ap-9-(meta-tert-Butyl­phenyl)­fluorene

The title compound, C₂₃H₂₂, (I), crystallizes in an ap conformation and its melt readily recrystallizes on cooling, in contrast to the corresponding 9-fluorenol compound, (II), which is sp and which melts without decomposition and fails to recrystallize over a long period. Both of these differences are ascribed to the intermolecular hydrogen bonding in (II), which is absent in (I) and which leads to distinctly different molecular packing in the two compounds.

S1. Comment

We have been studying the characteristics and variability of sp versus ap conformations of 9-(tert-butylphenyl and isopropylphenyl)fluorenes and their corresponding 9-fluorenols in solution and in the crystalline state (Hou, 1997; Meyers et al., 1997; Robinson et al., 1998; Meyers et al., 1999; Hou et al., 1999). The solution conformations were readily ascertained by ¹H NMR spectroscopy. In this context, we have now examined the title compound, 9-(meta-tert-butylphenyl)fluorene, (I), prepared from 9-(meta-tert-butylphenyl)-9-fluorenol, (II). While (II), as we recently reported, is freely rotating in solution, it crystallizes out 100% as its sp conformer, exhibits O—H···π(fluorene) intermolecular hydrogen bonds in its molecular packing, and melts undecomposed, but the melt fails to recrystallize over a long period (Meyers et al., 2003).

The structure of (I) with its atom-numbering scheme is shown in Fig. 1. No hydrogen bonding is evident, the shortest H9–fluorene distance being about 3.8 Å, which precludes the most reasonable C—H···π(arene)-type bond. Solution NMR clearly shows free rotation of the 9-aryl group, and the angle between the fluorene and aryl planes of crystalline (I) [78.71 (6)°] would easily accommodate either the sp or the ap rotomeric conformation. However, both figures show that crystalline (I) is ap, in contrast to its sp 9-fluorenol progenitor (II). The surprising difference in their rotational conformations in the crystalline state may well be associated with the difference in their molecular packing. The intermolecular O—H···π(fluorene) hydrogen bonding shown in the molecular packing of (II) (Meyers et al., 2003) requires the tert-butyl group and the C9—O bond to point in the same direction, hence the O1—C9—C10—C11 torsion angle of −11.6 (4)°, i.e. the sp conformation. In contrast, the preferred molecular packing of (I) requires the corresponding tert-butyl group and the C9—H bond to point in opposite directions, hence the H9—C9—C10—C11 torsion angle of 157°, i.e. the ap conformation.

When (I) is melted it recrystallizes readily, in contrast to the failure of melted (II) to recrystallize over a long period, a behavior which may be associated with the difficulty of reforming the intermolecular hydrogen bonds required for molecular packing of crystals of (II). This explanation, rather than one involving? conformational differences, is supported by our recent observation that the melt of 9-(para-tert-butylphenyl)-9-fluorenol, (III), which is devoid of this type of conformational isomerism but which exhibits intermolecular hydrogen bonding, likewise fails to recrystallize when cooled (McLean et al., 2003). In contrast, the corresponding fluorene (IV), which has no OH group and cannot undergo hydrogen bonding, produces a melt that readily recrystallizes on cooling.

S2. Experimental

Compound (I) was prepared from (II) in a manner similar to that used for the conversion of other 9-fluorenols to fluorenes (Hou, 1997; Robinson et al., 1998; Meyers et al., 1999). A stirred solution of iodine (14.2 mg, 0.0559 mmol), 50% aqueous H₃PO₂ solution (1.4 ml, 13.52 mmol) and glacial acetic acid (10 ml) was heated under argon until the mixture became colorless, and 9-(meta-tert-butylphenyl)-9-fluorenol, (II) (Meyers et al., 2003) (0.251 g, 0.799 mmol), was then added. The mixture was refluxed for 3 h, cooled to room temperature, diluted with water (50 ml) and extracted with ether. The extract was washed with saturated aqueous sodium bicarbonate, dried (anhydrous MgSO₄) and concentrated in vacuo, yielding a white solid (0.226 g, yield 95%, colorless crystals (from hexanes), m.p. 328.5–330 K). The melt recrystallized on cooling and remelted at the same temperature. ¹H NMR (CDCl₃): δ 1.31 (s, 9H), 5.05 (s, 1H), 6.71–6.74 (m, 1H), 7.12–7.40 (m, 9H), 7.787 (s, 1H), 7.813 (s, 1H); ¹³C NMR (CDCl₃): δ 31.38, 34.66, 54.70, 119.81, 123.71, 124.87, 125.32, 125.82, 127.20, 128.32, 140.98, 141.06, 147.86, 151.46. Compound (IV) was prepared from (III) by the method described above and recrystallized from hexanes (m.p. 433.5–435.5 K; literature m.p. 436–438 K; Tolbert et al., 1992]. The crystals that reformed from the cooled melt exhibited an identical m.p. ¹H NMR (CDCl₃): δ 1.29 (s, 9H), 5.04 (s, 1H), 7.01–7.03 (m, 2H), 7.22–7.40 (m, 8H), 7.78–7.81 (m, 2H); ¹³C NMR (CDCl₃): δ 31.59, 34.41, 54.18, 120.04, 125.61, 125.79, 127.44, 128.07, 138.55, 141.21, 148.22, 149.74, 154.93.

S3. Refinement

The rotational orientations of the methyl H atoms of the tert-butyl group were refined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997). All H atoms were treated as riding, with C—H distances ranging from 0.93 to 0.98 Å and U_iso(H) values equal to 1.5 (methyl H atoms) or 1.2 times (all other H atoms) U_eq of the parent atom.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Burla et al., 1989); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: TEXSAN, SHELXL97, and PLATON.

Figures

Fig. 1. The molecular structure and atom-numbering scheme for (I), with displacement ellipsoids at the 50% probablilty level.

ap-9-(meta-tert-Butylphenyl)fluorene

Crystal data

C23H22	F(000) = 640
Mr = 298.41	Dx = 1.140 Mg m^−3
Monoclinic, P21/n	Melting point = 328.5–330 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71069 Å
a = 10.069 (3) Å	Cell parameters from 25 reflections
b = 14.981 (3) Å	θ = 17.3–20.7°
c = 11.714 (3) Å	µ = 0.06 mm^−1
β = 100.17 (2)°	T = 296 K
V = 1739.2 (8) Å^3	Irregular fragment, colorless
Z = 4	0.54 × 0.43 × 0.33 mm

Data collection

Rigaku AFC-5S diffractometer	Rint = 0.013
Radiation source: fine-focus sealed tube	θmax = 25.1°, θmin = 2.2°
Graphite monochromator	h = 0→11
ω scans	k = 0→17
3263 measured reflections	l = −13→13
3080 independent reflections	3 standard reflections every 100 reflections
2043 reflections with I > 2σ(I)	intensity decay: 0.7%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	H-atom parameters constrained
wR(F^2) = 0.109	w = 1/[σ^2(Fo^2) + (0.0483P)^2 + 0.2217P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
3080 reflections	Δρmax = 0.15 e Å^−3
212 parameters	Δρmin = −0.14 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0174 (17)

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

	x	y	z	Uiso*/Ueq
C1	0.56269 (17)	0.72208 (12)	0.64909 (16)	0.0574 (5)
C2	0.60468 (19)	0.63648 (13)	0.68187 (18)	0.0684 (5)
C3	0.6701 (2)	0.61937 (13)	0.79321 (18)	0.0694 (5)
C4	0.69446 (17)	0.68630 (12)	0.87458 (16)	0.0596 (5)
C4A	0.65216 (14)	0.77243 (11)	0.84260 (13)	0.0461 (4)
C4B	0.66489 (14)	0.85634 (11)	0.90815 (13)	0.0451 (4)
C5	0.72398 (16)	0.87472 (13)	1.02220 (14)	0.0560 (5)
C6	0.72343 (18)	0.96137 (13)	1.06173 (16)	0.0628 (5)
C7	0.66601 (18)	1.02865 (13)	0.98982 (16)	0.0629 (5)
C8	0.60713 (16)	1.01129 (12)	0.87584 (15)	0.0546 (4)
C8A	0.60763 (14)	0.92482 (10)	0.83551 (13)	0.0428 (4)
C9	0.55028 (15)	0.88810 (10)	0.71566 (13)	0.0451 (4)
C9A	0.58670 (15)	0.79027 (11)	0.72969 (14)	0.0456 (4)
C10	0.40089 (15)	0.90825 (10)	0.68014 (12)	0.0424 (4)
C11	0.30464 (14)	0.85460 (10)	0.71907 (12)	0.0415 (4)
C12	0.16780 (15)	0.87381 (10)	0.69501 (13)	0.0438 (4)
C13	0.12901 (17)	0.95011 (11)	0.62963 (14)	0.0548 (4)
C14	0.22205 (18)	1.00394 (12)	0.59070 (15)	0.0609 (5)
C15	0.35826 (17)	0.98303 (11)	0.61511 (14)	0.0544 (4)
C16	0.06130 (15)	0.81638 (11)	0.73881 (15)	0.0517 (4)
C17	0.12213 (19)	0.73680 (12)	0.81064 (18)	0.0688 (5)
C18	−0.0126 (2)	0.87343 (14)	0.8162 (2)	0.0805 (6)
C19	−0.0402 (2)	0.78058 (14)	0.63534 (19)	0.0793 (6)
H1	0.5189	0.7336	0.5738	0.069*
H2	0.5887	0.5902	0.6284	0.082*
H3	0.6982	0.5615	0.8137	0.083*
H4	0.7385	0.6741	0.9496	0.072*
H5	0.7632	0.8293	1.0710	0.067*
H6	0.7624	0.9744	1.1379	0.075*
H7	0.6666	1.0867	1.0180	0.075*
H8	0.5681	1.0570	0.8276	0.066*
H9	0.5992	0.9146	0.6588	0.054*
H11	0.3333	0.8041	0.7628	0.050*
H13	0.0380	0.9650	0.6119	0.066*
H14	0.1935	1.0547	0.5477	0.073*
H15	0.4207	1.0193	0.5877	0.065*
H17A	0.1830	0.7577	0.8778	0.103*
H17B	0.1704	0.7000	0.7647	0.103*
H17C	0.0514	0.7025	0.8347	0.103*
H18A	−0.0781	0.8374	0.8454	0.121*
H18B	−0.0574	0.9221	0.7718	0.121*
H18C	0.0512	0.8966	0.8800	0.121*
H19A	0.0065	0.7453	0.5866	0.119*
H19B	−0.0843	0.8298	0.5916	0.119*
H19C	−0.1063	0.7443	0.6633	0.119*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0481 (10)	0.0711 (12)	0.0530 (10)	−0.0008 (9)	0.0091 (8)	−0.0130 (9)
C2	0.0642 (12)	0.0629 (12)	0.0795 (14)	0.0007 (10)	0.0165 (10)	−0.0231 (10)
C3	0.0692 (13)	0.0550 (11)	0.0841 (14)	0.0087 (9)	0.0141 (11)	−0.0026 (10)
C4	0.0565 (11)	0.0601 (11)	0.0619 (11)	0.0062 (9)	0.0096 (9)	0.0034 (9)
C4A	0.0354 (8)	0.0555 (10)	0.0481 (9)	−0.0006 (7)	0.0097 (7)	−0.0007 (7)
C4B	0.0331 (8)	0.0573 (10)	0.0453 (9)	−0.0041 (7)	0.0081 (6)	−0.0019 (7)
C5	0.0465 (9)	0.0738 (12)	0.0459 (9)	−0.0028 (9)	0.0029 (7)	0.0011 (9)
C6	0.0563 (11)	0.0794 (14)	0.0512 (10)	−0.0136 (10)	0.0052 (8)	−0.0158 (10)
C7	0.0590 (11)	0.0627 (12)	0.0668 (12)	−0.0153 (9)	0.0106 (9)	−0.0173 (10)
C8	0.0475 (9)	0.0541 (10)	0.0618 (11)	−0.0089 (8)	0.0084 (8)	−0.0011 (8)
C8A	0.0318 (8)	0.0521 (9)	0.0447 (8)	−0.0083 (7)	0.0071 (6)	−0.0022 (7)
C9	0.0400 (8)	0.0549 (10)	0.0411 (8)	−0.0058 (7)	0.0096 (6)	0.0031 (7)
C9A	0.0339 (8)	0.0555 (10)	0.0488 (9)	−0.0019 (7)	0.0109 (7)	−0.0049 (7)
C10	0.0422 (8)	0.0477 (9)	0.0357 (8)	−0.0020 (7)	0.0021 (6)	−0.0008 (7)
C11	0.0415 (8)	0.0417 (8)	0.0399 (8)	0.0014 (7)	0.0032 (6)	0.0018 (6)
C12	0.0410 (8)	0.0450 (9)	0.0430 (8)	0.0015 (7)	0.0012 (6)	−0.0049 (7)
C13	0.0446 (9)	0.0556 (10)	0.0582 (10)	0.0060 (8)	−0.0078 (8)	0.0019 (8)
C14	0.0648 (11)	0.0509 (10)	0.0595 (11)	0.0019 (9)	−0.0091 (9)	0.0135 (8)
C15	0.0574 (10)	0.0534 (10)	0.0491 (9)	−0.0088 (8)	0.0006 (8)	0.0097 (8)
C16	0.0389 (9)	0.0510 (10)	0.0648 (11)	−0.0022 (7)	0.0082 (7)	−0.0031 (8)
C17	0.0593 (11)	0.0676 (12)	0.0831 (14)	−0.0053 (9)	0.0225 (10)	0.0157 (10)
C18	0.0642 (13)	0.0759 (14)	0.1106 (17)	−0.0016 (11)	0.0405 (12)	−0.0098 (12)
C19	0.0587 (12)	0.0773 (14)	0.0946 (15)	−0.0183 (10)	−0.0065 (11)	−0.0040 (12)

Geometric parameters (Å, º)

C1—C9A	1.383 (2)	C16—C18	1.532 (2)
C1—C2	1.383 (3)	C16—C19	1.538 (2)
C2—C3	1.377 (3)	C1—H1	0.9300
C3—C4	1.375 (2)	C2—H2	0.9300
C4—C4A	1.389 (2)	C3—H3	0.9300
C4A—C9A	1.396 (2)	C4—H4	0.9300
C4A—C4B	1.467 (2)	C5—H5	0.9300
C4B—C5	1.391 (2)	C6—H6	0.9300
C4B—C8A	1.391 (2)	C7—H7	0.9300
C5—C6	1.379 (2)	C8—H8	0.9300
C6—C7	1.374 (3)	C9—H9	0.9800
C7—C8	1.387 (2)	C15—H15	0.9300
C8—C8A	1.379 (2)	C14—H14	0.9300
C8A—C9	1.523 (2)	C13—H13	0.9300
C9—C9A	1.513 (2)	C11—H11	0.9300
C9—C10	1.519 (2)	C17—H17A	0.9600
C10—C15	1.380 (2)	C17—H17B	0.9600
C10—C11	1.396 (2)	C17—H17C	0.9600
C15—C14	1.386 (2)	C18—H18A	0.9600
C14—C13	1.374 (2)	C18—H18B	0.9600
C13—C12	1.393 (2)	C18—H18C	0.9600
C12—C11	1.387 (2)	C19—H19A	0.9600
C12—C16	1.532 (2)	C19—H19B	0.9600
C16—C17	1.524 (2)	C19—H19C	0.9600
C9A—C1—C2	119.16 (17)	C1—C2—H2	119.8
C3—C2—C1	120.46 (18)	C4—C3—H3	119.4
C4—C3—C2	121.18 (18)	C2—C3—H3	119.4
C3—C4—C4A	118.77 (17)	C3—C4—H4	120.6
C4—C4A—C9A	120.30 (15)	C4A—C4—H4	120.6
C4—C4A—C4B	131.33 (15)	C6—C5—H5	120.6
C9A—C4A—C4B	108.36 (14)	C4B—C5—H5	120.6
C5—C4B—C8A	120.16 (15)	C7—C6—H6	119.6
C5—C4B—C4A	130.96 (15)	C5—C6—H6	119.6
C8A—C4B—C4A	108.86 (13)	C6—C7—H7	119.5
C6—C5—C4B	118.86 (17)	C8—C7—H7	119.5
C7—C6—C5	120.74 (17)	C8A—C8—H8	120.7
C6—C7—C8	120.98 (17)	C7—C8—H8	120.7
C8A—C8—C7	118.64 (17)	C9A—C9—H9	109.0
C8—C8A—C4B	120.61 (14)	C10—C9—H9	109.0
C8—C8A—C9	129.13 (14)	C8A—C9—H9	109.0
C4B—C8A—C9	110.25 (13)	C10—C15—H15	120.1
C9A—C9—C10	115.58 (12)	C14—C15—H15	120.1
C9A—C9—C8A	101.81 (12)	C13—C14—H14	119.8
C10—C9—C8A	112.13 (12)	C15—C14—H14	119.8
C1—C9A—C4A	120.12 (16)	C14—C13—H13	119.2
C1—C9A—C9	129.18 (15)	C12—C13—H13	119.2
C4A—C9A—C9	110.69 (13)	C12—C11—H11	118.8
C15—C10—C11	118.78 (14)	C10—C11—H11	118.8
C15—C10—C9	120.61 (14)	C16—C17—H17A	109.5
C11—C10—C9	120.48 (13)	C16—C17—H17B	109.5
C10—C15—C14	119.82 (15)	H17A—C17—H17B	109.5
C13—C14—C15	120.44 (16)	C16—C17—H17C	109.5
C14—C13—C12	121.52 (15)	H17A—C17—H17C	109.5
C11—C12—C13	117.00 (14)	H17B—C17—H17C	109.5
C11—C12—C16	122.98 (14)	C16—C18—H18A	109.5
C13—C12—C16	120.00 (14)	C16—C18—H18B	109.5
C12—C11—C10	122.42 (14)	H18A—C18—H18B	109.5
C17—C16—C18	107.44 (16)	C16—C18—H18C	109.5
C17—C16—C12	112.78 (13)	H18A—C18—H18C	109.5
C18—C16—C12	109.09 (14)	H18B—C18—H18C	109.5
C17—C16—C19	107.99 (15)	C16—C19—H19A	109.5
C18—C16—C19	109.65 (16)	C16—C19—H19B	109.5
C12—C16—C19	109.83 (15)	H19A—C19—H19B	109.5
C9A—C1—H1	120.4	C16—C19—H19C	109.5
C2—C1—H1	120.4	H19A—C19—H19C	109.5
C3—C2—H2	119.8	H19B—C19—H19C	109.5
C9A—C1—C2—C3	−0.3 (3)	C4B—C4A—C9A—C1	179.53 (14)
C1—C2—C3—C4	0.4 (3)	C4—C4A—C9A—C9	179.90 (14)
C2—C3—C4—C4A	−0.2 (3)	C4B—C4A—C9A—C9	−1.02 (16)
C3—C4—C4A—C9A	−0.3 (2)	C10—C9—C9A—C1	59.2 (2)
C3—C4—C4A—C4B	−179.12 (16)	C8A—C9—C9A—C1	−179.04 (15)
C4—C4A—C4B—C5	0.4 (3)	C10—C9—C9A—C4A	−120.20 (14)
C9A—C4A—C4B—C5	−178.58 (15)	C8A—C9—C9A—C4A	1.58 (15)
C4—C4A—C4B—C8A	178.88 (16)	C9A—C9—C10—C15	−150.03 (15)
C9A—C4A—C4B—C8A	−0.06 (16)	C8A—C9—C10—C15	93.89 (17)
C8A—C4B—C5—C6	0.6 (2)	C9A—C9—C10—C11	34.1 (2)
C4A—C4B—C5—C6	179.01 (16)	C8A—C9—C10—C11	−81.92 (17)
C4B—C5—C6—C7	−0.2 (3)	C11—C10—C15—C14	0.6 (2)
C5—C6—C7—C8	0.0 (3)	C9—C10—C15—C14	−175.26 (15)
C6—C7—C8—C8A	−0.2 (3)	C10—C15—C14—C13	−0.8 (3)
C7—C8—C8A—C4B	0.6 (2)	C15—C14—C13—C12	0.5 (3)
C7—C8—C8A—C9	179.84 (14)	C14—C13—C12—C11	0.0 (2)
C5—C4B—C8A—C8	−0.8 (2)	C14—C13—C12—C16	178.86 (16)
C4A—C4B—C8A—C8	−179.55 (14)	C13—C12—C11—C10	−0.2 (2)
C5—C4B—C8A—C9	179.81 (13)	C16—C12—C11—C10	−178.98 (14)
C4A—C4B—C8A—C9	1.11 (16)	C15—C10—C11—C12	−0.1 (2)
C8—C8A—C9—C9A	179.12 (15)	C9—C10—C11—C12	175.74 (14)
C4B—C8A—C9—C9A	−1.61 (15)	C11—C12—C16—C17	−0.1 (2)
C8—C8A—C9—C10	−56.7 (2)	C13—C12—C16—C17	−178.87 (15)
C4B—C8A—C9—C10	122.52 (14)	C11—C12—C16—C18	119.20 (17)
C2—C1—C9A—C4A	−0.2 (2)	C13—C12—C16—C18	−59.6 (2)
C2—C1—C9A—C9	−179.51 (16)	C11—C12—C16—C19	−120.60 (17)
C4—C4A—C9A—C1	0.5 (2)	C13—C12—C16—C19	60.6 (2)