Synthesis of Ir[μ2-(N-N)]M (M = Ir and Ru) homo- and heterobimetallic complexes through a condensation reaction of N-amino and formyl groups bound to mononuclear (ηn-CnMen)M units (n = 5 for M = Ir; N = 6 for M

Article abstract of DOI:10.1002/ejic.201100925

Reactions of [{CpIrCl(μ-Cl)}₂] (Cp* = η⁵-pentamethylcyclopentadienyl) with bidentate pyridine-imine ligands such as 2-(1-hydrazonoethyl)pyridine (L¹-NH₂) and 4-({[1-(pyridine-2-yl)ethylidene]hydrazono}methyl)ben

Full text of DOI:10.1002/ejic.201100925

FULL PAPER
DOI: 10.1002/ejic.201100925
Synthesis of Ir[μ2-(N-N)]M (M = Ir and Ru) Homo- and Heterobimetallic
Complexes through a Condensation Reaction of N-Amino and Formyl Groups
Bound to Mononuclear (ηn-CnMen)M Units (n = 5 for M = Ir; n = 6
for M = Ru)
Keisuke Nakao,[a] Gyeongshin Choi,[a] Yuki Konishi,[a] Hayato Tsurugi,[a] and
Kazushi Mashima*[a]
Keywords: Half-metallocene complexes / Bimetallic complexes / Iridium / Ruthenium / N ligands
Reactions of [{Cp*IrCl(μ-Cl)}2] (Cp* = η5-pentamethylcyclo- and 4-PF6. Dinuclearization of complex 1a-PF6 was achieved
pentadienyl) with bidentate pyridine–imine ligands such as by a condensation reaction of 1a-PF6 with dialdehydes. Reac-
2-(1-hydrazonoethyl)pyridine (L1-NH2) and 4-({[1-(pyridine-
2-yl)ethylidene]hydrazono}methyl)benzaldehyde (L3-CHO),
followed by salt exchange, afforded the corresponding irid-
ium mononuclear complexes [Cp*IrCl(L1-NH2)][PF6] (1a-
PF6) and [Cp* IrCl(L3-CHO)][PF6] (6-PF6) that bear N-amino
and formyl functionalities, whereas the reaction of
[{Cp*IrCl(μ-Cl)}2] with butane-2,3-diylidenebis(hydrazone)
[L2-(NH2)2; 2 equiv.] afforded the half-metallocene iridium
complex 2-PF6 with two free amino groups at the 2,5-posi-
tions of an irida-2,5-diazacyclopentene skeleton. Post-func-
tionalization of the N-amino groups of 1a-PF6 and 6-PF6 was
accomplished with 3,5-dimethoxybenzaldehyde in the pres-
ence of a catalytic amount of H2SO4 in CH3CN heated at
reflux. The condensation reaction proceeded to form N-
imino-functionalized iridium mononuclear complexes 3-PF6
tion of an N-amino functional group of 1a-PF6 with tere-
phthalaldehyde and isophthalaldehyde in the presence of a
catalytic amount of H2SO4 gave the corresponding homodi-
nuclear iridium complexes m-5-PF6 and p-5-PF6 in high
yield. The molecular structure of p-5-PF6, evaluated by X-
ray diffraction study, revealed that two {Cp*IrCl} fragments
coordinated to the tetradentate linked hydrazonoethyl skel-
eton in an anti fashion. Furthermore, treatment of the formyl
group of iridium complex 6-PF6 with the N-amino group of
ruthenium complex 1b-PF6 resulted in the selective forma-
tion of an Ir[μ2-(N-N)]Ru heterobimetallic complex (7-PF6)
under similar reaction conditions. The selectivity for the for-
mation of the Ru–Ir heterobimetallic complex was due to the
tolerance of the imine moiety to hydrolysis under acidic con-
ditions.
been successfully applied to prepare a diverse array of metal
complexes that range from binuclear to larger nuclear com-
plexes.[6–8] Another promising synthetic method is, in prin-
ciple, a bottom-up approach that uses mononuclear metal
species to create multimetallic complexes by means of an
intermolecular homo- and cross-coupling reaction of func-
tional groups on each ligand directly bound to the met-
als.[9,10] Although this method has advantages for synthesiz-
ing heterometallic complexes, few examples have been inves-
tigated to date.
Herein we report the condensation reactions of N-amino
and formyl moieties of functionalized hydrazone-based li-
gands [L1-NH2, L2-(NH2)2, L3-CHO in Scheme 1] coordi-
nated to a {Cp*IrCl} fragment; this is exemplified by the
reaction of an N-amino moiety of a pyridine–imine ligand
bound to a {Cp*IrCl} fragment with dialdehydes to give
the corresponding homodinuclear iridium complexes. Fur-
ther extension of the condensation methodology provided
access to the synthesis of heteromultimetallic complexes: a
formyl group of an iridium complex was treated with an N-
amino group of a half-metallocene ruthenium complex to
afford a Ru–Ir heterobimetallic complex.
Introduction
Multimetallic complexes have attracted much interest be-
cause of their unique and intriguing chemical behaviors,
distinct from the corresponding mononuclear com-
plexes,[1,2] which mimic metalloenzymes that contain more
than two metals at their active sites,[3] thereby providing
suitable molecular sources immobilized on the surface as
nanoscale materials and heterogeneous catalysts,[4] and cat-
alyzing unique transformations of organic compounds.[5]
For the construction of multimetallic complexes, a rational
approach is to design and synthesize the ligand architecture
as a key factor for controlling nuclearity as well as the as-
sembly of metal ions. In fact, multidentate ligands have
[a] Department of Chemistry, Graduate School of Engineering
Science, Osaka University, and CREST, JST,
Toyonaka, Osaka 560-8531, Japan
Fax: +81-6-6850-6245
E-mail: mashima@chem.es.osaka-u.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100925.
Eur. J. Inorg. Chem. 2012, 1469–1476
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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K. Nakao, G. Choi, Y. Konishi, H. Tsurugi, K. Mashima
FULL PAPER
Scheme 1. N-Amino- and formyl-functionalized hydrazone-based
ligands L1-NH2, L2-(NH2)2, and L3-CHO.
Results and Discussion
A cationic iridium complex, [Cp*IrCl(L1-NH2)][Cl] (1a-
Cl), was synthesized by treating [{Cp*IrCl(μ-Cl)}2] with L1-
NH2 (2 equiv.) [Equation (1)] following the literature pro-
cedure to the synthesis of half-metallocene iridium com-
plexes with pyridine-based ligands.[11,12] Subsequently, an
anion-exchange reaction of 1a-Cl with excess amounts of
[Bu4N][PF6] afforded the corresponding cationic complex
with a PF6 anion, [Cp*IrCl(L1-NH2)][PF6] (1a-PF6), which
Figure 1. ORTEP drawing of the cationic part of 1a-PF6. The ther-
mal ellipsoids are drawn at 30% probability level, and hydrogen
–
atoms and PF6 are omitted for clarity.
Table 1. Selected bond lengths [Å] and angles [°] of 1a-PF6.
1
was characterized by H and 13C NMR spectra together
Ir(1)–N(1)
Ir(1)–Cl(1)
C(11)–C(16)
N(2)–N(3)
2.097(8)
2.398(3)
1.467(14)
1.387(12)
Ir(1)–N(2)
N(1)–C(11)
N(2)–C(16)
2.074(8)
1.361(12)
1.291(13)
with combustion analysis. Notable spectroscopic data of 1a-
PF6 in CD3CN were a broad singlet at δH = 6.61 ppm as-
signable to a free NH2 group and a resonance at δC
=
N(1)–Ir(1)–N(2) 75.3(3)
N(2)–Ir(1)–Cl(1) 84.6(2)
N(1)–Ir(1)–Cl(1) 86.3(3)
157.2 ppm due to a ketimine carbon. The C=N stretching
frequency (1607 cm–1) shifted to lower field than that of the
free ligand (1637 cm–1) in the IR spectrum of 1a-PF6, thus
indicating the coordination of the imine moiety of the li-
gand to the iridium metal, and the presence of PF6 was
confirmed by a strong absorption at 840 cm–1 due to the
intrinsic P–F bond stretching frequency. The solid-state
structure of 1a-PF6 was determined by single-crystal X-ray
analysis, which revealed a three-legged piano-stool geome-
try around the iridium atom and the presence of a free N-
amino group, similar to other {Cp*IrCl} complexes with
N,N ligands (Figure 1, Table 1).[11,12] The iridium complex
1a is an interesting motif to generate an electron-rich
{Cp*Ir(α-diimine)} fragment that exhibits strong electronic
interaction between the metal center and the π-accepting
ligand.[11a,c] Furthermore, by introducing a Ru2+ fragment
to multimetallic assemblies, it is expected to show unique
electronic properties due to the redox processes of
exchange reaction with [Bu4N][PF6] to give complex 2-PF6
[Equation (2)], which has two free amino groups at the 2,5-
positions of an irida-2,5-diazacyclopentene skeleton. In the
1H NMR spectrum, one broad resonance was observed at
δH = 6.30 ppm assignable to two –NH2 groups, and a sing-
let resonance at δC = 154.3 ppm that corresponded to ket-
imine carbon atoms.
Ru2+/3+ [13]
We thus prepared a ruthenium complex 1b-PF6
.
by the reaction of [{(C6Me6)RuCl(μ-Cl)}2] with L1-NH2
(2 equiv.), followed by an anion-exchange reaction with
[Bu4N][PF6].
(2)
To check the reactivity of the N-NH2 group of these mo-
nonuclear half-metallocene complexes, we performed a
post-functionalization reaction of 1a-PF6 with 3,5-dimeth-
oxybenzaldehyde. When a mixture of 1a-PF6 and excess
amounts of 3,5-dimethoxybenzaldehyde (1.5 equiv.) was
heated to reflux in CH3CN in the presence of a catalytic
amount of sulfuric acid, the N-imino-functionalized prod-
uct 3-PF6 was isolated in 92% yield [Equation (3)]. Notably,
this condensation reaction proceeded selectively without
any decomposition of 1a-PF6, even though H2SO4 was
used. The formation of the imine moiety of 3-PF6 was con-
(1)
1
firmed by H and 13C NMR spectra: a singlet resonance at
The same synthetic strategy could be applied to the reac- δH = 8.68 ppm and a resonance at δC = 162.6 ppm clearly
tion of [{Cp*IrCl(μ-Cl)}2] with butane-2,3-diylidenebis- indicated the formation of an aldimine moiety after the
(hydrazone) [L2-(NH2)2; 2 equiv.] followed by an anion- condensation reaction.
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Synthesis of Ir/Ru Homo- and Heterobimetallic Complexes
verted to imine groups to afford 4-PF6 in 41% yield [Equa-
tion (4)]. In the 1H NMR spectrum of 4-PF6, a singlet reso-
nance at δH = 8.65 ppm due to imine protons and a singlet
at δH = 3.88 ppm due to two methoxy protons were ob-
served with a 1:2 relative intensity, thus indicating that 4-
PF6 has a symmetric structure in solution.
(3)
Figure 2 shows the molecular structure of 3-PF6, and the
selected bond lengths and angles are listed in Table 2. The
iridium metal adopts a three-legged piano-stool geometry,
the same as that observed for 1a-PF6. The Ir–N bond
lengths [2.104(6) and 2.122(6) Å] are slightly elongated rela-
tive to 1a-PF6 due to the bulky substituent on the N(2)
atom, whereas the angle of N(1)–Ir(1)–N(2) [75.4(2)°] is al-
most the same as that of 1a-PF6. The bond length of N(3)–
C(18) [1.266(10) Å] is the same as that of a normal carbon–
nitrogen double bond. The 3,5-dimethoxyphenyl group lo-
cates trans to the {Cp*IrCl} fragment across the N(3)–
C(18) double bond.
(4)
As the imine moieties of these iridium complexes are
stable under acidic conditions, we applied the imine conde-
nstation reaction to prepare homo and hetero dinuclear
complexes. First, we conducted a reaction of 1a-PF6 with
o-phthalaldehyde; however, the condensation reaction did
not proceed, presumably because of the steric repulsion be-
tween the two {Cp*IrCl} moieties. In contrast, the reaction
of 1a-PF6 with much longer organic spacers such as iso-
phthalaldehyde and terephthalaldehyde, yielded the corre-
sponding dinuclear iridium complexes m-5-PF6 and p-5-PF6
[Equation (5)]. The 1H NMR spectrum of m-5-PF6 at
–30 °C displayed two singlet signals at δH = 8.76 and
8.80 ppm due to two magnetically inequivalent imine pro-
tons, thereby indicating that the complex m-5-PF6 has a dis-
symmetric arrangement for avoiding the steric hindrance
between the two {Cp*IrCl} moieties. On the other hand,
rather simple resonances due to the symmetric structure of
1
p-5-PF6 were observed in the H NMR spectrum.
Figure 2. ORTEP drawing of the cationic part of 3-PF6. The ther-
mal ellipsoids are drawn at 50% probability level; hydrogen atoms
–
and PF6 are omitted for clarity.
Table 2. Selected bond lengths [Å] and angles [°] of 3-PF6.
Ir(1)–N(1)
Ir(1)–Cl(1)
C(11)–C(16)
N(2)–N(3)
N(1)–Ir(1)–N(2)
N(2)–Ir(1)–Cl(1)
2.104(6)
2.4018(18)
1.468(10)
1.404(8)
75.4(2)
Ir(1)–N(2)
2.122(6)
1.357(9)
1.304(10)
1.266(10)
86.53(18)
N(1)–C(11)
N(2)–C(16)
N(3)–C(18)
N(1)–Ir(1)–Cl(1)
88.52(18)
N(2)–N(3)–C(18) 113.7(6)
C(19)–C(18)–N(3) 122.4(7)
Under the optimized conditions established for the syn-
thesis of 3-PF6, the reaction of 2-PF6, which has two NH2
groups at the 1,4-positions of the diazabutadiene backbone,
with excess amounts (3 equiv.) of 3,5-dimethoxybenzalde-
hyde was conducted in the presence of a catalytic amount
of sulfuric acid. After heating the solution to reflux in
CH3CN for 40 h, two NH2 moieties of 2-PF6 were con-
(5)
Eur. J. Inorg. Chem. 2012, 1469–1476
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1471

K. Nakao, G. Choi, Y. Konishi, H. Tsurugi, K. Mashima
FULL PAPER
The solid-state structure of p-5-PF6 is depicted in Fig- terized by spectroscopic data together with a single-crystal
ure 3, and the selected bond lengths and angles are listed in X-ray diffraction study for 6-PF6 (Figure 4); selected bond
Table 3. Iridium atoms of p-5-PF6 are coordinated to the lengths and angles of 6-PF6 are listed in Table 4. Notably,
nitrogen atoms of a Schiff base ligand, terminal chloride the formyl group was observed as a singlet at δH
=
atoms, and η5-pentamethylcyclopentadienyl ligands, thus 10.13 ppm, and the aldimine group was observed as a sing-
1
leading to
a
typical piano-stool conformation. Two let at δH = 8.85 ppm in the H NMR spectrum of 6-PF6.
{Cp*IrCl} fragments locate in anti fashion to the tetraden-
tate ligand skeleton.[12n] Two metallacycle moieties are par-
allel, whereas the dihedral angle between one metallacycle
that contains Ir(1) and the central aromatic ring is 50.27°.
The average distance between the metal atoms and carbon
atoms of the Cp* rings is 2.17 Å, comparable to that in
related Cp*Ir complexes.[11,12] The Ir–N bond lengths and
the angles of N–Ir–N are similar to those of 3-PF6. In this
case, the short C=N and long C–C bonds for the metallacy-
cle were observed, clearly indicating the neutral coordina-
tion of pyridine–imine moiety to the metal center.[11]
(6)
Figure 4. ORTEP drawing of the cationic part of 6-PF6. The ther-
mal ellipsoids are drawn at 50% probability level, and hydrogen
atoms and [PF6]– are omitted for clarity.
Figure 3. ORTEP drawing of the cationic part of p-5-PF6. The ther-
mal ellipsoids are drawn at 50% probability level; hydrogen atoms
and [PF6]– are omitted for clarity.
Table 4. Selected bond lengths [Å] and angles [°] of 6-PF6.
Table 3. Selected bond lengths [Å] and angles [°] of p-5-PF6.
Ir(1)–N(1)
Ir(1)–Cl(1)
C(11)–C(16)
N(2)–N(3)
N(1)–Ir(1)–N(2)
N(2)–Ir(1)–Cl(1)
2.086(4)
2.4004(13)
1.471(6)
1.416(5)
75.16(15)
90.01(12)
Ir(1)–N(2)
N(1)–C(11)
N(2)–C(16)
N(3)–C(18)
N(1)–Ir(1)–Cl(1)
N(2)–N(3)–C(18)
2.098(4)
1.353(6)
1.288(6)
1.270(6)
85.71(12)
113.2(4)
Ir(1)–N(1)
Ir(1)–Cl(1)
N(2)–N(3)
N(1)–Ir(1)–N(2)
N(2)–Ir(1)–Cl(1)
2.080(5)
2.3878(17)
1.407(7)
75.73(19)
87.65(14)
Ir(1)–N(2)
N(2)–C(16)
C(18)–N(3)
N(1)–Ir(1)–Cl(1)
C(16)–N(2)–N(3)
2.092(5)
1.289(8)
1.280(8)
85.00(14)
116.7(5)
C(18)–N(3)–N(2) 113.5(5)
C(19)–C(18)–N(3) 121.8(4)
To prepare heterobimetallic complexes, we first tried to
We therefore examined the preparation of heterobimetal-
synthesize an iridium complex with a formyl functionality lic complexes by using formyl-substituted complex 6-PF6 as
in the ligand backbone. 4-({[1-(Pyridine-2-yl)ethylidene]- a heterobimetallic synthon. Treatment of 6-PF6 with
hydrazono}-methyl)benzaldehyde (L3-CHO) was prepared [(C6Me6)RuCl(L1-NH2)][PF6] (1b-PF6) in CH3CN heated
by a condensation reaction of L1-NH2 with 1 equiv. of to reflux in the presence of a catalytic amount of H2SO4
terephthalaldehyde in Et2O, and isolated in 54% yield by resulted in the selective formation of Ru–Ir heterobimetallic
silica gel column chromatography. Treatment of complex 7-PF6 [Equation (7)]. The formation of a new im-
1
[{Cp*IrCl(μ-Cl)}2] with L3-CHO (2 equiv.) followed by an ine moiety in 7-PF6 was confirmed by H and 13C NMR
anion-exchange reaction with [Bu4N][PF6] gave the iridium spectra. The 1H NMR spectrum of 7-PF6 displayed two sets
complex 6-PF6 [Equation (6)]. Complex 6-PF6 was charac- of resonances assignable to pyridine imine moieties, ald-
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Synthesis of Ir/Ru Homo- and Heterobimetallic Complexes
tilled from the corresponding magnesium alkoxide under argon.
Alternatively, CH3CN, CH2Cl2, THF, Et2O, and hexane were dried
and deoxygenated by using a Grubbs column (Glass Counter Sol-
imine, and phenyl groups: Two singlet signals were observed
at δH = 2.60 and 2.74 ppm for the two ketimine groups, δH
= 8.18 and 8.19 ppm for the phenyl groups, and δH = 8.82
and 8.87 ppm for the two aldimine groups.
vent Dispending System, Nikko Hansen
&
Co, Ltd.). 1H
(400 MHz), 19F (376 MHz), and 13C NMR (100 MHz) spectra were
measured with Bruker Avance III-400 spectrometers. 1H NMR
chemical shifts are reported in ppm (δ) relative to tetramethylsilane
or referenced to the chemical shifts of residual solvent resonances
(CH3CN was used as internal standard, δ = 1.94 ppm). 13C NMR
spectroscopic chemical shifts are reported in ppm (δ) relative to
carbon resonances in [D3]acetonitrile at δ = 1.32 ppm. Assignments
1
for H and 13C NMR peaks for some of the complexes were aided
by 2D 1H–1H COSY, 2D 1H–13C HMQC, and HMBC spectra.
Infrared spectra were recorded with a JASCO FT/IR-410 spectrom-
eter. Mass spectra were obtained with a Bruker Daltonics Micro-
TOF II-HB and JEOL JMS-700. The elemental analyses were re-
corded with a Perkin–Elmer 2400 instrument at the Faculty of
Engineering Science, Osaka University. All melting points were re-
corded with a Yanaco micro melting point apparatus. Flash column
chromatography was performed using silica gel 60 (230–400 mesh).
(7)
Pyridine–Imine Ligand L3-CHO: A solution of L1-NH2 (329.5 mg,
2.438 mmol) in Et2O was added dropwise to a solution of tereph-
thalaldehyde (331.9 mg, 2.438 mmol) in Et2O, and the mixture was
stirred at room temperature. After 1.5 h, the solvent was removed
in vacuo, and the residue was purified by column chromatography
on silica gel (hexane/EtOAc 85:15) to give a yellow powder (54%).
1H NMR (400 MHz, CDCl3, 35 °C): δ = 2.59 (s, 3 H, CH3), 7.34
Conclusion
3
4
(ddd, J = 4.8, 7.8 Hz, J = 1.1 Hz, 1 H, pyridine-H4), 7.76 (td, J
We prepared mononuclear half-metallocene iridium com-
plexes with amino and formyl functionalities at the ligand
backbone as units for synthesizing bimetallic complexes.
Post-functionalization of the N-amino groups attached to
the {Cp*Ir(Cl)} fragments was accomplished by treatment
with 3,5-dimethoxybenzaldehyde in the presence of a cata-
lytic amount of H2SO4, and the condensation reaction pro-
ceeded to form N-imino-functionalized iridium mononu-
clear complexes. Homobimetallic Ir2 complexes were iso-
lated by the condensation reaction of an iridium complex
with an N-amino group and dialdehydes. Heterodinucleari-
zation was accomplished by the condensation reaction of an
iridium complex that bore a formyl group with a ruthenium
complex that had an N-amino moiety. Tolerance of the
metal complexes to hydrolysis under acidic conditions was
a key factor for the condensation–dinuclearization reaction.
We are currently investigating further applications of this
reaction for the preparation of multinuclear complexes by
means of the condensation reaction of amine and aldehyde
groups bound to mononuclear metal complexes.
= 7.8, 1.7 Hz, 1 H, pyridine-H3), 7.96 (d, 3J = 8.3 Hz, 2 H, Ar),
8.01 (d, J = 8.3 Hz, 2 H, Ar), 8.21 (dt, J = 7.8 Hz, J = 1.1 Hz,
3
3
4
1 H, pyridine-H2), 8.39 (s, 1 H, NC-H), 8.67 (ddd, J = 4.8 Hz, J
= 1.7 Hz, 5J = 0.9 Hz, 1 H, pyridine-H5), 10.08 (s, 1 H, CH=O)
ppm. 13C NMR (100 MHz, CDCl3, 30 °C): δ = 14.4 (CH3), 121.6
(pyridine-C5), 124.7 (pyridine-C3), 128.9 (o-C of Ar), 130.2 (m-C
of Ar), 136.4 (pyridine-C4), 137.9 (p-C of Ar), 140.1 (ipso-C of
Ar), 149.1 (pyridine-C2), 155.7 (pyridine-C1), 156.1 (N=CH), 165.7
(N=CCH3), 191.8 (CH=O) ppm. MS (FAB): m/z = 252 ([L3-CHO
+ H]+). C15H13N3O (251.29): calcd. C 71.70, H 5.21, N 16.72;
found C 71.63, H 4.88, N 16.81; m.p. 119 °C.
3
4
[Cp*IrCl(L1-NH2)][PF6] (1a-PF6): A mixture of [{Cp*IrCl(μ-Cl)}2]
(122 mg, 1.54ϫ10–1 mmol) and L1-NH2 (42 mg, 3.1ϫ10–1 mmol)
in ethanol (10 mL) was stirred at room temperature for 5 min to
immediately give an orange solution, to which Bu4NPF6 (238 mg,
6.14 mmol) was added, thereby resulting in the precipitation of 1a-
PF6 as a yellow powder. After filtration, the residue was washed
with THF and ether, and then dried in vacuo to give a yellow pow-
1
der of 1a-PF6 (181 mg, 92% yield). H NMR (400 MHz, CD3CN,
35 °C): δ = 1.69 [s, 15 H, C5(CH3)5], 2.49 (s, 3 H, CH3), 6.61 (br.
3
4
s, 2 H, NH2), 7.62 (ddd, J = 5.7, 7.6 Hz, J = 1.4 Hz, 1 H, pyr-
idine-H4), 7.87 (ddd, J = 8.1 Hz, J = 1.4 Hz, J = 0.8 Hz, 1 H,
3
4
5
pyridine-H2), 8.09 (ddd, 3J = 7.6, 8.1 Hz, 4J = 1.4 Hz, 1 H, pyr-
idine-H3), 8.72 (ddd, J = 5.7 Hz, J = 1.4 Hz, J = 0.8 Hz, 1 H,
pyridine-H5) ppm. 13C NMR (100 MHz, CD3CN, 35 °C): δ = 9.0
[C5(CH3)5], 13.5 (CH3), 90.9 [C5(CH3)5], 125.8 (pyridine-C2), 128.2
(pyridine-C4), 140.9 (pyridine-C3), 152.5 (pyridine-C5), 152.7 (pyr-
idine-C1), 157.2 (C=N) ppm. MS (FAB): m/z = 498 ([1a]+).
C17H24ClF6IrN3P (643.03): calcd. C 31.75, H 3.76, N 6.53; found
C 31.73, H 3.44, N 6.52; m.p. 267 °C (dec.).
3
4
5
Experimental Section
General: All manipulations involving air- and moisture-sensitive or-
ganometallic compounds were operated using the standard Schlenk
techniques under argon. [{Cp*IrCl(μ-Cl)}2],[14] [{(C6Me6)RuCl(μ-
[16]
Cl)}2],[15] L1-NH2, and L2-(NH2)2
were prepared according to
the literature. Other chemicals were purchased and used without
further purification. CH3CN and CH2Cl2 were degassed and stored
with activated molecular sieves (3 and 4 Å, respectively). Et2O and
hexane were dried and deoxygenated by distillation with sodium
benzophenone ketyl under argon. Methanol and ethanol were dis-
[(η6-C6Me6)RuCl(L1-NH2)][PF6] (1b-PF6): A mixture of [{(η6-
C6Me6)RuCl(μ-Cl)}2] (149 mg, 2.22ϫ10–1 mmol) and L1-NH2
(61 mg, 4.5ϫ10–1 mmol) in ethanol was stirred at room tempera-
ture for 30 min to give a red solution, to which Bu4NPF6 (344 mg,
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K. Nakao, G. Choi, Y. Konishi, H. Tsurugi, K. Mashima
FULL PAPER
8.88ϫ10–1 mmol) was added. After all volatiles were removed un-
der reduced pressure, the resulting residue was washed with THF
and ether, and then dried in vacuo to give 1b-PF6 as a brown pow-
1.4 Hz, 1 H, pyridine-H3), 8.68 (s, 1 H, NC-H), 8.86 (ddd, 3J =
5.6 Hz, 4J = 1.4 Hz, 5J = 0.7 Hz, 1 H, pyridine-H5) ppm. 13C NMR
(100 MHz, CD3CN, 35 °C): δ = 9.4 [C5(CH3)5], 16.2 (CH3), 56.6
(OCH3), 91.6 [C5(CH3)5], 106.3 (para-Ar), 108.0 (ortho-Ar), 128.5
1
der (84% yield). H NMR (400 MHz, CD3CN, 35 °C): δ = 2.11 [s,
18 H, C6(CH3)6], 2.39 (s, 3 H, CH3), 6.44 (br. s, 2 H, NH2), 7.53 (pyridine-C2), 130.6 (pyridine-C4), 134.6 (ipso-Ar), 141.2 (pyridine-
3
4
(ddd, J = 5.7, 7.6 Hz, J = 1.3 Hz, 1 H, pyridine-H4), 7.75 (ddd,
C3), 152.9 (pyridine-C5), 156.3 (pyridine-C1), 162.6 (HC=N), 162.6
3J = 8.1 Hz, 4J = 1.3 Hz, 5J = 0.7 Hz, 1 H, pyridine-H2), 8.02 (ddd, (meta-Ar), 163.0 (MeC=N) ppm. MS (FAB): m/z = 646 ([3]+).
3J = 7.6, 8.1 Hz, 4J = 1.4 Hz, 1 H, pyridine-H3), 8.75 (ddd, J =
C26H32N3O2ClPF6Ir: C 39.47, H 4.08, N 5.31; found C 39.21, H
3
5.7 Hz, 4J = 1.4 Hz, 5J = 0.7 Hz, 1 H, pyridine-H5) ppm. 13C NMR 3.89, N 5.34; m.p. 272 °C (dec.).
(100 MHz, CD3CN, 35 °C): δ = 13.4 (CH3), 15.9 [C6(CH3)6], 97.3
[Cp*IrCl{L2-(N=CHAr)2}][PF6] [4-PF6; Ar = C6H3(OMe)2-3,5]:
[C6(CH3)6], 125.1 (pyridine-C2), 126.4 (pyridine-C4), 139.9 (pyr-
idine-C3), 151.4 (pyridine-C1), 153.9 (pyridine-C5), 156.4 (C=N)
ppm. MS (ESI): m/z = 434 ([1b]+). C19H28ClF6N4PRu (593.94):
calcd. C 39.42, H 4.70, N 7.26; found C 39.60, H 4.52, N 7.13;
m.p. 204 °C (dec.).
Similarly, a mixture of 2-PF6 (26 mg, 4.1ϫ10–2 mmol) and 3,5-di-
methoxybenzaldehyde (14 mg, 1.2ϫ10–1 mmol) in acetonitrile
(5 mL) in the presence of a catalytic amount of concentrated
H2SO4 afforded 4-PF6 as an orange powder (16 mg, 41% yield).
1H NMR (400 MHz, CD3CN, 35 °C):
δ = 1.59 [s, 15 H,
4
[Cp*IrCl{L2-(NH2)2}][PF6] (2-PF6): A mixture of [{Cp*IrCl(μ-
Cl)}2] (422 mg, 5.30ϫ10–1 mmol) and L2-(NH2)2 (121 mg,
1.06 mmol) in ethanol (20 mL) was stirred at room temperature.
Immediately, the solution turned orange. Bu4NPF6 (821 mg,
2.12 mmol) was added to the resulting solution, and then all vola-
tiles were removed in vacuo. The resulting residue was extracted
with THF, and all volatiles were removed under reduced pressure.
The residue was washed with a small volume of THF and ether,
and then dried in vacuo to give 2-PF6 as a pale yellow powder
(411 mg, 62% yield). 1H NMR (400 MHz, CD3CN, 35 °C): δ =
1.73 [s, 15 H, C5(CH3)5], 2.22 (s, 6 H, CH3), 6.30 (br. s, 4 H, NH2)
ppm. 13C NMR (100 MHz, CD3CN, 35 °C): δ = 9.1 [C5(CH3)5],
15.0 (CH3), 91.5 [C5(CH3)5] 154.3 (C=N) ppm. MS (ESI): m/z =
477 ([2]+). C14H25ClF6IrN4P (622.01): calcd. C 27.03, H 4.05, N
9.01; found C 27.11, H 3.70, N 8.92; m.p. 245 °C (dec.).
C5(CH3)5], 2.54 (s, 6 H, CH3), 3.88 (s, 6 H, OCH3), 6.77 (t, J =
2.3 Hz, 2 H, para-Ar), 7.11 (d, 4J = 2.3 Hz, 4 H, ortho-Ar), 8.65 (s,
1 H, NC-H) ppm. 13C NMR (100 MHz, CD3CN, 35 °C): δ = 9.8
[C5(CH3)5], 17.8 (CH3), 56.6 (OCH3), 93.4 [C5(CH3)5], 106.4 (para-
Ar), 108.2 (ortho-Ph), 134.4 (ipso-Ar), 162.6 (HC=N), 162.7
(MeC=N), 168.5 (meta-Ar) ppm. MS (FAB): m/z = 773 ([4]+).
C32H41ClF6IrN4O4P (918.34): calcd. C 41.85, H 4.50, N 6.10;
found C 41.84, H 4.34, N 5.96; m.p. 203 °C (dec).
p-[Cp*(Cl)Ir(L1-N=CHC6H4CH=N-L1)Ir(Cl)Cp*][PF6]2 (p-5-PF6):
A mixture of 1-PF6 (121 mg, 1.89ϫ10–1 mmol) and terephthalal-
dehyde (13 mg, 9.5ϫ10–2 mmol) in acetonitrile (5 mL) in the pres-
ence of a catalytic amount of concentrated H2SO4 (10 mol-%) was
similarly treated to give p-5-PF6 as an orange powder (87 mg, 52%
yield). 1H NMR (400 MHz, CD3CN, 30 °C): δ = 1.64 [s, 30 H,
C5(CH3)], 2.74 (s, 6 H, CH3), 7.85 (ddd, 3J = 5.6, 7.3 Hz, 4J =
1.9 Hz, 1 H, pyridine-H4), 8.19 (s, 4 H, Ph-H), 8.21 (ddd, 3J =
[Cp*IrCl(L3-CHO)][PF6] (6-PF6): The same operation as 1a-PF6
4
5
3
8.2 Hz, J = 1.9 Hz, J = 0.6 Hz, 1 H, pyridine-H2), 8.24 (ddd, J
= 7.3, 8.2 Hz, 4J = 1.4 Hz, 1 H, pyridine-H3), 8.87 (s, 2 H, NC-H),
8.88 (br. d, 3J = 5.6 Hz, 2 H, pyridine-H5) ppm. 13C NMR
(100 MHz, CD3CN, 30 °C): δ = 9.4 [C5(CH3)5], 16.3 (CH3), 91.7
[C5(CH3)5], 128.7 (pyridine-C2), 130.8 (pyridine-C4), 131.1 (Ar),
136.6 (ipso-Ar), 141.4 (pyridine-C3), 153.0 (pyridine-C5), 156.1
(pyridine-C1), 162.3 (HC=N), 167.8 (MeC=N) ppm. MS (ESI): m/z
= 547 ([p-5]2+). C42H50Cl2F12IrN6P2 (1191.95): calcd. C 36.44, H
3.64, N 6.07; found C 36.25, H 3.34, N 6.13; m.p. 258 °C (dec.).
was conducted for
a mixture of [{Cp*IrCl(μ-Cl)}2] (98 mg,
1.2ϫ10–1 mmol) and L3-CHO (62 mg, 2.5 mmol) in ethanol
(10 mL). Compound 6-PF6 was isolated as a yellow powder (87%
yield). 1H NMR (400 MHz, CD3CN, 35 °C): δ = 1.62 [s, 15 H,
C5(CH3)5], 2.72 (s, 1 H, CH3), 7.83 (ddd, 3J = 5.6, 7.3 Hz, 4J =
3
1.8 Hz, 1 H, pyridine-H4), 8.09 (d, J = 8.4 Hz, 2 H, Ar), 8.18 (d,
3J = 8.4 Hz, 2 H, Ar), 8.19 (ddd, 3J = 8.2 Hz, 4J = 1.8 Hz, 5J =
4
0.7 Hz, 1 H, pyridine-H2), 8.23 (ddd, 3J = 7.3, 8.2 Hz, J = 1.4 Hz,
4
1 H, pyridine-H3), 8.85 (s, 1 H, CH=N), 8.87 (ddd, 3J = 5.6 Hz, J
= 1.4 Hz, 5J = 0.7 Hz, 1 H, pyridine-H5), 10.13 (s, 1 H, CH=O)
ppm. 13C NMR (100 MHz, CD3CN, 35 °C): δ = 9.3 [C5(CH3)5],
16.2 (CH3), 91.6 [C5(CH3)5], 128.7 (pyridine-C2), 130.7 (pyridine-
C4), 130.9 (Ar), 131.1 (Ar), 137.5 (Ar), 140.5 (Ar), 141.3 (pyridine-
C3), 152.9 (pyridine-C5), 156.0 (pyridine-C1), 162.4 (HC=N), 162.8
(MeC=N), 193.2 (CH=O) ppm. MS (ESI): m/z = 614 ([6]+).
C25H28ClF6IrN3OP (759.15): calcd. C 39.55, H 3.72, N 5.54; found
C 39.77, H 3.36, N 5.52; m.p. 210 °C (dec.).
m-[Cp*(Cl)Ir(L1-N=CHC6H4CH=N-L1)Ir(Cl)Cp*][PF6]2
(m-5-
PF6): The same operation was conducted for the mixture of 1a-PF6
(102 mg, 1.58ϫ10–1 mmol) and isophthalaldehyde (11 mg,
7.9ϫ10–2 mmol) to give m-5-PF6 as an orange powder (73% yield).
1H NMR (400 MHz, CD3CN, –30 °C): δ = 1.55 [s, 30 H, C5(CH3)],
2.657 (s, 3 H, CH3), 2.664 (s, 3 H, CH3), 7.7–7.8 (m, 3 H, py and
Ar), 8.1–8.3 (m, 6 H, py and Ar), 8.46 (br. d, J = 16 Hz, 1 H, Ar),
8.76 (s, 1 H, NC-H), 8.80 (s, 1 H, NC-H), 8.81 (br. d, J = 5.6 Hz,
2 H, py) ppm. 13C NMR (100 MHz, CD3CN, –30 °C): δ = 8.27
[C5(CH3)5], 8.28 [C5(CH3)5], 15.20 (CH3), 15.21 (CH3), 90.26
[C5(CH3)5], 90.27 [C5(CH3)5], 127.46, 127.51, 129.68, 129.72, 130.0,
130.4, 131.0, 132.42, 132.44, 132.9, 133.3, 140.2, 151.75 (pyridine-
C5), 151.79 (pyridine-C5), 154.90 (pyridine-C1), 154.91 (pyridine-
C1), 161.0 (HC=N), 161.1 (HC=N), 166.6 (MeC=N), 166.9
[Cp*IrCl(L1-N=CHAr)][PF6] [3-PF6; Ar = C6H3(OMe)2-3,5]: A
mixture of 1a-PF6 (69 mg, 1.1ϫ10–1 mmol), 3,5-dimethoxybenzal-
dehyde (19 mg, 1.6ϫ10–1 mmol), and a catalytic amount (10 mol-
%) of concentrated H2SO4 in acetonitrile (3 mL) was heated to re-
flux for 10 h. A second portion of concentrated H2SO4 (10 mol-%)
was added, and then the reaction mixture was heated to reflux for
a further 10 h. The solvent was removed in vacuo, and the resulting
residue was washed with ethanol and hexane, then dried in vacuo
to give 3-PF6 as a yellow powder (77 mg, 92% yield). 1H NMR
(MeC=N) ppm. MS (ESI): m/z
=
547 ([m-5]2+).
C42H50Cl2F12IrN6P2 (1191.95): calcd. C 36.44, H 3.64, N 6.07;
found C 36.15, H 3.54, N 6.01; m.p. 235 °C (dec.).
(400 MHz, CD3CN, 35 °C): δ = 1.62 [s, 15 H, C5(CH3)5], 2.71 (s, 3 [(η6-C6Me6)Ru(Cl)(L1-N=CH-L3)Ir(Cl)Cp*][PF6]2 (7-PF6): A mix-
H, CH3), 3.87 (s, 6 H, OCH3), 6.77 (t, 4J = 2.3 Hz, 1 H, ortho-Ar),
ture of 6-PF6 (45.2 mg, 59.5 μmol), 1b-PF6 (34.5 mg, 59.6 μmol),
and a catalytic amount of concentrated H2SO4 in acetonitrile was
treated in a similar procedure to give 7-PF6 as an orange powder
4
3
4
7.12 (d, J = 2.3 Hz, 2 H, para-Ar), 7.82 (ddd, J = 5.6, 7.4 Hz, J
= 1.7 Hz, 1 H, pyridine-H4), 8.17 (ddd, J = 8.3 Hz, J = 1.7 Hz,
3
4
4
1
5J = 0.7 Hz, 1 H, pyridine-H2), 8.22 (ddd, 3J = 7.4, 8.3 Hz, J =
(76% yield). H NMR (400 MHz, CD3CN, 30 °C): δ = 1.64 [s, 15
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Synthesis of Ir/Ru Homo- and Heterobimetallic Complexes
[2]
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H, C5(CH3)5], 2.08 [s, 18 H, C6(CH3)6], 2.60 (s, 3 H, CH3), 2.74 (s,
4
3 H, CH3), 7.76 (ddd, 3J = 5.6, 7.3 Hz, J = 1.5 Hz, 1 H, pyridine-
H4), 7.85 (ddd, 3J = 5.5, 7.3 Hz, 4J = 1.8 Hz, 1 H, pyridine-H4),
8.06 (ddd, 3J = 7.8 Hz, 4J = 1.5 Hz, 5J = 0.6 Hz, 1 H, pyridine-
H2), 8.16 (ddd, 3J = 7.3, 7.8 Hz, 4J = 1.4 Hz, 1 H, pyridine-H3),
3
3
8.17 (d, J = 7.2 Hz, 2 H, Ar), 8.19 (d, J = 7.2 Hz, 2 H, Ar), 8.19
(ddd, 3J = 7.9 Hz, 4J = 1.8 Hz, 5J = 0.6 Hz, 1 H, pyridine-H2), 8.24
(ddd, 3J = 7.3, 7.9 Hz, 4J = 1.8 Hz, 1 H, pyridine-H3), 8.82 (s, 1 H,
3
4
NC-H), 8.87 (s, 1 H, NC-H), 8.88 (ddd, J = 5.5 Hz, J = 1.4 Hz,
5J = 0.6 Hz, 1 H, pyridine-H5), 8.89 (ddd, 3J = 5.6 Hz, 4J = 1.4 Hz,
5J = 0.6 Hz, 1 H, pyridine-H5) ppm. 13C NMR (100 MHz, CD3CN,
30 °C):
δ = 9.4 [C5(CH3)5], 16.2 (CH3), 16.3 (CH3), 16.4
[C6(CH3)6], 91.6 [C5(CH3)5], 97.8 [C6(CH3)6], 128.0 (pyridine-C2),
128.7 (pyridine-C2), 129.1 (pyridine-C4), 130.8 (pyridine-C4), 130.9
(Ar), 131.0 (Ar), 136.5 (Ar), 136.9 (Ar), 140.4 (pyridine-C3), 141.3
(pyridine-C3), 152.9 (pyridine-C5), 154.4 (pyridine-C5), 155.4 (pyr-
idine-C1), 156.0 (pyridine-C1), 161.0 (HC=N), 162.3 (HC=N),
165.8 (MeC=N), 167.8 (MeC=N) ppm. MS (ESI): m/z = 515
([7]2+). C42H53Cl2F12IrN6P2Ru (1296.04): calcd. C 40.03, H 4.05,
N 6.37; found C 39.71, H 4.12, N 6.22; m.p. 242 °C (dec.).
[6]
X-ray Crystallographic Analysis for 1a-PF6, 3-PF6, p-5-PF6, and 6-
PF6: All crystals were handled similarly. The crystals were mounted
on the CryoLoop (Hampton Research Crop.) with a layer of light
mineral oil and in a nitrogen stream at 120(1) K. Measurements
were made with a Rigaku Mercury CCD area detector with graph-
ite-monochromated Mo-Kα radiation (λ = 0.71075). Crystal data
and structure refinement parameters are summarized in Table SX
in the Supporting Information. The structures were solved by direct
methods (SIR 92, SIR2008, or SHELXS97) and refined on F2 by
full-matrix least-squares methods by using SHELXL-97.[17] Non-
hydrogen atoms were anisotropically refined. Hydrogen atoms were
included in the refinement on calculated positions riding on their
carrier atoms. The function minimized was [Σw(F2o – Fc2)2] {w =
1/[σ2(F2o) + (aP)2 + bP]}, in which P = [max(F2o,0) + 2F2c2]/3 with
σ2(F2o) from counting statistics. The functions R1 and wR2 were
(Σ||Fo| – |Fc||)/Σ|Fo| and [Σw(F2o – Fc2)2/Σ(wF4o)]1/2, respectively. The
ORTEP-3 program was used to draw the molecule.[18]
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CCDC-841812 (for 1a-PF6), -841813 (for 3-PF6), -841814 (for p-5-
PF6), and -841815 (for 6-PF6) contain the supplementary crystallo-
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www.ccdc.cam.ac.uk/data_request/cif..
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Acknowledgments
K. N. and G. C. thank the Global COE (Center of Excellence) Pro-
gram “Global Education and Research Center for Bio-Environ-
mental Chemistry” of Osaka University. This work was supported
by the Core Research for Evolutional Science and Technology
(CREST) program of the Japan Science and Technology Agency
(JST), Japan.
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Received: September 2, 2011
Published Online: December 7, 2011
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Eur. J. Inorg. Chem. 2012, 1469–1476