SrMn^II₂Mn^III(PO₄)₃

The title compound, strontium trimanganese tris­(ortho­phosphate), was synthesized under hydro­thermal conditions. Its structure is isotypic to that of the lead analogue PbMn^II₂Mn^III(PO₄)₃. Two O atoms are in general positions, whereas all others atoms are in special positions. The Sr and one P atom exhibit mm2 symmetry, the Mn^II atom 2/m symmetry, the Mn^III atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The three-dimensional network of the crystal structure is made up of two types of chains running parallel to [010]. One chain is linear and is composed of alternating Mn^IIIO₆ octa­hedra and PO₄ tetra­hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing Mn^IIO₆ octa­hedra connected to PO₄ tetra­hedra by edges and vertices. The two types of chains are linked through PO₄ tetra­hedra, leading to the formation of channels parallel to [100] and [010] in which the Sr^II ions are located. They are surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.

Related literature

For the isotypic lead analogue, see: Alhakmi et al. (2013). For compounds with related structures, see: Adam et al. (2009); Assani et al. (2011a,b,c); Moore & Ito (1979). For applications of related compounds, see: Trad et al. (2010). For the by-product phase, see: Moore & Araki (1973). For bond-valence analysis, see: Brown & Altermatt (1985).

Experimental

Crystal data

• SrMn₃(PO₄)₃

• M_r = 537.35

• Orthorhombic, I m m a

• a = 10.2373 (10) Å

• b = 13.8981 (15) Å

• c = 6.6230 (6) Å

• V = 942.31 (16) ų

• Z = 4

• Mo Kα radiation

• μ = 10.14 mm⁻¹

• T = 296 K

• 0.28 × 0.15 × 0.12 mm

Data collection

• Bruker APEXII diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2009) T_min = 0.164, T_max = 0.376

• 4726 measured reflections

• 991 independent reflections

• 877 reflections with I > 2σ(I)

• R_int = 0.040

Refinement

• R[F² > 2σ(F²)] = 0.025

• wR(F²) = 0.066

• S = 1.04

• 991 reflections

• 53 parameters

• Δρ_max = 0.83 e Å⁻³

• Δρ_min = −0.92 e Å⁻³

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Supporting information

S1. Comment

Hydrothermal studies in the systems A₂O–MO–P₂O₅ and M'O–MO–P₂O₅ led to new phosphates with framework structures closely related to that of the alluaudite [(Na,Ca)Mn^II(Fe^III,Mn^III,Fe^IIMg)₂(PO₄)₃] structure type. For instance, the phosphates Ag₂M₃(HPO₄)(PO₄)₂ (M = Co, Ni) (Assani et al., 2011a,b and PbMn^II₂Mn^III(PO₄)₃ (Alhakmi et al., 2013) were prepared this way. Their compositions can be represented by the general formula (A1)(A2)(M1)(M2)₂(PO₄)₃ as introduced by Moore & Ito (1979) for alluaudite-related compounds. In this nomenclature the order of the cations A and M is related to the decreasing size of the discrete sites. Mainly, the A sites can be occupied by either mono- or divalent medium-sized cations while the M cationic sites correspond to an octahedral environment generally occupied by transition metal cations. In the case of alluaudite-type compounds, a great field of applications such as positive electrodes in lithium and sodium batteries (Trad et al., 2010) has been established. Our focus of investigation is associated with mixed-cations orthophosphates that are related to the above mentioned compounds. By means of the hydrothermal synthesis method, we have recently prepared and structurally characterized (A1)(A2)(M1)(M2)₂(PO₄)₃ phosphates (Assani et al., 2011c). The present paper describes the synthesis and structural characterization of the mixed-valent Mn^II,III phosphate with composition SrMn^II₂Mn^III(PO₄)₃. Such Mn^II,III systems are rather scarce (Adam et al., 2009). The structure of the title compound is isotypic to that of the lead analogue PbMn^II₂Mn^III(PO₄)₃ (Alhakmi et al., 2013)

Except two oxygen atoms (O3, O4) in general positions, all other atoms are located on special positions of space group Imma. The connection of the metal-oxygen polyhedra, viz. SrO₈ polyhedra, MnO₆ octahedra and PO₄ tetrahedra is shown in Fig. 1. The crystal structure consists of two isolated PO₄ tetrahedra linked to two types of MnO₆ octahedra, building two different chains running parallel to [010]. The first chain is formed by alternating Mn^IIIO₆ octahedra and PO₄ tetrahedra by sharing vertices. The second chain is built up from two adjacent edge-sharing octahedra (Mn^II₂O₁₀ dimers) that are further linked to two PO₄ tetrahedra by a common edge. These two types of chains are linked together by common vertices of PO₄ tetrahedra to form a porous three-dimensional framework that delimits two types of tunnels parallel to [100] and [010] where the Sr^II ions are located (Fig. 2). The coordination sphere of the alkaline earth metal ions is that of a bicapped trigonal prism.

Bond valence calculations (Brown & Altermatt, 1985) of SrMn^II₂Mn^III(PO₄)₃ revealed bond valence sums for Sr1^II+, Mn1^III+, Mn2^II+, P1^V+ and P2^V+ that are close to the expected values, viz. 1.81, 3.06, 1.98, 5.02 and 4.87 valence units (v.u.), respectively. The bond valence sums calculated for all O atoms are in the range of 1.79 – 2.04 v.u., thus confirming the validity of the structure model.

The framework of the title compound shows some resemblance to that of Ag₂M₃(HPO₄)(PO₄)₂ phosphates (M = Ni, Co; Assani et al., 2011a,b), whereby the two Ag^I cations in the channels are replaced by Sr^II.

Related literature

For the isotypic lead analogue, see: Alhakmi et al. (2013). For compounds with related structures, see: Adam et al. (2009); Assani et al. (2011a,b,c); Moore & Ito (1979). For applications of related compounds, see: Trad et al. (2010). For the by-product phase, see: Moore & Araki (1973). For bond-valence analysis, see: Brown & Altermatt (1985).

S2. Experimental

Crystals of the title compound were isolated from the hydrothermal treatment of a reaction mixture of strontium, manganese and phosphate precursors in a proportion corresponding to the molar ratio Sr:Mn:P = 1: 3: 3. The hydrothermal reaction was conducted in a 23 ml Teflon-lined autoclave, filled to 50% with distilled water and under autogeneous pressure at 478 K for five days. After being filtered off, washed with deionized water and air dried, the reaction product consisted of brown sheet-shaped crystals corresponding to the title compound. Besides, parallelepipedic colourless crystals were present which were identified to be Mn₅(HPO₄)₂(PO₄)₂^.4H₂O (Moore & Araki, 1973).

S3. Refinement

The highest and lowest remaining electron density peaks in the final Fourier map are 0.71 Å and 0.49 Å, respectively, away from O3 and P2.

Computing details

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

Fig. 1. The main building units of the crystal structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x, -y + 1, -z; (ii) -x, y - 1/2, -z; (iii) x, y - 1/2, -z; (iv) -x, -y + 1, -z; (v) x, y, z - 1; (vi) -x, -y + 1/2, z - 1; (vii) -x, -y + 1/2, z; (viii) -x + 1/2, y - 1/2, z + 1/2; (ix) x - 1/2, -y + 1/2, -z + 1/2; (x) -x + 1/2, -y + 1/2, -z + 1/2; (xi) x - 1/2, y - 1/2, z + 1/2; (xii) -x, -y, -z + 1; (xiii) -x + 1/2, -y + 1, z + 1/2; (xiv) -x + 1/2, y, -z + 1/2.]

Fig. 2. Polyhedral representation of SrMn3(PO4)3 with channels running parallel to [100].

Strontium trimanganese tris(orthophosphate)

Crystal data

SrMn3(PO4)3	F(000) = 1016
Mr = 537.35	Dx = 3.788 Mg m^−3
Orthorhombic, Imma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2b 2	Cell parameters from 991 reflections
a = 10.2373 (10) Å	θ = 2.9–33.3°
b = 13.8981 (15) Å	µ = 10.14 mm^−1
c = 6.6230 (6) Å	T = 296 K
V = 942.31 (16) Å^3	Sheet, brown
Z = 4	0.28 × 0.15 × 0.12 mm

Data collection

Bruker APEXII diffractometer	991 independent reflections
Radiation source: fine-focus sealed tube	877 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
ϕ and ω scans	θmax = 33.3°, θmin = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −15→15
Tmin = 0.164, Tmax = 0.376	k = −21→10
4726 measured reflections	l = −9→10

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)] = 0.025	Secondary atom site location: difference Fourier map
wR(F^2) = 0.066	w = 1/[σ^2(Fo^2) + (0.0389P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
991 reflections	Δρmax = 0.83 e Å^−3
53 parameters	Δρmin = −0.92 e Å^−3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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
Sr1	0.0000	0.2500	−0.10600 (6)	0.00886 (11)
Mn1	0.0000	0.5000	0.5000	0.00446 (14)
Mn2	0.2500	0.36768 (4)	0.2500	0.00742 (12)
P1	0.0000	0.2500	0.40707 (15)	0.00402 (19)
P2	0.2500	0.57346 (6)	0.2500	0.00591 (16)
O1	0.0000	0.16039 (16)	0.5390 (3)	0.0089 (4)
O2	0.1174 (2)	0.2500	0.2602 (3)	0.0080 (4)
O3	0.20437 (17)	0.63359 (12)	0.0726 (2)	0.0101 (3)
O4	0.36220 (15)	0.50005 (12)	0.1971 (2)	0.0079 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sr1	0.01068 (19)	0.0107 (2)	0.00518 (18)	0.000	0.000	0.000
Mn1	0.0042 (3)	0.0064 (3)	0.0027 (3)	0.000	0.000	0.0000 (2)
Mn2	0.0095 (2)	0.0054 (2)	0.0073 (2)	0.000	−0.00037 (15)	0.000
P1	0.0052 (4)	0.0042 (5)	0.0027 (4)	0.000	0.000	0.000
P2	0.0072 (3)	0.0062 (4)	0.0043 (3)	0.000	0.0006 (2)	0.000
O1	0.0111 (10)	0.0067 (10)	0.0089 (9)	0.000	0.000	0.0021 (8)
O2	0.0075 (10)	0.0099 (10)	0.0065 (10)	0.000	0.0031 (7)	0.000
O3	0.0126 (7)	0.0102 (8)	0.0074 (7)	0.0023 (6)	0.0006 (6)	0.0026 (6)
O4	0.0087 (7)	0.0079 (7)	0.0072 (7)	0.0004 (6)	0.0033 (5)	0.0006 (5)

Geometric parameters (Å, º)

Sr1—O3^i	2.6540 (17)	Mn2—O2	2.1265 (15)
Sr1—O3^ii	2.6540 (17)	Mn2—O2^xiii	2.1265 (15)
Sr1—O3^iii	2.6540 (17)	Mn2—O3^i	2.1869 (16)
Sr1—O3^iv	2.6540 (17)	Mn2—O3^ix	2.1869 (16)
Sr1—O1^v	2.660 (2)	Mn2—O4	2.1969 (17)
Sr1—O1^vi	2.660 (2)	Mn2—O4^xi	2.1969 (17)
Sr1—O2	2.707 (2)	P1—O1^vii	1.522 (2)
Sr1—O2^vii	2.707 (2)	P1—O1	1.522 (2)
Mn1—O4^viii	1.9219 (15)	P1—O2^vii	1.546 (2)
Mn1—O4^ix	1.9219 (15)	P1—O2	1.546 (2)
Mn1—O4^x	1.9219 (15)	P2—O3^xi	1.5158 (16)
Mn1—O4^xi	1.9219 (15)	P2—O3	1.5158 (16)
Mn1—O1^xii	2.244 (2)	P2—O4^xi	1.5758 (17)
Mn1—O1^vii	2.244 (2)	P2—O4	1.5758 (17)
O3^i—Sr1—O3^ii	75.12 (8)	O4^ix—Mn1—O1^xii	94.51 (6)
O3^i—Sr1—O3^iii	170.43 (7)	O4^x—Mn1—O1^xii	94.51 (6)
O3^ii—Sr1—O3^iii	104.06 (8)	O4^xi—Mn1—O1^xii	85.49 (6)
O3^i—Sr1—O3^iv	104.06 (8)	O4^viii—Mn1—O1^vii	94.51 (6)
O3^ii—Sr1—O3^iv	170.43 (7)	O4^ix—Mn1—O1^vii	85.49 (6)
O3^iii—Sr1—O3^iv	75.12 (8)	O4^x—Mn1—O1^vii	85.49 (6)
O3^i—Sr1—O1^v	111.04 (5)	O4^xi—Mn1—O1^vii	94.51 (6)
O3^ii—Sr1—O1^v	77.78 (4)	O1^xii—Mn1—O1^vii	180.0
O3^iii—Sr1—O1^v	77.78 (4)	O2—Mn2—O2^xiii	79.45 (9)
O3^iv—Sr1—O1^v	111.04 (5)	O2—Mn2—O3^i	83.60 (7)
O3^i—Sr1—O1^vi	77.78 (4)	O2^xiii—Mn2—O3^i	95.69 (7)
O3^ii—Sr1—O1^vi	111.04 (5)	O2—Mn2—O3^ix	95.69 (7)
O3^iii—Sr1—O1^vi	111.04 (5)	O2^xiii—Mn2—O3^ix	83.60 (7)
O3^iv—Sr1—O1^vi	77.78 (4)	O3^i—Mn2—O3^ix	179.07 (9)
O1^v—Sr1—O1^vi	55.83 (10)	O2—Mn2—O4	169.37 (7)
O3^i—Sr1—O2	64.86 (5)	O2^xiii—Mn2—O4	107.77 (6)
O3^ii—Sr1—O2	64.86 (5)	O3^i—Mn2—O4	87.85 (6)
O3^iii—Sr1—O2	105.98 (5)	O3^ix—Mn2—O4	92.92 (6)
O3^iv—Sr1—O2	105.98 (5)	O2—Mn2—O4^xi	107.77 (6)
O1^v—Sr1—O2	142.35 (4)	O2^xiii—Mn2—O4^xi	169.37 (7)
O1^vi—Sr1—O2	142.35 (4)	O3^i—Mn2—O4^xi	92.92 (6)
O3^i—Sr1—O2^vii	105.98 (5)	O3^ix—Mn2—O4^xi	87.85 (6)
O3^ii—Sr1—O2^vii	105.98 (5)	O4—Mn2—O4^xi	66.27 (8)
O3^iii—Sr1—O2^vii	64.86 (5)	O1^vii—P1—O1	109.88 (18)
O3^iv—Sr1—O2^vii	64.86 (5)	O1^vii—P1—O2^vii	111.19 (6)
O1^v—Sr1—O2^vii	142.35 (4)	O1—P1—O2^vii	111.19 (6)
O1^vi—Sr1—O2^vii	142.35 (4)	O1^vii—P1—O2	111.19 (6)
O2—Sr1—O2^vii	52.72 (9)	O1—P1—O2	111.19 (6)
O4^viii—Mn1—O4^ix	180.0	O2^vii—P1—O2	102.03 (17)
O4^viii—Mn1—O4^x	85.55 (10)	O3^xi—P2—O3	113.08 (14)
O4^ix—Mn1—O4^x	94.45 (10)	O3^xi—P2—O4^xi	114.15 (9)
O4^viii—Mn1—O4^xi	94.45 (10)	O3—P2—O4^xi	107.75 (9)
O4^ix—Mn1—O4^xi	85.55 (10)	O3^xi—P2—O4	107.75 (9)
O4^x—Mn1—O4^xi	180.0	O3—P2—O4	114.15 (9)
O4^viii—Mn1—O1^xii	85.49 (6)	O4^xi—P2—O4	99.29 (12)

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