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The crystal structure of [Mn(C4H2N3O)2(H2O)4]·2H2O, conventionally abbreviated [Mn(cdm)2(H2O)4]·2H2O, where cdm is carbamoyldi­cyano­methanide, is described. The bond lengths and distances are comparable to those previously reported for the isomorphous Ni and Co analogs. Molecular units are formed by coordination of the nitrile N atoms of two cdm anions and four water mol­ecules to the manganese(II) cation. Although these mononuclear molecular species are connected via hydrogen bonding, no magnetic ordering was observed down to 1.55 K.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102020334/fg1671sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102020334/fg1671Isup2.hkl
Contains datablock I

CCDC reference: 204022

Comment top

Pseudohalide transition metal complexes have been increasingly studied over the past decade because of their interesting structural and magnetic properties. The dicyanamide anion, N(CN)2, has been shown to be a versatile ligand because it can coordinate to a metal ion in several ways (Manson, 2003). Bidentate bonding through the nitrile N atoms is a common mode for the formation of coordination polymers. Several of these materials exhibit cooperative magnetic behavior, including ferromagnetism at temperatures as high as 21 K for Ni[N(CN)2]2 (Kurmoo & Kepert, 1998). More recently, attention has turned to other polynitrile ligands as prospective building blocks for the construction of polymeric transition metal complexes. The tricyanomethanide (tcm) anion, C(CN)3, is one of the simplest that is capable of forming infinite chains or sheets (Hoshino et al., 1999). Another promising candidate is the carbamoyldicyanomethanide (cdm) anion (Trofimenko et al., 1962), CN2CC(O)NH2, which is a derivative of tcm in which one nitrile group is replaced by C(O)NH2. It is possible that cooperative magnetic behavior would occur in a polymeric structure in which cdm acts as a bidentate ligand coordinating to adjacent metal centers through its nitrile N atoms. While attempting to synthesize the anionic polymeric network [Mn(cdm)3], we obtained the previously unreported title salt, [Mn{(CN)2CC(O)NH2)}2(H2O)4]·2H2O, (I). \sch

The synthesis of [M(cdm)2]·6H2O, with M = Co, Ni, Cu, has been reported previously (Skopenko & Lampeka, 1981). It was erroneously inferred from the IR spectroscopic data of the Co and Ni salts that the inner coordination sphere contained only the cdm anion. Subsequently, the crystal structures of the Co (Shi et al., 2002) and Ni (Shi et al., 2001) salts, determined by single-crystal X-ray diffraction, revealed that these salts are mononuclear complexes, in which the metal atom is coordinated in a slightly distorted octahedron by the nitrile N atoms of two cdm anions and the O atoms of four water molecules. The crystal structure contains cavities in which non-coordinated water molecules reside.

The Mn derivative of [M{(CN)2CC(O)NH2)}2(H2O)4]·2H2O is isomorphous with the Co and Ni analogs. The structure is characterized by mononuclear molecular [Mn{(CN)2CC(O)NH2)}2(H2O)4] units (Fig. 1). The Mn atom is located on an inversion center. The coordination sphere consists of the O atoms of four water molecules and the nitrile N atoms of two cdm anions. The M—N and M—O bonds (Table 1) are about 0.10 to 0.15 Å longer in the Mn structure than in the Co and Ni derivatives, respectively. The cdm anion is essentially planar (r.m.s. deviation 0.0129 Å), with the greatest deviation from planarity being 0.0233 (10) Å for the methanide atom C3. The C—C—C angles about the methanide C atom are 118.04 (10), 119.76 (9), and 122.15 (9)°, and sum to 359.95°, indicating essentially sp2 hybridization.

It was clear from examination of difference-map plots that water atoms O3 and O4 had, in each case, one of the two H atoms disordered over two adjacent sites. Initial refinement of tied occupancy values for these disordered H atoms led to values which were not markedly different from a 50/50 disorder and, in the final refinement cycles, the disordered H atom occupancies were set at 0.5 (see Experimental).

The plane of the cdm ligand lies at an angle of 71.87 (3)° with respect to the N1—Mn1—O2 plane and 19.76 (5)° with respect to the N1—Mn1—O3 plane. The cdm ligands from neighboring molecules interdigitate along the a+c diagonal, forming cdm layers which are separated by a water-rich layer containing both the coordinated and non-coordinated water molecules (Fig. 2).

Extensive hydrogen bonding gives the structure of (I) three-dimensional character. The carbonyl atom O1 projects toward the water-rich layer, forming hydrogen-bonding interactions with all three (both the coordinated and non-coordinated) water molecules. The amine H atoms have interactions with both atom O4 of the non-coordinated water molecule and the non-coordinated nitrile atom N2. Atom N2 is also bound to one of the H atoms of O2. Hydrogen-bonding contacts are present between the coordinated water molecule associated with atom O3 and the non-coordinated water molecule associated with atom O4. This latter contact was found to be disordered where, half of the time, the hydrogen bonding was through atom H32, with atom O3 acting as the hydrogen-bond donor and atom O4 the acceptor, and the other half of the time, the hydrogen bonding was through atom H43, with atom O4 the donor and atom O3 the acceptor (see Table 2).

The closest Mn atoms in the structure of (I) are separated by 7.4144 (3) Å [Mn1 at (1/2,0,0) to Mn1 at (1,1/2,1/2)]. An efficient superexchange pathway, preferably one containing covalent bonds between magnetic centers, is required for long-range magnetic order to occur. The molecular nature of the structure of (I) is not conducive to magnetic ordering. An AC susceptibilty measurement down to 1.55 K confirmed that no magnetic ordering occurs in this structure. It is possible that magnetic ordering could occur in a related structure in which the coordinated water molecules are replaced with bridging ligands. Such a structure might be formed through the use of organic solvents or by introducing a neutral bidentate coordinating ligand such as pyrazine.

Experimental top

Tetrabutylammonium bromide (322 mg, 1 mmol) and potassium carbamoyldicyanomethanide (441 mg, 3 mmol) (Trofimenko et al., 1962) were combined in water (20 ml). This solution was layered on top of an aqueous solution (10 ml) of manganese(II) bromide (215 mg, 1 mmol). This crystallization mixture was allowed to evaporate slowly. After three months, clear colorless blocks of (I) were collected from the concentrated solution by filtration. Upon heating to 373 K, the crystals turned opaque white, presumably from the loss of the non-coordinated water. Further heating to 498 K resulted in decomposition.

Refinement top

The two H atoms bonded to atom N3 were placed geometrically and refined with a riding model. Coordinates for the disordered and non-disordered water H atoms were obtained from difference maps. These H-atom coordinates were then refined subject to an O—H DFIX restraint (SHELXTL; Sheldrick, 2001) of 0.82 (3) Å (eight restraints). All the H-atom Uiso values were constrained to be 1.2 times Ueq of the carrier atom.

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. A view of the mononuclear complex, (I), with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Unlabelled atoms are related by an inversion center to the labelled atoms. H-atom positions H32, H33, H42 and H43 are all half occupied. Thus, half of the time, hydrogen bonding occurs between atoms H32 and O4 (pictured), while the other half of the time, hydrogen bonding is between atoms H43 and O3 (not pictured).
[Figure 2] Fig. 2. A packing diagram for (I) projected approximately along the b axis. Equivalent isotropic spheres are drawn at the 50% probability level.
Tetraaquabis(carbamoyldicyanomethanido-κN)manganese(II) dihydrate top
Crystal data top
[Mn(C4H2N3O)2(H2O)4]·2H2OF(000) = 390
Mr = 379.21Dx = 1.541 Mg m3
Monoclinic, P21/nMelting point: 498 K
Hall symbol: -P 2ynMo Kα radiation, λ = 0.71073 Å
a = 9.5234 (4) ÅCell parameters from 834 reflections
b = 7.4343 (4) Åθ = 3.3–28.1°
c = 12.1939 (6) ŵ = 0.86 mm1
β = 108.777 (2)°T = 298 K
V = 817.38 (7) Å3Block, colorless
Z = 20.44 × 0.35 × 0.30 mm
Data collection top
Siemens SMART CCD area-detector
diffractometer
1927 independent reflections
Radiation source: fine-focus sealed tube1789 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.018
area detector ω scansθmax = 28.3°, θmin = 2.4°
Absorption correction: integration
(SHELXTL; Sheldrick, 2001)
h = 1212
Tmin = 0.728, Tmax = 0.807k = 97
5354 measured reflectionsl = 1616
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)] = 0.021Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.059H atoms treated by a mixture of independent and constrained refinement
S = 1.07 w = 1/[σ2(Fo2) + (0.0305P)2 + 0.1424P]
where P = (Fo2 + 2Fc2)/3
1927 reflections(Δ/σ)max < 0.001
131 parametersΔρmax = 0.30 e Å3
8 restraintsΔρmin = 0.17 e Å3
Crystal data top
[Mn(C4H2N3O)2(H2O)4]·2H2OV = 817.38 (7) Å3
Mr = 379.21Z = 2
Monoclinic, P21/nMo Kα radiation
a = 9.5234 (4) ŵ = 0.86 mm1
b = 7.4343 (4) ÅT = 298 K
c = 12.1939 (6) Å0.44 × 0.35 × 0.30 mm
β = 108.777 (2)°
Data collection top
Siemens SMART CCD area-detector
diffractometer
1927 independent reflections
Absorption correction: integration
(SHELXTL; Sheldrick, 2001)
1789 reflections with I > 2σ(I)
Tmin = 0.728, Tmax = 0.807Rint = 0.018
5354 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0218 restraints
wR(F2) = 0.059H atoms treated by a mixture of independent and constrained refinement
S = 1.07Δρmax = 0.30 e Å3
1927 reflectionsΔρmin = 0.17 e Å3
131 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 4.97 cm. Coverage of the unique set was over 95% complete to at least 28° 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*/UeqOcc. (<1)
Mn10.50000.00000.00000.02597 (8)
O10.07867 (8)0.26994 (11)0.18492 (7)0.03217 (17)
O20.65084 (10)0.10667 (13)0.15895 (8)0.0408 (2)
H210.7366 (17)0.146 (2)0.1678 (13)0.049*
H220.6214 (18)0.163 (2)0.2047 (14)0.049*
O30.52764 (10)0.26743 (11)0.08261 (7)0.03333 (17)
H310.5429 (16)0.260 (2)0.1501 (12)0.040*
H320.588 (3)0.337 (4)0.069 (2)0.040*0.50
H330.453 (3)0.338 (4)0.056 (2)0.040*0.50
N10.31415 (12)0.04414 (15)0.06808 (10)0.0392 (2)
N20.02456 (15)0.20122 (16)0.19245 (12)0.0550 (3)
N30.09450 (11)0.40125 (13)0.12320 (9)0.0392 (2)
H3A0.05830.50550.12890.047*
H3B0.17030.39200.09980.047*
C10.21594 (12)0.05957 (15)0.10211 (9)0.0294 (2)
C20.02883 (13)0.07441 (16)0.17037 (10)0.0346 (2)
C30.09456 (11)0.08143 (14)0.14216 (9)0.0285 (2)
C40.03310 (11)0.25416 (14)0.15057 (8)0.0260 (2)
O40.71227 (11)0.50752 (12)0.01857 (9)0.0401 (2)
H410.7683 (18)0.561 (2)0.0698 (13)0.048*
H420.648 (3)0.580 (4)0.008 (3)0.048*0.50
H430.673 (4)0.428 (4)0.042 (3)0.048*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Mn10.02304 (13)0.02747 (13)0.03187 (13)0.00011 (8)0.01506 (9)0.00169 (8)
O10.0262 (4)0.0377 (4)0.0381 (4)0.0030 (3)0.0180 (3)0.0016 (3)
O20.0315 (4)0.0558 (6)0.0401 (4)0.0114 (4)0.0183 (3)0.0142 (4)
O30.0370 (4)0.0323 (4)0.0330 (4)0.0018 (3)0.0145 (3)0.0001 (3)
N10.0338 (5)0.0417 (5)0.0510 (6)0.0047 (4)0.0260 (5)0.0006 (5)
N20.0552 (7)0.0427 (6)0.0762 (8)0.0006 (5)0.0336 (6)0.0172 (6)
N30.0370 (5)0.0306 (5)0.0582 (6)0.0003 (4)0.0267 (5)0.0023 (4)
C10.0276 (5)0.0300 (5)0.0332 (5)0.0026 (4)0.0134 (4)0.0006 (4)
C20.0318 (5)0.0346 (6)0.0424 (6)0.0061 (4)0.0188 (5)0.0064 (5)
C30.0255 (5)0.0313 (5)0.0337 (5)0.0016 (4)0.0165 (4)0.0027 (4)
C40.0218 (4)0.0330 (5)0.0245 (4)0.0006 (4)0.0091 (4)0.0006 (4)
O40.0333 (5)0.0351 (5)0.0533 (6)0.0028 (3)0.0159 (4)0.0037 (4)
Geometric parameters (Å, º) top
Mn1—O22.1580 (9)N2—C21.1436 (17)
Mn1—O32.2059 (8)N3—C41.3322 (14)
Mn1—N12.2081 (9)N3—H3A0.86
Mn1—Mn1i7.4144 (3)N3—H3B0.86
O1—C41.2686 (12)C1—C31.4016 (14)
O2—H210.841 (15)C2—C31.4111 (16)
O2—H220.815 (15)C3—C41.4285 (14)
O3—H310.790 (14)O4—H410.788 (15)
O3—H320.83 (2)O4—H420.80 (3)
O3—H330.86 (2)O4—H430.80 (2)
N1—C11.1445 (14)
O2—Mn1—O2ii180Mn1—O3—H33114.9 (19)
O2—Mn1—O388.51 (4)H31—O3—H33107 (2)
O2ii—Mn1—O391.49 (4)H32—O3—H3395 (3)
O2—Mn1—O3ii91.49 (4)C1—N1—Mn1177.06 (11)
O3—Mn1—O3ii180C4—N3—H3A120.0
O2—Mn1—N189.43 (4)C4—N3—H3B120.0
O2ii—Mn1—N190.57 (4)H3A—N3—H3B120.0
O3—Mn1—N187.39 (4)N1—C1—C3178.81 (13)
O3ii—Mn1—N192.61 (4)N2—C2—C3179.50 (14)
O2—Mn1—N1ii90.57 (4)C1—C3—C2118.04 (10)
O3—Mn1—N1ii92.61 (4)C1—C3—C4122.15 (9)
N1—Mn1—N1ii180C2—C3—C4119.76 (9)
Mn1—O2—H21125.5 (10)O1—C4—N3119.30 (10)
Mn1—O2—H22121.7 (12)O1—C4—C3120.90 (9)
H21—O2—H22105.6 (15)N3—C4—C3119.79 (9)
Mn1—O3—H31111.4 (11)H41—O4—H42102 (3)
Mn1—O3—H32117.6 (19)H41—O4—H43112 (3)
H31—O3—H32110 (2)H42—O4—H43105 (4)
C1—C3—C4—O1178.58 (10)C1—C3—C4—N32.11 (16)
C2—C3—C4—O11.15 (15)C2—C3—C4—N3179.55 (11)
Symmetry codes: (i) x+3/2, y+1/2, z+1/2; (ii) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3A···N2iii0.862.523.3688 (16)168
N3—H3B···O4ii0.862.263.0078 (14)145
O2—H21···O1iv0.84 (2)1.94 (2)2.7721 (12)172 (2)
O2—H22···N2v0.82 (2)2.05 (2)2.8587 (14)174 (2)
O3—H31···O1vi0.79 (1)1.94 (1)2.7317 (12)178 (2)
O3—H32···O40.83 (2)1.96 (2)2.7877 (12)173 (3)
O3—H33···O4vii0.86 (2)1.93 (2)2.7797 (13)174 (3)
O4—H41···O1viii0.79 (2)2.09 (2)2.8664 (13)171 (2)
O4—H42···O3vii0.80 (3)1.99 (3)2.7797 (13)173 (3)
O4—H43···O30.80 (2)2.01 (3)2.7877 (12)165 (3)
Symmetry codes: (ii) x+1, y, z; (iii) x, y+1, z; (iv) x+1, y, z; (v) x+1/2, y+1/2, z+1/2; (vi) x+1/2, y1/2, z+1/2; (vii) x+1, y1, z; (viii) x+1, y1, z.

Experimental details

Crystal data
Chemical formula[Mn(C4H2N3O)2(H2O)4]·2H2O
Mr379.21
Crystal system, space groupMonoclinic, P21/n
Temperature (K)298
a, b, c (Å)9.5234 (4), 7.4343 (4), 12.1939 (6)
β (°) 108.777 (2)
V3)817.38 (7)
Z2
Radiation typeMo Kα
µ (mm1)0.86
Crystal size (mm)0.44 × 0.35 × 0.30
Data collection
DiffractometerSiemens SMART CCD area-detector
diffractometer
Absorption correctionIntegration
(SHELXTL; Sheldrick, 2001)
Tmin, Tmax0.728, 0.807
No. of measured, independent and
observed [I > 2σ(I)] reflections
5354, 1927, 1789
Rint0.018
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.021, 0.059, 1.07
No. of reflections1927
No. of parameters131
No. of restraints8
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.30, 0.17

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

Selected geometric parameters (Å, º) top
Mn1—O22.1580 (9)N2—C21.1436 (17)
Mn1—O32.2059 (8)N3—C41.3322 (14)
Mn1—N12.2081 (9)C1—C31.4016 (14)
O1—C41.2686 (12)C2—C31.4111 (16)
N1—C11.1445 (14)C3—C41.4285 (14)
O2—Mn1—O388.51 (4)C1—C3—C4122.15 (9)
O3—Mn1—N187.39 (4)C2—C3—C4119.76 (9)
C1—N1—Mn1177.06 (11)O1—C4—N3119.30 (10)
N1—C1—C3178.81 (13)O1—C4—C3120.90 (9)
N2—C2—C3179.50 (14)N3—C4—C3119.79 (9)
C1—C3—C2118.04 (10)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3A···N2i0.862.523.3688 (16)168
N3—H3B···O4ii0.862.263.0078 (14)145
O2—H21···O1iii0.841 (15)1.937 (15)2.7721 (12)171.8 (15)
O2—H22···N2iv0.815 (15)2.048 (16)2.8587 (14)173.8 (16)
O3—H31···O1v0.790 (14)1.942 (14)2.7317 (12)177.6 (16)
O3—H32···O40.83 (2)1.96 (2)2.7877 (12)173 (3)
O3—H33···O4vi0.86 (2)1.93 (2)2.7797 (13)174 (3)
O4—H41···O1vii0.788 (15)2.086 (16)2.8664 (13)170.9 (16)
O4—H42···O3vi0.80 (3)1.99 (3)2.7797 (13)173 (3)
O4—H43···O30.80 (2)2.01 (3)2.7877 (12)165 (3)
Symmetry codes: (i) x, y+1, z; (ii) x+1, y, z; (iii) x+1, y, z; (iv) x+1/2, y+1/2, z+1/2; (v) x+1/2, y1/2, z+1/2; (vi) x+1, y1, z; (vii) x+1, y1, z.
 

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