Titanium(IV) chloride at 150 K

Titanium(IV) chloride, TiCl₄, is an air-sensitive liquid under ambient conditions. The crystal structure consists of tetrahedral mol­ecules weakly associated in pairs, and is isostructural with tin(IV) bromide.

Key indicators

• Powder X-ray study
• T = 150 K
• Mean [sigma](Ti-Cl) = 0.001 Å
• R factor = 0.020
• wR factor = 0.080
• Data-to-parameter ratio = 28.6

checkCIF results

No syntax errors found


 Alert Level A:



DIFF_019  Alert A _diffrn_standards_number is missing
          Number of standards used in measurement.

DIFF_020  Alert A _diffrn_standards_interval_count and
          _diffrn_standards_interval_time are missing. Number of measurements
          between standards or time (min) between standards.


 Alert Level B:



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           28.47
         From the CIF: _reflns_number_total               1345
         TEST2: Reflns within _diffrn_reflns_theta_max
         Count of symmetry unique reflns         1500
         Completeness (_total/calc)             89.67%
          Alert B: < 90% complete (theta max?)

PLAT_112  Alert B ADDSYM Detects Additional (Pseudo) Symm. Elem.          m

Author response: Higher symmetry rejected on grounds on merging statistics. Solution and refinement in higher symmetry unacceptable. Merging statistics (XPREP, Sheldrick, 2001) are given below. Search for higher metric symmetry Identical indices and Friedel opposites combined before calculating R(sym) Option A: FOM = 0.073 deg. ORTHORHOMBIC C-lattice R(sym) = 0.341 [ 1300] Cell: 12.157 15.058 6.474 90.00 90.00 89.93 Volume: 1185.03 Matrix: 1.0000 0.0000 1.0000 -1.0000 0.0000 1.0000 0.0000 -1.0000 0.0000 Option B: FOM = 0.000 deg. MONOCLINIC P-lattice R(sym) = 0.022 [ 677] Cell: 9.670 6.474 9.682 90.00 102.17 90.00 Volume: 592.51 Matrix: 1.0000 0.0000 0.0000 0.0000 1.0000 0.0000 0.0000 0.0000 1.0000 Option C: FOM = 0.073 deg. MONOCLINIC C-lattice R(sym) = 0.375 [ 783] Cell: 15.058 12.157 6.474 90.00 90.00 90.07 Volume: 1185.03 Matrix: 1.0000 0.0000 -1.0000 1.0000 0.0000 1.0000 0.0000 -1.0000 0.0000 Option D: FOM = 0.073 deg. MONOCLINIC C-lattice R(sym) = 0.428 [ 720] Cell: 12.157 15.058 6.474 90.00 90.00 89.93 Volume: 1185.03 Matrix:-1.0000 0.0000 -1.0000 1.0000 0.0000 -1.0000 0.0000 -1.0000 0.0000

 Alert Level C:



CRYSR_01  Alert C _exptl_crystal_size_rad not in the CIF when expected.


 2 Alert Level A = Potentially serious problem

 2 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Titanium(IV) chloride is an important chemical in the commercial production of titanium metal and titanium dioxide. Under ambient conditions of temperature and pressure, titanium(IV) chloride is an air-sensitive liquid which freezes at 248 K. Of the remaining titanium (IV) halides, TiF₄ (Bialowons et al., 1995) and TiI₄ (Troyanov, 1993) are polymeric, high-melting compounds (557 K and 423 K respectively), and TiBr₄ is monomeric (Brand & Schmidt, 1966; Troyanov et al., 1990), with a correspondingly low melting point (312 K). Here we report the structure of titanium(IV) chloride, (I), at 150 K.

The low-temperature solid-state structure of titanium(IV) chloride is composed of tetrahedral molecules (Fig. 1). The molecules form loose dimers (Fig. 2), with intermolecular Ti···Cl contacts of 3.994 (1) Å. This separation is significantly shorter than the other Ti···Cl separations, with the next shortest contact over 0.4 Å longer at 4.407 (1) Å. The structure can be considered to be based on hexagonal close packing of the chlorine atoms.

The structure is isostructural with tin(IV) bromide, consistent with the observations of Brand & Sackmann (1963). Titanium(IV) bromide has also been refined in the SnBr₄ structure (Brand & Schmidt, 1966). In common with TiBr₄, the Ti—halogen bond is short, with a mean value of 2.1646 (6) Å. A search of the CSD (Allen & Kennard, 1993) for four-coordinate titanium compounds containing Ti—Cl bonds gave a mean value for the Ti—Cl bond of 2.24 (4) Å for 49 fragments.

S2. Experimental

Titanium (IV) chloride was purchased from Aldrich and used as received. A crystal of titanium (IV) chloride was grown in situ in a capillary using the laser method of Boese (Boese & Nussbaumer, 1994), at a temperature of 244.2 K. Data were collected at 150 K.

S3. Refinement

Indexing of this crystal using GEMINI (Sparks, 1999) indicated that the crystal was not single, with two major (indexable) components. The data set was integrated using both orientation matrices. Data corresponding to the second crystal were used for structure solution and refinement; inclusion of the first component gave significantly worse refinement statistics, possibly because of contamination by reflections from further small, unindexed crystals.

The possibility of higher (C-centred orthorhombic) symmetry in the structure was noted during space-group determination. This was rejected on the basis of merging statistics: R(int) for primitive monoclinic was 0.022 compared with 0.341 for orthorhombic C (XPREP, Sheldrick, 2001). Structure solution and refinement in this higher symmetry was unacceptable.

Computing details

Data collection: SMART (Bruker-Nonius, 2001); cell refinement: SAINT (Bruker-Nonius, 2002); data reduction: SAINT; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 2001); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.

Figures

	Fig. 1. The molecular structure of titanium (IV) chloride, showing 50% probability displacement ellipsiods
	Fig. 2. Packing of titanium (IV) chloride, viewed down b. The dotted lines indicate the closest Ti—Cl contacts.

Titanium(IV) chloride

Crystal data

Cl4Ti	F(000) = 360.000
Mr = 189.71	Dx = 2.127 Mg m^−3
Monoclinic, P21/c	Melting point: 248 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 9.670 (2) Å	Cell parameters from 3737 reflections
b = 6.4737 (15) Å	θ = 3–29°
c = 9.682 (2) Å	µ = 3.09 mm^−1
β = 102.168 (4)°	T = 150 K
V = 592.5 (2) Å^3	Cylinder, colourless
Z = 4	1.00 × 0.41 × 0.41 mm

Data collection

Bruker SMART APEX diffractometer equipped with an Oxford Cryosystems low- temperature device and an OHCD laser-assisted crystallisation device (Scientific Consulting, Essen, Germany).	1228 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.04
ϕ & ω scans	θmax = 28.5°, θmin = 2.2°
Absorption correction: multi-scan (TWINABS; Sheldrick, 2002)	h = −12→9
Tmin = 0.08, Tmax = 0.28	k = −8→6
2765 measured reflections	l = −12→12
1345 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	W = [w1] * [1-(deltaF/6*sigmaF)^2]2 where w1 = Chebychev polynomial with coefficients 73.0 124. 77.2 33.7 8.14 (Carruthers & Watkin, 1979).
R[F^2 > 2σ(F^2)] = 0.020	(Δ/σ)max = 0.0002
wR(F^2) = 0.080	Δρmax = 0.44 e Å^−3
S = 0.99	Δρmin = −0.48 e Å^−3
1343 reflections	Extinction correction: Larson (1970) eq 22
47 parameters	Extinction coefficient: 134.8 (84)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ti1	0.25088 (3)	0.07670 (5)	0.13332 (3)	0.0191
Cl2	0.18975 (6)	0.39226 (8)	0.07654 (6)	0.0314
Cl3	0.07718 (5)	−0.08326 (8)	0.19569 (6)	0.0321
Cl4	0.30678 (6)	−0.07972 (8)	−0.04467 (5)	0.0314
Cl5	0.43145 (5)	0.07485 (8)	0.30888 (5)	0.0300

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ti1	0.0196 (2)	0.0173 (2)	0.0206 (2)	0.0001 (1)	0.00459 (13)	0.0001 (1)
Cl2	0.0373 (3)	0.0204 (2)	0.0361 (3)	0.00472 (17)	0.0068 (2)	0.00359 (18)
Cl3	0.0265 (3)	0.0351 (3)	0.0360 (3)	−0.00590 (18)	0.0091 (2)	0.00589 (19)
Cl4	0.0351 (3)	0.0325 (3)	0.0277 (3)	0.00338 (18)	0.0089 (2)	−0.00681 (17)
Cl5	0.0265 (3)	0.0319 (3)	0.0284 (3)	0.00021 (16)	−0.0015 (2)	−0.00142 (17)

Geometric parameters (Å, º)

Ti1—Cl2	2.1652 (6)	Ti1—Cl4	2.1634 (6)
Ti1—Cl3	2.1647 (6)	Ti1—Cl5	2.1651 (5)
Cl2—Ti1—Cl3	109.62 (2)	Cl2—Ti1—Cl5	109.66 (2)
Cl2—Ti1—Cl4	109.88 (2)	Cl3—Ti1—Cl5	108.86 (2)
Cl3—Ti1—Cl4	109.71 (3)	Cl4—Ti1—Cl5	109.10 (2)