Synthesis and reactivities of Cp*Ir amide and hydride complexes bearing C - N chelate ligands

Article abstract of DOI:10.1021/om800124f

A series of 16-electron Cp*Ir amide complexes with C-N chelating ligands, Cp*Ir[k²(N,C)-(NHCR₂-2-C₆H ₄)] (2a: R = C₆H₅, 2b: R = CH₃), and the chiral version, Cp*Ir[k²(N,C)-(R)-{NHCH(CH ₃)-2-C₁₀H₆}] (2e), were obtained in good to excellent yields from reactions of 18-electron iridium amine complexes, Cp*IrCl[k²(N,C)-(NH₂CR₂-2-C ₆H₄)] (la: R = C₆H₅, lb: R = CH ₃) and Cp*IrCl[k²(N,C)-(R)-(NH₂CH(CH ₃)-2-C₁₀H₆)] (1e), with a base. The amido complexes 2 readily reacted with 2-propanol to convert into hydrido(amine) complexes 3 in almost quantitative yields. The chiral amido complex has proven to serve as an efficient catalyst for asymmetric transfer hydrogenation of acetophenone with 2-propanol, giving 1-phenylethanol with a moderate ee. The Bronsted basicity on the metal-NH moiety in the amido complexes was evaluated by deprotonation of acetic acid, dimethyl malonate, and acetone, leading to the corresponding acetato(amine) complex 4 and alkyl(amine) complexes 5 and 6, respectively, indicating that the amido-Ir complexes bearing the C - N chelate have more basic properties than those with N-sulfonylated diamine ligands.

Full text of DOI:10.1021/om800124f

Organometallics 2008, 27, 2795–2802
2795
Synthesis and Reactivities of Cp*Ir Amide and Hydride Complexes
Bearing C-N Chelate Ligands
Sachiko Arita, Takashi Koike, Yoshihito Kayaki, and Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of
Technology, O-okayama 2-12-1, Meguro-ku, Tokyo 152-8552, Japan
ReceiVed February 13, 2008
A series of 16-electron Cp*Ir amide complexes with C-N chelating ligands, Cp*Ir[κ2(N,C)-(NHCR2-
2-C6H4)] (2a: R ) C6H5, 2b: R ) CH3), and the chiral version, Cp*Ir[κ2(N,C)-(R)-{NHCH(CH3)-2-
C10H6}] (2e), were obtained in good to excellent yields from reactions of 18-electron iridium amine
complexes, Cp*IrCl[κ2(N,C)-(NH2CR2-2-C6H4)] (1a: R ) C6H5, 1b: R ) CH3) and Cp*IrCl[κ2(N,C)-
(R)-{NH2CH(CH3)-2-C10H6}] (1e), with a base. The amido complexes 2 readily reacted with 2-propanol
to convert into hydrido(amine) complexes 3 in almost quantitative yields. The chiral amido complex has
proven to serve as an efficient catalyst for asymmetric transfer hydrogenation of acetophenone with
2-propanol, giving 1-phenylethanol with a moderate ee. The Brønsted basicity on the metal-NH moiety
in the amido complexes was evaluated by deprotonation of acetic acid, dimethyl malonate, and acetone,
leading to the corresponding acetato(amine) complex 4 and alkyl(amine) complexes 5 and 6, respectively,
indicating that the amido-Ir complexes bearing the C-N chelate have more basic properties than those
with N-sulfonylated diamine ligands.
Chart 1
Introduction
Much attention has been given to the design of chiral
bifunctional molecular catalysts to attain highly efficient mo-
lecular transformation for organic synthesis.1 We have developed
chiral transition metal amide complexes, Ru[κ2(N,N′)-
TsNCHC6H5CHC6H5NH](η6-arene) and Cp*M[κ2(N,N′)-
TsNCHC6H5CHC6H5NH] (M ) Rh and Ir, Cp* ) 1,2,3,4,5-
pentamethylcyclopentadienyl, Ts ) p-toluenesulfonyl), bearing
a metal/NH bifunctional moiety as efficient catalysts for the
asymmetric reduction of ketones with 2-propanol or formic
acid1note,2 as well as enantioselective C-C1note,3a–e and C-N
bond3f formation. Due to the nature of the metal-N bond, the
amido complex smoothly deprotonates the acidic compounds
to give the amine complex, which might be a key step in the
asymmetric transformation with high efficiency in terms of
reactivity and selectivity. We have also shown that changing
the ligand from N-sulfonylated diamines (Ts-diamine) to the
N,N-dimethylaminoethylamines (N-N) and 2-phosphinoethy-
lamines (P-N) (Chart 1) causes a drastic change in the catalyst
performance.4 For example, in contrast to the low reactivity of
Ru(Ts-diamine)(η6-arene) toward H2 under mild conditions, both
Cp*Ru(N-N) and Cp*Ru(P-N) complexes readily activate H2
with help from protic solvents4a,b,d,5 and can efficiently catalyze
* Corresponding author. Tel: +81-3-5734-2636. Fax: +81-3-5734-2637.
E-mail: tikariya@apc.titech.ac.jp.
(1) Recent review articles for metal-based bifunctional catalysts: (a)
Ikariya, T.; Murata, K.; Noyori, R. Org. Biomol. Chem. 2006, 4, 393–406.
(b) Mun˜iz, K. Angew. Chem., Int. Ed. 2005, 44, 6622–6627. (c) Shibasaki,
M.; Matsunaga, S. Chem. Soc. ReV. 2006, 35, 269–279. (d) Ma, J.-A.;
Cahard, D. Angew. Chem., Int. Ed. 2004, 43, 4566–4583. (e) Gro¨ger, H.
Chem.-Eur. J. 2001, 7, 5246–5251.
(2) (a) Ikariya, T.; Blacker, A. J. Acc. Chem. Res. 2007, 40, 1300–1308.
(b) Hashiguchi, S.; Fujii, A.; Takehara, J.; Ikariya, T.; Noyori, R. J. Am.
Chem. Soc. 1995, 117, 7562–7563. (c) Fujii, A.; Hashiguchi, S.; Uematsu,
N.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1996, 118, 2521–2522. (d)
Uematsu, N.; Fujii, A.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem.
Soc. 1996, 118, 4916–4917. (e) Haack, K.-J.; Hashiguchi, S.; Fujii, A.;
Ikariya, T.; Noyori, R. Angew. Chem., Int. Ed. Engl. 1997, 36, 285–288.
(f) Hashiguchi, S.; Fujii, A.; Haack, K.-J.; Matsumura, K.; Ikariya, T.;
Noyori, R. Angew. Chem., Int. Ed. Engl. 1997, 36, 288–290. (g) Murata,
K.; Ikariya, T.; Noyori, R. J. Org. Chem. 1999, 64, 2186–2187. (h) Murata,
K.; Okano, K.; Miyagi, M.; Iwane, H.; Noyori, R.; Ikariya, T. Org. Lett.
1999, 1, 1119–1121. (i) Koike, T.; Murata, K.; Ikariya, T. Org. Lett. 2000,
2, 3833–3836. (j) Okano, K.; Murata, K.; Ikariya, T. Tetrahedron Lett. 2000,
41, 9277–9280. (k) Watanabe, M.; Murata, K.; Ikariya, T. J. Org. Chem.
2002, 67, 1712–1715. (l) Hamada, T.; Torii, T.; Izawa, K.; Noyori, R.;
Ikariya, T. Org. Lett. 2002, 4, 4373–4376. (m) Hamada, T.; Torii, T.; Izawa,
K.; Ikariya, T. Tetrahedron 2004, 60, 7411–7417.
(3) (a) Murata, K.; Konishi, H.; Ito, M.; Ikariya, T. Organometallics
2002, 21, 253–255. (b) Watanabe, M.; Murata, K.; Ikariya, T. J. Am. Chem.
Soc. 2003, 125, 7508–7509. (c) Ikariya, T.; Wang, H.; Watanabe, M.;
Murata, K. J. Organomet. Chem. 2004, 689, 1377–1381. (d) Watanabe,
M.; Ikagawa, A.; Wang, H.; Murata, K.; Ikariya, T. J. Am. Chem. Soc.
2004, 126, 11148–11149. (e) Wang, H.; Watanabe, M.; Ikariya, T.
Tetrahedron Lett. 2005, 46, 963–966. (f) Hasegawa, Y.; Watanabe, M.;
Gridnev, I. D.; Ikariya, T. J. Am. Chem. Soc. 2008, 130, 2158-2159.
(4) (a) Ito, M.; Hirakawa, M.; Murata, K.; Ikariya, T. Organometallics
2001, 20, 379–381. (b) Ito, M.; Hirakawa, M.; Osaku, A.; Ikariya, T.
Organometallics 2003, 22, 4190–4192. (c) Ito, M.; Kitahara, S.; Ikariya,
T. J. Am. Chem. Soc. 2005, 127, 6172–6173. (d) Ito, M.; Sakaguchi, A.;
Kobayashi, C.; Ikariya, T. J. Am. Chem. Soc. 2007, 129, 290–291. (e) Ito,
M.; Osaku, A.; Shiibashi, A.; Ikariya, T. Org. Lett. 2007, 9, 1821–1824.
(5) Hedberg, C.; Ka¨llsto¨m, K.; Arvidsson, P. I.; Brandt, P.; Andersson,
P. G. J. Am. Chem. Soc. 2005, 127, 15083–15090.
10.1021/om800124f CCC: $40.75
2008 American Chemical Society
Publication on Web 05/15/2008

2796 Organometallics, Vol. 27, No. 12, 2008
Arita et al.
Scheme 1
1a (see the Supporting Information), as observed in analogous
1
amido- and (hydrido)amine-Ru complexes.2e The H NMR
spectrum of 2a in CD2Cl2 is consistent with its structure in the
solid state. The NH signal was observed at 8.00 ppm, which is
a lower chemical shift than the NH2 signals of the parent
complex 1a (4.97 and 5.72 ppm), possibly due to the sp2
1
hybridization at the nitrogen atom. Similarly, H NMR spec-
troscopic data in the amido complexes 2b and 2e display the
NH signal at 8.47 and 8.42 ppm, respectively.
The starting neutral chloride complexes 1a and 1b were
readily prepared from the reaction of [Cp*IrCl2]2 and primary
benzylamines (C6H5CR2NH2; R ) C6H5 and CH3) in the
presence of NaOCOCH3 in CH2Cl2 at room temperature.7 The
products were fully characterized by NMR spectroscopy,
elemental analysis, and X-ray crystallography (see Experimental
Section and the Supporting Information). The cycloiridation was
found to proceed through formation of the monomeric κ1(N)-
amine complex Cp*IrCl2[κ1(N)-NH2CR2C6H5] to give com-
plexes 1a and 1b. Notably, the cyclometalation step8 was
markedly accelerated in the presence of sodium acetate, sug-
gesting that the Ir acetate species acts as a key intermediate for
the electrophilic activation of a C-H bond of the aromatic
group, as observed by Davies9 and us.10 In fact, an isolable
bis(acetato)-Ir complex, Cp*Ir(OCOCH3)2, readily reacted with
triphenylmethylamine without any additives to give the corre-
sponding cyclometalated Ir complex 4, with the acetato ligand,
determined by X-ray crystallography and NMR spectroscopy
(Vide infra). Similarly, we obtained the cyclometalated com-
plexes 1c (R ) H, CH3), 1d (R ) H, H), 1e, and 1f (R ) H,
the hydrogenation of ketones and epoxides to secondary
alcohols. The difference in their reactivity can be attributed to
the electronic nature of the metal center induced by the tosylated
amido, the tertiary amino, and phosphino groups in the ligands.
These results prompted us to explore new catalysts with further
modification of the structure of the amine ligands that adjusts
the balance of the electronic factors, and we successfully isolated
a new type of C-N chelate amido-Ir complexes derived from
benzylic amines, Cp*Ir[κ2(N,C)-(NHCR2-2-C6H4)], and their
chiral version, Cp*Ir[κ2(N,C)-(R)-{NHCH(CH3)-2-C10H6}].
Related cationic transition metal complexes bearing cyclo-
metalated C-N ligands were intensively investigated by Pfeffer
and co-workers, but catalytically active amido and hydrido(am-
ine) complexes have not been isolated.6 Herein we disclose full
details of the synthesis of amido- and hydrido(amine)-Ir
complexes bearing C-N ligands and their properties including
catalytic activity.
Results and Discussion
t
CH2OSi(CH3)2 Bu), bearing sterically less hindered amines with
good yields and selectivities, although the reaction required a
higher reaction temperature of 60 °C in CH3CN. These results
imply that the substituents on the R-carbon bound to the NH2
group significantly influence the rate of the cyclometalation.
Synthesis and Structure of Cyclometalated Amido-Ir
Complexes. The cyclometalated amido-Ir complexes Cp*Ir[κ2-
(N,C)-(NHCR2-2-C6H4)] (2a: R ) C6H5, 2b: R ) CH3) and
Cp*Ir[κ2(N,C)-(R)-{NHCH(CH3)-2-C10H6}] (2e) were obtained
as purple solids in good yields from the reaction of the Ir
chloride complexes Cp*IrCl[κ2(N,C)-(NH2CR2-2-C6H4)] (1a: R
) C6H5, 1b: R ) CH3) and Cp*IrCl[κ2(N,C)-(R)-{NHCH(CH3)-
2-C10H6}] (1e) with 1.5 equiv of KOC(CH3)3 in CH2Cl2 at room
temperature (Scheme 1). Single-crystal X-ray crystallgraphy of
2a, illustrated in Figure 1, indicates that 2a is a monomeric
16-electron neutral complex with a planar geometry around the
metal center bearing Cp* and a C-N chelate ligand. The amido
complex has a relatively short Ir-N bond, 1.903(2) Å, compared
with that of the Ir-NH2 bond, 2.137 Å, in the chloro complex
Synthesis and Reactivities of Cyclometalated Hydrido-Ir
Complexes. The isolable 16-electron amido complex 2a was
found to react readily with 2-propanol at ambient temperature,
leading to the 18-electron hydrido(amine) complex Cp*IrH[κ2-
(N,C)-{NH2C(C6H5)2-2-C6H4}] (3a) in 88% yield (Scheme 2),
as previously observed in Ru- and Ir-Ts-diamine complexes.2e,g
Similarly, the amido complex 2b was readily converted to the
hydrido complex 3b. The IR spectra of 3a and 3b display Ir-H
stretching frequencies at 2024 and 2064 cm-1, respectively. The
1H NMR spectra of 3a and 3b in CD2Cl2 show hydride signals
at -12.9 and -13.2 ppm, respectively, in addition to two broad
peaks due to NH protons at 4.33 and 5.78 ppm for 3a and at
3.21 and 4.47 ppm for 3b.
(6) (a) Sortais, J.-B.; Ritleng, V.; Voelklin, A.; Holuigue, A.; Smail,
H.; Barloy, L.; Sirlin, C.; Verzijl, G. K. M.; Boogers, J. A. F.; de Vries,
A. H. M.; de Vries, J. G.; Pfeffer, M. Org. Lett. 2005, 7, 1247–1250. (b)
Sortais, J.-B.; Pannetier, N.; Holuigue, A.; Barloy, L.; Sirlin, C.; Pfeffer,
M.; Kyritsakas, N. Organometallics 2007, 26, 1856–1867. (c) Sortais, J.-
B.; Pannetier, N.; Cle´ment, N.; Barloy, L.; Sirlin, C.; Pfeffer, M.; Kyritsakas,
N. Organometallics 2007, 26, 1868–1874.
(7) Barloy and Pfeffer have reported that an analogous iridacycle was
not obtained as a single product by the reaction of the primary amine in
the presence of KPF6: see ref 6b.
(8) For reviews of cyclometalation, see for example: (a) Dehand, M.;
Pfeffer, M. Coord. Chem. ReV. 1976, 18, 327–352. (b) Omae, I. Coord.
Chem. ReV. 1988, 83, 137–167. (c) Ryabov, A. D. Chem. ReV. 1990, 90,
403–424. (d) van der Boom, M. E.; Milstein, D. Chem. ReV. 2003, 103,
1759–1792.
(9) (a) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.; Hilton,
S. T.; Russell, D. R. Dalton Trans. 2003, 4132-4138. (b) Davies, D. L.;
Donald, S. M. A.; Al-Duaij, O.; Macgregor, S. A.; Po¨lleth, M. J. Am. Chem.
Soc. 2006, 128, 4210–4211.
Figure 1. Molecular structure of Cp*Ir[κ2(N,C)-{NHC(C6H5)2-2-
C6H4}] (2a). The hydrogen atoms are omitted for clarity, and the
ellipsoids represent 50% probability.
(10) (a) Koike, T.; Ikariya, T. Organometallics 2005, 24, 724–730. (b)
Ishiwata, K.; Kuwata, S.; Ikariya, T. Organometallics 2006, 25, 5847–5849.

Cp*Ir Amide and Hydride Complexes with C-N Chelate Ligands
Organometallics, Vol. 27, No. 12, 2008 2797
Scheme 3
Figure 2. Molecular structure of Cp*Ir(OCOCH3)[κ2(N,C)-
{NH2C(C6H5)2-2-C6H4}] (4). Ellipsoids are shown at the 50%
probability level for the non-hydrogen atoms. The dashed line
indicates the hydrogen bond.
Scheme 2
via deprotonation as shown in Scheme 3 and as observed in
the related amido-Ru complexes.3a,14 The reaction of 2a with
1 equiv of acetic acid (pKa in DMSO ) 12.3)15 in CH2Cl2 at
room temperature gave the corresponding acetato complex
4, Cp*Ir(OCOCH3)[κ2(N,C)-{NH2C(C6H5)2-2-C6H4}], which
was also obtained from the cyclometalation of Cp*Ir-
(OCOCH3)2 with triphenylmethylamine, as mentioned above.
As shown in Figure 2, the molecular structure of 4, confirmed
by X-ray crystallography, showed that there is a short
N(H2) · · · OdC distance of 2.945(3) Å, indicating the presence
of an intramolecular hydrogen bond, as observed in the
analogous complexes.14,16 The N(H) · · · OdC interaction in
4 was further evidenced by a significant downfield shift of
one of the NH2 signals at 8.51 ppm in the 1H NMR spectrum.
Similarly, complex 2a deprotonated dimethyl malonate
(pKa in DMSO ) 15.9)15 to give the corresponding C-bound
malonato complex 5, Cp*Ir[CH(COOCH3)2][κ2(N,C)-{NH2C-
(C6H5)2-2-C6H4}], in 86% yield, as observed in the isolable
Ru complex.3b The 13C{1H} NMR of 5 in CD2Cl2 displayed
characteristic CdO signals of CH(COOCH3)2 at 175.3 and
177.7 ppm. The deprotonation by the amido-Ir complex 2
was also observed for less acidic acetone (pKa in DMSO )
26.5).15 When an acetone solution (1.0 × 10-2 M) of 2a
was stirred at room temperature, the acetonyl(amine) complex
6a, Cp*Ir(CH2COCH3)[κ2(N,C)-{NH2C(C6H5)2-2-C6H4}], was
obtained as an orange solid in 87% yield. The 1H NMR
spectrum in CD2Cl2 exhibits two doublet signals assigned to
the diastereotopic CH2 protons of the acetonyl ligand at 2.27
These hydrido complexes were found to be thermally stable
under an Ar atmosphere. Thermal treatment of the 18-electron
deuterido(amine) complex 3b-D in 1,4-dioxane at 100 °C
provided no deuterido scrambling on this complex, indicating
that neither reductive elimination of the hydrido ligand and
phenyl fragment on the C-N chelate ligand followed by
recyclometalation of the κ1(N)-amine complex nor an exchange
reaction between the hydrido ligand and coordinated amine
protons took place. Notably, the isolable hydrido complexes
have proven to react with oxygen under mild conditions,
providing the corresponding amido complexes.11
The hydrido complex 3a reacted smoothly with acetone (in
a mole ratio of 12 based on 3a) in CH2Cl2 at room temperature
to give 2-propanol, while it did not react with olefins such as
styrene, under identical conditions, due to the coordinatively
saturated structure of the hydrido(amine) complex, as observed
in analogous bifunctional catalysts.12 The hydrogen atoms in
the hydrido(amine) complex transfer to acetone possibly through
a six-membered pericyclic transition state as previously pro-
posed.13
2
and 3.00 ppm with JHH ) 5.9 Hz and two distinct signals
Reactivities of Cyclometalated Amido-Ir Complexes as
Brønsted Bases. Thanks to the nature of the Ir-NH group,
the amido-Ir complex readily reacted with acidic compounds
due to NH protons at 4.40 and 6.80 ppm. Because the
presence of the CdO moiety was confirmed by a 13C{1H}
NMR signal observed at 213.8 ppm and a CO stretching band
at 1596 cm-1 in the IR spectrum, we conclude that the
acetonyl ligand coordinates to the Ir center in a C-bound
mode, as observed in the Cp*Ir(CH2COCH3)(Tsdpen) (dpen
) 1,2-diphenylethylenediamine) complex. Similar spectro-
scopic features were observed for the related acetonyl(amine)
(11) (a) Arita, S.; Koike, T.; Kayaki, Y.; Ikariya, T. Angew. Chem., Int.
Ed. 2008, 47, 2447–2449. (b) Recently, dehydrogenation of hydrido(amine)
complex to amido complex by molecular oxygen was also reported in a
related Ts-diamine system: Heiden, Z. M.; Rauchfuss, T. B. J. Am. Chem.
Soc. 2007, 129, 14303–14310.
(12) Ohkuma, T.; Ooka, H.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am.
Chem. Soc. 1995, 117, 2675–2676.
(13) (a) Abdur-Rashid, K.; Clapham, S. E.; Hadzovic, A.; Harvey, J. N.;
Lough, A. J.; Morris, R. H. J. Am. Chem. Soc. 2002, 124, 15104–15118.
(b) Alonso, D. A.; Brandt, P.; Nordin, S. J. M.; Andersson, P. G. J. Am.
Chem. Soc. 1999, 121, 9580–9588. (c) Yamakawa, M.; Ito, H.; Noyori, R.
J. Am. Chem. Soc. 2000, 122, 1466–1478.
(14) Koike, T.; Ikariya, T. AdV. Synth. Catal. 2004, 346, 37–41.
(15) (a) Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456–463. (b) Arnett,
E. M.; Maroldo, S. G.; Schilling, S. L.; Harrelson, J. A. J. Am. Chem. Soc.
1984, 106, 6759–6767.
(16) Koike, T.; Ikariya, T. J. Organomet. Chem. 2007, 692, 408–419.

2798 Organometallics, Vol. 27, No. 12, 2008
Arita et al.
Figure 3. Molecular structure of Cp*Ir(CH2COCH3)[κ2(N,C)-
{NH2C(CH3)2-2-C6H4}] (6b). Only one of the two independent
molecules is shown. Ellipsoids are shown at the 50% probability
level for the non-hydrogen atoms. The dashed line indicates the
hydrogen bond.
Figure 4. Molecular structure of [Cp*Ir[κ2(N,C)-{NH2C(CH3)2-2-
C6H4}(CO)]BF4 (7b). Ellipsoids are shown at the 50% probability
level for the non-hydrogen atoms.
Scheme 4
complex 6b, Cp*Ir(CH2COCH3)[κ2(N,C)-{NH2C(CH3)2-2-
C6H4}], which was prepared by treatment of 2b with an
excess amount of acetone in 81% yield. The structure of the
C-bound acetonyl complex was also confirmed by X-ray
crystallography of 6b depicted in Figure 3. An average
distance of 2.824 Å for the N(H2) · · · OdC motif indicates
the presence of intramolecular hydrogen bonding.
Notably, the acetonyl complexes 6 proved to be labile in
solution and gradually converted into the amido complexes 2
and free acetone at room temperature. The thermodynamics of
the reversible process between the acetonyl complex and the
amido complex plus acetone indicate that the electronic proper-
ties of the chelating ligands delicately affect the basicity of the
amido complex. An equilibrium constant (Keq) determined from
the 1H NMR monitoring of the reaction of 2a with 60 equiv of
acetone in dioxane-d8 at 30 °C was 2.5 L/mol. In contrast,
treatment of complex 2b, having a more electron-donating
ligand, with an equimolar amount of acetone at 30 °C gave a
Keq value of 26.3 L/mol. These results are consistent with the
result obtained with the electron-withdrawing N-sulfonylamido
complex Cp*Ir[κ2(N,N′)-TsNCHC6H5CHC6H5NH], having Keq
) 2.9 × 10-2 L/mol in an acetone-d6 solution with a concentra-
tion of 0.014 mol/L, as shown in Scheme 3. From the Keq values
for 2a in a temperature range of 30 to 60 °C, the van’t Hoff
plots can be fit linearly to determine ∆H ) -53.1 kJ mol-1
and ∆S ) -173 J mol-1 K-1 (see Supporting Information).
Evaluation of Electronic Properties of the Cyclometalated
Complexes. As discussed in the previous section, the reactivity
of the amido complexes was significantly influenced by a change
in the amine ligands. In order to gain further insight into the
difference in the electronic properties on the C-N and Ts-
diamine ligands, we prepared cationic Cp*Ir-CO complexes
bearing various chelating primary amine ligands.4b,17 The
cationic carbonyl complexes 7, with the C-N chelating ligands,
were prepared as crystalline compounds from the reaction of 1
with an equimolar amount of AgBF4 in CH3CN, followed by
exposure to atmospheric pressure of CO in CH2Cl2. The related
Cp*Ir(Tscydn)CO complex 8 (cydn ) 1,2-cyclohexanediamine)
was similarly obtained. The molecular structure of the isolable
carbonyl complex 7b, [Cp*Ir{κ2(N,C)-(NH2C(CH3)2-2-C6H4)}-
(CO)]BF4, shown in Figure 4, confirmed that it has a three-
legged piano stool configuration around the metal center and
an Ir-CO distance of 1.855(3) Å.
The IR spectra of complexes 7a and 7b show the character-
istic stretching band of the CO ligand at 2030 and 2036 cm-1
,
respectively. The C-O stretching frequency in the carbonyl
complexes increases in the order 7a = 7b < 8 as shown in
Scheme 4, indicating the relatively electron-donating nature of
the Ir center with C-N chelate ligands compared to that with
Ts-cydn. This trend in the electron-donating properties is
consistent with the above-mentioned strong basicity of the amido
complexes with C-N ligands.
Catalytic Activity of Both Amido and Hydrido(amine)
Complexes. On the basis of detailed structural analysis and
reactivities of isolable amido complexes 2 and hydrido(amine)
complexes 3 discussed above, we examined catalytic transfer
hydrogenation with both complexes. The transfer hydrogenation
of acetophenone in 2-propanol containing 2a or 2b (substrate/
catalyst ) 100/1) at room temperature proceeded efficiently to
give 1-phenylethanol in 95-96% yield after 1 h. The hydri-
do(amine) complexes 3a and 3b also afforded 1-phenylethanol
in comparable yields of 98% and 88%, respectively. The
catalytic activity of 2 was found to be much higher than that of
(17) Ito, M.; Ikariya, T. Chem. Commun. 2007, 5134-5142.

Cp*Ir Amide and Hydride Complexes with C-N Chelate Ligands
Scheme 5a
Organometallics, Vol. 27, No. 12, 2008 2799
a
Catalysts 1 and Cp*Ir(Tscydn) required 1.2 equiv of KOC(CH3)3 to catalyst.
Cp*Ir(Ts-diamine) complexes (1% yield, 91% ee for the (S,S)-
Tsdpen complex and 17% yield, 99% ee for the (S,S)-Tscydn
complex) under the same conditions. Asymmetric reduction of
acetophenone with the chiral Cp*Ir(C-N) complexes 1e and
1f, derived from (R)-1-(1-naphthyl)ethylamine and (S)-2-tert-
butyldimethylsiloxy-1-phenylethylamine, in the presence of
KOC(CH3)3 gave (S)-1-phenylethanol in 91-95% yield albeit
with moderate ee (38-66%). These results indicate that
amido-Ir complexes with C-N chelating ligands could be
promising bifunctional catalysts for highly efficient transfer
hydrogenation, although fine-tuning of the chiral ligands might
be required for improvement in the enantioselectivity.
Experimental Section
General Procedures. All experiments were conducted under an
argon atmosphere using Schlenk techniques. All deuterated NMR
solvents were dried and degassed by appropriate methods. Solvents
were purchased from Kanto Chemical and dried by refluxing over
sodium benzophenone ketyl (THF, toluene, diethyl ether), P2O5
(dichloromethane, hexane, acetonitrile), or CaSO4 (acetone) and
distilled under argon. [Cp*IrCl2]2,18 Cp*Ir(OCOCH3)2,19 (S)-2-tert-
butyldimethylsiloxy-1-phenylethylamine,20 Cp*Ir[κ2(N,N′)-(S,S)-
TsNCHC6H5CHC6H5NH],2g and Cp*IrCl[κ2(N,N′)-(S,S)-Tscydn]2g
were prepared according to the literature. A deuterated alcohol,
3-pentanol-d1, was prepared by reduction of 3-pentanone with
NaBD4. Other reagents were used as delivered. H and 13C{1H}
1
NMR spectra were recorded on a JEOL JNM-LA300 spectrometer
and referenced to SiMe4 via the solvent resonance. Elemental
analyses were carried out using a PE2400 Series II CHNS/O
analyzer (Perkin-Elemer). IR spectra were recorded on a JASCO
FT/IR-610 spectrometer.
Conclusions
We isolated and characterized 16-electron cyclometalated
amido-Ir complexes 2 having the metal/NH bifunctionality.
These amido complexes 2 were readily converted into the
isolable hydrido(amine) complexes 3 in 2-propanol, and the
reverse hydrogen transfer from 3 to acetone was also demon-
strated. Because of the reversibility between 2 and 3, the C-N
chelate Ir complexes were successfully applied to catalytic
transfer hydrogenation of acetophenone, which showed greater
activity than the Cp*Ir(Ts-diamine) catalyst system. Due to a
relatively stronger basicity originating from the nature of the
amido complexes with the C-N ligand, they reacted smoothly
with acidic compounds such as acetic acid, dimethyl malonate,
and acetone to give the corresponding amine Ir complexes 4-6.
The basicity of the amido complexes was highly influenced by
the modification of the chelating amine ligands, as shown
by the equilibrium constants for the deprotonation of acetone.
IR analysis of the carbonyl complexes 7 and 8 also provides
good evidence for enhancement of the σ-donor capability of
the C-N chelating ligands, compared to the Ts-diamine
chelating ligand. The present work indicates that the C-N
ligands allow one to modulate the electronic properties of the
metal/NH bifunctional systems, leading to high catalytic per-
formance. Now we are working on the development of new
catalysis based on the reactivity of these C-N complexes.
The experimental and analytical procedures for catalytic transfer
hydrogenation were performed according to the literature.2g Ana-
lytical gas chromatography was performed with a Shimadzu GC-
17A gas chromatograph equipped with an Inert Cap Wax capillary
column (0.25 mm × 30 m) purchased from GL Sciences Inc.
Analytical chiral HPLC was performed on a Chiralcel OD column
(4.6 mm × 25 cm) purchased from Daicel Chemical Industries,
Ltd.
General Procedure for Synthesis of Cp*IrCl[K2(N,C)-(NH2CR2-
2-C6H4)] (1a: R ) C6H5, 1b: R ) CH3). A mixture of [Cp*IrCl2]2
(0.1 g, 0.13 mmol), the appropriate benzylamine (0.25 mmol), and
NaOAc (0.027 g, 0.33 mmol) in CH2Cl2 (5 mL) was stirred at room
temperature for 20 h. The solvent was removed under reduced
pressure. After the reaction mixture in toluene was filtered through
filter paper, evaporation of the filtrate to dryness gave the iridacycle
product.
(18) Kang, J. W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969,
91, 5970–5977.
(19) Kang, J. W.; Maitlis, P. M. J. Organomet. Chem. 1971, 30, 127–
133.
(20) Cheung, F. K.; Hayes, A. M.; Hannedouche, J.; Yim, A. S. Y.;
Wills, M. J. Org. Chem. 2005, 70, 3188–3197.

2800 Organometallics, Vol. 27, No. 12, 2008
Arita et al.
Cp*IrCl[K2(N,C)-{NH2C(C6H5)2-2-C6H4}] (1a). Orange crystals
suitable for X-ray crystallography were obtained by slow diffusion
of diethyl ether into the solution in CH2Cl2. Isolated yield: 76%
Cp*IrCl[K2(N,C)-(R)-{NH2CH(CH3)-2-C10H6}] (1e). Recrystal-
lization from toluene and hexane afforded orange crystals. Isolated
yield: 31% (0.047 g, 0.087 mmol). 1H NMR (300.4 MHz, CD2Cl2,
rt, δ/ppm): 1.54 (d, 3JHH ) 7.5 Hz, 3H; NH2CH(CH3)C10H6), 1.62
(s, 15H; C(CH3)5), 2.12 (m, 1H; NH2CH(CH3)C10H6), 3.69, 4.82
(each br, 1H; NH2CH(CH3)C10H6), 7.14-7.76 (m, 6H; NH2-
CH(CH3)C10H6). 13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm):
9.6 (C5(CH3)5), 22.7 (NH2CH(CH3)C10H6), 59.7 (NH2CH(CH3)C10H6),
87.2 (C5(CH3)5), 122.9, 123.7, 125.6, 126.2, 128.6, 131.4, 136.5,
146.0, 153.9 (NH2CH(CH3)C10H6). IR (cm-1, KBr): 3273 (m), 3221
(m), 2954 (m), 2928 (m), 1571 (m), 1257 (m), 1247 (m), 1102
1
(0.105 g, 0.17 mmol). H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
2
1.39 (s, 15H; C(CH3)5), 4.97, 5.72 (each d, JHH ) 10 Hz, 1H;
NH2C(C6H5)2C6H4), 6.22-7.58 (m, 14H; NH2C(C6H5)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 8.4 (C5(CH3)5),
80.5 (NH2C(C6H5)2C6H4), 88.4 (C5(CH3)5), 121.4, 125.9, 127.2,
128.0, 128.4, 128.5, 129.6, 129.7, 137.0, 147.6, 148.1, 152.3, 152.4,
152.6 (NH2C(C6H5)2C6H4). IR (cm-1, KBr): 3280 (w), 3232 (w),
3045 (w), 2983 (w), 2959 (w), 2913 (w), 1570 (m), 1493 (m), 1445
(m), 1091 (m), 731 (m). Anal. Calcd for C22H27NClIr (C6H5CH3)0.1
:
(m), 1034 (m), 702 (m). Anal. Calcd for C29H31NClIr(CH2Cl2)0.5
C 53.39, H 4.86, N 2.11. Found: C 53.50, H 4.92, N 2.09.
:
C 50.27, H 5.17, N 2.58. Found: C 50.07, H 5.21, N 2.20.
Cp*IrCl[K2(N,C)-{NH2C(CH3)2-2-C6H4}] (1b). Orange crystals
suitable for X-ray crystallography were obtained by slow diffusion
of diethyl ether into the solution in CH2Cl2. Isolated yield: 79%
Cp*IrCl[K2(N,C)-(S)-{NH2CH(CH2OSi(CH3)2tBu)-2-C6H4}] (1f).
Recrystallization from diethyl ether afforded orange crystals.
Isolated yield: 35% (0.25 g, 0.4 mmol). 1H NMR (300.4 MHz,
CD2Cl2, rt, δ/ppm): 0.12, 0.16 (each s, 3H; OSi(CH3)2C(CH3)3),
0.75 (s, 9H; OSi(CH3)2C(CH3)3), 1.72 (s, 15H; C(CH3)5), 3.03 (m,
1H; NH2CH), 3.64, 4.13 (each m, 1H; CH2), 4.39, 4.71 (each br,
1H; NH2), 6.78-7.46 (m, 4H; C6H4). 13C{1H} NMR (75.6 MHz,
CD2Cl2, rt, δ/ppm): 8.5 (C(CH3)3), 9.3 (C5(CH3)5), 18.3
(OSi(CH3)2(C(CH3)3), 26.0 (C(CH3)3), 65.7 (CH2), 68.3 (NH2CH),
87.0 (C5(CH3)5), 120.9, 122.3, 127.4, 137.2, 148.4, 156.5 (C6H4).
IR (cm-1, KBr): 3334 (m), 3042 (m), 3028 (m), 2924 (m), 2909
(m), 2866 (m), 2817 (m), 1611 (m), 1381 (m), 1029 (m). Anal.
Calcd for C24H39NOClIrSi: C 47.00, H 6.41, N 2.28. Found: C
46.85, H 6.53, N 2.33.
1
(0.095 g, 0.19 mmol). H NMR (300.4 MHz, CDCl3, rt, δ/ppm):
1.21, 1.56 (each s, 3H; NH2C(CH3)2C6H4), 1.70 (s, 15H; C(CH3)5),
3.88, 4.40 (each br, 1H; NH2C(CH3)2C6H4), 6.79-6.86 (m, 2H;
NH2C(CH3)2C6H4), 6.91-6.97 (m, 1H; NH2C(CH3)2C6H4), 7.42-7.45
(m, 1H; NH2C(CH3)2C6H4). 13C{1H} NMR (75.6 MHz, CDCl3, rt,
δ/ppm): 9.5 (C5(CH3)5), 30.9, 32.0 (NH2C(CH3)2C6H4), 66.5
(NH2C(CH3)2C6H4), 87.0 (C5(CH3)5), 121.4, 125.6, 127.1, 138.0,
154.2, 155.2 (NH2C(CH3)2C6H4). IR (cm-1, KBr): 3260 (m), 3219
(m), 2973 (w), 2911 (w), 1577 (m), 1450 (m), 1024 (m), 764 (m),
740 (m). Anal. Calcd for C19H27NClIr: C 45.91, H 5.47, N 2.82.
Found: C 46.00, H 5.53, N 2.84.
General Procedure for Synthesis of Cp*Ir[K2(N,C)-(NHCR2-2-
Ar)] (2a: R ) C6H5, 2b: R ) CH3, and 2e: (R)-1-(1-naphthyl)-
ethylamine). A mixture of Cp*IrCl[κ2(N,C)-NH2CR2-2-Ar] (0.35
mmol) and dry KOC(CH3)3 (0.53 mmol) in CH2Cl2 (9 mL) was
stirred at room temperature for 21 h. The solvent was removed
under reduced pressure. After the residue was dissolved in diethyl
ether, insoluble material was removed by filtration. Evaporation to
dryness of the filtrate gave the product.
General Procedure for Synthesis of Cp*IrCl[K2(N,C)-(NH2CHR-
2-Ar)] (1c: R ) CH3, 1d: R ) H, 1e: (R)-1-(1-naphthyl)ethy-
lamine, and 1f: (S)-2-tert-butyldimethylsiloxy-1-phenylethylamine).
A mixture of [Cp*IrCl2]2 (0.1 g, 0.13 mmol), the appropriate
benzylamine (0.25 mmol), and NaOAc (0.027 g, 0.33 mmol) in
CH3CN (5 mL) was stirred at 60 °C for 20 h. The solvent was
removed under reduced pressure. After the reaction mixture in
toluene was filtered through filter paper, evaporation of the filtrate
to dryness gave the iridacycle product.
Cp*Ir[K2(N,C)-{NHC(C6H5)2-2-C6H4}] (2a). Recrystallization from
a concentrated solution in diethyl ether afforded purple crystals. Isolated
Cp*IrCl[K2(N,C)-{NH2CH(CH3)-2-C6H4}] (1c). Recrystallization
from toluene and hexane afforded orange crystals in 34% yield
(0.083 g, 0.17 mmol) as a 5:2 mixture of diastereomers. 1H NMR
(300.4 MHz, CDCl3, rt, δ/ppm): major diastereomer, 1.54 (d, 3JHH
) 6.6 Hz, 1H; NH2CH(CH3)C6H4), 1.72 (s, 15H; C(CH3)5), 3.87
(m, 1H; NH2CH(CH3)C6H4), 3.77, 4.16 (each br, 1H; NH2CH-
(CH3)C6H4), 6.80-7.51 (4H; NH2CH(CH3)C6H4); minor diastere-
1
yield: 80% (0.16 g, 0.28 mmol). H NMR (300.4 MHz, CD2Cl2, rt,
δ/ppm): 1.95 (s, 15H; C(CH3)5), 6.81-8.09 (m, 14H;
NHC(C6H5)2C6H4), 8.00 (br, 1H; NHC(C6H5)2C6H4). 13C{1H} NMR
(75.6 MHz, CD2Cl2, rt, δ/ppm): 10.0 (C5(CH3)5), 87.3
(NHC(C6H5)2C6H4), 90.9 (C5(CH3)5), 122.6, 124.3, 125.0, 126.3, 127.6,
127.8, 136.8, 145.4, 160.7, 164.5 (NHC(C6H5)2C6H4). IR (cm-1, KBr):
3056 (w), 1488 (m), 1442 (m), 1370 (w), 1079 (w), 1026 (m), 779
(m), 727 (m), 696 (m), 636 (m). Anal. Calcd for C29H30NIr: C 59.56,
H 5.17, N 2.40. Found: C 59.53, H 5.36, N 2.05.
3
omer, 1.22 (d, JHH ) 6.6 Hz, 1H; NH2CH(CH3)C6H4), 1.72 (s,
15H; C(CH3)5), 4.34 (m, 1H; NH2CH(CH3)C6H4), 3.51, 4.72 (each
br, 1H; NH2CH(CH3)C6H4), 6.80-7.18 (m, 4H; NH2CH-
(CH3)C6H4). 13C{1H} NMR (75.6 MHz, CDCl3, rt, δ/ppm): major
diastereomer, 9.3 (C5(CH3)5), 22.8 (NH2CH(CH3)C6H4), 61.8
(NH2CH(CH3)C6H4), 86.4 (C5(CH3)5), 121.3, 122.4, 127.7, 128.2,
129.0, 136.6 (NH2CH(CH3)C6H4); minor diastereomer, 9.4
(C5(CH3)5), 24.7 (NH2CH(CH3)C6H4), 61.2 (NH2CH(CH3)C6H4),
86.6 (C5(CH3)5), 119.2, 120.1, 125.3, 131.7, 136.2, 137.2
(NH2CH(CH3)C6H4). IR (cm-1, KBr): 3265 (m), 3213 (m), 3047
(w), 2978 (w), 2910 (w), 1579 (m), 1451 (m), 1378 (w), 1026 (m),
741 (m). Anal. Calcd for C18H25NClIr: C 44.75, H 5.22, N 2.90.
Found: C 44.72, H 5.51, N 2.65.
Cp*Ir[K2(N,C)-{NHC(CH3)2-2-C6H4}] (2b). Recrystallization from
a concentrated solution in diethyl ether afforded purple crystals. Isolated
1
yield: 88% (0.10 g, 0.22 mmol). H NMR (300.4 MHz, CD2Cl2, rt,
δ/ppm): 1.32 (s, 6H; NHC(CH3)2C6H4), 1.94 (s, 15H; C(CH3)5),
3
6.82-6.96 (m, 2H; NHC(CH3)2C6H4), 7.13 (d, JHH ) 7.3 Hz, 1H;
3
NHC(CH3)2C6H4), 8.02 (d, JHH ) 7.3 Hz, 1H; NHC(CH3)2C6H4),
8.47 (br, 1H; NHC(CH3)2C6H4) 13C{1H} NMR (75.6 MHz, CD2Cl2,
rt, δ/ppm): 10.4 (C5(CH3)5), 27.9 (NHC(CH3)2C6H4), 78.9
(NHC(CH3)2C6H4), 87.1 (C5(CH3)5), 120.8, 122.6, 125.1, 136.8, 162.1,
163.3 (NHC(CH3)2C6H4). IR (cm-1, KBr): 3042 (w), 2964 (m), 2911
(m), 1576 (m), 1428 (m), 1381 (m), 1261 (m), 1099 (m), 1025 (m),
802 (m). Anal. Calcd for C19H26NIr: C 49.54, H 5.69, N 3.04. Found:
C 49.45, H 5.72, N 2.92.
Cp*IrCl[K2(N,C)-(NH2CH2-2-C6H4)] (1d). Recrystallization from
toluene and hexane afforded orange crystals. Isolated yield: 50%
1
Cp*Ir[K2(N,C)-(R)-{NHCH(CH3)-2-C10H6}] (2e). Recrystalliza-
tion from diethyl ether afforded purple crystals. Isolated yield: 63%
(0.092 g, 0.20 mmol). H NMR (300.4 MHz, CDCl3, rt, δ/ppm):
1.71 (s, 15H; C(CH3)5), 3.75-4.18 (4H; NH2CH2C6H4), 6.80-7.50
(m, 4H; NH2CH2C6H4). 13C{1H} NMR (75.6 MHz, CDCl3, rt,
δ/ppm): 9.27 (C5(CH3)5), 55.9 (NH2CH2C6H4), 86.4 (C5(CH3)5),
1
(0.083 g, 0.17 mmol). H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
3
1.48 (d, JHH ) 4.5 Hz, 3H; NHCH(CH3)C10H6), 1.97 (s, 15H;
120.1, 122.3, 127.2, 136.4, 146.5, 156.8 (NH2CH2C6H4). IR (cm-1
,
C(CH3)5), 2.91 (m, 1H; NHCH(CH3)C10H6), 7.22-8.28 (m, 6H;
NHCH(CH3)C10H6), 8.42 (br, 1H; NHCH(CH3)C10H6). 13C{1H}
NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.5 (C5(CH3)5), 21.8
(NHCH(CH3)C10H6), 74.5 (NHCH(CH3)C10H6), 87.7 (C5(CH3)5),
KBr): 3234 (m), 3136 (w), 3051 (w), 2983 (w), 2910 (m), 1580
(m), 1451 (m), 1367 (w), 1135 (m). Anal. Calcd for C17H23NClIr:
C 43.53, H 4.94, N 2.99. Found: C 43.17, H 4.93, N 2.95.

Cp*Ir Amide and Hydride Complexes with C-N Chelate Ligands
Organometallics, Vol. 27, No. 12, 2008 2801
123.1, 124.6, 125.2, 125.3, 128.3, 128.6, 131.5, 136.0, 155.8, 162.5
(NHC(CH3)2C10H6). IR (cm-1, KBr): 3335 (m), 3223 (m), 3143
(w), 3024 (w), 2974 (w), 2909 (w), 1575 (m), 1032 (m), 810 (m),
739 (m). Anal. Calcd for C22H26NIr: C 53.20, H 5.28, N 2.82.
Found: C 52.75, H 5.36, N 2.87.
General Procedure for Synthesis of Cp*IrH[K2(N,C)-(NH2CR2-
2-C6H4)] (3a: R ) C6H5, 3b: R ) CH3). Cp*Ir[κ2(N,C)-(NHCR2-
2-C6H4)] (2) (0.69 mmol) in 2-propanol (10 mL) was stirred at room
temperature overnight. The solvent was removed under reduced
pressure. The residue was washed with hexane and dried under
vacuum.
1445(m), 1367(m), 1314(m), 1035(w), 762(m), 752(m), 732(m),
701(m). Anal. Calcd for C31H34NO2Ir: C 57.74, H 5.31, N 2.17, O
4.96. Found: C 57.67, H 5.60, N 2.11, O 5.32.
Synthesis of Cp*Ir[CH(COOCH3)2][K2(N,C)-{NH2C(C6H5)2-2-
C6H4}] (5). Dimethyl malonate (0.031 mL, 0.27 mmol) was added to
a solution of Cp*Ir[κ2(N,C)-{NHC(C6H5)2-2-C6H4}] (2a) (0.158 g, 0.27
mmol) in CH2Cl2 (10 mL). The solution color turned from purple to
yellow. The reaction mixture was stirred at room temperature for 24 h.
The solvent was removed under reduced pressure. The residue was
washed with hexane and then dried in Vacuo. Isolated yield: 84% (0.16
1
g, 0.23 mmol). H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm): 1.30 (s,
Cp*IrH[K2(N,C)-{NH2C(C6H5)2-2-C6H4}] (3a). Isolated yield:
88% (0.23 g, 0.39 mmol). 1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
-12.92 (s, 1H; IrH), 1.84 (s, 15H; C(CH3)5), 4.33, 5.78 (each br, 1H;
NH2C(C6H5)2C6H4), 6.63-7.45 (m, 14H; NH2C(C6H5)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.9 (C5(CH3)5), 80.3
(NH2C(C6H5)2C6H4), 87.4 (C5(CH3)5), 120.0, 126.0, 126.2, 127.5,
128.3, 128.4, 128.6, 128.7, 129.1, 137.3, 146.5, 148.0, 152.9, 153.5
(NH2C(C6H5)2C6H4). IR (cm-1, KBr): 3363 (w), 3351 (w), 3298 (m),
3049 (m), 3019 (m), 2966 (m), 2902 (m), 2851 (m), 2024 (s), 1570
(s), 1261 (s), 1025 (m), 702 (m). Anal. Calcd for C29H32NIr: C 59.36,
H 5.50, N 2.39. Found: C 59.33, H 5.59, N 2.20.
15H; C(CH3)5), 2.80, 3.60 (each s, 3H; COOCH3), 4.09 (s, 1H; IrCH),
4.33, 7.19 (each br, 1H; NH2C(C6H5)2C6H4), 6.30-7.52 (m, 14H;
NH2C(C6H5)2C6H4). 13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm):
8.5 (C5(CH3)5), 49.8, 50.6 (COOCH3), 59.8 (IrCH), 80.5
(NH2C(C6H5)2C6H4), 88.4 (C5(CH3)5), 121.4, 125.9, 127.2, 128.1,
128.4, 128.5, 128.7, 129.6, 129.7, 137.0, 147.6, 148.1, 152.3, 155.6
(NH2C(C6H5)2C6H4), 175.3, 177.7 (COOCH3). IR (cm-1, KBr): 3299
(w), 3277 (w), 3056 (w), 2944 (w), 1674 (s), 1575 (m), 1443 (m),
1432 (m), 1263 (m), 1136 (m), 1059 (m), 703 (m). Anal. Calcd for
C34H38NO4Ir: C 56.96, H 5.34, N 1.95. Found: C 57.24, H 5.56, N
1.90.
Cp*IrH[K2(N,C)-{NH2C(CH3)2-2-C6H4}] (3b). Isolated yield: 86%
(0.27 g, 0.59 mmol). 1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
-13.23 (s, 1H; IrH), 1.27, 1.48 (each s, 3H; NH2C(CH3)2C6H4), 1.93
(s, 15H; C(CH3)5), 3.21, 4.47 (each br, 1H; NH2C(CH3)2C6H4), 6.62
General Procedure for the Synthesis of Cp*Ir(CH2COCH3)[K2(N,C)-
(NH2CR2-2-C6H4)] (6a: R ) C6H5, 6b: R ) CH3). A solution of
Cp*Ir[κ2(N,C)-(NHCR2-2-C6H4)] (2) (0.154 mmol) in acetone (15 mL)
was stirred at room temperature overnight. After the solvent was
removed under reduced pressure, the residue was washed with hexane.
Recrystallization from acetone afforded orange crystals.
3
3
(d, JHH ) 7.3 Hz, 1H; NH2C(CH3)2C6H4), 6.72 (t, JHH ) 7.3 Hz,
3
1H; NH2C(CH3)2C6H4), 6.79 (t, JHH
)
7.3 Hz, 1H;
NH2C(CH3)2C6H4), 7.32 (d, 3JHH ) 7.3 Hz, 1H; NH2C(CH3)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.4 (C5(CH3)5), 28.8,
30.9 (NH2C(CH3)2C6H4), 66.9 (NH2C(CH3)2C6H4), 87.2 (C5(CH3)5),
Cp*Ir(CH2COCH3)[K2(N,C)-{NH2C(C6H5)2-2-C6H4}] (6a). Iso-
lated yield: 87% (0.086 g, 0.13 mmol). 1H NMR (300.4 MHz,
CD2Cl2, rt, δ/ppm): 1.36 (s, 15H; C(CH3)5), 1.99 (s, 3H;
117.4, 118.2, 120.3, 120.6, 126.1, 137.3 (NH2C(CH3)2C6H4). IR (cm-1
,
2
IrCH2COCH3), 2.27, 3.00 (each d, JHH
) 5.9 Hz, 1H;
KBr): 3306 (m), 3262 (m), 3042 (m), 2968 (m), 2912 (m), 2064 (s),
1583 (m), 1571 (m), 1403 (m), 744 (m). Anal. Calcd for C19H28NIr:
C 49.33, H 6.10, N 3.03. Found: C 49.11, H 6.13, N 3.04.
IrCH2COCH3), 4.40, 6.80 (each br, 1H; NH2C(C6H5)2C6H4),
6.18-7.35 (m, 14H; NH2C(C6H5)2C6H4). 13C{1H} NMR (75.6
MHz, CD2Cl2, rt, δ/ppm): 8.8 (C5(CH3)5), 17.8 (CH2COCH3), 29.5
(CH2COCH3), 81.1 (NH2C(C6H5)2C6H4), 87.2 (C5(CH3)5), 121.0,
126.8, 127.1, 127.3, 128.1, 128.3, 128.6, 129.6, 129.8, 136.2, 146.8,
Synthesis of Cp*IrD[K2(N,C)-{NH2C(CH3)2-2-C6H4}] (3b-D).
C2H5CD(OH)C2H5 (0.031 mL, 0.28 mmol) was added to a solution
of Cp*Ir[κ2(N,C)-{NHC(CH3)2-2-C6H4}] (2b) (0.13 g, 0.28 mmol).
The solution color turned from purple to yellow. The reaction mixture
was stirred at room temperature for 4 weeks. Then, the solvent was
removed under reduced pressure. Deuteride complex 3b-D was
148.5, 152.5, 157.3 (NH2C(C6H5)2C6H4), 213.8 (CO). IR (cm-1
,
KBr): 3325 (w), 3144 (w), 3056 (w), 2971 (w), 2910 (w), 1596
(s), 1574 (s), 1443 (m), 1250 (s), 1047 (m). Anal. Calcd for
C32H36NOIr: C 59.79, H 5.64, N 2.18. Found: C 59.61, H 5.91, N
1.86.
1
obtained in 87% yield (0.11 g, 0.24 mmol). H NMR (300.4 MHz,
THF-d8, rt, δ/ppm): 1.12, 1.64 (each s, 3H; NH2C(CH3)2C6H4), 1.70
(s, 15H; C(CH3)5), 4.38, 4.92 (each br, 1H; NH2C(CH3)2C6H4), 6.67
Cp*Ir(CH2COCH3)[K2(N,C)-{NH2C(CH3)2-2-C6H4}] (6b). Iso-
lated yield: 81% (0.063 g, 0.12 mmol). 1H NMR (300.4 MHz,
CD2Cl2, rt, δ/ppm): 1.27, 1.46 (each s, 3H; NH2C(CH3)2C6H4), 1.65
(s, 3H; IrCH2COCH3), 1.70 (s, 15H; C(CH3)5), 2.55 (AB pattern,
2JHH ) 9.1 Hz, 2H; IrCH2COCH3), 3.12, 5.57 (each br, 1H;
NH2C(CH3)2C6H4), 6.63-6.72 (m, 2H; NH2C(CH3)2C6H4), 6.79-6.85
(m, 1H; NH2C(CH3)2C6H4), 7.18-7.21 (m, 1H; NH2C(CH3)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.1 (C5(CH3)5),
15.3 (CH2COCH3), 30.7 (CH2COCH3), 30.2, 32.4 (NH2C(CH3)2-
C6H4), 66.6 (NH2C(CH3)2C6H4), 86.8 (C5(CH3)5), 121.1, 121.3,
126.6, 136.6, 152.7, 155.1 (NH2C(CH3)2C6H4), 216.9 (CO). IR
(cm-1, KBr): 3309 (w), 3140 (w), 3107 (w), 3042 (w), 2963 (m),
2905 (m), 1553 (s), 1260 (m), 1094 (m), 1024 (m), 798 (m), 726
(m). Anal. Calcd for C22H32NOIr: C 50.94, H 6.22, N 2.70. Found:
C 50.58, H 6.36, N 2.40.
3
(d, JHH ) 4.6 Hz, 1H; NH2C(CH3)2C6H4), 6.75-6.81 (m, 2H;
NH2C(CH3)2C6H4), 7.35 (d, 3JHH ) 7.3 Hz, 1H; NH2C(CH3)2C6H4).
2H NMR (46.1 MHz, THF, rt, δ/ppm): -13.34 (s. 1H: Ir-D).
Synthesis of Cp*Ir(OCOCH3)[K2(N,C)-{NH2C(C6H5)2-2-C6H4}]
(4). Method A: Acetic acid (0.010 mL, 0.14 mmol) was added to a
solution of Cp*Ir[κ2(N,C)-{NHC(C6H5)2-2-C6H4}] (2a) (0.084 g, 0.14
mmol) in CH2Cl2 (5 mL). The solution color turned from purple to
yellow. The reaction mixture was stirred at room temperature for 21 h.
After the solvent was removed under reduced pressure, the residue
was recrystallized from toluene and hexane. Isolated yield: 53% (0.11
g, 0.074 mmol). Method B: A mixture of Cp*Ir(OCOCH3)2 (0.15 g,
0.30 mmol) and triphenylmethylamine (0.078 g, 0.30 mmol) in CH2Cl2
(6 mL) was stirred at room temperature for 20 h. The solvent was
removed under reduced pressure. Recrystallization from toluene and
hexane afforded yellow crystals. Isolated yield: 36% (0.076 g, 0.11
mmol). 1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm): 1.36 (s, 15H;
C(CH3)5), 1.91 (s, 3H; OCOCH3), 4.85, 8.51 (each br, 1H;
NH2C(C6H5)2C6H4), 6.26-7.77 (m, 14H; NH2C(C6H5)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 8.98 (C5(CH3)5), 25.7
(OCOCH3), 79.9 (NH2C(C6H5)2C6H4), 85.9 (C5(CH3)5), 122.4, 126.6,
127.1, 127.2, 127.4, 128.3, 128.4, 128.7, 129.0, 129.2, 136.0, 146.6,
155.2, 159.0 (NH2C(C6H5)2C6H4), 180.6 (OCOCH3). IR (cm-1, KBr):
3304(w), 3233 (w), 3051(w), 2982(w), 2909(w), 1604 (s), 1574(m),
General Procedure for Synthesis of Carbonyl Complexes
[Cp*Ir(CO)[K2(N,C)-{NH2CR2-2-C6H4}](BF4) (7a: R ) C6H5, 7b:
R ) CH3) and [Cp*Ir{K2(N,N′)-(S,S)-Tscydn}(CO)]BF4 (8). To an
acetonitrilesolution(8mL)ofthechloridecomplexCp*IrCl[κ2(N,C)-
(NH2CR2-2-C6H4)] (1) or Cp*IrCl[κ2(N,N′)-(S,S)-Tscydn]2g (0.15
mmol) was added AgBF4 (0.15 mmol). Then, the reaction
mixture was stirred at room temperature for 21 h. After filtration
through a Celite pad, the solvent was removed under reduced
pressure. The residue was redissolved in CH2Cl2. After bubbling
of CO gas (0.1 MPa) into the reaction mixture for 30 min, the

2802 Organometallics, Vol. 27, No. 12, 2008
Arita et al.
Table 1. Crystallographic Data for 2a, 4, 6b, and7b
2a
4
6b
7b
empirical formula
fw
C29H30IrN
584.78
C31H34IrNO2
644.84
C22H32IrN
518.72
C20H27BF4IrNO
576.46
cryst color
cryst syst
space group
a, Å
b, Å
c, Å
purple
orange
yellow
colorless
triclinic
monoclinic
P21/n (#14)
10.922(4)
19.511(7)
12.677(5)
triclinic
monoclinic
P21/c (#14)
8.626(3)
15.356(5)
16.209(5)
j
j
P1 (#2)
P1 (#2)
7.870(3)
10.155(4)
15.749(7)
73.934(12)
84.275(12)
74.846(15)
1166.9(8)
2
9.092(4)
9.101(5)
25.409(11)
90.061(8)
90.049(4)
104.137(10)
2038.7(17)
4
R, deg
, deg
95.293(5)
91.429(4)
γ, deg
V, Å3
2689.8(17)
4
1.592
1280.00
50.048
2.0
20929
6118
398
2146.3(12)
4
1.784
1120.00
62.813
10.0
16276
4845
286
Z
Dcalcd, g cm-3
F000
1.664
1.690
576.00
57.528
6.0
8570
4916
1024.00
65.763
2.0
15937
8888
µ, cm-1 (Mo KR)
exposure rate, sec/°
no. of reflections measured
nol of unique reflections
no. variables
R1 (I > 2.00σ(I))a
wR2 (all reflections)a
GOF on F2
310
521
0.0249
0.0654
0.999
0.0377
0.0913
1.000
0.0373
0.1014
1.001
0.0431
0.1122
1.001
2
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) [∑(w(Fo - Fc ) )/∑w(Fo2)2]1/2
.
solvent was evaporated under vacuum. Recrystallization from
CH2Cl2 and hexane afforded colorless crystals.
2926 (m), 2863 (m), 2056 (s), 1262 (m), 1031 (m), 888(w). The
isolated complex was not stable enough to be subjected to elemental
analysis.
[Cp*Ir{K2(N,C)-(NH2C(C6H5)2-2-C6H4)}(CO)]BF4 (7a). Isolated
yield: 62% (0.067 g, 0.090 mmol). 1H NMR (300.4 MHz, CD2Cl2,
rt, δ/ppm): 1.78 (s, 15H; C(CH3)5), 5.15, 6.65 (each br, 1H;
NH2C(C6H5)2C6H4), 6.40-7.45 (m, 14H; NH2C(C6H5)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 8.7 (C5(CH3)5),
81.3 (C5(CH3)5), 100.7 (NH2C(C6H5)2C6H4), 127.8, 128.1, 128.46,
128.54, 128.65, 128.75, 129.0, 129.2, 134.9, 136.7, 143.4, 144.45,
144.47, 154.8 (NH2C(C6H5)2C6H4), 168.3 (IrCO). IR (cm-1, KBr):
3057 (w), 2963 (w), 2030 (s), 1576 (m), 1261 (m), 1088 (m), 1022
(m), 801 (m). The isolated complex was not stable enough to be
subjected to elemental analysis.
X-ray Structure Determinations of 2a, 4, 6b, and 7b. All
measurements were made on a Rigaku Saturn CCD area detector
equipped with graphite-monochromated Mo KR radiation (λ )
0.71070 Å) under a nitrogen stream at 193 K. Indexing was
performed from seven images. The crystal-to-detector distance was
45.05 mm. The data were collected to a maximum 2θ value of
55.0°. A total of 720 oscillation images were collected. A sweep
of data was carried out using ω scans from -110.0° to 70.0° in
0.5° steps, at ꢀ ) 45.0° and ꢁ ) 0.0°. A second sweep was
performed using ω scans from -110.0° to 70.0° in 0.5° steps, at ꢀ
) 45.0° and ꢁ ) 90.0°. Intensity data were corrected for
Lorentz-polarization effects as well as absorption. Structure
solution and refinements were performed with the Crystal Structure
program package. The heavy atom positions were determined by a
direct program method (SIR2002), and the remaining non-hydrogen
atoms were found by subsequent Fourier techniques (DIRDIF99).
An empirical absorption correction based on equivalent reflections
was applied to all data. All non-hydrogen atoms were refined
anisotropically by full-matrix least-squares techniques based on F2.
All hydrogen atoms were constrained to ride on their parent atom.
Relevant crystallographic data are compiled in Table 1.
[Cp*Ir[K2(N,C)-{NH2C(CH3)2-2-C6H4}(CO)]BF4 (7b). Isolated
1
yield: 67% (0.064 g, 0.10 mmol). H NMR (300.4 MHz, CD2Cl2,
rt, δ/ppm): 1.50, 1.61 (each s, 3H; NH2C(CH3)2C6H4), 2.01 (s, 15H;
C(CH3)5), 4.46, 5.38 (each br, 1H; NH2C(CH3)2C6H4), 6.85 (d, 3JHH
)
7.1 Hz, 1H; NH2C(CH3)2C6H4), 7.05-7.15 (m, 2H;
NH2C(CH3)2C6H4), 7.23 (d, 3JHH ) 7.1 Hz, 1H; NH2C(CH3)2C6H4).
13C{1H} NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.1 (C5(CH3)5),
29.3, 30.8 (NH2C(CH3)2C6H4), 68.9 (C5(CH3)5), 100.8 (NH2C-
(CH3)2C6H4), 123.4, 126.0, 128.2, 131.9, 136.3, 157.2
(NH2C(CH3)2C6H4), 168.7 (IrCO). IR (cm-1, KBr): 3289 (m), 3262
(m), 3178 (w), 2983 (m), 2036 (s), 1456 (w), 1084 (m), 1029 (m).
The isolated complex was not stable enough to be subjected to
elemental analysis.
Acknowledgment. This work was financially supported
by a grant-in-aid from the Ministry of Education, Science,
Sports and Culture of Japan (No. 12305057, 14078209) and
partially supported by The 21st Century COE Program.
[Cp*Ir{K2(N,N′)-(S,S)-Tscydn}(CO)]BF4 (8). Isolated yield: 57%
(0.053 g, 0.075 mmol). 1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
1.97 (s, 15H; C(CH3)5), 2.23 (s, 3H; SO2C6H4CH3), 0.512.72 (m,
10H, N(C6H10)NH2), 4.63, 4.93 (each br, 2H, N(C6H10)NH2), 7.29,
7.69 (each d, J ) 7.8 Hz, J ) 8.1 Hz SO2C6H4CH3). 13C{1H}
NMR (75.6 MHz, CD2Cl2, rt, δ/ppm): 9.4 (C5(CH3)5), 21.6, 24.7,
25.0, 34.6, 34.8, 67.4, 69.4 ((C6H10)NH2, SO2C6H4CH3), 101.8
(C5(CH3)5), 127.9, 129.9, 138.6, 143.3, 167.7 (SO2C6H4CH3), 194.0
(IrCO). IR (cm-1, KBr): 3296 (m), 3263 (m), 3176 (w), 2960 (m),
Supporting Information Available: X-ray crystallographic data
of 1a, 1b, 2a, 2b, 4, 6b, and 7b and experimental details for
determination of thermodynamic parameters in the reaction of 2a
and acetone are available free of charge via the Internet at
http://pubs.acs.org.
OM800124F