464
Churchill, Churchill, Huynh, Takeuchi, Distefano, and Jameson
pentane was dissolved in a minimum amount of tolu-
ene. Cyclohexane was slowly added until cloudiness
was observed. A very small amount of toluene was
then carefully added until the mixture became clear.
The solution was left undisturbed in the dark and
uncovered until complete evaporation of the solvent
occurred (approximately 4 days). A number of clear,
colorless crystals (approximately 1 ϫ 1 ϫ 3 mm) were
The crystal gave rise to a diffraction pattern of
C2h (2/m) symmetry, indicative of the monoclinic
crystal system. The systematic absences (hkl for h ϩ
k ϭ 2n ϩ 1; h0l for both l ϭ 2n ϩ 1 and h ϭ 2n ϩ
1) are consistent with space groups Cc (No. 9)6a or
C2/c (No. 15).6b Intensity statistics7 favored the latter,
centrosymmetric, possibility. With Z ϭ 4, this re-
quires that the molecule lies on a site of crystallo-
graphic C2 (2) or Ci (l) symmetry;6b only the former
is possible for an ordered structure.
1
isolated from the container. The H NMR spectrum
of the crystals was consistent with the 1H NMR spec-
trum of 3,3-di(1-pyrazolyl)pentane and the melting
point of the crystals was 58–59ЊC.
A complete sphere of X-ray diffraction data (Mo
8
˚
KͰ radiation, ϭ 0.710730 A, 2 ϭ 5.0–45.0Њ), repre-
senting four equivalent general forms, was collected.
The 2933 observed reflections were reduced to a
unique set of 736 data (with the remarkably satisfac-
tory averaging index of R(int) ϭ 0.68%); 632 data
(85.9%) were observed with ͉Fo͉ Ͼ 6(͉Fo͉).
The crystallographic structural analysis
A colorless block, of approximate orthogonal
dimensions 0.5 ϫ 0.35 ϫ 0.25 mm, was cut from a
larger crystal and sealed into a thin-walled glass capil-
lary. It was aligned on a Siemens R3m/V automated
with its extended direction close-to-parallel with the
instrumental -axis. Diffraction data were collected
as described in general previously;5 details specific to
the present analysis are provided in Table 1.
The structure was solved by direct methods un-
der the SHELXTL PLUS Release 4.11 (VMS) system
of crystallographic routines.9,10 Calculations were
based upon the analytical expressions for neutral
atoms;11a corrections were made for the small real
(⌬fЈ) and imaginary (i⌬fЉ) components of anomalous
dispersion.11b Nonhydrogen atoms were quickly lo-
cated from an electron density map, which showed
the molecule to lie about a site of two-fold symmetry
at 1/2, y, 1/4 (Wyckoff notation e6b). Positional and
anisotropic displacement coefficients for all nonhy-
drogen atoms (with U12 ϭ U23 ϭ 0 for atom C(13),
which lies on a site of C2 symmetry11c) were refined,
following which all hydrogen atoms were located un-
ambiguously from a difference-Fourier map. Re-
finement of positional and anisotropic displacement
coefficients for non-hydrogen atoms, positional and
isotropic displacement coefficients for all hydrogen
atoms, the scale factor and a secondary extinction
parameter12 led to convergence [(⌬/)max ϭ 0.002]
with R ϭ 3.94% for all 736 reflections and R ϭ 3.40%
for those 632 reflections above 6(͉Fo͉). Final atomic
coordinates are given in Table 2.
Table 1. Crystal data and structure refinement
Compound
C11H16N4
CCDC deposit no.
Color
CCDC-1003/5553
Colorless
Formula weight
Temperature
Crystal system
Space group
204.3
296 K
Monoclinic
C2/c (No. 15)
˚
a ϭ 14.4005(23), A
Unit cell dimensions
˚
b ϭ 7.0494(12) A
c ϭ 11.2462(20) A
˚
˚
ͱ ϭ 101.572(13)
3
˚
Volume
1118.25(33) A
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.213 mg/m3
0.072 mmϪ1
440
2 range
5.0 to 45.0Њ
Index ranges
Ϫ15 Յ h Յ 15, Ϫ7 Յ k Յ 7,
Ϫ12 Յ l Յ 12
2933
736 (Rint ϭ 0.68%)
632 (F Ͼ 6.0(F))
͚w(Fo Ϫ Fc)2
ϭ 0.005(2), where
F* ϭ F[1 ϩ 0.002F2/sin(2)]Ϫ1/4
wϪ1 ϭ 2(F) ϩ 0.0003F2
Discussion
Reflections collected
Independent reflections
Observed reflections
Quantity minimized
Extinction correction
The 3,3-di(1-pyrazolyl)pentane molecule lies on
a site of crystallographic C2 symmetry, which passes
through atom C(13). The crystallographic asymmet-
ric unit consists of one-half of the molecule. The
atomic labeling scheme is shown in Fig. 1. Atoms in
the primary unit are labeled normally; those in the
‘‘other-half’’ of the molecule, related to the primary
unit by the transformation (1 Ϫ x, y, 1/2 Ϫ z), are
Weighting scheme
Number of parameters refined 102
Goodness of fit
2.23
Final R indices (obs. data)
R indices (all data)
R ϭ 0.0340, wR ϭ 0.0335
R1 ϭ 0.0394, wR ϭ 0.0507