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Acta Cryst. (2008). E64, m838-m839    [ doi:10.1107/S1600536808015237 ]

Tetrakis(1,1,1-trifluoroacetylacetonato-[kappa]2O,O')hafnium(IV) toluene disolvate

J. A. Viljoen, A. Muller and A. Roodt

Abstract top

In the title compound, [Hf(C5H4F3O2)4]·2C7H8, the HfIV atom, lying on a twofold rotation axis, is coordinated by eight O atoms from four 1,1,1-trifluoroacetylacetonate ligands with an average Hf-O distance of 2.173 (1) Å and O-Hf-O bite angles of 75.69 (5) and 75.54 (5)°. The coordination polyhedron shows a slightly distorted Archimedean square antiprismatic geometry. The asymmetric unit contains a toluene solvent molecule. The crystal structure involves C-H....F hydrogen bonds.

Comment top

This study was done as part of ongoing research in our group to investigate reactions of O,O'- and O,N-bidentate ligands with hafnium(IV) and zirconium(IV). The total separation of zircon ore (ZrSiO4) is important to have materials viable for nuclear applications. Previous work on hafnium(IV) complexes with β-diketone was done to determine their thermal decomposition to yield metal oxides (Chattoraj et al., 1968). Hafnium β-diketonates are also promising precursor materials for producing metal oxide films, providing the possibility to manufacture technologically important coatings (Zherikova et al., 2005).

The title compound crystallizes as the monoclinic polymorph (C2/c, Z = 4) (Fig. 1) with two toluene solvent molecules. The triclinic polymorph earlier reported by Zherikova et al. (2005) contains no solvent molecules and cannot be superimposed with the title compound due to differences in metal coordination modes. An isomorphous zirconium complex has been reported by Steyn et al. (2008). The HfIV atom in the title compound is situated on a twofold rotation axis, with four β-diketonate ligands, 1,1,1-trifluoroacetylacetonate (tfaa), coordinating to the HfIV atom adopting an Archimedean antiprism coordination geometry (Fig. 2). The Hf—O bond lengths vary from 2.1527 (13) Å to 2.1933 (13) Å, with the average Hf—O distance being 2.173 (1) Å. The O—Hf—O bite angles are 75.69 (5)° and 75.54 (5)° (Table 1). This average bond distance is somewhat larger than the average of 2.156 Å obtained from the Cambridge Structural Database (Allen, 2002) (data extracted from 19 hits, yielding 45 observations ranging from 2.039 to 2.248 Å). Pairs of toluene molecules are π-stacked (interplanar distance = 3.65 (1) Å, centroid–centroid distance = 4.92 (1) Å) in channels formed by the metal complex moieties parallel to the b-axis (Fig. 3). The preferred CF3-group conformation is probably due to weak C—H···F interactions (Table 2).

Related literature top

For the triclinic polymorph of the title compound, see: Zherikova et al. (2005). For related literature on hafnium β-diketone complexes, see: Chattoraj et al. (1968). For the isomorphous zirconium complex, see: Steyn et al. (2008). For a description of the Cambridge Structural Database, see: Allen (2002).

Experimental top

Chemicals were purchased from Sigma and Aldrich and used as received except for toluene, which was dried by passage over alumina. Syntheses were performed using modified Schlenk conditions. The ligand salt (Natfaa) was prepared by adding Htfaa (6.05 ml, 50 mmol) dropwise to NaOH (2.02 g, 50 mmol) over a period of 3 minutes. The resulting solids were washed with toluene and dried in vacuo. Natfaa (0.459 g, 2.6 mmol) was added to a suspension of HfCl4 (0.207 g, 0.65 mmol) in toluene (10 ml). Dissolution gave a slightly yellow solution after 10 min. After refluxing for ca 20 h the crude product was filtered and washed with toluene. The filtrate was slowly recrystallized at 253 K at near quantitative yield. Spectroscopy data: 19F {H} NMR (C6D6; 564.77 MHz): -75.49 p.p.m.; IR (ATR): ν(CO) 1533 cm-1.

Refinement top

H atoms were positioned geometrically and refined as riding atoms, with C—H = 0.93 (aromatic) and 0.96 Å (methyl) and with Uiso(H) = 1.2Ueq(C) for aromatic and 1.5Ueq(C) for methyl groups. Torsion angles for methyl H atoms were refined from electron density. The highest residual electron density lies within 1.0 Å from the Hf atom.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. Structure of the title compound. Displacement ellipsoids are drawn at the 30 % probability level. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. Slightly distorted Archimedean antiprism coordination polyhedron surrounding Hf atom.
[Figure 3] Fig. 3. Packing diagram of the title compound along the b-axis showing π-stacking of toluene molecule pairs. H atoms have been omitted for clarity.
Tetrakis(1,1,1-trifluoroacetylacetonato-κ2O,O')hafnium(IV) toluene disolvate top
Crystal data top
[Hf(C5H4F3O2)4]·2C7H8F000 = 1920
Mr = 975.09Dx = 1.784 Mg m−3
Monoclinic, C2/cMo Kα radiation
λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 6211 reflections
a = 22.4983 (15) Åθ = 2.7–28.3º
b = 8.0642 (5) ŵ = 2.98 mm−1
c = 22.712 (2) ÅT = 100 (2) K
β = 118.211 (2)ºBlock, colourless
V = 3631.2 (5) Å30.33 × 0.25 × 0.22 mm
Z = 4
Data collection top
Bruker X8 APEXII 4K KappaCCD
diffractometer		4518 independent reflections
Monochromator: graphite4256 reflections with I > 2σ(I)
Detector resolution: 8.4 pixels mm-1Rint = 0.023
T = 100(2) Kθmax = 28.4º
φ and ω scansθmin = 2.0º
Absorption correction: multi-scan
(SADABS; Bruker, 2001)		h = −30→26
Tmin = 0.439, Tmax = 0.560k = −10→10
18332 measured reflectionsl = −29→30
Refinement top
Refinement on F2H-atom parameters constrained
Least-squares matrix: full  w = 1/[σ2(Fo2) + (0.0173P)2 + 5.3839P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.019(Δ/σ)max = 0.002
wR(F2) = 0.042Δρmax = 1.12 e Å−3
S = 1.07Δρmin = −0.91 e Å−3
4518 reflectionsExtinction correction: none
252 parameters
Crystal data top
[Hf(C5H4F3O2)4]·2C7H8V = 3631.2 (5) Å3
Mr = 975.09Z = 4
Monoclinic, C2/cMo Kα
a = 22.4983 (15) ŵ = 2.98 mm−1
b = 8.0642 (5) ÅT = 100 (2) K
c = 22.712 (2) Å0.33 × 0.25 × 0.22 mm
β = 118.211 (2)º
Data collection top
Bruker X8 APEXII 4K KappaCCD
diffractometer		4518 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)		4256 reflections with I > 2σ(I)
Tmin = 0.439, Tmax = 0.560Rint = 0.023
18332 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.019252 parameters
wR(F2) = 0.042H-atom parameters constrained
S = 1.07Δρmax = 1.12 e Å−3
4518 reflectionsΔρmin = −0.91 e Å−3
Special details top

Experimental. The intensity data was collected on a Bruker X8 Apex II 4 K Kappa CCD diffractometer using an exposure time of 20 s/frame. A total of 1897 frames were collected with a frame width of 0.5° covering up to θ = 28.35° with 99.8% completeness accomplished.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Hf0.50.165295 (14)0.750.01071 (4)
O10.51936 (7)−0.05501 (17)0.81255 (6)0.0145 (3)
O20.49393 (7)0.25296 (17)0.83653 (6)0.0150 (3)
C10.50749 (11)−0.2808 (3)0.87229 (11)0.0220 (4)
H1A0.508−0.34480.83690.033*
H1B0.4696−0.31330.87830.033*
H1C0.5485−0.29980.91290.033*
C20.50184 (10)−0.1008 (3)0.85482 (9)0.0156 (4)
C30.47953 (10)0.0117 (3)0.88823 (10)0.0184 (4)
H30.4644−0.02840.91720.022*
C40.48009 (10)0.1778 (3)0.87820 (9)0.0154 (4)
C50.46372 (11)0.2975 (3)0.92078 (10)0.0207 (4)
F10.40902 (8)0.3862 (2)0.88355 (7)0.0409 (4)
F20.45382 (8)0.21987 (18)0.96725 (7)0.0343 (3)
F30.51363 (7)0.40485 (17)0.95280 (7)0.0316 (3)
O30.43603 (7)0.38624 (17)0.71276 (7)0.0146 (3)
O40.40009 (6)0.07826 (17)0.72464 (6)0.0136 (3)
C60.36205 (11)0.6104 (3)0.69597 (12)0.0229 (4)
H6A0.40120.67540.70490.034*
H6B0.34340.64750.7240.034*
H6C0.3290.62310.64990.034*
C70.38151 (10)0.4318 (2)0.71005 (9)0.0158 (4)
C80.33652 (10)0.3194 (2)0.71708 (10)0.0175 (4)
H80.29860.35950.71880.021*
C90.34868 (10)0.1536 (2)0.72125 (9)0.0148 (4)
C100.29459 (10)0.0341 (3)0.71829 (11)0.0197 (4)
F40.31970 (6)−0.07336 (16)0.76889 (6)0.0261 (3)
F50.24293 (7)0.11096 (17)0.72015 (8)0.0338 (3)
F60.26890 (6)−0.05534 (17)0.66195 (6)0.0274 (3)
C110.65622 (14)0.3966 (4)0.96674 (17)0.0550 (9)
H11A0.69430.4270.96080.082*
H11B0.65410.46760.99960.082*
H11C0.61560.40840.92510.082*
C120.66358 (11)0.2194 (3)0.98981 (12)0.0313 (5)
C130.66964 (12)0.1760 (3)1.05128 (12)0.0336 (6)
H130.66810.2581.07930.04*
C140.67800 (13)0.0117 (4)1.07158 (12)0.0376 (6)
H140.682−0.01561.11310.045*
C150.68046 (13)−0.1112 (4)1.03081 (14)0.0384 (6)
H150.6867−0.22131.04460.046*
C160.67360 (12)−0.0688 (4)0.96942 (14)0.0406 (7)
H160.6747−0.15090.94120.049*
C170.66513 (12)0.0941 (4)0.94935 (12)0.0372 (6)
H170.66030.12040.90750.045*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Hf0.01298 (6)0.00766 (6)0.01517 (6)00.00966 (4)0
O10.0157 (6)0.0118 (7)0.0192 (6)0.0011 (5)0.0108 (5)0.0027 (5)
O20.0207 (7)0.0117 (7)0.0170 (6)−0.0013 (6)0.0126 (6)0.0003 (5)
C10.0315 (12)0.0136 (10)0.0271 (11)0.0000 (9)0.0190 (9)0.0039 (8)
C20.0145 (9)0.0143 (10)0.0175 (9)−0.0012 (8)0.0071 (7)0.0020 (8)
C30.0239 (10)0.0171 (10)0.0195 (9)−0.0018 (8)0.0148 (8)0.0026 (8)
C40.0160 (9)0.0166 (10)0.0161 (8)−0.0014 (8)0.0097 (7)−0.0013 (8)
C50.0300 (11)0.0179 (11)0.0211 (10)0.0006 (8)0.0179 (9)0.0009 (8)
F10.0431 (9)0.0495 (10)0.0335 (8)0.0248 (8)0.0209 (7)−0.0008 (7)
F20.0647 (10)0.0234 (7)0.0379 (8)−0.0053 (7)0.0433 (8)−0.0026 (6)
F30.0485 (9)0.0217 (7)0.0361 (7)−0.0106 (6)0.0294 (7)−0.0127 (6)
O30.0160 (7)0.0110 (7)0.0210 (7)0.0019 (5)0.0122 (6)0.0026 (5)
O40.0136 (6)0.0109 (7)0.0194 (7)0.0020 (5)0.0104 (5)0.0003 (5)
C60.0229 (11)0.0131 (10)0.0375 (12)0.0034 (8)0.0183 (10)0.0040 (9)
C70.0187 (9)0.0124 (10)0.0183 (9)0.0012 (8)0.0104 (8)0.0008 (7)
C80.0164 (9)0.0131 (10)0.0288 (10)0.0017 (8)0.0155 (8)0.0005 (8)
C90.0147 (9)0.0147 (10)0.0186 (9)0.0005 (8)0.0109 (7)0.0002 (8)
C100.0185 (10)0.0143 (10)0.0312 (11)0.0008 (8)0.0158 (9)0.0002 (8)
F40.0291 (7)0.0205 (7)0.0348 (7)−0.0030 (5)0.0201 (6)0.0060 (6)
F50.0273 (7)0.0185 (7)0.0731 (10)0.0012 (6)0.0382 (7)−0.0005 (7)
F60.0228 (6)0.0246 (7)0.0335 (7)−0.0089 (5)0.0122 (6)−0.0067 (6)
C110.0259 (14)0.0496 (19)0.067 (2)−0.0055 (13)0.0033 (13)0.0194 (16)
C120.0156 (10)0.0374 (14)0.0306 (12)−0.0050 (10)0.0024 (9)0.0040 (11)
C130.0294 (12)0.0384 (15)0.0324 (12)−0.0058 (11)0.0141 (10)−0.0126 (11)
C140.0352 (13)0.0514 (18)0.0272 (12)−0.0092 (13)0.0154 (10)0.0039 (12)
C150.0270 (13)0.0302 (14)0.0523 (16)−0.0051 (11)0.0141 (12)−0.0008 (12)
C160.0235 (12)0.0549 (19)0.0425 (15)−0.0074 (12)0.0150 (11)−0.0250 (14)
C170.0229 (12)0.065 (2)0.0222 (11)−0.0077 (12)0.0094 (10)−0.0013 (12)
Geometric parameters (Å, °) top
Hf—O22.1527 (13)C6—H6B0.96
Hf—O2i2.1527 (13)C6—H6C0.96
Hf—O42.1571 (13)C7—C81.423 (3)
Hf—O4i2.1571 (13)C8—C91.359 (3)
Hf—O1i2.1861 (13)C8—H80.93
Hf—O12.1861 (13)C9—C101.529 (3)
Hf—O3i2.1933 (14)C10—F41.333 (2)
Hf—O32.1933 (13)C10—F51.335 (2)
O1—C21.253 (2)C10—F61.339 (2)
O2—C41.280 (2)C11—C121.504 (4)
C1—C21.494 (3)C11—H11A0.96
C1—H1A0.96C11—H11B0.96
C1—H1B0.96C11—H11C0.96
C1—H1C0.96C12—C171.377 (4)
C2—C31.418 (3)C12—C131.382 (4)
C3—C41.359 (3)C13—C141.386 (4)
C3—H30.93C13—H130.93
C4—C51.530 (3)C14—C151.375 (4)
C5—F11.325 (3)C14—H140.93
C5—F31.329 (3)C15—C161.372 (4)
C5—F21.333 (2)C15—H150.93
O3—C71.254 (2)C16—C171.374 (4)
O4—C91.276 (2)C16—H160.93
C6—C71.496 (3)C17—H170.93
C6—H6A0.96
O2—Hf—O2i141.66 (7)F3—C5—C4111.30 (17)
O2—Hf—O480.96 (5)F2—C5—C4112.58 (17)
O2i—Hf—O4111.77 (5)C7—O3—Hf134.87 (13)
O2—Hf—O4i111.77 (5)C9—O4—Hf131.43 (13)
O2i—Hf—O4i80.96 (5)C7—C6—H6A109.5
O4—Hf—O4i142.02 (7)C7—C6—H6B109.5
O2—Hf—O1i141.35 (5)H6A—C6—H6B109.5
O2i—Hf—O1i75.69 (5)C7—C6—H6C109.5
O4—Hf—O1i72.52 (5)H6A—C6—H6C109.5
O4i—Hf—O1i76.79 (5)H6B—C6—H6C109.5
O2—Hf—O175.69 (5)O3—C7—C8122.62 (18)
O2i—Hf—O1141.35 (5)O3—C7—C6118.27 (18)
O4—Hf—O176.79 (5)C8—C7—C6119.06 (18)
O4i—Hf—O172.52 (5)C9—C8—C7120.28 (18)
O1i—Hf—O171.28 (7)C9—C8—H8119.9
O2—Hf—O3i72.21 (5)C7—C8—H8119.9
O2i—Hf—O3i76.82 (5)O4—C9—C8128.26 (18)
O4—Hf—O3i141.11 (5)O4—C9—C10112.50 (17)
O4i—Hf—O3i75.54 (5)C8—C9—C10119.16 (17)
O1i—Hf—O3i143.48 (5)F4—C10—F5107.15 (16)
O1—Hf—O3i121.11 (5)F4—C10—F6106.83 (17)
O2—Hf—O376.82 (5)F5—C10—F6106.94 (17)
O2i—Hf—O372.21 (5)F4—C10—C9111.58 (16)
O4—Hf—O375.54 (5)F5—C10—C9113.11 (17)
O4i—Hf—O3141.11 (5)F6—C10—C9110.90 (16)
O1i—Hf—O3121.11 (5)C12—C11—H11A109.5
O1—Hf—O3143.48 (5)C12—C11—H11B109.5
O3i—Hf—O371.35 (7)H11A—C11—H11B109.5
C2—O1—Hf134.34 (13)C12—C11—H11C109.5
C4—O2—Hf131.45 (13)H11A—C11—H11C109.5
C2—C1—H1A109.5H11B—C11—H11C109.5
C2—C1—H1B109.5C17—C12—C13117.8 (3)
H1A—C1—H1B109.5C17—C12—C11119.9 (3)
C2—C1—H1C109.5C13—C12—C11122.3 (3)
H1A—C1—H1C109.5C12—C13—C14120.7 (2)
H1B—C1—H1C109.5C12—C13—H13119.6
O1—C2—C3122.69 (19)C14—C13—H13119.6
O1—C2—C1118.14 (18)C15—C14—C13120.5 (2)
C3—C2—C1119.12 (18)C15—C14—H14119.8
C4—C3—C2120.47 (18)C13—C14—H14119.8
C4—C3—H3119.8C16—C15—C14118.9 (3)
C2—C3—H3119.8C16—C15—H15120.5
O2—C4—C3127.96 (18)C14—C15—H15120.5
O2—C4—C5112.58 (17)C15—C16—C17120.5 (3)
C3—C4—C5119.46 (17)C15—C16—H16119.8
F1—C5—F3106.71 (18)C17—C16—H16119.8
F1—C5—F2107.83 (17)C16—C17—C12121.6 (2)
F3—C5—F2106.67 (17)C16—C17—H17119.2
F1—C5—C4111.44 (17)C12—C17—H17119.2
Symmetry codes: (i) −x+1, y, −z+3/2.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C3—H3···F20.932.372.712 (2)102
C8—H8···F50.932.372.721 (2)102
Table 1
Selected geometric parameters (Å, °) top
Hf—O22.1527 (13)Hf—O12.1861 (13)
Hf—O42.1571 (13)Hf—O32.1933 (13)
O2—Hf—O2i141.66 (7)O1i—Hf—O171.28 (7)
O2—Hf—O480.96 (5)O2—Hf—O3i72.21 (5)
O2i—Hf—O4111.77 (5)O4—Hf—O3i141.11 (5)
O4—Hf—O4i142.02 (7)O1—Hf—O3i121.11 (5)
O2—Hf—O1i141.35 (5)O2—Hf—O376.82 (5)
O4—Hf—O1i72.52 (5)O4—Hf—O375.54 (5)
O2—Hf—O175.69 (5)O1—Hf—O3143.48 (5)
O4—Hf—O176.79 (5)O3i—Hf—O371.35 (7)
Symmetry codes: (i) −x+1, y, −z+3/2.
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C3—H3···F20.932.372.712 (2)102
C8—H8···F50.932.372.721 (2)102
Acknowledgements top

Financial assistance from the Advanced Metals Initiative (AMI) and the Department of Science and Technology (DST) of South Africa, as well as the New Metals Development Network (NMDN) and the South African Nuclear Energy Corporation Limited (Necsa) is gratefully acknowledged. Dr R. Meijboom is aknowledged for his kind assistance in the use of modified Shlenck techniques.

references
References top

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