Crystal engineering in the gem-alkynol family: the key role of water in the structure of 2,3,5,6-tetrabromo-trans-1,4-diethynyl-cyclohexa-2,5-diene-1,4-diol dihydrate determined by X-ray and neutron diffraction at 150 K

The structure of the title compound has been determined using low-temperature (150 K) single-crystal X-ray and neutron diffraction data. Crystals adopt the uncommon space group P4₂/ncm and display a complex set of intermolecular interactions in which the water molecules play the crucial role: the water O-atom [O2(w)] accepts two hydrogen bonds and both water H atoms act as bifurcated donors. A set of O—H...O hydrogen bonds is formed around the 4₂ axis comprising (a) a cyclic tetrameric synthon involving four donor-H from two water molecules and two O(hydroxy) acceptors from two parent molecules, and (b) short discrete O(hydroxy)—H...O2(w) hydrogen bonds which link these tetramers along the c axis. Four Br...Br interactions [3.708 (1) Å] form cyclic Br₄ tetramers around the axis and are linked to the O—H...O system via O2(w)—H...Br bonds with H...Br = 2.995 (2) Å. Finally, the O—H...O system is further linked to the parent molecules via C≡C...H...O2(w) bonds of 2.354 (3) Å. The supramolecular structure of the title hydrate is compared with that of the non-hydrated parent molecule, which also forms cyclic O—H...O bonded tetrameric synthons, and with its (non-hydrated) tetrachloro analogue, which forms cyclic tetrameric Cl₄ synthons [Madhavi, Desiraju et al. (2000b). Acta Cryst. B56, 1063–1070].

Computing details

Data collection: Bruker SMART for nmbrX. Cell refinement: Bruker SMART for nmbrX. Data reduction: Bruker SAINT for nmbrX. Program(s) used to solve structure: SHELXS97 (Sheldrick, 1990) for nlmbrN; SHELXS97 (Sheldrick, 1997) for nmbrX. For both compounds, program(s) used to refine structure: SHELXL97 (Sheldrick, 1997). Molecular graphics: SHELXL97 (Sheldrick, 1997) for nmbrX. Software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) for nmbrX.

Figures

(nlmbrN)

Crystal data

C10H4Br4O2·2H2O	F(000) = 348
Mr = 511.80	Dx = 2.429 Mg m^−3
Tetragonal, P42/ncm	Neutron radiation, λ = 0.5-5.0 Å
Hall symbol: -P 4ac 2ac	µ = 0.00 mm^−1
a = 12.6551 (18) Å	T = 150 K
c = 8.7340 (17) Å	Block, colourless
V = 1398.8 (4) Å^3	3 × 2 × 2 mm
Z = 4

Data collection

`SXD' diffractometer	1654 reflections with I > 2σ(I)
Radiation source: ISIS spallation source	Rint = 0.000
None monochromator	θmax = 62.6°, θmin = 2.3°
time–of–flight LAUE diffraction scans	h = 0→28
1654 measured reflections	k = 0→18
1654 independent reflections	l = 0→21

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.061	All H-atom parameters refined
wR(F^2) = 0.082	w = 1/[σ^2(Fo^2) + (0.P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 6.19	(Δ/σ)max < 0.001
1654 reflections	Δρmax = 2.28 e Å^−3
70 parameters	Δρmin = −1.40 e Å^−3
0 restraints	Extinction correction: Becker-Coppens Lorentzian model
Primary atom site location: structure-invariant direct methods

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
Br1	0.58770 (6)	0.23168 (6)	0.11938 (8)	0.02118 (13)
C1	0.42464 (7)	0.07536 (7)	0.40923 (10)	0.0273 (2)
C2	0.43082 (6)	0.06918 (6)	0.27272 (8)	0.01656 (16)
C3	0.43183 (5)	0.06817 (5)	0.10514 (8)	0.01116 (13)
O1	0.35533 (6)	0.14467 (6)	0.05950 (10)	0.01517 (18)
C4	0.54095 (5)	0.09963 (5)	0.04716 (6)	0.01210 (10)
O2	0.34530 (8)	0.15470 (8)	−0.24746 (12)	0.0221 (2)
H1A	0.35202 (11)	0.14798 (11)	−0.0533 (2)	0.0266 (4)
H2A	0.36388 (17)	0.22016 (16)	−0.2936 (2)	0.0441 (4)
H1	0.41968 (19)	0.08032 (19)	0.5303 (2)	0.0579 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0198 (3)	0.0148 (3)	0.0290 (3)	−0.0038 (3)	0.0013 (2)	−0.0066 (2)
C1	0.0351 (4)	0.0351 (4)	0.0115 (3)	0.0004 (5)	0.0018 (2)	−0.0018 (2)
C2	0.0197 (3)	0.0197 (3)	0.0103 (2)	0.0001 (3)	0.00046 (18)	−0.00046 (18)
C3	0.0118 (2)	0.0118 (2)	0.0098 (2)	0.0007 (3)	0.00034 (16)	−0.00034 (16)
O1	0.0150 (3)	0.0150 (3)	0.0155 (3)	0.0039 (4)	−0.0004 (2)	0.0004 (2)
C4	0.0120 (2)	0.0117 (2)	0.01266 (17)	−0.0004 (2)	0.00044 (18)	−0.00126 (18)
O2	0.0235 (4)	0.0235 (4)	0.0194 (4)	−0.0053 (5)	−0.0027 (3)	0.0027 (3)
H1A	0.0291 (6)	0.0291 (6)	0.0215 (6)	0.0054 (8)	−0.0019 (5)	0.0019 (5)
H2A	0.0516 (12)	0.0348 (9)	0.0458 (9)	−0.0111 (9)	0.0012 (8)	0.0076 (7)
H1	0.0783 (14)	0.0783 (14)	0.0171 (8)	0.0032 (18)	0.0028 (7)	−0.0028 (7)

Geometric parameters (Å, º)

Br1—C4	1.8817 (9)	C3—C4^i	1.5237 (7)
C1—C2	1.1974 (11)	C3—C4	1.5237 (7)
C1—H1	1.061 (2)	O1—H1A	0.987 (2)
C2—C3	1.4637 (10)	C4—C4^ii	1.3347 (11)
C3—O1	1.4260 (13)	O2—H2A	0.951 (2)
C2—C1—H1	179.5 (3)	C2—C3—C4	109.75 (4)
C1—C2—C3	175.42 (11)	C4^i—C3—C4	111.30 (7)
O1—C3—C2	105.52 (7)	C3—O1—H1A	109.68 (14)
O1—C3—C4^i	110.18 (4)	C4^ii—C4—C3	124.33 (3)
C2—C3—C4^i	109.75 (4)	C4^ii—C4—Br1	121.74 (3)
O1—C3—C4	110.18 (4)	C3—C4—Br1	113.93 (5)

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

(nmbrX)

Crystal data

C10H8Br4O4	Dx = 2.430 Mg m^−3
Mr = 511.80	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42/ncm	Cell parameters from 999 reflections
Hall symbol: -P 4ac 2ac	θ = 2.3–23.3°
a = 12.6551 (18) Å	µ = 11.51 mm^−1
c = 8.7340 (17) Å	T = 150 K
V = 1398.8 (4) Å^3	Block, colourless
Z = 4	0.4 × 0.3 × 0.3 mm
F(000) = 960

Data collection

Brucker SMART CCD diffractometer	539 independent reflections
Radiation source: fine-focus sealed tube	501 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
Detector resolution: not relevant pixels mm^-1	θmax = 23.3°, θmin = 2.3°
ω scans	h = −13→14
Absorption correction: multi-scan multi-scan, using SADABS	k = −14→13
Tmin = 0.644, Tmax = 1.000	l = −8→9
6046 measured reflections

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)] = 0.020	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.053	w = 1/[σ^2(Fo^2) + (0.0231P)^2 + 2.4727P] where P = (Fo^2 + 2Fc^2)/3
S = 1.22	(Δ/σ)max < 0.001
539 reflections	Δρmax = 0.44 e Å^−3
58 parameters	Δρmin = −0.30 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0039 (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
Br1	0.58779 (3)	0.23210 (3)	0.11967 (4)	0.0307 (2)
C1	0.4246 (3)	0.0754 (3)	0.4094 (7)	0.0364 (14)
H1	0.4196	0.0804	0.5154	0.06 (2)*
C2	0.4310 (3)	0.0690 (3)	0.2751 (6)	0.0272 (12)
C3	0.4319 (3)	0.0681 (3)	0.1055 (5)	0.0247 (11)
O1	0.35500 (19)	0.14500 (19)	0.0611 (5)	0.0267 (8)
C4	0.5414 (3)	0.0995 (3)	0.0465 (4)	0.0235 (8)
O2	0.3458 (2)	0.1542 (2)	−0.2463 (4)	0.0322 (9)
H2B	0.357 (3)	0.208 (3)	−0.281 (4)	0.026 (11)*
H1A	0.348 (3)	0.152 (3)	−0.018 (6)	0.015 (16)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0304 (3)	0.0257 (3)	0.0360 (3)	−0.00322 (14)	0.00125 (15)	−0.00608 (15)
C1	0.040 (2)	0.040 (2)	0.029 (4)	0.004 (3)	0.0004 (17)	−0.0004 (17)
C2	0.0269 (18)	0.0269 (18)	0.028 (3)	−0.001 (2)	0.0008 (15)	−0.0008 (15)
C3	0.0256 (16)	0.0256 (16)	0.023 (3)	0.002 (2)	0.0005 (14)	−0.0005 (14)
O1	0.0302 (14)	0.0302 (14)	0.020 (2)	0.0044 (15)	−0.0015 (12)	0.0015 (12)
C4	0.0260 (19)	0.0243 (19)	0.0201 (18)	−0.0021 (14)	−0.0037 (13)	0.0010 (13)
O2	0.0328 (14)	0.0328 (14)	0.031 (2)	−0.0054 (18)	−0.0058 (13)	0.0058 (13)

Geometric parameters (Å, º)

Br1—C4	1.889 (3)	C3—C4	1.531 (4)
C1—C2	1.178 (7)	O1—H2B^ii	2.32 (4)
C1—H1	0.9300	O1—H1A	0.70 (5)
C2—C3	1.482 (7)	C4—C4^iii	1.319 (7)
C3—O1	1.429 (6)	O2—H1A	1.99 (5)
C3—C4^i	1.531 (4)	O2—H2B	0.76 (3)
C2—C1—H1	180.0	C3—O1—H2B^ii	112.1 (10)
C1—C2—C3	175.0 (6)	C3—O1—H1A	115 (4)
O1—C3—C2	105.1 (4)	H2B^ii—O1—H1A	120 (3)
O1—C3—C4^i	110.4 (3)	C4^iii—C4—C3	124.56 (19)
C2—C3—C4^i	110.0 (3)	C4^iii—C4—Br1	122.01 (10)
O1—C3—C4	110.4 (3)	C3—C4—Br1	113.4 (2)
C2—C3—C4	110.0 (3)	H1A—O2—H2B	114 (3)
C4^i—C3—C4	110.9 (4)

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