Reaction of terminal phosphinidene complexes with acetylenic alcohols: Intramolecular hydrophosphination of a phosphirene ring

Article abstract of DOI:10.1021/om049272r

The transient phosphinidene complex [PhP-Mo(CO)₅], as generated from the appropriate 7-phosphanorbornadiene complex at 110°C in toluene, selectively reacts with the C=≡C triple bond of 4-phenyl-3-butyn-1-ol to give the corresponding phosphirene complex 4. Upon further heating, this phosphirene evolves via two pathways. The minor pathway involves the formal addition of the OH bond of the alcohol function onto the phosphirene P-C ring bond to give the 3-benzylidene-1,2-oxaphospholane complex 5. The major pathway involves the reaction of a second molecule of [PhP-Mo(CO)₅] with the OH group of 4, giving an intermediate phosphirene with an additional secondary alkoxyphosphine functionality (7). An intramolecular hydrophosphination of one P-C bond of the phosphirene ring then immediately takes place to give the cis-1,2-bis(phosphino)ethene [MoCCO)₄] complex 8 as a mixture of two diastereomers. After methylation of the PH group of 8, decomplexation can be efficiently achieved by reaction with sulfur. Structures have been ascertained by X-ray analysis for 5, 8, and the disulfide 10.

Full text of DOI:10.1021/om049272r

696
Organometallics 2005, 24, 696-699
Reaction of Terminal Phosphinidene Complexes with
Acetylenic Alcohols: Intramolecular Hydrophosphination
of a Phosphirene Ring
Irina Kalinina,† Bruno Donnadieu,‡ and Franc¸ois Mathey*,‡
UCR-CNRS Joint Research Chemistry Laboratory, Department of Chemistry,
University of California Riverside, Riverside, California 92521-0403, and
A. M. Butlerov Chemical Institute, Kazan State University, 18 Kremlevskaja str.,
420008 Kazan, Russia
Received September 17, 2004
The transient phosphinidene complex [PhP-Mo(CO)5], as generated from the appropriate
7-phosphanorbornadiene complex at 110 °C in toluene, selectively reacts with the CtC triple
bond of 4-phenyl-3-butyn-1-ol to give the corresponding phosphirene complex 4. Upon further
heating, this phosphirene evolves via two pathways. The minor pathway involves the formal
addition of the OH bond of the alcohol function onto the phosphirene P-C ring bond to give
the 3-benzylidene-1,2-oxaphospholane complex 5. The major pathway involves the reaction
of a second molecule of [PhP-Mo(CO)5] with the OH group of 4, giving an intermediate
phosphirene with an additional secondary alkoxyphosphine functionality (7). An intramo-
lecular hydrophosphination of one P-C bond of the phosphirene ring then immediately takes
place to give the cis-1,2-bis(phosphino)ethene [Mo(CO)4] complex 8 as a mixture of two
diastereomers. After methylation of the PH group of 8, decomplexation can be efficiently
achieved by reaction with sulfur. Structures have been ascertained by X-ray analysis for 5,
8, and the disulfide 10.
Scheme 1
Introduction
The electrophilic terminal phosphinidene complexes
[RP-M] (M ) Cr, Mo, W(CO)5] are now well established
as powerful tools in organophosphorus synthesis.1 A sys-
tematic investigation of their reactions with all of the
basic organic functionalities has been carried out. Prom-
inent among these are the reactions with carbon-carbon
triple bonds, leading to phosphirene complexes,2 and
with alcohols, leading to secondary alkoxyphosphine com-
plexes.3 We wondered what would happen if two such
functionalities were present in the organic reagent
allowed to react with the phosphinidene species. More
precisely, what functionality (OH or CtC) would first
react and what kind of secondary reaction would take
place between the two installed organophosphorus func-
tionalities? We present hereafter the results of this
study, which led us to the discovery of an unprecedented
hydrophosphination reaction of the P-C ring bonds of
phosphirenes.
Monitoring the reaction mixture by 31P NMR spectros-
copy after 1.20 h showed the exclusive formation of the
phosphirene ring 4 by reaction of 3 with the CtC triple
bond of 1. The phosphirene ring displays the charac-
teristic upfield shift of three-membered phosphorus
heterocycles: δ(31P(4)) -132.4 ppm. The transformation
of 2 into 4 was complete after 18 h, but traces of other
products started to appear. Product 4 was purified and
completely characterized. After 4 days, compound 4 had
completely disappeared and three new products had
been formed. They were separated by chromatography
on silica gel. The first product was identified as the 1,2-
oxaphospholane complex 5 (Scheme 1). Its mass spec-
trum showed that it has the same molecular weight as
4 (m/z 492), but the 31P NMR spectrum indicated that
the three-membered ring had collapsed: δ(31P(5)) +147
Results and Discussion
Our study has been carried out with 4-phenyl-3-
butyn-1-ol (1) as the bifunctional organic substrate. The
reaction with a 7-phosphanorbornadiene precursor (2)4
of [PhP-Mo(CO)5] (3) was performed in boiling toluene.
† Kazan State University.
‡ University of California Riverside.
(1) Reviews: Mathey, F.; Tran Huy, N. H.; Marinetti, A. Helv. Chim.
Acta 2001, 84, 2938. Lammertsma, K.; Vlaar, M. J. M. Eur. J. Org.
Chem. 2002, 4, 1127.
(2) Marinetti, A.; Mathey, F.; Fischer, J.; Mitschler, A. J. Am. Chem.
Soc. 1982, 104, 4484.
(3) Marinetti, A.; Mathey, F. Organometallics 1982, 1, 1488.
(4) Marinetti, A.; Mathey, F.; Fischer, J.; Mitschler, A. J. Chem. Soc.,
Chem. Commun. 1982, 667.
10.1021/om049272r CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/13/2005

Hydrophosphination of a Phosphirene Ring
Organometallics, Vol. 24, No. 4, 2005 697
Figure 2. ORTEP drawing of one molecule of 8a. Main
bond lengths (Å) and angles (deg): P(1)-Mo(1) ) 2.4355(4),
P(2)-Mo(1) ) 2.5047(4), P(1)-C(9) ) 1.8043(16), P(1)-O(1)
) 1.6268(12), P(1)-C(6) ) 1.8214(17), P(2)-C(10) )
1.8494(15), P(2)-C(17) ) 1.8216(17), C(9)-C(10) ) 1.334(2);
P(1)-Mo(1)-P(2) ) 78.153(14), O(1)-P(1)-C(9) ) 92.61(7),
P(1)-C(9)-C(8) ) 106.13(12), C(9)-P(1)-Mo(1) ) 110.91(5),
C(10)-C(9)-P(1))123.44(12),C(9)-C(10)-P(2))115.01(11),
C(10)-P(2)-Mo(1) ) 111.16(5).
Figure 1. ORTEP drawing of one molecule of 5. Main bond
lengths (Å) and angles (deg): P(1)-Mo(1) ) 2.4600(6),
P(1)-O(1) ) 1.6198(16), P(1)-C(3) ) 1.812(2), P(1)-C(11)
) 1.826(2), C(3)-C(4) ) 1.341(3), C(3)-C(2) ) 1.509(3),
C(2)-C(1) ) 1.532(3), C(1)-O(1) ) 1.447(3); O(1)-P(1)-
C(3) ) 94.31(9), O(1)-P(1)-C(11) ) 103.50(10), C(3)-P(1)-
C(11) ) 102.33(9), O(1)-P(1)-Mo(1) ) 115.14(6), C(3)-
P(1)-Mo(1) ) 124.37(7), C(11)-P(1)-Mo(1) ) 113.82(8).
ppm (CDCl3). The structure was established by X-ray
analysis (Figure 1). At least formally, the product results
from the intramolecular hydrophosphination of the CtC
triple bond within the secondary alkoxyphosphine com-
plex 6 (Scheme 1). We cannot establish at the moment
whether our observation means that the phosphirene
complex 4 equilibrates with complex 6 or not. In any
event, the hydrophosphination of alkynes has been the
subject of numerous recent reports and has been shown
to be efficiently catalyzed by a variety of transition-
metal complexes.5 Another possible explanation for the
formation of 5 relies on the fact that the methanolysis
of a phosphirene complex has been shown to produce a
vinylmethoxyphosphine complex.6 Thus, an intramo-
lecular addition of the OH group of 4 onto one P-C ring
bond can also be envisaged. If the formation of 4 does
not come as a complete surprise, such is not the case
for the two other products of the reaction, 8a,b (Scheme
1), which are, in fact, formed in much larger quantities.
They appear as two AX systems: 8a (minor), δ(31P)
46.17 (P-H, 1JPH ) 328 Hz) and 163.75, JAX ) 13.2 Hz;
bond of the phosphirene ring. As far as we know, this
is the first time that the hydrophosphination of a P-C
single bond has been reported. It must be also stressed
that this P-C hydrophosphination takes place, rather
than the more expected reaction at the phosphirene
CdC double bond. Of course, the P-C ring bonds of
phosphirenes have a great deal of π-character (Walsh
orbitals) and cannot be considered as fully representa-
tive of classical P-C single bonds.
cis-1,2-Bis(phosphino)ethenes are the prototypes of
rigid chelating phosphorus ligands, but the study of
their coordination chemistry has been mainly restricted
to the readily available cis-1,2-bis(diphenylphosphino)-
ethene. In fact, the synthesis of dissymmetrical species
of this type is not so simple, the most general route
being the hydrophosphination of phosphinoalkynes in
the coordination sphere of transition metals (Ni2+, Pd2+
,
Pt2+).7 The cis stereochemistry is imposed by the che-
lation of the transition metal, and the process is
completed by a decomplexation of the ligands by cyanide
ion. In such a context, it seemed interesting to investi-
gate the possible use of the hydrophosphination of
phosphirenes as a route to dissymmetrical cis-1,2-bis-
(phosphino)ethenes. Our experiments are summarized
in Scheme 2. The initial methylation leads to a mixture
of two diastereomers: 9a (minor) δ(31P) 61.7 and 162.9
(THF) (JAX ) 13.3 Hz); 9b (major) δ(31P) 61.3 and 164.4
(JAX ) 13.3 Hz). The decomplexation by sulfurization
is extremely efficient. This might be, in some part,
explained by the destabilizing strain that exists in the
metal ring of 8 ( PMoP ) 78.2°). The bis(sulfide) was
obtained as a mixture of two diastereomers (major,
δ(31P) 39.52 and 86.04, JAX ) 13 Hz; minor, δ(31P) 36.48
and 84.81, JAX ) 13 Hz). Whatever the starting product
(8a or 8b), we get the same 80:20 mixture of disulfides.
This means that the two P anions initially obtained from
8a and 8b readily equilibrate at room temperature. The
1
8b (major), δ(31P) 43.35 (P-H, JPH ) 321 Hz) and
169.16, JAX ) 13.3 Hz. As can be noticed, in both cases,
the higher field resonance corresponds to a secondary
phosphine complex. The mass spectrum indicates the
presence of a single Mo(CO)4 unit: m/z 572 (M+), 516
(M - 2CO), 460 (M - 4CO). The structure was estab-
lished by X-ray analysis of the minor diastereomer 8a
(Figure 2). The formation of 8a,b implies that the P-H
bond of 7, transiently formed (but not detected) by
reaction of a second molecule of phosphinidene complex
3 with the OH group of 4, has added across the C-P
(5) Review: Tanaka, M. Top. Curr. Chem. 2004, 232, 25-54. Recent
reports: Mimeau, D.; Gaumont, A. C. J. Org. Chem. 2003, 68, 7016.
Takaki, K.; Koshoji, G.; Komeyama, K.; Takeda, M.; Shishido, T.;
Kitani, A.; Takehira, K. J. Org. Chem. 2003, 68, 6554. Je´roˆme, F.;
Monnier, F.; Lawicka, H.; De´rien, S.; Dixneuf, P. H. Chem. Commun.
2003, 696. Kazankova, M. A.; Efimova, I. V.; Kochetkov, A. N.;
Afanas’ev, V. V.; Beletskaya, I. P. Russ. J. Org. Chem. 2002, 38, 1465.
Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 2001,
123, 10221.
(7) Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc.
1979, 101, 5612.
(6) Marinetti, A.; Mathey, F. J. Am. Chem. Soc. 1985, 107, 4700.

698 Organometallics, Vol. 24, No. 4, 2005
Kalinina et al.
silica gel (6:1 hexane-Et2O) to afford 4-phenyl-3-butyn-1-ol
(0.90 g, 53% yield) as a light yellow liquid.
Synthesis of the Phosphirene Complex 4. The (7-phos-
phanobornadiene)pentacarbonylmolybdenum complex 2 (0.77
g, 1.37 mmol) and 4-phenyl-3-butyn-1-ol (1; 0.2 g, 1.37 mmol)
were heated at 110 °C in toluene (10 mL) for 18 h. After
evaporation, the residue was chromatographed with hexane-
Et2O (1:1).
Complex 4: Rf ≈ 0.3; yield 0.15 g (22%); 31P NMR (CDCl3)
1
δ -135.2; H NMR (CDCl3) δ 1.49 (s, br, OH), 3.20 (m, CH2),
3
3.97 (t, JH-H ) 6.3 Hz, OCH2), 7.27-7.68 (m, Ph); 13C NMR
2
(CDCl3) δ 30.58 (d, JC-P ) 6.3 Hz, CH2), 60.71 (s, CH2OH),
2
2
205.43 (d, JC-P ) 11.2 Hz, cis CO), 209.00 (d, JC-P ) 32.5
Hz, trans CO); mass spectrum (FAB, 98Mo): m/z 492 (M+, 15%),
380 (M - 4CO, 100%). Anal. Calcd for C21H15O6PMo: C, 51.45;
H, 3.08. Found: C, 51.58; H, 3.12.
Synthesis of Complexes 5 and 8a,b. The (7-phospha-
nobornadiene)pentacarbonylmolybdenum complex 2 (1.3 g, 2.3
mmol) and 4-phenyl-3-butyn-1-ol (1; 0.3 g, 2.3 mmol) were
heated at 110 °C in toluene (10 mL) for 4 days. After
evaporation, the residue was chromatographed with hexane-
Et2O (90:10).
Figure 3. ORTEP drawing of one molecule of 10 showing
the statistical disorder at P(2).
Scheme 2
Complex 5: Rf ≈ 0.8; yield 0.06 g (6%); 31P NMR (CDCl3) δ
147.1; 1H NMR (CDCl3) δ 2.89 (m, CH2), 4.12 (m, 1H, OCH2),
4.43 (m, 1H, OCH2); 13C NMR (CDCl3) δ 29.84 (d, 2JC-P ) 12.2
Hz, CH2), 71.75 (d, 2JC-P ) 10.5 Hz, OCH2), 205.11 (d, 2JC-P
)
10.5 Hz, cis CO); mass spectrum (FAB, 98Mo) m/z 492 (M+,
3%). Anal. Calcd for C21H15O6PMo: C, 51.45; H, 3.08. Found:
C, 51.42; H, 2.87.
Complexes 8a,b: Rf ≈ 0.7 (minor diastereomer) and Rf ≈
0.6 (major diastereomer); yield 0.18 g (29%).
1
Complex 8a: 31P NMR (CDCl3) δ 46.17 (P-H, JPH ) 328
Hz) and 163.75, JAX 13.2 Hz; 1H NMR (CDCl3) δ 2.44 (m, CH2),
4.32 (m, OCH2); 13C NMR (CDCl3) δ 28.07 (dd, JC-P ) 9.6 and
2
two diastereomers syn-crystallize, and the X-ray analy-
sis (Figure 3) shows a statistical disorder at P(2)
between the sulfur atom and the methyl group. As a
conclusion, the intramolecular hydrophosphination of
phosphirene complexes appears as a reasonably efficient
route to a series of original cis-1,2-bis(phosphino)ethenes
with two chiral phosphorus centers.
14.6 Hz, CH2), 71.80 (d, JC-P ) 9.5 Hz, OCH2), 147.03 (dd,
JC-P ) 25.6 and 32.0 Hz, dCP), 164.04 (dd, JC-P ) 33.5 and
45.5 Hz, dCP), 207.11 (t, CO), 208.84 (m, CO), 215.17 (t, CO),
215.58 (m, CO); mass spectrum (FAB, 98Mo) m/z 572 (M+, 33%),
516 (M - 2CO, 34%), 460 (M - 4CO, 42%).
1
Complex 8b: 31P NMR (CDCl3) δ 43.35 (P-H, JPH ) 321
Hz) and 169.16, JAX 13.3 Hz; 1H NMR (CDCl3) δ 2.53 (m, 1H,
CH2), 2.65 (m, 1H, CH2), 4.28 (m, OCH2); 13C NMR (CDCl3) δ
28.60 (dd, JC-P ) 9.4 and 15.0 Hz, CH2), 71.89 (d, 2JC-P ) 11.6
Hz, OCH2), 147.49 (dd, JC-P ) 28.4 and 33.4 Hz, dCP), 164.40
(dd, JC-P ) 33.8 and 45.2 Hz, dCP), 207.17 (dd, CO), 207.91
(t, CO), 215.58 (dd, CO), 216.05 (dd, CO). Anal. Calcd for
C26H20O5P2Mo: C, 54.75; H, 3.53. Found: C, 54.95; H, 3.27.
Experimental Section
Reactions were performed under nitrogen using oven-dried
glassware. Dry tetrahydrofuran was obtained by distillation
from Na/benzophenone. Silica gel (70-230 mesh) was used for
chromatographic separation. Nuclear magnetic resonance
spectra were obtained on Bruker Avance 3000 and Varian
Inova spectrometers operating at 300.13 MHz for 1H, 75.45
MHz for 13C, and 121.496 MHz for 31P. Chemical shifts are
expressed in parts per million downfield from external TMS
(1H and 13C) and external 85% H3PO4 (31P). Mass spectra were
obtained on VG 7070 and Hewlett-Packard 5989A GC/MS
spectrometers. Elemental analyses were performed by Desert
Analytics Laboratory, Tucson, AZ. Starting materials were
obtained from commercial suppliers.
Synthesis of 4-Phenyl-3-butyn-1-ol (1). To a solution of
phenylacetylene (1.21 g, 11.6 mmol) in THF (15 mL) was added
n-BuLi (7.25 mL, 1.6 M solution in hexane) at 0 °C. The
reaction mixture was stirred at 0 °C for 30 min and then was
cooled to -78 °C. Freshly distilled BF3‚OEt2 (4.6 mL, 17.4
mmol) in THF (5 mL) was then added, followed by an excess
of ethylene oxide (1 mL, 20 mmol), which was condensed into
THF (5 mL). The mixture was stirred for 30 min at -78 °C,
quenched with aqueous NH4Cl solution, and concentrated on
a rotary evaporator. The residue was taken up in Et2O, washed
with water and brine, dried (Na2SO4), and concentrated. The
crude product was purified by column chromatography on
Methylation-Decomplexation of Complex 8. Complex
8 (0.0096 g, 0.01 mmol) was treated with potassium tert-
butoxide (0.0038 g, 0.034 mmol) in THF (0.6 mL). After 3 min
at room temperature, methyl iodide (0.0027 mL, 0.043 mmol)
was added to the reaction mixture. After 1 h of stirring, KI
was removed by filtration, THF was evaporated, and the
residue was heated for 4 days with sulfur (0.0016 g, 0.05 mmol)
at 110 °C in toluene (0.7 mL). The reaction mixture was
purified by column chromatography with dichloromethane as
the eluent: Rf ≈ 0.8; yield 0.0071 g (95%).
Sulfide 10: 31P NMR (CDCl3) (major 80%) δ 39.52 (JPP
)
13 Hz) and 86.04, (minor 20%) δ 36.48 (JPP ) 13 Hz) and 84.81;
2
1H NMR (CDCl3) (major) δ 2.07 (d, JHP ) 13.5 Hz, Me), 2.67
(m, CH2), 4.15 (m, 1H, OCH2), and 4.33 (m, 1H, OCH2); 13C
NMR (CDCl3) (major) δ 24.03 (d, 1JCP ) 55.5 Hz, Me-P), 37.40
(dd, JCP ) 10.0 and 18.9 Hz, CH2), 65.88 (s, OCH2), 145.89
(dd, JCP ) 9.3 and 86.0 Hz, CdC), 146.51 (dd, JCP ) 12.9 and
67.1 Hz, CdC); mass spectrum (CI) m/z 441 (M + H, 100%).
X-ray Structure Determination of 5, 8a, and 10. Com-
pounds were measured at low temperature, T ) 180(2) K, on
a X8-APEX Bruker Kappa four-circle X-ray diffractometer
system (Mo radiation, λ ) 0.710 73 Å). An optimized data

Hydrophosphination of a Phosphirene Ring
Organometallics, Vol. 24, No. 4, 2005 699
collection strategy was defined using Cosmo.8 Frames were
integrated with the aid of Bruker Saint software9 included in
the Bruker APEX2 package software10 and using a narrow-
frame integration algorithm. The integrated frames yielded
the following.
Complex 5 had a total of 20 076 reflections at a maximum
2θ angle of 66.28° (0.65 Å resolution), of which 7715 were
independent reflections (Rint ) 0.0425, Rsig ) 0.0321, complete-
ness 97.9%) and 7320 (94.98%) reflections were greater than
2σ(I). A triclinic cell, space group P1h, was found, and the unit
cell parameters were a ) 8.4327(6) Å, b ) 10.8085(8) Å, c )
11.9867(10) Å, R ) 79.068(5)°, â ) 76.955(5)°, γ ) 79.595(5)°,
V ) 1034.12(14) Å3, Z ) 2, and calculated density Dc ) 1.574
Mg/m3.
Complex 8a had a a total of 56 946 reflections at a maximum
2θ angle of 66.34° (0.65 Å resolution), of which 9720 were
independent reflections (Rint ) 0.0480, Rsig ) 0.0577, complete-
ness 99.8%) and 8688 (89.38%) reflections were greater than
2σ(I). A monoclinic cell, space group P21/n, was found, and the
unit cell parameters were a ) 10.3259(5) Å, b ) 18.5007(8) Å,
c ) 13.7720(6) Å, â ) 104.500(3)°, V ) 2547.2(2) Å3, Z ) 4,
and calculated density Dc ) 1.487 Mg/m3.
determination and structure solution, followed by some sub-
sequent difference Fourier maps. From the primary electron
density map most of the non-hydrogen atoms were located,
and with the aid of subsequent isotropic refinement all of the
non-hydrogen atoms were identified. Atomic coordinates and
isotropic and anisotropic displacement parameters of all the
non-hydrogen atoms were refined by means of a full-matrix
least-squares procedure on F2. The H atoms were included in
the refinement in calculated positions riding on the C atoms
to which they were attached. Concerning the compound 10, a
statistical disorder between carbon and sulfur atoms linked
to the P(2) atom was found; the ratio of occupancy was refined
and found equal to 85%/15%. The refinement converged as
follows: for 5 at R1 ) 0.0401 and wR2 ) 0.0868 with intensity
I > 2σ(I) and with the largest peak/hole in the final difference
map being 0.625 and -0.860 e/Å3; for 8a at R1 ) 0.0296 and
wR2 ) 0.0660 with intensity I > 2σ(I) and with the largest
peak/hole in the final difference map being 0.535 and -0.442
e/Å3; for 10 at R1 ) 0.0355 and wR2 ) 0.0892 with intensity
I > 2σ(I) and with the largest peak/hole in the final difference
map being 0.596 and -0.307 e/Å3.
Drawings of molecules were carried out using ORTEP32.13
Complex 10 had a total of 60 020 reflections at a maximum
2θ angle of 78.06° (0.56 Å resolution), of which 11 182 were
independent reflections (Rint ) 0.0382, Rsig ) 0.0339, complete-
ness 89.6%) and 8688 (77.69%) reflections were greater than
2σ(I). A monoclinic cell, space group P21/n, was found, and the
unit cell parameters were a ) 12.1134(6) Å, b ) 12.2035(6) Å,
c ) 15.6203(8) Å, â ) 112.104(3)°, V ) 2139.37(19) Å3, Z ) 4,
and calculated density Dc ) 1.368 Mg/m3.
Acknowledgment. The authors thank the Univer-
sity of California Riverside and the CNRS for the
financial support of this work.
Supporting Information Available: X-ray crystal struc-
ture analyses of compounds 5, 8a, and 10, as CIF files. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Absorption corrections were applied for data using the
SADABS program.11 The program SIR9212 was used for phase
OM049272R
(12) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.
SIR92-A program for crystal structure solution. J. Appl. Crystallogr.
1993, 26, 343.
(13) Farrugia, L. J. ORTEP 3 for Windows. J. Appl. Crystallogr.
1997, 30, 565.
(8) COSMO, version 1.48; Bruker AXS Inc., Madison, WI, 2003.
(9) SAINT, version V7.06A; Bruker AXS Inc., Madison, WI, 2003.
(10) APEX 2, version 1.0-22; Bruker AXS Inc., Madison, WI, 2004.
(11) SADABS, version 2004/1; Bruker AXS Inc., Madison, WI, 2004.