Ruthenium(II) complexes containing bis(2-(diphenylphosphino)phenyl) ether and their catalytic activity in hydrogenation reactions

Article abstract of DOI:10.1021/ic061782l

The half-sandwich complexes [(η⁵-C₅H ₅)RuCl(DPEphos)] (1) and [{(η⁶-p-cymene)RuCl ₂}₂(μ-DPEphos)] (2) were synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride trihydrate and cyclopentadiene and with [(η⁶-p- cymene)RuCl₂]₂, respectively. Treatment of DPEphos with cis-[RuCl₂-(dmso)₄] afforded fac-[RuCl₂(κ ³-P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine, 2,2′-bipyridine, 4,4′-bipyridine, and PPh₃ to yield trans,cis-[RuCl₂(DPEphos)(C₅H₅N) ₂] (4), cis,cis-[RuCl₂(DPEphos)-(2,2′-bipyridine)] (5), trans,cis-[RuCl₂(DPEphos)(μ-4,4′-bipyridine)] _n (6), and mer,trans-[RuCl₂(κ³-P,P,O- DPEphos)-(PPh₃)] (7), respectively. Refluxing [(η⁶-p- cymene)RuCl₂]₂ with DPEphos in moist acetonitrile leads to the elimination of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl₂(DPEphos)(H₂O)(CH₃CN)] (8). The structures of the complexes 1-5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of these complexes for the hydrogenation of styrene is studied.

Full text of DOI:10.1021/ic061782l

Inorg. Chem. 2007, 46, 809−817
Ruthenium(II) Complexes Containing Bis(2-(diphenylphosphino)phenyl)
Ether and Their Catalytic Activity in Hydrogenation Reactions
Ramalingam Venkateswaran,† Joel T. Mague,‡ and Maravanji S. Balakrishna*,†
Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay,
Mumbai 400 076, India, and Department of Chemistry, Tulane UniVersity,
New Orleans, Lousiana 70118
Received September 20, 2006
The half-sandwich complexes [(
synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride
trihydrate and cyclopentadiene and with [(
6-p-cymene)RuCl2]2, respectively. Treatment of DPEphos with cis-[RuCl2-
(dmso)4] afforded fac-[RuCl2(κ3-P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine,
2,2 -bipyridine, 4,4 -bipyridine, and PPh3 to yield trans,cis-[RuCl2(DPEphos)(C5H5N)2] (4), cis,cis-[RuCl2(DPEphos)-
(2,2 -bipyridine)] (5), trans,cis-[RuCl2(DPEphos)( -4,4
-bipyridine)]n (6), and mer,trans-[RuCl2(κ3-P,P,O-DPEphos)-
(PPh3)] (7), respectively. Refluxing [(
6-p-cymene)RuCl2]2 with DPEphos in moist acetonitrile leads to the elimination
of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl2(DPEphos)(H2O)(CH3CN)] (8).
The structures of the complexes 1 5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of
these complexes for the hydrogenation of styrene is studied.
η {(η }2(µ-DPEphos)] (2) were
5-C5H5)RuCl(DPEphos)] (1) and [ 6-p-cymene)RuCl2
η
′
′
′
µ
′
η
−
Introduction
containing ligands such as PPh3, dppm, dppe, pyridines, and
dmso associated with Ru are well documented,5 whereas the
ruthenium chemistry of bis(2-(diphenylphosphino)phenyl)
ether (DPEphos) has not been studied. The large bite angle
DPEphos with a relatively rigid diphenyl ether backbone and
containing both oxygen and phosphorus donor sites6 offers
different coordination modes through the possibility of
behaving as a hemilabile ligand, thereby providing the
promise of rich coordination and organometallic chemistry
with various metal centers. van Leeuwen and co-workers7
and others8 have extensively studied the coordination chem-
istry and catalytic utility of DPEphos.9 As part of our research
interest,10 herein we report the syntheses of ruthenium
The chemistry of RuII complexes incorporating phosphorus
donor ligands has received considerable attention in recent
years since the discovery of Noyori’s BINAP-RuX2 catalysts,
which developed a practical way to prepare an intermediate
for the synthesis of prostaglandin and carbapenam antibiot-
ics,1 and Grubb’s L2X2RudCHR catalysts, leading to im-
pressive development in the field of olefin metathesis.2 RuII
complexes containing nitrogen donor ligands have acquired
considerable significance in supramolecular chemistry,3
photoredox processes for solar energy conversions, biosen-
sors, and catalysis.4 Phosphorus-, nitrogen-, and sulfur-
* To whom correspondence should be addressed. E-mail: krishna@
chem.iitb.ac.in. Fax: +91-22-5172-3480.
(5) (a) Fache, F.; Schulz, E.; Tommasino, M. L.; Lemaire, M. Chem. ReV.
2000, 100, 2159-2231. (b) Tang, W.; Zhang, X. Chem. ReV. 2003,
103, 3029-3069. (c) Drozdzak, R.; Allaert, B.; Ledoux, N.; Dragutan,
I.; Dragutan, V.; Verpoort, F. Coord. Chem. ReV. 2005, 249, 3055-
3074.
(6) Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Acc. Chem.
Res. 2001, 34, 895-904.
(7) (a) Kranenburg, M.; van der Burgt, Y. E. M.; Kamer, P. C. J.; van
Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J. Organometallics 1995,
14, 3081-3089. (b) van Haaren, R. J.; Zuidema, E.; Fraanje, J.;
Goubitz, K.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; van
Strijdonck, G. P. F. C. R. Chim. 2002, 5, 431-440. (c) Zuideveld, M.
A.; Swennenhuis, B. H. G.; Boele, M. D. K.; Guari, Y.; van Strijdonck,
G. P. F.; Reek, J. N. H.; Kamer, P. C. J.; Goubitz, K.; Fraanje, J.;
Lutz, M.; Spek, A. L.; van Leeuwen, P. W. N. M. J. Chem. Soc.,
Dalton Trans. 2002, 2308-2317.
† Indian Institute of Technology.
‡ Tulane University.
(1) (a) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40, 40-73.
(b) Noyori, R. Angew. Chem., Int. Ed. 2002, 41, 2008-2022. (c)
Mikami, K.; Korenaga, T.; Ohkuma, T.; Noyori, R. Angew. Chem.,
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Trnka, T. M.; Day, M. W.; Grubbs, R. H. Organometallics 2001, 20,
3845-3847.
(3) Cronin, L. Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem. 2005, 101,
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10.1021/ic061782l CCC: $37.00
Published on Web 01/06/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 3, 2007 809

Venkateswaran et al.
Scheme 1. Reactions of DPEphos with (i) RuCl3 and Cp in Ethanol,
(ii) [RuCl2(p-cymene)]2 in CH2Cl2, (iii) cis-[RuCl2(dmso)4] in CH2Cl2,
and (iv) [RuCl2(p-cymene)]2 in CH3CN
Figure 1. Molecular structure of complex 1. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms have been omitted for clarity.
complexes containing DPEphos and studies in the catalytic
hydrogenation of styrene.
Results and Discussion
Treatment of a mixture of DPEphos and cyclopentadiene
with ruthenium trichloride affords the half-sandwich complex
[(η5-C5H5)RuCl(DPEphos)] (1) in good yield (Scheme 1).
The 31P NMR spectrum of complex 1 shows single
resonance at 42.4 ppm. The cyclopentadiene group presents
Figure 2. Molecular structure of complex 2. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms have been omitted for clarity.
1
a single resonance at 4.10 ppm in the H NMR spectrum.
The mass spectrum (EI) and microanalysis supports the
structure, which is further confirmed by single-crystal X-ray
crystallography. The RuII center adopts distorted tetrahedral
geometry in which the P1-Ru-P2, P1-Ru-Cl, and P2-
Ru-Cl bond angles are 96.14(2)°, 88.19(2)°, and 95.52(2)°,
respectively. The Ru-P bond distances are 2.294(1) and
2.321(1) Å, and the Ru-C bond distances range from 2.192-
(2) to 2.222(2) Å with an average bond distance of 2.206(1)
Å, values which are consistent with the literature.11 The bite
angle of DPEphos in complex 1 is 96.14°, which is 5.86°
less than the natural bite angle (ân ) 102°)6 (Figure 1).
The reaction of DPEphos with [RuCl2(η6-p-cymene)]2 in
1:1 molar ratio results in the formation of the binuclear
complex [{(η6-p-cymene)RuCl2}2(µ-DPEphos)] (2). The 1H
NMR spectrum of 2 shows peaks at 1.16 (d), 1.80 (s), 2.87
(s, br), 4.79 (d), and 5.00 (d) ppm corresponding to the
p-cymene group. The 31P NMR spectrum shows single
resonance at 21.3 ppm. The structure of the complex 2 was
confirmed by single-crystal X-ray crystallography, which
shows that the molecule possesses crystallographically
imposed centrosymmetry. The Ru-C bond distances range
from 2.177(3) to 2.256(3) Å with an average bond distance
of 2.215(3) Å and the Ru-P bond distance is 2.3706(10) Å.
The Cl1-Ru-Cl2, Cl1-Ru-P, and Cl2-Ru-P bond angles
of 88.67(3)°, 90.06(3)°, and 85.04(3)° are in accordance with
the literature12(Figure 2).
(8) (a) Kim, D.; Park, B.-M.; Yun, J. Chem. Commun. 2005, 1755-1757.
(b) Kuang, S.-M.; Cuttell, D. G.; McMillin, D. R.; Fanwick, P. E.;
Walton, R. A. Inorg. Chem. 2002, 41, 3313-3322. (c) Kuang, S.-M.;
Fanwick, P. E.; Walton, R. A. Inorg. Chem. 2002, 41, 405-412. (d)
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Spek, A. L.; Vogt, D. Organometallics 2005, 24, 13-15. (e) Pintado-
Alba, A.; de la Riva, H.; Nieuwhuyzen, M.; Bautista, D.; Raithby, P.
R.; Sparkes, H. A.; Teat, S. J.; Lo´pez-de-Luzuriagae, J. M.; Lagunas,
M. C. Dalton Trans. 2004, 3459-3467.
(9) (a) van Leeuwen, P. W. N. M.; Kamer, P. C. J.; Reek, J. N. H.; Dierkes,
P. Chem. ReV. 2000, 100, 2741-2769. (b) Ahmed, M.; Seayad, A.
M.; Jackstell, R.; Beller, M. J. Am. Chem. Soc 2003, 125, 10311-
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Colobert, F. Org. Lett. 2004, 6, 4419-4422. (d) Chen, Y.; Zhang, X.
P. J. Org. Chem. 2003, 68, 4432-4438. (e) Csuk, R.; Barthel, A.;
Raschke, C. Tetrahedron 2004, 60, 5737-5750. (f) Gao, G.-Y.; Colvin,
A. J.; Chen, Y.; Zhang, X. P. Org. Lett. 2003, 5, 3261-3264. (g)
Kozawa, Y.; Mori, M. J. Org. Chem. 2003, 68, 3064-3067. (h)
Kuwano, R.; Kondo, Y.; Matsuyama, Y. J. Am. Chem. Soc. 2003,
125, 12104-12105. (i) Ogasawara, M.; Ikeda, H.; Nagano, T.;
Hayashi, T. Org. Lett. 2001, 3, 2615-2617. (j) Oh, C. H.; Reddy, V.
R. Tetrahedron Lett. 2004, 45, 5221-5224. (k) Willis, M. C.; Taylor,
D.; Gillmore, A. T. Org. Lett. 2004, 6, 4755-4757. (l) Wolfe, J. P.;
Rossi, M. A. J. Am. Chem. Soc. 2004, 126, 1620-1621.
(10) (a) Balakrishna, M. S.; Santarsiero, B. D.; Cavell, R. G. Inorg. Chem.
1994, 33, 3079-3084. (b) Balakrishna, M. S.; Panda, R.; Smith, D.
C. J.; Klaman, A.; Nolan, S. P. J. Organomet. Chem. 2000, 599, 159-
165. (c) Balakrishna, M. S.; Abhyankar, R. M.; Walawalker, M. G.
Tetrahedron Lett. 2001, 42, 2733-2734. (d) Balakrishna, M. S.; Teipel,
S.; Pinkerton, A. A.; Cavell, R. G. Inorg. Chem. 2001, 40, 1802-
1808. (e) Balakrishna, M. S.; Panda, R.; Mague, J. T. J. Chem. Soc.,
Dalton Trans. 2002, 4617-4621. (f) Balakrishna, M. S.; Panda, R.;
Mague, J. T. Polyhedron 2003, 22, 587-593. (g) Priya, S.; Bal-
akrishna, M. S.; Mobin, S. M.; McDonald, R. J. Organomet. Chem.
2003, 688, 227-235. (h) Chandrasekaran, P.; Mague, J. T.; Bal-
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3780-3783. (j) Chandrasekaran, P.; Mague, J. T.; Balakrishna, M. S.
Inorg. Chem. 2006, 45, 5893-5897. (k) Chandrasekaran, P.; Mague,
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The reaction of cis-[RuCl2(dmso)4] with DPEphos affords
exclusively fac-[RuCl2(κ3-P,O,P-DPEphos)(dmso)] (3) in
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556, 151-158.
810 Inorganic Chemistry, Vol. 46, No. 3, 2007

Ruthenium(II) Complexes and Their Catalytic ActiWity
Figure 3. Molecular structure of complex 3. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms and uncoordinated solvent
molecules have been omitted for clarity.
Figure 4. Molecular structure of complex 4. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms and uncoordinated solvent
molecules have been omitted for clarity.
good yield, irrespective of the stoichiometry and reaction
conditions. The 31P NMR spectrum of complex 3 exhibits a
singlet at 45.2 ppm and suggests that both the P atoms are
in the same environment either cis to each other and trans
to chlorides or mutually trans to each other. Proton NMR
displays a singlet at 2.91 ppm corresponding to the methyl
protons present in the coordinated dmso molecule. The (EI)
mass spectrum displays the isotopic pattern for ruthenium
with a molecular ion peak at m/z 752.96 [M - Cl]+. The
structure of complex 3 was confirmed by the single-crystal
X-ray diffraction study. In the molecular structure of 3,
DPEphos binds to ruthenium in the fac orientation with the
κ3-P,O,P mode of coordination in which the two phosphorus
centers are in cis positions and trans to the chlorides with
one dmso molecule (S-donor) coordinating trans to the
oxygen atom. The geometry around the ruthenium center is
distorted octahedral, as confirmed by P1-Ru-Cl1, P1-Ru-
S, and O-Ru-S bond angles of 164.45(3)°, 97.53(3)°, and
178.89(5)°, respectively. The bite angle of DPEphos in
complex 3 (99.16(3)°) is 2.8° less than the natural bite angle
value (102°).6 Both Ru-P and Ru-Cl bond lengths are
comparable to those for analogous compounds recorded in
the literature.
The RuII complex 3 undergoes substitution reaction with
2 equiv of pyridine to yield trans,cis-[RuCl2(DPEphos)-
(C5H5N)2] (4) in moderate yield. The 31P NMR spectrum of
complex 4 presents a broad single resonance at 38.0 ppm in
room temperature and becomes sharp at -50 °C. The mass
spectrum of complex 4 shows a fragment ion peak corre-
sponding to [M - C5H5N‚Cl]+ at m/z 754.03 with the
appropriate isotopic pattern. It is evident from the molecular
structure that in the formation of 4, the cis-{RuCl2} unit has
isomerized to the trans geometry and the coordinated oxygen
of DPEphos has been displaced. Although no detailed
mechanistic information is available, it is tempting to
speculate that the initial step in the substitution reaction is
replacement of the coordinated oxygen of the DPEphos by
the first pyridine ligand. The two phosphorus atoms occupy
cis positions and are mutually trans to the N-donors, whereas
Scheme 2. Reactions of 3 with (i) Pyridine(2 equiv), (ii)
2,2′-Bipyridine, (iii) 4,4′-Bipyridine, and (iv) PPh3 in CH2Cl2
the chlorides are in trans positions. The P1-Ru-P2, P1-
Ru-N1, Cl1-Ru-Cl2, and Cl1-Ru-P1 bond angles are
96.09(3)°, 169.57(7)°, 174.34(3)°, and 85.72(3)°, respec-
tively, and the P1-Ru-P2 bond angle (99.16(3)°) is 3.09°
less than that in complex 3. The Ru-P bond distances of
complex 4 are slightly longer (by 0.02 Å) with respect to
those in complex 3. The Ru-N bond distances are 2.164(3)
and 2.185(3) Å, which are slightly longer than the literature
values reported for analogous complexes (Figure 4).14
The reaction of complex 3 with 1 equiv of 2,2′-bipyridine
gives the mononuclear ruthenium complex cis,cis-[RuCl2-
(DPEphos)(2,2′-bipyridine)] (5) in good yield. The 31P NMR
spectrum of complex 5 displays two doublets centered at
2
31.0 and 37.0 ppm with a JPP value of 32.4 Hz which
indicates that the two phosphorus atoms are nonequivalent.
This implies that one phosphorus is trans to Cl and that the
other is trans to an N atom of 2,2′-bipyridine. Therefore,
cis,cis is the only possible isomer for the complex 5 as shown
in Scheme 2. The mass spectrum of the complex 5 supports
the suggested structure, which shows a molecular ion peak
at m/z 831.06 [M - Cl]+.
(13) Queiroz, S. L.; Batista, A. A.; Oliva, G.; Gambardella, M. T. P.; Santos,
R. H. A.; MacFarlane, K. S.; Rettig, S. J.; James, B. R. Inorg. Chim.
Acta 1998, 267, 209-221.
(14) Baratta, W.; Herdtweck, E.; Siega, K.; Toniutti, M.; Rigo, P.
Organometallics 2005, 24, 1660-1669.
Inorganic Chemistry, Vol. 46, No. 3, 2007 811

Venkateswaran et al.
Figure 6. Molecular structure of complex 7. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms and uncoordinated solvent
molecules have been omitted for clarity.
Figure 5. Molecular structure of complex 5. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms and uncoordinated solvent
molecules have been omitted for clarity.
The structure of the complex 5 was confirmed by X-ray
crystallography, which shows the presence of two isostruc-
tural molecules present in the asymmetric unit and the Ru
center is in a distorted octahedral geometry. The bond
parameters of both the molecules differ slightly. The Ru1-
Cl1, Ru1-Cl2, Ru1-P1, Ru1-P2, and Ru1-N1 bond
distances of 2.392(4), 2.451(4), 2.299(4), 2.332(4), and
2.122(14) Å, respectively, are comparable to complex 4,
whereas the Ru1-N2 bond distance is shorter by 0.1 Å.
The bite angle of the DPEphos ligand in complex 5
(100.85(14)°) is 1.64° less than the natural bite angle
and 4.76° greater than that in complex 4. The Cl1-Ru1-
Cl2 bond angle (88.87(14)°) is 4.83° greater than that in
complex 3, and the N1-Ru1-N2 bond angle is 78.0(4)°
(Figure 5).
Figure 7. Molecular structure of complex 8. Thermal ellipsoids are drawn
at 50% probability level. Hydrogen atoms and uncoordinated solvent
molecules have been omitted for clarity.
The reaction of 3 and 4,4′-bipyridine in an equimolar ratio
affords the polynuclear complex trans,cis-[RuCl2(DPEphos)-
(µ-4,4′-bipyridine)]n (6) in quantitative yield. The 31P NMR
spectrum of complex 6 exhibits a singlet at 36.5 ppm which
indicates that both the phosphorus atoms are chemically
equivalent. The similarity of the phosphorus chemical shifts
between complexes 6 and 4 suggests that the Ru center in
the former is in much the same environment as that in the
latter, leading to the structure proposed in Scheme 2.
Treatment of complex 3 with triphenylphosphine affords
the red crystalline solid formulated as mer,trans-[RuCl2(κ3-
P,P,O-DPEphos)(PPh3)] (7) (Figure 6) in good yield. The
31P NMR spectrum shows a triplet at 54.0 ppm and a doublet
centered at 27.2 ppm in the intensity ratio of 1:2 and with a
2JPP value of 29.4 Hz. The low field resonance is assigned
to PPh3 and the latter value to the two phosphorus atoms of
DPEphos. The (EI) mass spectrum of complex 7 shows a
molecular ion peak at m/z 937.07 [M - Cl]+. It is evident
from the 31P NMR spectrum that the two phosphorus in
DPEphos are equivalent; hence, the phosphorus atoms are
mutually trans to each other. The PPh3 group exhibits a very
significant downfield shift of 60 ppm due to the presence of
the O-donor in the trans position. The structure of complex
7 was confirmed by single-crystal X-ray crystallographic
studies. Although the DPEphos retains the tridentate mode
of coordination, the Ru center is transformed to the mer
isomer. The two chlorides are mutually trans to each other,
and PPh3 is trans to the oxygen of the DPEphos ligand. The
Cl1-Ru1-Cl2, P1-Ru1-P2, P1-Ru1-O, and Cl2-Ru1-
P1 bond angles are 166.93(4)°, 158.53(4)°, 79.10(9)°, and
85.77(4)°, respectively, confirming that the geometry of RuII
in complex 7 is a highly distorted octahedral. The bite angle
of DPEphos in complex 7 is 59.37° higher than that in
complex 3. The bond distance between Ru-P3 (PPh3) is 0.1
Å shorter than that of Ru-P1 (DPEphos). The Ru-Cl bond
distances (2.4086(12) and 2.3943(12) Å) are 0.03 Å shorter
in comparison with those of 3.
Refluxing DPEphos with [RuCl2(η6-p-cymene)]2 in a 2:1
molar ratio in moist acetonitrile affords the hydrated mono-
nuclear complex cis,cis-[RuCl2(DPEphos)(CH3CN)(H2O)] (8)
(Figure 7) via elimination of p-cymene. The 31P NMR
spectrum of complex 5 shows two doublets centered at 35.3
2
1
and 16.9 ppm with a JPP value of 31.1 Hz. The H NMR
spectrum displays peaks at 1.38 and 2.03 ppm corresponding
to coordinated water and acetonitrile molecules. The peaks
(as in complex 2) corresponding to p-cymene are not
1
observed in the H NMR, which confirms the elimination
812 Inorganic Chemistry, Vol. 46, No. 3, 2007

Ruthenium(II) Complexes and Their Catalytic ActiWity
Table 1. Crystallographic Information for Complexes 1-4
1
2
3‚3CH2Cl2
4‚2CHCl3
formula
fw
cryst syst
space group
a, Å
C41H33OP2RuCl
740.13
monoclinic
P21/n
10.656(1)
19.077(2)
16.153(2)
90
100.617(2)
90
3227.4(6)
4
1.523
0.702
1512
C56H56OP2Ru2Cl4
1150.89
orthorhombic
Pbcn
22.863(2)
15.076(1)
14.352(1)
90
90
90
4946.9(6)
4
1.545
C38H34O2P2RuSCl2
1043.41
triclinic
C46H38OP2RuN2Cl2
1107.43
monoclinic
P21/n
10.9687(7)
11.9749(8)
35.240(2)
90
94.482(1)
90
4614.6(5)
4
P-1
11.4515(9)
13.868(1)
15.372(1)
92.377(1)
106.488(1)
96.296(1)
2320.0(3)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
F
calc, g cm-3
1.494
0.946
1056
1.594
0.913
2240
µ (Mo KR), mm-1
F(000)
0.932
2344
cryst size (mm)
T (K)
0.11 × 0.14 × 0.22
0.04 × 0.13 × 0.14
0.09 × 0.12 × 0.19
0.12 × 0.14 × 0.19
100
100
100
100
2θ range, deg
total no. reflns
no. of indep reflns
GOF (F2)
1.7-28.3
28 076
7723 (Rint ) 0.027)
1.046
0.0301
0.0752
1.6-28.3
41 946
6077 (Rint ) 0.058)
1.111
0.0471
0.1103
1.4-27.5
20 369
10 418 (Rint ) 0.028)
1.032
0.0436
0.1146
1.8-28.3
40 572
11 126 (Rint ) 0.051)
1.033
0.0489
0.1168
Ra
b
Rw
2
2
2
2
2
2
a R ) Σ||Fo| - |Fc||/Σ|Fo|. b Rw ) {[Σw(Fo - Fc )/Σw(Fo )2]}1/2; w ) 1/[σ2(Fo ) + (xP)2], where P ) (Fo + 2Fc )/3.
of p-cymene during the reaction. The mass spectrum exhibits
a fragment peak at m/z 699.07 corresponding to [M - 2Cl]+.
The molecular structure of the complex 8, determined by
X-ray crystallography, shows that the geometry of RuII is
an octahedral one in which the two phosphorus and chloride
members are in cis positions. The Cl1-Ru-Cl2, Cl1-Ru-
P1, Cl1-Ru-P2, and P1-Ru-P2 bond angles are 85.82-
(3)°, 87.97(3)°, 104.70(3)°, and 99.22(3)°, respectively, and
the bite angle of DPEphos in complex 8 (99.22(3)°) is
comparable to that of complex 3. The Ru-Cl1 (trans
to N) bond distance is 0.052 Å shorter than the Ru-Cl2
(trans to P) bond distance. The Ru-P1 bond distance
(2.2921(9) Å) is comparable to that of complex 3, whereas
the bond distance of Ru-P2 is 0.029 Å longer than that of
Ru-P1.
The addition of excess DPEphos to complex 3 did not
afford the expected product, trans-[RuCl2(DPEphos)2]. Simi-
larly, the reaction of an excess of PPh3 with complex 7 did
not yield trans,cis-[RuCl2(DPEphos)(PPh3)2]. This is likely
due to the bulkiness of the coordinated DPEphos ligand,
which does not allow another bulky ligand to enter into the
coordination sphere. In contrast with these observations, the
reaction of 3 with 1 equiv of pyridine favors the formation
of trans,cis-[RuCl2(DPEphos)(pyridine)2] (4) as the predomi-
nant product; hence, the complex 4 was prepared in high
yield by the 2:1 reaction of pyridine with complex 3. It
indicates that complex 3 allows 2 equiv of less bulky N-donor
ligands such as pyridine, 4,4′-bipyridine, or 1 equiv of
chelating 2,2′-bipyridine to react with complex 3 (see Tables
1-5 for crystallographic and bond distance and angle
information for complexes 1-8)
(H2) ) 10 atm, and temperature ) 70 °C. The conversion
rate was periodically monitored by gas chromatography, and
1
the product was confirmed by H NMR spectroscopy. The
results are displayed in Table 6. Complete conversions were
observed in 4 h for the complexes 3 and 7, whereas the
complexes 1, 2, and 8 were near completion after 6, 5, and
4 h, respectively. In the case of complex 7, after the complete
conversion, 1.0 mmol of styrene was again added, the
reaction was continued under the same conditions, and
complete conversion was observed in 5 h. The slight delay
in completion may be due to the partial decomposition of
the catalyst. Addition of a drop of mercury to the reaction
mixture did not affect the activity of the catalyst, thus
indicating that the system is homogeneous. Addition of D2O
into the reaction mixture did not affect the conversion rate.
The 1H NMR spectrum of the product shows a triplet and a
quartet at 1.24 and 2.65 ppm for CH3 and CH2 groups of
ethylbenzene, respectively, which confirms the absence of
deuterium in the product. This also indicates the noninvolve-
ment of protic solvents in the catalytic reactions. Complex
5 shows less conversion (68.8% after 8 h) in comparison
with other complexes, suggesting a high stability and
resistance to oxidative addition. The polynuclear complex 6
did not show any appreciable activity, presumably due to
its poor solubility in THF. The RuII complexes of 1-4, 7,
and 8 are found to be more efficient in the catalytic
hydrogenation of styrene under mild conditions as compared
with the other catalysts such as [RuHCl(C6Me6)(PPh3)],15
[RuCl2(dppb)2],16 [RuCl(dppb)(µ-Cl)]2 (dppb ) 1,4-bis-
(diphenylphosphino)butane,17 [RuCl2(p-cymene)(PPh2Py)],
and [RuCl(p-cymene)(PPh2Py)][BF4].18
Catalytic Hydrogenation of Styrene
The catalytic activity of the complexes 1-8 toward the
hydrogenation of styrene was surveyed under the following
conditions; [catalyst] ) 0.1 mol %, medium ) THF, pressure
(15) Bennett, M. A.; Huang, T-N.; Smith, A. K.; Turney, T. W. J. Chem.
Soc., Chem. Commum. 1978, 582-583.
(16) Suarez, T.; Fontal, B.; Medina, H. J. Mol. Catal. 1985, 50, 355-363.
Inorganic Chemistry, Vol. 46, No. 3, 2007 813

Venkateswaran et al.
Table 2. Crystallographic Information for Complexes 5, 7, and 8
5
7‚CHCl3‚C0.5H0.5Cl2
8‚CH2Cl2
formula
fw
cryst syst
space group
a, Å
C47H38OP2RuN2Cl4
951.60
C54H43OP3RuCl2
1169.54
monoclinic
P21/c
12.252(1)
36.228(4)
12.190(1)
90
108.018(1)
90
5145.4(8)
4
C38H33O2P2RuNCl2
854.49
triclinic
orthorhombic
Pca21
26.076(3)
9.7320(10)
33.932(4)
90
P-1
11.0985(7)
12.2786(8)
15.715(1)
81.440(1)
83.965(1)
81.457(1)
2086.6(2)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
90
90
8611.0(17)
8
1.468
0.725
3872
F
calc, g cm-3
1.510
0.802
2374
1.360
0.741
868
µ (Mo KR), mm-1
F(000)
cryst size (mm)
T (K)
0.05 × 0.08 × 0.22
0.09 × 0.11 × 0.29
0.09 × 0.14 × 0.22
100
100
100
2θ range, deg
total no. reflns
no. of indep reflns
GOF (F2)
1.6-25.0
15 161
10 248 (Rint ) 0.148)
1.093
0.1050
0.2797
2.1-28.3
90 001
12 792 (Rint ) 0.078)
1.130
0.0655
0.1617
1.3-27.9
18 631
9568 (Rint ) 0.033)
1.046
0.0531
0.1350
Ra
b
Rw
2
2
2
2
2
2
a R ) Σ||Fo| - |Fc||/Σ|Fo|. b Rw ) {[Σw(Fo - Fc )/Σw(Fo )2]}1/2; w ) 1/[σ2(Fo ) + (xP)2] where P ) (Fo + 2Fc )/3.
Table 3. Selected Bond Distances (Å) and Bond Angles (deg) for Complexes 1 and 2
complex 1
complex 2
distance
angle
distance
2.4102(8)
angle
Ru-Cl
2.4528(6)
2.2937(5)
2.3209(5)
2.193(2)
2.222(2)
2.213(2)
2.211(2)
Cl-Ru-P1
88.19(2)
95.52(2)
149.87(6)
109.73(6)
117.15(6)
96.14(2)
Ru-Cl1
Ru-Cl2
Ru-P
Ru-C19
Ru-C20
Ru-C21
Ru-C22
Ru-C23
Ru-C24
Cl1-Ru-Cl2
Cl1-Ru-P
88.67(3)
90.06(3)
122.76(11)
158.91(10)
85.04(3)
94.88(10)
114.3(3)
Ru-P1
Cl-Ru-P2
2.4196(8)
2.3706(10)
2.256(3)
2.214(3)
2.177(3)
2.233(3)
2.206(3)
2.208(3)
Ru-P2
Cl-Ru-C37
Ru-P1-C1
Ru-P1-C7
P1-Ru-P2
C18-O-C19
Cl1-Ru-C19
Cl1-Ru-C20
Cl2-Ru-P
Ru-C37
Ru-C38
Ru-C39
Ru-C40
Ru-C41
P-Ru-C19
C6-O-C6_a
115.52(14)
Table 4. Selected Bond Distances (Å) and Bond Angles (deg) for Complexes 3-5
Complex 3 Complex 4
Complex 5
distance
Ru-Cl1 2.4321(8) Cl1-Ru-Cl2 84.04(3) Ru-Cl1 2.3988(8) Cl1-Ru-Cl2 174.34(3) Ru1-Cl1 2.392(4) Cl1-Ru1-Cl2 88.87(14)
Ru-Cl2 2.4354(8) Cl1-Ru-S 96.94(3) Ru-Cl2 2.4433(8) Cl1-Ru-P1 85.72(3) Ru1-Cl2 2.451(4) Cl1-Ru1-P1 88.22(14)
Ru-S 94.04(14)
angle
distance
angle
distance
angle
2.1875(8) Cl1-Ru-P1 164.45(3) Ru-N1 2.164(3) Cl1-Ru-P2 94.58(3) Ru1-N1 2.122(14) Cl1-Ru1-P2
Ru-P1 2.2940(8) Cl1-Ru-P2 84.65(3) Ru-N2 2.185(3) Cl1-Ru-N1 87.00(6) Ru1-N2 2.079(12) Cl1-Ru1-N1 88.1(4)
Ru-P2 2.2923(8) Cl1-Ru-O1 84.01(6) Ru-P1 2.3290(8) Cl1-Ru-N2 87.66(6) Ru1-P1 2.299(4) Cl1-Ru1-N2 166.1(3)
Ru-O1 2.209(2) Cl2-Ru-S
S-O2
P1-C13 1.832(3) Cl2-Ru-P2 165.23(3) P2-C24 1.832(3) Cl2-Ru-N1 89.20(6) Ru2-Cl4 2.450(4) Cl2-Ru1-N1 80.5(4)
93.65(3) Ru-P2 2.3233(8) Cl2-Ru-P1 97.48(3) Ru1-P2 2.332(4) Cl2-Ru1-P1 173.08(14)
1.483(2) Cl2-Ru-P1 89.38(3) P1-C13 1.862(3) Cl2-Ru-P2 89.74(3) Ru2-Cl3 2.368(4) Cl2-Ru1-P2 85.61(14)
P2-C25 1.844(3) Cl2-Ru-O1 85.88(6)
Cl2-Ru-N2 87.54(6) Ru2-P4 2.317(4) Cl2-Ru1-N2 89.1(4)
P1-Ru-S
P2-Ru-S
O1-S-Ru
P1-Ru-P2
P1-Ru-O1
P2-Ru-O1
97.53(3)
97.12(3)
178.89(5)
99.16(3)
81.47(6)
83.52(6)
P1-Ru-P2
96.09(3) Ru2-P3 2.341(4) P1-Ru1-P2
169.57(7) Ru2-N4 2.140(14) P1-Ru1-N1
92.35(7) Ru2-N3 2.086(12) P1-Ru1-N2
100.85(15)
93.1(4)
P1-Ru-N1
P1-Ru-N2
P2-Ru-N1
P2-Ru-N2
92.2(4)
166.0(4)
99.5(3)
91.92(7)
P2-Ru1-N1
P2-Ru1-N2
171.40(7)
N1-Ru-N2 79.89(10)
N1-Ru1-N2 78.0(4)
Cl3-Ru2-P3 93.13(15)
Cl3-Ru2-Cl4 88.81(14)
N3-Ru2-N4 77.2(4)
P3-Ru2-N4
P3-Ru2-N3
166.1(4)
100.6(3)
As complexes 3 and 7 showed an excellent conversion
rate in the initial studies, the catalytic activity of complex 3
was tested with a reduced catalytic loading of 0.01 mol %
under more strenuous conditions (pressure (H2) ) 15 atm,
T ) 70 °C) in an attempt to achieve a high-turnover
frequency (TOF). The conversion rate was monitored
periodically by gas chromatography, and the results are
displayed in Table 7 and graphically represented in Figure
8. The conversion of half of the styrene into ethylbenzene
was observed within 40 min with a turnover frequency of
(17) Joshi, A. M.; MacFarlane, K. S.; James, B. R. J. Organomet. Chem.
1995, 488, 161-167.
(18) Moldes, I.; de la Encarnacion, E.; Ros, J.; Alvarez-Larena, A.; Piniella,
J. F. J. Organomet. Chem. 1998, 566, 165-174.
814 Inorganic Chemistry, Vol. 46, No. 3, 2007

Ruthenium(II) Complexes and Their Catalytic ActiWity
Table 5. Selected Bond Distances (Å) and Bond Angles (deg) for Complexes 7 and 8
complex 7
complex 8
Cl1-Ru-Cl2
distance
angle
Cl1-Ru1-Cl2
distance
angle
Ru1-Cl1
Ru1-Cl2
Ru1-P1
Ru1-P2
Ru1-P3
Ru1-O
2.4086(12)
2.3943(12)
2.3556(13)
2.3481(13)
2.2563(12)
2.235(3)
166.93(4)
88.93(4)
95.53(4)
92.50(4)
85.94(8)
85.77(4)
85.29(4)
100.27(4)
81.33(8)
158.53(4)
101.93(4)
98.85(4)
79.10(9)
80.28(9)
178.13(9)
Ru-Cl1
Ru-Cl2
Ru-P1
Ru-P2
Ru-O2
Ru-N
2.4340(9)
2.4858(9)
2.2921(9)
2.3314(8)
2.160(3)
1.998(3)
85.82(3)
87.97(3)
104.70(3)
80.00(10)
167.71(8)
171.86(3)
87.46(3)
81.16(10)
93.75(9)
99.22(3)
92.59(10)
167.38(10)
91.19(9)
87.53(8)
87.79(12)
Cl1-Ru1-P1
Cl1-Ru1-P2
Cl1-Ru1-P3
Cl1-Ru1-O
Cl2-Ru1-P1
Cl2-Ru1-P2
Cl2-Ru1-P3
Cl2-Ru1-O
P1-Ru1-P2
P1-Ru1-P3
P2-Ru1-P3
P1-Ru1-O
P2-Ru1-O
P3-Ru1-O
Cl1-Ru-P1
Cl1-Ru-P2
Cl1-Ru-O2
Cl1-Ru-N
Cl2-Ru-P1
Cl2-Ru-P2
Cl2-Ru-O2
Cl2-Ru-N
P1-Ru-P2
P1-Ru-O2
P2-Ru-O2
P1-Ru-N
P2-Ru-N
O2-Ru-N
Table 6. Hydrogenation of Styrene Using Catalysts 1-5, 7, and 8a
activity. The catalytic activity was unaltered even in the
presence of base.
entry
catalyst
time (h)
conversion (%)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
6
5
4
5
8
4
4
4
96.5
94.3
100
96.4
68.8
4.1
Conclusion
Several new ruthenium(II) complexes containing DPEphos
in all possible coordination modes have been synthesized
and are well characterized. The large bite angle DPEphos
with a relatively rigid diphenyl ether backbone containing
both oxygen and phosphorus donor sites offers different
coordination modes and also behaves as a hemilabile ligand.
The half-sandwich ruthenium(II) complex was prepared in
excellent yield by interacting DPEphos directly with RuCl3·
3H2O in the presence of cyclopentadiene. The bulkiness of
the DPEphos ligand plays a key role in the formation of the
specific isomeric product. In the mixed ligand RuII complexes
3-7, depending upon the steric nature of the environment,
the DPEphos ligand offers different modes of coordination.
In complex 3, the DPEphos ligand binds with the ruthenium
center in fac orientation, whereas upon substitution of the
dmso ligand with PPh3, it isomerizes into the mer complex
7. The complexes 4 and 6 are obtained as trans,cis isomers
and 5 as the cis,cis isomer. Highly solvated complexes are
utilized to make mixed ligand complexes with interesting
binding properties. In many complexes, the oxygen atom of
DPEphos binds to the metal center to provide temporary
coordinative saturation until it is required to furnish the active
site for the incoming substrates, an important feature in
homogeneous catalysis which is thoroughly exploited by van
Leeuwen and others. The complexes 3 and 7 show excellent
catalytic activity in hydrogenation reactions. We are presently
employing some of these ruthenium complexes in transfer
hydrogenation reactions, and the work is in progress.
100
98.3
a Reagents and conditions: olefin (1.0 mmol), catalyst (0.1 mol %),
pressure (H2) ) 10 atm, THF (20 mL), 70 °C, stirring speed 400 rpm.
Table 7. Hydrogenation of Styrene Using Complex 3a
entry
time (min)
conversion (%)
TOF (h-1
)
1
2
3
4
5
6
7
8
9
10
20
30
40
50
12.3
23.8
41.7
52.1
58.7
70.8
89.9
97.6
99.4
7380
7140
8340
7815
7044
7080
4495
3253
2485
60
120
180
240
a Reagents and conditions: styrene (1.0 mmol), 3 (0.01 mol %), pressure
(H2) ) 15 atm, THF (30 mL), 70 °C, stirring speed 400 rpm.
Experimental Section
Figure 8. Graphical representation of catalytic hydrogenation of styrene
by using complex 3.
Materials. All manipulations were performed under an atmo-
sphere of dry nitrogen using standard Schlenk techniques. All the
solvents were purified by a conventional procedure19 and distilled
under nitrogen prior to use. The compounds DPEphos,7a cis-[RuCl2-
(dmso)4],20 and [(η6-p-cymene)RuCl2]212 were prepared according
to published procedures. RuCl3·3H2O, PPh3, 2,2′-bipyridine, 4,4′-
78 15 h-1 under these conditions. The reaction proceeds at
a faster rate in the initial stage, and the rate gradually
decreases with respect to time, which may be due to the
decrease in the concentration of the substrate and also due
to the partial decomposition of the catalyst. However,
addition of 1.0 mmol of substrate into the reaction mixture
increased the conversion rate but failed to show the full initial
(19) Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann Linacre House: Oxford,
U.K., 1996.
Inorganic Chemistry, Vol. 46, No. 3, 2007 815

Venkateswaran et al.
1
bipyridine, and cyclopentadiene were purchased from Lancaster and
used as received. Pyridine was purchased from S.D Fine Chemicals
and freshly distilled prior to use.
Instrumentation. The H, 13C{1H}, and 31P{1H} NMR (δ in
ppm) spectra were recorded using a Varian 400 Mercury Plus
spectrometer operating at the appropriate frequencies using TMS
and 85% H3PO4 as internal and external references, respectively.
Microanalyses were performed on a Carlo Erba model 1112
elemental analyzer. The absorption spectra were recorded on a
JASCO-V570 spectrophotometer. Electrospray ionization (EI) mass
spectrometry experiments were carried out using a Waters Q-TOF
micro-YA-105. Melting points were recorded using capillary tubes
and are uncorrected. GC analyses were performed using a Perkin-
Elmer Clarus 500 GC fitted with a packed column.
(5340), 241 (3331). H NMR (400 MHz, CDCl3): δ 6.80 (s, br,
6H, C5H5N), 6.97-7.52 (m, br, Ph, 28H), 8.67 (s, br, C5H5N, 4H).
31P{1H} NMR (162 MHz, CDCl3): δ 38.0 (s, br). Anal. Calcd for
C46H38OP2RuN2Cl2: C, 63.60; H, 4.41; N, 3.22. Found: C, 63.17;
H, 4.61; N, 3.49. MS (EI): m/z 754.03 [M - C5H5N‚Cl]+.
1
Synthesis of cis,cis-[RuCl2(DPEphos)(2,2′-bipyridine)] (5). A
solution of 2,2′-bipyridine (0.006 g, 0.038 mmol) in CH2Cl2 (5 mL)
was added dropwise to a solution of 3 (0.030 g, 0.038 mmol) in
CH2Cl2 (10 mL) at room temperature. The mixture was stirred for
12 h, concentrated to 5 mL, and layered with petroleum ether (5
mL) to obtain a red crystalline solid. Yield: 90% (0.029 g, 0.034
mmol). Mp: >250 °C. UV-vis [CH2Cl2, λ, nm, (ꢀ, cm-1 M-1)]:
449 (3466), 302 (19 233), 242 (36 912). 1H NMR (400 MHz,
CDCl3): δ 6.07 (m, bpy, 3H), 6.68-7.47 (m, Ph, 28H), 7.79 (d,
bpy,3JHH ) 7.2 Hz, 1H), 7.94 (d, bpy,3JHH ) 8.0 Hz, 1H), 8.34 (d,
bpy,3JHH ) 6.0 Hz, 1H), 9.05 (m, bpy, 1H). 31P{1H} NMR (162
MHz, CDCl3): δ 37.0 (d,2JPP ) 32.4 Hz), 31.0 (d,2JPP ) 31.1 Hz).
Anal. Calcd for C46H36OP2RuN2Cl2: C, 63.74; H, 4.19; N, 3.23.
Found: C, 63.44; H, 4.19; N, 3.30. MS (EI): m/z 831.06 [M -
Cl]+.
Synthesis of [(η5-C5H5)RuCl(DPEphos)] (1). A mixture of
DPEphos (0.412 g, 0.765 mmol) and freshly distilled cyclopenta-
diene (0.5 mL) in absolute ethanol (20 mL) was added dropwise
to a refluxing ethanol solution (30 mL) of RuCl3·3H2O (0.1 g, 0.382
mmol). After 4 h, the reaction mixture was cooled to room
temperature and then filtered and cooled to -30 °C to obtain red
crystals of 1. Yield: 72% (0.204 g, 0.275 mmol). Mp: >250 °C.
UV-vis [CH2Cl2, λ, nm, (ꢀ, cm-1 M-1)]: 389 (3421), 289 (13 283),
243 (36 886). 1H NMR (400 MHz, CDCl3): δ 4.10 (s, C5H5, 5H),
7.11-7.39 (m, Ph, 28H). 31P{1H} NMR (162 MHz, CDCl3): δ
42.4 (s). Anal. Calcd for C41H33OP2RuCl: C, 66.53; H, 4.49.
Found: C, 66.79; H, 4.55. MS (EI): m/z 705.08 [M - Cl]+.
Synthesis of [{(η6-p-cymene)RuCl2}2(µ-DPEphos)] (2). A
solution of [(η6-p-cymene)RuCl2]2 (0.050 g, 0.082 mmol) in CH2-
Cl2 (5 mL) was added dropwise to a stirring solution of DPEphos
(0.044 g, 0.082 mmol) also in CH2Cl2 (10 mL) at room temperature.
After 8 h, the reaction mixture was concentrated to 5 mL and diethyl
ether (10 mL) was added to give red crystals of 2. Yield: 87%
(0.082, 0.071 mmol). Mp: >250 °C. UV-vis [CH2Cl2, λ, nm, (ꢀ,
Synthesis of trans,cis-[RuCl2(DPEphos)(µ-4,4′-bipyridine)]n
(6). A solution of 4,4′-bipyridine (0.006 g, 0.038 mmol) in CH2Cl2
(5 mL) was added dropwise to a solution of 3 (0.030 g, 0.038 mmol)
in CH2Cl2 (10 mL) at room temperature. The mixture was stirred
for 12 h to obtain a red precipitate which was filtered, washed with
Et2O, and dried under vacuum to afford the analytically pure
compound 6. Yield: 95% (0.031 g). Mp: >250 °C. UV-vis [CH2-
Cl2, λ, nm, (ꢀ, cm-1M-1)]: 500 (5212), 395 (9827), 238 (39 857).
1H NMR (400 MHz, CDCl3): δ 6.79 - 7.45 (m, Ph, 28H), 7.56
(d, bpy,3JHH ) 6.0 Hz, 4H), 8.74 (d, bpy, 4H). 31P{1H} NMR (162
MHz, CDCl3): δ 36.5 (s). Anal. Calcd for C46H36OP2RuN2Cl2: C,
63.74; H, 4.19; N, 3.23. Found: C, 63.86; H, 4.21; N, 3.67.
Synthesis of mer,trans-[RuCl2(κ3-P,P,O-DPEphos)(PPh3)] (7).
A solution of PPh3 (0.010 g, 0.038 mmol) in CH2Cl2 (4 mL) was
added dropwise to a solution of 3 (0.030 g, 0.038 mmol) in CH2-
Cl2 (10 mL) at room temperature. After 12 h, the solution was
concentrated to 3 mL and layered with petroleum ether to obtain a
red crystalline solid. Yield: 78% (0.029 g, 0.030 mmol). Mp:
220 °C (dec). UV-vis [CH2Cl2, λ, nm, (ꢀ, cm-1 M-1)]: 360 (7473),
286 (34 467), 238 (28 031). 1H NMR (400 MHz, CDCl3): δ 6.80-
7.50 (m, Ph, 43H). 31P{1H} NMR (162 MHz, CDCl3): δ 54.0 (t,
PPh3,2JPP ) 29.4 Hz), 27.2 (d, 2P,2JPP ) 28.9 Hz). Anal. Calcd for
C54H43OP3RuCl2: C, 67.04; H, 4.41; N, 1.61. Found: C, 65.58;
H, 4.47; N, 1.98. MS (EI): m/z 937.07 [M - Cl]+.
1
cm-1 M-1)]: 378 (3377), 293 (13 762), 242 (34 532). H NMR
(400 MHz, CDCl3) δ 1.16 (d, ipr-CH3,3JHH ) 7.2 Hz, 6H), 1.80 (s,
p-CH3, 3H), 2.87 (s, br, ipr-CH, 1H), 4.79 (d, 2H, Ph-CH,3JHH
)
6.8 Hz), 5.00 (d, Ph-CH, 2H), 6.77-7.93 (m, Ph, 56H). 31P{1H}
NMR (162 MHz, CDCl3) δ 21.3 (s). Anal. Calcd for C56H56OP2-
Ru2Cl4: C, 58.44; H, 4.90. Found: C, 58.40; H, 4.78.
Synthesis of fac-[RuCl2(κ3-P,O,P-DPEphos)(dmso)] (3). A
solution of cis-[RuCl2(dmso)4] (0.200 g, 0.413 mmol) in CH2Cl2
(20 mL) was added dropwise to a solution of DPEphos (0.222 g,
0.413 mmol) in CH2Cl2 (30 mL) at room temperature. The reaction
mixture was stirred for 24 h. The clear yellow solution was
concentrated to 10 mL and kept at room temperature for 3 days to
afford yellow crystals of analytical purity. Yield: 82% (0.267 g,
0.339 mmol). Mp: 228 °C (dec). UV-vis [CH2Cl2, λ, nm, (ꢀ, cm-1
Synthesis of cis,cis-[RuCl2(DPEphos)(CH3CN)(H2O)] (8). The
mixture of [(η6-p-cymene)RuCl2]2 (0.050 g, 0.082 mmol) and
DPEphos (0.044 g, 0.082 mmol) was refluxed in moist acetonitrile
(20 mL). After 4 h, the reaction mixture was concentrated and
layered with diethyl ether (10 mL) to afford yellow crystals of 8.
Yield: 68% (0.029 g). Mp: 160 °C (dec). UV-vis [CH2Cl2, λ,
nm, (ꢀ, cm-1 M-1)]: 396 (3023), 248 (37 323). 1H NMR (400 MHz,
CDCl3): δ 1.38 (s, H2O, 2H), 2.03 (s, CH3CN, 3H), 6.57-7.74
1
M-1)]: 319 (2964), 261 (32 896), 244 (33 971). H NMR (400
MHz, CDCl3): δ 2.91 (s, CH3, 6H), 6.74-8.05 (m, Ph, 28H). 31P-
{1H} NMR (162 MHz, CDCl3): δ 45.0 (s). Anal. Calcd for
C38H34O2P2RuSCl2: C, 57.87; H, 4.34; S, 4.07. Found: C, 57.84;
H, 4.33; S, 3.98. MS (EI): m/z 752.96 [M - Cl]+.
Synthesis of trans,cis-[RuCl2(DPEphos)(C5H5N)2] (4). A solu-
tion of pyridine (0.006 g, 0.076 mmol) in CH2Cl2 (5 mL) was added
dropwise to a solution of 3 (0.030 g, 0.038 mmol) in CH2Cl2 (10
mL) at room temperature. The mixture was stirred for 12 h. The
solution was concentrated to 5 mL and layered with petroleum ether
(bp 60-80 °C) (5 mL) and kept at room temperature for 1 day to
obtain a yellow crystalline solid. Yield: 71% (0.023 g, 0.027 mmol).
Mp: >250 °C. UV-vis [CH2Cl2, λ, nm, (ꢀ, cm-1 M-1)]: 315
(m, Ph, 28H). 31P{1H} NMR (162 MHz, CDCl3): δ 35.3 (d,2JPP
)
31.1 Hz), 27.2 (d,2JPP ) 32.4 Hz). Anal. Calcd for C54H43OP3-
RuCl2: C, 59.30; H, 4.32; N, 1.82. Found: C, 59.89; H, 4.11; N,
1.68. MS (EI): m/z 699.07 [M - Cl2]+.
X-ray Crystallography. A crystal of each of the compounds
1-5, 7, and 8 suitable for X-ray crystal analysis was mounted in
a CryoLoop with a drop of Paratone oil and placed in the cold
nitrogen stream of the Kryoflex attachment of the Bruker APEX
CCD diffractometer. A full sphere of data for each crystal was
collected using 606 scans in ω (0.3° per scan) at φ ) 0, 120, and
(20) Evans, I. P.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton Trans.
1973, 204-209.
816 Inorganic Chemistry, Vol. 46, No. 3, 2007

Ruthenium(II) Complexes and Their Catalytic ActiWity
240° using the SMART software package.21 The raw data were
reduced to F2 values using the SAINT+ software,22 and global
refinement of unit cell parameters using ca. 4000-8000 reflections
chosen from the full data sets was performed. Multiple measure-
ments of equivalent reflections provided the basis for empirical
absorption corrections as well as corrections for any crystal
deterioration during the data collection (SADABS).23 The structures
were solved by direct methods (for 1, 2, 5, and 7), or the position
of the metal atoms was obtained from a sharpened Patterson
function (for 3, 4, and 8) and refined by full-matrix least-squares
procedures using the SHELXTL program package.24 Hydrogen
atoms were placed in calculated positions and included as riding
contributions with isotropic displacement parameters tied to those
of the attached non-hydrogen atoms.
times with hydrogen, and then the autoclave was pressurized with
10 or 15 atm of hydrogen. The reaction mixture was stirred at 70 °C,
and the progress of the reaction was determined by periodic GC
analysis.
Acknowledgment. We are grateful to the Department of
Science and Technology (DST), New Delhi, for funding
through Grant SR/S1/IC-05/2003. We also thank the Depart-
ment of Chemistry Instrumentation Facilities, IIT Bombay,
and the Sophisticated Analytical Instrument Facility (SAIF),
IIT Bombay, for spectral and analytical data. R.V. is thankful
to IIT Bombay for JRF and SRF Fellowships. J.T.M. thanks
The Louisiana Board of Regents through Grant LEQSF-
(2002-03)-ENH-TR-67 for the purchase of the CCD diffrac-
tometer and the Chemistry Department of Tulane University
for support of the X-ray laboratory. We are thankful to the
referees for their valuable suggestions during the revision
of this manuscript.
General Procedure for Catalytic Hydrogenation of Styrene.
A mixture of RuII complex (0.1 mol %), olefin (1.0 mmol), and 20
mL of THF was introduced to a 50 mL glass vessel. The glass
vessel containing the reaction mixture was placed in the steel
autoclave, and the reactor was sealed. The vessel was purged three
(21) SMART, version 5.625; Bruker-AXS: Madison, WI, 2000.
(22) INT+, version 6.35A; Bruker-AXS: Madison, WI, 2002.
(23) Sheldrick, G. M. SADABS, version 2.05; University of Gottingen:
Gottingen, Germany, 2002.
(24) (a) SHELXTL, version 6.10; Bruker-AXS: Madison, WI, 2000. (b)
Sheldrick, G. M. SHELXS97 and SHELXL97; University of Gottin-
gen: Gottingen, Germany, 1997.
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 1-5, 7, and 8.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC061782L
Inorganic Chemistry, Vol. 46, No. 3, 2007 817