metal-organic compounds
Ethylenediaminium niobium oxyfluoride
aSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
*Correspondence e-mail: pl@st-and.ac.uk
The title compound, bis(ethylenediaminium) μ-oxo-bis[tetrafluorooxoniobium(V)], (C2H10N2)2[Nb2O3F8], is a novel organically templated niobium oxyfluoride. It consists of isolated [Nb2O3F8]4− octahedral dimers charge balanced by ethylenediaminium cations, two of which lie about inversion centres. Two NbO2F4 octahedra are fused through a common O atom to form the dimers. Characteristic short terminal Nb=O bond lengths and longer Nb—F and bridging Nb—O bond lengths are observed, which result in the out-of-centre distortion of the octahedra, a manifestation of the second-order Jahn–Teller effect. Extensive hydrogen bonding between the dimers and the organic template is exhibited.
Comment
The title compound, (I), is the first organically templated niobium oxyfluoride. It also appears to be the first example of isolated dimeric niobium oxyfluoride units. In purely inorganic niobium oxyfluorides, a variety of building units have been reported: isolated [NbOF5]2− octahedra are found in Li2NbOF5 (Galy et al., 1969), and isolated pentagonal bipyramidal NbF7 and NbOF6 units are found in Rb5Nb3OF18 (Agulyanskii et al., 1991) and Ba4Nb2O3F12 (Crosnier-Lopez & Fourquet, 1993), respectively. The latter compound also contains cis corner-sharing octahedral tetramers. O-Atom-linked trans vertex-sharing chains are found in (NH4)[NbOF4] (Pakhomov & Kaidalova, 1974). Welk et al. (2002) have exploited metal-organic complexes in `directing' otherwise isolated [NbOF5]2− ions into specific crystallographic orientations.
The main feature of most of the previously reported niobium oxyfluorides is the out-of-centre octahedral distortion. Electronic and bond-network effects lead to the characteristic short Nb=O bond length and the longer Nb—X bond length trans to it. Along with non-centrosymmetry, the off-centre distortion is important in the non-linear properties of the structure. In the [NbOF5]2− anion (e.g. Izumi et al., 2005), the Nb atom is displaced from the centre of the octahedron towards the O atom to form a short Nb=O bond and a longer Nb—F bond.
(C2H10N2)2[Nb2O3F8] (Fig. 1) is built up from diprotonated ethylenediamine cations and dimeric [Nb2O3F8]4− units. Each dimer consists of two NbO2F4 octahedra, which share corners with each other via one O atom.
Bond-valence sums (Table 2) show that some of the F atoms are heavily underbonded, and this is compensated by substantial hydrogen bonding (Table 1) to the organic cations. For example, the two F atoms trans to the short Nb=O bonds (F1 and F6) accept three hydrogen bonds, while the two trans to the bridging O atom (F2 and F8) accept two each. Similarly, atom O1 is hydrogen bonded to two NH groups, while atom O2 is only bound to one, compatible with a small s(ij) of 1.48 for the Nb1—O1 bond and a larger s(ij) of 1.61 for the Nb2—O2 bond. The bridging O3 atom does not require hydrogen bonding. All H atoms of the ethylenediaminium moieties partake in hydrogen bonding. In one of the octahedra (Nb1) there is a slight tendency for displacement of Nb towards an edge (O1–O3) rather than a vertex of the octahedron.
The complex hydrogen-bonding scheme results in the crystal packing shown in Fig. 2. The dimers are aligned along the [010] direction in a herring-bone fashion.
Experimental
Niobium pentoxide (0.2658 g), water (5 ml) and a 40% solution of HF (0.5 ml) were heated in a polypropylene bottle at 373 K for 1 h. The contents of the bottle were washed into a Teflon-lined steel autoclave with ethylene glycol (5 ml). To this mixture was added ethylenediamine (0.25 ml) to give a pH of 4. The mixture was heated at 463 K for 5 d. The pH increased to 6.5 over this time. The final product was filtered off, washed with water and allowed to dry overnight at room temperature.
Crystal data
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Refinement
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Crystals of (I) are monoclinic, in the P21/n, which was chosen from the H atoms were refined as riding on their carrier atoms [C—H = 0.99 Å, N—H = 0.91 Å, and Uiso(H) = 1.2Ueq(C) and 1.5Ueq(N)].
Data collection: SMART (Bruker, 1997); cell SMART; data reduction: SAINT (Bruker, 1997) and SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S0108270105018032/sk1851sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S0108270105018032/sk1851Isup2.hkl
Niobium pentoxide (0.2658 g), water (5 ml) and a 40% solution of HF (0.5 ml) was heated in a polypropylene bottle at 373 K for 1 h. The contents of the bottle were washed into a Teflon-lined steel autoclave with ethylene glycol (5 ml). To this mixture was added ethylenediamine (0.25 ml) to give a pH of 4. The mixture was heated at 463 K for 5 d. The pH increased to 6.5 over this time. The final product was filtered off, washed in water and allowed to dry overnight at room temperature.
Crystals of (I) are monoclinic, in the
P21/n, which was chosen from the H atoms were refined as riding on their carrier atoms [C—H = 0.99 Å, N—H = 0.91 Å, and Uiso(H) = 1.2Ueq(C) and 1.5Ueq(N)].Data collection: SMART (Bruker, 1997); cell
SMART; data reduction: SAINT? and SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: WinGX (Farrugia, 1999); software used to prepare material for publication: program (reference)?.Fig. 1. The asymmetric unit of the title compound, with tdisplacement ellipsoids drawn at 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x, −y, 1 − z.] | |
Fig. 2. Projection of the structure down [010], showing the stacking of the dimers and cations. |
(C2H10N2)2[Nb2O3F8] | F(000) = 1000 |
Mr = 510.06 | Dx = 2.374 Mg m−3 |
Monoclinic, P21/n | Melting point: not measured K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 11.7121 (12) Å | Cell parameters from 72 reflections |
b = 10.1984 (10) Å | θ = 12–28° |
c = 11.9712 (12) Å | µ = 1.71 mm−1 |
β = 93.438 (2)° | T = 125 K |
V = 1427.3 (2) Å3 | Prism, colourless |
Z = 4 | 0.1 × 0.1 × 0.03 mm |
Bruker SMART CCD area-detector diffractometer | 2608 independent reflections |
Radiation source: sealed tube | 2419 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
Detector resolution: 0.83 pixels mm-1 | θmax = 25.4°, θmin = 2.4° |
ϕ and ω scans | h = −14→13 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1999) | k = −12→12 |
Tmin = 0.829, Tmax = 0.950 | l = −13→14 |
9021 measured reflections |
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)] = 0.023 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.060 | H-atom parameters constrained |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0284P)2 + 3.2384P] where P = (Fo2 + 2Fc2)/3 |
2608 reflections | (Δ/σ)max = 0.001 |
190 parameters | Δρmax = 0.52 e Å−3 |
0 restraints | Δρmin = −0.57 e Å−3 |
(C2H10N2)2[Nb2O3F8] | V = 1427.3 (2) Å3 |
Mr = 510.06 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 11.7121 (12) Å | µ = 1.71 mm−1 |
b = 10.1984 (10) Å | T = 125 K |
c = 11.9712 (12) Å | 0.1 × 0.1 × 0.03 mm |
β = 93.438 (2)° |
Bruker SMART CCD area-detector diffractometer | 2608 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1999) | 2419 reflections with I > 2σ(I) |
Tmin = 0.829, Tmax = 0.950 | Rint = 0.022 |
9021 measured reflections |
R[F2 > 2σ(F2)] = 0.023 | 0 restraints |
wR(F2) = 0.060 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.52 e Å−3 |
2608 reflections | Δρmin = −0.57 e Å−3 |
190 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Nb1 | −0.17207 (2) | 0.21651 (3) | 0.27665 (2) | 0.01009 (9) | |
Nb2 | 0.14196 (2) | 0.25446 (3) | 0.28676 (2) | 0.00937 (9) | |
F1 | −0.12504 (15) | 0.12615 (17) | 0.42995 (14) | 0.0141 (4) | |
F2 | −0.32349 (15) | 0.13283 (19) | 0.31959 (15) | 0.0178 (4) | |
F3 | −0.20968 (17) | 0.36420 (18) | 0.36999 (16) | 0.0194 (4) | |
F4 | −0.12574 (16) | 0.04264 (17) | 0.22446 (15) | 0.0164 (4) | |
F5 | 0.17347 (16) | 0.43056 (18) | 0.22768 (15) | 0.0163 (4) | |
F6 | 0.11837 (15) | 0.36782 (17) | 0.43726 (15) | 0.0145 (4) | |
F7 | 0.12141 (15) | 0.10116 (17) | 0.38028 (15) | 0.0165 (4) | |
F8 | 0.30005 (15) | 0.25464 (17) | 0.35584 (15) | 0.0148 (4) | |
O1 | −0.23627 (19) | 0.2669 (2) | 0.14641 (19) | 0.0150 (5) | |
O2 | 0.16808 (19) | 0.1754 (2) | 0.16245 (19) | 0.0178 (5) | |
O3 | −0.02119 (18) | 0.2823 (2) | 0.26320 (19) | 0.0138 (5) | |
C1 | 0.4741 (3) | 0.3018 (3) | 0.1796 (3) | 0.0154 (7) | |
H1 | 0.4060 | 0.3557 | 0.1933 | 0.018* | |
H2 | 0.5210 | 0.2948 | 0.2510 | 0.018* | |
C2 | 0.4361 (3) | 0.1666 (3) | 0.1420 (3) | 0.0145 (6) | |
H3 | 0.3820 | 0.1315 | 0.1951 | 0.017* | |
H4 | 0.3949 | 0.1730 | 0.0675 | 0.017* | |
C3 | 0.4614 (3) | 0.4421 (3) | 0.4861 (3) | 0.0140 (6) | |
H5 | 0.4738 | 0.4107 | 0.4095 | 0.017* | |
H6 | 0.4800 | 0.3695 | 0.5391 | 0.017* | |
C4 | 0.4621 (3) | 0.0600 (3) | 0.5047 (3) | 0.0150 (7) | |
H7 | 0.4785 | 0.1024 | 0.5784 | 0.018* | |
H8 | 0.4789 | 0.1240 | 0.4457 | 0.018* | |
N1 | 0.5417 (2) | 0.3679 (3) | 0.0954 (2) | 0.0138 (5) | |
H9 | 0.5639 | 0.4485 | 0.1212 | 0.021* | |
H10 | 0.4981 | 0.3770 | 0.0303 | 0.021* | |
H11 | 0.6046 | 0.3190 | 0.0829 | 0.021* | |
N2 | 0.5341 (2) | 0.0736 (2) | 0.1353 (2) | 0.0125 (5) | |
H12 | 0.5075 | −0.0061 | 0.1116 | 0.019* | |
H13 | 0.5707 | 0.0652 | 0.2042 | 0.019* | |
H14 | 0.5838 | 0.1050 | 0.0862 | 0.019* | |
N3 | 0.3404 (2) | 0.4813 (3) | 0.4936 (2) | 0.0124 (5) | |
H15 | 0.2942 | 0.4114 | 0.4769 | 0.019* | |
H16 | 0.3234 | 0.5474 | 0.4442 | 0.019* | |
H17 | 0.3292 | 0.5093 | 0.5643 | 0.019* | |
N4 | 0.3392 (2) | 0.0214 (3) | 0.4926 (2) | 0.0152 (6) | |
H18 | 0.2946 | 0.0938 | 0.4984 | 0.023* | |
H19 | 0.3238 | −0.0367 | 0.5475 | 0.023* | |
H20 | 0.3242 | −0.0166 | 0.4245 | 0.023* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nb1 | 0.00884 (15) | 0.01156 (14) | 0.00975 (15) | 0.00028 (10) | −0.00053 (10) | 0.00018 (10) |
Nb2 | 0.00891 (15) | 0.01045 (14) | 0.00870 (15) | 0.00046 (10) | 0.00011 (10) | −0.00057 (10) |
F1 | 0.0151 (9) | 0.0175 (9) | 0.0094 (9) | 0.0009 (7) | −0.0029 (7) | 0.0007 (7) |
F2 | 0.0122 (9) | 0.0276 (10) | 0.0133 (9) | −0.0051 (8) | −0.0015 (7) | 0.0038 (8) |
F3 | 0.0225 (10) | 0.0177 (9) | 0.0183 (10) | 0.0070 (8) | 0.0031 (8) | −0.0034 (8) |
F4 | 0.0222 (10) | 0.0142 (9) | 0.0126 (9) | 0.0008 (7) | −0.0013 (8) | −0.0021 (7) |
F5 | 0.0181 (10) | 0.0157 (9) | 0.0153 (10) | −0.0035 (7) | 0.0019 (8) | 0.0021 (7) |
F6 | 0.0161 (10) | 0.0169 (9) | 0.0106 (9) | 0.0026 (7) | 0.0016 (7) | −0.0024 (7) |
F7 | 0.0157 (10) | 0.0149 (9) | 0.0191 (10) | 0.0017 (7) | 0.0024 (8) | 0.0041 (7) |
F8 | 0.0115 (9) | 0.0186 (9) | 0.0141 (10) | 0.0009 (7) | −0.0008 (7) | −0.0007 (7) |
O1 | 0.0110 (11) | 0.0200 (11) | 0.0138 (12) | 0.0014 (9) | −0.0010 (9) | 0.0031 (9) |
O2 | 0.0151 (12) | 0.0238 (12) | 0.0145 (12) | 0.0017 (9) | 0.0005 (9) | −0.0069 (9) |
O3 | 0.0096 (11) | 0.0169 (11) | 0.0149 (12) | −0.0005 (8) | 0.0019 (9) | 0.0013 (9) |
C1 | 0.0170 (16) | 0.0160 (15) | 0.0136 (16) | 0.0009 (13) | 0.0048 (13) | 0.0006 (13) |
C2 | 0.0095 (15) | 0.0172 (16) | 0.0171 (17) | −0.0010 (12) | 0.0039 (12) | 0.0016 (13) |
C3 | 0.0116 (16) | 0.0138 (15) | 0.0167 (16) | −0.0004 (13) | 0.0017 (13) | −0.0016 (12) |
C4 | 0.0146 (16) | 0.0174 (16) | 0.0129 (16) | 0.0007 (13) | −0.0006 (12) | 0.0001 (12) |
N1 | 0.0132 (13) | 0.0138 (13) | 0.0140 (14) | 0.0004 (10) | −0.0017 (11) | 0.0009 (10) |
N2 | 0.0145 (14) | 0.0128 (12) | 0.0103 (13) | −0.0016 (10) | 0.0015 (10) | 0.0000 (10) |
N3 | 0.0120 (14) | 0.0147 (13) | 0.0104 (13) | −0.0011 (10) | −0.0007 (10) | 0.0006 (10) |
N4 | 0.0136 (14) | 0.0195 (14) | 0.0127 (14) | 0.0023 (11) | 0.0016 (11) | 0.0031 (11) |
Nb1—O1 | 1.766 (2) | C3—C3i | 1.513 (6) |
Nb1—O3 | 1.906 (2) | C3—H5 | 0.9900 |
Nb1—F3 | 1.9417 (18) | C3—H6 | 0.9900 |
Nb1—F4 | 1.9671 (18) | C4—N4 | 1.491 (4) |
Nb1—F2 | 2.0609 (18) | C4—C4ii | 1.520 (6) |
Nb1—F1 | 2.0975 (17) | C4—H7 | 0.9900 |
Nb2—O2 | 1.736 (2) | C4—H8 | 0.9900 |
Nb2—O3 | 1.936 (2) | N1—H9 | 0.9100 |
Nb2—F7 | 1.9462 (18) | N1—H10 | 0.9100 |
Nb2—F5 | 1.9731 (18) | N1—H11 | 0.9100 |
Nb2—F8 | 1.9821 (18) | N2—H12 | 0.9100 |
Nb2—F6 | 2.1723 (18) | N2—H13 | 0.9100 |
C1—N1 | 1.481 (4) | N2—H14 | 0.9100 |
C1—C2 | 1.510 (4) | N3—H15 | 0.9100 |
C1—H1 | 0.9900 | N3—H16 | 0.9100 |
C1—H2 | 0.9900 | N3—H17 | 0.9100 |
C2—N2 | 1.495 (4) | N4—H18 | 0.9100 |
C2—H3 | 0.9900 | N4—H19 | 0.9100 |
C2—H4 | 0.9900 | N4—H20 | 0.9100 |
C3—N3 | 1.481 (4) | ||
O1—Nb1—O3 | 99.84 (10) | N2—C2—H4 | 109.1 |
O1—Nb1—F3 | 100.55 (9) | C1—C2—H4 | 109.1 |
O3—Nb1—F3 | 91.08 (9) | H3—C2—H4 | 107.8 |
O1—Nb1—F4 | 95.32 (9) | N3—C3—C3i | 109.7 (3) |
O3—Nb1—F4 | 90.90 (9) | N3—C3—H5 | 109.7 |
F3—Nb1—F4 | 163.42 (8) | C3i—C3—H5 | 109.7 |
O1—Nb1—F2 | 90.77 (9) | N3—C3—H6 | 109.7 |
O3—Nb1—F2 | 169.39 (9) | C3i—C3—H6 | 109.7 |
F3—Nb1—F2 | 87.10 (8) | H5—C3—H6 | 108.2 |
F4—Nb1—F2 | 87.93 (8) | N4—C4—C4ii | 110.1 (3) |
O1—Nb1—F1 | 167.34 (9) | N4—C4—H7 | 109.6 |
O3—Nb1—F1 | 91.86 (8) | C4ii—C4—H7 | 109.6 |
F3—Nb1—F1 | 83.92 (8) | N4—C4—H8 | 109.6 |
F4—Nb1—F1 | 79.56 (7) | C4ii—C4—H8 | 109.6 |
F2—Nb1—F1 | 77.56 (7) | H7—C4—H8 | 108.1 |
O2—Nb2—O3 | 99.58 (10) | C1—N1—H9 | 109.5 |
O2—Nb2—F7 | 98.88 (10) | C1—N1—H10 | 109.5 |
O3—Nb2—F7 | 92.67 (8) | H9—N1—H10 | 109.5 |
O2—Nb2—F5 | 93.96 (10) | C1—N1—H11 | 109.5 |
O3—Nb2—F5 | 91.06 (8) | H9—N1—H11 | 109.5 |
F7—Nb2—F5 | 165.84 (8) | H10—N1—H11 | 109.5 |
O2—Nb2—F8 | 98.62 (9) | C2—N2—H12 | 109.5 |
O3—Nb2—F8 | 161.80 (9) | C2—N2—H13 | 109.5 |
F7—Nb2—F8 | 84.57 (8) | H12—N2—H13 | 109.5 |
F5—Nb2—F8 | 87.62 (7) | C2—N2—H14 | 109.5 |
O2—Nb2—F6 | 174.89 (9) | H12—N2—H14 | 109.5 |
O3—Nb2—F6 | 82.48 (8) | H13—N2—H14 | 109.5 |
F7—Nb2—F6 | 85.65 (7) | C3—N3—H15 | 109.5 |
F5—Nb2—F6 | 81.30 (7) | C3—N3—H16 | 109.5 |
F8—Nb2—F6 | 79.37 (7) | H15—N3—H16 | 109.5 |
Nb1—O3—Nb2 | 148.01 (12) | C3—N3—H17 | 109.5 |
N1—C1—C2 | 111.9 (3) | H15—N3—H17 | 109.5 |
N1—C1—H1 | 109.2 | H16—N3—H17 | 109.5 |
C2—C1—H1 | 109.2 | C4—N4—H18 | 109.5 |
N1—C1—H2 | 109.2 | C4—N4—H19 | 109.5 |
C2—C1—H2 | 109.2 | H18—N4—H19 | 109.5 |
H1—C1—H2 | 107.9 | C4—N4—H20 | 109.5 |
N2—C2—C1 | 112.4 (3) | H18—N4—H20 | 109.5 |
N2—C2—H3 | 109.1 | H19—N4—H20 | 109.5 |
C1—C2—H3 | 109.1 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H9···F1iii | 0.91 | 2.05 | 2.831 (3) | 142 |
N1—H10···F1iv | 0.91 | 1.82 | 2.697 (3) | 161 |
N1—H9···F4iii | 0.91 | 2.17 | 2.922 (3) | 140 |
N1—H11···O1v | 0.91 | 2.04 | 2.830 (3) | 144 |
N1—H11···F6iv | 0.91 | 2.59 | 3.221 (3) | 127 |
N2—H12···F6vi | 0.91 | 2.02 | 2.857 (3) | 153 |
N2—H12···O3vi | 0.91 | 2.63 | 3.216 (3) | 123 |
N2—H13···F2v | 0.91 | 1.93 | 2.752 (3) | 150 |
N2—H14···F6iv | 0.91 | 1.87 | 2.690 (3) | 148 |
N3—H15···F6 | 0.91 | 2.13 | 2.889 (3) | 140 |
N3—H15···F8 | 0.91 | 2.16 | 2.862 (3) | 133 |
N3—H16···O2iii | 0.91 | 1.83 | 2.719 (3) | 164 |
N3—H17···F4vii | 0.91 | 2.03 | 2.779 (3) | 139 |
N3—H17···F3viii | 0.91 | 2.09 | 2.792 (3) | 133 |
N4—H18···O1vii | 0.91 | 2.32 | 3.005 (4) | 132 |
N4—H18···F8 | 0.91 | 2.37 | 2.909 (3) | 118 |
N4—H18···F7 | 0.91 | 2.40 | 2.927 (3) | 117 |
N4—H19···F2ix | 0.91 | 1.87 | 2.759 (3) | 165 |
N4—H19···F1ix | 0.91 | 2.53 | 3.113 (3) | 122 |
N4—H20···F5vi | 0.91 | 1.90 | 2.791 (3) | 165 |
Symmetry codes: (iii) −x+1/2, y+1/2, −z+1/2; (iv) x+1/2, −y+1/2, z−1/2; (v) x+1, y, z; (vi) −x+1/2, y−1/2, −z+1/2; (vii) x+1/2, −y+1/2, z+1/2; (viii) −x, −y+1, −z+1; (ix) −x, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | (C2H10N2)2[Nb2O3F8] |
Mr | 510.06 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 125 |
a, b, c (Å) | 11.7121 (12), 10.1984 (10), 11.9712 (12) |
β (°) | 93.438 (2) |
V (Å3) | 1427.3 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.71 |
Crystal size (mm) | 0.1 × 0.1 × 0.03 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1999) |
Tmin, Tmax | 0.829, 0.950 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9021, 2608, 2419 |
Rint | 0.022 |
(sin θ/λ)max (Å−1) | 0.604 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.060, 1.10 |
No. of reflections | 2608 |
No. of parameters | 190 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.52, −0.57 |
Computer programs: SMART (Bruker, 1997), SMART, SAINT? and SHELXTL (Bruker, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), WinGX (Farrugia, 1999), program (reference)?.
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H9···F1i | 0.91 | 2.05 | 2.831 (3) | 142 |
N1—H10···F1ii | 0.91 | 1.82 | 2.697 (3) | 161 |
N1—H9···F4i | 0.91 | 2.17 | 2.922 (3) | 140 |
N1—H11···O1iii | 0.91 | 2.04 | 2.830 (3) | 144 |
N2—H12···F6iv | 0.91 | 2.02 | 2.857 (3) | 153 |
N2—H13···F2iii | 0.91 | 1.93 | 2.752 (3) | 150 |
N2—H14···F6ii | 0.91 | 1.87 | 2.690 (3) | 148 |
N3—H15···F6 | 0.91 | 2.13 | 2.889 (3) | 140 |
N3—H15···F8 | 0.91 | 2.16 | 2.862 (3) | 133 |
N3—H16···O2i | 0.91 | 1.83 | 2.719 (3) | 164 |
N3—H17···F4v | 0.91 | 2.03 | 2.779 (3) | 139 |
N3—H17···F3vi | 0.91 | 2.09 | 2.792 (3) | 133 |
N4—H18···O1v | 0.91 | 2.32 | 3.005 (4) | 132 |
N4—H18···F8 | 0.91 | 2.37 | 2.909 (3) | 118 |
N4—H18···F7 | 0.91 | 2.40 | 2.927 (3) | 117 |
N4—H19···F2vii | 0.91 | 1.87 | 2.759 (3) | 165 |
N4—H19···F1vii | 0.91 | 2.53 | 3.113 (3) | 122 |
N4—H20···F5iv | 0.91 | 1.90 | 2.791 (3) | 165 |
Symmetry codes: (i) −x+1/2, y+1/2, −z+1/2; (ii) x+1/2, −y+1/2, z−1/2; (iii) x+1, y, z; (iv) −x+1/2, y−1/2, −z+1/2; (v) x+1/2, −y+1/2, z+1/2; (vi) −x, −y+1, −z+1; (vii) −x, −y, −z+1. |
Atom | Σ s(ij) |
Nb1 | 5.22 |
Nb2 | 5.29 |
F1 | 0.54b |
F2 | 0.60b |
F3 | 0.82b |
F4 | 0.77b |
F5 | 0.76b |
F6 | 0.44b |
F7 | 0.81b |
F8 | 0.74b |
O1 | 1.48a |
O2 | 1.61a |
O3 | 1.95a |
s(ij) values calculated for B = 0.37: (a) Brown & Altermatt (1985) empirical; (b) Brese & O'Keeffe (1991) extrapolated. |
Acknowledgements
The authors thank Professor Alex Slawin for assistance in data collection, and the University of St Andrews for funding.
References
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The title compound, (I), is the first organically templated niobium oxyfluoride. It also appears to be the first example of isolated dimeric niobium oxyfluoride units. In purely inorganic niobium oxyfluorides, a variety of building units have been reported; isolated [NbOF5]2− octahedra are found in Li2NbOF5 (Galy et al., 1969), and isolated pentagonal bipyramidal NbF7 and NbOF6 units are found in Rb5Nb3OF18 (Agulyanskii et al., 1991) and Ba4Nb2O3F12 (Crosnier-Lopez & Fourquet, 1993), respectively. The latter compound also contains cis corner-sharing octahedral tetramers. O-atom-linked trans vertex-sharing chains are found in [NH4][NbOF4] (Pakhomov & Kaidalova, 1974). Poeppelmeier and coworkers (Welk et al., 2002) have exploited metal–organic complexes in `directing' otherwise isolated [NbOF5]2− ions into specific crystallographic orientations.
The main feature of most of the previously reported niobium oxofluorides is the out-of-centre octahedral distortion. Electronic effects and bond network effects lead to the characteristic short Nb═O bond length and the longer Nb—X bond length trans to it. Along with non-centrosymmetry, the off-centre distortion is important in the non-linear properties of the structure. In the [NbOF5]2− anion (e.g. Izumi et al., 2005), the Nb atom is displaced from the center of the octahedron towards the O atom to form a short Nb═O bond and a longer Nb—F bond.
(C2H10N2)2[Nb2O3F8] (Fig. 1) is built up from diprotonated ethylenediamine cations and dimeric [Nb2O3F8]4− units. Each dimer consists of two NbO2F4 octahedra, which share corners with each other via one O atom.
Bond-valence sums (Table 2) show that some of the F atoms are heavily underbonded, and this is compensated by substantial hydrogen bonding to the organic cations. For example, the two F atoms trans to the short Nb═ O bonds (F1 and F6) accept three hydrogen bonds, while the two trans to the bridging O atom (F2 and F8) accept two each. Similarly, atom O1 is hydrogen bonded to two NH groups, while atom O2 is only bound to one, compatible with a small s(ij) of 1.48 for the Nb1—O1 bond, and a larger s(ij) of 1.61 for the Nb2—O2 bond. The bridging O3 atom does not require hydrogen bonding. All H atoms of the ethylenediammonium moieties partake in hydrogen bonding. In one of the octahedra (Nb1) there is a slight tendency for displacement of Nb towards an edge (O1/O3) rather than a vertex of the octahedron.
The complex hydrogen-bonding scheme results in the crystal packing shown in Fig. 2. The dimers are aligned along the [010] direction in a herringbone fashion.