catena-Poly[bis­(ethane-1,2-diammonium) [manganese(II)-di-μ-phosphato-κ⁴O:O′]]: a one-dimensional ­manganese phosphate

The title compound, {(C₂H₁₀N₂)₂[Mn(PO₄)₂]}_n, contains anionic square-twisted chains of formula [Mn(PO₄)₂]⁴⁻ constructed from corner-sharing four-membered rings of alternating MnO₄ and PO₄ units. The Mn and P atoms have distorted tetra­hedral coordination and the Mn atom lies on a twofold axis. The linear manganese–phosphate chains are held together by hydrogen-bonding interactions involving the framework O atoms and the H atoms of the ethane-1,2-diammonium cations, which lie in the inter­chain spaces.

S1. Comment

Crystallization under solvothermal conditions has proved very successful for the synthesis of a wide range of metal–phosphate frameworks (Cheetham et al., 1999; Maspoch et al., 2007). Much of this work has focused on aluminium and gallium phosphates and their hetero-metal-substituted analogues, and many new materials with zeolite-like properties have been produced. The solvothermal method has also been used for the preparation of a range of transition-metal phosphates, including manganese(II) and manganese(III) compounds. Examples include Mn₇(HPO₄)₄(PO₄)₂ (Riou et al., 1987; Rojo et al., 2002), Mn₆(PO₄)₄·H₂O (Stock, 2002) and MnPO₄·H₂O (Lightfoot et al., 1987) and synthetic minerals, such as hureaulite, Mn₅(HPO₄)₂(PO₄)₂·4H₂O (Gerault et al., 1987), and gatehouseite, Mn₅(PO₄)₂(OH)₄ (Ruszala et al., 1977), as well as open-framework materials in which inorganic or organic cations are accommodated in pores or interlayer spaces in the metal–phosphate frameworks. Of these materials, which are rather few in number compared with the phosphates of other transition metals, such as iron, cobalt or zinc, only one example, NH₄Mn₄(PO₄)₃ (Neeraj et al., 2002), has a three-dimensional manganese–phosphate framework. The remainder, NH₄Mn₂O(PO₄)(HPO₄)·H₂O (Lightfoot & Cheetham, 1989), Na₂Mn₂O(PO₄)₂·H₂O (Tong et al., 2002), Ba(MnPO₄)₂·H₂O (Escobal et al., 1999), [Mn₆(H₂O)₂(HPO₄)₄(PO₄)₂](pipH₂)·H₂O (pip is piperazine; Kongshaug et al., 2001), [Mn₂(PO₄)₂](NH₃(CH₂)₂NH₃)·(H₂O)₂ (Song et al., 2003), [Mn₂(PO₄)₃](NH₃(CH₂)₂NH₃)·(H₂O)_x [x = 1 (Escobal et al., 2000) and x = 1/5 (Chippindale et al., 2001)], [Mn₂(PO₄)₃](NH₃(CH₂)2NH₃)_3/2·H₂PO₄ (Chippindale et al., 2001) and [Mn₃(PO₄)₄](trenH₃)₂·(H₂O)₆ [tren is tris(2-aminoethyl)amine; Thoma et al., 2004], all have two-dimensional manganese–phosphate frameworks. We describe here the synthesis and characterization of [Mn(PO₄)₂][NH₃(CH₂)₂NH₃]₂, the first example of an organically templated manganese phosphate with a one-dimensional chain-like structure.

The structure of [Mn(PO₄)₂][NH₃(CH₂)₂NH₃]₂ consists of inorganic chains of formula [Mn(PO₄)₂]⁴⁻ separated by ethylenediammonium cations. Atom Mn1 occupies a special position (4c), and is tetrahedrally coordinated to two O2 and two O3 atoms with an average Mn1—O distance of 2.024 Å (Table 1). The bond-valence summation around Mn1 is 2.14 (Brese & O'Keeffe, 1991), confirming that manganese is present in the compound in the +2 oxidation state. The Mn—O bond lengths are in close agreement with those found in other compounds in which Mn²⁺ is in a tetrahedral MnO₄ unit, for example in [Mn₃(PO₄)₄](trenH₃)₂·(H₂O)₆ (Thoma et al., 2004). Atom Mn1 is connected via Mn—O—P linkages through O2 and O3 atoms to an independent P atom, P1, which lies on a general position. In addition to the P1—O2 and P1—O3 bonds involved in bridging to atom Mn1, two terminal P1—O bonds, to atoms O1 and O4, complete the tetrahedral coordination around atom P1 (Fig. 1). The O—P—O angles lie in the range 107.5 (1)–110.2 (1)°. The P1—O1 and P1—O4 distances, at 1.536 (1) and 1.534 (1) Å, are somewhat longer than expected for terminal P═O bonds. Their elongation arises as a result of strong hydrogen-bonding interactions with the ethane-1,2-diammonium cations (see below).

The Mn1O₄ and P1O₄ tetrahedra are linked in strict alternation through their vertices to generate infinite square-twisted chains of formula [Mn(PO₄)₂]⁴⁻ containing four-membered Mn₂P₂ rings of alternating Mn- and P-based units [described as single 4-rings (S4R) in zeolite notation]. The Mn²⁺ cations are well separated from each other within the chains [Mn1··· Mn1^viii = 4.434 (1) Å]. The chains run parallel to the c axis (Fig. 2) and lie in layers in the bc plane. These layers are then stacked in an ABAB fashion along the a axis (Fig. 3), with the chains in layer A lying antiparallel to those in layer B.

In order to balance the negative charge of the manganese-phosphate chains, the ethane-1,2-diamine molecules located in the interlayer space must be diprotonated, and this is confirmed by the location of all H atoms in a difference Fourier map. A network of hydrogen bonds between the two NH₃ groups of the ethane-1,2-diammonium cations and the O atoms of the phosphate groups serves to link the chains together to generate a three-dimensional assembly (Table 2). Hydrogen bonds involving atom N1 link the manganese–phosphate chains into layers in the bc plane. Atom N1 is within ca 3.1 Å of four O atoms, three of which are within the same chain [N1···O2ⁱ = 2.816 (2) Å, N1···O3 = 3.064 (2) Å and N1···O4 = 2.811 (2) Å; symmetry codes as in Table 2] with the fourth in a neighbouring chain [N1···O4^v = 2.737 (2) Å]. Adjacent layers are then linked together by hydrogen bonds via atom N2, which is within ca 3.1 Å of five O atoms. Three of these O atoms are within the same chain (N2···O1ⁱⁱ = 2.877 (2) Å, N2···O1^vi = 2.729 (2) Å and N2···O3ⁱⁱ = 2.951 (2) Å] and the remaining two are in a chain in an adjacent layer [N2···O1^vii = 2.924 (2) and N2···O4^vii = 3.116 (3) Å].

Curiously, to date the title compound has only been synthesized by heating a mixture of pre-formed [Mn₂(HPO₄)₃][NH₃(CH₂)₂NH₃]_3/2·H₂PO₄ and ethane-1,2-diamine in an autoclave at 433 K. Attempts to prepare it directly from a manganese(II) salt, phosphoric acid and ethane-1,2-diamine in a conventional solvothermal reaction have not so far been successful. In [Mn₂(HPO₄)₃][NH₃(CH₂)₂NH₃]_3/2·H₂PO₄, Mn^II is present in MnO₆ units with octahedral geometry and in MnO₅ units with a geometry intermediate between square pyramidal and trigonal bipyramidal. These units are linked through HPO₄ tetrahedra to generate a layered structure with ethane-1,2-diammonium cations and hydrogen phosphate anions residing within the interlayer space. By contrast, the title compound contains Mn²⁺ in tetrahedral MnO₄ units. The change in the coordination geometry of manganese on heating [Mn₂(HPO₄)₃][NH₃(CH₂)₂NH₃]_3/2·H₂PO₄ in ethane-1,2-diamine probably proceeds via a dissolution process, although the mechanism is not yet known. Tetrahedral MnO₄ coordination geometry is still rather rare in manganese(II) phosphates and is most commonly found in mixed-metal phosphates, such as MnAlPOs and MnGaPOs, which have zeolite-like frameworks. With the exception of [Mn₃(PO₄)₄](trenH₃)₂·(H₂O)₆ (Thoma et al., 2004), all the compounds listed in the introduction contain manganese coordinated to five, six or seven O atoms.

A number of amine-templated metal phosphates with chain structures based on MO₄ and PO₄ units have been reported. Two chain structure types have been identified. The first, more common type, contains edge-sharing M₂P₂ four-membered rings forming ladder-like structures with additional pendant phosphate groups. Examples include [Al(PO₄)(HPO₄)][NH₃(CH₂)₂NH₃] (Wang et al., 2003) and [M(HPO₄)₂][NH₃(CH₂)₂NH₃] [M = Co (Cowley & Chippindale, 1999) and M = Zn (Chidambaram et al., 1999)]. The second chain type contains corner-sharing M₂P₂ rings of the sort described here, for example [Al(PO₄)₂](NH₄)[NH₃CH₂CH(NH₃)CH₃] (Ayi et al., 2001), [Ga(PO₄)(HPO₄)][NH₃(CH₂)₄NH₃] (Chippindale et al., 1998), [Co(HPO₄)₂](dmpH₂) (dmp is N,N'-dimethylpiperazine; Choudhury et al., 2000)) and [Zn(HPO₄)₂](pipH₂) (Natarajan, 2002).

In all cases, the packing together of the chains is driven by hydrogen-bonding interactions. Where the chains contain hydrogen phosphate groups, e.g. PO(OH) and PO(OH)₂ groups, the possibility exists for interchain hydrogen-bonding interactions in addition to chain–amine interactions, as is observed, for example in [Co(HPO₄)₂][NH₃(CH₂)₂NH₃] (Cowley & Chippindale, 1999). In the title compound {and [Al(PO₄)₂](NH₄)[NH₃CH₂CH(NH₃)CH₃]; Ayi et al., 2001}, no interchain interactions are possible and the metal–phosphate chains are well separated. Hydrogen-bonding networks in these cases therefore involve only chain–amine interactions.

Related literature

For related literature, see: Ayi et al. (2001); Brese & O'Keeffe (1991); Cheetham et al. (1999); Chidambaram et al. (1999); Chippindale et al. (1998, 2001); Choudhury et al. (2000); Cowley & Chippindale (1999); Escobal et al. (1999, 2000); Gerault et al. (1987); Kongshaug et al. (2001); Lightfoot & Cheetham (1989); Lightfoot et al. (1987); Maspoch et al. (2007); Natarajan (2002); Neeraj et al. (2002); Riou et al. (1987); Rojo et al. (2002); Ruszala et al. (1977); Thoma et al. (2004); Tong et al. (2002); Wang et al. (2003).

S2. Experimental

Single crystals of [Mn(PO₄)₂][NH₃(CH₂)₂NH₃]₂ were prepared under solvothermal conditions. [Mn₂(HPO₄)₃][NH₃(CH₂)₂NH₃]_3/2·H₂PO₄ (0.15 g; Chippindale et al., 2001) was stirred with ethane-1,2-diamine (6.00 ml) at room temperature until homogeneous, sealed in a Teflon-lined autoclave, and heated at 433 K for 3 d. The solid product was collected by filtration, washed with methanol and dried in air at room temperature. It consisted of a cream–white powder containing colourless rectangular plates of the title compound suitable for single-crystal X-ray analysis. The powder X-ray diffraction pattern of the bulk product could be indexed on the basis of the orthorhombic unit cell determined from the single-crystal determination with refined lattice parameters a = 8.5667 (13) Å, b = 8.8633 (16) Å and c = 17.207 (3) Å, confirming that the sample is monophasic. An IR spectrum of the product showed features consistent with the presence of ethane-1,2-diammonium cations. A series of strong broad bands occurred in the region 3500–2400 cm⁻¹ corresponding to –N—H and –CH₂– stretching modes. The two medium intensity sharp bands observed at 1645 and 1540 cm⁻¹ are due to NH₃⁺ bending modes (antisymmetric and symmetric, respectively). A number of strong sharp bands appearing below 1400 cm⁻¹ correspond to –CH₂– group bending modes with P—O and Mn—O stretching and bending modes. Unambiguous individual assignments of these bands are not possible. Thermogravimetric analysis under flowing N₂ showed weight losses of ca 15.8% over the range 443–521 K and ca 17% over the range 521–823 K. These correspond to the loss of two moles of ethylenediamine from [Mn(PO₄)₂][NH₃(CH₂)₂NH₃]₂ (the calculated value for the loss of one mole of ethane-1,2-diamine is 16.27%). Collapse of the framework occurred above 823 K to give an amorphous residue.

S3. Refinement

All H atoms were located in difference Fourier maps. The fractional coordinates and isotropic displacement parameters of the H atoms bonded to N were refined, whilst the remaining H atoms were placed geometrically and constrained to ride on their parent C atoms [C—H = 0.95 Å and U_iso(H) = 1.2U_eq(C)].

Computing details

Data collection: COLLECT (Nonius, 2001); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

Figures

	Fig. 1. The local coordination of atoms in [Mn(PO4)2][NH3(CH2)2NH3]2 (50% probability displacement ellipsoids). [Symmetry codes: (i) −x + 1/2, y, z + 1/2; (ii) x, −y + 1/2, z + 1/2; (iii) −x + 1/2, −y + 1/2, z; (iv) −x + 1/2, y, z − 1/2; (viii) x, y, z − 1/2; (ix) x, −y + 1/2, z − 1/2.]
	Fig. 2. A view of the title compound along the b axis, showing corner sharing of alternating MnO4 tetrahedra (white) and PO4 tetrahedra (grey) generating [Mn(PO4)2]^4− chains. Ethane-1,2,diammonium cations lie between the manganese–phosphate chains (key: C: light-grey spheres, N: dark-grey spheres, H atoms omitted).
	Fig. 3. A view along the c axis, showing the stacking of the manganese–phosphate chains. Key as for Fig. 2.

catena-Poly[bis(ethane-1,2-diammonium) [manganese(II)-di-µ-phosphato-κ⁴O:O']]

Crystal data

(C2H10N2)2[Mn(PO4)2]	F(000) = 764.000
Mr = 369.12	Dx = 1.871 Mg m^−3
Orthorhombic, Pccn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2ac	Cell parameters from 1717 reflections
a = 17.2363 (5) Å	θ = 0–27.4°
b = 8.5726 (2) Å	µ = 1.29 mm^−1
c = 8.8689 (2) Å	T = 293 K
V = 1310.47 (6) Å^3	Plate, colourless
Z = 4	0.19 × 0.07 × 0.03 mm

Data collection

Enraf–Nonius KappaCCD diffractometer	1167 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.051
ω scans	θmax = 27.4°, θmin = 5.2°
Absorption correction: multi-scan DENZO/SCALEPACK (Otwinowski & Minor, 1997)	h = 0→22
Tmin = 0.90, Tmax = 0.96	k = 0→11
1724 measured reflections	l = 0→11
1477 independent reflections

Refinement

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.026	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.026	Method = Prince modified Chebychev polynomial, (Watkin, 1994) W = [weight] * [1-(deltaF/6*sigmaF)^2]2 1.64 -0.625 1.22
S = 1.09	(Δ/σ)max = 0.001
1167 reflections	Δρmax = 0.33 e Å^−3
111 parameters	Δρmin = −0.35 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Mn1	0.2500	0.2500	0.46773 (4)	0.0118
P1	0.14663 (3)	0.44520 (5)	0.20374 (5)	0.0108
O1	0.07354 (8)	0.37075 (18)	0.13553 (16)	0.0235
O2	0.21401 (8)	0.43996 (16)	0.08917 (16)	0.0202
O3	0.16721 (8)	0.35338 (16)	0.34582 (16)	0.0194
O4	0.1301 (1)	0.61600 (15)	0.24409 (16)	0.0255
N1	0.15588 (11)	0.6357 (2)	0.55651 (19)	0.0187
N2	0.0462 (1)	0.3898 (2)	0.8330 (2)	0.0182
C1	0.09070 (11)	0.5403 (2)	0.6143 (2)	0.0197
C2	0.10116 (13)	0.5101 (2)	0.7810 (2)	0.0233
H11	0.1999 (19)	0.578 (4)	0.573 (4)	0.046 (9)*
H12	0.1502 (15)	0.643 (3)	0.463 (3)	0.027 (7)*
H13	0.1534 (15)	0.726 (4)	0.605 (4)	0.037 (7)*
H21	0.0536 (16)	0.307 (4)	0.780 (3)	0.033 (7)*
H22	0.0556 (16)	0.371 (3)	0.934 (3)	0.026 (6)*
H23	0.0032 (17)	0.426 (3)	0.826 (3)	0.022 (6)*
H111	0.0894	0.4436	0.5620	0.0237*
H112	0.0433	0.5944	0.5984	0.0237*
H211	0.1527	0.4754	0.7991	0.0280*
H212	0.0921	0.6040	0.8352	0.0280*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn1	0.01248 (17)	0.01190 (17)	0.01103 (16)	0.00225 (16)	0.0000	0.0000
P1	0.0123 (2)	0.0107 (2)	0.00932 (19)	0.00247 (15)	0.00069 (16)	0.00052 (16)
O1	0.0154 (6)	0.0378 (8)	0.0172 (7)	−0.0061 (6)	−0.0053 (5)	0.0051 (6)
O2	0.0203 (7)	0.0185 (6)	0.0219 (7)	−0.0020 (6)	0.0094 (6)	−0.0057 (6)
O3	0.0230 (7)	0.0195 (6)	0.0157 (6)	0.0040 (6)	−0.0056 (5)	0.0047 (5)
O4	0.0446 (9)	0.0123 (6)	0.0197 (7)	0.0100 (6)	0.0094 (6)	0.0021 (5)
N1	0.0264 (9)	0.0155 (7)	0.0141 (8)	0.0028 (7)	0.0018 (6)	−0.0023 (6)
N2	0.0167 (8)	0.0206 (9)	0.0173 (8)	0.0070 (7)	0.0002 (6)	0.0005 (6)
C1	0.0229 (9)	0.0199 (9)	0.0163 (8)	0.0022 (8)	−0.0013 (7)	−0.0022 (7)
C2	0.0319 (11)	0.0206 (9)	0.0176 (9)	−0.0041 (8)	−0.0059 (8)	0.0021 (8)

Geometric parameters (Å, º)

Mn1—O2^i	2.0486 (13)	N1—H13	0.89 (3)
Mn1—O2^ii	2.0486 (13)	N2—C2	1.474 (3)
Mn1—O3	1.9976 (13)	N2—H21	0.86 (3)
Mn1—O3^iii	1.9976 (13)	N2—H22	0.93 (3)
P1—O1	1.5363 (14)	N2—H23	0.80 (3)
P1—O2	1.5437 (13)	C1—C2	1.512 (3)
P1—O3	1.5275 (13)	C1—H111	0.950
P1—O4	1.5339 (13)	C1—H112	0.950
N1—C1	1.482 (3)	C2—H211	0.950
N1—H11	0.92 (3)	C2—H212	0.950
N1—H12	0.84 (3)
O2^i—Mn1—O2^ii	116.56 (8)	H12—N1—H13	114 (3)
O2^i—Mn1—O3	98.52 (5)	C2—N2—H21	108.0 (18)
O2^ii—Mn1—O3	114.89 (6)	C2—N2—H22	108.1 (16)
O2^i—Mn1—O3^iii	114.89 (6)	H21—N2—H22	111 (2)
O2^ii—Mn1—O3^iii	98.52 (5)	C2—N2—H23	107.5 (19)
O3—Mn1—O3^iii	114.47 (8)	H21—N2—H23	114 (3)
O1—P1—O2	110.22 (8)	H22—N2—H23	107 (3)
O1—P1—O3	107.53 (8)	N1—C1—C2	110.02 (16)
O2—P1—O3	110.69 (8)	N1—C1—H111	109.336
O1—P1—O4	109.66 (9)	C2—C1—H111	109.336
O2—P1—O4	108.71 (8)	N1—C1—H112	109.336
O3—P1—O4	110.03 (8)	C2—C1—H112	109.336
Mn1^iv—O2—P1	126.65 (8)	H111—C1—H112	109.467
Mn1—O3—P1	147.24 (9)	N2—C2—C1	110.41 (16)
C1—N1—H11	106 (2)	N2—C2—H211	109.239
C1—N1—H12	107.2 (18)	C1—C2—H211	109.238
H11—N1—H12	107 (3)	N2—C2—H212	109.238
C1—N1—H13	106.4 (18)	C1—C2—H212	109.238
H11—N1—H13	116 (3)	H211—C2—H212	109.467

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O2^i	0.92 (3)	1.91 (4)	2.816 (2)	173 (3)
N1—H12···O4	0.84 (3)	1.99 (3)	2.811 (2)	168 (3)
N1—H13···O4^v	0.89 (3)	1.88 (3)	2.737 (2)	163 (3)
N2—H21···O1^ii	0.86 (3)	2.02 (3)	2.877 (2)	174 (3)
N2—H22···O1^vi	0.93 (3)	1.81 (3)	2.729 (2)	170 (2)
N2—H23···O1^vii	0.80 (3)	2.21 (3)	2.924 (3)	147 (4)
N2—H23···O4^vii	0.80 (3)	2.41 (3)	3.116 (3)	147 (4)

Symmetry codes: (i) −x+1/2, y, z+1/2; (ii) x, −y+1/2, z+1/2; (v) x, −y+3/2, z+1/2; (vi) x, y, z+1; (vii) −x, −y+1, −z+1.