Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100009811/jz1419sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100009811/jz1419Isup2.hkl |
CCDC reference: 152593
Because of the extreme susceptibility of the titanium halides to hydrolysis, all operations were carried out under an inert gas atmosphere. 2,6-Dimethylpyridine (9.45 mmol, 1.1 ml) was added to a solution of TiBr4 (0.96 ml, 9.11 mmol) in hexane (30 ml). The red precipitate was washed with hexane and dried. Sublimation at 353 K yielded suitable crystals after approximately two weeks.
Using all reflections initially found on the first frames for determination of a preliminary cell, it turned out that several reflections with systematic deviations from integral indices did not fit to the derived cell. This result was a strong indication of twinning. However, these reflections could be indexed when the orientation matrix was transformed using the matrix (100/010/0.11,0,1). Thus, the transformation for the reflection indices of the two twin components is: htwin = −h, ktwin = −k, ltwin = l+h/9. This means that most of the reflections are sufficiently separated for a satisfactory data collection, but exact overlap occurred for the reflections with h = 9 m (with m integer). Since the reflections with |h| = 1,8,10 showed only partial overlap and their correct intensity cannot be derived they were discarded from the refinement process. For refinement, the data were read in via HKLF5 and an additional variable was introduced (using the BASF command) describing the fractional contributions of the two twin components for the reflections with h = 9 m; the ratio refined to 0.202 (3)/0.798 (3). All H atoms were located by difference Fourier synthesis and refined with fixed individual displacement parameters [U(H) = 1.5Ueq(Cmethyl) or U(H) = 1.2Ueq(Caromatic)] using a riding model with C—H(aromatic) = 0.95 Å or C—H(methyl) = 0.98 Å. The methyl groups were allowed to rotate about their local threefold axis.
Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL (Siemens, 1995).
[TiBr4(C7H9N)] | F(000) = 880 |
Mr = 474.69 | Dx = 2.462 Mg m−3 |
Monoclinic, C2 | Mo Kα radiation, λ = 0.71073 Å |
a = 11.6811 (2) Å | Cell parameters from 8192 reflections |
b = 9.8679 (2) Å | θ = 1–25° |
c = 11.1300 (2) Å | µ = 13.11 mm−1 |
β = 93.482 (1)° | T = 133 K |
V = 1280.56 (4) Å3 | Plate, red |
Z = 4 | 0.40 × 0.20 × 0.05 mm |
Siemens CCD three-circle diffractometer | 2002 independent reflections |
Radiation source: fine-focus sealed tube | 1798 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.073 |
ω scans | θmax = 26.5°, θmin = 1.8° |
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996) | h = −14→14 |
Tmin = 0.077, Tmax = 0.560 | k = −12→12 |
10417 measured reflections | l = 0→13 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.068 | w = 1/[σ2(Fo2) + (0.0257P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max = 0.001 |
2002 reflections | Δρmax = 0.61 e Å−3 |
124 parameters | Δρmin = −0.59 e Å−3 |
1 restraint | Absolute structure: Flack (1983) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.03 (2) |
[TiBr4(C7H9N)] | V = 1280.56 (4) Å3 |
Mr = 474.69 | Z = 4 |
Monoclinic, C2 | Mo Kα radiation |
a = 11.6811 (2) Å | µ = 13.11 mm−1 |
b = 9.8679 (2) Å | T = 133 K |
c = 11.1300 (2) Å | 0.40 × 0.20 × 0.05 mm |
β = 93.482 (1)° |
Siemens CCD three-circle diffractometer | 2002 independent reflections |
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996) | 1798 reflections with I > 2σ(I) |
Tmin = 0.077, Tmax = 0.560 | Rint = 0.073 |
10417 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.068 | Δρmax = 0.61 e Å−3 |
S = 1.00 | Δρmin = −0.59 e Å−3 |
2002 reflections | Absolute structure: Flack (1983) |
124 parameters | Absolute structure parameter: 0.03 (2) |
1 restraint |
Experimental. |
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. Coverage of the unique set is 100% complete to at least 25.0° in θ. Crystal decay was monitored by repeating the initial frames at the end of data collection and analyzing the duplicate reflections. |
x | y | z | Uiso*/Ueq | ||
Ti1 | 0.5000 | 0.50712 (19) | 1.0000 | 0.0157 (4) | |
Br1 | 0.62173 (6) | 0.46822 (7) | 1.18188 (7) | 0.0231 (2) | |
Br2 | 0.62667 (7) | 0.65623 (8) | 0.90897 (7) | 0.0252 (2) | |
N1 | 0.5000 | 0.2861 (8) | 1.0000 | 0.0134 (18) | |
C2 | 0.5799 (6) | 0.2151 (8) | 0.9421 (7) | 0.0199 (18) | |
C21 | 0.6665 (7) | 0.2981 (8) | 0.8765 (7) | 0.0236 (18) | |
H21A | 0.6264 | 0.3508 | 0.8122 | 0.035* | |
H21B | 0.7218 | 0.2372 | 0.8416 | 0.035* | |
H21C | 0.7071 | 0.3598 | 0.9334 | 0.035* | |
C3 | 0.5801 (7) | 0.0769 (8) | 0.9386 (7) | 0.0213 (18) | |
H3 | 0.6349 | 0.0304 | 0.8942 | 0.026* | |
C4 | 0.5000 | 0.0042 (12) | 1.0000 | 0.023 (3) | |
H4 | 0.5000 | −0.0920 | 1.0000 | 0.027* | |
Ti1A | 0.5000 | 0.96534 (19) | 0.5000 | 0.0151 (4) | |
Br1A | 0.39673 (7) | 0.92539 (7) | 0.68047 (7) | 0.0210 (2) | |
Br2A | 0.36461 (7) | 1.11412 (8) | 0.40588 (7) | 0.02206 (19) | |
N1A | 0.5000 | 0.7448 (9) | 0.5000 | 0.0151 (18) | |
C2A | 0.4120 (6) | 0.6738 (8) | 0.4433 (7) | 0.0204 (17) | |
C21A | 0.3150 (6) | 0.7575 (8) | 0.3819 (7) | 0.0201 (17) | |
H21D | 0.2832 | 0.8186 | 0.4408 | 0.030* | |
H21E | 0.2546 | 0.6967 | 0.3489 | 0.030* | |
H21F | 0.3450 | 0.8109 | 0.3165 | 0.030* | |
C3A | 0.4099 (7) | 0.5344 (8) | 0.4421 (7) | 0.0216 (18) | |
H3A | 0.3477 | 0.4871 | 0.4023 | 0.026* | |
C4A | 0.5000 | 0.4641 (12) | 0.5000 | 0.023 (3) | |
H4A | 0.5000 | 0.3678 | 0.5000 | 0.028* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ti1 | 0.0159 (11) | 0.0177 (10) | 0.0131 (10) | 0.000 | −0.0025 (8) | 0.000 |
Br1 | 0.0217 (4) | 0.0320 (5) | 0.0148 (4) | −0.0041 (3) | −0.0056 (3) | 0.0019 (3) |
Br2 | 0.0290 (5) | 0.0254 (4) | 0.0213 (5) | −0.0067 (4) | 0.0026 (3) | 0.0044 (3) |
N1 | 0.013 (5) | 0.018 (5) | 0.009 (4) | 0.000 | −0.004 (3) | 0.000 |
C2 | 0.012 (4) | 0.028 (4) | 0.020 (4) | −0.003 (3) | 0.001 (4) | −0.003 (3) |
C21 | 0.018 (4) | 0.021 (4) | 0.034 (5) | 0.001 (3) | 0.013 (4) | −0.001 (4) |
C3 | 0.023 (5) | 0.020 (4) | 0.020 (4) | 0.006 (3) | −0.008 (3) | 0.001 (3) |
C4 | 0.030 (7) | 0.023 (6) | 0.015 (6) | 0.000 | −0.005 (5) | 0.000 |
Ti1A | 0.0145 (9) | 0.0171 (10) | 0.0138 (9) | 0.000 | 0.0017 (7) | 0.000 |
Br1A | 0.0203 (4) | 0.0293 (5) | 0.0139 (4) | 0.0017 (3) | 0.0041 (3) | 0.0001 (3) |
Br2A | 0.0232 (4) | 0.0236 (4) | 0.0189 (4) | 0.0057 (3) | −0.0025 (3) | 0.0022 (3) |
N1A | 0.017 (5) | 0.018 (5) | 0.010 (4) | 0.000 | 0.002 (4) | 0.000 |
C2A | 0.012 (4) | 0.025 (4) | 0.024 (4) | 0.003 (3) | 0.003 (3) | −0.004 (3) |
C21A | 0.015 (4) | 0.030 (4) | 0.015 (4) | 0.001 (3) | −0.004 (3) | −0.002 (3) |
C3A | 0.017 (4) | 0.021 (4) | 0.026 (4) | −0.002 (3) | −0.001 (4) | 0.002 (4) |
C4A | 0.031 (7) | 0.017 (6) | 0.022 (6) | 0.000 | 0.007 (5) | 0.000 |
Ti1—N1 | 2.181 (8) | Ti1A—N1A | 2.176 (9) |
Ti1—Br2 | 2.3585 (14) | Ti1A—Br2Aii | 2.3564 (14) |
Ti1—Br2i | 2.3585 (14) | Ti1A—Br2A | 2.3564 (14) |
Ti1—Br1i | 2.4326 (8) | Ti1A—Br1Aii | 2.4372 (8) |
Ti1—Br1 | 2.4326 (8) | Ti1A—Br1A | 2.4372 (8) |
N1—C2i | 1.361 (9) | N1A—C2A | 1.367 (9) |
N1—C2 | 1.361 (9) | N1A—C2Aii | 1.367 (9) |
C2—C3 | 1.364 (11) | C2A—C3A | 1.376 (11) |
C2—C21 | 1.522 (11) | C2A—C21A | 1.529 (11) |
C3—C4 | 1.391 (10) | C3A—C4A | 1.387 (9) |
C4—C3i | 1.391 (10) | C4A—C3Aii | 1.387 (9) |
N1—Ti1—Br2 | 128.60 (4) | N1A—Ti1A—Br2Aii | 128.54 (4) |
N1—Ti1—Br2i | 128.60 (4) | N1A—Ti1A—Br2A | 128.54 (4) |
Br2—Ti1—Br2i | 102.81 (8) | Br2Aii—Ti1A—Br2A | 102.92 (8) |
N1—Ti1—Br1i | 80.92 (5) | N1A—Ti1A—Br1Aii | 80.69 (5) |
Br2—Ti1—Br1i | 95.23 (3) | Br2Aii—Ti1A—Br1Aii | 96.59 (4) |
Br2i—Ti1—Br1i | 96.07 (3) | Br2A—Ti1A—Br1Aii | 94.98 (3) |
N1—Ti1—Br1 | 80.92 (5) | N1A—Ti1A—Br1A | 80.69 (5) |
Br2—Ti1—Br1 | 96.07 (3) | Br2Aii—Ti1A—Br1A | 94.98 (3) |
Br2i—Ti1—Br1 | 95.23 (3) | Br2A—Ti1A—Br1A | 96.59 (4) |
Br1i—Ti1—Br1 | 161.84 (9) | Br1Aii—Ti1A—Br1A | 161.38 (9) |
C2i—N1—C2 | 118.0 (9) | C2A—N1A—C2Aii | 118.3 (9) |
C2i—N1—Ti1 | 121.0 (5) | C2A—N1A—Ti1A | 120.8 (5) |
C2—N1—Ti1 | 121.0 (5) | C2Aii—N1A—Ti1A | 120.8 (5) |
C3—C2—N1 | 122.0 (8) | N1A—C2A—C3A | 122.0 (7) |
C3—C2—C21 | 121.5 (7) | N1A—C2A—C21A | 116.5 (7) |
N1—C2—C21 | 116.4 (7) | C3A—C2A—C21A | 121.5 (7) |
C2—C3—C4 | 119.9 (8) | C2A—C3A—C4A | 118.9 (8) |
C3—C4—C3i | 117.9 (11) | C3Aii—C4A—C3A | 119.9 (11) |
Br2—Ti1—N1—C2i | 179.8 (4) | Br2Aii—Ti1A—N1A—C2A | 177.9 (4) |
Br2i—Ti1—N1—C2i | −0.2 (4) | Br2A—Ti1A—N1A—C2A | −2.1 (4) |
Br1i—Ti1—N1—C2i | −90.7 (4) | Br1Aii—Ti1A—N1A—C2A | −91.1 (4) |
Br1—Ti1—N1—C2i | 89.3 (4) | Br1A—Ti1A—N1A—C2A | 88.9 (4) |
Br2—Ti1—N1—C2 | −0.2 (4) | Br2Aii—Ti1A—N1A—C2Aii | −2.1 (4) |
Br2i—Ti1—N1—C2 | 179.8 (4) | Br2A—Ti1A—N1A—C2Aii | 177.9 (4) |
Br1i—Ti1—N1—C2 | 89.3 (4) | Br1Aii—Ti1A—N1A—C2Aii | 88.9 (4) |
Br1—Ti1—N1—C2 | −90.7 (4) | Br1A—Ti1A—N1A—C2Aii | −91.1 (4) |
C2i—N1—C2—C3 | 1.5 (6) | C2Aii—N1A—C2A—C3A | 0.1 (6) |
Ti1—N1—C2—C3 | −178.5 (6) | Ti1A—N1A—C2A—C3A | −179.9 (6) |
C2i—N1—C2—C21 | 178.9 (8) | C2Aii—N1A—C2A—C21A | 179.6 (8) |
Ti1—N1—C2—C21 | −1.1 (8) | Ti1A—N1A—C2A—C21A | −0.4 (8) |
N1—C2—C3—C4 | −2.9 (11) | N1A—C2A—C3A—C4A | −0.1 (11) |
C21—C2—C3—C4 | 179.8 (6) | C21A—C2A—C3A—C4A | −179.7 (6) |
C2—C3—C4—C3i | 1.4 (5) | C2A—C3A—C4A—C3Aii | 0.1 (5) |
Symmetry codes: (i) −x+1, y, −z+2; (ii) −x+1, y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [TiBr4(C7H9N)] |
Mr | 474.69 |
Crystal system, space group | Monoclinic, C2 |
Temperature (K) | 133 |
a, b, c (Å) | 11.6811 (2), 9.8679 (2), 11.1300 (2) |
β (°) | 93.482 (1) |
V (Å3) | 1280.56 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 13.11 |
Crystal size (mm) | 0.40 × 0.20 × 0.05 |
Data collection | |
Diffractometer | Siemens CCD three-circle diffractometer |
Absorption correction | Empirical (using intensity measurements) (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.077, 0.560 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10417, 2002, 1798 |
Rint | 0.073 |
(sin θ/λ)max (Å−1) | 0.628 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.068, 1.00 |
No. of reflections | 2002 |
No. of parameters | 124 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.61, −0.59 |
Absolute structure | Flack (1983) |
Absolute structure parameter | 0.03 (2) |
Computer programs: SMART (Siemens, 1995), SMART, SAINT (Siemens, 1995), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP in SHELXTL (Siemens, 1995).
Ti1—N1 | 2.181 (8) | Ti1A—N1A | 2.176 (9) |
Ti1—Br2 | 2.3585 (14) | Ti1A—Br2A | 2.3564 (14) |
Ti1—Br1 | 2.4326 (8) | Ti1A—Br1A | 2.4372 (8) |
N1—Ti1—Br2 | 128.60 (4) | N1A—Ti1A—Br2A | 128.54 (4) |
Br2—Ti1—Br2i | 102.81 (8) | Br2Aii—Ti1A—Br2A | 102.92 (8) |
N1—Ti1—Br1 | 80.92 (5) | N1A—Ti1A—Br1A | 80.69 (5) |
Br2—Ti1—Br1 | 96.07 (3) | Br2A—Ti1A—Br1A | 96.59 (4) |
Br1i—Ti1—Br1 | 161.84 (9) | Br1Aii—Ti1A—Br1A | 161.38 (9) |
Br2—Ti1—N1—C2 | −0.2 (4) | Br2A—Ti1A—N1A—C2A | −2.1 (4) |
Br1—Ti1—N1—C2 | −90.7 (4) | Br1Aii—Ti1A—N1A—C2A | −91.1 (4) |
Symmetry codes: (i) −x+1, y, −z+2; (ii) −x+1, y, −z+1. |
Titanium tetrahalides are strong Lewis acids and form Lewis acid–base adducts with electron-pair donors. These reactions have been of scientific interest for a long time (Emeléus & Rao, 1958; Rao, 1960; Hensen et al. 1997). Two representative examples of such adducts are the structures of TiCl4(pyridine)2 (Mazo et al., 1987) and bis(µ-dichloro)hexachlorobis(N-trimethylsilyl-imidazol-3-yl)dititanium (Hensen, Lemke & Näther, 1997). However, no neutral pentacoordinated TiX4L complexes (X is a halogen atom and L is a singly-bonded ligand) have yet been described. We present here the first example of such a complex, (I), with X = Br and L = 2,6-dimethylpyridine.
The asymmetric unit of (I) consists of two half molecules, in which the Ti1, N1 and C4 atoms of molecule 1 and the Ti1A, N1A and C4A atoms of molecule 2 are located on a special position of site symmetry 2. The two molecules (Fig. 1) are nearly identical; a least-squares fit of all non-H atoms gives an r.m.s. deviation of 0.026 Å. The environment of the titanium centres can be described as trigonal bipyramidal, with the nitrogen base occupying an equatorial position. According to the valence-shell electron-pair repulsion (VSEPR) model (Haaland, 1989; Gillespie & Robinson, 1996), an axial position of the base ligand should be expected. However, steric effects force this residue into the equatorial plane. The methyl groups of the pyridine ligands cause the equatorial N—Ti—Br angles to be widened, whereas the equatorial Br—Ti—Br angles are decreased (Table 1). The angles between the two axial Br ligands (Br1 and its symmetry equivalent) show that these atoms are displaced from the ideal linear arrangement in the direction of the aromatic ring. In contrast, the equatorial Br atoms lie nearly exactly in the plane of the aromatic ring and the axial Br—Ti bonds are almost perpendicular to the plane of the aromatic ring. The structure displays an interesting packing motif (Fig. 2); the two symmetry independent molecules lie on different parallel lines in a head-to-tail manner. One line is located on the twofold rotation axis coinciding with the b axis (0,y,0), whereas the other one is situated on the twofold rotation axis with coordinates 0,y,1/2. The displacement between the two molecules in the direction of the b axis (as defined by the difference in y coordinates between equivalent atoms) is approximately 0.46. The angle between the pyridyl rings of the two symmetry independent molecules is 66.6 (2)°.