Barium antimonide oxide, Ba₃Sb₂O

The antimonide oxide Ba₃Sb₂O consists of discrete [Sb₂]^4- and O^2- anions, and crystallizes with a new structure type. The Sb-Sb distances are comparable to those known from electron-precise zintl phases and the tetrahedral coordination of the O^2- anion is also observed in some other Ba-rich metallide oxides.

S1. Comment

Besides Ba₄Sb₂O, with isolated Sb^3- and O^2- anions (George & Röhr, 1996), Ba₃Sb₂O is the second ternary antimonide oxide to be reported. It crystallizes in the orthorhombic space group Pbam with a new structure type. The crystal structure contains [Sb₂]^4- and O^2- anions separated by charge-compensating Ba²⁺ cations. The Sb—Sb distances in the two crystallographically independent dumb-bells are 2.837 (2) (Sb1—Sb1) and 2.857 (2) Å (Sb2—Sb2), and are thus comparable to those observed in Ba₅Sb₄ [d(Sb—Sb) = 2.886 Å; Brechtel et al., 1981; Derrien et al., 1999], in the mixed antimonide K₂Ba₃Sb₄ [d(Sb—Sb) = 2.856 and 2.899 Å; Eisenmann et al., 1999] or in KBa₄Sb₃O [d(Sb—Sb) = 2.898 Å; Eisenmann et al., 1999]. In the only known binary alkaline phase with Sb dumb-bells, Cs₄Sb₂ (Hirschle & Röhr, 2001), the Sb—Sb bond is slightly longer (2.923 Å), showing that the distance is somewhat influenced by the crystal packing. The Sb atoms of the [Sb₂]^4- dumb-bells in all these compounds have a tricapped trigonal prismatic environment composed of six Ba atoms (Ba1 and Ba2, trigonal prism), two Ba atoms (Ba3) and their Sb partner (caps), shown in Figs. 1 and 2 for the title compound. The oxide ions are coordinated by four barium cations (Fig. 3) in a distorted tetrahedral geometry, with O—Ba distances ranging from 2.528 (9) to 2.630 (3) Å. Two additional Ba cations, with much longer O—Ba distances of 4.04 (1) (Ba1) and 4.06 (1) Å (Ba2), extend the coordination to an octahedron. A similar coordination and comparable O—Ba distances are known from other oxygen-poor Ba metallide oxides and are observed, for example, in KBa₄Sb₃O [d(O—Ba) = 2.5436 Å; Eisenmann et al., 1999] and Ba₁₀Ge₇O₃ [d(O—Ba) = 2.57–2.79 Å; von Schnering et al., 1997]. The O-centered Ba tetrahedra (center at z = 0) are connected via corners to form chains running along [001]. In the unit cell (Fig. 4), the Sb–Sb anions all Sb at z = 1/2) are located between these chains. The Sb2–Sb2 dumb-bells at the unit-cell origin and the center of the cell are oriented along [010], whereas the Sb1–Sb1 dumb-bells at the faces of the unit cell are oriented along [100]. The coordination spheres of the Ba cations are composed of one O and six Sb (Ba1 and Ba2) or two O and four Sb (Ba3) anions.

Related literature

For related literature, see: Brechtel et al. (1981); Derrien et al. (1999); Eisenmann et al. (1999); George & Röhr (1996); Hirschle & Röhr (2001); Pickhard & Röhr (2000).

S2. Experimental

Single crystals of Ba₃Sb₂O were first obtained from melts of stoichiometric mixtures of Ba (99%, Alkali-Metallhandelsgesellschaft mbH, Bonn), Sb (99%, ABCR, Karlsruhe) and Sb₂O₃ (99.999%, ABCR, Karlsruhe). Ba (2.455 g, 17.88 mmol), Sb (0.967 g, 7.943 mmol) and Sb₂O₃ (0.578 g, 1.98 mmol) were heated in corundum crucibles under an argon atmosphere up to 1170 K over a period of 3 h and then cooled to room temperature at a rate of 20 K h^-1. The X-ray powder patterns of these samples can be indexed on the basis of the reported single-crystal data but show additional reflections of BaSb₂ (Pickhard & Röhr, 2000) and BaO. Single-phase products were obtained by simultaneous decomposition of BaH₂ and the use of steel autoclaves as a container for the corundum crucibles: Ba (2.0531 g, 14.95 mmol) and BaH₂ (0.6943 g, 4.98 mmol) were reacted with Sb (1.0112 g, 8.31 mmol) and Sb₂O₃ (0.2414 g, 0.83 mmol) with the same temperature program as mentioned above. The title compound forms dark hydroscopic crystals with a metallic lustre, which were handled in a dry box and prepared in capillaries filled with dried oil.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP (Johnson, 1968) and DRAWxtl (Finger& Kroeker, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. ORTEP view (Johnson, 1968) of the [Sb1-=Sb1]^4- dumb-bell together with the coordinating Ba atoms (75% probability ellipsoids).
	Fig. 2. ORTEP view (Johnson, 1968) of the [Sb2–Sb2]^4- dumb-bell together with the coordinating Ba atoms (75% probability ellipsoids).
	Fig. 3. ORTEP view (Johnson, 1968) of the bicapped [OBa4] tetrahedron (75% probability ellipsoids).
	Fig. 4. View of the unit cell (projection down [001]) of the crystal structure of Ba3Sb2O (light gray balls represent Ba, light gray tetrahedra represent [OBa4] and dark gray balls represent Sb)

tribarium diantimonide oxide

Crystal data

Ba3Sb2O	F(000) = 1112
Mr = 671.52	Dx = 5.573 Mg m^−3
Orthorhombic, Pbam	Mo Kα radiation, λ = 0.71070 Å
Hall symbol: -P 2 2ab	Cell parameters from 848 reflections
a = 12.4228 (11) Å	θ = 6.5–56.6°
b = 12.630 (3) Å	µ = 21.10 mm^−1
c = 5.101 (3) Å	T = 293 K
V = 800.4 (4) Å^3	Irregular, metallic dark black
Z = 4	0.14 × 0.12 × 0.10 mm

Data collection

Bruker AXS CCD diffractometer	1026 independent reflections
Radiation source: fine-focus sealed tube	925 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ω scans	θmax = 27.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −15→16
Tmin = 0.068, Tmax = 0.121	k = −7→16
4726 measured reflections	l = −6→6

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.034	Secondary atom site location: difference Fourier map
wR(F^2) = 0.078	w = 1/[σ^2(Fo^2) + (0.0306P)^2 + 10.2529P] where P = (Fo^2 + 2Fc^2)/3
S = 1.23	(Δ/σ)max < 0.001
1026 reflections	Δρmax = 1.81 e Å^−3
37 parameters	Δρmin = −2.44 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ba1	0.02729 (6)	0.32611 (6)	0.0000	0.01668 (19)
Ba2	0.31945 (6)	0.48483 (6)	0.0000	0.0170 (2)
Ba3	0.25595 (6)	0.25882 (6)	0.5000	0.01663 (19)
Sb1	0.38734 (6)	0.01828 (7)	0.5000	0.0163 (2)
Sb2	0.01112 (6)	0.11257 (7)	0.5000	0.0155 (2)
O1	0.2293 (7)	0.3023 (8)	0.0000	0.0218 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba1	0.0184 (4)	0.0178 (4)	0.0139 (4)	0.0014 (3)	0.000	0.000
Ba2	0.0147 (3)	0.0223 (4)	0.0139 (4)	−0.0023 (3)	0.000	0.000
Ba3	0.0151 (3)	0.0170 (4)	0.0178 (4)	−0.0005 (3)	0.000	0.000
Sb1	0.0127 (4)	0.0197 (4)	0.0165 (4)	0.0010 (3)	0.000	0.000
Sb2	0.0155 (4)	0.0146 (4)	0.0164 (4)	−0.0006 (3)	0.000	0.000
O1	0.022 (5)	0.022 (5)	0.021 (5)	−0.005 (4)	0.000	0.000

Geometric parameters (Å, º)

Ba1—O1	2.528 (9)	Sb1—Ba2^x	3.6446 (12)
Ba1—Sb1^i	3.6592 (12)	Sb1—Ba2^xi	3.6446 (12)
Ba1—Sb1^ii	3.6592 (12)	Sb1—Ba1^xii	3.6592 (12)
Ba1—Sb1^iii	3.6770 (13)	Sb1—Ba1^vi	3.6592 (12)
Ba1—Sb1^iv	3.6770 (13)	Sb1—Ba1^x	3.6770 (13)
Ba1—Sb2^v	3.7174 (13)	Sb1—Ba1^xi	3.6770 (13)
Ba1—Sb2	3.7174 (13)	Sb1—Ba3^xi	3.7294 (13)
Ba2—O1	2.563 (9)	Sb2—Sb2^xiii	2.8571 (17)
Ba2—Sb1^iv	3.6446 (12)	Sb2—Ba3	3.5584 (11)
Ba2—Sb1^iii	3.6446 (12)	Sb2—Ba3^i	3.5618 (11)
Ba2—Sb2^iii	3.6795 (12)	Sb2—Ba2^xi	3.6794 (12)
Ba2—Sb2^iv	3.6795 (12)	Sb2—Ba2^x	3.6794 (12)
Ba2—Sb2^vi	3.6996 (12)	Sb2—Ba2^i	3.6997 (12)
Ba2—Sb2^vii	3.6996 (12)	Sb2—Ba2^xiv	3.6997 (12)
Ba3—O1^viii	2.630 (3)	Sb2—Ba1	3.7174 (13)
Ba3—O1	2.630 (3)	Sb2—Ba1^viii	3.7174 (13)
Ba3—Sb1	3.4487 (12)	O1—Ba1	2.528 (10)
Ba3—Sb2	3.5584 (11)	O1—Ba2	2.563 (10)
Ba3—Sb2^vi	3.5618 (11)	O1—Ba3^v	2.630 (3)
Ba3—Sb1^iii	3.7294 (13)	O1—Ba3	2.630 (3)
Sb1—Sb1^ix	2.8369 (16)	O1—Ba1^vi	4.041 (10)
Sb1—Ba3	3.4487 (12)	O1—Ba2^x	4.055 (10)
Ba1—O1—Ba2	109.1 (4)	Ba1—O1—Ba3	98.6 (2)
Ba1—O1—Ba3^v	98.6 (2)	Ba2—O1—Ba3	97.6 (2)
Ba2—O1—Ba3^v	97.6 (2)	Ba3^v—O1—Ba3	151.8 (4)

Symmetry codes: (i) x−1/2, −y+1/2, z; (ii) x−1/2, −y+1/2, z−1; (iii) −x+1/2, y+1/2, −z+1; (iv) −x+1/2, y+1/2, −z; (v) x, y, z−1; (vi) x+1/2, −y+1/2, z; (vii) x+1/2, −y+1/2, z−1; (viii) x, y, z+1; (ix) −x+1, −y, −z+1; (x) −x+1/2, y−1/2, −z; (xi) −x+1/2, y−1/2, −z+1; (xii) x+1/2, −y+1/2, z+1; (xiii) −x, −y, −z+1; (xiv) x−1/2, −y+1/2, z+1.