Hy­droxy­tropylium chloride: the first crystal structure of an unfunctionalized hy­droxy­tropylium ion

The crystal structure of hy­droxy­tropylium chloride, C₇H₆OH⁺·Cl⁻, the hydro­chloride salt of tropone, is described, which represents the first crystallographic characterization of an unfunctionalized hy­droxy­tropylium ion. Crystals were obtained serendipitously from a sample of chloro­tropylium chloride after partial hydrolysis. This highlights the role of hy­droxy­tropylium ions as an inter­mediate in the hydrolytic decomposition of halotropylium halides to tropone. The solid-state structure consists of layers, in which the hy­droxy­tropylium and chloride ions inter­act via both strong hydrogen bonds formed by the hy­droxy protons and weaker hydrogen bonds formed by the tropylium protons to produce a two-dimensional network.

Computing details

Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015)and ShelXle (Hübschle et al., 2011); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2006); software used to prepare material for publication: PLATON (Spek, 2009), enCIFer (Allen et al., 2004) and publCIF (Westrip, 2010).

Hydroxytropylium chloride

Crystal data

C7H7O^+·Cl^−	F(000) = 148
Mr = 142.58	Dx = 1.392 Mg m^−3
Monoclinic, Pc	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P -2yc	Cell parameters from 9915 reflections
a = 4.8622 (3) Å	θ = 2.9–36.4°
b = 6.9718 (4) Å	µ = 0.47 mm^−1
c = 10.1539 (5) Å	T = 123 K
β = 98.727 (3)°	Needle, colourless
V = 340.22 (3) Å^3	0.41 × 0.15 × 0.11 mm
Z = 2

Data collection

Bruker APEXII CCD diffractometer	1690 independent reflections
Radiation source: rotating anode FR591	1682 reflections with I > 2σ(I)
MONTEL optic monochromator	Rint = 0.031
Detector resolution: 16 pixels mm^-1	θmax = 28.3°, θmin = 2.9°
phi– and ω–rotation scans	h = −6→6
Absorption correction: multi-scan (SADABS; Bruker, 2012)	k = −9→9
Tmin = 0.698, Tmax = 0.747	l = −13→13
14261 measured reflections

Refinement

Refinement on F^2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.021	W = 1/[Σ^2(FO^2) + (0.0407P)^2 + 0.0399P] WHERE P = (FO^2 + 2FC^2)/3
wR(F^2) = 0.059	(Δ/σ)max = 0.001
S = 1.04	Δρmax = 0.34 e Å^−3
1690 reflections	Δρmin = −0.15 e Å^−3
86 parameters	Absolute structure: Flack (1983) and Parsons et al. (2013)
2 restraints	Absolute structure parameter: 0.097 (14)

Special details

Experimental. Diffractometer operator C Jandl scanspeed 10 s per frame dx 35 mm 4600 frames measured in 17 data sets phi-scans with delta_phi = 0.5 omega-scans with delta_omega = 0.5

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F² for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > 2sigma(F²) is used only for calculating -R-factor-obs 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
Cl1	0.83894 (12)	1.00722 (6)	0.32306 (7)	0.0269 (1)
O1	0.7122 (3)	0.61466 (18)	0.37565 (14)	0.0242 (3)
C1	0.5421 (3)	0.5794 (3)	0.46254 (16)	0.0191 (5)
C2	0.4481 (3)	0.7335 (2)	0.53459 (17)	0.0222 (5)
C3	0.2685 (4)	0.7279 (3)	0.62647 (18)	0.0240 (5)
C4	0.1276 (3)	0.5721 (3)	0.67384 (16)	0.0227 (5)
C5	0.1451 (3)	0.3822 (3)	0.64158 (19)	0.0242 (5)
C6	0.3053 (4)	0.2993 (2)	0.5518 (2)	0.0249 (5)
C7	0.4782 (4)	0.3835 (3)	0.47408 (18)	0.0223 (5)
H1	0.751 (6)	0.738 (5)	0.370 (4)	0.063 (9)*
H2	0.51830	0.85660	0.51710	0.0270*
H3	0.23370	0.84860	0.66420	0.0290*
H4	0.00560	0.60230	0.73560	0.0270*
H5	0.03630	0.29610	0.68480	0.0290*
H6	0.29120	0.16370	0.54410	0.0300*
H7	0.56700	0.29840	0.42070	0.0270*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0336 (2)	0.0171 (2)	0.0342 (2)	−0.0003 (2)	0.0185 (2)	0.0018 (1)
O1	0.0303 (6)	0.0195 (6)	0.0269 (6)	−0.0020 (5)	0.0176 (5)	−0.0018 (4)
C1	0.0205 (7)	0.0179 (10)	0.0194 (7)	−0.0008 (6)	0.0044 (6)	0.0000 (6)
C2	0.0275 (9)	0.0141 (7)	0.0280 (8)	−0.0004 (6)	0.0137 (7)	−0.0016 (6)
C3	0.0290 (9)	0.0191 (8)	0.0264 (9)	0.0029 (6)	0.0122 (7)	−0.0038 (6)
C4	0.0203 (8)	0.0294 (12)	0.0205 (8)	0.0009 (7)	0.0097 (6)	0.0022 (7)
C5	0.0230 (8)	0.0251 (9)	0.0257 (8)	−0.0050 (7)	0.0078 (7)	0.0063 (8)
C6	0.0294 (9)	0.0163 (7)	0.0299 (10)	−0.0025 (7)	0.0079 (7)	0.0016 (6)
C7	0.0275 (8)	0.0159 (8)	0.0248 (8)	−0.0003 (7)	0.0084 (7)	−0.0015 (6)

Geometric parameters (Å, º)

O1—C1	1.321 (2)	C6—C7	1.370 (3)
O1—H1	0.88 (3)	C2—H2	0.9500
C1—C7	1.410 (3)	C3—H3	0.9500
C1—C2	1.414 (2)	C4—H4	0.9500
C2—C3	1.372 (2)	C5—H5	0.9500
C3—C4	1.407 (3)	C6—H6	0.9500
C4—C5	1.370 (3)	C7—H7	0.9500
C5—C6	1.410 (3)
C1—O1—H1	113 (2)	C3—C2—H2	116.00
O1—C1—C2	119.24 (17)	C2—C3—H3	115.00
O1—C1—C7	113.84 (16)	C4—C3—H3	115.00
C2—C1—C7	126.91 (15)	C3—C4—H4	116.00
C1—C2—C3	128.26 (15)	C5—C4—H4	116.00
C2—C3—C4	130.36 (18)	C4—C5—H5	116.00
C3—C4—C5	127.82 (16)	C6—C5—H5	116.00
C4—C5—C6	127.70 (16)	C5—C6—H6	115.00
C5—C6—C7	130.14 (16)	C7—C6—H6	115.00
C1—C7—C6	128.73 (17)	C1—C7—H7	116.00
C1—C2—H2	116.00	C6—C7—H7	116.00
O1—C1—C2—C3	178.61 (17)	C2—C3—C4—C5	2.6 (3)
C7—C1—C2—C3	−2.7 (3)	C3—C4—C5—C6	−1.1 (3)
O1—C1—C7—C6	−178.33 (19)	C4—C5—C6—C7	−0.8 (3)
C2—C1—C7—C6	2.9 (3)	C5—C6—C7—C1	−0.3 (4)
C1—C2—C3—C4	−0.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···Cl1	0.88 (3)	2.00 (3)	2.8732 (14)	170 (4)
C2—H2···Cl1	0.95	2.89	3.620 (2)	135
C3—H3···Cl1^i	0.95	2.87	3.609 (2)	135
C4—H4···O1^ii	0.95	2.64	3.351 (2)	132
C5—H5···Cl1^ii	0.95	2.79	3.717 (2)	166
C7—H7···Cl1^iii	0.95	2.69	3.623 (2)	166

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