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In a new polymorph of hexaaquamagnesium(II) bis(hypophosphite), [Mg(H
2O)
6](H
2PO
2)
2, the planes of
trans water molecules forming the octahedral coordination sphere of the Mg atoms are in a staggered conformation. The magnesium(II) cations are in a pseudo-face-centered cubic arrangement, with
a 10.294 Å and tetrahedral cavities are occupied by P atoms. Hypophosphite anions are hydrogen bonded to the coordinated water molecules.
Supporting information
Key indicators
- Single-crystal X-ray study
- T = 295 K
- Mean (P-O) = 0.002 Å
- R factor = 0.021
- wR factor = 0.048
- Data-to-parameter ratio = 12.9
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
Alert Level C:
GOODF_01 Alert C The least squares goodness of fit parameter lies
outside the range 0.80 <> 2.00
Goodness of fit given = 0.739
PLAT_420 Alert C D-H Without Acceptor P(1) - H(1) ?
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
2 Alert Level C = Please check
[Mg(H2O)6](H2PO2)2 was synthesized by slow evaporation of an aqueous solution of magnesium(II) hypophosphite, prepared by adding a solution of calcium(II) hypophosphite, Ca(H2PO2)2, to a solution of magnesium(II) sulfate heptahydrate, MgSO4·7H2O. The reaction mixture was stored at room temperature for one week in air.
The H atoms were located from a difference electron-density map and refined without constraints.
Data collection: CD4CA0 (Enraf-Nonius, 1989); cell refinement: CD4CA0 (Enraf-Nonius, 1989); data reduction: CD4CA0 (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 (Sheldrick, 1997).
hexaaquamagnesium(II) bis(hypophosphite)
top
Crystal data top
H12MgO6·2(H2O2P) | Dx = 1.598 Mg m−3 |
Mr = 262.38 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, P42/nmc | Cell parameters from 22 reflections |
Hall symbol: -P 4ac 2a | θ = 11.7–14.9° |
a = 7.2187 (9) Å | µ = 0.48 mm−1 |
c = 10.4639 (13) Å | T = 295 K |
V = 545.27 (12) Å3 | Prism, colorless |
Z = 2 | 0.24 × 0.20 × 0.16 mm |
F(000) = 276 | |
Data collection top
Enraf-Nonius CAD4 diffractometer | 238 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.038 |
Graphite monochromator | θmax = 29.1°, θmin = 3.4° |
2θ/θ scans | h = 0→9 |
Absorption correction: empirical (using intensity measurements) CADDAT (Enraf-Nonius, 1989) | k = 0→9 |
Tmin = 0.904, Tmax = 0.925 | l = 0→14 |
809 measured reflections | 3 standard reflections every 60 min |
427 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) = 0.048 | w = 1/[σ2(Fo2) + (0.0118P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.74 | (Δ/σ)max < 0.001 |
427 reflections | Δρmax = 0.18 e Å−3 |
33 parameters | Δρmin = −0.20 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.016 (2) |
Crystal data top
H12MgO6·2(H2O2P) | Z = 2 |
Mr = 262.38 | Mo Kα radiation |
Tetragonal, P42/nmc | µ = 0.48 mm−1 |
a = 7.2187 (9) Å | T = 295 K |
c = 10.4639 (13) Å | 0.24 × 0.20 × 0.16 mm |
V = 545.27 (12) Å3 | |
Data collection top
Enraf-Nonius CAD4 diffractometer | 238 reflections with I > 2σ(I) |
Absorption correction: empirical (using intensity measurements) CADDAT (Enraf-Nonius, 1989) | Rint = 0.038 |
Tmin = 0.904, Tmax = 0.925 | 3 standard reflections every 60 min |
809 measured reflections | intensity decay: none |
427 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.021 | 0 restraints |
wR(F2) = 0.048 | All H-atom parameters refined |
S = 0.74 | Δρmax = 0.18 e Å−3 |
427 reflections | Δρmin = −0.20 e Å−3 |
33 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 | |
Mg1 | 0.2500 | 0.7500 | 0.2500 | 0.0319 (4) | |
P1 | 0.2500 | 0.2500 | 0.50851 (9) | 0.0335 (3) | |
H1 | 0.101 (3) | 0.2500 | 0.4297 (17) | 0.012 (5)* | |
O1 | 0.2500 | 0.4273 (2) | 0.58483 (15) | 0.0368 (5) | |
O1W | 0.2500 | 0.7500 | 0.0549 (3) | 0.0496 (8) | |
H1W | 0.342 (4) | 0.7500 | 0.011 (2) | 0.076 (13)* | |
O2W | 0.04819 (19) | 0.54819 (19) | 0.2500 | 0.0474 (5) | |
H2W | 0.048 (3) | 0.465 (2) | 0.2047 (14) | 0.045 (6)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Mg1 | 0.0335 (6) | 0.0335 (6) | 0.0285 (8) | 0.000 | 0.000 | 0.000 |
P1 | 0.0428 (8) | 0.0298 (7) | 0.0280 (5) | 0.000 | 0.000 | 0.000 |
O1 | 0.0442 (11) | 0.0312 (11) | 0.0351 (9) | 0.000 | 0.000 | −0.0021 (9) |
O1W | 0.0288 (18) | 0.090 (3) | 0.0302 (14) | 0.000 | 0.000 | 0.000 |
O2W | 0.0464 (8) | 0.0464 (8) | 0.0496 (12) | −0.0126 (10) | 0.0179 (9) | −0.0179 (9) |
Geometric parameters (Å, º) top
Mg1—O1Wi | 2.042 (3) | P1—H1iv | 1.36 (2) |
Mg1—O1W | 2.042 (3) | P1—O1 | 1.5088 (18) |
Mg1—O2W | 2.060 (2) | P1—O1iv | 1.5088 (18) |
Mg1—O2Wii | 2.060 (2) | P1—H1 | 1.356 (19) |
Mg1—O2Wiii | 2.060 (2) | O1W—H1W | 0.81 (2) |
Mg1—O2Wi | 2.060 (2) | O2W—H2W | 0.762 (14) |
| | | |
O1Wi—Mg1—O1W | 180.0 | O2W—Mg1—O2Wi | 90.0 |
O1Wi—Mg1—O2W | 90.0 | O2Wii—Mg1—O2Wi | 90.0 |
O1W—Mg1—O2W | 90.0 | O2Wiii—Mg1—O2Wi | 180.0 |
O1Wi—Mg1—O2Wii | 90.0 | H1iv—P1—O1 | 108.8 (3) |
O1W—Mg1—O2Wii | 90.0 | H1iv—P1—O1iv | 108.8 (3) |
O2W—Mg1—O2Wii | 180.0 | O1—P1—O1iv | 116.08 (14) |
O1Wi—Mg1—O2Wiii | 90.0 | H1iv—P1—H1 | 105.2 (15) |
O1W—Mg1—O2Wiii | 90.0 | O1—P1—H1 | 108.8 (3) |
O2W—Mg1—O2Wiii | 90.0 | O1iv—P1—H1 | 108.8 (3) |
O2Wii—Mg1—O2Wiii | 90.0 | Mg1—O1W—H1W | 124 (2) |
O1Wi—Mg1—O2Wi | 90.0 | Mg1—O2W—H2W | 123.7 (15) |
O1W—Mg1—O2Wi | 90.0 | | |
Symmetry codes: (i) y−1/2, −x+1, −z+1/2; (ii) −x+1/2, −y+3/2, z; (iii) −y+1, x+1/2, −z+1/2; (iv) −x+1/2, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1iii | 0.81 (2) | 1.94 (2) | 2.750 (2) | 177 (3) |
O2W—H2W···O1v | 0.762 (14) | 2.006 (14) | 2.7662 (14) | 175 (2) |
Symmetry codes: (iii) −y+1, x+1/2, −z+1/2; (v) −y+1/2, x, z−1/2. |
Experimental details
Crystal data |
Chemical formula | H12MgO6·2(H2O2P) |
Mr | 262.38 |
Crystal system, space group | Tetragonal, P42/nmc |
Temperature (K) | 295 |
a, c (Å) | 7.2187 (9), 10.4639 (13) |
V (Å3) | 545.27 (12) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.48 |
Crystal size (mm) | 0.24 × 0.20 × 0.16 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD4 diffractometer |
Absorption correction | Empirical (using intensity measurements) CADDAT (Enraf-Nonius, 1989) |
Tmin, Tmax | 0.904, 0.925 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 809, 427, 238 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.684 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.021, 0.048, 0.74 |
No. of reflections | 427 |
No. of parameters | 33 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.18, −0.20 |
Selected geometric parameters (Å, º) topMg1—O1W | 2.042 (3) | P1—O1 | 1.5088 (18) |
Mg1—O2W | 2.060 (2) | P1—H1 | 1.356 (19) |
| | | |
O1Wi—Mg1—O1W | 180.0 | O2W—Mg1—O2Wi | 90.0 |
O1W—Mg1—O2W | 90.0 | O1—P1—O1iii | 116.08 (14) |
O2W—Mg1—O2Wii | 180.0 | H1iii—P1—H1 | 105.2 (15) |
Symmetry codes: (i) y−1/2, −x+1, −z+1/2; (ii) −x+1/2, −y+3/2, z; (iii) −x+1/2, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O1iv | 0.81 (2) | 1.94 (2) | 2.750 (2) | 177 (3) |
O2W—H2W···O1v | 0.762 (14) | 2.006 (14) | 2.7662 (14) | 175 (2) |
Symmetry codes: (iv) −y+1, x+1/2, −z+1/2; (v) −y+1/2, x, z−1/2. |
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Studies of hexaaquametal(II) bis(hypophosphites) have been reported earlier (Ferrari & Colla, 1937; Pédrazuela et al., 1953; Galigné & Dumas, 1973; Kuratieva et al., 2002, 2003). The structure of a new polymorph, (I), of [Mg(H2O)6](H2PO2)2 is described here; this is different from that previously reported (Galigné & Dumas, 1973) but similar to that of [Mg(H2O)6](ClO2)2 (Marsh, 1991), excluding the H atoms present in the hypophosphite anion. The packing of the MgII cations, P and O atoms of hypophosphite anions is the same as in the structure of [Ni(H2O)6](H2PO2)2 and Cl and O atoms in [Mg(H2O)6](ClO2)2. The magnesium cations are in a pseudo-face-centered cubic arrangement, with a ≈ 10.294 Å (10.371 Å in [Mg(H2O)6](ClO2)2) and tetrahedral cavities occupied by P atoms.
The first coordination sphere of the MgII cation consists of six water molecules forming a slightly distorted octahedron and appearing in only one type of orientation. Planes of trans-coordinated water molecules are in a staggered conformation, as in [Ni(H2O)6](H2PO2)2 (Kuratieva et al., 2003) and [Mg(H2O)6](ClO2)2 (Marsh, 1991), but different from [Mg(H2O)6](H2PO2)2 (Galigné & Dumas, 1973), [Co(H2O)6](H2PO2)2, and [Co0.5Ni0.5(H2O)6](H2PO2)2 (Kuratieva et al., 2002), in which a pair of trans water molecules is in eclipsed conformation. The six coordinated water molecules occur in two groups. The two molecules corresponding to the O1w atoms [Mg—O 2.042 (3) Å] have their planes perpendicular to the basal plane formed by the four other molecules and the MgII cation. The angle between the normal to the planes of these water molecules is 90.0° {as in [Mg(H2O)6](ClO2)2}. The four molecules corresponding to the O2w atoms (Mg—O 2.060 (2) Å) have their planes perpendicular to the basal plane; the angle between the normal to the planes of trans coordinated molecules of this type is 83.3 (2)° {88.3 (3)° in [Mg(H2O)6](ClO2)2)}.
The second coordination sphere of the MgII cation consists of eight hypophosphite anions, which are hydrogen bonded to water molecules. Although the packing of MgII cations and P atoms is similar, the orientation of hypophosphite anions differs from that in [Mg(H2O)6](H2PO2)2 (Galigné & Dumas, 1973), [Co(H2O)6](H2PO2)2, and [Co0.5Ni0.5(H2O)6](H2PO2)2 (Kuratieva et al., 2002), and resembles that in [Ni(H2O)6](H2PO2)2 (Kuratieva et al., 2003) and [Mg(H2O)6](ClO2)2 (Marsh, 1991). The geometry of the hypophosphite anion remains practically the same as in previous structures (Naumov et al., 2001, 2002; Kuratieva et al., 2002, 2003) (Table 1). Each O atom of the hypophosphite anion is hydrogen bonded to three water molecules from different complex cations (Table 2; thick dashed lines in Fig. 2). Each H atom is surrounded by three water molecules from other complex cations; 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 average P—H···O contact is 2.87 (2) Å. The environment of the hypophosphite anion is similar to that found in the other hexaaquametal(II) bis(hypophosphites) listed above.