Copper(II) hypophosphite: the α- and β-forms at 270 and 100 K, and the γ-form at 270 K

Copper(II) hypophosphite has been shown to exist as several polymorphs. The crystal structures of monoclinic α-, ortho­rhombic β- and ortho­rhombic γ-Cu(H₂PO₂)₂ have been determined at different temperatures. The geometry of the hypophosphite anion in all three polymorphs is very close to the idealized one, with point symmetry mm2. Despite having different space groups, the structures of the α- and β-polymorphs are very similar. The polymeric layers formed by the Cu atoms and the hypophosphite ions, which are identical in the α- and β-polymorphs, stack in the third dimension in different ways. Each hypophosphite anion is coordinated to three Cu atoms. On cooling, a minimum amount of contraction was observed in the direction normal to the layers. The structure of the polymeric layers in the γ-­polymorph is quite different. There are two symmetry-independent hypophosphite anions; the first is coordinated to two Cu atoms, while the second is coordinated to four Cu atoms. In all three polymorphs, the Cu atoms are coordinated by six O atoms of six hypophosphite anions, forming tetragonal bipyramids; in the α- and β-polymorphs, there are four short and two long Cu—O distances, while in the γ-polymorph, there are four long and two short Cu—O distances.

S1. Comment

The first structural studies of ammonium hypophosphite and hexahydrates of cobalt, nickel and magnesium hypophosphites were reported 65 years ago (Zachariasen & Mooney, 1934; Ferrari & Colla, 1937). The crystal structures of hypophosphites of anhydrous calcium (Wyckoff, 1964), zinc (Tanner et al., 1997), germanium (Weakley, 1983), erbium (Aslanov et al., 1975), uranium (Tanner et al., 1992), and a urea complex of copper (Naumov et al., 2001) are known. No structural data for pure copper(II) hypophosphite have yet been reported. Since precise data on the structure of copper(II) hypophosphite are very important for understanding the mechanism of the decomposition of this salt, which finds numerous practical applications (Lomovsky & Boldyrev, 1994), we have undertaken its single-crystal X-ray structure determination.

Copper(II) hypophosphite is very unstable, therefore low temperatures were required both for crystal growth and data collection. A special device for crystal growth, based on the Oxford Cryosystems Cryostream cooler (Naumov, 2001), allowed us to obtain crystals of quality and dimensions acceptable for single-crystal diffraction analysis. Using a SMART CCD diffractometer has allowed us to decrease the time of data collection to 6 h without loss of crystal quality and to collect data at several different temperatures for the same crystal.

Our studies have shown copper(II) hypophosphite to exist as three polymorphs, which we have called the α-, β- and γ-polymorphs. Crystals of all three polymorphs grew from the same solution simultaneously. The α- and β-polymorphs have the same rhombic plate habit and can be distinguished only by structural analysis. The γ-polymorph grew as needles and could be recognized visually. Several powder patterns of copper hypophosphite have been reported (Balema et al., 1988; Brun & Dumail, 1971; Michailow et al., 1980), which are different and unindexed. The calculated powder pattern of the needle crystal of the γ-polymorph is in good agreement with the powder pattern published by Brun & Dumail (1971). The calculated powder pattern of the rhombic plate crystal of the first discovered α-polymorph does not completely describe the known powder pattern (Balema et al., 1988). The method of preparation used in the present study excludes the formation of different substances. We successfully undertook a search for additional phases and found two polymorphs of the rhombic plate crystal. The calculated powder patterns of the rhombic plate crystal of the α- and β-polymorphs are in good agreement with the powder patterns published by Balema et al. (1988) and Michailow et al. (1980). The crystal structures of the α- and β-polymorphs differ from those previously reported for other anhydrous hypophosphites, such as Zn(H₂PO₂)₂ (Tanner et al., 1997) and Ca(H₂PO₂)₂ (Wyckoff, 1964). It is worth mentioning, that the γ-polymorph is isostructural with zinc hypophosphite.

The geometry of the hypophosphite anion in all three polymorphs is very close to the idealized one, with point symmetry mm2. The average geometric parameters of the hypophosphite anion in anhydrous Cu(H₂PO₂)₂ [P—O 1.51 (2) Å and O—P—O 118.3 (17)°] are in good agreement with those of the urea complex of copper hypophosphite [P—O 1.515 (5) Å and O—P—O 117.84 (8)°; Naumov et al., 2001]. Despite having different space groups, the structures of the α- and β-polymorphs are very similar. The coordination of the Cu atoms and of the hypophospite anions in the structures are also identical. Each Cu atom is coordinated by six O atoms of six hypophosphite anions, forming a tetragonal bipyramid [α-polymorph (270 K): four short, 1.9454 (19) (× 2) and 1.987 (2) Å (× 2), and two long, 2.653 (2) Å (× 2); β-polymorph (270 K): four short, 1.9483 (16) (× 2) and 1.9829 (16) Å (× 2), and two long, 2.6496 (17) Å (× 2)]. The short Cu—O bonds do not alter during cooling (see Tables 1 and 3). Each hypophosphite anion is coordinated to three Cu atoms. The geometry of the hypophosphite anions (P—O distances and O—P—O angles) does not change during cooling (see Tables 1 and 3). The hypophosphite anions and Cu cations form polymeric layers in the (100) (Fig. 1) and the (001) planes (Fig. 2) for the α- and β-polymorphs, respectively. The copper cations form a distorted square pattern, with equal Cu···Cu distances [4.1131 (1) Å at 270 K and 4.0899 (1) Å at 100 K in the α-polymorph; 4.1141 (1) Å at 270 K and 4.0909 (1) Å at 100 K in the β-polymorph]. The layers, which are identical in the α- and β-polymorphs, are stacked in the third dimension in different ways. In the α-polymorph, they align identically above each other [AAAA] (Fig. 3) and in the β-polymorph they align as [ABAB] (Fig. 4), i.e. not vertically stacked, and it is this alternate stacking pattern which generates the cell edge doubling in the direction perpendicular to the layers [2a (I) ≈ c (II)].

The coordination of the Cu atoms and hypophospite anions in the γ-polymorph is quite different to that in the α- and β-polymorphs. Each Cu atom is coordinated by six O atoms of six hypophosphite anions, forming a tetragonal bipyramid [two short, 1.949 (2) Å (× 2), and four long, 2.2046 (14) Å (× 4) at 270 K]. There are two symmetry-independent hypophosphite anions in the structure of the γ-polymorph. The first is coordinated to two Cu atoms, while the second is coordinated to four Cu atoms. The hypophosphite anions and Cu cations form polymeric layers in the (001) planes (Fig. 5). The copper cations form a rectangle pattern with different Cu···Cu distances [3.3369 (3) Å and 5.4133 (5) Å]. The layers are aligned above each other (Fig. 6).

The P and O atoms of the γ-polymorph are rather anisotropic compared with the 270 K data for the α- and β-polymorphs. This can be explained by the existence of vibration freedom along the [100] and [010] directions of the coordinated hypophosphite anion and less closed packing. The calculated densities are 2.696, 2.699 and 2.472 Mg m^-3 at 270 K for the α-, β- and γ-polymorphs, respectively.

In all three polymorphs, separate layers are linked by van der Waals interactions. The shortest H···H distances between layers are 2.86 (5), 2.55 (4) and 2.67 (3) Å at 270 K for the α-, β- and γ-polymorphs, respectively.

On cooling to 100 K, the structure of the α-polymorph contracted anisotropically. The direction of minimum contraction [0.105 (2)%; axis 1 of the strain tensor in Fig. 1] is close to the normal to the planes of the polymeric layers. The direction of medium contraction [0.460 (4)%; axis 2 of the strain tensor in Fig. 1] coincided with the crystallographic b axis. The direction of maximum contraction [0.649 (4)%; axis 3 of the strain tensor in Fig. 1] is close to the crystallographic c axis.

On cooling to 100 K, the structure of the β-polymorph contracted anisotropically. The direction of minimum contraction [0.114 (4)%; axis 1 of the strain tensor in Fig. 2] coincided with the crystallographic c axis and was normal to the planes of the polymeric layers. The direction of medium contraction [0.460 (4)%; axis 2 of the strain tensor in Fig. 2] coincided with the crystallographic a axis. The direction of maximum contraction [0.639 (2)%; axis 3 of the strain tensor in Fig. 2] coincided with the crystallographic b axis.

The contractions on cooling in the α- and β-polymorphs are very similar. The direction of minimum contraction can be correlated with the repulsive H···H interactions between different layers. The directions of medium and maximum contraction in the layer can be correlated with the contraction of the long Cu1—O2ⁱⁱ distances on cooling [symmetry codes: (ii) x, y - 1, z, for (I); x - 1, y, z, for (II)].

On cooling to 100 K, the crystal of the γ-polymorph cracked at about 120 K.

S2. Experimental

Copper(II) hypophosphite was synthesized by adding hypophosphorous acid, H₃PO₂ (2.3771 g of 50% solution in 35 ml of water), to basic copper carbonate, CuCO₃·Cu(OH)₂ (1 g). The reaction mixture was evacuated until carbon dioxide evolution had stopped (about 10 min). Crystals were grown at 278 K from a solution in water under a nitrogen atmosphere. During crystal growth, initial formation of crystals with a rhombic plate habit was observed. The quantity of needle crystals can be increased by adding glycerinum and increasing the temperature of the solution to 288 K.

S3. Refinement

In all three structures, the H atoms were located from a difference electron-density map. The positions of the H atoms in the α- and β-polymorphs were refined without constraints. The positions of H atoms in γ-polymorph were refined as CH₂ groups with fixed O—P—H angles and free P—H bond lengths.

Computing details

Data collection: SMART (Siemens, 1994) for alpha270, alpha100, beta270, beta100; CAD-4 Software (Enraf-Nonius, 1989) for gamma270. Cell refinement: SAINT (Siemens, 1994) for alpha270, alpha100, beta270, beta100; CAD-4 Software for gamma270. Data reduction: SAINT for alpha270, alpha100, beta270, beta100; CAD-4 Software for gamma270. For all compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Siemens, 1994); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The layer formed by the Cu^II cations and hypophosphite anions of the α-polymorph at 270 K, projected on to the (100) plane. Displacement ellipsoids are plotted at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The crystallographic axes and the axes of the strain tensor on cooling (1 = minimum, 2 = medium and 3 = maximum contraction) are shown.
	Fig. 2. The layer formed by the Cu^II cations and hypophosphite anions of the β-polymorph at 270 K, projected on to the (001) plane. Displacement ellipsoids are plotted at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The crystallographic axes and the axes of the strain tensor on cooling (1 = minimum, 2 = medium and 3 = maximum contraction) are shown. Axis 1 is normal to the projection plane.
	Fig. 3. Packing diagram of the α-polymorph viewed along [010].
	Fig. 4. Packing diagram of the β-polymorph viewed along [100].
	Fig. 5. The layer formed by the Cu^II cations and hypophosphite anions of the γ-polymorph at 270 K viewed along [001]. Displacement ellipsoids are plotted at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 6. Packing diagram of the α-polymorph viewed along [010].

(alpha270)

Crystal data

Cu(H2PO2)2	F(000) = 190
Mr = 193.51	Dx = 2.696 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.2186 (1) Å	Cell parameters from 993 reflections
b = 5.3462 (2) Å	θ = 2.9–29.1°
c = 6.2521 (3) Å	µ = 5.14 mm^−1
β = 98.8352 (11)°	T = 270 K
V = 238.42 (2) Å^3	Prism, blue
Z = 2	0.19 × 0.11 × 0.03 mm

Data collection

Siemens SMART CCD diffractometer	620 independent reflections
Radiation source: fine-focus sealed tube	578 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
Detector resolution: 8.192 pixels mm^-1	θmax = 29.1°, θmin = 2.9°
ω scans	h = −7→9
Absorption correction: analytical (XPREP; Siemens, 1995)	k = −7→7
Tmin = 0.521, Tmax = 0.859	l = −8→8
1697 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	All H-atom parameters refined
wR(F^2) = 0.068	w = 1/[σ^2(Fo^2) + (0.0273P)^2 + 0.2371P] where P = (Fo^2 + 2Fc^2)/3
S = 1.18	(Δ/σ)max < 0.001
620 reflections	Δρmax = 0.47 e Å^−3
43 parameters	Δρmin = −0.36 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.033 (5)

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
Cu1	0.0000	0.0000	0.0000	0.01620 (19)
P1	0.26355 (10)	0.45280 (13)	0.15910 (12)	0.0166 (2)
H1	0.404 (6)	0.483 (6)	0.272 (7)	0.031 (11)*
H2	0.308 (5)	0.566 (6)	−0.001 (5)	0.015 (8)*
O1	0.2302 (3)	0.1773 (4)	0.1104 (3)	0.0188 (4)
O2	0.1080 (3)	0.6010 (4)	0.2392 (3)	0.0190 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0181 (3)	0.0163 (3)	0.0151 (3)	−0.00162 (18)	0.00534 (18)	−0.00335 (18)
P1	0.0177 (4)	0.0166 (4)	0.0164 (4)	−0.0015 (2)	0.0053 (3)	−0.0005 (2)
O1	0.0191 (10)	0.0174 (9)	0.0203 (10)	−0.0001 (8)	0.0042 (8)	−0.0034 (8)
O2	0.0259 (11)	0.0163 (9)	0.0161 (10)	0.0021 (8)	0.0074 (8)	0.0014 (8)

Geometric parameters (Å, º)

Cu1—O1	1.9454 (19)	P1—O2	1.521 (2)
Cu1—O2^i	1.987 (2)	P1—H1	1.16 (4)
Cu1—O2^ii	2.653 (2)	P1—H2	1.25 (3)
P1—O1	1.516 (2)
O1^iii—Cu1—O1	180.00 (17)	O1—P1—H2	111.1 (15)
O1—Cu1—O2^i	89.88 (8)	O2—P1—H2	107.7 (16)
O2^iv—Cu1—O2^i	180.00 (10)	H1—P1—H2	96 (3)
O1—Cu1—O2^ii	91.76 (7)	P1—O1—Cu1	130.18 (12)
O2^i—Cu1—O2^ii	82.78 (5)	P1—O2—Cu1^v	122.09 (12)
O1—P1—O2	118.04 (12)	P1—O2—Cu1^vi	113.66 (10)
O1—P1—H1	110.8 (17)	Cu1^v—O2—Cu1^vi	124.25 (9)
O2—P1—H1	111 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
P1—H1···O1^vii	1.16 (4)	2.76 (4)	2.952 (2)	88 (2)
P1—H2···O1^iv	1.25 (3)	2.74 (3)	3.472 (2)	116.0 (19)
P1—H2···O2^viii	1.25 (3)	2.68 (3)	3.597 (2)	129 (2)
P1—H1···O1^ix	1.16 (4)	2.82 (4)	3.905 (2)	155 (3)

Symmetry codes: (iv) x, −y+1/2, z−1/2; (vii) x, −y+1/2, z+1/2; (viii) x, −y+3/2, z−1/2; (ix) −x+1, y+1/2, −z+1/2.

(alpha100)

Crystal data

Cu(H2PO2)2	F(000) = 190
Mr = 193.51	Dx = 2.729 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.2079 (3) Å	Cell parameters from 1117 reflections
b = 5.3216 (1) Å	θ = 2.9–29.1°
c = 6.2121 (2) Å	µ = 5.21 mm^−1
β = 98.709 (2)°	T = 100 K
V = 235.53 (1) Å^3	Prism, blue
Z = 2	0.19 × 0.11 × 0.03 mm

Data collection

Siemens SMART CCD diffractometer	612 independent reflections
Radiation source: fine-focus sealed tube	575 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.033
Detector resolution: 8.192 pixels mm^-1	θmax = 29.1°, θmin = 2.9°
ω scans	h = −7→9
Absorption correction: analytical (XPREP; Siemens, 1995)	k = −7→7
Tmin = 0.518, Tmax = 0.857	l = −8→8
1689 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	All H-atom parameters refined
wR(F^2) = 0.062	w = 1/[σ^2(Fo^2) + (0.0249P)^2 + 0.3031P] where P = (Fo^2 + 2Fc^2)/3
S = 1.18	(Δ/σ)max < 0.001
612 reflections	Δρmax = 0.47 e Å^−3
43 parameters	Δρmin = −0.42 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.022 (4)

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
Cu1	0.0000	0.0000	0.0000	0.00775 (17)
P1	0.26394 (9)	0.45455 (12)	0.15685 (11)	0.00832 (18)
H1	0.412 (5)	0.477 (6)	0.271 (6)	0.014 (9)*
H2	0.311 (5)	0.571 (6)	−0.009 (5)	0.005 (7)*
O1	0.2317 (3)	0.1764 (3)	0.1092 (3)	0.0094 (4)
O2	0.1069 (3)	0.6034 (3)	0.2369 (3)	0.0097 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0086 (3)	0.0078 (2)	0.0072 (2)	−0.00083 (15)	0.00234 (16)	−0.00176 (15)
P1	0.0093 (3)	0.0080 (3)	0.0080 (3)	−0.0002 (2)	0.0026 (2)	−0.0002 (2)
O1	0.0088 (9)	0.0096 (8)	0.0098 (9)	0.0004 (7)	0.0012 (7)	−0.0024 (7)
O2	0.0134 (9)	0.0074 (8)	0.0089 (9)	0.0008 (7)	0.0040 (7)	−0.0002 (7)

Geometric parameters (Å, º)

Cu1—O1	1.9461 (18)	P1—O2	1.5252 (19)
Cu1—O2^i	1.9872 (18)	P1—H1	1.20 (4)
Cu1—O2^ii	2.6213 (18)	P1—H2	1.29 (3)
P1—O1	1.5203 (18)
O1^iii—Cu1—O1	180.00 (16)	O1—P1—H2	111.3 (14)
O1—Cu1—O2^i	89.94 (7)	O2—P1—H2	108.0 (14)
O2^iv—Cu1—O2^i	180.00 (9)	H1—P1—H2	96 (2)
O1—Cu1—O2^ii	91.66 (7)	P1—O1—Cu1	129.45 (11)
O2^i—Cu1—O2^ii	83.05 (5)	P1—O2—Cu1^v	121.58 (11)
O1—P1—O2	118.03 (11)	P1—O2—Cu1^vi	113.87 (9)
O1—P1—H1	108.0 (15)	Cu1^v—O2—Cu1^vi	124.54 (8)
O2—P1—H1	113.4 (17)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
P1—H1···O1^vii	1.20 (4)	2.76 (4)	2.9384 (19)	86.4 (19)
P1—H2···O1^iv	1.29 (3)	2.70 (3)	3.4460 (19)	114.9 (18)
P1—H2···O2^viii	1.29 (3)	2.64 (3)	3.5671 (19)	127.0 (19)
P1—H1···O1^ix	1.20 (4)	2.77 (4)	3.8890 (19)	155 (2)

Symmetry codes: (iv) x, −y+1/2, z−1/2; (vii) x, −y+1/2, z+1/2; (viii) x, −y+3/2, z−1/2; (ix) −x+1, y+1/2, −z+1/2.

(beta270)

Crystal data

Cu(H2PO2)2	Dx = 2.699 Mg m^−3
Mr = 193.51	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 1781 reflections
a = 5.3259 (2) Å	θ = 2.9–29.1°
b = 6.2720 (2) Å	µ = 5.15 mm^−1
c = 14.2590 (6) Å	T = 270 K
V = 476.31 (3) Å^3	Prism, blue
Z = 4	0.23 × 0.13 × 0.05 mm
F(000) = 380

Data collection

Siemens SMART CCD diffractometer	631 independent reflections
Radiation source: fine-focus sealed tube	567 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 8.192 pixels mm^-1	θmax = 29.1°, θmin = 2.9°
ω scans	h = −7→7
Absorption correction: analytical (XPREP; Siemens, 1995)	k = −7→8
Tmin = 0.420, Tmax = 0.811	l = −17→19
3218 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.024	All H-atom parameters refined
wR(F^2) = 0.059	w = 1/[σ^2(Fo^2) + (0.0226P)^2 + 0.5274P] where P = (Fo^2 + 2Fc^2)/3
S = 1.27	(Δ/σ)max < 0.001
631 reflections	Δρmax = 0.62 e Å^−3
43 parameters	Δρmin = −0.30 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0090 (16)

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
Cu1	0.0000	0.0000	0.0000	0.01518 (16)
P1	0.45389 (11)	0.11030 (10)	0.13084 (4)	0.01553 (17)
H1	0.471 (5)	0.214 (5)	0.209 (2)	0.023 (8)*
H2	0.571 (6)	−0.053 (5)	0.145 (2)	0.015 (7)*
O1	0.1767 (3)	0.0678 (3)	0.11585 (11)	0.0183 (4)
O2	0.5997 (3)	0.2201 (3)	0.05291 (12)	0.0174 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0157 (2)	0.0131 (2)	0.0168 (2)	−0.00277 (14)	−0.00103 (14)	0.00228 (15)
P1	0.0158 (3)	0.0148 (3)	0.0160 (3)	0.0004 (2)	−0.0010 (2)	0.0023 (2)
O1	0.0175 (8)	0.0190 (8)	0.0183 (8)	−0.0028 (6)	0.0010 (6)	0.0001 (6)
O2	0.0143 (7)	0.0149 (8)	0.0231 (8)	0.0012 (6)	0.0016 (7)	0.0038 (6)

Geometric parameters (Å, º)

Cu1—O1	1.9483 (16)	P1—O2	1.5207 (17)
Cu1—O2^i	1.9829 (16)	P1—H1	1.30 (3)
Cu1—O2^ii	2.6496 (17)	P1—H2	1.21 (3)
P1—O1	1.5151 (18)
O1—Cu1—O1^iii	180.00 (5)	O1—P1—H2	112.0 (15)
O1—Cu1—O2^i	90.00 (7)	O2—P1—H2	103.9 (14)
O2^iv—Cu1—O2^i	180.00 (10)	H1—P1—H2	104.3 (19)
O1—Cu1—O2^ii	91.92 (6)	P1—O1—Cu1	128.95 (10)
O2^i—Cu1—O2^ii	82.10 (4)	P1—O2—Cu1^v	122.84 (10)
O1—P1—O2	118.31 (10)	P1—O2—Cu1^vi	112.51 (8)
O1—P1—H1	106.1 (12)	Cu1^v—O2—Cu1^vi	124.64 (7)
O2—P1—H1	111.5 (14)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
P1—H1···O1^vii	1.30 (3)	2.70 (3)	2.9605 (17)	88.2 (16)
P1—H2···O1^iv	1.21 (3)	2.75 (3)	3.4793 (17)	117.3 (19)
P1—H2···O2^viii	1.21 (3)	2.61 (3)	3.5881 (18)	136.1 (19)
P1—H1···O1^ix	1.30 (3)	2.88 (3)	3.8112 (17)	127.8 (19)

Symmetry codes: (iv) −x+1/2, y−1/2, z; (vii) −x+1/2, y+1/2, z; (viii) −x+3/2, y−1/2, z; (ix) x+1/2, y, −z+1/2.

(beta100)

Crystal data

Cu(H2PO2)2	Dx = 2.732 Mg m^−3
Mr = 193.51	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 1900 reflections
a = 5.3014 (2) Å	θ = 2.9–29.1°
b = 6.2319 (2) Å	µ = 5.21 mm^−1
c = 14.2427 (2) Å	T = 100 K
V = 470.55 (2) Å^3	Prism, blue
Z = 4	0.23 × 0.13 × 0.05 mm
F(000) = 380

Data collection

Siemens SMART CCD diffractometer	624 independent reflections
Radiation source: fine-focus sealed tube	606 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 8.192 pixels mm^-1	θmax = 29.1°, θmin = 2.9°
ω scans	h = −7→7
Absorption correction: analytical (XPREP; Siemens, 1995)	k = −7→8
Tmin = 0.417, Tmax = 0.809	l = −17→19
2974 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	All H-atom parameters refined
wR(F^2) = 0.062	w = 1/[σ^2(Fo^2) + (0.0198P)^2 + 1.149P] where P = (Fo^2 + 2Fc^2)/3
S = 1.29	(Δ/σ)max < 0.001
624 reflections	Δρmax = 0.68 e Å^−3
43 parameters	Δρmin = −0.33 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0101 (17)

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
Cu1	0.0000	0.0000	0.0000	0.00728 (17)
P1	0.45577 (12)	0.10826 (10)	0.13094 (5)	0.00789 (18)
H1	0.480 (6)	0.214 (6)	0.211 (2)	0.009 (8)*
H2	0.573 (7)	−0.066 (5)	0.145 (2)	0.008 (8)*
O1	0.1756 (3)	0.0667 (3)	0.11692 (12)	0.0095 (4)
O2	0.6015 (3)	0.2177 (3)	0.05204 (13)	0.0091 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0077 (2)	0.0066 (2)	0.0075 (2)	−0.00120 (15)	−0.00048 (14)	0.00108 (16)
P1	0.0081 (3)	0.0079 (3)	0.0076 (3)	0.0004 (2)	−0.0003 (2)	0.0009 (2)
O1	0.0093 (8)	0.0098 (8)	0.0094 (8)	−0.0011 (6)	0.0007 (6)	−0.0007 (7)
O2	0.0073 (8)	0.0091 (8)	0.0108 (8)	0.0012 (7)	0.0004 (7)	0.0009 (7)

Geometric parameters (Å, º)

Cu1—O1	1.9526 (18)	P1—O2	1.5247 (19)
Cu1—O2^i	1.9835 (18)	P1—H1	1.32 (3)
Cu1—O2^ii	2.6178 (18)	P1—H2	1.27 (3)
P1—O1	1.5209 (19)
O1—Cu1—O1^iii	180.00 (5)	O1—P1—H2	110.6 (16)
O1—Cu1—O2^i	90.03 (7)	O2—P1—H2	104.4 (16)
O2^iv—Cu1—O2^i	180.00 (10)	H1—P1—H2	104 (2)
O1—Cu1—O2^ii	91.89 (7)	P1—O1—Cu1	127.87 (11)
O2^i—Cu1—O2^ii	82.25 (5)	P1—O2—Cu1^v	122.32 (11)
O1—P1—O2	118.31 (10)	P1—O2—Cu1^vi	112.70 (9)
O1—P1—H1	107.0 (13)	Cu1^v—O2—Cu1^vi	124.94 (8)
O2—P1—H1	111.3 (15)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
P1—H1···O1^vii	1.32 (3)	2.70 (3)	2.9475 (19)	87.1 (16)
P1—H2···O1^iv	1.27 (3)	2.67 (3)	3.4517 (19)	118 (2)
P1—H2···O2^viii	1.27 (3)	2.56 (3)	3.5632 (19)	135 (2)
P1—H1···O1^ix	1.32 (3)	2.82 (3)	3.7843 (19)	129 (2)

Symmetry codes: (iv) −x+1/2, y−1/2, z; (vii) −x+1/2, y+1/2, z; (viii) −x+3/2, y−1/2, z; (ix) x+1/2, y, −z+1/2.

(gamma270)

Crystal data

Cu(H2PO2)2	Dx = 2.472 Mg m^−3
Mr = 193.51	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pmma	Cell parameters from 24 reflections
a = 6.6738 (6) Å	θ = 10–15°
b = 5.4133 (5) Å	µ = 4.72 mm^−1
c = 7.1954 (6) Å	T = 270 K
V = 259.95 (4) Å^3	Needle, blue
Z = 2	0.52 × 0.03 × 0.01 mm
F(000) = 190

Data collection

Enraf-Nonius CAD-4 diffractometer	341 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.042
Graphite monochromator	θmax = 29.1°, θmin = 2.8°
2θ/θ scans	h = −1→8
Absorption correction: analytical (XPREP; Siemens, 1995)	k = −1→7
Tmin = 0.501, Tmax = 0.605	l = −1→9
939 measured reflections	3 standard reflections every 60 min
405 independent reflections	intensity decay: none

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)] = 0.033	Hydrogen site location: difference Fourier map
wR(F^2) = 0.045	H atoms treated by a mixture of independent and constrained refinement
S = 1.10	w = 1/[σ^2(Fo^2)]
405 reflections	(Δ/σ)max < 0.001
27 parameters	Δρmax = 0.42 e Å^−3
0 restraints	Δρmin = −0.51 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	Occ. (<1)
Cu1	0.0000	0.5000	0.0000	0.01590 (16)
P1	0.2500	0.0000	−0.1476 (2)	0.0364 (4)
H1A	0.414 (5)	0.0000	−0.259 (3)	0.044*	0.50
H1B	0.086 (5)	0.0000	−0.259 (3)	0.044*	0.50
O1	0.2500	0.2382 (4)	−0.0362 (3)	0.0340 (7)
P2	0.2500	0.5000	0.36694 (19)	0.0310 (4)
H2A	0.2500	0.292 (5)	0.484 (3)	0.037*	0.50
H2B	0.2500	0.708 (5)	0.484 (3)	0.037*	0.50
O2	0.0560 (3)	0.5000	0.2659 (3)	0.0246 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0104 (3)	0.0149 (2)	0.0224 (3)	0.000	0.0008 (3)	0.000
P1	0.0614 (13)	0.0170 (6)	0.0308 (8)	0.000	0.000	0.000
O1	0.0481 (18)	0.0155 (11)	0.0385 (16)	0.000	0.000	−0.0053 (12)
P2	0.0165 (8)	0.0544 (9)	0.0220 (7)	0.000	0.000	0.000
O2	0.0101 (12)	0.0419 (15)	0.0219 (12)	0.000	−0.0021 (10)	0.000

Geometric parameters (Å, º)

Cu1—O1	2.2046 (14)	P1—H1A	1.3585
Cu1—O2	1.949 (2)	P2—O2	1.485 (2)
P1—O1	1.518 (2)	P2—H2A	1.4058
O1—Cu1—O1^i	80.01 (9)	O1—P1—H1A	108.2
O2—Cu1—O1	88.33 (8)	O1—P1—H1B	108.2
O2—Cu1—O1^i	88.33 (8)	H1A—P1—H1B	107.4
O2—Cu1—O2^ii	180.0	O2—P2—O2^i	121.4 (2)
O1^i—Cu1—O1^iii	180.0	O2—P2—H2A	107.0
O2—Cu1—Cu1^i	78.95 (7)	O2—P2—H2B	107.0
O2^ii—Cu1—Cu1^i	101.05 (7)	H2A—P2—H2B	106.7
O1^i—Cu1—Cu1^i	40.82 (4)	P1—O1—Cu1	127.47 (6)
O1^iii—Cu1—Cu1^i	139.18 (4)	P2—O2—Cu1	130.37 (15)
O1—Cu1—Cu1^i	40.82 (4)	Cu1—O1—Cu1^i	98.36 (9)
O1—P1—O1^iv	116.3 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
P1—H1A···O2^v	1.36	2.87	3.4958 (15)	106
P1—H1A···O2^vi	1.36	2.87	3.4958 (15)	106
P2—H2A···O2^vii	1.41	2.95	3.339 (2)	93
P2—H2B···O2^viii	1.41	2.95	3.339 (2)	93

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