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The structure of hexa­aqua­nickel(II) bis­(hypophosphite), [Ni(H2O)6](H2PO2)2, has been determined. The crystals are prismatic. The packing of the Ni and P atoms (not the entire hypophosphite anions) is the same as in the structures of [Co(H2O)6](H2PO2)2 and [Co0.5Ni0.5(H2O)6](H2PO2)2. The NiII cations have a pseudo-face-centered cubic cell, with cell parameter a \simeq 10.216 Å and tetrahedral cavities occupied by P atoms. The NiII cation has crystallographically imposed twofold symmetry and has an octahedral coordination sphere consisting of six water O atoms, two of which also lie on the twofold axis. The planes of oppositely coordinated water mol­ecules are in a cross conformation. The geometry of the hypophosphite anion is close to point symmetry mm2. The hypophosphite anions are hydrogen bonded to the coordinated water molecules.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102018541/sk1594sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102018541/sk1594Isup2.hkl
Contains datablock I

Comment top

Studies of hexaaquametal(II) bis(hypophosphite)s have been reported previously by Ferrari & Colla (1937), Pédrazuela et al. (1953), Galigné & Dumas (1973) and Kuratieva et al. (2002). This paper presents the results of the single-crystal X-ray diffraction analysis of hexaaquanickel(II) bis(hypophosphite), [Ni(H2O)6](H2PO2)2. The calculated powder pattern of this compound is in good agreement with the experimental powder pattern, but is different from those of hexaaquacobalt(II) bis(hypophosphite) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite) (Kuratieva et al., 2002).

The packing of the NiII cations and P atoms (not the complete hypophosphite anion) is the same as in the structures of [Co(H2O)6](H2PO2)2 and [Co0.5Ni0.5(H2O)6](H2PO2)2. The nickel cations form a pseudo-face-centered cubic cell, with cell-parameter a 10.216 Å and tetrahedral cavities occupied by P atoms. The powder pattern for this compound was reported previously by Ferrari & Colla (1937) and the compound was indexed as acubic system with an a cell parameter of 10.30 Å. The explanation for this mismatch has been discussed by Kuratieva et al. (2002).

The first coordination sphere of the NiII cation consists of six water molecules, which form a slightly distorted octahedron. The hypophosphite anions do not coordinate to the NiII cation. According to previously reported data, the average M—O distance for hexahydrated bivalent metal hypophosphites is 2.05 (1) Å for magnesium(II) (Galigné & Dumas, 1973), 2.074 (3) Å for cobalt(II) and 2.055 (2) Å for cobalt(II)/nickel(II) (Kuratieva et al., 2002). The average Ni—O distance in the present study is 2.045 (7) Å.

There is only one orientation of the coordinated water molecules. The planes of the oppositely coordinated water molecules are in a cross conformation. The first coordination sphere differs from those in [Co(H2O)6](H2PO2)2 and [Co0.5Ni0.5(H2O)6](H2PO2)2, which have one pair of oppositely coordinated water molecules with their planes in an eclipsed conformation.

The oppositely coordinated water molecules can be classified into three logical groups. The first group consists of molecules O1W and O2W [Ni—O distances of 2.038 (3) and 2.054 (2) Å, respectively]. The planes of these water molecules (i.e. consisting of the O and two H atoms of each molecule) are perpendicular to the plane formed by the O atoms of the other four coordinated water molecules and the NiII atom (basal plane). The dihedral angle between the planes of these water molecules is 86.5(?)°. The second group consists of molecules O3W and O3Wi [Ni—O distances of 2.0403 (17) Å; symmetry code: (i) −x, y, 1/2 − z]; the planes of these water molecules are tilted from the normal to the basal plane by an angle of 13.5(?)°. The third group consists of molecules O4W and O4Wi [Ni—O distances of 2.0469 (18) Å; symmetry code: (i) −x, y, 1/2 − z]; the planes of these water molecules are tilted from the normal to the basal plane by an angle of 30.1(?)° (Fig. 1 and Table 1). The planes of all the coordinated water molecules in [Co(H2O)6](H2PO2)2 {[Co0.5Ni0.5(H2O)6](H2PO2)2} are perpendicular to the basal plane.

The second coordination sphere of the NiII cation consists of eight hypophosphite anions, which are hydrogen bonded to water molecules coordinated to the NiII cation (Fig. 1). In spite of the similarities in the packing of the NiII cations and P atoms (Fig. 2), the orientation of the hypophosphite anions differs from that in the structures of [Co(H2O)6](H2PO2)2 and [Co0.5Ni0.5(H2O)6](H2PO2)2 due to distinctions in the first coordination spheres.

The geometry of the hypophosphite anion remains practically the same, with point symmetry mm2 (Naumov et al., 2001, 2002; Kuratieva et al., 2002), to the previously reported structures, with respective P—O distances and O—P—O angles of 1.507 (3) Å and 116.2 (3)° in [Mg(H2O)6](H2PO2)2 (Galigné & Dumas, 1973), 1.527 (1)/1.516 (1) Å and 115.3° in Co(H2PO2)Cl(H2O) (Marcos et al., 1991), 1.541 (2)/1.480 (2) Å and 118.7 (3)° in Ni(H2PO2)Cl(H2O) (Marcos et al., 1993), 1.5076 (13) Å and 115.74 (13)° in [Co(H2O)6](H2PO2)2, and 1.5092 (12) Å and 115.90 (11)° in [Co0.5Ni0.5(H2O)6](H2PO2)2 (Kuratieva et al., 2002) (Table 1).

Each hypophosphite O atom is hydrogen bonded to three water molecules from different complex cations (Table 2; thick dashed line in Fig. 2), while each hypophosphite H atom is surrounded by three water molecules from other (different) complex cations, and these H atoms are situated directly above the centers of the triangles formed by the O atoms of these three water molecules (thin dashed lines in Fig. 2). The distances between hypophosphite atom H1 and water atoms O1Wi, O3Wii and O4Wiii [symmetry codes: (i) 1/2 − x, 1/2 − y, −z; (ii) 1/2 − x, y − 1/2, 1/2 − z; (iii) x, −y, z − 1/2] are 2.94 (2), 2.91 (2) and 2.97 (2) Å, and between hypophosphite atom H2 and water atoms O2Wiv, O3Wv and O4Wvi [symmetry codes: (iv) −x, −y, −z; (v) −x, y, 1/2 − z; (vi) 1/2 − x, 1/2 − y, −z] are 2.92 (2), 2.90 (2) and 2.83 (2) Å [the average P—H···O bond length is 2.91 (2) Å]. This environment of the hypophosphite anion is similar to that in the structures of the hexaaquamagnesium(II), hexaaquacobalt(II) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite)s.

Experimental top

The title compound was synthesized by slow evaporation of an aqueous solution of nickel(II) hypophosphite, prepared by adding a solution of hypophosphorous acid, H3PO2, to the nickel(II) carbonate hydroxide, NiCO3.nNi(OH)2.mH2O. The reaction mixture was evacuated in a vacuum to separate the carbon dioxide, CO2. The crystals were grown at 293 K in air.

Refinement top

The H atoms were located from a difference electron-density map and refined without constraints.

Computing details top

Data collection: CD4CA0 (Enraf-Nonius, 1989); cell refinement: CD4CA0; data reduction: CADDAT (Enraf-Nonius, 1989); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The environment of the hexaaquanickel(II) cation in relation to the hypophosphite anions. Displacement ellipsoids are plotted at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii [symmetry codes: (i) −x, y, 1/2 − z; (ii) 1/2 − y, 1/2 + y, 1/2 − z; (iii) x, −y, 1/2 + z; (iv) x − 1/2, 1/2 − y, 1/2 + z].
[Figure 2] Fig. 2. The environment of the hypophosphite anion of [Ni(H2O)6](H2PO2)2 in relation to the hexaaquanickel(II) cations, viewed along b. The thick dashed lines indicate O—H···O—P hydrogen bonds. The thin dashed lines indicate OW···H—P contacts. Displacement ellipsoids are plotted at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii.
(I) top
Crystal data top
[Ni(H2O)6](H2PO2)2F(000) = 616
Mr = 296.78Dx = 1.851 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 20 reflections
a = 10.1453 (3) Åθ = 12.5–13.0°
b = 10.1467 (4) ŵ = 2.15 mm1
c = 10.3571 (3) ÅT = 293 K
β = 92.632 (3)°Prism, green
V = 1065.05 (6) Å30.2 × 0.1 × 0.05 mm
Z = 4
Data collection top
Enraf-Nonius CAD-4
diffractometer
1243 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.024
Graphite monochromatorθmax = 28.3°, θmin = 2.8°
2θ/θ scansh = 013
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
k = 013
Tmin = 0.636, Tmax = 0.898l = 1313
1401 measured reflections3 standard reflections every 60 min
1331 independent reflections intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028All H-atom parameters refined
wR(F2) = 0.081 w = 1/[σ2(Fo2) + (0.0402P)2 + 1.2793P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max < 0.001
1331 reflectionsΔρmax = 0.47 e Å3
94 parametersΔρmin = 0.42 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0116 (9)
Crystal data top
[Ni(H2O)6](H2PO2)2V = 1065.05 (6) Å3
Mr = 296.78Z = 4
Monoclinic, C2/cMo Kα radiation
a = 10.1453 (3) ŵ = 2.15 mm1
b = 10.1467 (4) ÅT = 293 K
c = 10.3571 (3) Å0.2 × 0.1 × 0.05 mm
β = 92.632 (3)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1243 reflections with I > 2σ(I)
Absorption correction: empirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Rint = 0.024
Tmin = 0.636, Tmax = 0.8983 standard reflections every 60 min
1401 measured reflections intensity decay: none
1331 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.081All H-atom parameters refined
S = 1.06Δρmax = 0.47 e Å3
1331 reflectionsΔρmin = 0.42 e Å3
94 parameters
Special details top

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 (Å2) top
xyzUiso*/Ueq
Ni10.00000.26480 (4)0.25000.02570 (16)
P10.23511 (5)0.01455 (5)0.00603 (5)0.02685 (17)
H10.292 (3)0.051 (3)0.080 (3)0.036 (7)*
H20.160 (2)0.089 (3)0.061 (2)0.034 (7)*
O10.33259 (14)0.10033 (15)0.08183 (13)0.0308 (3)
O20.15387 (14)0.07785 (14)0.08486 (14)0.0310 (3)
O1W0.00000.4657 (2)0.25000.0464 (7)
H1W0.047 (3)0.504 (3)0.293 (3)0.040 (8)*
O2W0.00000.0624 (2)0.25000.0453 (6)
H2W0.044 (3)0.022 (3)0.210 (3)0.058 (10)*
O3W0.02103 (19)0.27242 (19)0.44672 (16)0.0395 (4)
H3W0.034 (4)0.304 (4)0.489 (4)0.058 (10)*
H4W0.048 (3)0.213 (3)0.481 (3)0.039 (8)*
O4W0.20136 (18)0.2663 (2)0.2438 (2)0.0453 (5)
H5W0.243 (4)0.217 (4)0.208 (4)0.057 (10)*
H6W0.245 (3)0.306 (3)0.294 (3)0.042 (8)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ni10.0267 (2)0.0271 (2)0.0236 (2)0.0000.00420 (13)0.000
P10.0280 (3)0.0289 (3)0.0237 (3)0.00492 (18)0.00267 (19)0.00028 (17)
O10.0301 (7)0.0309 (7)0.0315 (7)0.0065 (6)0.0022 (6)0.0014 (6)
O20.0303 (7)0.0317 (7)0.0314 (7)0.0070 (6)0.0052 (6)0.0018 (6)
O1W0.0612 (17)0.0273 (11)0.0482 (14)0.0000.0255 (13)0.000
O2W0.0598 (16)0.0275 (11)0.0515 (15)0.0000.0341 (13)0.000
O3W0.0466 (10)0.0470 (10)0.0252 (7)0.0250 (8)0.0070 (7)0.0037 (7)
O4W0.0268 (8)0.0609 (12)0.0488 (11)0.0034 (8)0.0061 (7)0.0283 (9)
Geometric parameters (Å, º) top
Ni1—O1W2.038 (3)P1—H21.26 (2)
Ni1—O2W2.054 (2)O1W—H1W0.74 (3)
Ni1—O3W2.0403 (17)O2W—H2W0.74 (3)
Ni1—O4W2.0469 (18)O3W—H3W0.79 (4)
P1—O11.5102 (14)O3W—H4W0.75 (3)
P1—O21.5122 (14)O4W—H5W0.76 (4)
P1—H11.27 (3)O4W—H6W0.77 (3)
O1W—Ni1—O3W87.83 (5)O3W—Ni1—O2W92.17 (5)
O1W—Ni1—O3Wi87.83 (5)O3Wi—Ni1—O2W92.17 (5)
O3W—Ni1—O3Wi175.66 (11)O4Wi—Ni1—O2W90.41 (6)
O1W—Ni1—O4Wi89.59 (6)O4W—Ni1—O2W90.41 (6)
O3W—Ni1—O4Wi91.55 (8)O1—P1—O2115.90 (8)
O3Wi—Ni1—O4Wi88.42 (8)H1—P1—H2102.2 (16)
O1W—Ni1—O4W89.59 (6)H1Wi—O1W—H1W117 (5)
O3W—Ni1—O4W88.42 (8)H2Wi—O2W—H2W113 (5)
O3Wi—Ni1—O4W91.55 (8)H3W—O3W—H4W108 (4)
O4Wi—Ni1—O4W179.17 (12)H5W—O4W—H6W111 (4)
O1W—Ni1—O2W180
Symmetry code: (i) x, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1W—H1W···O1ii0.74 (3)2.00 (3)2.7412 (19)176 (3)
O2W—H2W···O20.74 (3)2.03 (3)2.7628 (19)174 (4)
O3W—H3W···O1iii0.79 (4)1.96 (4)2.743 (2)173 (4)
O3W—H4W···O2iv0.75 (3)2.02 (3)2.754 (2)168 (3)
O4W—H5W···O10.76 (4)2.01 (4)2.761 (2)169 (4)
O4W—H6W···O2ii0.77 (3)1.98 (4)2.751 (2)174 (3)
Symmetry codes: (ii) x+1/2, y+1/2, z+1/2; (iii) x1/2, y+1/2, z+1/2; (iv) x, y, z+1/2.

Experimental details

Crystal data
Chemical formula[Ni(H2O)6](H2PO2)2
Mr296.78
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)10.1453 (3), 10.1467 (4), 10.3571 (3)
β (°) 92.632 (3)
V3)1065.05 (6)
Z4
Radiation typeMo Kα
µ (mm1)2.15
Crystal size (mm)0.2 × 0.1 × 0.05
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(CADDAT; Enraf-Nonius, 1989)
Tmin, Tmax0.636, 0.898
No. of measured, independent and
observed [I > 2σ(I)] reflections
1401, 1331, 1243
Rint0.024
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.081, 1.06
No. of reflections1331
No. of parameters94
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.47, 0.42

Computer programs: CD4CA0 (Enraf-Nonius, 1989), CD4CA0, CADDAT (Enraf-Nonius, 1989), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPIII (Burnett & Johnson, 1996), SHELXL97.

Selected geometric parameters (Å, º) top
Ni1—O1W2.038 (3)P1—O11.5102 (14)
Ni1—O2W2.054 (2)P1—O21.5122 (14)
Ni1—O3W2.0403 (17)P1—H11.27 (3)
Ni1—O4W2.0469 (18)P1—H21.26 (2)
O1W—Ni1—O3W87.83 (5)O4Wi—Ni1—O4W179.17 (12)
O3W—Ni1—O3Wi175.66 (11)O1W—Ni1—O2W180
O1W—Ni1—O4W89.59 (6)O1—P1—O2115.90 (8)
O3W—Ni1—O4W88.42 (8)H1—P1—H2102.2 (16)
Symmetry code: (i) x, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1W—H1W···O1ii0.74 (3)2.00 (3)2.7412 (19)176 (3)
O2W—H2W···O20.74 (3)2.03 (3)2.7628 (19)174 (4)
O3W—H3W···O1iii0.79 (4)1.96 (4)2.743 (2)173 (4)
O3W—H4W···O2iv0.75 (3)2.02 (3)2.754 (2)168 (3)
O4W—H5W···O10.76 (4)2.01 (4)2.761 (2)169 (4)
O4W—H6W···O2ii0.77 (3)1.98 (4)2.751 (2)174 (3)
Symmetry codes: (ii) x+1/2, y+1/2, z+1/2; (iii) x1/2, y+1/2, z+1/2; (iv) x, y, z+1/2.
 

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