Reactions of 16-electron iridium(III) dithiolene complexes with diazoalkanes: Formation and properties of novel mononuclear and binuclear alkylidene adducts of iridium dithiolene complexes

Article abstract of DOI:10.1021/om050169r

Some 16-electron pentacoordinated iridium dithiolene complexes were synthesized by the reactions of [Cp*Ir(Cl)(μ-Cl)]₂ (Cp* = C₅Me₅) with 1,3-dithiol-2-one derivatives. The iridium dithiolene complex [Cp*Ir{S₂C₂(COOMe) ₂}] (1) reacted with ethyl diazoacetate or (trimethylsilyl) diazomethane to give the 1:1 alkylidene adducts of iridium dithiolene complexes [Cp*Ir{S₂C₂(COOMe)₂}(CHR)] (R = COOEt (3a), SiMe₃ (3b)), respectively. The structures of complexes 3a,b were determined by X-ray crystal structure analyses: the COOEt unit of complex 3a is located at the exo position with respect to the iridadithiolene ring, and the SiMe₃ group of complex 3b is located at the corresponding endo position with respect to the same ring. In solution, the endo (3b-1) and exo (3b-2) isomers of complex 3b were observed. In an electrochemical investigation, the oxidized species of the exo isomer (3b-2⁺) was isomerized to the stable endo isomer (3b-l⁺). The reaction of complex 1 with diazomethane gave the novel 2:2 methylene adduct of a binuclear iridium dithiolene complex [Cp*Ir-{S₂C₂(COOMe) ₂}(CH₂)][Cp*Ir{SC₂(COOMe) ₂S}(CH₂)] (4). This complex 4 has a five-membered iridadithiolene ring and a six-membered iridacycle. The dimeric complex 4 was also formed from the desilylation of the monomeric complex 3b with TBAF. The complex (5a) that includes a six-membered iridacycle [Cp*Ir{SC ₂(COOMe)₂S}(CHCOOEt)(P(OMe)₃)] was obtained by the reaction of the alkylidene-bridged complex 3a with trimethyl phosphite. The reactions of complex 3b with HCl gave [Cp*Ir(Cl){S(SCH ₂SiMe₃)C₂(COOMe)₂}] (6b) due to Ir-C bond cleavage.

Full text of DOI:10.1021/om050169r

Organometallics 2005, 24, 2811-2818
2811
Reactions of 16-Electron Iridium(III) Dithiolene
Complexes with Diazoalkanes: Formation and
Properties of Novel Mononuclear and Binuclear
Alkylidene Adducts of Iridium Dithiolene Complexes
Mitsushiro Nomura,*,† Akiko Kusui, and Masatsugu Kajitani*
Department of Chemistry, Faculty of Science and Technology, Sophia University, Kioi-cho 7-1,
Chiyoda-ku, Tokyo 102-8554, Japan
Received March 9, 2005
Some 16-electron pentacoordinated iridium dithiolene complexes were synthesized by the
reactions of [Cp*Ir(Cl)(µ-Cl)]2 (Cp* ) C5Me5) with 1,3-dithiol-2-one derivatives. The iridium
dithiolene complex [Cp*Ir{S2C2(COOMe)2}] (1) reacted with ethyl diazoacetate or (trimeth-
ylsilyl)diazomethane to give the 1:1 alkylidene adducts of iridium dithiolene complexes
[Cp*Ir{S2C2(COOMe)2}(CHR)] (R ) COOEt (3a), SiMe3 (3b)), respectively. The structures
of complexes 3a,b were determined by X-ray crystal structure analyses: the COOEt unit of
complex 3a is located at the exo position with respect to the iridadithiolene ring, and the
SiMe3 group of complex 3b is located at the corresponding endo position with respect to the
same ring. In solution, the endo (3b-1) and exo (3b-2) isomers of complex 3b were observed.
In an electrochemical investigation, the oxidized species of the exo isomer (3b-2+) was
isomerized to the stable endo isomer (3b-1+). The reaction of complex 1 with diazomethane
gave the novel 2:2 methylene adduct of a binuclear iridium dithiolene complex [Cp*Ir-
{S2C2(COOMe)2}(CH2)][Cp*Ir{SC2(COOMe)2S}(CH2)] (4). This complex 4 has a five-
membered iridadithiolene ring and a six-membered iridacycle. The dimeric complex 4 was
also formed from the desilylation of the monomeric complex 3b with TBAF. The complex
(5a) that includes a six-membered iridacycle [Cp*Ir{SC2(COOMe)2S}(CHCOOEt)(P(OMe)3)]
was obtained by the reaction of the alkylidene-bridged complex 3a with trimethyl phosphite.
The reactions of complex 3b with HCl gave [Cp*Ir(Cl){S(SCH2SiMe3)C2(COOMe)2}] (6b) due
to Ir-C bond cleavage.
Introduction
various alkylidene complexes are obtained (Figure 1):
(1) the metal carbene complex having a MdC bond (type
1),5,6 (2) the complex in which an alkylidene group is
bridging into two metal atoms (type 2),7,8 and (3) the
complex in which an alkylidene group is bridging
between a metal and the coordination atom (type 3).9
On the other hand, an alkylidene group occasionally
Alkylidene complexes are useful organometallic com-
plexes for metathesis reactions,1 olefin cyclopropana-
tions,2 and C-H activations of an alkane.3 One of the
synthetic methods for an alkylidene complex is the
reaction of a diazoalkane with a metal complex.4 This
reaction includes the N2 loss of a diazoalkane, and then
(5) (a) Werner, H.; Braun, T.; Daniel, T.; Gevert, O.; Schulz, M. J.
Organomet. Chem. 1997, 541, 127. (b) Schwab, P.; Mahr, N.; Wolf, J.;
Werner, H. Angew. Chem., Int. Ed. Engl. 1993, 32, 1480. (c) Werner,
H. J. Organomet. Chem. 1995, 500, 331.
(6) (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18. (b)
Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2039. (c) Schwab, P.; Grubbs, R. H.; Ziller, J.
W. J. Am. Chem. Soc. 1996, 118, 100. (d) Sanford, M. S.; Valdez, M.
R.; Grubbs, R. H. Organometallics 2001, 20, 5455.
(7) (a) McKeer, I. R.; Sherlock, S. J.; Cowie, M. J. Organomet. Chem.
1988, 352, 205. (b) Chetcuti, M. J.; Grant, B. E.; Fanwick, P. E.
Organometallics 1990, 9, 1345. (c) Dickson, R. S.; Fallon, G. D.; Nesbit,
R. J.; Pain, G. N. Organometallics 1985, 4, 355. (d) Delgado, E.; Hein,
J.; Jeffery, J. C.; Ratermann, A. L.; Stone, F. G. A. J. Organomet. Chem.
1986, 307, C23.
(8) (a) Trepanier, S. J.; Sterenberg, B. T.; McDonald, R.; Cowie, M.
J. Am. Chem. Soc. 1999, 121, 2613. (b) Trepanier, S. J.; Dennett, J. N.
L.; Sterenberg, B. T.; McDonald, R.; Cowie, M. J. Am. Chem. Soc. 2004,
126, 8046. (c) Rowsell, B. D.; Trepanier, S. J.; Lam, R.; McDonald, R.;
Cowie, M. Organometallics 2002, 21, 3228. (d) Dell’Anna, M. M.;
Trepanier, S. J.; McDonald, R.; Cowie, M. Organometallics 2001, 20,
88. (e) Rowsell, B. D.; McDonald, R.; Ferguson, M. J.; Cowie, M.
Organometallics 2003, 22, 2944.
† Present address: Laboratoire Chimie, Inge´nierie Mole´culaire et
Mate´riaux d’Angers (CIMMA), UMR 6200 CNRS-Universite´ d’Angers,
UFR Sciences, Baˆt. K, 2 Bd. Lavoisier, 49045 Angers, France.
(1) (a) Schrock, R. R. J. Mol. Catal. A 2004, 213, 21. (b) Schrock, R.
R.; Hoveyda, A. H. Angew. Chem., Int. Ed. Engl. 2003, 42, 4592. (c)
Tsang, W. C. P.; Jernelius, J. A.; Cortez, G. A.; Weatherhead, G. S.;
Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2003, 125, 2591. (d)
Lesage, A.; Emsley, L.; Chabanas, M.; Coperet, C.; Basset, J.-M. Angew.
Chem., Int. Ed. 2002, 41, 4535. (e) Wakamatsu, H.; Blechert, S. Angew.
Chem., Int. Ed. 2002, 41, 794. (f) Sanford, M. S.; Henling, L. M.; Day,
M. W.; Grubbs, R. H. Angew. Chem., Int. Ed. 2000, 39, 3451.
(2) (a) Padwa, A.; Weingarten, M. D. Chem. Rev. 1996, 96, 223. (b)
Doyle, M. P.; Forbes, D. C. Chem. Rev. 1998, 98, 911. (c) Davies, H.
M. L.; Panaro, S. A. Tetrahedron 2000, 56, 4871.
(3) Davies, H. M. L.; Antoulinakis, E. G. J. Organomet. Chem. 2001,
617-618, 47.
(4) (a) Herrmann, W. A. Adv. Organomet. Chem. 1982, 20, 159. (b)
Herrmann, W. A. Angew. Chem., Int. Ed. Engl. 1978, 17, 800. (c)
Mizobe, Y.; Ishii, Y.; Hidai, M. Coord. Chem. Rev. 1995, 139, 281. (d)
Putala, M.; Lemenovskii, D. A. Russ. Chem. Rev. (Engl. Transl.) 1994,
63, 197.
10.1021/om050169r CCC: $30.25 © 2005 American Chemical Society
Publication on Web 04/30/2005

2812 Organometallics, Vol. 24, No. 11, 2005
Nomura et al.
Scheme 1
Figure 1.
undergoes an addition reaction to a ligand (e.g. coordi-
nated alkyne10).
The reaction of a diazoalkane with a metal complex
does not always give alkylidene complexes directly.11 In
some cases, a diazoalkane reacts with a metal complex
without N2 loss. One such case is the reaction where
the terminal nitrogen atom of a diazoalkane coordinates
a metal center12 or bridges two metal atoms,13 and
another such reaction involves two nitrogen atoms
coordinating to a metal center.14 In most cases, these
diazoalkane complexes cause N2 elimination in the
diazoalkane ligand to form alkylidene complexes;15
however, it has been also reported that an alkylidene
moiety is eliminated to give a N2-bound complex.16
We have studied the chemistry of the metalladithi-
olene ring,17 which consists of one metal, two sulfur
atoms, and two unsaturated carbons. Coordinatively
unsaturated species of metal dithiolene complexes are
well-known, because the π-electron donation of the
dithiolate ligand alleviates the electron deficiency and
the coordinative unsaturation around the transition-
metal center. In such complexes, a Lewis base (e.g. PR3)
is added to the unsaturated metal center,18 and in the
solid state, these often form the dimers of a metal
dithiolene complex.19 We have focused on the reactions
of metal dithiolene complexes with nucleophiles such
as 1,3-dipoles: for example, the cyclopentadienylcobalt
or -rhodium dithiolene complex [CpMIII(S2C2Y2)] (M )
Co, Rh) reacts with diazoalkane to give the coordina-
tively saturated adduct in which an alkylidene bridges
into the metal-sulfur bond of the metalladithiolene ring
(Scheme 1).20 Therefore, this alkylidene complex is
classified into type 3, as noted above (Figure 1). Similar
reactions have been reported by Kang et al. in their
studies of o-carborane dithiolato complexes.21 In addi-
tion, dimethyl diazomalonate (N2C(COOMe)2) reacts
with [CpCo(dmit)] (dmit ) S2C2S2CdS) to form [CoCo-
{S2C2S2CdC(COOMe)2}] by the substitution of a ter-
minal sulfur atom (Scheme 1).22 The square-planar
nickel dithiolene complex [Ni(S2C2Ph2)2] reacts with
diazomethane to cause the elimination of a central
nickel atom, and then the methylene-bridged macrocycle
is formed.23
We report here on the reactions of diazoalkanes with
coordinatively unsaturated iridium dithiolene complexes
[Cp*Ir(S2C2Y2)] to give the alkylidene adducts of iridium
dithiolene complexes. The stereoisomers of alkylidene
adducts were selectively synthesized, and the isomer-
izations of the alkylidene moiety were observed. In
addition, we report on the reaction of diazomethane with
iridium dithiolene complexes. This reaction included
unique alkylidene addition and resulted in an unprec-
edented binuclear complex.
(9) (a) Strecker, B.; Ho¨rlin, G.; Schulz, M.; Werner, H. Chem. Ber.
1991, 124, 285. (b) Strecker, B.; Werner, H. Angew. Chem., Int. Ed.
Engl. 1990, 29, 9, 275.
(10) (a) Nucciarone, D.; Taylor, N. J.; Carty, A. J. Organometallics
1986, 5, 1179. (b) Colborn, R. E.; Dyke, A. F.; Knox, S. A. R.;
Macpherson, K. A.; Orpen, A. G. J. Organomet. Chem. 1982, 239, C15.
(11) (a) Sutton, D. Chem. Rev. 1993, 93, 995. (b) Dartiguenave, M.;
Menu, M. J.; Deydier, E.; Dartiguenave, Y.; Siebald, H. Coord. Chem.
Rev. 1998, 178-180, 623.
(12) (a) Curtis, M. D.; Messerle, L. Organometallics 1987, 6, 1713.
(b) Howard, J. A. K.; James, A. P.; Jelfs, A. N.; de, M.; Nunn, C. M.;
Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1987, 1221. (c) Martin,
J.; Moise, C. J. Organomet. Chem. 1980, 193, C57. (d) Albertin, G.;
Antoniutti, S.; Bordignon, E.; Carrera, B. Inorg. Chem. 2000, 39, 4646.
(e) Werner, H.; Mahr, N.; Wolf, J.; Fries, A.; Laubender, M.; Bleuel,
E.; Garde, R.; Lahuerta, P. Organometallics 2003, 22, 3566.
(13) Hanna, T. A.; Baranger, A. M.; Bergman, R. G. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 653.
(14) (a) Polse, J. L.; Kaplan, A. W.; Andersen, R. A.; Bergman, R.
G. J. Am. Chem. Soc. 1998, 120, 6316. (b) Polse, J. L.; Andersen, R.
A.; Bergman, R. G. J. Am. Chem. Soc. 1996, 118, 8737. (c) Kaplan, A.
W.; Polse, J. L.; Ball, G. E.; Andersen, R. A.; Bergman, R. G. J. Am.
Chem. Soc. 1998, 120, 11649.
(15) (a) Cohen, R.; Rybtchinski, B.; Gandelman, M.; Rozenberg, H.;
Martin, J. M. L.; Milstein, D. J. Am. Chem. Soc. 2003, 125, 6532. (b)
Werner, H.; Stuer, W.; Wolf, J.; Laubender, M.; Weberndorfer, B.;
Herbst-Irmer, R.; Lehmann, C. Eur. J. Inorg. Chem. 1999, 11, 1889.
(c) Werner, H.; Mahr, N.; Frenking, G.; Jonas, V. Organometallics 1995,
14, 619. (d) Messerle, L.; Curtis, M. D. J. Am. Chem. Soc. 1980, 102,
7791.
Results and Discussion
1. Preparations of Iridium Dithiolene Com-
plexes. Dimethyl 1,3-dithiol-2-one-4,5-dicarboxylate,
[OdC{S2C2(COOMe)2}], was treated with 2 equiv of
sodium methoxide in methanol, and the colorless solu-
tion changed to yellow. After the iridium complex
[Cp*Ir(Cl)(µ-Cl)]2 (Cp* ) C5Me5) was added into the
(19) (a) Miller, E. J.; Brill, T. B.; Rheingold, A. L.; Fultz, W. C. J.
Am. Chem. Soc. 1983, 105, 7580. (b) Don, M.-J.; Yang, K.; Bott, S. G.;
Richmond, M. G. J. Organomet. Chem. 1997, 544, 15. (c) Xi, R.; Abe,
M.; Suzuki, T.; Nishioka, T.; Isobe, K. J. Organomet. Chem. 1997, 549,
117.
(20) (a) Takayama, C.; Kajitani, M.; Sugiyama, T.; Sugimori, A. J.
Organomet. Chem. 1998, 563, 161. (b) Kajitani, M.; Sakurada, M.;
Dohki, K.; Suetsugu, T.; Akiyama, T.; Sugimori, A. J. Chem. Soc.,
Chem. Commun. 1990, 19. (c) Sakurada, M.; Kajitani, M.; Dohki, K.;
Akiyama, T.; Sugimori, A. J. Organomet. Chem. 1992, 423, 144. (d)
Kajitani, M.; Kawakita, F.; Chikuma, E.; Sakurada, M.; Akiyama, T.;
Sugimori, A. Chem. Lett. 1995, 85. (e) Takayama, C.; Sakamoto, N.;
Harada, T.; Kajitani, M.; Sugiyama, T.; Akiyama, T.; Sugimori, A.
Organometallics 1996, 15, 5077.
(21) (a) Bae, J.-Y.; Lee, Y.-J.; Kim, S.-J.; Ko, J.; Cho, S.; Kang, S. O.
Organometallics 2000, 19, 1514. (b) Won, J.-H.; Lim, H.-G.; Kim, B.
Y.; Lee, J.-D.; Lee, C.; Lee, Y.-J.; Cho, S.; Ko, J.; Kang, S. O.
Organometallics 2002, 21, 5703. (c) Won, J.-H.; Kim, D.-H.; Kim, B.
Y.; Kim, S.-J.; Lee, C.; Cho, S.; Ko, J.; Kang, S. O. Organometallics
2002, 21, 1443. (d) Kim, D.-H.; Ko, J.; Park, K.; Cho, S.; Kang, S. O.
Organometallics 1999, 18, 2738.
(16) Busetto, C.; D’Alfonso, A.; Maspero, F.; Perego, G.; Zazzetta,
A. J. Chem. Soc., Dalton Trans. 1977, 1828.
(17) (a) Schrauzer, G. N. Acc. Chem. Res. 1969, 2, 72. (b) McCleverty,
J. A. Prog. Inorg. Chem. 1969, 10, 49. (c) Sugimori, A.; Akiyama, T.;
Kajitani, M.; Sugiyama, T. Bull. Chem. Soc. Jpn. 1999, 72, 879. (d)
Fourmigue´, M. Coord. Chem. Rev. 1998, 178, 823.
(18) (a) Henderson, S. D.; Stephenson, T. A.; Wharton, E. J. J.
Organomet. Chem. 1979, 179, 43. (b) Kajitani, M.; Igarashi, A.; Hatano,
H.; Akiyama, T.; Sugimori, A.; Matsumoto, S.; Iguchi, Y.; Bo¨nnemann,
H.; Shimizu, K.; Satoˆ, G. P. J. Organomet. Chem. 1995, 485, 31. (c)
Hatano, H.; Kajitani, M.; Akiyama, T.; Sakaguchi, Y.; Nakamura, J.;
Hayashi, H.; Sugimori, A. Chem. Lett. 1990, 1089.
(22) (a) Takayama, C.; Suzuki, E.; Kajitani, M.; Sugiyama, T.;
Sugimori, A. Organometallics 1998, 17, 4341. (b) Takayama, C.;
Kajitani, M.; Sugiyama, T.; Akiyama, T.; Shimizu, K.; Sugimori, A.
Organometallics 1997, 16, 3498.
(23) Sakurada, M.; Schlemper, E. O.; Schrauzer, G. N. Chem. Lett.
1995, 651.

Alkylidene Adducts of Iridium Dithiolene Complexes
Organometallics, Vol. 24, No. 11, 2005 2813
Scheme 2
Scheme 3
Figure 2. ORTEP drawing of [Cp*Ir{S2C2(COOMe)2}-
(CHCOOEt)] (3a). Selected bond lengths (Å): Ir1-S1 )
2.317(1), Ir1-S2 ) 2.339(2), S1-C1 ) 1.699(8), S2-C2 )
1.781(6), C1-C2 ) 1.354(9), Ir1-C7 ) 2.088(7), S2-C7 )
1.820(7). Selected bond angles (deg): S1-Ir1-S2 ) 86.48-
(6), Ir1-S1-C1 ) 104.9(2), Ir1-S2-C2 ) 104.3(3), S1-
C1-C2 ) 124.8(5), S2-C2-C1 ) 118.7(6), Ir1-C7-S2 )
73.2(2), Ir1-S2-C7 ) 58.7(2), S2-Ir1-C7 ) 48.1(2).
yellow solution, the reaction mixture was stirred at room
temperature. After the products were separated by
column chromatography, the red solid of the iridium
dithiolene complex [Cp*Ir{S2C2(COOMe)2}] (1) was
obtained in 73% yield. Whereas the synthetic procedure
for complex 1 previously reported24 is inefficient, our
synthetic route is efficient enough to synthesize complex
1. Similarly, the iridium complex [Cp*Ir{S2C2(Ph)(H)}]
(2), having a phenyl substituent, was obtained from
4-phenyl-1,3-dithiole-2-one, [OdC{S2C2(Ph)(H)}], in 70%
of the iridium dithiolene adduct 3b, when the molar
ratio of stereoisomers was determined by 1H NMR, the
endo isomer (3b-1) was richer than the exo isomer (3b-
2) (Scheme 3). Moreover, the molar ratio of isomers
depended on temperature (3b-1:3b-2 ) 2:1 (80 °C), 4.5:1
(40 °C), 12.5:1 (0 °C), 13:1 (-40 °C) in toluene-d8). On
the other hand, the acetate adduct 3a was only one
isomer.
1
yield (Scheme 2). The H NMR spectrum of complex 2
showed the signal of a dithiolene proton at 8.49 ppm, a
location whose value is more downfield than that of a
typical olefin proton. This provides some evidence for
the ring current25 on the iridadithiolene ring.
The X-ray structures of complexes 3a,b are shown in
Figures 2 and 3, respectively. These alkylidene com-
plexes have a three-legged piano-stool geometry and
coordinatively saturated metal centers. The five-mem-
bered iridadithiolene rings are planar: mean deviation
from iridadithiolene plane 0.0595 Å (3a), 0.0771 Å (3b).
The three-membered ring of the bridging alkylidene
moiety (iridathiirane ring) is extremely distorted (e.g.
the bond angles of S2-Ir1-C7 are 48.1° in 3a and 51.9°
in 3b), and the iridathiirane ring is located at a position
almost perpendicular to the iridadithiolene ring, be-
cause of the dihedral angles between the iridadithiolene
and the iridathiirane rings being 92.374° in 3a and
92.413° in 3b. In complex 3a, the COOEt unit is located
at the exo position with respect to the iridadithiolene
ring. On the other hand, the SiMe3 group of complex
3b is located at the endo position. We assume that the
major endo isomer 3b-1 in solution was well crystallized.
We did not find any single crystals of the exo isomer
3b-2. Such an endo type complex is the first case in the
alkylidene-bridged adducts of metal dithiolene com-
2. Reactions of Iridium Dithiolene Complexes
with Diazoalkanes. The reaction of complex 1 with
ethyl diazoacetate (N2CHCOOEt) or (trimethylsilyl)-
diazomethane (N2CHSiMe3) gave the alkylidene-bridged
adduct [Cp*Ir{S2C2(COOMe)2}(CHR)] (R ) COOEt (3a),
SiMe3 (3b)) in 68% or 81% yield, respectively (Scheme
3). The elemental analyses and spectroscopic data of
complexes 3a and 3b revealed that these complexes
were the 1:1 adducts of complex 1 with an alkyli-
dene (dCHR) moiety. In the 1H NMR spectrum of
complex 3b, two geometrical isomers were observed. We
previously reported two geometrical isomers in the
CHSiMe3 adducts of the cobalt dithiazole complex
[CpCo{S2NC(Ph)}(CHSiMe3)].26 According to this report,
in the major addition product, the SiMe3 group is located
at the exo position with respect to the cobaltadithiazole
ring, and in the minor product, the SiMe3 group is
placed at the endo position. The δ value of the endo-
SiMe3 group (δ(1H) 0.045 ppm) is more upfield than that
of the exo-SiMe3 group (δ(1H) 0.19 ppm).26 In this case
plexes formulated as [(CnRn)M(S2C2Y2)(CHR′)] (M ) Co,
Rh (n ) 5)20 and M ) Ru (n ) 6);27 R′ ) SiMe3, COOEt).
The reaction of complex 1 with diazomethane did not
produce a 1:1 alkylidene adduct such as that of the
(24) (a) Nagao, S.; Seino, H.; Okada, T.; Mizobe, Y.; Hidai, M. Dalton
2000, 3546. (b) Jin, G.-X.; Herberhold, M.; Reingold, A. L. New J. Chem.
1998, 22, 1035.
(25) Boyde, S.; Garner, C. D.; Joule, J. A.; Rowe, D. J. J. Chem. Soc.,
Chem. Commun. 1987, 800.
(26) Mori, Y.; Takehara, M.; Sugiyama, T.; Kajitani, M.; Akiyama,
T.; Yamasaki, M.; Sugimori, A. J. Organomet. Chem. 1995, 494, 81.
(27) Nomura, M.; Fujii, M.; Fukuda, K.; Sugiyama, T.; Yokoyama,
Y.; Kajitani, M. J. Organomet. Chem. 2005, 690, 1627.

2814 Organometallics, Vol. 24, No. 11, 2005
Nomura et al.
Scheme 4
Scheme 5
olene complex [Cp*Ir{S2C2(COOMe)2}(CH2)][Cp*Ir{SC2-
Figure 3. ORTEP drawing of [Cp*Ir{S2C2(COOMe)2}-
(COOMe)2S}(CH2)] (4 in Scheme 4). The complex 4 has
an asymmetric binuclear structure, which has a five-
membered iridadithiolene ring and a six-membered
iridacycle formulated as Ir(CH2)S2C2. One methylene
carbon (C14) is inserted into the Ir2-S3 bond of the
iridadithiolene ring to make the six-membered irida-
cycle, and another methylene carbon (C13) bridges
between Ir1 and the S4 atom. The five-membered
iridadithiolene ring is extremely planar (mean deviation
0.0167 Å). Although the six-membered iridacycle itself
is not planar, the C14-S3-C3-C4-S4 plane excluding
Ir2 is planar (mean deviation 0.0477 Å).
(CHSiMe3)] (3b). Selected bond lengths (Å): Ir1-S1 )
2.340(1), Ir1-S2 ) 2.2325(8), S1-C1 ) 1.646(4), S2-C2
) 1.766(5), C1-C2 ) 1.363(5), Ir1-C7 ) 2.029(4), S2-C7
) 1.875(4). Selected bond angles (deg): S1-Ir1-S2 )
88.84(4), Ir1-S1-C1 ) 103.1(2), Ir1-S2-C2 ) 102.1(1),
S1-C1-C2 ) 122.5(4), S2-C2-C1 ) 122.6(3), Ir1-C7-
S2 ) 69.6(2), Ir1-S2-C7 ) 58.4(1), S2-Ir1-C7 ) 51.9-
(1).
3. Reactivities of the Alkylidene Adduct of the
Iridium Dithiolene Complex. The synthesis of a
monomeric methylene-bridged adduct was attempted by
another route. The reaction of complex 3b with tetrabu-
tylammonium fluoride (TBAF) aimed for the desilylation
reaction. However, a monomeric methylene-bridged
adduct was not found; rather, the dimeric complex 4 was
unexpectedly obtained in 80% yield (Scheme 4). We
propose that the monomeric methylene-bridged adduct
is very unstable and, thus, is rapidly dimerized to form
the dimeric complex 4. In cobalt and rhodium dithiolene
complexes, in contrast, such methylene-bridged adducts
are stable and can be isolated as monomeric com-
plexes.20
Figure 4. ORTEP drawing of [Cp*Ir{S2C2(COOMe)2}-
(CH2)][Cp*Ir{SC2(COOMe)2S}(CH2)](CH2Cl2) (4). The hy-
The alkylidene-bridged adduct 3a reacted with tri-
methyl phosphite to undergo the ring expansion of the
iridadithiolene ring, and then the six-membered-ring
drogen atoms are not shown for the sake of simplicity.
Selected bond lengths (Å): Ir1-S1 ) 2.252(1), Ir1-S2 )
2.2451(6), S1-C1 ) 1.735(3), S2-C2 ) 1.742(4), C1-C2
) 1.338(5), Ir1-C13 ) 2.08(1), Ir2-S1 ) 2.388(3), Ir2-S4
) 2.301(3), S3-C3 ) 1.72(1), S4-C4 ) 1.76(1), C3-C4 )
1.32(2), Ir2-C14 ) 2.08(1), S3-C14 ) 1.77(1), S4-C13 )
1.79(2). Selected bond angles (deg): S1-Ir1-S2 ) 86.98-
(3), Ir1-S1-C1 ) 106.0(1), Ir1-S2-C2 ) 106.3(1), S1-
C1-C2 ) 120.9(3), S2-C2-C1 ) 119.9(2), S4-Ir2-C14
) 86.9(4), Ir2-S4-C4 ) 109.5(5), Ir2-C14-S3 ) 118.8-
(8), S4-C4-C3 ) 129(1), S3-C3-C4 ) 130(1), C3-S3-
C14 ) 108.1(6).
complex [Cp*Ir{SC2(COOMe)2S}(CHCOOEt)(P(OMe)3)]
(5a) was obtained in 52% yield (Scheme 5). The struc-
ture of complex 5a was determined by X-ray structure
analysis (Figure 5). Trimethyl phosphite coordinates to
the iridium center. The Ir1 and the S2 atoms are not
combined thus, the C7 atom inserts between the Ir1 and
S2 atoms. Therefore, the Ir-S bond of complex 3a is
cleaved by the nucleophilic attack of trimethyl phosphite
at the iridium center. The structure of the six-membered
iridacycle of complex 5a is similar to that of complex 4
(Figure 4). After studying the formation of complex 4,
we conclude that when a monomeric methylene-bridged
adduct is dimerized, a ring expansion of the iridadithi-
olene ring is produced by a nucleophilic attack of sulfur
atom at the iridium center.
alkylidene complexes 3a,b. The spectroscopic data
of this reaction product showed the signals of a di-
meric iridium dithiolene complex. The X-ray structure
analysis (Figure 4) revealed the structure of a 2:2
methylene-bridged adduct of the dimeric iridium dithi-

Alkylidene Adducts of Iridium Dithiolene Complexes
Organometallics, Vol. 24, No. 11, 2005 2815
Figure 5. ORTEP drawing of [Cp*Ir{SC2(COOMe)2S}-
Figure 6. ORTEP drawing of [Cp*Ir(Cl){S(SCH2SiMe3)-
C2(COOMe)2}] (6b). Selected bond lengths (Å): Ir1-S1 )
2.346(1), Ir1-S2 ) 2.3421(8), S1-C1 ) 1.719(4), S2-C2
) 1.772(4), C1-C2 ) 1.340(6), Ir1-Cl1 ) 2.392(1), S2-
C7 ) 1.832(4). Selected bond angles (deg): S1-Ir1-S2 )
85.78(3), Ir1-S1-C1 ) 102.8(1), Ir1-S2-C2 ) 103.6(1),
S1-C1-C2 ) 124.6(3), S2-C2-C1 ) 119.4(3).
(CHCOOEt)(P(OMe)3)] (5a). The hydrogen atoms are not
shown for the sake of simplicity. Selected bond lengths
(Å): Ir1-S1 ) 2.351(2), Ir1-C7 ) 2.101(7), Ir1-P1 )
2.206(2), S1-C1 ) 1.738(7), S2-C2 ) 1.757(7), C1-C2 )
1.35(1), S2-C7 ) 1.861(7). Selected bond angles (deg): S1-
Ir1-C7 ) 83.6(2), Ir1-S1-C1 ) 110.5(3), Ir1-C7-S2 )
114.9(4), S1-C1-C2 ) 130.3(6), S2-C2-C1 ) 129.1(5),
C2-S2-C7 ) 105.0(3).
Scheme 6
The reaction of complex 3b with hydrochloric acid
caused the Ir-C bond cleavage on the alkylidene-
bridged moiety (Scheme 6). The structure of the product
[Cp*Ir(Cl){S(SCH2SiMe3)C2(COOMe)2}] (6b) was deter-
mined by X-ray structure analysis (Figure 6). Complex
6b has a structure similar to that of cobalt dithiolene
complexes previously reported.28 The chloride coordi-
nates to the iridium center, and the CH2SiMe3 group
binds to the sulfur atom. We have observed two geo-
metrical isomers of such cobalt dithiolene complexes.
In one, the halide and alkyl groups are located at the
same side of the cobaltadithiolene ring (syn form), and
in the other, the groups take the anti form. Complex
6b has the syn form, as shown in Figure 6. The
alkylidene complex 3a reacted with hydrochloric acid
to give a similar product, formulated as [Cp*Ir(Cl)-
{S(SCH2COOEt)C2(COOMe)2}] (6a). Complex 6a was
identified by elemental analysis and spectroscopic data.
4. Electrochemical Behavior of Iridium Dithi-
olene Complexes. Cyclic voltammetry was performed
on iridium dithiolene complexes. The cyclic voltammo-
grams (CV) and their redox potentials are indicated in
Figure 7 and Table 1, respectively. The CV of complex
1 showed a reversible reduction wave at -2.11 V and
Figure 7. Cyclic voltammograms of 1 mM solutions in
dichloromethane containing 0.1 M TBAP of (a) complex 1,
(b) complex 2, (c) complex 3a, (d) complex 3b, and (f)
complex 4 (v ) 100 mV s-1, 1.6 mm i.d. Pt disk) and (e)
complex 3b (v ) 5 mV s-1, Pt mesh in an OTTLE cell).
an irreversible oxidation wave at 0.78 V (vs Fc/Fc+). The
redox potentials of complex 2 and those of the alkylidene
complexes 3a-c were more negative than those of
complex 1, but the reduction wave of complex 3b was
not found in the potential window for these measure-
(28) (a) Harada, T.; Takayama, C.; Kajitani, M.; Sugiyama, T.;
Akiyama, T.; Sugimori, A. Bull. Chem. Soc. Jpn. 1998, 71, 2645. (b)
Takayama, C.; Takeuchi, K.; Ohkoshi, S.; Kajitani, M.; Sugimori, A.
Organometallics 1999, 18, 4032.

2816 Organometallics, Vol. 24, No. 11, 2005
Nomura et al.
Table 1. Redox Potentials of Iridium Dithiolene
Complexesa
first redn
first oxidn
complex E1/2/V ∆E/mV ∆Ep/mV E1/2/V ∆E/mV ∆Ep/mV
1
-2.11 r
-2.29 ir
-2.15 ir
b
94
88
134
0.78 ir
0.41 ir
0.46 r
78
68
70
68
68
2
3a
3b
4
126
94
88
94
0.10 r
-2.15 ir
134
-0.02 r
a Legend: r, reversible wave; ir, irreversible wave. E1/2 ) (Ep +
Ep/2)/2, ∆E ) |Ep - Ep/2|, ∆Ep ) |Epc - Epa|. b Not observed in the
potential window of TBAP-CH2Cl2.
ment conditions. In complexes 3a-c, complex 3a was
the easiest one to be reduced and was the hardest one
to be oxidized. The CV of complex 3b resulted in an
oxidation wave of four steps; the first and third oxida-
tion currents were larger than the second and fourth
ones. From these results, we conclude that (1) the redox
potentials of iridium dithiolene complexes can be con-
trolled by the substituent effects on the iridadithiolene
ring and on the alkylidene moiety, (2) the 16-electron
complex has lower redox potentials than those of the
corresponding 18-electron alkylidene adducts, and (3)
in complex 3b, the oxidation waves of the endo isomer
3b-1 and the exo isomer 3b-2 are observed, and the first
and third waves correspond to the first and second
oxidations of the major isomer 3b-1.
Figure 8. Spectral changes in the visible region of complex
3b during (a) oxidation (+0.40 V, sampling time 2 min,
sampling interval 4 s) and (b) rereduction after oxidation
(-0.50 V, sampling time 2 min, sampling interval 4 s) using
an OTTLE cell.
The oxidation behavior of complex 3b was investi-
gated in detail. Figure 7e is the CV of complex 3b
measured by a slow scan rate (v ) 5 mV s-1) in an
optically transparent thin-layer electrode (OTTLE) cell.
The first oxidation wave of the endo isomer 3b-1 showed
a reversible response, but the second wave of the exo
isomer 3b-2 was irreversible. This result suggests that
the oxidized species of the isomer 3b-2 is unstable on
the time scale of the slow scan. Figure 8 shows the
visible absorption spectral changes during electrolysis
of complex 3b using the OTTLE cell. When a mixture
of the isomers 3b-1 and 3b-2 was oxidized at +0.4 V,
the spectrum was remarkably changed and did not show
an isosbestic point (Figure 8a). The reason for the
absence of an isosbestic point is a chemical reaction of
the unstable cation 3b-2+ after the electrochemical
oxidation. However, when the stable cation 3b-1+ was
rereduced at -0.5 V, the spectrum recovered the original
absorbance before electrolysis; moreover, these spectral
changes showed an isosbestic point (at 520 nm in Figure
8b). We propose that the oxidant of the exo isomer (3b-
2+) is quantitatively converted to the oxidized endo
isomer (3b-1+) and, when it is rereduced, the neutral
endo isomer 3b-1 is formed electrochemically (Scheme
7).
Scheme 7
olene ring has both aromaticity and unsaturation, like
cobalta- and rhodadithiolene rings.
When diazoacetate or (trimethylsilyl)diazomethane
was used for the synthesis of the alkylidene adduct, the
alkylidene-bridged complex 3a or 3b was obtained,
respectively. The alkylidene groups were bridging into
the Ir-S bond of the iridadithiolene ring, and this case
is classified as type 3 in Figure 1. In such alkylidene
adducts [Cp*Ir{S2C2(COOMe)2}(CHR)], the stereoiso-
mer of exo (R ) COOEt in Figure 2) or endo (R ) SiMe3
in Figure 3) form could be selectively synthesized.
Especially, the endo type of alkylidene adduct is the first
example found for a Cp metal dithiolene complex. If we
were to use such alkylidene complexes as a catalyst or
a carbene source, stereoselective reactions could be
expected for metathesis reactions1 and olefin cyclopro-
panations.2
The reaction of a iridium dithiolene complex with
diazomethane gave the novel binuclear iridium dithi-
olene adduct 4 (Figure 4). Complex 4 is a novel alkyli-
dene complex, which cannot be classified into any of the
types 1-3 noted in Figure 1.
Conclusion
In this work, we carried out the reactions of the 16-
electron coordinatively unsaturated iridium dithiolene
complex 1 with diazoalkanes. These reactions resulted
in the formations of 18-electron alkylidene adducts of
iridium dithiolene complexes. This is a reaction based
on the unsaturation of the iridadithiolene ring. On the
other hand, the iridadithiolene ring proton (δ(1H) 8.49
ppm in complex 2) provided some evidence for the ring
current of an aromatic ring. Therefore, the iridadithi-

Alkylidene Adducts of Iridium Dithiolene Complexes
Organometallics, Vol. 24, No. 11, 2005 2817
4.21 (m, 2H, CH2Me). 13C NMR (CDCl3, 125 MHz, vs TMS): δ
9.1 (C5Me5), 14.5 (COOCH2Me), 29.3 (CH), 52.2, 53.1, 60.5
(COOMe or COOCH2Me), 92.7 (C5Me5), 113.0, 163.0 (dithiolene
carbon), 169.0, 170.1, 175.3 (COOMe or COOEt). UV-vis (CH2-
Cl2): λmax/nm (ꢀ) 346 (5500), 397 (5000), 443 (6000). IR (KBr
disk): 1730.0, 1697.2, 1469.7, 1423.4, 1380.9, 1363.6, 1298.0,
1230.5, 1153.4, 1085.8, 1026.1, 759.9 cm-1. Anal. Calcd for
C20H27O6S2Ir: C, 38.76; H, 4.39. Found: C, 38.76; H, 4.40.
Reaction of Complex 1 with (Trimethylsilyl)diazo-
methane. A 2.0 mmol dm-3 n-hexane solution of (trimethyl-
silyl)diazomethane (1.9 mL, 3.8 mmol) was added into a
benzene solution (20 mL) of complex 1 (100 mg, 0.26 mmol).
The reaction mixture was stirred at room temperature for 2
h. After the solvent was removed under reduced pressure, the
residue was separated by column chromatography (silica gel,
eluent dichloromethane). The orange residue was purified by
recrystallization (n-hexane/dichloromethane). Adduct 3b was
obtained as an orange solid in 78% (94 mg, 0.20 mmol) yield.
Experimental Section
General Remarks. All reactions were carried out under
an argon atmosphere by means of standard Schlenk tech-
niques. All solvents for reactions were purified by Na-
benzophenone or CaH2 before use. The precursor of complexes
1 and 2, [Cp*Ir(Cl)(µ-Cl)]2, was synthesized by literature
methods.29 Dimethyl 1,3-dithiol-2-one-4,5-dicarboxylate (Od
C{S2C2(COOMe)2}) was obtained from the reaction of dimethyl
1,3-dithiol-2-thione-4,5-dicarboxylate (from Tokyo Kasei Kogyo
Co., Ltd.) with Hg(OAc)2.30 (Trimethylsilyl)diazomethane in
n-hexane solution and TBAF in THF solution were produced
by Sigma-Aldrich Fine Chemicals. Silica gel (Wakogel C-300)
was obtained from Wako Pure Chemical Industries, Ltd. Mass
and IR spectra were recorded on JEOL JMS-D300 and
Shimadzu Model FTIR 8600PC instruments, respectively.
NMR spectra were measured with a JEOL LA500 spectrom-
eter. UV-vis spectra were recorded on a Hitachi Model UV-
2500PC spectrometer. Elemental analyses were determined
by using a Shimadzu PE2400-II instrument.
Preparations of the Iridium Dithiolene Complexes
[Cp*Ir{S2C2(COOMe)2}] (1) and [Cp*Ir{S2C2(Ph)(H)}] (2).
Dimethyl 1,3-dithiol-2-one-4,5-dicarboxylate (1.62 mmol; Od
C{S2C2(COOMe)2}) was treated with 2 equiv of sodium meth-
oxide in methanol solution (50 mL) at room temperature. The
color of the initial solution changed to yellow after 1 h. When
the iridium complex dimer [Cp*Ir(Cl)(µ-Cl)]2 (0.62 mmol) was
added into this solution, the yellow solution changed to brown.
The reaction mixture was stirred at room temperature for 24
h. After the solvent was removed under reduced pressure, the
residue was extracted by dichloromethane/water and the
organic layer was purified by column chromatography (silica
gel, eluent dichloromethane). Complex 1 was obtained as a
brown solid in 80% yield. Complex 2 was obtained from
4-phenyl-1,3-dithiol-2-one (OdC{S2C2(Ph)(H)}) with [Cp*Ir-
(Cl)(µ-Cl)]2 in 70% yield.
[Cp*Ir{S2C2(COOMe)2}(CHSiMe3)] (3b). Mass (EI+, 70
eV): m/z (relative intensity) 620 ([M+], 35.1), 605 ([M+ - Me],
100). UV-vis (CH2Cl2): λmax/nm (ꢀ) 469.5 (5590). 1H NMR
(CDCl3, 500 MHz, vs TMS): major isomer, δ 0.04 (s, 9H,
SiMe3), 1.96 (s, 15H, C5Me5), 2.11 (s, 1H, CH), 3.73 (s, 3H,
COOMe), 3.83 (s, 3H, COOMe); minor isomer, δ 0.11 (s, 9H,
SiMe3), 2.00 (s, 15H, C5Me5), 2.13 (s, 1H, CH), 3.72 (s, 3H,
COOMe), 3.85 (s, 3H, COOMe). IR (KBr disk): 2949.0, 2333.7,
1732.0, 1676.0, 1477.4, 1259.4, 1230.5, 1026.1, 871.8, 833.2
cm-1. Anal. Calcd for C20H31O4SiS2Ir: C, 38.75; H, 5.04.
Found: C, 38.72; H, 5.05.
Reaction of Complex 1 with Diazomethane. Diazo-
methane was prepared by a literature method.20c Excess
diazomethane gas was blown into a dichloromethane solution
of complex 1 (98 mg, 0.254 mmol) at 0 °C. After the solvent
was removed under reduced pressure, the residue was sepa-
rated by column chromatography (silica gel, eluent dichlo-
romethane). The orange residue was purified by recrystalli-
zation (n-hexane/dichloromethane). Adduct 4 was obtained as
an orange solid in 80% yield (81 mg, 0.203 mmol).
[Cp*Ir{S2C2(COOMe)2}] (1). UV-vis (CH2Cl2): λmax/nm (ꢀ)
305 (16 000), 416 (8000). Anal. Calcd for C16H21O4S2Ir: C,
36.01; H, 3.97. Found: C, 36.19; H, 3.95. The mass, NMR, and
IR spectral data of complex 1 are given in the literature
previously reported.24b
[Cp*Ir{S2C2(COOMe)2}(CH2)][Cp*Ir{SC2(COOMe)2S}-
[Cp*Ir{S2C2(Ph)(H)}] (2). Mass (EI+, 70 eV): m/z (relative
(CH2)] (4). Mass (FAB+, 70 eV, NBA): m/z (relative intensity)
1096 ([M+], 39.1), 548 ([M+]/2, 100). 1H NMR (CDCl3, 500 MHz,
vs TMS): δ 1.71 (s, 15H, C5Me5), 1.72 (s, 15H, C5Me5), 2.71 (q,
J ) 5.03 Hz, 2H, CH2), 2.96 (q, J ) 6.77 Hz, 2H, CH2), 3.64 (s,
intensity) 494 ([M+], 100), 392 ([C5Me5IrS2+], 30.4). H NMR
1
(CDCl3, 500 MHz, vs TMS): δ 2.19 (s, 15H, C5Me5), 7.20-7.23
(tt, J ) 1.81, 7.39 Hz, 1H, Ph), 7.30-7.33 (m, 2H, Ph), 7.76-
7.78 (m, 2H, Ph), 8.49 (s, 1H, dithiolene proton). UV-vis (CH2-
Cl2): λmax/nm (ꢀ) 295 (14 700), 450 (8800). IR (KBr disk):
2960.5, 2912.3, 1591.1, 1504.4, 1438.8, 1380.9, 1261.4, 1215.1,
1031.8, 796.5, 761.8, 696.3 cm-1. Anal. Calcd for C18H21S2Ir:
C, 43.79; H, 4.29. Found: C, 43.83; H, 4.21.
Reactions of Complex 1 with Ethyl Diazoacetate. Ethyl
diazoacetate was prepared by a literature method.31 A solution
of complex 1 (0.23 mmol) and ethyl diazoacetate (2.0 mmol)
in benzene (90 mL) was stirred at room temperature for 2 h.
After the solvent was removed under reduced pressure, the
residue was separated by column chromatography (silica gel,
eluent dichloromethane). The orange residue was purified by
recrystallization (n-hexane/dichloromethane). Adduct 3a was
obtained as an orange solid in 94% yield.
3H, COOMe), 3.73 (s, 3H, COOMe), 3.81 (s, 6H, COOMe). 13
C
NMR (CDCl3, 125 MHz, vs TMS): δ 8.3, 8.4 (C5Me5), 10.5, 36.7
(CH2), 52.1, 52.4, 52.5, 52.8 (COOMe), 92.0, 93.4 (C5Me5), 111.8,
121.8, 157.9, 159.4 (dithiolene carbon), 165.9, 166.8, 167.0,
168.2 (COOMe). IR (KBr disk): 2947.0, 2906.5, 1732.0, 1701.1,
1508.2, 1456.2, 1431.1, 1230.5, 1070.4, 1022.2, 748.3 cm-1
.
Anal. Calcd for [C17H23O4S2Ir]2(CH2Cl2): C, 35.61; H, 4.10.
Found: C, 35.59; H, 4.03.
Reaction of Complex 3b with Tetrabutylammonium
Fluoride (TBAF). The 2.0 mmol dm-3 THF solution of TBAF
(30 µL, 0.107 mmol) was added into a THF solution (2 mL) of
complex 3b (10 mg, 0.016 mmol). The reaction mixture was
stirred at room temperature for 10 min, and then a few drops
of water were added. The reaction mixture was separated by
column chromatography (silica gel, eluent dichloromethane).
The adduct 4 was formed in 80% yield.
Reaction of Complex 3a with Trimethyl Phosphite. A
solution of complex 3a (53.7 mg, 0.087 mmol) and trimethyl
phosphite (110 µL, 0.87 mmol) in dichloromethane (5 mL) was
stirred at room temperature for 3 days. After the solvent was
removed under reduced pressure, the residue was separated
by column chromatography (silica gel, eluent dichloromethane).
The orange residue was purified by recrystallization (n-hexane/
dichloromethane). Complex 5a was obtained as a yellow solid
in 52% yield.
[Cp*Ir{S2C2(COOMe)2}(CHCOOEt)] (3a). Mass (FAB+,
70 eV, NBA): m/z (relative intensity) 621 ([M+ + 1], 68.9), 547
1
([M+ - COOMe], 100). H NMR (CDCl3, 500 MHz, vs TMS):
δ 1.27 (t, J ) 7.26 Hz, 3H, CH2Me), 1.96 (s, 15H, C5Me5), 2.86
(s, 1H, CH), 3.73 (s, 3H, COOMe), 3.85 (s, 3H, COOMe), 4.07-
(29) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228.
(30) Challenger, F.; Mason, E. A.; Holdsworth, E. C.; Emmott, R. J.
Chem. Soc. 1953, 292.
(31) Womack, E. B.; Nelson, A. B. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. III, p 392.

2818 Organometallics, Vol. 24, No. 11, 2005
Nomura et al.
Table 2. Crystallographic Data of Iridium Dithiolene Complexes 3a,b, 4, 5a, and 6b
3a
3b
4‚CH2Cl2
5a
6b
formula
formula wt
cryst color
cryst habit
cryst size (mm)
cryst syst
space group
a (Å)
C
20H27IrO6S2
C
20H31IrO4S2Si
C35H48Cl2Ir2O8S4
1180.35
C
23H36IrO9PS2
C
20H32ClIrO4S2Si
619.77
619.89
743.85
656.35
orange
block
0.15 × 0.12 × 0.10
triclinic
P1h (No. 2)
8.5846
orange
orange
yellow
block
yellow
block
platelet
0.15 × 0.15 × 0.10
triclinic
P1h (No. 2)
10.90150(10)
11.1238(2)
11.3765(4)
89.846(5)
70.899(4)
67.032(3)
1187.83(5)
2
block
0.15 × 0.15 × 0.15
monoclinic
P21/n (No. 14)
17.9309(5)
13.0331(4)
20.1731(7)
0.15 × 0.12 × 0.06
monoclinic
P21/c (No. 14)
8.1750(8)
31.572(3)
11.2418(10)
0.09 × 0.09 × 0.06
triclinic
P1h (No. 2)
7.8461(4)
10.8280(5)
16.3196(9)
100.320(2)
103.658(2)
97.870(2)
1301.97(11)
2
b (Å)
10.7532
14.1927
70.386(9)
73.927(10)
71.420(9)
1148.434 89(10)
2
c (Å)
R (deg)
â (deg)
106.1368(5)
103.0624(11)
γ (deg)
V (Å-3
)
4528.6(2)
4
2826.5(4)
4
Z
Dcalcd (g cm-3
)
1.792
1.733
1.731
1.748
1.674
µ(Mo KR) (cm-1
2θmax (deg)
)
60.43
58.84
62.32
49.88
54.72
54.9
55.0
55.0
55.0
55.0
no. of unique data (Rint
)
4993 (0.030)
3757
5028 (0.022)
4320
10 240 (0.020)
7580
6267 (0.048)
3222
5674 (0.019)
4741
no. of observns
no. of variables
289
284
508
361
294
R1, wR2 (I > 3.00σ(I))
goodness of fit on F2
0.030, 0.029
1.049
0.023, 0.025
1.121
0.056, 0.096
1.437
0.032, 0.028
0.862
0.024, 0.025
1.322
n-hexane into those solutions. Measurements were made on
a Rigaku MERCURY diffractometer with graphite-monochro-
mated Mo KR radiation. The data were corrected for Lorentz
and polarization effects. The structure was solved by direct
methods and expanded using Fourier techniques. The non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were refined using the riding model. All the calculations were
carried out using the Crystal Structure crystallographic
software package. Crystallographic data are summarized in
Table 2.
Electrochemical Measurements. All electrochemical mea-
surements were performed under an argon atmosphere. Sol-
vents for electrochemical measurements were dried by molec-
ular sieve 4A before use. A platinum wire served as a counter
electrode, and the reference electrode is Ag/AgCl, corrected for
junction potentials by being referenced internally to the
ferrocene/ferrocenium (Fc/Fc+) couple. Cyclic voltammograms
were measured with a Model CV-50W instrument from BAS
Co. Visible and near-IR absorption spectra during electrolysis
were measured with Model MCPD-7000 and MC-2530 instru-
ments from Otsuka Electronics Co. Ltd.
CV Measurements. CV measurements were done in 1
mmol dm-3 dichloromethane solutions of complexes containing
0.1 mol dm-3 tetrabutylammonium perchlorate (TBAP) at 25
°C. A stationary platinum disk (1.6 mm in diameter) was used
as a working electrode.
Visible Absorption Spectral Measurements during
Electrolysis. The visible absorption spectra during electroly-
sis were obtained for 1 mmol dm-3 dichloromethane solutions
of complexes containing 0.1 mol dm-3 TBAP at 25 °C in an
optically transparent thin-layer electrode (OTTLE, thin-layer
thickness 0.4 mm) cell by using a Photal MCPD-7000 rapid
scan spectrometer. The working electrode was stationary
platinum mesh in thin-layer form.
[Cp*Ir{SC2(COOMe)2S}(CHCOOEt)(P(OMe)3)] (5a). Mass
(EI+, 70 eV) m/z (relative intensity) 744 ([M+], 12.6), 559 ([M+
- OOEt - P(OMe)3], 24.1), 547 ([M+ - COOEt - P(OMe)3],
100), 484 ([Cp*IrS2C3(CO)2+], 18.4). 1H NMR (CDCl3, 500 MHz,
vs TMS): δ 1.25 (t, J ) 7.23 Hz, 3H, CH2Me), 1.74 (d, J )
3.16 Hz, 15H, C5Me5), 3.68 (s, 3H, COOMe), 3.69 (d, J ) 10.29
Hz, 9H, P(OMe)3), 3.83 (s, 3H, COOMe), 3.95-3.98 (m, 1H,
CH2Me), 4.18-4.22 (m, 1H, CH2Me), 4.61 (d, J ) 4.69 Hz, 1H,
CH). UV-vis (CH2Cl2): λmax/nm (ꢀ) 285 (14 000), 379 (4600).
IR (KBr disk): 2989.4, 2949.0, 2896.9, 1716.5, 1693.4, 1508.2,
1429.2, 1232.4, 1141.8, 1029.9 cm-1. Anal. Calcd for C23H36O9-
PS2Ir: C, 37.14; H, 4.88. Found: C, 37.32; H, 4.54.
Reaction of Complex 3a or 3b with Hydrochloric Acid.
Excess hydrochloric acid (a few drops) was added into the
dichloromethane (10 mL) solution of complex 3a (12 mg, 0.019
mmol) or 3b (20 mg, 0.032 mmol). The reaction mixture was
reacted at room temperature for 10 min; then the solution was
extracted by dichloromethane/H2O, and the organic layer was
dried with MgSO4. After the solvent was removed under
reduced pressure, the yellow residue was purified by recrys-
tallization (n-hexane/dichloromethane). Complex 6a or 6b was
obtained as a yellow solid in 96% or 97% yield, respectively.
[Cp*Ir(Cl){S(SCH2COOEt)C2(COOMe)2}] (6a). Mass (EI+,
70 eV): m/z (relative intensity) 656 ([M+], 42.6), 569 ([M+
-
CH2COOEt], 80.1), 534 ([M+ - CH2COOEt - Cl], 100). 1H
NMR (CDCl3, 500 MHz, vs TMS): δ 1.27 (t, J ) 7.25 Hz, 3H,
CH2Me), 1.79 (s, 15H, C5Me5), 3.51 (d, J ) 15.8 Hz, 1H, CH),
3.74 (s, 3H, COOMe), 3.86 (s, 3H, COOMe), 4.14-4.18 (m, 2H,
CH2Me), 4.62 (d, J ) 15.8 Hz, 1H, CH). UV-vis (CH2Cl2): λmax
nm (ꢀ) 357 (7700). IR (KBr disk): 2993.3, 2979.8, 2948.9,
1737.7, 1699.2, 1685.7, 1508.2, 1249.8, 1182.3, 1026.1 cm-1
/
.
Anal. Calcd for C20H28ClO6S2Ir: C, 36.60; H, 4.30. Found: C,
36.51; H, 4.10.
[Cp*Ir(Cl){S(SCH2SiMe3)C2(COOMe)2}] (6b). Mass (EI+,
70 eV): m/z (relative intensity) 656 ([M+], 100), 621 ([M+
-
Cl], 17.1), 569 ([M+ - CH2SiMe3], 62.9), 534 ([M+ - CH2SiMe3
- Cl], 93.5). 1H NMR (CDCl3, 500 MHz, vs TMS): δ ) 0.17 (s,
9H, SiMe3), 1.33 (d, J ) 13.3 Hz, 1H, CH), 1.73 (s, 15H, C5Me5),
3.50 (d, J ) 13.3 Hz, 1H, CH), 3.73 (s, 3H, COOMe), 3.85 (s,
3H, COOMe). UV-vis (CH2Cl2): λmax/nm (ꢀ) 359 (9300). IR
(KBr disk): 2956.7, 2894.9, 2883.4, 1737.7, 1699.2, 1517.9,
1236.3, 1029.9 cm-1. Anal. Calcd for C20H32ClO4S2SiIr: C,
36.60; H, 4.91. Found: C, 36.90; H, 4.75.
Acknowledgment. We thank Professor F. Scott
Howell (Sophia University) for correction of manuscript.
Supporting Information Available: CIF files giving
crystallographic data for complexes 3a,b, 4, 5a, and 6b. This
material is available free of charge via the Internet at
http://pubs.acs.org.
X-ray Diffraction Study. Single crystals of complexes
3a,b, 4, 5a, and 6b were obtained by recrystallization from
the dichloromethane solutions and then vapor diffusion of
OM050169R