A stable iridabenzene formed from an iridacyclopentadiene where the additional ring-carbon atom is derived from a thiocarbonyl ligand

Article abstract of DOI:10.1021/om700951j

The cationic thiocarbonyl complex [Ir(CS)(MeCN)-(PPh₃) ₂][CF₃SO₃] (1) reacts sequentially with ethyne and LiCl to give the iridacyclopentadiene Ir[C₄H₄]Cl(CS) (PPh₃)₂ (2), which in turn when heated with methyl triflate followed by addition of LiCl produces the stable, purple, iridabenzene Ir[C₅H₄(SMe-1)]Cl₂(PPh₃) ₂ (3). This iridabenzene undergoes electrophilic aromatic bromination in the position para to the SMe substituent to form Ir[C₅H ₃(SMe-1)(Br-4)]Br₂(PPh₃)₂ (4).

Full text of DOI:10.1021/om700951j

Organometallics 2008, 27, 451–454
451
Notes
A Stable Iridabenzene Formed from an Iridacyclopentadiene Where
the Additional Ring-Carbon Atom Is Derived from a Thiocarbonyl
Ligand
George R. Clark, Paul M. Johns, Warren R. Roper,* and L. James Wright*
Department of Chemistry, The UniVersity of Auckland, PriVate Bag 92019, Auckland, New Zealand
ReceiVed September 25, 2007
complexes of iridium are well-known8 and the propensity of
the thiocarbonyl ligand to participate in migratory insertion
reactions is well-established,9 it is perhaps surprising that a
similar approach has not been reported for iridabenzenes. Herein
we describe that an iridacyclopentadiene incorporating a thio-
carbonyl ligand can be induced, in the presence of methyl
triflate, to insert the carbon atom of the CS ligand to form an
iridabenzene bearing only one ring substituent. The lack of
substituents allows examination of electrophilic substitution
reactions, and it is demonstrated that this iridabenzene undergoes
facile ring bromination in the position para to the SMe
substituent.
Summary: The cationic thiocarbonyl complex [Ir(CS)(MeCN)-
(PPh3)2][CF3SO3] (1) reacts sequentially with ethyne and LiCl
to giVe the iridacyclopentadiene Ir[C4H4]Cl(CS)(PPh3)2 (2),
which in turn when heated with methyl triflate followed by
addition of LiCl produces the stable, purple, iridabenzene
Ir[C5H4(SMe-1)]Cl2(PPh3)2 (3). This iridabenzene undergoes
electrophilic aromatic bromination in the position para to the
SMe substituent to form Ir[C5H3(SMe-1)(Br-4)]Br2(PPh3)2 (4).
Introduction
Iridabenzenes are now well-established as a distinct class of
compounds,1 having been synthesized by four main approaches,
involving (a) deprotonation of an iridacyclohexadiene (formed
from initial introduction of a pentadienide ligand followed by
ring closure from a C-H activation),2 (b) rearrangement of a
cyclopropenylvinyl ligand,3 (c) formal insertion of a either a
vinylidene or carbene ligand into an iridacyclopentadiene
followed by aromatization,4 and (d) oxidative ring contraction
of an iridacycloheptatriene.5 These routes provide access to both
five-coordinate and six-coordinate examples of iridabenzenes.
Computational studies show that most metallabenzenes are
unstable with respect to rearrangement to metal cyclopentadienyl
complexes; however, of the model systems studied, six-
coordinate iridium examples alone were more stable than the
rearranged Cp complexes.6
Results and Discussion
Following the precedent established for the formation of the
iridacyclopentadiene [Ir[C4H4](CO)(MeCN)(PPh3)2]+10 from
[Ir(CO)(MeCN)(PPh3)2]+11 and ethyne, we treated the thiocar-
bonyl complex analogue [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1)
(derived from IrCl(CS)(PPh3)2 12 and AgCF3SO3; characterizing
data for 1 as well as for 2–4 are given in the Experimental
Section) with ethyne, followed by LiCl, to form the neutral
thiocarbonyl iridacyclopentadiene Ir[C4H4]Cl(CS)(PPh3)2 (2)
(see Scheme 1).
Complex 2 has been thoroughly characterized, including by
a crystal structure determination (see below). In the 13C NMR
spectrum of 2 the two iridium-bound carbon atoms of the
iridacyclopentadiene ring appear as triplets (due to coupling with
The first metallabenzene was assembled from an osmium
thiocarbonyl complex and ethyne,7 and since thiocarbonyl
1
phosphorus) at 157.14 and 145.13 ppm, while in the H NMR
spectrum the protons attached to these carbon atoms are
* Corresponding authors. E-mail: lj.wright@auckland.ac.nz; w.roper@
auckland.ac.nz.
(8) (a) Yagupsky, M. P.; Wilkinson, G. J. Chem. Soc. A 1968, 2813.
(b) Kubota, M.; Carey, C. R. J. Organomet. Chem. 1970, 24, 491. (c)
Broadhurst, P. V. Polyhedron 1985, 4, 1801.
(1) (a) Bleeke, J. R. Chem. ReV. 2001, 101, 1205. (b) Landorf, C. W.;
Haley, M. M. Angew. Chem., Int. Ed. 2006, 45, 3914. (c) Wright, L. J.
J. Chem. Soc., Dalton Trans. 2006, 1821.
(9) (a) Collins, T. J.; Roper, W. R. J. Chem. Soc., Chem. Commun. 1976,
1044. (b) Roper, W. R.; Town, K. G. J. Chem. Soc., Chem. Commun. 1977,
781. (c) Clark, G. R.; Collins, T. J.; Marsden, K.; Roper, W. R. J.
Organomet. Chem. 1978, 157, C23. (d) Rickard, C. E. F.; Roper, W. R.;
Salter, D. M.; Wright, L. J. Organometallics 1992, 11, 3931. (e) Irvine,
G. J.; Lesley, M. J. G.; Marder, T. B.; Norman, N. C.; Rice, C. R.; Robins,
E. G.; Roper, W. R.; Whittell, G. R.; Wright, L. J. Chem. ReV. 1998, 98,
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(2) Bleeke, J. R.; Xie, Y.-F.; Peng, W.-J.; Chiang, M. J. Am. Chem.
Soc. 1989, 111, 4118.
(3) Gilbertson, R. D.; Weakley, T. J. R.; Haley, M. M. J. Am. Chem.
Soc. 1999, 121, 2597.
(4) (a) Chin, C. S.; Lee, H. Chem.-Eur. J. 2004, 10, 4518. (b) Álvarez,
E.; Paneque, M.; Poveda, M. L.; Rendón, N. Angew. Chem., Int. Ed. 2006,
45, 474.
(5) Paneque, M.; Posadas, C. M.; Poveda, M. L.; Rendón, N.; Salazar,
V.; Oñate, E.; Mereiter, K. J. Am. Chem. Soc., 2003, 125, 9898.
(6) (a) Iron, M. A.; Martin, J. M. L.; van der Boom, M. E. J. Am. Chem.
Soc. 2003, 125, 13020. (b) Iron, M. A.; Lucassen, A. C. B.; Cohen, H.;
van der Boom, M. E.; Martin, J. M. L. J. Am. Chem. Soc. 2004, 126, 11699.
(7) Elliott, G. P.; Roper, W. R.; Waters, J. M. J. Chem. Soc., Chem.
Commun. 1982, 811.
(10) Chin, C. S.; Park, Y.; Kim, J.; Lee, B. J. Chem. Soc., Chem.
Commun. 1995, 1495.
(11) Reed, C. A.; Roper, W. R. J. Chem. Soc., Dalton Trans. 1973,
1365.
(12) (a) Hill, A. F.; Wilton-Ely, J. D. E. T. Inorg. Synth. 2002, 33, 244.
(b) Lu, G.-L.; Roper, W. R.; Wright, L. J.; Clark, G. R. J. Organomet.
Chem. 2005, 690, 972.
10.1021/om700951j CCC: $40.75
2008 American Chemical Society
Publication on Web 01/17/2008

452 Organometallics, Vol. 27, No. 3, 2008
Notes
Scheme 1. Synthesis of the Iridabenzene, 3, and Bromination
of the Iridabenzene Ring to Give 4
observed as multiplets at 7.39 and 5.63 ppm. Complex 2 is a
thermally stable compound and shows no evidence for insertion
of the thiocarbonyl ligand into the iridacyclopentadiene ring on
heating under reflux in benzene. However, when 2 is heated in
the presence of methyl triflate, a color change is observed and
addition of LiCl allows isolation of the purple, iridabenzene
Ir[C5H4(SMe-1)]Cl2(PPh3)2 (3) in good yield (see Scheme 1).
Possible explanations for the role of methyl triflate in promoting
this reaction include either methylation at sulfur to form an
intermediate cationic thiocarbyne (t CSMe) complex, which
then undergoes insertion of the CSMe ligand to form 3 after
addition of chloride, or chloride abstraction by methyl triflate,
giving the cation [Ir[C4H4](CS)(PPh3)2]+, which would be more
prone to undergo a migratory insertion reaction before eventual
methylation at sulfur and chloride addition to give 3. The first
possibility does not seem likely in view of the general
observation that thiocarbonyl complexes with a ν(CS) absorption
above 1200 cm-1 do not undergo methylation at sulfur,13 and
the second possibility seems no more likely since we have
prepared the cation [Ir[C4H4](MeCN)(CS)(PPh3)2]+ and have
been unable to induce CS insertion in this cation.14 A third
possibility that cannot be excluded is that there is an equilibrium
between compound 2 and the corresponding insertion product,
which strongly favors 2, but in the presence of methyl triflate
this insertion product can be trapped by methylation, giving
eventually 3. In the absence of definitive evidence for the
mechanism further speculation is unwarranted.
Figure 1. Molecular structure of 2 with thermal ellipsoids at the
50% probability level. Selected distances [Å]: Ir-C(5) 1.871(4),
Ir-C(1) 2.051(3), Ir-C(4) 2.093(3), C(1)-C(2) 1.327(4), C(2)-C(3)
1.446(5), C(3)-C(4) 1.350(5), C(5)-S 1.555(4), Ir-Cl 2.4668(10).
ligand, ultimately methylated on sulfur.7 Theoretical studies
suggest that the osmabenzene is assembled by a sequence of
reactions that begins with combination of the thiocarbonyl with
one ethyne to form a four-membered ring, which then undergoes
ring-expansion with a second ethyne.6b On the other hand the
synthesis of the iridabenzene 3 involves a different order of
assembly in that two ethyne molecules combine at iridium to
first form an iridacyclopentadiene (complex 2), which then
incorporates the thiocarbonyl ligand in the presence of methyl
triflate.
The crystal structure of complex 2 was determined and the
molecular structure is shown in Figure 1 (crystal data for 2 as
well as for 3 and 4 are given in the Supporting Information).
Significant features are almost perfect planarity of the IrC4 ring
and bond distances appropriate for the localized bonding
depicted in Scheme 1.
The crystal structure of complex 3 was determined and the
molecular geometry is shown in Figure 2. The structural
parameters are fully in accord with a metallabenzene formulation
with equal Ir-C distances and with C-C ring distances
reflecting delocalization.1 There is distinct nonplanarity of the
ring in that Ir is displaced 0.3072 Å from the least-squares plane
through C(1), C(2), C(3), C(4), and C(5), while the five ring-
carbon atoms are essentially planar. This kind of distortion is
not uncommon in iridabenzenes, and a recent theoretical study
reveals that such distortions do not compromise the aromaticity
of metallabenzenes.15
In addition to the structural and spectroscopic evidence
discussed above for the aromaticity of 3, the absence of
substituents at four of the ring-carbon atoms allows investigation
of the reactivity of 3 toward electrophilic aromatic substitution.
Bromination proceeds cleanly to give the monobrominated
product Ir[C5H3(SMe-1)(Br-4)]Br2(PPh3)2 (4) in high yield (see
Scheme 1). This appears to be the first instance of an
iridabenzene undergoing electrophilic aromatic substitution. It
can be noted that bromine is introduced at the site para to the
SMe substituent and ꢀ to the metal as expected. The same
In common with other related metallabenzenes,1 complex 3
shows a characteristic low-field resonance for the iridium-bound
CH at 12.31 ppm in the 1H NMR spectrum, and the other ring
protons have chemical shifts in the aromatic region. In the 13
C
NMR spectrum, characteristic1 low-field triplet resonances
(229.12 and 198.19 ppm) are also observed for the metal-bound
carbon atoms of the iridabenzene ring. It is interesting that
although this synthesis involves a thermal reaction, there is no
evidence for the rearrangement of the iridabenzene to an iridium
cyclopentadienyl complex. This observation is consistent with
computational results on model compounds, which suggest that
iridabenzenes with a six-coordinate iridium atom are resistant
to this rearrangement.6
Complex 3 is obviously closely related to the blue osmaben-
zene Os[C5H4(SMe-1)]I(CO)(PPh3)2, where the metallabenzene
ring is also assembled from two ethyne molecules and a CS
(13) Dombek, B. D.; Angelici, R. J. J. Am. Chem. Soc. 1975, 97, 1261.
(14) Johns, P. M.; Roper, W. R.; Wright, L. J. Unpublished work.
(15) Zhu, J.; Jia, G.; Lin, Z. Organometallics 2007, 26, 1986.

Notes
Organometallics, Vol. 27, No. 3, 2008 453
Figure 2. Molecular structure of 3 with thermal ellipsoids at the 50% probability level. Selected distances [Å]: Ir-C(1) 1.993(4), Ir-C(5)
1.992(4), C(1)-C(2) 1.427(6), C(2)-C(3) 1.363(6), C(3)-C(4) 1.413(6), C(4)-C(5) 1.352(6), Ir-Cl(1) 2.4606(11), Ir-Cl(2) 2.4846(10).
The molecular structure of 4 with thermal ellipsoids at the 50% probability level. Selected distances [Å]: Ir-C(1) 2.015(7), Ir-C(5) 1.987(8),
C(1)-C(2) 1.423(10), C(2)-C(3) 1.360(11), C(3)-C(4) 1.405(10), C(4)-C(5) 1.359(10), Br(3)-C(4) 1.926(7), Ir-Br(2) 2.6033(7), Ir-Br(1)
2.6130(8).
C37H30191IrP2S requires 759.11495 [M
-
MeCN]+ and
position of substitution was observed for the closely related
osmabenzene Os[C5H4(SMe-1)(Br-4)]I(CO)(PPh3)2.16 The crys-
tal structure of 4, confirming the position of bromination, is
shown in Figure 2. The bond distances within the iridabenzene
ring are again compatible with a delocalized system, and for
this compound the iridabenzene ring is very close to planar,
there being very little displacement of the Ir atom (0.0209 Å)
from the least-squares C5 plane.
C37H30193IrP2S requires 761.11729 [M - MeCN]+. Satisfactory
elemental analysis could not be obtained, presumably because of
the extreme sensitivity of this compound toward oxygen and
moisture. IR (cm-1): 2290w ν(CN), 1334s ν(CS). 1H NMR (CDCl3,
δ): 1.59 (m, MeCN, 3H), 7.51–7.56 (m, PPh3, 18H), 7.68–7.78 (m,
PPh3, 12H). 13C (CDCl3, δ): 2.01 (s, MeCN), 128.12 (s, MeCN),
2,4
1,3
128.83 (t′17, o-PPh3,
J
CP
) 10.8 Hz), 129.33 (t′, i-PPh3,
J
CP
3,5
) 56.2 Hz), 131.54 (s, p-PPh3), 134.40 (t′, m-PPh3,
J
CP
) 12.3
Hz), 249.49 (br s, CS). 31P (CDCl3, δ): 28.05.
Preparation of Ir(C4H4)Cl(CS)(PPh3)2 (2). Ethyne was bubbled
slowly through a stirred solution of a freshly prepared sample of
[Ir(CS)(MeCN)(PPh3)2][CF3SO3] (325 mg) in CH2Cl2 (15 mL) for
75 min. The CH2Cl2 was removed from the resulting green-black
solution under vacuum. The resulting solid was dissolved in EtOH
(15 mL), LiCl (270 mg) was added, and the solution was stirred
for 2 h. During this time crude 2 precipitated as a pale brown solid.
This was collected, washed with EtOH, and recrystallized twice
from dichloromethane/ethanol to give pure 2 (225 mg, 65%). m/z
(FAB+): 846.11573, 848.11665, and 850.11750; C41H3435Cl191IrP2S
requires 846.11511 [M+], C41H3435Cl193IrP2S requires 848.11744
[M+], and C41H3437Cl193IrP2S requires 850.11449 [M+]. Anal. Calc
for C41H34ClIrP2S · CH2Cl2: C, 54.05; H 3.89. Found: C, 54.55; H,
3.72. (NMR spectroscopy showed the presence of approximately
1 molar equiv of CH2Cl2 of crystallization in the analytical sample.)
The crystal used for X-ray structure determination was grown from
dichloromethane/methanol and proved to be a methanol solvate.
IR (cm-1): 1297s ν(CS). 1H NMR (CDCl3, δ): 5.63 (m, H1 or H4,
1H), 6.02 (m, H2 and H3, 2H), 7.28–7.36 (m, PPh3, 18H), 7.39
(m, H1 or H4, 1H), 7.67–7.75 (m, PPh3, 12H). 13C (CDCl3, δ):
Experimental Section
General Procedures and Instruments. Standard laboratory
procedures were followed, as have been described previously.17
12
The compound IrCl(CS)(PPh3)2 was prepared according to the
literature methods. Infrared spectra (4000–400 cm-1) were recorded
as Nujol mulls between KBr plates on a Perkin-Elmer Paragon 1000
spectrometer. NMR spectra were obtained on either a Bruker DRX
400 or a Bruker Avance 300 at 25 °C. For the Bruker DRX 400,
1H, 13C, and 31P NMR spectra were obtained operating at 400.1
(1H), 100.6 (13C), and 162.0 (31P) MHz, respectively. For the Bruker
Avance 300, 1H, 13C, and 31P NMR spectra were obtained operating
at 300.13 (1H), 75.48 (13C), and 121.50 (31P) MHz, respectively.
Resonances are quoted in ppm and 1H NMR spectra referenced to
either tetramethylsilane (0.00 ppm) or the proteo-impurity in the
solvent (7.25 ppm for CHCl3). 13C NMR spectra were referenced
to CDCl3 (77.00 ppm), and 31P NMR spectra to 85% orthophos-
phoric acid (0.00 ppm) as an external standard. Mass spectra were
recorded using the fast atom bombardment technique with a Varian
VG 70-SE mass spectrometer. Elemental analyses were obtained
from the Microanalytical Laboratory, University of Otago.
2,4
1,3
127.24 (t′, o-PPh3,
58.2 Hz), 130.12 (s, p-PPh3), 135.25 (t′, m-PPh3,
J
) 10.2 Hz), 130.03 (t′, i-PPh3,
J
)
CP
CP
Preparation of [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1). To Ir-
Cl(CS)(PPh3)2 (336 mg) in MeCN (15 mL, distilled from CaCl2)
was added AgCF3SO3 (110 mg). The mixture was stirred for 30
min, then filtered through Celite, and the orange solution was
collected. The solvent was removed to give pure 1 as an orange
solid (325 mg, 96%). m/z (FAB+): 759.11587 and 761.11637;
3,5
J
) 10.2
CP
Hz), 138.50 (s, C2 or C3), 142.35 (sbr, C2 or C3), 145.13 (t, C1 or
C4, 2JCP ) 4.6 Hz), 157.14 (t, C1 or C4, 2JCP ) 11.8 Hz), 284.33
2
(t, CS, JCP ) 9.3 Hz). 31P (CDCl3, δ): -1.57.
Preparation of Ir[C5H4(SMe-1)]Cl2(PPh3)2 (3). Methyl triflate
(48 µL, 69.6 mg) was added to a solution of Ir(C4H4)Cl(CS)(PPh3)2
(72 mg) in 1,2-dichloroethane (8 mL). The solution was heated at
60 °C for 80 min. To the resulting deep red solution was added
LiCl (36 mg) dissolved in n-propanol (1.5 mL), and heating at
60 °C continued for 30 min. n-Propanol (8 mL) was then added
(16) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J.
Angew. Chem., Int. Ed. 2000, 39, 750.
(17) Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J.
Organometallics 1996, 15, 1793.

454 Organometallics, Vol. 27, No. 3, 2008
Notes
to the purple solution, and the 1,2-dichloroethane removed under
vacuum to give crude 3 as a purple solid. Recrystallization of
this from dichloromethane/ethanol gave pure 3 as purple crystals
(42.8 mg, 56%). m/z (FAB+): 861.13749, 863.14100, and
865.14007; C42H3735Cl191IrP2S+ requires 861.13858 [M - Cl]+,
C42H3735Cl193IrP2S+ requires 863.14092 [M - Cl]+, and
C42H3737Cl193IrP2S+ requires 865.13797 [M - Cl]+. Anal. Calc
for C42H37Cl2IrP2S: C, 56.12; H 4.15. Found: C, 56.34; H 4.09.
X-ray Crystal Structure Determinations for Complexes 2–
4. X-ray intensities were recorded on a Siemens SMART diffrac-
tometer with a CCD area detector using graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å) at 87 K. Data were integrated
and corrected for Lorentz and polarization effects using SAINT.18
Semiempirical absorption corrections were applied based on
equivalent reflections using SADABS.19 The structures were solved
by direct or Patterson methods and refined by full-matrix least-
squares on F2 using the programs SHELXS9720 and SHELXL97.21
All hydrogen atoms were located geometrically and refined using
a riding model. Diagrams were produced using ORTEP3.22 For
complex 2, Squeeze23 indicates that the crystals also contain three
disordered molecules of methanol of solvation.
3
1H NMR (CDCl3, δ): 1.69 (s, Me, 3H), 6.25 (d, H2, JHH ) 9.4
3
Hz, 1H), 6.38 (apparent t, H4, JHH ) 7.7 Hz, 1H), 6.99 (m, H3,
1H), 7.22–7.31 (m, PPh3, 18H), 7.68–7.73 (m, PPh3, 12H), 12.31
(m, H5, 1H). 13C (CDCl3, δ): 21.55 (s, Me), 120.31 (s, H2), 121.64
2,4
(s, H4), 127.07 (t′, o-PPh3,
J
CP
) 9.7 Hz), 129.73 (s, p-PPh3),
1,3
3,5
Acknowledgment. We thank the Marsden Fund, admin-
istered by the Royal Society of New Zealand, for granting a
scholarship to P.M.J. We also thank The University of
Auckland Research Committee for partial support of this
work through grants-in-aid.
130.16 (t′, i-PPh3,
J
CP
) 55.6 Hz), 135.29 (t′, m-PPh3,
J
CP
)
2
9.3 Hz), 149.82 (s, C3), 198.19 (t, C5, JCP ) 6.6 Hz), 229.12 (t,
C1, JCP ) 5.2 Hz). 31P (CDCl3, δ): -13.25.
2
Preparation of Ir[C5H3(SMe-1)(Br-4)]Br2(PPh3)2 (4). A solu-
tion of pyridinium tribromide (46 mg) in methanol (1.5 mL) was
added dropwise to a solution of Ir[C5H4(SMe-1)]Cl2(PPh3)2 (43 mg)
in CH2Cl2 (15 mL), and the mixture was stirred at rt for 45 min.
Crystallization of a black product was effected by addition of
methanol (15 mL) and removal of CH2Cl2. This black product was
redissolved in CH2Cl2 (15 mL), and a solution of LiBr (140 mg)
in methanol (1.5 mL) was added. The mixture was stirred at rt for
15 h to complete halide substitution at iridium. The solvents were
removed under vacuum until dark purple crystals were obtained.
These were recrystallized from dichloromethane/ethanol to give pure
4 as dark purple crystals (44.4 mg, 87%). Anal. Calc for
Supporting Information Available: Crystal and refinement data
for compounds 2–4 and crystal data in CIF format for complexes
2–4 are available free of charge via the Internet at http://pubs.acs.org
and from the Cambridge Crystallographic Data Centre (fax: +44-
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or http://www.
ccdc.cam.ac.uk) as supplementary publication nos. CCDC 646238–
646240, respectively.
OM700951J
(18) SAINT, Area detector integration software; Siemens Analytical
Instruments Inc.: Madison, WI, 1995.
1
C42H36Br3IrP2S: C, 47.29; H, 3.40. Found: C, 47.09; H, 3.50. H
(19) Sheldrick, G. M. SADABS, Program for semi-empirical absorption
correction; University of Göttingen: Göttingen, Germany, 1997.
(20) Sheldrick, G. M. SHELXS97, Program for crystal structure deter-
mination, University of Göttingen, Göttingen, Germany, 1977.
(21) Sheldrick, G. M. SHELXL97, Program for crystal structure refine-
ment; University of Göttingen: Göttingen, Germany, 1997.
(22) Burnett, M. N.; Johnson, C. K. ORTEP-III: Oak Ridge Thermal
Ellipsoid Plot Program for Crystal Structure Illustrations; Oak Ridge
National Laboratory Report ORNL-6895, 1996.
3
NMR (CDCl3, δ): 1.73 (s, Me, 3H), 6.35 (d, H2, JHH ) 9.9 Hz,
1H), 6.92 (dd, H3, 3JHH ) 9.8, 4JHH ) 3.1 Hz 1H), 7.24–7.32 (m,
PPh3, 18H), 7.69–7.75 (m, PPh3, 12H), 11.86 (m, H5, 1H). 13C
(CDCl3, δ): 23.19 (s, Me), 104.78 (s, C4), 125.68 (s, C2), 127.24
2,4
(t′, o-PPh3,
J
CP
) 9.9 Hz), 129.98 (s, p-PPh3), 130.13 (t′, i-PPh3,
1,3
3,5
J
CP
) 55.8 Hz), 135.35 (t′, m-PPh3,
J
CP
) 8.7 Hz), 151.01 (s,
C3), 186.02 (t, C5, 2JCP ) 6.8 Hz), 229.85 (t, C1, 2JCP ) 5.2 Hz).
(23) Sluis, P. v. d.; Speck, A. L. Acta Crystallogr. 1990, A46, 194–
201.
31P (CDCl3, δ): -18.77.