Annulation of an iridabenzene through formal cycloaddition reactions with organonitriles

Article abstract of DOI:10.1021/om900581h

The cationic iridacyclopentadiene complex [Ir(C₄H ₄)(CS)(MeCN)(PPh₃)₂][CF₃SO ₃] (2), which is derived from the reaction between [Ir(CS)(MeCN)(PPh₃)₂][CF₃SO<

Full text of DOI:10.1021/om900581h

5536 Organometallics 2009, 28, 5536–5540
DOI: 10.1021/om900581h
Annulation of an Iridabenzene through Formal Cycloaddition Reactions
with Organonitriles
Andrew F. Dalebrook and L. James Wright*
Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand
Received July 7, 2009
The cationic iridacyclopentadiene complex [Ir(C4H4)(CS)(MeCN)(PPh3)2][CF3SO3] (2), which is
derived from the reaction between [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1) and ethyne, undergoes a
thermally induced migratory insertion reaction involving the thiocarbonyl ligand to form the cationic
iridabenzene [Ir(C5H4{S-1})(MeCN)(PPh3)2][CF3SO3] (3) in very high yield. The addition of methyl
triflate to this iridabenzene in the presence of NCMe results in methylation of the sulfur atom, and the
red dicationic iridabenzene [Ir(C5H4{SMe-1})(MeCN)2(PPh3)2][PF6]2 (4) is obtained after the
addition of NH4PF6. Upon treatment of 3 with RCN (R = Me or p-tolyl) and acid, a cyclization
reaction ensues between the organonitrile and the η2-C(S)Ir function of the iridabenzene to give
the corresponding iridabenzothiazolium complexes [Ir(C5H4{NHdC(R)S-1})(RCN)(PPh3)2][PF6]2
[R = Me (6a); p-tolyl (6b)], where the iridium occupies a ring junction position.
Introduction
tethering arms have also been formed by C-protonation of
the metallafuran rings of these metallabenzofurans.6,7 In this
paper, we now report that the new fused heterocyclic ring
metallabenzenes, the cationic iridabenzothiazolium com-
plexes [Ir(C5H4{NHdC(R)S-1})(RCN)(PPh3)2][PF6]2 [R =
Me (6a); p-tolyl (6b)], can be prepared by the formal [2 þ 3]
cycloaddition reaction between organonitriles and the η2-
C(S)Ir function of the cationic iridabenzene [Ir(C5H4{S-1})-
(MeCN)(PPh3)2][CF3SO3] (3) in the presence of acid. The
crystal structures of 3 and 6b are also reported.
Metallabenzenes have now become a well-established class
of metalla-aromatic compounds, and a considerable number
of papers have appeared addressing the syntheses, structures,
reactions, and bonding of these compounds.1 In contrast,
stable metallabenzenoids with fused benzene or heterocyclic
rings are much rarer. Reported examples include an irida-
naphthalene2 and an osmanaphthalene,3 an iridabenzothio-
phene,4 as well as ruthena-5,6 and osmabenzofurans.7 The
fused heterocyclic ring metallabenzenes were prepared using
two different synthetic approaches. The iridabenzothio-
phene was obtained by the cycloaddition of two methylpro-
piolate molecules to a thiocarbonyl ligand to form a fused
iridacyclobutadiene iridathiophene complex followed by the
insertion of both carbon atoms of a third methylpropiolate
into the four-membered iridacyclic ring.4 The metallabenzo-
furans formally resulted from metal-mediated cyclization
reactions of methylpropiolate and coordination to the
metal center of the carbonyl oxygen of incipient metallaben-
zene ester substituents.5,7 Metallabenzenes with saturated
Results and Discussion
In a recent paper, we noted that the neutral thiocarbonyl
iridacyclopentadiene Ir(C4H4)Cl(CS)(PPh3)2 can be pre-
pared by the treatment of [Ir(CS)(MeCN)(PPh3)2][CF3SO3]
(1) first with ethyne and then chloride.8 Ir(C4H4)Cl(CS)-
(PPh3)2 resists rearrangement on heating in solution, but
when heated in the presence of methyl triflate, S-methylation
and migratory insertion ensues, and after the addition of
chloride, the neutral iridabenzene Ir(C5H4{SMe-1})Cl2-
(PPh3)2 can be isolated.8 We have investigated this reaction
in more detail with the aim of discovering a way to induce a
migratory insertion reaction of the iridacyclopentadiene and
CS groups without concomitant alkylation of the sulfur
atom. Our interest in this approach was inspired by the
expectation that the η2-C(S) function of the resulting irida-
benzene could serve as an important reaction center for the
development of new metallabenzene chemistry. Because
migratory insertions of σ-organyl and CS ligands may be
more favorable in cationic complexes,9 we focused our
*Corresponding author. E-mail: lj.wright@auckland.ac.nz.
(1) (a) Bleeke, J. R. Chem. Rev. 2001, 101, 1205–1227. (b) Landorf, C.
W.; Haley, M. M. Angew. Chem., Int. Ed. 2006, 45, 3914–3916. (c) Wright,
L. J. J. Chem. Soc., Dalton Trans. 2006, 1821–1827.
(2) Paneque, M.; Posadas, C. M.; Poveda, M. L.; Rendon, N.;
Salazar, V.; Onate, E.; Mereiter, K. J. Am. Chem. Soc. 2003, 125,
ꢀ
~
9898–9899.
(3) Liu, B.; Xie, H.; Wang, H.; Wu, L.; Zhao, Q.; Chen, J.; Wen, T. B.;
Cao, Z.; Xia, H. Angew. Chem., Int. Ed. 2009, 48, “Early View” DOI:
10.1002/anie.200902238.
(4) Clark, G. R.; Lu, G.-L.; Roper, W. R.; Wright, L. J. Organome-
tallics 2007, 26, 2167–2177.
(5) Yamazaki, H.; Aoki, K. J. Organomet. Chem. 1976, 122, C54–
C58.
(6) Clark, G. R.; O’Neale, T. R.; Roper, W. R.; Tonei, D. M.; Wright,
L. J. Organometallics 2009, 28, 567–572.
(7) Clark, G. R.; Johns, P. M.; Roper, W. R.; Wright, L. J. Organo-
metallics 2006, 25, 1771–1777.
(8) Clark, G. R.; Johns, P. M.; Roper, W. R.; Wright, L. J. Organo-
metallics 2008, 27, 451–454.
(9) Green, J. C.; Hector, A. L.; Hill, A. F.; Lin, S.; Wilton-Ely, J. D. E.
T. Organometallics 2008, 27, 5548–5558.
r
pubs.acs.org/Organometallics
Published on Web 08/24/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 18, 2009 5537
Scheme 1
Figure 1. Molecular structure of 3 with thermal ellipsoids at the
50% probability level. Hydrogen atoms on the phenyl rings and
the triflate counterion have been omitted for clarity.
(see the Experimental Section). When carried out in this way,
the overall yield of pure 3 based on IrCl(CS)(PPh3)2 is 91%,
and this is one of the highest percentages reported for a
metallabenzene synthesis.
studies on the cationic thiocarbonyl iridacyclopentadiene
[Ir(C4H4)(CS)(MeCN)(PPh3)2][CF3SO3] (2).
The crystal structure of 3 has been determined, and the
molecular structure is shown in Figure 1 (crystal data for 3 as
well as 6b are given in the Supporting Information). The
metallabenzene ring and the acetonitrile ligand occupy the
equatorial positions, and the two trans-PPh3 ligands are axial
with P1-Ir-P2 = 169.768(16)°. The iridabenzene ring is
nearly planar, with the iridium atom deviating the most
Complex 2 is formed when a solution of 1 is treated with
ethyne, and isolation of pure samples is possible by the
careful addition of hexane (see Scheme 1). Characterizing
data for 2 and the other new compounds are given in the
Experimental Section. The ring-numbering system used for
discussion of the NMR spectra is indicated in Scheme 1.
The metal-bound carbon atoms of the iridacyclopenta-
diene ring in 2 appear in the 13C NMR spectrum at 152.6 and
136.0 ppm, and the signals for the protons attached to
these carbon atoms are observed in the 1H NMR spectrum
at 7.20 and 6.53 ppm. Unlike the related neutral complex
Ir(C4H4)Cl(CS)(PPh3)2,8 we have found that pure samples of
2 undergo migratory insertion on heating under reflux in
dichloromethane and that complete rearrangement to the
cationic iridabenzene 3 occurs after 15 h under these condi-
tions (see Scheme 1). The metal-bound carbon atoms in the
iridabenzene 3 display low-field resonances in the 13C NMR
spectrum at 243.9 (C1) and 176.9 (C5) ppm. The proton H5
that is attached to C5 also gives rise to a very low-field signal
in the 1H NMR spectrum at 12.47 ppm.
These resonances, which are shifted conspicuously down-
field compared to those observed for the corresponding
nuclei in the iridacyclopentadiene 2, are consistent with
increased π bonding between the metal and ring carbon
atoms in 3 and are a characteristic feature of metallaben-
zenes.1 As expected, the other metallabenzene ring atoms in 3
give rise to signals in the 1H and 13C NMR spectra that fall in
the normal aromatic regions [7.50 (H3), 6.81 (H4), and 6.24
(H2) ppm and 153.9 (C3), 127.4 (C4), and 117.6 (C2) ppm,
respectively]. The single resonance observed for the two
triphenylphosphine ligands in the 31P NMR spectrum at
5.77 ppm indicates that these groups are mutually trans in
solution. One important aspect of the synthesis of 3 is that
the three steps starting from IrCl(CS)(PPh3)2 can be carried
out in one pot without isolation and purification of 1 and 2
˚
[0.039(1) A] from the mean plane through Ir, C1-C5, and
˚
˚
S(1). The Ir-C1 [1.933(2) A] and Ir-C5 [1.989(2) A] distances
are relatively short and are consistent with these bonds
having some multiple character.
There is a very slight but significant alternation in the
length of the C-C distances within the iridabenzene ring
˚
˚
[C1-C2, 1.398(3) A; C2-C3, 1.366(4) A; C3-C4, 1.421(4)
˚
˚
A; C4-C5, 1.365(3) A], although all distances clearly fall in
the aromatic range and are typical of those observed in other
metallabenzenes.1
An important aspect of the structure of 3 is the η2-C(S)
function associated with the iridabenzene ring. Within this
˚
group, the Ir-S distance is 2.6325(6) A, the C1-S distance is
˚
1.664(2) A, and the Ir-C1-S angle is 93.80(9)°. In compar-
ison, for the related neutral osmabenzene Os(C5H2{S-1}-
{Me-2}{Me-5})(CO)(PPh3)2,10 the Os-S distance is shorter
˚
˚
[2.4990(12) A], the Os-C(S) distance is longer [1.689(6) A],
and the Os-C-S angle is smaller (84.00°). This indicates
that in 3 the sulfur of the η2-C(S) function does not interact as
strongly with the metal as it does in the related osmabenzene.
The Ir-S interaction in 3 is also weaker than that found in
the dihaptothiocarbamoyl complex Ir(η2-C(S)NMe2)Cl2-
(PPh3)2,11 where the relevant parameters are as follows:
˚
˚
Ir-S, 2.4265(17) A; C-S, 1.704(7) A; Ir-C-S, 82.3(3)°.
(10) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J.
J. Organomet. Chem. 2001, 623, 109–115.
(11) Hill, A. F.; Tocher, D. A.; White, A. J. P.; Williams, D. J.;
Wilton-Ely, J. D. E. T. Organometallics 2005, 24, 5342–5355.

5538 Organometallics, Vol. 28, No. 18, 2009
Dalebrook and Wright
Although the iridabenzene 3 is cationic, the sulfur atom of
the η2-C(S) function still shows significant nucleophilic
character, and this is probably enhanced as a result of the
relatively weak Ir-S interaction noted above. The addition
of methyl triflate to 3 in a dichloromethane solution contain-
ing acetonitrile results in S-methylation, and the red dica-
tionic iridabenzene [Ir(C5H4{SMe-1})(MeCN)2(PPh3)2]-
[PF6]2 (4) can be isolated after the addition of NH4PF6 in
ethanol (see Scheme 1). In the 1H NMR spectrum, the
iridabenzene protons of 4 appear at 11.59 (H5), 7.03 (H4),
6.90 (H3), and 6.29 (H2) ppm and the methyl protons of the
two inequivalent acetonitrile ligands are observed at 2.17 and
1.99 ppm. In the 31P NMR spectrum, a singlet at -2.45 ppm
is observed for the two mutually trans phosphorus atoms.
Attempts were made to synthesize the analogue of 4 that
has an SH rather than an SMe iridabenzene ring substituent
by treating a dichloromethane/acetonitrile solution of 3 with
triflic acid. The brown solution of 3 immediately turned red
upon the addition of the acid, but a pure sample of the red
product could not be obtained either by solvent evaporation
or by the addition of a precipitating solvent such as hexane.
In an attempt to isolate the product in this red solution as a
hexafluorophosphate salt, an ethanol solution of NH4PF6
was added. Unexpectedly, this caused the red solution to
quickly turn deep green, and upon removal of the dichlor-
omethane solvent under reduced pressure, dark-green
crystals of the iridabenzothiazolium complex [Ir(C5H4-
{NHdC(Me)S-1})(MeCN)(PPh3)2][PF6]2 (6a) were isolated
in high yield (see Scheme 1). The ν(NH) band of 6a is
Figure 2. Molecular structure of 6b with thermal ellipsoids at
the 50% probability level. The triphenylphosphine phenyl rings
and one hexafluorophosphate counterion have been omitted for
clarity. The included PF6 anion is disordered over two sites,
and only the most popular orientation is depicted.
-
˚
plane through Ir, C1-C6, S, and N1 is 0.064(3) A for N1),
with iridium occupying a ring junction position. The Ir-C1
˚
˚
[1.953(5) A] and Ir-C5 [2.009(5) A] distances are similar to
those found in 3 and the related neutral iridabenzene Ir-
˚
[C5H4(SMe-1)]Cl2(PPh3)2 [Ir-C1, 1.993(4) A; Ir-C5,
8
˚
1.992(4) A]. The C-C distances around the iridabenzene
˚
˚
ring of 6b [C1-C2 1.396(7) A; C2-C3, 1.385(7) A; C3-C4,
1
observed in the IR spectrum at 3289 cm-1. In the H and
˚
˚
1.402(7) A; C4-C5, 1.360(7) A] are all close to normal
aromatic bond lengths and show no significant bond-length
alternation. Within the iridathiazolium ring, the C1-S and
13C NMR spectra, the chemical shifts of the iridabenzene
ring protons [12.35 (H5), 6.86 (H2), 6.75 (H4), and 6.55 (H3)
ppm] and carbon atoms [232.3 (C1), 210.9 (C5), 170.2 (C3),
127.2 (C4), 125.5 (C2), and 123.5 ppm] are very close to those
observed in 3 and 4, suggesting that the aromatic character of
this six-membered ring is not diminished by the fused
thiazolium ring. The NH signal is observed in the 1H
NMR spectrum as a broad singlet at 10.23 ppm that inte-
grates for one proton. The thiazolium ring carbon atom, C6,
is observed at 190.0 ppm in the 13C NMR spectrum, a
position considerably downfield from the nitrile carbon
(C8, 128.3 ppm) of the coordinated acetonitrile ligand.
The cyclization reaction that produces the fused thiazo-
lium ring is not restricted to acetonitrile. If a dichloro-
methane solution of 3 containing p-tolunitrile is treated
first with triflic acid and then an ethanol solution of NH4PF6,
the iridabenzothiazolium complex [Ir(C5H4{NHdC(p-
tolyl)S-1})(p-tolylCN)(PPh3)2][PF6]2 (6b) can be isolated
from the solution (see Scheme 1) in good yield. Complex
6b is an analogue of 6a, and the 1H and 13C NMR chemical
shifts for the corresponding ring protons and carbon atoms
in the fused iridabenzothiazolium ring are very similar. The
crystal structure of 6b has been determined, and the molec-
ular structure is shown in Figure 2. The solution of the
structure was complicated because there was disorder invol-
ving the solvents of crystallization, one PF6- anion, and two
of the phenyl rings on the PPh3 ligands. Details of how each
of these disorder problems was resolved are given in the
Supporting Information. There was no disorder associated
with the iridabenzothiazolium group.
˚
S-C6 distances are 1.754(5) and 1.757(5) A, respectively.
These are similar to the distances recorded for the corre-
sponding bonds in the 2-methylbenzo[d]thiazolium cation
12
˚
[1.717(9) and 1.741(9) A, respectively]. The C6-N1 dis-
tance within the iridathiazolium ring of 6b is 1.290(6) A,
˚
which is consistent with a C-N double bond. The corre-
sponding C-N bond distance in the 2-methylbenzo-
[d]thiazolium cation is 1.278(11) A. One of the PF6
12
-
˚
anions in 6b makes a close approach to N1 (see Figure 2).
-
The fluorine atoms of this PF6 anion are disordered over
two sites and were refined with occupancies of 0.669 (F1-6)
˚
and 0.331 (F1a-6a). The F1 N1 distance of 2.969(9) A
3 3 3
is smaller than the sum of the covalent radii of N and F
˚
(ca. 3.15 A)13 and is close to the upper range of N-H
F
3 3 3
hydrogen-bonded distances,14,15 pointing to the presence of
a weak hydrogen bond between these atoms. The F1a N1
3 3 3
˚
distance, however, is longer at 3.45(2) A, indicating that
there is no significant interaction in this case.
In order to learn more about the cyclization reactions that
produce these iridabenzothiazolium cations, the conversion
of 3 to 6a was followed by 1H NMR spectroscopy. A sample
of the cationic iridabenzene 3 was dissolved in CD2Cl2
containing 10 equiv of NCMe. Upon the addition of 5 equiv
of CF3SO3H to this brown solution, the color immediately
changed to bright red. On the basis of the 1H and 31P NMR
(12) Teo, S.-B.; Teoh, S.-G.; Okechukwu, R. C.; Fun, H.-K. J.
Organomet. Chem. 1993, 454, 67–71.
(13) Bondi, A. J. Phys. Chem. 1964, 68, 441.
The geometry about iridium is approximately octahedral,
with the two PPh3 ligands mutually trans. The fused five- and
six-membered metallacyclic rings form an essentially planar
bicyclic ring system (the maximum deviation from the mean
(14) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements;
Pergamon Press: New York, 1989; ISBN 0-08-022057-6.
(15) Braga, D.; Giaffreda, S. L.; Polito, M.; Grepioni, F. Eur. J.
Inorg. Chem. 2005, 2737–2746.

Article
Organometallics, Vol. 28, No. 18, 2009 5539
spectra of this solution, the red product formed was
tentatively formulated as the SH-substituted iridaben-
zene [Ir(C5H4{SH-1})(MeCN)2(PPh3)2][CF3SO3]2 (5) (see
Scheme 1). The 1H NMR spectrum revealed new signals at
11.50 (1H, H5), 7.23 (1H, SH), 7.04 (1H, H4), 6.90 (1H, H3),
6.89 (1H, H2), 2.03 (3H, NCCH3), and 2.02 (3H, NCCH3)
ppm. In the 31P NMR spectrum, a singlet at -0.83 ppm was
observed for the two PPh3 ligands. These signals are remark-
ably similar to those observed for the red SCH3-substituted
iridabenzene 4 described above, with the exception that the
SCH3 signal in 4 was replaced by a new signal at 7.23 ppm
(SH) and the resonance for H2, which is vicinal to SH, shows
a slight downfield shift. If protected from the atmosphere,
solutions of 5 formed in this way are stable for days.
The addition of ethanol (ca. 15 equiv) to a red CD2Cl2
solution of 5 caused the color to turn deep green rapidly,
and signals identical with those observed for 6a were
observed in the 1H and 31P NMR spectra. This transforma-
tion to 6a was also brought about by the addition of water
(ca. 15 equiv) to the acidic CD2Cl2 solution. These results
confirm that NH4PF6, which is added in the synthesis of 6a
and 6b to facilitate the isolation of crystalline products, does
not play a role in the formation of the iridabenzothiazolium
cations. We do not have any evidence concerning the
mechanism for the conversion of 5 into 6a. However, one
possibility is that the addition of the proton acceptors
ethanol or water to the solution containing 5 facilitates
partial deprotonation of the SH group. The deprotonated
sulfur atom then attacks the adjacent coordinated nitrile
carbon atom, and the nitrogen atom is protonated to form
6a. Ample precedents for reactions of this type are provided
by the numerous addition reactions that have been reported
for metal-activated organonitriles with water, alcohols,
amines, and related compounds.16 It has also been reported
recently that acetonitrile can undergo a formal [2 þ 4]
cycloaddition reaction with an osmium hydride, vinylcar-
byne complex to give an osmapyridinium derivative.17
Deprotonation of the nitrogen in this metallacycle with
n-butyllithium gives the corresponding osmapyridine
without promoting any reversal of the cycloaddition. Metal-
coordinated organonitriles have also been reported to under-
go [2 þ 3] cycloaddition reactions with azides or nitrones to
form tetrazoles or oxadiazolines, respectively.16 The overall
transformation of 3 into 6a, which can be described as a
metal-mediated formal [2 þ 3] cycloaddition between acet-
onitrile and the η2-C(S)Ir group, is most closely related to
these latter reactions.
Concluding Remarks
In conclusion, the cationic iridabenzene 3 can be formed in
high yield through a one-pot reaction sequence starting from
IrCl(CS)(PPh3)2. The nucleophilic sulfur atom in 3 is rapidly
alkylated by methyl triflate, leading to the iridabenzene 4.
However, upon treatment of 3 with acetonitrile, triflic acid,
and ethanol, the iridabenzothiazolium complex 6a is formed
in high yield. The analogue 6b is obtained if the acetonitrile in
this reaction is replaced by p-tolunitrile. The reactions that
form these new fused heterocyclic ring iridabenzenes involve
formal [2 þ 3] cycloaddition reactions between the organo-
nitrile and the η2-C(S)Ir group of 3. This cycloaddition
reaction is reversible, and upon treatment of 6a or 6b with
base in the presence of acetonitrile, the iridathiazolium
nitrogen is deprotonated and 3 is returned quantitatively.
Experimental Section
General Comments. Standard laboratory procedures were
followed, as have been described previously.18 In addition,
acetonitrile was distilled from calcium hydride before use. IrCl-
(CS)(PPh3)2 was prepared by the literature method.19
IR spectra (4000-400 cm-1) of solid samples were recorded
on a Perkin-Elmer Spectrum 400 spectrometer using an ATR
accessory. NMR spectra were obtained on a Bruker Avance 300
at 25 °C. 1H, 13C, 31P, and 19F NMR spectra were obtained by
operating at 300.13 (1H NMR), 75.48 (13C NMR), 121.50
(31P NMR), and 282.4 (19F NMR) MHz, respectively. Reso-
1
nances are quoted in ppm and H NMR spectra referenced to
either tetramethylsilane (0.00 ppm) or the proteoimpurity in the
solvent (7.25 ppm for CHCl3). 13C NMR spectra were refer-
enced to CDCl3 (77.00 ppm), 31P NMR spectra to 85% ortho-
phosphoric acid (0.00 ppm) as an external standard, and 19F
NMR spectra to CFCl3 (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. Elemen-
tal analyses were obtained from the Microanalytical Labora-
tory, University of Otago, Dunedin, New Zealand.
[Ir(MeCN)(CS)(PPh3)2][CF3SO3] (1). An improved proce-
dure for the synthesis of 18 is as follows. With rigorous exclusion
of moisture, IrCl(CS)(PPh3)2 (1.500 g, 1.88 mmol) and AgCF3-
SO3 (0.489 g, 1.90 mmol, 1.01 equiv) were added to a flask
followed by acetonitrile (75 mL). A precipitate of silver chloride
formed immediately, and the solution turned bright orange. The
mixture was stirred for 20 min, then the acetonitrile removed
in vacuo, and the orange solid dried under vacuum for a further 1
h. The residue was extracted with dichloromethane (70 mL) and
filtered through a Celite pad to remove AgCl. Pure 1 was
crystallized as a bright-orange crystalline solid by the slow
addition of n-hexane (yield = 1.362 g, 76%). Anal. Calcd for
C40H33F3IrNO3P2S2: C, 50.52; H, 3.50; N, 1.47. Found: C,
50.38; H, 3.43; N, 1.46. The spectral data were identical with
those previously reported.8
The iridabenzothiazolium complexes 6a and 6b are stable
for days in solutions that contain traces of acid, even upon
exposure to the atmosphere. However, in the absence of acid,
the stability of these compounds in solution is much reduced.
Upon the addition of bases such as NEt3 or NaO2CCH3 to
solutions of 6a (or 6b in the presence of acetonitrile), the
iridathiazolium nitrogen atom is rapidly deprotonated and
the iridabenzene 3 is reformed almost quantitatively. The
cycloaddition reactions that form 6a and 6b are therefore
reversible, unlike the situation with the osmapyridinium
complex described above.
[Ir(C4H4)(CS)(MeCN)(PPh3)2][CF3SO3] (2). Ethyne was
slowly bubbled at atmospheric pressure through a dichloro-
methane solution (70 mL) containing 1 (1.79 g, 1.88 mmol) for
1 h at 10 °C, turning the solution yellow. Pure 2 was crystallized
as a yellow solid by the slow addition of n-hexane at low
temperature to prevent isomerization to the iridabenzene 3
(see below) (yield = 1.36 g, 72%). Anal. Calcd for C44H37NO3-
F3IrP2S2 H2O: C, 51.76; H, 3.85; N, 1.37. Found: C, 51.97; H,
3
4.01; N, 1.33 (NMR spectroscopy showed the presence of ca.
1 mol equiv of water in the analytical sample). MS (FABþ,
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Organometallics 1996, 15, 1793.
(19) Lu, G.-L.; Roper, W. R.; Wright, L. J.; Clark, G. R. J.
Organomet. Chem. 2005, 690, 972.

5540 Organometallics, Vol. 28, No. 18, 2009
Dalebrook and Wright
NBA). Calcd for C43H37193IrNP2S [M - (CF3SO3-]þ: m/z
854.17514. Found: m/z 854.17604. IR (cm-1): 2291 ν(CN);
1305 ν(CS); 1264, 1141, 1028, 636 (CF3SO3-). 1H NMR
(CDCl3, δ): 7.13-7.75, m, 30H (PPh3), 7.20 (partially obscured
by phenyl, d(from DQF-COSY), H1 or H4), 6.53 (d, 3JHH = 6.0
Hz, 1H, H1 or H4), 5.84 (m, 2H, H2 and H3), 1.94 (s, 3H,
CH3CN). 13C NMR (CDCl3, δ): 279.1 (t, 2JCP = 8.3 Hz, CS),
152.6 (t, 2JCP = 10.6 Hz, C1 or C4), 144.5 (t, 3JCP = 3.0 Hz, C2
or C3), 142.4 (s, C2 or C3), 136.0 (t, 2JCP = 6.8 Hz, C1 or C4),
134.7 (t0,18 3,5JCP = 10.6 Hz, m-PPh3), 131.4 (s, p-PPh3), 128.0
[Ir(C5H4{NHdC(Me)S-1})(MeCN)(PPh3)2][PF6]2 (6a).
(100 mg, 0.100 mmol) was dissolved in dichloromethane
(5 mL), and acetonitrile (52 μL, 1.0 mmol) and then triflic acid
(18 μL, 0.20 mmol) were added. The solution instantly turned
red upon the addition of the acid. After 15 min, ammonium
hexafluorophosphate (96 mg, 0.59 mmol) dissolved in ethanol
(5 mL) was added to the stirred solution. The solution turned
green, and a green precipitate was formed. Further precipitation
was effected by the removal of dichloromethane under reduced
pressure, and dark-green crystals of pure 6a were collected by
filtration and washed with ethanol (2 ꢀ 3 mL, 100 mg, 81%).
Anal. Calcd for C45H41F12IrN2P4S: C, 45.57; H, 3.48; N, 2.36.
Found: C, 45.55; H, 3.68; N, 2.38. MS (FABþ, NBA). Calcd for
C45H41193IrN2P3SF6 [M - (PF6-)]þ: m/z 1041.173 70. Found:
m/z 1041.174 58. IR (cm-1): 3289 ν(NH); 2325, 2295 ν(CN); 824
ν(PF). 1H NMR (CD2Cl2, δ): 12.35 (d, 3JHH = 8.4 Hz, 1H, H5),
3
2,4
1,3
(t0,
J
= 10.6 Hz, o-PPh3), 126.8 (t0,
J
CP
= 58.9 Hz, i-
CP
PPh3), 123.9 (s, CH3CN), 2.9 (s, CH3CN). 31P NMR (CDCl3, δ):
5.80. 19F NMR (CDCl3, δ): -78.99.
[Ir(C5H4{S-1})(MeCN)(PPh3)2][CF3SO3] (3). 2 (1.89 g, 1.88
mmol) was dissolved in dichloromethane (70 mL) and the
solution heated under reflux for 15 h, over which time the
solution turned brown. The solution was cooled to room
temperature and n-hexane slowly added to afford brown crystals
of pure 3 (1.72 g, 91%). Anal. Calcd for C44H37F3IrNO3P2S2: C,
52.69; H, 3.72; N, 1.40. Found: C, 52.66; H, 3.86; N, 1.38. The
crystal used for X-ray structure determination was grown from
dichloromethane/n-hexane and contained one molecule of di-
chloromethane per molecule of complex. MS (FABþ, NBA).
Calcd for C41H34193IrNP2Sþ [M - (CF3SO3-) - MeCN]þ: m/z
813.14859. Found: m/z 813.14834. IR (cm-1): 1261, 1150, 1030,
637 (CF3SO3-). 1H NMR (CDCl3, δ): 12.47 (d, 3JHH = 6.3 Hz,
1H, H5), 7.27-7.50 (m, 30H, PPh3), 7.50 (partially obscured
by phenyl, m, 1H, H3), 6.81 (apparent t, 7.8 Hz, 1H, H4), 6.24 (d,
3JHH = 9.0 Hz, 1H, H2), 1.83 (s, 3H, CH3CN). 13C NMR
(CDCl3, δ): 243.9 (t, 2JCP = 5.3 Hz, C1), 176.9 (t, 2JCP = 8.3 Hz,
C5), 153.9 (s, C3), 134.2 (t0, 3,5JCP = 10.6 Hz, m-PPh3), 131.5 (s,
10.23 (br s, 1H, NH), 7.36-7.58 (m, 30H, PPh3), 6.86 (d, 3JHH
=
8.7 Hz, 1H, H2), 6.75 (apparent t, 8.1 Hz, 1H, H4), 6.55
(apparent t, 7.8 Hz, 1H, H3), 1.92 (s, 3H, CH3CN), 1.87 (s,
3H, CH3C(N)S). 13C NMR (CD2Cl2, δ): 232.3 (s, C1), 210.9 (s,
C5), 190.0 (s, C6), 170.2 (s, C3), 134.6 (t0, 3,5JCP = 9.0 Hz, m-
2,4
PPh3), 133.1 (s, p-PPh3), 129.4 (t0,
J
CP
= 10.6 Hz, o-PPh3),
128.3 (s, CH3CN), 127.2 (s, C4), 125.5 (s, C2), 123.5 (t0, 1,3JCP
=
58.9 Hz, i-PPh3), 21.9 (s, CH3C(N)S), 3.0 (s, CH3CN). 31P NMR
(CD2Cl2, δ): 12.18 (s, PPh3), -144.18 (sep, 1JPF = 711 Hz, PF6).
19F NMR (CD2Cl2, δ): -73.2 (d, 1JFP = 709 Hz, PF6).
[Ir(C5H4{NHdC(p-tolyl)S-1})(p-tolyl-CN)(PPh3)2][PF6]2 (6b).
6b was prepared by the same procedure as that used for 6a, except
that the acetonitrile was replaced by p-tolunitrile (117 mg, 1.00
mmol; yield=107 mg, 80%). Anal. Calcd for C57H49F12IrN2P4S
3
EtOH: C, 45.57; H, 3.48; N, 2.36. Found: C, 45.55; H, 3.68; N, 2.38
(NMR spectroscopy showed the presence of 1 mol equiv of EtOH
of crystallization). The crystal for X-ray structural analysis was
grown from dichloromethane/n-hexane and proven to be a di-
chloromethane solvate. IR (cm-1): 3291 ν(NH); 2258 ν(CN); 824
ν(PF). 1H NMR (CD2Cl2, δ): 12.87 (d, 3JHH=8.4 Hz, 1H, H5),
10.36 (br s, 1H, NH), 7.55-7.26 (m, 38H, PPh3 and tolyl CH),
7.22 (apparent t (partially obscured), H4), 6.91 (d, 3JHH= 8.7 Hz,
1H, H2), 6.65 (apparent t, 7.8 Hz, 1H, H3), 2.49 (s, 3H, tolyl CH3),
2.44 (s, 3H, tolyl CH3). 13C NMR (CD2Cl2, δ): 229.8 (s, C1), 209.7
(s, C5), 185.6 (s, C6), 168.8 (s, C3), 147.0 (s, tolyl CCH3), 146.5 (s,
tolyl CCH3), 134.1 (t0, 3,5JCP=10.6 Hz, m-PPh3), 133.9 (s, tolyl
CH), 132.4 (s, p-PPh3), 129.60 (s, tolyl CH), 129.58 (s, tolyl CH),
129.2 (t0, 2,4JCP=11.3 Hz, o-PPh3), 128.1 (s, tolyl C-C6 or tolyl
C-CN), 128.0 (s, tolyl CH), 127.4 (s, C4), 126.6 (s, tolyl C-C6
or tolyl C-CN), 125.4 (s, C2), 123.0 (t0, 1,3JCP=58.9 Hz, i-PPh3),
p-PPh3), 128.5 (t0, 2,4JCP = 10.6 Hz, o-PPh3), 126.8 (t0, 1,3JCP
56.6 Hz, i-PPh3), 127.5 (s, CH3CN), 127.4 (t, JCP = 1.9 Hz,
CH3CN), 117.6 (s, C2) 2.4 (s, C7). 31P NMR (CDCl3, δ): 5.77.
19F NMR (CDCl3, δ): -79.03.
=
3
One-Pot Synthesis of 3 Starting from IrCl(CS)(PPh3)2. The
procedures for synthesizing 1 and 2 detailed above were fol-
lowed except that solid products were not isolated. Instead, the
dichloromethane solutions of 1 and 2 obtained were used
directly in the subsequent reactions. Compound 3 was prepared
from the dichloromethane solution of 2 and isolated as indicated
above in an overall yield of 91% based on IrCl(CS)(PPh3)2.
[Ir(C5H4{SMe-1})(MeCN)2(PPh3)2][PF6]2 (4). 3 (100 mg,
0.100 mmol) was dissolved in dichloromethane (5 mL), and
acetonitrile (52 μL, 1.0 mmol) and then methyl triflate (23 μL,
0.20 mmol) were added. The solution instantly turned red upon
the addition of methyl triflate. After 15 min, ammonium hexa-
fluorophosphate (81 mg, 0.50 mmol) dissolved in ethanol (5 mL)
was added to the stirred solution and dichloromethane removed
under reduced pressure. Maroon crystals of pure 4 were col-
lected by filtration and washed with ethanol (2 ꢀ 3 mL, 103 mg,
86%). Anal. Calcd for C46H43F12IrN2P4S: C, 46.04; H, 3.61; N,
2.33. Found: C, 45.74; H, 3.48; N, 2.33. MS (FABþ, NBA).
Calcd for C46H43193IrN2PSF6 [M - (PF6-)]þ: m/z 1055.189 35.
Found: m/z 1055.186 92. IR (cm-1): 2320, 2295 ν(CN); 824
104.5 (s, tolyl CN), 22.1 (s, tolyl CH3), 21.7 (s, tolyl CH3).
31P NMR (CD2Cl2, δ): 11.68 (s, PPh3), -143.96 (sep, JPF
1
=
713 Hz, PF6). 19F NMR (CD2Cl2, δ): -73.1 (d, 1JFP = 712 Hz,
PF6).
Acknowledgment. We thank The University of Auck-
land for granting a scholarship to A.F.D. and for support
of this work through grants-in-aid. We also thank
Professor W. R. Roper for valuable discussions and
comments.
1
3
ν(PF). H NMR (CD2Cl2, δ): 11.59 (d, JHH = 8.4 Hz, 1H,
H5), 7.53-7.34 (m, 30H, PPh3), 7.03 (apparent t, 7.5 Hz, 1H,
H4), 6.90 (apparent t, 7.2 Hz, 1H, H3), 6.29 (d, 3JHH = 9.3 Hz,
1H, H2), 2.52 (s, 3H, SCH3), 2.17 (s, 3H, CH3CN), 1.99, (s, 3H,
CH3CN). 13C NMR (CD2Cl2, δ): 224.4, (t, 2JCP = 4.5 Hz, C1),
Supporting Information Available: Crystal and refinement
data as well as crystal data in CIF format for complexes 3 and
6b. This material is available free of charge via the Internet at
http://pubs.acs.org. The atom coordinates can also be obtained,
upon request, from the Director, Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge, CB2 1EZ, U.K. (fax
þ44-1223-336-033; e-mail deposit@ccdc.cam.ac.uk, or http://
www.ccdc.cam.ac.uk) as supplementary publication nos.
CCDC 739119 and 739118, respectively.
2
3,5
180.9 (t, JCP = 7.5 Hz, C5), 155.4 (s, C3), 134.5 (t0,
J
CP
=
10.6 Hz, m-PPh3), 132.6 (s, p-PPh3), 129.2 (t0, 2,4JCP = 12.0 Hz,
o-PPh3), 127.5 (s, C4), 127.4 (s, CH3CN), 126.5 (s, CH3CN),
125.3 (t0, 1,3JCP = 58.1 Hz, i-PPh3), 123.6 (s, C2), 22.6 (s, SCH3),
3.6 (s, CH3CN), 3.3 (s, CH3CN). 31P NMR (CD2Cl2, δ): -2.45
(s, PPh3), -144.28 (sep, JPF = 711 Hz, PF6). 19F NMR
1
(CD2Cl2, δ): -73.5 (d, 1JFP = 709 Hz, PF6).