catena-Poly[tris(ethylenediamine-κ²N,N′)nickel(II) [[trithiocyanato-κ³N-sodium(I)]-μ-aqua-κ²O:O]]

The title complex, {[Ni(C₂H₈N₂)₃][Na(NCS)₃(H₂O)]}_n, con­sists of discrete [Ni(en)₃]²⁺ dications (en is ethyl­enedi­amine) and polymeric [(H₂O)_0.5Na(NCS)₃(H₂O)_0.5]_n²ⁿ⁻ anions. The compound crystallizes in space group Pc1. The Ni^II atom lies on a threefold axis and has a distorted octahedral coordination geometry. The Na⁺ cation also lies on a site with imposed crystallographic threefold symmetry and is coordinated by the thio­cyanate N atoms (the thio­cyanates are in general posi­tions), by one water mol­ecule with crystallographically imposed 32 symmetry and by a second water mol­ecule with crystallographically imposed symmetry. The unique Na atom thus has trigonal–bipyramidal coordination. The O atoms of the water mol­ecules bridge the Na⁺ cations to form one-dimensional polymeric chains in the crystal structure. The [Ni(en)₃]²⁺ dications are distributed around and between the chains and are linked to them via N—H...S hydrogen bonds.

S1. Comment

The Na⁺ cation plays an important role in the growth of organisms and exists extensively in various kinds of organisms in the form of complexes of biological function. Research into the coordination environment of the Na⁺ cation is conducive to further understanding of its biological function. The Na⁺ cation usually forms four- or six-coordinated complexes (Goher & Mautner, 1994; Paixão et al., 2000). Five-, seven- or eight-coordinated sodium complexes are relatively rare (Hauptmann et al., 1999; Farrugia & Watson, 1999; Krishnakumar et al., 2001). We report here the preparation and crystal structure of the title five-coordinated Na complex, (I), which has trigonal-bipyramidal geometry. \sch

The molecular structure of (I) is shown in Fig. 1. The complex comprises discrete [Ni(en)₃]²⁺ cations (en is ethylenediamine) and polymeric anionic [(H₂O)_0.5Na(NCS)₃(H₂O)_0.5]_n^2n- chains in space group P3c1. The Ni^II atom lies on a threefold axis and has slightly distorted octahedral geometry, being coordinated by six N atoms from three ethylenediamine ligands. All bond lengths and angles involving the Ni atom are similar to those found in comparable complexes (e.g. Huang & Huang, 1984).

The Na atom in the anion lies on a threefold axis and has trigonal-bipyramidal coordination geometry, with the equatorial positions occupied by the three N atoms from three symmetry-related thiocyanate anions and the axial positions by the O atoms of the bridging water molecules. The thiocyanate ion is in a general position. Water atom O1 lies on a site with crystallographic 32 symmetry, while water atom O2 lies on a site with 3 crystallographic symmetry.

The N—Na—N angles are 120 (2)° and the Na—O2 bond [2.1719 (18) Å] is slightly longer than Na—O1 [2.1224 (18) Å]. These Na—O distances in (I) are significantly shorter than the Na—O(bridging aqua) distances in other water O-bridged complexes, e.g. [NaMn(pyz)(N₃)(H₂O)] [2.455 (2) Å; pyz is pyrazine; Goher et al., 1993] and [NaCu{C₆H₃(COO)₃}(H₂O)₄]·2H₂O [2.469 (2) Å; Chui et al., 1999]. Na—O distances of 2.366 (4) and 2.375 (4) Å were found in [NaCu(pic)₂(N₃)(H₂O)₂]_n (pic is picolinate; (Goher et al.,. 1994). The Na—N—C angle in (I) is 175.8 (5)°, deviating slightly from the expected 180°. Other thiocyanate dimensions are normal.

It was not possible to locate the water H atoms, which have to be disordered because of the imposed 32 and 3 symmetry at the water O atoms. In the crystal structure of (I), the O atoms of the water molecules bridge Na⁺ cations to form infinite –O–Na–O–Na– chains, in which the monomer is the [(H₂O)_0.5Na(NCS)₃(H₂O)_0.5]^2- anion. The space-group symmetry ensures that adjacent [Na(NCS)₃]^2- moieties in the polymeric chains are arranged in a staggered stacking fashion along the c axis (Fig. 2). The [Ni(en)₃]²⁺ cations connect the [(H₂O)_0.5Na(NCS)₃(H₂O)_0.5]_n^2n- anion chains by both electrostatic and hydrogen-bond interactions, involving the N—H moieties of the en ligands and the S atoms of the thiocyanate groups, to yield a three-dimensional network.

S2. Experimental

To an aqueous solution (15 ml) of Ni(NO₃)₂·6H₂O (0.37 g, 1 mmol) and ethylenediamine (0.18 g, 3 mmol), an aqueous solution (15 ml) containing NaSCN (0.24 g, 3 mmol) was added with stirring. After stirring for 30 min at room temperature, the purple solution was filtered. Purple single crystals of (I) were obtained from the solution by slow evaporation of the solvent over a week.

S3. Refinement

The systematic absences and Laue symmetry allowed the space group to be either P3c1 or P3c1; P3c1 was selected and confirmed by the analysis. The eight H atoms of the unique en ligand were allowed for as riding atoms (C—H = 0.97 Å and N—H = 0.90 Å). It was not possible to locate the H atoms of the water molecules on the 32 and 3 special positions.

Computing details

Data collection: XSCANS (Siemens, 1991); cell refinement: XSCANS; data reduction: SHELXTL-Plus (Sheldrick, 1990a); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990b); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus; software used to prepare material for publication: SHELXTL-Plus.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and with 35% probability displacement ellipsoids. H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. A molecular packing diagram for (I) projected along the c direction. Some of the hydrogen bonds are shown by dashed lines.

catena-Poly[tris(ethylenediamine-κ²N)nickel(II) [[trithiocyanato-κ³N-sodium(I)]-µ-aqua-κ²O:O]]

Crystal data

[Ni(C2H8N2)3][Na(NCS)3(H2O)]	Dx = 1.511 Mg m^−3
Mr = 454.27	Mo Kα radiation, λ = 0.71073 Å
Trigonal, P3c1	Cell parameters from 22 reflections
Hall symbol: -P 3 2"c	θ = 3.1–16.1°
a = 11.588 (1) Å	µ = 1.32 mm^−1
c = 17.177 (2) Å	T = 293 K
V = 1997.5 (3) Å^3	Prism, purple
Z = 4	0.48 × 0.46 × 0.40 mm
F(000) = 952

Data collection

Siemens P4 diffractometer	1001 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.025
Graphite monochromator	θmax = 27.0°, θmin = 2.0°
ω scans	h = 0→14
Absorption correction: empirical (using intensity measurements) (North et al., 1968)	k = −14→1
Tmin = 0.552, Tmax = 0.589	l = 0→21
3084 measured reflections	3 standard reflections every 97 reflections
1462 independent reflections	intensity decay: 1.8%

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)] = 0.038	H-atom parameters constrained
wR(F^2) = 0.130	w = 1/[σ^2(Fo^2) + (0.068P)^2 + 1.1204P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max < 0.001
1462 reflections	Δρmax = 0.50 e Å^−3
75 parameters	Δρmin = −0.29 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0111 (14)

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
Ni	0.6667	0.3333	0.37758 (3)	0.0361 (3)
Na	1.0000	0.0000	0.37356 (10)	0.0324 (4)
S	0.52065 (11)	−0.13980 (11)	0.36888 (5)	0.0669 (4)
O1	1.0000	0.0000	0.2500	0.086 (2)
O2	1.0000	0.0000	0.5000	0.0611 (16)
N1	0.8306 (3)	0.3599 (3)	0.30894 (14)	0.0475 (7)
H1A	0.8067	0.3456	0.2585	0.057*
H1B	0.8984	0.4441	0.3139	0.057*
N2	0.7250 (3)	0.2179 (3)	0.44568 (14)	0.0489 (7)
H2A	0.7226	0.2348	0.4966	0.059*
H2B	0.6693	0.1305	0.4373	0.059*
N3	0.7892 (5)	−0.0666 (5)	0.3746 (3)	0.1108 (16)
C1	0.8732 (4)	0.2664 (4)	0.33454 (19)	0.0604 (10)
H1C	0.9646	0.2983	0.3187	0.072*
H1D	0.8172	0.1798	0.3110	0.072*
C2	0.8622 (4)	0.2550 (4)	0.4223 (2)	0.0602 (10)
H2C	0.8826	0.1878	0.4401	0.072*
H2D	0.9254	0.3394	0.4459	0.072*
C3	0.6769 (5)	−0.0970 (4)	0.3715 (2)	0.0666 (11)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.0398 (3)	0.0398 (3)	0.0285 (3)	0.01992 (15)	0.000	0.000
Na	0.0272 (6)	0.0272 (6)	0.0427 (10)	0.0136 (3)	0.000	0.000
S	0.0730 (7)	0.0755 (7)	0.0499 (5)	0.0355 (6)	−0.0101 (4)	0.0023 (5)
O1	0.102 (4)	0.102 (4)	0.053 (4)	0.0509 (19)	0.000	0.000
O2	0.067 (2)	0.067 (2)	0.050 (3)	0.0333 (12)	0.000	0.000
N1	0.0514 (17)	0.0565 (18)	0.0376 (12)	0.0292 (14)	0.0049 (12)	0.0044 (12)
N2	0.0569 (17)	0.0529 (16)	0.0374 (12)	0.0279 (15)	−0.0007 (12)	0.0035 (12)
N3	0.074 (3)	0.081 (3)	0.179 (5)	0.039 (2)	0.007 (3)	0.005 (3)
C1	0.074 (3)	0.081 (3)	0.0471 (18)	0.054 (2)	0.0100 (18)	0.0084 (18)
C2	0.067 (2)	0.081 (3)	0.0505 (19)	0.050 (2)	−0.0030 (17)	0.0057 (18)
C3	0.075 (3)	0.044 (2)	0.081 (3)	0.030 (2)	0.005 (2)	−0.0004 (18)

Geometric parameters (Å, º)

Ni—N1	2.123 (3)	C1—C2	1.514 (5)
Ni—N2	2.125 (3)	N1—H1A	0.90
Na—O1	2.1224 (18)	N1—H1B	0.90
Na—O2	2.1719 (18)	N2—H2A	0.90
Na—N3	2.163 (5)	N2—H2B	0.90
S—C3	1.621 (5)	C1—H1C	0.97
N1—C1	1.465 (4)	C1—H1D	0.97
N2—C2	1.480 (5)	C2—H2C	0.97
N3—C3	1.167 (5)	C2—H2D	0.97
N1—Ni—N2	81.61 (10)	Ni—N1—H1B	109.7
N1—Ni—N1^i	92.15 (10)	Ni—N1—H1A	109.7
N1^ii—Ni—N2	94.28 (11)	H1A—N1—H1B	108.2
N1—Ni—N2^ii	171.19 (10)	C1—N1—H1B	109.8
N1—Ni—N2^i	94.28 (11)	Ni—N2—H2B	110.2
N2—Ni—N2^i	92.62 (10)	H2A—N2—H2B	108.5
O1—Na—N3	90.46 (16)	Ni—N2—H2A	110.1
O2—Na—N3	89.54 (16)	C2—N2—H2B	110.2
N3—Na—N3^iii	120.0 (2)	C2—N2—H2A	110.3
O1—Na—O2	180.0	N1—C1—H1C	110.0
Na—O1—Na^iv	180.0	N1—C1—H1D	110.0
Na^v—O2—Na	180.0	C2—C1—H1C	109.9
C1—N1—Ni	109.5 (2)	C2—C1—H1D	110.0
C2—N2—Ni	107.5 (2)	H1C—C1—H1D	108.4
C3—N3—Na	175.8 (5)	N2—C2—H2C	109.8
N1—C1—C2	108.6 (3)	N2—C2—H2D	109.8
N2—C2—C1	109.1 (3)	C1—C2—H2C	109.9
N3—C3—S	178.9 (5)	C1—C2—H2D	109.9
C1—N1—H1A	109.9	H2C—C2—H2D	108.3

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···S^vi	0.90	2.83	3.504 (3)	132
N1—H1B···S^i	0.90	2.83	3.681 (3)	159
N2—H2A···S^vii	0.90	2.72	3.518 (3)	148
N2—H2B···S	0.90	2.96	3.836 (3)	165

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