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The title compounds, hexaaquacobalt(II) bis(hypophosphite), [Co(H2O)6](H2PO2)2, and hexaaquacobalt(II)/nickel(II) bis(hypophosphite), [Co0.5Ni0.5(H2O)6](H2PO2)2, are shown to adopt the same structure as hexaaquamagnesium(II) bis(hypophosphite). The packing of the Co(Ni) and P atoms is the same as in the structure of CaF2. The CoII(NiII) atoms have a pseudo-face-centred cubic cell, with a = b ∼ 10.3 Å, and the P atoms occupy the tetrahedral cavities. The central metal cation has a slightly distorted octahedral coordination sphere. The geometry of the hypophosphite anion in the structure is very close to ideal, with point symmetry mm2. Each O atom of the hypophosphite anion is hydrogen bonded to three water molecules from different cation complexes, and each H atom of the hypophosphite anion is surrounded by three water molecules from further different cation complexes.
Supporting information
Compound (I) was synthesized by the slow evaporation of an aqueous solution of
cobalt(II) hypophosphite, which was prepared by adding a solution of calcium
hypophosphite, Ca(H2PO2)2, to cobalt(II) sulfate, CoSO4, in an
equimolar ratio. The reaction mixture was filtered and crystals of (I) were
grown at 293 K in air. Compound (II) was synthesized by mixing aqueous
solutions of cobalt(II) and nickel(II) bis(hypophosphite)s in an equimolar
ratio. Purple-green crystals of (II) were grown at 293 K in air Please clarify
- light-green given below, and their chemical composition was determined by UV
spectroscopy. The UV spectrum of the hexaaquacobalt(II) cation has no overlap
with that for Ni (maximum absorption 317 and 288 nm, respectively). The
quantities of each cation in the crystals were calculated using calibration
solutions of the pure cobalt(II) and nickel(II) bis(hypophosphite)s. The
actual ratio of metals in the crystals was found to be the same as that
calculated based on the preparation experiment.
In both structures, the H atoms were located from a difference electron-density
map. The positions of the H atoms were refined without any constraints.
For both compounds, 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.
(I) hexaaquacobalt(II) bis(hypophosphite)
top
Crystal data top
[Co(H2O)6](H2PO2)2 | Dx = 1.809 Mg m−3 |
Mr = 297.00 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, I41/acd | Cell parameters from 24 reflections |
Hall symbol: -I 4bd 2c | θ = 9.7–12.0° |
a = 10.3406 (15) Å | µ = 1.89 mm−1 |
c = 20.402 (3) Å | T = 293 K |
V = 2181.6 (6) Å3 | Prism, purple |
Z = 8 | 0.64 × 0.36 × 0.36 mm |
F(000) = 1224 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 419 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.030 |
Graphite monochromator | θmax = 28.3°, θmin = 3.4° |
2θ/θ scans | h = 0→13 |
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) | k = 0→13 |
Tmin = 0.477, Tmax = 0.506 | l = 0→27 |
1315 measured reflections | 3 standard reflections every 60 min |
686 independent reflections | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | All H-atom parameters refined |
wR(F2) = 0.093 | w = 1/[σ2(Fo2) + (0.0536P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.92 | (Δ/σ)max < 0.001 |
686 reflections | Δρmax = 0.51 e Å−3 |
49 parameters | Δρmin = −0.41 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0004 (1) |
Crystal data top
[Co(H2O)6](H2PO2)2 | Z = 8 |
Mr = 297.00 | Mo Kα radiation |
Tetragonal, I41/acd | µ = 1.89 mm−1 |
a = 10.3406 (15) Å | T = 293 K |
c = 20.402 (3) Å | 0.64 × 0.36 × 0.36 mm |
V = 2181.6 (6) Å3 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 419 reflections with I > 2σ(I) |
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) | Rint = 0.030 |
Tmin = 0.477, Tmax = 0.506 | 3 standard reflections every 60 min |
1315 measured reflections | intensity decay: none |
686 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.093 | All H-atom parameters refined |
S = 0.92 | Δρmax = 0.51 e Å−3 |
686 reflections | Δρmin = −0.41 e Å−3 |
49 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 | x | y | z | Uiso*/Ueq | |
Co1 | 0.0000 | 0.2500 | 0.1250 | 0.0307 (2) | |
P1 | 0.24094 (8) | 0.0000 | 0.2500 | 0.0326 (3) | |
H1 | 0.317 (2) | −0.063 (2) | 0.2823 (9) | 0.043 (7)* | |
O1 | 0.16340 (15) | 0.08764 (15) | 0.29407 (6) | 0.0358 (4) | |
O1W | 0.0000 | 0.2500 | 0.22648 (12) | 0.0518 (7) | |
H1W | 0.045 (3) | 0.208 (3) | 0.2457 (13) | 0.037 (6)* | |
O2W | 0.0026 (2) | 0.04922 (17) | 0.12380 (13) | 0.0552 (6) | |
H2W | 0.043 (3) | 0.016 (3) | 0.1410 (11) | 0.035 (9)* | |
H3W | −0.047 (3) | 0.015 (3) | 0.1044 (11) | 0.054 (9)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Co1 | 0.0301 (3) | 0.0301 (3) | 0.0318 (4) | −0.00244 (18) | 0.000 | 0.000 |
P1 | 0.0265 (7) | 0.0371 (8) | 0.0342 (4) | 0.000 | 0.000 | −0.0085 (3) |
O1 | 0.0350 (9) | 0.0364 (9) | 0.0360 (7) | −0.0004 (6) | 0.0012 (6) | −0.0085 (7) |
O1W | 0.055 (3) | 0.067 (3) | 0.0326 (13) | 0.0300 (13) | 0.000 | 0.000 |
O2W | 0.0658 (13) | 0.0304 (9) | 0.0694 (12) | −0.0049 (9) | −0.0427 (10) | 0.0025 (18) |
Geometric parameters (Å, º) top
Co1—O1W | 2.070 (3) | O1W—H1W | 0.75 (2) |
Co1—O2W | 2.0765 (18) | O2W—H2W | 0.64 (2) |
P1—O1 | 1.5076 (13) | O2W—H3W | 0.74 (3) |
P1—H1 | 1.21 (2) | | |
| | | |
O1W—Co1—O2W | 90.68 (7) | O2Wi—Co1—O2Wiii | 178.65 (14) |
O1W—Co1—O2Wi | 89.32 (7) | O1iv—P1—O1 | 115.74 (13) |
O2W—Co1—O2Wi | 88.50 (14) | H1iv—P1—H1 | 99 (2) |
O2W—Co1—O2Wii | 178.65 (14) | H1Wii—O1W—H1W | 117 (4) |
O2W—Co1—O2Wiii | 91.51 (14) | H2W—O2W—H3W | 119 (3) |
Symmetry codes: (i) −y+1/4, −x+1/4, −z+1/4; (ii) −x, −y+1/2, z; (iii) y−1/4, x+1/4, −z+1/4; (iv) x, −y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1 | 0.75 (2) | 2.01 (2) | 2.7524 (18) | 177 (3) |
O2W—H2W···O1iv | 0.64 (2) | 2.11 (3) | 2.752 (3) | 174 (3) |
O2W—H3W···O1v | 0.74 (3) | 2.01 (3) | 2.744 (3) | 173 (3) |
Symmetry codes: (iv) x, −y, −z+1/2; (v) y−1/4, x−1/4, z−1/4. |
(II) hexaaquacobalt(II)/nickel(II) (0.5/0.5) bis(hypophosphite)
top
Crystal data top
[Co0.5Ni0.5(H2O)6](H2PO2)2 | Dx = 1.823 Mg m−3 |
Mr = 296.89 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, I41/acd | Cell parameters from 24 reflections |
Hall symbol: -I 4bd 2c | θ = 9.7–12.1° |
a = 10.3111 (13) Å | µ = 2.01 mm−1 |
c = 20.346 (3) Å | T = 293 K |
V = 2163.2 (5) Å3 | Octahedron, light green |
Z = 8 | 0.65 × 0.63 × 0.57 mm |
F(000) = 1228 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 407 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.016 |
Graphite monochromator | θmax = 27.5°, θmin = 3.4° |
2θ/θ scans | h = 0→13 |
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) | k = 0→13 |
Tmin = 0.288, Tmax = 0.317 | l = 0→26 |
1187 measured reflections | 3 standard reflections every 60 min |
621 independent reflections | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.021 | All H-atom parameters refined |
wR(F2) = 0.073 | w = 1/[σ2(Fo2) + (0.0365P)2 + 0.3503P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
621 reflections | Δρmax = 0.23 e Å−3 |
49 parameters | Δρmin = −0.19 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0030 (3) |
Crystal data top
[Co0.5Ni0.5(H2O)6](H2PO2)2 | Z = 8 |
Mr = 296.89 | Mo Kα radiation |
Tetragonal, I41/acd | µ = 2.01 mm−1 |
a = 10.3111 (13) Å | T = 293 K |
c = 20.346 (3) Å | 0.65 × 0.63 × 0.57 mm |
V = 2163.2 (5) Å3 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | 407 reflections with I > 2σ(I) |
Absorption correction: empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) | Rint = 0.016 |
Tmin = 0.288, Tmax = 0.317 | 3 standard reflections every 60 min |
1187 measured reflections | intensity decay: none |
621 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.021 | 0 restraints |
wR(F2) = 0.073 | All H-atom parameters refined |
S = 1.06 | Δρmax = 0.23 e Å−3 |
621 reflections | Δρmin = −0.19 e Å−3 |
49 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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
Co1 | 0.0000 | 0.2500 | 0.1250 | 0.0293 (2) | 0.50 |
Ni1 | 0.0000 | 0.2500 | 0.1250 | 0.0293 (2) | 0.50 |
P1 | 0.24135 (6) | 0.0000 | 0.2500 | 0.0319 (2) | |
O1 | 0.16368 (12) | 0.08744 (12) | 0.29460 (5) | 0.0349 (4) | |
H1 | 0.3229 (16) | −0.0665 (17) | 0.2876 (7) | 0.023 (4)* | |
O1W | 0.0000 | 0.2500 | 0.22614 (10) | 0.0516 (6) | |
H1W | 0.049 (3) | 0.200 (2) | 0.2487 (15) | 0.071 (8)* | |
O2W | 0.00205 (18) | 0.05080 (15) | 0.12382 (10) | 0.0548 (5) | |
H2W | 0.048 (2) | 0.014 (2) | 0.1409 (8) | 0.033 (6)* | |
H3W | −0.052 (2) | 0.015 (2) | 0.1052 (9) | 0.048 (7)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Co1 | 0.0286 (2) | 0.0286 (2) | 0.0308 (3) | −0.00289 (14) | 0.000 | 0.000 |
Ni1 | 0.0286 (2) | 0.0286 (2) | 0.0308 (3) | −0.00289 (14) | 0.000 | 0.000 |
P1 | 0.0254 (5) | 0.0357 (6) | 0.0346 (4) | 0.000 | 0.000 | −0.0102 (2) |
O1 | 0.0337 (7) | 0.0355 (7) | 0.0355 (6) | 0.0003 (5) | 0.0017 (5) | −0.0104 (5) |
O1W | 0.054 (2) | 0.068 (2) | 0.0326 (10) | 0.0296 (11) | 0.000 | 0.000 |
O2W | 0.0648 (11) | 0.0279 (8) | 0.0718 (10) | −0.0053 (7) | −0.0441 (8) | 0.0039 (12) |
Geometric parameters (Å, º) top
Co1—O1W | 2.058 (2) | P1—H1 | 1.328 (15) |
Co1—O2W | 2.0542 (16) | O1W—H1W | 0.86 (3) |
Ni1—O1W | 2.058 (2) | O2W—H2W | 0.70 (2) |
Ni1—O2W | 2.0542 (16) | O2W—H3W | 0.77 (2) |
P1—O1 | 1.5092 (12) | | |
| | | |
O1W—Co1—O2W | 90.67 (5) | O2W—Ni1—O2Wi | 88.83 (10) |
O1W—Co1—O2Wi | 89.33 (5) | O2W—Ni1—O2Wii | 178.66 (11) |
O2W—Co1—O2Wi | 88.83 (10) | O2W—Ni1—O2Wiii | 91.19 (10) |
O2W—Co1—O2Wii | 178.66 (11) | O2Wi—Ni1—O2Wiii | 178.66 (11) |
O2W—Co1—O2Wiii | 91.19 (10) | O1iv—P1—O1 | 115.90 (11) |
O2Wi—Co1—O2Wiii | 178.66 (11) | H1iv—P1—H1 | 101.4 (15) |
O1W—Ni1—O2W | 90.67 (5) | H1Wii—O1W—H1W | 115 (4) |
O1W—Ni1—O2Wi | 89.33 (5) | H2W—O2W—H3W | 119 (3) |
Symmetry codes: (i) −y+1/4, −x+1/4, −z+1/4; (ii) −x, −y+1/2, z; (iii) y−1/4, x+1/4, −z+1/4; (iv) x, −y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1 | 0.86 (3) | 1.90 (3) | 2.7565 (16) | 177 (3) |
O2W—H2W···O1iv | 0.70 (2) | 2.06 (2) | 2.750 (2) | 170 (2) |
O2W—H3W···O1v | 0.77 (2) | 1.98 (2) | 2.735 (2) | 168 (2) |
Symmetry codes: (iv) x, −y, −z+1/2; (v) y−1/4, x−1/4, z−1/4. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | [Co(H2O)6](H2PO2)2 | [Co0.5Ni0.5(H2O)6](H2PO2)2 |
Mr | 297.00 | 296.89 |
Crystal system, space group | Tetragonal, I41/acd | Tetragonal, I41/acd |
Temperature (K) | 293 | 293 |
a, c (Å) | 10.3406 (15), 20.402 (3) | 10.3111 (13), 20.346 (3) |
V (Å3) | 2181.6 (6) | 2163.2 (5) |
Z | 8 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 1.89 | 2.01 |
Crystal size (mm) | 0.64 × 0.36 × 0.36 | 0.65 × 0.63 × 0.57 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | Empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) | Empirical (using intensity measurements) (CADDAT; Enraf-Nonius, 1989) |
Tmin, Tmax | 0.477, 0.506 | 0.288, 0.317 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1315, 686, 419 | 1187, 621, 407 |
Rint | 0.030 | 0.016 |
(sin θ/λ)max (Å−1) | 0.666 | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.093, 0.92 | 0.021, 0.073, 1.06 |
No. of reflections | 686 | 621 |
No. of parameters | 49 | 49 |
H-atom treatment | All H-atom parameters refined | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.51, −0.41 | 0.23, −0.19 |
Selected geometric parameters (Å, º) for (I) topCo1—O1W | 2.070 (3) | P1—O1 | 1.5076 (13) |
Co1—O2W | 2.0765 (18) | P1—H1 | 1.21 (2) |
| | | |
O1W—Co1—O2W | 90.68 (7) | O2W—Co1—O2Wi | 88.50 (14) |
O1W—Co1—O2Wi | 89.32 (7) | O1ii—P1—O1 | 115.74 (13) |
Symmetry codes: (i) −y+1/4, −x+1/4, −z+1/4; (ii) x, −y, −z+1/2. |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1 | 0.75 (2) | 2.01 (2) | 2.7524 (18) | 177 (3) |
O2W—H2W···O1ii | 0.64 (2) | 2.11 (3) | 2.752 (3) | 174 (3) |
O2W—H3W···O1iii | 0.74 (3) | 2.01 (3) | 2.744 (3) | 173 (3) |
Symmetry codes: (ii) x, −y, −z+1/2; (iii) y−1/4, x−1/4, z−1/4. |
Selected geometric parameters (Å, º) for (II) topCo1—O1W | 2.058 (2) | P1—O1 | 1.5092 (12) |
Co1—O2W | 2.0542 (16) | P1—H1 | 1.328 (15) |
| | | |
O1W—Co1—O2W | 90.67 (5) | O2W—Co1—O2Wi | 88.83 (10) |
O1W—Co1—O2Wi | 89.33 (5) | O1ii—P1—O1 | 115.90 (11) |
Symmetry codes: (i) −y+1/4, −x+1/4, −z+1/4; (ii) x, −y, −z+1/2. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1 | 0.86 (3) | 1.90 (3) | 2.7565 (16) | 177 (3) |
O2W—H2W···O1ii | 0.70 (2) | 2.06 (2) | 2.750 (2) | 170 (2) |
O2W—H3W···O1iii | 0.77 (2) | 1.98 (2) | 2.735 (2) | 168 (2) |
Symmetry codes: (ii) x, −y, −z+1/2; (iii) y−1/4, x−1/4, z−1/4. |
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Investigations of hexahydrate bivalent metal hypophosphites have been reported by Ferrari & Colla (1937), Pedrazuela et al. (1953) and Galigné & Dumas (1973). Here, we report the results of the single-crystal X-ray diffraction analysis of hexaaquacobalt(II) bis(hypophosphite), [Co(H2O)6](H2PO2)2, (I), and hexaaquacobalt(II)/nickel(II) (0.5/0.5) bis(hypophosphite), [Co0.5Ni0.5(H2O)6](H2PO2)2, (II), which are very similar to the structure of hexaaquamagnesium(II) bis(hypophosphite) (Galigné & Dumas, 1973). The crystals of (II) are a solid solution of the CoII and NiII hypophosphites. The calculated powder pattern of (II) is in good agreement with the experimental one. \sch
The packing of the CoII(NiII) and P atoms (not the hypophosphite anion) is the same as the structure of CaF2. The CoII(NiII) atoms have a pseudo-face-centred cubic cell with a = b ~10.3 Å, and the P atoms occupy the tetrahedral cavities. The powder pattern for (I) was reported earlier by Ferrari & Colla (1937), and it was indexed as a cubic system with a cell parameter of 10.22 Å. Some differences between the work of Ferrari & Colla and our studies are in evidence, in that reflections at high angles could be indexed as a Cu Kα1 - Cu Kα2 relation; indeed, this is the complex result of an unclear ratio for c = 2a, because of an incomplete range for the powder data (only from d = 3.090 Å) and a real Cu Kα1 - Cu Kα2 relation. The experimental powder patterns are in good agreement with the known powder pattern at high angles, but the reflections responsible for the c parameter at small angles were missed in the conditions used by Ferrari & Colla (1937).
The coordination number of six for bivalent metals (Mg, Co, Ni) is achieved by water molecules; the hypophosphite anion does not coordinate to the metal cation. The metal cation has a slightly distorted octahedral coordination sphere. The average M—O distances are 2.05 (1) Å in magnesium(II) bis(hypophosphite) (Galigné & Dumas, 1973), 2.074 (3) Å in (I) and 2.055 (2) Å in (II). There are two types of orientation for the water molecules relative to the oppositely coordinated water molecule. The torsion angles between the two planes, consisting of one O atom and two H atoms of oppositely coordinated water molecules, are: type 1 [two pairs, O2W and O2Wi with their opposite symmetry equivalents; symmetry code: (i) ?] 65.1 (1)° in magnesium(II) bis(hypophosphite) (Galigné & Dumas, 1973), 78.0 (1)° in (I) and 69.8 (1)° in (II); type 2 (one pair, O1W with its opposite symmetry equivalent) 3.0 (1)° in magnesium(II) bis(hypophosphite) (Galigné & Dumas, 1973), 2.8 (1)° in (I) and 1.6 (1)° in (II) (Fig. 1).
The second coordination sphere of the metal atom consists of eight hypophosphite anions, which are hydrogen bonded to the water molecules coordinated to the [Co(H2O)6]2+ ([Ni(H2O)6]2+) cation (Fig. 1). This rigid construction is three-dimensional, like the structure of CaF2.
The geometry of the hypophosphite anion in the structures of (I) and (II) is very close to the ideal, with point symmetry mm2 (Naumov et al., 2001, 2002). The geometric parameters for the anion (Tables 1 and 2) are comparable with earlier reported data, with P—O distances and O—P—O angles, respectively, of 1.507 (3) Å and 116.2 (3)° in [Mg(H2O)6](H2PO2)2 (Galigné & Dumas, 1973), 1.527 (1) and 1.516 (1) Å, and 115.3 (3)° in Co(H2PO2)Cl(H2O) (Marcos et al., 1991), and 1.541 (2) and 1.480 (2) Å, and 118.7 (3)° in Ni(H2PO2)Cl(H2O) (Marcos et al., 1993).
Each O atom of the hypophosphite anion is hydrogen bonded to three water molecules from different cation complexes (Tables 1 and 2; thick dotted lines in Fig. 2). Each H atom of the hypophosphite anion is surrounded by three water molecules from further different cation complexes, and these H atoms are situated directly above the centres of the triangles formed by the O atom and two H atoms of the water molecules (thin dotted lines in Fig. 2). The distances between atom H1 of the hypophosphite and the O atoms [O2Wi, O1Wii and O2Wiii; symmetry codes: (i) 1/4 - y, x - 1/4, 1/4 + z; (ii) 1/2 + x, -y, z; (iii) 1/2 + x, y, 1/2 - z] of the water molecules are 2.93 (2), 2.94 (2) and 2.95 (2) Å (average 2.94 Å) for (I), and 2.865 (16), 2.912 (17) and 2.850 (16) Å (average 2.88 Å) for (II). This environment can be found in all three structures of hexaaquamagnesium(II), -cobalt(II) and -cobalt(II)/nickel(II) bis(hypophosphite)s.
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