Hexa-μ-chlorido-hexa­chlorido(η6-hexa­methyl­benzene)trialuminium(III)lanthanum(III) benzene solvate

Alexander S Filatov; Sarah N Gifford; D Krishna Kumar; Marina A Petrukhina

doi:10.1107/S1600536809004899

. 2009 Feb 18;65(Pt 3):m286–m287. doi: 10.1107/S1600536809004899

Hexa-μ-chlorido-hexachlorido(η⁶-hexamethylbenzene)trialuminium(III)lanthanum(III) benzene solvate

Alexander S Filatov ^a, Sarah N Gifford ^a, D Krishna Kumar ^a, Marina A Petrukhina ^a,^*

PMCID: PMC2968558 PMID: 21582071

Abstract

In the title compound, [Al₃LaCl₁₂(C₁₂H₁₈)]·C₆H₆, all molecules are located on a mirror plane. Three chloridoaluminate groups and a hexamethylbenzene molecule are bound to the central lanthanum(III) ion, forming a distorted pentagonal bipyramid with the η⁶-coordinated arene located at the apical position. The hexamethylbenzene ligand disordered between two orientations in a 1:1 ratio is also involved in parallel-slipped π–π stacking intermolecular interactions with a benzene solvent molecule [centroid–centroid distance 3.612 (4) Å].

Related literature

For the previously characterized lanthanum chloroaluminate and chlorogallate complexes, see: Filatov et al. (2008 ▶). For a recent review of other lanthanide chloroaluminate complexes, see: Bochkarev (2002 ▶). For complexes of lanthanide chlorogallates with polycyclic aromatic systems, see: Gorlov et al. (2008 ▶).

Experimental

Crystal data

[Al₃LaCl₁₂(C₁₂H₁₈)]·C₆H₆
M _r = 885.62
Orthorhombic,
a = 12.2127 (6) Å
b = 16.4205 (8) Å
c = 16.9790 (8) Å
V = 3404.9 (3) Å³
Z = 4
Mo- Kα radiation
μ = 2.28 mm⁻¹
T = 173 K
0.22 × 0.20 × 0.16 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2003 ▶) T _min = 0.613, T _max = 0.697
28535 measured reflections
4250 independent reflections
3911 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.063
S = 1.05
4250 reflections
189 parameters
H-atom parameters not refined
Δρ_max = 0.89 e Å⁻³
Δρ_min = −0.99 e Å⁻³

Data collection: SMART (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809004899/cv2516sup1.cif

e-65-0m286-sup1.cif^{(20.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809004899/cv2516Isup2.hkl

e-65-0m286-Isup2.hkl^{(208.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

La1—C1	2.945 (3)
La1—C2	2.965 (2)
La1—C3	2.957 (3)
La1—C4	2.941 (4)
La1—Cl3	2.9128 (5)
La1—Cl4	2.9298 (6)
La1—Cl5	2.9083 (7)
La1—Cl6	2.9097 (7)
La1—Cg1	2.613 (3)

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Acknowledgments

We thank the National Science Foundation for financial support (CHE-0546945). We are also very grateful to the University at Albany for supporting the X-ray center at the Department of Chemistry.

supplementary crystallographic information

Comment

We have recently reported X-ray structural characterization of the first two lanthanum(III) chloroaluminate complexes with neutral arenes, [La(η⁶-C₆H₅Me)(AlCl₄)₃] and [La(η⁶-C₆Me₆)(AlCl₄)₃], as well as of the first lanthanum(III) chlorogallate complex, [La(η⁶-C₆Me₆)(GaCl₄)₃] (Filatov et al., 2008). The [La(η⁶-C₆Me₆)(AlCl₄)₃]^.0.5C₆H₆ complex crystallizes in the monoclinic P2₁/c space group with the β angle being close to 90° (β = 90.27°). We later found that under slightly different experimental conditions, namely at a higher temperature (285 versus 273 K), the lanthanum complex with hexamethylbenzene, [La(η⁶-C₆Me₆)(AlCl₄)₃]^.C₆H₆ (I), is crystallized.

The molecular structure of (I) is comprised of the three chloroaluminate groups and a hexamethylbenzene molecule bound to the central lanthanum(III) ion (Fig.1). The coordination polyhedron is a distorted pentagonal bipyramid with the η⁶-arene located at the apical position. The La–C bond distances span from 2.941 (4) to 2.965 (2) Å with a La–centroid distance being 2.613 (3) Å. These distances are comparable to those found in the previously reported complex [La(η⁶-C₆Me₆)(AlCl₄)₃]^.0.5C₆H₆ (II) [La—C 2.927 (7)–3.035 (7)Å; La–centroid 2.633 (7)Å].

In (I), coordinated hexamethylbenzene is engaged into π-π stacking interactions with a solvent benzene molecule. The intercentroid distance between their 6-membered rings is 3.612 (4) Å. The two ring planes are not parallel and the dihedral angle is 12.7° (Fig.2). In the above hemisolvate (II), on the contrary, both benzene faces are involved in π-π stacking interactions as benzene is sandwiched between two hexamethylbenzene molecules. The distance between the centroids of the hexamethylbenzene and benzene rings (3.688 (4) Å) is noticeably longer than that found in (I).

Experimental

LaCl₃ (100 mg, 0.41 mmol), AlCl₃ (163 mg, 1.22 mmol), hexamethylbenzene (66 mg, 0.41 mmol) and an excess of aluminium foil were placed into a Schlenk flask inside the glove box. Benzene (10 ml) was added to the flask and the mixture was refluxed for two hours. The LaCl₃, AlCl₃, and hexamethylbenzene dissolved completely to give a yellow solution. The solution was filtered while hot through a pad of Celite and then kept at 12°C under argon for 2 days to afford a yellow crystalline material. Yield: 240 mg (65%). IR data (cm^-1): 3091 (w), 3071 (w), 3036 (w), 1598 (m), 1531 (w), 1478 (m), 1423 (s), 1382 (m), 1332 (m), 1272 (m), 1180 (w), 1076 (w), 983 (w), 824 (w), 677 (s).