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The title compound, hexa­ammonium tetra-μ3-selenido-tetra­kis­(tri­cyano­molybdenum) hexahydrate, is isostructural with the Mo/S, W/S and W/Se analogues. The structure contains disordered cyclic hydrogen-bonded [{(NH4)(H2O)}3]3+ cations and [Mo4Se4(CN)12]6− cluster anions with \overline 43m symmetry. The cation assembly consists of alternating ammonium and water mol­ecules linked by N—H...O hydrogen bonds. The anion has a typical cubane cluster structure. The cations and anions are linked together by hydrogen bonds involving the terminal N atoms of the CN groups.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199015644/gs1060sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270199015644/gs1060Isup2.hkl
Contains datablock I

Comment top

Cuboidal clusters with bridging chalcogenide ligands are known for a wide variety of transition metals (Holm, 1992; Coucouvanis, 1991; Saito, 1995, 1997; Shibahara, 1991, 1993; Müller, 1986). Previously, we have prepared and structurally investigated some salts of alkali metal cations and cyanide cluster anions of the general formula [M4Q4(CN)12]n-, where M = Mo, Q = Te, or M = W, Q = S, Se or Te (Fedin, Kalinina et al., 1999). All these compounds belong to triclinic, monoclinic or orthorhombic crystal systems and the anions are slightly distorted from ideal Td point symmetry.

Recently, we have found that Mo/W/S/Se anions can give high symmetry cubic crystal structures with six ammonium cations and six water molecules. Three of them, for M = Mo/Q = S and M = W/Q = S or Se, were structurally investigated at room temperature (Fedin, Samsonenko et al., 2000). They appeared to be isostructural, the anions having the ideal Td point symmetry for metal and chalcogen atoms. Unfortunately, our attemts to find the H atom positions was unsuccessful, due to the disorder of the cations.

In the present article, we report the synthesis and low temperature crystal structure investigation of (NH4)6[Mo4Se4(CN)12]·6H2O, (I), which is isostructural with the Mo/S, W/S and W/Se analogues.

The structure of (I) contains an unusual [{(NH4)(H2O)}3]3+ cation (Fig 1a). This is a ring of alternating ammonium and water molecules linked by NH···O hydrogen bonds. The ring is not planar; it has a chair conformation. The cation assembly is disordered relative to the pseudo-rotation around the centre of the ring in such a way that each position is statistically occupied by one half of NH4+ and one half of H2O. Therefore, the central atom, O1, has a mixed atomic scattering factor, 0.5 N + 0.5O. Due to the low temperature of the experiment we have found the positions of the H atoms. Two of them, H1 and H3, are fully occupied. They correspond to the water molecule or two of the four H atoms of the NH4+ cations. The position of H2 is half-occupied and corresponds to the other two H atoms of the ammonium cations. The N···O hydrogen-bond distance is 2.80 (2) Å, with an angle of 166 (5)° at the H atom.

The anion (Fig. 1 b) has a typical cubane cluster structure and possesses the highest possible point symmetry, Td. Mo—Mo and Mo—Se distances are close to those found for [W4Se4(CN)12]6- (Fedin, Kalinina et al., 1999; Fedin, Samsonenko et al., 1999).

The cations and anions are linked together by hydrogen bonds involving the terminal N atoms of the CN groups (Fig. 2). For each disordered water/ammonium site, there is a hydrogen bond with O/N···N = 2.86 (3) Å and an angle of 174 (17)° at the H1 atom.

Experimental top

A mixture of Mo3Se7Br4 (1.00 g, 0.862 mmol) and KCN (1.00 g, 15.3 mmol) was heated in a sealed Pyrex tube at 703 K for 48 h. The product was added to water (20 ml) and the mixture was refluxed for 1 h and filtered. The potassium salt isolated by addition of methanol was dissolved in CH3COONH4 (1M, 10 ml) and the mixture was allowed to stand at 293 K for 5–7 d. Dark red-brown octahedral crystals were isolated by filtration, washed with methanol and dried in air (yield 0.10 g, 12%). Analysis calculated for C12H36Mo4N18O6Se4: C 11.74, H 2.95, N 20.53%; found: C 11.54, H 3.00, N 20.20%; IR (KBr): 2132 (CN) cm-1; UV-visible absorption spectrum of an aqueous solution, λ (ε in M-1cm-1): 340 (9680), 460 (1950) sh, 530 s h, 690 (310) nm.

Refinement top

The largest difference peak is near the anion, 0.6 Å from Se1. The deepest hole is near the disordered cation, 1.36 Å from H3.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Figures top
[Figure 1] Fig. 1. View of the structure of (a) the cation and (b) the anion of (I). The disordered positions of the H atoms are shown as dashed circles and displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. The crystal packing in (I). Hydrogen bonds are shown as dashed lines.
hexaammonium tetra-µ3-selenido-tetrakis[tricyanomolybdenum] hexahydrate top
Crystal data top
(NH4)6[Mo4Se4(CN)12]·6H2ODx = 2.257 Mg m3
Mr = 1228.19Mo Kα radiation, λ = 0.71073 Å
Cubic, Pn3mCell parameters from 4887 reflections
Hall symbol: -P 4bc 2bc 3θ = 2.9–28.6°
a = 12.180 (1) ŵ = 5.44 mm1
V = 1806.9 (3) Å3T = 160 K
Z = 2Octahedron, black
F(000) = 11720.20 × 0.18 × 0.15 mm
Data collection top
Siemens SMART CCD
diffractometer
468 independent reflections
Radiation source: fine-focus sealed tube384 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.039
Detector resolution: 8.125 pixels mm-1θmax = 28.7°, θmin = 2.4°
ω rotation with narrow frames scansh = 716
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)
k = 1615
Tmin = 0.784, Tmax = 0.928l = 1515
10436 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.068Only H-atom coordinates refined
wR(F2) = 0.184 w = 1/[σ2(Fo2) + (0.0111P)2 + 84.4748P]
where P = (Fo2 + 2Fc2)/3
S = 1.48(Δ/σ)max = 0.007
468 reflectionsΔρmax = 0.97 e Å3
33 parametersΔρmin = 1.13 e Å3
4 restraintsExtinction correction: SHELXTL (Sheldrick, 1998), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.00004 (14)
Crystal data top
(NH4)6[Mo4Se4(CN)12]·6H2OZ = 2
Mr = 1228.19Mo Kα radiation
Cubic, Pn3mµ = 5.44 mm1
a = 12.180 (1) ÅT = 160 K
V = 1806.9 (3) Å30.20 × 0.18 × 0.15 mm
Data collection top
Siemens SMART CCD
diffractometer
468 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)
384 reflections with I > 2σ(I)
Tmin = 0.784, Tmax = 0.928Rint = 0.039
10436 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0684 restraints
wR(F2) = 0.184Only H-atom coordinates refined
S = 1.48 w = 1/[σ2(Fo2) + (0.0111P)2 + 84.4748P]
where P = (Fo2 + 2Fc2)/3
468 reflectionsΔρmax = 0.97 e Å3
33 parametersΔρmin = 1.13 e Å3
Special details top

Experimental. none

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)
Mo10.33379 (12)0.33379 (12)0.16621 (12)0.0184 (7)
Se10.13358 (15)0.36642 (15)0.13358 (15)0.0191 (7)
C10.3450 (11)0.5115 (16)0.1550 (11)0.031 (4)
N10.3495 (12)0.6041 (14)0.1505 (12)0.046 (5)
O10.1056 (9)0.6695 (14)0.1056 (9)0.033 (3)0.50
N20.1056 (9)0.6695 (14)0.1056 (9)0.033 (3)0.50
H10.117 (11)0.749 (4)0.117 (11)0.030*
H20.029 (9)0.64 (2)0.116 (9)0.030*0.50
H30.159 (4)0.641 (15)0.159 (4)0.030*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Mo10.0184 (7)0.0184 (7)0.0184 (7)0.0006 (6)0.0006 (6)0.0006 (6)
Se10.0191 (7)0.0191 (7)0.0191 (7)0.0005 (7)0.0005 (7)0.0005 (7)
C10.031 (6)0.032 (10)0.031 (6)0.013 (5)0.005 (8)0.013 (5)
N10.057 (8)0.024 (9)0.057 (8)0.006 (6)0.005 (11)0.006 (6)
O10.035 (5)0.028 (8)0.035 (5)0.001 (5)0.002 (7)0.001 (5)
N20.035 (5)0.028 (8)0.035 (5)0.001 (5)0.002 (7)0.001 (5)
Geometric parameters (Å, º) top
Mo1—Mo1i2.886 (4)Mo1—C1v2.17 (2)
Mo1—Mo1ii2.887 (4)Se1—Mo1i2.502 (3)
Mo1—Mo1iii2.887 (4)Se1—Mo1ii2.502 (3)
Mo1—Se12.502 (3)C1—N11.13 (2)
Mo1—Se1i2.502 (3)O1—H10.99 (3)
Mo1—Se1ii2.503 (3)O1—H20.99 (3)
Mo1—C12.17 (2)O1—H30.99 (3)
Mo1—C1iv2.17 (2)
Mo1i—Mo1—Mo1ii60.0C1—Mo1—Mo1iii138.5 (3)
Mo1i—Mo1—Mo1iii60.0C1v—Mo1—Mo1iii95.1 (5)
Mo1ii—Mo1—Mo1iii60.0C1iv—Mo1—Se1i83.9 (3)
Se1i—Mo1—Mo1i54.78 (6)C1—Mo1—Se1i161.9 (5)
Se1—Mo1—Mo1i54.78 (6)C1v—Mo1—Se1i83.9 (3)
Se1ii—Mo1—Mo1i102.98 (7)C1iv—Mo1—Se183.9 (3)
Se1i—Mo1—Mo1ii102.98 (7)C1—Mo1—Se183.9 (3)
Se1—Mo1—Mo1ii54.78 (6)C1v—Mo1—Se1161.9 (5)
Se1ii—Mo1—Mo1ii54.78 (6)C1iv—Mo1—Se1ii161.9 (5)
Se1i—Mo1—Mo1iii54.78 (6)C1—Mo1—Se1ii83.9 (3)
Se1—Mo1—Mo1iii102.98 (7)C1v—Mo1—Se1ii83.9 (3)
Se1ii—Mo1—Mo1iii54.78 (6)C1iv—Mo1—C182.6 (8)
Se1i—Mo1—Se1106.52 (8)C1iv—Mo1—C1v82.6 (8)
Se1i—Mo1—Se1ii106.52 (8)C1—Mo1—C1v82.6 (8)
Se1—Mo1—Se1ii106.52 (8)Mo1i—Se1—Mo170.4 (1)
C1iv—Mo1—Mo1i95.1 (5)Mo1i—Se1—Mo1ii70.4 (1)
C1—Mo1—Mo1i138.5 (3)Mo1—Se1—Mo1ii70.4 (1)
C1v—Mo1—Mo1i138.5 (3)N1—C1—Mo1179 (2)
C1iv—Mo1—Mo1ii138.5 (3)H1—O1—H2116 (10)
C1—Mo1—Mo1ii95.1 (5)H1—O1—H399 (10)
C1v—Mo1—Mo1ii138.5 (3)H2—O1—H3115 (10)
C1iv—Mo1—Mo1iii138.5 (3)
Symmetry codes: (i) x+1/2, y+1/2, z; (ii) x+1/2, y, z+1/2; (iii) x, y+1/2, z+1/2; (iv) z+1/2, x, y+1/2; (v) y, z+1/2, x+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N1vi0.99 (3)1.88 (4)2.86 (3)174 (17)
O1—H2···O1vii0.99 (3)1.82 (3)2.80 (2)166 (5)
Symmetry codes: (vi) x+1/2, y+3/2, z; (vii) z, x+1/2, y1/2.

Experimental details

Crystal data
Chemical formula(NH4)6[Mo4Se4(CN)12]·6H2O
Mr1228.19
Crystal system, space groupCubic, Pn3m
Temperature (K)160
a (Å)12.180 (1)
V3)1806.9 (3)
Z2
Radiation typeMo Kα
µ (mm1)5.44
Crystal size (mm)0.20 × 0.18 × 0.15
Data collection
DiffractometerSiemens SMART CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1997)
Tmin, Tmax0.784, 0.928
No. of measured, independent and
observed [I > 2σ(I)] reflections
10436, 468, 384
Rint0.039
(sin θ/λ)max1)0.675
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.184, 1.48
No. of reflections468
No. of parameters33
No. of restraints4
H-atom treatmentOnly H-atom coordinates refined
w = 1/[σ2(Fo2) + (0.0111P)2 + 84.4748P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)0.97, 1.13

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SAINT, SHELXTL (Sheldrick, 1998), SHELXTL and local programs.

Selected geometric parameters (Å, º) top
Mo1—Mo1i2.886 (4)Mo1—C12.17 (2)
Mo1—Se12.502 (3)C1—N11.13 (2)
Se1—Mo1—Mo1i54.78 (6)C1—Mo1—Mo1iii95.1 (5)
Se1—Mo1—Mo1ii102.98 (7)C1—Mo1—C1iv82.6 (8)
Se1—Mo1—Se1iii106.52 (8)Mo1—Se1—Mo1iii70.4 (1)
C1—Mo1—Mo1i138.5 (3)N1—C1—Mo1179 (2)
Symmetry codes: (i) x+1/2, y+1/2, z; (ii) x, y+1/2, z+1/2; (iii) x+1/2, y, z+1/2; (iv) y, z+1/2, x+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N1v0.99 (3)1.88 (4)2.86 (3)174 (17)
O1—H2···O1vi0.99 (3)1.82 (3)2.80 (2)166 (5)
Symmetry codes: (v) x+1/2, y+3/2, z; (vi) z, x+1/2, y1/2.
 

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