Reactivity of the bis(dihydrogen) complex [RuH2(η2-H2)2 (PCy3)2] toward N-heteroaromatic compounds. Regioselective hydrogenation of acridine to 1,2,3,4,5,6,7,8-octahydroacridine

Article abstract of DOI:10.1021/om020995p

The reaction of pyridine (Py), pyrrole (Pyr), or acridine with the bis(dihydrogen) complex [RuH₂(η²-H₂)₂ (PCy₃)₂] (1) produces compounds containing heteroaromatic ([RuH₂(η²-H₂)(η¹-(N)- C₅H₅N)(PCy₃)₂] (2), [RuH(η⁵-C₄H₄N) (PCy₃)₂]·Pyr (3)) or aromatic rings ([RuH₂(η⁴-C₁₃H₉N) (PCy₃)₂] (5)) coordinated in η¹(N) (2), η⁵(N,C) (3), or η⁴(C,C) (5) modes for Py, Pyr, and acridine, respectively. Complex 3 has been characterized by X-ray crystallography. Its protonation by HBF₄ affords the cationic dihydride complex [RuH₂(η⁵-C₄H₄N) (PCy₃)₂] [BF₄] (4). The coordinated Py ligand in 2 and acridine in 5 can readily be displaced by dihydrogen, with regeneration of 1. Regioselective hydrogenation of representative polynuclear heteroaromatic nitrogen compounds is achieved in the presence of 1 under mild reaction conditions (80°C, 3 bar of H₂). Quinoline (Q) and isoquinoline (iQ) are hydrogenated to 5,6,7,8-tetrahydro derivatives, while acridine is quickly reduced to 1,2,3,4-tetrahydroacridine followed by much slower saturation to 1,2,3,4,5,6,7,8-octahydroacridine (8H-Acr), the nitrogen-containing aromatic ring remaining intact. 8H-Acr has been isolated in analytically pure form and characterized by ¹H and ¹³C NMR as well as by X-ray crystallography. 5 is also active for catalytic acridine hydrogenation and can be regarded as an intermediate in the catalytic cycle. Saturation of a five-membered indole ring proceeds much slower than hydrogenation of six-membered aromatic rings in Q and iQ. Pyridine, pyrrole, and 7,8-benzoquinoline are not hydrogenated under the applied reaction conditions, as a result of the formation of new stable complexes.

Full text of DOI:10.1021/om020995p

1630
Organometallics 2003, 22, 1630-1637
Rea ctivity of th e Bis(d ih yd r ogen ) Com p lex
[Ru H2(η2-H2)2(P Cy3)2] tow a r d N-Heter oa r om a tic
Com p ou n d s. Regioselective Hyd r ogen a tion of Acr id in e
to 1,2,3,4,5,6,7,8-Octa h yd r oa cr id in e
Andrzej F. Borowski,*,†,‡ Sylviane Sabo-Etienne,*,‡,§ Bruno Donnadieu,‡ and
Bruno Chaudret‡
Institute of Coal Chemistry, Polish Academy of Sciences, 5, Sowinskiego Street,
44-121 Gliwice, Poland, and Laboratoire de Chimie de Coordination du CNRS,
Universite´ Paul Sabatier, 205 Route de Narbonne, 31 077 Toulouse Cedex 04, France
Received December 10, 2002
The reaction of pyridine (Py), pyrrole (Pyr), or acridine with the bis(dihydrogen) complex
[RuH2(η2-H2)2(PCy3)2] (1) produces compounds containing heteroaromatic ([RuH2(η2-H2)(η1-
(N)-C5H5N)(PCy3)2] (2), [RuH(η5-C4H4N)(PCy3)2]‚Pyr (3)) or aromatic rings ([RuH2(η4-C13H9N)-
(PCy3)2] (5)) coordinated in η1(N) (2), η5(N,C) (3), or η4(C,C) (5) modes for Py, Pyr, and acridine,
respectively. Complex 3 has been characterized by X-ray crystallography. Its protonation
by HBF4 affords the cationic dihydride complex [RuH2(η5-C4H4N)(PCy3)2][BF4] (4). The
coordinated Py ligand in 2 and acridine in 5 can readily be displaced by dihydrogen, with
regeneration of 1. Regioselective hydrogenation of representative polynuclear heteroaromatic
nitrogen compounds is achieved in the presence of 1 under mild reaction conditions (80 °C,
3 bar of H2). Quinoline (Q) and isoquinoline (iQ) are hydrogenated to 5,6,7,8-tetrahydro
derivatives, while acridine is quickly reduced to 1,2,3,4-tetrahydroacridine followed by much
slower saturation to 1,2,3,4,5,6,7,8-octahydroacridine (8H-Acr), the nitrogen-containing
aromatic ring remaining intact. 8H-Acr has been isolated in analytically pure form and
1
characterized by H and 13C NMR as well as by X-ray crystallography. 5 is also active for
catalytic acridine hydrogenation and can be regarded as an intermediate in the catalytic
cycle. Saturation of a five-membered indole ring proceeds much slower than hydrogenation
of six-membered aromatic rings in Q and iQ. Pyridine, pyrrole, and 7,8-benzoquinoline are
not hydrogenated under the applied reaction conditions, as a result of the formation of new
stable complexes.
In tr od u ction
thus, they are more likely to interact through their
π-electron system.3 Many HDN catalytic studies indi-
cate that nitrogen removal from N-heteroaromatic
compounds requires saturation of the N-aromatic ring,
before rapid hydrogenolysis of the C-N bond occurs (at
least with the typically used Ni-Mo/Al2O3 catalysts).
In this respect, selective hydrogenation of the N-
aromatic ring of a polynuclear compound is a critical
step that needs to be controlled.1,4,5 Reports on C-N
bond scission in heteroaromatic rings with formation
of heterometallacycles are quite numerous, and hydro-
genolysis of C-N bonds has also been described.2,6-8
Catalytic hydrodenitrogenation (HDN) of petroleum-
and coal-based feedstocks is one of the most important
industrial processes. The ultimate purpose of HDN is
the removal of nitrogen as NH3 by the use of dihydro-
gen.1 Non-heterocyclic nitrogen compounds such as
aliphatic amines and anilines or nitriles undergo HDN
quite rapidly under “normal” HDN catalysis. In con-
trast, heterocyclic compounds (six-membered pyridine
and five-membered pyrrole rings) are much more dif-
ficult to process.2 The nitrogen heterocyclic compounds
can be classified in two families. The bases, as for
example pyridine, quinoline, and acridine, contain a lone
pair on the nitrogen atom, and hence, the compounds
are easy to protonate or can interact with acidic sites.
The second type refers to substrates such as pyrrole,
indole, and carbazole, in which the unshared pair of
electrons on the nitrogen atom is needed for aromaticity;
(3) March, J . Advanced Organic Chemistry: Mechanisms and
Structure, 4th ed.; Wiley: New York, 1992.
(4) Baralt, E.; Smith, S. J .; Hurwitz, J .; Horva´th, I. T.; Fish, R. H.
J . Am. Chem. Soc. 1992, 114, 5187.
(5) (a) Topsøe, H.; Clausen, B. S.; Massoth, F. E. Hydrotreating
Catalysis. In Catalysis: Science and Technology; Anderson, J . R.,
Boudart, M., Eds.; Springer-Verlag: Berlin, Heidelberg, 1996; Vol. 11.
(b) Satterfield, C. N. Heterogeneous Catalysis in Industrial Practice;
McGraw-Hill: New York, 1991; p 378.
(6) Angelici, R. J . Polyhedron 1997, 16, 3037 and references therein.
(7) Kvietok, F.; Allured, V.; Carperos, V.; Rakowski DuBois, M.
Organometallics 1994, 13, 60.
(8) (a) Vicic, D. A.; J ones, W. D. Organometallics 1999, 18, 134. (b)
Morikita, T.; Hirano, M.; Sasaki, A.; Komiya, S. Inorg. Chim. Acta
1999, 291, 341. (c) Werner, H.; Hoerlin, G.; J ones, W. D. J . Organomet.
Chem. 1998, 562, 45.
† Polish Academy of Sciences.
‡ Universite´ Paul Sabatier.
§ E-mail: sabo@lcc-toulouse.fr.
(1) Girgis, M. J .; Gates, B. C. Ind. Eng. Chem. Res. 1991, 30, 2021.
(2) Weller, K. J .; Fox, P. A.; Gray, S. D.; Wigley, D. E. Polyhedron
1997, 16, 3139 and references therein.
10.1021/om020995p CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/15/2003

1,2,3,4,5,6,7,8-Octahydroacridine
Organometallics, Vol. 22, No. 8, 2003 1631
Sch em e 1. Rea ctivity of [Ru H2(η2-H2)2(P Cy3)2]
The complex chemical composition of petroleum has
led to the examination of model compounds that re-
semble the nitrogen contaminants in petroleum distil-
lates and other feedstocks.2,6,9 There are thus numerous
reports on the reactivity of N-heteroaromatic compounds
with metal complexes, leading to the coordination of the
heteroaromatic ligand to the metal center.7,10 Several
homogeneous systems based on transition-metal com-
plexes are active in hydrogenation reactions of poly-
nuclear heteroaromatics.2,4,6 In the specific case of
dihydrogen complexes, which are known to be active
homogeneous reduction catalysts,11 no relevant report
involving polynuclear heteroaromatics has been found.
We have recently shown that the bis(dihydrogen)
complex [RuH2(η2-H2)2(PCy3)2] (1)12 can be an active
catalyst precursor for arene hydrogenation under mild
conditions.13 We now describe the syntheses and prop-
erties of new ruthenium complexes resulting from the
reactivity of 1 with some selected nitrogen heteroaro-
matics. We report an evaluation of the catalytic activity
of 1 for hydrogenation of the selected substrates and
show that the results are highly dependent on the
capacity of the aromatic compounds to adopt different
bonding modes.
tow a r d P yr id in e, P yr r ole, a n d Acr id in e
Resu lts a n d Discu ssion
transformed into a quintet upon selective decoupling of
PCy3 protons, thus suggesting the presence of four
hydrogens around the metal. The presence of a coordi-
Rea ction of 1 w ith P yr id in e. Treating a pentane
suspension of 1 with excess pyridine results in a color
change of the reaction mixture with concomitant gas
evolution. After workup, we obtained a yellow solid that
was characterized by NMR. The data indicate the
presence of unreacted starting bis(dihydrogen) complex
1 (ca. 10%) and formation of a new compound formu-
lated as the dihydrogen pyridine complex [RuH2(η2-H2)-
(η1(N)-C5H5N)(PCy3)2] (2) (Scheme 1). Any efforts to
isolate 2 in a pure form have failed. Complex 2 is
characterized by three broad resonances in the 1H NMR
spectrum at δ 9.11, 6.77, and 6.35 and a triplet at δ
-9.47 (J P-H ) 13.5 Hz), integrated in the ratio 2:1:2:4.
The low-field resonances are assigned to the protons of
one pyridine ligand coordinated to the metal through
the lone pair of the nitrogen atom. Integration of the
hydride signal is in favor of the presence of four
hydrogen atoms around the coordination sphere of the
metal. This is confirmed by the observation of a singlet
at δ 71.9 in the 31P{1H} NMR spectrum, which is
min
nated dihydrogen molecule is supported by the T1
value of 55 ms at 253 K (C7D8, 400 MHz). The observa-
tion of an H/D exchange between the solvent (C6D6,
C7D8) and the hydrides is also in agreement with a
dihydride dihydrogen formulation. Unfortunately, no
decoalescence of the hydride/dihydrogen signal could be
measured down to 183 K, as observed recently for the
structurally similar complex [RuH2(η2-H2)(PCy3)2(2-
phenyl-3,4-dimethylphosphaferrocene)], but with the
phosphaferrocene ligand being a better π-acceptor.14
2
is fairly stable in C6D6 or C7D8 solution, and no signs of
decomposition have been observed after 24 h. H/D
1
exchange was evidenced by H NMR (the triplet at δ
-9.47 changed into a broad signal disappearing after a
few hours) with no change in the 31P NMR spectrum.
Decoordination of pyridine from 2 was readily achieved
by bubbling dihydrogen (5 min, room temperature)
through a C6D6 solution containing the yellow product.
This resulted in total conversion into 1 and pyridine
characterized by three new multiplets at δ 8.66, 7.08,
and 6.77. Hydrogenation of pyridine was thus not
observed, as evidenced by the absence of resonances
corresponding to piperidine protons. The same result
was obtained when testing pyridine hydrogenation in
the presence of 1 under 3 bar of H2 at 80 °C, with no
conversion after 24 h. Indeed, examples of homogeneous
catalytic hydrogenation of pyridine derivatives are
rare.15
(9) Chisholm, M. H. Polyhedron 1997, 16, 3071.
(10) (a) McComas, C. C.; Ziller, J . W.; Van Vranken, D. L. Organo-
metallics 2000, 19, 2853. (b) Schulte, J . L.; Laschat, S.; Kotila, S.;
Hecht, J .; Fro¨hlich, R.; Wibbeling, B. Heterocycles 1996, 43, 2713. (c)
J oachim, J . E.; Apostolidis, C.; Kanellakopulos, B.; Meyer, D.; Raptis,
K.; Rebizant, J .; Ziegler, M. L. J . Organomet. Chem. 1994, 476, 77. (d)
Laschat, S.; Noe, R.; Riedel, M.; Kru¨ger, C. Organometallics 1993, 12,
3738. (e) Myers, W. H.; Koontz, J . I.; Harman, W. D. J . Am. Chem.
Soc. 1992, 114, 5684. (f) Myers, W. H.; Sabat, M.; Harman, W. D. J .
Am. Chem. Soc. 1991, 113, 6682. (g) Glueck, D. S.; Hollander, F. J .;
Bergman, R. G. J . Am. Chem. Soc. 1991, 113, 6682. (h) Cordone, R.;
Harman, W. D.; Taube, H. J . Am. Chem. Soc. 1991, 113, 5969. (i)
Chaudret, B.; J alon, F.; Perez-Manrique, M.; Lahoz, F. J .; Plou, F. J .;
Sanchez-Delgado, R. New J . Chem. 1990, 14, 331. (j) Kershner, D. L.;
Rheingold, A. L.; Basolo, F. Organometallics 1987, 6, 196. (k) Pysh-
nograeva, N. I.; Setkina, V. N.; Adrianow, V. G.; Struchov, Yu. T.;
Kursanov, D. N. J . Organomet. Chem. 1980, 186, 331.
Hyd r ogen a tion of Qu in olin e (Q), Isoqu in olin e
(iQ), a n d In d ole (In ). We were more successful when
(11) Esteruelas, M. A.; Oro, L. A. Chem. Rev. 1998, 98, 577.
(12) (a) Sabo-Etienne, S.; Chaudret, B. Coord. Chem. Rev. 1998,
170-180, 381. (b) Borowski, A. F.; Donnadieu, B.; Daran. J .-C.; Sabo-
Etienne, S.; Chaudret, B. Chem. Commun. 2000, 543, 1697.
(13) Borowski, A. F.; Sabo-Etienne, S.; Chaudret, B. J . Mol. Catal.
A: Chem. 2001, 174, 69.
(14) Toner, A. J .; Donnadieu, B.; Sabo-Etienne, S.; Chaudret, B.;
Sava, X.; Mathey, F.; Le Floch, P. Inorg. Chem. 2001, 40, 3034.
(15) (a) Fish, R. H.; Baralt, E.; Smith, S. J . Organometallics 1991,
10, 54. (b) Borowski, A. F.; Cole-Hamilton, D. J . Polyhedron 1993, 12,
1757. (c) Studer, M.; Wedemayer-Exl, C.; Spindler, F.; Baser, H. U.
Monatsh. Chem. 2000, 131, 1335.

1632 Organometallics, Vol. 22, No. 8, 2003
Borowski et al.
Ta ble 1. Hyd r ogen a tion of N-Heter oa r om a tics
Sch em e 2. Hyd r ogen a tion of N-Ar om a tic
Com p ou n d s Ca ta lyzed by [Ru H2(η2-H2)2(P Cy3)2]
Ca ta lyzed by [Ru H2(η2-H2)2(P Cy3)2] (1) a t 80 °C
a
u n d er 3 ba r of H2
substrate
pyridine
conversn (%) productsb (amt (%)) TONc
0
none
0
quinoline
100.0
5,6,7,8-THQ (99)
1,2,3,4-THQ (1)
5,6,7,8-THiQ (100)
none
indoline (100)
none
4H-Acr (4.5)
8H-Acr (95.5)
4H-Acr (12.5)
8H-Acr (87.5)
49.5
0.5
44.2
0
isoquinoline
7,8-benzoquinoline
indole
pyrrole
acridine
88.5
0
24.6
0
12.3
0
100.0
50.0d
47.2d
50.0d
43.8d
acridinee
100.0
a
Unless stated otherwise, 1 is the catalyst precursor. Condi-
tions: solvent, cyclohexane (10 mL); [Ru] ) 3 × 10-3 M; [substrate]
) 0.15 M; substrate/Ru ) 50; 80 °C; 3 bar of H2; 24 h. The products
b
were analyzed by GC. Products: THQ ) tetrahydroquinoline;
THiQ ) tetrahydroisoquinoline; 4H-Acr ) 1,2,3,4-tetrahydroacri-
dine; 8H-Acr ) 1,2,3,4,5,6,7,8-octahydroacridine. c TON is defined
d
as mole of product formed per mole of Ru. Calculations based
on the assumption that 8H-Acr is formed in a two-stage reaction.
It involves hydrogenation of acridine to 4H-Acr (stage 1) followed
by its hydrogenation to 8H-Acr (stage 2). e [RuH2(η4-C13H9N)(PCy3)2]
(5) was used as a catalyst precursor. The reaction time was 18 h.
the higher basicity of the nitrogen atom in iQ compared
to that in Q, which could have an influence on the
stabilization of the postulated intermediate involving
an η1(N) coordination of the substrate. In our system,
virtually the same catalytic activity is observed toward
both isomers, and we have found that hydrogenation
leads, almost exclusively, to saturated arene rings. A
possible explanation for this difference could be the
coordination of the substrate through the aromatic ring
in a way similar to that reported for η4-arene com-
plexes.19 It is noteworthy that we have previously
demonstrated that the η4-arene complex [RuH2(η4-
C14H10)(PCy3)2] is involved in the catalytic hydrogena-
tion of anthracene.13 We cannot, however, exclude an
η1(N) coordination mode of the substrate and subse-
quent rearrangement to form a π-arene, as reported for
some Cp ruthenium complexes.20,10i
To get some information on the binding mode of the
substrate during the catalytic reaction, we have per-
formed a stoichiometric study of the reaction of 1 with
Q. We could not isolate any pure complex, but NMR
data of a C6D6 mixture of 1 with Q support the
formation of a new species tentatively formulated as
[RuH2(η4-C9H7N)(PCy3)2]. The η4(C,C)-coordinated quin-
oline ligand is characterized by four signals at δ 5.99
(br), 5.63 (br), 4.44 (d, 5.6 Hz), and 3.83 (d, 5.6 Hz), very
similar in shape and very close to the positions of the
four proton signals assigned to the arene protons of the
acridine ligand, coordinated in an η4(C,C) mode in
[RuH2(η4-C13H9N)(PCy3)2] (5) (see below and Experi-
mental Section). Moreover, the hydride resonance of the
new species at δ -11.58 (t, J P-H ) 28 Hz) and the
phosphorus resonance at δ 70.1 are very close to the
corresponding resonances in 5. In addition, we have
testing hydrogenation of quinoline (Q) and isoquinoline
(iQ). We have used 1 as a catalyst precursor under
standard conditions (3 bar of H2, 80 °C) (Scheme 2,
Table 1). In both cases, reductions are efficient and
regioselective, leading to 5,6,7,8-tetrahydro derivatives.
Slightly higher conversion has been obtained for Q (99%)
as compared to iQ (88.5%) after a 24 h process. It is
remarkable that, in our system, saturation of the
aromatic ring is observed, in contrast to the results
reported using [Cp*RhL]2+ (L ) (NCMe)3, p-xylene),15a,16
[RuH(CO)(NCMe)2(PPh3)2]+,17 or [Rh(COD)(PPh3)2]+ 18
as catalyst precursor, respectively. In the first two cases,
considerable difference in activity (ca. 30 times) for Q
and iQ reduction was observed. This was explained by
(16) Fish, R. H.; Kim, H. S.; Babin, J . E.; Adams, R. D. Organome-
tallics 1988, 7, 2250.
(17) (a) Rosales, M.; Navarro, J .; Sa´nchez, L.; Gonza´lez, A.; Alvorado,
Y.; Rubio, R.; De La Cruz, C.; Ramajkina, T. Transition Met. Chem.
1996, 21, 11. (b) Rosales, M.; Alvorado, Y.; Boves, M.; Rubio, R.; Soscu´n,
H. Transition Met. Chem. 1995, 20, 246.
(19) (a) Albright, J . O.; Datta, S.; Dezube, B.; Kouba, J . K.; Marynick,
D. S.; Wreford, S. S.; Foxman, B. M. J . Am. Chem. Soc. 1979, 101,
611. (b) Leong, V. S.; Cooper, N. J . Organometallics 1988, 7, 2058. (c)
Thompson, R. L.; Lee, S.; Rheingold, A. L.; Cooper, N. J . Organoma-
tallics 1991, 10, 1657. (d) Bennett, M. A.; Lu, Z.; Wang, X.; Brown,
M.; Hockless, D. C. R. J . Am. Chem. Soc. 1998, 120, 10409.
(20) Fish, R. H.; Kim, H. S.; Fong, R. H. Organometallics 1991, 10,
770.
(18) Sanchez-Delgado, R. A.; Rondon, D.; Andriollo, A.; Herrera, V.;
Martin, G.; Chaudret, B. Organometallics 1993, 12, 4291.

1,2,3,4,5,6,7,8-Octahydroacridine
Organometallics, Vol. 22, No. 8, 2003 1633
detected the concomitant formation of 5,6,7,8-tetrahy-
droquinoline (5,6,7,8-THQ), characterized by two triplets
at δ 3.00 and 2.37 (J H-H ) 6.9 Hz). We have excluded
the presence of 1,2,3,4-tetrahydroquinoline (1,2,3,4-
THQ) on the basis of the lack of the expected broad
resonance of the N-H proton at δ ca. 4-3.5 ppm. The
GC/MS spectra of the Q hydrogenation products, of both
the catalytic and stoichiometric mixtures, confirm that
the 5,6,7,8-tetrahydro derivative is obtained as the main
reaction product.
We have recently reported the hydrogenation of
naphthalene to tetralin (and not to decalin) in the
presence of 1 under the same conditions.13 The reaction
proceeds at a rate ca. one-third of that found for Q and
iQ reduction studied in this work. In this respect, more
facile hydrogenation of the aromatic rings in Q and iQ
as compared with that of naphthalene seems to be
connected to the presence of the nitrogen atom in the
adjacent heteroaromatic ring and the tendency of these
substrates to coordinate in an η4(C,C) rather than an
η1(N) fashion. In contrast, easier hydrogenation of
N-heteroaromatic rings in Q and iQ to form 1,2,3,4-
tetrahydro derivatives has been explained by the lower
stabilization energy of the heteroaromatic ring, as
shown by ab initio SCF-MO calculations reported by
Rosales et al.17b
slower than hydrogenation of the aromatic rings of Q
and iQ. By comparison, Rosales et al. reported a similar
activity for indole and iQ hydrogenation, but lower than
that for Q (see above),17 whereas virtually identical
hydrogenation activities for these three substrates were
reported for other Rh and Ir cationic complexes (50 °C,
5 bar of H2).23 In these latter systems, the authors
proposed that the formation of metallic rhodium and
iridium powders was responsible for the activity.
Rea ction of 1 w ith P yr r ole. Syn th esis of [Ru H-
(η5-C4H4N)(P Cy3)2]‚P yr (3). Pyrrole has a much lower
degree of aromaticity than benzene and thiophene
(resonance energies for these three compounds are
respectively 88, 152, and 121 kJ /mol).3 Despite this
property, we could not reduce pyrrole under our stan-
dard conditions, using 1 as a hydrogenation catalyst
precursor. However, the change of color from beige to
yellow upon addition of pyrrole to the solution contain-
ing 1 suggested that some reaction had occurred.
Indeed, stirring a suspension of 1 in pentane with an
excess of pyrrole leads after workup to the isolation of
yellow crystals. The new complex [RuH(η5-C4H4N)-
(PCy3)2]‚Pyr (3) was characterized by NMR and X-ray
data as a hydride complex with a pyrrolyl coordinated
to the ruthenium via an η5 mode (Scheme 1). The 31P-
{1H} NMR spectrum (C6D6, 293 K) shows a single
resonance at δ 66.5. The 1H NMR spectrum of 3 displays
two singlets of equal intensity for the pyrrolyl ligand
at δ 6.05 (H2,5) and 5.14 (H3,4) and a high-field hydride
triplet at δ -15.86 (J P-H ) 36.8 Hz) in a good integra-
tion ratio (2:2:1). Moreover, three other resonances
observed at δ 6.52 (H2,5), 6.38 (H3,4), and 8.02 (N-H1),
also in a 2:2:1 ratio, are assigned to the protons of one
solvate pyrrole molecule. This was confirmed by mi-
croanalysis and X-ray data. In 3, the pyrrolyl protons
are shifted to high field as a consequence of η5 coordina-
tion to ruthenium. Further support is given by the 13C
NMR spectrum (C6D6), showing for 3 two signals at δ
105.7 and 78.0 for the C2,5 and C3,4 carbons of the η5-
coordinated pyrrolyl ligand, whereas the carbons for the
free pyrrole resonate at δ 117.7 (C2,5) and 108.5 (C3,4).
The structure determined in solution for 3 was found
to be the same in the solid state, as confirmed by an
X-ray determination (Table 2). The molecular structure
of 3, depicted in Figure 1, exhibits a three-legged piano-
stool geometry. The central ruthenium atom is bound
to one hydride atom, a pyrrolyl ligand, and two tricy-
clohexylphosphines with a P-Ru-P angle of 106.87(3)°.
The pyrrolyl ligand is essentially planar with almost
identical C-C ring bonds of 1.398 Å (average) and
slightly shorter C-N ring bonds of 1.378 Å (average).
The distances between the ruthenium and each ring
atom of the pyrrolyl ligand indicate a slight shift of the
ring centroid, with shorter metal distances to C1 and
C4 atoms (2.235(3) Å, average) than to C2 and C3
(2.243(3) Å, average) and the N atom (2.335(2) Å).
Similar shifts have been noted in structural studies on
other pyrrolyl complexes of Mn and Ru.7,10a,j
In the case of 7,8-benzoquinoline (7,8-BQ), we did not
get any evidence of hydrogenation under our standard
conditions in the presence of 1 as catalyst precursor. It
is noteworthy that phenanthrene, the hydrocarbon
analogue of 7,8-BQ, was also found to be totally resis-
tant to hydrogenation under analogous conditions
(Scheme 2).13 In contrast, the homogeneous hydrogena-
tion of 7,8-BQ to the 1,2,3,4-tetrahydro derivative was
reported by Fish et al. with the catalyst precursor they
used for Q and iQ hydrogenation (see above).15a In our
case, the lack of reduction of 7,8-BQ might be explained
by the stability of a new organometallic complex result-
ing from the reaction of 7,8-BQ with 1. Indeed, in the
course of our studies on C-H activation, we have
previously reported the synthesis of [RuH(η2-H2)L-
i
(PR3)2] (R ) Pr, Cy), containing an ortho-metalated
ligand L such as phenylpyridine or functionalized
aromatic ketones.21 In this latter case, we have dem-
onstrated that these compounds are efficient catalysts
for ethylene insertion into functional arenes at room
temperature. More recently, we have isolated a similar
complex, [RuH(η2-H2)(NC13H8)(PiPr3)2], by addition of
7,8-BQ to the analogous complex of 1, but with triiso-
propylphosphine.22 The benzoquinolyl ligand is coordi-
nated to the ruthenium via the nitrogen atom and an
ortho carbon bond of the external aromatic ring. This
ortho-metalated complex proved to be very stable under
dihydrogen pressure.
Using indole as a substrate, hydrogenation to indoline
is selectively carried out (Scheme 2, Table 1). However,
hydrogenation of the five-membered heteroaromatic
ring occurs at a very slow rate of 0.5 TON/h, ca. 4 times
It is worth noting that bubbling dihydrogen (15 min,
20 °C) through a C6D6 solution of 3 did not cause any
(21) (a) Guari, Y.; Sabo-Etienne, S.; Chaudret, B. J . Am. Chem. Soc.
1998, 120, 4228. (b) Toner, A. J .; Grundemann, S.; Clot, E.; Limbach,
H.-H.; Donnadieu, B.; Sabo-Etienne, S.; Chaudret, B. J . Am. Chem.
Soc. 2000, 122, 6777.
(22) Grundemann, S.; Toner, A.; Matthes, J .; Guari, Y.; Donnadieu,
B.; Sabo-Etienne, S.; Clot, E.; Limbach, H.-H.; Chaudret, B. To be
submitted for publication.
1
change in the H and 31P NMR spectra. Moreover, the
stability of the pyrrolyl η5-coordinated to the ruthenium
is illustrated by the protonation reaction. Addition at
(23) Chin, C. S.; Park, Y.; Lee, B. Catal. Lett. 1995, 31, 239.

1634 Organometallics, Vol. 22, No. 8, 2003
Borowski et al.
Ta ble 2. Cr ysta l Da ta for
[Ru H(η5-C4H4N)(P Cy3)2]‚P yr (3) a n d
1,2,3,4,5,6,7,8-Octa h yd r oa cr id in e (8H-Acr )
3
8H-Acr
C13H17
187.28
chem formula
fw
C
44H76N2P2Ru
N
796.08
cryst syst, space group
triclinic, P1h
monoclinic, P21/n
2; 1.193
0.069
Z; calcd density, Mg/m3 2; 1.255
abs coeff, mm-1
F(000)
0.480
856
204
a, Å
b, Å
c, Å
10.7406(16)
14.063(2)
15.132(3)
73.759(19)
85.968(19)
73.722(18)
2106.3(6)
160(2)
9.252(2)
6.4870(10)
9.726(2)
R, deg
â, deg
116.71(3)
γ, deg
V, Å3
521.44(18)
180(2)
temp, K
no. of data/restraints/
params
6089/0/450
978/0/69
F igu r e 1. Molecular structure of [RuH(η5-C4H4N)(PCy3)2]-
(3). Selected bond lengths (Å) and angles (deg): Ru-H1,
1.56(3); Ru-C1, 2.233(3); Ru-C2, 2.242(3); Ru-C3, 2.244-
(3); Ru-C4, 2.237(3); Ru-P1, 2.3096(8); Ru-P2, 2.3203-
(7); C1-N1, 1.379(4); C2-C3, 1.404(4); C3-C4, 1.397(4);
C4-N1, 1.376(4); P1-Ru-P2, 106.87(3); P1-Ru-H1, 77.3-
(11); P2-Ru-H1, 81.5(11).
goodness of fit on F2
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
R1 (all data)
wR2 (all data)
largest diff peak and
hole, e Å-3
1.073
1.062
0.0299
0.0666
0.0379
0.0697
0.0462
0.1202
0.0562
0.1274
0.674 and -0.454 0.157 and -0.217
-50 °C of 1 equiv of HBF4 to an acetone solution of 3
1
The pattern of the H NMR spectrum of 5 resembles
yields after workup a new product analyzed as [RuH2-
that of the complex [RuH2(η4-C14H10)(PCy3)2] (C14H10
)
1
(η5-C4H4N)(PCy3)2][BF4] (4) (Scheme 1). The H NMR
anthracene), coordinating anthracene in an η4 mode.13
Similar 31P chemical shifts are obtained for these two
complexes (δ 70.5 for 5 vs 67.9 ppm for the anthracene
complex) as well as similar hydride resonances (a triplet
at δ -11.2 with J P-H ) 28 Hz) and IR spectra (ν(Ru-
H) 2015 and 1987 cm-1 for 5 vs 2013 and 1975 cm-1 for
the anthracene complex). All these data are in agree-
ment with an η4 coordination mode of one arene ring of
acridine, thus allowing the complex to reach an 18-
valence-electron configuration. It is worth mentioning
that the number of transition-metal complexes coordi-
nating acridine is scarce, and most of them contain
N-bound heterocycles or η6-arene coordination.25,10i
Hyd r ogen a tion of Acr id in e. Total conversion of
acridine was accomplished using 1 as catalyst precursor
under our standard conditions (80 °C, 3 bar of H2),
producing within less than 2 h a mixture of 1,2,3,4-
tetrahydroacridine (4H-Acr) and 1,2,3,4,5,6,7,8-octahy-
droacridine (8H-Acr) (Scheme 2, Table 1). The hydro-
genation rate of the first arene ring of acridine to
produce 4H-Acr is fairly high: at least 25 TON/h.
Keeping the reaction mixture under a dihydrogen
atmosphere causes a gradual increase of 8H-Acr con-
centration at the expense of 4H-Acr (Figure 2). We can
assume that total conversion of acridine into 4H-Acr is
first achieved. After hydrogenation of the first aromatic
ring, the reaction proceeds, leading to hydrogenation of
the second external ring, but with a considerably slower
rate. The final hydrogenation product 8H-Acr has been
isolated as a white solid after a 30 h process and
spectrum of 4 in d6-acetone (298 K) shows two singlets
at δ 6.96 and 6.37 for the protons of the pyrrolyl ring
and a hydride triplet at δ -10.30 (J P-H ) 24.4 Hz). The
singlet at δ 79.5 in the 31P{1H} NMR spectrum trans-
forms into a triplet upon selective decoupling of the
protons of the phosphine ligands, confirming the pres-
ence of two hydrides. These data indicate that proto-
nation does not take place on the pyrrolyl ring but on
the metal. The initial kinetic product could be a dihy-
drogen complex, which would then isomerize to the
dihydride tautomer, as previously reported for the
protonation of several phosphine complexes of the type
[Cp*RuHL2].24
Rea ction of 1 w ith Acr id in e. Reaction of 1 with a
2-fold molar excess of acridine in pentane yields a yellow
microcrystalline product analyzed as [RuH2(η4-C13H9N)-
(PCy3)2] (5) (Scheme 1). The 1H NMR spectrum of 5
shows four proton resonance signals of equal intensity
for the coordinated arene ring of the acridine ligand at
δ 5.72 (H4), 5.43 (H1), 4.58 (H3), and 4.07 (H2). They are
shifted upfield by ca. 2-3 ppm as compared with the
resonances of the corresponding aromatic protons of free
acridine. The resonances of the remaining protons lie
close to the positions observed for the uncomplexed
aromatic and heteroaromatic rings of free acridine
between δ 8.06 and 6.78 (see Experimental Section). The
hydrides resonate as a triplet at δ -11.22 (J P-H ) 28.0
Hz), which is transformed into a singlet upon phospho-
rus decoupling. The 31P{1H} NMR spectrum (293 K,
C6D6) shows a single peak at δ 70.5, which upon
selective decoupling of protons of the cyclohexyl groups
is transformed into a triplet with J P-H ) 28.0 Hz,
indicative of the presence of two hydrides. We were
unable to obtain a 13C NMR spectrum due to the limited
solubility and the instability of the complex in solution.
1
characterized by GC/MS, H and 13C NMR, and X-ray
crystallography.
Crystals of 8H-Acr suitable for X-ray analysis have
been obtained from acetone solutions (Table 2). The
molecular structure along with selected bond lengths
(24) (a) J ia, G.; Lough, A. J .; Morris, R. H. Organometallics 1992,
11, 161. (b) Chinn, M. S.; Heinekey, D. M. J . Am. Chem. Soc. 1990,
112, 5166.
(25) (a) Sloufova, I.; Slouf, M. Acta Crystallogr., Sect. C: Cryst.
Commun. 2000, 56, 1312. (b) Sloufova. I.; Slouf. M. Acta Crystallogr.,
Sect. C: Cryst. Commun. 2001, 57, 248.

1,2,3,4,5,6,7,8-Octahydroacridine
Organometallics, Vol. 22, No. 8, 2003 1635
Sch em e 3. Ca ta lytic Cycle for P a r tia l
Hyd r ogen a tion of Acr id in e
F igu r e 2. Product distribution profile for acridine hydro-
genation: (9) 1,2,3,4-tetrahydroacridine (4H-Acr); ([)
1,2,3,4,5,6,7,8-octahydroacridine (8H-Acr). Catalyst precur-
sor: 1. Reaction conditions: T ) 80 °C, P ) 3 bar of H2.
number of mono- and polynuclear heteroaromatics,
including acridine.15a,27 Unlike those processes, for
anthracene hydrogenation, the structural hydrocarbon
analogue of acridine, a radical mechanism for the
reduction of C9 and C10 carbons has been postulated.29
Interestingly, during our studies no 9,10-2H-Acr has
been detected. Apparently, in the reduction of acridine
catalyzed by 1, neither of the two mechanisms (η1(N)
coordination or radical pathway) is operating.
Formation of 8H-Acr has also been observed in the
course of heterogeneous hydrogenation of acridine cata-
lyzed by Pd/Al2O3. In the mechanism postulated by
Mochida et al., the primary hydrogenation product, 9,-
10-2H-Acr, undergoes hydrogenative isomerization to
form the more stable 4H-Acr. Further hydrogenation
leads to 8H-Acr, the process being thermodynamically
favorable at a temperature of 250 °C.30 Our process
occurs at much lower temperature (80 °C), and the
presence of 9,10-2H-Acr has not been observed.
Hyd r ogen a tion of Acr id in e w ith 5 Used a s a
Ca ta lyst P r ecu r sor . 5 acts also as a hydrogenation
catalyst precursor, leading to a total conversion of
acridine into a mixture of 4H-Acr (12.5%) and 8H-Acr
(87.5%) after an 18 h process (Table 1). Since 5 readily
forms from 1 by substitution of the two dihydrogen
molecules, it is very likely that 5 may be involved, as a
transient form, in a catalytic cycle for acridine hydro-
genation. This hypothesis is supported by the observa-
tion that bubbling dihydrogen (10 min, 296 K) through
a C6D6 solution of 5 in an NMR tube restores 1. 4H-Acr
and 8H-Acr are also detected, with no traces of free
acridine.
The above findings allow us to propose a very simple
catalytic cycle for the hydrogenation of acridine to 4H-
Acr (Scheme 3), which begins with the dissociation of
two dihydrogen molecules, creating two vacant sites for
the coordination of acridine through an arene ring to
form an η4-bound substrate. The rest of the catalytic
cycle, although not investigated, is presumably straight-
forward. At the end of the catalytic reaction cycle, either
a new acridine molecule coordinates to Ru, forming 5
and restarting a new catalytic cycle, or the bis(dihydro-
gen) complex 1 regenerates upon coordination of two
F igu r e 3. Molecular structure of 1,2,3,4,5,6,7,8-octahy-
droacridine (8H-Acr). Selected bond lengths (Å) and angles
(deg): C2-C3, 1.514(2); C2-C7′, 1.515(2); C4-C5′, 1.3996-
(19); C6-C7, 1.518(2); C5-N1, 1.3575(18); C5-C6, 1.5062-
(17); C4-N1, 1.3632 (18); C5-N1-C4, 120.59(11); N1-C5-
C4′, 119.65(12); C5′-C4-C3, 121.49(12); C3-C2-C7′,
110.33(12); C4-C3-C2, 113.14(12); C2′-C7-C6, 110.01-
(12).
are depicted in Figure 3. The central ring containing
the nitrogen atom is virtually planar and retains its
aromatic character, as evidenced by a comparison with
the data reported for the heteroaromatic ring of acridine
previously characterized by X-ray crystallography.26
Hydrogenation of the two external aromatic rings of
acridine is confirmed with C-C bond distances and
angles close to 1.52 Å and 112°, respectively, as is
commonly found for cyclohexyl rings.
There are very few reports in the literature concern-
ing the process of homogeneous hydrogenation of acri-
dine. In all cases but one, selective hydrogenation of the
central ring was obtained, leading to the formation of
9,10-dihydroacridine (9,10-2H-Acr).15a,17,23,27,28 The only
exception, to our knowledge, concerns the formation of
4H-Acr (36%) along with 9,10-2H-Acr (64%) in the
course of acridine hydrogenation (85 °C, 21.4 bar of H2)
in the presence of [RhCl(PPh3)3].27b Rosales et al.
proposed a mechanism involving substrate coordination
to the ruthenium through the nitrogen atom and het-
erolytic activation of dihydrogen.17 In the work of Fish
et al., the importance of initial η1(N) bonding to the
metal center for catalytic activity is highlighted for a
(26) Phillips, D. C.; Ahmed, F. R.; Barnes, W. H. Acta Crystallogr.
1960, 13, 365.
(27) (a) Fish, R. H.; Thormodsen, A. D.; Cremer, G. A. J . Am. Chem.
Soc. 1982, 104, 5234. (b) Fish, R. H.; Tan, J . L.; Thormodsen, A. D. J .
Org. Chem. 1984, 49, 4500.
(28) Lee, C.; Steele, B. R.; Sutherland, R. G. J . Organomet. Chem.
1980, 186, 265.
(29) Feder, H. M.; Halpern, J . J . Am. Chem. Soc. 1975, 97, 7186.
(30) Sakanishi, K.; Ohira, M.; Mochida, I. J . Chem. Soc., Perkin
Trans. 1988, 1769.

1636 Organometallics, Vol. 22, No. 8, 2003
Borowski et al.
agents and thoroughly degassed under argon prior to use.
Acridine (Aldrich) was purified by sublimation. RuCl3‚3H2O
was purchased from J ohnson Mattey Ltd., and all other
reagents were purchased from Aldrich or Fluka and were used
as obtained but degassed before use. Reaction products were
analyzed by GC on a Hewlett-Packard 5890 apparatus fitted
with a FID detector using a capillary column (30 mm × 0.32
mm) packed with cross-linked methyl silicone. GC/MS (EI, 70
eV) determinations were performed on an HP 5970 MSD
apparatus. Special care must be taken in considering GC/MS
analysis data of the hydrogenation products of Q and iQ.
Results based on the mass spectra libraries may be ambiguous.
Homogeneity of the reaction mixtures has been confirmed by
tests with liquid mercury, which is known to inhibit colloidal
catalysis.34 1 was prepared by the published method, and
hydrogenations were performed as previously described.13
[Ru H2(η2-H2)(η1(N)-C5H5N)(P Cy3)2] (2). On addition of
pyridine (0.036 mL, 0.45 mmol) to a suspension of 1 (0.100 g,
0.15 mmol) in pentane (3 mL), an immediate change of color
of the mixture from beige to yellow-orange was observed, with
gas evolution and formation of a yellow solid. The suspension
was stirred overnight, after which the yellow precipitate was
filtered off, washed with pentane (3 × 1.5 mL), and dried under
a stream of argon followed by vacuum drying. The solid was
characterized by 1H and 31P NMR as [RuH2(η2-H2)(η1(N)-
C5H5N)(PCy3)2] (2) contaminated with 1 (ca. 10%). 1H NMR
(400 MHz, C7D8, 293 K): δ 9.11 (br, 2H, H2,6), 6.77 (br, 1H,
H4), 6.35 (br, 2H, H3,5), 2.3-1.2 (m, 66H, PCy3), -9.47 (t, 4H,
J P-H ) 13.5 Hz, Ru-H). 31P{1H} NMR (121 MHz): δ 71.9 (s).
13C{1H} NMR (100 MHz): δ 158.4 (br, C2,6), 122.9 (s, C3,5); the
other Py signals were obscured by solvent resonances.
dihydrogen molecules. Reduction of the second arene
ring of 4H-Acr begins presumably when most (or all) of
the acridine is consumed. Further experiments, par-
ticularly the influence of dihydrogen pressure, will be
necessary to get more information.
Con clu sion
Our group has extensively studied the properties of
the bis(dihydrogen) complex 1 and shown its versatile
reactivity toward, in particular, substitution reactions,
hydrogen transfer, and catalytic C-H, Si-H, and (very
recently) B-H activation.12,13,21,22,31 The present results
show that 1 can also activate N-heteroaromatic com-
pounds to produce new pyridine, pyrrole, or acridine
complexes. Similar studies on the reactivity of [Mo-
(PMe3)6] toward heterocyclic nitrogen compounds have
just been reported by Parkin et al.32 All these new
N-heteroaromatic complexes serve as models for HDN
catalysis. In our system, 1 catalyzes the hydrogenation
of quinoline and isoquinoline. Reduction into 5,6,7,8-
tetrahydro derivatives differs from what is generally
observed with other catalysts. Moreover, we have suc-
cessfully achieved acridine reduction into 1,2,3,4,5,6,7,8-
octahydroacridine and identified at least one interme-
diate in the catalytic cycle. Selective hydrogenation of
polynuclear N-heteroaromatic compounds, such as acri-
dine, is important for the production of useful function-
alized organic intermediates. In this respect, a synthesis
aimed at a large-scale production of 8H-Acr has been
recently described.33 It is a multistep process that
requires the not readily available starting material
2,2′-methylenebis(cyclohexanone) or 2-hydroxytricyclo-
[7.3.1.02,7]tridecan-13-one. In contrast, our synthesis is
a one-pot catalytic reaction, using commercially avail-
able acridine. This result emphasizes the interest in
simple mechanistic studies of hydrogenation reactions.
Similar studies, but with S-heteroaromatic substrates,
will be reported in due course.
[Ru H(η5-C4H4N)(P Cy3)2]‚P yr (3). Pyrrole (0.11 mL, 1.59
mmol) was added to a suspension of 1 (0.06 g, 0.09 mmol) in
pentane (3 mL). A gradual dissolution of 1 was observed with
formation of a yellow solution. After 2 h, the solvent was
evaporated under vacuum and 5 mL of diethyl ether was
added. After filtration, the solution was concentrated to ca. 2
mL, yielding a yellow crystalline product. It was filtered off
and washed with methyl alcohol (2 × 2 mL) before drying in
vacuo. Yield: 0.06 g (84%). Anal. Calcd for C44H76N2P2Ru (the
complex crystallizes with one pyrrole molecule): C, 66.38; H,
9.62; N, 3.52. Found: C, 66.25; H, 9.57; N, 3.64. 1H NMR (300
MHz, C6D6, 293 K): δ 6.05 (s, 2H, η5-C4H42,5N), 5.14 (s, 2H,
η5-C4H43,4N), 2.3-1.2 (m, 66H, PCy3), -15.86 (t, 1H, J P-H
)
Exp er im en ta l Section
36.8 Hz, Ru-H). 31P{1H} NMR (81 MHz): δ 66.5 (s). 13C NMR
(75 MHz): δ 105.7 (d, J C-H ) 185 Hz, C2), 78.0 (d, J C-H ) 179
Hz, C3).
Gen er a l P r oced u r es. Microanalyses were performed by
the Laboratoire de Chimie de Coordination Microanalytical
Service. Proton and phosphorus spectra were recorded on a
Bruker AC 200 (at 200.132 and 81.015 MHz, respectively) and
[Ru H2(η5-C4H4N)(P Cy3)2][BF 4] (4). A diethyl ether solu-
tion of HBF4‚O(CH2CH3)2 (85%; 0.037 mL, 0.21 mmol) was
added to a cooled (-50 °C) suspension of 2 (0.17 g, 0.21 mmol)
in dry acetone (5 mL). The mixture was warmed to room
temperature with stirring. The resulting colorless solution was
stirred for 0.5 h followed by evaporation to dryness. The
colorless crystalline product that formed was washed with cold
(-10 °C) acetone (2 × 1 mL) and dried under vacuum. Yield:
0.124 g (71%). Anal. Calcd for C40H72BF4NP2Ru: C, 58.80; H,
9.24; N, 1.71. Found: C, 58.70; H, 9.24; N, 1.62. 1H NMR (300
MHz, (CD3)2CO, 298 K): δ 6.96 (s, 2H, η5-C4H42,5N), 6.37 (s,
2H, η5-C4H43,4N), 2.3-1.2 (m, 66H, PCy3), -10.30 (t, 2H, J P-H
) 24.4 Hz, Ru-H2). 31P{1H} NMR (81 MHz): δ 79.5 (s). 13C-
{1H} NMR (50 MHz): δ 109.5 (s, C2), 95.1 (s, C3).
1
on an AMX 400 (at 400.130 and 161.985 MHz) apparatus. H
and 13C NMR spectra of acridine and 8H-Acr were recorded
on a Varian Inova-300 instrument (300.078 and 75.455 MHz,
respectively). Other 13C NMR spectra were obtained by using
Bruker AM 250 (50.323 MHz) and AMX 400 (100.624 MHz)
spectrometers, all operating in the Fourier transform mode.
IR spectra (KBr) were recorded on an Bio-Rad FTS 165
spectrometer at the Institute of Coal Chemistry, Polish
Academy of Sciences, Gliwice, Poland. All manipulations were
carried out under argon using standard Schlenk-line tech-
niques. All solvents were freshly distilled from standard drying
(31) See for example: (a) Delpech, F.; Sabo-Etienne, S.; Daran, J .-
C.; Chaudret, B.; Hussein, K.; Marsden, C. J .; Barthelat, J .-C. J . Am.
Chem. Soc. 1999, 121, 6668. (b) Atheaux, I.; Donnadieu, B.; Rodriguez,
V.; Sabo-Etienne, S.; Chaudret, B.; Hussein, K.; Barthelat, J .-C. J . Am.
Chem. Soc. 2000, 122, 5664. (c) Delpech, F.; Mansas, J .; Leuser, H.;
Sabo-Etienne, S.; Chaudret, B. Organometallics 2000, 19, 5750. (d)
Montiel-Palma, V.; Lumbierres, M.; Donnadieu, B.; Sabo-Etienne, S.;
Chaudret, B. J . Am. Chem. Soc. 2002, 124, 5624.
[Ru H2(η4-C13H9N)(P Cy3)2] (5). A suspension of 1 (0.108 g,
0.162 mmol) with acridine purified by sublimation (0.058 g,
0.324 mmol) in 4 mL of pentane was stirred for 2 h, yielding
a yellow microcrystalline product that was separated, washed
with pentane (3 × 2 mL), and dried in vacuo. Yield: ca. 0.12
g (88.1%). Anal. Calcd for C49H77NP2Ru: C, 69.78; H, 9.21; N,
(32) Zhu, G.; Tanski, J . M.; Churchill, D. G.; J anak, K. E.; Parkin,
G. J . Am. Chem. Soc. 2002, 124, 13658.
(33) Pilato, M. L.; Catalano, V. J .; Bell, T. W. J . Org. Chem. 2001,
66, 1525.
(34) (a) Anton, D. R.; Crabtree, R. H. Organometallics 1983, 2, 855.
(b) Morton, D.; Cole-Hamilton, D. J .; Utuk, I. D.; Paneque-Sosa, M.;
Lo´pez-Poveda, M. J . Chem. Soc., Dalton Trans. 1989, 489.

1,2,3,4,5,6,7,8-Octahydroacridine
Organometallics, Vol. 22, No. 8, 2003 1637
1.66. Found: C, 69.87; H, 9.93; N, 1.63. IR: ν(Ru-H) 2015
squares procedures on F2 using SHELXL-97.36 All hydrogen
atoms were located on a difference Fourier map, but they were
introduced in calculations in idealized positions with an
isotropic thermal parameter fixed at 20% higher than those
of the carbon atoms to which they were connected. The hydride
H(1) and the hydrogen H(2) connected to the pyrrole molecule
in 3 and the hydrogen atom H(1) connected to C(1) in 8H-Acr
were isotropically refined. All non-hydrogen atoms were aniso-
tropically refined. Concerning the molecule of 1,2,3,4,5,6,7,8-
octahydroacridine (8H-Acr), although the model does not show
any centrosymmetry settle on an inversion center, the atoms
C(1) and N(1) sit on two different sites. Therefore, these two
atoms were refined by using a mixing of 50% of C(1) and 50%
of N(1) on two distinct positions. Least-squares refinements
were carried out by minimizing the function ∑w(|Fo| - |Fc|)2,
where Fo and Fc are the observed and calculated structure
factors. A weighting scheme was used in the last refinement
cycles, where weights are calculated from the following expres-
sion: w ) [weight] × [1 - (∆(F)/6σ(F)]2.36 Models reached
convergence with Rw ) [∑w(||Fo| - ||Fc|)2/∑(|Fo|)2]1/2. The
criteria for a satisfactory complete analysis were the ratios of
rms shift to standard deviation being less than 0.1 and no
significant features in the final difference maps. All calcula-
tions were performed by using the program WinGX, version
1.64-04.37 The molecules were drawn with the aid of ORTEP32,38
and the atomic scattering factors were taken from ref 39.
Further details on the crystal structure investigation are
available on request from the Director of the Cambridge
Crystallographic Data Centre, 12 Union Road, GB-Cambridge
CB21EZ, U.K., on quoting the full journal citation.
1
(vs) and 1987 (vs) cm-1. H NMR (200 MHz, C6D6, 293 K): δ
8.06 (d, 1H, H5, J H-H ) 7.9 Hz), 7.4-7.1 (m, 3H, H6,7,8), 6.78
(s, 1H, H9), 5.72 (br, 1H, H4), 5.43 (br, 1H, H1), 4.58 (d, 1H,
H3, J H-H ) 5.9 Hz), 4.07 (d, 1H, H2, J H-H ) 5.9 Hz), 2.3-1.2
(m, 66H, PCy3), -11.22 (t, 2H, J P-H ) 28.0 Hz, Ru-H). 31P-
{1H} NMR (81 MHz): δ 70.5 (s).
Acr id in e (NMR data given for comparison, C6D6, 293 K.)
1H NMR (300 MHz): δ 8.56 (d, 2H, H4,5, J 3-4,5-6 ) 8.8 Hz),
8.20 (s, 1H, H9), 7.66 (d, 2H, H1,8, J 1-2,7-8 ) 8.0 Hz), 7.49 (dd,
2H, H3,6, J 2-3,6-7 ) 8.0 Hz, J 3-4,5-6 ) 8.8 Hz), 7.25 (dd, 2H,
H2,7, J 1-2,7-8 ) 8.0 Hz, J 2-3,6-7 ) 8.0 Hz). 13C{1H} NMR (75
MHz): δ 152.2 (s, C4a,10a), 137.9 (s, C9), 132.8 (s, C1,8), 132.3 (s,
C4,5), 130.7 (s, C3,6), 129.2 (s, C8a,9a), 128.0 (s, C2,7).
1,2,3,4,5,6,7,8-Octa h yd r oa cr id in e (8H-Acr ). 1 (0.02 g,
0.03 mmol) and acridine (purified by sublimation) (0.2688 g,
1.5 mmol) were placed in a Fisher-Porter flask under argon.
Degassed cyclohexane (10 mL) was then added, and after
pressurization with dihydrogen to 3 bar, the reactor was placed
in an oil bath. During the course of warming the initially
yellow suspension dissolved, giving a yellow solution. The
reaction mixture was heated at 80 °C for 30 h, after which
the reactor was cooled to room temperature and depressurized.
The solvent was removed in vacuo, and the remaining solid
was extracted with several portions of pentane. The pentane
extracts were passed through “Celite” to remove solid impuri-
ties, after which pentane was removed under vacuum to give
a colorless crystalline solid. Yield: 0.21 g (ca. 75%). Anal. Calcd
for C13H17N: C, 83.37; H, 9.15; N, 7.48. Found: C, 83.38; H,
9.07; N, 7.43. 1H NMR (300 MHz, CDCl3, 293 K): δ 7.02 (s,
1H, H9), 2.85 (t, 4H, H4,5, J H-H ) 6.2 Hz), 2.68 (t, 4H, H1,8
,
J H-H ) 6.2 Hz), 1.86 (quint, 4H, H3,6, J H-H ) 6.1 Hz), 1.77
(quint, 4H, H2,7, J H-H ) 6.1 Hz). 13C{1H} NMR (75 MHz): δ
154.0 (s, C4a,10a), 137.4 (s, C9), 129.2 (s, C8a,9a), 32.3 (s, C1,8),
28.4 (s, C4,5), 23.4 (s, C3,6), 22.9 (s, C2,7).
Ack n ow led gm en t. This work was supported by the
Polish Academy of Sciences and the CNRS under
Contract No. 9774 and the Committee for Scientific
Research (KBN) (A.F.B.) under Contract No. PBZ-KBN
15/T09/99/01d.
X-r a y Da ta . Data were collected at low temperature, T )
160 K for 3 and T ) 180 K for 8H-Acr, on a Stoe imaging plate
diffraction system (IPDS) equipped with an Oxford Cryosys-
tems cooler device.The crystal-to-detector distance was 70 mm,
and 192 exposures were obtained for 3 and 133 for 8H-Acr,
with the crystals oscillating 1.3 and 1.5° in æ, respectively.
The final unit cell parameters were obtained by least-squares
refinement of 5000 reflections. No significant fluctuation of
the intensity was observed. Structures were solved by direct
methods using the program SIR9235 and refined by least-
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
crystallographic data for 3 and 8H-Acr. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM020995P
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