New insight into the reactivity of pyridine-functionalized phosphine complexes of ruthenium(II) with respect to olefin metathesis and transfer hydrogenation

Article abstract of DOI:10.1021/om7012106

The present paper deals with the synthesis and full characterization of a series of pyridine-functionalized phosphine complexes of Ru(II), namely, RuCl₂(L^nx)(PPh₃) (L^nx = R ₂PCH₂(C₅H₂R′R″TN)), differing in the nature of the substituents on the phosphorus (superscript label x in L^nx defined as n = 1 for R = Ph, n = 2 for R = Cy) and/or on the pyridyl group (superscript label x in L^nx defined as x = a for picolyl, noted pic, and x = b for quinolyl, noted quin) and discloses new aspects of their reactivity with respect to catalysis. The ligands 2-[(diphenylphosphino)methyl]-6-methylpyridine, L^1a, 2- [(diphenylphosphino) methyl]quinoline, L^1b, 2- [(dicyclohexylphosphino)methyl]-6-methylpyridine, L^2a, and 2-[(dicyclohexylphosphino)methyl]quinoline, L^2b, were prepared and respectively reacted with RuCl₂(PPh₃)₃ under optimized experimental conditions. In a preliminary test, the reaction of RuCl₂(PPh₃)₃ with L^1a using a stoichiometric 1/1 metal/ligand ratio gave three complexes, namely, [RuCl ₂(PPh₃)₂]₂ (1), [(PPh ₃)₂ClRu(μ-Cl)₃Ru(L^1a)(PPh ₃)] (2_1a), and RuCl₂(L^1a) ₂ (3_1a). These were isolated by fractional crystallization and, at that stage, identified only by single-crystal X-ray diffraction. The formation of 1 and 2_1a reflects the existence of the elusive 14 e^- fragment "RuCl₂(PPh₃) ₂", which tends to relieve its unsaturation by intermolecular association. By contrast, controlled addition of 2-(phosphinomethyl)pyridine type ligands L^nx to RuCl₂(PPh₃)₂ leads selectively to the desired 16 e^- species RuCl ₂(L^nx)(PPh₃) (4_nx). For example, with L^1b, the green complex RuCl₂(L^1b)(PPh ₃) (4_1b-trans-Cl) was identified as the kinetic product of ligand addition. It slowly and irreversibly converts into the more stable isomer RuCl₂(L^1b)(PPh₃) (4_1b-cis-Cl) , representing the thermodynamic product. Both isomers were fully characterized by NMR spectroscopy and X-ray diffraction. Similar transformations, taking place at different rates, were observed within the ligand series examined here. All isomeric forms of type 4_na complexes react cleanly with a terminal alkyne-like phenylacetylene to give a new complex identified by NMR spectroscopy as the vinylidene species RuCl₂(L)(CCHPh)(PPh₃) (5 _na). The reaction of 4_nb-cis-Cl with an excess of ethyl diazoacetate at -60 °C gives the novel complex RuCl₂(L ^na){cis-EtO(O)C(H)C=C(H)C(O)OEt} (6_na) with concomitant elimination of the phosphonium ylide, Ph₃P=C(H)C(O)OEt. Whereas 1 equiv of diazoalkane thus serves as phosphine scavenger, the uptake of two more carbene units by the remaining 14 e^- fragment "RuCl ₂(L^1a)" results in their coupling, providing diethyl maleate, intercepted in 6_na as a coordinated ligand. Preliminary catalytic tests indicate that the complexes 4_nx act as catalyst precursors for the ROMP of norbornene in the presence of trimethylsilyldiazomethane as the carbene source. The same compounds 4 _nx are also used as catalyst precursors in the transfer hydrogenation of a series of ketone substrates using alcohol as the hydrogen source. For example, the hydrogenation of cyclohexanone is achieved in 99% yield within 45 s with only 0.01 mol (0.1 mol %) of the precatalyst RuCl₂(Ph ₂PCH₂pic)-(PPh₃)-trans-Cl (4_1a), representing a turnover frequency of 272 571h^-1. The X-ray structure analyses of 1, 2_1a, 3_1a, 4_1b (both trans-Cl and cis-Cl isomers), and 6_1a are reported.

Full text of DOI:10.1021/om7012106

Organometallics 2008, 27, 1193–1206
1193
New Insight into the Reactivity of Pyridine-Functionalized
Phosphine Complexes of Ruthenium(II) with Respect to Olefin
Metathesis and Transfer Hydrogenation
Emmanuelle Mothes, Stephane Sentets, Maria Asuncion Luquin, René Mathieu,
Noël Lugan,* and Guy Lavigne*
Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex, France
ReceiVed December 3, 2007
The present paper deals with the synthesis and full characterization of a series of pyridine-functionalized
phosphine complexes of Ru(II), namely, RuCl2(Lnx)(PPh3) (Lnx ) R2PCH2(C5H2R′R′′N)), differing in
the nature of the substituents on the phosphorus (superscript label n in Lnx defined as n ) 1 for R ) Ph,
n ) 2 for R ) Cy) and/or on the pyridyl group (superscript label x in Lnx defined as x ) a for picolyl,
noted pic, and x ) b for quinolyl, noted quin) and discloses new aspects of their reactivity with respect
to catalysis. The ligands 2-[(diphenylphosphino)methyl]-6-methylpyridine, L1a, 2-[(diphenylphosphino)
methyl]quinoline, L1b, 2-[(dicyclohexylphosphino)methyl]-6-methylpyridine, L2a, and 2-[(dicyclohexy-
lphosphino)methyl]quinoline, L2b, were prepared and respectively reacted with RuCl2(PPh3)3 under
optimized experimental conditions. In a preliminary test, the reaction of RuCl2(PPh3)3 with L1a using a
stoichiometric 1/1 metal/ligand ratio gave three complexes, namely, [RuCl2(PPh3)2]2 (1), [(PPh3)2ClRu(µ-
Cl)3Ru(L1a)(PPh3)] (21a), and RuCl2(L1a)2 (31a). These were isolated by fractional crystallization and, at
that stage, identified only by single-crystal X-ray diffraction. The formation of 1 and 21a reflects the
existence of the elusive 14 e- fragment “RuCl2(PPh3)2”, which tends to relieve its unsaturation by
intermolecular association. By contrast, controlled addition of 2-(phosphinomethyl)pyridine type ligands
Lnx to RuCl2(PPh3)2 leads selectively to the desired 16 e- species RuCl2(Lnx)(PPh3) (4nx). For example,
with L1b, the green complex RuCl2(L1b)(PPh3) (41b-trans-Cl) was identified as the kinetic product of
ligand addition. It slowly and irreversibly converts into the more stable isomer RuCl2(L1b)(PPh3) (41b-
cis-Cl), representing the thermodynamic product. Both isomers were fully characterized by NMR
spectroscopy and X-ray diffraction. Similar transformations, taking place at different rates, were observed
within the ligand series examined here. All isomeric forms of type 4na complexes react cleanly with a
terminal alkyne-like phenylacetylene to give a new complex identified by NMR spectroscopy as the
vinylidene species RuCl2(L)(CCHPh)(PPh3) (5na). The reaction of 4nb-cis-Cl with an excess of ethyl
diazoacetate at –60 °C gives the novel complex RuCl2(Lna){cis-EtO(O)C(H)CdC(H)C(O)OEt} (6na)
with concomitant elimination of the phosphonium ylide, Ph3PdC(H)C(O)OEt. Whereas 1 equiv of
diazoalkane thus serves as phosphine scavenger, the uptake of two more carbene units by the remaining
14 e- fragment “RuCl2(L1a)” results in their coupling, providing diethyl maleate, intercepted in 6na as a
coordinated ligand. Preliminary catalytic tests indicate that the complexes 4nx act as catalyst precursors
for the ROMP of norbornene in the presence of trimethylsilyldiazomethane as the carbene source. The
same compounds 4nx are also used as catalyst precursors in the transfer hydrogenation of a series of
ketone substrates using alcohol as the hydrogen source. For example, the hydrogenation of cyclohexanone
is achieved in 99% yield within 45 s with only 0.01 mol (0.1 mol %) of the precatalyst RuCl2(Ph2PCH2pic)-
(PPh3)-trans-Cl (41a), representing a turnover frequency of 272 571 h-1. The X-ray structure analyses of
1, 21a, 31a, 41b (both trans-Cl and cis-Cl isomers), and 61a are reported.
With these considerations in mind, and taking Grubbs’ third-
generation catalyst (“NHC”)(C5H4NBr)2Cl2RudCHPh2a,b as a
convenient structural model A (see below), the initial objective
of the present work was to devise a potentially active hypotheti-
cal target species of structural type B capable of being “self-
assembled” in situ from a readily accessible ruthenium precursor
and a commercially available carbene source. In brief, it was
hoped that a pyridine-functionalized phosphine ligand7 of the
type shown in B might constitute a viable alternative to the
ideal ligand combination existing in complex A, based on a
strongly coordinating N-heterocyclic carbene ligand and weakly
bound bromopyridine molecules.
Introduction
In addition to recent investigations on new generations of
advanced Grubbs type olefin metathesis catalysts,1–3 there is
also a stimulating challenge in the search for simpler, cheaper,
and possibly more archaic systems, albeit in which an active
catalytic species could be readily self-generated in situ and at
low cost upon mixing simple ingredients.4–6 Remember, in
particular, that a number of ill-defined olefin metathesis catalysts
of effective industrial relevance are generated in situ from
precursors as simple as RuCl3 or [Ru(H2O)6](OTs)2.4
* Corresponding authors. E-mail lugan@lcc-toulouse.fr; lavigne@
lcc-toulouse.fr.
10.1021/om7012106 CCC: $40.75
2008 American Chemical Society
Publication on Web 02/22/2008

1194 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
variations in the nature of the substituents on the phosphorus,
the central methylenic carbon, or the pyridyl group and was
even found convenient for the synthesis of optically active
versions based on P-chiral or C-chiral centers.8b–d
The readily accessible complex RuCl2(PPh3)3 was selected
as a convenient starting compound for our investigations on
account of its well-established substitutional lability, cor-
roborated here by new observations disclosed below.
The present paper describes the directed synthesis and full
characterization of new members of the extended family of 16
e- phosphinopyridine type complexes RuCl2(Lnx)(PPh3) (Lnx
) R2PCH2(C5H2R′R′′N)) differing in the nature of substituents
on the phosphorus atom (superscript label n in Lnx defined as
n ) 1 for R ) Ph, n ) 2 for R ) Cy) and on the pyridyl group
(superscript label x in Lnx defined as x ) a for picolyl, noted
pic, and x ) b for quinolyl, noted quin).9 It also presents a
hitherto unknown aspect of their reactivity toward a diazoalkane,
suggesting a realistic rational pathway for the “in situ” genera-
tion of an active olefin metathesis catalyst. Possibilities and
limitations of these complexes as readily available catalyst
precursors for the ROMP of norbornene10 or the transfer
hydrogenation of ketones11 are discussed on the basis of
preliminary catalytic tests.
A convenient modular approach to a palette of such pyridine-
functionalized phosphine ligands was developed some years ago
in our laboratory and applied to the synthesis of a number of
their Ru and Rh complexes.8 The procedure allowed multiple
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Organometallics 2001, 20, 5314. (b) Love, J. A.; Morgan, J. P.; Trnka,
T. M.; Grubbs, R. H. Angew. Chem., Int. Ed. 2002, 41, 4035. (c) Garber,
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Results and Discussion
Preparation of the Ligands. Both 2-[(diphenylphosphino)
methyl]pyridine and 2-[(diphenylphosphino)methyl]-6-meth-
ylpyridine (L1a) were previously prepared in good yields by
reaction of diphenylchlorophosphine with 2-pyridynylmethyl-
lithium and 6-methyl-2-pyridynylmethyllithium, respectively, at
low temperature.8 Such a procedure was extended here to the
synthesis of 2-[(diphenylphosphino)methyl]quinoline (L1b) from
Ph2PCl and 2-quinolynylmethyllithium, 2-[(dicyclohexylphos-
(7) (a) For various reviews and articles on the coordination chemistry
of phosphinopyridines and related P, N ligands, see: Newkome, G. R. Chem.
ReV. 1993, 93, 2067. (b) Espinet, P.; Soulantica, K. Coord. Chem. ReV.
1999, 193–195, 499. (c) Guiry, P. J.; Saunders, C. P. AdV. Synth. Catal.
2004, 346, 497. (d) Gomez, R.; Adrio, J.; Carretero, J. C. Angew. Chem.,
Int. Ed. 2006, 45, 7674. (e) Gianneschi, N. C.; Masar III, M. S.; Mirkin,
C. A. Acc. Chem. Res. 2005, 38, 825. (f) Chen, H.-P.; Liu, Y.-H.; Peng,
S.-M.; Liu, S.-T. Dalton Trans. 2003, 1419. (g) Speiser, F.; Braunstein, P.;
Saussine, L. Organometallics 2004, 23, 2625.
(3) (a) For selected applications of olefin metathesis, see: Nicolaou,
K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int. Ed. 2005, 44, 4490. (b)
Gradillas, A.; Perez-Castells, J. Angew. Chem., Int. Ed. 2006, 45, 6086. (c)
Watson, K. J.; Anderson, D. R.; Nguyen, S. T. Macromolecules 2001, 34,
3507. (d) Clavier, H.; Grela, K.; Kirschning, A.; Mauduit, M.; Nolan, S. P.
Angew. Chem., Int. Ed. 2007, 46, 6786.
(8) (a) Alvarez, M.; Lugan, N.; Mathieu, R. J. Chem. Soc., Dalton Trans.
1994, 2755. (b) Yang, H.; Alvarez, M.; Lugan, N.; Mathieu, R. J. Chem.
Soc., Chem. Commun. 1995, 1721. (c) Yang, H.; Lugan, N.; Mathieu, R.
Organometallics 1997, 16, 2089. (d) Yang, H.; Alvarez-Gressier, M.; Lugan,
N.; Mathieu, R. Organometallics 1997, 16, 1401. (e) Yang, H.; Lugan, N.;
Mathieu, R. C. R. Acad. Sci. Paris, 2, Sér. II 1999, 251–258. (f) Esquius,
G.; Pons, J.; Yanez, R.; Ros, J.; Mathieu, R.; Lugan, N.; Donnadieu, B. J.
Organomet. Chem. 2003, 667, 126.
(4) For a review, see: Mecking, S.; Held, A.; Bauers, F. M. Angew.
Chem., Int. Ed. 2002, 41, 544.
(5) (a) For examples of in situ generated catalytic systems where the
precatalyst is not a carbene complex, see: Herrmann, W. A.; Schattenman,
W. C.; Nuyken, O.; Glander, S. C. Angew. Chem., Int. Ed. Engl. 1996, 35,
1087. (b) Demonceau, A.; Stumpf, A. W.; Saive, E.; Noëls, A. F.
Macromolecules 1997, 30, 3127. (c) Bartz, M.; Küther, J.; Seshadri, R.;
Tremel, W. Angew. Chem., Int. Ed. 1998, 37, 2466. (d) Amoroso, D.; Fogg,
D. E. Macromolecules 2000, 33, 2815. (e) Jan, D.; Delaude, L.; Demonceau,
A.; Noëls, A. F. J. Organomet. Chem. 2000, 606, 55. (f) Sémeril, D.; Cléran,
M.; Bruneau, C.; Dixneuf, P. H. AdV. Synth. Catal. 2001, 343, 184. (g)
Castarlenas, R.; Fischmeister, C.; Dixneuf, P. New J. Chem. 2003, 27, 215.
(h) Matos, J. M. E.; Lima-Neto, B. S. J. Mol. Catal. A 2004, 222, 81. (i)
Matos, J. M. E.; Lima-Neto, B. S. Catal. Today 2005, 107–108, 282. (j)
Bernechea, M.; Lugan, N.; Gil, B.; Lalinde, E.; Lavigne, G. Organometallics
2006, 25, 684. (k) Castarlenas, R.; Vovard, C.; Fischmeister, C.; Dixneuf,
P. H. J. Am. Chem. Soc. 2006, 128, 4079. (l) Sauvage, X.; Borguet, Y.;
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(9) The specific case of the ligand R2PCH2(C5H4N) based on an unsub-
stituted pyridyl group was not included in the present report, a complicating
factor being that relevant complexes RuCl2{ R2PCH2(C5H4N)}(PPh3) are
obtained as mixtures of inseparable isomers (Lugan, N.; Lavigne, G. Unpub-
lished observations).
(10) (a) For leading references on ROMP, see: Nguyen, S. T.; Johnson,
L. K.; Grubbs, R. H. J. Am. Chem. Soc. 1992, 114, 3974. (b) Lynn, D. M.;
Kanaoka, S.; Grubbs, R. J. Am. Chem. Soc. 1996, 118, 784. (c) Bielawski,
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(6) (a) Let us also state here the existence of the remarkably ingenuous
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Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1195
Scheme 1. General Synthetic Procedure and Labeling Scheme
for Various 2-(Phosphinomethyl)pyridine Type Ligands
As detailed below, the results of these preliminary experi-
ments proved to be very useful to allow further adjustment of
the experimental conditions in such a way to obtain the desired
product in a selective manner. Importantly, they also revealed
a peculiar aspect of the reactivity of the precursor RuCl2(PPh3)3
itself, discussed in the next section.
New Evidence for the High Substitutional Lability of
RuCl2(PPh3)3: Isolation and Characterization of the Bime-
tallic Halide-Bridged Complexes [RuCl2(PPh3)2]2 (1) and
[(PPh3)2ClRu(µ-Cl)3Ru(L1a)(PPh3)] (21a). Characterization
of [RuCl2(PPh3)2]2 (1). Among the products isolated from the
above reaction (see Scheme 2), one did not contain the ligand
L1a. Such a complex could be unambiguously formulated as
[RuCl2(PPh3)2]2 (1) on the basis of an X-ray structure analysis.
Relevant crystallographic data are listed in Table 1, whereas a
selection of interatomic distances and bond angles is given in
Table 2. As shown in Figure 1, this is effectively the bimetallic
species originally identified by Wilkinson,14 now fully charac-
terized here for the first time. Its bimetallic ensemble consists
of the juxtaposition of two asymmetric “RuCl2(PPh3)2” units
related through an inversion center and sharing one of the two
chloride atoms, namely, Cl2, thus forming a double µ-Cl bridge.
The P1, Cl1, Cl2, and Cl2* atoms constitute the square base of
a distorted pyramidal arrangement around the metal center. They
are essentially coplanar, with an average deviation from the
mean plane of 0.0327 Å (maximum of 0.0341 associated with
Cl2). The ruthenium atom lies 0.3895(7) Å above the mean
plane thus defined. The observed distortion may be reasonably
understood as a result of steric repulsions between the two
adjacent triphenylphosphine ligands occupying axial and equa-
torial sites of the square pyramid, respectively. The overall
geometric situation encountered here, with the two edge-sharing
pyramids being oriented apart from the basal plane of the
dimeric unit, appears to be different from the one originally
proposed in Wilkinson’s paper.14a Such a geometry is also
reflecting the need to accommodate steric repulsions and
probably represents the only viable isomeric form of this species.
phino)methyl]-6-methylpyridine (L2a), and 2-[(dicyclohexylphos-
phino)methyl]quinoline (L2b) by reaction of dicyclohexylchlo-
rophosphine with the appropriate lithiated reagent (see Scheme
1). These reactions are straightforward and afford the corre-
sponding ligands in good yield.
Preliminary Reaction between RuCl2(PPh3)3 and 2-[(Diphe-
nylphosphino)methyl]-6-methylpyridine (L1a) under Non-
optimized Conditions, Using a 1/1 Stoichiometric Ratio. The
dichlorotris(triphenylphosphine)ruthenium(II) complex RuCl2-
(PPh3)3 has been widely used as a valuable starting material
for the preparation of a variety of Ru(II) complexes, including
the very popular Grubbs type olefin metathesis catalyst.12 Its
success as a synthetic tool is due both to its direct accessibility
from commercial RuCl3 · nH2O by a simple and efficient
preparative procedure13 and to its high substitutional lability.14
Such a property is understood in terms of the existence of an
elusive four-coordinate 14 e- complex “RuCl2(PPh3)2” resulting
from a spontaneous loss of one PPh3 ligand observable in
solution.14 Earlier studies have previously led to the proposal
that this elusive subcoordinated species tends to relieve its
unsaturation by forming a dimeric halide-bridged species,
originally mentioned by Wilkinson14a and existing also with
chelating ligands,14b–e but still never fully characterized in the
case of triphenylphosphine.
In a preliminary attempt to synthesize a 16 e- complex of
the type RuCl2(Lnx)(PPh3) capable of serving as a precursor to
the desired type B catalyst mentioned in the introduction,
equimolecular amounts of both the complex RuCl2(PPh3)3 and
the ligand L1a were dissolved in dichloromethane at room
temperature, and the reaction mixture was stirred for 4 h. After
workup and extraction of the released triphenylphosphine with
hexane, a 31P{1H} NMR spectrum of the recovered residue
revealed the presence of an intricate mixture of complexes.
Three main species were subsequently isolated from the mixture
by fractional crystallization and identified in the solid state by
single-crystal X-ray diffraction analyses. As shown in Scheme
2, these included two dimeric complexes, [RuCl2(PPh3)2]2 (1)
and [(PPh3)2ClRu(µ-Cl)3Ru(L1a)(PPh3)] (21a), and the mono-
nuclear complex RuCl2(L1a)2 (31a).
The presence of complex 1 under the conditions of the above
stoichiometric (1/1) reaction reflects the fact that 2 equiv of the
ligand L1a were consumed in the formation of the species 31a,
leaving part of the initial complex RuCl2(PPh3)3 unreacted.
Clearly, this initial complex is engaged in a predissociation
equilibrium leading to the formation of a transient 14 e-
complex “RuCl2(PPh3)2”, which tends to relieve its unsaturation
by an intermolecular association involving the formation of
halide bridges. The condensation of unsaturated RuCl2(PPh3)2
fragments as dimeric units in the solid state appears to be also
facilitated by workup with hexane, in which triphenylphosphine
is particularly soluble. Let us mention that the formation of edge-
or face-sharing bioctahedral species is now common for Ru(II)
halide complexes.15–17
Characterization of (PPh3)2ClRu(µ-Cl)3Ru(L1a)(PPh3)
(15) (a) Cotton, F. A.; Torralba, R. C.; Matusz, M. Inorg. Chem. 1989,
28, 1516. (b) Cotton, F. A.; Torralba, R. C.; Matusz, M. Inorg. Chem. 1991,
30, 2196. (c) Huang, D.; Folting, K.; Caulton, K. G. Inorg. Chem. 1996,
35, 7035. (d) da Silva, A. C.; Piotrowski, H.; Mayer, P.; Polborn, K.; Severin,
K. Eur. J. Inorg. Chem. 2001, 685. (e) Drouin, S. D.; Monfette, S.; Amoroso,
D.; Yap, G. P. A.; Fogg, D. E. Organometallics 2005, 24, 4721. (f) Foucault,
H. M.; Bryce, D. L.; Fogg, D. E. Inorg. Chem. 2006, 45, 10293.
(12) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996,
118, 100.
(13) (a) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth.
1970, 12, 237. (b) Stephenson, T. A.; Wilkinson, G. Inorg. Nucl. Chem.
1966, 28, 945.
(16) (a) Amoroso, D.; Yap, G. P. A.; Fogg, D. E. Organometallics 2002,
21, 3335. (b) Drouin, S. D.; Foucault, H. M.; Yap, G. P. A.; Fogg, D. E.
Organometallics 2004, 23, 2583. (c) Drouin, S. D.; Monfette, S.; Amoroso,
D.; Yap, G. P. A.; Fogg, D. E. Organometallics 2005, 24, 4721. (d) da
Silva, A. C.; Piotrowski, H.; Mayer, P.; Polborn, K.; Severin, K. Eur.
J. Inorg. Chem. 2001, 685. (e) Dell’Amico, D. B.; Calderazzo, F.; Englert,
U.; Labella, L.; Marchetti, F.; Specos, M. Eur. J. Inorg. Chem. 2004, 3938.
(14) (a) Gilbert, J. D.; Wilkinson, G. J. Chem. Soc. (A) 1969, 1749. (b)
Jung, C. W.; Garrou, P. E.; Hoffman, P. R.; Caulton, K. G. Inorg. Chem.
1984, 23, 726. (c) Fogg, D. E.; James, B. R. Inorg. Chem. 1997, 36, 1961.
(d) Joshi, A. M.; Thorburn, I. S.; Rettig, J. S.; James, B. R. Inorg. Chim.
Acta 1992, 198–200, 283. (e) Amoroso, D.; Yap, G. P. A.; Fogg, D. E.
Can. J. Chem. 2001, 79, 958.

1196 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
Scheme 2. Preliminary Stoichiometric Reaction of RuCl2(PPh3)3 with L1a under Nonoptimized Reaction Conditions
Table 1. Crystal Data and Structure Refinements for Complexes 1, 21a, 31a, 42a-cis, 42a-trans, and 61a
1 · CH2Cl2
21a · 1.5CH2Cl2
31a · CH2Cl2
42a-cis · 3CH2Cl2
42a-trans · 0.75CH2Cl2
37.75H46.5Cl3.5NP2RuP
61a · 0.33CH2Cl2
empirical formula
molecular weight (g)
temp (K)
λ (Å)
cryst syst
space group
a (Å)
C
73H62Cl6P4Ru2
C
74.50H66Cl7NP4Ru2
C
39H38Cl4N2P2Ru
C
40H51Cl7NP2Ru
C
C
82H92Cl8N3O12P3Ru3
1477.95
180
1549.56
180
839.52
180
992.43
180
801.34
180
1990.81
180
triclinic
monoclinic
P21/n (#14)
14.196(2)
33.708(3)
16.8163(14)
triclinic
monoclinic
P21/n (#14)
12.5688(9)
20.0030(13)
17.9037(12)
monoclinic
I2/a (#19)
20.306(3)
12.791(2)
30.984(4)
trigonal
j
j
j
P1 (#2)
P1 (#2)
R3 (#148)
10.793(6)
12.856(6)
13.174(7)
96.96(6)
91.14(7)
109.87(6)
1702.8(17)
1
11.6100(15)
12.953(3)
13.1890(15)
78.390(19)
80.520(15)
86.84(2)
1915.8(6)
2
26.3433(7)
26.3433(7)
21.6192(4)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
109.211(11)
102.123(6)
90.238(19)
γ (deg)
volume (Å3)
Z
7598.8(15)
4
1.354
0.768
3148
4400.9(5)
4
1.498
0.945
2032
8048(2)
8
1.323
0.727
3308
12993.0(5)
6
1.527
0.878
6083
Dcalcd. (g cm-3
)
1.441
0.814
750
1.455
0.802
856
µ (mm-1
)
F000
instrument
θmax (deg)
completeness to θmax
index range
Stoe IPDS
26.20
92.0
-13 < h < 13 -16 < h < 12
-15 < k < 15 -40 < l < 40
-16 < l < 16 -19 < l < 19
24 217
6254
Oxford Inst. Xcalibur Stoe IPDS
Oxford Inst. Xcalibur Stoe IPDS
Oxford Inst. Xcalibur
32.2
99.0
-39 < h < 38
-35 < h < 38
-31 < l < 28
47 410
25.00
99.0
26.10
92.0
32.2
26.01
97.9
99.0
-12 < h < 13
-15 < k < 16
-15 < l < 16
20 590
-18 < h < 18
-29 < k < 28
-26 < l < 24
44 137
-24 < h < 24
-15 < h < 15
-38 < l < 38
32 099
no. of reflns collected
no. of indep reflns
487 020
13 339
7004
14 478
7844
9716
no. of data/restraints/params 6254/0/424
13 339/0/626
0.933
7004/0/435
1.03
14 478/0/416
0.992
7844/0/389
1.01
9716/0/346
1.04
g.o.f.
1.057
R, Rw [I > 2σ(I)]
R1 ) 0.0623
R1 ) 0.1124
R1 ) 0.0413
wR2 ) 0.1106
R1 ) 0.0481
wR2 ) 0.1152
0.80/-0.79
R1 ) 0.0754
wR2 ) 0.1295
R1 ) 0.1811
wR2 ) 0.2069
1.51/-1.035
R1 ) 0.0302
wR2 ) 0.0770
R1 ) 0.0381
wR2 ) 0.0793
0.42/-0.34
R1 ) 0.0693
wR2 ) 0.0770
R1 ) 0.0381
wR2 ) 0.2267
1/-0.34
wR2 ) 0.1691 wR2 ) 0.2635
R, Rw (all data)
R1 ) 0.0729
wR2 ) 0.1801 wR2 ) 0.3027
1.85/-0.94 2.06/-1.28
R1 ) 0.2021
resid electr dens (e Å-3
)
Table 2. Selected Interatomic Distances [Å] and Bond Angles [deg]
for Complex 1
(21a). Just like the previous complex identified above, the present
one belongs to the closely related family of interconvertible
edge- and face-sharing bioctahedral species (ESBO/FSBO) of
which numerous examples are found in the literature.15 A less
common situation, here, is that the two organometallic fragments
fused together are of different nature. Indeed, as shown in Figure
2 (see also Table 1 and Table 3), complex 21a results from the
intermolecular association between the 14 e- fragment
“RuCl2(PPh3)2” and the elusive complex RuCl2(L1a)(PPh3) (41a),
the latter being in fact the target 16 e- species we were looking
for, and which was ultimately prepared in a selective manner
(Vide infra). It was subsequently verified (see Experimental Part)
that complex 21a can be more conveniently prepared in 43%
yield upon reaction of RuCl2(PPh3)3 with 41a. It should be noted,
Bond Distances
Ru1-Cl1
Ru1-Cl2
Ru1-P1
2.3646(16)
2.3932(14)
2.2637(14)
2.2048(13)
2.4652(14)
Ru1-P2
Ru1-Cl2_a
Bond Angles
Cl1-Ru1-Cl2
Cl1-Ru1-P1
Cl1-Ru1-P2
Cl1-Ru1-Cl2_a
Cl2-Ru1-P1
Cl2-Ru1-P2
Cl2-Ru1-Cl2_a
P1-Ru1-P2
160.81(6)
93.00(6)
95.27(6)
89.07(5)
92.04(6)
101.97(6)
79.70(5)
100.65(6)
158.74(5)
100.22(5)
100.30(6)
Cl2_a-Ru1-P1
Cl2_a -Ru1-P2
Ru1-Cl2-Ru1_a
(17) (a) Mashima, K.; Hino, T.; Takaya, H. J. Chem. Soc., Dalton Trans.
1992, 2099. (b) Ohta, T.; Tonomura, Y.; Nozaki, K.; Takaya, H. Organo-
metallics 1996, 15, 1521. (c) Dias, E. L.; Grubbs, R. H. Organometallics
1998, 17, 2758. (d) Fabre, S.; Kalck, P.; Lavigne, G. Angew. Chem., Int.
Ed. Engl. 1997, 36, 1092. Faure, M.; Maurette, L.; Donnadieu, B.; Lavigne,
G. Angew. Chem., Int. Ed. 1999, 38, 518. (f) Hansen, S. M.; Volland,
M. A. O.; Rominger, F.; Eisenträger, F.; Hofman, P. Angew. Chem., Int.
Ed. 1999, 38, 1273.
however, that, just like 1, such a complex exists mainly as a
solid, whereas a rapid dissociation and redistribution of the
fragments takes place in solution. The occurrence of complex
21a provides further evidence for the ability of the 14 e-

Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1197
Table 3. Selected Interatomic Distances [Å] and Bond Angles [deg]
for Complex 21a
Bond Distances
Ru1-Cl
Ru1-Cl2
Ru1-Cl3
Ru1-P1
Ru1-P2
Ru1-N1
Ru2-Cl1
Ru2-Cl2
Ru2-Cl3
Ru2-Cl4
Ru2-P3
Ru2-P4
P1-C1
P1-C21
P1-C31
P2-C41
P2-C51
P2-C61
P3-C71
P3-C81
P3-C91
P4-C101
P4-C111
P4-C121
N1-C12
N1-C16
2.403(3)
2.499(3)
2.464(3)
2.230(4)
2.282(4)
2.143(11)
2.480(3)
2.398(3)
2.506(4)
2.391(5)
2.272(4)
2.286(4)
1.821(14)
1.846(11)
1.847(11)
1.857(8)
1.873(9)
1.839(10)
1.831(10)
1.857(9)
1.856(9)
1.835(10)
1.857(9)
1.834(9)
1.367(17)
1.397(19)
Figure 1. Perspective view of complex [RuCl2(PPh3)2]2 (1).
Ellipsoids are shown at the 30% probability level.
Bond Angles
Cl1-Ru1-Cl2
Cl1-Ru1-Cl3
Cl1-Ru1-P1
Cl1-Ru1-P2
Cl1-Ru1-N1
Cl2-Ru1-Cl3
Cl2-Ru1-P1
Cl2-Ru1-P2
Cl2-Ru1-N1
Cl3-Ru1-P1
Cl3-Ru1-P2
Cl3-Ru1-N1
P1 -Ru1-P2
P1 -Ru1-N1
P2 -Ru1-N1
Cl1-Ru2-Cl2
Cl1-Ru2-Cl3
Cl1-Ru2-Cl4
Cl1-Ru2-P3
Cl1-Ru2-P4
Cl2-Ru2-Cl3
76.94(11)
82.47(12)
102.29(13)
89.15(13)
166.2(3)
77.56(12)
165.58(14)
98.56(12)
95.6(3)
88.05(14)
171.36(14)
84.7(3)
95.82(15)
82.1(3)
Figure 2. Perspective view of complex (PPh3)2ClRuCl(µ-Cl)3Ru(L1a)-
(PPh3) (21a). Ellipsoids are shown at the 30% probability level.
103.5(3)
77.39(11)
80.08(12)
84.55(14)
97.38(13)
164.24(15)
78.62(11)
fragment “RuCl2(PPh3)2” to form elusive adducts with other
well-defined electron-deficient complexes, thereby possibly
masking some of their potentially reactive sites. Whereas the
formation of halide-bridged bimetallic species has been ef-
fectively often regarded as undesirable for the purpose of
catalytic applications,16 opposed evidence has also been obtained
in other cases that they may alternatively represent the catalyst’s
resting state,17 capable of liberating an active species upon
dissociation via halide bridge opening.
chelating units of the L1a ligand are in equatorial position and
mutually adopt a head-to-head arrangement, a situation that can
Directed Synthesis and Characterization of RuCl2(L1a)2
(31a). As predictable from the above preliminary observations,
the reaction of RuCl2(PPh3)3 with 2 equiv of L1a produced 31a
in almost quantitative yield. Under such conditions (see
Experimental Part), and after extraction of the slight excess of
PPh3, the 31P{1H} NMR spectrum of the crude reaction mixture
showed only a singlet, consistent with the formulation estab-
lished by X-ray diffraction, thereby also confirming the existence
of only one isomer, unlike what had been previously found in
the case of slightly different “PN” ligands of a closely related
family.8 A perspective view of complex 31a is shown in Figure
3, whereas a selection of interatomic distances and bond angles
is displayed in Table 4.
The coordination geometry around the Ru center consists of
a distorted octahedron. The two chlorine atoms occupy apical
trans positions, whereas the P and N donor atoms of the two
Figure 3. Perspective view of complex RuCl2(L1a)2 · (31a). El-
lipsoids are shown at the 30% probability level.

1198 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
Scheme 3. Stoichiometric Reaction of RuCl2(PPh3)3 with L2a
Giving RuCl2 (L2a)(PPh3)(42a-trans-Cl) Followed by Isomerization
of the Latter to RuCl2(L2a)(PPh3) (42a-cis-Cl)
Table 4. Selected Interatomic Distances [Å] and Bond Angles [deg]
for Complex 31a
Bond Distances
Cl(1)-Ru(1)
Cl(2)-Ru(1)
N(1)-Ru(1)
N(2)-Ru(1)
P(1)-Ru(1)
P(2)-Ru(1)
2.4021(9)
2.4373(9)
2.274(2)
2.313(2)
2.2282(10)
2.2593(9)
Bond Angles
P(1)-Ru(1)-P(2)
P(1)-Ru(1)-N(1)
P(2)-Ru(1)-N(1)
P(1)-Ru(1)-N(2)
P(2)-Ru(1)-N(2)
N(1)-Ru(1)-N(2)
P(1)-Ru(1)-Cl(1)
P(2)-Ru(1)-Cl(1)
N(1)-Ru(1)-Cl(1)
N(2)-Ru(1)-Cl(1)
P(1)-Ru(1)-Cl(2)
P(2)-Ru(1)-Cl(2)
N(1)-Ru(1)-Cl(2)
N(2)-Ru(1)--Cl(2)
Cl(1)-Ru(1)-Cl(2)
101.78(3)
79.18(7)
170.95(7)
176.31(6)
77.97(6)
101.69(9)
91.17(3)
86.35(3)
84.63(7)
92.49(6)
87.80(3)
100.51(3)
88.51(7)
88.63(6)
173.13(3)
experiments. A reaction time of 15 min between RuCl2(PPh3)3
and L2a afforded a green solid, recovered in 95% yield. NMR
data of the crude material revealed the occurrence of a mixture
of the two isomers in a 1/9 ratio, subsequently identified as 42a-
cis-Cl and 42a-trans-Cl, respectively. Rapid recrystallization of
the green solution from a dichloromethane/hexane mixture at
low temperature allowed to intercept the green isomer 42a-trans-
Cl, obtained as single crystals that could be unambiguously
identified by X-ray diffraction. By contrast, slow recrystallization
of the green solution at room temperature produced brown
crystals of 42a-cis-Cl, also fully identified by X-ray diffraction
(Scheme 3).
be rationalized in terms of the well-documented “trans” effect.
Each of the two five-membered rings formed by the chelating
bidentate ligand units adopts a half-chair conformation, allowing
the two methyl substituents of the pyridyl moieties to be shifted
apart from the equatorial plane, an apparent requirement for
relieving steric crowding between these groups. As a logical
consequence, the molecule possesses a noncrystallographic C2
symmetry, with the pseudo -C2 axis bisecting the P-Ru-P (and
N-Ru-N) angle(s). Let us remember that the structural
arrangement observed here is relatively classical for PN
ligands.18
The green complex RuCl2(L2a)(PPh3) (42a-trans-Cl) was thus
identified as the kinetic product of ligand addition, progressively
converted into the more stable isomer RuCl2(L2a)(PPh3) (42a-
cis-Cl), representing the thermodynamic product. The observa-
tion by 31P NMR of JPP coupling constants, of 33 and 40 Hz
for 42a-trans-Cl and 42a-cis-Cl, respectively, is consistent with
the cis arrangement of the two phosphorus atoms observed in
both cases in the solid state. For the green isomer, the
equivalence of the two methylenic H atoms is consistent with
the existence of a mirror plane containing the two phosphorus
ligands, thus implying that the chloride atoms are in trans
position. These observations are corroborated by the X-ray
structure analyses of the two complexes (Figure 4 and Table 5;
Figure 5 and Table 6). Both complexes exhibit a square-
pyramidal geometry where the phosphorus atom of L2a is
occupying the apical position, whereas the donor nitrogen atom,
the two chlorides, and the remaining triphenyl phosphine are
Directed Synthesis and Characterization of RuCl2(Lnx)-
(PPh3) (4nx). The preferential formation of the disubstituted
complex 31a, even from a stoichiometric 1/1 RuCl2(PPh3)3/L1a
ratio, probably reflects the fact that nucleophilic attack of a
second molecule of L1a onto the initial elusive monosubstituted
P-bound intermediate “RuCl2(PPh3)2L1a” is kinetically preferred
over the intramolecular formation of a metallacycle by closure
of the Ru-N bond. Thus, a simple way to circumvent the
problem would be to maintain the lowest possible ligand-to-
metal ratio over the whole reaction course. Effectively, we found
that very slow dropwise addition of L1a to a dichloromethane
solution of RuCl2(PPh3)3 at room temperature over a period of
1 h by using an automatic syringe produces a new compound,
41a, existing as a mixture of two isomers in a ca. 1/1 ratio.
Recrystallization from a dichloromethane/hexane mixture at
room temperature gave a pure sample of an orange crystalline
material, which was subsequently identified as 41a-cis-Cl (69%
isolated yield) on the basis of an X-ray structure analysis (see
Experimental Part; structure provided as Supporting Informa-
tion).
The isolation of the elusive alternate isomer as a solid
appeared to be easier in the case of the ligand L2a. In that case,
there is no need for a very slow ligand addition, just because
the steric bulk of the cyclohexyl group precludes the uptake of
a second molecule of L2a, thus preventing the formation of the
undesirable hypothetical species 32a, never detected in our
(18) (a) Shen, J.-Y.; Slugovc, C.; Wiede, P.; Mreiter, K.; Schmid, R.;
Kirchner, K. Inorg. Chim. Acta 1998, 268, 69. (b) Crochet, P.; Gimeno, J.;
Garcia-Granda, S.; Borge, J. Organometallics 2001, 20, 4369. (c) Li, T.;
Churlaud, R.; Lough, A. J.; Abdur-Rashid, K.; Morris, R. H. Organome-
tallics 2004, 23, 6239.
Figure 4. Perspective view of complex RuCl2(L2a)(PPh3) (42a-trans-
Cl). Ellipsoids are shown at the 30% probability level.

Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1199
Table 5. Selected Interatomic Distances [Å] and Bond Angles [deg]
Scheme4. RepresentativeReactionofType41x Phosphinopyridine
Ru(II) Complexes with a Terminal Alkyne; Stoichiometric
Reaction of RuCl2(L1a)(PPh3) (41a) (mixture of cis and trans
derivatives) with Phenylacetylene Giving the Corresponding
Vinylidene Species RuCl2(L1a)(CCHPh)(PPh3) (51a) Obtained as
a Unique Single Isomer
for Complex 42a-trans-Cl
Bond Distances
Ru1-Cl1
Ru1-Cl2
Ru1-P1
Ru1-P2
Ru1-N1
P1-C2
2.3944(7)
2.3822(7)
2.1989(7)
2.3031(6)
2.1442(17)
1.836(2)
C2-C12
1.490(3)
Bond Angles
Cl1-Ru1-Cl2
Cl1-Ru1-P1
Cl1-Ru1-P2
Cl1-Ru1-N1
Cl2-Ru1-P1
Cl2-Ru1-P2
Cl2-Ru1-N1
P1 -Ru1-P2
P1-Ru1-N1
P2-Ru1-N1
161.84(3)
96.04(3)
94.32(3)
83.86(5)
99.69(3)
90.15(3)
88.92(5)
105.69(3)
83.46(5)
170.82(5)
relative stability of the principal isomers of complex 4nx appears
to be strongly dependent on the steric and/or electronic
properties of the substituents. Although the complex RuCl2(L2b)-
(PPh3) (42b-trans-Cl) (L2b ) Cy2PCH2quin) was generated under
the same conditions as the previous one, its isomerization into
the cis derivative RuCl2(L2b)(PPh3) (42b-cis-Cl) was found to
require a much longer time for completion. The same very slow
isomerization of the other quinolynyl derivative, RuCl2(L1b)-
(PPh3) (41b-trans-Cl), was noted.
all in equatorial position. Let us specify that similar types of
isomerization reactions have been observed in the case of other
Ru(II)-halide complexes, including alkylidene complexes.19
Whereas the same synthetic strategy proved to be convenient
for the whole series of phosphino-pyridine type ligands con-
sidered in this work, further experiments confirmed that the
Reactivity of RuCl2(L1x)(PPh3) (41x) toward Alkynes and
Formation of Vinylidene RuCl2(L1x)(dCdCHR)(PPh3) (51x).
It was found that all isomeric forms of 41x complexes react
cleanly with terminal alkynes to afford a new complex 51x
existing under the form of a unique isomer. The latter was
identified by NMR spectroscopy as the vinylidene species
RuCl2(L1x)(dCdCHR)(PPh3) (51x), exhibiting the geometry
shown in Scheme 4. Such a geometry can be reasonably inferred
by comparison with that of the allenylidene compound
RuCl2(L2a)(CdCdCPh2)(PPh3), exhibiting comparable 31P NMR
data, and for which a preliminary X-ray structure analysis was
done.20 As shown in Scheme 4, the vinylidene ligand occupies
a coordination site in cis position relative to both P and N donor
atoms of the PN ligand, whereas the two chloride ligands are
in cis position. The remaining triphenylphosphine ligand oc-
cupies the site trans to the nitrogen atom. It is noteworthy that,
in contrast to the reaction of terminal alkynes with RuCl2(PPh3)3,
which was previously shown by Wakatsuki to give the 16 e-
vinylidene complex RuCl2(PPh3)2(CCHR) with concomitant loss
of triphenylphosphine,21 the reaction observed here is an addition
rather than a substitution, thus taking place without phosphine
displacement and leading to an 18 e- species. This may be
indicative that a phosphinopyridine ligand is less sterically
demanding than two phosphines and might then have a lower
cis-labilizing ability.
Figure 5. Perspective view of complex RuCl2(L2a)(PPh3) (42a-cis-
Cl). Ellipsoids are shown at the 30% probability level.
Table 6. Selected Interatomic Distances [Å] and Bond Angles [deg]
for Complex 42a-cis-Cl
Bond Distances
Ru1-Cl1
Ru1-Cl2
Ru1-P1
Ru1-P2
Ru1-N1
P1-C2
2.3822(13)
2.4430(13)
2.1956(12)
2.2728(12)
2.082(4)
1.840(5)
1.351(6)
1.493(7)
Given that vinylidenes can be regarded as “carbenoids”,22
one might reasonably anticipate that the reaction of 41x with a
diazoalkane might generate a potentially metathesis-active
carbene species. Indeed, it was previously found by Fogg5d that
N1-C12
C2-C12
(19) (a) For some examples, see: Queiroz, S. L.; Batista, A. A.; Oliva,
G.; Gambardella, M. T.; Santos, R. H. A.; MacFarlane, K. S.; Rettig, S. J.;
James, B. R. Inorg. Chim. Acta 1998, 267, 209. (b) Hansen, S. M.; Volland,
M. A. O.; Rominger, F.; Eisenträger, F.; Hofman, P. Angew. Chem., Int.
Ed. 1999, 38, 1273. (c) Hansen, S. M.; Rominger, F.; Metz, M.; Hofman,
P. Chem.-Eur. J. 1999, 5, 557. (d) Volland, M. A. O.; Straub, B. F.; Gruber,
I.; Rominger, F.; Hofman, P. J. Organomet. Chem. 2001, 617, 288.
(20) The allenylidene complex RuCl2(L2a)(dCdCdCPh2)(PPh3) was
obtained by reaction of 41a with 1,1-diphenyl-2-propyn-1-ol under the same
experimental conditions as those used for the preparation of the vinylidene
species. Though not publishable due to the poor quality of the crystals, the
X-ray analysis allowed an accurate determination of the overall geometry
of the complex (Lugan, N.; Lavigne, G. Unpublished observations).
(21) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J. Am.
Chem. Soc. 1994, 116, 8105.
Bond Angles
Cl1-Ru1-Cl2
Cl1-Ru1-P1
Cl1-Ru1-P2
Cl1-Ru1-N1
Cl2-Ru1-P1
Cl2-Ru1-P2
Cl2-Ru1-N1
P1-Ru1-P2
P1-Ru1-N1
P2-Ru1-N1
Ru1-P1-C2
Ru1-N1-C12
P1-C2-C12
N1-C12-C2
85.14(4)
103.27(4)
94.28(4)
168.99(11)
104.27(5)
160.92(5)
85.01(11)
94.44(4)
83.96(11)
93.41(11)
101.95(17)
120.7(3)
110.1(3)
116.7(4)
(22) (a) Bruce, M. I. Chem. ReV 1991, 91, 197. (b) Katayama, H.; Ozawa,
F. Coord. Chem. ReV. 2004, 248, 1703.

1200 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
Scheme 5. Reaction of RuCl2(L1a)(PPh3) (41a) (mixture of cis
and trans isomers) with an Excess of Ethyl Diazoacetate Giving
the Diethyl Maleate Complex RuCl2(L1a){cis-EtO(O)C(H)CdC
(H)C(O)OEt} (61a) as a Unique Isomer
Table 7. Bond Lengths [Å] and Angles [deg] for Complex 61a
Bond Distances
Ru1-Cl1
Ru1-Cl2
Ru1-P1
Ru1-O3
Ru1-N1
Ru1-C6
Ru1-C7
P1-C2
P1-C31
P1-C21
O1-C5
O2-C4
O2-C5
O3-C8
O4-C9
O4-C8
N1-C12
C2-C12
C3-C4
C5-C6
C6-C7
C7-C8
C9-C10
2.3899(15)
2.4003(15)
2.1987(15)
2.414(5)
2.142(5)
2.179(5)
2.131(5)
1.819(5)
1.808(6)
1.808(5)
1.189(9)
1.461(9)
1.345(6)
1.226(9)
1.401(12)
1.355(8)
1.373(6)
1.488(8)
1.502(9)
1.465(10)
1.394(6)
1.440(10)
1.460(13)
closely related complexes RuCl2(diphosphine)(PPh3) do not
require PPh3 ligand abstraction to achieve high reactivity in
ROMP in the presence of a carbene source, possibly meaning
that loss of PPh3 is spontaneous under room-temperature reaction
conditions. We were thus led to examine the case of our
phosphinopyridine complexes. However, our attempts to use
type 5 vinylidene complexes as catalyst precursors for the
ROMP of norbornene at room temperature proved to be
negative, probably due to the fact that they are fully saturated
18 e- species.
Bond Angles
Reactivity of RuCl2(L1x)(PPh3) (41x) toward Ethyl Diaz-
oacetate. The reaction of RuCl2(L1x)(PPh3) (41x) (mixture of
cis–trans isomers) with ethyl diazoacetate was carried out at
-60 °C. Monitoring by NMR spectroscopy revealed that total
consumption of the precursor complex 41x required at least 3
equiv of the carbene precursor. Typically, upon addition of an
excess of ethyl diazoacetate (5 equiv) at low temperature, the
reaction proceeded cleanly toward the formation of a unique
complex exhibiting a single phosphorus resonance, along with
concomitant elimination of phosphonium ylide Ph3Pd
C(H)C(O)OEt. Isolation and characterization of the new com-
plex 61x by NMR spectroscopy and X-ray diffraction (in the
case of 61a) allowed its formulation as RuCl2(L1x){cis-
EtO(O)C(H)CdC(H)C(O)OEt} (61x) (Scheme 5, Figure 6, Table
7). The formation of this uncommon olefinic complex can be
reasonably understood in terms of a reaction sequence involving
(i) the coordination of the incoming carbene moiety to the metal
center, (ii) its coupling with the triphenylphosphine ligand to
produce the phosphonium ylide Ph3PdC(H)C(O)OEt, which is
readily eliminated, and (iii) the uptake of two more carbene
units by the remaining 14 e- fragment “RuCl2(L1x)”, resulting
in a metal-mediated CC bond formation between these units to
give the coordinated diethyl maleate ligand intercepted here.
Cl1-Ru1-Cl2
Cl1-Ru1-P1
Cl1-Ru1-O3
Cl1-Ru1-N1
Cl1-Ru1-C6
Cl1-Ru1-C7
Cl2-Ru1-P1
Cl2-Ru1-O3
Cl2-Ru1-N1
Cl2-Ru1-C6
Cl2-Ru1-C7
P1-Ru1-O3
P1-Ru1-N1
P1-Ru1-C6
P1-Ru1-C7
O3-Ru1-N1
O3-Ru1-C6
O3-Ru1-C7
N1-Ru1-C6
N1-Ru1-C7
Ru1-P1-C2
Ru1-O3-C8
Ru1-N1-C12
P1-C2-C12
Ru1-C6-C5
Ru1-C6-C7
C5-C6-C7
84.11(5)
94.59(5)
98.40(12)
82.29(12)
164.73(19)
153.62(13)
92.75(6)
85.33(12)
165.69(12)
111.15(18)
78.72(16)
166.59(13)
83.94(14)
85.44(17)
106.02(19)
101.04(17)
82.91(18)
60.6(2)
82.5(2)
115.58(19)
102.41(18)
86.5(4)
117.4(4)
110.9(3)
113.1(5)
69.3(3)
121.2(6)
73.0(3)
93.3(4)
Ru1-C7-C6
Ru1-C7-C8
C6-C7-C8
O4-C8-C7
O3-C8-O4
O3-C8-O7
120.9(7)
114.6(6)
125.9(7)
119.5(6)
Interestingly, a comparable reaction pathway involving similar
generation of a phosphonium ylide from the cyclopentadienyl
Ru(II) complex Cp*RuCl{CHC(O)OEt}(PPh3) has been previ-
ously described by Baratta.23 It has also been recently shown
that one of the identified pathways to decomposition of Grubbs
catalysts is a coupling reaction between the propagating carbene
and a free phosphine.24
(23) (a) Baratta, W.; Del Zotto, A.; Rigo, P. Organometallics 1999, 18,
5091. (b) Pedro, F. M.; Santos, A. M.; Baratta, W.; Kühn, F. E.
Organometallics 2007, 26, 302.
(24) (a) Sanford, M. S.; Henling, L. M.; Day, M. W.; Grubbs, R. H.
Angew. Chem., Int. Ed. 2000, 39, 3451. (b) Conrad, J. C.; Amoroso, D.;
Czechura, P.; Yap, G. P. A.; Fogg, D. E. Organometallics 2003, 22, 3634.
(c) Dinger, M. B.; Mol, J. C. Organometallics 2003, 22, 1089.
Figure 6. Perspective view of complex RuCl2(L1a){cis-EtO(O)-
C(H)CdC(H)C(O)OEt} (61a). Ellipsoids are shown at the 30%
probability level.

Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1201
Table 8. ROMP of Norbornene Using Complexes 4nx and 21a as
Precatalysts at 22 °C and Trimethylsilyldiazomethane as Initiator
situ” generated catalysts exhibit a moderate activity at room
temperature in nonoptimized standard tests where the poly-
merization was quenched after 30 min. It is noteworthy that
the complexes are more active than the precursor RuCl2(PPh3)3,
known to polymerize norbornene only at 50 °C.5h Changes in
the nature of the substituents on the ligand affect only
moderately the activity of the catalyst. Interestingly, the
bimetallic species 21a is also seen to be active as a catalyst
precursor, exhibiting the fastest initiation rate (50% conversion
after 2 min). However, in that case, considering that both a 14e-
fragment, “RuCl2(PPh3)2” (the latter possibly acting as a
phosphine scavenger) and a 16 e- fragment “RuCl2(L1a)(PPh3)”
may be liberated in solution upon dissociation of the bimetallic
unit, a complicating factor arises from the fact that both
fragments are prone to be attacked by the incoming carbene
and may thus each produce an independent active species
propagating at a different rate.
b
d
precatalysta [substr]/[cat.] time (min)
yieldc
Mn
PDd
41a
41b
42a
42b
21a
21a
21a
100
100
100
100
100
100
100
30
30
30
30
2
59
61
53
45
50e
60e
79
1.81 × 105 2.53
1.91 × 105 2.30
1.80 × 105 2.30
4.41 × 105 1.70
8
30
4.40 × 104 2.39
a General conditions (see Experimental Part): solvent, CH2Cl2; reaction
initiated by addition of trimethylsilyldiazomethane ([TMSD]/[cat.] ) 5).
b Time at which the polymerization was quenched by addition of
2,6-di(tert-butyl)-4-methylphenol in methanol. c Isolated by precipitating in
methanol. d Determined by SEC in microfiltrated THF solutions. e The
yields obtained for 2a upon quenching the polymerization at short time are
indicative of a fast initiation rate, but the relevant Mn values at intermediate
stage were not measured.
Spectroscopic and crystallographic data reveal that the olefinic
bond of the newly assembled diethyl maleate ligand is π-bound
to the Ru center and is coordinated in cis position relative to
both the phosphorus and the nitrogen atom of the ancillary PN
ligand. Maleate and fumarate ligands have been previously used
as suitable leaving groups in a series of ruthenium complexes
prepared by Kondo and Mitsudo.25 Here, an additional bonding
interaction is seen to occur between one of the donor oxygens
of the diethyl maleate unit and the ruthenium center, thereby
blocking the coordination site opposite to the phosphorus ligand.
The octahedral basis set of the complex is completed by the
two chloride ligands adopting a cis- arrangement.
On the basis of the expectation that the olefin is only weakly
bound to the metal, we were reasonably anticipating that further
reaction of 61a with one more equivalent of diazoalkane would
result in the formation of a carbene complex via simple
displacement of the coordinated ester function of the olefin.
Surprisingly, however, additional experiments indicated that
such a reaction does not spontaneously occur (at least under
ambient conditions), which probably reflects a rather high
stability of the complex inherent to the chelating coordination
mode of the diethyl maleate ligand. Preliminary experimental
tests under catalytic conditions effectively confirmed that
complex 61a is inefficient as a catalyst precursor for the ROMP
of norbornene, at least under ambient conditions.
With this in mind, we were logically prompted to carry out
further catalytic experiments by using a carbene source devoid
of potentially coordinating oxygen. Trimethylsilyldiazomethane,
also commercially available, was thus logically selected as an
alternate carbene source for that purpose. The results of relevant
catalytic tests are reported in the next section.
ROMP of Norbornenes Using RuCl2(Lnx)(PPh3) (4nx-cis-
Cl) and Related Species as Catalyst Precursors in the
Presence of Trimethylsilydiazomethane as the Carbene
Source. Noëls and co-workers5b,e,l have previously shown that
a number of noncarbene Ru(II) precursors are prone to catalyze
the ROMP of norbornenes upon in situ activation by trimeth-
ylsilyl diazomethane, and we have recently exploited such a
strategy in a published report showing that some alkynyl-
phosphine complexes can act similarly as fast ROMP
precatalysts.5j Attempts to evaluate the efficiency of our new
complexes were thus made under the same experimental
conditions. The results, listed in Table 8, indicate that our “in
The precatalysts studied in this work tolerate small amounts
of HCl, but are dramatically altered by the presence of traces
of base, such as residues that might incidentally remain on the
glassware after cleansing treatment with an ethanolic KOH bath
(this is avoided by routine neutralization of the glassware with
an aqueous HCl bath). The deleterious effect of bases noted
here may be understood in terms of pioneering observations
made by Grubbs on the ROMP reaction initiated by well-defined
Ru carbene complexes.10a The degradation of the catalyst in
that case may be ascribed to the facile displacement of the
chlorides by anionic ligands,26 a transformation that may be
exploited for other types of catalytic reactions, as exemplified
below in the next section. Let us mention here that a positive
effect of acid additives on the performances of well-defined
ROMP precatalysts has been observed by Grubbs27 and recently
investigated in depth by Schanz.28
At the present stage of our investigation, the principal
drawback of these in situ generated catalysts is that they are
unable to polymerize more synthetically useful cyclic olefins
being less strained than norbornene. One reason for such a
limitation might be that, contrary to our original expectations,
the pyridyl group does not behave as a hemilabile ligand and
probably remains coordinated to the metal, even in the active
form of the catalyst. In this respect, the introduction of bromo
substituents on the pyridyl ring (as seen in third-generation
Grubbs’ catalyst) might allow enhancing its leaving group
properties. So, it is no doubt that further modifications of the
ligand backbone will be needed in view of future improvements
(see our conclusions).
Transfer Hydrogenation of Ketones Using RuCl2(Lnx)-
(PPh3) (4nx) as a Catalyst Precursor. A number of authoritative
recent reviews have highlighted the importance of chemose-
lective transition-metal-catalyzed transfer hydrogenation of
ketones,11 which has now gained considerable significance and
has been successfully applied to selective organic transforma-
(26) Hong, S. H.; Wenzel, A. G.; Salguero, T. T.; Day, M. W.; Grubbs,
R. H. J. Am. Chem. Soc. 2007, 129, 7961.
(27) Lynn, D. M.; Mohr, B.; Grubbs, R. H.; Henling, L. M.; Day, M. W.
J. Am. Chem. Soc. 2000, 122, 6601.
(28) P’Pool, S. J.; Schanz, H.-J. J. Am. Chem. Soc. 2007, 129, 14200.
(29) (a) Yamakawa, M.; Ito, H.; Noyori, R. J. Am. Chem. Soc. 2000,
122, 1466. (b) Noyori, R.; Yamakawa, M.; Hashiguchi, S. J. Org. Chem.
2001, 66, 7931. (c) Pamies, O. Bäckvall.; J.-E., Chem.-Eur. J. 2001, 7,
5052. (d) Abdur-Rashid, K.; Clapham, S. E.; Hadzovic, A.; Harvey, J. N.;
Lough, A. J.; Morris, R. H. J. Am. Chem. Soc. 2002, 124, 15104. (e)
Clapham, S. E.; Hadzovic, A.; Morris, R. H. Coord. Chem. ReV. 2004,
248, 2201. (f) Samec, J. S.; Ell, A. H.; Aberg, J. B.; Privalov, T.; Eriksson,
L.; Bäckvall, J.-E. J. Am. Chem. Soc. 2006, 128, 14293. (g) Comas-Vives,
A.; Ujaque, G.; Llenos, A. Organometallics 2007, 26, 4135.
(25) (a) Mitsudo, T.; Suzuki, T.; Zhang, S.-W.; Imai, D.; Fujita, K.;
Manabe, T.; Shiotsuki, M.; Watanabe, Y.; Wada, K.; Kondo, T. J. Am.
Chem. Soc. 1999, 121, 1839. (b) Shiotsuki, M.; Suzuki, T.; Kondo, T.; Wada,
K.; Mitsudo, T. Organometallics 2000, 19, 5733.

1202 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
Table 9. Transfer Hydrogenation of Various Ketones, Using
Complexes 4nx as Precatalystsa
tions including enantioselective reactions. Significantly, accord-
ing to these reviews, there is not one, but several types of
operative specific mechanisms for transfer hydrogenation,29
depending both on the classes of transition-metal complexes
used as precatalysts and on the peculiar ligand combinations
adopted in the construction of such complexes. Since the early
pioneering reports of Sasson and Blum,30 where RuCl2(PPh3)3
was used for the first time as a catalyst precursor for the transfer
hydrogenation from alcohols to ketones, and the equally very
important work by Bäckvall,31 who originally defined the most
convenient experimental conditions, a multitude of ruthenium
complexes were investigated and proved to function as efficient
catalyst precursors.11 Significantly, the reports by Noyori32 on
the spectacular performances of RuCl2(diamine)(diphosphine)
complexes, giving rise to “bifunctional” RuH/NH2 catalysts
capable of promoting a concerted transfer of proton and hydride
to the incoming ketone, have oriented the quest for ligand
acceleration effects toward diverse combinations of soft phos-
phines and hard nitrogen ligands as well as hybrid “PN”
ligands.33–35 Some of the relevant complexes, however, are
implying mechanisms different from that proposed by Noyori.
A representative example is the case of Ru(II) complexes of
the chiral ferrocenyloxazolinylphosphine (“FOXAP”),34 some-
times generated in situ, and subsequently formulated as
RuCl2(FOXAP)(PPh3), which were found to be of particular
efficiency for various highly enantioselective reduction reactions
including hydrogen transfer.
substrate
catalyst TOF(h-1 yield after 60s final yieldb
)
Cyclohexanone
41a
42a
41b
42b
273 000
239 000
172 000
140 000
99%
99%
93%
98%
99%
99%
99%
99%
2-Hexanone
41a
42a
41b
42b
200 000
164 000
225 000
211 000
90%
91%
92%
91%
91%
92%
92%
91%
Acetophenone
41a
42a
41b
42b
99 000
124 000
82 000
83%
77%
74%
70%
88%
88%
88%
88%
100 000
5-Methyl-5-hexen-2-one
Benzophenone
41a
42a
41b
42b
78 000
35 000
129 000
100 000
75%
52%
87%
84%
94%
92%
94%
93%
41a
42a
41b
42b
93 000
29 000
150 000
49 000
69%
49%
90%
55%
93%
57%
94%
60%
a Reactions were carried out on a 10 mmol scale, using 0.01 mole of
catalyst in 10 mL iPrOH at T ) 82 °C under N2 with [NaOH]/[RU] )
22.5. The conversion rates were determined by GC from samplings
made every 15 seconds. Turnover frequencies, corresponding to the
number of moles of ketone converted per mole of catalyst per hour,
were determined at 50% conversion. The table gives both the
intermediate yield obtained within 60 seconds and the final maximum
yield reached. b Final yields were respectively measured after 2 min for
cyclohexanone,5minfor2-hexanoneandacetophenone,10minfor5-methyl-
5-hexen-2-one, and 30 min for benzophenone.
Among numerous approaches,11,30–36 including several early
reports by two of us,8a,b the Ru-based systems recently reported
by Baratta,35 in particular those involving a terdentate pincer
ligand or a cyclometallated N-heterocyclic carbene,35d,e are of
(30) Sasson, Y.; Blum, J. J. Org. Chem. 1975, 40, 1887.
(31) (a) Bäckvall, J. E.; Chowdhury, R. L.; Karlsson, U. J. Chem. Soc.,
Chem. Commun. 1991, 473. (b) Chowdhury, R. L.; Bäckvall, J. E. J. Chem.
Soc., Chem. Commun. 1991, 1063. (c) Aranyos, A.; Csjernyik, G.; Szabo,
K. J.; Bäckvall, J.-E. J. Chem. Soc., Chem. Commun. 1999, 351. (d)
Bäckvall, J.-E. J. Organomet. Chem. 2002, 652, 105.
spectacular efficiency and presently remain the best transfer
hydrogenation catalysts reported so far.
With the above literature data in mind, we were curious to
examine whether a very simple metal–ligand system using our
series of type 4nx complexes as catalyst precursors could
compete with the more elaborated catalyst prototypes cited
above. From an experimental point of view and for comparative
purposes, all catalytic tests were made under Bäckvall’s
conditions. In such a way to ascertain our results, we cautiously
made a blank test, keeping in mind that hydrogen transfer is
also known to proceed without catalyst, but then at much slower
rates, and via a different mechanism.37 The blank test, carried
out on acetophenone under the experimental conditions of all
our catalytic runs, albeit in the absence of catalyst, gave 0.6%
yield in 5 min, 1.3% yield in 10 min, and 94% yield in 70 h.
The results of our catalytic experiments carried out with
complexes 4nx-cis-Cl (Table 9, Figure 7) reveal that these rank
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(36) (a) Thoumazet, C.; Melaimi, M.; Ricard, L.; Mathey, F.; Le Floch,
P. Organometallics 2003, 22, 1580. (b) Boubekeur, L.; Ulmer, S.; Ricard,
L.; Mézailles, N.; Le Floch, P. Organometallics 2006, 25, 315.
(37) (a) Bagnell, L.; Strauss, C. R. Chem. Commun. 1999, 287. (b) Le
Page, M. D.; James, B. R. Chem. Commun. 2000, 1647.

Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1203
designed as probe systems enabling convenient preliminary
assays in metathesis, and, in this respect, our initial objective
is only partly attained. Indeed, though the corresponding “in
situ” generated catalysts proved to be moderately efficient
initiators for the ROMP of norbornene under ambient conditions,
they still do have some important limitations, being in particular
unable to polymerize unstrained cyclic olefins such as cy-
clooctene or to catalyze other types of metathesis reactions.
Importantly, however, one outgrowth of the present investiga-
tion is to provide insight into the mechanism by which an active
olefin metathesis catalyst can be generated in situ upon reaction
of a phosphine-containing Ru(II) complex with a carbene source.
Indeed, a typical diazoalkane such as ethyl diazoacetate was
seen to act not only as the effective source of the propagating
carbene but also as a phosphine scavenger, via concomitant
formation of the corresponding phosphonium ylide, thereby
contributing to the creation of an unsaturation, as obviously
required for olefin coordination and metathesis.
Figure 7. TOF values (h-1) recorded for type 4nx precatalysts in
the transfer hydrogenation of various ketone substrates.
In parallel, we have also shown that most complexes within
the series RuCl2{R2PCH2(C5H2R′R′′N)}(PPh3) are acting as
remarkably efficient “instant” catalysts for the transfer hydro-
genation of ketones, matching the performances of the best
catalytic system reported so far, and in particular those based
on more sophisticated ligands. Of course, further modifications
of our ligands by introduction of chiral centers are still required
in view of developing relevant synthetically useful applications
in catalytic hydrogenation.
More generally, a logical continuation of this work in our
laboratory is currently involving the parallel design and
development of related in situ generated catalysts based on
pyridine-functionalized N-heterocyclic carbene ligands, which
are also easily available.39 Relevant results will be published
in due course.
among the fastest precatalysts reported so far for this reaction.
They appear to exhibit higher efficiency than the already
excellent Ru(II)/PCP-pincer complexes reported by Fogg33h and
van Koten,33e,q with the additional advantage that they are
simpler and do not require any pretreatment. Our results also
indicate that for a given ketonic substrate it is certainly possible
to select the fastest catalyst within the present family. However,
one must admit that subtle variations of the electronic and steric
properties of the ligands are only moderately affecting the
performances of the catalyst. In particular, the comparative
diagram displayed in Figure 7 reveals that, whereas electron-
rich ligands have been previously shown to exhibit particular
efficiency, this does not appear to be the case here, where 41a
and 41b are even often slightly better than 42a and 42b. Our best
result was recorded with the precatalyst 41a, using cyclohexanone
as the substrate. The latter ketone was hydrogenated in 99%
yield within 45 s with only 0.01 mol (1 ×10-3 mol %) of 41a,
representing a turnover frequency of 272 571 h-1. The TOF
was indeed measured at 50% conversion, namely, after 7 s in
the present case! Indeed, the first sampling at 15 s already gave
89.8% yield. Such performances rank only slightly below those
recorded with Baratta’s catalysts, and it is noteworthy that the
turnover rates obtained with our new ligands are about 2 times
higher than those recorded with the bulkier and more sophis-
ticated “P-N-O” ligand “1-(diphenylphosphino)-2-ethoxy-1-
(2-pyridyl)ethane” previously tested in our group.8b Though no
mechanistic studies were made during the course of the present
work, it can be reasonably assumed that the mechanism
previously established by Bäckvall for RuCl2(PPh3)3 and involv-
ing the formation of a dihydride species31c is also operative for
the present catalytic system.
Experimental Part
General Considerations. THF and diethyl ether were distilled
from sodium/benzophenone ketyl just before use. Toluene, pentane,
and dichloromethane were dried and distilled following standard
procedures and stored under nitrogen. RuCl2(PPh3)340 and 2-[(diphe-
nylphosphino)methyl]-6-methyl-pyridine,8c (L1a) were prepared
following literature procedures. Other reagent grade chemicals such
as 2-picolin, 2,6-lutidin, 2-methylquinolin, phenylacetylene, ethyl
diazoacetate, and nBuLi (1.6 M solution in hexane) were obtained
from Aldrich and used without further purification. All synthetic
manipulations were carried out using standard Schlenk techniques
under an atmosphere of dry nitrogen. A liquid N2/2-propanol slush
bath was used to maintain samples at the desired low temperature.
NMR spectra were recorded on Bruker AC200, WM250, DPX300,
AV300, AMX400, or AV500 spectrometers and were referenced
to the residual signals of the deuterated solvent. Infrared spectra
were obtained as solutions on Perkin-Elmer 1725 FT-IR or 983G
spectrometers with 0.1 mm cells equipped with CaF2 windows.
Microanalyses of C, H, and N elements were performed by the
Laboratoire de Chimie de Coordination Microanalysis Service on
a Perkin-Elmer 2400 CHN analyzer. Note: Most of the compounds
isolated in this work were found by X-ray diffraction to contain
Conclusion
At a time where tandem catalysis is attracting growing
attention,38 the ability for a given transition-metal complex to
catalyze several types of substrate transformations is appearing
as a valuable property. In the present investigation, we have
shown that certain phosphinopyridine complexes of the type
RuCl2{R2PCH2(C5H2R′R′′N)}(PPh3) where the pyridyl moiety
is a picolyl or a quinolyl group are simple and readily accessible
at low cost from RuCl2(PPh3)3 under a simple experimental
protocol, which has now been precisely defined. They were
(39) (b) Tulloch, A. A. D.; Danopoulos, A. A.; Winston, S.; Kleinhenz,
S.; Eastham, G. J. Chem. Soc., Dalton Trans. 2000, 4499. (c) Gründemann,
S.; Kovacevic, A.; Albrecht, M.; Faller, J. W.; Crabtree, R. J. Am. Chem.
Soc. 2002, 124, 10473. (d) Danopoulos, A. A.; Tsoureas, N.; Macgregor,
S. A.; Smith, C. Organometallics 2007, 26, 253. (e) Wright, J. A.;
Danopoulos, A. A.; Motherwell, W. B.; Carroll, R. J.; Ellwood, S. J.
Organomet. Chem. 2006, 691, 5204.
(38) (a) Fogg, D. E.; dos Santos, E. N. Coord. Chem. ReV. 2004, 248,
2365.
(40) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,
12, 237.

1204 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
nonstoichiometric amounts of dichloromethane in the lattice (Vide
infra). The presence of such Volatile molecules in the solid samples
is belieVed to affect the precision of microanalyses. The charac-
terization of polynorbornene was carried out by size exclusion
chromatography: Analytical SEC data were obtained at 298 K using
a SFD RI 2000 differential refractometer, a multiangle laser light
scattering detector (Wyatt Technology, miniDAWN), a PLgel 5
µm MIXED-D column (300 × 7.5 mm), and microfiltrated THF
as eluant with a nominal flow of 0.85 mL/min; results are reported
relative to poly(styrene) standards. The products of transfer
hydrogenation were analyzed by gas chromatography on a Hewlett-
Packard HP4890AHP equipped with a flame ionization detector
and an Alltech EC-1000 column (0.32 mm i.d., 15 m long).
Synthesis of Ph2PCH2quin (L1b), Ph2PCH2pic (L2a), and
Cy2PCH2quin (L2b). The typical procedure for the preparation of
these ligands is exemplified here by the case of L2a. A solution
containing 2.5 mL of 2,6-lutidine (21.5 mmol) in 20 mL of Et2O
was added dropwise at 0 °C to a solution containing 1 molar equiv
of 1.6 M nBuLi diluted in 13.5 mL of hexane. The resulting solution
was found to gradually turn red-orange during the addition. At the
end of the addition, it was stirred for 30 min more at 0 °C, then
allowed to warm to room temperature. The resulting solution of
picCH2Li thus prepared was added dropwise over a period of 3 h
by means of an automatic syringe to a solution containing 5 g of
dicyclohexylchlorophosphine (21.5 mmol) in 100 mL of Et2O
maintained at -80 °C. At the end of the addition, the cold bath
was removed in such a way as to allow warming of the solution to
ambient temperature. Degased water (100 mL) was added to the
reaction medium, and the phosphine was extracted with ether. The
organic phase was dried over MgSO4 and then evaporated under
high vacuum, leaving a pale yellow oil ultimately producing a solid
residue when stored at -30 °C in a freezer. This residue was
subsequently recrystallized at -30 °C from a Et2O/hexane mixture,
producing the pure phosphine Cy2PCH2pic (L2a, 4.6 g, 1.40 mmol,
71% yield).
a heterogeneous crystalline material, from which single crystals of
[RuCl2(PPh3)2]2 (1), [(PPh3)2ClRu(µ-Cl)3Ru(L1a)(PPh3)] (21a), and
RuCl2(L1a)2(31a) were selected for X-ray diffraction analyses.
Synthesis of [(PPh3)2ClRu(µ-Cl)3Ru(L1a)(PPh3)] (21a). Com-
plex RuCl2(Ph2PCH2pic)(PPh3) (41a, as ca. 1:1 mixture of cis/trans
isomers (Vide infra), 73 mg, 0.10 mmol) and crystals of
RuCl2(PPh3)3 (95 mg, 0.10 mmol) were introduced in a Schlenk
flask and dissolved in 15 mL of dichloromethane at room temper-
ature. After stirring for 4 h, the solvent was eliminated under
reduced pressure and the resulting brown residue was washed with
n-hexane (2 × 10 mL) and dried under vacuum. Recrystallization
from a dichloromethane/hexane mixture afforded a homogeneous
dark orange crystalline material, which analyzed as [(PPh3)2ClRu(µ-
Cl)3Ru(L1a)(PPh3)] (21a) (60 mg, 0.043 mmol, 43% yield).
21a. Anal. Calcd for C73H63Cl4NP4Ru2: C, 61.65; H, 4.47; N,
0.98. Anal. Calcd for [C73H63Cl4NP4Ru2 + 1.5CH2Cl2] (X-ray
structure analysis): C, 57.74; H, 4.29; N, 0.90. Found: C, 56.05;
H, 3.86; N, 0.83.
Synthesis of RuCl2(L1a)2 (31a). Crystals of RuCl2(PPh3)3(95 mg,
0.10 mmol.) and Ph2PCH2pic (L1a, 58 mg, 0.20 mmol) were
introduced in a Schlenk flask, and 15 mL of dichloromethane was
added at room temperature. After stirring overnight, the dichlo-
romethane was removed under vacuum. The orange residue was
washed with n-hexane (2 × 10 mL) and dried under vacuum.
Recrystallization from a dichloromethane/hexane mixture afforded
RuCl2(L1a)2 (31a) as a microcrystalline material (69 mg, 0.092
mmol, 92% yield).
31a. NMR 1H (500 MHz, CD2Cl2, 25 °C): δ 7.47–7.00 (m, 26H,
C6H5andMeC5H3N), 5.44 (dt, 2H, JHH ) 15 Hz, JHP ) 5 Hz, CHH),
3.98 (dt, 2H, JHH ) 15 Hz, JHP ) 10 Hz, CHH), 2.83 (s, 6H,
MeC5H3N). NMR 31P{1H} (101 MHz, CD2Cl2, 25 °C): δ 63.6 (s).
Anal. Calcd for C38H36Cl2N2P2Ru: C, 60.48; H, 4.81; N, 3.71. Anal.
Calcd for C38H36Cl2N2P2Ru: C, 60.48; H, 4.81; N, 3.71. Anal. Calcd
for [C38H36Cl2N2P2Ru + CH2Cl2] (X-ray analysis): C, 55.79; H,
4.56; N, 3.35. Found: C, 55.89; H, 4.34; N, 3.12.
Synthesis of RuCl2(Ph2PCH2pic)(PPh3) (41a). Crystals of
RuCl2(PPh3)3(95 mg, 0.10 mmol) were introduced in a Schlenk flask
and dissolved in 15 mL of dichloromethane at room temperature.
A solution of the ligand Ph2PCH2pic (L1a, 29 mg, 0.10 mmol) in
5 mL of degassed CH2Cl2 was prepared separately and introduced
slowly into the previous one over a period of 4 h, using an automatic
syringe. At the end of the addition, the solvent was evaporated under
reduced pressure and the resulting brown solid was washed twice
with n-hexane (10 mL) and dried under vacuum. NMR data of the
crude product revealed the occurrence of a mixture of cis-Cl and
trans-Cl isomers in a ca. 1/1 ratio. Recrystallization from a CH2Cl2/
hexane mixture at room temperature gave pure samples of 41a-cis-
Cl isolated as an orange crystalline material (50 mg, 0.069 mmol,
69% yield), subsequently used for the catalytic runs.
The other two new phosphinomethyl pyridine ligands, namely,
Ph2PCH2quin (L1b) and Cy2PCH2quin (L2b), were synthesized
according to the same preparative procedure, using on one hand
the chlorophosphines Ph2PCl and Cy2PCl for L1 and L2, respec-
tively, and on the other hand, 2-methylquinoline.
L
1b (pale yellow solid, 56% yield). NMR 1H (250 MHz, CD2Cl2):
δ 7.97 (d, 1H, JHH ) 7 Hz, C9H6N), 7.62 (d, 1H, JHH ) 7 Hz,
C9H6N), 7.75 (d, 1H, C9H6N), 7.65 (t, 1H, C9H6N), 7.53 (t, 1H,
C9H6N), 7.17 (d, 1H, C9H6N), 3.82 (s, 2H, CH2), 7.48–7.35 (m,
5H, Ph). NMR 31P{1H} (101 MHz, CD2Cl2): δ -9.33. Anal. Calcd
for C22H18NP: C, 80.72; H, 5.54; N, 4.28. Found: C, 80.39; H,
5.35; N, 4.23.
1
L2a (white solid, 71% yield). NMR H (250 MHz, CD2Cl2): δ
7.39 (t, 1H, JHH ) 9.6 Hz, C5H3N), 7.07 (d, 1H C5H3N), 6.86 (d,
1H, C5H3N), 2.94 (d, 2H, CH2, JPH ) 3.7 Hz), 2.45 (s, 3H, CH3).
NMR 31P (101 MHz, CD2Cl2): δ 5.89. Anal. Calcd for C19H30NP:
C, 75.21; H, 9.97; N, 4.62. Found: C, 75.00; H, 9.62; N, 4.38.
41a-trans-Cl (from a 41a-cis-Cl /41a-trans-Cl mixture). NMR 1H
(250 MHz, CD2Cl2, 25 °C): δ 8.15–6.91 (m, C6H5andMeC5H3N),
4.33 (d, 2H, JHP ) 10.3 Hz, CH2), 2.69 (s, 3H, MeC5H3N). NMR
31P{1H} (101 MHz, CD2Cl2, 25 °C): δ 88.9 (d, JPP ) 44.0 Hz,
Ph2P), 50.7 (d, JPP ) 44.0 Hz, PPh3).
L
2b (pale yellow solid, 68% yield). NMR 1H (250 MHz, CD2Cl2):
δ 8.05 (d, 1H, JHH ) 7 Hz, C9H6N), 9.97 (d, 1H, JHH ) 7 Hz,
C9H6N), 7.79 (d, 1H, C9H6N), 7.66 (t, 1H, C9H6N), 7.53 (t, 1H,
C9H6N), 7.47 (d, 1H, C9H6N), 3.18 (s, 2H, CH2), 1.30–1.75 (m,
11H, C6H11). NMR 31P (101 MHz, CD2Cl2): δ 6.11. Anal. Calcd
for C22H30NP C, 77.84; H, 8.91; N, 4.13. Found: C, 77.56; H, 8.68;
N, 4.02.
Reaction of Ph2PCH2pic (L1a) with RuCl2(PPh3) under
Nonoptimized Conditions. Crystals of RuCl2(PPh3)3 (95 mg, 0.10
mmol) and Ph2PCH2pic (L1a, 29 mg, 0.10 mmol) were introduced
in a Schlenk flask equipped with a stirring bar, and dichloromethane
(15 mL) was added at room temperature. After stirring for 4 h, the
dichloromethane was removed under vacuum. The brown residue
was washed with n-hexane (2 × 10 mL) and dried under vacuum.
Recrystallization from a dichloromethane/hexane mixture afforded
1
41a-cis-Cl. NMR H (250 MHz, CD2Cl2, 25 °C): δ 8.15–6.91
(m, C6H5andMeC5H3N), 3.88 (dd, 1H, JHH ) 14 Hz, JHP ) 11 Hz,
CHH), 3.07 (dd, 1H, JHH ) 14 Hz, JHP ) 10 Hz, CHH), 2.14 (s,
3H, MeC5H3N). NMR 31P{1H} (101 MHz, CD2Cl2, 25 °C): δ 86.2
(d, JPP ) 37 Hz, Ph2P), 47.3 (d, JPP ) 37 Hz, PPh3). Anal. Calcd
for C37H33Cl2NP2Ru: C, 61.25; H, 4.58; N, 1.93. Anal. Calcd for
[C37H33Cl2NP2Ru + CH2Cl2] (X-ray analysis):41 C, 56.31; H, 4.35;
N, 1.73. Found: C, 57.61; H, 3.97; N, 1.53.
(41) Crystal data for 41a-cis-Cl · CH2Cl2: monoclinic, a ) 10.530(5) Å,
b ) 13.425(5) Å, c ) 25.056(5) Å, ꢀ ) 95.832(5)°, V ) 35242 Å-3, T )
180 K, space group P21/n, Z ) 4, µ(MoKR) ) 0.868 mm-1, 26 159
reflections measured, 6816 unique Rint ) 0.0458, which were used in all
calculations. The final wR(F2) was 0.0428 for all data.

Pyridine-Functionalized Phosphine Complexes of Ru(II)
Organometallics, Vol. 27, No. 6, 2008 1205
Synthesis of RuCl2(Cy2PCH2pic)(PPh3) (42a). Crystals of
RuCl2(PPh3)3 (239 mg, 0.25 mmol) and of the ligand Cy2PCH2pic
(L2a, 75 mg, 0.25 mmol) were introduced in a Schlenk flask and
dissolved in 20 mL of dichloromethane under a nitrogen atmo-
sphere. After 15 min, the solution was evaporated to dryness, and
the resulting green solid was washed twice with n-hexane (10 mL)
and dried in Vacuo (70 mg, 0.95 mmol, 95%). At this stage, NMR
data of the crude product revealed the occurrence of a mixture of
cis-Cl and trans-Cl isomers in a ca. 1/9 ratio. Rapid recrystallization
from a CH2Cl2/hexane mixture in the cold mixture gave pure 41a-
trans-Cl as a dark green crystalline material, some single crystals
being suitable for X-ray diffraction analyses. Alternatively, slow
recrystallization from a CH2Cl2/hexane mixture at room temperature
eventually gives pure 41a-cis-Cl as an orange crystalline material,
which was used for both the X-ray diffraction analysis and the
catalytic tests.
isomers. Slow recrystallization from a CH2Cl2/hexane mixture at
room temperature eventually gave pure 41a-cis-Cl as an orange
crystalline material, which was used for the catalytic runs.
42b-trans-Cl (from a 42b-cis-Cl/42b-trans-Cl mixture). NMR H
(250 MHz, CD2Cl2, 25 °C): δ 8.21–7.44 (m, 11H, C6H5 and
1
C9H6N), 3.83 (d, 2H, JHP ) 12 Hz, CH2), 2.17–1.04 (m, 22H,
C6H11). NMR 31P (101 MHz, CD2Cl2, 25 °C): δ 102.8 (d, JPP
32 Hz, PCy2), 46.5 (d, JPP ) 32 Hz, PPh3).
)
42b-cis-Cl. NMR NMR 1H (250 MHz, CD2Cl2, 25 °C): δ
8.19–7.04 (m, C6H5), 3.02 (dd, 1H, JHH ) 18 Hz, JHP ) 13 Hz,
CH2), 2.81 (m, 1H, CH2); 2.12–0.88 (m, 22H, C6H11). NMR 31P
(101 MHz, CD2Cl2, 25 °C): δ 106.9 (d, JPP ) 40 Hz, PCy2), 54.2
(d, JPP ) 40 Hz, PPh3). Anal. Calcd for C40H45Cl2NP2Ru: C, 62.09;
H, 5.86; N, 1.81. Anal. Calcd for [C40H45Cl2NP2Ru + CH2Cl2] (X-
ray analysis):42 C, 57.35; H, 5.52; N, 1.63. Found: C, 61.11; H,
5.36; N, 1.71.43.
42a-trans-Cl. NMR 1H (250 MHz, CD2Cl2, 25 °C): δ 7.83–7.02
(m, C6H5 and MeC5H3N), 3.61 (d, 2H, JHP ) 12 Hz, CH2), 2.58
(s, 3H, MeC5H3N), 2.12–1.05 (m, 22H, C6H11). NMR 31P (101
MHz, CD2Cl2, 25 °C): δ 99.9 (d, JPP ) 33.5 Hz, PCy2), 45.7 (d,
JPP ) 33.5 Hz, PPh3). Anal. Calcd for C37H45Cl2NP2Ru: C, 60.24;
H, 6.15; N, 1.90. Anal. Calcd for [C37H45Cl2NP2Ru + 0.75CH2Cl2]
(X-ray analysis): C, 58.54; H, 6.01; N, 1.83. Found: C, 57.52; H,
5.91; N, 1.73.
Synthesis of RuCl2(CCHPh)(Ph2PCH2pic)(PPh3) (51a) and
RuCl2(CCHPh)(Ph2PCH2quin)(PPh3) (51b). In a typical experi-
ment, the complex 41a (as a ca. 1:1 mixture of cis-Cl and trans-Cl
isomers, 108 mg, 0.15 mmol) was introduced in a Schlenk flask
and dissolved in 20 mL of degassed CH2Cl2. Phenylacetylene (0.33
mL, 3 mmol) was added, and the resulting mixture was stirred
overnight at room temperature. The solvent was then evaporated
to dryness and the resulting brown-orange solid was washed twice
with n-hexane (10 mL) and dried under vacuum. Recrystallization
1
42a-cis-Cl. NMR H (250 MHz, CD2Cl2, 25 °C): δ 7.81–7.15
from
a CH2Cl2/hexane mixture afforded RuCl2(CCHPh)-
(m, C6H5andMeC5H3N), 2.89 (dd, 1H, JHH ) 14 Hz, JHP ) 11 Hz,
CHH), 2.67 (m(br), 1H, CHH), 2.07 (s, 3H, MeC5H3N), 1.84–1.03
(m, 22H, C6H11). NMR 31P (101 MHz, CD2Cl2, 25 °C): δ 105.7
(d, JPP ) 40 Hz, PCy2), 53.7 (d, JPP ) 40 Hz, PPh3). Anal. Calcd
for C37H45Cl2NP2Ru: C, 60.24; H, 6.15; N, 1.90. Anal. Calcd for
[C37H45Cl2NP2Ru + 3CH2Cl2] (X-ray analysis): C, 48.41; H, 5.18;
N, 1.41. Found: C, 55.89; H, 5.46; N, 1.56.
(Ph2PCH2pic)(PPh3) (51a) as a brown microcrystalline material (90
mg, 0.11 mmol, 72% yield).
Complex RuCl2(CCHPh)(Ph2PCH2quin)(PPh3) (51b) was obtained
in 83% yield following a similar procedure starting from 41b (as a
ca. 1/9 mixture of cis-Cl and trans-Cl isomers, 115 mg, 0.15 mmol).
51a. NMR 1H (250 MHz, CDCl3, 25 °C): δ 7.78–6.56 (m, C6H5
and MeC5H3N), 5.33 (dd, 1H, JHH ) 17 Hz, JHP ) 10 Hz, CH2),
3.96 (dd, 1H, JHH ) 17 Hz, JHP ) 10 Hz, CH2), 3.32 (s, 3H,
MeC5H3N), 2.69 (t, JHP ) 4 Hz, dCHPh). NMR 13C (63 MHz,
CD2Cl2, 25 °C): δ 351.5 (dd, JCP ) 22 Hz, JCP ) 17 Hz, RudC),
145.5–118.6 (C6H5 and MeC5H3N), 111.9 (d, JCH ) 154 Hz,
dCHPh), 48.7 (dt, JCP ) 36 Hz, JCH ) 133 Hz, CH2), 28.8 (q, JCH
) 138 Hz, MeC5H3N). NMR 31P{1H} (101 MHz, CD2Cl2, 25 °C):
δ 42.9 (d, JPP ) 27 Hz, PPh2), 33.8 (d, JPP ) 27 Hz, PPh3). IR
(CH2Cl2): 1623 (νCdC). Anal. Calcd for C45H39Cl2NP2Ru: C, 65.30;
H, 4.75; N, 1.69. Found: C, 65.12; H, 4.65; N, 1.65.
Synthesis of RuCl2(Ph2PCH2quin)(PPh3) (41b). Crystals of
RuCl2(PPh3)3 (143 mg, 0.15 mmol.) were introduced in a Schlenk
flask and dissolved in 5 mL of dichloromethane at room temper-
ature. A solution of the ligand Ph2PCH2quin (L1b, 49 mg, 0.15
mmol) in 5 mL of degassed CH2Cl2 was prepared separately and
introduced slowly into the previous one over a period of 1 h, using
an automatic syringe. At the end of the addition, magnetic agitation
was maintained for about 30 min more. The solvent was then
removed under vacuum, and the resulting brown residue was
washed twice with 10 mL of n-hexane and dried under vacuum.
NMR data of the crude product revealed the occurrence of a mixture
of cis-Cl and trans-Cl isomers in a ca. 1/9 ratio. Slow recrystalli-
zation from a CH2Cl2 hexane mixture at room temperature gave
pure 41b-cis-Cl as an orange crystalline material (85 mg, 0.11 mmol,
74% yield). Such samples were subsequently used for the catalytic
runs.
51b. NMR 1H (250 MHz, CD2Cl2, 25 °C): δ 9.77–6.64 (m, C6H5
and C9H6N), 5.46 (dd, 1H, JHH ) 17 Hz, JHP ) 10 Hz, CH2), 4.33
(dd, 1H, JHH ) 17 Hz, JHP ) 13 Hz, CH2), 2.83 (t, JHP ) 4 Hz,
dCPhH). NMR 13C (63 MHz, CD2Cl2, 25 °C): δ 350.6 (dd, JCP
)
21 Hz, JCP ) 15 Hz, RudC), 154.5–119.6 (C6H5 and C9H6N), 112.0
(d, JCH ) 154 Hz, dCHPh), 49.9 (dt, JCP ) 38 Hz, JCH ) 134 Hz,
CH2). NMR 31P (101 MHz, CD2Cl2, 25 °C): δ 46.0 (d, JPP ) 29
Hz, PCy2), 40.7 (d, PPh3). IR (CH2Cl2): 1623 (νCdC). Anal. Calcd
for C48H39Cl2NP2Ru: C, 66.75; H, 4.55; N, 1.62. Found: C, 66.55;
H, 4.46; N, 1.60.
1
41b-trans-Cl (from a 41b-cis-Cl/41b-trans-Cl mixture). NMR H
(250 MHz, CD2Cl2, 25 °C): δ 9.25–6.46 (m, C6H5 and C9H6N),
4.57 (d, 2H, JPH ) 12 Hz, CH2). NMR 31P (101 MHz, CD2Cl2, 25
°C): δ 88.1 (d, JPP ) 37.0 Hz, PPh2), 49.6 (d, JPP ) 37.0 Hz, PPh3).
Synthesis of RuCl2(η3-EtO(O)CHdCHC(O)OEt)(Ph2PCH2pic)
(61a) and RuCl2(η3-EtO(O)CHdCHC(O)OEt)(Ph2PCH2quin) (61b).
In a typical experiment, complex 41a (as a ca. 1/9 mixture of cis-
Cl and trans-Cl isomers, 145 mg, 0.20 mmol) was introduced in a
Schlenk flask and dissolved in 20 mL of degassed CH2Cl2. The
solution was cooled to -60 °C, and an excess of ethyl diazoacetate
(0.210 mL, 2 mmol) was syringed into the flask. The solution was
then allowed to slowly warm to room temperature over a period of
1
41b-cis-Cl. NMR H (250 MHz, CD2Cl2, 25 °C): δ 9.25–6.46
(m, C6H5 and C9H6N), 4.10 (dd, 1H, JHH ) 19 Hz, JHP ) 13 Hz,
CH2), 3.36 (dd, 1H, JHH ) 19 Hz, JHP ) 12 Hz, CH2). NMR 31P
(101 MHz, CD2Cl2, 25 °C): δ 90.7 (d, JPP ) 44 Hz, PPh2), 51.8
(d, JPP ) 44 Hz, PPh3). Anal. Calcd for C40H33Cl2NP2Ru: C, 63.08;
H, 4.37; N, 1.84. Anal. Calcd for [C40H33Cl2NP2Ru + CH2Cl2]: C,
58.17; H, 4.17; N, 1.65. Found: C, 58.19; H, 3.96; N, 1.64.
RuCl2(Cy2PCH2quin)(PPh3) (42b-trans). Crystals of RuCl2-
(PPh3)3 (479 mg, 0.5 mmol) and of the ligand Cy2PCH2quin (L2b,
168 mg, 0.5 mmol) were introduced in a Schlenk flask and dissolved
in 20 mL of degassed dichloromethane. The resulting green solution
was stirred for 1 h and concentrated to dryness, giving a green
powder, which was washed twice with n-hexane (10 mL) and dried
in Vacuo (350 mg, 0.09 mmol, 90% yield). NMR analysis showed
the material to consist of a ca. 1/9 mixture of trans-Cl and cis-Cl
ca. 4 h, after which the solvent was removed under vacuum. A 31
P
NMR spectrum of the crude reaction mixture showed a singlet at
(42) Crystal data for 42b-cis-Cl · CH2Cl2: monoclinic, a ) 13.0145 Å, b
) 16.2875 Å, c ) 18.698(5) Å, ꢀ ) 95.832(5)°, V ) 39372 Å-3, T ) 180
K, space group P21/n, Z ) 4, µ(Mo KR) ) 0.782 mm-1, 40 155 reflections
measured, 12 968 unique (Rint ) 0.1666), which were used in all calcula-
tions. The final wR(F2) was 0.1671 for all data.

1206 Organometallics, Vol. 27, No. 6, 2008
Mothes et al.
65.6 ppm attributed to the newly formed complex 61a and two
relatively broad singlets at 18.6 and 20.18 ppm, which were
attributed to the phosphonium ylide Ph3PdCH-C(O)OEt by com-
parison with an authentic sample. The yellow solid residue was
then recrystallized from a dichloromethane/hexane mixture at room
temperature to afford RuCl2(η3-EtO(O)CHdCHC(O)OEt)(Ph2-
PCH2pic) (61a) as a yellow crystalline material (70 mg, 0.11 mmol,
56% yield).
in Fc. All non-hydrogen atoms were allowed to vibrate anisotro-
pically. All hydrogen atoms were introduced in idealized positions
(R3CH, C-H ) 0.96 Å; R2CH2, C-H ) 0.97 Å; RCH3, C-H )
0.98 Å; C(sp2)-H ) 0.93 Å; Uiso 1.2 or 1.5 time greater than the
Ueq of the carbon atom to which the hydrogen atom is attached)
and refined as “riding” atoms. After completing the initial structure
solution for 21a, it was found that 26% of the total cell volume was
filled with disordered solvent molecules, which could not be
modeled in terms of atomic sites. From this point on, residual peaks
were removed and the solvent region was refined as a diffuse
contribution without specific atom positions by using the PLA-
TON46 module SQUEEZE,47 which subtracts electron density from
the void regions by appropriately modifying the diffraction intensi-
ties of the overall structure. An electron count over the solvent
region provided an estimate for the number of solvent molecules
removed from the cell. The number of electrons thus located,
namely, 148 per unit cell, was assigned to 1.00 and 0.50 molecule
of dichloromethane on two different sites per molecule of 21a (148/4
) 37 electrons per molecule of 21a; 1.5 molecules of dichlo-
romethane would give 37.5 electrons) and were included in the
formula, formula weight, calculated density, absorption coefficient,
and F(000). Applying this procedure led to a dramatic improvement
in all refinement parameters and a minimization of residuals. The
SQUEEZE module was also used to treat disordered solvent
molecules in the structure of 41b-trans-Cl. In that case, 142 electrons
per unit cell were located and were assigned to 0.50 and 0.25
molecule of dichloromethane on two different sites per molecule
of 41b-trans-Cl (142/8 ) 17.75 electrons per molecule of 41b-trans-
Cl; 0.75 molecule of dichloromethane would give 18.75 electrons)
and were included in the formula, formula weight, calculated
density, absorption coefficient, and F(000).
ROMP Procedure. The reactions were carried out under inert
atmosphere. To the monomer solution (2.5 mmol) in 10 mL of
CH2Cl2 was added the precatalyst (0.01 equiv) and then the initiator
Me3SiCHN2 (0.05 equiv) by means of a syringe. The polymerization
was quenched after 1 h, and the polymer was precipitated by adding
40 mL of a solution of 2,6-di(tert-butyl)-4-methylphenol in
methanol. The resulting polymer was dried under vacuum, weighted,
and analyzed by size exclusion chromatography (Vide supra).
Catalytic Transfer Hydrogenation. The catalyst precusrsor
(0.01 mmol) was dissolved in 2-propanol (8 mL), and the solution
was heated under reflux. After 10 min, distilled ketone (10 mmol)
was added. After an additional 10 min, the transfer hydrogena-
tion was initiated by addition of sodium hydroxide (9.9 mg, 0.24
mmol) dissolved in 2 mL of 2-propanol. The progress of the reaction
was monitored by gas chromatographic analysis on periodic
sampling every 15 s.
Complex 61b was obtained in 43% yield following a similar
procedure starting from 41b (as a ca. 1/9 mixture of cis-Cl and trans-
Cl isomers, 78 mg, 0.10 mmol).
61a. NMR 1H (500.3 MHz, CDCl3, 25 °C): δ 7.89–7.20 (m, C6H5
and MeC5H3N), 4.735 (d, 1H, JHH ) 8.5 Hz, CHdCH), 4.529
(ABX3pattern, 2H, -OCH2CH3), 4.419 (ABX pattern, 2H, JHaHb
) 16.8 Hz, JHaP ) 10.3 Hz, JHbP) 13.4 Hz, PCH2), 3.921 (dd, 1H,
JHH ) 8.5 Hz, JHP ) 4.5 Hz, CHdCH), 3.635 (dq, 1H,
-OCHHCH3, JHH ) 10.9 Hz, JHH(Me) ) 7.2 Hz), 3.085 (dd, 1H,
-OCHHCH3, JHH ) 10.9 Hz, JHH ) 7.2 Hz), 2.63 (s, 3H,
MeC5H3N), 1.44 (t, JHH ) 7.2 Hz, -OCH2CH3), 0.85 (t, JHH ) 7.2
Hz, -OCH2CH3). NMR 13C (125.8 MHz, CDCl3, 25 °C): δ 176.61;
171.49 (CdO), 167.09–120.26 (C6H5 and MeC5H3N), 70.79 (d, JCH
) 177 Hz, HCdCH), 63.60 (t, JCH ) 142 Hz, CH2), 60.61 (d, JCH
) 162 Hz, HCdCH), 60.62 (t, JCH ) 147 Hz, CH2), 43.86 (dt, JCP
) 35 Hz, JCH ) 130 Hz, PCH2), 25.36 (q, JCH ) 130 Hz,
MeC5H3N), 13.89 (q, JCH ) 128 Hz, CH3), 13.47 (q, JCH ) 128
Hz, CH3). NMR 31P{1H} (202.6 MHz, CD2Cl2, 25 °C): δ 63.48
(s). Anal. Calcd for C27H30Cl2NO4PRu: C, 51.03; H, 4.76; N, 2.20.
Anal. Calcd for [C27H30Cl2NO4PRu + 0.33CH2Cl2] (X-ray analy-
sis): C, 49.46; H, 4.66; N, 2.11. Found: C, 49.61; H, 4.45; N, 2.06.
61b. NMR 1H (250 MHz, CDCl3, 25 °C): δ 8.58–7.15 (m, C6H5
and C9H6N), 4.74 (d, 1H, JHH ) 9 Hz, HCdCH), 4.58 (m, 2H,
PCH2), 4.53 (ABX3 pattern, 2H, JHaHb ) 11 Hz, JHaH(Me) ) JHbH(Me)
) 7 Hz, OCH2CH3), 3.89 (dd, 1H, JHH ) 9 Hz, JHP ) 4 Hz,
HCdCH), 2.62 (m, 2H, OCH2CH3), 1.40 (t, 3H, JHH ) 7 Hz,
OCH2CH3), 0.56 (t, 3H, JHH ) 7 Hz, OCH2CH3). NMR 13C (63
MHz, CDCl3, 25 °C): δ 176.9, 170.8 (CdO), 167.09–120.26 (C6H5
and C9H6N), 69.8 (d, JCH ) 178 Hz, HCdCH), 63.9 (t, JCH ) 142
Hz, CH2), 62.7 (JCH ) 160 Hz, HCdCH), 60.2 (JCH ) 148 Hz,
CH2), 45.9 (dt, JCP ) 33 Hz, JCH ) 131 Hz, PCH2), 14.0 (q, JCH
128 Hz, CH3), 13.3 (q, JCH ) 127 Hz, CH3). NMR 31P{1H} (101
MHz, CD2Cl2, 25 °C): 65.56 (s). Anal. Calcd for
)
δ
C30H30Cl2NO4PRu: C, 53.66; H, 4.50; N, 2.09. Found: C, 53.12;
H, 4.32; N, 1.98.
X-Ray Diffraction Studies. Crystals of 1, 21a, 31a, 42a-cis-Cl,
42a-trans-Cl, and 61a suitable for X-ray diffraction were obtained
by recrystallization of the relevant compounds from dichlo-
romethane/hexane solutions in the cold. Additional X-ray data for
compounds 41a-cis-Cl and 42b-cis-Cl are also available as Supporting
Information. Intensity data were collected at low temperature (see
Table 1 for exact temperature and specific conditions) on a Stoe
IPDS diffractometer (for 1, 31a, and 42a-trans-Cl) or an Oxford
Diffraction Xcalibur (21a, 42a-cis-Cl, and 61a) diffractometer. All
calculations were performed on a PC-compatible computer using
the WinGX system.43 Full crystallographic data are given in Table
1. The structures were solved by using the SIR92 program,44 which
revealed in each instance the position of most non-hydrogen atoms.
All remaining non-hydrogen atoms were located by the usual
combination of full matrix least-squares refinement and difference
electron density syntheses by using the SHELXL97 program.45
Atomic scattering factors were taken from the usual tabulations.
Anomalous dispersion terms for Ru, P, and Cl atoms were included
Acknowledgment. This research was supported by the
CNRS and a European Community Marie Curie Action
(contract no. HMPT-CT-2001-00398). We thank the Min-
istère de l’Education Nationale for a fellowship to S.S., and
Johnson Matthey for a generous gift of RuCl3 · nH2O. CIF
files giving crystallographic data and including a full list of
interatomic bond lengths and angles for compounds 1-4 and
5. Additional X-ray data for compounds 41a-cis-Cl and 42b-
cis-Cl. This material is available free of charge via the
Internet at http://pubs.acs.org.
Supporting Information Available: This material is available
free of charge via the Internet at http://pubs.acs.org.
OM7012106
(43) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(44) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343.
(45) Sheldrick, G. M. SHELX97 [Includes SHELXS97, SHELXL97,
CIFTAB], Programs for Crystal Structure Analysis (Release 97-2); Institüt
für Anorganische Chemie der Universität Göttingen: Germany, 1998.
(46) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University: Utrecht, The Netherlands, 1998.
(47) Sluis, P. V. D.; Spek, A. L. Acta Crystallogr., Sect. A 1990, 46,
194.