Disodium diaqua­bis­(methyl­enedi­phos­pho­nato-κ2O,O′)cobaltate(II) dihydrate

Merwe, K. van der; Visser, H.G.; Venter, J.A.

doi:10.1107/S1600536811038530

metal-organic compounds

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ISSN: 2056-9890

Volume 67| Part 10| October 2011| Pages m1468-m1469

https://doi.org/10.1107/S1600536811038530

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Disodium diaquabis(methylenediphosphonato-κ²O,O′)cobaltate(II) dihydrate

Kina van der Merwe,^a ^* Hendrik G. Visser ^a and Johan A. Venter ^a

^aDepartment of Chemistry, University of the Free State, PO Box 339, Bloemfontein, 9330, South Africa
^*Correspondence e-mail: vandermerwe@gmail.com

(Received 5 August 2011; accepted 20 September 2011; online 30 September 2011)

In the title compound, Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]·2H₂O, the asymmetric unit is composed of one methylenediphosphonate ligand and one water molecule, which both are coordinated to a Co^II atom, as well as a non-coordinated water molecule and a sodium cation. The Co^II atom occupies a special position on a crystallographic inversion centre. The slightly distorted Co^IIO₆ octahedral coordination environment is composed of two bidentate methylenediphosphonate ligands and two coordinated water molecules in trans positions. The sodium ion is octahedrally coordinated to six O atoms with Na—O distances ranging from 2.3149 (12) to 2.6243 (12) Å. An extensive three-dimensional network of intermolecular as well as intramolecular O—H⋯O and C—H⋯O hydrogen bonding interacions is present.

Related literature

For general background to organic diphosphonic acids, see: Vega et al. (1996 ). For related structures, see: Bon et al. (2010 ); DeLaMatter et al. (1973 ); Harmony et al. (1984 ); Jurisson et al. (1983 ); Van der Merwe et al. (2010 ). For bond lengths and angles in related structures, see: Bao et al. (2003 ); Cao et al. (2007 ); Gong et al. (2006 ); Van der Merwe et al. (2009 ); Visser et al. (2010 ); Yin et al. (2003 ).

Experimental

Crystal data

Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]·2H₂O
M_r = 524.94
Monoclinic, P 2₁ /c
a = 6.8694 (2) Å
b = 13.2860 (4) Å
c = 8.3541 (3) Å
β = 91.375 (1)°
V = 762.23 (4) Å³
Z = 2
Mo Kα radiation
μ = 1.69 mm⁻¹
T = 100 K
0.52 × 0.24 × 0.09 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS, Bruker, 2007 ) T_min = 0.474, T_max = 0.863
8742 measured reflections
1901 independent reflections
1838 reflections with I > 2σ(I)
R_int = 0.022

Refinement

R[F² > 2σ(F²)] = 0.019
wR(F²) = 0.055
S = 1.13
1901 reflections
146 parameters
7 restraints
All H-atom parameters refined
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.57 e Å⁻³

Table 1
Selected bond lengths (Å)

Co1—O1	2.0886 (10)
Co1—O7	2.0900 (10)
Co1—O2ⁱ	2.1141 (10)
Symmetry code: (i) -x+1, -y+1, -z+1.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O8—H6⋯O7	0.86 (1)	1.88 (1)	2.7154 (15)	164 (2)
C1—H4⋯O1ⁱ	0.92 (2)	2.54 (2)	3.1449 (17)	123.9 (15)
C1—H3⋯O4ⁱⁱ	0.92 (2)	2.53 (2)	3.4366 (17)	168.4 (17)
O3—H2⋯O2ⁱⁱ	0.81 (3)	1.84 (3)	2.6394 (14)	176 (3)
O1—H1A⋯O6ⁱⁱⁱ	0.83 (2)	1.98 (2)	2.8008 (14)	173 (2)
O8—H7⋯O1ⁱⁱⁱ	0.83 (1)	2.57 (2)	3.2763 (15)	143 (2)
O1—H1B⋯O4^iv	0.83 (2)	1.84 (2)	2.6634 (15)	175 (2)
O5—H5⋯O6^v	0.82 (2)	1.81 (2)	2.6272 (14)	177 (3)
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) -x, -y+1, -z+1; (iv) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (v) -x, -y+1, -z.

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536811038530/wm2520sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811038530/wm2520Isup2.hkl

checkCIF report

Comment top

The title compound forms part of an ongoing study involving methylene diphosphonate, and its coordination to various metal cores.

In the past 20 years numerous diphosphonate compounds have undergone intensive pharmacological studies primarily because of their possible use in treating bone diseases. This can be attributed to the fact that bisphosphonic acids are excellent anti-hypercalcemics and have a high affinity for bone tissue (Vega et al., 1996).

In the title compound, Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]^.2H₂O, (Fig. 1, Table 1), the asymmetric unit is composed of one methylene diphosphonate ligand and one aqueous molecule which are coordinated to a Co(II) atom, as well as a non-coordinated aqueous solvent molecule and a sodium cation. The Co(II) atom occupies a special position on a crystallographic inversion centre. The sodium ion is octahedrally coordinated to six oxygen atoms with Na—O distances ranging from 2.3149 (12) to 2.6243 (12) Å. The octahedral geometry around the Co^II metal center is slightly distorted with O—Co—O angles ranging between 86.63 (4) ° and 93.14 (4) °. The Co—O bond lengths vary between 2.0886 (10) and 2.1141 (10) Å. These distances correspond to literature values (Bao et al. (2003); Cao et al. (2007); Gong et al. (2006); Yin et al. (2003); Van der Merwe et al. (2009); Visser et al. (2010).

A three-dimensional network is provided by numerous C—H–O and O—H–O hydrogen bonds (Figs. 2, 3 and Table 2).

Related literature top

For general background to organic diphosphonic acids, see: Vega et al. (1996). For related structures, see: Bon et al. (2010); DeLaMatter et al. (1973); Harmony et al. (1984); Jurisson et al. (1983); Van der Merwe et al. (2010). For bond lengths and angles in related structures, see: Bao et al. (2003); Cao et al. (2007); Gong et al. (2006); Van der Merwe et al. (2009); Visser et al. (2010); Yin et al. (2003).

Experimental top

CoCl₂^.6H₂O (0,1696 g, 0,00071 mol) and methylene diphosphonate (0,3726 g, 0,00212 mol) were dissolved in distilled water (5 cm³). Sodium hydroxide (3 cm³, 1 M) was gradually added to the solution mixture which was heated for three days at 413 K. The final pH of the solution was adjusted to 1.23 with hydrochloric acid. Pink crystals, suitable for X-ray diffraction, were obtained. (Yield: 27.6%)

Structure description top

The title compound forms part of an ongoing study involving methylene diphosphonate, and its coordination to various metal cores.

A three-dimensional network is provided by numerous C—H–O and O—H–O hydrogen bonds (Figs. 2, 3 and Table 2).

For general background to organic diphosphonic acids, see: Vega et al. (1996). For related structures, see: Bon et al. (2010); DeLaMatter et al. (1973); Harmony et al. (1984); Jurisson et al. (1983); Van der Merwe et al. (2010). For bond lengths and angles in related structures, see: Bao et al. (2003); Cao et al. (2007); Gong et al. (2006); Van der Merwe et al. (2009); Visser et al. (2010); Yin et al. (2003).

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. Representation of the title compound, showing the numbering scheme and displacement ellipsoids drawn at the 50% probability level. [Symmetry code: (i) 1-x, 1-y, -z].
	Fig. 2. The crystal packing of the title compound viewed along the a axis. Green dashed lines are employed to represent intermolecular hydrogen bonding and an orange dashed line was used to displace the intramolecular hydrogen bonding.
	Fig. 3. The packing diagram of the title compound viewed along the b axis. Green dashed lines are utilized to display the extensive intermolecular hydrogen bonding.

Disodium diaquabis(methylenediphosphonato-κ²O,O')cobaltate(II) dihydrate top

Crystal data top

Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]·2H₂O	F(000) = 530
M_r = 524.94	D_x = 2.287 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 6202 reflections
a = 6.8694 (2) Å	θ = 2.9–28.4°
b = 13.2860 (4) Å	µ = 1.69 mm⁻¹
c = 8.3541 (3) Å	T = 100 K
β = 91.375 (1)°	Plate, pink
V = 762.23 (4) Å³	0.52 × 0.24 × 0.09 mm
Z = 2

Data collection top

Bruker APEXII CCD diffractometer	1838 reflections with I > 2σ(I)
phi and ω scans	R_int = 0.022
Absorption correction: multi-scan (SADABS, Bruker, 2007)	θ_max = 28.4°, θ_min = 3.1°
T_min = 0.474, T_max = 0.863	h = −8→9
8742 measured reflections	k = −17→16
1901 independent reflections	l = −11→8

Refinement top

Refinement on F²	7 restraints
Least-squares matrix: full	All H-atom parameters refined
R[F² > 2σ(F²)] = 0.019	w = 1/[σ²(F_o²) + (0.0289P)² + 0.4299P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.055	(Δ/σ)_max = 0.001
S = 1.13	Δρ_max = 0.36 e Å⁻³
1901 reflections	Δρ_min = −0.57 e Å⁻³
146 parameters

Crystal data top

Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]·2H₂O	V = 762.23 (4) Å³
M_r = 524.94	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 6.8694 (2) Å	µ = 1.69 mm⁻¹
b = 13.2860 (4) Å	T = 100 K
c = 8.3541 (3) Å	0.52 × 0.24 × 0.09 mm
β = 91.375 (1)°

Data collection top

Bruker APEXII CCD diffractometer	1901 independent reflections
Absorption correction: multi-scan (SADABS, Bruker, 2007)	1838 reflections with I > 2σ(I)
T_min = 0.474, T_max = 0.863	R_int = 0.022
8742 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.019	7 restraints
wR(F²) = 0.055	All H-atom parameters refined
S = 1.13	Δρ_max = 0.36 e Å⁻³
1901 reflections	Δρ_min = −0.57 e Å⁻³
146 parameters

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Co1	0.5	0.5	0.5	0.00488 (8)
P1	0.43774 (5)	0.30632 (3)	0.26142 (4)	0.00528 (9)
P2	0.17626 (5)	0.48657 (3)	0.20454 (4)	0.00578 (9)
Na1	0.06611 (8)	0.75775 (4)	0.22722 (7)	0.01006 (13)
O1	0.33424 (15)	0.45566 (8)	0.69412 (12)	0.0092 (2)
O2	0.52678 (14)	0.35119 (7)	0.41366 (11)	0.00758 (19)
O3	0.61219 (15)	0.25484 (8)	0.17312 (12)	0.0084 (2)
O4	0.27445 (14)	0.23364 (8)	0.28565 (12)	0.0087 (2)
O5	0.17550 (15)	0.58645 (8)	0.10142 (12)	0.0091 (2)
O6	−0.02026 (14)	0.43517 (8)	0.18700 (11)	0.00828 (19)
O7	0.23609 (15)	0.51625 (8)	0.37290 (12)	0.0081 (2)
O8	0.02069 (15)	0.67436 (8)	0.47388 (12)	0.0114 (2)
C1	0.3604 (2)	0.40539 (10)	0.12696 (15)	0.0072 (2)
H1A	0.241 (3)	0.4908 (15)	0.722 (3)	0.025 (6)*
H1B	0.321 (3)	0.3969 (13)	0.726 (3)	0.029 (6)*
H2	0.582 (4)	0.225 (2)	0.093 (3)	0.037 (7)*
H3	0.320 (3)	0.3732 (15)	0.035 (2)	0.015 (5)*
H4	0.469 (3)	0.4420 (15)	0.103 (2)	0.012 (4)*
H5	0.131 (4)	0.5780 (19)	0.011 (2)	0.038 (7)*
H6	0.092 (3)	0.6221 (13)	0.461 (3)	0.035 (5)*
H7	−0.091 (2)	0.6498 (18)	0.474 (3)	0.035 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Co1	0.00514 (14)	0.00495 (14)	0.00451 (13)	−0.00021 (8)	−0.00063 (9)	−0.00021 (8)
P1	0.00519 (16)	0.00539 (17)	0.00524 (15)	0.00033 (12)	−0.00009 (11)	−0.00059 (11)
P2	0.00623 (17)	0.00582 (17)	0.00523 (17)	0.00061 (12)	−0.00118 (12)	−0.00022 (11)
Na1	0.0087 (3)	0.0113 (3)	0.0102 (3)	0.0003 (2)	−0.0008 (2)	0.0009 (2)
O1	0.0100 (5)	0.0072 (5)	0.0105 (4)	0.0011 (4)	0.0035 (4)	0.0019 (4)
O2	0.0107 (5)	0.0061 (5)	0.0059 (4)	0.0008 (4)	−0.0019 (3)	−0.0008 (3)
O3	0.0068 (5)	0.0104 (5)	0.0081 (4)	0.0017 (4)	−0.0002 (4)	−0.0032 (4)
O4	0.0072 (5)	0.0074 (5)	0.0116 (4)	−0.0008 (4)	0.0001 (3)	0.0000 (4)
O5	0.0121 (5)	0.0067 (5)	0.0084 (4)	0.0001 (4)	−0.0035 (4)	0.0013 (4)
O6	0.0071 (4)	0.0094 (5)	0.0083 (4)	−0.0004 (4)	−0.0013 (3)	−0.0002 (4)
O7	0.0080 (5)	0.0098 (5)	0.0064 (4)	0.0021 (4)	−0.0021 (3)	−0.0015 (3)
O8	0.0091 (5)	0.0141 (5)	0.0109 (5)	0.0018 (4)	0.0006 (4)	−0.0003 (4)
C1	0.0076 (6)	0.0077 (6)	0.0061 (6)	0.0001 (5)	0.0000 (5)	0.0000 (5)

Geometric parameters (Å, º) top

Co1—O1	2.0886 (10)	Na1—O3ⁱⁱⁱ	2.3431 (12)
Co1—O1ⁱ	2.0886 (10)	Na1—O4^iv	2.3612 (11)
Co1—O7	2.0900 (10)	Na1—O6^iv	2.4860 (12)
Co1—O7	2.0900 (10)	Na1—O5	2.6243 (12)
Co1—O7ⁱ	2.0900 (10)	O1—H1A	0.831 (16)
Co1—O2	2.1141 (10)	O1—H1B	0.830 (16)
Co1—O2ⁱ	2.1141 (10)	O3—Na1^v	2.3431 (12)
P1—O4	1.4975 (10)	O3—H2	0.81 (3)
P1—O2	1.5198 (10)	O4—Na1^vi	2.3612 (11)
P1—O3	1.5781 (10)	O5—H5	0.815 (16)
P1—C1	1.8021 (14)	O6—Na1^vi	2.4860 (12)
P2—O7	1.5083 (10)	O8—Na1^vii	2.3149 (12)
P2—O7	1.5083 (10)	O8—H6	0.856 (13)
P2—O6	1.5169 (10)	O8—H7	0.834 (13)
P2—O5	1.5820 (10)	C1—H3	0.92 (2)
P2—C1	1.7954 (14)	C1—H4	0.92 (2)
Na1—O8ⁱⁱ	2.3149 (12)

O1—Co1—O1ⁱ	180	O5—P2—C1	107.49 (6)
O1—Co1—O7	86.63 (4)	O8ⁱⁱ—Na1—O3ⁱⁱⁱ	115.88 (4)
O1ⁱ—Co1—O7	93.37 (4)	O8ⁱⁱ—Na1—O4^iv	84.24 (4)
O1—Co1—O7	86.63 (4)	O3ⁱⁱⁱ—Na1—O4^iv	159.88 (4)
O1ⁱ—Co1—O7	93.37 (4)	O8ⁱⁱ—Na1—O6^iv	83.04 (4)
O1—Co1—O7ⁱ	93.37 (4)	O3ⁱⁱⁱ—Na1—O6^iv	92.19 (4)
O1ⁱ—Co1—O7ⁱ	86.63 (4)	O4^iv—Na1—O6^iv	90.55 (4)
O7—Co1—O7ⁱ	180	O8ⁱⁱ—Na1—O5	90.31 (4)
O7—Co1—O7ⁱ	180	O3ⁱⁱⁱ—Na1—O5	81.45 (4)
O1—Co1—O2	93.14 (4)	O4^iv—Na1—O5	99.03 (4)
O1ⁱ—Co1—O2	86.86 (4)	O6^iv—Na1—O5	167.75 (4)
O7—Co1—O2	90.28 (4)	Co1—O1—H1A	119.7 (16)
O7—Co1—O2	90.28 (4)	Co1—O1—H1B	125.4 (16)
O7ⁱ—Co1—O2	89.73 (4)	H1A—O1—H1B	110 (2)
O1—Co1—O2ⁱ	86.86 (4)	P1—O2—Co1	128.01 (6)
O1ⁱ—Co1—O2ⁱ	93.14 (4)	P1—O3—Na1^v	123.17 (6)
O7—Co1—O2ⁱ	89.72 (4)	P1—O3—H2	114.8 (19)
O7—Co1—O2ⁱ	89.72 (4)	Na1^v—O3—H2	122.0 (19)
O7ⁱ—Co1—O2ⁱ	90.27 (4)	P1—O4—Na1^vi	130.61 (6)
O2—Co1—O2ⁱ	180.00 (5)	P2—O5—Na1	120.44 (5)
O4—P1—O2	115.31 (6)	P2—O5—H5	112.6 (18)
O4—P1—O3	111.31 (6)	Na1—O5—H5	112.6 (18)
O2—P1—O3	105.44 (6)	P2—O6—Na1^vi	121.18 (5)
O4—P1—C1	110.17 (6)	P2—O7—Co1	131.33 (6)
O2—P1—C1	109.98 (6)	Na1^vii—O8—H6	111.4 (16)
O3—P1—C1	103.94 (6)	Na1^vii—O8—H7	104.6 (17)
O7—P2—O6	115.45 (6)	H6—O8—H7	102 (2)
O7—P2—O6	115.45 (6)	P2—C1—P1	114.42 (7)
O7—P2—O5	106.61 (6)	P2—C1—H3	112.4 (12)
O7—P2—O5	106.61 (6)	P1—C1—H3	105.2 (12)
O6—P2—O5	109.49 (6)	P2—C1—H4	110.3 (12)
O7—P2—C1	108.36 (6)	P1—C1—H4	107.1 (12)
O7—P2—C1	108.36 (6)	H3—C1—H4	107.0 (17)
O6—P2—C1	109.14 (6)

O4—P1—O2—Co1	−108.16 (8)	O6^iv—Na1—O5—P2	140.99 (16)
O3—P1—O2—Co1	128.63 (7)	Na1ⁱⁱ—Na1—O5—P2	−161.48 (7)
C1—P1—O2—Co1	17.13 (9)	Na1^vii—Na1—O5—P2	16.59 (7)
O1—Co1—O2—P1	111.59 (7)	O7—P2—O6—Na1^vi	−74.24 (8)
O1ⁱ—Co1—O2—P1	−68.41 (7)	O7—P2—O6—Na1^vi	−74.24 (8)
O7—Co1—O2—P1	24.95 (7)	O5—P2—O6—Na1^vi	165.48 (5)
O7—Co1—O2—P1	24.95 (7)	C1—P2—O6—Na1^vi	48.07 (7)
O7ⁱ—Co1—O2—P1	−155.05 (7)	O6—P2—O7—Co1	134.82 (7)
O4—P1—O3—Na1^v	−126.78 (7)	O5—P2—O7—Co1	−103.34 (8)
O2—P1—O3—Na1^v	−1.06 (8)	C1—P2—O7—Co1	12.09 (10)
C1—P1—O3—Na1^v	114.66 (7)	O1—Co1—O7—P2	−136.95 (8)
O2—P1—O4—Na1^vi	97.12 (8)	O1ⁱ—Co1—O7—P2	43.05 (8)
O3—P1—O4—Na1^vi	−142.84 (7)	O2—Co1—O7—P2	−43.82 (8)
C1—P1—O4—Na1^vi	−28.09 (9)	O2ⁱ—Co1—O7—P2	136.18 (8)
O7—P2—O5—Na1	−35.73 (8)	O7—P2—C1—P1	46.92 (9)
O7—P2—O5—Na1	−35.73 (8)	O7—P2—C1—P1	46.92 (9)
O6—P2—O5—Na1	89.81 (7)	O6—P2—C1—P1	−79.55 (8)
C1—P2—O5—Na1	−151.75 (6)	O5—P2—C1—P1	161.78 (7)
O8ⁱⁱ—Na1—O5—P2	−162.13 (6)	O4—P1—C1—P2	66.52 (9)
O3ⁱⁱⁱ—Na1—O5—P2	81.72 (6)	O2—P1—C1—P2	−61.67 (9)
O4^iv—Na1—O5—P2	−77.92 (7)	O3—P1—C1—P2	−174.14 (7)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O8—H6···O7	0.86 (1)	1.88 (1)	2.7154 (15)	164 (2)
C1—H4···O1ⁱ	0.92 (2)	2.54 (2)	3.1449 (17)	123.9 (15)
C1—H3···O4^viii	0.92 (2)	2.53 (2)	3.4366 (17)	168.4 (17)
O3—H2···O2^viii	0.81 (3)	1.84 (3)	2.6394 (14)	176 (3)
O1—H1A···O6^ix	0.83 (2)	1.98 (2)	2.8008 (14)	173 (2)
O8—H7···O1^ix	0.83 (1)	2.57 (2)	3.2763 (15)	143 (2)
O1—H1B···O4^x	0.83 (2)	1.84 (2)	2.6634 (15)	175 (2)
O5—H5···O6^xi	0.82 (2)	1.81 (2)	2.6272 (14)	177 (3)

Symmetry codes: (i) −x+1, −y+1, −z+1; (viii) x, −y+1/2, z−1/2; (ix) −x, −y+1, −z+1; (x) x, −y+1/2, z+1/2; (xi) −x, −y+1, −z.

Experimental details

Crystal data
Chemical formula	Na₂[Co(CH₄O₆P₂)₂(H₂O)₂]·2H₂O
M_r	524.94
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	6.8694 (2), 13.2860 (4), 8.3541 (3)
β (°)	91.375 (1)
V (Å³)	762.23 (4)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	1.69
Crystal size (mm)	0.52 × 0.24 × 0.09

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS, Bruker, 2007)
T_min, T_max	0.474, 0.863
No. of measured, independent and observed [I > 2σ(I)] reflections	8742, 1901, 1838
R_int	0.022
(sin θ/λ)_max (Å⁻¹)	0.670

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.019, 0.055, 1.13
No. of reflections	1901
No. of parameters	146
No. of restraints	7
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.36, −0.57

Computer programs: APEX2 (Bruker, 2007), SAINT-Plus (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg & Putz, 2005), WinGX (Farrugia, 1999).

Selected bond lengths (Å) top

Co1—O1	2.0886 (10)	Co1—O2ⁱ	2.1141 (10)
Co1—O7	2.0900 (10)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O8—H6···O7	0.856 (13)	1.882 (14)	2.7154 (15)	164 (2)
C1—H4···O1ⁱ	0.92 (2)	2.54 (2)	3.1449 (17)	123.9 (15)
C1—H3···O4ⁱⁱ	0.92 (2)	2.53 (2)	3.4366 (17)	168.4 (17)
O3—H2···O2ⁱⁱ	0.81 (3)	1.84 (3)	2.6394 (14)	176 (3)
O1—H1A···O6ⁱⁱⁱ	0.831 (16)	1.975 (16)	2.8008 (14)	173 (2)
O8—H7···O1ⁱⁱⁱ	0.834 (13)	2.573 (18)	3.2763 (15)	143 (2)
O1—H1B···O4^iv	0.830 (16)	1.835 (16)	2.6634 (15)	175 (2)
O5—H5···O6^v	0.815 (16)	1.813 (17)	2.6272 (14)	177 (3)

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

Acknowledgements

The University of the Free State and Professor A. Roodt are gratefully acknowledged for financial support.

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