110 (13) | Bi1—Cd2—Ba2ii | 68.0 (4) |
Bi2v—Ba1—Ba1i | 107.110 (13) | Bi3xi—Cd2—Ba2ii | 68.47 (4) |
Oi—Ba1—Ba1v | 38.81 (2) | Bi3iii—Cd2—Ba2ii | 138.99 (16) |
O—Ba1—Ba1v | 103.24 (10) | Bi3xiii—Cd2—Ba2ii | 138.99 (16) |
Oii—Ba1—Ba1v | 103.24 (10) | Bi3—Cd2—Ba2ii | 68.47 (4) |
Oiii—Ba1—Ba1v | 38.81 (2) | Cd2xv—Cd2—Ba2ii | 112.0 (4) |
Bi2iv—Ba1—Ba1v | 107.110 (12) | Ba2i—Cd2—Ba2ii | 82.0 (3) |
Bi2i—Ba1—Ba1v | 107.110 (13) | Ba2iv—Cd2—Ba2ii | 82.0 (3) |
Bi2ii—Ba1—Ba1v | 173.23 (11) | Ba2v—Cd2—Ba2ii | 136.1 (7) |
Bi2v—Ba1—Ba1v | 66.13 (3) | Cd2—Bi1—Cd1 | 129.16 (3) |
Ba1i—Ba1—Ba1v | 69.33 (7) | Cd2—Bi1—Cd1xiii | 129.17 (3) |
Oi—Ba1—Ba1ii | 103.24 (10) | Cd1—Bi1—Cd1xiii | 66.49 (4) |
O—Ba1—Ba1ii | 38.81 (2) | Cd2—Bi1—Cd1xi | 129.17 (3) |
Oii—Ba1—Ba1ii | 38.81 (2) | Cd1—Bi1—Cd1xi | 66.49 (4) |
Oiii—Ba1—Ba1ii | 103.24 (10) | Cd1xiii—Bi1—Cd1xi | 101.67 (7) |
Bi2iv—Ba1—Ba1ii | 107.110 (12) | Cd2—Bi1—Cd1iii | 129.17 (3) |
Bi2i—Ba1—Ba1ii | 107.110 (13) | Cd1—Bi1—Cd1iii | 101.67 (7) |
Bi2ii—Ba1—Ba1ii | 66.13 (3) | Cd1xiii—Bi1—Cd1iii | 66.49 (4) |
Bi2v—Ba1—Ba1ii | 173.23 (11) | Cd1xi—Bi1—Cd1iii | 66.49 (4) |
Ba1i—Ba1—Ba1ii | 69.33 (7) | Cd2—Bi1—Ba2iv | 69.60 (4) |
Ba1v—Ba1—Ba1ii | 107.10 (14) | Cd1—Bi1—Ba2iv | 137.22 (3) |
Oi—Ba1—Ba1iv | 103.24 (10) | Cd1xiii—Bi1—Ba2iv | 137.22 (3) |
O—Ba1—Ba1iv | 103.24 (10) | Cd1xi—Bi1—Ba2iv | 72.92 (3) |
Oii—Ba1—Ba1iv | 38.81 (2) | Cd1iii—Bi1—Ba2iv | 72.92 (3) |
Oiii—Ba1—Ba1iv | 38.81 (2) | Cd2—Bi1—Ba2i | 69.60 (4) |
Bi2iv—Ba1—Ba1iv | 66.13 (3) | Cd1—Bi1—Ba2i | 72.92 (3) |
Bi2i—Ba1—Ba1iv | 173.23 (11) | Cd1xiii—Bi1—Ba2i | 72.92 (3) |
Bi2ii—Ba1—Ba1iv | 107.110 (12) | Cd1xi—Bi1—Ba2i | 137.22 (3) |
Bi2v—Ba1—Ba1iv | 107.110 (12) | Cd1iii—Bi1—Ba2i | 137.22 (3) |
Ba1i—Ba1—Ba1iv | 107.10 (14) | Ba2iv—Bi1—Ba2i | 139.21 (8) |
Ba1v—Ba1—Ba1iv | 69.33 (7) | Cd2—Bi1—Ba2ii | 69.60 (4) |
Ba1ii—Ba1—Ba1iv | 69.33 (7) | Cd1—Bi1—Ba2ii | 72.92 (3) |
Bi1iv—Ba2—Bi1i | 139.21 (8) | Cd1xiii—Bi1—Ba2ii | 137.22 (3) |
Bi1iv—Ba2—Bi1ii | 83.02 (3) | Cd1xi—Bi1—Ba2ii | 72.92 (3) |
Bi1i—Ba2—Bi1ii | 83.02 (3) | Cd1iii—Bi1—Ba2ii | 137.22 (3) |
Bi1iv—Ba2—Bi1v | 83.02 (3) | Ba2iv—Bi1—Ba2ii | 83.02 (3) |
Bi1i—Ba2—Bi1v | 83.02 (3) | Ba2i—Bi1—Ba2ii | 83.02 (3) |
Bi1ii—Ba2—Bi1v | 139.21 (8) | Cd2—Bi1—Ba2v | 69.60 (4) |
Bi1iv—Ba2—Cd2i | 178.4 (4) | Cd1—Bi1—Ba2v | 137.22 (3) |
Bi1i—Ba2—Cd2i | 42.3 (4) | Cd1xiii—Bi1—Ba2v | 72.92 (3) |
Bi1ii—Ba2—Cd2i | 97.49 (12) | Cd1xi—Bi1—Ba2v | 137.22 (3) |
Bi1v—Ba2—Cd2i | 97.49 (12) | Cd1iii—Bi1—Ba2v | 72.92 (3) |
Bi1iv—Ba2—Cd2iv | 42.3 (4) | Ba2iv—Bi1—Ba2v | 83.02 (3) |
Bi1i—Ba2—Cd2iv | 178.4 (4) | Ba2i—Bi1—Ba2v | 83.02 (3) |
Bi1ii—Ba2—Cd2iv | 97.49 (12) | Ba2ii—Bi1—Ba2v | 139.21 (8) |
Bi1v—Ba2—Cd2iv | 97.49 (12) | Cd1xvi—Bi2—Cd1i | 68.73 (4) |
Cd2i—Ba2—Cd2iv | 136.1 (7) | Cd1xvi—Bi2—Cd1xvii | 105.92 (7) |
Bi1iv—Ba2—Cd2ii | 97.49 (12) | Cd1i—Bi2—Cd1xvii | 68.73 (4) |
Bi1i—Ba2—Cd2ii | 97.49 (12) | Cd1xvi—Bi2—Cd1ii | 68.73 (4) |
Bi1ii—Ba2—Cd2ii | 42.3 (4) | Cd1i—Bi2—Cd1ii | 105.92 (7) |
Bi1v—Ba2—Cd2ii | 178.4 (4) | Cd1xvii—Bi2—Cd1ii | 68.73 (4) |
Cd2i—Ba2—Cd2ii | 82.0 (3) | Cd1xvi—Bi2—Ba1iv | 142.059 (16) |
Cd2iv—Ba2—Cd2ii | 82.0 (3) | Cd1i—Bi2—Ba1iv | 142.059 (16) |
Bi1iv—Ba2—Cd2v | 97.49 (12) | Cd1xvii—Bi2—Ba1iv | 78.92 (4) |
Bi1i—Ba2—Cd2v | 97.49 (12) | Cd1ii—Bi2—Ba1iv | 78.92 (4) |
Bi1ii—Ba2—Cd2v | 178.4 (4) | Cd1xvi—Bi2—Ba1i | 78.92 (4) |
Bi1v—Ba2—Cd2v | 42.3 (4) | Cd1i—Bi2—Ba1i | 78.92 (4) |
Cd2i—Ba2—Cd2v | 82.0 (3) | Cd1xvii—Bi2—Ba1i | 142.059 (17) |
Cd2iv—Ba2—Cd2v | 82.0 (3) | Cd1ii—Bi2—Ba1i | 142.059 (17) |
Cd2ii—Ba2—Cd2v | 136.1 (7) | Ba1iv—Bi2—Ba1i | 120.64 (8) |
Bi1iv—Ba2—Bi3vi | 134.01 (4) | Cd1xvi—Bi2—Ba1v | 142.059 (17) |
Bi1i—Ba2—Bi3vi | 80.58 (2) | Cd1i—Bi2—Ba1v | 78.92 (4) |
Bi1ii—Ba2—Bi3vi | 80.58 (2) | Cd1xvii—Bi2—Ba1v | 78.92 (4) |
Bi1v—Ba2—Bi3vi | 134.01 (4) | Cd1ii—Bi2—Ba1v | 142.059 (17) |
Cd2i—Ba2—Bi3vi | 44.8 (3) | Ba1iv—Bi2—Ba1v | 75.81 (4) |
Cd2iv—Ba2—Bi3vi | 98.0 (3) | Ba1i—Bi2—Ba1v | 75.81 (4) |
Cd2ii—Ba2—Bi3vi | 44.8 (3) | Cd1xvi—Bi2—Ba1ii | 78.92 (4) |
Cd2v—Ba2—Bi3vi | 98.0 (3) | Cd1i—Bi2—Ba1ii | 142.059 (17) |
Bi1iv—Ba2—Bi3vii | 134.01 (4) | Cd1xvii—Bi2—Ba1ii | 142.059 (16) |
Bi1i—Ba2—Bi3vii | 80.58 (2) | Cd1ii—Bi2—Ba1ii | 78.92 (4) |
Bi1ii—Ba2—Bi3vii | 134.01 (4) | Ba1iv—Bi2—Ba1ii | 75.81 (4) |
Bi1v—Ba2—Bi3vii | 80.58 (2) | Ba1i—Bi2—Ba1ii | 75.81 (4) |
Cd2i—Ba2—Bi3vii | 44.8 (3) | Ba1v—Bi2—Ba1ii | 120.64 (8) |
Cd2iv—Ba2—Bi3vii | 98.0 (3) | Cd2—Bi3—Cd2xv | 62.5 (9) |
Cd2ii—Ba2—Bi3vii | 98.0 (3) | Cd2—Bi3—Cd2x | 117.5 (9) |
Cd2v—Ba2—Bi3vii | 44.8 (3) | Cd2xv—Bi3—Cd2x | 180.0 (9) |
Bi3vi—Ba2—Bi3vii | 54.51 (3) | Cd2—Bi3—Cd2xviii | 179.997 (2) |
Bi1iv—Ba2—Bi3viii | 80.58 (2) | Cd2xv—Bi3—Cd2xviii | 117.5 (9) |
Bi1i—Ba2—Bi3viii | 134.01 (4) | Cd2x—Bi3—Cd2xviii | 62.5 (9) |
Bi1ii—Ba2—Bi3viii | 134.01 (4) | Cd2—Bi3—Bi3xii | 127.2 (2) |
Bi1v—Ba2—Bi3viii | 80.58 (2) | Cd2xv—Bi3—Bi3xii | 127.2 (2) |
Cd2i—Ba2—Bi3viii | 98.0 (3) | Cd2x—Bi3—Bi3xii | 52.8 (2) |
Cd2iv—Ba2—Bi3viii | 44.8 (3) | Cd2xviii—Bi3—Bi3xii | 52.8 (2) |
Cd2ii—Ba2—Bi3viii | 98.0 (3) | Cd2—Bi3—Bi3xi | 52.8 (2) |
Cd2v—Ba2—Bi3viii | 44.8 (3) | Cd2xv—Bi3—Bi3xi | 52.8 (2) |
Bi3vi—Ba2—Bi3viii | 80.74 (4) | Cd2x—Bi3—Bi3xi | 127.2 (2) |
Bi3vii—Ba2—Bi3viii | 54.51 (3) | Cd2xviii—Bi3—Bi3xi | 127.2 (2) |
Bi1iv—Ba2—Bi3ix | 80.58 (2) | Bi3xii—Bi3—Bi3xi | 180.0 |
Bi1i—Ba2—Bi3ix | 134.01 (4) | Cd2—Bi3—Bi3xiv | 127.2 (2) |
Bi1ii—Ba2—Bi3ix | 80.58 (2) | Cd2xv—Bi3—Bi3xiv | 127.2 (2) |
Bi1v—Ba2—Bi3ix | 134.01 (4) | Cd2x—Bi3—Bi3xiv | 52.8 (2) |
Cd2i—Ba2—Bi3ix | 98.0 (3) | Cd2xviii—Bi3—Bi3xiv | 52.8 (2) |
Cd2iv—Ba2—Bi3ix | 44.8 (3) | Bi3xii—Bi3—Bi3xiv | 90.0 |
Cd2ii—Ba2—Bi3ix | 44.8 (3) | Bi3xi—Bi3—Bi3xiv | 90.0 |
Cd2v—Ba2—Bi3ix | 98.0 (3) | Cd2—Bi3—Bi3xiii | 52.8 (2) |
Bi3vi—Ba2—Bi3ix | 54.51 (3) | Cd2xv—Bi3—Bi3xiii | 52.8 (2) |
Bi3vii—Ba2—Bi3ix | 80.74 (4) | Cd2x—Bi3—Bi3xiii | 127.2 (2) |
Bi3viii—Ba2—Bi3ix | 54.51 (3) | Cd2xviii—Bi3—Bi3xiii | 127.2 (2) |
Bi2i—Cd1—Bi2ii | 105.92 (7) | Bi3xii—Bi3—Bi3xiii | 90.0 |
Bi2i—Cd1—Bi1 | 112.360 (17) | Bi3xi—Bi3—Bi3xiii | 90.0 |
Bi2ii—Cd1—Bi1 | 112.360 (17) | Bi3xiv—Bi3—Bi3xiii | 180.0 |
Bi2i—Cd1—Bi1x | 112.360 (17) | Cd2—Bi3—Ba2i | 66.7 (3) |
Bi2ii—Cd1—Bi1x | 112.360 (17) | Cd2xv—Bi3—Ba2i | 113.3 (3) |
Bi1—Cd1—Bi1x | 101.67 (7) | Cd2x—Bi3—Ba2i | 66.7 (3) |
Bi2i—Cd1—Cd1xi | 124.361 (18) | Cd2xviii—Bi3—Ba2i | 113.3 (3) |
Bi2ii—Cd1—Cd1xi | 55.637 (18) | Bi3xii—Bi3—Ba2i | 62.743 (13) |
Bi1—Cd1—Cd1xi | 56.755 (18) | Bi3xi—Bi3—Ba2i | 117.257 (13) |
Bi1x—Cd1—Cd1xi | 123.248 (18) | Bi3xiv—Bi3—Ba2i | 117.257 (13) |
Bi2i—Cd1—Cd1xii | 55.636 (18) | Bi3xiii—Bi3—Ba2i | 62.743 (13) |
Bi2ii—Cd1—Cd1xii | 124.361 (18) | Cd2—Bi3—Ba2xix | 113.3 (3) |
Bi1—Cd1—Cd1xii | 123.248 (18) | Cd2xv—Bi3—Ba2xix | 66.7 (3) |
Bi1x—Cd1—Cd1xii | 56.755 (18) | Cd2x—Bi3—Ba2xix | 113.3 (3) |
Cd1xi—Cd1—Cd1xii | 180.0 | Cd2xviii—Bi3—Ba2xix | 66.7 (3) |
Bi2i—Cd1—Cd1xiii | 55.637 (18) | Bi3xii—Bi3—Ba2xix | 117.257 (13) |
Bi2ii—Cd1—Cd1xiii | 124.361 (18) | Bi3xi—Bi3—Ba2xix | 62.743 (13) |
Bi1—Cd1—Cd1xiii | 56.755 (18) | Bi3xiv—Bi3—Ba2xix | 62.743 (13) |
Bi1x—Cd1—Cd1xiii | 123.248 (18) | Bi3xiii—Bi3—Ba2xix | 117.257 (13) |
Cd1xi—Cd1—Cd1xiii | 90.0 | Ba2i—Bi3—Ba2xix | 180.00 (4) |
Cd1xii—Cd1—Cd1xiii | 90.0 | Cd2—Bi3—Ba2xx | 113.3 (3) |
Bi2i—Cd1—Cd1xiv | 124.361 (18) | Cd2xv—Bi3—Ba2xx | 66.7 (3) |
Bi2ii—Cd1—Cd1xiv | 55.637 (18) | Cd2x—Bi3—Ba2xx | 113.3 (3) |
Bi1—Cd1—Cd1xiv | 123.248 (18) | Cd2xviii—Bi3—Ba2xx | 66.7 (3) |
Bi1x—Cd1—Cd1xiv | 56.755 (18) | Bi3xii—Bi3—Ba2xx | 62.743 (13) |
Cd1xi—Cd1—Cd1xiv | 90.0 | Bi3xi—Bi3—Ba2xx | 117.257 (13) |
Cd1xii—Cd1—Cd1xiv | 90.0 | Bi3xiv—Bi3—Ba2xx | 117.257 (13) |
Cd1xiii—Cd1—Cd1xiv | 180.0 | Bi3xiii—Bi3—Ba2xx | 62.743 (13) |
Bi2i—Cd1—Ba2ii | 163.77 (5) | Ba2i—Bi3—Ba2xx | 99.26 (4) |
Bi2ii—Cd1—Ba2ii | 90.31 (3) | Ba2xix—Bi3—Ba2xx | 80.74 (4) |
Bi1—Cd1—Ba2ii | 59.59 (3) | Cd2—Bi3—Ba2ii | 66.7 (3) |
Bi1x—Cd1—Ba2ii | 59.59 (3) | Cd2xv—Bi3—Ba2ii | 113.3 (3) |
Cd1xi—Cd1—Ba2ii | 64.988 (15) | Cd2x—Bi3—Ba2ii | 66.7 (3) |
Cd1xii—Cd1—Ba2ii | 115.015 (15) | Cd2xviii—Bi3—Ba2ii | 113.3 (3) |
Cd1xiii—Cd1—Ba2ii | 115.015 (15) | Bi3xii—Bi3—Ba2ii | 117.257 (13) |
Cd1xiv—Cd1—Ba2ii | 64.988 (15) | Bi3xi—Bi3—Ba2ii | 62.743 (13) |
Bi2i—Cd1—Ba2i | 90.31 (3) | Bi3xiv—Bi3—Ba2ii | 62.743 (13) |
Bi2ii—Cd1—Ba2i | 163.77 (5) | Bi3xiii—Bi3—Ba2ii | 117.257 (13) |
Bi1—Cd1—Ba2i | 59.59 (3) | Ba2i—Bi3—Ba2ii | 80.74 (4) |
Bi1x—Cd1—Ba2i | 59.59 (3) | Ba2xix—Bi3—Ba2ii | 99.26 (4) |
Cd1xi—Cd1—Ba2i | 115.015 (15) | Ba2xx—Bi3—Ba2ii | 180.00 (4) |
Cd1xii—Cd1—Ba2i | 64.988 (15) | Ba1—O—Ba1i | 102.38 (5) |
Cd1xiii—Cd1—Ba2i | 64.988 (15) | Ba1—O—Ba1x | 124.84 (12) |
Cd1xiv—Cd1—Ba2i | 115.015 (15) | Ba1i—O—Ba1x | 102.38 (5) |
Ba2ii—Cd1—Ba2i | 73.45 (5) | Ba1—O—Ba1ii | 102.38 (5) |
Bi1—Cd2—Bi3xi | 121.2 (4) | Ba1i—O—Ba1ii | 124.84 (12) |
Bi1—Cd2—Bi3iii | 121.2 (4) | Ba1x—O—Ba1ii | 102.38 (5) |
Symmetry codes: (i) −x+1/2, −y+1/2, −z+1/2; (ii) −x−1/2, −y+1/2, −z+1/2; (iii) x, y−1, z; (iv) −x−1/2, −y−1/2, −z+1/2; (v) −x+1/2, −y−1/2, −z+1/2; (vi) −y+1/2, x+1/2, z+1/2; (vii) x+1/2, y−1/2, z+1/2; (viii) −y+1/2, x−1/2, z+1/2; (ix) x−1/2, y−1/2, z+1/2; (x) x, y+1, z; (xi) −y, x, z; (xii) −y+1, x+1, z; (xiii) −y+1, x, z; (xiv) −y, x+1, z; (xv) −x, −y, −z; (xvi) y−1/2, −x+1/2, −z+1/2; (xvii) y−1/2, −x−1/2, −z+1/2; (xviii) −x, −y+1, −z; (xix) x−1/2, y+1/2, z−1/2; (xx) x+1/2, y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | Ba2Cd2.13Bi3O |
Mr | 1148.47 |
Crystal system, space group | Tetragonal, I4/mmm |
Temperature (K) | 120 |
a, c (Å) | 4.7396 (4), 43.601 (7) |
V (Å3) | 979.5 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 66.05 |
Crystal size (mm) | 0.05 × 0.05 × 0.02 |
Data collection | |
Diffractometer | Bruker SMART APEX |
Absorption correction | Multi-scan (SADABS; Bruker, 2002) |
Tmin, Tmax | 0.137, 0.352 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5274, 433, 386 |
Rint | 0.066 |
(sin θ/λ)max (Å−1) | 0.665 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.073, 1.22 |
No. of reflections | 433 |
No. of parameters | 25 |
w = 1/[σ2(Fo2) + (0.0055P)2 + 124.164P] where P = (Fo2 + 2Fc2)/3 | |
Δρmax, Δρmin (e Å−3) | 4.75, −1.93 |
Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), XP in SHELXTL (Sheldrick, 2008) and CrystalMaker (CrystalMaker, 2009).
Acknowledgements
The authors acknowledge financial support from the University of Delaware and the Petroleum Research Fund (ACS–PRF).
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Our previous work in the A–Cd–Bi systems, where the symbol 'A' is used to denote Ca, Sr, Ba, Eu, and Yb, led to the identification of several novel compounds such as Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008), among others. During these exploratory investigations, a new phase was serendipitously discovered. Upon subsequent structural work by means of single-crystal X-ray diffraction, it turned out to be the quaternary bismuthide(-I,-III) oxide Ba2Cd2.13Bi3O. It crystallizes in space group I4/mmm in what appears to be a structure with a previously unreported structure type.
The crystal structure of the title compound is shown schematically in Figure 1. In this representation, the layered nature of the structure and the basic building blocks are emphasized. As seen from the plot, it can be readily described as consisting of PbO-type layers of fused [CdBi4] tetrahedra, running parallel to the ab plane and which are alternately stacked along the c axis with BaO slabs and Bi square-nets (Figure 1). The actual structure is more complicated due to the partially occupied Cd2 site. The Cd2 atoms cap the Bi square-nets from above and below and link these fragments to the CdBi slabs. Figure 2 shows a representation with anisotropic displacement ellipsoids.
The observed Cd–Bi (from 2.9688 (14) to 3.0565 (14) Å) and Bi–Bi distances (3.3514 (3) Å) are comparable to those reported for other cadmium-bismuthides such as BaCdBi2 (Brechtel et al., 1981), Ba11Cd8Bi14 (Xia & Bobev, 2006a), Eu10Cd8Bi12 (Xia & Bobev, 2007), Sr21Cd4Bi18 (Xia & Bobev, 2008), Ba2Cd3Bi4 (Cordier et al., 1982; Xia & Bobev, 2006b). The Cd–Bi distances involving the Cd2 atoms are shorter, but due to the very low occupancy of the Cd site (close to 1/8 occupied), the physical significance of such contacts is hard to be rationalized. The Ba–O contacts (2.6736 (14) Å) match well the recently reported Ba–O distances for Ba5Cd2Sb5Ox (0.5<x<0.7) (Saparov & Bobev, 2010).
Being a new structure type, it is important to relate the structure of the title compound to the structure(s) of previously reported phases with known structure types (Villars & Calvert, 1991). A good starting point for a discussion is BaCdBi2 (Brechtel et al., 1981), reported with the ZrAl3 type (Villars & Calvert, 1991). Coincidentally, BaCdBi2 also crystallizes in space group I4/mmm and with cell parameters a = 4.77 Å and c = 23.6 Å. This structure features the very same PbO-type CdBi layers, stacked along the c-axis in alternating order with Bi square-nets. Not considering the partially occupied Cd2 site (for simplicity), one can then immediately reason that replacing every other BaBi slab in BaCdBi2 with a BaO slab will yield a hypothetical Ba2Cd2Bi3O compound. The latter can be considered as a super-structure of BaCdBi2 with doubled periodicity along the stacking detection, i.e., the c axis. Another way to relate the structure under consideration to other structure types is to consider the Cd2 site fully occupied and rationalize the structure of such an ordered Ba2Cd3Bi3O compound as an intergrowth of two types of slabs – BaCdBiO with the ZrCuSiAs type and BaCd2Bi2 with the CeMg2Si2 type, respectively. This line of thinking is schematically illustrated in Figure 1.