A dinuclear Co^II complex: bis(μ-di­hydrogen phosphato-κ²O:O′)­bis­[(bipyridine-κ²N,N′)(di­hydrogen phosphato-κO)­cobalt(II)]

The title compound, [Co₂(H₂PO₄)₄(C₁₀H₈N₂)₂], is dinuclear, centred on a symmetry centre of the P space group. Each Co atom has a distorted square-pyramidal coordination involving two N atoms from a bi­pyridine mol­ecule and three O atoms from two bridging and one terminal di­hydrogen ortho­phosphate anion. The molecular structure and packing are stabilized by intermolecular hydrogen-bond interactions.

S1. Comment

Metal phosphonate or ortho-phosphate materials are of increasing interest due to their potential applications in ion exchange, catalysis and sensing (Liang et al., 2003; Wang et al., 2002). An extraordinarily large number of orthophosphates have been characterized in the past two decades (Wilson et al., 1982; Gier & Stucky, 1991). Here, we report the crystal structure of the title compound, (I). \sch

The structure of (I) contains two Co^II ions, two 2,2'-bipyridine ligands and four dihydrogen-orthophosphate anions. It is built up of centrosymmetric dinuclear entities. The coordination sphere of the Co^II ions is best described as a distorted square pyramid. The basal coordination positions are occupied by two N atoms and two O atoms belonging to two bridging dihydrogen-orthophosphate anions. The axial position is occupied by an O atom from the terminal dihydrogen-orthophosphate anions.

The 2,2'-bipyridine ligands chelate the Co atom and form a five-membered CoN₂C₂ ring. The Co—N bond lengths of 2.067 (3) and 2.117 (3) Å are in good agreement with the corresponding five-coordination Co—N distances reported previously (Du et al., 2001). The N1—Co1—N2 bite angle is 77.15 (10)°, which is narrower than that in [Co(phen)₂(H₂O)₂](NO₃)₃·2H₂O [84.5 (1)°; Ye et al., 1994].

The two Co atoms are bridged by two orthophosphate anions. The O atoms are bound asymmetrically to Co, with distances of 1.968 (2) and 2.064 (2) Å. The axial Co—O bond length is 1.993 (2) Å. The Co—O bond lengths in this structure are slightly longer than found in a similar structure (Murugavel et al., 2001).

The five-membered chelate ring (P1) is fairly planar, the displacement of atom Co1 from the weighted least-squares plane through N1/C5/C6/N2 being 0.029 (2) Å. The dihedral angles between P1 and the planes N2/C6—C10 (P2) and N1/C1—C5 (P3) are 5.3 (1) and 4.7 (1)°, respectively. Planes P2 and P3 form a dihedral angle of 8.5 (1)°.

There is one intermolecular O—H···O hydrogen bond interaction in the crystal of (I) (Table 2), and these hydrogen-bond interactions stabilize the structure.

S2. Experimental

The title compound was prepared by the reaction of cobalt dichloride with 2,2'-bipyridine in phosphoric acid solution (Ratios or quantities of starting materials?) by means of hydrothermal synthesis in a stainless-steel reactor with a Teflon liner at 383 K for 24 h.

S3. Refinement

H atoms were fixed geometrically and allowed to ride on their attached atoms, with C—H distances of 0.93 Å and O—H distances of 0.82 Å, and with U_iso = 1.2U_eq(parent). Please check added text.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SHELXTL (Sheldrick, 1997a); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997b); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The packing of the molecules of (I), viewed down the c axis.

bis(µ-dihydrogen phosphato-κO:O')bis[(bipyridine-κ²N,N')(dihydrogen phosphato-κO)cobalt(II)]

Crystal data

[Co(H2PO4)4(C10H8N2)2]	Z = 1
Mr = 818.17	F(000) = 414
Triclinic, P1	Dx = 1.857 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.6797 (17) Å	Cell parameters from 20 reflections
b = 8.7749 (18) Å	θ = 2–11°
c = 10.057 (2) Å	µ = 1.44 mm^−1
α = 96.09 (3)°	T = 293 K
β = 100.55 (3)°	Block, red
γ = 100.89 (3)°	0.20 × 0.20 × 0.10 mm
V = 731.6 (3) Å^3

Data collection

Siemens SMART CCD area-detector diffractometer	2902 independent reflections
Radiation source: fine-focus sealed tube	2415 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.016
ϕ and ω scans	θmax = 26.2°, θmin = 2.1°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.758, Tmax = 0.866	k = −8→11
3435 measured reflections	l = −12→12

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0452P)^2] where P = (Fo^2 + 2Fc^2)/3
2902 reflections	(Δ/σ)max < 0.001
208 parameters	Δρmax = 0.41 e Å^−3
0 restraints	Δρmin = −0.32 e Å^−3

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
Co1	0.05455 (5)	0.21267 (5)	0.21455 (4)	0.02718 (14)
P1	0.29540 (10)	0.43255 (9)	0.08031 (8)	0.0313 (2)
P2	−0.18636 (9)	0.09242 (9)	−0.07621 (7)	0.0272 (2)
O1	0.2346 (2)	0.3861 (2)	0.2034 (2)	0.0342 (5)
O2	0.3964 (3)	0.5947 (2)	0.0984 (2)	0.0391 (6)
O3	0.3985 (3)	0.3126 (3)	0.0402 (3)	0.0468 (6)
H3A	0.4615	0.3525	−0.0044	0.070*
O4	0.1532 (3)	0.4170 (3)	−0.0428 (2)	0.0495 (6)
H4A	0.0741	0.3576	−0.0298	0.074*
O5	−0.0776 (2)	0.2252 (2)	0.02482 (19)	0.0307 (5)
O6	−0.2948 (3)	0.1614 (3)	−0.1843 (2)	0.0443 (6)
H6A	−0.3205	0.2376	−0.1470	0.067*
O7	−0.2958 (3)	0.0015 (3)	0.0081 (2)	0.0516 (7)
H7A	−0.3151	−0.0926	−0.0206	0.077*
O8	−0.1073 (3)	−0.0116 (3)	−0.1538 (2)	0.0363 (5)
N1	−0.1037 (3)	0.2795 (3)	0.3281 (3)	0.0347 (6)
N2	0.1626 (3)	0.1908 (3)	0.4162 (2)	0.0354 (6)
C1	−0.2323 (4)	0.3335 (5)	0.2773 (4)	0.0493 (10)
H1A	−0.2580	0.3346	0.1835	0.059*
C2	−0.3290 (5)	0.3878 (5)	0.3577 (4)	0.0623 (12)
H2B	−0.4192	0.4231	0.3191	0.075*
C3	−0.2888 (5)	0.3883 (5)	0.4956 (4)	0.0640 (12)
H3B	−0.3501	0.4268	0.5527	0.077*
C4	−0.1580 (5)	0.3320 (5)	0.5493 (4)	0.0548 (11)
H4B	−0.1308	0.3308	0.6430	0.066*
C5	−0.0668 (4)	0.2772 (4)	0.4643 (3)	0.0375 (8)
C6	0.0784 (4)	0.2174 (4)	0.5119 (3)	0.0375 (8)
C7	0.1283 (5)	0.1898 (5)	0.6450 (3)	0.0574 (11)
H7B	0.0676	0.2053	0.7104	0.069*
C8	0.2696 (6)	0.1390 (5)	0.6781 (4)	0.0653 (12)
H8A	0.3053	0.1203	0.7666	0.078*
C9	0.3558 (6)	0.1165 (5)	0.5816 (4)	0.0636 (12)
H9A	0.4525	0.0845	0.6031	0.076*
C10	0.2980 (5)	0.1416 (5)	0.4507 (4)	0.0510 (10)
H10A	0.3561	0.1234	0.3838	0.061*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.0312 (2)	0.0306 (3)	0.0212 (2)	0.00929 (18)	0.00780 (17)	0.00115 (17)
P1	0.0341 (5)	0.0272 (5)	0.0342 (4)	0.0056 (4)	0.0127 (4)	0.0035 (4)
P2	0.0307 (4)	0.0270 (4)	0.0242 (4)	0.0096 (3)	0.0042 (3)	0.0014 (3)
O1	0.0343 (12)	0.0358 (13)	0.0289 (11)	−0.0016 (10)	0.0089 (9)	0.0009 (10)
O2	0.0379 (13)	0.0239 (12)	0.0578 (15)	0.0044 (10)	0.0209 (11)	0.0010 (11)
O3	0.0532 (15)	0.0272 (13)	0.0699 (17)	0.0091 (11)	0.0362 (13)	0.0092 (12)
O4	0.0477 (15)	0.0590 (17)	0.0372 (13)	−0.0017 (12)	0.0049 (11)	0.0167 (12)
O5	0.0359 (12)	0.0287 (12)	0.0251 (10)	0.0079 (9)	0.0015 (9)	0.0004 (9)
O6	0.0564 (15)	0.0429 (14)	0.0304 (12)	0.0266 (12)	−0.0093 (11)	−0.0069 (11)
O7	0.0644 (17)	0.0352 (14)	0.0567 (15)	−0.0017 (12)	0.0328 (13)	−0.0002 (12)
O8	0.0435 (13)	0.0371 (13)	0.0305 (11)	0.0190 (11)	0.0062 (10)	−0.0008 (10)
N1	0.0364 (15)	0.0406 (16)	0.0273 (13)	0.0067 (13)	0.0110 (12)	0.0006 (12)
N2	0.0399 (16)	0.0395 (16)	0.0248 (13)	0.0098 (13)	0.0028 (12)	0.0004 (12)
C1	0.048 (2)	0.061 (3)	0.041 (2)	0.0222 (19)	0.0093 (17)	−0.0019 (18)
C2	0.048 (2)	0.077 (3)	0.060 (3)	0.021 (2)	0.013 (2)	−0.015 (2)
C3	0.055 (3)	0.075 (3)	0.061 (3)	0.012 (2)	0.028 (2)	−0.019 (2)
C4	0.062 (3)	0.065 (3)	0.037 (2)	0.005 (2)	0.0236 (19)	−0.0043 (19)
C5	0.043 (2)	0.038 (2)	0.0289 (16)	0.0008 (16)	0.0139 (15)	−0.0019 (15)
C6	0.050 (2)	0.0349 (19)	0.0233 (15)	−0.0004 (16)	0.0080 (15)	0.0000 (14)
C7	0.079 (3)	0.063 (3)	0.0278 (18)	0.004 (2)	0.0144 (19)	0.0062 (19)
C8	0.090 (3)	0.068 (3)	0.0297 (19)	0.015 (3)	−0.007 (2)	0.010 (2)
C9	0.073 (3)	0.070 (3)	0.042 (2)	0.028 (2)	−0.014 (2)	0.002 (2)
C10	0.053 (2)	0.062 (3)	0.0370 (19)	0.022 (2)	0.0012 (17)	0.0008 (18)

Geometric parameters (Å, º)

Co1—O8^i	1.968 (2)	N2—C10	1.327 (4)
Co1—O1	1.993 (2)	N2—C6	1.337 (4)
Co1—O5	2.064 (2)	C1—C2	1.381 (5)
Co1—N1	2.067 (3)	C1—H1A	0.9300
Co1—N2	2.117 (3)	C2—C3	1.366 (6)
P1—O1	1.497 (2)	C2—H2B	0.9300
P1—O2	1.497 (2)	C3—C4	1.367 (5)
P1—O3	1.572 (2)	C3—H3B	0.9300
P1—O4	1.554 (2)	C4—C5	1.376 (4)
P2—O5	1.505 (2)	C4—H4B	0.9300
P2—O6	1.554 (2)	C5—C6	1.475 (5)
P2—O7	1.553 (2)	C6—C7	1.390 (4)
P2—O8	1.481 (2)	C7—C8	1.379 (6)
O3—H3A	0.8200	C7—H7B	0.9300
O4—H4A	0.8200	C8—C9	1.350 (6)
O6—H6A	0.8200	C8—H8A	0.9300
O7—H7A	0.8200	C9—C10	1.376 (5)
O8—P2	1.481 (2)	C9—H9A	0.9300
N1—C1	1.332 (4)	C10—H10A	0.9300
N1—C5	1.352 (4)
O8^i—Co1—O1	108.57 (9)	C10—N2—Co1	125.0 (2)
O8^i—Co1—O5	93.73 (9)	C6—N2—Co1	115.8 (2)
O1—Co1—O5	93.94 (9)	N1—C1—C2	122.8 (3)
O8^i—Co1—N1	134.82 (11)	N1—C1—H1A	118.6
O1—Co1—N1	114.27 (10)	C2—C1—H1A	118.6
O5—Co1—N1	96.96 (9)	C3—C2—C1	118.2 (4)
O8^i—Co1—N2	87.81 (10)	C3—C2—H2B	120.9
O1—Co1—N2	92.14 (10)	C1—C2—H2B	120.9
O5—Co1—N2	172.90 (9)	C2—C3—C4	119.7 (3)
N1—Co1—N2	77.15 (10)	C2—C3—H3B	120.2
O1—P1—O2	115.58 (13)	C4—C3—H3B	120.2
O1—P1—O4	110.35 (13)	C3—C4—C5	119.8 (3)
O2—P1—O4	107.98 (14)	C3—C4—H4B	120.1
O1—P1—O3	107.30 (13)	C5—C4—H4B	120.1
O2—P1—O3	108.24 (13)	N1—C5—C4	120.9 (3)
O4—P1—O3	107.05 (14)	N1—C5—C6	114.9 (3)
O8—P2—O5	116.54 (13)	C4—C5—C6	124.1 (3)
O8—P2—O7	112.26 (14)	N2—C6—C7	121.0 (3)
O5—P2—O7	104.93 (13)	N2—C6—C5	114.8 (3)
O8—P2—O6	106.23 (12)	C7—C6—C5	124.2 (3)
O5—P2—O6	108.87 (12)	C8—C7—C6	118.7 (4)
O7—P2—O6	107.72 (14)	C8—C7—H7B	120.6
P1—O1—Co1	129.07 (13)	C6—C7—H7B	120.6
P1—O3—H3A	109.5	C9—C8—C7	119.8 (4)
P1—O4—H4A	109.5	C9—C8—H8A	120.1
P2—O5—Co1	127.55 (12)	C7—C8—H8A	120.1
P2—O6—H6A	109.5	C8—C9—C10	118.8 (4)
P2—O7—H7A	109.5	C8—C9—H9A	120.6
P2—O8—Co1^i	155.17 (16)	C10—C9—H9A	120.6
C1—N1—C5	118.6 (3)	N2—C10—C9	122.6 (4)
C1—N1—Co1	124.4 (2)	N2—C10—H10A	118.7
C5—N1—Co1	116.9 (2)	C9—C10—H10A	118.7
C10—N2—C6	119.0 (3)

Symmetry code: (i) −x, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3A···O2^ii	0.82	1.71	2.522 (4)	170
O4—H4A···O5	0.82	1.79	2.603 (3)	170
O6—H6A···O2^iii	0.82	1.78	2.589 (3)	169
O7—H7A···O3^i	0.82	1.90	2.694 (4)	161

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