Synthesis, structure, spectroscopy, and reactivity of a metallathiabenzene

Article abstract of DOI:10.1021/om010050s

Treatment of (Cl)Ir(PEt₃)₃ with lithium 2,3-dimethyl-5-thiapentadienide leads to the production of mer-CH=C(Me)C(Me)=CHSIr(PEt₃)₃(H) (4) via C-H bond activation. Oxidation of 4 with silver tetrafluoroborate in t

Full text of DOI:10.1021/om010050s

Organometallics 2001, 20, 1939-1951
1939
Syn th esis, Str u ctu r e, Sp ectr oscop y, a n d Rea ctivity of a
Meta lla th ia ben zen e1
J ohn R. Bleeke* and Paul V. Hinkle
Department of Chemistry, Washington University, One Brookings Drive,
St. Louis, Missouri 63130
Nigam P. Rath
Department of Chemistry, University of MissourisSt. Louis, 8001 Natural Bridge Road,
St. Louis, Missouri 63121
Received J anuary 22, 2001
Treatment of (Cl)Ir(PEt3)3 with lithium 2,3-dimethyl-5-thiapentadienide leads to the
production of mer-CHdC(Me)C(Me)dCHSIr(PEt3)3(H) (4) via C-H bond activation. Oxidation
of 4 with silver tetrafluoroborate in tetrahydrofuran generates “iridathiabenzene”,
-
[CHdC(Me)C(Me)dCHSdIr(PEt3)3]+BF4 (3). The structural and spectroscopic features of
3 are consistent with the presence of an aromatic ring in which the iridium center participates
in ring π-bonding. Treatment of 3 with excess PMe3 or with PPN+Cl- leads to the production
+
of CHdC(Me)C(Me)dCHSIr(PMe3)4 BF4- (5) or mer-CHdC(Me)C(Me)dCHSIr(PEt3)3(Cl) (6),
respectively. Each of these products features an iridathiacyclohexa-1,3-diene ring system.
1
The reaction of 6 with /2 equiv of silver trifluoromethanesulfonate leads to the production
-
of a novel iridium dimer, [(CHdC(Me)C(Me)dCHSIr(PEt3)2)2(µ-Cl)]+O3SCF3 (7), in which
the two iridium centers are bridged by the two sulfur atoms of the iridathiacyclohexa-1,3-
diene rings, as well as a chloride ligand. Treatment of 3 with nitrosobenzene generates a [4
+
-
+ 2] cycloadduct, [CHdC(Me)C(Me)CHdSIrON(Ph)](PEt3)3 BF4 (8), containing an iri-
dathiacyclohexa-1,4-diene ring. Compound 3 cleanly displaces p-xylene from (η6-p-xylene)-
+
-
Mo(CO)3 in tetrahydrofuran, generating [η6-CHdC(Me)C(Me)dCHSdIr(PEt3)3]Mo(CO)3 BF4
(9). When 9 is reacted with excess trimethylphosphine, PMe3 adds to the molybdenum center,
causing the iridathiabenzene ring to slip from η6 to η4 coordination and forming [η4-CHd
C(Me)C(Me)dCHSdIr(PEt3)2(CO)]Mo(PMe3)2(CO)2 BF4 (10). Finally, treatment of (η5-C5-
+
-
+
-
Me5)Ru(NCMe)3 O3SCF3 with 3 leads to clean displacement of the acetonitrile ligands by
the iridathiabenzene ring and generation of the Ru sandwich compound [η6-CHdC(Me)C-
-
(Me)dCHSdIr(PEt3)3]Ru(η5-C5Me5)2+BF4-O3SCF3 (11). Compounds 3, 4, 6a , 7, 9, and 10
have been structurally characterized by X-ray diffraction.
In tr od u ction
containing analogue of benzene. Our synthetic approach
During the past decade, we have been studying the
chemistry of the “iridabenzene” 1,2 a rare3,4 metal-
(1) Metallacyclohexadiene and Metallabenzene Chemistry. 17. Part
16: Bleeke, J . R.; Blanchard, J . M. B.; Donnay, E. Organometallics
2001, 20, 324.
(2) (a) Bleeke, J . R.; Xie, Y.-F.; Peng, W.-J .; Chiang, M. J . Am. Chem.
Soc. 1989, 111, 4118. (b) Bleeke, J . R. Acc. Chem. Res. 1991, 24, 271.
(c) Bleeke, J . R.; Behm, R.; Xie, Y.-F.; Chiang, M. Y.; Robinson, K. D.;
Beatty, A. M. Organometallics 1997, 16, 606. (d) Bleeke, J . R.; Behm,
R. J . Am. Chem. Soc. 1997, 119, 8503.
(3) For examples of other stable metallabenzenes, see: (a) Elliott,
G. P.; Roper, W. R.; Waters, J . M. J . Chem. Soc., Chem. Commun. 1982,
811. (b) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J .
Angew. Chem., Int. Ed. 2000, 39, 750. (c) Gilbertson, R. D.; Weakley,
T. J . R.; Haley, M. M. J . Am. Chem. Soc. 1999, 121, 2597. (d)
Gilbertson, R. D.; Weakley, T. J . R.; Haley, M. M. Chem. Eur. J . 2000,
6, 437.
to this novel aromatic molecule involves use of a
pentadienide reagent to supply the ring carbon atoms.
(4) Detection of a thermally unstable metallabenzene at low tem-
perature has also been reported: Yang, J .; J ones, W. M.; Dixon, J . K.;
Allison, N. J . Am. Chem. Soc. 1995, 117, 9976.
10.1021/om010050s CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/07/2001

1940 Organometallics, Vol. 20, No. 10, 2001
Bleeke et al.
Sch em e 1
Sch em e 2
Sch em e 3
The key ring-forming step is metal-mediated activation
of a pentadienyl C-H bond. Using a similar synthetic
strategy, we have recently succeeded in producing an
oxygen-containing relative of 1, iridapyrylium 2.5 We
now report that this same approach can be adapted to
generate a sulfur-containing member of this unique
aromatic family, iridathiabenzene 3. In this paper, we
describe the synthesis, structure, spectroscopy, and
reaction chemistry of compound 3 and comment on the
extent to which it exhibits aromatic character.6
It should be noted that several related examples of
metallathiabenzenes have previously been reported. For
example, Angelici7 has synthesized iridathiabenzene A,
while J ones8 has reported the low-temperature detection
of rhodium analogue B. Bianchini,9 in turn, has gener-
ously demonstrated that treatment of (Cl)Ir(PEt3)3 with
unmethylated thiapentadienide leads to C-H2 bond
activation and production of a five-membered metalla-
cycle.11
To prevent this reaction pathway and promote six-
membered-ring formation, we synthesized a new thia-
pentadienide reagent with methyl groups at the C2 and
C3 positions. This synthesis, which culminates in base-
initiated ring opening of the dimethyldihydrothiophene
reagent, is summarized in Scheme 2.12 As expected,
treatment of (Cl)Ir(PEt3)3 with this new dimethylated
(5) (a) Bleeke, J . R.; Blanchard, J . M. B. J . Am. Chem. Soc. 1997,
119, 5443. (b) Bleeke, J . R.; Blanchard, J . M. B.; Donnay, E. Organo-
metallics 2001, 20, 324.
(6) A portion of this work has been communicated: Bleeke, J . R.;
Hinkle, P. V.; Rath, N. P. J . Am. Chem. Soc. 1999, 121, 595.
(7) (a) Chen, J .; Daniels, L. M.; Angelici, R. J . J . Am. Chem. Soc.
1990, 112, 199. (b) Chen, J .; Daniels, L. M.; Angelici, R. J . Polyhedron
1990, 9, 1883.
(8) Chin, R. M.; J ones, W. D. Angew. Chem., Int. Ed. Engl. 1992,
31, 357.
(9) (a) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Frediani, P.;
Herrera, V.; Sanchez-Delgado, R. A. J . Am. Chem. Soc. 1993, 115, 2731.
(b) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Moneti, S.; Herrera,
V.; Sanchez-Delgado, R. A. J . Am. Chem. Soc. 1994, 116, 4370.
(10) Several other metal-mediated thiophene bond activations have
led to metallathiacyclohexa-1,3-diene products. These molecules are
related to metallathiabenzenes but do not exhibit the bond delocal-
ization characteristic of aromatic species. See, for example: (a) J ones,
W. D.; Dong, L. J . Am. Chem. Soc. 1991, 113, 559. (b) Selnau, H. E.;
Merola, J . S. Organometallics 1993, 12, 1583. (c) J ones, W. D.; Chin,
R. M.; Crane, T. W.; Baruch, D. M. Organometallics 1994, 13, 4448.
(d) Buys, I. E.; Field, L. D.; Hambly, T. W.; McQueen, A. E. D. J . Chem.
Soc., Chem. Commun. 1994, 557. (e) Garcia, J . J .; Mann, B. E.; Adams,
H.; Bailey, N. A.; Maitlis, P. M. J . Am. Chem. Soc. 1995, 117, 2179. (f)
Arevalo, A.; Bernes, S.; Garcia, J . J .; Maitlis, P. M. Organometallics
1999, 18, 1680.
ated iridathiabenzene C, together with a close analogue
containing a fused benzene ring. These previous syn-
theses differ from our approach in that they involve
thiophene C-S bond activation as the key ring-forming
step.10
(11) (a) Bleeke, J . R.; Ortwerth, M. F.; Chiang, M. Y. Organome-
tallics 1992, 11, 2740. (b) Bleeke, J . R.; Ortwerth, M. F.; Rohde, A. M.
Organometallics 1995, 14, 2813.
Resu lts a n d Discu ssion
(12) Kloosterziel first demonstrated the feasibility of this “cyclo-
reversion” reaction: Kloosterziel, H.; Van Drunen, J . A. A.; Galama,
P. J . Chem. Soc. D 1969, 885.
A. Syn th esis, Sp ectr oscop y, a n d Str u ctu r e of
Ir id a th ia ben zen e 3. As shown in Scheme 1, we previ-

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1941
iridathiabenzene 3, presumably through the interme-
diacy of the 17e- oxidation product (see Scheme 4).14
The 1H NMR spectrum of 3 shows downfield shifting
for ring protons H1 and H4, consistent with its formula-
tion as an aromatic species. Proton H1 resonates at δ
10.36 and is a quartet (J H-P ) 8.4 Hz) due to coupling
to three equivalent 31P nuclei (vide infra), while H4
resonates at δ 8.61. The ring carbons resonate at δ 165.1
(C1), 143.6 (C2), 134.9 (C3), and 130.0 (C4), and C1 (like
H1) appears as a phosphorus-coupled quartet (J C-P
)
21.6 Hz). The 31P{1H} NMR signal for 3, like those for
analogues 12 and 2,5 is a singlet at room temperature,
indicating that the three phosphine ligands are exchang-
ing rapidly in solution. However, when the temperature
is lowered to -90 °C, the 31P{1H} NMR signal broadens
and ultimately resolves into two sharp resonances with
an intensity ratio of 2:1. Simulation of the variable-
temperature 31P{1H} NMR spectra yields a ∆Gq value
of 9.5(0.2) kcal/mol for this intramolecular phosphine
exchange process.15
F igu r e 1. ORTEP drawing of mer-CHdC(Me)C(Me)d
The molecular structure of 3 has been determined by
X-ray diffraction and is presented in Figure 2. Consis-
tent with the low-temperature 31P NMR spectrum
described above, the molecule displays approximate
(although not crystallographically imposed) mirror plane
symmetry. The symmetry plane includes the metalla-
cyclic ring and phosphorus atom P3, while bisecting the
P1-Ir-P2 angle. The coordination geometry of the
molecule is probably best described as a distorted
trigonal bipyramid with C1 and P3 occupying the axial
sites and S1, P1, and P2 occupying the equatorial sites.
However, the equatorial ligands are significantly dis-
placed from idealized positions. Hence, the three equa-
torial L-Ir-L angles, which ideally should each be 120°,
are actually 136.8(1), 127.2(1), and 95.9(1)°. Surpris-
ingly, the smallest of these angles involves the two bulky
PEt3 ligands!16
Bonding within the metallacycle in 3 is delocalized,
consistent with an aromatic system. The carbon-carbon
bond distances C1-C2, C2-C3, and C3-C4 have moved
toward equalization, while bonds Ir1-C1 and Ir1-S1
have both shortened substantially (vs their lengths in
4), indicating significant metal participation in the ring
π-bonding.17 The nonmetal portion of the ring (C1/C2/
C3/C4/S1) is very nearly planar (mean deviation 0.015
Å), while the iridium center lies 0.185 Å out of this
plane. The dihedral angle between planes C1/C2/C3/C4/
S1 and C1/Ir1/S1 is 7.0°.
CHSIr(PEt3)3(H) (4), using thermal ellipsoids at the 20%
probability level. The metal-bound hydrogen atom was
placed at an idealized position but not refined. Selected
bond distances (Å): Ir1-P1, 2.341(3); Ir1-P2, 2.341(3);
Ir1-P3, 2.363(3); Ir1-S1, 2.433(3); Ir1-C1, 2.093(10); S1-
C4, 1.731(12); C1-C2, 1.340(14); C2-C3, 1.456(18); C3-
C4, 1.380(19). Selected bond angles (deg): P1-Ir1-P2,
159.9(1); P1-Ir1-P3, 101.5(1); P1-Ir1-S1, 97.0(1); P1-
Ir1-C1, 79.8(3); P2-Ir1-P3, 94.6(1); P2-Ir1-S1, 95.4(1);
P2-Ir1-C1, 84.4(3); P3-Ir1-S1, 88.3(1); P3-Ir1-C1,
178.5(3); S1-Ir1-C1, 90.8(3); Ir1-C1-C2, 133.7(8); C1-
C2-C3, 127.4(10); C2-C3-C4, 126.7(10); C3-C4-S1,
130.8(10); C4-S1-Ir1, 110.1(4).
thiapentadienide reagent leads to the production of the
desired six-membered metallacycle, iridathiacyclohexa-
1,3-diene 4, via C-H1 bond activation (Scheme 3).
The 1H NMR spectrum of 4 exhibits downfield signals
for ring protons H1 and H4 at δ 7.05 and 5.78,
respectively, while the metal-hydride signal appears
far upfield at δ -16.10. In the 13C{1H} NMR spectrum,
the ring carbons resonate at δ 118.8 (C1), 127.3 (C2),
127.3 (C3), and 120.9 (C4). The signal for C1 is a
characteristic doublet (J C-P ) 72.0 Hz) of triplets (J C-P
) 15.0 Hz) due to coupling to the 31P nuclei of the trans
equatorial and axial phosphines, respectively. The 31P-
{1H} NMR spectrum consists of a doublet of intensity 2
(axial phosphines) and a triplet of intensity 1 (equatorial
phosphine).
B. Rea ctivity of Ir id a th ia ben zen e 3: Ad d ition to
The solid-state structure of 4, determined by single-
crystal X-ray diffraction, is shown in Figure 1; selected
bond distances and angles are given in the figure
caption. The structure confirms the octahedral coordi-
nation geometry and mer arrangement of the phosphine
ligands. The metallacyclic ring is essentially planar and
exhibits localized single and double bonds within the
carbon/sulfur portion of the metallacycle. The Ir1-C1
and Ir1-S1 distances (2.093(10) and 2.433(3) Å, respec-
tively) are typical single-bond lengths.13
th e Ir id iu m Cen ter . One can write three reasonable
(14) The fate of the metal-bound hydrogen is not known.
(15) The exchange probably proceeds via a Berry pseudorotation or
turnstile mechanism: Cotton, F. A.; Wilkinson, G. Advanced
a
Inorganic Chemistry, 4th ed.; Wiley: New York, 1980; pp 1218-1220.
(16) Iridabenzene 1 adopts a coordination geometry in the solid state
that is best described as square pyramidal. It also exhibits approximate
mirror plane symmetry, but in this case the symmetry plane bisects
the metallacyclic ring.2
(17) According to recent Fenske-Hall MO calculations by Harris,
the key orbital interaction involves the filled 3π orbital on the
thiapentadienyl moiety, which is centered largely on sulfur, and on
an empty metal d orbital of appropriate symmetry. Overlap between
these orbitals produces a filled bonding MO with significant Ir-S π
character, as well as the molecule’s LUMO, which is primarily metal
in character. See: (a) Harris, S. Organometallics 1994, 13, 2628. (b)
Palmer, M.; Carter, K.; Harris, S. Organometallics 1997, 16, 2448. (c)
Blonski, C.; Myers, A. W.; Palmer, M.; Harris, S.; J ones, W. D.
Organometallics 1997, 16, 3819.
Treatment of the yellow-orange iridathiacyclohexa-
1,3-diene 4 with silver tetrafluoroborate in tetrahydro-
furan leads to the immediate production of deep red
(13) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . Chem. Soc., Dalton Trans 1989, S1.

1942 Organometallics, Vol. 20, No. 10, 2001
Bleeke et al.
Sch em e 4
toward 2e- donor ligands, leading to the formation of
six-coordinate iridathiacyclohexa-1,3-diene compounds.19
For example, treatment of 3 with excess trimeth-
ylphosphine at 22 °C leads to PMe3 addition at the
iridium center and complete replacement of the three
bulky PEt3 ligands with PMe3’s, generating the tetrakis-
(trimethylphosphine) product 5 (Scheme 5). This reac-
tion contrasts sharply with the room-temperature re-
action of iridabenzene 1 with excess PMe3, which results
in replacement of just one PEt3 ligand with PMe3 and
retention of the aromatic ring system.2 The reason for
this difference in behavior is that 1 reacts with PMe3
by a dissociative mechanism (i.e., PEt3 must dissociate
before PMe3 can add), while 3 reacts with PMe3 in an
associative fashion (see Scheme 6). This associative
mechanism is made possible by the fact that the Ir-S
π electrons can be localized on the sulfur atom (cf.,
resonance structure F ), rendering the iridium atom a
reactive 16e- center.
The 31P{1H} NMR spectrum of 5 consists of three
signalssa doublet of doublets due to the two equivalent
axial phosphines and two triplets of doublets due to the
inequivalent equatorial phosphines. In the 13C{1H}
NMR spectrum, ring carbons C1-C4 resonate in a
rather narrow chemical shift range, δ 115.8-132.0, and
the signal for C1 is a doublet-of-triplets-of-doublets
pattern. The large doublet coupling (J C-P ) 70.5 Hz) is
due to the trans-equatorial phosphine, while the smaller
triplet (J C-P ) 12.0 Hz) and doublet (J C-P ) 6.0 Hz)
couplings result from the axial and cis-equatorial phos-
phines, respectively. In the 1H NMR spectrum, ring
protons H1 and H4 resonate at δ 6.85 and 5.54,
respectively, and both exhibit strong coupling to the cis-
equatorial PMe3 ligand (J H1-P ) 14.7 Hz; J H4-P ) 14.1
Hz).
F igu r e 2. ORTEP drawing of CHdC(Me)C(Me)dCHSdIr-
-
(PEt3)3+BF4 (3), using thermal ellipsoids at the 20%
probability level. Selected bond distances (Å): Ir1-P1,
2.305(3); Ir1-P2, 2.275(3); Ir1-P3, 2.450(3); Ir1-S1, 2.249-
(3); Ir1-C1, 2.019(10); S1-C4, 1.713(12); C1-C2, 1.396-
(16); C2-C3, 1.415(15); C3-C4, 1.361(16). Selected bond
angles (deg): P1-Ir1-P2, 95.9(1); P1-Ir1-P3, 97.5(1);
P1-Ir1-S1, 136.8(1); P1-Ir1-C1, 88.8(3); P2-Ir1-P3,
95.5(1); P2-Ir1-S1, 127.2(1); P2-Ir1-C1, 88.3(3); P3-
Ir1-S1, 83.0(1); P3-Ir1-C1, 172.3(3); S1-Ir1-C1, 89.3-
(3); Ir1-C1-C2, 134.1(8); C1-C2-C3, 126.7(10); C2-C3-
C4, 125.0(11); C3-C4-S1, 127.7(9); C4-S1-Ir1, 116.4(4).
When iridathiabenzene 3 is treated with bis(triph-
enylphosphoranylidene)ammonium chloride (PPN+Cl-),
resonance structures for iridathiabenzene 3 (D-F ). In
the chloride addition product, mer-CHdC(Me)C(Me)d
CHSIr(PEt3)3(Cl), is generated as a mixture of isomers,
6a and 6b (see Scheme 5). Isomer 6a can be crystallized
cleanly from this mixture and exhibits NMR spectra
that are very similar to those of hydride 4. In particular,
the 31P{1H} NMR spectrum of 6a consists of a doublet
and a triplet characteristic of an octahedral coordination
geometry and a mer phosphine arrangement. The trans
relationship of ring carbon C1 to a phosphine ligand is
indicated by the large C-P coupling (J C-P ) 84.0 Hz).
The solid-state structure of 6a has been confirmed by
X-ray crystallography (see Figure 3). As expected, the
metallacycle is virtually planar and exhibits localized
structures D and E, the iridium center possesses 18
valence electrons, while in F it possesses 16 electrons.
Structures E and F differ only in the position of one
electron pair. In E, it resides between sulfur and
iridium, forming the π bond, while in F it resides on
the sulfur atom.18 Because of the contribution from
resonance structure F , the iridium atom in 3 is reactive
(18) Note that in structures D and E, the formal positive charge
resides on sulfur, while in F it resides on the iridium center.
(19) Analogous iridathiabenzene reactivity toward 2e- donor ligands
has been observed by Angelici7b and Bianchini.9 Harris16 has attributed
this reactivity to a low-lying metal-based LUMO.

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1943
Sch em e 5
Sch em e 6
bonding around the carbon/sulfur portion of the ring.
The Ir1-S1 bond in 6a (2.321(3) Å) is somewhat shorter
than the Ir1-S1 bond in 4 (2.433(3) Å), reflecting the
weaker trans influence of chloride.20
When crystalline 6a (light orange) is dissolved in
polar solvents such as acetone, it gives a deep red
solution, and it rapidly establishes an equilibrium with
compound 6b, the isomer in which PEt3 and Cl- have
exchanged positions in the equatorial plane.21 At room
temperature in acetone, the equilibrium ratio 6a :6b is
approximately 60:40.
iridathiabenzenes G and H and that these species are
responsible for the intense red color of the solutions.22
Interestingly, the NMR signals for 6b are very broad
at room temperature (22 °C) and do not fully sharpen
until a temperature of -20 °C is reached. This behavior
suggests a rapid equilibrium with intermediate H
(Scheme 7) at 22 °C. The NMR signals for 6a , on the
other hand, are sharp at 22 °C but begin to broaden as
the temperature is raised. At 40 °C, P-P coupling is
lost in the 31P{1H} NMR spectrum of 6a .
We expected that treatment of 6a /6b in acetone with
Once again, the arrangement of the ligands in 6b can
be readily established by NMR. The 31P{1H} NMR
spectrum consists of a doublet and a triplet, diagnostic
for mer phosphines. However, ring carbon C1 shows no
strong phosphorus coupling in the 13C{1H} NMR, indi-
cating that it resides trans to chloride, not to a PEt3
ligand. Furthermore, ring protons H1 and H4 are both
silver trifluoromethanesulfonate might lead to chloride
abstraction and regeneration of iridathiabenzene 3. In
1
fact,
/ equiv of silver chloride is produced in this
2
reaction, but the organometallic product is a novel
chloride-bridged dimer, 7 (see Scheme 8), not the
expected 3.
Although the detailed mechanism of this reaction is
not known, it seems likely that the dimerization pro-
ceeds through the intermediacy of the five-coordinate
iridathiabenzene species H implicated earlier in the
isomerization of 6a to 6b (cf. Scheme 7). As shown in
Scheme 8, dimerization of H through the ring sulfur
strongly phosphorus coupled (J H1-P ) 14.7 Hz; J H4-P
)
13.2 Hz), confirming the presence of a PEt3 ligand cis
to C1 in the equatorial plane.
As shown in Scheme 7, we suggest that the isomer-
ization process proceeds through the intermediacy of
(20) Huheey, J . E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry:
Principles of Structure and Reactivity, 4th ed.; HarperCollins: New
York, 1993; pp 543-547.
(21) A close analogue of this species with PMe3 ligands has been
reported by Merola.10b
(22) We can rule out the intermediacy of iridathiabenzene 3 in this
reaction because addition of excess PMe3 to the red solution does not
yield the cationic tetrakis(trimethylphosphine) product 5. Rather,
neutral chloro-containing substitution products are obtained.

1944 Organometallics, Vol. 20, No. 10, 2001
Bleeke et al.
The chloride bridge is symmetrical with respect to the
two iridium centers, while the sulfur bridges are un-
symmetrical. The iridium-sulfur distances within the
metallacycles (average 2.37 Å) are shorter than those
to sulfur atoms on neighboring rings (average 2.43 Å).
The bond distances and angles within the iridathiacy-
clohexa-1,3-diene rings in 7 are similar to those ob-
served in 6a . However, a close comparison reveals that
the Ir-C bonds in 7 (2.014(12) and 2.039(15) Å) are
slightly shorter than the Ir-C bond in 6a (2.055(10) Å),
probably reflecting the weaker trans influence of chlo-
ride vs PEt3.20 Consistent with this interpretation is the
observation that the Ir-S bonds within the metalla-
cycles of 7 are slightly longer than the Ir-S bond in 6a
(2.376(3) and 2.364(3) Å in 7 vs 2.321(3) Å in 6a ). The
presence of the bridging chloride ligand causes the rings
to twist out of register, so that they do not exactly eclipse
one another. In addition, the rings are slightly canted,
instead of being parallel. The dihedral angle between
the two metallacycle mean planes is 25.9°.
Compound 7 possesses 2-fold rotation symmetry in
F igu r e 3. ORTEP drawing of mer-CHdC(Me)C(Me)d
solution; therefore, the two metallacyclic rings appear
1
equivalent by H and 13C{1H} NMR. The H1 and H4
CHSIr(PEt3)3(Cl) (6a ), using thermal ellipsoids at the 20%
probability level. Selected bond distances (Å): Ir1-Cl1,
2.445(3); Ir1-P1, 2.375(3); Ir1-P2, 2.374(3); Ir1-P3, 2.430-
(3); Ir1-S1, 2.321(3); Ir1-C1, 2.055(10); S1-C4, 1.741(12);
C1-C2, 1.352(16); C2-C3, 1.470(17); C3-C4, 1.334(17).
Selected bond angles (deg): Cl1-Ir1-P1, 86.6(1); Cl1-Ir1-
P2, 89.8(1); Cl1-Ir1-P3, 92.8(1); Cl1-Ir1-S1, 180.0(1);
Cl1-Ir1-C1, 87.7(3); P1-Ir1-P2, 169.2(1); P1-Ir1-P3,
94.0(1); P1-Ir1-S1, 93.4(1); P1-Ir1-C1, 82.9(3); P2-Ir1-
P3, 96.4(1); P2-Ir1-S1, 90.3(1); P2-Ir1-C1, 86.8(3); P3-
Ir1-S1, 87.2(1); P3-Ir1-C1, 176.8(3); S1-Ir1-C1, 92.3(3);
Ir1-C1-C2, 133.3(9); C1-C2-C3, 125.6(11); C2-C3-C4,
125.9(11); C3-C4-S1, 131.9(10); C4-S1-Ir1, 109.9(4).
protons resonate at δ 8.07 and 5.51, respectively, and
both are strongly coupled doublets due to the presence
of a phosphine ligand cis to C1 in the equatorial plane
(J H1-P ) 9.9 Hz; J H4-P ) 11.7 Hz). The ring carbons
resonate in the expected region of the 13C NMR spec-
trum (δ 107.1-141.7), and C1 is not strongly coupled
to phosphorus, because it lies trans to chloride rather
than PEt3.
The 31P{1H} spectrum of 7 is a classic AA′XX′ second-
order pattern. This results from the fact that each
iridium center has two kinds of phosphine ligands, an
A type and an X type, and although the two A-type
ligands are chemically equivalent (as are the two X-type
ligands), they are not magnetically equivalent due to
long-range coupling. The A-type phosphines and the
X-type phosphines each give rise to identical 10-line
patterns at δ -12.9 and -17.6, respectively. Each
pattern consists of a strong doublet, which is centered
on the frequency of δA (or δX), and two symmetrical
quartets, which are likewise centered on δA (or δX) (see
Figure 5). From the separation between the various
lines, one can calculate all of the coupling constants.23
In this case, J AA′ and J XX′ are calculated to be 27.5 and
14.3 Hz, while J AX and J AX′ are 17.9 and 3.3 Hz.24
Sch em e 7
C. Rea ctivity of Ir id a th ia ben zen e 3: Cycloa d d i-
tion .25 Both iridabenzene 12 and iridapyrylium 25 react
with a wide variety of unsaturated substrates to produce
[4 + 2] cycloadducts. Although iridathiabenzene 3 seems
to be less prone to exhibit this type of reactivity, we have
discovered one such cycloaddition reaction, namely the
reaction of 3 with nitrosobenzene to produce 8 (Scheme
9). The iridathiacyclohexa-1,4-diene ring in 8 is char-
centers would lead to dimer I, which could then react
with AgO3SCF3 to generate 7 and AgCl.
The structure of 7 has been confirmed by X-ray
diffraction. An ORTEP drawing is presented in Figure
4. Each of the iridium centers in 7 is approximately
octahedral, and in each case, the four equatorial sites
are occupied by the metallacycle, a PEt3 ligand, and the
bridging chloride. The sulfur atom from the neighboring
ring and a second PEt3 ligand occupy the axial sites.
The bridging chloride ligand resides cis to the ring
sulfur and trans to the ring carbon in both equatorial
planes.
(23) (a) Pople, J . A.; Schneider, W. G.; Bernstein, H. J . High-
Resolution Nuclear Magnetic Resonance; McGraw-Hill: New York,
1959, pp 140-151. (b) Wiberg, K. B.; Nist, B. J . The Interpretation of
NMR Spectra; W. A. Benjamin: New York, 1962; pp 309-317.
(24) From the data analysis, one cannot distinguish between J AA′
and J XX′ nor between J AX and J AX′
.
(25) For a good summary of cycloaddition reactions involving organic
components, see: Lowry, T. H.; Richardson, K. S. Mechanism and
Theory in Organic Chemistry, 3rd ed.; Harper and Row: New York,
1987; pp 903-931.

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1945
Sch em e 8
acterized by a relatively upfield 13C NMR chemical shift
for sp3 carbon C3 (δ50.8) and a corresponding downfield
shift for thioaldehyde carbon C4 (δ154.2). Olefinic
carbons C1 and C2 resonate at δ 136.4 and 149.6,
respectively, and C1 exhibits strong phosphorus cou-
pling due to the trans PEt3 ligand (J C-P ) 93.0 Hz). In
the 1H NMR spectrum, the signal for thioaldehyde
proton H4 appears downfield at δ 8.31, while the ring
proton H1 resonates at δ 6.79 and appears as a
phosphorus-coupled triplet (J H-P ) 10.0 Hz). The 31P-
{1H} spectrum consists of three separate doublet-of-
doublet patterns, consistent with a fac geometry for the
three PEt3 ligands.
respectively, and C1 exhibits strong coupling to the 31P
nucleus that lies trans to it (J C-P ) 61.8 Hz). Unlike 3,
which undergoes intramolecular phosphine exchange in
solution at room temperature (vide supra), 9 is stere-
ochemically rigid. Hence, the 31P{1H} NMR spectrum
at 22 °C consists of three discrete signals for the three
inequivalent phosphine ligands. However, the 13C{1H}
NMR spectrum of 9 exhibits a single peak for the three
carbonyl ligands (at δ 220.9), indicating that the iri-
dathiabenzene ring is rotating freely with respect to the
Mo(CO)3 moiety.
The infrared spectrum of 9 shows the presence of two
intense ν(CO) bands (A1 and E) at 1962 and 1895 cm-1
.
By comparison, the ν(CO) bands for (η6-iridabenzene)-
Mo(CO)3 appear at 1918 and 1836 cm-1. The higher
energy of the bands in 9 reflects the positive charge on
9 and, consequently, the reduced π-back-bonding into
CO π* orbitals.
D. Rea ctivity of Ir id a th ia ben zen e 3: Coor d in a -
tion to Oth er Meta l-Liga n d F r a gm en ts. Earlier, we
showed that iridabenzene 1 could be coordinated to a
Mo(CO)3 fragment to produce (η6-iridabenzene)Mo-
(CO)3.26 Similarly, treatment of 3 with (η6-p-xylene)Mo-
(CO)3 in tetrahydrofuran leads to arene exchange and
clean production of the deep violet (η6-iridathiabenzene)-
Mo(CO)3 species 9 (Scheme 10).27
The X-ray crystal structure of 9 (see Figure 6) shows
that the molybdenum atom is strongly π-complexed to
all six atoms of the iridathiabenzene ring and that the
bonding within this ring is still delocalized. However,
the bond lengths in the complexed ring are slightly
longer than those in the free iridathiabenzene, because
π-electron density is being removed from the ring by
the Mo(CO)3 moiety. The circumference of the ring in 3
is 10.15 Å, while that in 9 is 10.37 Å. The metallacyclic
ring in 9 is close to planar. The iridium atom is displaced
0.21 Å out of the carbon/sulfur ring plane (and away
from Mo). The dihedral angle between the planes C1/
C2/C3/C4/S and C1/Ir/S is 7.7°.
The NMR signals for the ring protons and carbons in
9 shift upfield from their positions in 3, as is normally
observed when arenes π-coordinate to transition met-
als.28 Protons H1 and H4 in 9 resonate at δ 8.27 and
6.59, respectively, and are strongly coupled to the basal
phosphine that resides cis to C1. Carbons C1, C2, C3,
and C4 resonate at δ 129.0, 117.6, 109.5, and 89.0,
(26) Bleeke, J . R.; Bass, L. A.; Xie, Y.-F.; Chiang, M. Y. J . Am. Chem.
Soc. 1992, 114, 4213.
(27) Angelici has also coordinated his iridathiabenzene to M(CO)3
fragments, where M ) Cr, Mo, W: Chen, J .; Young, V. G., J r.; Angelici,
R. J . J . Am. Chem. Soc. 1995, 117, 6362.
(28) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; pp 158-164.
The coordination geometry at the iridium center in 9
is best described as a square pyramid, where atoms C1,
S, P2, and P3 define the basal ligand set while phos-
phorus atom P1 occupies the unique axial site. This shift
in coordination geometry from a distorted trigonal

1946 Organometallics, Vol. 20, No. 10, 2001
Bleeke et al.
F igu r e 4. ORTEP drawing of [(CHdC(Me)C(Me)dCHSIr-
-
(PEt3)2)2(µ-Cl)]+O3SCF3 (7) with ethyl groups removed
from PEt3 ligands for clarity. Thermal ellipsoids are shown
at the 50% probability level. Selected bond distances (Å):
Ir1-Cl1, 2.559(3); Ir1-P1, 2.320(3); Ir1-P2, 2.329(3); Ir1-
S2, 2.434(3); Ir1-S1, 2.376(3); Ir1-C1, 2.014(12); S1-C4,
1.753(14); C1-C2, 1.359(18); C2-C3, 1.445(19); C3-C4,
1.358(18); Ir2-Cl1, 2.542(3); Ir2-P3, 2.324(3); Ir2-P4,
2.320(4); Ir2-S1, 2.432(3); Ir2-S2, 2.364(3); Ir2-C51,
2.039(15); S2-C54, 1.732(14); C51-C52, 1.34(2); C52-C53,
1.46(2); C53-C54, 1.351(19). Selected bond angles (deg):
P1-Ir1-S2, 169.98(12); P2-Ir1-S1, 167.79(12); Cl1-Ir1-
C1, 170.1(3); S1-Ir1-C1, 92.7(4); Ir1-C1-C2, 129.9(9);
C1-C2-C3, 128.0(12); C2-C3-C4, 125.7(12); C3-C4-S1,
129.4(10); C4-S1-Ir1, 106.5(4); Ir1-C11-Ir2, 82.24(8);
Ir1-S1-Ir2, 88.51(11); Ir1-S2-Ir2, 88.74(11); P3-Ir2-
S2, 171.15(12); P4-Ir2-S1, 170.84(12); Cl1-Ir2-C51,
167.6(4); S2-Ir2-C51, 92.5(4); Ir2-C51-C52, 131.6(12);
C51-C52-C53, 127.6(13); C52-C53-C54, 128.0(13); C53-
C54-S2, 128.3(12); C54-S2-Ir2, 110.6(5).
F igu r e 5. (A) Portion of the observed 31P{1H} NMR
spectrum for [(CHdC(Me)C(Me)dCHSIr(PEt3)2)2(µ-Cl)]+-
-
O3SCF3 (7). Shown here is the 10-line signal due to the
two X-type phosphines in this AA′XX′ spin system. The
signal due to the two A-type phosphines (δ -12.9) is
identical. (B) Simulated spectrum for the X-type phos-
phines in 7, obtained using the following P-P coupling
constants: J AA′ ) 27.5 Hz, J XX′ ) 14.3 Hz, J AX ) 17.9 Hz,
J AX′ ) 3.3 Hz.
bipyramid in 3 to a square pyramid in 9 is undoubtedly
a response to the steric demands of the Mo(CO)3 moiety.
Sch em e 9
Treatment of 9 with PMe3 leads to the production of
a novel η4-iridathiabenzene complex 10 (see Scheme 10).
In this product, two PMe3 ligands have been added to
the molybdenum center and a CO ligand (formerly
bonded to Mo) has replaced a PEt3 ligand on iridium.
To accommodate the two PMe3 and two CO ligands
while retaining an 18e- count, the molybdenum center
shifts to an η4 interaction with the iridathiabenzene
ring.
1
The H NMR signals for ring protons H1 and H4 in
10 are shifted upfield from their position in 9, reflecting
the disruption of the aromatic ring system. They reso-
nate at δ 7.60 and 5.92, respectively (vs δ 8.27 and 6.59
in 9), and both are singlets due to the absence of a
phosphine cis to C1 in the basal plane. In the 13C{1H}
NMR spectrum of 10, the two CO ligands on molybde-
num resonate at δ 235.0 and 232.1, respectively, while
the CO on iridium resonates farther upfield at δ 176.7.
Interestingly, all of the ring carbon signals shift down-
field with respect to their positions in 9. As in 9, C1 is
strongly coupled to the trans PEt3 ligand (J C-P ) 70.3
Hz). All four phosphine ligands give rise to discrete
signals in the 31P{1H} NMR. The two PMe3 ligands on
molybdenum couple strongly to each other (J P-P ) 43.2
Hz), and one of them shows a long-range coupling to
the axial PEt3 ligand on iridium (J P-P ) 14.5 Hz).
The X-ray crystal structure of 10 is shown in Figure
7. The molybdenum center is coordinated in an η4
fashion to an iridathiadiene fragment consisting of S,
Ir, C1, and C2. In response to this coordination mode,
the ring adopts a bent conformation in which uncoor-
dinated carbons C3 and C4 are displaced away from the
molybdenum center. The dihedral angle between planes

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1947
F igu r e 7. ORTEP drawing of [η4-CHdC(Me)C(Me)d
CHSdIr(PEt3)2(CO)]Mo(PMe3)2(CO)2+BF4- (10), using ther-
mal ellipsoids at the 50% probability level. Selected bond
distances (Å): Ir-P1, 2.330(5); Ir-P2, 2.402(4); Ir-C9,
1.88(2); Ir-S, 2.362(4); Ir-C1, 2.061(19); S-C4, 1.74(2);
C1-C2, 1.35(3); C2-C3, 1.52(3); C3-C4, 1.37(3); Mo-Ir,
2.8586(16); Mo-S, 2.500(4); Mo-C1, 2.413(17); Mo-C2,
2.618(18); Mo-P3, 2.483(5); Mo-P4, 2.542(5); Mo-C7,
1.970(19); Mo-C8, 1.934(19). Selected bond angles (deg):
P1-Ir-P2, 98.11(16); P1-Ir-C9, 93.3(6); P1-Ir-S, 100.06-
(16); P1-Ir-C1, 96.5(5); P2-Ir-C9, 94.4(5); P2-Ir-S,
90.06(16); P2-Ir-C1, 165.1(5); C9-Ir-S, 165.2(6); C9-Ir-
C1, 88.1(7); S-Ir-C1, 84.2(5); Ir-C1-C2, 132.8(14); C1-
C2-C3, 122.0(17); C2-C3-C4, 121.1(16); C3-C4-S, 122.1-
(15); C4-S-Ir, 105.8(6); S-Mo-P3, 168.22(18); C7-Mo-
P4, 150.8(6); C1-Mo-C8, 158.0(7); C2-Mo-C8, 162.1(7).
F igu r e 6. ORTEP drawing of [η6-CHdC(Me)C(Me)d
CHSdIr(PEt3)3]Mo(CO)3+BF4- (9), using thermal ellipsoids
at the 40% probability level. Compound 9 crystallized with
two independent molecules in the unit cell; molecule 1 is
reported here. Selected bond distances (Å): Ir-P1, 2.274-
(5); Ir-P2, 2.371(5); Ir-P3, 2.424(4); Ir-S, 2.312(4); Ir-
C1, 2.049(15); S-C4, 1.766(16); C1-C2, 1.42(2); C2-C3,
1.40(3); C3-C4, 1.42(2); Mo-Ir, 3.0180(16); Mo-S, 2.544-
(5); Mo-C1, 2.459(16); Mo-C2, 2.382(19); Mo-C3, 2.399-
(18); Mo-C4, 2.382(17); Mo-C7, 1.968(19); Mo-C8, 2.01(2);
Mo-C9, 2.01(2). Selected bond angles (deg): P1-Ir-P2,
96.13(17); P1-Ir-P3, 101.54(16); P1-Ir-S, 99.49(19); P1-
Ir-C1, 90.6(4); P2-Ir-P3, 92.42(15); P2-Ir-S, 164.37(18);
P2-Ir-C1, 90.1(6); P3-Ir-S, 84.59(15); P3-Ir-C1, 167.2-
(4); S-Ir-C1, 89.6(6); Ir-C1-C2, 135.5(15); C1-C2-C3,
126.5(17); C2-C3-C4, 125.3(16); C3-C4-S, 128.1(13);
C4-S-Ir, 114.0(7); C1-Mo-C8, 167.2(8); C3-Mo-C7,
160.6(7); S-Mo-C9, 161.7(5).
resonance structure J (cf. the Ir-S distance of 2.312(4)
Å in 9). This suggests that a second resonance structure
Sch em e 10
(K) involving coordination of a sulfur lone pair rather
than the Ir-S double bond may also contribute to the
overall bonding picture in 10. This view is further
supported by the observation that the angle at S (angle
Ir-S-C4) in 10 is significantly smaller than the same
angle in 9 (105.8(6) vs 116.4(4)°). As in 9, the coordina-
tion geometry around iridium is best described as
square pyramidal with ring atoms C1 and S, carbonyl
carbon C9, and phosphorus P2 occupying the basal
positions and phosphorus P1 occupying the unique axial
site.
C2/C3/C4/S and S/Ir/C1/C2 is 46.7°. Disruption of the
aromaticity in the iridathiabenzene ring also causes the
ring bonding to become much more localized. This is
particularly evident in the ring C-C bond distances,
which are 1.35(3), 1.52(3), and 1.37(3) Å for C1-C2, C2-
C3, and C3-C4, respectively. The Ir-S distance of
2.362(4) Å is a bit longer than might be expected from
Finally, treatment of iridathiabenzene 3 with (η5-
pentamethylcyclopentadienyl)Ru(NCMe)3+O3SCF3- leads
to clean acetonitrile displacement and production of
“sandwich” complex 11 (Scheme 11). The 1H NMR
spectrum of 11 is strikingly similar to that of 9.
Iridathiabenzene ring protons H1 and H4 resonate
at δ 8.83 and 6.33, respectively, and each exhibits strong

1948 Organometallics, Vol. 20, No. 10, 2001
Bleeke et al.
Sch em e 11
reaction of [(cyclooctene)2IrCl]2 with 6 equiv of PEt3. (η6-p-
xylene)Mo(CO)332 and [(η5-C5Me5)Ru(NCMe)3]+O3SCF3- 33 were
synthesized by literature procedures.
31
coupling to the PEt3 ligand that resides cis to C1 in the
basal plane of iridium (J H1-P ) 15.6 Hz; J H4-P ) 9.0
Hz). The chemical shifts of the iridathiabenzene ring
carbons are also similar to those of 9. C1, C2, C3, and
C4 resonate at δ 116.8, 110.6, 100.5, and 77.9, respec-
tively, and C1 shows strong coupling to the trans-basal
PEt3 ligand (J C-P ) 62.7 Hz). In the 31P{1H} NMR
spectrum of 11, three separate signals are observed for
the three inequivalent PEt3 ligands, again indicating
stereochemical rigidity at iridium.
NMR experiments were performed on a Varian Unity Plus-
300 spectrometer (1H, 300 MHz; 13C, 75 MHz; 31P, 121 MHz),
a Varian Unity Plus-500 spectrometer (1H, 500 MHz; 13C, 125
MHz; 31P, 202 MHz), or a Varian Unity-600 spectrometer (1H,
600 MHz; 13C, 150 MHz; 31P, 242 MHz). 1H and 13C spectra
were referenced to tetramethylsilane, while 31P spectra were
referenced to external H3PO4. HMQC (1H-detected multiple
quantum coherence) and HMBC (heteronuclear multiple bond
1
correlation) experiments aided in assigning some of the H and
13C peaks.
Su m m a r y
The infrared spectra were recorded on a Mattson Polaris
FT IR spectrometer.
We have synthesized a new iridathiabenzene complex,
3, using thiapentadienide as the source of ring carbon
and sulfur atoms and exploiting C-H bond activation
in the key ring-forming step. The X-ray crystal structure
of this species and its solution-phase NMR spectra are
consistent with the presence of an aromatic ring system
in which the metal center participates in ring π-bonding.
Two-electron donors such as PMe3 and chloride react
associatively with 3 at the iridium center, generating
six-coordinate Ir(III) products with the iridathiacyclo-
hexa-1,3-diene ring skeleton. This reactivity results
primarily from the fact that the electrons in the Ir-S π
bond of 3 can be localized on sulfur, rendering the
iridium atom a reactive 16e- center. Iridathiabenzene
3 also engages in a [4 + 2] cycloaddition reaction with
nitrosobenzene, producing an iridathiacyclohexa-1,4-
diene product. Finally, 3 behaves like a conventional
arene in its reactions with organometallic reagents,
forming η6 π complexes with the Mo(CO)3 and (C5Me5)-
Ru+ metal-ligand fragments.
Microanalyses were performed by Galbraith Laboratories,
Inc., Knoxville, TN.
Syn th esis of Lith iu m 2,3-Dim eth yl-5-th ia p en ta d ien -
id e. 3,4-Dimethyl-2,5-dihydrothiophene (1.04 g, 9.13 mmol)
was dissolved in 40 mL of tetrahydrofuran (THF) and the
solution cooled to -25 °C. To this solution was added 1.67 M
n-butyllithium in hexanes (5.8 mL, 9.28 mmol) over a 15 min
period. The resulting lemon yellow solution was stirred at -25
°C for 6.5 h, followed by removal of the volatiles in vacuo,
leaving an orange-brown waxy solid. To this residue was added
50 mL of pentane, and the resulting slurry was filtered
through a medium-porosity frit. The collected solid was rinsed
with pentane (20 and 5 mL portions) and then with diethyl
ether (3 × 5 mL portions), leaving a white powder of the
desired product. Yield: 0.75 g (68%).
1H NMR (tetrahydrofuran-d8, 22 °C): δ 6.87 (s, 1, H4), 4.87
(d, J H-H ) 3.0 Hz, 1, H1), 4.50 (br s, 1, H1), 2.32 (s, 3, CH3),
1.74 (s, 3, CH3).
-
Syn th esis of CHdC(Me)C(Me)dCHSdIr (P Et3)3+BF 4
(3). Compound 4, mer-CHdC(Me)C(Me)dCHSIr(PEt3)3(H)
(0.26 g, 0.39 mmol), was dissolved in 10 mL of tetrahydrofuran
(THF) and the solution cooled to -70 °C. AgBF4 (0.076 g, 0.39
mmol) in 3 mL of THF was added, and the resulting solution
was warmed to room temperature. After filtration, the solvent
was removed in vacuo, leaving a red oil. Compound 3 was
extracted from this oil with toluene and crystallized as deep
red needles from toluene/pentane at -30 °C. Yield: 0.13 g
(44%).
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations were carried out
under a nitrogen atmosphere, using either glovebox or double-
manifold Schlenk techniques. Solvents were stored under
nitrogen after being distilled from the appropriate drying
agents. Deuterated NMR solvents were obtained from Cam-
bridge Isotope Laboratories or from Aldrich in sealed vials and
used as received. The following reagents were used as obtained
from the supplier indicated: n-butyllithium (Aldrich), silver
tetrafluoroborate (Aldrich), silver trifluoromethanesulfonate
(Aldrich), bis(triphenylphosphoranylidene)ammonium chloride
(PPN+Cl-; Aldrich), trimethylphosphine (Strem), and ni-
trosobenzene (Aldrich).
1H NMR (acetone-d6, 22 °C): δ 10.36 (quartet, J H-P ) 8.4
Hz, 1, H1), 8.61 (quartet, J H-P ) 3.3 Hz, 1, H4), 2.51 (s, 3,
ring CH3), 2.22 (s, 3, ring CH3), 2.22 (d of quartets, J H-P
)
(30) Butler, G. B.; Ottenbrite, R. M. Tetrahedron Lett. 1967, 48,
4873.
(31) Herde, J . L.; Lambert, J . C.; Senoff, C. V. In Inorganic
Syntheses; Parshall, G. W., Ed.; McGraw-Hill: New York, 1974; Vol.
15, pp 18-20.
(32) (a) Fischer, E. O.; O¨ fele, K.; Essler, H.; Fro¨hlich, W.; Mortensen,
J . P.; Semmlinger, W. Chem. Ber. 1958, 91, 2763. (b) Strohmeier, W.
Chem. Ber. 1961, 94, 3337.
3,4-Dimethyl-2,5-dihydrothiophene29 was obtained by di-
isobutylaluminum hydride (DIBAL-H) reduction of the corre-
sponding sulfone.30 (Cl)Ir(PEt3)3 was produced in situ via the
(29) Pettett, M. G.; Holmes, A. B. J . Chem. Soc., Perkin Trans. 1
1985, 1161.
(33) Fagan, P. J .; Ward, M. D.; Calabrese, J . C. J . Am. Chem. Soc.
1989, 111, 1698.

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1949
J H-H ) 7.8 Hz, 18, PEt3 CH2’s), 0.99 (d of t, J H-P ) 15.6 Hz,
J H-H ) 7.8 Hz, 27, PEt3 CH3’s). 13C{1H} NMR (acetone-d6, 22
°C): δ 165.1 (quartet, J C-P ) 21.6 Hz, C1), 143.6 (s, C2), 134.9
(s, C3), 130.0 (s, C4), 27.9 (quartet, J C-P ) 3.0 Hz, ring CH3),
25.8 (s, ring CH3), 21.1 (d, J C-P ) 31.5 Hz, PEt3 CH2’s), 9.3
(quartet, J C-P ) 4.5 Hz, PEt3 CH3’s). 31P{1H} NMR (acetone-
d6, 22 °C): δ 1.94 (br s). 31P{1H} NMR (acetone-d6, -90 °C):
δ 11.9 (s, 2, equatorial PEt3’s), -15.4 (s, 1, axial PEt3).
1.82 (s, 3, ring CH3), 2.15-1.95 (m, 18, PEt3 CH2’s), 1.25-1.00
(m, 27, PEt3 CH3’s). 13C{1H} NMR (acetone-d6, 22 °C): δ 131.2
(d of t, J C-P ) 84.0 Hz, 12.0 Hz, C1), 128.0 (s, C2), 125.6 (s,
C3), 114.8 (d, J C-P ) 6.0 Hz, C4), 26.7 (s, J C-P ) 9.0 Hz, ring
CH3), 25.2 (s, ring CH3), 18.2 (d, J C-P ) 21.0 Hz, equatorial
PEt3 CH2’s), 14.2 (virtual t, J C-P ) 31.5 Hz, axial PEt3 CH2’s),
9.0 (d, J C-P ) 4.5 Hz, equatorial PEt3 CH3’s), 8.7 (virtual t,
J C-P ) 4.5 Hz, axial PEt3 CH3’s). 31P{1H} NMR (acetone-d6,
22 °C): δ -32.1 (d, J P-P ) 16.5 Hz, 2, axial PEt3’s), -41.0 (t,
J P-P ) 16.5 Hz, 1, equatorial PEt3).
Syn t h esis of m er -CHdC(Me)C(Me)dCHSIr (P E t3)3(H)
(4). (Cl)Ir(PEt3)3 (2.91 g, 5.00 mmol) was dissolved in 200 mL
of tetrahydrofuran (THF) and the solution cooled to -25 °C.
To this solution was added lithium 2,3-dimethyl-5-thiapenta-
dienide (0.60 g, 5.00 mmol) in 25 mL of THF dropwise over a
10 min period. After the mixture was stirred for 7 h and
warmed to ambient temperature, the solvent was removed in
vacuo, affording a light yellow powder. Compound 4 was
extracted from this powder with 40 mL of pentane and
crystallized as orange prisms from acetone at -30 °C. Yield:
2.71 g (82%).
1H NMR (acetone-d6, 22 °C): δ 7.05 (s, 1, H1), 5.78 (s, 1,
H4), 1.90 (m, 3, ring CH3), 1.80 (s, 3, ring CH3), 1.95-1.60 (m,
18, PEt3 CH2’s), 1.15-0.95 (m, 27, PEt3 CH3’s), -16.10 (d of t,
J H-P ) 13.2 Hz, 15.9 Hz, 1, Ir-H). 13C{1H} NMR (acetone-d6,
22 °C): δ127.3 (s, C2), 127.3 (s, C3), 120.9 (d, J C-P ) 6.0 Hz,
C4), 118.8 (d of t, J C-P ) 72.0 Hz, 15.0 Hz, C1), 28.7 (d, J C-P
) 9.0 Hz, ring CH3), 26.4 (s, ring CH3), 21.1 (d, J C-P ) 24.0
Hz, equatorial PEt3 CH2’s), 17.4 (virtual t, J C-P ) 33.0 Hz,
axial PEt3 CH2’s), 8.6 (s, PEt3 CH3’s). 31P{1H} NMR (acetone-
d6, 22 °C): δ -18.9 (d, J P-P ) 16.0 Hz, 2, axial PEt3’s), -28.3
(t, J P-P ) 16.0 Hz, 1, equatorial PEt3).
1
NMR Da ta for Isom er 6b. H NMR (acetone-d6, -20 °C):
δ 7.43 (d, J H-P ) 14.7 Hz, 1, H1), 5.66 (d, J H-P ) 13.2 Hz, 1,
H4), 1.85 (obscured, ring CH3), 1.73 (s, 3, ring CH3), 2.25-
1.85 (m, 18, PEt3 CH2’s), 1.30-1.00 (m, 27, PEt3 CH3’s). 13C-
{1H} NMR (acetone-d6, -20 °C): δ 128.0 (s, C2), 126.8 (s, C3),
122.1 (s, C4), 106.4 (m, C1), 27.7 (s, ring CH3), 25.6 (s, ring
CH3), 17.1 (d, J C-P ) 27.8 Hz, equatorial PEt3 CH2’s), 14.6
(virtual t, J C-P ) 31.5 Hz, axial PEt3 CH2’s), 9.4 (d, J C-P ) 5.2
Hz, equatorial PEt3 CH3’s), 8.8 (virtual t, J C-P ) 4.5 Hz, axial
PEt3 CH3’s). 31P{1H} NMR (acetone-d6, -20 °C): δ -29.9 (d,
J P-P ) 18.6 Hz, 2, axial PEt3’s), -32.6 (t, J P-P ) 18.6 Hz, 1,
equatorial PEt3).
Syn th esis of [(CHdC(Me)C(Me)dCHSIr (P Et3)2)2(µ-Cl)]+-
O3SCF 3- (7). Compound 6, CHdC(Me)C(Me)dCHSIr(PEt3)3-
(Cl) (0.050 g, 0.072 mmol), was dissolved in 7 mL of acetone,
and AgO3SCF3 (0.008 g, 0.031 mmol, 0.43 equiv) in 1 mL of
acetone was added at ambient temperature with vigorous
stirring. The solution became red, and a precipitate (AgCl)
formed. After it was stirred for 1 h and cooled to -30 °C, the
solution was filtered. The volatiles were then removed in
vacuo, and the residue was washed with three 5 mL portions
of pentane to remove unreacted 6. The remaining solid was
dissolved in 1:6 acetone/diethyl ether and the solution cooled
to -30 °C to produce light yellow prisms. Yield: 0.033 g (84%).
1H NMR (acetone-d6, 22 °C): δ 8.07 (d, J H-P ) 9.9 Hz, 2,
H1’s), 5.51 (d, J H-P ) 11.7 Hz, 2, H4’s), 2.30-1.90 (m, 24, PEt3
CH2’s), 2.12 (s, 6, ring CH3’s), 1.75 (s, 6, ring CH3’s), 1.30-
1.00 (m, 36, PEt3 CH3’s). 13C{1H} NMR (acetone-d6, 22 °C): δ
141.7 (s, C2’s), 127.7 (s, C3’s), 116.5 (s, C1’s), 107.1 (s, C4’s),
27.3 (s, ring CH3’s), 26.7 (s, ring CH3’s), 16.9 (filled-in d, J C-P
) 33.7 Hz, PEt3 CH2’s), 16.0 (filled-in d, J C-P ) 31.9 Hz, PEt3
CH2’s), 8.1 (s, PEt3 CH3’s). 31P{1H} NMR (acetone-d6, 22 °C):
δ -12.9 (A2X2 pattern, 2, A-type PEt3’s), -17.6 (A2X2 pattern,
2, X-type PEt3’s). The four coupling constants calculated from
the spectra are J AA′ ) 27.5 Hz, J XX′ ) 14.3 Hz, J AX ) 17.9 Hz,
and J AX′ ) 3.3 Hz.
Syn th esis of CHdC(Me)C(Me)dCHSIr (P Me3)4+BF4- (5).
-
Compound 3, CHdC(Me)C(Me)dCHSdIr(PEt3)3+BF4 (0.057
g, 0.076 mmol), was dissolved in tetrahydrofuran and the
solution cooled to -30 °C. Trimethylphosphine was added
dropwise with swirling until the color of the solution remained
yellow. (Approximately 0.05 mL, 0.48 mmol PMe3 was added.)
After the mixture was warmed to room temperature, the
volatiles were removed in vacuo. The residue was rinsed with
toluene and then dissolved in acetone/diethyl ether. Cooling
to -30 °C caused compound 5 to crystallize as yellow prisms.
Yield: 0.040 g (75%).
1H NMR (acetone-d6, 22 °C): δ 6.85 (d, J H-P ) 14.7 Hz, 1,
H1), 5.54 (d, J H-P ) 14.1 Hz, 1, H4), 2.09 (br s, 3, ring CH3),
1.89 (s, 3, ring CH3), 1.88 (d, J H-P ) 8.7 Hz, 9, equatorial
PMe3), 1.71 (d, J H-P ) 8.4 Hz, 9, equatorial PMe3), 1.60 (virtual
t, J H-P ) 7.2 Hz, 18, axial PMe3’s). 13C{1H} NMR (acetone-d6,
22 °C): δ 130.2 (s, C2), 129.5 (s, C3), 116.8 (d of d, J C-P ) 9.0
Hz, 3.0 Hz, C4), 115.8 (d of t of d, J C-P ) 70.5 Hz, 12.0 Hz, 6.0
Hz, C1), 27.8 (d, J C-P ) 10.5 Hz, ring CH3), 25.2 (s, ring CH3),
19.1 (d, J C-P ) 30.0 Hz, equatorial PMe3), 18.8 (d, J C-P ) 36.0
Hz, equatorial PMe3), 16.1 (virtual t, J C-P ) 40.5 Hz, axial
PMe3’s). 31P{1H} NMR (acetone-d6, 22 °C): δ -49.9 (d of d,
+
Syn th esis of [CHdC(Me)C(Me)CHdSIr ON(P h )](P Et3)3
-
-
BF4- (8). Compound 3, CHdC(Me)C(Me)dCHSdIr(PEt3)3+BF4
(0.040 g, 0.054 mmol), and nitrosobenzene (0.007 g, 0.065
mmol) were placed in a vial, and 5 mL of tetrahydrofuran
(THF) was added at room temperature. The resulting yellow
solution was stirred for 10 min before removal of the solvent
in vacuo. The residue was rinsed with diethyl ether and then
dissolved in THF. Addition of diethyl ether and cooling to -30
°C caused compound 8 to crystallize as a light yellow waxy
solid. Yield: 0.011 g (24%).
1H NMR (acetone-d6, 22 °C): δ 8.31 (s, 1, H4), 7.66-7.56
(m, 5, phenyl H’s), 6.79 (t, J H-P ) 10.0 Hz, 1, H1), 2.40-2.00
(m, 18, PEt3 CH2’s), 1.96 (d, J H-P ) 1.5 Hz, 3, ring CH3), 1.59
(d, J H-P ) 1.0 Hz, 3, ring CH3), 1.40-1.00 (m, 27, PEt3 CH3’s).
13C{1H} NMR (acetone-d6, 22 °C): δ 154.2 (s, C4), 149.6 (d,
J C-P ) 3.8 Hz, C2), 147.5 (s, ipso phenyl C), 136.4 (d of t, J C-P
) 93.0 Hz, 7.5 Hz, C1), 131.1 (s, para phenyl C), 130.5, 123.2
(s’s, ortho and meta phenyl C’s), 50.8 (d, J C-P ) 11.3 Hz, C3),
28.7 (d, J C-P ) 4.9 Hz, ring CH3), 21.8 (d, J C-P ) 8.0 Hz, ring
CH3), 21.0 (d, J C-P ) 38.6 Hz, PEt3 CH2’s), 18.2 (d, J C-P ) 24.0
Hz, PEt3 CH2’s), 17.1 (d, J C-P ) 30.5 Hz, PEt3 CH2’s), 9.7 (d,
J C-P ) 6.4 Hz, PEt3 CH3’s), 9.5 (d, J C-P ) 6.4 Hz, PEt3 CH3’s),
J P-P ) 20.2 Hz, 15.9 Hz, 2, axial PMe3’s), -52.0 (t of d, J P-P
20.2 Hz, 15.2 Hz, 1, equatorial PMe3), -65.4 (t of d, J P-P
15.9 Hz, 15.2 Hz, 1, equatorial PMe3).
)
)
Syn th esis of m er -CHdC(Me)C(Me)dCHSIr (P Et3)3(Cl)
-
(6). Compound 3, CHdC(Me)C(Me)dCHSdIr(PEt3)3+BF4
(0.049 g, 0.066 mmol), was dissolved in 2 mL of methylene
chloride and cooled to -30 °C. PPN+Cl- (0.070 g, 0.12 mmol)
in 3 mL of methylene chloride was added, and the resulting
solution was swirled as it was warmed to room temperature.
After the solution sat at room temperature overnight, the
solvent was removed in vacuo. Compound 6 was extracted from
the residue with pentane and crystallized as orange prisms
from a concentrated pentane solution at -30 °C. Yield: 0.021
g (46%).
NMR Da ta for Isom er 6a . 1H NMR (acetone-d6, 22 °C): δ
7.92 (br s, 1, H1), 5.10 (s, 1, H4), 2.02 (obscured, ring CH3),

1950 Organometallics, Vol. 20, No. 10, 2001
Ta ble 1. X-r a y Diffr a ction Str u ctu r e Su m m a r y
Bleeke et al.
3
4
6a
7
9
10
formula
C
24H53BF4Ir-
P3S
C24H54IrP3S
C24H53ClIrP3S
C37H76ClF3-
Ir2O3P4S3
1265.89
C27H53BF4Ir-
MoO3P3S
925.61
C27H56BF4Ir-
MoO3P4S
959.61
fw
745.6
659.8
694.3
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21/c
14.483(7)
10.331(5)
21.842(7)
90.0
93.85(3)
90.0
3261(2)
4
monoclinic
P21/n
10.416(5)
16.780(4)
17.166(4)
90.0
90.49(3)
90.0
3000.0(17)
4
monoclinic
P21/n
11.291(3)
15.222(4)
17.654(4)
90.0
94.32(2)
90.0
3025.6(13)
4
triclinic
P1h
orthorhombic
Pca21
19.6927(2)
10.4724(1)
36.9242(2)
90.0
90.0
90.0
7614.87(11)
8
monoclinic
P21
10.5336(4)
11.8771(4)
15.5186(6)
90.0
99.845(3)
90.0
1912.92(12)
2
10.2481(7)
14.8876(10)
17.6583(14)
104.782(7)
106.746(5)
98.483(5)
2422.4(3)
2
R, deg
â, deg
γ, deg
V, Å3
Z
cryst dimens, mm
0.40 × 0.40 ×
0.26 × 0.28 ×
0.40 × 0.34 ×
0.22 × 0.20 ×
0.36 × 0.24 ×
0.33 × 0.26 ×
0.50
0.31
0.32
0.02
0.06
0.04
cryst color, habit
calcd density, g/cm3
radiation; λ, Å
temp, K
2θ range, deg
data collected
h
red prism
1.519
orange prism
1.461
orange prism
1.524
orange plate
1.736
violet plate
1.615
red plate
1.666
Mo KR; 0.710 73
298
3.0-50.0
298
3.0-50.0
298
218(2)
2.54-52.00
218(2)
3.88-50.00
218(2)
3.92-50.00
3.0-50.0
0-17
0-12
0-13
0-18
-12 to +11
-18 to +17
-21 to +21
0-23
-12 to +12
-14 to +14
0-18
k
l
0-12
0-19
0-12
-26 to +25
-20 to +20
-21 to +20
-43 to +43
total decay
none obsd
no. of data collected
no. of unique data
Mo KR linear abs
coeff, cm-1
5999
5758
43.41
5611
5303
46.90
5647
5359
47.39
31 280
9482
58.49
87 736
13 441
40.46
20 917
6736
40.70
abs cor applied
semiempirical
13.7:1
semiempirical
12.6:1
semiempirical
10.6:1
empirical,
sadabs
18.5:1
empirical,
sadabs
18.6:1
empirical,
sadabs
18.1:1
data to param ratio
final R indices
(obsd data)a
R1
0.0403
0.0553
0.0423
0.0547
0.0385
0.0409
0.0695
0.1688
0.0619
0.1300
0.0731
0.1741
wR2
R indices (all data)
R1
wR2
0.0687
0.0664
1.00
0.0769
0.0706
0.89
0.0912
0.0545
0.98
0.1039
0.2065
1.072
0.1053
0.1493
1.028
0.0898
0.1810
1.035
goodness of fit
a
For 7, 9, and 10, I > 2σ(I); for 3, 4, and 6a , I > 3σ(I).
9.3 (d, J C-P ) 6.5 Hz, PEt3 CH3’s). 31P{1H} NMR (acetone-d6,
22 °C): δ -19.5 (dd, J P-P ) 15.1 Hz, 15.1 Hz, 1, PEt3), -24.2
(dd, J P-P ) 15.1 Hz, 7.5 Hz, 1, PEt3), -24.4 (dd, J P-P ) 15.1
Hz, 7.5 Hz, 1, PEt3).
-
CHSdIr(PEt3)3]Mo(CO)3+BF4 (0.033 g, 0.036 mmol), was
dissolved in 5 mL of acetone, producing a dark purple solution.
At ambient temperature, PMe3 (0.010 g, 0.13 mmol) in 7 mL
of acetone was added to this solution with stirring, causing
the color to change to dark red. After the mixture was stirred
for an additional 1 h, the volatiles were removed in vacuo,
leaving a red oil. This residue was dissolved in acetone/diethyl
ether and the solution cooled to -30 °C, causing deep red
plates of 10 to crystallize. Yield: 0.017 g (50%).
Syn t h esis of [η6-CHdC(Me)C(Me)dCH SdIr (P E t3)3]-
Mo(CO)3+BF 4- (9). Compound 3, CHdC(Me)C(Me)dCHSdIr-
(PEt3)3+BF4- (0.050 g, 0.067 mmol), and (η6-p-xylene)Mo(CO)3
(0.018 g, 0.063 mmol) were placed in a vial, and 6 mL of
tetrahydrofuran was added at room temperature. The result-
ing purple solution was stirred for 1 h before removal of the
solvent in vacuo. The residue was dissolved in acetone/diethyl
ether and cooled to -30 °C, causing deep violet plates of
compound 9 to crystallize. Yield: 0.042 g (72%).
1H NMR (acetone-d6, 22 °C): δ 7.60 (s, 1, H1), 5.92 (s, 1,
H4), 2.50-2.00 (m, 12, PEt3 CH2’s), 1.96 (s, 3, ring CH3), 1.89
(d, J H-P ) 7.8 Hz, 9, PMe3), 1.87 (s, 3, ring CH3), 1.52 (d, J H-P
) 7.8 Hz, 9, PMe3), 1.30-1.10 (m, 18, PEt3 CH3’s). 13C{1H}
NMR (acetone-d6, 22 °C): δ 235.0 (d, J C-P ) 29.1 Hz, CO on
Mo), 232.1 (m, CO on Mo), 176.7 (t, J C-P ) 7.2 Hz, CO on Ir),
148.6 (s, C2), 138.5 (d, J C-P ) 70.3 Hz, C1), 121.1 (s, C3), 116.0
(m, C4), 25.8 (d, J C-P ) 4.5 Hz, ring CH3), 22.4 (d, J C-P ) 31.6
Hz, PEt3 CH2’s), 20.9 (s, ring CH3), 19.4 (d, J C-P ) 29.1 Hz,
1H NMR (acetone-d6, 22 °C): δ 8.27 (d of d, J H-P ) 15.6 Hz,
2.7 Hz, 1, H1), 6.59 (d, J H-P ) 9.6 Hz, 1, H4), 2.54 (s, 3, ring
CH3), 2.53 (s, 3, ring CH3), 2.52-1.82 (m, 18, PEt3 CH2’s),
1.44-0.98 (m, 27, PEt3 CH3’s). 13C{1H} NMR (acetone-d6, 22
°C): δ 220.9 (s, CO’s), 129.0 (d of d, J C-P ) 61.8 Hz, 6.9 Hz,
C1), 117.6 (s, C2), 109.5 (s, C3), 89.0 (d, J C-P ) 9.1 Hz, C4),
28.4 (d, J C-P ) 4.5 Hz, ring CH3), 24.9 (d, J C-P ) 34.3 Hz, PEt3
CH2’s), 24.4 (s, ring CH3), 20.6 (d, J C-P ) 32.1 Hz, PEt3 CH2’s),
20.3 (d, J C-P ) 25.2 Hz, PEt3 CH2’s), 10.4 (d, J C-P ) 6.7 Hz,
PEt3 CH2’s), 19.0 (d, J C-P ) 24.3 Hz, PMe3), 18.3 (d, J C-P
)
26.1 Hz, PMe3), 8.6 (d, J C-P ) 4.8 Hz, PEt3 CH3’s), 7.5 (d, J C-P
) 4.2 Hz, PEt3 CH3’s). 31P{1H} NMR (acetone-d6, 22 °C): δ
7.6 (d, J P-P ) 14.5 Hz, 1, axial PEt3), -0.5 (dd, J P-P ) 43.2
Hz, 14.5 Hz, 1, PMe3), -19.4 (d, J P-P ) 43.2 Hz, 1, PMe3),
-29.0 (s, 1, basal PEt3).
PEt3 CH3’s), 9.9 (d, J C-P ) 6.9 Hz, PEt3 CH3’s), 9.6 (d, J C-P
)
6.9 Hz, PEt3 CH3’s). 31P{1H} NMR (acetone-d6, 22 °C): δ 32.2
(d, J P-P ) 12.2 Hz, 1, axial PEt3), -14.6 (d of d, J P-P ) 20.1
Hz, 12.2 Hz, 1, basal PEt3), -28.6 (d, J P-P ) 20.1 Hz, 1, basal
PEt3).
Syn t h esis of [η6-CHdC(Me)C(Me)dCH SdIr (P E t3)3]-
Ru (η5-C5Me5)2+BF4-O3SCF3- (11). Compound 3, CHdC(Me)C-
(Me)dCHSdIr(PEt3)3+BF4 (0.044 g, 0.059 mmol), was dis-
-
Syn th esis of [η4-CHdC(Me)C(Me)dCHSdIr (P Et3)2(CO)]-
Mo(P Me3)2(CO)2 (10). Compound 9, [η6-CHdC(Me)C(Me)d
solved in 2 mL of acetone and cooled to -30 °C. This solution
was then added to a cold (-30 °C), stirred solution of (η5-C5-

Metallathiabenzenes
Organometallics, Vol. 20, No. 10, 2001 1951
-
Me5)Ru(NCMe)3+O3SCF3 (0.028 g, 0.055 mmol) in 10 mL of
acetone. The resulting solution was warmed to ambient
temperature and stirred for an additional 1 h, during which
time the color changed from burgundy to orange-red. Filtra-
tion, followed by removal of the volatiles in vacuo, resulted in
an orange film of 11. Yield: 0.058 g (94%).
The remaining non-hydrogen atoms were found by successive
full-matrix least-squares refinement and difference Fourier
map calculations. In general, non-hydrogen atoms were refined
anisotropically, while hydrogen atoms were placed at idealized
positions and assumed the riding model.
Crystal data and details of both collection and structure
analysis are listed in Table 1.
1H NMR (acetone-d6, 22 °C): δ 8.83 (d of t, J H-P ) 15.6 Hz,
3.0 Hz, 1, H1), 6.63 (d, J H-P ) 9.0 Hz, 1, H4), 2.47 (s, 3, ring
CH3), 2.43 (s, 3, ring CH3), 2.60-1.80 (m, 18, PEt3 CH2’s), 1.94
(s, 15, cyclopentadienyl CH3’s), 1.46 (d of t, J H-P ) 14.7 Hz,
J H-H ) 7.4 Hz, 9, PEt3 CH3’s), 1.36 (d of t, J H-P ) 14.7 Hz,
J H-H ) 7.4 Hz, 9, PEt3 CH3’s), 0.94 (d of t, J H-P ) 17.7 Hz,
J H-H ) 7.5 Hz, 9, PEt3 CH3’s). 13C{1H} NMR (acetone-d6, 22
°C): δ 116.8 (d of d, J C-P ) 62.7 Hz, 6.8 Hz, C1), 110.6 (s, C2),
Dyn a m ic NMR Stu d ies. Deter m in a tion of ∆Gq for th e
F lu xion a l P r ocess Exh ibited by 3. 31P{1H} NMR spectra
were recorded at 10 °C intervals over the temperature range
where fluxional behavior was exhibited (+10 °C f -80 °C).
Theoretical line shapes were calculated for a series of rates
using the method of J ohnson.35,36 The experimental spectra
were then matched against the theoretical spectra, and in this
way, exchange rate constants were determined for each
temperature. These exchange rate constants, k, were used to
calculate the free energy of activation, ∆Gq, at each temper-
ature, T, using the Eyring equation. The reported ∆Gq is the
average value over all of the temperatures in the simulation,
and the uncertainty is the estimated standard deviation.
100.5 (s, C3), 99.0 (s, cyclopentadienyl C’s), 77.9 (d, J C-P
)
7.6 Hz, C4), 24.8 (d, J C-P ) 36.2 Hz, PEt3 CH2’s), 23.9 (d, J C-P
) 4.5 Hz, ring CH3), 21.9 (d, J C-P ) 30.2 Hz, PEt3 CH2’s), 20.6
(d, J C-P ) 25.7 Hz, PEt3 CH2’s), 20.0 (s, ring CH3), 11.0 (d,
J C-P ) 7.6 Hz, PEt3 CH3’s), 10.7 (s, cyclopentadienyl CH3’s),
10.3 (d, J C-P ) 6.0 Hz, PEt3 CH3’s), 9.7 (d, J C-P ) 6.0 Hz, PEt3
CH3’s). 31P{1H} NMR (acetone-d6, 22 °C): δ 30.1 (d, J P-P
)
11.4 Hz, 1, axial PEt3), -10.3 (d of d, J P-P ) 18.3 Hz, 11.4 Hz,
1, basal PEt3), -22.5 (d, J P-P ) 18.3 Hz, 1, basal PEt3).
Ack n ow led gm en t. Support from the National Sci-
ence Foundation and the donors of the Petroleum
Research Fund, administered by the American Chemi-
cal Society, is gratefully acknowledged. We also thank
J ohnson Matthey Alfa/Aesar for a loan of IrCl3‚3H2O.
Washington University’s High Resolution NMR Service
Facility was funded in part by NIH Support Instrument
Grants (Nos. RR-02004, RR-05018, and RR-07155).
X-r a y Diffr a ct ion St u d ies of [CHdC(Me)C(Me)d
CHSdIr (P Et3)3]+BF 4- (3), m er -CHdC(Me)C(Me)dCHSIr -
(P Et3)3(H) (4), m er -CHdC(Me)C(Me)dCHSIr (P Et3)3(Cl)
(6a ), [(CHdC(Me)C(Me)dCHSIr (P Et3)2)2(µ-Cl)]+O3SCF 3
-
-
(7), [η6-CHdC(Me)C(Me)dCHSdIr (P Et3)3]Mo(CO)3+BF 4
(9), a n d [η4-CHdC(Me)C(Me)dCHSdIr (P Et3)2(CO)]Mo-
Su p p or tin g In for m a tion Ava ila ble: Structure determi-
nation summaries and listings of final atomic coordinates,
thermal parameters, bond lengths, and bond angles for
compounds 3, 4, 6a , 7, 9, and 10 and a summary of analytical
data. This material is available free of charge via the Internet
at http://pubs.acs.org.
-
(P Me3)2(CO)2+BF 4 (10). Single crystals of compounds 3, 4,
6a , 7, 9, and 10 were either sealed in a glass capillary or
mounted on a glass fiber under a nitrogen atmosphere. X-ray
data for 3, 4, and 6a were collected on a Siemens R3m/V
diffractometer at room temperature, while data for 7, 9, and
10 were obtained using a Bruker SMART charge coupled
device (CCD) detector system at 218 K. In each case, graphite-
monochromated Mo KR radiation was supplied by a sealed-
tube X-ray source.
OM010050S
(34) Sheldrick, G. M. Bruker Analytical X-ray Division, Madison,
WI, 1997.
(35) J ohnson, C. S., J r. Am. J . Phys. 1967, 35, 929.
(36) Martin, M. L.; Martin, G. J .; Delpuech, J .-J . Practical NMR
Spectroscopy; Heydon: London, 1980; pp 303-309.
Structure solution and refinement were carried out using
the SHELXTL-PLUS software package (PC version).34 The
iridium atom positions were determined by direct methods.