A three-dimensional supra­molecular vanadium hydroxy­lamide complex: poly[di-μ₂-aqua-bis(hydroxylamido)-μ₃-malonato-oxidosodiumvanadium(V)]

The crystal structure of the title compound, [NaV(C₃H₂O₄)(NH₂O)₂O(H₂O)₂], is built up of NaO₆ and VO₅N₂ polyhedra connected through malonate bridges. The NaO₆ octa­hedra are linked by edge sharing in the equatorial plane to form one-dimensional infinite chains. These chains are linked together by the malonate bridges to form two-dimensional layers. The distorted VO₅N₂ penta­gonal bipyramid is grafted on to the layer by a malonate carboxylate O atom. Adjacent layers are connected through O—H...O and N—H...O hydrogen bonds to build up a three-dimensional supra­molecular structure.

S1. Comment

Simple vanadium salts such as NaVO₃ and VOSO₄ can lower blood glucose levels by activating glucose uptake by cells for metabolism in humans, but numerous studies have shown that organic vanadium complexes are less toxic and several times more effective in lowering blood glucose levels (Thompson et al., 2002). Therefore, much research has gone into exploring the synthesis and structure of insulin-mimetic vanadium complexes. Vanadium hydroxylamide compounds are known to be promising candidates in the study of insulin-mimetic activity of vanadium compounds (Tracey, 2000). Several vanadium hydroxylamide compounds have been reported, such as [VO(NH₂O)(dipic)(H₂O)] (Nuber et al., 1981), [VO(NH₂O)₂L].H₂O (L = glycine, serine and glycylglycine), [VO(NH₂O)₂(imidazole)]Cl (Keramidas et al., 1997), but no vanadium hydroxylamide complexes with carboxylate ligands have been reported to date. Investigation of the preparation and crystal structure of vanadium hydroxylamide complexes with malonic acid provides not only useful information on vanadium chemistry but also promising new candidates for the study of the insulin-mimetic activity of vanadium. Therefore, we report here the preparation and crystal structure of the title vanadium hydroxylamide complex with malonic acid, (I).

In the structure of (I), the V^V ion is seven-coordinated in a pentagonal–bipyramidal geometry by two bidentate hydroxylamide ligands, one oxo ligand and two O atoms from the malonate ligand (Fig. 1). The hydroxylamide ligands coordinate in a side-on manner, as observed in related structures (Paul et al., 1997; Keramidas et al., 1997; Nuber et al., 1981). The malonate behaves as a chelating ligand to the V^V ion. The centroids of the two hydroxylamide ligands and atom O2 of the malonate define the equatorial plane perpendicular to the V═O bond. The other chelating atom, O1, is in an axial position trans to the oxo ligand, with an axial angle O1—V1—O7 = 171.06 (5)° (Table 1). The terminal V═O distance is 1.6017 (10) Å, leading to the expected trans lengthening of the V—O1 distance to 2.1470 (9) Å, which is longer than V—O2 (Table 1). The O—N, V—O and V—N distances and O—V—N angle involving the hydroxylamide ligands are comparable, within experimental error, with related vanadium hydroxylamide complexes reported in the literature (Table 3).

The coordination environment around the Na^I ion can be described as a distorted octahedron. The vertices are occupied by the six O atoms, of which four belong to water molecules [Na—O distances in the range 2.4132 (13)–2.4305 (13) Å] located in the equatorial plane, with two O atoms from two different malonate ligands at the apices [Na—O distances of 2.6027 (13) and 2.5303 (14) Å] (Table 1, Fig. 1). In the crystal structure, adjacent Na polyhedra are linked by a shared edge on opposite sides in the equatorial plane to form an infinite one-dimensional chain. These chains are connected by malonate bridges to form two-dimensional layers (Fig. 2). The VO₅N₂ polyhedra are grafted onto this layer via carboxyl atoms O1 and O2 of the malonate ligands, which are distributed on both sides of the layers owing to the alternating orientation of the two carboxyl groups (Fig. 2). This arrangement model for VO₅N₂ favours the minimization of steric hindrance and boosts the stability of the crystal structure.

The remarkable organization of the crystal structure of (I) can be recognized in a view along the c axis (Fig. 3), which shows the two-dimensional layers parallel to the (010) plane. An extensive hydrogen-bonding network (Table 2) links the different layers through different functional groups, such as hydroxylamide O and water O, or hydroxylamide N and carboxyl O. This leads to the formation of a stable three-dimensional supramolecular structure.

S2. Experimental

NH₄VO₃ (1.375 mmol), malonic acid (2.637 mmol) and NaOH (7.863 mmol) were dissolved in H₂O (10 ml) at room temperature. The resulting light-yellow solution was stirred for approximately 0.5 h in an ice bath. NH₂OH.HCl (7.326 mmol) was added gradually with constant stirring for 0.5–1.0 h. The resulting yellow solution (pH 6.02) was filtered. Colourless crystals of (I) suitable for single-crystal X-ray diffraction were obtained by slow evaporation of the filtrate in anhydrous ethanol at 277 K for a few days.

S3. Refinement

All H atoms are placed in calculated positions and refined using a riding model, with U_iso(H) values of 1.2U_eq(carrier) for NH₂ and CH₂ groups or 1.5U_eq(carrier) for water molecules.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: APEX2 (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of the asymmetric unit of (I), showing the atom connectivities and coordination environment.
	Fig. 2. The two-dimensional layer structure of (I), in the ac plane.
	Fig. 3. A packing view of (I), showing the two-dimensional layers parallel to the (010) plane.

poly[di-µ₂-aqua-bis(hydroxylamido)-µ₃-malonato-oxidosodiumvanadium(V)]

Crystal data

[NaV(C3H2O4)(NH2O)2O(H2O)2]	F(000) = 592
Mr = 292.06	Dx = 1.892 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2ybc	Cell parameters from 8964 reflections
a = 9.6393 (2) Å	θ = 2.3–28.3°
b = 15.4265 (4) Å	µ = 1.05 mm^−1
c = 7.4346 (2) Å	T = 296 K
β = 111.984 (1)°	Block, colourless
V = 1025.14 (4) Å^3	0.33 × 0.15 × 0.13 mm
Z = 4

Data collection

Bruker APEXII CCD area-detector diffractometer	2529 independent reflections
Radiation source: fine-focus sealed tube	2306 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ϕ and ω scans	θmax = 28.3°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2005)	h = −12→12
Tmin = 0.825, Tmax = 0.873	k = −20→20
13757 measured reflections	l = −9→9

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)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.065	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0352P)^2 + 0.4548P] where P = (Fo^2 + 2Fc^2)/3
2529 reflections	(Δ/σ)max = 0.001
145 parameters	Δρmax = 0.36 e Å^−3
0 restraints	Δρmin = −0.30 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
V1	0.66549 (2)	0.030524 (13)	0.82126 (3)	0.01925 (8)
Na1	1.01299 (8)	0.26225 (4)	0.99029 (10)	0.04198 (17)
O1	0.73448 (10)	0.16375 (6)	0.86457 (14)	0.02439 (19)
O1W	1.03107 (12)	0.15091 (7)	1.22936 (17)	0.0368 (2)
H1WA	0.9586	0.1172	1.1700	0.055*
H1WB	1.1134	0.1237	1.2765	0.055*
O2	0.45932 (10)	0.08666 (6)	0.72781 (14)	0.0251 (2)
O2W	1.03287 (12)	0.15212 (7)	0.77066 (17)	0.0377 (3)
H2WA	0.9806	0.1082	0.7740	0.057*
H2WB	1.1141	0.1274	0.8406	0.057*
O3	0.73206 (12)	0.30576 (6)	0.83574 (16)	0.0303 (2)
O4	0.27930 (13)	0.18351 (9)	0.6450 (2)	0.0495 (3)
O5	0.82068 (11)	0.01576 (6)	0.72403 (15)	0.0274 (2)
O6	0.81309 (11)	0.01388 (6)	1.07294 (14)	0.0275 (2)
O7	0.58800 (12)	−0.06300 (6)	0.77496 (15)	0.0301 (2)
N1	0.69554 (13)	0.04561 (8)	0.56848 (17)	0.0266 (2)
H1A	0.7124	0.0933	0.5251	0.032*
H2A	0.6598	0.0076	0.4816	0.032*
N2	0.68257 (14)	0.03947 (7)	1.09821 (17)	0.0259 (2)
H1B	0.6483	0.0002	1.1499	0.031*
H2B	0.6895	0.0886	1.1516	0.031*
C1	0.40806 (14)	0.16396 (9)	0.67419 (19)	0.0241 (3)
C2	0.51172 (15)	0.23007 (9)	0.6398 (2)	0.0262 (3)
H2C	0.4669	0.2870	0.6316	0.031*
H2D	0.5178	0.2180	0.5149	0.031*
C3	0.67016 (14)	0.23368 (8)	0.79161 (18)	0.0205 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
V1	0.02139 (12)	0.01616 (11)	0.01975 (12)	−0.00077 (7)	0.00718 (9)	0.00044 (7)
Na1	0.0529 (4)	0.0390 (4)	0.0382 (4)	0.0112 (3)	0.0220 (3)	0.0050 (3)
O1	0.0218 (4)	0.0185 (4)	0.0294 (5)	−0.0005 (3)	0.0056 (4)	0.0003 (4)
O1W	0.0327 (5)	0.0303 (5)	0.0417 (6)	0.0012 (4)	0.0073 (5)	−0.0039 (4)
O2	0.0215 (4)	0.0226 (4)	0.0299 (5)	−0.0025 (3)	0.0080 (4)	0.0026 (4)
O2W	0.0334 (6)	0.0302 (5)	0.0496 (7)	0.0033 (4)	0.0157 (5)	0.0052 (5)
O3	0.0325 (5)	0.0189 (4)	0.0386 (6)	−0.0045 (4)	0.0124 (4)	−0.0016 (4)
O4	0.0235 (5)	0.0487 (7)	0.0756 (9)	0.0069 (5)	0.0177 (6)	0.0131 (6)
O5	0.0266 (5)	0.0265 (5)	0.0305 (5)	0.0030 (4)	0.0125 (4)	0.0003 (4)
O6	0.0268 (5)	0.0273 (5)	0.0251 (5)	0.0048 (4)	0.0059 (4)	0.0034 (4)
O7	0.0357 (5)	0.0213 (5)	0.0324 (5)	−0.0060 (4)	0.0116 (4)	−0.0009 (4)
N1	0.0339 (6)	0.0244 (5)	0.0224 (6)	−0.0012 (5)	0.0115 (5)	−0.0003 (4)
N2	0.0328 (6)	0.0238 (5)	0.0226 (5)	−0.0005 (4)	0.0122 (5)	0.0010 (4)
C1	0.0208 (6)	0.0265 (6)	0.0229 (6)	−0.0003 (5)	0.0059 (5)	−0.0004 (5)
C2	0.0250 (6)	0.0224 (6)	0.0287 (7)	0.0013 (5)	0.0071 (5)	0.0062 (5)
C3	0.0229 (6)	0.0202 (6)	0.0218 (6)	−0.0008 (4)	0.0120 (5)	−0.0005 (4)

Geometric parameters (Å, º)

V1—N1	2.0193 (11)	O1W—H1WB	0.8497
V1—N2	2.0080 (12)	O2—C1	1.2952 (16)
V1—O1	2.1470 (9)	O2W—H2WA	0.8498
V1—O2	2.0368 (9)	O2W—H2WB	0.8506
V1—O5	1.9030 (10)	O3—C3	1.2464 (16)
V1—O6	1.8969 (10)	O4—C1	1.2153 (17)
V1—O7	1.6017 (10)	N1—O5	1.4000 (15)
Na1—O1	2.9173 (12)	N2—O6	1.3969 (15)
Na1—O1W	2.4305 (13)	N1—H1A	0.8436
Na1—O1W^i	2.4169 (13)	N1—H2A	0.8448
Na1—O2W	2.4132 (13)	N2—H1B	0.8479
Na1—O2W^ii	2.4140 (13)	N2—H2B	0.8457
Na1—O3	2.6027 (13)	C1—C2	1.5149 (18)
Na1—O4^iii	2.5303 (14)	C2—C3	1.5228 (18)
Na1—C3	3.1052 (15)	C2—H2C	0.9700
O1—C3	1.2612 (16)	C2—H2D	0.9700
O1W—H1WA	0.8500
O1—V1—O6	84.60 (4)	O2W—Na1—Na1^ii	129.16 (4)
O1—V1—O7	171.06 (5)	O2W^ii—Na1—Na1^ii	39.27 (3)
O2—V1—O5	136.61 (4)	O1W^i—Na1—Na1^ii	151.82 (4)
O2—V1—O6	132.05 (4)	O1W—Na1—Na1^ii	39.44 (3)
O2—V1—O7	89.58 (5)	O4^iii—Na1—Na1^ii	87.65 (4)
O5—V1—O6	87.28 (4)	O3—Na1—Na1^ii	94.46 (3)
O5—V1—O7	100.38 (5)	O1—Na1—Na1^ii	85.60 (3)
O6—V1—O7	101.96 (5)	C3—Na1—Na1^ii	93.59 (3)
N1—V1—N2	163.98 (5)	Na1^i—Na1—Na1^ii	168.39 (4)
N1—V1—O2	95.46 (4)	C3—O1—V1	132.80 (8)
N1—V1—O5	41.69 (5)	C3—O1—Na1	86.42 (7)
N1—V1—O6	128.15 (5)	V1—O1—Na1	137.98 (4)
N1—V1—O7	96.99 (5)	Na1^ii—O1W—Na1	100.85 (4)
N2—V1—O2	90.89 (4)	Na1^ii—O1W—H1WA	117.6
N2—V1—O5	128.56 (5)	Na1—O1W—H1WA	103.5
N2—V1—O6	41.80 (5)	Na1^ii—O1W—H1WB	106.3
N2—V1—O7	97.75 (5)	Na1—O1W—H1WB	116.9
O1—V1—O2	81.49 (4)	H1WA—O1W—H1WB	111.7
O1—V1—O5	85.88 (4)	C1—O2—V1	135.03 (8)
N2—V1—O1	83.02 (4)	Na1—O2W—Na1^i	101.44 (4)
N1—V1—O1	83.39 (4)	Na1—O2W—H2WA	110.1
O2W—Na1—O2W^ii	165.64 (5)	Na1^i—O2W—H2WA	127.2
O2W—Na1—O1W^i	78.42 (4)	Na1—O2W—H2WB	100.9
O2W^ii—Na1—O1W^i	112.55 (5)	Na1^i—O2W—H2WB	122.0
O2W—Na1—O1W	89.73 (4)	H2WA—O2W—H2WB	92.6
O2W^ii—Na1—O1W	78.14 (4)	C3—O3—Na1	101.69 (8)
O1W^i—Na1—O1W	166.33 (5)	C1—O4—Na1^iv	163.29 (12)
O2W—Na1—O4^iii	102.50 (5)	N1—O5—V1	73.60 (6)
O2W^ii—Na1—O4^iii	71.78 (4)	N2—O6—V1	73.36 (6)
O1W^i—Na1—O4^iii	79.39 (5)	O5—N1—V1	64.70 (6)
O1W—Na1—O4^iii	96.80 (5)	O5—N1—H1A	111.9
O2W—Na1—O3	102.47 (4)	V1—N1—H1A	124.9
O2W^ii—Na1—O3	88.47 (4)	O5—N1—H2A	112.5
O1W^i—Na1—O3	83.02 (4)	V1—N1—H2A	118.1
O1W—Na1—O3	106.44 (4)	H1A—N1—H2A	113.3
O3—Na1—O4^iii	145.72 (5)	O6—N2—V1	64.84 (6)
O2W—Na1—O1	73.33 (4)	O6—N2—H1B	112.5
O2W^ii—Na1—O1	109.13 (4)	V1—N2—H1B	121.3
O1W^i—Na1—O1	111.45 (4)	O6—N2—H2B	113.5
O1W—Na1—O1	70.83 (4)	V1—N2—H2B	120.3
O4^iii—Na1—O1	166.70 (5)	H1B—N2—H2B	113.8
O3—Na1—O1	46.55 (3)	O4—C1—O2	121.99 (13)
O2W—Na1—C3	85.31 (4)	O4—C1—C2	119.79 (13)
O2W^ii—Na1—C3	102.40 (4)	O2—C1—C2	118.17 (11)
O1W^i—Na1—C3	94.62 (4)	C1—C2—C3	116.19 (11)
O1W—Na1—C3	91.13 (4)	C1—C2—H2C	108.2
O4^iii—Na1—C3	168.85 (5)	C3—C2—H2C	108.2
O3—Na1—C3	23.15 (3)	C1—C2—H2D	108.2
O1—Na1—C3	23.91 (3)	C3—C2—H2D	108.2
O2W—Na1—Na1^i	39.29 (3)	H2C—C2—H2D	107.4
O2W^ii—Na1—Na1^i	152.23 (4)	O3—C3—O1	122.68 (12)
O1W^i—Na1—Na1^i	39.71 (3)	O3—C3—C2	118.44 (12)
O1W—Na1—Na1^i	129.00 (4)	O1—C3—C2	118.86 (11)
O4^iii—Na1—Na1^i	96.19 (4)	O3—C3—Na1	55.16 (7)
O3—Na1—Na1^i	88.53 (3)	O1—C3—Na1	69.66 (7)
O1—Na1—Na1^i	88.35 (3)	C2—C3—Na1	162.03 (9)
C3—Na1—Na1^i	84.76 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WA···O1	0.85	2.58	3.1245 (15)	123
O1W—H1WB···O5^v	0.85	2.24	2.8987 (14)	134
O1W—H1WA···O6	0.85	2.07	2.8994 (15)	166
O2W—H2WA···O5	0.85	2.03	2.8633 (15)	167
O2W—H2WB···O6^v	0.85	2.31	2.9701 (14)	135
N1—H1A···O3^i	0.84	2.15	2.9717 (15)	163
N1—H2A···O2^vi	0.84	2.13	2.9635 (15)	172
N2—H1B···O2^vii	0.85	2.10	2.9418 (15)	173
N2—H2B···O3^ii	0.85	2.07	2.9010 (15)	168

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