Synthesis, characterization, and reactivity of a rhenium complex with a corannulene-based ligand

Article abstract of DOI:10.1021/om034111t

A new rhenium carbonyl complex, exo-(η⁵-C₂₀H₁₇)Re(CO)₃ (3), containing a corannulene-derived ligand has been synthesized in 12% yield. The X-ray structure determination of 3 shows that the rhenium center is bound to the exo face of the bowl-shaped ligand. The reaction of 3 with PPh₃ in benzene at 70°C produces trans,mer-Re(H)(PPh₃)₂(CO)₃ and C₂₀H₁₆ (4), a bowl-shaped dibenzofulvene type molecule. The reaction of 3 with PPh₃ proceeds via an η⁵-η³-η¹ ring slip followed by a β-hydride elimination.

Full text of DOI:10.1021/om034111t

Organometallics 2003, 22, 4829-4832
4829
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity of a
Rh en iu m Com p lex w ith a Cor a n n u len e-Ba sed Liga n d
Robert M. Chin,* Benjamin Baird, Michael J arosh, Shane Rassman, and
Brian Barry
Department of Chemistry, University of Northern Iowa, Cedar Falls, Iowa 50614-0423
William D. J ones
Department of Chemistry, University of Rochester, Rochester, New York 14627
Received August 14, 2003
Summary: A new rhenium carbonyl complex, exo-(η5-
C20H17)Re(CO)3 (3), containing a corannulene-derived
ligand has been synthesized in 12% yield. The X-ray
structure determination of 3 shows that the rhenium
center is bound to the exo face of the bowl-shaped ligand.
The reaction of 3 with PPh3 in benzene at 70 °C produces
trans,mer-Re(H)(PPh3)2(CO)3 and C20H16 (4), a bowl-
shaped dibenzofulvene type molecule. The reaction of 3
hexahydrocorannulene. We recently reported the hy-
drogenation of hexahydrocorannulene to give C H (2),
2
0
18
which is electronically similar to a 1,4,5,8,9-pentaalky-
lated fluorene.10
5
3
1
with PPh3 proceeds via an η -η -η ring slip followed by
a â-hydride elimination.
In tr od u ction
Deprotonation of 2 with n-BuLi yields the analogous
Due to recent improvements in the synthesis of
fluorenyl anion, which can then bind to CpZrCl2 to form
1
-5
corannulene, C20H10 (1),
the transition metal chem-
5
5
exo-(η -C20H17)(η -C5H5)ZrCl2. Herein we report the use
of 2 in synthesizing a new rhenium tricarbonyl complex.
istry of corannulene has received a great deal of atten-
tion in recent years.
Resu lts a n d Discu ssion
Deprotonation of 2 with n-BuLi in Et2O/C6H6 followed
5
by addition of [Re(CO)3(THF)Br]2 afforded exo-(η -
C20H17)Re(CO)3, 3, in 12% yield as a bright yellow
powder (eq 1).
Examples of corannulene transition metal complexes
6
6
6
include [(Cp*)Ru(η -C20H10)]O3SCF3, [Cp*Ir (η -C20H10)]-
7
(
BF4)2, and [(Rh2(O2CCF3)4)m‚(C20H10)n] (m:n ) 1:1 and
:2).
We are interested in using the inner five-membered
8
3
ring of the corannulene core as a cyclopentadienyl
mimic. To do this, corannulene has to be partially
hydrogenated to have a removable proton to generate
the anionic center. Recent work by Rabideau and co-
workers provided the starting point for our studies.
Reaction of corannulene in a Na/THF/NH3 mixture at
The synthesis of 3 requires a fairly nonpolar solvent
medium, as attempted syntheses in THF and ether
yielded only uncharacterizable products in the corre-
9
1
1
13
sponding H NMR spectra. The H and C NMR
spectral data of 3 are consistent with the predicted Cs
symmetry. The CO stretching frequencies for 3 are at
-
33 °C, followed by an inverse ammonium chloride
quench, yields the partially hydrogenated corannulene,
-
1
5
lower energy (νCO ) 2009, 1896 cm ) than (η -C13H9)-
*
Corresponding author. E-mail: martin.chin@uni.edu.
-1 11
Re(CO)3 (νCO ) 2027, 1935 cm ), which is consistent
(1) Scott, L. T.; Cheng, P. C.; Hashemi, M. M.; Bratcher, M. S.;
with 2 being a better electron donor than the unsub-
stituted fluorenyl ligand. An X-ray structure study was
undertaken in order to determine which face of the bowl-
shaped ligand the rhenium was attached to, the exo
Meyer, D. T.; Warren, H. B. J . Am. Chem. Soc. 1997, 119, 10963-
1
0968.
(
2) Sygula, A.; Rabideau, P. W. J . Am. Chem. Soc. 1999, 121, 7800-
7
803.
(3) Seiders, T. J .; Elliott, E. L.; Grube, G. H.; Siegel, J . S. J . Am.
Chem. Soc. 1999, 121, 7804-7813.
(convex) or endo (concave) face. The study revealed that
(
4) Sygula, A.; Rabideau, P. W. J . Am. Chem. Soc. 2000, 122, 6323-
the rhenium metal center was on the exo side of the
6
324.
(
5) Sygula, A.; Xu, G.; Marcinow, Z.; Rabideau, P. W. Tetrahedron
bowl, which is the same side for the previously reported
exo-(η -C20H17)(η -C5H5)ZrCl2 (Figure 1).
2
001, 57, 3637-3644.
(
5
5
6) Seiders, T. J .; Baldridge, K. K.; O’Connor, J . M.; Siegel, J . S. J .
Am. Chem. Soc. 1997, 119, 4781-4782.
7) Alvarez, C. M.; Angelici, R. J .; Sygula, A.; Sygula, R.; Rabideau,
P. W. Organometallics, 2003, 22, 624-626.
8) Petrukhina, M. A.; Andreini, K. W.; Mack, J .; Scott, L. T. Angew.
Chem. Int. Ed. 2003, 42, 3375-3379.
(
(9) Rabideau, P. W.; Marcinow, Z.; Sygula, R.; Sygula, A. Tetrahe-
dron Lett. 1993, 34, 6351-6354.
(10) Chin, R. M.; J arosh, M. S.; Russell, J . D.; Lachicotte, R. J .
Organometallics 2002, 21, 2027-2029.
(
1
0.1021/om034111t CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/07/2003

4
830 Organometallics, Vol. 22, No. 23, 2003
Notes
F igu r e 2. POAV1 angles (deg) of corannulene-based
ligand in 3.
effect that 2 would have on CO substitution reaction in
F igu r e 1. ORTEP plot of 3 (30% probability level).
3
. We initially predicted that 3 would have a slower rate
5
of substitution than (η -C13H9)Re(CO)3 due to the larger
size of 2. However, heating a mixture of 3 and PPh3 (2.5
equiv) in a Teflon-capped NMR tube at 70 °C for 1 h
Ta ble 1. Selected List of Bon d Len gth s (Å) a n d
An gles (d eg) for 3
Re(1)-C(21)
Re(1)-C(23)
Re(1)-C(22)
Re(1)-C(5)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-C(1)
Re(1)-C(4)
1.881(9)
1.911(4)
1.928(8)
2.290(5)
2.337(6)
2.346(5)
2.352(5)
2.374(4)
C(21)-O(1)
C(22)-O(1)
C(23)-O(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(1)-C(5)
1.167(10)
1.147(11)
1.148(5)
1.401(8)
1.420(7)
1.388(6)
1.434(6)
1.431(8)
1
did not yield a CO substitution reaction. The H NMR
spectrum of the reaction mixture showed that the
corannulene-based ligand had left the metal center to
form a dibenzofulvene type molecule, C20H16 (4), and
trans,mer-Re(H)(PPh3)2(CO)3 (eq 2).
C(21)-Re(1)-C(23)
C(21)-Re(1)-C(22)
C(23)-Re(1)-C(22)
C(2)-C(1)-C(8)
C(2)-C(1)-C(5)
C(8)-C(1)-C(5)
C(1)-C(2)-C(11)
C(1)-C(2)-C(3)
C(11)-C(2)-C(3)
89.7(4)
C(4)-C(3)-C(14) 124.2(4)
108.0(5)
C(14)-C(3)-C(2) 124.8(5)
C(3)-C(4)-C(17) 121.9(4)
91.01(17) C(4)-C(3)-C(2)
92.8(4)
121.9(5)
109.8(6)
127.2(5)
123.6(5)
107.2(5)
125.1(5)
C(3)-C(4)-C(5)
109.9(4)
C(17)-C(4)-C(5) 126.5(4)
1
The H NMR spectrum for trans,mer-Re(H)(PPh3)2-
C(4)-C(5)-C(1)
C(4)-C(5)-C(20) 124.4(4)
C(1)-C(5)-C(20) 123.0(5)
104.3(5)
(
CO)3 matched the spectral data reported by J ones and
Maguire, with the rhenium hydride having a chemical
shift of δ -4.51 and J P-H ) 18.2 Hz.
We have previously synthesized 4 by an acid-cata-
lyzed isomerization of hexahydrocorannulene. Heating
a solution of hexahydrocorannulene with trifluoroacetic
acid in benzene at 110 °C for 20 h afforded 4 in 50%
yield (eq 3).
1
6
Selected bond lengths and angles of 3 are given in
Table 1.
5
The η binding is confirmed by the Re-C bond lengths
(
2.29-2.374 Å), which are similar in value to the
5
12
reported values for (η -C13H9)Re(CO)3 (2.288-2.351 Å).
Also the average OC-Re-CO bond angle for 3 (91.2°)
5
is similar to that of (η -C13H9)Re(CO)3 (90.5°), which
suggests that even though 2 is larger than fluorene, the
steric footprint of 2 around the rhenium center is
roughly the same as that of fluorene. This similar
spatial occupancy around the metal center can be
attributed to the fact that the bowl-shaped ligand curves
away from the metal center.
1
The lack of exo and endo resonances in the H NMR
The curvature of the coordinated ligand was deter-
spectrum of 4 at 20 °C indicates that 4 either is
undergoing a rapid bowl-to-bowl inversion or is planar.
Cooling a CD2Cl2 solution of 4 to -90 °C broadened the
methylene resonances, thereby indicating that 4 is
undergoing a rapid bowl-to-bowl inversion. However, we
were unable to reach the low-temperature limit to
resolve the exo and endo H resonances. Also in the H
NMR spectrum of 4, the aromatic region has only one
resonance, a singlet, rather than the expected two
doublets for the two nonequivalent hydrogens. We be-
lieve this apparent inconsistency is due to the hydrogens
being chemical shift equivalent, where δν/J ) 0. The
mined using the π-orbital axis vector (POAV1, θp ) θσπ
3,14
-
90) method.1
The pyramidalization angles for the
inside ring of the modified corannulene ligand are
shown in Figure 2. C5 has the largest θp angle of 9.6°,
while C1 and C4 have the smallest pyramidalization
angles of 3.5° and 4.3°, respectively. The average
pyramidalization angle of the inner Cp core is 6.0°
1
1
5
5
compared with 5.9° for exo-(η -C20H17)(η -C5H5)ZrCl2.
Rea ction of 3 w ith P P h 3. The CO substitution
reactions of indenyl and fluorenyl manganese carbonyl
complexes have been reported to proceed via an associa-
1
5
tive ring slip mechanism by Basolo and co-workers.
Therefore, we were interested in determining the steric
13
C NMR spectrum of 4 is consistent with the proposed
structure, displaying 11 different C resonances.
13
Our proposed mechanism for the formation of 4 and
trans,mer-Re(H)(PPh3)2(CO)3 in the reaction of 3 with
(
11) Young, K. M.; Miller, T. M.; Wrighton, M. S. J . Am. Chem. Soc.
990, 112, 1529-1537.
12) Mejdrich, A. L.; Hanks, T. W. Synth. React. Inorg. Met.-Org.
Chem. 1998, 28, 953-973.
13) Haddon, R. C.; Scott, L. T. Pure Appl. Chem. 1986, 58, 137-
42.
14) Haddon, R. C. J . Am. Chem. Soc. 1990, 112, 3385-3389.
1
(
(15) J i, L. N.; Rerek, M. E.; Basolo, F. Organometallics 1984, 3, 740-
(
745.
1
(16) J ones, W. D.; Maguire, J . A. Organometallics 1987, 6, 1728-
1737.
(

Notes
Organometallics, Vol. 22, No. 23, 2003 4831
Sch em e 1
Therefore, the results of the labeling study are
consistent with 3 undergoing successive ring slips in the
presence of PPh3 followed by a â-hydride elimination.
Con clu sion
To summarize, the reaction of C20H18 (2), a partially
hydrogenated corannulene ligand, with n-BuLi and [Re-
Sch em e 2
5
(CO)3(THF)Br]2 yields exo-(η -C20H17)Re(CO)3 (3), a new
rhenium complex with a bowl-shaped ligand. Reaction
of 3 with PPh3 yields trans,mer-Re(H)(PPh3)2(CO)3 and
C20H16 (4), a dibenzofulvene type molecule, rather than
the expected CO substitution reaction. A deuterium
labeling study is consistent with the proposed mecha-
5
3
1
nism of an η -η -η ring slip followed by a â-hydride
elimination step.
Exp er im en ta l Section
Gen er a l P r oced u r es. Reactions that required inert condi-
tions were performed using modified Schlenk techniques or
in a MBraun Unilab glovebox under a nitrogen atmosphere.
1
13
H and C NMR spectra were recorded on a GE-QE300 MHz
1
13
spectrometer running Tecmag Aquarius software. H and
C
5
3
1
NMR chemical shifts are given relative to the residual proton
or 13C solvent resonances. Mass spectra were recorded on a
Hewlett-Packard 6890-5973 GC-MS.
Solven ts a n d Rea gen ts. Unless otherwise indicated, all
chemicals were used as received (reagents from Aldrich, Acros,
or Strem Chemical Company). Deuterated solvents and deu-
terium gas (D, 99.8%) were obtained from Cambridge Isotope
Laboratories. Tetrahydrofuran (THF), toluene, and diethyl
ether were distilled from dark purple solutions of sodium
benzophenone ketyl. Methylene chloride was distilled from
PPh3 includes an η -η -η ring slip of the fluorenyl type
ligand, followed by a â-hydride elimination of the
hydrogen on the â-carbon to the Re metal center
(
Scheme 1).
5
1
η -η ring slip of a fluorenyl rhenium complex has
been previously reported by Hanks and co-workers in
the reaction of (η -C13H9)Re(CO)3 with 1 atm of CO to
yield (η -C13H9)Re(CO)5. Other examples of (η -X)Re-
CO)3 (X ) C5H5 , C9H7 ) complexes undergoing η -η
ring slip have been reported by Casey and co-work-
In those examples, added PMe3 to the corre-
sponding (η -X)Re(CO)3 complexes gave fac-Re(η -X)-
5
1
12
5
-
-
5
1
(
CaH
2 6
before use. Benzene-d was distilled under vacuum from
ers.1
7,18
sodium benzophenone ketyl. CDCl and CD Cl were distilled
3
2
2
5
1
under vacuum from CaH
by Atlantic Microlab Inc., Norcross, GA. Re(CO)
2
. Elemental analyses were performed
Br was
5
(CO)3(PMe3)2.
purchased from Strem Chemical Co. and used as received.
To test the proposed â-hydride elimination step, we
synthesized (η -C20H16D)Re(CO)3, 3-d 1, where the deu-
terium was in the â-position (Scheme 2).
Corannulene (1), hexahydrocorannulene, and octahydrocoran-
5
4,9,10
nulene (2) were prepared according to literature methods.
Crabtree’s catalyst, [Ir(cod)py(PCy
3 6
)]PF , was either purchased
The first step in the synthesis of 3-d 1 was achieved
by deuteration of the hexahydrocorannulene using
Crabtree’s catalyst and D2 to give 2-d 2. The mass
spectrum of 2-d 2 (m/z 260) confirmed the presence of
the two deuteriums. Dedeuteration of 2-d 2 with 1 equiv
of n-BuLi followed by addition of [Re(CO)3(THF)Br]2
from Strem Chemical Co. or prepared according to the method
1
9
3 2
described by Stork et al. [ReBr(CO) (THF)] was prepared
as described.20
P r ep a r a tion of exo-(η -C20
5
H
17)Re(CO)
3
(3). 2 (889.0 mg,
3
.45 mmol) was dissolved in 25 mL of C
6
H
6
and 5 mL of ether.
n-BuLi (2.5 M in hexane, 1.24 mL) was added to the solution.
The color of the solution changed to a dark red. The solution
was stirred for 5 min at 20 °C. [ReBr(CO) (THF)] (1.2974 g,
3 2
l.54 mmol) was then added, and the reaction mixture was
stirred for 15 min at 20 °C. The solvent was removed under
2
gave 3-d 1 in 18% yield. The H NMR spectrum of 3-d 1
(δ 3.51, C6H6/C6D6) confirmed that the deuterium was
at the â-carbon when the Re metal center slips to the
1
η configuration.
reduced pressure, and CH
2 2
Cl was added to the resulting
Reaction of 3-d 1 with PPh3 at 70 °C for 13 min in a
residue. The CH Cl solution was filtered through a Celite pad,
2
2
1
:1 mixture of C6H6/C6D6 yielded the corresponding
the filtrate collected, and the solvent removed. The crude
product was dissolved in C and filtered through a silica
gel packed frit. The resulting filtrate was collected and the
solvent removed. The crude orange-yellow solid was washed
trans,mer-Re(D)(PPh3)2(CO)3 and 4 (eq 4). The presence
6 6
H
of the metal deuteride was confirmed by 2H NMR
spectroscopy (δ ) -4.45, C6D6/C6H6), with no noticeable
deuterium remaining on 4.
2
× 1 mL of toluene, yielding a bright yellow powder (262.4
1
mg, 12% yield). H NMR (CDCl
3
, 20 °C): δ 6.82 (m, 4H), 3.64
(
m, 2H), 3.56 (m, 1H), 3.09 (m, 4H), 2.81 (m, 2H), 2.52 (m,
(
17) Casey, C. P.; O’Connor, J . M.; J ones, W. D.; Haller, K. J .
Organometallics 1983, 2, 535-538.
18) Casey, C. P.; O’Connor, J . M. Organometallics 1985, 4, 384-
88.
(
(19) Stork, G.; Kahne, D. E. J . Am. Chem. Soc. 1983, 105, 1072-1073.
(20) Vitali, D.; Calderazzo, F. Gazz. Chim. Ital. 1972, 102, 587-596.
3

4
832 Organometallics, Vol. 22, No. 23, 2003
Notes
1
2
1
1
2
H), 0.96 (m, 2H). 13C{ H} NMR (CDCl
3
, 20 °C): δ 193.55 (CO),
Ta ble 2. Su m m a r y of Cr ysta l Da ta for 3
34.61 (quat C), 131.99 (quat C), 125.52 (CH), 121.27 (CH),
16.97 (quat C), 99.58 (quat C), 74.15, 35.19 (CH ), 29.74 (CH),
). IR (KBr) ν (cm ): 2009, 1896. Anal.
Re: C, 52.36; H, 3.25 Found: C, 51.97; H,
empirical formula
C23H17O3Re
527.57
2
fw
temp
-1
2 2
8.23 (CH ), 28.15 (CH
193(2) K
Calcd for C23
.28.
Rea ction of 3 w ith P P h
PPh
(37.3 mg, 0.1423 mmol) were dissolved in ∼0.5 mL of
and placed in a Teflon-capped NMR tube. The mixture
H
17
O
3
wavelength
cryst syst
space group
unit cell dimens
0.71073 Å
monoclinic
P2(1)
3
3
. 3 (30 mg, 0.0569 mmol) and
a ) 7.7279(3) Å
b ) 14.1402(6) Å
c ) 8.3068(4) Å
R ) 90°
3
6 6
C D
1
was heated at 70 °C for 1 h, at which time the H NMR spec-
trum showed no starting material remaining. A mixture of
â ) 92.1560(10)°
trans,mer-Re(H)(PPh
P r ep a r a tion of C20
orannulene (298.0 mg, 1.164 mmol) was dissolved in benzene
33 g) and trifluoroacetic acid (679 mg) added to the resulting
3
)
2
3
(CO) and 4 was observed in a 1:1 ratio.
γ ) 90°
H
16 (4). In the glovebox, hexahydroc-
volume, Z
density (calcd)
abs coeff
907.08(7) Å3 , 2
3
1.932 Mg/m
-
1
(
6.719 mm
508
F(000)
solution. The mixture was placed into a Teflon-stoppered
ampule and heated to 110 °C for 20 h. The solvent was
removed under reduced pressure, and the residue was sub-
cryst size
θ range for data collection
limiting indices
0.12 × 0.20 × 0.40 mm
2.45 to 28.27°
-10 e h e 10, -18 e k e 18,
limed at 105 °C for 24 h, yielding a white solid (149 mg, 50%).
-3 e l e 10
1
H NMR (300 MHz, CDCl
.06 (t, J ) 7.4 Hz, 4H), 2.41 (t, J ) 7.6 Hz, 4H). C{ H} NMR
CDCl , 20 °C): δ 139.2 (quat C), 138.9 (quat C), 137.5 (quat
C), 131.1 (quat C), 130.5 (quat C), 126.8 (CH), 126.5 (CH),
21.8 (quat C), 32.9 (CH ), 28.1 (CH ), 27.3 (CH ). Anal. Calcd
for C20 C, 93.71; H, 6.29 Found: C, 92.73; H, 6.66.
HRMS: calc 256.1252, found 256.1249.
P r ep a r a tion of 2-d . 4 (170.5 mg, 0.666 mmol), Crabtree’s
catalyst, [Ir(PCy) (cod)py]PF (80.1 mg, 0.1 mmol), and 5 mL
of CH Cl were placed in a 25 mL Schlenk flask. A 250 mL
round-bottom flask was inverted over the Schlenk flask and
the apparatus evacuated and refilled with D gas three times.
After 2.5 h at 20 °C, the solvent was removed and the product
extracted with 30 mL of C and filtered through a silica gel
packed frit. The crude product was sublimed at 100 °C for 2
days and afforded pure 2-d
CHCl , 20 °C): 4.01 (br s, 1D), 2.73 (br s, 1D). GC-MS: m/z
60.
P r ep a r a tion of 3-d
dissolved in 5.7 mL of C
M in hexane, 0.28 mL) was added to the solution. The color of
the solution changed to a dark red. The solution was stirred
for 3 min at 20 °C. [ReBr(CO)
was then added and the reaction mixture stirred for 5 min at
0 °C. The solvent was removed under reduced pressure, and
CH Cl was added to the resulting residue. The CH Cl
2
3
, 25 °C): δ 6.89 (s, 4H), 3.12 (s, 4H),
no. of reflns collected
no. of ind reflns
abs corr
5367
1
3
1
3
(
3777 [R(int) ) 0.0129]
Sadabs
3
max. and min. transmn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σI)]
R indices (all data)
abs structure param
extinction coeff
0.928 and 0.625
full-matrix least-squares on F
3777/1/246
2
1
2
2
2
16
H :
1.346
R1 ) 0.0198, wR2 ) 0.0508
R1 ) 0.0200, wR2 ) 0.0509
0.234(10)
2
3
6
2
2
0.0100(5)
1.174 and -1.034 e Å
-3
largest diff peak and hole
2
to yield a total of 5367 reflections, of which 3777 were
6
H
6
21
independent (Rint ) 1.29%). Laue symmetry revealed a
monoclinic crystal system, and the final unit cell parameters
2
2 3
(113.8 mg, 66%). H NMR (CDCl /
(
at -80 °C) were determined from the least-squares refinement
3
of three-dimensional centroids of 5367 reflections. Data were
2
22
corrected for absorption with the SADABS program.
1
. 2-d
2
(199.1 mg, 0.766 mmol) was
1
The space group was assigned as P2 , and the structure was
6
H
6
and 1.10 mL of ether. n-BuLi (2.5
solved by using direct methods and refined employing full-
matrix least-squares on F2 (Siemens, SHELXTL,23 version
5
.04). For a Z value of 2, there is one molecule in the
3 2
(THF)] (290.7 g, 0.344 mmol)
asymmetric unit. All of the atoms were refined with anisotropic
thermal parameters, and hydrogen atoms were included in
idealized positions giving a data to parameter ratio of slightly
greater than 10:1. The structure refined to a goodness of fit
2
2
2
2
solution was filtered through a Celite pad, the filtrate collected,
and the solvent removed. The crude product was dissolved in
C H and filtered through a silica-packed frit. The resulting
6 6
24
25
(
(
GOF) of 1.346 and final residuals of R
1
) 1.98% (I > 2σ-
I)), wR ) 2.92% (I > 2σ(I)). A summary of crystallographic
2
data for 3 is given in Table 2.
filtrate was collected and the solvent removed. The crude
orange-yellow solid was recrystallized using 1 mL of toluene
2
Ack n ow led gm en t. We thank the Research Corpo-
at - 40 °C (72.0 mg, 18%). H NMR (C
6
H
6
/C
(38.2 mg, 0.0722 mmol)
(44.8 mg, 0.171 mmol) were dissolved in ∼1.0 mL of
a 1:1 mixture of C /C and placed in a Teflon-capped NMR
tube. The mixture was heated for 13 min at 70 °C. H NMR
/C , 20 °C): δ -4.45.
X-r a y Str u ctu r a l Deter m in a tion of 3. A yellow crystal
6 6
D , 20 °C): δ 2.81.
ration (CC-5024) for funding this work and Kirk Man-
Rea ction of 3-d
and PPh
1 3 1
w ith P P h . 3-d
2
fredi for help in obtaining the H NMR spectra. We also
3
thank Lynne Teesch and Vic Parcell at the University
of Iowa for the HRMS data and J ason Telford for the
VT-NMR data on 4.
6
H
6
6 6
D
2
(C
6
H
6
6 6
D
of approximate dimensions 0.12 × 0.2 × 0.4 mm was mounted
under Paratone-8277 on a glass fiber and immediately placed
in a cold nitrogen stream at -80 °C on the X-ray diffractome-
ter. The X-ray intensity data were collected on a standard
Siemens SMART CCD area detector system equipped with a
normal focus molybdenum-target X-ray tube operated at 2.0
kW (50 kV, 40 mA). A total of 1321 frames of data (1.3
hemispheres) were collected using a narrow frame method
with scan widths of 0.3° in ω and exposure times of 30 s/frame
using a detector-to-crystal distance of 5.09 cm (maximum 2θ
angle of 56.5°). The total data collection time was approxi-
mately 12 h. Frames were collected and integrated to a
maximum 2θ angle of 46.5° with the Siemens SAINT program
Su p p or tin g In for m a tion Ava ila ble: X-ray structural
data (PDF and CIF file) for 3. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM034111T
2
2
2].
o
(
(
21) Rint ) ∑|F
o
- F
o
(mean)|/∑[F
22) The SADABS program is based on the method of Blessing;
see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.
(23) SHELXTL: Structure Analysis Program, version 5.04; Siemens
Industrial Automation Inc.: Madison, WI, 1995.
o c
- F
) ]/(n - p)]1/2, where n and p denote the
2
2 2
(
24) GOF ) [∑[w(F
number of data and parameters.
2
2
2
2)2]]1/2
(
25) R
1
) (∑||F
o
| - |F
c
||)/∑|F
o
|; wR
2
) [∑[w(F
o
- F
c
) ]/∑[w(F
o
c
2
2
2
2
2
where w ) 1/[σ (F
o
) + (aP) + bP] and P ) [Max; 0,F
o
) + 2F
]/3.