Preferential geometry and reactivity of neutral iridium(III) and rhodium(III) complexes bearing a flexible heterochelate PN ligand (PN = o-Ph2PC6H4CH2OCH2C 5H4N-2)

Article abstract of DOI:10.1021/om060405d

Reactions of [IrCl(coe)₂]₂ (coe = cyclooctene) with 1 equiv of the PN ligand (PN = o-Ph₂PC₆H₄CH ₂OCH₂C₅H₄N-2) in the presence of several phosphines or pyridine (1 equiv) at room temperature afforded a neutral iridium(III) hydride complex, (PCN-κ³P,C,N)Ir(H)(Cl)(L) (PCN = Ph₂PC₆H₄CHOCH₂C₅H ₄N) [L = PPy₃ (1a), PCy₃ (1b), PBu₃ (1c), PMePh₂ (1d), Py (1e)] in good isolated yield. The PCN ligand is coordinated in a meridional manner, which was confirmed by spectral analyses and X-ray analysis of 1a. The related rhodium(III) hydride complex (PCN-κ³P,C,N)Rh(H)(Cl)(L) (PCN = Ph₂PC ₆H₄CHOCH₂C₅H₄N) [L = PPh₃ (4a), PCy₃ (4b)] was also prepared from the reactions of [RhCl(coe)₂]₂ with 1 equiv of the PN ligand in the presence of 1 equiv of PPh₃ or PCy₃. The structure of 4a and 4b was determined by spectral analyses and X-ray analysis of 4a. In contrast to the iridium complexes, the PCN ligand in the rhodium-(III) complexes coordinated to the metal center in a facial manner. A ligand exchange reaction of the PPh₃ iridium(III) complex la with PCy₃ did not proceed well (20% conversion), while a similar reaction of the PPh₃ rhodium(III) complex 4a with PCy₃ afforded the PCy₃ complex 4b quantitatively. We examined the ligand exchange reactions of the iridium(III) and rhodium(III) complexes with various phosphines to explain the different reactivities. Using Tolman's parameter, we demonstrated that the ligand exchange reaction in the iridium(III) complexes bearing the meridional-coordinated PCN ligand is controlled by the steric factor of the phosphines and the ligand exchange reaction in the rhodium(III) complexes bearing the facial-coordinated PCN ligand is controlled by their electronic factors. The meridional coordination of the PCN ligand makes the environment around the iridium center sensitive to the steric nature due to the steric repulsion between the diphenyl group in the PCN ligand and the phosphines. The facial coordination of the PCN ligand decreases their repulsion, and reactivity of the metal center depends on the basicity of the phosphines.

Full text of DOI:10.1021/om060405d

110
Organometallics 2007, 26, 110-118
Preferential Geometry and Reactivity of Neutral Iridium(III) and
Rhodium(III) Complexes Bearing a Flexible Heterochelate PN
Ligand (PN ) o-Ph2PC6H4CH2OCH2C5H4N-2)
Takeshi Hara, Tsuneaki Yamagata, and Kazushi Mashima
Department of Chemistry, Graduate School of Engineering Science, Osaka UniVersity,
Toyonaka, Osaka 560-8531, Japan
Yasutaka Kataoka*
Department of Chemistry, Faculty of Science, Nara Women’s UniVersity, Nara 630-8506, Japan
ReceiVed May 11, 2006
Reactions of [IrCl(coe)2]2 (coe ) cyclooctene) with 1 equiv of the PN ligand (PN ) o-Ph2PC6H4CH2-
OCH2C5H4N-2) in the presence of several phosphines or pyridine (1 equiv) at room temperature afforded
a neutral iridium(III) hydride complex, (PCN-κ3P,C,N)Ir(H)(Cl)(L) (PCN ) Ph2PC6H4CHOCH2C5H4N)
[L ) PPh3 (1a), PCy3 (1b), PBu3 (1c), PMePh2 (1d), Py (1e)] in good isolated yield. The PCN ligand is
coordinated in a meridional manner, which was confirmed by spectral analyses and X-ray analysis of 1a.
The related rhodium(III) hydride complex (PCN-κ3P,C,N)Rh(H)(Cl)(L) (PCN ) Ph2PC6H4CHOCH2C5H4N)
[L ) PPh3 (4a), PCy3 (4b)] was also prepared from the reactions of [RhCl(coe)2]2 with 1 equiv of the PN
ligand in the presence of 1 equiv of PPh3 or PCy3. The structure of 4a and 4b was determined by spectral
analyses and X-ray analysis of 4a. In contrast to the iridium complexes, the PCN ligand in the rhodium-
(III) complexes coordinated to the metal center in a facial manner. A ligand exchange reaction of the
PPh3 iridium(III) complex 1a with PCy3 did not proceed well (20% conversion), while a similar reaction
of the PPh3 rhodium(III) complex 4a with PCy3 afforded the PCy3 complex 4b quantitatively. We examined
the ligand exchange reactions of the iridium(III) and rhodium(III) complexes with various phosphines to
explain the different reactivities. Using Tolman’s parameter, we demonstrated that the ligand exchange
reaction in the iridium(III) complexes bearing the meridional-coordinated PCN ligand is controlled by
the steric factor of the phosphines and the ligand exchange reaction in the rhodium(III) complexes bearing
the facial-coordinated PCN ligand is controlled by their electronic factors. The meridional coordination
of the PCN ligand makes the environment around the iridium center sensitive to the steric nature due to
the steric repulsion between the diphenyl group in the PCN ligand and the phosphines. The facial
coordination of the PCN ligand decreases their repulsion, and reactivity of the metal center depends on
the basicity of the phosphines.
these ligands with substitutionally inert and labile parts is
generally called a hemilabile ligand, and the chemistry of
transition metal complexes bearing these ligands has received
considerable attention. Several hemilabile ligands have been
synthesized and complexed to various metal centers to construct
systems mediated or catalyzed by complexes focused on opening
a coordination site by dissociation of the weaker functional
group for small molecule activation and closing it by recoor-
dination for the stabilization of reactive and unsaturated metal
species. For example, Braunstein and co-workers reported that
Pd complexes bearing the tridentate NPN ligand and showing
reactivity at the Pd center are controlled by the hemilability of
the ligand.7
Introduction
Hybrid chelate ligands containing mixed functionalities
connected by an appropriate spacer are widely used in both
organic chemistry as an optically active chiral ligand for highly
selective asymmetric reactions and in coordination chemistry
as an auxiliary ligand for the isolation of interesting and
important metal complexes.1-18 In particular, a special class of
(1) Slone, C. S.; Weinberger, D. A.; Mirkin, C. A. Prog. Inorg. Chem.
1999, 48, 233.
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2000, 19, 2676.
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Trans. 2000, 1067.
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Rettig, S. J. Organometallics 2001, 20, 2966.
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Organometallics 1997, 16, 3981.
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22, 4295.
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10.1021/om060405d CCC: $37.00 © 2007 American Chemical Society
Publication on Web 11/29/2006

Ir(III) and Rh(III) Complexes with a Heterochelate PN Ligand
Organometallics, Vol. 26, No. 1, 2007 111
Chart 1
Herein, our main objective was to prepare the first neutral
iridium(III) complexes bearing our PN ligand by intramolecular
C-H bond activation as well as neutral rhodium(III) complexes,
although we did not achieve C-H bond activation of the cationic
rhodium complexes bearing the PN ligand. Despite using the
same ligand system, the structure of the complexes was
completely different because the metal center was changed from
iridium to rhodium. To this end, we report unexpected different
reactivities of the iridium(III) and rhodium(III) complexes in
the ligand exchange reaction of phosphines, which are caused
by different steric environments around the metal center due to
the coordination pattern of the PCN ligand.
Transition metal complexes bearing hybrid chelate ligands
have also been used for bond activation chemistry. Andersson
reported that P-O heterochelate ligands undergo C-H bond
activation in the benzylic position.19-21 Tejel described that P-N
heterochelate ligands undergo C(sp3)-H activation reactions.22,23
Milstein reported that iridium and rhodium complexes bearing
the PCN pincer ligands control whether the C-H or C-C bond
is activated.13-16
Results and Discussion
Another interesting feature inherent to hemilabile ligands is
their flexibility. A flexible ligand can change its coordination
pattern to the metal center due to a subtle modification of the
reaction conditions and transform the structure of the complex.
If the complex before and after the transformation has a unique
and characteristic reactivity, the complex can work as a
multifunctional catalyst. It is a challenging project, however,
to construct systems in which the reactivity of complexes bearing
the same ligands is dramatically changed.
In our laboratories, we have studied the chemistry of
hemilabile ligands and designed a heterochelate PN hybrid
ligand (PN ) o-Ph2PC6H4CH2OCH2C5H4N-2) (Chart 1). We
demonstrated that the PN ligand has the flexibility to act as a
P-N bidentate, a P-O-N tridentate, and a P-C-N tridentate
ligand.24-31 One characteristic behavior of this flexibility is that
both iridium(I) and iridium(III) cationic complexes before and
after an intermolecular C-H bond activation can be isolated as
a result of changing the coordination mode of the PN ligand.28
Subsequent studies of our hybrid chelate ligand demonstrated
the stereoselective activation of a prochiral C-H bond by
iridium complexes bearing the optically active PN ligand.31 The
selectivity was controlled by a difference in the thermodynamic
stability of the iridium(III) hydride complexes obtained by
repeated and reversible C-H bond activation due to the
flexibility of the PN ligand. Compared to the cationic system
of iridium complexes bearing the PN ligand, the chemistry of
a neutral complex bearing the same PN ligand has not been
explored because the polymeric species [(PN)IrCl(cod)]n ob-
tained by the reaction of [IrCl(cod)]2 with the PN ligand could
not cleanly induce the intramolecular C-H bond activation.
Synthesis of Neutral Iridium(III) Complexes Bearing the
PN Ligand. When 0.5 equiv of [IrCl(coe)]2 (coe ) cyclooctene)
was treated with 1 equiv of the PN ligand in the presence of
PPh3 (1 equiv) in toluene at 120 °C for 3 h, an intramolecular
C-H bond activation occurred to give a neutral iridium(III)
hydride complex, (PCN-κ3P,C,N)Ir(H)(Cl)(PPh3) (PCN )
Ph2PC6H4CHOCH2C5H4N) (1a), in 80% isolated yield as a
white solid (eq 1). The reaction proceeded even at room
temperature for 12 h to afford 1a in a similar yield. In the
cationic iridium system, both iridium(I) and iridium(III) com-
plexes could be isolated; however, we did not observe the
iridium(I) species such as (PN-κ2P, N)Ir(Cl)(coe) or (PN-κ2P,N)-
Ir(Cl)(PPh3) at the initial stage of the reaction.28
1
The H NMR spectrum of 1a in C6D6 displayed a hydride
signal with a doublet of doublet pattern (J ) 11.3, 19.9 Hz) at
-20.40 ppm, which is the typical chemical shift of a hydride
ligand bound to iridium(III), indicating that the hydride atom
is placed in a cis position to two phosphorus atoms.32-34 The
presence of the hydride ligand was also confirmed by the IR
spectrum (2196 cm-1). The PN ligand acts as a P-C-N
tridentate ligand and coordinates to the iridium(III) center in a
meridional manner. The one-proton signal with a doublet pattern
(J ) 6.7 Hz) at 6.23 ppm was assigned to the proton on the
carbon directly bound to the iridium(III) center. When using a
deuterium-labeled PN ligand (o-Ph2PC6H4CD2OCH2C5H4N-2),
both the hydride signal and the signal at 6.23 ppm disappeared
completely in the 1H NMR spectrum of the corresponding
complex, indicating that the intramolecular C-H bond activation
occurred at the benzylic position of the PN ligand. The 31P NMR
spectrum displayed two singlet signals (δ 6.16 and 13.24), whose
integration, chemical shifts, and very weak coupling constants
indicated that two kinds of phosphorus atoms, derived from the
diphenylphosphino group in the PCN ligand, and PPh3 coordi-
nated to the iridium(III) center in a cis position.35,36 Coordination
of the pyridyl group in the PN ligand was confirmed by IR and
1H NMR spectra. The CdN stretching vibration at 1606 cm-1
(19) Sjo¨vall, S.; Johansson, M.; Andersson, C. Organometallics 1999,
18, 2198.
(20) Sjo¨vall, S.; Svensson, P. H.; Andersson, C. Organometallics 1999,
18, 5412.
(21) Sjo¨vall, S.; Andersson, C.; Wendt, O. F. Organometallics 2001, 20,
4919.
(22) Tejel, C.; Bravi, R.; Ciriano, M. A.; Oro, L. A.; Bordonaba, M.;
Graiff, C.; Tiripicchio, A.; Burini, A. Organometallics 2000, 19, 3115.
(23) Tejel, C.; Ciriano, M. A.; Jimenez, S.; Oro, L. A.; Graiff, C.;
Tiripicchio, A. Organometallics 2005, 24, 1105.
(24) Tani, K.; Nakamura, S.; Yamagata, T.; Kataoka, Y. Inorg. Chem.
1993, 32, 5398.
(25) Tani, K.; Yabuta, M.; Nakamura, S.; Yamagata, T. Dalton Trans.
1993, 2781.
(26) Yabuta, M.; Nakamura, S.; Yamagata, T.; Tani, K. Chem. Lett. 1993,
323.
(27) Kataoka, Y.; Tsuji, Y.; Matsumoto, O.; Ohashi, M.; Yamagata, T.;
Tani, K. Chem. Commun. 1995, 2099.
(28) Kataoka, Y.; Imanishi, M.; Yamagata, T.; Tani, K. Organometallics
1999, 18, 3563.
(29) Kataoka, Y.; Shizuma, K.; Yamagata, T.; Tani, K. Chem. Lett. 2001,
300.
(30) Kataoka, Y.; Nakamura, T.; Tani, K. Chem. Lett. 2003, 66.
(31) Kataoka, Y.; Shizuma, K.; Imanishi, M.; Yamagata, T.; Tani, K. J.
Organomet. Chem. 2004, 689, 3-7.
(32) Hays, M. K.; Eisenberg, R. Inorg. Chem. 1991, 30, 2623.
(33) Carmona, D.; Ferrer, J.; Lorenzo, M.; Santander, M.; Ponz, S.;
Lahoz, F. J.; Lo´pez, J. A.; Oro, L. A. Chem. Commun. 2002, 870.
(34) Navarro, J.; Sola, E.; Martin, M.; Dobrinovitch, I. T.; Lahoz, F. J.;
Oro, L. A. Organometallics 2004, 23, 1908.
(35) Pregosin, P. S.; Kund, R. W. 31P and 13C Transition Metal Phosphine
Complexes; Springer: Berlin, 1979.

112 Organometallics, Vol. 26, No. 1, 2007
Hara et al.
Figure 2. ORTEP drawing of complex 1a with the atom-
numbering scheme. The enantiomer, (S)-OC-6-64-C, is shown. The
hydride ligand was not located in the actual structure determination.
Figure 1. Isomers of the iridium complexes 1.
Table 1. Selected Bond Lengths (Å) and Bond Angles (deg)
for 1a
was shifted to a higher wavenumber by ca. 10 cm-1 compared
to that of the free PN ligand (1590 cm-1), which is a
characteristic shift for the coordination of the pyridine ring in
the PN and PCN ligands to the metal center. The proton at the
6-position of the pyridine ring appeared at 8.31-8.41 ppm,
which was not shifted from that of the free PN ligand (8.38-
8.43 ppm), and had the characteristic shape of a trans-
coordinated PN ligand, indicating meridional coordination of
the PCN ligand. Two inequivalent methylene protons at the
R-position of the 2-pyridyl group in the PCN ligand appeared
at 4.75 and 5.18 ppm as a doublet pattern (J ) 12.6 Hz),
indicating that the PCN ligand formed a rigid bicyclo chelating
ring by forming an Ir-C bond.
Ir-P(1)
Ir-P(2)
Ir-N
2.2559(7)
2.3922(7)
2.162(2)
Ir-C(7)
Ir-Cl
2.139(3)
2.4919(7)
C(7)-Ir-N
C(7)-Ir-P(1)
N-Ir-P(1)
C(7)-Ir-P(2)
N-Ir-P(2)
89.19(10)
P(1)-Ir-P(2)
C(7)-Ir-Cl
N-Ir-Cl
P(1)-Ir-Cl
P(2)-Ir-Cl
99.77(2)
87.36(8)
90.54(6)
98.68(2)
90.04(2)
78.48(8)
164.17(6)
176.59(8)
93.03(7)
1
was confirmed by the H NMR and IR spectra. Two bulkier
ligands, PPh3 and the diphenylphosphino group in the PCN
ligand, cause distortion around the iridium center. For example,
the angle of C(7)-Ir-P(1) [78.48(8)°] was significantly smaller
than 90° and P(1)-Ir-P(2) [99.77(2)°] was larger than 90°,
although that of C(7)-Ir-N [89.19(10)°] was nearly a right
angle. The angle of N-Ir-P(1) [164.17(6)°] was also markedly
different from 180°.
Complex 1a has at least two diastereomers [(S)-OC-6-64-C/
(R)-OC-6-64-A and (R)-OC-6-64-C/(S)-OC-6-64-A] arising from
two stereogenic central chiralities due to a carbon center in the
1
PCN ligand and the iridium center (Figure 1). The H and 31P
NMR spectra of the reaction mixture before the purification
revealed that complex 1a formed as a single isomer. A nuclear
Overhauser effect was not detected between the hydride proton
at -20.40 ppm and the proton on the carbon directly bound to
the iridium(III) center at 6.23 ppm. These spectral data suggested
that complex 1a was an (S)-OC-6-64-C/(R)-OC-6-64-A isomer
in which the relative position of the two protons was trans, and
this observation was consistent with the structure determined
by the following X-ray analysis of 1a (vide infra).
Recrystallization of 1a from hexanes and THF gave colorless
single crystals suitable for X-ray analysis. An ORTEP drawing
is shown in Figure 2, selected bond distances and angles are
given in Table 1, and relevant crystal and data parameters are
presented in Table 3 (see Experimental Section). Although both
(S)-OC-6-64-C and its enantiomer (R)-OC-6-64-A crystallized
in the unit cell due to the centrosymmetric space group P21/c,
the structure of only one isomer [(S)-OC-6-64-C] is shown in
Figure 2. A notable structural feature is that the PCN ligand
coordinates to the iridium(III) center by P(1), C(7), and N atoms
in a meridional manner, in sharp contrast to the facial geometry
of the PCN ligand in a cationic iridium(III) hydride complex
[(PCN-κ3P,C,N)Ir(H)(cod)]PF6 (cod ) cyclooctadiene).28 The
geometry around the iridium(III) center is distorted octahedral
with one coordination site occupied by the hydride ligand, which
In our previous studies of cationic complexes bearing the
PCN/CH3 ligand, the facial isomer of the iridium(III) hydride
complex was gradually converted to the meridional isomer.29
1
In the H NMR analysis of the reaction for the preparation of
1a from [IrCl(coe)2]2, the PN ligand, and PPh3, we could not
confirm the presence of the facial isomer. There was no reaction
when a solution of 1a was heated in toluene at 150 °C, and
complex 1a was recovered without decomposition.
Reaction of the PN ligand with [IrCl(coe)]2 in the absence
of PPh3 at room temperature in toluene afforded a similar neutral
iridium(III) complex, (PCN-κ3P,C,N)Ir(H)(Cl)(coe) (2), quan-
titatively as an orange powder (Scheme 1). Complete purification
of 2 was not successful due to its instability and high solubility
in solvents. Complex 2, however, was characterized by the usual
spectroscopic and physical data. The chemical shift and a
characteristic coupling pattern for the proton at the 6-position
of the pyridine ring indicated that the PCN ligand was
coordinated to the iridium(III) center in a meridional manner.
1
The H and 31P NMR spectra of the reaction mixture before
purification revealed that complex 2 was obtained as a single
isomer. Although the relative configuration of 2 could not be
determined from the spectral data, we estimated that complex
2 also formed as an (S)-OC-6-64-C/(R)-OC-6-64-A isomer from
the structure of the phosphine complex obtained by the following
ligand exchange reaction. Complex 2 reacted with PPh3 in C6D6
at room temperature within 1 h to afford 1a as a single (S)-
OC-6-64-C/(R)-OC-6-64-A isomer quantitatively along with 1
equiv of free cyclooctene.
(36) For recent examples of iridium phosphine complexes showing very
weak couplings, see: (a) Janka, M.; Atesin, A. C.; Fox, D. J.; Flaschenriem,
C.; Brennessel, W. W.; Eisenberg, R. Inorg. Chem. 2006, 45, 6559. (b)
Janka, M.; He, W.; Frontier, A. J.; Flaschenriemand, C.; Eisenberg, R.
Tetrahedron 2005, 61, 6193. (c) Janka, M.; He, W.; Frontier, A. J.;
Eisenberg, R. J. Am. Chem. Soc. 2004, 126, 6864. (d) Albietz, P. J., Jr.;
Cleary, B. P.; Paw, W.; Eisenberg, R. J. Am. Chem. Soc. 2001, 123, 12091.
Reactions of the PN ligand with [IrCl(coe)2]2 in the presence
of other phosphines such as PCy3, PBu3, and PMePh2 or pyridine

Ir(III) and Rh(III) Complexes with a Heterochelate PN Ligand
Organometallics, Vol. 26, No. 1, 2007 113
Scheme 1
Scheme 2
Scheme 3
()Py) afforded a series of neutral iridium(III) hydride com-
plexes, (PCN-κ3P,C,N)Ir(H)(Cl)(L) [L ) PCy3 (1b), PBu3 (1c),
PMePh2 (1d), Py (1e)]. The reactions of the phosphines
proceeded at room temperature, while the reaction of the
pyridine required reflux conditions. All the complexes were
isolated in good yield, and the PCN ligand coordinated to the
iridium(III) center in a meridional manner (Scheme 1). The 31
P
1
NMR and H NMR spectra of PCy3 complex 1b and pyridine
complex 1e indicated the formation of only one isomer, which
had a structure similar to that of the PPh3 complex 1a and the
coe complex 2, while those of other phosphine complexes 1c
and 1d exhibited a mixture of two isomers. For example, the
phosphorus signals of 1d-minor in the 31P NMR spectrum
appeared at -14.46 (singlet) and 15.97 ppm (singlet) and that
of 1d-major at -15.96 (singlet) and 15.27 ppm (singlet). The
hydride signal of 1d-minor in the 1H NMR spectrum appeared
at -20.73 ppm with a doublet of doublets pattern (J ) 11.8,
20.2 Hz) and that of 1d-major at -10.00 ppm with a doublet
of doublets pattern (J ) 19.8, 160.6 Hz). The coupling constants
of 1d-minor were similar to those of the PPh3 complex 1a and
the PCy3 complex 1b, and that of 1d-major was clearly different.
The complexes 1c-major and 1c-minor also had similar coupling
constants. As shown in Scheme 1, we determined that the
structure of the minor isomer of 1c and 1d was A, which is
similar to the structure of 1a and 1b, and the structure of major
isomers was B, in which one of the two phosphorus atoms was
placed in the cis position to the hydride ligand and another was
in the trans position.33
chelate chain of the PN ligand showed rapid dynamic behavior,
including coordination and dissociation of the oxygen atom. In
contrast to [(PN-κ2P,N)Ir(cod)]PF6, intramolecular C-H bond
activation of 3 did not proceed at all in CDCl3 at 30 °C or even
in 1,2-dichloroethane at 80 °C, and complex 3 was recovered
without decomposition. When [RhCl(coe)2]2 was used as a
starting rhodium(I) complex instead of [RhCl(cod)]2, the reaction
afforded a complex mixture and neither the rhodium(I) com-
plexes [(PN-κ2P,N)Rh(coe)]PF6 nor the rhodium(III) hydride
complex [(PCN-κ3P,C,N)Rh(H)(coe)2]PF6 was observed.
In a neutral rhodium system, intramolecular C-H bond
activation proceeded similarly to the neutral iridium system to
afford the corresponding rhodium(III) hydride complex. Treat-
ment of [RhCl(coe)2]2 with the PN ligand in the presence of
PR3 (R ) Ph, Cy) in toluene afforded the neutral rhodium(III)
hydride complexes (PCN-κ3P,C,N)Rh(H)(Cl)(PR3) [R ) Ph
(4a), Cy (4b)] as pale yellow powders in modest isolated yields
Synthesis of Neutral Rhodium(III) Complexes Bearing the
PN Ligand. The cationic rhodium(I) complex bearing the PN
ligand, [(PN-κ2P,N)Rh(cod)]PF6 (3), could be prepared using a
method similar to that for the synthesis of the iridium(I)
analogue [(PN-κ2P,N)Ir(cod)]PF6.28 Reaction of [RhCl(cod)]2
with 2 equiv of the PN ligand in the presence of excess AgPF6
in ethanol at room temperature for 5 h gave 3 as an orange
powder in 87% yield (Scheme 2). The structure of 3 was fully
characterized by spectral and physical data including elemental
(Scheme 3). Similar to the iridium complex 1a, the 1H and 31
P
NMR analysis of the reaction mixture demonstrated that
complexes 4a and 4b were also composed of a single diaste-
reomer.
The structure of 4a, which was determined by the usual
spectroscopic and physical data as well as X-ray analysis, was
clearly different from that of the iridium analogue complex 1a.
Recrystallization of 4a from hexanes and THF gave single
orange crystals suitable for X-ray analysis. The ORTEP drawing
of 4a is shown in Figure 3, selected bonds and angles are listed
in Table 2, and relevant crystal and data parameters are presented
1
analysis. The H NMR of 3 in CDCl3 at 30 °C showed broad
signals, especially for the protons at two kinds of methylene
protons in the PN ligand. As the temperature decreased, the
signals sharpened to provide four inequivalent doublet peaks
at 4.73 (J ) 13.1 Hz), 4.81 (J ) 15.6 Hz), 5.13 (J ) 13.1 Hz),
and 5.30 (J ) 15.6 Hz) ppm at -20 °C, indicating that the

114 Organometallics, Vol. 26, No. 1, 2007
Hara et al.
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg)
for 4a
Rh-P(1)
Rh-P(2)
Rh-N
2.302(3)
2.279(3)
2.201(4)
Rh-C(7)
Rh-Cl
2.068(7)
2.5207(12)
C(7)-Rh-N
C(7)-Rh-P(1)
N-Rh-P(1)
C(7)-Rh-P(2)
N-Rh-P(2)
91.7(2)
94.4(2)
94.7(3)
82.2(2)
95.5(3)
P(2)-Rh-P(1)
C(7)-Rh-Cl
N-Rh-Cl
P(2)-Rh-Cl
P(1)-Rh-Cl
169.30(5)
172.8(2)
91.13(12)
90.94(11)
91.93(11)
Figure 4. H6 of the pyridine ring monitored by 1HNMR
spectroscopy.
1
afforded a yellow solution, in which the H NMR displayed
that all the red solids were converted to 4a (Figure 4c). The
1
hydride signal in the H NMR spectrum also transformed to
the signals for 4a. Although the red solids could not be isolated
as a pure solid and the structure of two rhodium species observed
1
in the H NMR spectrum of Figure 4a was not determined
Figure 3. ORTEP drawing of complex 4a with the atom-
numbering scheme. The enantiomer, (S)-OC-6-53-C, is shown. The
hydride ligand was not located in the actual structure determination.
completely, we assumed the formation of a rhodium(I) complex
such as cis-(PN-κ2P,N)RhCl(coe) and the rhodium(III) hydride
complex bearing the PCN ligand in a meridional manner. In
the reaction for the preparation of 4 from [RhCl(coe)2]2, the
rhodium(I) complexes formed and then the intramolecular C-H
bond activation afforded the meridional rhodium(III) hydride
complex, followed by isomerization to give thermodynamically
stable complex 4a or 4c.
Ligand Exchange Reaction. The coordination ability of
various tertiary phosphines (PR3) to the metal center can be
controlled by changing the substituent (R) of the phosphines
electronically and sterically. C. A. Tolman quantified the steric
and electronic factors of the phosphine ligand.38 The reactivities
of most organometallic compounds in the ligand exchange
reaction of phosphines, however, are explained by the combina-
tion of both factors, and it is very difficult to make proper use
of both factors in a similar ligand system. Using the phosphine
ligand exchange reaction as one of the most primitive metal-
meditated reactions, we demonstrated an unexpected difference
in the reactivity of iridium(III) and rhodium(III) hydride
complexes and showed that the coordination geometry of the
PCN ligand to the metal center is the predominant factor for
controlling the reactivity of the complexes using Tolman’s
parameter.
We examined the ligand exchange reaction of these iridium-
(III) and rhodium(III) complexes with various tertiary phos-
phines. When the iridium PPh3 complex 1a bearing the
meridional-coordinated PCN ligand was treated with 1 equiv
of PCy3 in toluene at room temperature for 24 h, the phosphine
ligand exchange reaction proceeded to some extent to afford
the PCy3 complex 1b in 20% yield along with the recovered
1a in 80% yield and free PPh3 and PCy3 (eq 2), whereas
complex 1b reacted with 1 equiv of PPh3 smoothly under similar
conditions to afford 1a quantitatively (eq 3). According to
Tolman’s parameter, the steric factor of PPh3 (145°) was smaller
than that of PCy3 (170°), which indicates that the coordination
of PPh3 was favorable under the steric controls. In addition,
the electronic factor of PCy3 [ν(CO) 2056.4 cm-1] was larger
than that for PPh3 [ν(CO) 2068.9 cm-1], which indicates that
the coordination of PCy3 was favorable under the electronic
controls (Figure 5).
in Table 3 (see Experimental Section). The centrosymmetric
space group P21 indicated that the crystals of 4a also included
a pair of enantiomers, (S)-OC-6-53-C and (R)-OC-6-53-A, and
Figure 2 shows only the structure of the (S)-OC-6-53-C isoform.
The structure has an octahedral geometry around the rhodium-
(III) center. The PN ligand acted as a P-C-N tridentate ligand
and coordinated to the rhodium(III) center in a facial manner.
Each phosphine atom bound to the rhodium atom was located
at a trans position. A similar metal coordination system is
observed in cationic iridium complexes bearing PCN or PCN/
CH3 ligands.28,29
When the rhodium complex [RhCl(coe)2]2 was treated with
the PN ligand in the presence of PPh3 in toluene at room
temperature, the reaction mixture immediately turned to a red
solution and then slowly changed to a yellow solution. Five
minutes after starting the reaction, before the color of the
reaction mixture turned yellow, the addition of hexanes to the
1
reaction mixture afforded an orange precipitation. H NMR
analysis of the orange solid in C6D6 indicated the formation of
two complexes bearing the PN and/or PCN ligand. Two signals
of the proton at the 6-position of the pyridine ring appeared at
9.24 and 10.28 ppm (Figure 4a), neither of which are the signal
of 4a (9.58 ppm). A coupling pattern of the signal at 9.24 ppm
showed a characteristic shape for the cis or facial coordination
of the PN or PCN ligand, and that at 10.28 ppm indicated the
trans or meridional coordination. In the hydride signal region,
only one signal was observed at -19.04 ppm with a doublet of
doublets pattern (J ) 19.2, 31.0 Hz), indicating that one of the
two signals described above was derived from a rhodium(I)
complex with no hydride ligand.37
1
In the H NMR of a C6D6 solution of the orange solid after
18 h at room temperature, the signal of 4a appeared along with
the signals described above (Figure 4b). Heating a toluene
solution of the orange solid under reflux conditions for 3 h
(37) The 31P NMR spectrum for the orange solids in C6D6 indicated the
presence of more than two species except 4a: one species at 47.8 ppm
(broad multiplet), second species at 51.35 (dd, J ) 44.8, 194.5 Hz) and
53.29 (dd, J ) 44.8, 194.5 Hz), and another species at 58.58 (d, J ) 163.4
Hz).
(38) Tolman, C. A. Chem. ReV. 1977, 77, 313.

Ir(III) and Rh(III) Complexes with a Heterochelate PN Ligand
Organometallics, Vol. 26, No. 1, 2007 115
Scheme 4
Figure 5. Cone angle and electronic parameter of various tertiary
phosphine ligands.
The results shown in eqs 2 and 3 suggest that the ligand
exchange reaction of phosphines in the iridium(III) complexes
bearing the meridional-coordinated PCN ligand was controlled
primarily by the steric effect of the coming phosphine ligand.
Similar reactivity was observed in the reaction with other
phosphines. Under conditions similar to those described above,
the PCy3 complex 1b reacted easily with PBu3 or PMePh2,
which had smaller cone angles than that of PCy3, to afford the
corresponding phosphine complex 1c or 1d, but did not react
with P(o-tolyl)3, which has a larger cone angle.
was controlled by a combination of the steric factor and the
trans influence. A higher trans influence of the hydride ligand
compared to the carbon in the PCN ligand facilitates the
isomerization of the A isomer to the B isomer.39 The steric effect
of the phosphine ligand was superior to the trans influence:
when using bulkier phosphines such as PPh3, the B isomer was
not observed at all, but for 1c and 1d, which have smaller
phosphines such as PBu3 or PMePh2, the decreased steric
repulsion allowed for the formation of the B isomer as a kinetic
product. The meridional coordination geometry of the PCN
ligand creates an environment around the iridium center that is
sensitive to the steric nature.
Interestingly, phosphine complexes 1c and 1d were obtained
as a mixture of two isomers, 1c-A and 1c-B and 1d-A and 1d-
B, which were the same two isomers observed in the reaction
1
of [IrCl(coe)2]2 with the PN ligand (vide supra). The H and
In contrast to the phosphine ligand exchange reaction of the
iridium complexes, the corresponding rhodium complexes
bearing the facial-coordinated PCN ligand had different reac-
tivities. For example, the rhodium PPh3 complex 4a reacted
easily with PCy3, which had a larger cone angle than PPh3, in
toluene at room temperature for 12 h to afford the PCy3 complex
4b with 80% conversion, while the ligand exchange reaction
did not proceed at all between the iridium PCy3 complex 4b
and PPh3 (Scheme 4). These observations suggest that the ligand
exchange reaction in the rhodium complexes bearing the facial-
coordinated PCN ligand was controlled not by the bulkiness of
the phosphine ligand (steric factor) but rather by the basicity
of the phosphine ligand (electronic factor).
31P NMR spectra of the ligand exchange reaction after 1 day
showed that the ratios of A and B isomers were 14:86 for 1c
and 38:62 for 1d. Isomerization from A to B occurred gradually
in C6D6 at room temperature, and the ratios of the A isomer
after 5 days increased to 26% and 57%, respectively, indicating
that the A isomer was a thermodynamic product and the B
isomer was a kinetic product. Selectivity of A and B isomers
To confirm our findings, we examined the ligand exchange
reaction with other phosphines. Although PCy3 of 4b could not
be substituted for PBu3, PMePh2, and P(o-tolyl)3, which had
smaller electronic parameters, the rhodium PPh3 complex 4a
reacted with PBu3 and PMePh2 in toluene at room temperature
to afford the corresponding phosphine complexes. Through all
ligand exchange reactions, the obtained rhodium complexes were
a single isomer, (S)-OC-6-53-C and (R)-OC-6-53-A. Other
isomers, including (R)-OC-6-53-C and (S)-OC-6-53-A, were not
1
observed in the H and 31P NMR analysis. The stability of the
rhodium complexes with the facial-coordinated PCN ligand was
controlled only by the electronic factor of the phosphines: the
environment around the rhodium center constructed by the PCN
ligand with a facial coordination geometry was not very sensitive
to the steric nature that the coordination ability to the metal
center depended on the basicity of the incoming phosphines.
Although the iridium(III) and rhodium(III) hydride complexes
bearing the same PCN ligand system are different only with
regard to the coordination pattern of the ligand, the controlling
factor for the proceeding ligand exchange reaction is dramati-
cally changed.

116 Organometallics, Vol. 26, No. 1, 2007
Hara et al.
Table 3. Crystal and Refinement Data for 1a and 4a
1a 4a
Experimental Section
All reactions and manipulations were performed under argon by
use of standard vacuum line and Schlenk tube techniques. 1H NMR
spectra were recorded at either 300 MHz on a Varian Mercury 300
spectrometer or at 270 MHz on a JEOL JNM-GSX270 spectrom-
eter. Chemical shifts are reported in ppm (δ) relative to tetram-
ethylsilane or referenced to the chemical shifts of residual solvent
resonances (C6H6 or CH3Cl was used as internal standard, δ 7.20
or 7.26). 31P{1H} NMR spectra were recorded at 121.49 MHz on
a Varian Mercury 300 spectrometer or at 109.25 MHz on a JEOL
JNM-GSX270 spectrometer, and chemical shifts were referenced
to external 85% H3PO4. Infrared spectra were recorded on a JASCO
FT/IR-230 instrument. Mass spectra were obtained on a JEOL JMS
DX-303HF spectrometer. Elemental analyses were recorded on a
Perkin-Elmer 2400 instrument at the Faculty of Engineering
Science, Osaka University. All melting points were recorded on a
Yanaco MP-52982 instrument and were not corrected.
Unless otherwise noted, reagents were purchased from com-
mercial suppliers and used without further purification. Dichlo-
romethane was distilled from calcium hydride under argon prior
to use. Tetrahydrofuran, toluene, and hexanes were distilled over
sodium benzophenone ketyl under argon prior to use, and other
solvents for recrystallization were dried using standard procedures.
The starting materials, [IrCl(coe)2]2, [RhCl(coe)2]2, [RhCl(cod)]2,
and the PN ligand, o-Ph2PC6H4CH2OCH2C5H4N-2, were prepared
according to published procedures.25,26,40,41 PPh3 and PCy3 were
recrystallized from ethanol prior to use.
color
colorless
colorless
empirical formula
fw
C43H37P2NOIr
873.33
C43H37ClRhNOP2
784.04
radiation/Å
Mo KR (monochr)
0.71075
Mo KR (monochr)
0.71075
T/K
120
120
cryst syst
space group
monoclinic
P21/c
monoclinic
P21
unit cell dimens
a/Å
b/Å
c/Å
16.5795(8)
10.2514(4)
22.4112(9)
109.4691(16)
3591.3(2)
4
9.2620(5)
23.8082(13)
9.1824(4)
117.471(2)
1796.51(15)
2
â/deg
V/Å3
Z
d
calc/g cm-3
1.615
3.917
1.449
0.674
µ/mm-1 (Mo KR)
cryst size/mm
no. of total, unique
reflns
0.27 × 0.20 × 0.12
0.37 × 0.20 × 0.10
12 7780, 10 473
64 480, 10 811
Rint
0.0738
0.0659
transmn range
no. of params,
restraints
0.4845-0.7111
0.5705-0.9349
590, 0
241, 27
R,a Rw,b GOF
resid density/e Å-3
0.0289, 0.0667, 1.110
-1.69 < 1.787
0.0744, 0.2054, 1.078
-1.059 < 3.164
a R ) (∑||Fo| - |Fc||)/∑|Fo|, for all I > 2.0σ(I). b Rw ) [∑w(Fo2 - Fc2)2/
4
∑(wFo )]1/2
.
Preparation of mer-(PCN-κ3P,C,N)Ir(H)(Cl)(PPh3) (1a). A
stirred mixture of [IrCl(coe)2]2 (317 mg, 0.350 mmol), the PN ligand
(290 mg, 0.760 mmol), and PPh3 (203 mg, 0.780 mmol) in toluene
(5 mL) was heated to 120 °C for 3 h. The mixture was cooled to
ambient temperature for a period of 30 min. After the solvent was
removed in vacuo, the residue was dissolved in THF (1 mL), and
then hexanes (5 mL) were added. A white precipitate was collected
by removal of the solvent with syringe and washed with hexanes
(5 mL). The residue was dried in vacuo to give 1a as white solids
Calcd for C43H55IrClNOP2: C, 57.93; H, 6.22; N, 1.57. Found: C,
57.54; H, 6.11; N, 1.56.
Preparation of (PCN-κ3P,C,N)Ir(H)(Cl)(PBu3) (1c). Method
A: A toluene (1 mL) solution of PBu3 (11 mg, 0.053 mmol) was
added dropwise to a stirred toluene (1 mL) solution of [IrCl(coe)2]2
(24 mg, 0.027 mmol) and the PN (21 mg, 0.053 mmol). The solution
was stirred at room temperature for 12 h. Solvent was removed in
vacuo to give 1c as an orange powder (quantitative yield) as a
mixture of 1c-A and 1c-B (1c-A:1c-B ) 11:89; the ratio was
determined by 1H and 31P NMR). Method B: A toluene (1.5 mL)
solution of PBu3 (3 mg, 0.016 mmol) was added dropwise to a
stirred toluene (1 mL) solution of 1a (14 mg, 0.016 mmol). The
solution was stirred at room temperature for 24 h. Solvent was
removed in vacuo to give 1c as an orange powder (14 mg,
quantitative yield) as a mixture of 1c-A and 1c-B (1c-A:1c-B )
1
(530 mg, 80% yield). Mp: 187 °C (dec). H NMR (300 MHz,
C6D6): δ -20.40 (dd, JH-P ) 11.3, 19.9 Hz, 1H, Ir-H), 4.75 (d,
JH-H ) 12.6 Hz, 1H, O-CH2-Py), 5.18 (d, JH-H ) 12.6 Hz, 1H,
O-CH2-Py), 5.40-5.47 (m, 1H, H4 of Py), 6.23 (d, JH-H ) 6.7
Hz, 1H, Ar-CH-O), 6.26-7.43 (m, 30H, H of arom), 7.79-7.89
(m, 1H, H5 of Py), 8.31-8.41(m, 1H, H6 of Py). 31P{1H} NMR
(121 MHz, C6D6): δ 6.16 (s), 13.24 (s). FABMS: m/z ) 836 (M+
- Cl). IR (KBr tablet, cm-1): ν 2196, 1606, 1095. Anal. Calcd
for C43H37IrClNOP2: C, 59.13; H, 4.27; N, 1.60. Found: C, 58.48;
H, 4.20; N, 1.56.
1
14:86; the ratio was determined by H and 31P NMR). IR (NaCl
nujol, cm-1): ν 2362, 1582,1090. 1H NMR (300 MHz, C6D6): 1c-
A, δ -20.69 (dd, JP-H ) 12.7 18.8 Hz, 1H, Ir-H), 0.18-1.85 (m,
PBu3), 4.74 (d, JH-H ) 12.4 Hz, 1H, -O-CH2-py), 5.36 (d, JH-H
) 12.4 Hz, 1H, -O-CH2-py), 6.38-8.55 (m, arom), 9.68-9.76
(m, 1H, H6 of py); 1c-B, δ -10.04 (dd, JP-H ) 20.0 150.4 Hz,
1H, Ir-H), 0.18-1.85 (m, PBu3), 4.43 (d, JH-H ) 13.6 Hz, 1H,
-O-CH2-py), 4.84 (d, JH-H ) 13.6 Hz, 1H, -O-CH2-py), 6.38-
8.55 (m, arom), 10.30-10.38 (m, 1H, H6 of py). 31P{1H} NMR
(121 MHz, C6D6): 1c-A, -21.11 (s), 23.20 (s); 1c-B, δ -18.60
(s), 15.79 (s). FABMS: m/z ) 778 (M+ - Cl), 573 (M+ - PBu3-
Cl). Complete purification of 1e for satisfaction of elemental
analysis was not successful due to high solubility to solvents and
its instability.
Preparation of mer-(PCN-κ3P,C,N)Ir(H)(Cl)(PCy3) (1b). A
mixture of [IrCl(coe)2]2 (99 mg, 0.110 mmol), the PN ligand (84
mg, 0.220 mmol), and PCy3 (63 mg, 0.220 mmol) in toluene (5
mL) was stirred at room temperature for 3 h. After the solvent was
removed in vacuo, the residue was dissolved in THF (1 mL) and
then hexanes (5 mL) were added. A white precipitate was collected
by removal of the solvent with syringe and washed with hexanes
(5 mL). The residue was dried in vacuo to give 1b as a white solid
1
(163 mg, 83% yield). Mp: 189 °C (dec). H NMR (300 MHz,
C6D6): δ -20.38 (t, JH-P ) 16.1 Hz, 1H, Ir-H), 0.40-2.40 (m,
33H, H of PCy3), 4.79 (d, JH-H ) 11.8 Hz, 1H, O-CH2-Py), 5.62
(d, JH-H ) 11.8 Hz, 1H, O-CH2-Py), 6.41 (d, J ) 2.5 Hz, 1H,
Ar-CH-O), 6.50-7.25 (m, 18H, H of arom), 9.83-9.88 (m, 1H,
H6 of Py). 31P{1H} NMR (121 MHz, C6D6): δ 1.46 (s), 22.32 (s).
Preparation of (PCN-κ3P,C,N)Ir(H)(Cl)(PMePh2) (1d). Method
A: A toluene (1 mL) solution of PMePh2 (33 mg, 0.164 mmol)
was added dropwise to a stirred toluene (1 mL) solution of [IrCl-
(coe)2]2 (73 mg, 0.082 mmol) and the PN (63 mg, 0.164 mmol).
The solution was stirred at room temperature for 12 h. Solvent was
removed in vacuo to give 1d as an orange powder (quantitative
yield) as a mixture of 1d-A and 1d-B (1d-A:1d-B ) 30:70; the
ratio was determined by 1H and 31P NMR). Method B: A toluene
(1.5 mL) solution of PMePh2 (13 mg, 0.064 mmol) was added
dropwise to a stirred toluene (1 mL) solution of 1a (56 mg, 0.064
mmol). The solution was stirred at room temperature for 24 h.
FABMS: m/z ) 856 (M+ - Cl), 610 (M+ - PCy3), 573 (M+
-
Cl - PCy3). IR (KBr tablet, cm-1): ν 2239, 1605, 1043. Anal.
(39) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Cood. Chem. ReV.
1973, 10, 335.
(40) van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28, 90.
(41) van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28, 91.

Ir(III) and Rh(III) Complexes with a Heterochelate PN Ligand
Organometallics, Vol. 26, No. 1, 2007 117
Solvent was removed in vacuo to give 1d as an orange powder (68
mg) as a mixture of 1d-A and 1d-B (1d-A:1d-B ) 38:62; the ratio
7.72 (m, 3H, arom), 7.96-8.17 (m, 2H, arom), 8.84 (d, J ) 5.4,
1H, H6 of py). 31P{1H} NMR (30 °C, CDCl3): δ 15.8 (d, J ) 141
Hz). FABMS: m/z ) 594 (M+ - PF6). IR (nujol, cm-1): ν 1604,
1083, 840, 753, 702. Anal. Found: C, 49.27; H, 4.27; N, 1.90.
Calcd for C33H34F6RhNOP2: C, 49.54; H, 4.40; N, 1.94.
1
was determined by H and 31P NMR). IR (NaCl nujol, cm-1): ν
2190, 2054, 1606,1095. 1H NMR (300 MHz, C6D6): 1d-A, δ
-20.73 (dd, JP-H ) 11.8, 20.2 Hz, 1H, Ir-H), 1.65 (d, JP-H ) 7.4
Hz, 3H, PCH3Ph2), 4.32 (d, JH-H ) 13.7 Hz, 1H, -O-CH2-py),
4.80 (d, JH-H ) 13.7 Hz, 1H, -O-CH2-py), 6.04 (t, JH-H ) 6.6,
1H, H4 of py), 6.26 (d, J ) 7.5 Hz, 1H, Ar-CH-O), 5.82-8.52 (m,
Preparation of fac-(PCN-κ3P,C,N)Rh(H)(Cl)(PPh3) (4a). Solid
PPh3 (31 mg, 0.120 mmol) was added to a stirred toluene (1 mL)
suspension of [RhCl(coe)2]2 (46 mg, 0.060 mmol) and the PN ligand
(43 mg, 0.120 mmol). The solution was stirred at 120 °C for 3 h.
After the solvent was removed in vacuo, the residue was dissolved
in THF (1 mL) and then hexanes (5 mL) were added. A white
precipitate was collected by removal of the solvent with syringe
and washed with hexanes (10 mL). The residue was dried in vacuo
to give 4a as a white powder (87 mg, 92% yield) as a single isomer.
Mp: 158 °C (dec). 1H NMR (300 MHz, C6D6): δ -15.52 (ddd, J
) 11.5, 11.5, 18.9 Hz, 1H, H of Ir-H), 3.76 (d, JH-H ) 15.4 Hz,
1H, H of O-CH2-Py), 3.86 (d, JH-H ) 15.4 Hz, 1H, H of O-CH2-
Py), 5.73 (d, J ) 7.4 Hz, 1H), 5.98-8.35 (m, H of Ar), 9.58 (d, ,
J ) 4.4 Hz, 1H, H6 of Py). 31P{1H} NMR (121 MHz, C6D6): δ
arom), 9.58-9.62 (m, 1H, H6 of py); 1d-B, δ -10.00 (dd, JP-H
)
19.8, 160.6 Hz, 1H, Ir-H), 1.94 (d, JP-H ) 7.4 Hz, 3H, PCH3Ph2),
5.07 (d, JH-H ) 12.6 Hz, 1H, -O-CH2-py), 5.16 (d, JH-H ) 12.6
Hz, 1H, -O-CH2-py), 5.85 (t, JH-H ) 6.4, 1H, H4 of py), 6.51 (d,
J ) 8.4 Hz, 1H, Ar-CH-O), 5.82-8.52 (m, arom), 8.66-8.73 (m,
1H, H6 of py). 31P{1H} NMR (121 MHz, C6D6): 1d-A, δ -14.46
(s), 15.97 (s); 1d-B, δ -15.96 (s), 15.27 (s). FABMS: m/z ) 776
(M+ - Cl), 573 (M+ - PMePh2- Cl). Complete purification of
1e for satisfaction of elemental analysis was not successful due to
high solubility to solvents and its instability.
Preparation of (PCN-κ3P,C,N)Ir(H)(Cl)(Py) (1e). A toluene
(1 mL) solution of pyridine (0.05 mL, excess) was added dropwise
to a stirred toluene (1 mL) solution of [IrCl(coe)2]2 (74 mg, 0.083
mmol) and the PN (63 mg, 0.164 mmol). The solution was stirred
at 120 °C for 3 h. After the solvent was removed in vacuo, the
residue was washed with hexanes (5 mL). The residue was dried
in vacuo to give 1e as a white powder (91 mg, 60% yield) as a
39.39 (dd, JP-P ) 117.9 Hz, JRh-P ) 407.1 Hz), 60.91 (dd, JP-P
)
117.9 Hz, JRh-P ) 407.1 Hz). FABMS: m/z ) 748 (M+ - Cl). IR
(KBr tablet, cm-1): ν 2020, 1604, 1096. Anal. Calcd for C43H37-
ClNOP2Rh: C, 65.87; H, 4.76; N, 1.79. Found: C, 65.40; H, 4.88;
N, 1.80.
Preparation of fac-(PCN-κ3P,C,N)Rh(H)(Cl)(PCy3) (4b). A
mixture of [RhCl(coe)2]2 (51 mg, 0.071 mmol), the PN ligand (54
mg, 0.141 mmol), and PCy3 (39 mg, 0.141 mmol) in toluene (1
mL) was stirred at room temperature for 3 h. After the solvent was
removed in vacuo, the residue was dissolved in THF (1 mL) and
then hexanes (5 mL) were added. A white precipitate was collected
by removal of the solvent in vacuo and washed with a mixed solvent
(30 mL) of THF and hexanes (THF/hexanes, 1:2). The residue was
dried in vacuo to give 4b as a white solid (99 mg, 87% yield). Mp:
184 °C (dec). IR (KBr tablet, cm-1): ν 2063, 1602, 1099. 1H NMR
(300 MHz, C6D6): δ -16.33 (ddd, J ) 8.8, 14.3, 21.5 Hz, 1H, H
of Ir-H), 0.95-2.97 (m, H of PCy3), 3.97 (d, JH-H ) 15.4 Hz, 1H,
H of O-CH2-Py), 4.12 (d, JH-H ) 15.4 Hz, 1H, H of O-CH2-Py),
5.85 (d, J ) 8.0 Hz, 1H), 6.20-8.41 (m, H of Ar), 10.24 (d, J )
5.5 Hz, 1H, H6 of Py). 31P{1H} NMR (121 MHz, C6D6): δ 31.34
(dd, JP-P ) 111.2 Hz, JRh-P ) 387.6 Hz), 61.36 (dd, JP-P ) 111.2
Hz, JRh-P ) 387.6 Hz). FABMS: m/z ) 766 (M+ - Cl). Anal.
Calcd for C43H55ClNOP2Rh: C, 64.38; H, 6.91; N, 1.75. Found:
C, 64.49; H, 6.72; N, 1.75.
single isomer. Mp: 187 °C (dec). IR (KBr nujol, cm-1): ν 2196,
1
1606, 1095. H NMR (300 MHz, C6D6): δ -20.86 (d, JH-P
)
23.4 Hz, 1H, Ir-H), 4.49 (d, JH-H ) 13.2 Hz, 1H, -O-CH2-py),
5.08 (d, JH-H ) 13.2 Hz, 1H, -O-CH2-py), 6.11-7.47 (m, arom)
8.19-8.31 (m, 1H, H6 of py), 9.68-9.80 (m, 1H, H6 of py of
PN). 31P{1H} NMR (121 MHz, C6D6): δ 20.61 (s). FABMS: m/z
) 728 (M+ + Cl), 655 (M+ - Cl), 573 (M+ - Cl - py). Anal.
Calcd for C30H27IrClN2OP: C, 52.21; H, 3.94; N, 4.06. Found: C,
52.20; H, 3.98; N, 4.12.
Preparation of (PCN-κ3P,C,N)Ir(H)(Cl)(coe) (2). A mixture
of [IrCl(coe)2]2 (22 mg, 0.025 mmol) and the PN ligand (18 mg,
0.047 mmol) in toluene (4 mL) was stirred at room temperature
for 1 h. The solvent was removed in vacuo to give 2 as an orange
1
powder (36 mg, quantitative yield). Mp: 134 °C (dec). H NMR
(300 MHz, C6D6): δ -24.54 (d, JH-P ) 20.6 Hz, 1H, Ir-H), 1.01-
2.72 (m, H of COE), 4.56 (d, JH-H ) 13.7 Hz, 1H, O-CH2-Py),
4.76 (d, JH-H ) 13.7 Hz, 1H, O-CH2-Py), 6.45 (d, JH-H ) 6.9 Hz,
1H, Ar-CH-O), 6.80-8.25 (m, H of Ar), 10.49-10.52 (m, 1H, H6
of Py). 31P{1H} NMR (121 MHz, C6D6): δ 19.89 (s). FABMS:
m/z ) 573 (M+ - Cl - PCy3). IR (KBr tablet, cm-1): ν 2360,
1606 cm-1. Complete purification of 2 for satisfaction of elemental
analysis was not successful due to high solubility to solvents and
its instability.
Preparation of fac-(PCN-κ3P,C,N)Rh(H)(Cl)(PBu3) (4c). A
toluene (3 mL) solution of PBu3 (5 mg, 0.027 mmol) was added
dropwise to a stirred toluene (3 mL) solution of 4a (21 mg, 0.027
mmol). The solution was stirred at room temperature for 20 h. The
solvent was removed in vacuo to give 4c as a white powder (24
mg, quantitative yield) as a single isomer. IR (KBr tablet, cm-1):
Preparation of [(PN-κ3P,N)Rh(cod)]PF6 (3). An EtOH (2 mL)
solution (2 mL) of AgPF6 (120 mg, 0.475 mmol) was added
dropwise to a stirred EtOH (5 mL) suspension of [RhCl(cod)]2 (72
mg, 0.146 mmol) at room temperature. The reaction mixture was
stirred at room temperature for 90 min. After removal of insoluble
materials by filtration, the filtrate was added to an EtOH (2 mL)
solution of the PN ligand (119 mg, 0.310 mmol) at room
temperature. The reaction mixture was stirred at room temperature
for 5 h. After the solvent was removed with a syringe, the obtained
yellow solid was washed with EtOH (3 mL × 2) to give 3 (187
mg, 0.253 mmol) as an orenge powder. Recrystallization of the
crude product from dichloromethane and ether gave a pure orange
1
ν 2065, 1603, 1097. H NMR (300 MHz, C6D6): δ -16.15 (ddd,
J ) 12.5, 21.5, 31.5 Hz, 1H, Ir-H), 0.66-2.33 (m, PBu3), 3.92 (d,
JH-H ) 15.6 Hz, 1H, -O-CH2-py), 3.99 (d, JH-H ) 15.6 Hz, 1H,
-O-CH2-py), 5.66-8.41 (m, arom) 10.19-10.29 (m, 1H, H6 of
py). 31P{1H} NMR (121 MHz, C6D6): δ 13.97 (dd, JP-P ) 115.7,
JRh-P ) 405.5 Hz), 58.60 (dd, JP-P ) 115.7, JRh-P ) 405.5 Hz).
FABMS: m/z ) 706 (M+ - Cl). Complete purification of 4c for
satisfaction of elemental analysis was not successful due to high
solubility to solvents and its instability.
Preparation of fac-(PCN-κ3P,C,N)Rh(H)(Cl)(PMePh2) (4d).
A toluene (3 mL) solution of PMePh2 (6 mg, 0.032 mmol) was
added dropwise to a stirred toluene (3 mL) solution of 4a (24 mg,
0.032 mmol). The solution was stirred at room temperature for 20
h. The solvent was dried in vacuo to give 4d as a white powder
(27 mg, quantitative yield) as a single isomer. IR (KBr tablet, cm-1):
ν 2062, 1571, 1097. 1H NMR (300 MHz, C6D6): δ -15.52 (ddd,
J ) 7.8, 11.9, 31.5 Hz, 1H, Ir-H), 2.16-2.23 (m, 3H, PCH3Ph2),
3.79 (d, JH-H ) 5.3 Hz, 1H, -O-CH2-py), 3.81 (d, JH-H ) 5.3 Hz,
1
crystal. Mp: 207.5 °C (dec). H NMR (CDCl3, -20 °C, 270.05
MHz): δ 1.90-2.25 (m, 4H, methylene of COD), 2.45-2.72 (m,
4H, methylene of COD), 4.25-4.46 (br, 4H, olefin of COD), 4.73
(d, J ) 13.1 Hz, 1H, O-CH2-py), 4.81 (d, J ) 15.6 Hz, 1H, Ar-
CH2-O), 5.13 (d, J ) 13.1 Hz, 1H, O-CH2-py), 5.30 (d, J ) 15.6
Hz, Ar-CH2-O), 6.30-6.43 (m, 1H, arom), 6.86-7.03 (m, 5H,
arom), 7.20-7.38 (m, 4H, arom), 7.38-7.52 (m, 2H, arom), 7.58-

118 Organometallics, Vol. 26, No. 1, 2007
Hara et al.
1H, -O-CH2-py), 5.66-8.41 (m, arom) 9.47-9.53 (m, 1H, H6 of
py). 31P{1H} NMR (121 MHz, C6D6): δ 20.60 (dd, JP-P ) 127.6,
JRh-P ) 409.7 Hz), 58.60 (dd, JP-P ) 127.6, JRh-P ) 409.7 Hz).
FABMS: m/z ) 704 (M+ - Cl). Complete purification of 4d for
satisfaction of elemental analysis was not successful due to high
solubility to solvents and its instability.
97)43 and refined on F2 by full-matrix least-squares methods, using
SHELXL-97.44 The positions of all non-hydrogen atoms of 1a and
4a were determined from a difference Fourier electron density map
and refined anisotropically. All hydrogen atoms for each complex
were placed at the calculated positions and kept fixed. All
calculations were performed using the TEXSAN crystallographic
software package, and illustrations were drawn with ORTEP in
Figure 2 for 1a and Figure 3 for 4a. Crystallographic data are
collected in Table 3. Additional crystallographic data are available
in the Supporting Information.
Ligand Exchange Reaction of 1b with PPh3. To a toluene (3
mL) solution of 1b (8 mg, 0.009 mmol) was added PPh3 (3 mg,
0.011 mmol) at room temperature. The reaction mixture was stirred
at room temperature for 24 h. The solvent was removed in vacuo
to give 1a quantitatively, which was confirmed by 1H and 31P NMR.
Ligand Exchange Reaction of 4a with PCy3. To a toluene (6
mL) solution of 4a (20 mg, 0.026 mmol) was added PCy3 (7 mg,
0.026 mmol) at room temperature. The reaction mixture was stirred
at room temperature for 24 h. The solvent was removed in vacuo
to give 4b along with 4a, PPh3, and PCy3 (4b:4a ) 80:20; the
Acknowledgment. This work was supported in part by
Grants-in-Aid for Scientific Research from the Ministry of
Education, Science, Sports. T.H. acknowledges Culture of Japan
and 21st Century COE Program, Creation of Integrated Eco-
Chemistry, Osaka University.
1
ratio was determined by H and 31P NMR).
Crystallographic Data Collection and Structural Determi-
nation of Complexes 1a and 4a. The crystals of 1a and 4a suitable
for X-ray diffraction study were fixed on the end of glass fibers
with cyanoacrylate adhesive and placed in a nitrogen stream at 120-
(1) K. Data for 1a and 4a were collected by a Rigaku RAXIS-
RAPID equipped with a sealed-tube X-ray generator (50 kV, 40
mA) with monochromatized Mo KR (0.71075 Å) radiation in a
nitrogen stream at 120(1) K. Indexing was performed from three
oscillations, which were exposed for 90 s. The unit cell parameters
and the orientation matrix for data collection were determined by
the least-squares refinement. A symmetry-related absorption was
corrected by use of the program ABSCOR42 with transmission
factors. Details of the data collection are summarized in Table 3.
The structure of 1a and 4a was solved by direct methods (SIR-
Supporting Information Available: Detailed crystallographic
data, atomic positional parameters, and bond lengths and angle for
1a and 4a. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM060405D
(42) Higashi, T. ABSCOR: Program for Absorption Correction; R. C.:
Tokyo, Japan, 1995.
(43) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(44) Sheldrick, G. M. SHELX-97, Programs for Crystal Structure Analysis
(Release 97-2); University of Go¨ttingen: Germany, 1997.