Disodium diaqua­bis­(methyl­enedi­phos­pho­nato-κ2 O,O′)cobaltate(II) dihydrate

Kina van Merwe; Hendrik G Visser; Johan A Venter

doi:10.1107/S1600536811038530

. 2011 Sep 30;67(Pt 10):m1468–m1469. doi: 10.1107/S1600536811038530

Disodium diaquabis(methylenediphosphonato-κ² O,O′)cobaltate(II) dihydrate

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

PMCID: PMC3201543 PMID: 22058722

Abstract

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,
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[F ² > 2σ(F ²)] = 0.019
wR(F ²) = 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

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 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811038530/wm2520sup1.cif

e-67-m1468-sup1.cif^{(16.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811038530/wm2520Isup2.hkl

e-67-m1468-Isup2.hkl^{(91.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

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

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Symmetry code: (i) Inline graphic .

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)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

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

supplementary crystallographic information

Comment

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).

Experimental

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%)