Poly[bis­[μ₂-(dimethyl­aza­nium­yl)methyl­enediphospho­nato]magnesium]

Abstract

The title compound, [Mg(C₃H₁₀NO₆P₂)₂]_n, synthesized by a hydro­thermal method, adopts a one-dimensional polymeric chain structure and is isotypic with the previously reported Cd complex based on the ligand N,N-dimethyl­amino­methane-1,1-diphospho­nic acid (H₄ L). The asymmetric unit contains one half Mg²⁺ ion and one H₃ L ⁻ anion. The unique Mg²⁺ ion lies on an inversion center and is octa­hedrally coordinated by O atoms from six phospho­nate groups of four different H₃ L ⁻ anions. Each H₃ L ⁻ anion, with one protonated N atom and two phospho­nate OH groups, serves as a tridentate ligand. Two of its six phospho­nate O atoms chelate to a Mg²⁺ cation in a bidentate fashion, while a third O atom bridges to a neighbouring Mg²⁺ ion. The inter­connection of Mg²⁺ ions by the H₃ L ⁻anions leads to the formation of a polymer chain along the a axis in which the adjacent Mg²⁺ ions are doubly bridged by two equivalent H₃ L ⁻ anions. These discrete chains are further assembled into a three-dimensional supra­molecular network via O—H⋯O and N—H⋯O hydrogen bonds involving the non-coordin­ated phospho­nate O atoms and the protonated N atoms.

Related literature

For other metal complexes based on the N,N-dimethyl­amino­methane-1,1- diphospho­nate ligand, see: Du et al. (2009 ▶, 2010a ▶,b ▶). For bond-length data, see: Lutz & Muller (1995 ▶); Distler et al. (1999 ▶); Stock & Bein (2004 ▶).

Experimental

Crystal data

• [Mg(C₃H₁₀NO₆P₂)₂]

• M _r = 460.43

• Monoclinic,

• a = 5.4507 (3) Å

• b = 11.2166 (6) Å

• c = 12.5770 (7) Å

• β = 94.984 (1)°

• V = 766.03 (7) ų

• Z = 2

• Mo Kα radiation

• μ = 0.61 mm⁻¹

• T = 296 K

• 0.40 × 0.30 × 0.24 mm

Data collection

• Bruker SMART APEX CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.675, T _max = 0.746

• 4801 measured reflections

• 1492 independent reflections

• 1447 reflections with I > 2σ(I)

• R _int = 0.014

Refinement

• R[F ² > 2σ(F ²)] = 0.024

• wR(F ²) = 0.066

• S = 1.09

• 1492 reflections

• 115 parameters

• H-atom parameters constrained

• Δρ_max = 0.38 e Å⁻³

• Δρ_min = −0.33 e Å⁻³

Data collection: SMART (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1B⋯O3	0.91	2.57	3.0997 (18)	118
N1—H1B⋯O4i	0.91	2.31	3.1346 (18)	151
O3—H3D⋯O6ii	0.82	1.70	2.5011 (16)	166
O4—H4A⋯O2iii	0.82	1.81	2.6037 (16)	163

Symmetry codes: (i) ; (ii) ; (iii) .

supplementary crystallographic information

Comment

Among many of the phosphonate ligands studied so far, methylenediphosphonic acid and its derivatives are quite unique because they feature a close connection of two phosphonate moieties via one carbon atom, which facilitate their combined coordination ability to act as a [CP₂O₆] unit rather than two [CPO₃] units. As a result, they show diversified coordination capabilities with metal ions and thus lead to the formation of new structural types. Recently, by using such ligand types, i.e. N,N-dimethylaminomethane-1,1-diphosphonate, we have isolated a series of diphosphonate complexes of metals such as Al^III, Fe^III, Cd^II, Pb^II and Ba^II, which exhibit variable structures such as zero-dimensional, one-dimensional, double-1-dimensional, double-2-dimensional, and three-dimensional structures (Du et al., 2009, 2010a,b). As an expansion of our previous work, we have also obtained a one-dimensional magnesium(II) diphosphonate, namely [Mg(C₆H₂₀N₂O₁₂P₄)]_n, which is isostructural with the previously reported cadmium(II) complex based on the same ligand and shows a one-dimensional chain structure. The asymmetric unit contains a half Mg²⁺ cation and one H₃L^- anion. The unique Mg²⁺ cation lies on an inversion center and is octahedrally coordinated by the O atoms of six phosphonate groups from four H₃L^- anions. The Mg—O [2.0448 (11) – 2.1879 (11) Å] bond lengths are comparable to those reported for other Mg^II phosphonate complexes (Lutz & Muller, 1995; Distler et al., 1999; Stock & Bein, 2004). The unique H₃L^- anion, with one protonated N atom and two phosphonate OH groups, serves as a tridentate ligand. By using three of its six phosphonate O atoms, it chelates in a bidentate fashion with one Mg²⁺ cation and also bridges to a second Mg²⁺ ion. The interconnection of Mg²⁺ cations by the H₃L^- anions leads to the formation of a one-dimensional chain along the a-axis, in which the adjacent Mg²⁺ ions are doubly bridged by two equivalent H₃L^- anions. These discrete one-dimensional chains are further assembled into a three-dimensional supramolecular network via O—H···O and N—H···O hydrogen bonds involving the non-coordinated phosphonate O atoms and the protonated N atoms.

Experimental

For the preparation of (I), a mixture of Mg(NO₃)₂ (0.20 mmol) and H₄L (0.50 mmol) and ethanol (3 ml) in 10 ml distilled water, was sealed into a Parr Teflon-lined autoclave (23 ml) and heated at 393 K for 3 d. Colorless block-shaped crystals were collected in ca 55% yield based on Mg. Analysis calculated for C₆H₂₀N₂O₁₂Mg₁P₄: C 15.65, H 4.38, N 6.08%; found: C 15.59, H 4.48, N 6.03%.

Refinement

The N-bound and the tertiary C-bound H atoms were positioned geometrically and refined using a riding model: N—H = 0.91 and C—H = 0.98 Å, with Uiso(H) = 1.2U_eq(N, C); while the O-bound and the primary C-bound H atoms were placed in idealized positions and constrained to ride on their parent atoms: O—H = 0.82 and C—H = 0.96 Å, with U_iso(H) = 1.5 times U_eq(O, C).

Figures

Fig. 1.

A view of the selected unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity. [Symmetry codes: (i) x - 1, y, z; (ii) -x + 1, -y + 1, -z + 1; (iii) -x, -y + 1, -z + 1; (iv) x + 1, y, z.]

Fig. 2.

A view of the chain structure of (I) along the a-axis. The CPO3 tetrahedra are shaded in purple. Mg, N and C atoms are drawn as cyan, blue and grey circles, respectively. Hydrogen atoms have been omitted for clarity.

Fig. 3.

A view of the three-dimensional supramolecular structure of (I) down the a-axis. The MgO6 octahedra and CPO3 tetrahedra are shaded in cyan and purple, respectively. N, C and H atoms are drawn as blue, grey and green circles, respectively. Hydrogen bonds are represented by dashed lines.

Crystal data

[Mg(C3H10NO6P2)2]	F(000) = 476
Mr = 460.43	Dx = 1.996 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4647 reflections
a = 5.4507 (3) Å	θ = 2.4–29.4°
b = 11.2166 (6) Å	µ = 0.61 mm−1
c = 12.5770 (7) Å	T = 296 K
β = 94.984 (1)°	Block, colourless
V = 766.03 (7) Å3	0.40 × 0.30 × 0.24 mm
Z = 2

Data collection

Bruker SMART APEX CCD area-detector diffractometer	1492 independent reflections
Radiation source: fine-focus sealed tube	1447 reflections with I > 2σ(I)
graphite	Rint = 0.014
φ and ω scans	θmax = 26.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −6→6
Tmin = 0.675, Tmax = 0.746	k = −13→13
4801 measured reflections	l = −15→15

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.024	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.066	H-atom parameters constrained
S = 1.09	w = 1/[σ2(Fo2) + (0.0347P)2 + 0.6187P] where P = (Fo2 + 2Fc2)/3
1492 reflections	(Δ/σ)max = 0.001
115 parameters	Δρmax = 0.38 e Å−3
0 restraints	Δρmin = −0.33 e Å−3

Special details

Experimental. IR data (KBr, ν, cm-1): 3437 (m), 3137 (s), 3071 (m), 2986 (m), 2826 (m), 2280 (m), 1815 (m), 1473 (m), 1457 (m), 1421 (m), 1388 (m), 1256 (s), 1225 (s), 1200 (versus), 1155 (s), 1128 (s), 1088 (s), 1036 (s), 995 (s), 950 (s), 928 (s), 854 (m), 827 (m), 725 (m), 615 (m), 573 (s), 517 (m), 476 (m).

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
Mg1	0.0000	0.5000	0.5000	0.01237 (17)
P1	0.52519 (7)	0.34374 (3)	0.59421 (3)	0.01109 (12)
P2	0.34788 (7)	0.55738 (3)	0.72234 (3)	0.01225 (13)
N1	0.5807 (3)	0.35032 (12)	0.81729 (11)	0.0161 (3)
H1B	0.6307	0.2757	0.8007	0.019*
C1	0.4187 (3)	0.39596 (14)	0.72149 (12)	0.0126 (3)
H1A	0.2596	0.3565	0.7262	0.015*
C2	0.4447 (4)	0.33952 (16)	0.91574 (13)	0.0217 (4)
H2A	0.5545	0.3102	0.9737	0.032*
H2B	0.3096	0.2851	0.9024	0.032*
H2C	0.3831	0.4163	0.9341	0.032*
C3	0.8076 (3)	0.42374 (19)	0.84083 (15)	0.0264 (4)
H3A	0.9027	0.3918	0.9021	0.040*
H3B	0.7620	0.5045	0.8550	0.040*
H3C	0.9041	0.4221	0.7805	0.040*
O1	0.7774 (2)	0.38860 (10)	0.57970 (9)	0.0168 (3)
O2	0.3180 (2)	0.38023 (10)	0.51279 (9)	0.0160 (2)
O3	0.5417 (2)	0.20563 (10)	0.60652 (10)	0.0182 (3)
H3D	0.4114	0.1800	0.6253	0.027*
O4	0.5780 (2)	0.62560 (11)	0.68532 (9)	0.0177 (3)
H4A	0.5846	0.6161	0.6210	0.027*
O5	0.1277 (2)	0.57125 (10)	0.64393 (9)	0.0167 (3)
O6	0.3209 (2)	0.59441 (11)	0.83501 (9)	0.0187 (3)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Mg1	0.0099 (4)	0.0144 (4)	0.0127 (4)	−0.0013 (3)	0.0006 (3)	0.0007 (3)
P1	0.0111 (2)	0.0108 (2)	0.0117 (2)	−0.00042 (14)	0.00234 (15)	0.00033 (14)
P2	0.0116 (2)	0.0127 (2)	0.0124 (2)	0.00185 (14)	0.00060 (15)	−0.00118 (14)
N1	0.0179 (7)	0.0157 (7)	0.0144 (6)	0.0044 (5)	−0.0008 (5)	0.0006 (5)
C1	0.0116 (7)	0.0146 (7)	0.0114 (7)	0.0011 (6)	0.0004 (6)	0.0000 (6)
C2	0.0286 (10)	0.0216 (9)	0.0150 (8)	0.0014 (7)	0.0029 (7)	0.0032 (6)
C3	0.0153 (9)	0.0371 (10)	0.0257 (9)	−0.0014 (8)	−0.0047 (7)	0.0022 (8)
O1	0.0137 (6)	0.0172 (6)	0.0200 (6)	−0.0027 (4)	0.0041 (4)	0.0022 (5)
O2	0.0142 (6)	0.0197 (6)	0.0141 (5)	0.0016 (4)	0.0008 (4)	0.0009 (4)
O3	0.0178 (6)	0.0122 (6)	0.0253 (6)	−0.0009 (4)	0.0067 (5)	0.0010 (5)
O4	0.0171 (6)	0.0191 (6)	0.0171 (5)	−0.0036 (5)	0.0022 (5)	−0.0025 (5)
O5	0.0147 (6)	0.0173 (6)	0.0174 (6)	0.0022 (4)	−0.0018 (5)	−0.0004 (4)
O6	0.0196 (6)	0.0217 (6)	0.0148 (6)	0.0060 (5)	0.0015 (5)	−0.0033 (5)

Geometric parameters (Å, °)

Mg1—O5i	2.0448 (11)	N1—C3	1.494 (2)
Mg1—O5	2.0448 (11)	N1—C2	1.502 (2)
Mg1—O1ii	2.0615 (11)	N1—C1	1.5196 (19)
Mg1—O1iii	2.0616 (11)	N1—H1B	0.9100
Mg1—O2	2.1879 (11)	C1—H1A	0.9800
Mg1—O2i	2.1879 (11)	C2—H2A	0.9600
P1—O1	1.4898 (12)	C2—H2B	0.9600
P1—O2	1.5134 (12)	C2—H2C	0.9600
P1—O3	1.5587 (12)	C3—H3A	0.9600
P1—C1	1.8451 (15)	C3—H3B	0.9600
P2—O5	1.4938 (12)	C3—H3C	0.9600
P2—O6	1.4961 (12)	O1—Mg1iv	2.0615 (11)
P2—O4	1.5737 (12)	O3—H3D	0.8200
P2—C1	1.8515 (16)	O4—H4A	0.8200
O5i—Mg1—O5	179.999 (1)	C3—N1—C1	112.68 (13)
O5i—Mg1—O1ii	88.62 (5)	C2—N1—C1	112.71 (13)
O5—Mg1—O1ii	91.38 (5)	C3—N1—H1B	107.1
O5i—Mg1—O1iii	91.38 (5)	C2—N1—H1B	107.1
O5—Mg1—O1iii	88.62 (5)	C1—N1—H1B	107.1
O1ii—Mg1—O1iii	180.0	N1—C1—P1	112.08 (10)
O5i—Mg1—O2	91.82 (4)	N1—C1—P2	115.59 (10)
O5—Mg1—O2	88.18 (4)	P1—C1—P2	113.39 (8)
O1ii—Mg1—O2	84.94 (4)	N1—C1—H1A	104.8
O1iii—Mg1—O2	95.06 (4)	P1—C1—H1A	104.8
O5i—Mg1—O2i	88.19 (4)	P2—C1—H1A	104.8
O5—Mg1—O2i	91.82 (4)	N1—C2—H2A	109.5
O1ii—Mg1—O2i	95.06 (4)	N1—C2—H2B	109.5
O1iii—Mg1—O2i	84.94 (4)	H2A—C2—H2B	109.5
O2—Mg1—O2i	180.00 (6)	N1—C2—H2C	109.5
O1—P1—O2	117.90 (7)	H2A—C2—H2C	109.5
O1—P1—O3	107.58 (7)	H2B—C2—H2C	109.5
O2—P1—O3	111.67 (7)	N1—C3—H3A	109.5
O1—P1—C1	111.24 (7)	N1—C3—H3B	109.5
O2—P1—C1	103.22 (7)	H3A—C3—H3B	109.5
O3—P1—C1	104.42 (7)	N1—C3—H3C	109.5
O5—P2—O6	117.19 (7)	H3A—C3—H3C	109.5
O5—P2—O4	111.67 (7)	H3B—C3—H3C	109.5
O6—P2—O4	106.96 (7)	P1—O1—Mg1iv	148.50 (8)
O5—P2—C1	104.71 (7)	P1—O2—Mg1	139.08 (7)
O6—P2—C1	108.34 (7)	P1—O3—H3D	109.5
O4—P2—C1	107.57 (7)	P2—O4—H4A	109.5
C3—N1—C2	109.91 (14)	P2—O5—Mg1	137.38 (7)

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

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···O3	0.91	2.57	3.0997 (18)	118
N1—H1B···O4v	0.91	2.31	3.1346 (18)	151
O3—H3D···O6vi	0.82	1.70	2.5011 (16)	166
O4—H4A···O2ii	0.82	1.81	2.6037 (16)	163

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