Mononuclear ruthenium(II) complexes bearing the (S,S)-iPr-pybox ligand

Article abstract of DOI:10.1016/j.jorganchem.2011.02.025

The complexes trans-[RuCl₂(L){(S,S)-ⁱPr-pybox}] ((S,S)-ⁱPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′- yl]pyridine, L = PMe₃ (1), P(OMe)₃ (2), PPh ₂(CH₂CHCH₂) (3), CNBn (5), CNCy (6) and MeCN (7)) have been synthesized by substitution of ethylene on the precursor trans-[RuCl₂(η²-C₂H₄){(S,S)- ⁱPr-pybox}]. This complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF₆, in refluxing methanol, giving the coordination compounds [RuCl(η⁴-cod){(S,S)-ⁱPr-pybox}] [PF₆] (8) and [RuCl(η⁴-nbd){(S,S)-ⁱPr- pybox}][PF₆] (9). The structures of complexes [RuCl(CO)(PPh ₃)(H-pybox)][BF₄] (H-pybox = 2,6-bis(dihydrooxazolin- 2′-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.

Full text of DOI:10.1016/j.jorganchem.2011.02.025

Journal of Organometallic Chemistry 696 (2011) 1861e1867
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Mononuclear ruthenium(II) complexes bearing the (S,S)-iPr-pybox ligand
*
Darío Cuervo, Estefanía Menéndez-Pedregal, Josefina Díez, M. Pilar Gamasa
Departamento de Química Orgánica e Inorgánica, Instituto de Química Organometálica “Enrique Moles” (Unidad Asociada al CSIC), Universidad de Oviedo, 33006 Oviedo, Spain
a r t i c l e i n f o
a b s t r a c t
The complexes trans-[RuCl2(L){(S,S)-iPr-pybox}] ((S,S)-iPr-pybox ¼ 2,6-bis[40-(S)-isopropyloxazolin-20-yl]
pyridine, L ¼ PMe3 (1), P(OMe)3 (2), PPh2(CH2CH]CH2) (3), CNBn (5), CNCy (6) and MeCN (7)) have been
Article history:
Received 17 December 2010
Received in revised form
21 February 2011
synthesized by substitution of ethylene on the precursor trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}]. This
complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF6, in refluxing methanol,
Accepted 22 February 2011
giving the coordination compounds [RuCl(
h
4-cod){(S,S)-iPr-pybox}][PF6] (8) and [RuCl( 4-nbd){(S,S)-iPr-
h
pybox}][PF6] (9). The structures of complexes [RuCl(CO)(PPh3)(H-pybox)][BF4] (H-pybox ¼ 2,6-bis(dihy-
drooxazolin-20-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic
activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Ruthenium/Pybox
Complexes/Cyclooctadiene
Norbornadiene complexes/Phosphine
ligands/Isocyanide ligands
1. Introduction
without further purification. Solvents were dried by standard
methods and distilled under nitrogen before use. The compounds
A number of enantiopure rutheniumepybox complexes have
been synthesized during the last two decades and some of them
have been demonstrated useful in several catalytic enantioselective
transformations [1e3]. In particular, some of these complexes are
efficient catalysts for the enantioselective cyclopropanation of
olefins [2a], epoxidation of olefins [2b], and CeH amination [2c].
Moreover, we have reported [3] that ruthenium complexes trans-
and cis-[RuCl2(L){(R,R)-Ph-pybox}] (L ¼ phosphine or phosphite)
catalyze the asymmetric transfer hydrogenation of aromatic ketones
with up to 94% ee and very high TOF. On the ground of these finding,
we became interested in exploring the synthesis of new ruthenium
(II)-pybox complexes with potential capability to act as catalysts.
Therefore, herein the synthesis of ruthenium(II) complexes con-
taining the enantiopure (S,S)-iPr-pybox ligand is reported.
trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] [2a], trans-[RuCl2(PPh3)
(H-pybox)] [4] and the phosphine PPh2CH2CH]CH2 [5] were
prepared by reported methods. Infrared spectra were recorded on
a PerkineElmer 1720-XFT spectrometer. The conductivities were
measured at room temperature, in ca. 10ꢀ4 mol dmꢀ3 acetone
solutions, with a Jenway PCM3 conductimeter. The C, H, N analyses
were carried out with LECO CHNS-TruSpec and PerkineElmer 240-
B microanalyzers. Electrospray mass spectra (ESI-MS) were recor-
ded on a Bruker Esquire 6000 instrument, operating in the positive
mode and using methanol solutions. NMR spectra were recorded
on a Bruker DPX-300 spectrometer operating at 300.13 (1H), 75.48
(
13C) and 121.49 (31P) MHz and using SiMe4 or 85% H3PO4 as
standards. DEPT experiments have been carried out for all the
complexes. Coupling constants J are given in hertz. The following
atom labels have been used for the 1H and 13C{1H} spectroscopic
data of the pybox ligand.
2. Experimental
4
2.1. General procedures
5
6
3
2
The reactions were performed under an atmosphere of dry
nitrogen using vacuum-line and standard Schlenk techniques. The
reagents were obtained from commercial suppliers and used
O
O
2´
N
5´
N
N
4´
i
i
Pr
Pr
* Corresponding author. Fax: þ34 985103446.
E-mail address: pgb@uniovi.es (M.P. Gamasa).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.02.025

1862
D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
2.2. Synthesis of complexes trans-[RuCl2(L){(S,S)-iPr-pybox}]
(L ¼ PMe3 (1), P(OMe)3 (2))
suspension was then filtered and the resulting solution was
concentrated to ca. 3 mL. Afterwards, a mixture of hexane/diethyl
ether (2:1, 30 mL) was added yielding a dark pink solid which was
washed with hexane/diethyl ether (2:1, 2 ꢂ 30 mL) and vacuum
dried. Yield 95% (0.069 g). Anal. Calc. for C30H26BClF4N3O3PRu: C,
49.30; H, 3.59; N, 5.75. Found: C, 49.50; H, 3.45; N, 5.85. Conduc-
tivity (acetone, 20 ꢁC, Uꢀ1 cm2 molꢀ1): 100. IR (KBr, cmꢀ1): v(CO)
A solution of complex trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}]
(0.150 g, 0.3 mmol) and trimethylphosphine or trimethylphosphite
(1.5 mmol) in dichloromethane (10 mL) was stirred at room
temperature for 5 h (for PMe3) or heated at 40 ꢁC for 1 h (for P
(OMe)3). The solvent was then concentrated to ca. 3 mL and the
residue transferred to a silica gel chromatography column. Elution
with a mixture of dichloromethane/methanol (50:1) gave a purple
(for 1) or dark pink band (for 2) from which complexes 1 and 2 were
isolated by solvent removal.
1984 (s), v(BF4ꢀ) 1057 (s). 31P{1H} NMR (CD2Cl2, 298 K):
d 36.2 (s).
1H NMR (CD2Cl2, 298 K):
d
8.46 (t, 1H, JHH ¼ 7.8 Hz, H4 C5H3N), 8.19
(d, 2H, JHH ¼ 7.8 Hz, H3,5 C5H3N), 7.95 (m, 6H), 7.56 (m, 7H) and 7.27
(m, 2H) (Ph), 5.81 (br, 1H), 5.37 (m, 1H), 4.93 (m, 4H) and 3.49 (m,
2H) (OCH2, NCH2) ppm. 13C{1H} NMR (CD2Cl2, 298 K):
d 190.3 (d,
Complex 1: Yield 65% (0.107 g). Anal. Calc. for C20H32Cl2N3O2PRu:
2JCP ¼ 15.0 Hz, CO), 169.4 (s, OCN), 146.3 (s, C2,6 C5H3N), 142.5 (s, C4
C5H3N), 134.7e127.7 (Ph and C3,5 C5H3N), 73.5 (s, OCH2), 54.6 (s,
NCH2) ppm.
C, 43.72; H, 5.87; N, 7.65. Found: C, 43.52; H, 5.56; N, 7.45. 31P{1H}
NMR (CDCl3, 298 K): d d 7.73 (s,
1.2 (s) ppm. 1H NMR (CDCl3, 298 K):
3H, H3,4,5 C5H3N), 4.70 (m, 4H, OCH2), 3.95 (m, 2H, CHiPr), 2.20 (m,
2
2H, CHMe2), 1.83 (d, 9H, JHP ¼ 8.2 Hz, PMe3), 0.92 (d, 6H,
2.5. Synthesis of complexes trans-[RuCl2(CNR){(S,S)-iPr-pybox}]
(R ¼ Bn (5), Cy (6))
JHH ¼ 7.1 Hz, CHMe2), 0.70 (d, 6H, JHH ¼ 6.8 Hz, CHMe2) ppm. 13C{1H}
NMR (CDCl3, 298 K):
d
165.1, 165.0 (2s, OCN), 148.1 (s, C2,6 C5H3N),
132.5 (s, C4 C5H3N), 122.5 (s, C3,5 C5H3N), 71.2 (s, CHiPr), 70.8 (s,
OCH2), 28.7 (s, CHMe2), 17.9 (d, JCP ¼ 25.6 Hz, PMe3), 19.1, 14.4 (2s,
CHMe2) ppm.
A solution of trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] (0.060 g,
0.12 mmol) and isocyanide (0.36 mmol) in 10 mL of dichloro-
methane was stirred at room temperature (for 5) or heated under
reflux (for 6). The solvent was then concentrated to ca. 2 mL and
a mixture of diethyl ether/hexane (3:1, 40 mL) was added, yielding
a solid which was washed with diethyl ether (3 ꢂ 10 mL) and
vacuum-dried.
Complex 2: Yield 55% (0.063 g). Anal. Calc. for C20H32Cl2N3O5
-
PRu: C, 40.21; H, 5.40; N, 7.03. Found: C, 40.43; H, 5.74; N, 6.90. 31
P
{1H} NMR (CDCl3, 298 K):
d
d
147.9 (s) ppm. 1H NMR (CDCl3, 298 K):
7.86 (m, 1H, H4 C5H3N), 7.70 (m, 2H, H3,5 C5H3N), 4.69 (m, 4H,
OCH2), 4.09 (m, 2H, CHiPr), 3.92 (d, 9H, JHP ¼ 10.3 Hz, P(OMe)3),
Complex 5: Reaction time: 5.5 h. Color: dark pink. Yield 89%
(0.063 g). Anal. Calc. for C25H30Cl2N4O2Ru: C, 50.85; H, 5.12; N, 9.49.
Found: C, 50.78; H, 4.64; N, 9.23. MS-ESI (MeOH): m/z ¼ 672.2
([RuCl(CNBn)2(iPr-pybox)]þ, 11%), m/z ¼ 555.2 ([RuCl(CNBn)(iPr-
pybox)]þ, 33%). IR (KBr, cmꢀ1): v(C^N) 2098 (s). 1H NMR (CD2Cl2,
3
2.57 (m, 2H, CHMe2), 0.90 (d, 6H, JHH ¼ 6.8 Hz, CHMe2), 0.70 (d, 6H,
JHH ¼ 6.3 Hz, CHMe2) ppm. 13C{1H} NMR (CDCl3, 298 K):
d 164.2,
164.1 (2s, OCN), 147.9 (s, C2,6 C5H3N), 136.2 (s, C4 C5H3N), 122.6 (s,
C3,5 C5H3N), 71.5 (s, CHiPr), 71.1 (s, OCH2), 52.4 (d, JCP ¼ 5.2 Hz, P
2
(OMe)3), 28.0 (s, CHMe2), 19.6, 14.6 (2s, CHMe2) ppm.
298 K): d
7.91 (m,1H, H4 C5H3N), 7.79 (m, 2H, H3,5 C5H3N), 7.69e7.40
(3m, 5H, Ph), 5.42 (s, 2H, CH2Ph), 4.83 (m, 2H, OCH2), 4.72 (m, 2H,
OCH2), 4.15 (m, 2H, CHiPr), 2.51 (m, 2H, CHMe2), 0.90 (d, 6H,
JHH ¼ 7.2 Hz, CHMe2), 0.87 (d, 6H, JHH ¼ 6.8, CHMe2) ppm. 13C{1H}
2.3. Synthesis of complex trans-[RuCl2{PPh2(CH2CH]CH2)}
{(S,S)-iPr-pybox}] (3)
NMR (CD2Cl2, 298 K):
d 166.5 (s, C^NCH2), 164.1 (s, OCN), 148.3 (s,
A solution of complex trans-[RuCl2(
h
2-C2H4){(S,S)-iPr-pybox}]
C2,6 C5H3N), 135.4 (s, C4 C5H3N), 135.0 (s, Cipso of Ph), 128.9 (s, C3,5
Ph), 128.0 (s, C4 Ph), 126.8 (s, C2,6 Ph), 122.3 (s, C3,5 C5H3N), 71.8 (s,
OCH2), 70.9 (s, CHiPr), 48.7 (s, CH2Ph), 29.6 (s, CHMe2), 18.9,15.2 (2s,
CHMe2) ppm.
(0.150 g, 0.3 mmol) and allyldiphenylphosphine (0.060 mL,
0.6 mmol) in dichloromethane (25 mL) was heated at 50 ꢁC in
a sealed tube over 6 h. The solution was then concentrated to ca.
3 mL and a mixture of pentane/diethyl ether (2:1, 50 mL) was
added, yielding a purple solid which was washed with diethyl ether
(3 ꢂ 30 mL) and vacuum-dried. Yield 76% (0.159 g). Anal. Calc. for
C32H38Cl2N3O2PRu: C, 54.94; H, 5.47; N, 6.01. Found: C, 54.84; H,
5.34; N, 5.91. MS-ESI (MeOH): m/z ¼ 664.1 ([RuCl{PPh2(C3H5)}(iPr-
pybox)]þ, 100%), m/z ¼ 628.1 ([Ru{PPh2(C3H5)}(iPr-pybox)]þ, 76%).
Complex 6: Reaction time: 3.5 h. Color: Purple. Yield 83%
(0.058 g). Anal. Calc. for C24H34Cl2N4O2Ru: C, 49.48; H, 5.88; N, 9.62.
Found: C, 49.15; H, 5.57; N, 9.44. MS-ESI (MeOH): m/z ¼ 656.2
([RuCl(CNCy)2(iPr-pybox)]þ, 41%), m/z ¼ 547.2 ([RuCl(CNCy)(iPr-
pybox)]þ, 92%). IR (KBr, cmꢀ1): v(C^N) 2114 (s). 1H NMR (CD2Cl2,
298 K): d
7.87 (m, 1H, H4 C5H3N), 7.77 (m, 2H, H3,5 C5H3N), 4.84 (m,
31P{1H} NMR (CDCl3, 298 K):
d
23.0 (s) ppm. 1H NMR (CDCl3, 298 K):
2H, OCH2), 4.74 (m, 2H, OCH2), 4.37 (m, 1H, CH Cy), 4.19 (m, 2H,
CHiPr), 2.63 (m, 2H, CHMe2), 2.06 (m, 6H, Cy), 1.57 (m, 4H, Cy), 1.04
(d, 6H, JHH ¼ 7.2 Hz, CHMe2), 0.92 (d, 6H, JHH ¼ 6.4 Hz, CHMe2) ppm.
d
8.19e8.08 (m, 3H), 7.87e7.79 (m, 3H) and 7.47e7.35 (m, 7H) (Ph
and H3,4,5 C5H3N), 6.09 (m, 1H, CH]CH2), 5.19e5.07 (m, 2H,
CH2CH]CH2), 4.59 (m, 4H, OCH2), 4.03 (m, 1H, CH2CH]CH2), 3.80
(m,1H, CH2CH]CH2), 3.54 (m, 2H, CHiPr),1.55 (m, 2H, CHMe2), 0.55
(d, 6H, JHH ¼ 6.6 Hz, CHMe2), 0.39 (d, 6H, JHH ¼ 7.2 Hz, CHMe2) ppm.
13C{1H} NMR (CD2Cl2, 298 K):
d 164.2 (s, OCN), 162.8 (s, C^NCH),
148.5 (s, C2,6 C5H3N), 134.8 (s, C4 C5H3N), 122.1 (s, C3,5 C5H3N), 71.8
(s, OCH2), 71.0 (s, CHiPr), 54.7 (s, CH Cy), 33.6 (s, CH2 Cy), 29.7 (s,
CHMe2), 25.4, 22.7 (2s, CH2 Cy), 19.0, 15.3 (2s, CHMe2) ppm.
13C{1H} NMR (CDCl3, 298 K):
d
165.5, 165.4 (2s, OCN), 149.4 (s, C2,6
C5H3N), 139.0 (d, JCP ¼ 31.8 Hz, Cipso Ph), 137.1 (d, JCP ¼ 32.3 Hz, Cipso
Ph), 134.2e133.4 and 129.5e128.2 (Ph, C4 C5H3N and CH]CH2),
2.6. Synthesis of complex trans-[RuCl2(MeCN){(S,S)-iPr-pybox}] (7)
3
122.8 (s, C3,5 C5H3N), 117.8 (d, JCP ¼ 8.9 Hz, CH]CH2), 70.5 (s,
OCH2), 70.0 (s, CHiPr), 33.1 (d, JCP ¼ 22.9 Hz, PCH2), 28.1 (s, CHMe2),
18.9, 14.5 (2s, CHMe2) ppm.
A solution of trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] (0.060 g,
0.12 mmol) and acetonitrile (0.038, 0.72 mmol) in dichloromethane
(10 mL) was heated at 50 ꢁC for 6 h. The resulting solution was then
concentrated to ca. 2 mL and a diethyl ether/hexane mixture (3:1,
50 mL) was added, yielding a dark purple solid which was washed
with diethyl ether (3 ꢂ 10 mL) and vacuum-dried. Yield 83%
(0.051 g). Anal. Calc. for C19H26Cl2N4O2Ru: C, 44.36; H, 5.09; N,
10.89. Found: C, 44.31, H, 4.68; N, 10.22. MS-ESI (MeOH): m/
z ¼ 514.1 ([RuCl2(MeCN)(iPr-pybox)]þ, 74%), m/z ¼ 479.2 ([RuCl
2.4. Synthesis of complex [RuCl(CO)(PPh3)(H-pybox)][BF4] (4)
A solution of complex trans-[RuCl2(PPh3)(H-pybox)] (0.065 g,
0.1 mmol) and silver tetrafluoroborate (0.026 mg, 0.12 mmol) in
dichloromethane (5 mL) was stirred in the dark, at room temper-
ature, for 1 h under an atmosphere of carbon monoxide. The

D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
1863
(MeCN)(iPr-pybox)]þ, 85%), 438.1 ([RuCl(iPr-pybox)]þ, 100%). IR
96.7, 95.4, 92.6, 92.4 (4s, CH cod), 74.2, 72.5, 71.7, 69.3 (4s, OCH2 and
CHiPr), 31.2, 30.9, 30.5, 30.4 (4s, CH2 cod), 29.1, 28.4 (2s, CHMe2),
19.8, 19.4, 14.9, 14.8 (4s, CHMe2) ppm.
(KBr, cmꢀ1): v(C^N) 2273 (w). 1H NMR (CD2Cl2, 298 K):
d 7.69 (m,
2H, C3,5 C5H3N), 7.57 (m, 1H, C4 C5H3N), 4.88 (m, 2H, OCH2), 4.80 (m,
2H, OCH2), 4.31 (m, 2H, CHiPr), 2.80 (s, 3H, NCMe), 2.53 (m, 2H,
CHMe2), 1.07 (d, 6H, JHH ¼ 7.2 Hz, CHMe2), 0.96 (d, 6H, JHH ¼ 6.6 Hz,
Complex 9: Yield 84% (0.114 g). Anal. Calc. for C24H31ClF6N3O2
-
PRu: C, 42.70; H, 4.63; N, 6.22. Found: C, 42.60; H, 4.74; N, 6.02.
CHMe2) ppm. 13C{1H} NMR (CD2Cl2, 298 K):
d
165.5 (s, OCN), 151.5
Conductivity (acetone, 20 ꢁC, ꢀ1 cm2 molꢀ1): 137. IR (KBr, cmꢀ1): v
U
(s, C2,6 C5H3N), 128.3 (s, C4 C5H3N), 128.0 (s, NCMe), 122.5 (s, C3,5
C5H3N), 71.9 (s, OCH2), 70.2 (s, CHiPr), 30.0 (s, CHMe2), 19.1, 15.6 (2s,
CHMe2), 4.7 (s, NCMe) ppm.
(PF6ꢀ) 840 (s). 1H NMR (CDCl3, 298 K):
d 8.05 (br s, 3H, C5H3N),
5.25e4.73 (m, 8H, OCH2, CHiPr and CHCH2 nbd), 4.15, 4.06, 4.01,
3.88 (br s, 1H each one, HC]CH nbd), 2.87, 2.44 (2m, 1H each one,
CHMe2), 1.75 (d, 1H, JHH ¼ 9.4 Hz, CH2 nbd), 1.55 (d, 1H, JHH ¼ 8.8 Hz,
CH2 nbd), 1.19 (d, 3H, JHH ¼ 6.7 Hz, CHMe2), 1.14 (d, 3H, JHH ¼ 6.9 Hz,
CHMe2), 1.07 (d, 3H, JHH ¼ 7.1 Hz, CHMe2), 0.83 (d, 3H, JHH ¼ 6.3 Hz,
2.7. Synthesis of complexes [RuCl(h
4-diene){(S,S)-iPr-pybox}][PF6]
(diene ¼ cod (8), nbd (9))
CHMe2) ppm. 13C{1H} NMR (CDCl3, 298 K):
d 164.7, 166.4 (2s, OCN),
145.1, 144.0 (2s, C2,6 C5H3N), 137.5 (s, C4 C5H3N), 127.1, 126.9 (2s, C3,5
C5H3N), 75.9, 74.1, 73.0, 72.6, 71.9, 71.2, 70.0 (7s, OCH2, CHiPr and
HC]CH nbd), 60.2 (s, CH2 nbd), 50.8, 49.6 (2s, CHCH2 nbd), 30.1,
28.7 (2s, CHMe2), 19.7, 19.2, 14.7, 14.6 (4s, CHMe2) ppm.
A solution of trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] (0.100 g,
0.2 mmol), NaPF6 (0.170 g, 1 mmol) and 1,5-cyclooctadiene
(0.25 mL, 2 mmol) or 2,5-norbornadiene (0.218 mL, 2 mmol) in
methanol (25 mL) was heated at 65 ꢁC for 2 h. The solvent was then
removed under vacuum and the solid residue was extracted with
dichloromethane and filtered. The resulting solution was then
concentrated to ca. 5 mL and a hexane/diethyl ether mixture (1:1,
30 mL) was added, yielding an orange solid that was washed with
diethyl ether (4 ꢂ 30 mL) and vacuum-dried.
2.8. General procedure for hydrogen transfer reactions
Acetophenone (5 mmol) and the catalyst (0.01 mmol) were
placed in a three-bottomed Schlenk flask under a dry nitrogen
atmosphere and 2-propanol (50 mL) was added. The solution was
heated at 82 ꢁC and the corresponding amount of base from
a 0.080 M solution in 2-propanol was added after 15 min. The
reaction was monitored by gas chromatography. The corresponding
alcohol and acetone were the only products detected in all cases.
Complex 8: Yield 73% (0.101 g). Anal. Calc. for C25H35ClF6N3O2
-
PRu: C, 43.45; H, 5.10; N, 6.08. Found: C, 43.70; H, 5.26; N, 5.85.
Conductivity (acetone, 20 ꢁC, ꢀ1 cm2 molꢀ1): 124. IR (KBr, cmꢀ1): v
U
(PF6ꢀ) 841(s). 1H NMR (CD2Cl2, 298 K):
d
8.26e8.09 (br, 3H, H3,4,5
C5H3N), 5.10 (m, 4H, OCH2), 4.77 (t, 1H, JHH ¼ 9.1 Hz, CHiPr), 4.55 (m,
1H, CH cod), 4.48 (t, 1H, JHH ¼ 8.8 Hz, CHiPr), 3.70 (br s, 2H, CH cod),
3.06 (m, 1H, CH cod), 2.69e2.28 (m, 10H, CHMe2 and CH2 cod), 1.15
(d, 3H, JHH ¼ 6.8 Hz, CHMe2), 1.06 (d, 3H, JHH ¼ 6.8 Hz, CHMe2), 1.02
(d, 3H, JHH ¼ 7.1 Hz, CHMe2), 0.75 (d, 3H, JHH ¼ 6.5 Hz, CHMe2) ppm.
2.9. X-ray diffraction
Suitable crystals for X-ray diffraction analysis were obtained, in
all cases, by diffusion of diethyl ether into a solution of the
complexes in dichloromethane. The unit cell of the complex 4
13C{1H} NMR (CDCl3, 298 K):
d 167.3, 165.5 (2s, OCN), 145.7, 144.7
(2s, C2,6 C5H3N), 138.6 (s, C4 C5H3N), 127.3, 127.2 (2s, C3,5 C5H3N),
Table 1
Crystal data and structure refinement for complexes 4, 6 and 8.
4$CH2Cl2
6
8$1/2 Et2O
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
31H28BCl3F4N3O3PRu
C24H34Cl2N4O2Ru
582.52
293(2)
1.5418
Orthorhombic
P212121
C27H40Cl2F6N3O2.5PRu
728.12
293(2)
0.71073
Orthorhombic
P212121
815.76
293(2)
0.71073
Monoclinic
P21/c
16.002(14)
8.6082(1)
7.887(4)
b (Å)
10.888(7)
8.6352(1)
23.484(8)
c (Å)
b
Volume (Å3)
20.069(9)
103.17(9)
3405(4)
4
1.592
0.802
35.4208(6)
90
2632.95(6)
4
1.467
6.906
33.853(18)
90
6270(5)
(ꢁ)
Z
8
rcalculated (Mg mꢀ3
)
1.543
0.703
m
(mmꢀ1
)
F (000)
Crystal size (mm3)
range (ꢁ)
1640
1196
2984
0.26 ꢂ 0.26 ꢂ 0.10
0.152 ꢂ 0.074 ꢂ 0.052
4.99e71.97
ꢀ10 ꢃ h ꢃ 9
ꢀ6 ꢃ k ꢃ 10
ꢀ35 ꢃ l ꢃ 43
15,252
0.33 ꢂ 0.33 ꢂ 0.33
1.06e25.97
ꢀ9 ꢃ h ꢃ 9
ꢀ28 ꢃ k ꢃ 28
ꢀ31 ꢃ l ꢃ 31
13,429
q
1.31e25.97
Index ranges
ꢀ19 ꢃ h ꢃ 19
0 ꢃ k ꢃ 13
0 ꢃ l ꢃ 24
No. of reflns. collected
No. of independent reflns.
Completeness to qmax (%)
Refinement method
6877
6672 [R(int) ¼ 0.0327]
4803 [R(int) ¼ 0.0269]
11,205 [R(int) ¼ 0.0565]
100
98.9
90.7
Full-matrix least-squares on F2
530/0
Full-matrix least-squares on F2
297/0
Full-matrix least-squares on F2
669/7
No. of parameters/restraints
Goodness-of-fit on F2
0.978
1.179
1.078
Weight function (a, b)
0.0579, 0
0.0271, 3.7361
R1 ¼ 0.0306, wR2 ¼ 0.0850
R1 ¼ 0.0318, wR2 ¼ 0.0855
0.017(13)
0.0341, 39.6999
R1 ¼ 0.0665, wR2 ¼ 0.1291
R1 ¼ 0.1604, wR2 ¼ 0.1725
ꢀ0.08(7)
R1 [I > 2
s
(I)]a
R1 ¼ 0.0445, wR2 ¼ 0.0997
R (all data)
R1 ¼ 0.1437, wR2 ¼ 0.1309
Absolute structure parameter
Largest diff. peak and hole (e Åꢀ3
)
0.641 and ꢀ0.845
0.565 and ꢀ0.656
0.777 and ꢀ0.907
a
2
½
R1 ¼ S(jFoj ꢀ jFcj)/SjFoj; wR2 ¼ {S[w(Fo ꢀ Fc2)2]/S[w(Fo2)2]}
.

1864
D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
Table 2
contains dichloromethane (1:1). In the crystal of complex 8, one
diethyl ether solvation molecule per two formula units of the
complex was found. The most relevant crystal and refinement data
are collected in Table 1.
Data collection for 4 and 8 were collected on a Nonius CAD4
single-crystal diffractometer using graphite-monocromated, Mo-
Selected bond distances (Å) and angles (ꢁ) for complexes 4, 6, and 8.
Complex 4$CH2Cl2
Bond
Ru(1)eN(1)
Ru(1)eN(2)
Ru(1)eN(3)
Ru(1)eP(1)
Distance
2.109(4)
2.054(4)
2.101(5)
2.311(3)
Value
Bond
Distance
2.429(3)
1.873(6)
1.105(6)
Ru(1)eCl(1)
Ru(1)eC(30)
O(3)eC(30)
Ka
radiation (
l
¼ 0.71013 Å). The unit cell parameters were
obtained from a least-squares fit of 25 reflections (20ꢁ<
q
< 25ꢁ).
Angle
Angle
Value
N(3)eRu(1)eN(1)
N(1)eRu(1)eN(2)
N(2)eRu(1)eN(3)
N(1)eRu(1)eP(1)
152.64(18)
76.19(18)
76.53(19)
89.67(14)
O(3)eC(30)eRu(1)
N(3)eRu(1)eP(1)
C(30)eRu(1)eCl(1)
173.4(6)
94.60(14)
86.3(2)
The intensities were measured using the scan technique with a scan
angle of 1.5ꢁ and a variable scan rate with a maximum scan time of
60 s per reflection. The intensity of the primary beam was checked
throughout the collection by monitoring three standard reflections
every 60 min. Profile analysis was performed on all reflections [6].
Symmetry-equivalent reflections were averaged and Lorentz and
polarization corrections were applied.
Complex 6
Bond
Distance
2.084(3)
2.022(3)
2.098(4)
1.144(6)
Value
Bond
Distance
2.4051(13)
2.4036(13)
1.955(5)
1.457(6)
Value
179.61(5)
175.7(5)
169.2(5)
Ru(1)eN(1)
Ru(1)eN(2)
Ru(1)eN(3)
C(18)eN(4)
Angle
N(1)eRu(1)eN(2)
N(1)eRu(1)eN(3)
N(2)eRu(1)eN(3)
Cl(1)eRu(1)
Cl(2)eRu(1)
Ru(1)eC(18)
C(19)eN(4)
Data collection for 6 were performed on a Oxford Diffraction
Xcalibur Nova single-crystal diffractometer, using Cu-Ka radiation
Angle
(
l
¼ 1.5418 Å). Images were collected at a 75 mm fixed crystal-
77.40(16)
154.50(17)
77.21(18)
Cl(1)eRu(1)eCl(2)
Ru(1)eC(18)eN(4)
C(18)eN(4)eC(19)
detector distance, using the oscillation method, with 1ꢁ oscillation
and variable exposure time per image (2e8 s). Data collection
strategy was calculated with the program CrysAlis Pro CCD [7]. Data
reduction and cell refinement were performed with the program
CrysAlis Pro RED [7]. An empirical absorption correction was
applied using the SCALE3 ABSPACK algorithm as implemented in
the program CrysAlis Pro RED [7].
Complex 8$1/2 Et2O
Bond
Ru(1)eN(1)
Ru(1)eN(2)
Ru(1)eN(3)
Ru(1)eCl(1)
Ru(1)eC(18)
Angle
N(1)eRu(1)eN(3)
N(1)eRu(1)eN(2)
N(2)eRu(1)eN(3)
N(2)eRu(1)eCl(1)
N(3)eRu(1)eCl(1)
Distance
2.119(9)
2.019(9)
2.151(9)
2.399(3)
2.262(12)
Value
Bond
Ru(1)eC(19)
Ru(1)eC(22)
Ru(1)eC(23)
C(18)eC(19)
C(22)eC(23)
Angle
Distance
2.260(11)
2.233(11)
2.205(11)
1.367(14)
1.396(16)
Value
77.8(4)
87.5(3)
82.5(4)
80.7(4)
The structures were solved by direct methods using SHELXS97
(for 4 and 8) [8], and using SIR2004 (for 6) [9]. Isotropic least-
squares refinement on F2 using SHELXL97 was performed [10].
During the final stages of the refinements, all positional parame-
ters and the anisotropic temperature factors of all the non-H atoms
were refined (the atoms of the disordered diethyl ether solvent
were refined isotropically). For 4 and 6 the H atoms were
geometrically located and their coordinates were refined riding on
their parent atoms. For 8, the coordinates of H atoms were found
from different Fourier maps, and included in a refinement with
isotropic parameters (with the exception of H atoms of solvent
which were geometrically located and their coordinates were
refined riding on their parent atoms.). The function minimized was
151.3(3)
76.5(4)
76.3(4)
89.2(3)
83.1(2)
N(1)eRu(1)eC(18)
N(1)eRu(1)eCl(1)
N(1)eRu(1)eC(23)
N(3)eRu(1)eC(19)
N(3)eRu(1)eC(22)
88.0(4)
presence of a C2 symmetry axis, singlet resonance signals for the
methylene groups and for the CHiPr groups of both oxazoline
rings were observed.
P
P
([ wFo2 ꢀ Fc2)/ w(Fo2)]1/2 where w ¼ 1/[
(a and b values are collected in Table 2) with
s
2(Fo2) þ (aP)2 þ bP]
s
(Fo2) from counting
statistics and P ¼ (Max (Fo2, o) þ 2Fc2)/3. Atomic scattering factors
were taken from International Tables for X-ray Crystallography
[11]. The crystallographic plots were made with PLATON [12].
Geometrical calculations were made with PARST [13].
Scheme 1. Synthesis of complexes 1e3.
3. Results and discussion
3.1. Synthesis of complexes trans-[RuCl2(L){(S,S)-iPr-pybox}]
3.2. Synthesis of complex [RuCl(CO)(PPh3)(H-pybox)][BF4] (4)
(L ¼ PMe3 (1), P(OMe)3 (2), PPh2(CH2CH]CH2) (3))
Then we have assayed the substitution of chloride by CO in
complexes 1, 2 and in the analogous complex trans-[RuCl2(PPh3)
{(S,S)-iPr-pybox}] [4]. The reaction of these precursors with CO in
the presence of a chloride extractor AgX (X ¼ PF6 or BF4) gives rise
to a mixture of unidentified complexes. However, this procedure
was found appropriate in the case of the complex trans-
[RuCl2(PPh3)(H-pybox)] (H-pybox ¼ 2,6-bis(dihydrooxazolin-20-yl)
pyridine) [4] and AgBF4 affording the complex [RuCl(CO)(PPh3)(H-
pybox)][BF4] in 95% yield. Apparently, the use of an unsubstituted,
less steric-demanding pybox ligand is highly beneficial (Scheme 2).
The structure of complex 4 has been established by X-ray crys-
tallographic analysis. An ORTEP view of the molecular structure is
shown in Fig.1. The more significant bond distances and angle values
are collected in Table 2. The cation complex shows a distorted
octahedral structure around the ruthenium atom which is bonded
to the three nitrogen atoms of H-pybox ligand, the chloride atom,
The complexes 1e3 have been synthesized following the
synthetic procedure reported previously for the preparation of
the complex trans-[RuCl2(PPh3){(S,S)-iPr-pybox}] [4] (Scheme 1).
Thus, stereoselective substitution of the ethylene ligand in the
complex trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] by phosphines
(PMe3, PPh2(CH2CH]CH2)) or phosphite P(OMe)3 was accom-
plished in dichloromethane at room temperature (for 1) or under
reflux (for 2 and 3) to afford complexes 1e3 in moderate yields.
All the complexes reported in this article have been characterized
by IR, NMR spectroscopy, elemental analysis and some of them
by electrospray mass spectra (see Experimental Section). In
particular, the 31P{1H} NMR spectra of complexes 1e3 show
a singlet resonance at
d
¼ 1.2 (1), 147.9 (2) and 23.0 ppm (3). The
stereochemistry of these complexes is readily determined on the
basis of the 13C{1H} NMR spectra. In accordance with the

D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
1865
Scheme 3. Synthesis of complexes 5e7.
Scheme 2. Synthesis of complex 4.
and angle values are collected in Table 2. The structure exhibits
a distorted octahedral geometry around the ruthenium atom which
is bonded to the three nitrogen atoms of Pr-pybox ligand, the
the phosphorous atom of the PPh3 and the CO group. The triphe-
nylphosphine and the carbonyl ligands are arranged in a cis dispo-
sition. The N(3)eRu(1)eN(1) angle (152.64(18)ꢁ) is in the range
found in other six-coordinate octahedral pybox complexes [4,14].
i
carbon atom of the cyclohexylisocyanide group and two chlorine
atoms. The chlorine atoms are located in a trans disposition with an
angle value Cl(1)eRueCl(2) of 179.61(5)ꢁ. The cyclohexylisocyanide
group presents a slightly distorted linear arrangement (Ru(1)eC
(18)eN(4) of 175.7(5)ꢁ), this angle value as well as the distances
ruthenium-carbon isocyanide (Ru(1)eC(18), 1.955(5) Å) and C^N
(C(18)eN(4), 1.144(6) Å) are in the range found for other ruthenium
(II)-isocyanide complexes [16].
3.3. Synthesis of complexes trans-[RuCl2(CNR){(S,S)-iPr-pybox}]
(R ¼ Bn (5), Cy(6)) and trans-[RuCl2(MeCN){(S,S)-iPr-pybox}] (7)
The ethylene ligand of the precursor trans-[RuCl2(h
2-C2H4)
{(S,S)-iPr-pybox}] can also be replaced by isocyanides and nitriles.
Thus, its reaction with three equivalents of isocyanide in dichloro-
methane (rt for 5; reflux for 6) leads to the stereoselective formation
of the complexes trans-[RuCl2(CNR){(S,S)-iPr-pybox}] (R ¼ Bn (5), Cy
(6)) (83e89% yield) as air-stable solids. Analogously, the reaction of
3.4. Synthesis of the complexes [RuCl(
(8) and [RuCl(
4-nbd){(S,S)-iPr-pybox}][PF6] (9)
h
4-cod){(S,S)-iPr-pybox}][PF6]
h
trans-[RuCl2(h
2-C2H4){(S,S)-iPr-pybox}] with acetonitrile (6 equiv) in
The treatment of a solution of the complex trans-[RuCl2(h2
-
refluxing dichlorometane leads to the complex trans-[RuCl2(MeCN)
{(S,S)-iPr-pybox}] (7) (83% yield) [15] (Scheme 3). Characteristic
features of the spectroscopic data for these complexes are: i) the IR
spectra of complexes 5 and 6 show the expected v(C^N) absorp-
tions in the range of 2098e2114 cmꢀ1 and the IR spectrum of
complex 7 shows the v(C^N) absorption at 2273 cmꢀ1; ii) the 13C
{1H} NMR spectra show a singlet signal for the isocyanide carbon
CNR at 166.5 (5) and 162.8 ppm (6); iii) the NMR resonances of the
acetonitrile ligand of complex 7 appear as singlets at 2.80 ppm (1H
NMR) and at 128.0 (C^N) and 4.7 (MeCN) ppm (13C NMR); iv) the 1H
and 13C resonance signals (298 K) of complexes 5e7 are consistent
with a structure having a C2 symmetry axis, thus indicating a trans
arrangement of the chloride ligands.
C2H4){(S,S)-iPr-pybox}] in refluxing methanol with NaPF6 and
excess of cyclooctadiene (cod) or norbornadiene (nbd) results in
the formation of the complexes 8 and 9, respectively, isolated as
orange air-stable solids in good yield (73e84%) (Scheme 4). The
molar conductivity values of complexes 8 and 9 are in the range
expected for 1:1 electrolytes [17]. The 1H and 13C{1H} NMR spectra
of complexes 8 and 9 reveals the lack of a C2 symmetry axis in
contrast with the free ligand (see Experimental Section for details).
Thus, the 13C{1H} NMR spectrum of complex 8 shows unequivalent
signals for the olefinic carbons (96.7, 95.4, 92.6 and 92.4 ppm) and
the CH2 carbons (31.2, 30.8, 30.5 and 30.4 ppm) of the cod ligand. In
the same way, double signals are observed for the isopropyl groups
The stereochemistry of complex 6 has been confirmed by
a single-crystal X-ray analysis. An ORTEP view of the molecular
structure is shown in Fig. 2. The more significant bond distances
Fig. 1. An ORTEP drawing of complex 4 showing atom-labeling scheme. Thermal
ꢀ
ellipsoids are shown at 10% probability. Hydrogen atoms and the BF4 anion are
Fig. 2. An ORTEP drawing of complex 6 showing atom-labeling scheme. Thermal
omitted for clarity. Only the Cipso-aryl of the PPh3 ligand are drawn.
ellipsoids are shown at 10% probability. Hydrogen atoms are omitted for clarity.

1866
D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
Table 3
Catalytic transfer hydrogenation of acetophenone using Ruthenium(II) complexes
containing iPr-pybox.a
Catalyst
t[min]
Conversion
(%)b
e.e. (%)c
1
2
3
4
5
6
7
8
trans-[RuCl2(PMe3)
15
97
20 (S)
(iPr-pybox)] (1)
trans-[RuCl2{P(OMe)3}
30
97
17 (R)
(iPr-pybox)] (2)d
trans-[RuCl2{PPh2(C3H5)}
(iPr-pybox)] (3)
45
98
33 (R)
trans-[RuCl2(CNBn)
15 (45)
30 (45)
15 (45)
480
92 (97)
86 (92)
47 (56)
70
36 (25) (R)
27 (19) (R)
58 (39) (R)
10 (S)
(iPr-pybox)] (5)
trans-[RuCl2(CNCy)
(iPr-pybox)] (6)
trans-[RuCl2(MeCN)
(iPr-pybox)] (7)
Scheme 4. Synthesis of complexes 8e9.
[RuCl(
[PF6] (8)
[RuCl(
4-nbd)(iPr-pybox)]
[PF6] (9)
h
4-cod)(iPr-pybox)]
of both oxazoline rings as well as for the C-2,6 and C-3,5 carbon
h
480
47
6 (R)
i
atoms of the pyridine ring of Pr-pybox ligand.
a
The reactions were carried out at 82 ꢁC using a 0.1 M acetophenone solution in
The structure of complex 8 has been confirmed by a single-
crystal X-ray analysis. ORTEP-type view of the cation complex 8 is
shown in Fig. 3 and selected bonding data are listed in Table 2. The
50 mL of 2-propanol (ketone/catalyst/NaOH 500:1:6).
b
Determined by GC analysis with a Supelco
All the major secondary alcohols had the R configuration except for entries 1 and
b
-DEX 120 chiral capillary column.
c
structure of complex 8 shows a mononuclear cation [RuCl(h
4-cod)
7; absolute configuration was determined by comparing optical rotations with
ꢀ
{(S,S)-iPr-pybox}]þ and an uncoordinated PF6 anion. The cation
unit exhibits a distorted octahedral geometry around the ruthe-
nium atom that is bonded to the nitrogen atoms of iPr-pybox ligand,
to the chlorine atom, and to the midpoint of both olefin groups of
the 1,5-cyclooctadiene ligand (Fig. 3). The chlorine and the N(2)
atoms are located in a trans disposition with respect to both olefin
groups and the angle values are 173.38(8)ꢁ [(CT01eRu(1)eCl(1)]
and 176.9(3)ꢁ [CT02eRu(2)eN(2)]. On the other hand, the ruthe-
nium-olefinic carbons distances [Ru(1)eC(18), Ru(1)eC(19), Ru(1)e
C(22) and Ru(1)eC(23)] is 2.237(11) Å on average in accordance
with other Ru-cod complexes [18].
literature values.
d
Published results (ketone/catalyst/NaOH 500:1:24) [3].
(7)), [RuCl(h h
4-cod){(S,S)-iPr-pybox}][PF6] (8) and [RuCl( 4-nbd)
{(S,S)-iPr-pybox}][PF6] (9) were found to catalyze the reduction of
acetophenone to 1-phenylethanol in 2-propanol via transfer
hydrogenation. In a typical experiment the ruthenium catalyst
precursor (0.2 mol %) was added to a 0.1 M solution of acetophe-
none in 50 mL of 2-propanol and stirred for 15 min at 82 ꢁC. Then
NaOH was added (ketone/catalyst/NaOH 500:1:6) and the reaction
monitored by gas chromatography. While all the complexes are
active and the conversion vary from low/medium (entries 6e8) to
high (entries 1e5), the chiral induction was unfortunately unsat-
isfactory (ee 6e58%) (Table 3).
The formation of complexes 8 and 9presumablyinvolvesfirstly the
chloride extraction by NaPF6 followed by
ligand through an alkene unit. Then, displacement of the ethylene
ligand would allow for the
4-coordination of the cod or nbd groups.
h
2-coordination to the diene
h
4. Summary
3.5. Catalytic transfer hydrogenation of ketones
In summary, we report the synthesis of new ruthenium(II)
complexes with potential catalytic activity. The complexes trans-
[RuCl2(L){(S,S)-iPr-pybox}] (L ¼ PMe3 (1), P(OMe)3 (2), PPh2(CH2CH]
CH2) (3), CNBn (5), CNCy (6) and MeCN (7)) have been prepared from
The new ruthenium complexes trans-[RuCl2(L){(S,S)-iPr-pybox}]
(L ¼ PMe3 (1), PPh2(CH2CH]CH2) (3), CNBn (5), CNCy (6), MeCN
trans-[RuCl2(
tion of ethylene by L ligand. Moreover, new diolefin coordination
compounds [RuCl(
4-cod){(S,S)-iPr-pybox}][PF6] (8) and [RuCl(h4
nbd){(S,S)-iPr-pybox}][PF6] (9) have been synthesized by reaction of
the complex trans-[RuCl2(
2-C2H4){(S,S)-iPr-pybox}] with cyclo-
h
2-C2H4){(S,S)-iPr-pybox}] by stereoselective substitu-
h
-
h
octadiene (cod) or norbornadiene (nbd) using NaPF6 as chloride
extractor. The new complexes have been assayed as catalysts in the
transfer hydrogenation of acetophenone. Interestingly, the facile
accessibility of the diolefin (8, 9) and acetonitrile (7) complexes opens
a way to study the potential of new ruthenium pybox complexes
containing labile ligands in other asymmetric catalytic processes.
Acknowledgments
This work was supported by the Ministerio de Educación y
Ciencia of Spain (CTQ2006-08485) and Consolider Ingenio 2010
(CSD2007-00006).
Appendix A. Supplementary material
Fig. 3. An ORTEP drawing of complex 8 showing atom-labeling scheme. Thermal
ellipsoids are shown at 10% probability. Hydrogen atoms and the PF6 anion are
ꢀ
CCDC804962 (4$CH2Cl2), CCDC804963 (6) and CCDC804964
(8$1/2 Et2O) contain the supplementary crystallographic data for
omitted for clarity. CT01 and CT02 are the centroids of the C(18)eC(19) and C(22)eC
(23) bonds.

D. Cuervo et al. / Journal of Organometallic Chemistry 696 (2011) 1861e1867
1867
[8] G.M. Sheldrick, SHELXS-97. Program for the Solution of Crystal Structures.
University of Göttingen, Göttingen, Germany, 1997.
[9] M.C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G.L. Cascarano, L. De Caro,
C. Giacovazzo, G. Polidori, R. Spagna, J. Appl. Cryst. 38 (2005) 381e388
SIR2004.
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[10] G.M. Sheldrick, SHELXL-97; Program for the Refinement of Crystal Structures.
University of Göttingen, Göttingen, Germany, 1997.
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[18] For example, the average RueC distance for the complex [RuBr{HB(pz)3}(h4-
[6] (a) M.S. Lehman, F.K. Larsen, Acta Crystallogr. A 30 (1974) 580e584;
(b) D.F. Grant, E.J. Gabe, J. Appl. Cryst. 11 (1978) 114e120.
[7] CrysAlisPro CCD, CrysAlisPro RED. Oxford Diffraction Ltd., Abingdon, Oxford-
shire, UK, 2008.
cod)] (HB(pz)3 ¼ tris(pyrazolyl)borate) is 2.213(2) Å C. Gemel, G. Trimmel,
C. Slugovc, S. Kremel, K. Mereiter, R. Schmid, K. Kirchner, Organometallics 15
(1996) 3998e4004.