Ruthenium(II) diphosphine/diamine/diimine complexes and catalyzed hydrogen-transfer to ketones

Article abstract of DOI:10.1021/om060987z

An in situ product, presumed to be RuCl₂(DPPF)(PPh₃), formed in CH₂Cl₂ from a 1:1 mixture of 1,1′-bis(diphenylphosphino)ferrocene (DPPF) and RuCl₂(PPh ₃)₃, reacts with 1 equiv of a diamine or a diimine (N-N donors) dissolved in MeOH to generate RuCl₂(DPPF)(N-N) complexes: N-N is ethylenediamine (en), N,N′-dimethyl(ethylenediamine) (dimen), 1,3-diaminopropane (diap), 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), and 1S,2S-diaminocyclohexane (1S,2S-dach). Diethylenetriamine (dien), a tridentate N-donor, generates a monochloro cationic complex. The isolated complexes are trans-RuCl₂-(DPPF)(en) (1), trans-RuCl ₂(DPPF)(dimen) (2), [RuCl(DPPF)(dien)]Cl (3), trans-RuCl ₂(DPPF)(diap) (4), cis-RuCl₂(DPPF)(bipy) (5), cis-RuCl₂(DPPF)(phen) (6), and trans-RuCl₂(DPPF)(1S,2S- dach) (7). The known complex trans-RuCl₂(DPPB)(en) (8) was similarly made using RuCl(DPPB)₂(μ-Cl)₃ as precursor, where DPPB is 1,4-bis(diphenylphosphino)butane. Complexes 1, 2, 5, and 8 were characterized crystallographically. Complexes 1-8 are effective precursor catalysts in basic 2-propanol solutions for the hydrogen-transfer hydrogenation of acetophenone; the chiral phosphine system (7) gives only ～12% ee at high conversions to 1-phenylethanol, while at 25% conversion the ee reaches 36%. Greater activity for precursor catalyst 1 versus that of 2 qualitatively supports the metal-ligand bifunctional mechanism for such diphosphine/diamine systems; however, the NH-free diimine bipy and phen systems are as active at 80°C as the diamine systems and must operate by a different mechanism. Complex 8 is also an effective precursor hydrogen-transfer catalyst for other alkyl-aryl and dialkyl ketones, which were used as model substrates for components of lignin; a substituted styrene was not hydrogenated.

Full text of DOI:10.1021/om060987z

846
Organometallics 2007, 26, 846-854
Ruthenium(II) Diphosphine/Diamine/Diimine Complexes and
Catalyzed Hydrogen-Transfer to Ketones
Guibin Ma,† Robert McDonald,† Michael Ferguson,† Ronald G Cavell,† Brian O. Patrick,‡
Brian R. James,*,‡ and Thomas Q. Hu#
Department of Chemistry, UniVersity of Alberta, Edmonton, Alberta, Canada T6G 2G2, Department of
Chemistry, UniVersity of British Columbia, VancouVer, British Columbia, Canada V6T 1Z1, and Pulp and
Paper Research Institute of Canada, VancouVer Laboratory, 3800 Wesbrook Mall, VancouVer,
British Columbia, Canada V6S 2L9
ReceiVed October 25, 2006
An in situ product, presumed to be RuCl2(DPPF)(PPh3), formed in CH2Cl2 from a 1:1 mixture of
1,1′-bis(diphenylphosphino)ferrocene (DPPF) and RuCl2(PPh3)3, reacts with 1 equiv of a diamine or a
diimine (N-N donors) dissolved in MeOH to generate RuCl2(DPPF)(N-N) complexes: N-N is
ethylenediamine (en), N,N′-dimethyl(ethylenediamine) (dimen), 1,3-diaminopropane (diap), 2,2′-bipyridine
(bipy), 1,10-phenanthroline (phen), and 1S,2S-diaminocyclohexane (1S,2S-dach). Diethylenetriamine (dien),
a tridentate N-donor, generates a monochloro cationic complex. The isolated complexes are trans-RuCl2-
(DPPF)(en) (1), trans-RuCl2(DPPF)(dimen) (2), [RuCl(DPPF)(dien)]Cl (3), trans-RuCl2(DPPF)(diap) (4),
cis-RuCl2(DPPF)(bipy) (5), cis-RuCl2(DPPF)(phen) (6), and trans-RuCl2(DPPF)(1S,2S-dach) (7). The
known complex trans-RuCl2(DPPB)(en) (8) was similarly made using RuCl(DPPB)2(µ-Cl)3 as precursor,
where DPPB is 1,4-bis(diphenylphosphino)butane. Complexes 1, 2, 5, and 8 were characterized
crystallographically. Complexes 1-8 are effective precursor catalysts in basic 2-propanol solutions for
the hydrogen-transfer hydrogenation of acetophenone; the chiral phosphine system (7) gives only ∼12%
ee at high conversions to 1-phenylethanol, while at 25% conversion the ee reaches 36%. Greater activity
for precursor catalyst 1 versus that of 2 qualitatively supports the “metal-ligand bifunctional” mechanism
for such diphosphine/diamine systems; however, the “NH-free” diimine bipy and phen systems are as
active at 80 °C as the diamine systems and must operate by a different mechanism. Complex 8 is also
an effective precursor hydrogen-transfer catalyst for other alkyl-aryl and dialkyl ketones, which were
used as model substrates for components of lignin; a substituted styrene was not hydrogenated.
for selective hydrogenation of ketones.4 When the P-P ligand
is chiral, and the H2N---NH2 ligand is achiral (but optimally
Introduction
The catalytic hydrogenation of unsaturated organics, espe-
cially those with polar CdO and CdN bonds, is important in
the fine chemical industry, and homogeneous catalysts based
on Ru have proven particularly useful for many syntheses.1,2
Ruthenium homogeneous hydrogenation catalysts have been
known for four decades,3 but it is only relatively recently that
Noyori and co-workers have developed highly active catalyst
precursors of the type trans-RuCl2(diphosphine)(1,2-diamine)
chiral), the systems can generate alcohol products with high ee
values4 (or chiral amine products from prochiral ketimines).1j,2b
The general “metal-ligand bifunctional catalysis” mechanism
(or so-called ‘ionic hydrogenations’) for reduction of ketones5
was invoked by Noyori’s group for these Ru systems4,6 and
implied no direct bonding of the substrate at the Ru, but instead
an outer-sphere, H-bonding interaction between an “RuH---NH”
unit and the ketone was proposed, with the added H2 being
derived from the metal hydride and an amine proton. Subsequent
detailed studies, especially by Morris’s group,1j have substanti-
ated such a mechanism, particularly for a binap-tmen system
(where tmen ) H2NC(Me)2C(Me)2NH2) in which the key
intermediates involve trans-dihydrido species.1j,7 It is worth
noting that hydrogenation of substrates via a mechanism not
involving direct bonding of the substrate at the metal was first
* Corresponding author. E-mail: brj@chem.ubc.ca. Tel: 1-604-822-6645.
† University of Alberta.
‡ University of British Columbia.
# Pulp and Paper Research Institute.
(1) For example: (a) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem.
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Huskens, J. Synthesis 1994, 1007. (c) James, B. R. Catal. Today 1997, 37,
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10.1021/om060987z CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/19/2007

Ruthenium(II) Diphosphine/Diamine/Diimine Complexes
Organometallics, Vol. 26, No. 4, 2007 847
Scheme 1. Synthesized Complexes 1-8
chromophore units present in lignin, the aim of the hydrogena-
tion being to reduce the degree of conjugation in lignin in a
search for new procedures for the bleaching of pulps.12
Of note is that DPPF has also been used within the
isocyanide-containing complexes trans-RuCl2(DPPF)(CNR)2 in
2-propanol for catalyzed hydrogen-transfer hydrogenation of
ketones.13
Experimental Section
General Procedures. Unless otherwise noted, all reactions,
recrystallizations, and routine manipulations were performed at
ambient conditions in an Ar-filled glovebox or by using standard
Schlenk techniques under N2. Acetone, CH2Cl2, CHCl3, Et2O, and
EtOH were dried (over B2O3, CaH2, P2O5, Na/benzophenone, and
Mg, respectively) and were vacuum-transferred before use. Deu-
terated solvents were obtained from Cambridge Isotope Laboratories
(CIL).
NMR spectra were recorded at room temperature (∼20 °C) in
CD2Cl2 solution, unless otherwise stated, on a Bruker AV 400
instrument (400.0 MHz for 1H, 162.0 MHz for 31P{1H}, and 100.6
MHz for 13C{1H/31P}). Residual protonated species in deuterated
1
solvents were used as internal references; all H and 13C shifts (s
) singlet, d ) doublet, t ) triplet, sept ) septet, m ) multiplet, br
) broad) are reported relative to external TMS, while 31P{1H} NMR
shifts are reported relative to external 85% aqueous H3PO4; J values
are given in Hz. IR spectral data for complex 8 (in KBr) were
recorded on a Nicolet Magna 750 FTIR spectrometer and, for
complexes 1-7, on a Nic-Plan FTIR microscope. Elemental
analyses were carried out on a Carlo Erba CHNS-O EA1108
analyzer. UV-vis spectra were recorded on a Hewlett-Packard 8453
DAD spectrophotometer and are presented as λmax (ꢀmax, mol L-1
cm-1). Conductivity data (presented as Ω-1 cm2 mol-1) were
obtained in CH2Cl2 using a Thomas Serfass conductance bridge
model RCM151B1 (Arthur H. Thomas Co. Ltd.) connected to a
3404 cell (Yellow Springs Instrument Co.); measurements were
made at 25 °C using ∼10-3 mol L-1 solutions of the complexes.
Gas chromatography (GC) analyses were performed using a
Hewlett-Packard 5890 GC or 5970 MSD instrument, fitted with
either an HP-FFAP polar column (50 m × 0.32 mm × 0.52 µm
phase thickness) or a chiral CP-Cyclodex (â-cyclodextrin) column
(25 m × 0.25 mm × 0.25 µm); the oven temperature ranged from
100 to 220 °C (10 °C/min) with an injection and detector
temperature of 220 °C.
demonstrated in the late 1960s for some CoH(CN)53- systems,8
an important point commonly overlooked in recent literature.9
In studies described in this paper, we selected 1,1′-bis-
(diphenylphosphino)ferrocene (DPPF) as a “constant” bidentate,
P-P ligand (Scheme 1) and varied the bidentate N-N ligand
using different diamine and diimine ligands; a tridentate N-donor
was also used. The RuCl2(DPPF)(N-N) complexes were
synthesized from RuCl2(PPh3)3, where N-N is, respectively,
ethylenediamine (en, complex 1), N,N’-dimethyl(ethylenedi-
amine) (dimen, complex 2), 1,3-diaminopropane (diap, complex
4), 2,2′-bipyridine (bipy, complex 5), 1,10-phenanthroline (phen,
complex 6), and 1S,2S-diaminocyclohexane (1S,2S-dach, com-
plex 7); diethylenetriamine generated [RuCl(DPPF)(dien)]Cl (3).
Complexes 2-7 are new, while 1 has been made previously by
a less efficient route, for use as a catalyst precursor for
dehydrogenation of diols to lactones.10 We report also an
improved synthetic route for the known complex11 trans-RuCl2-
(DPPB)(en) (8), where DPPB ) 1,4-bis(diphenylphosphino)-
butane, and describe the use of 1-8 as catalyst precursors for
hydrogen-transfer activity in basic 2-propanol for ketone reduc-
tion, in order to gain some insight into reaction mechanisms.
Some of the ketone substrates were chosen as models for
Materials. The phosphines (DPPF and DPPB), the amines and
imines (en, dimen, dien, diap, bipy, phen, and 1S,2S-dach), and
the ketones, were used as received from Aldrich. RuCl3‚3H2O was
14
donated by Colonial Metals, Inc.; RuCl2(PPh3)3 and [RuCl-
15
(DPPB)]2(µ-Cl)3 were synthesized by the literature methods.
[RuCl(p-cymene)]2(µ-Cl)2 was obtained from Strem Chemicals.
trans-RuCl2(DPPF)(en) (1). To a rapidly stirred, 10 mL CH2-
Cl2 suspension of RuCl2(PPh3)3 (96 mg, 0.1 mmol) was added DPPF
(55 mg, 0.1 mmol), the color changing from purple-black to red
within a few minutes. The solution was stirred for 30 min, when
50 µL of a MeOH solution of 2 M en (0.1 mmol) was added, giving
an immediate color change to yellow-green. After a further 30 min,
(12) (a) Hu, T. Q.; Cairns, G. R.; James, B. R. Holzforschung 2000, 54,
127. (b) Hu, T. Q.; James, B. R. In Chemical Modification, Properties and
Usage of Lignin; Hu, T. Q., Ed.; Kluwer Publishers: Dordrecht, The
Netherlands, 2002; p 247.
(13) Cadierno, V.; Crochet, P.; Diez, J.; Garcia-Garrido, S. E.; Gimeno,
J. Organometallics 2004, 23, 4836.
(14) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,
12, 237.
(15) (a) Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chem. 1986,
25, 234. (b) Joshi, A. M.; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg.
Chim. Acta 1992, 198-200, 283. (c) K. S. MacFarlane, K. S.; Thorburn, I.
S.; Cyr, P. W.; Chau, D. E. K.-Y.; Rettig, S. J.; James, B. R. Inorg. Chim.
Acta 1998, 270, 130.
(7) (a) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics
2001, 20, 1047. (b) Abdur-Rashid, K.; Clapham, S. E.; Hadzovic, A.;
Harvey, J. N.; Lough, A. J.; Morris, R. H. J. Am. Chem. Soc. 2002, 124,
15104.
(8) Halpern, J.; Wong, L.-Y. J. Am. Chem. Soc. 1968, 90, 6665.
(9) James, B. R. Chem. Eng. News 2002, March 11, 8.
(10) Zhao, J.; Hartwig, J. F. Organometallics 2005, 24, 2441.
(11) Queiroz, S. L.; Batista, A. A.; Oliva, G.; Gambardella, M. T. do
Pi.; Santos, R. H. A.; MacFarlane, K. S.; Rettig, S. J.; James, B. R. Inorg.
Chim. Acta 1998, 267, 209.

848 Organometallics, Vol. 26, No. 4, 2007
Ma et al.
the solvent was removed in vacuo and 5 mL of Et2O was added.
{1H} NMR: 44.2 (d, 2JPP ) 30.0), 38.6 (d, 2JPP ) 30.0). 13C{1H,31P}
NMR: 65.0, 69.7, 70.3, 73.1, 75.1, 76.9, 77.8, 84.8 (s, C5H4), 121.6,
123.4, 125.2, 125.3, 125.8, 125.9, 126.0, 126.1, 126.5, 127.5, 127.6,
127.8, 128.7, 130.0, 131.7, 133.2, 133.5, 133.6, 133.7, 133.8, 136.6,
150.2, 151.3, 157.4 (s, Ph and bipy rings). ESI-MS (THF): m/z
847 [M - Cl]+. IR (cm-1): 3099, 3076, 3050 (νN-H and νC-H),
1482, 1443, 1432 (νCdC, and C-H bending), 1164, 1091, 1039,
751, 696 (νC-C, νC-N, νC-P and bending). UV-vis: 220 (7.30 ×
104), 303 (1.58 × 104), 456 (4490), 545 sh (2200). ΛM ≈ 0. Anal.
Calcd for C44H36N2Cl2P2FeRu: C, 59.89; H, 4.08; N, 3.17. Found:
C, 60.27; H, 4.45; N, 3.16. Red, hexagon-shaped single crystals of
5 were obtained by slow evaporation of solvent from a CH2Cl2
solution of the complex.
The yellow product was filtered off, washed twice with ether (2 ×
1
5 mL), and then dried under vacuum. Yield: 74 mg (94%). H
NMR (CD3Cl): 1.55 (br s, 4H, NH2), 2.70 (br s, 4H, CH2), 4.19
(s, 4H, C5H4), 4.62 (s, 4H, C5H4), 7.10-7.44 (m, 20H, Ph). 31P-
{1H} NMR (CD3Cl): 50.9 (s). 13C{1H} NMR (CD3Cl): 43.5 (s,
3
2
CH2), 70.4 (t, JCP ) 2.7, C5H4), 76.6 (t, JCP ) 3.6, C5H4), 87.7
1
4
(d, JCP ) 24.4, C5H4), 127.6 (t, JCP ) 4.3, Ph), 129.3 (s, Ph),
134.7 (t, JCP ) 5.0, Ph), 139.4 (t, JCP ) 18.7, Ph). 13C{1H,31P}
NMR (CD3Cl): the above 13C{1H} signals became singlets. The
NMR data are in excellent agreement with those in the literature10
(but see Results and Discussion). ESI-MS (THF): m/z 787 [M +
H]+. IR (cm-1): 3329, 3252, 3055, 2938 (νN-H and νC-H); 1562,
1482, 1434 (νCdC, and C-H, N-H bending), 1161, 1094, 1028,
750, 694 (νC-C, νC-N, νC-P and bending). UV-vis: 221 (1.30 ×
105), 335 sh (3450), 456 (550). Anal. Calcd for C36H36N2Cl2P2-
FeRu‚0.5C4H10O: C, 55.41; H, 4.98; N, 3.40. Found: C, 55.78;
H, 4.89; N, 3.37. (The ether solvate was estimated by intensities
2
1
1
Cis-RuCl2(DPPF)(phen) (6). Yield: 81 mg (94%) H NMR:
3.37(s, 1H), 4.14 (s, 1H), 4.26 (s, 1H), 4.36 (s, 1H), 4.41 (s, 1H),
4.50 (s, 1H), 5.06 (s, 1H), 6.12 (s, 1H) (the signals between 3.30
and 6.20 are due to the eight C5H4 protons), 6.70-8.30 (m, 28H,
Ph). 31P{1H} NMR: δ 43.6 (d, 2JPP ) 30.6), 37.4 (d, 2JPP ) 30.6).
13C{1H,31P} NMR: 66.1, 70.7, 71.3, 73.8, 74.1, 76.2, 78.0, 79.0,
85.6 (s, C5H4), 122.6, 124.5, 124.9, 126.3, 126.6, 127.0, 127.6,
128.5, 128.8, 129.6, 129.8, 130.0, 131.0, 132.9, 134.4, 134.7, 134.9,
137.7, 148.2, 151.3, 152.4, 156.1, 158.5 (s, Ph and phen rings).
ESI-MS (THF): m/z 871 [M - Cl]+. IR (cm-1): 3099, 3046, 3017
(νN-H and νC-H), 1585, 1482, 1431 (νCdC, and C-H bending), 1152,
1091, 1038, 846, 694 (νC-C, νC-N, νC-P and bending). UV-vis:
220 (1.04 × 105), 274 (3.66 × 104), 442 (5250), 547 sh (1570).
ΛM ≈ 0. Anal. Calcd for C46H36N2Cl2P2FeRu: C, 60.93; H, 3.97;
N, 3.09. Found: C, 60.58; H, 4.11; N, 3.12.
1
of the H NMR signals for the ether-CH3 and en-CH2 groups.)
Rhombus-shaped single crystals of 1 (and 2, see below) were
obtained by slow evaporation of solvent from a CH2Cl2 solution
of the complex.
Complexes 2-6 were synthesized using the same procedure and
solvents as described for the synthesis of 1.
trans-RuCl2(DPPF)(dimen) (2). Yield: 73 mg (90%). 1H NMR
(CD2Cl2): 1.58 (br s, 2H, NH), 2.01 (d, 6H, CH3), 2.92 (br, s, 4H,
CH2), 4.10 (s, 4H, C5H4), 4.26 (s, 4H, C5H4), 7.10-7.44 (m, 20H,
Ph). 31P{1H} NMR: 44.5 (br s). 13C{1H}: 37.8 (s, CH2), 51.9 (s,
CH3), 69.8 (s, C5H4), 76.0 (t, C5H4), 88.2 (t, C5H4), 126.9 (d, Ph),
128.2 (t, Ph), 128.9 (s, Ph), 129.8 (s, Ph), 135.0 (s, Ph), 135.6 (s,
Ph). ESI-MS (THF): m/z 815 [M + H]+. IR (cm-1): 3292, 3269,
3058, 2919 (νN-H and νC-H), 1482, 1433, 1397 (νCdC, and C-H,
N-H bending), 1183, 1180, 1038, 937, 820, 700 (νC-C, νC-N, νC-P
and bending). UV-vis: 220 (1.09 × 105), 339 sh (1800), 464 (350).
Anal. Calcd for C38H40N2Cl2P2FeRu: C, 56.03; H, 4.91; N, 3.44.
Found: C, 56.04; H, 4.93; N, 3.40.
trans-RuCl2(DPPF)(1S,2S-dach) (7). The synthesis follows that
given for 1, except that after evaporation of the CH2Cl2, 2-propanol
was added to precipitate the product, which was then washed with
MeOH (5 mL) and dried under vacuum. Yield: 50.0 mg, 60%. 1H
NMR: 1.04 (m, 4H), 1.55 (s, 4H), 1.71(d, 2H), 2.43 (d, 2H), 2.65
(m, 4H), 4.20 (s, 2H, C5H4), 4.23 (s, 2H, C5H4), 4.57 (s, 2H, C5H4),
4.71 (s, 2H, C5H4), 7.20-7.60 (m, 12H, Ph ring), 7.87 (d, 8H, Ph
ring); trace peaks at 1.17 (d), 2.18 (s), and 4.00 (sept) are due to
2-propanol. 31P{1H} NMR: 51.4 (s). 13C{1H,31P} NMR: 24.9, 36.1,
57.5 (1S,2S-cyclohexyl ring), 70.2, 70.4, 76.5, 76.8, 88.9 (s, C5H4),
127.5, 127.7, 128.9, 129.2, 129.4, 132.2, 132.3, 134.6, 134.9, 139.3,
139.4 (s, Ph rings). ESI-MS (THF): m/z 805.1 [M - Cl]+. IR
(cm-1): 3329, 3053, 2935, 2858 (νN-H and νC-H), 1565, 1481, 1433
(νCdC, and C-H, N-H bending), 1185, 1178, 1092, 1028, 746,
697 (νC-C, νC-N, νC-P and bending). Anal. Calcd for C40H42N2-
Cl2P2FeRu: C, 57.15; H, 5.00; N, 3.33. Found: C, 57.27; H, 5.04;
N, 3.11.
[Ru(DPPF)(dien)Cl]Cl (3). Yield: 54 mg (65%). 1H NMR: 2.00
(s, 1H, NH), 2.12 (s, 4H, NH2), 2.33-2.86 (m, 8H, CH2), 3.29 (s,
1H), 3.91(s, 1H), 3.99 (s, 1H), 4.21 (s, 2H), 4.49 (s, 1H), 4.66 (s,
1H), 6.03 (s, 1H) (the 7 signals from δ 3.29-6.03 correspond to
the C5H4 protons), 7.10-7.44 (m, 20H, Ph). 31P{1H} NMR: 52.8
2
2
(d, JPP ) 36.5), 37.7 (d, Jpp ) 36.5). 13C{1H} NMR: 42.7 (s,
NH2CH2), 53.3 (s, CH2NH), 69.3 (d, C5H4), 76.1 (d, C5H4), 91.7
(t, C5H4), 126.6 (m, Ph), 127.7 (m, Ph), 128.8 (m, Ph), 131.7 (m,
Ph), 134.5 (m, Ph), 137.5 (m, Ph). ESI-MS (THF): m/z 795 [M -
Cl]+. IR (cm-1): 3341, 3234, 3054 (νN-H and νC-H), 1573, 1481,
1431 (νCdC, and C-H, N-H bending), 1149, 1087, 972, 817, 745,
700 (νC-C, νC-N, νC-P and bending). UV-vis: 221 (7.34 × 104),
349 sh (2500), 459 (1000). ΛM ) 10.9 Ω-1 cm2 mol-1. Anal. Calcd
for C38H41N3Cl2P2FeRu: C, 55.02; H, 4.95; N, 5.07. Found: C,
54.77; H, 5.07; N, 4.92.
trans-RuCl2(DPPB)(en) (8). Two procedures were used to
synthesize 8: (i). To [RuCl(DPPB)]2(µ-Cl)3 (123.3 mg, 0.2 mmol
of Ru) dissolved in 5 mL of CH2Cl2 was added 0.1 mL of an EtOH
solution of 2 M en (0.2 mmol). The color changed from red to
green when the solution was stirred for 2 h. The solvent was then
removed under vacuum to give a residue, to which 5 mL of EtOH
was added; the remaining solid was filtered off, washed with more
EtOH (10 mL), and dried under vacuum. Yield: 94 mg (71%). (ii)
[RuCl(DPPB)]2(µ-Cl)3 (0.123.3 mg) was suspended in EtOH (10
mL), and 1 equiv of en was added as the mixture was stirred and
heated to ∼ 50 °C for 10 h, when the color changed from red to
green. The solid product was filtered off, washed with EtOH (2 ×
5 mL), and dried under vacuum. Yield: 84 mg (64%). The 1H and
31P{1H} NMR data in CDCl3 were in excellent agreement with the
literature data.11 ESI-MS (THF): m/z 659, [M + H]+. IR (cm-1):
3052, 2922 (νN-H and νC-H), 1566, 1509, 1449, 1434 (νCdC, and
C-H, N-H bending), 1028, 898, 876, 743, 534 (νC-C, νC-N, νC-P
and bending). Anal. Calcd for C30H36N2Cl2P2Ru: C, 54.67; H, 5.47;
N, 4.25. Found: C, 54.61; H, 5.50; N, 4.24. Block single crystals
of 8 were obtained by slow evaporation of the solvents from a mixed
CH2Cl2/EtOH solution (1:1 v/v) of the complex.
trans-RuCl2(DPPF)(diap) (4). Yield: 76 mg (95%). 1H NMR:
1.59 (s, 4H, NH2), 2.82 (s, 6H, CH2), 4.17 (s, 4H, C5H4), 4.59 (s,
4H, C5H4), 7.10-7.44 (m, 20H, Ph). 31P{1H} NMR: 49.4 (s). 13C-
{1H} NMR: 29.1 (s, CH2CH2CH2), 39.4 (s, NH2CH2), 70.7 (t,
C5H4), 76.5 (t, C5H4), 86.4 (t, C5H4), 127.7 (m, Ph), 128.5 (m, Ph),
129.3 (s, Ph), 131.5 (m, Ph), 133.1 (m, Ph), 135.4 (m, Ph). ESI-
MS (THF): m/z 800 [M + H]+. IR (cm-1): 3329, 3313, 3243,
3054, 2927 (νN-H and νC-H), 1560, 1482, 1434 (νCdC, and C-H,
N-H bending), 1092, 750, 695 (νC-C, νC-N, νC-P and bending).
UV-vis: 221 (1.37 × 105), 340 sh (2330), 456 (430). Anal. Calcd
for C37H38N2Cl2P2FeRu: C, 55.50; H, 4.75; N, 3.50. Found: C,
55.79; H, 5.01; N, 3.38.
1
Cis-RuCl2(DPPF)(bipy) (5). Yield: 84 mg (95%). H NMR:
3.44 (s, 1H), 4.19 (s, 1H), 4.29 (s, 1H), 4.39 (s, 1H), 4.52 (s, 2H),
5.01 (s, 1H), 6.02 (s, 1H) (the 7 signals from δ 3.44-6.02
correspond to the C5H4 protons), 6.80-8.50 (m, 20H, Ph). 31P-

Ruthenium(II) Diphosphine/Diamine/Diimine Complexes
Organometallics, Vol. 26, No. 4, 2007 849
Table 1. Crystal Data and Structure Refinement Details for Complexes 1, 2, 5, and 8
empirical formula
C36H36N2P2Cl2FeRu‚
2CH2Cl2 (1)
C38H40N2P2Cl2FeRu‚
CH2Cl2 (2)
C44H36N2P2Cl2FeRu‚
2CH2Cl2 (5)
C30H36N2P2Cl2Ru (8)
fw
956.28
899.41
1052.36
658.52
cryst color, habit
cryst syst
cryst dimens
space group
unit cell dimens
a (Å)
yellow, block
triclinic
yellow, block
monoclinic
red, block
orthorhombic
green, block
monoclinic
0.25 × 0.24 × 0.17 mm
0.50 × 0.26 × 0.11 mm
0.56 × 0.49 × 0.25 mm
0.30 × 0.20 × 0.10 mm
P1h (No. 2)
P21/c (No. 14)
Pna21/ (No. 33)
P21/c (No. 14)
11.3221(13)
11.8585(14)
16.4254(19)
102.8433(16)
103.6783(17)
104.7914(16)
1975.8(4)
14.8147(19)
14.895(2)
17.335(2)
13.0207(18)
16.928(2)
19.903(3)
13.584(1)
12.8507(7)
18.122(1)
b (Å)
c (Å)
R (deg)
â (deg)
92.937(9)
111.750(3)
γ (deg)
volume (Å3)
Z
3820.3(9)
4
1.564
193.2(1)
1.170
10.02 to 12.5
-17 e h e 0
-17 e k e 0
-20 e l e 20
7000
4386.8(11)
4
1.593
193.2(1)
1.150
11.05 to 28.8
-16 e h e 16
-21 e k e 21
-24 e l e 24
9391
2928.4(3)
4
1.494
173.2(1)
0.850
2.27 to 27.87
-17 e h e 16
-16 e k e 15
-21 e l e 22
26014
2
calcd density (g cm-3
temp, K
)
1.607
193.2(1)
1.267
2.57 to 26.39
-14 e h e 14
-14 e k e 14
-20 e l e 20
23533
µ(Mo KR), (mm-1
)
θ range for data collection (deg)
index ranges
no. of reflns collected
no. of indep reflns
8067
6724
9086
6633
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
8067/4/448
1.064
R1 ) 0.0483
wR2 ) 0.1386
2.077 and -1.381 e/Å3
6724/0/429
1.032
R1 ) 0.0638
wR2 ) 0.1642
0.939 and -0.701 e/Å3
9086/0/524
1.062
R1 ) 0.0619
wR2 ) 0.1516
0.873 and -0.722 e/Å3
6633/0/350
1.082
R1 ) 0.045
wR2 ) 0.139
0.77 and -1.15 e/Å3
largest diff peak and hole
Crystal Structure Determination. Suitable crystals were mounted
on glass fibers by means of mineral oil, and the data were collected
using graphite-monochromated Mo KR radiation (0.71073 Å). Data
collections were performed on a Bruker PLATFORM/SMART 1000
CCD diffractometer (for compound 1), a Siemens P4/RA diffrac-
tometer (for 2 and 5), and a Rigaku/ADSC area detector diffrac-
tometer (for 8). The structures of 1, 2, and 5 were solved at the
University of Alberta, and that of 8 at the University of British
Columbia. The structures were solved by direct methods using
SHELXL-86 (for 1 and 2),16 SIR97 (for 8),16 or the Patterson search/
structure expansion (DIRDIF-99) (for 5),17 and were refined using
full-matrix least-squares on F2 (SHELXL-93) (for 1, 2, and 5)16
and F2 (SHELXL-97) (for 8).18 All the non-hydrogen atoms in the
four structures were refined with anisotropic displacement param-
eters. The selected crystal data and structure refinement details for
1, 2, 5, and 8 are listed in Table 1.
General Procedure for the Catalytic Studies. The procedure
used follows standard literature methods, the hydrogen-transfer
experiments being carried out in standard Schlenk glassware.4,19
All reactions were set up in a dry glovebox under N2 using 10-5
M catalyst in 2-propanol (10 mL) and a molar ratio of catalyst/
KOH/substrate ) 1:20:1000, and the magnetically stirred reaction
mixture was heated at 80 °C for selected times. For the high-
pressure H2 experiments, catalyst, base, solvent, and substrate were
placed (inside the dry glovebox) in a glass sleeve containing a
magnetic stir-bar; the sleeve was then placed and sealed in a Parr
reactor autoclave (30 mL capacity), which was subsequently purged
with H2 and filled to a selected H2 pressure. The reaction mixture
was then stirred and heated at 80 °C, usually for 24 h. The pressure
was then released, and a 0.1 mL reaction sample was collected
and diluted with 1 mL of ethyl acetate and acetone (4:1 v/v). The
reaction products were isolated and identified by GC by comparison
with data for known compounds.
Results and Discussion
Synthesis and Characterization of Complexes. Complexes
1, 2, and 4-7, of formulation RuCl2(DPPF)(N-N) [N-N )
en (1), dimen (2), diap (4), bipy (5), phen (6), and 1S,2S-dach
(7)], and [RuCl(DPPF)(dien)]Cl (3) (see Scheme 1) were
synthesized from RuCl2(PPh3)3 via consecutive substitution
reactions. Addition of 1 equiv of DPPF to a CH2Cl2 solution of
RuCl2(PPh3)3 under aerobic conditions resulted in a rapid color
change from blackish-purple to red, presumably due to formation
of RuCl2(DPPF)(PPh3), analogous to formation of the corre-
sponding DPPB complex;11,15b subsequent addition of 1 equiv
of diamine, dien, or diimine resulted in further color changes,
and straightforward workup of the solutions gave good to high
yields of high-purity products: complexes 1-4 and 7 are yellow,
while 5 and 6 are red. The ligand substitution reactions could
be readily monitored by the 31P{1H} signal of the PPh3
generated. Complex 1 has been synthesized recently in lower
yield using [RuCl2(C6H6)]2 as precursor.10
The attempted synthesis of trans-RuCl2(DPPB)(en) (8) from
RuCl2(PPh3)3 via the same procedure was unsatisfactory in that
a pure product could not be isolated from a mixture of Ru(II)
complexes that were formed in solution; however, pure 8 was
obtained when [RuCl(DPPB)]2(µ-Cl)315 was used as the precur-
sor. The green complex 8 has been made previously, in a similar
yield, from RuCl2(DPPB)(PPh3).11
(16) (a) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467. (b) Sheldrick,
G. M. SHELXL-93, Program for crystal structure determination; University
of Go¨ttingen: Germany, 1993. (c) SIR9: Altomare, A.; Burla, M. C.;
Camalli, M.; Cascarano, G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni,
A. G. G.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 1999, 32, 115.
(17) (a) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Garcia-Granda,
S.; Israel, R.; Gould, R. O.; Smits, J. M. M. DIRDIF-99; University of
Nijmegen, The Netherlands, 1999. (b) Flack, H. D. Acta Crystallogr. 1983,
A39, 876. (c) Flack, H. D.; Bernardinelli, G. Acta Crystallogr. 1999, A55,
908. (d) Flack, H. D.; Bernardinelli, G. J. Appl. Crystallogr. 2000, 33, 1143.
The Flack parameter refines to a value near zero for the correct configuration
of the structure and to a value of about one for the inverted configuration.
(18) Sheldrick, G. M. SHELXL-97, Program for crystal structure
determination; University of Go¨ttingen: Germany, 1997.
(19) For example: (a) James, B. R.; Morris, R. H. J. Chem. Soc., Chem.
Commun. 1978, 929. (b) Mizushima, E.; Yamaguchi, M.; Yamagishi, T. J.
Mol. Catal. A 1999, 148, 69. (c) Lindner, E.; Warad, I.; Eichele, K.; Mayer,
H. A. Inorg. Chim. Acta 2003, 350, 49.
The electrospray mass spectra in THF solution of complexes
1, 2, 4, and 8, which have trans-chlorides (see below), show a

850 Organometallics, Vol. 26, No. 4, 2007
Ma et al.
Figure 3. ORTEP diagram of cis-RuCl2(DPPF)(bipy) (5) with 20%
probability Gaussian ellipsoids; H atoms not shown.
Figure 1. ORTEP diagram of trans-RuCl2(DPPF)(en) (1) with 20%
probability Gaussian ellipsoids; H atoms on phenyl and cyclopen-
tadienyl rings not shown.
Figure 4. ORTEP diagram of trans-RuCl2(DPPB)(en) (8) with
20% probability Gaussian ellipsoids; H atoms not shown except
for those on the N atoms.
Figure 2. ORTEP diagram of trans-RuCl2(DPPF)(dimen) (2) with
20% probability Gaussian ellipsoids; H atoms not shown except
for those on the N atoms.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
trans-RuCl2(DPPF)(en) (1) with Estimated Standard
Deviations in Parentheses
peak corresponding to monoprotonated RuCl2(DPPF)(diamine)
species, while complexes 5 and 6, which have cis-chlorides (see
below), reveal a peak corresponding to [RuCl(DPPF)(di-
amine)]+. There is no general pattern in the MS data, however,
in that 7 (a trans-dichloro species) gives a major peak for [RuCl-
(DPPF)(dach)]+. Complex 3, the ionic species [RuCl(DPPF)-
(dien)]Cl, containing the tridentate dien ligand, gives a major
MS peak corresponding to that of the cation.
Crystal Structures of trans-RuCl2(DPPF)(en) (1), trans-
RuCl2(DPPF)(dimen) (2), cis-RuCl2(DPPF)(bipy) (5), and
trans-RuCl2(DPPB)(en) (8). The X-ray diffraction analyses of
1, 2, and 8 (Figures 1, 2, and 4, respectively) reveal trans-
dichloro structures, with the bidentate ligands necessarily being
cis; selected bond lengths and angles are listed in Tables 2, 3,
and 5, respectively. The geometry at the metal is distorted
octahedral, as seen by the P-Ru-P angles (in the 95.1-95.9°
range), the N-Ru-N angles (78.3-79.9°), and the Cl-Ru-
Cl angles (165.5-167.3°). These angles and the average Ru-
ligand bond lengths to Cl, N, and P are close to those determined
previouslyinstructuresofothertrans-andcis-RuCl2(diphosphine)-
(diamine or diimine) complexes, where the diphosphine is chiral
Ru-N(1)
Ru-N(2)
Ru-Cl(1)
Ru-Cl(2)
Ru-P(1)
Ru-P(2)
Fe-C(1)
Fe-C(2)
Fe-C(3)
Fe-C(4)
Fe-C(5)
Fe-C(6)
Fe-C(7)
Fe-C(8)
Fe-C(9)
Fe-C(10)
2.167(3)
2.171(3)
2.4030(10)
2.4279(10)
2.2957(10)
2.2865(9)
2.068(4)
2.053(4)
2.048(4)
2.031(4)
2.029(4)
2.039(4)
2.048(4)
2.050(4)
2.051(4)
2.030(4)
Cl(1)-Ru-Cl(2)
Cl(1)-Ru-P(1)
Cl(1)-Ru-P(2)
Cl(1)-Ru-N(1)
Cl(1)-Ru-N(2)
Cl(2)-Ru-P(1)
Cl(2)-Ru-P(2)
Cl(2)-Ru-N(1)
Cl(2)-Ru-N(2)
P(1)-Ru-P(2)
P(1)-Ru-N(1)
P(1)-Ru-N(2)
P(2)-Ru-N(1)
P(2)-Ru-N(2)
N(1)-Ru-N(2)
Ru-N(1)-C(51)
Ru-N(2)-C(52)
166.31(4)
87.40(4)
96.61(4)
83.68(10)
84.06(9)
104.05(4)
89.74(4)
83.95(10)
87.70(9)
95.87(4)
168.53(10)
93.65(9)
92.33(10)
170.47(9)
78.28(13)
111.0(2)
111.1(2)
or nonchiral and the N-N donor is chiral or nonchiral;4a,11,20,21
the major interest in the chiral systems is their use as catalysts,
particularly for asymmetric hydrogen-transfer hydrogenation of
ketones.4a,20 For all the trans-dichloro complexes, including 1,
2, and 8, the Ru-Cl distances are all within 0.025 Å of each
other. The crystal structure of 5 (Figure 3) revealed cis-

Ruthenium(II) Diphosphine/Diamine/Diimine Complexes
Organometallics, Vol. 26, No. 4, 2007 851
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
trans-RuCl2(DPPF)(dimen) (2) with Estimated Standard
Deviations in Parenthesesa
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
cis-RuCl2(DPPF)(bipy) (5) with Estimated Standard
Deviations in Parentheses
Ru-N(1)
Ru-N(2)
Ru-Cl(1)
Ru-Cl(2)
Ru-P(1)
Ru-P(2)
2.229(6)
2.205(7)
2.422(2)
2.419(2)
2.307(2)
2.294(2)
Cl(1)-Ru-Cl(2)
Cl(1)-Ru-P(1)
Cl(1)-Ru-P(2)
Cl(1)-Ru-N(1)
Cl(2)-Ru-P(1)
Cl(2)-Ru-P(2)
Cl(2)-Ru-N(1)
Cl(2)-Ru-N(2)
P(1)-Ru-P(2)
167.34(7)
87.78(7)
97.53(8)
86.73(18)
104.14(7)
85.74(7)
80.84(18)
90.45(19)
95.42(7)
Ru-N(1)
Ru-N(2)
Ru-Cl(1)
Ru-Cl(2)
Ru-P(1)
Ru-P(2)
N(1)-C(6)
N(2)-C(1)
2.086(6)
2.118(6)
2.4876(19)
2.433(2)
2.289(2)
2.345(2)
1.355(11)
1.329(11)
Cl(1)-Ru-Cl(2)
Cl(1)-Ru-P(1)
Cl(1)-Ru-P(2)
Cl(1)-Ru-N(1)
Cl(2)-Ru-P(1)
Cl(2)-Ru-P(2)
Cl(2)-Ru-N(1)
Cl(2)-Ru-N(2)
P(1)-Ru-P(2)
P(1)-Ru-N(1)
P(2)-Ru-N(1)
N(1)-Ru-N(2)
92.08(7)
172.91(7)
89.71(7)
82.38(18)
90.94(7)
87.05(7)
167.3(2)
89.9(2)
96.86(7)
93.36(18)
104.3(2)
78.0(3)
Ru-N(1)-C(1)
Ru-N(2)-C(4)
120.9(5)
118.0(5)
a Other bond lengths and bond angles are within 0.02 Å and 3°,
respectively, of the corresponding values given for complex 1 in Table 2.
a The bond lengths and angles within the coordinated DPPF are within
0.02 Å and 3°, respectively, of the corresponding values given for complex
1 in Table 2.
dichloride ligands, with one chlorine necessarily being trans to
a P atom and one trans to a N atom; the Ru-Cl bond length
for the chlorine trans to phosphorus (2.488 Å) is about 0.055
Å longer than for that trans to nitrogen, in line with the expected
trans-effect.22 More generally, differences in the Ru-Cl bond
of the cis-dichloro complexes are in the 0.05-0.09 Å
range.4a,11,20,21 Such RuCl2(P-P)(N-N) structures have been
discussed extensively,4a,11,20,21 and, at least in one set of
complexes, the trans- and cis-species have been shown to be
the kinetic and thermodynamic products, respectively.11
The two planar, cyclopentadienyl rings of ferrocene within
structures 1, 2, and 5 are eclipsed and are essentially coplanar,
the average torsion angle (H-C---C-H) between the C-H of
one ring and the most adjacent one of the other ring being 8.39°
(for 1), 8.00° (for 2), and 13.6° (for 5); the corresponding P-C-
C-P torsion angles are 8.04°, 9.06°, and 19.7°. In the solution
1H NMR spectra of 1 and 2 at room temperature, two signals
are seen for the ferrocene rings (see below), implying that the
small twist seen in the solid state is not evident in solution. For
complex 5, there is more splitting of the ferrocene-1H signals
(see below), consistent with the greater twist evident in the solid
state.
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
trans-RuCl2(DPPB)(en) (8) with Estimated Standard
Deviations in Parenthesesa
Ru(1)-N(1)
Ru(1)-N(2)
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-P(1)
Ru(1)-P(2)
P(1)-C(3)
2.185(3)
2.172(3)
2.4228(9)
2.4332(9)
2.2888(9)
2.2791(9)
1.852(4)
1.832(4)
1.516(6)
N(2)-Ru(1)-N(1)
N(2)-Ru(1)-P(2)
N(2)-Ru(1)-P(1)
N(1)-Ru(1)-P(1)
P(2)-Ru(1)-P(1)
N(1)-Ru1-Cl(1)
P(1)-Ru(1)-Cl(1)
P(2)-Ru(1)-Cl(2)
P(1)-Ru(1)-Cl(2)
Cl(1)-Ru(1)-Cl(2)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
78.7(1)
93.51(9)
170.60(8)
92.26(9)
95.12(3)
84.0(1)
91.26(3)
103.57(3)
96.32(3)
165.57(3)
116.1(3)
116.4(3)
P(2)-C(6)
C(4)-C(5)
Ru(1)-P(1)-C(3)
Ru(1)-P(2)-C(6)
117.7(1)
113.5(1)
a The bond lengths and angles within the coordinated en are within 0.02
Å and 3°, respectively, of the corresponding values given for complex 1
in Table 2.
axis (see Scheme 1), essentially that of the solid-state structure
without the minor distortions. Complexes 4 and 7 similarly show
31P{1H} singlets at δ 49.4 and 51.4, respectively, and are thus
also assumed to have trans-dichloro structures. In contrast,
solutions of complexes 3, 5, and 6 show a typical AX doublet
of doublets pattern in their 31P{1H} NMR spectra. For 5 and 6
(which were nonelectrolytes in CH2Cl2), the spectra are very
similar with equal intensity doublets centered, respectively, at
NMR Characterization. The 31P{1H} and 1H solution spectra
(in CD2Cl2 or CD3Cl) of each complex (1-8) revealed the
presence of just a single species. The 31P{1H} NMR spectra in
CD2Cl2 of the structurally characterized trans-dichloro com-
plexes 1, 2, and 8 show a singlet in the δ 44.5-50.9 range,
consistent with a regular octahedral structure containing a C2
2
δ ∼44 and ∼38 with JPP values of 30.6 Hz; presumably both
5 and 6 in solution have the cis-dichloro structure (see Scheme
1), consistent with the solid-state structure determined for 5.
Complex 3 is a 1:1 electrolyte as expected, as evidenced by
conductivity data in CH2Cl2 (ΛM ) 10.9 Ω-1 cm2 mol-1).23
The dien ligand is tridentate, enforcing a cis-disposition of the
P atoms in a structure like that shown in Scheme 1 for 5 and 6,
but with one chloride replaced by a dien N atom; the 31P{1H}
data for 3 (δ 52.8 and 38.6, 2JPP ) 35.5 Hz) are similar to those
of 5 and 6, suggesting that the Cl trans to PA is replaced (see
Scheme 1).
(20) For example: (a) Gao, J.-X.; Ikariya, T.; Noyori, R. Organometallics
1996, 15, 1087. (b) Akotsi, O. M.; Metera, K.; Reid, R. D.; McDonald, R.;
Bergens, S. H. Chirality 2000, 12, 514. (c) Doherty, S.; Newman, C. R.;
Hardacre, C.; Nieuwenhuyzen, M.; Knight, J. G. Organometallics 2003,
22, 1452. (d) Lindner, E.; Mayer, H. A.; Warad, I.; Eichele, K. J. Organomet.
Chem. 2003, 665, 176. (e) Lindner, E.; Warad, I.; Eichele, K.; Mayer, H.
A. Inorg. Chim. Acta 2003, 350, 49. (f) Leong, C. G.; Akotsi, O. M.;
Ferguson, M. J.; Bergens, S. H. Chem. Commun. 2003, 750 and 1779
(correction). (g) Baratta, W.; Herdtweck, E.; Siega, K.; Toniutti, M.; Rigo,
P. Organometallics 2005, 24, 1660. (h) de Araujo, M. P.; de Figueiredo,
A. T.; Bogado, A. L.; Poelhsitz, G. V.; Ellena, J.; Castellano, E. E.; Donnici,
C. L.; Comasseto, J. V.; Batista, A. A. Organometallics 2005, 24, 6159.
(21) For example: (a) Song, J.-H.; Cho, D.-J.; Jeon, S.-J.; Kim, Y.-H.;
Kim, T.-J.; Jeong, J. H. Inorg. Chem. 1999, 38, 893. (b) Santra, P. K.;
Sinha, C.; Sheen, W.-J.; Liao, F.-L.; Lu, T.-H. Polyhedron 2001, 20, 599.
(c) Korenaga, T.; Aikawa, K.; Terada, M.; Kawauchi, S.; Mikami, K. AdV.
Synth. Catal. 2001, 343, 284. (d) Butler, I. R.; Coles, S. J.; Fontani, M.;
Hursthouse, M. B.; Lewis, E.; Abdul Malik, K. L. M.; Meunier, M.; Zanello,
P. J. Organomet. Chem. 2001, 637-639, 538. (e) Wong, W.-K.; Chen,
X.-P.; Guo, J.-P.; Chi, Y.-G.; Pan, W.-X.; Wong, W.-Y. J. Chem. Soc.,
Dalton Trans. 2002, 1139. (f) Nachtigal, C.; Al-Gharabli, S.; Eichele, K.;
Lindner, E.; Mayer, H. A. Organometallics 2002, 21, 105. (g) Harvey, B.
G.; Arif, A. M.; Ernst, R. D. Polyhedron 2004, 23, 2725. (h) Santiago, M.
O.; Batista, A. A.; de Arau´jo, M. P.; Donnici, C. L.; Moreira, I. de S.;
Castellano, E. E.; Ellena, J.; Santos, S. dos; Queiroz, S. Transition Met.
Chem. 2005, 30, 170.
Of note, it is the bidentate-diimine ligand systems, 5 and 6,
that generate the cis-dichloro species, while the bidentate-
diamine species (1, 2, 4, 7, and 8) exist as trans-dichloro species.
Presumably the rigid diimines, compared to the more flexible
diamines, have considerably less steric interaction with cis-
chlorides (see Figure 3, for 5) than with trans-dichlorides (cf.
Figure 3 vs Figures 1 and 2 for complexes 1 and 2). Attempts
to synthesize RuCl2(DPPF)(2,2′-biquinoline) with the bulkier
diimine were unsuccessful. Of note, within the series of RuCl2-
(DPPB)(N-N) complexes, when N-N is bipy or phen, both
the cis- and trans-dichloro species have been isolated, the former
(22) (a) Cotton, F. A.; Wilkinson, G. AdVanced Inorganic Chemistry,
5th ed.; John Wiley & Sons: New York, 1988; p 1299.
(23) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.

852 Organometallics, Vol. 26, No. 4, 2007
Ma et al.
being the thermodynamic product;11 this is consistent with the
DPPB ligand being less bulky and more flexible that DPPF.
Although only trans-RuCl2(DPPB)(en) has been isolated (ref
11 and this work), the overall findings imply that the cis-isomer
should be isolable under appropriate conditions.
Table 6. Catalyzed Hydrogen-Transfer Hydrogenation of
Acetophenonea
precursor catalysts
t)trans, c)cis
conversion (%)
t-RuCl2(DPPF)(en) (1)
91; 32b
90;c 16b
75; 29b
86
t-RuCl2(DPPF)(dimen) (2)
[RuCl(DPPF)(dien)]Cl (3)
t-RuCl2(DPPF)(diap) (4)
c-RuCl2(DPPF)(bipy) (5)
c-RuCl2(DPPF)(phen) (6)
t-RuCl2(DPPF)(1S,2S-dach) (7)
t-RuCl2(DPPB)(en) (8)
1
The H NMR spectra for the eight cyclopentadienyl (Cp)
protons of the DPPF ligand provide information of the degree
of deformity of the ferrocene rings. For CD2Cl2 solutions of
the trans-dichloro complexes, 1, 2, and 4, two equal intensity
singlets are observed in the δ 4.1-4.6 range, each corresponding
to four protons, presumably, for example, for 1 (see Figure 1)
on C atoms C2, C5, C7, and C10 and on C atoms C3, C4, C8,
and C9; these data are consistent with the solid-state structures
determined for 1 and 2, where the two ferrocene rings are
eclipsed and are essentially coplanar. The structure of 4 is
presumably similar. The corresponding 1H spectrum for trans-
RuCl2(DPPF)(1S,2S-dach) (7) is different in that four singlets
of two protons each are seen in the δ 4.2-4.7 range, implying
that in a structure that must be similar to that of 1 (Figure 1)
the C2- and C5-protons must be magnetically slightly different
than those on C7 and C10, and similarly the C3/C4 protons
differ from the C8/C9 set; five 13C resonances are seen for the
C atoms of the two Cp rings.
82
91
92; 69d
93; 95e
45; 61f
[RuCl(p-cymene)]2(µ-Cl)2
a Experimental conditions (see Experimental Section), unless stated
b
otherwise: under N2, 80 °C for 24 h, Cat:Base:S ) 1:20:1000. At 35 °C.
d
f
c48 h. At 45 °C. e Under 1 atm H2. 0.1 mL of 2.0 M en (0.2 mmol) added.
sort of virtual coupling between the two P atoms). Complexes
2-4 show six 13C{1H} signals, but the spectra are complicated,
as the resonances are a mixture of singlets, doublets, triplets,
and multiplets because of coupling to P atoms. In the 13C-
{1H,31P} data for 7, the phenyl carbons appear as two sets of
six singlets (with a maximum of 0.3 ppm between each pair of
corresponding singlets), presumably implying magnetic in-
equivalence of the two phenyl substituents at each P atom. The
13C{1H}-phenyl region for complexes 5 and 6 is more compli-
cated because of the presence of the bipy/phen ligands.
The absorption spectra of complexes 1-6 were measured in
CH2Cl2 solution; free DPPF has absorption maxima at 221 and
251 nm, with respective ꢀ values of 4.03 × 104 and 2.56 × 104
mol L-1 cm-1. The complexes reveal three UV-vis absorption
maxima (for 5 and 6) or two absorption maxima and a shoulder
band (for 1-4, see Figure S2). On the basis of literature data,24
the shoulder peaks (335-349 nm) are tentatively assigned to
charge transfer from the Ru(II) to a ligand (presumably the P
atom donors). The intense absorption at ∼220 nm essentially
arises from the DPPF, but the increased molar extinction
coefficients of the complexes (vs that of free DPPF) suggest
that metal-to-ligand charge transfer may also contribute to this
peak. The relatively weak absorption maxima around 460 nm
for complexes 1-4 and small shoulders at 545 and 547 nm for
5 and 6 may be d-d transitions. For 5 and 6, the bipy- and
phen-containing species, the more intense absorption bands at
456 and 442 nm, respectively, are almost certainly metal-to-
imine MLCT bands,24 and these give rise to the red color of
these complexes compared with the yellow colors of 1-4. The
absorption bands at 303 and 274 nm for 5 and 6, respectively,
are thought to be π f π* transitions of the aromatic imine
ligands.24
1
The H NMR spectra for the eight Cp protons of the ionic
monochloro complex 3 and the cis-dichloro complexes 5 and 6
are more complex, with signals covering the range δ 3.2-6.2.
For 3 and 5, seven resonances are seen with one at δ 4.21 and
4.52, respectively, having twice the intensity of the others; for
1
6, eight signals of equal intensity are observed. The H-1H
COSY spectrum of 6 (Figure S1) shows clearly the eight
resonances, and the cross-peaks confirm that signals 1, 2, 3,
and 4 come from one ring and that signals 5, 6, 7, and 8 come
from the other ring. The more complex spectra are consistent
with less symmetrical structures (cf. the above crystal structure
section). For all the complexes 1-7, the expected 3JHH coupling
for the Cp protons is not resolved, and the resonances are seen
as singlets.
Generally, the more flexible amine-containing structures
reveal, as expected, a lower number of 13C resonances than do
the more rigid imine-containing species. For complexes 1-4,
three singlet 13C resonances are seen for the Cp carbon atoms,
which correspond to the three types of Cp-carbons; for example,
for 1, signals at δ 70.4, 76.6, and 87.7 must correspond to C3,-
C4,C8,C9; C2,C5,C7,C10; and C1,C6, respectively (Figure 1),
and an APT measurement (Attached Proton Test) confirmed
these assignments. For 7, five resonances are seen at δ 70.2,
70.4, 76.5, 76.8, and 88.9, suggesting that the two sets of close
singlets (e.g., at δ 70.2/70.4 and at 76.5/76.8) are each seen as
one singlet for complexes 1-4. The cis-complexes 5 and 6 have
less symmetry and show eight and nine resonances, respectively;
for example, for 6, there are two sets of singlets at δ 66.1, 71.3,
74.1, 78.0 and at δ 70.7, 73.8, 76.2, 79.0, which correspond to
the eight C-H carbons of the two Cp rings, and a singlet at δ
85.6 that is characteristic of the two C-P carbons.
Similar complications arise when trying to assign 13C{1H}
signals for the phenyl carbon atoms. Complex 1 shows es-
sentially four signals (corresponding to the four types of
carbons), which are in excellent agreement with values in the
literature,10 where, however, the multiplicity of the 13C{1H}
signals was not discussed (note that this complex is incorrectly
numbered in the Experimental Section of ref 10); the doublet
and triplet patterns are necessarily due to coupling to P atoms,
and this was shown in our work by measuring the 13C{1H,31P}
signals, which are all singlets (the triplets must result from some
Catalytic Transfer Hydrogenation of Ketones. Complexes
of formulation RuCl2(P-P)(N-N) have been widely used as
hydrogenation precursor catalysts, using either H2 or 2-propanol
as the hydrogen source (see Introduction and refs 1j, 4, 6, 7,
20). Complexes 1-8 were similarly tested for hydrogenation
of acetophenone by hydrogen-transfer from a basic solution of
2-propanol (eq 1, Table 6), using the complex (10.0 µmol),
added KOH (0.2 mmol), and the ketone (1.2 g, 10.0 mmol) in
2-propanol (10 mL) at 80 °C, i.e., a catalyst/base/substrate (Cat/
Base/S) ratio of 1:20:1000. The data indicate that complexes
1-8 are all reasonably efficient hydrogen-transfer catalysts
under a nitrogen atmosphere. The complexes are air-stable in
(24) (a) Ford, P. C.; Rudd, D. P.; Gaunder, R.; Taube. H. J. Am. Chem.
Soc. 1968, 90, 1187. (b) Clarke, R. E.; Ford, P. C. Inorg. Chem. 1970, 9,
227. (c) Silva, H. A. S.; Carlos, R. M.; Camargo, A. J.; Picchi, C. M. C.;
de Almeida Santos, R. H.; McGarvey, B. R. Franco, D. W. Inorg. Chim.
Acta 2004, 357, 3147.

Ruthenium(II) Diphosphine/Diamine/Diimine Complexes
Organometallics, Vol. 26, No. 4, 2007 853
Table 7. Transfer-Hydrogenation of Substrates Catalyzed
by Complex 8a
Figure 5. Conversion versus reaction time for conditions given in
the Experimental Section. Precursor catalyst systems shown are for
complex 1 (black line), 2 (blue line), 5 (red line), and 6 (green
line).
of the hydrogenations (see Figure 5), and so the imine systems
are not considered to involve any extraneously formed amine
ligand.
Presumably, the hydrogenations catalyzed by trans-RuCl2-
(P-P)(en) operate via the bifunctional mechanism in which the
“RuH-NH” unit plays a key role.1j,4-7 Although we have no
definitive data to support this premise, we can select “fortuitous”
data for systems based on complexes 1 and 2 (the en and dimen
species) that appear to! For example, for the first 2 h at 80 °C
(Figure 5), conversions achieved using 1 are about twice those
achieved with 2, a factor consistent with the fact that 1
statistically has twice as many H atoms available compared to
2 for forming the required H-bonded reaction intermediates. To
the best of our knowledge, our report is the first to describe
such Ru(II)-diphosphine-diamine complexes with the varying
amine donor groups being -NH2 and -NHMe, and further
detailed kinetic studies are planned with these diamine and
diimine systems.
a Experimental conditions: as in footnote a of Table 6, unless noted
b
c
otherwise. Under 700 psi H2. 0.02 M KOH, no Ru catalyst. d 0.66 M KOH,
no Ru catalyst.
the solid state and in solution, but the catalysis requires an
oxygen-free environment; exposure of the reacting systems to
air completely inhibited the catalysis.
PhCOCH3 + (CH3)2CH(OH) catalyst, KOH8 PhCH(OH)CH3 +
80 °C, N2
(CH3)2CO (1)
The activities of the cis-dichloro species 5 and 6 under N2
are similar to those of cis-RuCl2(DPPB)(N-N), where N-N
) bipy or phen, when these were used under similar hydrogen-
transfer conditions but also under 1 atm H2 (78% conversion
after 3 h).20h Under an Ar atmosphere, the DPPB systems
showed lower activity: for example, the bipy system gave 50%
conversion after 24 h20h versus the 82% for cis-RuCl2(DPPF)-
(bipy) (5) (Table 6). The activities of complexes 1-7 for
acetophenone reduction are less than those of the corresponding
isocyanide complexes, trans-RuCl2(DPPF)(CNR)2, under cor-
responding conditions.13
The effect of using an atmosphere of H2 above the hydrogen-
transfer conditions for reduction of acetophenone was also
studied with trans-RuCl2(DPPB)(en) (8). Some experimental
data are shown in Table 6 and Figure S3, where there is little
difference in the conversions after 2 or 24 h; the presence of
H2 is thus not essential for the reduction, which is in contrast
to data reported for the RuCl2(DPPB)(diimine) systems.20h Data
for reduction of 4-methylacetophenone, 4-phenyl-2-butanone,
A “blank” experiment in the absence of a Ru complex (using
0.02 M KOH in 2-propanol, S/Base ) 50) showed just 6%
conversion of acetophenone after 24 h, although at higher
[KOH] (0.66 M KOH and 1.0 M acetophenone, S/Base ) 1.5),
91% conversion was observed (see Table 7). Such metal-free,
base-catalyzed conversions are well documented.25
Conversion versus time plots for the four DPPF-containing
precursor catalysts 1, 2, 5, and 6 (N-N ) en, dimen, bipy, and
phen, respectively) are shown in Figure 5. The systems give
∼50% conversions after 1-3 h, and the relative activity
sequence up to ∼10 h is en ∼ phen > bipy ∼ dimen. The
activities of the imine-containing species 5 and 6 are thus
comparable to those of the amine species 1 and 2, showing that
active hydrogens on the N atoms are not essential for hydro-
genation and that mechanisms other than ionic hydrogenation,1j,4-7
such as the more classical “hydride” or “unsaturated” mech-
anisms,1j,6,20b,26,27 must be operative in these Ru(II) systems.
Such findings for “NH-free” active Ru(II) systems are not novel
and have been discussed.20f,h The imine ligands are not reduced
to amine; further, there is no induction period at the beginning
(26) Standfest-Hauser, C.; Slugovc, C.; Mereiter, K.; Schmid, R.;
Kirchner, K.; Xiao, L.; Weissensteiner, W. J. Chem. Soc., Dalton Trans.
2001, 2989.
(27) (a) James, B. R. AdV. Organomet. Chem. 1979, 17, 319. (b)
Johnstone, R. A. W.; Wilby, A. H.; Entwistle, I. D. Chem. ReV. 1985, 85,
129.
(25) For example: (a) Le Page, M. D.; James, B. R. Chem. Commun.
2000, 1647. (b) Crochet, P.; Gimeno, J.; Garcia-Granda, S.; Borge, J.
Organometallics 2001, 20, 4369. (c) Thoumazet, C.; Melaimi, M.; Ricard,
L.; Mathey, F.; Floch, P. L. Organometallics 2003, 22, 1580.

854 Organometallics, Vol. 26, No. 4, 2007
Ma et al.
and 4-methoxypropiophenone (see Table 7) similarly reveal that
H2 is not essential.
addition of en does promote activity, at least for a phosphine-
free, nonchiral system.
There was no reduction of the CdC bond in styrene or the
lignin model compound 3,4-dimethoxystyrene when this sub-
strate was tested under the same hydrogen-transfer conditions
(under N2), further demonstrating the general selectivity of the
RuCl2(P-P)(N-N) systems for reduction of the polar CdO
bond.1h,4,19b,20e,25b,c However, there are exceptions; for example,
both the olefinic CdC and the CdO bonds are reduced in the
catalyzed hydrogen-transfer hydrogenation of trans-4-phenyl-
3-buten-2-one using trans-RuCl2(DPPP)(1,2-diaminobenzene)
as catalyst, where DPPP ) 1,3-(diphenylphosphino)propane.20d
Of complexes 1-8, only 7 contains a chiral diamine moiety
(1S,2S-dach), and use of this complex as catalyst precursor did
induce some enantiomeric excess into the alcohol product
formed from acetophenone. The measured ee values are higher
at lower temperatures, and the higher values were recorded at
lower conversions. For example, a maximum ee value of 36%
was noted at ∼25% conversion at 45 °C, while empirically the
R/S ratio decreases almost linearly with reaction time at both
80 and 45 °C (with similar slopes; see Figure S4); use of the
S,S-form of the diamine generated the R-alcohol, not an unusual
finding.28
Conclusions
Five new complexes of the type cis- or trans-RuCl2(P-P)-
(N-N) are reported, where P-P ) DPPF and N-N ) a
diamine or diimine ligand; the cationic complex [RuCl(DPPF)-
(dien)]Cl is also described, as well as improved syntheses for
trans-RuCl2(DPPF)(en) and trans-RuCl2(DPPB)(en). Crystal
structures are presented for these two ethylenediamine com-
plexes as well as for trans-RuCl2(DPPF)(dimen) and cis-RuCl2-
(DPPF)(bipy). Preliminary data are presented on the use of the
eight complexes as precursor catalysts for transfer hydrogenation
(from 2-propanol) of acetophenone and some related ketones;
the catalysis is effective under either a nitrogen or a hydrogen
atmosphere, although yields of the 1-phenylethanol product are
typically marginally higher when H2 is used. There is little
difference between the activities of the diamine and diimine
systems, implying that classical “hydride” and/or “unsaturated”
mechanistic pathways may be competitive with any bifunctional
mechanism that might be operating in the diamine systems (i.e.,
where the H2 is derived from a metal-hydride and an amine
proton).
Use of the precursor catalyst trans-RuCl2(DPPF)(1S,2S-dach),
containing the chiral diamine, does generate chirality in the
alcohol product, but only to a maximum extent of 36% at the
low conversion of 25%.
Of complexes 1-8, trans-RuCl2(DPPB)(en) (8) marginally
shows the highest activity (93% for the conditions shown in
Table 6) for hydrogen-transfer hydrogenation of acetophenone.
This catalyst system was thus tested with several alkyl-aryl
ketones, selected as model substrates for carbonyl components
of lignin (see Table 7); p-Me and p-OMe substituents in the
aryl moiety do not seriously inhibit the hydrogenation, but
introduction of a p-OH group likely does, as evidenced by the
ineffective reduction of acetovanillone, The phenyl-substituted
dialkyl ketone, 4-phenyl-2-butanone, was readily reduced.
Acknowledgment. The authors thank the Natural Sciences
and Engineering Research Council (NSERC) of Canada for
financial support in terms of a Discovery Grant (to R.G.C.) and
a Strategic Project Grant (to B.R.J. and T.Q.H.), and Colonial
Metals, Inc. for a gift of RuCl3‚3H2O.
Reetz and Li have recently reported use of the p-cymene-
containing precursor [RuCl(C10H14)]2(µ-Cl)2 in the presence of
BINOL-derived diphosphonites for extremely effective asym-
metric hydrogen-transfer hydrogenation (from 2-propanol) of
ketones; it is notable that these systems do not require the
presence of ancillary diamine ligands.1k In addition, Deng’s
group29a and Noyori’s group29b have earlier used the same
precursor in the presence of a chiral diamine (with no diphos-
phine) for similar ketone hydrogenation in either aqueous media
using sodium formate29a or basic 2-propanol29b as hydrogen
donor. We tested this precursor alone in the absence of a
diphosphine and in the presence of en (Table 6): conversions
after 24 h were, respectively, 45% and 61%, showing that
Note Added after ASAP Publication. In the version of this
paper that was published on the Web on Jan 19, 2007, the â
values for compounds 2 and 8 (92.937(9) and 111.750(3),
respectively) were incorrectly shown as being R values. This
was due to a production error. The version of the table that
now appears is correct.
Supporting Information Available: Crystallographic data (as
CIF files) for complexes trans-RuCl2(DPPF)(en) (1), trans-RuCl2-
(DPPF)(dimen) (2), cis-RuCl2(DPPF)(bipy) (5), and trans-RuCl2-
(DPPB)(en) (8). Figures S1-S4. These materials are available free
of charge via the Internet at http://pubs.acs.org.
OM060987Z
(28) (a) Ito, M.; Hirakawa, M.; Murata, K.; Ikariya, T. Organometallics
2001, 20, 379. (b) Ohkuma, T.; Koizumi, M.; Muniz, K.; Hilt, G.; Kabuto,
C.; Noyori, R. J. Am. Chem. Soc. 2002, 124, 6508.
(29) (a) Ma, Y.; Liu, H.; Chen, L.; Cui, X.; Zhu, J.; Deng, J. Org. Lett.
2003, 5, 2103. (b) Yamakawa, M.; Yamada, I.; Noyori, R. Angew. Chem.,
Int. Ed. 2001, 40, 2818.