Syntheses and structural characterizations of novel mono- and dinuclear iridium hydrido complexes with polydentate nitrogen donor ligands

Article abstract of DOI:10.1016/j.ica.2004.03.052

New five mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, [Ir(H)₂(PPh₃)₂(tptz)]PF₆ (1), [Ir₂(H)₄(PPh₃)₄(tptz)](PF ₆)₂·2H₂O (2·2H₂O), [Ir(H)₂(PPh₃)₂(tppz)]BF₄ (3), [Ir₂(H)₄(PPh₃)₄(tppz)](BF ₄)₂ (4) and [Ir₂(H)₄(PPh ₃)₄(bted)](BF₄)₂·6CHCl ₃ (5·6CHCl₃), were systematically prepared by the reactions of the precursor Ir hydrido complex [Ir(H)₂(PPh ₃)₂(Me₂CO)₂]X (X=PF₆ and BF₄) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 1,4-bis(2,2^′: 6^′,2″-terpyridine-4^′-yl)benzene (bted), and their structures and properties were characterized in the solid state and in solution. Each of the Ir hydrido complexes with polydentate nitrogen ligands crystallographically described a unique coordination mode. Their ¹H NMR spectra demonstrated unusual ¹H NMR chemical shifts of pyridyl rings that are likely induced by the ring current effect of neighboring ligands.

Full text of DOI:10.1016/j.ica.2004.03.052

Inorganica Chimica Acta 357 (2004) 3456–3472
www.elsevier.com/locate/ica
Syntheses and structural characterizations of novel mono-
and dinuclear iridium hydrido complexes with polydentate
nitrogen donor ligands
a,
b
c
d
Masahiko Maekawa *, Toshie Minematsu , Hisashi Konaka , Kunihisa Sugimoto ,
c
Takayoshi Kuroda-Sowa , Yusaku Suenaga , Megumu Munakata
c
c
a
Research Institute for Science and Technology, Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
b
School of Pharmaceutical Sciences, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
c
Department of Chemistry, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
d
Rigaku Corporation, Matsubara-cho, Akishima, Tokyo 196-8666, Japan
Received 14 November 2003; accepted 24 March 2004
Available online 15 June 2004
Abstract
New five mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, [Ir(H)2(PPh3)2(tptz)]PF6 (1),
[Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O), [Ir(H)2(PPh3)2(tppz)]BF4 (3), [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4) and [Ir2(H)4(PPh3)4
(bted)](BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CHCl3), were systematically prepared by the reactions of the precursor Ir hydrido complex
[Ir(H)2(PPh3)2(Me2CO)2]X (X ¼ PF6 and BF4) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine
(tppz) and 1,4-bis(2,20:60,200-terpyridine-40-yl)benzene (bted), and their structures and properties were characterized in the solid state
and in solution. Each of the Ir hydrido complexes with polydentate nitrogen ligands crystallographically described a unique co-
ordination mode. Their 1H NMR spectra demonstrated unusual 1H NMR chemical shifts of pyridyl rings that are likely induced by
the ring current effect of neighboring ligands.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Iridium complexes; Hydrido complexes; Polydentate nitrogen ligands; Crystal structures; 2D NMR
1. Introduction
polydentate nitrogen ligands to provide mono- and di-
nuclear metal complexes in various coordination modes
(Scheme 1). In particular, the tptz ligand is the best
potential polydentate pyridyl ligand since it has thus far
been used as an analytical reagent for various metal ions
[4a,4b]. The tptz ligand that can function simultaneously
as bidentate and tridentate ligands has attracted con-
siderable interest because of their potential use as
spacers in the design of supramolecular complexes [5a–
5d]. A number of transition metal and lanthanide
complexes with the tptz ligand have been prepared.
Mononuclear tptz complexes of Sm, Eu, Pr, Rh, Ru and
Pb have been structurally characterized in the coordi-
nation mode (a) [3a,3c,6a–6d]. However, a mononuclear
tptz complex in the coordination mode (b) has only been
presented in a Re complex [3e]. A few dinuclear tptz
complexes in the coordination modes (c) [3d,3e] and
In recent years, polynuclear metal complexes with
aromatic nitrogen heterocycles as bridging ligands have
been desirable for use in the study of photo-induced
applications [1a–1d], extraction reagents [2a,2b] and
specific catalytic reactions [3a–3e]. The design of these
metal complexes requires N-donor bridging ligands
having two or more bidentate sets of coordination sites
to incorporate molecular components. For instance, the
ligands 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,3,5,6-
tetrakis(2-pyridyl)pyrazine (tppz) and 1,4-bis(2,20:60,200-
terpyridine-40-yl)benzene (bted) have been utilized as
* Corresponding author. Tel.: +81-6-6721-2332x4714; fax: +81-6-
6730-5896.
E-mail address: maekawa@rist.kindai.ac.jp (M. Maekawa).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.03.052

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3457
Scheme 1. The known coordination modes of metal complexes with polydentate nitrogen ligands.
(d) [5c] have been found in Ru, Os and Re complexes.
More recently, it has been reported that interesting hy-
drolysis [3a,3b,3c], hydroxylation [3d] and methoxyla-
tion [3e] in tptz complexes of Rh, Ru and Os occurred
on reflux in ethanol–water. On the other hand, the tppz
ligand was synthesized by Goodwin et al. in the 1950s
[7]. There have been reports on the synthesis and char-
acterization of mononuclear tppz complexes of Re, Cu,
Ru, Fe, Zn, Ir and Ni in the coordination modes (e) [8],
(g) [9a–9f] and (f) [8,10]. Homobimetallic dinuclear tppz
complexes of Pd, Cu, Ru, Ni, Zn and Co in the coor-
dination mode (j) [9a,9d,11a–11h] have also been ob-
served. However, observation of dinuclear tppz
complexes in the coordination modes (h) [8] and (i) [12]
and trinuclear tppz complex in the coordination mode
(k) [8] has been quite limited. Finally, the bted ligand
has been of interest in the study of photo-induced ap-
plications due to its relationship to the tptz and tppz
polydentate nitrogen ligands. However, our survey in
SciFinder shows no crystallographic study of metal bted
complexes. There have been a few structural NMR
studies of the mononuclear Pt bted complex in the co-
ordination mode (l) [13] and dinuclear bted complexes of
Rh, Ir, Re and Ru in the coordination mode (m)
[13,14a,14b]. Altogether, the preparative and structural
studies of metal complexes with polydentate pyridyl li-
gands have not been sufficiently thorough.
We have recently been interested in exploring Rh
and Ir complexes with bi- and polydentate nitrogen
ligands to prepare mono- and dinuclear complexes with

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M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
functions that can be utilized as building blocks to de-
velop a supramolecular system. Because Rh and Ir hy-
drido complexes of formula [M(H)2(L)2(solvent)2]X
(M ¼ Rh and Ir; L ¼ phosphine ligand) have been found
to be active catalysts [15] if the thus-reactive Rh or Ir
metal centers can be joined by the N,N0-donor bridging
ligands, these complexes are expected to produce coor-
dination polymers with interesting structures and supe-
rior reactivities and properties due to a cooperative
effect of the assembled metal site. We have examined the
reactions of Rh and Ir hydrido complex [M(H)2-
(PPh3)2(EtOH)2]X (M ¼ Rh and Ir; X ¼ ClO4 and BF4)
with bidentate N,N0-donor bridging ligands such as
pyrazine and 4,40-bipyridine derivatives in various or-
ganic solvents [16a,16b,16c]. It has been illustrated that
these reaction processes are closely related to the sol-
vents and the structural feature of nitrogen-bridging li-
gands, resulting in the formation of unique dinuclear Rh
and Ir complexes with hydrido or non-hydrido ligands.
However, there still have been no investigative reports
on the reaction of the Ir hydrido complex with a
polydentate pyridyl ligand as described above. As such,
the aim of the present study was to determine the re-
actions of the Ir hydrido complex [Ir(H)2(PPh3)2-
(Me2CO)2]X (X ¼ PF6 and BF4) with tptz, tppz and
bted ligands as polydentate nitrogen ligands, according
to Scheme 2. A series of mono- and dinuclear Ir hydrido
complexes with polydentate nitrogen ligands [Ir(H)2-
(PPh3)2(tptz)]PF6(1), [Ir2(H)4(PPh3)4 (tptz)](PF6)2 ꢀ
2H2O (2 ꢀ 2H2O), [Ir(H)2(PPh3)2( tppz)]BF4 (3), [Ir2(H)4-
(PPh3)4(tppz)](BF4)2 (4) and [Ir2(H)4(PPh3)4(bted)]-
(BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CHCl3) were obtained and their
structures were crystallographically characterized. Their
dynamic structures and spectroscopic properties were
1
further examined by H NMR, UV–Vis and IR tech-
niques in solution and in the solid state.
2. Experimental
2.1. General procedures and reagents
All procedures were carried out using standard
Schlenk techniques under an argon atmosphere.
IrCl3 ꢀ 3H2O, 2,4,6-tris(2-pyridyl)-1,3,5-pyridyltriazine
(tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 1,4-
bis(2,20:60,200-terpyridine-40-yl)-benzene (bted) were pur-
chased from Johnson–Matthey and Aldrich, and these
chemicals were used without further purification. The
precursor Ir hydrido complexes [Ir(H)2(PPh3)2-
(Me2CO)2]X (X ¼ PF6 and BF4) were prepared according
to the literature [17a,17b], with some modifications. All
organic solvents were generally dried and distilled before
use. IR spectra were measured on a JASCO FT/IR-430
Scheme 2.

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3459
spectrometer as a KBr pellet. UV–Vis spectra in the solid
state were measured on a SHIMAZU UV-2450 spec-
trometer as a KBr pellet. The 1-D and 2-D NMR spectra
were measured at room temperature and at )90 °C on
JEOL ECA-500 and ECA-700 FT NMR spectrometers.
Trimethylsilane was used as an internal reference for 1H
NMR measurements.
(92.2 mg, 0.10 mmol) with tppz (9.7 mg, 0.05 mmol) in
CH2Cl2 (10 ml). Dark-red brick crystals were collected
at room temperature 3 days later. Yield. 45 mg (45%).
Anal. Calc. for Ir2P4F8N6C96B2H80: C, 57.66; H, 4.03;
N, 4.20. Found: C, 56.93; H, 4.13; N, 4.21%. IR(KBr
pellet, cmꢁ1): 2284 (Ir–H), 2233 (Ir–H), 1586, 1480,
1434, 1385 and 1057 (BF4ꢁ). UV–Vis(KBr pellet, nm):
375 and 535.
2.2. Syntheses
2.2.1. [Ir(H)2(PPh3)2(tptz)]PF6 (1)
2.2.5. [Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ 6CHCl3 (5ꢀ 6CH-
Cl3)
A 5 ml THF solution of [Ir(H)2(PPh3)2(Me2CO)2]PF6
(49.0 mg, 0.05 mmol) was added to tptz (15.6 mg, 0.05
mmol) in THF (5 ml). After stirring for 15 min, the
reaction solution was filtered. The light-yellow filtrates
were placed in 5-mm diameter glass tubes and layered
with pentane. The glass tubes were sealed and allowed to
stand at room temperature for 3 days. Yellow brick
crystals were collected. Yield. 32 mg (54%). Anal. Calc.
for IrP3F6C54H44N6: C, 55.15; H, 3.77; N, 7.15. Found:
C, 54.87; H, 3.88; N, 7.01%. IR(KBr pellet, cmꢁ1): 2250
(Ir–H), 2205 (Ir–H), 1572, 1544, 1505, 1481, 1435, 1402,
1384, 1358 and 840 (PFꢁ6 ). UV–Vis(KBr pellet, nm): 400
and 480.
[Ir(H)2(PPh3)2(Me2CO)2]BF4 (46.1 mg, 0.05 mmol)
and bted (27.0 mg, 0.05 mmol) were mixed in CHCl3 (10
ml) overnight and the suspension solution was filtered.
The pale-yellow filtrates were placed in 5-mm diameter
glass tubes and layered with hexane. The glass tubes
were sealed and the solution was allowed to stand at
room temperature for 3 days. Yellow brick crystals of
5 ꢀ 6CHCl3 were collected. Yield. 40 mg (28%). Anal.
Calc. for Ir2Cl18P4F8N6C114B2H94: C, 57.66; H, 4.03; N,
4.20. Found: C, 56.93; H, 4.13; N, 4.21%. IR(KBr pellet,
cmꢁ1): 2282 (Ir–H), 1617, 1481, 1434 and 1083 (BFꢁ4 ).
UV–Vis(KBr pellet, nm): 310 and 400.
The detailed NMR data of complexes 1–5 ꢀ 6CHCl3
are summarized in Table 4 together with other spec-
troscopic data.
2.2.2. [Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O)
Complex 2 ꢀ 2H2O was prepared by the reaction of
[Ir(H)2(PPh3)2(Me2CO)2]PF6 (98.0 mg, 0.10 mmol) with
tptz (15.6 mg, 0.05 mmol) in THF (10 ml) in the same
manner as for 1. Red brick crystals of 2 ꢀ 2H2O were
obtained at room temperature after 3 days. Yield. 50 mg
(48%). Anal. Calc. for Ir2P6F12O2N6C90H80: C, 52.99;
H, 3.76; N, 4.12. Found: C, 53.01; H, 4.13; N, 3.91%.
IR(KBr, cmꢁ1): 2248 (Ir–H), 1529, 1482, 1435 and 840
(PFꢁ6 ). UV–Vis(KBr pellet, nm): 430 and 510.
2.3. X-ray data collection and structure solution
For each Ir hydrido complex of 1–5 ꢀ 6CHCl3, a
suitable crystal was mounted on a glass fiber. The X-ray
measurements for 1, 2 ꢀ 2H2O and 3 were made on a
Rigaku/MSC Mercury CCD diffractometer with
graphite-monochromated Mo Ka radiation (k ¼
ꢀ
0:71069 A) at )123 °C for 1 and 3 and at )150 °C for
2 ꢀ 2H2O. The measurements for 4 and 5 ꢀ 6CHCl3 were
made on a Quantum CCD detector coupled with a
Rigaku AFC-8 diffractometer with graphite-monochro-
2.2.3. [Ir(H)2(PPh3)2(tppz)]BF4 (3)
ꢀ
A 5 ml Me2CO solution of [Ir(H)2(PPh3)2(Me2CO)2]-
BF4 (46.1 mg, 0.05 mmol) was added to tppz (9.7 mg,
0.05 mmol) in Me2CO (5 ml). After stirring for 15 min,
the reaction solution was filtered. The orange filtrates
were placed in 5-mm diameter glass tubes and layered
with pentane. The glass tubes were sealed and the so-
lution was allowed to stand at room temperature for 3
days. Orange plate crystals of 3 were obtained. Yield. 33
mg (56%). Anal. Calc. for IrP2F4N6C60BH48: C, 60.35;
H, 4.05; N, 7.04. Found: C, 58.45; H, 3.93; N, 7.48%.
IR(KBr pellet, cmꢁ1): 2291 (Ir–H), 2192 (Ir–H), 1586,
1568, 1480, 1434, 1393 and 1058 (BFꢁ4 ). UV–Vis(KBr
pellet, nm): 360 and 465.
mated Mo Ka radiation (k ¼ 0:71069 A) at )123 °C.
The structures of 1, 2 ꢀ 2H2O, 3, 4 and 5 ꢀ 6CHCl3 were
solved by a direct method (SAPI-91 for 1, 4 and
5 ꢀ 6CHCl3; SIR-92 for 3) [18]. All of the structures were
expanded using Fourier techniques [19]. The two hydr-
ido atoms were located at the calculated positions in 1
and 2 ꢀ 2H2O, whereas they were located from a density
map and refined isotropically in 3, 4 and 5 ꢀ 6CHCl3. In
complex 2 ꢀ 2H2O, one phenyl group including C(1)–
C(6) atoms and one pyridyl group including N(4) and
C(44)–C(48) atoms were treated as ideal models and
were isotropically refined. The C(43) atom of triazine
ring and the O(1) atom of H2O molecule were isotrop-
ically refined. In all complexes 1–5 ꢀ 6CHCl3 all other
hydrogen atoms were placed at the calculated positions
and were included, but not refined. The atomic-scatter-
ing factors and anomalous dispersion terms were taken
2.2.4. [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4)
In the same manner as for 3, complex 4 was synthe-
sized by the reaction of [Ir(H)2(PPh3)2(Me2CO)2]BF4

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M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
Table 1
Crystallographic data for mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, 1–5 ꢀ 6CHCl3
[Ir(H)2(PPh3)2-
(tptz)]PF6 (1)
[Ir2(H)4(PPh3)4(tptz)]-
(PF6)2 ꢀ 2H2O (2 ꢀ 2H2O)
IrP3F6C54H44N6 Ir2P6F12O2N6C90H80
[Ir(H)2(PPh3)2-
(tppz)]BF4 (3)
[Ir2(H)4(PPh3)4-
(tppz)](BF4)2 (4)
[Ir2(H)4(PPh3)4(bted)]-
(BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CHCl3)
Ir2Cl18P4F8N6C114B2H94
Formula
IrP2F4N6C60BH48
1194.05
triclinic
Ir2P4F8N6C96B2H80
1999.67
triclinic
Formula weight
Crystal system
Space group
1176.11
orthorhombic
2075.92
monoclinic
C2
2868.13
triclinic
ꢁ
ꢁ
ꢁ
P212121
P1
P1
P1
ꢀ
a (A)
16.842(4)
16.624(4)
17.544(4)
24.420(8)
15.445(4)
18.629(6)
13.946(6)
14.136(6)
15.410(6)
106.646(4)
90.151(1)
115.860(5)
2590(1)
12.2187(9)
13.106(1)
14.025(1)
91.802(1)
97.071(1)
112.987(2)
2044.2(3)
1
11.7996(5)
15.666(2)
16.587(1)
93.435(2)
102.2082(5)
94.7508(8)
2977.2(4)
1
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
137.769(4)
3
ꢀ
V (A )
4912(2)
4
28.91
4722(2)
2
29.96
Z
2
2.707
150
l(Mo Ka) (cmꢁ1
Temperature (K)
No. of reflections
measured
)
34.11
150
27.58
150
150
123
38 778 (total);
6134 (unique)
10 291 (all data) 10 630 (all data)
0.034a
0.059d
18 720 (total);
5589 (unique)
30 359 (total);
11 742 (unique)
10 296 (all data)
23 984 (total);
9276 (unique)
8772 (all data)
0.020a
49 234 (total);
13 681 (unique)
12 811 (all data)
0.035a
No. of reflections
R
0.078,b 0.047(I > 2:0rðIÞ)c 0.037a
Rw
0.118d
0.071d
0.047d
0.090d
P
P
P
a R ¼ jjFoj ꢁ jFcjj= jFoj.
P
P
b R ¼ ðFo2 ꢁ Fc2Þ= Fo2.
P
P
c R1 ¼ jjFoj ꢁ jFcjj= jFoj.
P
2
2 1=2
d Rw ¼ ½ wðFo2 ꢁ Fc2Þ = wðFo2Þ ꢂ
.
from [20]. All of the calculations were performed using
the TEXSAN crystallographic software package of Mo-
lecular Structure Corporation [21]. Crystal data and
details of the structure determination are summarized in
Table 1.
nuclear Re tptz complex [3e]. The UV–Vis spectra of 1
and 2 ꢀ 2H2O in the solid state are provided in Fig. 1.
Mononuclear complex 1 gave two absorptions at 400
and 480 nm, whereas dinuclear complex 2 ꢀ 2H2O ex-
hibited two absorptions at 430 and 510 nm. It is inter-
esting that the UV–Vis spectra of mononuclear and
dinuclear complexes show significant differences: the
absorption of dinuclear complex 2 ꢀ 2H2O exhibits a
significant red-shift (30 nm) compared to that of
mononuclear complex 1. These absorptions were
assigned as the dp (Ir) ! p* (tptz) charge-transfer tran-
sition (MLCT) on the basis of the assignments of mono-
and dinuclear tptz complexes of Ru, Os and Re [3d,3e].
Generally, it has been reported that the addition of a
second metal ion at the remote coordination site of the
bridging ligand results in stabilization of the p* level of
the bridging ligand, leading to dp ! p* orbital overlap.
This effect lowers the HOMO–LUMO gap, resulting in a
low-energy shift of the MLCT bands in the dinuclear
complexes. Our observation in this study is quite con-
sistent with other reports of tptz complexes of Ru, Os
and Re [3d,3e].
3. Results and discussion
3.1. Preparations and spectroscopic data
As mentioned in Section 1, the tptz ligand generally
can provide tptz complexes with several coordination
modes (a)–(d) in Scheme 1. However, there are still no
reports of an Ir complex with the tptz ligand. Attempts
at carrying out stoichiometric 1:1 and 2:1 reactions of
the precursor Ir hydrido complex [Ir(H)2(PPh3)2-
(Me2CO)2]PF6 and tptz in THF afforded yellow and red
crystals that were later crystallographically character-
ized as mononuclear complex [Ir(H)2(PPh3)2(tptz)]PF6
(1) and dinuclear complex [Ir2(H)4(PPh3)4(tptz)]-
(PF6)2 ꢀ 2H2O (2 ꢀ 2H2O), respectively. Excess addition
of the precursor Ir hydrido complex only provided red
brick crystals of 2 ꢀ 2H2O, suggesting that the dinuclear
structure in the coordination mode (c) is preferable to
the other coordination modes and that a trinuclear
structure could not be formed due to the steric effects
between tptz and PPh3 ligands. A similar suggestion has
been made regarding the formation process of the di-
Similarly, the stoichiometric 1:1 and 2:1 reactions of
the precursor Ir hydrido complex [Ir(H)2(PPh3)2-
(Me2CO)2]BF4 and tppz ligand provided orange crystals
of mononuclear complex [Ir(H)2(PPh3)2(tppz)]BF4 (3)
and dark-red crystals of dinuclear complex
[Ir2(H)4(PPh3)4(tppz)](BF4)2 (4), respectively. Excess
addition of the precursor Ir hydrido complex only pro-
duced dinuclear complex 4 as well as complex 2 ꢀ 2H2O.

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3461
drogen as a ligand should exhibit the characteristic in-
frared spectrum in the range of 1500–2300 (m(M–H))
and {2400 – 3100 (m(H–H)) and 850–950 (ms(M–(H2)))}
cmꢁ1 [22a,22b], depending on the coordination modes of
H–M–H and M–(H2), respectively. When it is difficult to
crystallographically determine the coordination mode of
the coordinating hydrogen atom, the IR measurement is
utilized as the most convenient analytical method to
characterize a hydrido complex in the solid state, in
addition to NMR techniques in solution. As shown
in Section 2, all of the Ir–H stretching absorptions
in complexes 1–5 ꢀ 6CHCl3 were within the range found in
Ir hydrido complexes with the M–H mode. These IR
data support each of the structures established in the
following X-ray crystal structure determinations. These
spectroscopic data are summarized in Table 4 together
Fig. 1. UV–Vis spectra of [Ir(H)2(PPh3)2(tptz)]PF6 (1) (a) and
[Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O) (b) as a KBr pellet in
the solid state.
1
with the H NMR data.
This result suggests that the dinuclear structure in the
coordination mode (h) should be selectively produced
among several coordination modes (h)–(k) due to the
steric effects between tppz and PPh3 ligands without
formation of another polynuclear species. Complexes 3
and 4 in the solid state exhibited broad absorptions at
{360 and 465} and {375 and 535} nm, respectively,
which are assigned as the MLCT band according to
other tppz complexes [9e,11c,11g]. Similar to the above
Ir tptz complexes 1 and 2, the meaningful red-shifts
(Dd ¼ 15 and 70 nm) could be confirmed in Ir tppz
complexes 3 and 4, accompanying by formation of a
dinuclear complex.
Finally, the bted ligand is relatively insoluble in
general organic solvents. We could not perform the
stoichiometric reaction of the precursor Ir hydrido
complex [Ir(H)2(PPh3)2(Me2CO)2]BF4 and the bted li-
gand. However, the precursor Ir hydrido complex and
bted were stirred in CHCl3 overnight and the yellow
suspension was then filtrated. Yellow brick crystals of
dinuclear complex 5 ꢀ 6CHCl3 were collected from the
diffusion solution of the filtrates. It is therefore thought
that dinuclear complex 5 ꢀ 6CHCl3 was deposited as the
most low-soluble and stable species in the reaction so-
lution. Although a small number of apparently red
crystals were sometimes collected in the same sample
tubes, the red crystals were crystallographically identical
to the yellow crystals of 5 ꢀ 6CHCl3. At the present time,
we have not isolated the formation of any other species.
Dinuclear complex 5 ꢀ 6CHCl3 exhibited two absorp-
tions at 310 and 400 nm in the solid state.
3.2. Crystal structures
3.2.1. [Ir(H)2(PPh3)2(tptz)]PF6 (1)
The 1:1 reaction of [Ir(H)2(PPh3)2(Me2CO)2]PF6
and tptz in THF afforded yellow crystals of 1. The
crystal structure of 1 is shown in Fig. 2 together with
the atomic labeling scheme. The Ir atom is coordinated
by the two N atoms among the six potentially coor-
dinative N atoms of tptz to provide a mononuclear
structure in the coordination mode (b). The Ir atom is
also coordinated by two trans PPh3 ligands and two cis
hydrido ligands in a distorted octahedral geometry.
The two cis hydrido atoms are located at the calculated
positions, which were confirmed by the IR determina-
tions described above. To our knowledge, the tptz li-
gand can produce various tptz complexes in
Complex 1 showed well-resolved Ir–H stretching vi-
brations at {2250 and 2205} cmꢁ1. Complexes 2 ꢀ 2H2O,
3, 4 and 5 ꢀ 6CHCl3 also gave the Ir–H stretching vi-
brations at 2248, {2291 and 2192}, {2284 and 2233} and
2282 cmꢁ1, respectively. Generally, it has been known
that metal complexes with hydrido and molecular hy-
Fig. 2. The X-ray crystal structure of [Ir(H)2(PPh3)2(tptz)]PF6 (1).

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M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
coordination modes (a)–(d). Our survey in SciFinder
indicates that most mononuclear tptz complexes have
been structurally characterized in the coordination mode
(a): [Ru(tptz)2]PF6 ꢀ H2O [3a], [Rh(tptz)Cl3]2 ꢀ 2H2O [3c],
H2O molecules in the unit cell. The solvated H2O mol-
ecules exhibited no specific interaction such as a hy-
drogen bond. The two Ir atoms are bridged by the four
N atoms among the six possibly coordinative N atoms
of tptz to provide a dinuclear structure in the coordi-
nation mode (c). Here, in contrast to complex 1, the tptz
ligand acts as a bridging ligand. Each of the Ir atoms is
coordinated by two trans PPh3 ligands and two cis hy-
drido ligands in a distorted octahedral geometry. The
two cis hydrido atoms are located at the calculated po-
sitions. Regarding a dinuclear complex of tptz, it has
been known that there are a few tptz complexes of Ru
and Re, [{M(bpy)2}2(tptz-OH)](PF6)3 ꢀ H2O (M ¼ Ru
and Os) [3d] and (l-tptz)[ReX(CO)3]2 (X ¼ Cl and Br)
[3e] in the coordination mode (c) and [Ru(tpy)(tptz)]-
(ClO4)2 ꢀ 0.5AgClO4 ꢀ 2H2O [5c] in the coordination
mode (d). Therefore, complex 2 ꢀ 2H2O is the first iden-
tificated dinuclear Ir tptz complex in the coordination
mode (c).
[Sm(NO3)3(tptz)(H2O)] ꢀ 2H2O
[6a],
[Eu(tptz)Cl3-
(MeOH)2] ꢀ MeOH [6b], [Pr(tptz)Cl3-(OAc)3]2 ꢀ 2MeOH
[6b], [Pb(tptz)X2] ꢀ solvent (X ¼ Cl, Br, I and SCN) [6c],
[Pb(tptz)(NO3)2] ꢀ solvent [6c] and [Ni(tptz)(H2O)3]-
(NO3)3 ꢀ H2O [6d]. In contrast, the Re complex [ReX-
(CO)3-(tptz)] (X ¼ Cl and Br) [3e] has only been
presented as a mononuclear tptz complex in the coordi-
nation mode (b), in addition to a few examples of dinu-
clearcomplexes[{M(bpy)2}2(tptz-OH)](PF6)3 ꢀ H2O(M ¼
Ru and Os) [3d] and (l-tptz)[ReX(CO)3]2 (X ¼ Cl and
Br) [3e] in the coordination mode (c) and [Ru(tpy)(tptz)]
(ClO4)2 ꢀ 0.5AgClO4 ꢀ 2H2O [5c] in the coordination
mode (d). Therefore, complex 1 is the first mononuclear
Ir tptz complex to be presented in the coordination mode
(b). This structural feature is greatly different from
the coordination mode (a) of the Rh tptz complex
[Rh(tptz)Cl3]2 ꢀ 2H2O [3c], which has only been reported
as an homologous complex.
The average Ir–P and Ir–N distances of 2.312 and
ꢀ
2.180 A are similar to those of complex 1 and other Ir
hydrido complexes with a nitrogen donor ligand [16b].
The P(1)–Ir(1)–P(2) of 164.7(1)° is smaller than the
corresponding angle (173.22(4)°) of 1, whereas the P(1)–
Ir(1)–N(2) of 101.7(2)° is larger than that (91.17(8)°) of
1, resulting in a decrease in repulsion with respect to
PPh3 groups on the neighboring Ir atom and pyridyl
groups of the tptz ligand. The dihedral angle of 5.02°
between the coordinated pyridyl rings {(A) and (B)} and
the central triazine ring (D) is smaller than that (6.83°)
of 1 and those (10.9° and 11.3°) of the similar Re
complex [Re2(Cl)2(CO)6(tptz)] [3e]. The [Ir2(tptz)] co-
ordination plane formed by two Ir atoms, two coordi-
nated pyridyl groups {(A) and (B)} and the central
triazine ring (D) is almost planar. In contrast, the di-
hedral angle of 79.45° between the uncoordinated pyr-
idyl ring (C) and the central triazine ring (D) is larger
than that (64.7°) of [Re2(Cl)2(CO)6(tptz)] [3e]. It is in-
teresting that the uncoordinated pyridyl ring (C) is al-
most located vertically against the [Ir2(tptz)]
coordination plane to minimize the steric interaction
with respect to pyridyl and PPh3 groups. The selected
bond distances, bond angles and dihedral angles are
listed in Tables 2 and 3, respectively.
The average Ir–P and Ir–N distances of 2.311 and
ꢀ
2.166 A are within those of other Ir hydrido complexes
with a nitrogen donor ligand [16b]. The P(1)–Ir(1)–P(2)
and N(1)–Ir(1)–N(2) angles are 173.22(4)° and 76.8(1)°,
respectively. In the metal-free tptz ligand, it has been re-
ported that the dihedral angles between the three pyridyl
groups and the central triazine ring are 15.7(1)°, 19.8(1)°
and 33.8(1)°, respectively [23]. In the similar Re com-
plexes [ReX(CO)3(tptz)] (X ¼ Cl and Br) [3e], the dihedral
angles between the coordinated pyridyl ring (A) and the
central triazine ring (D) are 9.0 (X ¼ Cl) and 8.4°
(X ¼ Br), respectively. The dihedral angles between the
uncoordinated pyridyl ring (B) and the central triazine
ring (D) are 45.3 (X ¼ Cl) and 43.2° (X ¼ Br), respectively.
In contrast, in our complex 1, the dihedral angle between
the coordinated pyridyl ring (A) and the central triazine
ring (D) is 6.83°, which is slightly smaller than those (9.0°
and 8.4°) of the above [ReX(CO)3(tptz)] complex [3e].
The uncoordinated pyridyl ring (B) is considerably
twisted 45.67° from the central triazine ring (D) to
minimize the steric interaction from the adjacent Ir
fragment, compared with the interaction (19.86°) be-
tween the coordinated pyridyl ring (C) and the central
triazine ring (D). The selected bond distances, bond an-
gles and dihedral angles of 1 are listed in Tables 2 and 3,
respectively.
3.2.3. [Ir(H)2(PPh3)2(tppz)]BF4 (3)
Similar to complex 1, the 1:1 reaction of [Ir(H)2-
(PPh3)2(Me2CO)2]BF4 and tppz in Me2CO provided
orange crystals of 3. The crystal structure of 3 is shown
in Fig. 4 together with the atomic labeling scheme. The
Ir atom is coordinated by the two N atoms among the
six potentially coordinative N atoms of tppz to provide
a mononuclear structure in the coordination mode (f).
The Ir atom is bonded to two trans PPh3 ligands and
two cis hydrido ligands in a distorted octahedral
3.2.2. [Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O)
The 2:1 reaction of [Ir(H)2(PPh3)2(Me2CO)2]PF6 and
tptz in THF afforded red brick crystals of 2 ꢀ 2H2O. The
crystal structure of 2 ꢀ 2H2O is shown in Fig. 3 together
with the atomic labeling scheme. There is one
[Ir2(H)4(PPh3)4(tptz)](PF6)2 complex and two solvated

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3463
Table 2
ꢀ
Selected bond distances (A) and bond angles (°) of mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, 1–5 ꢀ 6CHCl3
(a) [Ir(H)2(PPh3)2(tptz)]PF6 (1)
Ir(1)–P(1)
Ir(1)–N(1)
Ir(1)–H(1)a
2.3092(9)
2.171(3)
1.50
Ir(1)–P(2)
Ir(1)–N(2)
Ir(1)–H(2)a
2.313(1)
2.161(3)
1.50
P(1)–Ir(1)–P(2)
P(1)–Ir(1)–N(2)
P(2)–Ir(1)–N(2)
173.22(4)
91.17(8)
90.91(8)
P(1)–Ir(1)–N(1)
P(2)–Ir(1)–N(1)
N(1)–Ir(1)–N(2)
93.25(9)
93.51(9)
76.8(1)
(b) [Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O)
Ir(1)–P(1)
Ir(1)–N(1)
Ir(1)–H(39)a
2.312(2)
2.162(6)
1.50
Ir(1)–P(2)
Ir(1)–N(2)
Ir(1)–H(40)a
2.311(2)
2.20(1)
1.50
P(1)–Ir(1)–P(2)
P(1)–Ir(1)–N(2)
P(2)–Ir(1)–N(2)
164.7(1)
101.7(2)
93.5(2)
P(1)–Ir(1)–N(1)
P(2)–Ir(1)–N(1)
N(1)–Ir(1)–N(2)
93.7(2)
91.7(2)
75.8(3)
(c) [Ir(H)2(PPh3)2(tppz)]BF4 (3)
Ir(1)–P(1)
Ir(1)–N(1)
Ir(1)–H(1)
2.317(1)
2.155(4)
1.45(4)
Ir(1)–P(2)
Ir(1)–N(3)
Ir(1)–H(2)
2.302(1)
2.155(2)
1.50(4)
P(1)–Ir(1)–P(2)
P(2)–Ir(1)–N(3)
P(2)–Ir(1)–N(3)
P(1)–Ir(1)–H(1)
P(2)–Ir(1)–H(1)
N(1)–Ir(1)–H(1)
N(3)–Ir(1)–H(1)
H(1)–Ir(1)–H(2)
165.59(3)
92.08(8)
99.36(8)
85(1)
P(1)–Ir(1)–N(1)
P(2)–Ir(1)–N(1)
N(1)–Ir(1)–N(3)
P(1)–Ir(1)–H(2)
P(2)–Ir(1)–H(2)
N(1)–Ir(1)–H(2)
N(3)–Ir(1)–H(2)
93.95(8)
97.21(8)
76.5(1)
87(1)
83(1)
81(1)
176(1)
99(1)
100(1)
176(1)
83(2)
(d) [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4)
Ir(1)–P(1)
Ir(1)–N(1)
Ir(1)–H(1)
2.3184(7)
2.137(2)
1.40(3)
Ir(1)–P(2)
Ir(1)–N(2)
Ir(1)–H(2)
2.3113(7)
2.220(2)
1.37(3)
P(1)–Ir(1)–P(2)
P(1)–Ir(1)–N(2)
P(1)–Ir(1)–H(2)
P(2)–Ir(1)–N(2)
P(2)–Ir(1)–H(2)
N(1)–Ir(1)–H(1)
N(2)–Ir(1)–H(1)
H(1)–Ir(1)–H(2)
160.20(2)
103.24(6)
75.0(11)
96.03(6)
86.0(11)
175.6(10)
101.1(11)
82.2(15)
P(1)–Ir(1)–N(1)
P(1)–Ir(1)–H(1)
P(2)–Ir(1)–N(1)
P(2)–Ir(1)–H(1)
N(1)–Ir(1)–N(2)
N(1)–Ir(1)–H(2)
N(2)–Ir(1)–H(2)
97.48(6)
80.7(11)
91.70(6)
91.3(11)
75.32(6)
101.3(11)
176.0(11)
(e) [Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CHCl3)
Ir(1)–P(1)
Ir(1)–N(1)
Ir(1)–H(1)
2.3027(8)
2.147(3)
1.48(5)
Ir(1)–P(2)
Ir(1)–N(2)
Ir(1)–H(2)
2.2969(9)
2.168(3)
1.34(5)
P(1)–Ir(1)–P(2)
P(1)–Ir(1)–N(2)
P(1)–Ir(1)–H(2)
P(2)–Ir(1)–N(2)
P(2)–Ir(1)–H(2)
N(1)–Ir(1)–H(1)
N(2)–Ir(1)–H(1)
H(1)–Ir(1)–H(2)
a
161.84(3)
94.88(8)
83(2)
P(1)–Ir(1)–N(1)
P(1)–Ir(1)–H(1)
P(2)–Ir(1)–N(1)
P(2)–Ir(1)–H(1)
N(1)–Ir(1)–N(2)
N(1)–Ir(1)–H(2)
N(2)–Ir(1)–H(2)
98.43(8)
83(1)
94.33(8)
81(1)
100.54(8)
86(2)
98(1)
77.1(1)
175(2)
98(2)
175(1)
86(3)
ꢀ
The Ir–H distance is fixed as 1.50 A.
geometry. To the best of our knowledge, several
mononuclear tppz complexes have been structurally
characterized as follows: [ReCl(CO)3(tppz)] ꢀ 2H2O [8] in
the coordination mode (e); [Cu2Cl2(tppz)] [9a],
[Ru(tppz)(4,40-Me2bpy)Cl]PF6 [9b], [Fe(tppz)2][(di-
pic)2Fe]3 ꢀ H3O ꢀ 11H2O
[9c],
[Zn(tppz)Cl]2
[9d],

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M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
Table 3
Dihedral angles (°) of mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, 1–5 ꢀ 6CHCl3
Complexes
Plane 1
Plane 2
Dihedral angles (°)
Plane 1
Plane 2
Dihedral angles (°)
[Ir(H)2(PPh3)2(tptz)]PF6 (1)
A
A
C
B
D
B
50.60
6.83
31.60
A
B
C
C
D
D
21.74
45.67
19.86
[Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O
(2 ꢀ 2H2O)
A
A
C
B
D
B
8.44
5.02
A
B
C
C
D
D
82.22
5.02
79.45
82.16
[Ir(H)2(PPh3)2(tppz)]BF4 (3)
A
A
B
B
E
B
C
C
E
C
69.15
57.07
78.00
68.22
45.08
A
A
B
E
12.06
73.23
51.93
51.48
67.58
D
D
C
D
D
E
[Ir2(H)4(PPh3)4(tppz)](BF4)2 (4)
A
A
B
B
E
B
D
C
E
C
69.36
69.36
69.36
71.60
15.20
A
A
B
C
E
0
15.20
0
D
C
D
D
E
69.36
71.60
[Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ 6CHCl3
(5 ꢀ 6CHCl3)
A
A
A
B
B
D
F
C
E
G
E
G
F
D
F
11.56
63.50
0
A
A
A
B
C
E
G
D
F
D
F
E
F
E
63.50
11.56
44.11
54.68
11.56
0
54.68
0
B
B
B
37.88
54.68
71.41
63.50
71.41
44.11
C
C
D
E
C
C
D
G
G
63.50
54.68
11.56
37.88
G
Metal free tptza
Metal-free tppzb
Metal-free tppzc
A
C
D
D
15.7(1)
33.8(1)
B
D
E
E
19.8(1)
59.0
A
D
B
E
60.4
46.4
A
A
A
D
B
E
62.4
51.7
48.9
a Ref. [23].
b Ref. [24] (tetragonal form).
c Ref. [24] (monoclinic form).
[Ir(tppz)Cl3] [9e], [Cu(tppz)Cl2] ꢀ CH3CN [9f], [Cu-
(tppz)2]ClO4 [9f] and [Ni(tppz)2](BF4)2 [9f] in the coor-
dination mode (g). Although Re and Ru complexes
[Re(X)(CO)3(tppz)] (X ¼ Cl and Br) [8] and [Ru(phen)2-
(tppz)](PF6)2 [10] have recently been found as a mono-
nuclear tppz complex in the coordination mode (f),

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3465
Fig. 3. The X-ray crystal structure of [Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O).
form, and {48.9° for rings (A) and (E), and 51.7° for
rings (D) and (E)} for the monoclinic form, respectively
[24]. In the similar Re complex [ReCl(CO)3(tppz)] ꢀ
MeOH [8], it has also been reported that the uncoordi-
nated pyridyl ring (D) is rotated at an angle of 59.0°
with respect to the central pyrazine ring (E) and 56.7°
with respect to the coordinated pyridyl ring (A). The
coordinated pyridyl ring (A) is twisted 26.7° with respect
to the central pyrazine ring (E). In contrast, in our
complex 3, the dihedral angle between the coordinated
pyridyl ring (A) and the central pyrazine ring (E) is
12.06°, which is smaller than that of the [ReCl(CO)3-
(tppz)] ꢀ MeOH complex [8]. The uncoordinated pyridyl
ring (D) is rotated 67.58° and 73.23° against the central
pyrazine ring (E) and the coordinated pyridine ring (A),
respectively. It was obvious that the three uncoordinated
groups were almost vertical against the central pyrazine
ring (E) compared with the coordinated pyridyl ring (A).
The selected bond distances, bond angles and dihedral
angles are listed in Tables 2 and 3, respectively.
Fig. 4. The X-ray crystal structure of [Ir(H)2(PPh3)2(tppz)]BF4 (3).
complex 3 is the first tppz complex of Ir in the coordi-
nation mode (f).
The average Ir–P and Ir–N distances of 2.310 and
3.2.4. [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4)
ꢀ
2.155 A are close to those of other Ir–hydrido complexes
with a nitrogen donor ligand [16b]. The Ir–H distances
The 2:1 reaction of [Ir(H)2(PPh3)2(Me2CO)2]BF4 and
tppz in Me2CO provided dark-red crystals of 4. The
crystal structure of 4 is shown in Fig. 5 together with the
atomic labeling scheme. The center of symmetry for
complex 4 is at the middle of the central pyrazine ring.
The tppz ligand acts as a bridging ligand, as does the
tptz ligand in 2 ꢀ 2H2O. The two Ir atoms are coordi-
nated by the four N atoms among the six potentially
coordinative N atoms of tppz to form a dinuclear
structure in the coordination mode (h). Each of the Ir
atoms is coordinated by two trans PPh3 ligands and two
cis hydrido ligands in a distorted octahedral geometry.
ꢀ
of 1.45(4) and 1.50(4) A, and the H(1)ꢀ ꢀ ꢀH(2) distance of
ꢀ
1.95 A are similar to those of other Ir hydrido complexes
with a nitrogen donor ligand [16b]. The N(1)–Ir(1)–N(3)
angle is 76.5(1)°. The P(1)–Ir(1)–P(2) angle of 165.59(3)°
is smaller than that (173.22(4)°) of mononuclear tppz
complex 1, indicative of the larger distortion from
the octahedral geometry. In the metal-free tppz ligand,
the dihedral angles between four pyridyl groups and the
central pyrazine ring are {59.0° for rings (A) and
(E), and 46.4° for rings (D) and (E)} for the tetragonal

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M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
hydrido complexes [16a]. The N(1)–Ir(1)–N(2) angle is
75.32(6)°. The P(1)–Ir(1)–P(2) angle of 160.20(2)° is
smaller than that of 173.22(4) (1) and 165.59(3)° (3). The
dihedral angle of 15.20° between the coordinated pyridyl
ring (A) and the central pyrazine ring (E) is distorted
from the plane, whereas that between the uncoordinated
pyridyl group (D) and the central pyrazine ring (E) is
71.60°. The selected bond distances, bond angles and
dihedral angles are listed in Tables 2 and 3, respectively.
3.2.5. [Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CH-
Cl3)
According to the procedures in the experimental
section, yellow brick crystals of 5 ꢀ 6CHCl3 were col-
lected. The crystal structure of 5 ꢀ 6CHCl3 is shown in
Fig. 6 together with the atomic labeling scheme. There is
one [Ir2(H)4(PPh3)4(bted)](BF4)2 complex and six sol-
vated CHCl3 molecules in the unit cell. The center of
symmetry for complex 5 ꢀ 6CHCl3 is at the middle point
of the central benzene ring in the betd ligand. Similar to
complex 4, the bted ligand acts as a bridging ligand to
afford a dinuclear Ir hydrido complex by coordination
of the four N atoms among the six possibly coordinative
N atoms. Each of the Ir atoms is coordinated by two
trans PPh3 ligands and two cis hydrido ligands in a
distorted octahedral geometry. Our survey in SciFinder
showed no crystallographic study of metal bted com-
plexes. There have been very few structural NMR
studies of mononuclear bted complex [Pt(C6F4CF3)2-
(betd)] [13] in the coordination mode (l), and dinuclear
bted complexes [{Pt(C6F4CF3)2}2(betd)] [13], [{Re-
Br(CO)3}2(betd)] [13], [(Cp*MCl)2(bted)](BF4)2 (M ¼
Rh and Ir) [14a] and [{CpRu(PPh3)}2(betd)] [14b] in the
coordination mode (m). Therefore, this is the first
crystallographic study of a metal complex with the bted
ligand.
Fig. 5. The X-ray crystal structure of [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4).
To the best of our knowledge, there are many dinuclear
tppz complexes in the coordination mode (j): [Cu2-
(H2O)2(NO3)(tppz)]2þ [9a], [Cu2Cl4(tppz)] [9a], [Cu2-
(tppz)(H2O)4](ClO4)4 [9d], [Cu2(tppz)Cl]2(ClO4)4 [9d],
[Pd2(NO3)2(tppz)](NO3)2 ꢀ 0.5H2O [11a], [{Cu2(tppz)-
(H2O)2 [11b], cis-[Cl(dmb)Ru(tppz)Ru(dmb)Cl](PF6)2
[11c], [Cu2(tppz)Cl4] ꢀ 5H2O [11d], [Ni2(tppz)(H2O)6]-
(NO3)4 ꢀ 2.5H2O [11d], [Ni2(tppz)(H2O)6]- (squarate)2 ꢀ
5H2O [11d], [Zn5Cl10(tppz)(H2O)2] [11e], [{(l-Cl)2-
(MeCN)Co(tppz)Co(CoCl4)}n] [11f] and [{(L4)ClRu}2-
(tppz)](ClO4)2 ꢀ 2H2O [11g]. However, there are very few
dinuclear complexes [{ReBr(CO)3}2-(l-tppz)] [8] in the
coordination mode (h) and [{Pt(PEt3)Cl}2(l-tppz)]-
[Pt(SnCl3)4(PEt3)] [12] in the coordination mode (i), in
addition to trinuclear complex [{ReBr(CO)3}3(l-tppz)]
in the coordination mode (k) [8]. Therefore, complex 3 is
the first dinuclear Ir tppz complex to be identified in the
coordination mode (h).
The average Ir–P and Ir–N distances of 2.315 and
ꢀ
ꢀ
2.178 A are similar to those (2.310 and 2.155 A) of 3.
The average Ir–P and Ir–N distances of 2.300 and 2.158
ꢀ
The Ir–H distances of 1.40(3) and 1.37(3) A, and the
ꢀ
A are similar to those of complexes 1, 2 ꢀ 2H2O, 3 and 4.
ꢀ
H(1)ꢀ ꢀ ꢀH(2) distance of 1.83 A are close to that of other
The N(1)–Ir(1)–N(2) angle is 77.1(1)° and the P(1)–Ir(1)–
Fig. 6. The X-ray crystal structure of [Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ 6CHCl3 (5 ꢀ 6CHCl3).

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3467
1
P(2) angle of 161.84(3)° is close to that (160.20(3)°) of 4.
The Ir–H distances are 1.48(5) and 1.34(5) A, and the
complex 1 suggests that there are three sets of four H
NMR signals that can be assigned to different pyridyl
rings (A), (B) and (C), together with the overlapping 1H
NMR signals of PPh3. The two coordinated hydrido
ꢀ
ꢀ
H(1)ꢀ ꢀ ꢀH(2) distance of 1.92 A is slightly shorter than that
ꢀ
(1.83 A) of 4. The dihedral angle of 11.56° between the
1
coordinated pyridyl ring (A) and the pyridyl ring (B) is
somewhat smaller than that (54.68°) between the unco-
ordinated pyridyl (C) ring and the pyridyl ring (B). The
dihedral angle between the pyridyl ring (B) and the central
benzene ring (G) is not coplanar at 37.88°. The selected
bond distances, bond angles and dihedral angles are listed
in Tables 2 and 3, respectively.
atoms also showed two well-resolved H NMR signals
2
at )19.54 (1JH–H ¼ 8.2 and JP–H ¼ 16.1 Hz) and )20.10
(1JH–H ¼ 8.2 and 2JP–H ¼ 14.6 Hz) ppm. The correlations
between each of the hydrido atoms and the P atom in
the PPh3 ligand could be confirmed by the 31P–1H
COSY NMR spectrum. The four proton atoms of the
coordinated pyridyl ring (A) gave two doublet signals
{8.62 (H1) and 8.40 (H4) ppm}, one triplet signal {7.98
(H2) ppm} and the overlapping signal to PPh3 {7.26
(H3) ppm}. These signals were shifted to the up-field
region in comparison with those {8.92 (d, H4;8;12), 8.81
(d, H1;5;9), 7.99 (t, H2;6;10) and 7.56 (t, H3;7;11) ppm} of
the metal-free tptz ligand. It is interesting that the H4
proton exhibited a larger shift of Dd ¼ 0:52 ppm com-
3.3. Dynamic structures in solution
3.3.1. Mono- and dinuclear Ir hydrido complexes with the
tptz ligand, 1 and 2 ꢀ 2H2O
Complexes 1 and 2 ꢀ 2H2O showed quite complicated
1
1-D H NMR signals in CD2Cl2 at 23 °C because three
1
pyridyl groups of the tptz ligand and several phenyl
groups of the PPh3 ligands are simultaneously pre-
sented. We attempted to assign these signals by the use
of 1H–1H COSY NMR techniques. The numberings for
protons of each pyridine rings are denoted in the caption
of Table 3. The 1H–1H COSY spectrum (Fig. 7) of
pared with those (Dd ¼ 0:01–0.30 ppm) of the other H
NMR signals in the pyridyl ring (A). In contrast, the
uncoordinated pyridyl ring (B), adjacent to the Ir core,
exhibited two triplet signals {7.67 (H6) and 7.41 (H7)
ppm}, a superimposed H8 signal (7.62 ppm) and a
doublet signal {7.03 (H5) ppm}. It is remarkable that
Fig. 7. 1H–1H COSY NMR spectrum in the aromatic region of [Ir(H)2(PPh3)2(tptz)]PF6 (1) in CD2Cl2 at 23 °C.

3468
M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
these signals were quite shifted to the up-field region
(Dd ¼ 0:15–1.78 ppm) compared with the metal-free tptz
ligand. In particular, the H5 signal represented an un-
usual up-field shift (Dd ¼ 1:78 ppm). It is likely that
shielding of the H5 proton results from its interaction
with the coordinated [Ir(H)2(PPh3)2] fragment. Our
crystallographic study showed that the uncoordinated
pyridine ring (B) of complex 1 is surrounded by phenyl
groups of the neighboring PPh3. These findings seem to
indicate that the uncoordinated pyridyl ring (B) is highly
shielded by the neighboring PPh3 ligands to give a larger
up-field shift, as it appears that the neighboring CO li-
gands could not significantly contribute to the shielding
or deshieldings by the ring current effect in similar
mononuclear Re complex [ReX(CO)3(tptz)] (X ¼ Cl and
Br) [3e] with the coordination mode (b). When predict-
(t, H10) and 7.62 (t, H11) ppm} were essentially unshifted
with respect to those of the metal-free tptz ligand. This
behavior is similar to that observed in the mononuclear
Re complex [ReX(CO)3(tptz)] [3e]. It is interesting that
the shift (Dd ¼ 0:25 ppm) of the H9 proton is larger than
1
those (Dd ¼ 0:03–0.05 ppm) of other H NMR signals.
In complex 2 ꢀ 2H2O, the 1H–1H COSY spectrum
1
exhibited two sets (intensity ratio 2:1) of four H NMR
signals assignable to 12 pyridyl protons in the tptz li-
gand (Fig. 8), which is the number expected for two
magnetically equivalent coordinated pyridyl rings (A)
and (B) and one nonequivalent pyridyl ring (C). Con-
trary to complex 1, two hydrido atoms in 2 ꢀ 2H2O
showed multiple1H NMR signals at )20.65 ppm, in-
dicative of an overlapping of two hydrido signals. The
coordinated pyridyl rings (A) and (B) showed two
doublet signals {8.61 (H1;5) and 7.56 (H4;8) ppm}, one
triplet signal {8.07 (H2;6) ppm} and the overlapping
signal to PPh3 {7.15 (H3;7) ppm}. The shift (Dd ¼ 1:36
ppm) at the H4;8 position in pyridyl rings (A) and (B) is
larger than that (Dd ¼ 0:49 ppm) of the corresponding
complex 1. Furthermore, the uncoordinated pyridyl ring
(C) showed two triplet signals {7.50 (H11) and 7.34 (H10)
ppm}, the superimposed H12 signal (7.47 ppm) and the
doublet signal {6.29 (H9) ppm}. It is worth nothing that
these signals were unusually shifted to the up-field re-
gion (Dd ¼ 0:06–2.52 ppm). In particular, the larger up-
field shift of Dd ¼ 2:52 ppm at the H9 position than that
(Dd ¼ 0:25 ppm) in complex 1 is surprising. In similar
dinuclear Ru and Os complexes with the tptz ligand
1
ing the H NMR shifts of complex 1 on the basis of the
crystallographic study, the pyridine ring (A) was as-
sumed to give the largest up-field shift among the pyr-
idyl rings (A), (B) and (C) due to the contribution of the
largest ring current effects of the PPh3 group. However,
our NMR study indicated that the pyridyl ring (B) had a
larger up-field shift (Dd ¼ 0:15–1.78 ppm) than that
(Dd ¼ 0:01–0.52 ppm) in the pyridyl ring (A). It is
thought that the up-field shift based on the ring current
effect is compensated for the down-field shift based on
the coordination shift of the Ir atom to the pyridyl ring
(A), resulting in a decrease of the up-field shifts. Finally,
1
the H NMR signals of the remaining uncoordinated
pyridine ring (C) at {8.87 (d, H12), 8.56 (d, H9), 8.02
Fig. 8. 1H–1H COSY NMR spectrum in the aromatic region of [Ir2(H)4(PPh3)4(tptz)](PF6)2 ꢀ 2H2O (2 ꢀ 2H2O) in CD2Cl2 at 23 °C.

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3469
rac-[M(bpy)2}2(tptz-H)](PF6)3 (M ¼ Ru and Os) [3d], it
has been reported that the signals of the uncoordinated
pyridine ring (C) in the coordinated tptz ligand exhibit
the up-field shifts of {Dd ¼ 2:80 (H9), 1.84 (H10), 1.19
(H11) and 2.17 (H12) ppm}. These behaviors have been
explained as being ring current effects produced by the
neighboring 2,20-bipyridine ligands. Our crystallo-
graphic study of complex 2 showed that the uncoordi-
nated pyridyl ring (C) is close to the Ph groups in the
neighboring PPh3 and other pyridyl rings in the tptz li-
gand. As with complex 1, it is thought that unusual
chemical shifts are likely induced by the ring current
effects of the neighboring ligands. The detailed 1H NMR
chemical shifts of complexes 1 and 2 ꢀ 2H2O are listed in
Table 4.
up-field shift (Dd ¼ 0:26–1.30 ppm), although these
signals should apparently be canceled by the down-field
shift based on the coordination shift. The H1 proton
exhibits a shift of Dd ¼ 1:30 ppm, which is larger than
that (Dd ¼ 0:52 ppm) of the H4 proton in complex 1.
The uncoordinated pyridyl rings (B) and (C) also show
smaller shifts of Dd ¼ 0:05–0.27 and 0.17–0.49 ppm,
1
respectively. Although it is expected that H NMR sig-
nals of the uncoordinated pyridine rings (B) and (C)
should be nearly unshifted, these signals were partially
shifted by each current ring effect and the coordination
shift to the Ir atom.
In contrast to mononuclear tppz complex 3, dinuclear
tppz complex 4 redissolved in CD2Cl2 showed two kinds
of 1H NMR signals at 23 °C. The major species exhibited
1
the broadened H NMR signals at {8.39, 7.61, 6.47 and
3.3.2. Mono- and dinuclear Ir hydrido complexes with the
tppz ligand, 3 and 4
6.32 ppm} for pyridyl groups in the tppz ligand and at
{)19.12 and )20.95 ppm} for the two hydrido atoms
together with those of the PPh3 ligands at {7.32 and 7.16
ppm}, whereas the minor species presented the well-re-
Complex 3 showed 16 well-resolved 1H NMR signals
1
of the tppz ligand in CD2Cl2 at 23 °C together with H
NMR signals (7.26 ppm) of the PPh3 ligands. The H–
1
1
solved H NMR signals of complex 3. These behaviors
1
1H COSY NMR techniques described four sets of H
indicate that dinuclear tppz complex 4 is partially dis-
sociated in CD2Cl2 to afford a small amount of complex
3. The variable-temperature 1H NMR spectra were
measured to determine the broadened species at low
temperature (Fig. 9). At )90 °C, the broadened species
could be separately observed as well as the six well-re-
NMR signals that can be assigned to different pyridyl
rings (A), (B), (C) and (D) in the tppz ligand. To assign
each of the pyridyl rings (A)–(D), 1H–1H ROESY NMR
techniques were also employed. The results show that
1H NMR signals of PPh3 are obviously correlated to the
H4 atom in the pyridyl ring (A) and the H13;16 atoms in
the pyridyl ring (D). Furthermore, the H1 atom in the
pyridyl ring (A) is related to the H5 atom in the pyridyl
ring (B). The H8 and H6 atoms in the pyridyl ring (B) are
related to the H11;12 and H10 atoms in the pyridyl ring
(C), respectively. These findings indicate that the pyridyl
rings (A) and (D) are located close to the Ph groups of
the coordinated PPh3 ligands. The pyridyl ring (A) is
neighboring the pyridyl rings {(B) and (D)} and the
pyridyl ring (B) is close to the pyridyl ring (C). Unco-
ordinated pyridyl rings (B), (C) and (d) can be fluxional
in solution and their orientation is different from those
in the solid state. On the basis of these correlations and
the assignments of complexes 1 and 2 ꢀ 2H2O, the as-
signments of four pyridyl rings (A)–(D) were finally
defined as the scheme in the caption of Table 3. The two
1
solved H NMR signals at {8.53, 7.66, 7.63, 6.40, 6.29
and 6.04 ppm} and the two 1H NMR signals for the two
hydrido atoms at {)18.85 and )21.70 ppm}, together
with those of complex 3. These signals could be assigned
1
by the H–1H COSY NMR techniques as follows: the
coordinated pyridyl rings (A) and (C) showed the two
doublet signals {8.53 (H4;12) and 6.04 (H1;9) ppm} and
two triplet signals {7.66 (H3;11) and 7.63 (H2;10) ppm},
whereas the uncoordinated pyridyl rings (B) and (D)
gave one doublet signal {6.40 (H8;16) ppm} and one
triplet signal {6.29 (H6;14) ppm} together with two
overlapping signals {7.13 (H7;15) and 7.03 (H5;13) ppm}
to PPh3. At present, the specific dissociation process of
complex 4 is not clear. However, suggesting by the var-
iable-temperature 1H NMR spectra, it is considered that
two Ir atoms in complex 4 are instantaneously replaced
between the two coordination sites formed by the central
pyrazine ring and pyridyl rings {(A) and (C)} and other
pyridyl rings {(B) and (D)}, since the major species 4
showed the broad 1H NMR signals at room temperature
coordinated hydrido atoms showed two well-resolved
2
1H NMR signals at )19.48 (1JH–H ¼ 7.9 and JP–H
¼
2
17.4 Hz) and )20.67 (1JH–H ¼ 7.6 and JP–H ¼ 14.6 Hz)
1
ppm. Detailed H NMR chemical shifts of complex 3
1
1
are listed in Table 4. Similar to complexes 1 and 2, H
and relatively sharp H NMR signals with lower tem-
NMR signals of the uncoordinated pyridyl ring (D),
adjacent to the Ir core, indicate a larger up-field shift
(Dd ¼ 0:13–2.58 ppm) compared with those of the
metal-free tppz ligand. In particular, it is surprising that
the H13 signal represents an unusual up-field shift
(Dd ¼ 2:58 ppm), which is larger than those (Dd ¼ 1:78
and 2.52 ppm) of complexes 1 and 2. The 1H NMR
signals of the coordinated pyridyl ring (A) showed an
peratures. A small amount of complex 3 should be pro-
duced on this fluxional behavior. The resultant complex
3 is stably kept in CD2Cl2 without the reformation to
complex 4, since the minor species 3 showed the well-
1
resolved H NMR signals even at room temperature.
These findings could be supported by the presence of
fluxional behaviors in mono- and dinuclear complexes
with tptz [6b,25a,25b] and betd ligands [13,14a]. It is

3470
M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
Table 4
Spectroscopic data of mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, 1–5 ꢀ 6CHCl3
Compounds
1H NMRa (Dd, ppm)
UV–Vise (kmax, nm) IR(Ir–H)e (cmꢁ1
)
[Ir(H)2(PPh3)2(tptz)]PF6 (1)a
{8.62(d, H1), 8.40 (d, H4), 7.98 (dt, H2) and 7.26 (t, H3)}
for ring (A); {7.67 (dt, H6), 7.62 (dd, H8), 7.41 (dt, H7) and
7.03 (d, H5)} for ring (B); {8.87 (dddd, H12), 8.56 (td, H9),
8.02 (dt, H10) and 7.62 (dt, H11)} for ring (C); 7.27 (m, PPh3);
)19.54 (dt, Ir–H) and )20.10 (dt, Ir–H)
400, 480
2250, 2205
[Ir2(H)4(PPh3)4(tptz)](PF6)2
2H2O (2 ꢀ 2H2O)a
ꢀ
{8.61(d, H1;5), 8.07 (dt, H2;6), 7.56 (d, H4;8) and 7.15
(dt, H3;7)} for rings (A) and (B); {7.50 (dt, H11), 7.47
(dddd, H12), 7.34 (dt, H10) and 6.29 (dd, H9)} for ring (C);
7.22 (m, PPh3); )20.65 (m, Ir–H)
430, 510
360, 465
2248
[Ir(H)2(PPh3)2(tppz)]BF4 (3)a
{8.10(d, H4), 7.30 (t, H2), 6.76 (dt, H3) and 6.73 (d, H1)}
for ring (A); {8.56 (dddd, H8), 8.09 (dt, H6), 7.98 (td, H5)
and 7.55 (dt, H7)} for ring (B); {8.16 (dddd, H12), 7.62 (dt,
H10), 7.54 (dd, H9) and 7.11 (dt, H11)} for ring (C); {7.51
(dddd, H16), 7.17 (dt, H14), 7.15 (dt, H15) and 5.45 (td, H13)}
for ring (D); 7.26 (m, PPh3); )19.48 (dt, Ir–H) and )20.67
(dt, Ir–H)
2291, 2192
[Ir2(H)4(PPh3)4(tppz)](BF4)2 (4)a;d
{8.39(br), 7.61 (br), 6.47 (br) and 6.32 (br)}for tppz; 7.32
(br, PPh3), 7.16 (br, PPh3); )19.12 (t, Ir–H) and )20.95
(t, Ir–H) at 23 °C. {8.53 (d, H4;12), 7.66 (dt, H3;11), 7.63
(t, H2;10) and 6.04 (d, H1;9)} for rings (A) and (C); {7.13
(H7;15) and 7.03 (H5;13), 6.40 (d, H8;16) and 6.29 (t, H6;14)}
for rings (B) and (D); )18.85 (dt, Ir–H) and )21.70
(dt, Ir–H) at )90 °C.
375, 535
2284, 2233
[Ir2(H)4(PPh3)4(bted)](BF4)2 ꢀ
6CHCl3 (5 ꢀ 6CHCl3)b
{8.55(d, H1;13), 8.49 (d, H4;16), 7.98 (t, H3;15) and 7.15
(dt, H2;14)} for rings (A) and (F); {8.54(d, H9;21) and 7.68
(d, H10;22)} for rings (B) and (E); {7.64 (d, H8;20), 7.59
(dt, H6;18), 7.41 (dt, H7;19) and 6.29 (d, H5;17)} for rings (C)
and (D); 8.19 (s, H11;12;23;24) for ring (G); 7.37 (m, PPh3);
)19.30 (dt, Ir–H) and )20.22 (dt, Ir–H)
310, 400
2282
Metal-free tptza
Metal-free tppza
8.92 (dddd, H4;8;12), 8.81 (dddd, H1;5;9), 7.99 (dt, H2;6;10
and 7.56 (dt, H3;7;11
)
)
8.36 (dddd, H4;8;12;16), 8.03 (dddd, H1;5;9;13), 7.84
(dt, H2;6;10;14) and 7.28 (dt, H3;7;11;15) at 23 °C. 8.31
(d, H4;8;12;16), 7.99 (d, H1;5;9;13), 7.85 (t, H2;6;10;14) and 7.28
(t, H3;7;11;15) at )90 °C.
Metal-free btedc
8.81 (s, H9;10;21;22), 8.77 (dddd, H4;8;16;20), 8.71
(dddd, H1;5;13;17), 8.07 (s, H11;12;23;24), 7.91 (dt, H2;6;14;18
)
and 7.37 (dt, H3;7;15;19
)
a In CD2Cl2 at 23 °C.
b In (CD3)2CO at 23 °C.
c In CDCl3 at 23 °C.
d
1H NMR signals of a small amount of complex 3 were simultaneously observed.
e In the solid state with KBr disk.
1
interesting that the coordinated pyridyl rings (A) and (C)
exhibited a larger shift (Dd ¼ 0:22–1.95 ppm) at )90 °C
The detailed H NMR chemical shifts of complexes 3
and 4 are summarized in Table 4.
1
compared with H NMR signals {8.31, 7.99, 7.85 and
7.28 ppm} of the metal-free tppz ligand. In particular, it
is surprising that the H1;9 signals represented the unusual
up-field shift (Dd ¼ 1:95 ppm). In contrast, the uncoor-
dinated pyridyl rings (B) and (D), adjacent to the Ir core,
3.3.3. Dinuclear Ir hydrido complexes with the betd
ligand, 5 ꢀ CHCl3
Complex 5 ꢀ 6CHCl3 exhibited 11 well-resolved 1H
NMR signals in the betd ligand in (CD3)2CO at 23 °C,
that could be assigned to pyridyl rings (A), (B), (C)
and (G) in the betd ligand by 1H–1H COSY NMR
techniques. The well-resolved 1H NMR spectrum in-
dicated that a dinuclear structure is maintained at
room temperature without the dissociation and the
1
gave the up-field shifted H NMR signals of Dd ¼ 1:91
1
(H8;16) and 1.56 (H6;14) ppm. Similar to the H NMR
spectra of complexes 1–3, these results suggest that un-
usual shifts should be induced by the ring current effect
on the basis of the crystallographic features of complex 4.

M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
3471
Fig. 9. The variable-temperature 1H NMR spectra of [Ir2(H)4(PPh3)4(tppz)](BF4)2 (4) in CD2Cl2.
equilibrium. In the NMR study of dinuclear bted
complexes [{Pt(C6F4CF3)2}2(betd)] [13], [{Re-
NMR signals except for complex 4 at room temperature.
The complex 4 showed interesting fluxional behaviors at
low temperature. All of the dynamic structures in solu-
tion demonstrated that the ring current effect should
primarily be reflected in the chemical shifts of each
pyridyl ring in polydentate nitrogen ligands. In partic-
ular, it was found that the uncoordinated pyridyl ring,
adjacent to the Ir core, has the larger up-field shift due
to the ring current effect.
Br(CO)3}2(betd)] [13], and [(Cp*MCl)2(bted)](BF4)2
(M ¼ Rh and Ir) [14a], fluxional behaviors have been
reported among several species at ambient and high
temperatures. The dynamic behaviors of Ir complex
5 ꢀ 6CHCl3 are different than those of other bted com-
plexes [13,14a], suggesting that Ir complex 5 ꢀ 6CHCl3 is
not labile in (CD3)2CO. The two hydrido signals were
2
observed at )19.30 (1JH–H ¼ 7.6 and JP–H ¼ 17.0 Hz)
2
and )20.22 (1JH–H ¼ 7.8 and JP–H ¼ 15.4 Hz) ppm.
The coordinated pyridyl rings {(A) and (F)} showed
1H NMR signals at {8.55 (d, H1;13), 8.49 (d, H4;16),
7.98 (t, H2;14) and 7.15 (t, H3;15) ppm}, whereas the
uncoordinated pyridyl rings {(C) and (D)} exhibited
4. Supplementary materials
Crystallographic data for the X-ray crystal structural
analysis have been deposited with the Cambridge
Crystallographic Data Center, CCDC, Nos. 209702 –
209706 for complexes 1, 2 ꢀ 2H2O, 3, 4 and 5 ꢀ 6CHCl3,
respectively. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: +44-1233-
336033; e-mail: deposit@cced.cam.ac.uk or www:htter-
phenyl://www.ccdc.cam.ac.uk).
1
well-resolved H NMR signals at {7.64 (d, H8;20), 7.59
(t, H6;18), 7.41 (t, H7;19) and 6.29 (d, H5;17) ppm}. The
1H NMR resonances of rings {(B) and (E)} and (G)
were also exhibited at {8.54 (d, H9;21), 7.68 (d, H10;22)}
and 8.19 (s, H11;12;23;24) ppm, respectively, together with
1
that (7.37 (m, PPh3) ppm) of PPh3. H NMR signals of
the uncoordinated pyridyl rings (C) and (D), adjacent
to the Ir core, showed the largest up-field shift
(Dd ¼ 0:5–2.42 ppm) among the other signals, with the
H5;17 signals having the largest up-field shift (Dd ¼ 2:42
Acknowledgements
1
ppm). The detailed H NMR chemical shifts of com-
plex 5 ꢀ 6CHCl3 were summarized in Table 4.
We thank Mr. T. Morita, Mr. T. Kanzaki and Mr. D.
Tomomatsu for their assistance. This work was partially
supported by a Grant-in-Aid for Scientific Research
In summary, a series of Ir hydrido complexes with
polydentate nitrogen ligands gave well-resolved 1H

3472
M. Maekawa et al. / Inorganica Chimica Acta 357 (2004) 3456–3472
[11] (a) Y. Yamada, Y. Miyashita, K. Fujisawa, K. Okamoto, Bull.
Chem. Soc. Jpn. 73 (2000) 1843;
from the Ministry of Education, Science, Sports, Cul-
ture and Technology of Japan.
(b) D. Hargrman, P. Hagrman, J. Zubieta, Inorg. Chim. Acta 300
(2000) 212;
(c) C.M. Hartshorn, N. Daire, V. Tondreau, B. Loeb, T.J. Meyer,
P.S. White, Inorg. Chem. 38 (1999) 3200;
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