Tetra­ammonium diaqua­diperoxidoocta­molybdate(VI) tetra­hydrate

Ward, A.J.; Arrow, G.J.; Maschmeyer, T.; Masters, A.F.; Turner, P.; Clegg, J.K.

doi:10.1107/S1600536809023460

inorganic compounds

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ISSN: 2056-9890

Volume 65| Part 7| July 2009| Pages i53-i54

doi:10.1107/S1600536809023460

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Tetraammonium diaquadiperoxidooctamolybdate(VI) tetrahydrate

Antony J. Ward,^a Gregory J. Arrow,^a Thomas Maschmeyer,^a Anthony F. Masters,^a ^* Peter Turner ^b and Jack K. Clegg ^b

^aLaboratory of Advanced Catalysis for Sustainability, School of Chemistry, F11, The University of Sydney, Sydney, NSW 2006, Australia, and ^bCrystal Structure Analysis Facility, School of Chemistry, F11, The University of Sydney, Sydney, NSW 2006, Australia
^*Correspondence e-mail: a.masters@chem.usyd.edu.au

(Received 11 May 2009; accepted 18 June 2009; online 27 June 2009)

The title compound (NH₄)₄[Mo₈O₂₄(O₂)₂(H₂O)₂]·4H₂O, consists of an octamolybdate cluster with a crystallographic centre of symmetry. The clusters pack in a cubic close packing arrangement defining channels containing water molecules and ammonium cations, which exhibit hydrogen bonding with neighbouring clusters. Hydrogen bonding also exists between the coordinated water molecules of one cluster with one of the O atoms of the peroxido fragment in a neighbouring cluster.

Related literature

For work on polyoxidomolybdates, see: Pope (1983 ); Pope & Müller (2001 ); Hill (1998 ). Baerwald (1885 ) probably reported the first peroxidomolybdate. Stomberg et al. have prepared a range of peroxidomolybdates and obtained crystal structures of these species, see: Larking & Stomberg (1970 , 1972 ); Olson & Stomberg (1996 , 1997a ,b ); Persdotter et al. (1986a ,b ,c ); Stomberg (1968 , 1969 , 1970 , 1988a ,b , 1992 , 1995 ); Stomberg & Trysberg (1969 ); Stomberg & Olson (1996 ); Trysberg & Stomberg (1968 , 1981 ). The versatile MoO₆ octahedron building block [see: Pope & Müller (1991 ); Chen & Zubieta (1992 )] results in an exceptionally large family of polyoxidomolybdates, see: Michailovski & Patzke (2006 ). For a review of the structural chemistry of peroxidomolybdates, see: Dickman & Pope (1994 ): Sergienko (2008 ). The tetraammonium salt of the centrosymmetric [Mo₈O₂₄(O₂)₂(H₂O)₂]⁴⁻ anion has been characterized with moderate precision, see: Trysberg & Stomberg (1981): Olson & Stomberg (1997a). For bonds lengths in polyoxidomolybdates, see: Feng & Mao (2004 ); Long et al. (2003 ); Shi et al. (2006 ).

Experimental

Crystal data

(NH₄)₄[Mo₈O₂₄(O₂)₂(H₂O)₂]·4H₂O
M_r = 1395.78
Monoclinic, P 2₁ /n
a = 10.405 (3) Å
b = 7.8706 (19) Å
c = 18.063 (4) Å
β = 96.991 (4)°
V = 1468.3 (6) Å³
Z = 2
Mo Kα radiation
μ = 3.43 mm⁻¹
T = 150 K
0.32 × 0.19 × 0.08 mm

Data collection

Bruker SMART 1000 CCD diffractometer
Absorption correction: gaussian (XPREP; Bruker, 1995 ; Coppens et al., 1965 ) T_min = 0.398, T_max = 0.773
14005 measured reflections
3542 independent reflections
3434 reflections with I > 2σ(I)
R_int = 0.032

Refinement

R[F² > 2σ(F²)] = 0.019
wR(F²) = 0.043
S = 1.16
3542 reflections
250 parameters
14 restraints
Only H-atom coordinates refined
Δρ_max = 1.02 e Å⁻³
Δρ_min = −0.70 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O12—H12A⋯O2ⁱ	0.947 (10)	1.802 (15)	2.715 (3)	161 (3)
O12—H12A⋯O1ⁱ	0.947 (10)	2.391 (16)	3.299 (3)	161 (3)
O12—H12B⋯O17ⁱⁱ	0.949 (10)	1.658 (12)	2.599 (3)	171 (4)
O16—H16B⋯O4ⁱⁱⁱ	0.94 (3)	2.01 (3)	2.939 (3)	170 (3)
O16—H16A⋯O7	0.943 (10)	2.00 (2)	2.803 (3)	142 (3)
O17—H17A⋯O1	0.94 (3)	1.883 (16)	2.776 (3)	159 (3)
O17—H17B⋯O7^iv	0.939 (10)	1.983 (12)	2.909 (3)	169 (3)
N1—H1B⋯O10^iv	0.948 (10)	2.09 (3)	2.795 (3)	130 (3)
N1—H1B⋯O10ⁱⁱ	0.948 (10)	2.24 (3)	2.929 (3)	129 (3)
N1—H1A⋯O9ⁱⁱ	0.94 (3)	2.16 (2)	2.992 (3)	146 (3)
N1—H1A⋯O14	0.94 (3)	2.40 (3)	2.985 (3)	120 (3)
N1—H1C⋯O16ⁱⁱ	0.948 (10)	1.96 (2)	2.811 (3)	148 (3)
N1—H1C⋯O6^v	0.948 (10)	2.36 (3)	3.038 (3)	128 (3)
N1—H1D⋯O17	0.95 (3)	2.17 (3)	2.859 (3)	129 (3)
N1—H1D⋯O8^v	0.95 (3)	2.47 (3)	3.097 (3)	124 (3)
N1—H1D⋯O5	0.95 (3)	2.60 (3)	3.203 (3)	122 (3)
N2—H2A⋯O16	0.946 (10)	2.001 (14)	2.923 (3)	164 (3)
N2—H2B⋯O4	0.945 (10)	1.927 (14)	2.852 (3)	165 (3)
N2—H2C⋯O11^vi	0.946 (10)	1.999 (15)	2.912 (3)	162 (3)
N2—H2C⋯O7ⁱⁱⁱ	0.946 (10)	2.65 (3)	3.169 (3)	115 (3)
N2—H2D⋯O3^vii	0.94 (3)	2.36 (3)	3.089 (3)	134 (3)
N2—H2D⋯O14ⁱⁱ	0.94 (3)	2.29 (3)	2.961 (3)	128 (3)
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (ii) -x+1, -y+1, -z+1; (iii) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) x+1, y, z; (v) -x+1, -y, -z+1; (vi) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (vii) x, y+1, z.

Data collection: SMART (Bruker, 1995); cell refinement: SAINT (Bruker, 1995); data reduction: SAINT and XPREP (Bruker, 1995; Coppens et al., 1965); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: TEXSAN for Windows (Molecular Structure Corporation, 1998 ), Xtal3.7 (Hall et al., 2000 ), ORTEPII (Johnson, 1976 ) and WinGX (Farrugia, 1999 ); software used to prepare material for publication: enCIFer (Allen et al., 2004 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809023460/br2108sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809023460/br2108Isup2.hkl

checkCIF report

Comment top

Polyoxometalates, which constitute an enormous class of metal-oxygen cluster compounds, have become very widely utilized inorganic components due to the extreme variability of their composition, molecular characteristics and properties - see Pope (1983), Pope & Muller (2001), Hill (1998).

The aqueous chemistry of molybdenum is dominated by the formation of polyoxoanions, the key structural motif being the MoO₆ octahedron - see Pope & Muller (1991), Chen & Zubieta (1992). This motif is a versatile building block that gives rise to an exceptionally large family of polyoxomolybdates which range from 3 to 368 metal ions in a single molecule - see Michailovski & Patzke (2006). Baerwald (1885) probably reported the first peroxomolybdate, the species resulting from the dissolution of ammonium paramolybdate in excess H₂O₂, which was formulated as 14NH₃.18MoO₃.3H₂O₂.18H₂O, .

The structure of the title complex consists of an octamolybdate unit possessing an inversion centre (Figure 1). In the complex there is a peroxide ligand coordinated to Mo1, one water molecule bound to Mo3, two triply coordinated oxygen atoms, O9, O13, and one quadruply coordinated oxygen atom, O15. The Mo—O bond lengths with the polyvalent O atoms range from 2.0125 (18) to 2.3338 (19) Å. The bridging Mo—O bonds range in length length from 1.8753 (19) to 1.9753 (19) Å. The bond lengths for the terminal Mo=O bonds range from 1.686 (2) to 1.722 (2) Å. These bonds lengths are in good agreement with previously published polyoxomolybdate structures - see Long et al. (2003), Feng & Mao (2004), Shi et al. (2006). However, there are two bond lengths that show significant deviation from the expected: the Mo1—O5 bond length of 2.2836 (19) Å is extremely long for a bridging Mo—O bond while the Mo4—O9 bond length of 1.86089 (19) Å is considerably shorter than expected for a bond involving a triply bridging oxygen.

The packing of the title complex (Figure 2) shows the individual units to be stacked in a cubic close packing arrangement with water and ammonium ions distributed in the channels formed. Hydrogen bonding interactions exist between ammonium ions and the molybdenum cluster: H2B with O4, H1B with O10. In addition there exist hydrogen bonding interactions between the ammonium ions and the O atoms of neighbouring clusters: H2C with 011, H2D with O3, H1A with O9, and H1B with O10. The water molecules also hydrogen bond with the ammonium ions: O16 with H2A, O16 with H1C, and O17 with H1D. There is H-bonding between the H atoms of the water molecules with oxygen atoms of the molybdenum cluster: the strongest being that between O1 and H17A while 07 and H16A has a slightly longer hydrogen bond length. There also exists hydrogen bonding with the protons of the coordinated water molecules (H12A) of one cluster with the O2 atom in a neighbouring cluster while the other proton (H12B) has a strong hydrogen bond to 017. The water molecules also exhibit weak interactions with neighbouring clusters whereby H16A and H16B interact with O3 and H17A and H17B interact with O10.

Related literature top

For work on polyoxometalates, see: Pope (1983); Pope & Muller (2001); Hill (1998). Baerwald (1885) probably reported the first peroxomolybdate. Stomberg et al. have prepared a range of peroxomolybdates and obtained crystal structures of these species, see: Larking & Stomberg (1970, 1972); Olson & Stomberg (1996, 1997a,b); Persdotter et al. (1986a,b,c); Stomberg (1968, 1969, 1970, 1988a,b, 1992, 1995); Stomberg & Trysberg (1969); Stomberg & Olson (1996); Trysberg & Stomberg (1968, 1981). The versatile MoO₆ octahedron building block [see: Pope & Muller (1991); Chen & Zubieta (1992)] results in an exceptionally large family of polyoxomolybdates, see: Michailovski & Patzke (2006). For a review of the structural chemistry of peroxomolybdates, see: Dickman & Pope (1994): Sergienko (2008). The tetraammonium salt of the centrosymmetric [Mo₈O₂₄(O₂)₂(H₂O)₂]^4- anion has been characterized with moderate precision, see: Trysberg & Stomberg (1981): Olson & Stomberg (1997a). For bonds lengths in polyoxomolybdates, see: Feng & Mao (2004); Long et al. (2003); Shi et al. (2006).

Experimental top

Ammonium molybdate tetrahydrate (10 g, 8.1 mmol) was dissolved in a solution of hydrogen peroxide (30%, 50 ml) acidified to pH 2 with nitric acid (70%, 5 ml). Slow evaporation of the yellow solution afforded crystals of the title compound (7.45 g, 93%). Crystals suitable for XRD studies were obtained from an aqueous solution of the complex that was kept at 288 K and 80% humidity in order to reduce the rate of evaporation.

Computing details top

Data collection: SMART (Bruker, 1995); cell refinement: SAINT (Bruker, 1995); data reduction: SAINT and XPREP (Bruker, 1995; Coppens et al., 1965); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: TEXSAN for Windows (Molecular Structure Corporation, 1998), Xtal3.7 (Hall et al., 2000), ORTEPII (Johnson, 1976) and WinGX (Farrugia, 1999); software used to prepare material for publication: enCIFer (Allen et al., 2004).

Figures top

	Fig. 1. The molecular structure of the title complex, with displacement ellipsoids drawn at 50% probability level. Water solvent and ammonnium ions omitted for clarity. Symmetry code used for generating equivalent atoms: 1 - x, -y, 1 - z.
	Fig. 2. View along (a) the a axis and (b) the b axis of the crystal lattice of the title complex.

Tetraammonium dihydroxydiperoxooctamolybdate(VI) tetrahydrate top

Crystal data top

(NH₄)₄[Mo₈O₂₄(O2)₂(H₂O)₂]·4H₂O	F(000) = 1328
M_r = 1395.78	D_x = 3.157 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1023 reflections
a = 10.405 (3) Å	θ = 2.8–28.3°
b = 7.8706 (19) Å	µ = 3.43 mm⁻¹
c = 18.063 (4) Å	T = 150 K
β = 96.991 (4)°	Blade, yellow
V = 1468.3 (6) Å³	0.32 × 0.19 × 0.08 mm
Z = 2

Data collection top

Bruker SMART 1000 CCD diffractometer	3542 independent reflections
Radiation source: sealed tube	3434 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.032
ω scans	θ_max = 28.3°, θ_min = 2.2°
Absorption correction: gaussian (XPREP; Bruker, 1995; Coppens et al., 1965)	h = −13→13
T_min = 0.398, T_max = 0.773	k = −10→10
14005 measured reflections	l = −24→24

Refinement top

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)] = 0.019	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.043	Only H-atom coordinates refined
S = 1.16	w = 1/[σ²(F_o²) + (0.016P)² + 2.2853P] where P = (F_o² + 2F_c²)/3
3542 reflections	(Δ/σ)_max = 0.001
250 parameters	Δρ_max = 1.02 e Å⁻³
14 restraints	Δρ_min = −0.70 e Å⁻³

Crystal data top

(NH₄)₄[Mo₈O₂₄(O2)₂(H₂O)₂]·4H₂O	V = 1468.3 (6) Å³
M_r = 1395.78	Z = 2
Monoclinic, P2₁/n	Mo Kα radiation
a = 10.405 (3) Å	µ = 3.43 mm⁻¹
b = 7.8706 (19) Å	T = 150 K
c = 18.063 (4) Å	0.32 × 0.19 × 0.08 mm
β = 96.991 (4)°

Data collection top

Bruker SMART 1000 CCD diffractometer	3542 independent reflections
Absorption correction: gaussian (XPREP; Bruker, 1995; Coppens et al., 1965)	3434 reflections with I > 2σ(I)
T_min = 0.398, T_max = 0.773	R_int = 0.032
14005 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.019	14 restraints
wR(F²) = 0.043	Only H-atom coordinates refined
S = 1.16	Δρ_max = 1.02 e Å⁻³
3542 reflections	Δρ_min = −0.70 e Å⁻³
250 parameters

Special details top

Experimental. attached with Exxon Paratone N, to a short length of fibre supported on a thin piece of copper wire inserted in a copper mounting pin. The crystal was quenched in a cold nitrogen gas stream from an Oxford Cryosystems Cryostream.

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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

	x	y	z	U_iso*/U_eq
Mo1	0.578257 (18)	0.03860 (2)	0.654717 (10)	0.00883 (5)
Mo2	0.267481 (18)	0.07806 (2)	0.612704 (10)	0.00964 (5)
Mo3	0.153081 (18)	0.16838 (2)	0.442190 (11)	0.00992 (5)
Mo4	0.473839 (18)	0.21902 (2)	0.486860 (10)	0.00802 (5)
O1	0.75337 (18)	0.1060 (2)	0.69344 (10)	0.0214 (4)
O2	0.65823 (18)	0.2109 (2)	0.72269 (10)	0.0216 (4)
O3	0.54977 (16)	−0.1215 (2)	0.71260 (9)	0.0146 (3)
O4	0.42192 (15)	0.1707 (2)	0.66940 (9)	0.0111 (3)
O5	0.59440 (16)	0.2362 (2)	0.56376 (9)	0.0117 (3)
O6	0.25417 (17)	−0.1077 (2)	0.65969 (9)	0.0153 (3)
O7	0.15724 (16)	0.2132 (2)	0.64528 (10)	0.0154 (3)
O8	0.17259 (16)	0.0052 (2)	0.51832 (9)	0.0123 (3)
O9	0.32211 (15)	0.2731 (2)	0.52672 (9)	0.0112 (3)
O10	0.06078 (16)	0.3204 (2)	0.47923 (10)	0.0154 (3)
O11	0.05378 (17)	0.0689 (2)	0.37343 (10)	0.0178 (4)
O12	0.20013 (18)	0.3722 (2)	0.36953 (10)	0.0165 (3)
O13	0.32947 (15)	0.0976 (2)	0.41274 (9)	0.0108 (3)
O14	0.50583 (16)	0.3819 (2)	0.42998 (9)	0.0133 (3)
O15	0.55751 (15)	0.02784 (19)	0.43622 (9)	0.0095 (3)
O16	0.1645 (2)	0.5543 (2)	0.69018 (11)	0.0235 (4)
O17	0.89009 (18)	0.3251 (2)	0.61140 (10)	0.0181 (4)
N1	0.7945 (2)	0.3830 (3)	0.45833 (12)	0.0163 (4)
N2	0.4450 (3)	0.5128 (3)	0.72139 (13)	0.0225 (5)
H12A	0.203 (3)	0.354 (5)	0.3179 (7)	0.034*
H12B	0.162 (3)	0.481 (2)	0.372 (2)	0.034*
H16B	0.128 (3)	0.597 (4)	0.7317 (13)	0.034*
H16A	0.135 (3)	0.441 (2)	0.691 (2)	0.034*
H17A	0.854 (3)	0.267 (4)	0.6492 (15)	0.034*
H17B	0.9770 (14)	0.290 (4)	0.615 (2)	0.034*
H1B	0.8775 (17)	0.434 (4)	0.465 (2)	0.034*
H1A	0.728 (2)	0.462 (4)	0.463 (2)	0.034*
H1C	0.797 (3)	0.361 (5)	0.4069 (7)	0.034*
H1D	0.797 (4)	0.303 (4)	0.4976 (14)	0.034*
H2A	0.3570 (14)	0.546 (5)	0.716 (2)	0.034*
H2B	0.447 (4)	0.405 (2)	0.6981 (19)	0.034*
H2C	0.468 (3)	0.505 (5)	0.7736 (7)	0.034*
H2D	0.494 (3)	0.589 (4)	0.6960 (18)	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Mo1	0.00872 (9)	0.00944 (9)	0.00819 (9)	0.00024 (6)	0.00051 (7)	−0.00073 (6)
Mo2	0.00888 (9)	0.01032 (9)	0.00991 (9)	−0.00013 (7)	0.00191 (7)	−0.00078 (7)
Mo3	0.00759 (9)	0.01116 (9)	0.01077 (9)	0.00088 (7)	0.00020 (7)	−0.00090 (7)
Mo4	0.00759 (9)	0.00779 (9)	0.00865 (9)	0.00016 (6)	0.00085 (7)	−0.00025 (6)
O1	0.0209 (9)	0.0228 (9)	0.0195 (9)	−0.0036 (8)	−0.0015 (7)	−0.0021 (7)
O2	0.0199 (9)	0.0253 (10)	0.0186 (9)	−0.0046 (8)	−0.0013 (7)	−0.0022 (7)
O3	0.0155 (8)	0.0143 (8)	0.0137 (8)	0.0014 (7)	0.0009 (6)	0.0009 (6)
O4	0.0108 (7)	0.0116 (7)	0.0111 (7)	0.0002 (6)	0.0016 (6)	−0.0033 (6)
O5	0.0115 (8)	0.0109 (7)	0.0126 (8)	−0.0006 (6)	0.0012 (6)	−0.0001 (6)
O6	0.0167 (8)	0.0146 (8)	0.0148 (8)	−0.0021 (7)	0.0030 (7)	−0.0002 (6)
O7	0.0119 (8)	0.0166 (8)	0.0183 (8)	0.0013 (6)	0.0045 (7)	−0.0031 (7)
O8	0.0120 (7)	0.0119 (7)	0.0129 (8)	−0.0017 (6)	0.0010 (6)	−0.0009 (6)
O9	0.0105 (7)	0.0099 (7)	0.0132 (8)	−0.0002 (6)	0.0010 (6)	−0.0007 (6)
O10	0.0108 (8)	0.0181 (8)	0.0177 (8)	0.0022 (7)	0.0029 (6)	−0.0019 (7)
O11	0.0145 (8)	0.0201 (9)	0.0177 (8)	0.0001 (7)	−0.0019 (7)	−0.0040 (7)
O12	0.0211 (9)	0.0143 (8)	0.0144 (8)	0.0035 (7)	0.0031 (7)	0.0034 (7)
O13	0.0093 (7)	0.0116 (7)	0.0113 (7)	−0.0001 (6)	0.0001 (6)	−0.0013 (6)
O14	0.0144 (8)	0.0123 (8)	0.0129 (8)	0.0003 (6)	0.0005 (6)	0.0008 (6)
O15	0.0090 (7)	0.0100 (7)	0.0093 (7)	0.0008 (6)	0.0008 (6)	−0.0012 (6)
O16	0.0344 (11)	0.0182 (9)	0.0186 (9)	−0.0031 (8)	0.0056 (8)	−0.0005 (7)
O17	0.0171 (9)	0.0166 (8)	0.0207 (9)	0.0037 (7)	0.0023 (7)	0.0026 (7)
N1	0.0146 (10)	0.0173 (10)	0.0166 (10)	−0.0010 (8)	−0.0004 (8)	−0.0002 (8)
N2	0.0322 (13)	0.0187 (11)	0.0159 (10)	−0.0009 (10)	0.0001 (9)	0.0021 (9)

Geometric parameters (Å, º) top

Mo1—O3	1.6864 (17)	Mo4—O15	2.0131 (16)
Mo1—O1	1.9443 (19)	Mo4—O13	2.1148 (16)
Mo1—O2	1.9468 (19)	Mo4—O15ⁱ	2.4335 (16)
Mo1—O13ⁱ	1.9599 (16)	O1—O2	1.438 (3)
Mo1—O4	1.9755 (16)	O12—H12A	0.947 (10)
Mo1—O15ⁱ	2.0983 (16)	O12—H12B	0.949 (10)
Mo1—O5	2.2836 (17)	O13—Mo1ⁱ	1.9599 (16)
Mo2—O6	1.7045 (18)	O15—Mo1ⁱ	2.0983 (16)
Mo2—O7	1.7200 (17)	O15—Mo2ⁱ	2.2768 (16)
Mo2—O4	1.9397 (16)	O15—Mo4ⁱ	2.4335 (16)
Mo2—O8	1.9496 (16)	O16—H16B	0.94 (3)
Mo2—O15ⁱ	2.2768 (16)	O16—H16A	0.943 (10)
Mo2—O9	2.3037 (17)	O17—H17A	0.94 (3)
Mo3—O11	1.7062 (18)	O17—H17B	0.939 (10)
Mo3—O10	1.7198 (17)	N1—H1B	0.948 (10)
Mo3—O8	1.8744 (17)	N1—H1A	0.94 (3)
Mo3—O13	2.0493 (17)	N1—H1C	0.948 (10)
Mo3—O12	2.1663 (18)	N1—H1D	0.95 (3)
Mo3—O9	2.3348 (16)	N2—H2A	0.946 (10)
Mo4—O14	1.7007 (17)	N2—H2B	0.945 (10)
Mo4—O5	1.7600 (16)	N2—H2C	0.946 (10)
Mo4—O9	1.8626 (17)	N2—H2D	0.94 (3)

O3—Mo1—O1	102.03 (8)	O12—Mo3—O9	85.81 (6)
O3—Mo1—O2	102.90 (8)	O14—Mo4—O5	104.22 (8)
O1—Mo1—O2	43.38 (8)	O14—Mo4—O9	107.38 (8)
O3—Mo1—O13ⁱ	96.49 (8)	O5—Mo4—O9	103.51 (8)
O1—Mo1—O13ⁱ	82.20 (8)	O14—Mo4—O15	99.30 (7)
O2—Mo1—O13ⁱ	124.68 (8)	O5—Mo4—O15	96.32 (7)
O3—Mo1—O4	95.75 (8)	O9—Mo4—O15	141.30 (7)
O1—Mo1—O4	123.99 (8)	O14—Mo4—O13	97.71 (7)
O2—Mo1—O4	81.05 (8)	O5—Mo4—O13	156.59 (7)
O13ⁱ—Mo1—O4	147.69 (7)	O9—Mo4—O13	77.16 (7)
O3—Mo1—O15ⁱ	98.44 (7)	O15—Mo4—O13	71.81 (6)
O1—Mo1—O15ⁱ	149.52 (7)	O14—Mo4—O15ⁱ	175.07 (7)
O2—Mo1—O15ⁱ	149.62 (7)	O5—Mo4—O15ⁱ	75.11 (7)
O13ⁱ—Mo1—O15ⁱ	73.21 (7)	O9—Mo4—O15ⁱ	77.47 (6)
O4—Mo1—O15ⁱ	75.48 (6)	O15—Mo4—O15ⁱ	76.00 (7)
O3—Mo1—O5	171.45 (7)	O13—Mo4—O15ⁱ	82.33 (6)
O1—Mo1—O5	85.71 (7)	O2—O1—Mo1	68.40 (11)
O2—Mo1—O5	85.18 (7)	O1—O2—Mo1	68.21 (11)
O13ⁱ—Mo1—O5	80.85 (7)	Mo2—O4—Mo1	111.97 (8)
O4—Mo1—O5	82.64 (6)	Mo4—O5—Mo1	114.05 (8)
O15ⁱ—Mo1—O5	73.02 (6)	Mo3—O8—Mo2	115.98 (8)
O6—Mo2—O7	105.20 (9)	Mo4—O9—Mo2	113.49 (7)
O6—Mo2—O4	99.89 (8)	Mo4—O9—Mo3	105.84 (7)
O7—Mo2—O4	97.53 (8)	Mo2—O9—Mo3	88.71 (6)
O6—Mo2—O8	96.89 (8)	Mo3—O12—H12A	121 (2)
O7—Mo2—O8	101.14 (8)	Mo3—O12—H12B	121 (2)
O4—Mo2—O8	150.60 (7)	H12A—O12—H12B	104 (3)
O6—Mo2—O15ⁱ	89.80 (7)	Mo1ⁱ—O13—Mo3	146.31 (9)
O7—Mo2—O15ⁱ	163.24 (7)	Mo1ⁱ—O13—Mo4	106.07 (7)
O4—Mo2—O15ⁱ	72.07 (6)	Mo3—O13—Mo4	107.61 (7)
O8—Mo2—O15ⁱ	84.07 (6)	Mo4—O15—Mo1ⁱ	104.76 (7)
O6—Mo2—O9	161.61 (7)	Mo4—O15—Mo2ⁱ	149.38 (8)
O7—Mo2—O9	92.75 (7)	Mo1ⁱ—O15—Mo2ⁱ	95.68 (6)
O4—Mo2—O9	81.31 (6)	Mo4—O15—Mo4ⁱ	104.00 (7)
O8—Mo2—O9	75.33 (6)	Mo1ⁱ—O15—Mo4ⁱ	97.11 (6)
O15ⁱ—Mo2—O9	73.00 (6)	Mo2ⁱ—O15—Mo4ⁱ	95.65 (6)
O11—Mo3—O10	106.56 (9)	H16B—O16—H16A	99 (3)
O11—Mo3—O8	102.80 (8)	H17A—O17—H17B	105 (3)
O10—Mo3—O8	101.94 (8)	H1B—N1—H1A	112 (3)
O11—Mo3—O13	99.70 (8)	H1B—N1—H1C	94 (3)
O10—Mo3—O13	148.24 (7)	H1A—N1—H1C	108 (3)
O8—Mo3—O13	89.08 (7)	H1B—N1—H1D	104 (3)
O11—Mo3—O12	93.46 (8)	H1A—N1—H1D	110 (3)
O10—Mo3—O12	84.18 (8)	H1C—N1—H1D	128 (3)
O8—Mo3—O12	159.99 (7)	H2A—N2—H2B	106 (3)
O13—Mo3—O12	76.61 (7)	H2A—N2—H2C	104 (3)
O11—Mo3—O9	168.36 (7)	H2B—N2—H2C	112 (3)
O10—Mo3—O9	84.95 (7)	H2A—N2—H2D	111 (3)
O8—Mo3—O9	75.90 (6)	H2B—N2—H2D	108 (3)
O13—Mo3—O9	68.81 (6)	H2C—N2—H2D	116 (3)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O12—H12A···O2ⁱⁱ	0.95 (1)	1.80 (2)	2.715 (3)	161 (3)
O12—H12A···O1ⁱⁱ	0.95 (1)	2.39 (2)	3.299 (3)	161 (3)
O12—H12B···O17ⁱⁱⁱ	0.95 (1)	1.66 (1)	2.599 (3)	171 (4)
O16—H16B···O4^iv	0.94 (3)	2.01 (3)	2.939 (3)	170 (3)
O16—H16A···O7	0.94 (1)	2.00 (2)	2.803 (3)	142 (3)
O17—H17A···O1	0.94 (3)	1.88 (2)	2.776 (3)	159 (3)
O17—H17B···O7^v	0.94 (1)	1.98 (1)	2.909 (3)	169 (3)
N1—H1B···O10^v	0.95 (1)	2.09 (3)	2.795 (3)	130 (3)
N1—H1B···O10ⁱⁱⁱ	0.95 (1)	2.24 (3)	2.929 (3)	129 (3)
N1—H1A···O9ⁱⁱⁱ	0.94 (3)	2.16 (2)	2.992 (3)	146 (3)
N1—H1A···O14	0.94 (3)	2.40 (3)	2.985 (3)	120 (3)
N1—H1C···O16ⁱⁱⁱ	0.95 (1)	1.96 (2)	2.811 (3)	148 (3)
N1—H1C···O6ⁱ	0.95 (1)	2.36 (3)	3.038 (3)	128 (3)
N1—H1D···O17	0.95 (3)	2.17 (3)	2.859 (3)	129 (3)
N1—H1D···O8ⁱ	0.95 (3)	2.47 (3)	3.097 (3)	124 (3)
N1—H1D···O5	0.95 (3)	2.60 (3)	3.203 (3)	122 (3)
N2—H2A···O16	0.95 (1)	2.00 (1)	2.923 (3)	164 (3)
N2—H2B···O4	0.95 (1)	1.93 (1)	2.852 (3)	165 (3)
N2—H2C···O11^vi	0.95 (1)	2.00 (2)	2.912 (3)	162 (3)
N2—H2C···O7^iv	0.95 (1)	2.65 (3)	3.169 (3)	115 (3)
N2—H2D···O3^vii	0.94 (3)	2.36 (3)	3.089 (3)	134 (3)
N2—H2D···O14ⁱⁱⁱ	0.94 (3)	2.29 (3)	2.961 (3)	128 (3)

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

Experimental details

Crystal data
Chemical formula	(NH₄)₄[Mo₈O₂₄(O2)₂(H₂O)₂]·4H₂O
M_r	1395.78
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	150
a, b, c (Å)	10.405 (3), 7.8706 (19), 18.063 (4)
β (°)	96.991 (4)
V (Å³)	1468.3 (6)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	3.43
Crystal size (mm)	0.32 × 0.19 × 0.08

Data collection
Diffractometer	Bruker SMART 1000 CCD diffractometer
Absorption correction	Gaussian (XPREP; Bruker, 1995; Coppens et al., 1965)
T_min, T_max	0.398, 0.773
No. of measured, independent and observed [I > 2σ(I)] reflections	14005, 3542, 3434
R_int	0.032
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.019, 0.043, 1.16
No. of reflections	3542
No. of parameters	250
No. of restraints	14
H-atom treatment	Only H-atom coordinates refined
Δρ_max, Δρ_min (e Å⁻³)	1.02, −0.70

Computer programs: SMART (Bruker, 1995), SAINT (Bruker, 1995), SAINT and XPREP (Bruker, 1995; Coppens et al., 1965), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), TEXSAN for Windows (Molecular Structure Corporation, 1998), Xtal3.7 (Hall et al., 2000), ORTEPII (Johnson, 1976) and WinGX (Farrugia, 1999), enCIFer (Allen et al., 2004).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O12—H12A···O2ⁱ	0.947 (10)	1.802 (15)	2.715 (3)	161 (3)
O12—H12A···O1ⁱ	0.947 (10)	2.391 (16)	3.299 (3)	161 (3)
O12—H12B···O17ⁱⁱ	0.949 (10)	1.658 (12)	2.599 (3)	171 (4)
O16—H16B···O4ⁱⁱⁱ	0.94 (3)	2.01 (3)	2.939 (3)	170 (3)
O16—H16A···O7	0.943 (10)	2.00 (2)	2.803 (3)	142 (3)
O17—H17A···O1	0.94 (3)	1.883 (16)	2.776 (3)	159 (3)
O17—H17B···O7^iv	0.939 (10)	1.983 (12)	2.909 (3)	169 (3)
N1—H1B···O10^iv	0.948 (10)	2.09 (3)	2.795 (3)	130 (3)
N1—H1B···O10ⁱⁱ	0.948 (10)	2.24 (3)	2.929 (3)	129 (3)
N1—H1A···O9ⁱⁱ	0.94 (3)	2.16 (2)	2.992 (3)	146 (3)
N1—H1A···O14	0.94 (3)	2.40 (3)	2.985 (3)	120 (3)
N1—H1C···O16ⁱⁱ	0.948 (10)	1.96 (2)	2.811 (3)	148 (3)
N1—H1C···O6^v	0.948 (10)	2.36 (3)	3.038 (3)	128 (3)
N1—H1D···O17	0.95 (3)	2.17 (3)	2.859 (3)	129 (3)
N1—H1D···O8^v	0.95 (3)	2.47 (3)	3.097 (3)	124 (3)
N1—H1D···O5	0.95 (3)	2.60 (3)	3.203 (3)	122 (3)
N2—H2A···O16	0.946 (10)	2.001 (14)	2.923 (3)	164 (3)
N2—H2B···O4	0.945 (10)	1.927 (14)	2.852 (3)	165 (3)
N2—H2C···O11^vi	0.946 (10)	1.999 (15)	2.912 (3)	162 (3)
N2—H2C···O7ⁱⁱⁱ	0.946 (10)	2.65 (3)	3.169 (3)	115 (3)
N2—H2D···O3^vii	0.94 (3)	2.36 (3)	3.089 (3)	134 (3)
N2—H2D···O14ⁱⁱ	0.94 (3)	2.29 (3)	2.961 (3)	128 (3)

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

Acknowledgements

The authors acknowledge funding from the Australian Research Council.

References

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