Poly[tetra­aquadi-μ₃-malonato-cobalt(II)­calcium(II)]

The structure of the polymeric title compound, [CaCo(C₃H₂O₄)₂(H₂O)₄]_n, consists of CaO₈ and CoO₆ polyhedra linked together by malonate groups. The Co atom lies on a centre of symmetry in an octa­hedral arrangement, and is coordinated by four malonate O atoms in a planar arrangement and two water mol­ecules in a trans conformation. The geometry around the Ca atom, which lies on a twofold axis, may be described as a distorted square anti­prism, which involves two water mol­ecules and six malonate O atoms. The Co—O and Ca—O bond lengths are in the ranges 2.0711 (12)–2.1004 (14) and 2.3775 (12)–2.6329 (12) Å, respectively.

S1. Comment

The most commonly employed synthetic design strategy that is used to assemble coordination frameworks is the building-block methodology, which relies upon utilizing the specific geometries of both metal cations and ligands. Typically, dicarboxylate ligands, such as malonate, have been used to construct coordination polymers by acting as chelating bidentate ligands or as simple bridges between metal centers. Consequently, a great number of homonuclear or heteronuclear malonate complexes are well known and structurally characterized (Alderighi et al., 1999; Barbaro et al., 1997; Benmerad et al., 2000; Filippova et al., 2000; Gil de Muro et al., 1998, 1999, 2000; Hodgson & Asplund, 1991; Rodriguez-Martin et al., 2002; Ruiz-Perez, Hernandez-Molina et al., 2000; Ruiz-Perez, Sanchiz et al., 2000; Tapparo et al., 1996; Zhang et al., 2000). In the course of our study of heterobimetallic malonate complexes involving transition and alkaline-earth metals, we have synthesized the complex [CaCo(C₃H₂O₄)₂(H₂O)₄], (I), which has already been reported (Gil de Muro et al., 2000), but its crystal structure was not determined until now. The single-crystal X-ray diffraction study reveals that the title compound consists of a honeycomb framework built up from calcium(II), cobalt(II) malonate and water molecules. A view of the coordination around the two metal centres is shown in Fig. 1. The Co atom lies on a crystallographic inversion centre and has an octahedral coordination, involving four O atoms from two bidentate malonate ligands in a planar arrangement, and two water O atoms in axial positions. The bond lengths in the coordination sphere of the Co^II atoms are quite similar. The Co—O equatorial bonds, ranging from 2.0711 (12) to 2.0900 (11) Å, have a mean value of 2.081 (9) Å, while the axial Co—O distances are 2.1004 (14) Å (Table 1). The O—Co—O bond angles range from 87.30 (5) to 92.70 (5)° and vary little from ideal octahedral geometry. These bond lengths and angles agree well with those previously reported for other cobalt(II) complexes containing carboxylate ligands (Gil de Muro et al., 1998, 1999; Livage et al.,1998,1999; Suresh et al., 1997; Zheng et al., 2000). The six-membered chelate rings Co/O2 /C1/C2 /C3/O3 and Co/O2ⁱⁱ/C1ⁱⁱ/C2ⁱⁱ/C3ⁱⁱ/O3ⁱⁱ [symmetry code: (ii) −x, −y, −z] have boat conformations, with atoms Co and C2 lying 0.44 and 0.48 Å out of the C1/O2/C3/O3 mean plane. The Ca atom, lying on a twofold axis, is coordinated by two water molecules (O6 and O6ⁱ), two bridging carboxyl O atoms (O1 and O1ⁱ) [symmetry code: (i) −x, y, −z + 1/2] and the O atoms of two chelated carboxyl groups (O3/C3/O4 and O3ⁱ/C3ⁱ/O4ⁱ). The geometry around the Ca^II atom may be described as a distorted square antiprism. The four-membered chelate rings linked to the Ca atom, are bonded to the six-membered rings surrounding the Co atom via the C3—O3 bond. The Ca—O bond lengths display different value in the chelating and bridging malonate groups. While the bridging carboxylate Ca—O1 bond lengths [2.3775 (12) Å] are similar to the Ca—O_water distances [Ca—O6 = 2.3970 (14) Å], the Ca—O bonds of the chelating malonate ligands are quite different [2.4410 (13) to 2.6329 (12) Å]. The longest Ca—O distance is observed for the Ca—O3 bond, atom O3 being three-coordinated to one Ca atom, one Co atom and one C atom. The increase of these bond lengths is related to the requirements of the conformation of the fused-ring system. Each Ca atom is connected to two Ca atoms through bis-carboxylate bridges, defining infinite chains of CaO₈ polyhedra, running parallel to the [010] axis and forming 12-membered binuclear rings [Ca/O1/C1–C3/O4]₂. The Ca···Ca separation within these rings is 7.531 (12) Å. The same carboxylate bridges bind each Ca atom to four Co atoms, leading to the formation of 12-membered tetranuclear rings [Ca/Co/O1/C1/O2/O3]₂. The Ca···Ca and Co···Co separations within these rings are, respectively, 7.054 and 7.531 Å, while the Ca···Co distances are shorter, at 5.794 and 4.434 Å. The two carboxylate groups have the same dimensions, with a mean value of 1.257 (2) Å, and are inclined at 40.4 (1)° to each other. The crystal structure may be described as a three-dimensionnel network. The two different 12-membered rings create wide channels. The two crystallography independent water molecules are hydrogen bonded to the carboxyl O atoms, and the supramolecular assembly of this heterobinuclear complex is realised by this hydrogen bonding (Table 2 and Fig. 1).

S2. Experimental

Under continuous stirring, malonic acid (0.208 g, 2 mmol), CoCl₂·6H₂O (0.238 g, 1 mmol) and Ca(OH)₂·8H₂O (0.315 g, 1 mmol) were successively dissolved in water (100 ml). A pink solution was obtained after filtration, and the filtrate was kept at 313 K. Pink prismatic crystals were grown after several weeks.

S3. Refinement

H atoms bonded to C atoms were included in geometrically idealized positions using a riding model, with C—H distances of 0.95 Å and U_iso(H) values of 1.2U_eq(C). Those bonded to O were found by difference Fourier methods and refined isotropically.

Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1993); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A view of the coordination polyhedra for calcium and cobalt ions in (I), with the atom numbering (50% probability displacement ellipsoids). Hydrogen bonds are shown as dotted lines.

Poly[tetraaquadi-µ₃-malonato-cobalt(II)calcium(II)]

Crystal data

[CaCo(C3H2O4)2(H2O)4]	F(000) = 764
Mr = 375.17	Dx = 2.087 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 25 reflections
a = 13.874 (2) Å	θ = 5.4–13.6°
b = 7.531 (1) Å	µ = 1.93 mm^−1
c = 13.615 (2) Å	T = 298 K
β = 122.94 (2)°	Prism, pink
V = 1193.9 (4) Å^3	0.26 × 0.22 × 0.14 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	1177 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.007
Graphite monochromator	θmax = 27.0°, θmin = 3.2°
ω/2θ scans	h = 0→17
Absorption correction: ψ scan (North et al., 1968)	k = 0→9
Tmin = 0.660, Tmax = 0.768	l = −17→14
1353 measured reflections	3 standard reflections every 60 min
1300 independent reflections	intensity decay: 0.0%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.020	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.050	w = 1/[σ^2(Fo^2) + (0.0246P)^2 + 0.8504P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max < 0.001
1300 reflections	Δρmax = 0.28 e Å^−3
110 parameters	Δρmin = −0.25 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0020 (4)

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
Ca	0.5000	−0.12268 (6)	0.2500	0.01694 (12)
Co	0.5000	0.5000	0.5000	0.01770 (11)
O1	0.37589 (10)	0.10287 (15)	0.24175 (10)	0.0252 (3)
O2	0.45750 (10)	0.26466 (15)	0.40366 (10)	0.0255 (3)
O3	0.43766 (10)	0.63445 (15)	0.34394 (9)	0.0246 (3)
O4	0.33859 (11)	0.67075 (16)	0.15464 (10)	0.0286 (3)
O5	0.33756 (11)	0.5107 (2)	0.47682 (13)	0.0326 (3)
O6	0.40284 (12)	−0.03139 (19)	0.04940 (11)	0.0283 (3)
C2	0.31086 (13)	0.3977 (2)	0.22178 (13)	0.0216 (3)
H2A	0.2761	0.3682	0.1415	0.026*
H2B	0.2511	0.4070	0.2359	0.026*
C1	0.38792 (12)	0.2455 (2)	0.29424 (13)	0.0177 (3)
C3	0.36624 (13)	0.5778 (2)	0.24204 (13)	0.0174 (3)
H5A	0.283 (2)	0.544 (3)	0.422 (2)	0.051 (8)*
H5B	0.329 (2)	0.459 (3)	0.521 (2)	0.046 (7)*
H6A	0.435 (2)	0.062 (4)	0.047 (2)	0.055 (8)*
H6B	0.399 (2)	−0.091 (4)	0.003 (2)	0.052 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ca	0.0171 (2)	0.0144 (2)	0.0163 (2)	0.000	0.00716 (17)	0.000
Co	0.01973 (16)	0.01414 (16)	0.01387 (15)	−0.00079 (11)	0.00566 (12)	−0.00127 (11)
O1	0.0235 (6)	0.0196 (6)	0.0247 (6)	0.0020 (5)	0.0079 (5)	−0.0070 (5)
O2	0.0305 (6)	0.0165 (5)	0.0183 (5)	0.0022 (5)	0.0060 (5)	−0.0015 (4)
O3	0.0278 (6)	0.0181 (5)	0.0182 (5)	−0.0051 (5)	0.0061 (5)	0.0001 (4)
O4	0.0382 (7)	0.0230 (6)	0.0196 (6)	−0.0044 (5)	0.0125 (5)	0.0027 (5)
O5	0.0218 (6)	0.0488 (9)	0.0243 (7)	0.0033 (6)	0.0106 (6)	0.0093 (6)
O6	0.0322 (7)	0.0254 (7)	0.0211 (6)	−0.0042 (5)	0.0105 (5)	−0.0018 (5)
C2	0.0194 (7)	0.0165 (7)	0.0192 (7)	−0.0016 (6)	0.0042 (6)	−0.0005 (6)
C1	0.0175 (7)	0.0159 (7)	0.0195 (7)	−0.0018 (6)	0.0098 (6)	−0.0017 (6)
C3	0.0170 (7)	0.0158 (7)	0.0196 (7)	0.0026 (6)	0.0101 (6)	0.0005 (6)

Geometric parameters (Å, º)

Ca—O1^i	2.3775 (12)	O1—C1	1.2500 (18)
Ca—O1	2.3775 (12)	O2—C1	1.2681 (19)
Ca—O6^i	2.3970 (14)	O3—C3	1.2623 (19)
Ca—O6	2.3970 (14)	O4—C3	1.2476 (19)
Ca—O4^ii	2.4410 (13)	O4—Ca^v	2.4410 (13)
Ca—O4^iii	2.4410 (13)	O5—H5A	0.77 (3)
Ca—O3^iii	2.6329 (12)	O5—H5B	0.78 (3)
Ca—O3^ii	2.6329 (12)	O6—H6A	0.84 (3)
Co—O3	2.0711 (12)	O6—H6B	0.75 (3)
Co—O3^iv	2.0711 (12)	C2—C3	1.509 (2)
Co—O2	2.0900 (11)	C2—C1	1.511 (2)
Co—O2^iv	2.0900 (11)	C2—H2A	0.9500
Co—O5^iv	2.1004 (14)	C2—H2B	0.9500
Co—O5	2.1004 (14)
O1^i—Ca—O1	88.80 (6)	O6^i—Ca—H6A	132.1 (6)
O1^i—Ca—O6^i	78.29 (5)	O6—Ca—H6A	16.8 (6)
O1—Ca—O6^i	78.05 (5)	O4^ii—Ca—H6A	94.6 (6)
O1^i—Ca—O6	78.05 (5)	O4^iii—Ca—H6A	123.9 (5)
O1—Ca—O6	78.29 (5)	O3^iii—Ca—H6A	83.0 (5)
O6^i—Ca—O6	146.66 (7)	O3^ii—Ca—H6A	144.8 (6)
O1^i—Ca—O4^ii	155.76 (4)	C3^iii—Ca—H6A	106.5 (5)
O1—Ca—O4^ii	89.93 (4)	C3^ii—Ca—H6A	120.0 (6)
O6^i—Ca—O4^ii	125.01 (5)	O3—Co—O3^iv	180.00 (4)
O6—Ca—O4^ii	77.99 (5)	O3—Co—O2	87.30 (5)
O1^i—Ca—O4^iii	89.93 (4)	O3^iv—Co—O2	92.70 (5)
O1—Ca—O4^iii	155.76 (4)	O3—Co—O2^iv	92.70 (5)
O6^i—Ca—O4^iii	77.99 (5)	O3^iv—Co—O2^iv	87.30 (5)
O6—Ca—O4^iii	125.01 (5)	O2—Co—O2^iv	180.0
O4^ii—Ca—O4^iii	100.82 (6)	O3—Co—O5^iv	89.32 (6)
O1^i—Ca—O3^iii	95.65 (4)	O3^iv—Co—O5^iv	90.68 (6)
O1—Ca—O3^iii	153.40 (4)	O2—Co—O5^iv	88.59 (5)
O6^i—Ca—O3^iii	128.54 (4)	O2^iv—Co—O5^iv	91.41 (5)
O6—Ca—O3^iii	77.03 (4)	O3—Co—O5	90.68 (6)
O4^ii—Ca—O3^iii	75.38 (4)	O3^iv—Co—O5	89.32 (6)
O4^iii—Ca—O3^iii	50.73 (4)	O2—Co—O5	91.41 (5)
O1^i—Ca—O3^ii	153.40 (4)	O2^iv—Co—O5	88.59 (5)
O1—Ca—O3^ii	95.65 (4)	O5^iv—Co—O5	180.0
O6^i—Ca—O3^ii	77.03 (4)	C1—O1—Ca	135.95 (10)
O6—Ca—O3^ii	128.54 (4)	C1—O2—Co	127.49 (10)
O4^ii—Ca—O3^ii	50.73 (4)	C3—O3—Co	127.06 (10)
O4^iii—Ca—O3^ii	75.38 (4)	C3—O3—Ca^v	88.26 (9)
O3^iii—Ca—O3^ii	92.00 (6)	Co—O3—Ca^v	140.69 (5)
O1^i—Ca—C3^iii	97.02 (4)	C3—O4—Ca^v	97.63 (10)
O1—Ca—C3^iii	174.17 (4)	Co—O5—H5A	125.2 (19)
O6^i—Ca—C3^iii	103.28 (5)	Co—O5—H5B	117.8 (18)
O6—Ca—C3^iii	102.64 (5)	H5A—O5—H5B	116 (3)
O4^ii—Ca—C3^iii	84.67 (5)	Ca—O6—H6A	107.9 (17)
O4^iii—Ca—C3^iii	25.38 (4)	Ca—O6—H6B	121 (2)
O3^iii—Ca—C3^iii	25.93 (4)	H6A—O6—H6B	106 (3)
O3^ii—Ca—C3^iii	79.23 (4)	C3—C2—C1	116.97 (13)
O1^i—Ca—C3^ii	174.17 (4)	C3—C2—H2A	108.1
O1—Ca—C3^ii	97.02 (4)	C1—C2—H2A	108.1
O6^i—Ca—C3^ii	102.64 (5)	C3—C2—H2B	108.1
O6—Ca—C3^ii	103.28 (5)	C1—C2—H2B	108.1
O4^ii—Ca—C3^ii	25.38 (4)	H2A—C2—H2B	107.3
O4^iii—Ca—C3^ii	84.67 (5)	O1—C1—O2	123.31 (14)
O3^iii—Ca—C3^ii	79.23 (4)	O1—C1—C2	116.83 (13)
O3^ii—Ca—C3^ii	25.93 (4)	O2—C1—C2	119.81 (13)
C3^iii—Ca—C3^ii	77.16 (6)	O4—C3—O3	120.61 (14)
O1^i—Ca—H6A	61.6 (6)	O4—C3—C2	117.91 (13)
O1—Ca—H6A	76.1 (5)	O3—C3—C2	121.47 (14)
O1^i—Ca—O1—C1	−44.71 (14)	O5^iv—Co—O3—Ca^v	−37.82 (9)
O6^i—Ca—O1—C1	33.57 (15)	O5—Co—O3—Ca^v	142.18 (9)
O6—Ca—O1—C1	−122.76 (16)	Ca—O1—C1—O2	−41.1 (2)
O4^ii—Ca—O1—C1	159.49 (15)	Ca—O1—C1—C2	141.51 (12)
O4^iii—Ca—O1—C1	42.5 (2)	Co—O2—C1—O1	172.61 (11)
O3^iii—Ca—O1—C1	−144.98 (14)	Co—O2—C1—C2	−10.0 (2)
O3^ii—Ca—O1—C1	109.00 (15)	C3—C2—C1—O1	−135.66 (15)
C3^ii—Ca—O1—C1	135.06 (15)	C3—C2—C1—O2	46.8 (2)
O3—Co—O2—C1	−19.46 (13)	Ca^v—O4—C3—O3	17.75 (16)
O3^iv—Co—O2—C1	160.54 (13)	Ca^v—O4—C3—C2	−162.82 (12)
O5^iv—Co—O2—C1	−108.85 (13)	Co—O3—C3—O4	−177.58 (11)
O5—Co—O2—C1	71.15 (13)	Ca^v—O3—C3—O4	−16.28 (15)
O2—Co—O3—C3	23.17 (13)	Co—O3—C3—C2	3.0 (2)
O2^iv—Co—O3—C3	−156.83 (13)	Ca^v—O3—C3—C2	164.32 (13)
O5^iv—Co—O3—C3	111.79 (13)	Co—O3—C3—Ca^v	−161.30 (12)
O5—Co—O3—C3	−68.21 (13)	C1—C2—C3—O4	137.15 (15)
O2—Co—O3—Ca^v	−126.44 (9)	C1—C2—C3—O3	−43.4 (2)
O2^iv—Co—O3—Ca^v	53.56 (9)	C1—C2—C3—Ca^v	70.4 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H5A···O1^vi	0.77 (3)	2.16 (3)	2.920 (2)	173 (3)
O5—H5B···O4^vii	0.78 (3)	2.00 (3)	2.773 (2)	169 (3)
O6—H6A···O2^i	0.84 (3)	1.98 (3)	2.7905 (18)	161 (2)
O6—H6B···O2^viii	0.75 (3)	2.33 (3)	3.0388 (19)	159 (3)

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