Reaction of Cr(CH2SiMe3)2[N(SiMe2CH2PPh2)2]
6
with
istics. A successful direct-methods solution was calculated
ethylene. Addition of one atmosphere of ethylene to a bomb
containing a 10 mL toluene solution of Cr(CH2SiMe3)2[N(Si-
Me2CH2PPh2)2] 6 (0.05 g, 0.07 mmol) caused no immediate
colour change but over twelve hours a small amount of white
solid, presumably polyethylene, had been produced. After 24
hours, the solution had changed from green to dark brown-red
and no further polymer formation was observed.
which provided most non-hydrogen atoms from the E-map.
Several full-matrix least squares/difference Fourier cycles were
performed which located the remainder of the non-hydrogen
atoms. All non-hydrogen atoms were refined with anisotropic
displacement parameters. All hydrogen atoms were placed in
ideal positions and refined as riding atoms with individual (or
group if appropriate) isotropic displacement parameters. Func-
2
tion minimized Σw(|Fo| Ϫ |Fc|)2 where wϪ1 = σ2(Fo) ϩ 0.0010Fo ,
¹
¹
²
²
R = Σ|Fo Ϫ |Fc|/Σ|Fo| and Rw = Σ|(w (Fo Ϫ Fc)|/Σ|(w) Fo|. Final
R = 0.072, Rw = 0.166 for 6318 reflections with I у 2σ(I). The
crystal was twinned; the twin was a minor component ran-
domly oriented with respect to the major component. No
integration of the minor component was necessary. Selected
bond lengths and angles appear in Tables 2 and 3.
X-Ray crystallographic analysis
Cr(Me)Br[N(SiMe2CH2PPh2)2] 2. Crystal data. C31H39-
BrCrNP2Si2, M = 675.67, triclinic, a = 10.217(3), b = 19.705(5),
c = 9.353(3) Å, α = 101.94(2), β = 109.69(2), γ = 95.21(2)Њ,
U = 1707(1) Å3 (by least-squares refinement on the setting
angles for 25 reflections with 12Њ < 2θ < 18Њ, λ = 0.710 69 Å,
Ϫ3
¯
T = 21 ЊC), space group P1 (no. 2), Z = 2, Dc = 1.314 g cm
,
Cr(CH2SiMe3)2[N(SiMe2CH2PPh2)2] 6. Crystal data.
C38H58CrNP2Si4, M = 755.15, monoclinic, a = 12.9279(6),
b = 19.5790(9), c = 17.1414(8) Å, β = 95.295(1)Њ, U = 4320.2(3)
F(000) = 698. Brown irregular crystals. Crystal dimensions:
0.20 × 0.30 × 0.35 mm, µ(Mo-Kα) = 16.92 cmϪ1
.
Data collection and processing.67 Rigaku AFC6S diffract-
ometer, ω–2θ scan mode, ω scan width 1.37 ϩ 0.35 tan θ, ω
scan speed 16 minϪ1 (up to 8 rescans), graphite-mono-
chromated Mo-Kα radiation; 7846 unique reflections measured
(1 ≤ θ ≤ 27.5Њ, h, k, l), 4106 having I у 3σ(I). Absorption
correction: azimuthal scans (relative transmission factors 0.88–
1.00). The intensities of three standard reflections, measured
each 200 reflections, decayed linearly by 6.9% (correction
applied).
Å3, space group P21/c (no. 14), Z = 4, Dc = 1.161 g cmϪ3
,
F(000) = 1612. Black needle crystals. Crystal dimensions:
0.48 × 0.16 × 0.10 mm, µ(Mo-Kα) = 4.75 cmϪ1
.
Data collection and processing. Siemens SMART CCD
diffractometer, ω–2θ scan mode. Graphite-monochromated
Mo-Kα radiation; 7471 unique reflections measured (1 ≤ θ ≤ 25,
h, k, l), 7469 having I у 2σ(I). Absorption correction:
SADABS.68 The data collection for 6 is analogous to that for 5
(above). Orientation matrices for initial cell constant calcul-
ations were determined from 24 reflections. Final cell constants
were calculated from a set of 6991 strong reflections from the
actual data collection. The sample diffracted poorly and was
collected with 45 second frames.
Structure analysis and refinement. Direct methods followed
by Fourier synthesis. Full-matrix least-squares with all non-
hydrogen atoms anisotropic and hydrogen atoms in calculated
positions [C–H = 0.99 Å, Biso = 1.2B(parent atom)]. Statistical
weights = 4Fo/σ2(F2).67 Final R = Σ |Fo| Ϫ |Fc| /Σ|Fo| = 0.067,
Structure analysis and refinement. The structure analysis and
2
2
¹
²
Rw = (Σw(|Fo| Ϫ |Fc|) /Σw|Fo| ) = 0.030 for 4106 reflections with
I у 3σ(I). Computer programs and source of scattering factors
are given in ref. 67. Selected bond lengths and bond angles
appear in Tables 2 and 3.
refinement for 6 is analogous to that for 5 (above). Function
2
minimized Σ(|Fo| Ϫ |Fc|)2 where
w
Ϫ1 = σ2(Fo) ϩ 0.0010Fo ,
¹
¹
²
²
R = Σ|Fo Ϫ |Fc|/Σ|Fo| and Rw = Σ|(w (Fo Ϫ Fc)|/Σ|(w) Fo|. Final
R = 0.073, Rw = 0.127 for 7469 reflections with I у 2σ(I).
Selected bond lengths and angles appear in Tables 2 and 3.
CCDC reference number 186/1243.
Cr(CH2SiMe3)Cl[N(SiMe2CH2PPh2)2] 5. Crystal data.
C34H47ClCrNP2Si3, M = 703.39, triclinic, a = 11.0802(3),
b = 11.2193(3), c = 17.9349(1) Å, α = 95.385(1), β = 100.353(1),
Acknowledgements
Financial support was provided by NSERC of Canada in the
form of a Research grant (to M. D. F.) and a 1967 Science and
Engineering Research Scholarship (to D. B. L.).
3
¯
γ = 118.882(1)Њ, U = 1877.71(7) Å , space group P1 (no. 2),
Z = 2, Dc = 1.244 g cmϪ3, F(000) = 742. Brown wedge crystals.
Crystal dimensions: 0.35 × 0.20 × 0.12 mm, µ(Mo-Kα) = 5.80
cmϪ1
.
Data collection and processing. Siemens SMART CCD
diffractometer, ω–2θ scan mode. Graphite-monochromated
Mo-Kα radiation; 6320 unique reflections measured (1 ≤ θ
≤ 25Њ, h, k, l), 6318 having I у 2σ(I). Absorption correction:
SADABS.68 A crystal of 5, sealed in a glass capillary, was
mounted on the Siemens SMART system for a data collection
at 173(2) K. An initial set of cell constants was calculated from
reflections harvested from three sets of 20 frames. These initial
sets of frames are oriented such that orthogonal wedges of
reciprocal space were surveyed. This produces orientation
matrices determined from 80 reflections. Final cell constants are
calculated from a set of 3459 strong reflections from the actual
data collection. Final cell constants reported in this manner
usually are about one order of magnitude better in precision
than reported from four-circle diffractometers.
The data technique used for this specimen is generally known
as a hemisphere collection. Here, a randomly oriented region of
reciprocal space is surveyed to the extent of 1.3 hemispheres to
a resolution of 0.84 Å. Three major swaths of frames are
collected with 0.30Њ steps in ω. This collection strategy provides
a high degree of redundancy. The redundant data provide good
ψ input in the event an empirical absorption correction is
applied.
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153
Fryzuk, Michael D.
