In contrast to 1, where all alkynes are involved in extended
CH···p networks, only two of eight independent alkyne termini
of 2 participate in close contacts. One alkyne hydrogen atom
points directly at the face of a neighboring near-perpendicular
phenyl ring, with CH···C(Ph) approaches of 2.55, 2.60 and
2.75 Å, a typical CH···p interaction mode. The other close
contact is an almost antiparallel (side-by-side) approach
between two C·CH termini related by a 2-fold rotation, with a
C···H distance of 2.60 Å and a C···C distance of 3.17 Å
(expected6 van der Waals contacts are 2.9 and 3.4 Å). Similar
alkynyl contacts of both types have been reported before.2a,8
In summary, the crystal structure of 1 is the first example of
a diamondoid packing motif formed by weak hydrogen bonding
between acetylenic groups. We are currently investigating
hydrogen bonding of 1 and 2 with other compounds and
expanding the family of ethynyl-substituted tetrahedral building
blocks.
This work was supported by the U.S. National Science
Foundation (CHE-9709330) and the Office of Naval Research.
We thank Ms Jagruti Patel for synthesizing 3.
Fig. 2 A schematic view of the three interwoven diamondoid nets, one of
which is accented in bold. For clarity, the phenyl groups have been replaced
by three ‘atoms’ in a straight line.
Notes and references
‡ Intensity data for 1 and 2 were measured on a Bruker diffractometer with
Cu-Ka radiation (l = 1.54178 Å) at T = 293 K. Structures were solved by
direct methods, aided by program XS, and refined with full-matrix least-
The repetition of a single linked cage by crystal lattice
translations produces a three-dimensional network, but origin
molecules located at +c and +2c serve as generators of two more
networks which penetrate the holes of the first network, and
coexist without (close) interaction. The assembly is thus
comprised of three identical interwoven diamondoid networks
(Fig. 2). The hydrogen bonded alkyne moieties are neither
perpendicular (inter-line angle of 90°) nor antiparallel (180°),
but approach at an intermediate inclination, with an inter-linear
angle of 110.6° between lines passing through the ethynes of H-
bonded neighbors in the cluster. The inter-alkyne hydrogen
bond H4B···C4BA (2.76 Å), is the only intermolecular distance
less than the expected van der Waals’ contact (2.90 Å).6
Hydrogen atom positions were normalized to give linear 1.08 Å
C–H bonds before calculating all H-bond parameters. The
closest C–H approach is to the terminal C atom; distances to the
other alkyne C atom and to the midpoint of the alkyne bond are
greater.
squares program XL, from SHELXTL (ref. 9). Crystal data for 1: C33H20
,
¯
M = 416.49, tetragonal space group I4; a = b = 12.9197(4), c = 7.2357(5)
Å, V = 1207.8(1) Å3, Z = 2, and D(X-ray) = 1.145 mg mm23. Clear
colorless 0.54 3 0.26 3 0.17 mm crystal; 1204 data measured to a 2q max
of 116°. Absorption correction by integration over crystal volume (m =
0.493 mm21). Least-squares refinement on F2 differences; R-factors: R =
0.0367, wR2 = 0.0993 for all 848 unique refl. For 2: C42H32·1/4(C6H6), M
= 556.20, monoclinic space group C2/c, a = 48.460(4), b = 10.5467(13),
c = 28.759(3) Å, b = 121.896(4)°, V = 12479(2) Å3, Z = 16, and D(X-
ray) = 1.184 mg mm23. Clear colorless 0.48 3 0.11 3 0.05 mm crystal;
8609 data measured to 2q = 90°[ < I > was measured to be < 2s(I) at
higher angles]. Absorption correction by integration over crystal volume (m
= 0.504 mm21). Least-squares refinement on F2 differences varied a total
of 785 parameters. R factors were R = 0.0574 for 2985 unique reflections
with [I > 2s(I)], and R = 0.1141, wR2 = 0.1376 for all 5051 unique
reflections. CCDC 182/1111. The crystallographic data is available in CIF
1999/173/
§ Selected data for 1: dH NMR (500 MHz, CDCl3) 7.36 (d, J 4.5, 8H), 7.32
(d, J 4.5, 8H), 3.04 (s, 4 H, C·CH); dC (125 MHz, CDCl3) 146.17, 131.64,
130.72, 120.25, 83.13 (C·CH), 77.60 (C·CH), 64.77 (CPh4). HRMS
(FAB): calc. for C33H20: 416.1565, found 416.1565. For 2: dH (500 MHz,
CDCl3) 7.46 (d, J 8.5, 8H), 7.39 (d, J 8.5, 8H), 3.03 (s, 4 H, C·CH), 2.10
(br s, 12H, CH2); 13C dC (125 MHz, CDCl3) 149.65, 132.23, 124.99, 120.06,
83.43 (C·CH), 76.90 (C·CH), 46.70 [C(ad)-Ph], 39.27 (CH2) HRMS
(FAB): calc. for C42H32: 536.2504, found 536.2504.
To assess whether a diamondoid motif would occur upon
changing the tetrahedral core, we prepared 1,3,5,7-tetrakis(4-
ethynylphenyl)adamantane 2§ (Scheme 1.)7 In the crystal
structure‡ of 2, both C·CH···C·C and C·CH···Ph interactions
are present, but the lattice is not diamondoid. Compound 2
crystallizes from benzene–hexane in a monoclinic packing
arrangement (C2/c), with two molecules of 2 and a half-
molecule of benzene in the asymmetric unit of the crystal
(Fig. 3). Crystals of 2 grown from a few solvents other than
benzene also showed asymmetric lattices.
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116, 7588; (b) K. S. Feldman, C. M. Kraebel, M. Parvez, J. Am. Chem.
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3 P. J. Stang and F. Diederich, Modern Acetylene Chemistry, Wiley-VCH,
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4 (a) T. Steiner, E. B. Starikov, A. Amado and J. J. C. Teixeira-Dias,
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Radhakrishnan, J. Bandekar and G. R. Desiraju, J. Am. Chem. Soc., 1993,
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6 R. S. Rowland and R. Taylor. J. Phys. Chem., 1996, 100, 7384.
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1994, 27, 7015.
Fig. 3 Crystal structure of 2. Sixteen molecules of 2 and four benzene
molecules occupy each cell; those on the bottom and top faces are shown
twice. For clarity, the phenyl groups have been replaced by three ‘atoms’ in
a straight line.
8 H. E. Zimmerman and Z. Zhu, J. Am. Chem. Soc., 1995, 117, 5245.
9 G. Sheldrick, SHELXTL96, Acta Crystallogr., Sect. A, 1990, 46, 467.
Communication 8/07993E
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Chem. Commun., 1999, 173–174