Synthesis and structural characterization of novel ruthenium(II) complexes featuring an N,N,O-scorpionate ligand: A versatile synthetic precursor for open-face scorpionatoruthenium(II) complexes

Article abstract of DOI:10.1016/j.poly.2010.01.016

The syntheses and characterization of novel ruthenium(II) complexes containing bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza), a new class of scorpionate ligands, are reported herein. [RuCl(bdmpza)(η⁴-1,5-cyclooctadiene)] (1) was found to be a versatile precursor to synthesize a wide range of new ruthenium(II) complexes with the bdmpza ligand. The treatment of 1 with pyridine (py), diphenylphosphinoethane (dppe), 2,2′-bipyridyl (bpy), 1,10-phenanethroline (phen), or bispicolylamine (Hbpica) in refluxing N,N-dimethylformamide resulted in displacement of the 1,5-cyclooctadiene ligand to afford [RuCl(bdmpza)(py)₂] (2), [RuCl(bdmpza)(dppe)] (3), [RuCl(bdmpza)(bpy)] (4), [RuCl(bdmpza)(phen)] (5), and [Ru(bdmpza)(Hbpica)]Cl (6Cl) in good yields, respectively. The structures of 1-4, and 6 were determined by X-ray structure analyses.

Full text of DOI:10.1016/j.poly.2010.01.016

Polyhedron 29 (2010) 1508–1514
Contents lists available at ScienceDirect
Polyhedron
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Synthesis and structural characterization of novel ruthenium(II) complexes
featuring an N,N,O-scorpionate ligand: A versatile synthetic precursor for open-face
scorpionatoruthenium(II) complexes
Akira Yogi a, Jae-Hwan Oh a, Takanori Nishioka b, Rika Tanaka c, Eiji Asato a,
Isamu Kinoshita b, Satoshi Takara a,
*
a Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
b Division of Molecular Materials Science, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
c X-ray Structural Analysis Laboratory, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The syntheses and characterization of novel ruthenium(II) complexes containing bis(3,5-dim-
ethylpyrazol-1-yl)acetato (bdmpza), a new class of scorpionate ligands, are reported herein. [RuCl(bdmp-
Received 26 October 2009
Accepted 13 January 2010
Available online 22 January 2010
za)(g
4-1,5-cyclooctadiene)] (1) was found to be a versatile precursor to synthesize a wide range of new
ruthenium(II) complexes with the bdmpza ligand. The treatment of 1 with pyridine (py), diphenylphos-
phinoethane (dppe), 2,20-bipyridyl (bpy), 1,10-phenanethroline (phen), or bispicolylamine (Hbpica) in
refluxing N,N-dimethylformamide resulted in displacement of the 1,5-cyclooctadiene ligand to afford
[RuCl(bdmpza)(py)2] (2), [RuCl(bdmpza)(dppe)] (3), [RuCl(bdmpza)(bpy)] (4), [RuCl(bdmpza)(phen)]
(5), and [Ru(bdmpza)(Hbpica)]Cl (6Cl) in good yields, respectively. The structures of 1–4, and 6 were
determined by X-ray structure analyses.
Keywords:
N,N,O-scorpionate ligand
Ru(II) complex
Ligand substitution
Crystal Structure
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
lyst precursors for polymerization catalysis [6b]. Burzlaff and co-
workers reported their iron(II) and zinc(II) complexes to mimic
The metal complexes bearing monoanionic terdentate fac-type
ligands such as tris(pyrazol-1-yl)borato, HBðpzÞꢀ3 (Tp) [1], and
the structural motif ‘‘facial 2-His-1-carboxylate triad” found in
metalloenzymes [6k,6f–g]. However, ruthenium complexes featur-
ing the N,N,O-scorpionate ligands are rather underdeveloped [7]. In
order to extend the chemistry of mononuclear ruthenium com-
plexes of the N,N,O-scorpionate ligands we describe the synthesis
and characterization of the neutral complex of [RuCl(bdmp-
ꢀ
g
5-C5R5 (Cp, R = H; Cp , R = Me) [2]
*
cyclopentadienyl derivatives,
have been prominently studied in inorganic and organometallic
chemistry because of their rich chemistry (Fig. 1). It has been
widely recognized that the properties of the complexes bearing
these ligands are considerably distinct in several cases [3]. In addi-
tion, a new class of this ligand type, the N,N,O-scorpionates,
bis(pyrazol-1-yl)acetato (bpza) and bis(3,5-dimethylpyrazol-1-
yl)acetato (bdmpza), has been introduced by Otero and his team
in 1999 [4]. Recently Burzlaff and co-workers reported a simple
and convenient synthetic method for Hbdmpza in 2001 [5].
za)(g
4-cod)] (1) (cod = 1,5-cyclooctadiene); a versatile starting
material which allows for a new synthetic route to a wide variety
of ruthenium(II) complexes featuring the bdmpza ligand. A series
of new ruthenium(II) complexes of the types [RuCl(bdmpza)(L1)2],
[RuCl(bdmpza)(L2)], and [Ru(bdmpza)(L3)]Cl (L1(monoden-
tate) = pyridine (py), (2); L2 (bidentate) = 1,2-diphenylphosphino-
ethane (dppe), (3); L2 = 2,20-bipyridyl (bpy), (4); L2 = 1,10-
phenanethroline (phen), (5); L3 (terdentate) = bispicolylamine
(Hbpica), (6) is also reported.
*
The bpza and bdmpza ligands are isoelectronic to Tp, Cp, or Cp
but exhibit different binding properties and trans influences due to
the carboxylate group, a less bulky and weaker -donor. It is of
r
particular interest to survey the complexes of bpza and bdmpza
for comparison. Thus, the chemistry of transition-metal complexes
of bpza or bdmpza has been the subject of increasing attention
[6,7]. Otero synthesized a series of titanium, zirconium, and nio-
bium complexes to develop new ‘‘single site” group 4 and 5 cata-
2. Experimental
2.1. General
The synthesis and manipulation of all metal complexes were
performed under an inert atmosphere of argon using standard
Schlenk techniques unless otherwise stated. Diethyl ether was
* Corresponding author. Tel.: +81 98 895 8535; fax: +81 98 895 8565.
E-mail address: stakara@sci.u-ryukyu.ac.jp (S. Takara).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.01.016

A. Yogi et al. / Polyhedron 29 (2010) 1508–1514
1509
or SHELX97 [13] for 4ꢁ0.5 H2O and refined with crystals [14] using
CRYSTALSTRUCTURE 3.8 [15] as a graphical interface. All non-hydrogen
atoms were refined anisotropically. All hydrogen atoms were lo-
cated on calculated positions and refined as riding models.
2.3. Synthesis
2.3.1. Synthesis of [RuCl(bdmpza)(
g
4-cod)] (1)
4-cod)]n (100 mg, 0.36 mmol)
A brown suspension of [RuCl2(
g
and Hbdmpza (177 mg, 0.71 mmol) in absolute ethanol (10 mL)
was refluxed for 21 h. Insoluble materials were filtered off and
the solvent was removed in vacuo to produce orange crystalline
solids. The solids were dissolved in MeOH and allowed to stand
for 1 day at room temperature to afford 1. Yield: 70 mg (20%). Anal.
Calc. for C20H27ClN4O2Ru: C, 48.82; H, 5.53; N, 11.39. Found: C,
48.57; H, 5.24; N, 11.38%. 1H NMR (CDCl3, 500 MHz): d = 6.50 (s,
1H, CH), 5.95 (s, 2H, H4), 5.43 (m, 2H, olefinic H of cod), 4.43 (m,
2H, olefinic H of cod), 2.67 (m, 2H, aliphatic H of cod), 2.58 (m,
2H, aliphatic H of cod), 2.54 (s, 6H, Me5), 2.43 (s, 6H, Me3), 2.19
(m, 2H, aliphatic H of cod), 2.00 (m, 2H, aliphatic H of cod). ESI-
MS (+) CH3CN (m/z) 493 [1 + H+]+.
Fig. 1. Monoanionic terdentate facial-type ligands related to the chemistry
described herein.
distilled from sodium-benzophenone ketyl prior to use. Methanol
and ethanol were distilled over magnesium methoxide and magne-
sium ethoxide, respectively. N,N-dimethylformamide (DMF) was
distilled over BaO. Pyridine, CDCl3 and acetonitrile were dried over
CaH2 and distilled. All solvents used in this study were degassed by
three freeze-pump-thaw cycles. Bis(3,5-dimethylpyrazol-1-yl)ace-
tic acid (Hbdmpza) [5], bispicolylamine (Hbpica) [8], and
2.3.2. Synthesis of [RuCl(bdmpza)(py)2] (2)
[RuCl2(g
4-cod)]n [9] were prepared according to the literature.
A solution of 1 (100 mg, 0.203 mmol) and pyridine (py) (32 mg,
0.406 mmol) in DMF (10 mL) was refluxed for 8 h. The solvent was
removed in vacuo. The obtained orange solids were dissolved in
methanol and allowed to stand for 1 day at room temperature to
afford 2. Yield: 89 mg (81%). Anal. Calc. for C22H25ClN6O2Ru: C,
48.75; H, 4.65; N, 15.51. Found: C, 48.42; H, 4.86; N, 15.26%. 1H
NMR (CDCl3, 500 MHz): d = 9.06 (d, 4H, J = 5.13 Hz, H2py), 7.56 (t,
2H, J = 1.62 Hz, H4py), 7.14 (t, 4H, J = 5.13 Hz, Hp3y), 6.54 (s, 1H, CH),
5.95 (s, 2H, H4), 2.56 (s, 6H, Me5), 1.92 (s, 6H, Me3). ESI-MS (+)
CH3CN (m/z) 543 [2 + H+]+.
All other chemicals were used without further purification unless
noted. 1H and 31P spectra were recorded on a JEOL JNM-Alpha
500 spectrometer. 1H NMR chemical shifts are referenced to resid-
ual solvent resonance or using TMS as an internal standard. 31P
NMR chemical shifts are referenced to external trimethylphosph-
ite. Infrared spectra (cmꢀ1) were recorded on a JASCO FT/IR 800
spectrometer using KBr disks. Elemental analyses were performed
on a J-Science Co., Ltd. JM10 equipped with an auto-sampler at the
Instrumental Research Center, University of the Ryukyus. The elec-
trospray ionization mass spectra were obtained with Waters Quat-
tro micro API by using ESI in positive-ion (PI) mode.
2.3.3. Synthesis of [RuCl(bdmpza)(dppe)] (3)
A solution of 1 (100 mg, 0.203 mmol) and diphenylphosphino-
ethane (dppe) (81 mg, 0.203 mmol) in DMF (10 mL) was refluxed
for 8 h. The solvent was removed in vacuo. The remaining yellow
solids were dissolved in MeOH and allowed to stand for 1 day at
room temperature to afford 3 as yellow crystals. Yield: 130 mg
(84%). Anal. Calc. for C38H39ClN4O2P2Ru: C, 58.35; H, 5.03; N,
7.16%. Found: C, 58.39; H, 4.95; N, 7.33%. 1H NMR (CDCl3,
500 MHz): d = 8.00 (s, 4H, Ph), 7.37–7.11 (m, 16H, Ph), 6.23 (s,
1H, CH), 5.76 (s, 2H, H4), 2.77 (m, 2H, CH2), 2.38 (m, 2H, CH2),
2.33 (s, 6H, Me5), 2.24 (s, 6H, Me3). 13P NMR (CDCl3, 202.3 MHz):
d = 40.0. ESI-MS (+) CH3CN (m/z) 783 [3 + H+]+.
2.2. X-ray crystallography
Crystal data are summarized in Table 2. Each single crystal was
mounted on a glass fiber. Diffraction data were collected on a Rig-
aku AFC7/CCD Mercury diffractometer. The data were integrated,
scaled, sorted, and averaged using CRYSTALCLEAR software [10].
Absorption corrections were applied using Multi Scan method for
1ꢁ(H2O), 3, and 6Clꢁ2H2O or Coppens numerical method for
2ꢁ(H2O)(CH3OH) and 4. The structures were solved using SIR97
[11] for 1ꢁ(H2O), 3, and 6Clꢁ2H2O, SIR92 [12] for 2ꢁ(H2O)(CH3OH),
Table 1
Pertinent bond distances (Å) and angles (°) for 1–4, and 6.
1
2
3
4A
4B
6
a (Å)
b (Å)
c (Å)
d (Å)
e (Å)
f (Å)
h (°)
u (°)
2.146(2)
2.151(2)
2.4095(7)
2.070(4)
2.078(3)
2.4082(8)
2.065(4)
2.101(3)
2.115(2)
87.98(14)
91.42(14)
2.1509(17)
2.1655(17)
2.4131(5)
2.2748(5)
2.2869(5)
2.1128(14)
85.10(7)
2.119(4)
2.110(4)
2.098(4)
2.102(5)
2.3975(15)
2.3962(12)
2.027(4)
2.019(4)
2.019(4)
2.035(4)
2.090(3)
2.103(3)
83.99(16)
85.36(18)
79.12(18)
78.54(19)
2.155(2)
2.105(1)
2.139(2)
2.031(2)
2.045(2)
2.0876(18)
86.04(8)
89.82(8)
2.1178(18)
84.94(8)
81.21(2)

1510
A. Yogi et al. / Polyhedron 29 (2010) 1508–1514
2.3.4. Synthesis of [RuCl(bdmpza)(bpy)] (4)
2H, H5py), 7.06–7.04 (m, 2H, Hp3y), 6.43 (s, 1H, CH), 5.92 (s, 2H, H4),
5.25 (dd, 2H, J = 7.50 Hz, CH2), 4.05 (d, 2H, J = 9.0 Hz, CH2), 2.46
(s, 6H, Me5), 1.93 (s, 6H, Me3). ESI-MS (+) CH3CN (m/z) 549 [6 –
Clꢀ]+.
A solution of 1 (100 mg, 0.203 mmol) and 2,20-bipyridyl (bpy)
(32 mg, 0.203 mmol) in DMF (10 mL) was refluxed for 8 h. The sol-
vent was removed in vacuo to give a purple solid. The product was
recrystallized by layered solvent diffusion of diethyl ether into a
concentrated solution of 4 in MeOH at room temperature. Yield:
91 mg (83%). Anal. Calc. for C22H25ClN6O3Ru (as 4ꢁH2O): C, 47.35;
H, 4.52; N, 15.06. Found: C, 47.15; H, 4.57; N, 14.90%. 1H NMR
(CDCl3, 500 MHz): d = 8.81 (br, 2H, H3py)), 8.07 (d, 2H, J = 7.56 Hz,
H6py)), 7.63 (t, 2H, J = 8.10 Hz, Hp5y)) 7.26 (m, 2H, Hp4y)), 6.56 (s, 1H,
CH), 6.14 (s, 2H, H4), 2.69 (s, 6H, Me5), 2.59 (s, 6H, Me3). ESI-MS
(+) CH3CN (m/z) 541 [4 + H+]+.
3. Results and discussion
3.1. Synthesis and structure of [RuCl(bdmpza)(g
4-cod)] (1)
[RuCl(bdmpza)(g
4-cod)] (1) was successfully obtained by the
reaction of Hbdmpza with [RuCl2(
4-cod)]n in ethanol. Complex
g
1 is stable to air and moisture in both the solid state and in solu-
tion. A mas (COOꢀ) absorption was observed at 1671 cmꢀ1 in the
IR spectrum (KBr). The two pyrazolyl groups in 1 are equivalent
showing only one set of signals in the 1H NMR spectrum: d = 5.95
(s, 2H, H4), 2.54 (s, 6H, Me5), and 2.43 (s, 6H, Me3). The structure
of 1 was unequivocally determined by X-ray crystallography as de-
picted in Fig. 2 along with the selected bond lengths and angles. A
water molecule (not shown in Fig. 2) is bound by hydrogen-bond-
ing to O1 with a distance of 2.798 Å. The Cl ligand is trans to the
carboxylate group. The complex is approximately octahedral with
respect to Ru. The cod ligand coordinates to Ru with the average
Ru–C distance of 2.223(15) Å, no significant difference with that
2.3.5. Synthesis of [RuCl(bdmpza)(phen)] (5)
A solution of 1 (100 mg, 0.203 mmol) and 1,10-phenanethroline
(phen) (40 mg, 0.203 mmol) in DMF (10 mL) was refluxed for 20 h.
Removal of the solvent in vacuo afforded deep purple solids which
were dissolved in MeOH followed by Et2O diffusion at room tem-
perature to generate 5 as deep purple crystals. Yield: 103 mg
(90%). Anal. Calc. for C24H27ClN6O4Ru (as 5ꢁ2H2O): C, 48.04; H,
4.54; N, 14.01%. Found: C, 48.30; H, 4.43; N, 14.03%. 1H NMR
(CDCl3, 500 MHz): d = 9.35 (d, 2H, J = 5.67 Hz, H2phen), 8.13 (d, 2H,
J = 7.29 Hz, Hp4hen), 7.89 (s, 2H, Hp6hen), 7.59 (q, 2H, H3phen), 6.54 (s,
1H, CH), 6.21 (s, 2H, H4), 2.81 (s, 6H, Me5), 2.57 (s, 6H, Me3). ESI-
MS (+) CH3CN (m/z) 565 [5 + H+]+.
of [RuBrTp(g
4-cod)] (Ru–C, 2.213(2) Å) [16]. Note that two of
methylene groups (C19 and C20) of the cod ligand were disordered
and atoms with higher occupancies are shown in the figure. The
average Ru–N distance is 2.149(3) Å while the Ru1–Cl1 and Ru1–
O2 distances are 2.4095(7) Å and 2.1177(18) Å, respectively. The
angles N2–Ru1–O2, N4–Ru1–O2, N(2)–Ru1–Cl1, and N4–Ru1–Cl1
are, 84.94(8)°, 86.36(8)°, 83.33(7)°, 86.59(6)°, and 85.61(6)°,
respectively, which are slightly distorted from 90°. The Cl1–Ru1–
O2 angle is 166.28(5)°.
2.3.6. Synthesis of [Ru(bdmpza)(Hbpica)]Cl (6Cl)
A solution of 1 (100 mg, 0.203 mmol) and bispicolylamine
(Hbpica) (40.4 mg, 0.203 mmol) in DMF (10 mL) was refluxed for
12 h. The solvent was removed in vacuo. The isolated solid was dis-
solved in MeOH and followed by diffusion of diethyl ether yielded
brown crystals suitable for X-ray analysis. Yield: 61 mg (49%). Anal.
Calc. for C24H32ClN7O4Ru (as 6Clꢂ2H2O): C, 46.56; H, 5.21; N, 15.84.
Found: C, 46.82; H, 5.28; N, 15.75%. 1H NMR (CDCl3, 500 MHz):
d = 8.96 (d, 2H, J = 2.97 Hz, H2py), 7.54 (m, 2H, Hp4y), 7.26–7.23 (m,
Complex 1 is a versatile precursor to obtain a wide range of
ruthenium(II) complexes of the bdmpza ligand as discussed vide
infra.
Table 2
XRD experimental details.
1ꢁ(H2O)
2ꢁ(H2O)(CH3OH)
3
4ꢁ0.5 H2O
6Clꢁ2H2O
Formula
Formula weight
T (K)
C20H29ClN4O3Ru
509.99
200(2)
C23H31ClN6O4Ru
592.06
193(2)
C38H39ClN4O2P2Ru
782.19
200(2)
C22H24ClN6O2.5Ru
548.99
200(2)
C24H32ClN7O4Ru
619.08
200(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
13.445(2)
11.2466(14)
15.666(2)
90
113.626(4)
90
2170.3(5)
0.30 ꢃ 0.30 ꢃ 0.17
4
triclinic
monoclinic
P21/n
7.8530(3)
25.4696(10)
17.7904(7)
90
93.8644(18)
90
3550.2(2)
0.38 ꢃ 0.20 ꢃ 0.20
4
triclinic
monoclinic
P21/n
11.2600(17)
17.440(3)
13.410(2)
90
95.600(3)
90
2620.8(7)
0.25 ꢃ 0.10 ꢃ 0.05
4
ꢀ
ꢀ
P1
P1
8.3315(8)
10.2038(9)
16.703(2)
97.056(10)
101.007(12)
112.831(9)
1253.8(2)
0.35 ꢃ 0.15 ꢃ 0.05
2
10.1339(16)
14.9377(18)
16.296(3)
71.536(9)
87.762(13)
74.603(10)
2253.2(6)
0.30 ꢃ 0.10 ꢃ 0.03
4
a
(°)
b (°)
c
(°)
V (Å3)
Crystal size
Z
Dcalc (g cmꢀ3
)
1.561
8.740
1.568
7.736
1.463
6.470
1.618
8.495
1.569
7.450
l
(cmꢀ1
)
Maximum and minimum
transmission
0.8656 and 0.7795
0.962 and 0.821
0.8815 and 0.7911
0.975 and 0.831
0.805 and 0.963
Reflections collected
Independent reflections
20 664
4929 (0.032)
12 086
5368 (0.029)
26 612
7787 (0.0231)
22 043
9720 (0.056)
25 137
5896 (0.054)
(Rint
)
Data/parameter
4929/380
5368/347
7787/440
9720/634
5896/462
Final R indicates [I > 2
r
(I)]
R1 = 0.0374, wR2 (all
data) = 0.0845a
1.000
R1 = 0.0483, wR2 (all
data) = 0.1480a
1.002
R1 = 0.0302,wR2 (all
data) = 0.0692a
1.000
R1 = 0.0566wR2 (all
data) = 0.1111a
1.005
R1 = 0.0330,wR2 (all
data) = 0.0741a
1.013
Goodness –of-fit (GOF) on
F2
Largest difference peak and 0.664 and ꢀ0.567
1.96 and ꢀ1.16
0.410 and ꢀ0.609
2.19 and ꢀ1.78
0.71 and ꢀ0.75
hole (eAꢀ3
)
P
P
2
2 1=2
wR2 ¼ ½ ðwðF20 ꢀ Fc2Þ Þ= wðF20Þ ꢄ
.
a

A. Yogi et al. / Polyhedron 29 (2010) 1508–1514
1511
Treatment of 1 with two equivalents of pyridine in refluxing
DMF produced 2. Fig. 3 shows the structure of 2 in which the
geometry around the Ru is octahedral and two pyridine ligands
are positioned trans to the pyrazolyl groups. A mas (COOꢀ) absorp-
tion was observed at 1640 cmꢀ1 in the IR spectrum (KBr).
The two pyridine ligands in 2 are equivalent showing only one
set of signals in the 1H NMR spectrum: d = 9.06 (d, 4H, Hp2y), 7.56
(t, 4H, Hp4y), and 7.14 (t, 4H, Hp3y). The distances of Ru–Npyridine in
2 (Ru1–N5 is 2.101(13) Å and Ru1–N6 is 2.065(4) Å) are signifi-
cantly longer than those in 4 and 6 (see Table 1), indicating two
pyridines coordinate to Ru more weakly.
The reaction of 1 with one equivalent of dppe gave 3 in 84%
yield. The structure of 3 is shown in Fig. 4. The geometry around
Ru is approximately octahedral and the Cl ligand positioned trans
to the carboxylato group. A mas (COOꢀ) absorption was observed
at 1657 cmꢀ1 in the IR spectrum (KBr).
Fig. 2. Perspective view of [RuCl(bdmpza)(g
4-cod)] (1). Hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles (°): Ru1–O2, 2.1177(18);
Ru1–N2, 2.146(2); Ru1–N4, 2.151(2); Ru1–C13, 2.229(3); Ru1–C14, 2.201(3); Ru1–
C17, 2.218(3); Ru1–C18, 2.242(3); Ru1–Cl1, 2.4095(7); Cl1–Ru1–O1, 166.28(5); N2–
Ru1–N4, 84.94(8).
3.2. Reactivity of complex 1 towards N- or P-donor ligands: Synthesis
and characterization of [RuCl(bdmpza)(L1)2], [RuCl(bdmpza)(L2)], or
[Ru(bdmpza)(L3)]Cl (L1 = py, 2; L2 = dppe, 3; bpy, 4; phen, 5;
L3 = Hbpica, 6)
The cod ligand in 1 can be replaced with other ligands. Reac-
tions of 1 with L1 (monodentate), L2 (bidentate), or L3 (terdentate)
such as py, dppe, bpy, phen, or Hbpica in refluxing DMF produced
2–6 in good yield, respectively. Complexes 2–6 are also stable to air
and moisture in both the solid state in solution. Kirchner et al. re-
ported that the reactions of [RuClTp(g
4-cod)] with Ph2PCH2PPh2
(dppm), Ph2PCH2CH2NMe2 (pn), Me2NCH2CH2NMe2 (tmeda), py,
or 3-methylpyridine (3-Mepy) in refluxing DMF generated two
types of [RuClTp(L1)2] or [RuClTp(L2)] complexes [16]. As de-
scribed by Kirchner, the replacement of the cod ligand in 1 is also
substitutionally rather inert due to the presence of the bdmpza li-
gand, contrasting sharply to the case of the Cp-type ligands [17]
(see Scheme 1).
The molecular structures of 2–4, and 6 were determined by X-
ray crystallography. (The pertinent bond distances and angles are
summarized in Table 1, and the crystallographic information is in
Table 2.) Structural data were further provided by NMR and IR
spectroscopy, elemental analysis, and electrospray ionization
(ESI) mass spectrometry.
Fig. 3. Perspective view of [RuCl(bdmpza)(py)2] (2). Hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles (°): Ru1–O1, 2.115(2);
Ru1–N2, 2.078(3); Ru1–N4, 2.070(4); Ru1–N5, 2.101(3); Ru1–N6, 2.065(4); Ru1–
Cl1, 2.4082(8). Cl1–Ru1–O1, 177.61(5); N2–Ru1–N4, 87.98(14); N5–Ru1–N6,
91.42(14).
Scheme 1. Summary of the reactions to prepare complexes 2–6. Reagents and conditions: (a) 2 equiv of pyridine, DMF, reflux for 8 h, yield 81%; (b) 1 equiv of
diphenylphosphinoethane (dppe), DMF, reflux for 8 h, yield 84%; (c) 1 equiv. of 2,2’-bipyridyl (bpy), DMF, reflux for 8 h, yield 83%; (d) 1 equiv. of 1,10-phenanethroline (phen),
DMF, reflux for 20 h, yield 90%; (e) 1 equiv. of bispicolylamine (Hbpica), DMF, reflux for 12 h, yield 49%.

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A. Yogi et al. / Polyhedron 29 (2010) 1508–1514
one of them, 4A is depicted in Fig. 6. The bpy ligand binds to Ru
in a bidentate fashion and resides trans to the two pyrazolyl
groups. The bite angles of the bpy ligand in 4A and 4B are
79.12(18) Å and 78.54(19) Å, respectively. The overall geometry
about the Ru center can be described as a slightly distorted octahe-
dral in both 4A and 4B. As expected, distances of Ru–Npyridyl
(2.019(4) Å, 2.027(4) Å in 4A and 2.035(4) Å, 2.019(4) Å in 4B) in
4 are significantly shorter than those in 2 and 6. This may be
caused by synergistic bonding between Ru(II) t2g orbitals and the
*
p
orbitals in the planar bpy ligand. The crystallographic results
are consistent with the 1H NMR data: the two pyrazolyl groups
in 4 are equivalent showing only one set of signals at d = 6.14,
2.69 and 2.59. In addition, the signals at d = 8.81, 8.12, 7.63, and
7.26 are assigned to the bpy ligand. A mas (COOꢀ) absorption was
observed at 1655 cmꢀ1 in the IR spectrum (KBr).
The complex 5 was obtained in 82% yield by the reaction of 1
and phen, thoroughly characterized by NMR, IR spectroscopy, ele-
mental analysis, and ESI-mass spectrometry. The two pyrazolyl
groups in 5 are also equivalent because only one set of signals at
d = 6.21, 2.81, and 2.57 was observed in the 1H NMR spectrum. In
addition, the signals at d = 9.35, 8.13, 7.89, and 7.59 are attributed
to the phen ligand indicating that the phen ligand coordinates to
the Ru center in a bidentate fashion similar to the bpy in 4. A mas
(COOꢀ) absorption was observed at 1660 cmꢀ1 in the IR spectrum
(KBr). It is concluded that the structure of 5 is essentially identical
with that of 4.
Shown in Fig. 7 is the structure of 6, which has a distorted octa-
hedral geometry around the Ru center with bdmpza and Hbpica
acting as a terdentate ligand in a facial arrangement. A mas (COOꢀ)
absorption was observed at 1620 cmꢀ1 in the IR spectrum (KBr).
The number of reports on Ru(II) complexes bearing Hbpica is sur-
prisingly limited, to the best of our knowledge, there are only two
previous reports [18]. The Ru–Namino distance (2.139(2) Å) is longer
than the distances of Ru–Npyridine (2.045(2) and 2.031(2) Å) which
are relatively shorter than those in 2 with the pyridine ligand
(Ru1–N5 is 2.101(13) Å and Ru1–N6 is 2.065(4) Å). The 1H NMR
spectrum of 6Cl indicated that the pyridyl groups are equivalent.
One of the diastereotopic methylene protons appeared as a doublet
of doublets centered at d = 5.25 (two protons) due to a coupling
with an NH proton and a doublet at d = 4.05 (two protons). A broad
singlet at d = 8.13 was assigned to the NH proton because this sig-
nal was not observed after the treatment of the solution of 6Cl in
Fig. 4. Perspective view of [RuCl(bdmpza)(dppe)] (3). Hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles(°): Ru1–O2, 2.1128(14);
Ru1–2, 2.1655(17); Ru1–N4, 2.1509(17); Ru1–P1, 2.2748(5); Ru1–P2, 2.2869(5);
Ru1–Cl1, 2.4131(5), Cl1–Ru1–O2, 171.60(4); N2–Ru1–N4, 85.10(7); P1–Ru1–P2,
81.21(2).
The Ru1–Cl1 and Ru1–O2 distances are 2.4131(5) Å and
2.1128(14) Å, respectively. The Ru–P distances in 3 are 2.2748(5)
Å and 2.2869(5) Å. The Ru–N distances are 2.166(2) Å and
2.151(2) Å, longer than those of 1, due to the trans influence of
dppe. In [RuCl(bdmpza)(PPh3)2] (Fig. 5), the two PPh3 ligands re-
side trans to the pyrazolyl group with the Ru–P distances of
2.3555(17) Å and 2.3688(18) Å and with the Ru–N distances of
2.199(4) Å and 2.173(4) Å. Thus, the Ru–P and Ru–N distances in
3 are appreciably shorter than those of [RuCl(bdmpza)(PPh3)2]
[7a]. It is noteworthy to point out that, as mentioned above, 3 is
stable to air and moisture in both the solid state and in solution,
while [RuCl(bdmpza)(PPh3)2] is rather sensitive due to the steric
hindrance of the two PPh3 groups residing trans to the dimethylpy-
razolyl groups [7a]. In the analogous complex [RuCl(bpza)(PPh3)2],
(Fig. 5) in which bpza is less sterically hindered, one PPh3 resides
trans to the carboxylato group, the Ru–P (trans to the carboxylato
group) and Ru–N (trans to Cl) distances are 2.360(3) Å and
2.100(6) Å, respectively. The remaining Ru–P and Ru–N distances
are 2.378(4) Å and 2.157(6) Å, respectively.
CDCl3 in a NMR tube with one drop of D2O. A m(NH) and absorption
was observed at 2900 cmꢀ1 in the IR spectrum.
4. Conclusion
A novel ruthenium(II) complex [RuCl(bdmpza)(g
4-1,5-cyclo-
The complex 1 reacted with one equivalent of bpy in refluxing
DMF to afford 4 in 83% yield. The asymmetric unit contains two
crystallographic independent molecules (4A and 4B). As they are
not significantly different in terms of bond distances and angles,
octadiene)] (1) with a N,N,O-scorpionate ligand was synthesized
and fully characterized. Complex 1 is a promising precursor for
the formation of a number of new ruthenium(II) complexes with
the bdmpza ligand.
Fig. 5. Molecular structures of 3 (this work), [RuCl(bdmpza)(PPh3)2], and [RuCl(bpza)Cl(PPh3)2].

A. Yogi et al. / Polyhedron 29 (2010) 1508–1514
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tre, 12 Union Road, Cambridge, CB2 1EZ, UK; Fax: +44 1223
336033; email: deposit@ccdc.cam.ac.uk).
Acknowledgments
The authors would like to thank the University of the Ryukyus.
J.-H. O. acknowledges the Japan-Korea Joint Exchange Program. Mr.
Takayuki Nakasone, Mr. Genta Koja, Mr. Kazuto Asato (Department
of Chemistry, Biology and Marine Science, University of the Ryu-
kyus), Ms. Kiyoko Ikehara and Mr. Shin-ichi Gima (Instrumental
Research Center, University of the Ryukyus) are gratefully
acknowledged for their assistance in this work. The drawing of a
scorpion in the Graphical Abstract is by courtesy of Mr. Satoshi
Tamashiro. The authors thank Ms. Janice A. Kunishige (Department
of Chemistry, University of Hawai’i at Manoa) for reviewing the
¯
manuscript.
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