Crystal structure of magnesium copper(II) bis­[orthophosphate(V)] monohydrate

Khmiyas, J.; Assani, A.; Saadi, M.; El Ammari, L.

doi:10.1107/S2056989014026930

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Volume 71| Part 1| January 2015| Pages 55-57

https://doi.org/10.1107/S2056989014026930

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Crystal structure of magnesium copper(II) bis[orthophosphate(V)] monohydrate

Jamal Khmiyas,^a ^* Abderrazzak Assani,^a Mohamed Saadi ^b and Lahcen El Ammari ^a

^aLaboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco, and ^bLaboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
^*Correspondence e-mail: j_khmiyas@yahoo.fr

Edited by M. Weil, Vienna University of Technology, Austria (Received 26 November 2014; accepted 8 December 2014; online 1 January 2015)

Single crystals of magnesium copper(II) bis[orthophosphate(V)] monohydrate, Mg_1.65Cu_1.35(PO₄)₂·H₂O, were grown under hydrothermal conditions. The crystal structure is formed by three types of cationic sites and by two unique (PO₄)³⁻ anions. One site is occupied by Cu²⁺, the second site by Mg²⁺and the third site by a mixture of the two cations with an Mg²⁺:Cu²⁺ occupancy ratio of 0.657 (3):0.343 (3). The structure is built up from more or less distorted [MgO₆] and [(Mg/Cu)O₅(H₂O)] octahedra, [CuO₅] square-pyramids and regular PO₄ tetrahedra, leading to a framework structure. Within this framework, two types of layers parallel to (-101) can be distinguished. The first layer is formed by [Cu₂O₈] dimers linked to PO₄ tetrahedra via common edges. The second, more corrugated layer results from the linkage between [(Cu/Mg)₂O₈(H₂O)₂] dimers and [MgO₆] octahedra by common edges. The PO₄ units link the two types of layers, leaving space for channels parallel [101], into which the H atoms of the water molecules protrude. The latter are involved in O—H⋯O hydrogen-bonding interactions (one bifurcated) with framework O atoms across the channels.

Keywords: crystal structure; magnesium copper(II) bis[orthophosphate(V)] monohydrate; hydrogen bonding; transition metal phosphates; hydrothermal synthesis.

CCDC reference: 1038224

1. Chemical context

Transition metal phosphates are an important class of materials characterized by a great structural diversity originating from the presence of different coordination polyhedra MO_n (with n = 4, 5 and 6) or the possibility of phosphate groups to condense. The alternation of PO₄ tetrahedra and MO_n polyhedra can give rise to different anionic frameworks [M^IIPO₄]⁻ with pores or channels offering suitable environments to accommodate different other cations (Gao & Gao, 2005 ; Viter & Nagornyi, 2009 ). In previous studies, our focus of research was dedicated to the examination of mixed divalent orthophosphates with general formula (M,M′)₃(PO₄)₂·nH₂O. For instance, we have succeeded in the preparation and structure determination of some new phosphates such as Ni₂Sr(PO₄)₂·2H₂O (Assani et al., 2010a ).

In the context of our main research, we report here the hydrothermal synthesis and structural characterization of the mixed-metal orthophosphate Mg_1.65Cu_1.35(PO₄)₂·H₂O, isolated during investigation of the quinternary system Ag₂O/MgO/CuO/P₂O₅/H₂O. The title compound crystallizes in the Fe₃(PO₄)₂·H₂O structure type (Moore & Araki, 1975 ) and is isotypic with other phases of the type (M,M')₃(PO₄)₂·H₂O (Liao et al., 1995 ), viz. Co_2.59Zn_0.41(PO₄)₂·H₂O (Sørensen et al., 2005 ), Co_2.39Cu_0.61(PO₄)₂·H₂O (Assani et al., 2010b ), (Cu_1−xCo_x)₃(PO₄)₂·H₂O (0 < x < 0.20 and 0.55 < x < 0.65), and (Cu_1−xZn_x)₃(PO₄)₂·H₂O (0 < x < 0.19) (Viter & Nagornyi, 2006 ).

2. Structural commentary

The principal building units of the crystal structure of the title compound are represented in Fig. 1. The metal cations are located in three crystallographically independent sites, one octahedrally surrounded site entirely occupied by Mg²⁺, one site with a square-pyramidal coordination completely occupied by Cu²⁺ and one mixed-occupied (Mg²⁺/Cu²⁺) site with an octahedral coordination. The [Cu1O₅] square pyramid is distorted, with Cu—O bond lengths ranging from 1.9073 (17) to 2.2782 (16) Å. Two [Cu1O₅] polyhedra are linked together by edge-sharing to build up a [Cu₂O₈] dimer. By sharing corners with PO₄ tetrahedra, a layered arrangement parallel to ( $[\overline{1}]$ 01) is formed (Fig. 2). The mixed-occupied [(Mg/Cu)O₅(H₂O)] octahedron is likewise distorted, with (Mg/Cu)—O distances varying between 2.0038 (18) and 2.384 (2) Å. Two [(Mg/Cu)O₅(H₂O)] octahedra share a common edge to built up another dimer [(Mg/Cu)₂O₈(H₂O)₂] that links [MgO₆] octahedra and PO₄ tetrahedra via common vertices to build the second type of layer lying parallel to the first (Fig. 2). Adjacent layers are connected into a three-dimensional framework by common edges and vertices, and delimit channels parallel to [101], into which the hydrogen atoms of the water molecules protrude. O—H⋯O hydrogen-bonding interactions between the water molecules and framework O atoms are present (Table 1, Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O9—H9A⋯O1ⁱ	0.86	2.22	2.867 (2)	132
O9—H9A⋯O6ⁱⁱ	0.86	2.38	2.934 (2)	123
O9—H9B⋯O8ⁱⁱⁱ	0.86	1.93	2.778 (2)	170
Symmetry codes: (i) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) -x+2, -y+1, -z+1; (iii) $[-x+{\script{5\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 1
The principal building units in the crystal structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: x − $[{1\over 2}]$ , −y + $[{1\over 2}]$ , z − $[{1\over 2}]$ ; (ii) −x + 1, −y + 1, −z + 1; (iii) −x + 2, −y + 1, −z + 1; (iv) x + $[{1\over 2}]$ , −y + $[{3\over 2}]$ , z + $[{1\over 2}]$ ; (v) −x + $[{3\over 2}]$ , y + $[{1\over 2}]$ , −z + $[{3\over 2}]$ ; (vi) −x + 2, −y + 1, −z + 2; (vii) −x + $[{3\over 2}]$ , y + $[{1\over 2}]$ , −z + $[{1\over 2}]$ ; (viii) −x + 2, −y + 2, −z + 1.]

Figure 2
A polyhedral view of the title compound, showing the three-dimensional framework structure and O—H⋯O hydrogen bonding (dashed lines) in the channels.

3. Synthesis and crystallization

The title compound, Mg_1.65Cu_1.35(PO₄)₂·H₂O, was synthesized hydrothermally form a reaction mixture of AgNO₃, MgO, metallic copper, and 85wt% phosphoric acid in the molar ratio Ag: Mg: Cu: P = 1: 4: 4.5: 6 in 12.5 ml of water. The hydrothermal reaction was conducted in a 23 ml Teflon-lined autoclave under autogenous pressure at 493 K for three days. The resulting product was filtered off, washed with deionized water and dried in air. The obtained blue crystals correspond to the title compound.

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The M2 site features mixed occupation by Mg²⁺ and Cu²⁺ whereas the other two cationic sites do not show any significant disorder. Refinement of the occupancy of M2 resulted in a ratio of Mg²⁺:Cu²⁺ = 0.657 (3):0.343 (3). The O-bound H atoms were initially located in a difference map and refined with O—H distance restraints of 0.83 (5). In the last refinement cycle, the distances were fixed at 0.86 Å and the H atoms refined in the riding-model approximation with U_iso(H) set to 1.5U_eq(O). The highest remaining positive and negative electron densities observed in the final Fourier map are at 0.81 Å and 0.43 Å, respectively, from Cu1.

Table 2
Experimental details

Crystal data
Chemical formula	Mg_1.65Cu_1.35(PO₄)₂·H₂O
M_r	333.65
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	296
a, b, c (Å)	8.0701 (1), 9.8661 (2), 8.9944 (2)
β (°)	115.242 (1)
V (Å³)	647.76 (2)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	5.16
Crystal size (mm)	0.31 × 0.27 × 0.18

Data collection
Diffractometer	Bruker X8 APEX
Absorption correction	Multi-scan (SADABS; Bruker, 2009 )
T_min, T_max	0.574, 0.748
No. of measured, independent and observed [I > 2σ(I)] reflections	9233, 1673, 1617
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.676

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.058, 1.24
No. of reflections	1673
No. of parameters	129
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.55, −0.34
Computer programs: APEX2 and SAINT (Bruker, 2009), SHELXS97 and SHELXL97 (Sheldrick, 2008 ), ORTEP-3 for Windows (Farrugia, 2012 ), DIAMOND (Brandenburg, 2006 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1038224

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989014026930/wm5097sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989014026930/wm5097Isup2.hkl

checkCIF report

Computing details top

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).

Magnesium copper(II) bis[orthophosphate(V)] monohydrate top

Crystal data top

Mg_1.65Cu_1.35(PO₄)₂·H₂O	F(000) = 651
M_r = 333.65	D_x = 3.421 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -p 2yn	Cell parameters from 1673 reflections
a = 8.0701 (1) Å	θ = 2.9–28.7°
b = 9.8661 (2) Å	µ = 5.16 mm⁻¹
c = 8.9944 (2) Å	T = 296 K
β = 115.242 (1)°	Prism, blue
V = 647.76 (2) Å³	0.31 × 0.27 × 0.18 mm
Z = 4

Data collection top

Bruker X8 APEX diffractometer	1673 independent reflections
Radiation source: fine-focus sealed tube	1617 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
φ and ω scans	θ_max = 28.7°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −10→10
T_min = 0.574, T_max = 0.748	k = −11→13
9233 measured reflections	l = −12→12

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.020	H-atom parameters constrained
wR(F²) = 0.058	w = 1/[σ²(F_o²) + (0.0209P)² + 1.2623P] where P = (F_o² + 2F_c²)/3
S = 1.24	(Δ/σ)_max = 0.001
1673 reflections	Δρ_max = 0.55 e Å⁻³
129 parameters	Δρ_min = −0.34 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0022 (6)

Special details top

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 > 2σ(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 (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cu1	0.64417 (4)	0.37312 (3)	0.56030 (3)	0.00781 (10)
Mg1	0.98357 (10)	0.62883 (7)	0.72316 (9)	0.00506 (16)
Cu2	0.88601 (7)	0.86606 (5)	0.46685 (6)	0.00771 (19)	0.343 (3)
Mg2	0.88601 (7)	0.86606 (5)	0.46685 (6)	0.00771 (19)	0.657 (3)
P1	0.70807 (7)	0.57775 (6)	0.32947 (7)	0.00456 (13)
P2	0.88138 (7)	0.33721 (6)	0.86197 (7)	0.00517 (13)
O1	0.5825 (2)	0.51553 (17)	0.4023 (2)	0.0088 (3)
O4	0.8713 (2)	0.64903 (17)	0.4655 (2)	0.0092 (3)
O3	0.5882 (2)	0.68080 (16)	0.19945 (19)	0.0068 (3)
O2	0.7722 (2)	0.46440 (16)	0.2486 (2)	0.0071 (3)
O5	0.8579 (2)	0.36647 (17)	1.0187 (2)	0.0088 (3)
O6	0.7227 (2)	0.24356 (17)	0.7487 (2)	0.0081 (3)
O7	0.8521 (2)	0.46259 (17)	0.75021 (19)	0.0078 (3)
O8	1.0684 (2)	0.27408 (17)	0.9037 (2)	0.0094 (3)
O9	1.1046 (2)	0.9118 (2)	0.4255 (2)	0.0139 (4)
H9A	1.0944	0.9060	0.3265	0.021*
H9B	1.2106	0.8782	0.4857	0.021*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.01066 (15)	0.00588 (15)	0.00473 (15)	−0.00143 (9)	0.00122 (11)	0.00069 (9)
Mg1	0.0054 (3)	0.0042 (3)	0.0049 (3)	−0.0001 (2)	0.0016 (3)	0.0003 (3)
Cu2	0.0060 (3)	0.0097 (3)	0.0068 (3)	0.00074 (16)	0.00216 (19)	0.00187 (17)
Mg2	0.0060 (3)	0.0097 (3)	0.0068 (3)	0.00074 (16)	0.00216 (19)	0.00187 (17)
P1	0.0056 (2)	0.0043 (3)	0.0034 (2)	0.00024 (18)	0.00156 (19)	−0.00019 (18)
P2	0.0064 (2)	0.0046 (2)	0.0041 (2)	−0.00022 (19)	0.00177 (19)	0.00026 (19)
O1	0.0092 (7)	0.0097 (8)	0.0091 (7)	0.0016 (6)	0.0054 (6)	0.0036 (6)
O4	0.0084 (7)	0.0097 (8)	0.0062 (7)	−0.0017 (6)	−0.0001 (6)	−0.0025 (6)
O3	0.0088 (7)	0.0052 (7)	0.0050 (7)	0.0016 (6)	0.0017 (6)	0.0011 (6)
O2	0.0084 (7)	0.0061 (7)	0.0064 (7)	0.0022 (6)	0.0027 (6)	−0.0014 (6)
O5	0.0111 (8)	0.0102 (8)	0.0053 (7)	−0.0004 (6)	0.0036 (6)	−0.0014 (6)
O6	0.0091 (7)	0.0078 (7)	0.0060 (7)	−0.0027 (6)	0.0019 (6)	0.0005 (6)
O7	0.0083 (7)	0.0056 (7)	0.0071 (7)	−0.0014 (6)	0.0011 (6)	0.0021 (6)
O8	0.0086 (7)	0.0099 (8)	0.0094 (8)	0.0025 (6)	0.0035 (6)	0.0030 (6)
O9	0.0085 (7)	0.0256 (10)	0.0073 (8)	0.0035 (7)	0.0032 (6)	0.0045 (7)

Geometric parameters (Å, º) top

Cu1—O1	1.9073 (17)	Cu2—O3^iv	2.0837 (16)
Cu1—O8ⁱ	1.9322 (17)	Cu2—O4	2.1442 (18)
Cu1—O6	1.9980 (16)	Cu2—O9^viii	2.384 (2)
Cu1—O7	2.0169 (16)	P1—O4	1.5340 (17)
Cu1—O1ⁱⁱ	2.2782 (16)	P1—O2	1.5392 (16)
Mg1—O7	2.0236 (18)	P1—O3	1.5401 (16)
Mg1—O2ⁱⁱⁱ	2.0898 (17)	P1—O1	1.5491 (17)
Mg1—O4	2.1070 (18)	P2—O8	1.5241 (17)
Mg1—O3^iv	2.1071 (17)	P2—O5	1.5279 (17)
Mg1—O6^v	2.1156 (17)	P2—O7	1.5473 (17)
Mg1—O5^vi	2.1205 (18)	P2—O6	1.5550 (17)
Cu2—O9	2.0038 (18)	O9—H9A	0.8600
Cu2—O5^v	2.0268 (17)	O9—H9B	0.8600
Cu2—O2^vii	2.0535 (17)

O1—Cu1—O8ⁱ	96.29 (7)	O5^v—Cu2—O2^vii	80.18 (7)
O1—Cu1—O6	172.25 (7)	O9—Cu2—O3^iv	82.06 (7)
O8ⁱ—Cu1—O6	91.43 (7)	O5^v—Cu2—O3^iv	107.59 (7)
O1—Cu1—O7	99.62 (7)	O2^vii—Cu2—O3^iv	163.32 (7)
O8ⁱ—Cu1—O7	146.81 (7)	O9—Cu2—O4	105.96 (8)
O6—Cu1—O7	73.33 (7)	O5^v—Cu2—O4	87.11 (7)
O1—Cu1—O1ⁱⁱ	77.52 (7)	O2^vii—Cu2—O4	117.13 (7)
O8ⁱ—Cu1—O1ⁱⁱ	116.46 (6)	O3^iv—Cu2—O4	78.56 (6)
O6—Cu1—O1ⁱⁱ	99.65 (6)	O9—Cu2—O9^viii	89.45 (7)
O7—Cu1—O1ⁱⁱ	95.41 (6)	O5^v—Cu2—O9^viii	80.53 (6)
O7—Mg1—O2ⁱⁱⁱ	98.29 (7)	O2^vii—Cu2—O9^viii	81.28 (6)
O7—Mg1—O4	101.96 (7)	O3^iv—Cu2—O9^viii	85.44 (6)
O2ⁱⁱⁱ—Mg1—O4	96.67 (7)	O4—Cu2—O9^viii	155.82 (7)
O7—Mg1—O3^iv	171.09 (8)	O4—P1—O2	111.26 (9)
O2ⁱⁱⁱ—Mg1—O3^iv	90.39 (7)	O4—P1—O3	110.54 (9)
O4—Mg1—O3^iv	78.89 (7)	O2—P1—O3	110.47 (9)
O7—Mg1—O6^v	86.54 (7)	O4—P1—O1	109.79 (9)
O2ⁱⁱⁱ—Mg1—O6^v	166.01 (7)	O2—P1—O1	108.93 (9)
O4—Mg1—O6^v	95.14 (7)	O3—P1—O1	105.69 (9)
O3^iv—Mg1—O6^v	84.55 (7)	O8—P2—O5	110.47 (9)
O7—Mg1—O5^vi	89.35 (7)	O8—P2—O7	110.33 (9)
O2ⁱⁱⁱ—Mg1—O5^vi	77.24 (7)	O5—P2—O7	113.81 (9)
O4—Mg1—O5^vi	167.90 (8)	O8—P2—O6	111.75 (10)
O3^iv—Mg1—O5^vi	90.60 (7)	O5—P2—O6	108.96 (9)
O6^v—Mg1—O5^vi	89.76 (7)	O7—P2—O6	101.22 (9)
O9—Cu2—O5^v	165.32 (8)	H9A—O9—H9B	104.9
O9—Cu2—O2^vii	87.74 (7)

Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1; (iii) −x+2, −y+1, −z+1; (iv) x+1/2, −y+3/2, z+1/2; (v) −x+3/2, y+1/2, −z+3/2; (vi) −x+2, −y+1, −z+2; (vii) −x+3/2, y+1/2, −z+1/2; (viii) −x+2, −y+2, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O9—H9A···O1^vii	0.86	2.22	2.867 (2)	132
O9—H9A···O6ⁱⁱⁱ	0.86	2.38	2.934 (2)	123
O9—H9B···O8^ix	0.86	1.93	2.778 (2)	170

Symmetry codes: (iii) −x+2, −y+1, −z+1; (vii) −x+3/2, y+1/2, −z+1/2; (ix) −x+5/2, y+1/2, −z+3/2.

Acknowledgements

The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements and the University Mohammed V, Rabat, Morocco, for financial support.

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