Triphen­yl(tetra­hydro­furan)­aluminium(III)

In the title compound, [Al(C₆H₅)₃(C₄H₈O)], the Al atom has a distorted tetra­hedral geometry. The C—Al—C angles range from 113.25 (7) to 116.27 (8)°, much larger than the O—Al—C angles, which range from 103.39 (7) to 103.90 (6)°. The tetra­hydro­furan ring adopts an envelope conformation. The crystal packing is stabilized by C—H...π inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.048
• wR factor = 0.162
• Data-to-parameter ratio = 17.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT241_ALERT_2_B Check High      Ueq as Compared to Neighbors for        C19

Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.799     1.000
            Tmin(prime) and Tmax expected:      0.938     0.977
            RR(prime) =      0.833
            Please check that your absorption correction is appropriate.
            Value of measurement temperature given =   293.000
            Value of melting point given =     0.000
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.63 Ratio
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C3     --  C4      ..       5.83 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Al1    --  C7      ..       5.31 su
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for        C16
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         O1
PLAT061_ALERT_4_C Tmax/Tmin Range Test RR' too Large .............       0.83
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.98

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.977
            Tmax scaled      0.977 Tmin scaled      0.781
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   8 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   6 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Triphenylaluminium was first reported 40 years ago and the solid-state study revealed a dimeric Al₂Ph₆ structure bridging through two phenyl groups (Malone & McDonald, 1967). For synthesis of monomeric triarylaluminium complexes, two synthetic strategies were used. The first route employed a reaction of dimesitylmercury with Al/HgCl₂, furnishing three-coordinate trimesitylaluminium (Jerius et al., 1986) which possesses a trigonal planar structure. The second synthetic route used a strategy of providing an additional neutral ligand, such as tetrahydrofuran (THF) or diethyl ether (OEt₂), giving four-coordinate monomeric AlAr₃(L) complexes (L = THF or OEt₂) (Barber et al., 1982; De Mel & Oliver, 1989). In addition to structural studies, organoaluminium reagents had been demonstrated as excellent nucleophiles in organic synthesis, owing to their higher reactivity and the Lewis acidity of the aluminium center. Recently, we reported applications of AlAr₃(THF) in asymmetric aryl additions to aldehydes (Wu & Gau, 2006) and to ketones (Chen et al., 2007) and in coupling reactions (Ku et al., 2007). Due to their diversified applications in catalysis, we report herein the synthesis and structure of a four-coordinate triphenylaluminium compound, [Al(C₆H₅)₃(OC₄H₈)].

The molecule of the title compound contains unsubstituted phenyl ligands and has a distorted tetrahedral geometry around the aluminium metal center (Fig. 1). The Al—O(THF) bond length of 1.8972 (13) Å is shorter by 0.08 Å than the Al—C bond distances of 1.9783 (18), 1.9800 (18) and 1.9809 (19) Å. This complex has similar Al—C bond distances with the four-coordinate (o-tol)₃Al(OEt₂) complex (Barber et al., 1982). The C—Al—O bond angles in the title complex [103.39 (7), 103.90 (6) and 103.75 (7)°] are much smaller than the C—Al—C bond angles [113.25 (7), 114.23 (7) and 116.27 (8)°]. In contrast, the bulky mesityl ligands in trimesityl(tetrahydrofuran)aluminium complex (De Mel & Oliver, 1989) repel each other, giving longer Al—C bond lengths of 2.011 (7), 2.020 (7) and 2.021 (6) Å. Similarly, the Al—O(THF) bond distance of 1.969 (5) Å in the above complex is longer by 0.07 Å than the Al—O(THF) bond length in the title compound.

Related literature

For general background, see: Chen et al. (2007); Ku et al. (2007); Wu & Gau (2006). For related structures, see: Barber et al. (1982); De Mel & Oliver (1989); Jerius et al. (1986); Malone & McDonald (1967).

S2. Experimental

A solution of phenylmagnesium bromide (90.0 mmol) in THF (50 ml) was slowly added to a solution of AlCl₃ (4.00 g, 30.0 mmol) in THF (20 ml) at 273 K. The mixture was stirred at room temperature for 12 h and the solvent was removed under reduced pressure to afford a residue which was extracted with toluene (2 × 40 ml). The extracts were combined and concentrated to about 50 ml. Colourless crystals of the title compound (8.92 g, 90.0% yield) were obtained by cooling the concentrated solution at 273 K. The above synthetic procedures were conducted strictly under nitrogen atmosphere. ¹H NMR (CDCl₃, 400 MHz): δ 7.80–7.76 (m, 6H), 7.34–7.30 (m, 9H), 4.16 (m, 4H), 2.01 (m, 4H) p.p.m. ¹³C{¹H} NMR (CDCl₃, 100 MHz): δ 146.74, 137.99, 127.50, 127.06, 75.59, 24.97 p.p.m. Analysis calculated for C₂₂H₂₃OAl: C 79.97, H 7.02%;found: C 79.44, H 6.75%.

S3. Refinement

All H atoms were fixed geometrically [C—H = 0.93 Å or 0.97 Å] and treated as riding, with U_iso(H) = 1.2U_eq(C). The C atoms of the tetrahydrofuran ring display large displacement parameters, but no suitable refinement model for disorder was found.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure of the title compound with atom-numbering and displacement ellipsoids drawn at the 20% probability level.

Triphenyl(tetrahydrofuran)aluminium(III)

Crystal data

[Al(C6H5)3(C4H8O)]	F(000) = 704
Mr = 330.38	Dx = 1.128 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3804 reflections
a = 9.649 (2) Å	θ = 2.1–26.0°
b = 12.966 (3) Å	µ = 0.11 mm^−1
c = 16.038 (4) Å	T = 293 K
β = 104.210 (4)°	Block, colourless
V = 1945.1 (8) Å^3	0.58 × 0.42 × 0.21 mm
Z = 4

Data collection

Bruker SMART 1000 CCD diffractometer	3804 independent reflections
Radiation source: fine-focus sealed tube	2971 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ϕ and ω scans	θmax = 26.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→11
Tmin = 0.799, Tmax = 1.000	k = −15→15
10682 measured reflections	l = −19→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.162	H-atom parameters constrained
S = 1.33	w = 1/[σ^2(Fo^2) + (0.0861P)^2] where P = (Fo^2 + 2Fc^2)/3
3804 reflections	(Δ/σ)max = 0.001
217 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

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.

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

	x	y	z	Uiso*/Ueq
Al1	0.39089 (5)	0.69171 (4)	0.18576 (3)	0.0508 (2)
O1	0.38837 (12)	0.75437 (10)	0.29228 (7)	0.0623 (4)
C1	0.27597 (17)	0.56515 (13)	0.18473 (11)	0.0540 (4)
C2	0.2690 (2)	0.51194 (15)	0.25899 (13)	0.0668 (5)
H2	0.3158	0.5394	0.3120	0.080*
C3	0.1956 (3)	0.42013 (17)	0.25735 (17)	0.0818 (6)
H3	0.1936	0.3872	0.3086	0.098*
C4	0.1265 (2)	0.37804 (17)	0.1810 (2)	0.0880 (7)
H4	0.0771	0.3162	0.1797	0.106*
C5	0.1296 (2)	0.42674 (18)	0.10597 (17)	0.0836 (7)
H5	0.0820	0.3982	0.0536	0.100*
C6	0.2037 (2)	0.51857 (15)	0.10780 (13)	0.0672 (5)
H6	0.2053	0.5503	0.0560	0.081*
C7	0.30029 (18)	0.79599 (14)	0.09920 (11)	0.0573 (4)
C8	0.1554 (2)	0.78994 (17)	0.05675 (12)	0.0699 (5)
H8	0.1016	0.7356	0.0700	0.084*
C9	0.0891 (2)	0.8605 (2)	−0.00356 (15)	0.0864 (7)
H9	−0.0075	0.8535	−0.0302	0.104*
C10	0.1641 (3)	0.9404 (2)	−0.02443 (16)	0.0907 (7)
H10	0.1195	0.9879	−0.0658	0.109*
C11	0.3064 (3)	0.95119 (19)	0.01558 (16)	0.0891 (7)
H11	0.3581	1.0065	0.0019	0.107*
C12	0.3729 (2)	0.87933 (16)	0.07661 (13)	0.0728 (5)
H12	0.4694	0.8875	0.1032	0.087*
C13	0.59598 (17)	0.66352 (14)	0.19566 (12)	0.0585 (4)
C14	0.6632 (2)	0.68758 (18)	0.13121 (16)	0.0793 (6)
H14	0.6130	0.7237	0.0831	0.095*
C15	0.8054 (3)	0.6587 (3)	0.1368 (3)	0.1220 (12)
H15	0.8478	0.6752	0.0924	0.146*
C16	0.8810 (3)	0.6072 (3)	0.2061 (4)	0.1415 (18)
H16	0.9759	0.5898	0.2100	0.170*
C17	0.8176 (3)	0.5803 (2)	0.2712 (3)	0.1196 (13)
H17	0.8686	0.5430	0.3183	0.144*
C18	0.6776 (2)	0.60906 (17)	0.26599 (15)	0.0801 (6)
H18	0.6364	0.5916	0.3108	0.096*
C19	0.5018 (3)	0.8175 (3)	0.3436 (2)	0.1160 (11)
H19A	0.5475	0.8572	0.3066	0.139*
H19B	0.5734	0.7742	0.3805	0.139*
C20	0.4384 (3)	0.8856 (2)	0.39505 (16)	0.0958 (8)
H20A	0.4383	0.9560	0.3745	0.115*
H20B	0.4921	0.8834	0.4547	0.115*
C21	0.2920 (3)	0.8503 (2)	0.38737 (17)	0.1015 (8)
H21A	0.2860	0.8115	0.4381	0.122*
H21B	0.2275	0.9087	0.3815	0.122*
C22	0.2540 (3)	0.7853 (2)	0.31139 (17)	0.0937 (8)
H22A	0.1952	0.8232	0.2634	0.112*
H22B	0.2013	0.7253	0.3223	0.112*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Al1	0.0376 (3)	0.0578 (3)	0.0577 (3)	−0.00033 (19)	0.0129 (2)	−0.0031 (2)
O1	0.0481 (7)	0.0751 (8)	0.0667 (8)	−0.0054 (6)	0.0197 (5)	−0.0148 (6)
C1	0.0381 (8)	0.0582 (10)	0.0664 (10)	0.0042 (7)	0.0140 (7)	−0.0002 (7)
C2	0.0603 (11)	0.0681 (11)	0.0727 (12)	0.0086 (9)	0.0174 (9)	0.0077 (9)
C3	0.0814 (15)	0.0639 (12)	0.1086 (17)	0.0102 (11)	0.0395 (13)	0.0202 (12)
C4	0.0677 (13)	0.0540 (11)	0.152 (2)	−0.0030 (10)	0.0462 (15)	−0.0004 (14)
C5	0.0645 (13)	0.0739 (14)	0.1074 (17)	−0.0091 (10)	0.0115 (12)	−0.0236 (12)
C6	0.0617 (11)	0.0696 (12)	0.0696 (11)	−0.0052 (9)	0.0147 (8)	−0.0044 (9)
C7	0.0494 (10)	0.0637 (10)	0.0604 (10)	0.0024 (8)	0.0166 (7)	−0.0036 (7)
C8	0.0520 (11)	0.0782 (13)	0.0780 (13)	0.0087 (9)	0.0132 (9)	0.0022 (10)
C9	0.0616 (12)	0.1058 (18)	0.0869 (14)	0.0202 (13)	0.0090 (10)	0.0061 (13)
C10	0.0918 (17)	0.0995 (17)	0.0817 (14)	0.0332 (14)	0.0230 (12)	0.0228 (12)
C11	0.0990 (19)	0.0791 (14)	0.0950 (16)	0.0011 (13)	0.0351 (14)	0.0210 (12)
C12	0.0638 (12)	0.0744 (12)	0.0788 (12)	−0.0017 (10)	0.0149 (9)	0.0058 (10)
C13	0.0416 (8)	0.0606 (10)	0.0736 (11)	−0.0031 (8)	0.0149 (7)	−0.0177 (8)
C14	0.0639 (12)	0.0857 (14)	0.0985 (15)	−0.0117 (10)	0.0397 (11)	−0.0284 (12)
C15	0.0816 (19)	0.121 (2)	0.192 (3)	−0.0240 (18)	0.088 (2)	−0.069 (2)
C16	0.0459 (14)	0.126 (3)	0.248 (5)	0.0064 (16)	0.027 (2)	−0.093 (3)
C17	0.0632 (16)	0.0994 (19)	0.167 (3)	0.0286 (14)	−0.0274 (18)	−0.054 (2)
C18	0.0604 (12)	0.0780 (14)	0.0911 (14)	0.0149 (10)	−0.0020 (10)	−0.0159 (11)
C19	0.0805 (16)	0.150 (3)	0.124 (2)	−0.0434 (17)	0.0365 (15)	−0.0780 (19)
C20	0.115 (2)	0.0881 (16)	0.0816 (15)	−0.0032 (15)	0.0194 (13)	−0.0192 (12)
C21	0.125 (2)	0.0909 (17)	0.1067 (19)	0.0074 (16)	0.0622 (16)	−0.0156 (14)
C22	0.0641 (13)	0.122 (2)	0.1058 (17)	−0.0033 (13)	0.0421 (12)	−0.0335 (15)

Geometric parameters (Å, º)

Al1—O1	1.8972 (13)	C11—C12	1.389 (3)
Al1—C1	1.9783 (18)	C11—H11	0.93
Al1—C13	1.9800 (18)	C12—H12	0.93
Al1—C7	1.9809 (19)	C13—C14	1.384 (3)
O1—C19	1.450 (2)	C13—C18	1.398 (3)
O1—C22	1.460 (2)	C14—C15	1.404 (4)
C1—C2	1.392 (3)	C14—H14	0.93
C1—C6	1.397 (3)	C15—C16	1.346 (5)
C2—C3	1.382 (3)	C15—H15	0.93
C2—H2	0.93	C16—C17	1.378 (5)
C3—C4	1.357 (3)	C16—H16	0.93
C3—H3	0.93	C17—C18	1.384 (4)
C4—C5	1.365 (3)	C17—H17	0.93
C4—H4	0.93	C18—H18	0.93
C5—C6	1.385 (3)	C19—C20	1.443 (3)
C5—H5	0.93	C19—H19A	0.97
C6—H6	0.93	C19—H19B	0.97
C7—C12	1.384 (3)	C20—C21	1.461 (4)
C7—C8	1.399 (2)	C20—H20A	0.97
C8—C9	1.371 (3)	C20—H20B	0.97
C8—H8	0.93	C21—C22	1.452 (3)
C9—C10	1.351 (4)	C21—H21A	0.97
C9—H9	0.93	C21—H21B	0.97
C10—C11	1.372 (4)	C22—H22A	0.97
C10—H10	0.93	C22—H22B	0.97
O1—Al1—C1	103.39 (7)	C11—C12—H12	118.9
O1—Al1—C13	103.90 (6)	C14—C13—C18	116.2 (2)
C1—Al1—C13	113.25 (7)	C14—C13—Al1	122.74 (16)
O1—Al1—C7	103.75 (7)	C18—C13—Al1	120.78 (16)
C1—Al1—C7	114.23 (7)	C15—C14—C13	121.4 (3)
C13—Al1—C7	116.27 (8)	C15—C14—H14	119.3
C19—O1—C22	108.11 (17)	C13—C14—H14	119.3
C19—O1—Al1	125.33 (13)	C14—C15—C16	120.6 (3)
C22—O1—Al1	121.01 (12)	C14—C15—H15	119.7
C2—C1—C6	115.02 (17)	C16—C15—H15	119.7
C2—C1—Al1	123.27 (13)	C15—C16—C17	119.9 (3)
C6—C1—Al1	121.56 (14)	C15—C16—H16	120.0
C3—C2—C1	122.9 (2)	C17—C16—H16	120.0
C3—C2—H2	118.6	C18—C17—C16	119.6 (3)
C1—C2—H2	118.6	C18—C17—H17	120.2
C4—C3—C2	120.0 (2)	C16—C17—H17	120.2
C4—C3—H3	120.0	C17—C18—C13	122.2 (3)
C2—C3—H3	120.0	C17—C18—H18	118.9
C3—C4—C5	119.8 (2)	C13—C18—H18	118.9
C3—C4—H4	120.1	O1—C19—C20	107.6 (2)
C5—C4—H4	120.1	O1—C19—H19A	110.2
C6—C5—C4	120.1 (2)	C20—C19—H19A	110.2
C6—C5—H5	119.9	O1—C19—H19B	110.2
C4—C5—H5	119.9	C20—C19—H19B	110.2
C5—C6—C1	122.2 (2)	H19A—C19—H19B	108.5
C5—C6—H6	118.9	C19—C20—C21	107.3 (2)
C1—C6—H6	118.9	C19—C20—H20A	110.3
C12—C7—C8	115.23 (18)	C21—C20—H20A	110.3
C12—C7—Al1	123.50 (14)	C19—C20—H20B	110.3
C8—C7—Al1	121.27 (15)	C21—C20—H20B	110.3
C9—C8—C7	122.9 (2)	H20A—C20—H20B	108.5
C9—C8—H8	118.6	C22—C21—C20	107.0 (2)
C7—C8—H8	118.6	C22—C21—H21A	110.3
C10—C9—C8	120.1 (2)	C20—C21—H21A	110.3
C10—C9—H9	120.0	C22—C21—H21B	110.3
C8—C9—H9	120.0	C20—C21—H21B	110.3
C9—C10—C11	119.8 (2)	H21A—C21—H21B	108.6
C9—C10—H10	120.1	C21—C22—O1	106.4 (2)
C11—C10—H10	120.1	C21—C22—H22A	110.5
C12—C11—C10	119.8 (2)	O1—C22—H22A	110.5
C12—C11—H11	120.1	C21—C22—H22B	110.5
C10—C11—H11	120.1	O1—C22—H22B	110.5
C7—C12—C11	122.2 (2)	H22A—C22—H22B	108.6
C7—C12—H12	118.9

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C16—H16···Cg1^i	0.93	2.78	3.654 (4)	156
C19—H19A···Cg1^ii	0.97	2.81	3.600 (4)	139

Symmetry codes: (i) x+1, y, z; (ii) −x+1, y+1/2, −z+1/2.