Reaction of 16-electron ruthenium and iridium amide complexes with acidic alcohols: Intramolecular C-H bond activation and the isolation of cyclometalated complexes

Article abstract of DOI:10.1021/om049205x

The 16-electron transition metal amide complexes, Cp*M[k ²(N,N′)-(S,S)-TsNCHPhCH-PhNH] (M = Ir, Rh, Cp* = pentamethylcyclopentadienyl, Ts = p-toluenesulfonyl, Ph = C₆H ₅) and Ru[k²(N,N′)-(S,S)-TsNCHPhCHPhNH](p-c

Full text of DOI:10.1021/om049205x

724
Organometallics 2005, 24, 724-730
Reaction of 16-Electron Ruthenium and Iridium Amide
Complexes with Acidic Alcohols: Intramolecular C-H
Bond Activation and the Isolation of Cyclometalated
Complexes
Takashi Koike and Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering and
Frontier Collaborative Research Center, Tokyo Institute of Technology, O-okayama,
Meguro-ku, Tokyo 152-8552, Japan
Received October 13, 2004
The 16-electron transition metal amide complexes, Cp*M[κ2(N,N′)-(S,S)-TsNCHPhCH-
PhNH] (M ) Ir, Rh, Cp* ) pentamethylcyclopentadienyl, Ts ) p-toluenesulfonyl, Ph ) C6H5)
and Ru[κ2(N,N′)-(S,S)-TsNCHPhCHPhNH](p-cymene), react with acidic alcohols, CF3CH2-
OH or phenols, to give the corresponding alkoxide complexes, which are readily convertible
to metallacycles via intramolecular C-H bond activation of the aromatic group on the diamine
ligand. For example, the Ir and Rh amide complexes are transformed to the metallacycles
Cp*M[κ3(N,N′,C)-(S,S)-CH3C6H3SO2NCHPhCHPhNH2] (M ) Ir, Rh), while the Ru amide
complex having structures isoelectronic with the Cp*Ir complex gives two types of
metallacycles, Ru[κ3(N,N′,C)-(S,S)-CH3C6H3SO2NCHPhCHPhNH2](p-cymene) and Ru[κ3-
(N,N′,C)-(S,S)-TsNCHPhCH(C6H4)NH2](p-cymene), which are formed by the C-H bond
activation of an aromatic ring in either the Ts group or the diamine ligand. NMR study for
the cyclometalation of the Ir amide complex with phenols suggests that the reaction proceeds
through the phenoxide complexes as intermediates.
Introduction
catalysts for asymmetric hydrogen transfer reduction1
and C-C bond formation.2 Thanks to sufficient Brøn-
sted basicity originating from the metal/NH bifunctional
effect, the amide complexes can effectively cleave a O-H
bond of 2-propanol or formic acid and a C-H bond of
acidic compounds such as nitromethane, dimethylma-
lonate, phenylacetylene, and acetone, giving the corre-
sponding hydrido amine complexes and alkyl amine
complexes, Cp*M(R)[κ2(N,N′)-Ts-diamine] and Ru(R)[κ2-
(N,N′)-Ts-diamine](p-cymene) (M ) Ir, Rh, R ) H, CH2-
NO2, CH(COOCH3)2, CtCC6H5, and CH2COCH3), re-
spectively.1,2 When alcohols having â-hydrogen atoms
such as 2-propanol were used as acidic compounds, the
reaction gave the corresponding hydrido amine com-
plexes possibly through a pericyclic transition state,4 in
which the formation of the hydride complex from the
alkoxide complex through â-H elimination was energeti-
cally unfavorable as discussed in previous papers.4a,b On
the other hand, the reaction of the amide complex with
formic acid proceeds in a stepwise manner possibly via
ion pair formation, leading to the corresponding formate
complex, which subsequently undergoes decarboxylation
to give the hydrido amine complex with the release of
carbon dioxide.5 These results prompted us to reinves-
tigate the scope of the deprotonation of acidic com-
Well-defined chiral transition metal amide complexes
with metal/NH bifunctionality,1-3 Cp*M[κ2(N,N′)-(S,S)-
TsNCHPhCHPhNH] (M ) Ir (1a), Rh (2a), Cp* )
pentamethylcyclopentadienyl, Ts ) p-toluenesulfonyl,
Ph ) C6H5) and Ru[κ2(N,N′)-(S,S)-TsNCHPhCHPhNH]-
(p-cymene) (3a), have been developed as practical
(1) (a) Hashiguchi, S.; Fujii, A.; Takehara, J.; Ikariya, T.; Noyori,
R. J. Am. Chem. Soc. 1995, 117, 7562-7563. (b) Fujii, A.; Hashiguchi,
S.; Uematsu, N.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1996, 118,
2521-2522. (c) Uematsu, N.; Fujii, A.; Hashiguchi, S.; Ikariya, T.;
Noyori, R. J. Am. Chem. Soc. 1996, 118, 4916-4917. (d) Haack, K.-J.;
Hashiguchi, S.; Fujii, A.; Ikariya, T.; Noyori, R. Angew. Chem., Int.
Ed. Engl. 1997, 36, 285-288. (e) Hashiguchi, S.; Fujii, A.; Haack, K.-
J.; Matsumura, K.; Ikariya, T.; Noyori, R. Angew. Chem., Int. Ed. Engl.
1997, 36, 288-290. (f) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998,
1199-1200. (g) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 1201-
1202. (h) Murata, K.; Ikariya, T.; Noyori, R. J. Org. Chem. 1999, 64,
2186-2187. (i) Murata, K.; Okano, K.; Miyagi, M.; Iwane, H.; Noyori,
R.; Ikariya, T. Org. Lett. 1999, 1, 1119-1121. (j) Mao, J.; Baker, D. C.
Org. Lett. 1999, 1, 841-843. (k) Koike, T.; Murata, K.; Ikariya, T. Org.
Lett. 2000, 2, 3833-3836. (l) Okano, K.; Murata, K.; Ikariya, T.
Tetrahedron Lett. 2000, 41, 9277-9280. (m) Cossy, J.; Eustache, F.;
Daiko, P. I. Tetrahedron Lett. 2001, 42, 5005-5007. (n) Watanabe, M.;
Murata, K.; Ikariya, T. J. Org. Chem. 2002, 67, 1712-1715. (o)
Hamada, T.; Torii, T.; Izawa, K.; Noyori, R.; Ikariya, T. Org. Lett. 2002,
4, 4373-4376.
(2) (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.
(3) (a) Fulton, J. R.; Holland, A. W.; Fox, D. J.; Bergman, R. G. Acc.
Chem. Res. 2002, 35, 44-56. (b) Fulton, J. R.; Sklenak, S.; Bouwkamp,
M. W.; Bergman, R. G. J. Am. Chem. Soc. 2002, 124, 4722-4737. (c)
Holland, A. W.; Bergman, R. G. J. Am. Chem. Soc. 2002, 124, 14684-
14695. (d) Conner, D.; Jayaprakash, K. N.; Wells, M. B.; Manzer, S.;
Gunnoe, T. B.; Boyle, P. D. Inorg. Chem. 2003, 42, 4759-4772.
(4) (a) Alonso, D. A.; Brandt, P.; Nordin, S. J. M.; Andersson, P. G.
J. Am. Chem. Soc. 1999, 121, 9580-9588. (b) Yamakawa, M.; Ito, H.;
Noyori, R. J. Am. Chem. Soc. 2000, 122, 1466-1478. (c) Casey, C. P.;
Singer, S. W.; Powell, D. R.; Hayashi, R. K.; Kavana, M. J. Am. Chem.
Soc. 2001, 123, 1090-1101. (d) 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. (e) Casey, C. P.; Johnson, J. B. J. Org.
Chem. 2003, 68, 1998-2001.
(5) Koike, T.; Ikariya, T. Adv. Synth. Catal. 2004, 346, 37-41.
10.1021/om049205x CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/19/2005

16-Electron Ru and Ir Amide Complexes
Organometallics, Vol. 24, No. 4, 2005 725
Scheme 1
Figure 1. Structural view of Cp*Ir[κ3(N,N′,C)-(S,S)-
CH3C6H3SO2NCHPhCHPhNH2] (1b).
and Ir-N(amido) distances have mean values of 2.039,6e
2.133, and 2.125 Å, respectively. The chirality of the
(S,S)-diamine ligand determines the R configuration
around the central metal, as observed in the analogous
complexes.1d,2a NMR spectroscopic data in CD2Cl2 are
consistent with the structure of 1b in solution. Two
nonequivalent NH protons were observed at 3.21 and
3.89 ppm because of their coordination to the chiral
metal center. In the 13C{1H} NMR, six carbon peaks,
due to the Ts group attached to the metallacycle ring,
were observed at 136.1, 139.2, 140.4, 143.3, 147.3, and
147.4 ppm.6e
pounds with the amide complexes, and we found that
the amide complexes Cp*M[κ2(N,N′)-(S,S)-TsNCHPh-
CHPhNH] (M ) Ir (1a), Rh (2a)) and Ru[κ2(N,N′)-(S,S)-
TsNCHPhCHPhNH](p-cymene) (3a) readily reacted
with acidic alcohols, CF3CH2OH or phenols, to give
cyclometalated complexes6 in good to excellent yields.
These complexes might be formed via intramolecular
C-H bond cleavage of the aromatic ring on the Ts-
diamine ligand possibly through the alkoxide complexes
as intermediates.
An analogous Rh metallacyclic compound, Cp*Rh[κ3-
(N,N′,C)-(S,S)-CH3C6H3SO2NCHPhCHPhNH2] (2b), could
be obtained from the reaction of Cp*RhCl[κ2(N,N′)-(S,S)-
TsNCHPhCHPhNH2] with C6H5ONa in good yield. An
X-ray crystallographic analysis of complex 2b confirmed
that it has a similar structure to that of complex 1b (see
Supporting Information).9 The Rh-C(metallacycle), Rh-
Results and Discussion
Reaction of the Amide Complexes 1a-3a with
Acidic Alcohols, CF3CH2OH or Phenol. The purple-
colored 16-electron Ir amide complex 1a in CF3CH2OH
as solvent has been proven to convert at 50 °C to a
yellow-colored cyclometalated complex, Cp*Ir[κ3(N,N′,C)-
(S,S)-CH3C6H3SO2NCHPhCHPhNH2] (1b), as a single
diastereomer almost quantitatively (Scheme 1).7 The
complex 1b was also obtained by the treatment of
complex 1a in toluene with 1.1 equiv of C6H5OH at 50
°C. Notably, in the absence of the alcohols under
otherwise identical conditions, the reaction of the com-
plex 1a proceeded very slowly, suggesting that the
alcohol is crucial for transformation to the metallacycle
1b. The complex 1b can be conveniently obtained by
reaction of Cp*IrCl[κ2(N,N′)-(S,S)-TsNCHPhCHPhNH2]
with C6H5ONa in good yield (Scheme 1).
N(amino), and Rh-N(amido) distances have mean values of
2.037, 2.123, and 2.129 Å, respectively. NMR spectro-
scopic data in CD2Cl2 are consistent with the structure
of the metallacycle 2b in solution. Two nonequivalent
NH protons were observed at 2.53 and 3.04 ppm. In the
13C{1H} NMR spectrum, six carbon peaks, assigned to
the Ts group attached to the central metal, were
observed at 137.4, 139.9, 140.2, 144.4, 149.6, and 162.2
ppm; each signal was coupled with Rh (see Experimen-
tal Section).
When the Ru amide complex 3a, having structures
isoelectronic with the Cp*Ir complex, was treated with
CF3CH2OH, the reaction proceeded smoothly to give a
mixture of two metallacycles, Ru[κ3(N,N′,C)-(S,S)-
CH3C6H3SO2NCHPhCHPhNH2](p-cymene) (3b)10 and
Ru[κ3(N,N′,C)-(S,S)-TsNCHPhCH(C6H4)NH2](p-cy-
mene) (3c)11 (Scheme 2). The aromatic C-H bonds, in
An X-ray crystallographic analysis of complex 1b, as
illustrated in Figure 1, confirmed that it has a three-
legged piano stool coordination environment with Cp*,
sulfonamido, amino, and tolyl ligands.8 Crystallographic
data and selected bond distances and angles are given
in Table 1 and Table 2. The Ir-C(metallacycle), Ir-N(amino)
,
(6) 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. For cyclometalation of half-sandwich complexes,
see: (e) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.; Hilton,
S. T.; Russell, D. R. Dalton Trans. 2003, 4132-4138. The references
of the related cyclometalated complexes are reported in this paper.
(7) This cyclometalation proceeds cleanly with high selectively.
(8) An X-ray crystallographic analysis of the metallacycle 1b was
performed. In Figure 1, there are omissions of the crystal solvent and
the other molecule of the same structure. Crystallographic data and
structure refinement parameters of complex 1b are shown in Table 1.
All hydrogen atoms were calculated from ideal geometries. See
Supporting Information.
(9) An X-ray crystallographic analysis of the metallacycle 2b was
performed (see Supporting Information). Crystallographic data and
structure refinement parameters of the complex 2b are shown in Table
1.
(10) An X-ray crystallographic analysis of the metallacycles 3b and
3c was performed. In Figure 2 (upper view), the crystal solvent and
the other type of metallacycle 3c are omitted. Crystallographic data
and structure refinement parameters of the complexes 3b and 3c are
shown in Table 1. All hydrogen atoms were calculated from ideal
geometries. See Supporting Information.
(11) An X-ray crystallographic analysis of the metallacycle 3c was
performed. In Figure 2 (bottom view), the crystal solvent is omitted.
Crystallographic data and structure refinement parameters of complex
3c are shown in Table 1. All hydrogen atoms were calculated from
ideal geometries. See Supporting Information.

726 Organometallics, Vol. 24, No. 4, 2005
Table 1. Crystallographic Data for Complexes 1b, 2b, 3b, 3c, and 5b
Koike and Ikariya
1b
2b
3b and 3c
3c
5b
formula
C
38H43IrN2O2S
C32.50H37N2O2SRhCl3
728.99
0.2 × 0.2 × 0.2
P212121(#19)
19.211(3)
29.506(5)
11.965(2)
C32H36N2O2SRuCl2
684.68
C35H40F6N2O4RuS
799.83
0.3 × 0.15 × 0.1
P212121(#19)
13.333(6)
15.768(8)
16.512(8)
C21H31IrN2O2S
567.77
0.3 × 0.3 × 0.1
P21/n (#14)
8.854(3)
fw
784.05
cryst size, mm
space group
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
0.4 × 0.3 × 0.1
P212121(#19)
11.851(4)
19.851(7)
29.288(9)
0.2 × 0.2 × 0.2
P21(#4)
9.488(1)
23.927(2)
13.586(3)
94.39(1)
3075.3(9)
4
15.7638(5)
15.134(5)
98.693(3)
2087.9(12)
4
6889.7(39)
8
6782.5(21)
8
3471.4(29)
4
F
calc, g cm-3
1.512
1.428
1.479
1.530
1.806
T, K
173
123
253
173
173
µ, cm-1(Mo KR)
absorption corr
transmn factors,
min./max.
39.82
8.31
7.83
5.85
65.31
empirical
0.8104/1.0000
empirical
0.8101/1.0000
empirical
1.00/1.00
empirical
0.8984/1.0000
empirical
0.4718/1.0000
2θmax, deg
55.0
69 309
8611
55.0
60.1
55.0
27 251
4392
14 543
447
0.066
0.169
-4.37/11.80
55.0
16 336
4676
4643
276
0.047
0.255
-3.21/1.45
no. of reflns measd
no. of unique reflns
no. of reflns (I > 3.00σ(I))
no. of variables
R1 (I > 3.00 σ(I))a
wR2 (I > 3.00σ(I))a
diff Four peaks,
min./max., e Å-3
57 332
15 548
11 413
771
8817
8811
45 363
840
881c
780
0.050b
0.060b
-5.94/8.87
0.087
0.109
-2.68/3.97
0.055d
0.133c
-0.96/1.25
2 2
a R ) ∑||Fo| - |Fc||/∑|Fo|, wR) [∑(w(Fo2 - Fc ) )/∑(w(Fo2)2)]1/2.
.
.
b R) ∑||Fo| - |Fc||/∑|Fo|, wR) [∑(w(|Fo| - |Fc|)2)/∑(wFo2)]1/2 c I > 0.00σ(I).
d I > 2.00σ(I).
Table 2. Selected Bond Distances (Å) and Angles
(deg) for Complexes 1b, 2b, 3b, 3c, and 5b
1ba
2ba
3b
3c
5b
M-N(amino)
2.133 2.123 2.130(5) 2.140(5) 2.168(7)
2.125 2.129 2.134(5) 2.136(4) 2.136(6)
2.039 2.037 2.069(6) 2.079(6) 2.056(7)
77.7 79.6 80.3(2) 77.7(2) 80.0(3)
M-N(amido)
M-C(metallacycle)
N(amino)-M-N(amino)
N(amino)-M-C(metallacycle) 86.3 85.9 85.5(2) 76.9(2) 89.5(3)
N(amino)-M-C(metallacycle) 83.6 83.6 82.8(2) 80.8(2) 82.4(3)
M-N(amino)-C1
M-N(amino)-C2
M-N(amino)-S
S-N(amino)-C2
108.7 107.4 107.2(3) 103.4(3) 106.7(5)
115.2 113.9 112.5(3) 114.1(3) 112.2(5)
108.7 108.0 108.6(3) 125.7(3) 107.5(3)
113.1 112.7 111.6(4) 115.4(4) 117.0(6)
a Mean value.
Scheme 2
either the Ts group or the phenyl group on the diamine
backbone, participated in intramolecular activation with
the aid of added alcohols to facilitate metallacycle
formation. The 1H NMR spectrum of the reaction
mixture showed that complex 3c was formed as the
major product (3b:3c ) 1:4). An X-ray crystallographic
analysis of the single crystals obtained by recrystalli-
zation of the crude mixture from a mixed solvent of CH2-
Cl2 and diethyl ether revealed that the crystal lattice
contains two different metallacycles, 3b and 3c, per unit
cell. ORTEP drawings for complexes 3b and 3c are
shown in Figure 2, respectively. Complex 3b has a
three-legged piano stool structure similar to 1b and 2b.
The Ru-C(metallacycle), Ru-N(amino), and Ru-N(amido) dis-
tances are 2.069(6), 2.130(5), and 2.134(5) Å, respec-
tively. The coordination environment around the Ru
atom in complex 3c can be described as a three-legged
Figure 2. Structural views of complexes Ru[κ3(N,N′,C)-
(S,S)-CH3C6H3SO2NCHPhCHPhNH2](p-cymene) (3b) and
Ru[κ3(N,N′,C)-(S,S)-TsNCHPhCH(C6H4)NH2](p-cymene) (3c).
piano stool with p-cymene, sulfonamido, amino, and
phenyl ligands. The Ru-C(metallacycle), Ru-N(amino), and
Ru-N(amido) distances are 2.079(6), 2.140(5), and 2.136(4)

16-Electron Ru and Ir Amide Complexes
Organometallics, Vol. 24, No. 4, 2005 727
Scheme 3
Scheme 4
Å, respectively. NMR spectroscopic data of complexes
3b and 3c are consistent with the solid state structure
1
of these complexes in solution. The H NMR spectrum
of 3c shows nonequivalent signals for NHH at 2.82 and
3.34 ppm. The 13C{1H} NMR spectrum of isolated 3c
displays six carbon peaks derived from a phenyl group
bonded to the Ru metal center.
Reaction of the Amide Complex with 1 Equiv of
CF3CH2OH: Attempts to Isolate the Metal Alkox-
ide Complexes. On the basis of the experimental re-
sults discussed above, alkoxide or phenoxide complexes
could be possible intermediates in the metallacycle
formation. The 1H NMR spectrum of a CD2Cl2 solution
containing the Ir amide complex 1a and 1 equiv of CF3-
CH2OH in an NMR tube gave no signals that could be
assigned to the corresponding alkoxide complex even at
low temperature, possibly because the reversible reac-
tion was too rapid to detect the alkoxide complex under
the conditions for NMR study. However, in the reaction
Figure 3. Structural view of Cp*Ir[κ3(N,N′,C)-CH3C6H3-
SO2NCH2CH2N(CH3)2] (5b).
methylene protons of OCHHCF3 at 4.07 and 4.34 ppm.
These spectroscopic data were consistent with the
nitrogen and oxygen being bound to the chiral metal
center on the NMR time scale. The analogous Ru
alkoxide complex, Ru(OCH2CF3)[κ2(N,N′)-TsNCH2CH2N-
(CH3)2](p-cy-mene) (6a), was isolable in a manner
similar to the Ir complex. The structure of 6a was also
confirmed by NMR spectroscopy and X-ray crystal-
lographic analysis (see Supporting Information).13
It should be noted that the isolable Ir alkoxide
complex 5a was found to undergo intramolecular cyclo-
metalation at 50 °C, leading to the metallacycle product
Cp*Ir[κ3(N,N′,C)-CH3C6H3SO2NCH2CH2N(CH3)2] (5b),
as shown in Scheme 4 and Figure 3.14 An X-ray
crystallographic analysis of the complex 5b confirmed
that it has a three-legged piano stool coordination
environment. The Ir-C(mettallacycle), Ir-N(amino), and Ir-
1
of Ru complex 3a with CF3CH2OH, the H NMR spec-
trum of a reaction mixture of 3a and 1 equiv of CF3-
CH2OH in an NMR tube gave a set of broad signals at
room temperature. On cooling the purple-colored reac-
tion mixture below -30 °C, the color of the solution
changed to orange and the spectrum displayed a mix-
ture of the starting amide complex 3a, the alkoxide
complex, Ru(OCH2CF3)[κ2(N,N′)-(S,S)-TsNCHPhCHPh-
NH2](p-cymene) (4), and unreacted CF3CH2OH (Scheme
3). The 1H NMR spectrum of the alkoxide complex 4 in
CD2Cl2 at -30 °C displays two doublet quartets due to
the diastereotopic methylene protons of the OCHHCF3
group at 4.20 and 4.63 ppm, respectively (see Supporting
Information), indicating that the alcohol oxygen bonds
to the chiral metal center. An increase in the amount
of added alcohol caused an increase in the signals due
to the alkoxide complex, indicating that the alkoxide
complex 4 existed in a temperature-dependent equilib-
rium with 3a and free CF3CH2OH. These results
showed that the reverse reaction from the alkoxide to
amide complexes is facile because an intramolecular
deprotonation of very acidic NH protons of the alkoxo
amine complexes bearing the basic metal-OR units3a
rapidly proceeds to form the amide complexes in solu-
tion.
N
(amido) distances are 2.056(7), 2.168(7), and 2.136(6) Å,
1
respectively. The H NMR spectrum of 5b shows non-
equivalent signals, 3.21 and 3.89 ppm in CD2Cl2, for
N(CH3)2. This nonequivalence is consistent with the
expected structure in which the nitrogen can coordinate
to the chiral metal center on the NMR time scale. The
(12) An X-ray crystallographic analysis of the alkoxide complex 5a
was performed. Crystal and structure refinement parameters of
complex 5a: C24H36F3IrN2O3SCl2, Mr ) 752.74, triclinic, space group
P1h (# 2), a ) 8.1777(9) Å, b ) 8.6253(4) Å, c ) 21.909(2) Å, V ) 1439.9-
(2) Å3, Z ) 2, Dc ) 1.736 g/cm3, µ(Mo KR) ) 49.54 cm-1, T ) 193 K, R1
(wR2) ) 0.095 (0.249) for 9967 observed reflections (I > 3.00σ(I)). All
hydrogen atoms were calculated from ideal geometries. See Supporting
Information.
(13) An X-ray crystallographic analysis of the alkoxide complex 6a
was performed. Crystal and structure refinement parameters of
complex 6a: C23H33F3N2O3RuS, Mr ) 575.65, triclinic, space group P1h(#
2), a ) 8.56(6) Å, b ) 12.32(10) Å, c ) 13.11(10) Å, V ) 1253.1(16) Å3,
Z ) 2, Dc ) 1.525 g/cm3, µ(Mo KR) ) 7.58 cm-1, T ) 173 K, R1 (wR2)
) 0.078 (0.182) for 3704 observed reflections (I > 3.00σ(I)). All hydrogen
atoms were calculated from ideal geometries. See Supporting Informa-
tion.
Although alkoxide complexes could not be isolated
from the reaction of 1a or 3a with CF3CH2OH, an
analogous Ir alkoxide complex having no NH protons
in the diamine ligand, Cp*Ir(OCH2CF3)[κ2(N,N′)-TsNCH2-
CH2N(CH3)2] (5a), was isolable from the reaction of the
Ir chloride complex, Cp*IrCl[κ2(N,N′)-TsNCH2CH2N-
(CH3)2], with CF3CH2OH containing a base, KOt-Bu.
The structure of 5a was confirmed by NMR spectroscopy
as well as X-ray crystallographic analysis.12 The 1H
NMR spectrum of 5a in CD2Cl2 shows two signals due
to the methyl proton of the N(CH3)2 group at 2.66 and
2.97 ppm and two doublet quartets assigned to the
(14) An X-ray crystallographic analysis of the metallacycle 5b was
performed. Crystallographic data and structure refinement parameters
of complex 5b are shown in Table 1. All hydrogen atoms were
calculated from ideal geometries. See Supporting Information.

728 Organometallics, Vol. 24, No. 4, 2005
Koike and Ikariya
Figure 4. Time dependence of the concentration of
p-CF3C6H4OH.
1H NMR spectrum shows only three proton signals due
to the Ts group of 5b. The 13C{1H} NMR spectrum
displays six carbon signals derived from the Ts group
as observed in complexes 1b and 2b.
Figure 5. Dependence of the phenol’s substituent on the
reaction rate.
A Possible Mechanism for the Cyclometalation
of the Amide Complex in the Presence of Phenols.
As discussed in the previous section, the addition of the
acidic alcohol, CF3CH2OH or phenol, facilitated C-H
bond activation to give cyclometalation products. Tri-
fluoromethyl-substituted phenol, p-CF3C6H4OH (7), with
stronger acidity than CF3CH2OH, promoted the cyclo-
metalation; monitoring the profile of the reaction of 1a
with 7, determined by NMR spectroscopy, provided a
deeper insight into the reaction pathways. Figure 4
shows the time dependence curves of the yield of the
cyclometalation product 1b as a function of the concen-
tration of 7 at 50 °C in CD3CN. Noticeably, the reaction
profiles show a complex dependency on the concentra-
tion of the phenol. Because of the intricacy of the
reaction profiles, full analysis of the reaction kinetics
could not be performed. It should be noted that the
reaction of 1a with 0.25 equiv of p-CF3C6H4OH 7 to 1a
(1.07 × 10-2 M) proceeded very slowly but reached
complete conversion to give the product 1b after 3 days.
The rate of the reaction increases with the concentration
of 7 but reaches a maximum at about 2 equiv (8.60 ×
10-2 M) of 1a. After the maximum is reached, the
reaction is strongly retarded by the addition of a large
amount of 7, suggesting that free p-CF3C6H4OH possibly
interacts with the basic phenoxo complex 8 via hydrogen
bonding to form a stabilized adduct 915 as shown in
Scheme 5. The hydrogen bonding interaction of 7 might
cause reduction of the basicity of the complex 8, leading
to the resting stage of the reaction as shown in Scheme
5.
Scheme 5
7, showing that phenoxide complex 8 existed in an
equilibrium with the amide complex 1a and free phenol,
as observed in the reaction of 1a with CF3CH2OH
(Scheme 5). The use of a large excess of 7 to 1a gave
only one broad 19F signal around 62.0 ppm even at -90
°C, suggesting that a rapid exchange reaction between
the phenoxo ligand of 8 and free p-CF3C6H4OH possibly
takes place via 9 under the reaction conditions.
An 19F NMR spectrum of a reaction mixture contain-
ing the Ir amide complex 1a and 1 equiv of p-CF3C6H4-
OH (7) shows two broad signals at -60.5 and -61.2 ppm
at -90 °C. On increasing the temperature to room
temperature, a sharp singlet was observed at -62.1
ppm, which is close to the position for the free phenol
Monitoring the reaction of Ir amide complex 1a with
1 equiv of various phenols by the disappearance of the
1
signals due to 1a, in the H NMR spectra at 50 °C in
(15) (a) Kegley, S. E.; Schaverien, C. J.; Freudenberger, J. H.;
Bergman, R. G. J. Am. Chem. Soc. 1987, 109, 6563-6565. (b) Kim, Y.
J.; Osakada, K.; Takenaka, A.; Yamamoto, A. J. Am. Chem. Soc. 1990,
112, 1096-1104.
CD3CN, revealed the transformation profile shown in
Figure 5. It should be noted that the phenol’s substitu-
ent has a significant effect on the rate of the cyclo-

16-Electron Ru and Ir Amide Complexes
Organometallics, Vol. 24, No. 4, 2005 729
made on a Rigaku Saturn or Rigaku RAXIS CS using graphite-
monochromated Mo KR radiation (λ ) 0.71070 Å). Elemental
analysis was performed on a Perkin-Elmer 2400II CHNS/O
or LECO CHNS-932.
metalation, as the conversion rate of 1a increases in the
order p-CH3OC6H4OH < C6H5OH < p-CF3C6H4OH. In
the absence of phenols under otherwise identical condi-
tions, the reaction proceeded very slowly, indicating that
the presence of the alcoholic compounds could facilitate
the reaction and the phenoxo complex might be involved
in the rate-limiting step in the present transformation.
Based on these experimental results, the overall
reaction pathways of the cyclometalation promoted by
alcohols are described in Scheme 5. The cyclometalation
proceeds possibly through the phenoxide complex 8,
which exists in a temperature-dependent equilibrium
with the amide complex 1a, the free phenol, and the
adduct 9. At a low phenol concentration compared to
1a, the reaction rate depends on the concentration of
both phenol and complex 1a, in which the formation of
adduct 9 was minimized at an early stage in the
reaction. Electronic tuning of the substituents on the
phenols significantly affects the rate of the reaction,
while the transformation of 1a to 1b is strongly inhib-
ited by a large amount of the phenol because of the
formation of kinetically stable adduct 9. Then, the
cyclometalation irreversibly proceeds to the thermody-
namically stable metallacycle. There are three possible
C-H activation pathways from the phenoxide complex
8, leading to the metallacycle 1b: (1) the dissociation
of the alkoxo anion leading to an ion pair intermediate,5
followed by electrophilic substitution,16 and generation
of a vacant site either by dissociation of the NH2 ligand
or by ring-slippage, followed by either (2) concerted
activation6e,17 with the aid of the metal-OR bond or (3)
the oxidative addition of the aromatic C-H bond.
Further investigations including details of the reaction
kinetics as well as computational analysis on the
reaction pathways are still required.
Cp*Ir[K3(N,N′,C)-(S,S)-CH3C6H3SO2NCHPhCHPh-
NH2] (1b). (a) The Ir amide complex 1a (1.20 × 10-1 g, 1.73 ×
10-4 mol) in CF3CH2OH (3.5 mL) was stirred at 50 °C for 7.5
h. The solvent was removed under reduced pressure. The
resulting product was almost quantitatively Cp*Ir[κ3(N,N′,C)-
(S,S)-CH3C6H3SO2NCHPhCHPhNH2] (1b). Recrystallization
from CH2ClCH2Cl afforded crystals. Isolated yield: 23%. (b)
To a toluene solution (3 mL) of the Ir amide complex 1a (1.08
× 10-1 g, 1.56 × 10-4 mol) was added a toluene solution (0.18
mL) of C6H5OH (1.47 × 10-2 g, 1.56 × 10-4 mol). The reaction
was conducted at 50 °C. After 2 days, the product was
recrystallized from toluene. Cp*Ir[κ3(N,N′,C)-(S,S)-CH3C6H3-
SO2NCHPhCHPhNH2] (1b) was obtained for isolated yield,
1
51%. H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm): 1.79 (s, 15H;
C5(CH3)5), 2.29 (s, 3H; p-CH3C6H3SO2N), 3.21 (br dd, 1H;
p-CH3C6H3SO2NCHPhCHPhNHH), 3.65 (m, 1H; p-CH3C6H3-
SO2NCHPhCHPhNH2), 3.89 (br, 2H; p-CH3C6H3SO2-
NCHPhCHPhNHH), 6.78-7.37 (13H; p-CH3C6H3SO2NCH-
(C6H5)CH(C6H5)NH2). 13C{1H} NMR (75.6 MHz, CD2Cl2, rt,
δ/ppm): 9.2 (C5(CH3)5), 21.5 (p-CH3C6H3SO2N), 69.6, 76.2 (p-
CH3C6H3SO2NCHPhCHPhNH2), 87.9 (C5(CH3)5), 124.6-147.4
(p-CH3C6H3SO2NCH(C6H5)CH(C6H5)NH2). Anal. Calcd. for
C31H35O2N2S1Ir1: C 53.81, H 5.10, N 4.05, S 4.63. Found: C
53.87, H 5.07, N 4.01, S 4.41.
Cp*Rh[K3(N,N′,C)-CH3C6H3SO2NCHPhCHPhNH2] (2b).
To a CH2Cl2 solution (5 mL) of Cp*RhCl[κ2(N,N′)-TsNCHPh-
CHPhNH2] (1.01 × 10-1 g, 1.58 × 10-4 mol) was added C6H5-
ONa‚3H2O (3.20 × 10-2 g, 1.88 × 10-4 mol). The reaction was
conducted at room temperature for 2 days. The reaction
mixture was filtered through filter paper. Recrystallization
from CH2Cl2 and diethyl ether afforded the yellow crystals.
Isolated yield: 15%. 1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm):
1.76 (s, 15H; C5(CH3)5), 2.38 (s, 3H; p-CH3C6H3SO2N), 2.53 (br
dd, 1H; p-CH3C6H3SO2NCHPhCHPhNHH), 3.04 (br d, 1H;
p-CH3C6H3SO2NCHPhCHPhNHH), 3.78 (m, 2H; p-CH3C6H3-
SO2NCHPhCHPhNH2), 6.77-7.35 (13H; p-CH3C6H3SO2NCH-
(C6H5)CH(C6H5)NH2). 13C{1H} NMR (75.6 MHz, CD2Cl2, rt,
δ/ppm): 9.4 (C5(CH3)5), 21.6 (p-CH3C6H3SO2N), 69.7, 72.8 (p-
Conclusions
We have shown intramolecular orthometalation pro-
moted by the metal alkoxide intermediates derived from
the 16-electron amide complexes and acidic alcohols.
The Brønsted basicity of the amide complex as well as
the alkoxide intermediate contribute to the C-H bond
activation. However, the present intramolecular C-H
bond activation irreversibly proceeds to give the stable
cyclometalated complex, which is an inactive species for
catalytic asymmetric reduction1 and C-C bond forma-
tion.2 The fine-tuning of the structures as well as
electronic factors in the chiral amide catalysts are
crucial for attaining superior catalyst performance in
terms of reactivity and selectivity.
1
CH3C6H3SO2NCHPhCHPhNH2), 95.4 (d, JRhC ) 6.5 Hz; C5-
(CH3)5), 124.9-129.0 (p-CH3C6H3SO2NCH(C6H5)CH(C6H5)-
NH2), 137.4, 139.9, 140.2, 144.4, 149.6, 162.2 (each d, JRhC
)
1.1, 1.1, 1.5, 0.8, 1.5, 32.4 Hz, respectively; p-CH3C6H3SO2N).
Anal. Calcd for C31H35O2N2S1Rh1: C 61.79, H 5.85, N 4.65, S
5.32. Found: C 62.03, H 6.07, N 4.53, S 5.14.
Ru[K3(N,N′,C)-(S,S)-CH3C6H3SO2NCHPhCHPhNH2](p-
cymene) (3b) and Ru[K3(N,N′,C)-(S,S)-TsNCHPhCH(C6H4)-
NH2](p-cymene) (3c). The Ru amide complex 3a (9.11 × 10-2
g, 1.52 × 10-4 mol) in CF3CH2OH (3.5 mL) was stirred at 50
°C for 7.5 h. The solvent was removed under reduced pressure.
(a) Recrystallization from CH2Cl2 and diethyl ether afforded
yellow crystals including the metallacycles 3b and 3c. It was
determined by X-ray analysis. (b) Recrystallization from CF3-
CH2OH afforded the metallacycle 3c. Isolated yield: 27%.
Spectral data for 3b. 1H NMR (300.4 MHz, CD2Cl2, rt,
δ/ppm): 1.29 (dd, 6H; CH3C6H4CH(CH3)2), 2.21, 2.38 (each s,
3H;CH3C6H4CH(CH3)2,p-CH3C6H3SO2N),2.38(br,1H;p-CH3C6H3-
SO2NCHPhCHPhNHH), 2.96 (m, 1H; CH3C6H4CH(CH3)2), 3.52
(d, 3JHH ) 11 Hz, 1H; p-CH3C6H3SO2NCHPhCHPhNH2), 3.96
(m, 1H; p-CH3C6H3SO2NCHPhCHPhNH2), 4.01 (br, 1H;
p-CH3C6H3SO2NCHPhCHPhNHH),4.92,5.36,5.45(4H;CH3C6H4-
CH(CH3)2), 6.70-7.52 (13H; p-CH3C6H3SO2NCH(C6H5)CH-
(C6H5)NH2).
Experimental Section
All experiments were conducted under an argon atmosphere
using Schlenk techniques. All deuterated NMR solvents were
dehydrated and degassed by appropriate methods. Amide
complexes 1a and 3a and chloro complexes were prepared
according to reported procedures.1d,g,h 1H and 13C NMR were
recorded on a JEOL JNM-LA300 Fourier transform spectrom-
eter. X-ray single-crystal structural analysis studies were
Spectral data for 3c. 1H NMR (300.4 MHz, CD2Cl2, rt,
δ/ppm): 0.95 (d, 3JHH ) 7.1 Hz, 3H; CH3C6H4CH(CH3)(CH3)),
1.25 (d, 3JHH ) 6.8 Hz, 3H; CH3C6H4CH(CH3)(CH3)), 2.26, 2.39
(each s, 3H; CH3C6H4CH(CH3)2, p-CH3C6H4SO2N), 2.82 (br, 1H;
TsNCHPhCH(C6H4)NHH), 2.96 (m, 1H; CH3C6H4CH(CH3)2),
(16) (a) Sommer, J.; Bukala, J. Acc. Chem. Res. 1993, 26, 370-376.
(b) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633-
639.
(17) Oxgaard, J.; Muller, R. P.; Goddard, W. A., III; Periana, R. A.
J. Am. Chem. Soc. 2004, 126, 352-363.

730 Organometallics, Vol. 24, No. 4, 2005
Koike and Ikariya
3.34 (br, 1H; TsNCHPhCH(C6H4)NHH) 4.02 (br s, 1H;
TsNCHPhCH(C6H4)NH2), 4.10 (br s, 1H; TsNCHPhCH(C6H4)-
NH2), 5.09, 5.14, 5.52 (4H; CH3C6H4CH(CH3)2), 6.68-7.73
(13H; p-CH3C6H4SO2NCH(C6H5)CH(C6H4)NH2). 13C{1H} NMR
(75.6 MHz, CD2Cl2, rt, δ/ppm): 18.5, 21.3, 21.8, 23.8, 30.3
(CH3C6H4CH(CH3)2, p-CH3C6H4SO2N), 63.3, 69.9 (TsNCHPhCH-
(C6H4)NH2), 78.1, 82.1, 82.4, 88.5, 99.8, 107.6 (CH3C6H4CH-
(CH3)2), 126.1-167.5 (p-CH3C6H4SO2NCH(C6H5)CH(C6H4)-
conducted at room temperature for 12 h. The solvent was then
removed under reduced pressure. Toluene was added to the
residue. The reaction mixture was filtered through filter paper.
Recrystallization from CH2Cl2 and diethyl ether afforded
yellow crystals. Isolated yield: 37%. 1H NMR (300.4 MHz, CD2-
Cl2, rt, δ/ppm): 1.22 (dd, 6H; CH3C6H4CH(CH3)2), 1.50 (m, 1H;
TsNCH2CHHN(CH3)2), 2.11, 2.37, 2.68, 2.94 (each s, 3H;
CH3C6H4CH(CH3)2, p-CH3C6H4SO2NCH2CH2N(CH3)(CH3)), 2.49,
2.85, 2.90 (each m., 1H; TsNCH2CHHN(CH3)2), 5.11, 5.22, 5.51,
NH2). Anal. Calcd for C31H34O2N2S1Ru1‚(CF3CH2OH)1.75
: C
3
53.48, H 5.11, N 3.62, S 4.14. Found: C 53.26, H 5.41, N 3.70,
S 3.97.
5.66 (4H; CH3C6H4CH(CH3)2), 7.22 (d, JHH ) 8.1 Hz, 2H;
p-CH3C6H2H2SO2N), 7.68 (d, 3JHH ) 8.1 Hz, 2H; p-CH3C6H2H2-
SO2N). 19F NMR (282.65 MHz, CD2Cl2, rt, δ/ppm): -77.0 (dd,
CF3CH2ORu). Anal. Calcd for C23H33O3N2S1F3Ru1: C 47.99,
H 5.78, N 4.87, S 5.57. Found: C 48.04, H 6.03, N 4.80, S 5.48.
Experimental Procedure for Cyclometalation of Iri-
dium Amide Complex 1a with p-CF3C6H4OH. A CD3CN
solution of 1 equiv of p-CF3C6H4OH 7 (2.15 × 10-5 mol) was
added to a solution of complex 1a (1.47 × 10-2 g, 2.12 × 10-5
mol), dihexyl ether (2 × 10-3 mL) as internal standard, and
CD3CN (0.46 mL) in an NMR tube. The tube was sealed and
the resultant metallacycle 1b was traced by 1H NMR at 323.15
K. The resulting reaction profile is shown in Figure 4. In a
similar manner, the reaction of the amide complex 1a with
Cp*Ir(OCH2CF3)[K2(N,N′)-TsNCH2CH2N(CH3)2] (5a). To
a CF3CH2OH solution (4 mL) of Cp*IrCl[κ2(N,N′)-TsNCH2-
CH2N(CH3)2] (1.17 × 10-1 g, 1.94 × 10-4 mol) was added KOt-
Bu (2.89 × 10-2 g, 2.56 × 10-4 mol). The reaction was
conducted at room temperature overnight. The solvent was
removed under reduced pressure. Toluene was added to the
residue,. The toluene solution was filtered through filter paper.
Recrystallization from CH2Cl2 and hexane afforded yellow
crystals. Isolated yield: 48%. These crystals were air-sensitive.
1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm): 1.55-1.72, 2.68-
2.97 (m, 4H; TsNCH2CH2N(CH3)2), 1.57 (s, 15H; C5(CH3)5), 2.38
(s, 3H; p-CH3C6H4SO2N), 2.66 (s, 3H; N(CH3)(CH3)), 2.97 (s,
3H; N(CH3)(CH3)), 4.07 (m, 1H; CF3CHHOIr), 4.34 (m, 1H;
CF3CHHOIr), 7.22 (d, 3JHH ) 7.8 Hz, 2H; p-CH3C6H2H2SO2N),
0.25, 0.5, 2, 8, and 16 equiv of p-CF3C6H4OH 7 (1.07 × 10-2
,
2.16 × 10-2, 8.60 × 10-2, 3.48 × 10-1, 7.05 × 10-1 M) gave
3
7.66 (d, JHH ) 8.1 Hz, 2H; p-CH3C6H2H2SO2N). 19F NMR
transformation profiles as shown in Figure 4.
(282.65 MHz, CD2Cl2, rt, δ/ppm): -77.0 (dd, CF3CH2OIr). Anal.
Calcd for C23H34O3N2S1F3Ir1: C 41.37, H 5.13, N 4.19. Found:
C 40.94, H 5.58, N 4.14.
Experimental Procedure for Cyclometalation of Iri-
dium Amide Complex 1a Using Various Phenols. A CD3-
CN solution of 1 equiv of C6H5OH (1.80 × 10-2 mL, 1.89 ×
10-5 mol) was added to a solution of the Ir amide complex 1a
(1.28 × 10-2 g, 1.85 × 10-5 mol), dihexyl ether (2 × 10-3 mL)
as internal standard, and CD3CN (0.4 mL) in an NMR tube.
The tube was sealed and the disappearing amide complex 1a
was traced by 1H NMR at 323.15 K. The resulting reaction
profile is shown in Figure 5. In a similar manner, the reaction
of the Ir amide complex 1a with p-CH3OC6H4OH or no alcohol
gave transformation profiles as shown in Figure 5.
Cp*Ir[K3(N,N′,C)-CH3C6H3SO2NCH2CH2N(CH3)2] (5b).
To a CF3CH2OH solution (3.5 mL) of Cp*IrCl[κ2(N,N′)-TsNCH2-
CH2N(CH3)2] (1.15 × 10-1 g, 1.89 × 10-4 mol) was added KOt-
Bu (2.76 × 10-2 g, 2.46 × 10-4 mol). The reaction was
conducted at room temperature. After 12 h, the solvent was
removed under reduced pressure. The residue was the alkoxide
complex 5a. Then, CH3CN (5 mL) was added to the alkoxide
complex 5a and stirred at 50 °C overnight. The reaction
mixture was filtered through filter paper. Recrystallization
from CH3CN afforded pale yellow crystals. Isolated yield: 16%.
1H NMR (300.4 MHz, CD2Cl2, rt, δ/ppm): 1.45, 1.90, 3.00, 3.55
(m, 4H; p-CH3C6H3SO2NCH2CH2N(CH3)2), 1.60 (s, 15H; C5-
(CH3)5), 2.29 (s, 3H; p-CH3C6H3SO2), 2.58 (s, 3H; N(CH3)(CH3)),
3.05 (s, 3H; N(CH3)(CH3)), 7.18, 7.21, 7.40 (m, each 1H;
p-CH3C6H3SO2N). 13C{1H} NMR (75.6 MHz, CD2Cl2, rt,
δ/ppm): 9.3 (C5(CH3)5), 21.4 (p-CH3C6H3SO2N), 52.2, 53.3, 57.0,
66.7 (p-CH3C6H3SO2NCH2CH2N(CH3)(CH3)), 88.5 (C5(CH3)5),
122.9, 124.2, 138.7, 139.2, 146.6, 150.3 (p-CH3C6H3SO2N).
Anal. Calcd for C21H31O2N2S1Ir1: C 44.42, H 5.50, N 4.93, S
5.65. Found: C 44.31, H 5.43, N 4.83, S 5.41.
Acknowledgment. This work was financially sup-
ported 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. K.T. gratefully acknowledges financial
support from a JSPS Research Fellowship for Young
Scientists. X-ray crystallographic measurement of com-
plex 2b was supported by Rigaku Corporation.
Supporting Information Available: NMR data of the Ru
alkoxide complex 4 and X-ray crystallographic data of 1b, 2b,
3b, 3c, 5a, 5b, and 6a. This material is available free of charge
via the Internet at http://pubs.acs.org.
Ru(OCH2CF3)[K2(N,N′)-TsNCH2CH2N(CH3)2] (6a). To a
CF3CH2OH solution (3.5 mL) of RuCl[κ2(N,N′)-TsNCH2CH2N-
(CH3)2](p-cymene) (1.07 × 10-1 g, 2.08 × 10-4 mol) was added
KOt-Bu (2.67 × 10-2 g, 2.38 × 10-4 mol). The reaction was
OM049205X