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The crystal structure of the title compound, [Mn(C9H5N4O)2(H2O)2], conventionally denoted Mn(EtO-TCA)2(H2O)2, where EtO-TCA is 2-ethoxy-1,1,3,3-tetra­cyano­propenide, is described. The EtO-TCA anions bridge MnII centers through one of the nitrile N atoms of each of their two di­cyano­methanide groups, thus forming dibridged chains along ab. These chains are linked into two-dimensional sheets through hydrogen bonding. The seven-atom bridge, which results in a long Mn...Mn intrachain interaction [9.0044 (4) Å], as well as the large interchain separations [8.3288 (4) and 8.5220 (4) Å] prohibit long-range magnetic ordering down to temperatures as low as 1.55 K.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103004360/sq1009sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103004360/sq1009Isup2.hkl
Contains datablock I

CCDC reference: 211733

Comment top

Coordination polymers formed by linking various transition metal centers with pseudohalides have been intensely studied over the past decade in an attempt to correlate their structural and magnetic properties. The dicyanamide (dca) anion, N(CN)2, which has a propensity to act as a bidentate ligand, mediates ferromagnetic coupling in Ni(dca)2 at a temperature as high as 21 K (Kurmoo & Kepert, 1998). More recently, various cyanocarbons have been investigated as potential superexchange ligands. We have found that the carbamoyldicyanomethanide (cdm) anion, (CN)2CC(O)NH2, favors the formation of the mononuclear [M(cdm)2(H2O)4]·2H2O complex (M is Mn, Co, Ni or Cu; Schlueter et al., 2003). In an attempt to provide additional nitrile binding sites, and thus enhance the probability of forming polymeric structures, we have turned our attention to the crystallization of various polynitrile transition metal complexes.

2-Alkoxytetracyanoallyl anions have recently been used as components of charge-transfer salts because of their synthetic versitility, large polarizabilities and potential for intermolecular contacts with the donor molecules. The 2-ethoxy-1,1,3,3-tetracyanopropenide (EtO-TCA) salts of tetrathiotetracene (TTT), (TTT)(EtO-TCA)(thf)0.25 (thf is tetrahydrofuran) and (TTT)(EtO-TCA)2, exhibit semiconducting behavior (Sekizaki, Tada et al., 2001). The salt with bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF), α-(BEDT-TTF)2(EtO-TCA)(thf)0.5, is also a semiconductor (Sekizaki Yamochi & Saito, 2001). The bis(ethylenedioxo)tetrathiafulvalene (BEDO-TTF) salt, (BEDO-TTF)2(EtO-TCA), exhibits successive metal-semiconductor and semiconductor-metal transitions near 150 K and 40 K, respectively (Sekizaki et al., 2002). Until this work, EtO-TCA has not been studied as the bridging component of transition-metal-based coordination polymers. In this paper, we report that EtO-TCA is capable of bridging transition metal ions to form the title Mn(EtO-TCA)2(H2O)2 complex, (I). \sch

Similar to the data reported for other structures of the EtO-TCA anion (Sekizaki, Tada et al., 2001), the C—C bond lengths of the tetracyanopropenide moiety of (I), 1.4022 (15)–1.4177 (16) Å, are intermediate between typical single and double bonds, indicating a delocalized electronic structure. The Cmethanide—Cnitrile bonds are about 0.01 Å longer for the non-coordinated nitrile groups than for the coordinated ones.

The EtO-TCA anions in (I) bridge two Mn atoms through one of the nitrile N atoms of each of its two dicyanomethanide units (Fig. 1). With respect to the ethoxy group, one coordinating nitrile is cis while the second is trans. The five-atom bridging moiety is markedly distorted from planarity. Intramolecular EtO-TCA planes are defined as by Sekizaki (Sekizaki, Tada et al., 2001). The propyl C atoms (C5, C6 and C7) define plane 1 (P1). The two dicyanomethanide planes, P2 (N1, C1, C5, C2 and N2) and P3 (N3, C3, C7, C4 and N4) are canted 32.08 (8)° with respect to each other. The r.m.s. deviation of P2 is 0.006 Å, with the greatest deviation, 0.010 (1) Å, occurring for atom C2. Similarly, for P3, the r.m.s. deviation is 0.004 Å, with the greatest deviation, 0.007 (1) Å, occurring for atom C3. The dihedral angles of P1 with P2 and P3 are 14.83 (15) and 20.64 (15)°, respectively. The C1—C5···C7—C4 torsion angle is 55.7 (3)°. Atoms C6, O1 and C8 define plane 4 (P4), which has a dihedral angle of 28.7 (1)° with P1.

Crystal-packing forces are responsible for distorting the EtO-TCA anion from the planar structure predicted by molecular orbital calculations. RHF/6–31 G* calculations have been used to predict the P1—P2, P2—P3, P1—P3, and P1—P4 dihedral angles as a function of the C1—C5···C7—C4 torsion angle (Sekizaki, Tada et al., 2001). These calculations are in line with the molecular structure of EtO-TCA as observed in (I), except for the P1—P4 dihedral angle, which is significantly less than predicted. A similar discrepancy was also observed in (TTT)(BuO-TCA) and attributed to crystal-packing forces by Sekizaki, Tada et al. (2001).

The centrosymmetric coordination sphere about the Mn atom in (I) consists of the O atoms of two water molecules and the nitrile N atoms (N2 and N4) of four EtO-TCA anions in an essentially octahedral environment. A distortion of 2.81 (5)° is seen in the N2—Mn—N4 angle (Table 1). The Mn—N and Mn—O bond lengths (Table 1) are typical for nitrile coordination to Mn (see e.g. Dalai et al., 2002; Schlueter et al., 2003).

The EtO-TCA anions act as bidentate ligands in (I), forming dibridged chains along the ab direction (Fig 2). The coordinating nitrile N atoms are on opposing dicyanomethanide groups of EtO-TCA, resulting in a seven-atom bridge and an intrachain Mn···Mn separation of 9.0044 (4) Å. Slightly shorter interchain Mn···Mn separations of 8.3288 (4) and 8.5220 (4) Å are also present.

Hydrogen bonding is observed with the H atoms of the coordinated water molecule. An intrachain hydrogen bond occurs between atom H21 and nitrile atom N3 (Fig. 1). Adjacent chains are assembled into sheets [parallel to the (111) plane] by interchain hydrogen bonding between atoms H22 and N1.

The large Mn···Mn separation and non-planar geometry of EtO-TCA in (I) are not conducive to magnetic ordering, and AC (alternating current) susceptibility measurements down to 1.55 K confirmed that no long-range magnetic order occurs in this structure. It is possible that magnetic ordering could occur in a related structure in which the EtO-TCA anions link transition metals via the nitrile N atoms on the same dicyanomethanide group. This would reduce the superexchange pathway from seven to five atoms and shorten the interchain metal···metal separation by more than an ångstrøm. Such a structure might be formed through the use of organic solvents, which would open the coordination site occupied by water, or by increasing the metal concentration during the crystallization process, thus increasing the chance of coordination to more than two of the four available nitrile N atoms.

Experimental top

Sodium 2-ethoxy-1,1,3,3-tetracyanopropenide (150 mg, 0.72 mmol), prepared according to the literature procedure of Middleton et al. (1957), was dissolved in water (10 ml) and combined with an ethanolic solution (10 ml) of pyrazine (Aldrich, 58 mg, 0.72 mmol). This solution was layered on top of an aqueous solution (10 ml) of manganese(II) nitrate hydrate (Aldrich, 64 mg, 0.36 mmol). After one month, clear colorless blocky crystals of (I) were collected from the concentrated solution by filtration. Decomposition begins near 453 K as the clear crystals become opaque, possibly as a result of water loss.

Refinement top

Ethoxy H atoms were placed geometrically and refined with a riding model, and with Uiso constrained to be 1.2 or 1.5Ueq of the methylene and methyl C atoms, respectively. Water H-atom positions were refined under distance and angle restraints, with Uiso constrained to be 1.5Ueq of atom O2.

Computing details top

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The atomic numbering scheme of (I), illustrating the EtO-TCA anion and including the coordination sphere of the Mn atoms that it is bound to. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The dashed line indicates interchain hydrogen bonding between atoms H21 and N3.
[Figure 2] Fig. 2. The dibridged chain structure of (I), which runs along the ab direction. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
catena-poly[[diaquamanganese(II)]-di-µ-1,1,3,3-tetracyano- 2-ethoxypropenido-κ4N1:N3] top
Crystal data top
[Mn(C9H5N4O)2(H2O)2]Z = 1
Mr = 461.31F(000) = 235
Triclinic, P1Dx = 1.363 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 8.3288 (4) ÅCell parameters from 1000 reflections
b = 8.5220 (4) Åθ = 2.3–32.0°
c = 9.3793 (5) ŵ = 0.63 mm1
α = 81.387 (2)°T = 298 K
β = 69.135 (2)°Block, colorless
γ = 64.589 (2)°0.56 × 0.30 × 0.17 mm
V = 561.88 (5) Å3
Data collection top
Siemens SMART CCD area-detector
diffractometer
3763 independent reflections
Radiation source: fine-focus sealed tube3321 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.022
area detector ω scansθmax = 32.0°, θmin = 2.3°
Absorption correction: integration
(SHELXTL; Sheldrick, 2001)
h = 1212
Tmin = 0.802, Tmax = 0.898k = 1212
7918 measured reflectionsl = 1313
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.091H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.0485P)2 + 0.0745P]
where P = (Fo2 + 2Fc2)/3
3763 reflections(Δ/σ)max = 0.014
148 parametersΔρmax = 0.30 e Å3
3 restraintsΔρmin = 0.29 e Å3
Crystal data top
[Mn(C9H5N4O)2(H2O)2]γ = 64.589 (2)°
Mr = 461.31V = 561.88 (5) Å3
Triclinic, P1Z = 1
a = 8.3288 (4) ÅMo Kα radiation
b = 8.5220 (4) ŵ = 0.63 mm1
c = 9.3793 (5) ÅT = 298 K
α = 81.387 (2)°0.56 × 0.30 × 0.17 mm
β = 69.135 (2)°
Data collection top
Siemens SMART CCD area-detector
diffractometer
3763 independent reflections
Absorption correction: integration
(SHELXTL; Sheldrick, 2001)
3321 reflections with I > 2σ(I)
Tmin = 0.802, Tmax = 0.898Rint = 0.022
7918 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0323 restraints
wR(F2) = 0.091H atoms treated by a mixture of independent and constrained refinement
S = 1.02Δρmax = 0.30 e Å3
3763 reflectionsΔρmin = 0.29 e Å3
148 parameters
Special details top

Experimental. The data collection nominally covered over a hemisphere of reciprocal space, by a combination of three sets of exposures; each set had a different ϕ angle for the crystal and each exposure covered 0.3° in ω. The crystal-to-detector distance was 4.02 cm. Coverage of the unique set was over 95% complete to at least 30.8° in θ, over 99% complete to at least 30.5° in θ. Crystal decay was monitored by repeating the initial 50 frames at the end of data collection and analyzing the duplicate reflections. Decay was found to be less than 1%, and no decay correction was therefore applied.

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
xyzUiso*/Ueq
Mn10.50000.00000.00000.03213 (8)
O10.43193 (12)0.39205 (13)0.33564 (11)0.0485 (2)
N10.2798 (2)0.0179 (2)0.51965 (15)0.0693 (4)
N20.20933 (14)0.03498 (16)0.13662 (13)0.0479 (3)
N30.05351 (17)0.22325 (18)0.14891 (14)0.0563 (3)
N40.38877 (17)0.71315 (14)0.02737 (15)0.0524 (3)
C10.21734 (17)0.08245 (18)0.41148 (14)0.0447 (3)
C20.05068 (15)0.09102 (15)0.19925 (13)0.0367 (2)
C30.06721 (16)0.29736 (15)0.04356 (14)0.0389 (2)
C40.31460 (17)0.56999 (15)0.05451 (15)0.0402 (2)
C50.14447 (14)0.16424 (15)0.27649 (12)0.0356 (2)
C60.26621 (14)0.31830 (14)0.22797 (13)0.0342 (2)
C70.21947 (15)0.39306 (14)0.08284 (13)0.0359 (2)
C80.60236 (18)0.4995 (2)0.3007 (2)0.0629 (4)
H8A0.59430.46500.20360.075*
H8B0.62050.62040.29390.075*
C90.7618 (2)0.4773 (3)0.4244 (3)0.0895 (7)
H9A0.87680.54740.40330.134*
H9B0.76910.51270.51980.134*
H9C0.74260.35750.43010.134*
O20.44706 (13)0.01725 (14)0.20677 (10)0.0471 (2)
H210.343 (2)0.048 (2)0.212 (2)0.071*
H220.521 (2)0.004 (2)0.2875 (18)0.071*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Mn10.02289 (11)0.02929 (12)0.03303 (12)0.00629 (8)0.00370 (8)0.00433 (8)
O10.0269 (4)0.0551 (5)0.0424 (5)0.0024 (4)0.0020 (3)0.0088 (4)
N10.0577 (8)0.0906 (10)0.0434 (7)0.0326 (8)0.0029 (6)0.0191 (6)
N20.0275 (4)0.0568 (6)0.0438 (6)0.0116 (4)0.0065 (4)0.0140 (5)
N30.0455 (6)0.0587 (7)0.0424 (6)0.0071 (5)0.0063 (5)0.0020 (5)
N40.0489 (6)0.0341 (5)0.0607 (7)0.0092 (5)0.0140 (5)0.0049 (5)
C10.0330 (5)0.0551 (7)0.0341 (6)0.0143 (5)0.0043 (4)0.0056 (5)
C20.0284 (5)0.0400 (5)0.0337 (5)0.0117 (4)0.0075 (4)0.0086 (4)
C30.0338 (5)0.0355 (5)0.0389 (6)0.0089 (4)0.0109 (4)0.0055 (4)
C40.0351 (5)0.0334 (5)0.0455 (6)0.0102 (4)0.0108 (5)0.0007 (4)
C50.0252 (4)0.0388 (5)0.0324 (5)0.0101 (4)0.0030 (4)0.0039 (4)
C60.0248 (4)0.0344 (5)0.0361 (5)0.0082 (4)0.0048 (4)0.0037 (4)
C70.0302 (5)0.0290 (5)0.0396 (5)0.0068 (4)0.0084 (4)0.0012 (4)
C80.0264 (5)0.0716 (10)0.0674 (10)0.0058 (6)0.0069 (6)0.0002 (8)
C90.0359 (8)0.1136 (18)0.0956 (15)0.0259 (10)0.0007 (9)0.0035 (13)
O20.0347 (4)0.0611 (6)0.0339 (4)0.0147 (4)0.0049 (3)0.0012 (4)
Geometric parameters (Å, º) top
Mn1—O22.1743 (10)C1—C51.4172 (16)
Mn1—N22.2084 (10)C2—C51.4079 (14)
Mn1—N4i2.2221 (11)C3—C71.4177 (16)
O1—C61.3314 (12)C4—C71.4059 (15)
O1—C81.4447 (17)C5—C61.4022 (15)
N1—C11.1424 (17)C6—C71.4093 (16)
N2—C21.1439 (14)C8—C91.482 (2)
N3—C31.1491 (16)O2—H210.824 (14)
N4—C41.1432 (16)O2—H220.816 (14)
O2ii—Mn1—O2180.00 (5)N1—C1—C5178.48 (15)
O2ii—Mn1—N289.89 (4)N2—C2—C5178.50 (14)
O2—Mn1—N290.11 (4)N3—C3—C7177.92 (13)
O2ii—Mn1—N2ii90.11 (4)N4—C4—C7178.11 (15)
O2—Mn1—N2ii89.89 (4)C6—C5—C2122.20 (10)
N2—Mn1—N2ii180.00 (3)C6—C5—C1119.45 (10)
O2ii—Mn1—N4i88.59 (5)C2—C5—C1118.29 (10)
O2—Mn1—N4i91.41 (5)O1—C6—C5112.98 (10)
N2—Mn1—N4i92.81 (5)O1—C6—C7122.44 (10)
N2ii—Mn1—N4i87.19 (5)C5—C6—C7124.55 (10)
O2ii—Mn1—N4iii91.41 (5)C4—C7—C6122.47 (10)
O2—Mn1—N4iii88.59 (5)C4—C7—C3115.00 (10)
N2—Mn1—N4iii87.19 (5)C6—C7—C3122.46 (10)
N2ii—Mn1—N4iii92.81 (5)O1—C8—C9107.99 (15)
N4i—Mn1—N4iii180.00 (7)Mn1—O2—H21116.5 (14)
C6—O1—C8122.62 (11)Mn1—O2—H22116.8 (14)
C2—N2—Mn1164.73 (11)H21—O2—H22104.6 (18)
C4—N4—Mn1iv168.27 (12)
O2ii—Mn1—N2—C293.5 (4)C2—C5—C6—C715.74 (19)
O2—Mn1—N2—C286.5 (4)C1—C5—C6—C7167.15 (12)
N4i—Mn1—N2—C2178.0 (4)O1—C6—C7—C419.80 (18)
N4iii—Mn1—N2—C22.0 (4)C5—C6—C7—C4158.06 (12)
C8—O1—C6—C5152.09 (13)O1—C6—C7—C3163.34 (12)
C8—O1—C6—C729.82 (19)C5—C6—C7—C318.80 (19)
C2—C5—C6—O1162.30 (11)C6—O1—C8—C9148.17 (16)
C1—C5—C6—O114.81 (17)
Symmetry codes: (i) x+1, y1, z; (ii) x+1, y, z; (iii) x, y+1, z; (iv) x1, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H21···N30.82 (1)2.13 (2)2.9223 (16)161 (2)
O2—H22···N1v0.82 (1)2.02 (1)2.8366 (15)176 (2)
Symmetry code: (v) x+1, y, z1.

Experimental details

Crystal data
Chemical formula[Mn(C9H5N4O)2(H2O)2]
Mr461.31
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)8.3288 (4), 8.5220 (4), 9.3793 (5)
α, β, γ (°)81.387 (2), 69.135 (2), 64.589 (2)
V3)561.88 (5)
Z1
Radiation typeMo Kα
µ (mm1)0.63
Crystal size (mm)0.56 × 0.30 × 0.17
Data collection
DiffractometerSiemens SMART CCD area-detector
diffractometer
Absorption correctionIntegration
(SHELXTL; Sheldrick, 2001)
Tmin, Tmax0.802, 0.898
No. of measured, independent and
observed [I > 2σ(I)] reflections
7918, 3763, 3321
Rint0.022
(sin θ/λ)max1)0.746
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.091, 1.02
No. of reflections3763
No. of parameters148
No. of restraints3
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.30, 0.29

Computer programs: SMART (Siemens, 1995), SAINT (Bruker, 2001), SAINT, SHELXTL (Sheldrick, 2001), SHELXTL.

Selected geometric parameters (Å, º) top
Mn1—O22.1743 (10)N4—C41.1432 (16)
Mn1—N22.2084 (10)C1—C51.4172 (16)
Mn1—N4i2.2221 (11)C2—C51.4079 (14)
O1—C61.3314 (12)C3—C71.4177 (16)
O1—C81.4447 (17)C4—C71.4059 (15)
N1—C11.1424 (17)C5—C61.4022 (15)
N2—C21.1439 (14)C6—C71.4093 (16)
N3—C31.1491 (16)C8—C91.482 (2)
O2ii—Mn1—N289.89 (4)C6—C5—C2122.20 (10)
O2ii—Mn1—N4i88.59 (5)C6—C5—C1119.45 (10)
N2ii—Mn1—N4i87.19 (5)C2—C5—C1118.29 (10)
C6—O1—C8122.62 (11)O1—C6—C5112.98 (10)
C2—N2—Mn1164.73 (11)O1—C6—C7122.44 (10)
C4—N4—Mn1iii168.27 (12)C5—C6—C7124.55 (10)
N1—C1—C5178.48 (15)C4—C7—C6122.47 (10)
N2—C2—C5178.50 (14)C4—C7—C3115.00 (10)
N3—C3—C7177.92 (13)C6—C7—C3122.46 (10)
N4—C4—C7178.11 (15)O1—C8—C9107.99 (15)
C8—O1—C6—C5152.09 (13)O1—C6—C7—C419.80 (18)
C8—O1—C6—C729.82 (19)C5—C6—C7—C4158.06 (12)
C2—C5—C6—O1162.30 (11)O1—C6—C7—C3163.34 (12)
C1—C5—C6—O114.81 (17)C5—C6—C7—C318.80 (19)
C2—C5—C6—C715.74 (19)C6—O1—C8—C9148.17 (16)
C1—C5—C6—C7167.15 (12)
Symmetry codes: (i) x+1, y1, z; (ii) x+1, y, z; (iii) x1, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H21···N30.824 (14)2.130 (15)2.9223 (16)161.3 (19)
O2—H22···N1iv0.816 (14)2.022 (14)2.8366 (15)175.6 (19)
Symmetry code: (iv) x+1, y, z1.
 

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