Octahedral ruthenium(II) complexes cis,cis-[RuX2(CNR)(CO)(P∧P)] and cis,cis,cis-[RuX2(CO)2(P∧P)] (X = Cl, Br; P∧P = 1,1′-bis(diphenylphosphino)ferrocene, 1,1′-bis(diisopropylphosphino)ferrocene): Synthesis and catalytic applications in transfer hydrogenation of acetophenone and cycloisomerization of...

Article abstract of DOI:10.1016/j.jorganchem.2007.07.050

Full title: Octahedral ruthenium(II) complexes cis,cis-[RuX₂(CNR)(CO)(P^∧P)] and cis,cis,cis-[RuX₂(CO)₂(P^∧P)] (X = Cl, Br; P^∧P = 1,1′-bis(diphenylphosphino)ferrocene, 1,1′-bis(diisopropylphosphino)ferrocene): Synthesis and catalytic applications in transfer hydrogenation of acetophenone and cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol. Carbonyl-isocyanide-ruthenium(II) complexes cis,cis-[RuX₂(CNR)(CO)(P^∧P)] (P^∧P = dppf, dippf; X = Cl, Br; R = Bn, Cy, ^tBu, 2,6-C₆H₃Me₂, (S)-(-)-C(H)MePh) (3-6a-e) have been prepared in high yields by treatment of the dimeric derivatives [{RuX(μ-X)(CO)(P^∧P)}₂] (P^∧P = dppf, dippf; X = Cl, Br) (1-2a-b) with isocyanides. Dimers 1-2a-b also react with carbon monoxide to afford the dicarbonyl species cis,cis,cis-[RuX₂(CO)₂(P^∧P)] (7-8a-b). The catalytic activity of these compounds in transfer hydrogenation of acetophenone by propan-2-ol as well as in cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has been studied.

Full text of DOI:10.1016/j.jorganchem.2007.07.050

Journal of Organometallic Chemistry 692 (2007) 5234–5244
www.elsevier.com/locate/jorganchem
Octahedral ruthenium(II) complexes cis,cis-[RuX2(CNR)(CO)(PꢀP)]
and cis,cis,cis-[RuX2(CO)2(PꢀP)] (X = Cl, Br; PꢀP = 1,
10-bis(diphenylphosphino)ferrocene, 1,10-bis(diisopropylphosphino)
ferrocene): Synthesis and catalytic applications in transfer
hydrogenation of acetophenone and cycloisomerization
of (Z)-3-methylpent-2-en-4-yn-1-ol
*
´
Joachim Albers, Victorio Cadierno , Pascale Crochet, Sergio E. Garcıa-Garrido,
*
´
Jose Gimeno
Departamento de Quı´mica Orga´nica e Inorga´nica, Instituto Universitario de Quı´mica Organometa´lica ‘‘Enrique Moles’’ (Unidad Asociada al CSIC),
Facultad de Quı´mica, Universidad de Oviedo, E-33071 Oviedo, Spain
Received 19 July 2007; received in revised form 30 July 2007; accepted 30 July 2007
Available online 6 August 2007
In memoriam of our friend and colleague Prof. Lorenzo Pueyo.
Abstract
t
Carbonyl–isocyanide-ruthenium(II) complexes cis,cis-[RuX2(CNR)(CO)(PꢀP)] (PꢀP = dppf, dippf; X = Cl, Br; R = Bn, Cy, Bu,
2,6-C6H3Me2, (S)-(ꢀ)-C(H)MePh) (3–6a–e) have been prepared in high yields by treatment of the dimeric derivatives [{RuX-
(l-X)(CO)(PꢀP)}2] (PꢀP = dppf, dippf; X = Cl, Br) (1–2a–b) with isocyanides. Dimers 1–2a–b also react with carbon monoxide to afford
the dicarbonyl species cis,cis,cis-[RuX2(CO)2(PꢀP)] (7–8a–b). The catalytic activity of these compounds in transfer hydrogenation of ace-
tophenone by propan-2-ol as well as in cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has been studied.
ꢁ 2007 Elsevier B.V. All rights reserved.
Keywords: Carbonyl complexes; Isocyanide complexes; Ruthenium; Transfer hydrogenation; Cycloisomerization
1. Introduction
routes to alcohols and constitutes a good alternative to
the widely used catalytic hydrogenation [4]. Despite the fact
that the later route has a much greater potential for indus-
trial applications [5], there has been a continuous interest in
catalytic TH reactions, since alcohols can be obtained in
high yields, under relatively mild conditions, avoiding the
use of H2 gas [4]. In this context, we have recently reported
that octahedral bis(isocyanide)–ruthenium(II) complexes
trans,cis,cis-[RuX2(CNR)2(dppf)] (X = Cl, Br; dppf =
1,10-bis(diphenylphosphino)ferrocene; R = alkyl or aryl
group) (I in Fig. 1) are valuable precursors of active cata-
lytic species for TH of ketones (TOF values up to
1500 hꢀ1) [6].
Over the last decades the interest in ruthenium-catalyzed
reactions directed to organic synthesis has spectacularly
increased and a large number of highly efficient synthetic
approaches are nowadays well documented [1–3]. In partic-
ular, the transfer hydrogenation (TH) of ketones by
H2-donor solvents, such as propan-2-ol, using ruthe-
nium(II) catalysts is currently one of the most appealing
*
Corresponding authors. Tel.: +34 985 103 461; fax: +34 985 103 446.
E-mail addresses: vcm@uniovi.es (V. Cadierno), jgh@uniovi.es
(J. Gimeno).
0022-328X/$ - see front matter ꢁ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.07.050

J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
5235
Fig. 1. Structure of the octahedral ruthenium(II) complexes I, II and III.
The efficiency shown by the bis(isocyanide)–Ru(II) com-
plexes I is remarkable since precatalysts featuring a Ru–
NH2R linkage commonly offer the highest level of activity
in TH of ketones [4,7]. This ‘‘NH effect’’ has been rational-
ized in terms of an outer-sphere mechanism in which the
concerted transfer of H2 from an hydride intermediate
[H–Ru–NH2R] to the ketone, via a six-membered metalla-
cyclic transition state, takes place [8]. As a consequence,
much effort has been devoted to the design of new ligands
containing NH donor units during the last years [4].
Simultaneously, in order to overcome such a structural pre-
requisite, the development of alternative classes of efficient
Ru-based TH catalysts has also gained a considerable
interest, becoming an important and highly rewarding
target [9].
With these precedents in mind and encouraged by the
effectiveness shown by complexes trans,cis,cis-[RuX2-
(CNR)2(dppf)] (I), we believed it of interest to explore
the ability of related ferrocenyl-diphosphine-based octahe-
dral ruthenium(II) complex to promote the catalytic trans-
fer hydrogenation of ketones [10]. Thus, in this paper we
report the high yield preparation of the novel carbonyl–
isocyanide and dicarbonyl complexes cis,cis-[RuX2(CNR)-
(CO)(PꢀP)] (II in Fig. 1) and cis,cis,cis-[RuX2(CO)2(PꢀP)]
(III in Fig. 1), respectively, and their behaviour in TH
catalysis. In addition, the application of these compounds
in the catalytic synthesis of 2,3-dimethylfuran, via cycloiso-
merization of (Z)-3-methylpent-2-en-4-yn-1-ol, will be also
presented.
furan solution of dimers 1–2a–b with a twofold excess of
the appropriate isocyanide (Scheme 1).
Compounds 3–6a–e, isolated as air-stable yellow-orange
solids, have been characterized by means of standard spec-
1
troscopic techniques (IR and H, 31P{1H}, and 13C{1H}
NMR) as well as elemental analysis, being all data fully con-
sistent with the proposed formulations and stereochemistry
(details are given in Section 4 and Table 1). Relevant spec-
troscopic features are the following: (i) (IR) The presence of
two absorption bands in the ranges 1950–1979 cmꢀ1 and
2156–2221 cmꢀ1 (see Table 1), characteristic for metal-
coordinated carbonyl and isocyanide ligands, respectively.
(ii) (31P{1H} NMR) The appearance of two doublet reso-
nances (dP 12.7–53.3 ppm; 2JPP = 17.4–25.7 Hz) as a typical
sign of unequivalent phosphorus nuclei of the ferrocenyl-
diphosphine ligand (see Table 1). (iii) (13C{1H} NMR) A
characteristic downfield signal (dC 197.4–200.2 ppm) for
the carbonyl group which appears as a doublet of doublets
2
with JCP values of 12.1–14.0 Hz, indicating that the car-
bonyl group is located in a cis disposition with respect to
both phosphorus nuclei of the diphosphine. And, (iv) in
the case of complexes 5–6a–e, containing the ferrocenyl-
diphosphine dippf, the appearance in the 13C{1H} NMR
spectra of a doublet of doublets resonance at dC 138.2–
156.0 ppm assigned to the isocyanide ligand (for the dppf-
containing compounds 3–4a–e this signal falls within the
2
aromatic carbon region). The JPP values observed, in the
ranges 119.3–122.6 and 21.6–24.1 Hz, are in complete
accord with the proposed stereochemistry, i.e. the isocya-
nide group is located in a trans and cis disposition with
respect to the phosphorous nuclei of the dippf ligand.
It is also worth to note that the chiral complexes 3–6e,
containing the optically active (S)-(ꢀ)-a-methylbenzyl iso-
cyanide, are formed as a non-separable mixture of two dia-
stereoisomers (ca. 1:1 ratio) arising as a consequence of the
stereogenic character of the ruthenium atom in this family
of compounds (Fig. 2).
2. Results and discussion
2.1. Synthesis and characterization of complexes
cis,cis-[RuX2(CNR)(CO)(PꢀP)] and cis,cis,cis-
[RuX2-(CO)2(PꢀP)]
We have recently shown that, upon treatment with two-
electron donor ligands L, the carbonyl-halide dimers
[{RuX(l-X)(CO)(PꢀP)}2] (PꢀP = dppf, X = Cl (1a), Br
(1b); PꢀP = dippf, X = Cl (2a), Br (2b)) are useful precur-
sors for the preparation of octahedral mononuclear ruthe-
nium(II) derivatives cis,cis-[RuX2(L)(CO)(PꢀP)], via the
expected cleavage of the halide bridges [11]. Following this
synthetic methodology, the carbonyl–isocyanide complexes
cis,cis-[RuX2(CNR)(CO)(PꢀP)] (3–6a–e) have been synthe-
sized in excellent yields (75–99%) by reacting a tetrahydro-
The dicarbonyl complexes cis,cis,cis-[RuX2(CO)2(PꢀP)]
(PꢀP = dppf, X = Cl (7a), Br (7b); PꢀP = dippf, X = Cl
(8a), Br (8b)) have been prepared (79–87% isolated yield)
by bubbling carbon monoxide at atmospheric pressure
through a refluxing THF solution of the corresponding
dimeric species [{RuX(l-X)(CO)(PꢀP)}2] (1–2a–b) (Scheme
1). They have been characterized by IR and NMR spectros-
copy, which support the mutually cis arrangement of both
the carbonyl and halide ligands, and elemental analyses

5236
J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
Scheme 1. Synthesis of the mononuclear ruthenium(II) complexes 3–6a–e and 7–8a–b (dippf = 1,10-bis(diisopropylphosphino)ferrocene).
Table 1
IR and 31P{1H} NMR data for the carbonyl–isocyanide complexes cis,cis-
[RuX2(CNR)(CO)(PꢀP)] (3–6a–e)
Complex
IRa
31P{1H} NMRb
m(CO)
m(CN)
dP
2JPP
3ac
3b
1977
1975
1976
1977
1974
2221
2207
2191
2172
2200
17.3 (d), 42.8 (d)
17.0 (d), 43.2 (d)
17.4 (d), 43.3 (d)
16.6 (d), 42.9 (d)
17.1 (d), 42.6 (d)
17.6 (d), 43.3 (d)
25.7
25.3
25.3
25.7
25.7
25.7
Fig. 2. The two enantiomeric forms of the carbonyl–isocyanide complexes
3–6a–e.
3c
3d
3ed
(details are given in Section 4 and Table 2). Key spectro-
scopic data are the following: (i) The two strong m(CO)
absorption bands that appear within the range 1978–
2077 cmꢀ1 in the IR spectra (see Table 2). (ii) The typical
AB pattern of the phosphorus resonances (dP 11.8–26.2
4a
4b
4c
1978
1979
1979
1974
1978
2208
2203
2186
2170
2198
14.4 (d), 42.7 (d)
14.3 (d), 43.3 (d)
14.7 (d), 43.5 (d)
12.7 (d), 41.6 (d)
14.3 (d), 42.7 (d)
14.7 (d), 43.3 (d)
25.3
23.5
23.8
25.3
24.4
24.4
4d
4ed
2
and 38.6–53.9 ppm; JPP = 16.6–24.6 Hz; see Table 2).
And, (iii) the two doublet of doublets carbonyl resonances
in the 13C{1H} NMR spectra at 189.7–192.5 (2JCP
110.3–120.5 and 9.8–12.8 Hz) and 195.1–196.5 (2JCP
=
=
5a
5b
5c
1955
1952
1951
1956
1956
2197
2189
2186
2156
2187
26.9 (d), 52.8 (d)
27.0 (d), 52.9 (d)
27.1 (d), 53.1 (d)
27.0 (d), 53.3 (d)
26.9 (d), 52.9 (d)
27.1 (d), 53.0 (d)
18.5
18.9
18.5
18.5
17.9
17.9
5d
5ed
Table 2
IR and 31P{1H} NMR data for the dicarbonyl complexes cis,cis,cis-
[RuX2(CO)2(PꢀP)] (7–8a–b)
6a
6b
6c
1951
1950
1952
1958
1956
2195
2191
2182
2158
2183
21.9 (d), 52.4 (d)
22.1 (d), 52.4 (d)
22.3 (d), 52.6 (d)
22.3 (d), 53.1 (d)
22.1 (d), 52.5 (d)
22.3 (d), 52.6 (d)
18.1
17.8
17.4
17.8
18.9
18.9
Complex
IRa
31P{1H} NMRb
m(CO)
dP
2JPP
6d
6ed
7ac
7b
8a
8b
a
2009, 2070
2000, 2077
1978, 2048
1982, 2047
15.3 (d), 38.8 (d)
11.8 (d), 38.6 (d)
26.2 (d), 53.5 (d)
21.5 (d), 53.9 (d)
25.3
24.6
17.4
16.6
a
Spectra recorded in KBr; m in cmꢀ1
Spectra recorded in CD2Cl2; d in ppm and J in Hz.
Data taken from Ref. [11].
Obtained as a non-separable mixture of two diastereoisomers in ca. 1:1
.
b
c
Spectra recorded in KBr; m in cmꢀ1
.
Spectra recorded in CD2Cl2; d in ppm and J in Hz.
d
b
c
ratio.
Data taken from Ref. [11].

J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
5237
Table 3
13.6–14.4 and 11.3–12.1 Hz) ppm, which reveal a trans,cis
and a cis,cis arrangement, respectively, of the carbonyl
groups with respect the phosphorus nuclei of the diphos-
phine ligand.
Catalytic transfer hydrogenation of acetophenone by complexes 3–6a–ea
Entry
Catalyst
Time (h)
Yield (%)b
TOF (hꢀ1 c
)
1
2
3
4
5
6
7
8
9
3a
3b
3c
6
7
8
24
7
24
24
24
24
8
3
6
7
10
5
6
7
8
24
7
98
98
98
98
96
98
99
99
97
92
98
97
94
98
98
98
96
97
98
97
41 (480)
35 (390)
31 (450)
11 (360)
34 (390)
11 (150)
11 (360)
11 (210)
11 (210)
29 (240)
82 (750)
40 (600)
34 (630)
24 (1200)
49 (900)
41 (1080)
34 (810)
30 (660)
10 (660)
35 (1110)
2.2. Catalytic transfer hydrogenation of acetophenone
3d
3ed
4a
4b
4c
Following our interest in ruthenium-catalyzed transfer
hydrogenation reactions [6,9e,9f,11,12], the catalytic activ-
ity in TH of acetophenone by propan-2-ol of the car-
bonyl–isocyanide and dicarbonyl complexes 3–6a–e and
7–8a–b, respectively, has been explored (Scheme 2). Thus,
in a typical experiment, the ruthenium catalyst precursor
(0.4 mol%) and NaOH (9.6 mol%) were added to a 0.1 M
4d
4ed
5a
5b
5c
10
11
12
13
14
15
16
17
18
19
20
a
i
5d
5ed
6a
6b
6c
solution of acetophenone in PrOH at 82 ꢂC, the reaction
being monitored by gas chromatography. Selected results
are shown in Table 3.
Concerning the carbonyl–isocyanide complexes 3–6a–e,
all of them have proven to be efficient catalysts, leading
to nearly quantitative conversions (yield P92%) of aceto-
phenone into 1-phenylethanol within 3–24 h (Table 3).
From the results depicted in Table 3, the following features
deserve to be commented: (i) The catalytic performances
shown by complexes containing the bulkier and more basic
dippf ligands 5–6a–e are in general higher than those of
their corresponding dppf counterparts 3–4a–e (final
TOF = 10–82 versus 11–41 hꢀ1). (ii) There is a strong influ-
ence of the isocyanide substituents on the catalytic activity,
increasing in the order Bn > C(H)MePh ꢁ Cy > tBu ꢂ 2,6-
C6H3Me2. This indicates clearly that the steric require-
ments of the isocyanide ligands play a crucial role in the
reaction. (iii) The chloride complexes 3, 5a–e are, in all
cases, more efficient than their bromide counterparts 4,
6a–e. This behaviour stems from the higher ability of the
Ru–Cl versus Ru–Br bonds to undergo metathesis reac-
tions, favouring therefore the formation of the correspond-
ing hydride-ruthenium(II) intermediates which are the real
catalytically active species [13].
6d
6ed
Conditions: reactions were carried out at 82 ꢂC using 5 mmol of ace-
i
tophenone (0.1 M in PrOH). Ketone/Ru/NaOH ratio: 250/1/24.
b
Yield of 1-phenylethanol determined by GC.
Turnover frequencies ((mol product/mol catalyst)/time) were calcu-
c
lated at the time indicated in each case (TOF values after 5 min in
parentheses).
d
No chiral induction (0% ee) was observed when the optically active
derivatives 3–6e were used as catalysts. All the values given in the table are
the average of two runs.
confirming the crucial role of the quantity of NaOH used
on the performance of this catalyst. Thus, as it can be
observed in Fig. 3, when a ketone/Ru/NaOH ratio of
250/1/5 versus 250/1/24 is used the activity of 5a was visi-
bly increased (the TOF value after 10 min increased from
476 to 636 hꢀ1).
The catalytic activity of the dicarbonyl complexes cis,cis,-
cis-[RuX2(CO)2(PꢀP)] (7–8a–b) was also tested (Fig. 4). The
All the observations mentioned above are in complete
accord with the behaviour shown previously by the bis(iso-
cyanide) precatalysts trans,cis,cis-[RuX2(CNR)2(dppf)] (I
in Fig. 1) [6]. Nevertheless, it is important to note that
the catalytic performances of the carbonyl–isocyanide spe-
cies 3–6a–e are lower than those of the bis(isocyanide) com-
plexes I. This difference could be associated to the lower
stability of the active hydride species derived from 3–6a–e
versus I under the strong basic reaction conditions
employed [13]. In order to investigate this behaviour in
more detail, the activity of complex cis,cis-[RuCl2(CNBn)-
(CO)(dippf)] (5a) was tested under different conditions
Fig. 3. Influence of the quantity of NaOH used on the catalytic activity
Scheme 2. Ru-catalyzed transfer hydrogenation of acetophenone.
of 5a.

5238
J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
Scheme 3. Ru-catalyzed cycloisomerization of (Z)-3-methylpent-2-en-4-
yn-1-ol.
As shown in Table 4, all the carbonyl–isocyanide com-
plexes 3–6a–e (entries 1–20), as well as the dicarbonyl com-
plexes 7–8a, b (entries 21–24), are able to convert the enynol
into 2,3-dimethylfuran in good yields (78–99%) after 0.5–
24 h. The results clearly evidence that, as it was observed
for the catalytic transfer hydrogenation of acetophenone,
there is a strong influence of the isocyanide substituents
on the catalytic activity of complexes 3–6a–e, increasing
in almost the same order Bn > C(H)MePh > Cy > tBu >
2,6-C6H3Me2. Analogously, the catalytic performances
shown by complexes containing the bulkier and more basic
dippf ligands 5–6a–e (TOF = 4–66 hꢀ1; entries 11–20) and
8a–b (TOF = 20–198 hꢀ1; entries 23–24) are higher than
those of their corresponding dppf counterparts 3–4a–e
Fig. 4. Catalytic activity of complexes 7–8a–b in TH of acetophenone.
reactions were carried out at 82 ꢂC using 5 mmol of aceto-
phenone (0.1 M in iPrOH) and an acetophenone/Ru/NaOH
ratio of 250/1/5. Under these conditions the four complexes
efficiently reduced acetophenone into 1-phenylethanol
(P91% yield within 2–24 h; final TOF = 9–121 hꢀ1), the
dichloride derivative cis,cis,cis-[RuCl2(CO)2(dippf)] (8a)
showing the best performance. Thus, this complex was able
to reduce acetophenone in 97% yield after only 2 h (TOF
after 10 min = 1245 hꢀ1; final TOF = 121 hꢀ1). As it was
observed for complexes 2–6a–e, when 24 instead of 5 equiv-
alents of NaOH were used the rate of the catalytic reaction
decreased probably due to the same reasons explained
above.
(TOF = 3–7 hꢀ1; entries 1–10) and 7a–b (TOF = 3 hꢀ1
;
entries 21–22), respectively. This increase in the catalytic
activity is particularly remarkable in the case of dicarbonyl
complexes (see entries 23–24 versus 21–22), with the
derivative cis,cis,cis-[RuCl2(CO)2(dippf)] (8a) showing the
Table 4
2.3. Catalytic cycloisomerization of (Z)-3-methylpent-
2-en-4-yn-1-ol into 2,3-dimethylfuran
Catalytic cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol by com-
plexes 3–6a–e and 7–8a–ba
Entry
Catalyst
Time (h)
Yield (%)b
TOF (hꢀ1 c
)
The synthesis of furans is of particular interest since they
can be found in many naturally occurring compounds
being also key structural units in several important phar-
maceuticals, as well as in flavour and fragrance compounds
[14]. Furthermore, furans are useful and versatile building
blocks in organic synthesis [15]. Among the plethora of
alternatives [14], the most direct synthetic strategies pres-
ently available for the construction of furan rings involve
metal-mediated cycloisomerization of appropriate acyclic
precursors. Among them, (Z)-2-en-4-yn-1-ols are particu-
larly appealing since they are readily available starting
materials [14]. In this context, several palladium [16], cop-
per [17], silver [18], gold [19], rhodium [20], iridium [20b],
and specially ruthenium [16a,20b,21] catalysts have been
successfully used to promote the cycloisomerization of
(Z)-2-en-4-yn-1-ol substrates into the corresponding fur-
ans. Owing to these facts, we decided to explore the cata-
lytic activity of our carbonyl–isocyanide and dicarbonyl
complexes 3–6a–e and 7–8a–b, respectively, in the cycliza-
tion of the commercially available (Z)-3-methylpent-2-en-
4-yn-1-ol into 2,3-dimethylfuran (Scheme 3).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
a
3a
3b
3c
3d
3e
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
7a
7b
8a
8b
14
24
24
24
15
24
24
24
24
24
1.5
2
2.5
2.5
1.5
9
15
24
24
9.5
24
24
0.5
5
99
99
99
93
99
97
93
85
78
96
99
99
99
99
99
99
99
99
99
99
85
72
99
99
7
4
4
4
7
4
4
3
3
4
66
50
40
40
66
11
7
4
4
10
3
3
198
20
Conditions: reactions were carried out at 75 ꢂC using 5 mmol of (Z)-3-
The reactions were performed at 75 ꢂC using 5 mmol of
(Z)-3-methylpent-2-en-4-yn-1-ol and 1 mol% of the ruthe-
nium catalyst precursor, the reaction being monitored by
gas chromatography. It is worthy to note that no addi-
tional solvents are added to the reaction mixture [22].
methylpent-2-en-4-yn-1-ol and 1 mol% of catalyst.
b
Yield of 2,3-dimethylfuran determined by GC.
Turnover frequencies ((mol product/mol catalyst)/time) were calcu-
c
lated at the time indicated in each case. The values given in the table are
the average of two runs.

J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
5239
for the cycloisomerization of the commercially available
(Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran,
with the dicarbonyl species cis,cis,cis-[RuCl2(CO)2(dippf)]
(8a) showing a remarkable activity.
4. Experimental
4.1. General information
Scheme 4. Mechanism of the Ru-catalyzed cycloisomerization process.
All manipulations were performed under an atmosphere
of dry nitrogen using vacuum-line and standard Schlenk
techniques. Solvents were dried by standard methods and
distilled under nitrogen before use. All reagents were
obtained from commercial suppliers and used without fur-
ther purification, with the exception of the compounds
[{RuX(l-X)(CO)(PꢀP)}2] (PꢀP = dppf, X = Cl (1a), Br
(1b); PꢀP = dippf, X = Cl (2a), Br (2b)), cis,cis-[RuCl2-
(CNBn)(CO)(dppf)] (3a) and cis,cis,cis-[RuCl2(CO)2(dppf)]
(7a), which were prepared by following the methods reported
in the literature [11]. Infrared spectra were recorded on a
Perkin–Elmer 1720-XFT spectrometer. The C, H, and N
analyses were carried out with a Perkin–Elmer 2400 micro-
analyzer. Gas chromatographic measurements were made
on a Hewlett–Packard HP6890 equipment using a HP-
INNOWAX cross-linked poly(ethyleneglycol) (30 m,
250 lm) or a Supelco Beta-Dexꢃ 120 (30 m, 250 lm) col-
umn. NMR spectra were recorded on a Bruker DPX-300
instrument at 300 MHz (1H), 121.5 MHz (31P), or
75.4 MHz (13C) using SiMe4 or 85% H3PO4 as standards.
DEPT experiments have been carried out for all the com-
pounds reported. IR and 31P{1H} NMR data are collected
in Tables 1 and 2.
highest activity (99% yield in only 0.5 h; TOF = 198 hꢀ1
;
entry 23). It should be noted that, although the efficiency
shown by this complex is comparable to that shown by
other Ru(II) catalysts previously described [23], it still
remains less efficient than AuCl3 (TOF = 999 hꢀ1 at r.t.)
which is the best catalyst reported to date for this cycloiso-
merization reaction [19].
Finally, it is also interesting to note that, as observed in
the TH reactions, the catalytic performances shown by the
chloride complexes 3, 5a–e and 7, 8a are, in all cases, better
than those of their bromide counterparts 4, 6a–e and 7, 8b,
respectively (entries 1–5 versus 6–10, 11–15 versus 16–20
and 21/23 versus 22/24). Assuming that this cycloisomer-
ization reaction proceeds through the classical pathway,
i.e. via initial p-coordination of the C„C of the enynol
on the metal and subsequent intramolecular endo nucleo-
philic attack of the pendant OH group on the coordinated
alkyne unit (Scheme 4) [16], the higher catalytic activities
shown by the chloride versus bromide complexes can be
explained on the basis of greater tendency of the former
to undergo dissociation, generating more easily the
required vacant coordination site.
4.2. Synthesis of carbonyl–isocyanide complexes cis,cis-
[RuX2(CNR)(CO)(PꢀP)] (PꢀP = dppf, X = Cl, R = Cy
3. Conclusion
t
(3b), Bu (3c), 2,6-C6H3Me2 (3d), (S)-(ꢀ)-C(H)MePh
In summary, in this paper we have described an efficient
and straightforward synthetic protocol for the stereoselec-
tive preparation of novel carbonyl–isocyanide and
dicarbonyl–ruthenium(II) complexes, namely cis,cis-
[RuX2(CNR)(CO)(PꢀP)] (PꢀP = dppf, dippf; X = Cl, Br;
(3e); PꢀP = dppf, X = Br, R = Bn (4a), Cy (4b), tBu (4c),
2,6-C6H3Me2 (4d), (S)-(ꢀ)-C(H)MePh (4e);
t
PꢀP = dippf, X = Cl, R = Bn (5a), Cy (5b), Bu (5c),
2,6-C6H3Me2 (5d), (S)-(ꢀ)-C(H)MePh (5e);
t
PꢀP = dippf, X = Br, R = Bn (6a), Cy (6b), Bu (6c),
t
R = Bn, Cy, Bu, 2,6-C6H3Me2, (S)-(ꢀ)-C(H)MePh; 3–
2,6-C6H3Me2 (6d), (S)-(ꢀ)-C(H)MePh (6e))
6a–e) and cis,cis,cis-[RuX2(CO)2(PꢀP)] (PꢀP = dppf, dippf;
X = Cl, Br; 7–8a–b), by the reaction of the readily available
dimers [{RuX(l-X)(CO)(PꢀP)}2] (1–2a–b) [11] with an
excess of the appropriate isocyanide or carbon monoxide,
respectively. All the complexes tested have proven to be
active catalysts for the transfer hydrogenation of acetophe-
none using 2-propanol as hydrogen source. Nevertheless,
their catalytic performances are lower than those of the
closely related bis(isocyanide) complexes trans,cis,cis-
[RuX2(CNR)2(dppf)] (I in Fig. 1) previously reported by
us [6], probably due to the instability of the corresponding
catalytic active dihydride species in the strong basic media
required for this transformation. In addition, both the car-
bonyl–isocyanide (3–6a–e) and dicarbonyl–ruthenium(II)
(7–8a, b) derivatives have shown to be efficient catalysts
A solution of the corresponding dimeric precursor
[{RuX(l-X)(CO)(PꢀP)}2] (1–2a–b; 0.5 mmol) in 30 ml of
THF was treated, at 70 ꢂC (3b–e and 4a–e) or at room tem-
perature (5–6a–e), with the appropriate isocyanide
(1.1 mmol) for 3 h. The solvent was then removed under
reduced pressure and the resulting yellow-orange solid res-
idue washed with hexanes (3 · 30 ml) and vacuum-dried.
Compounds 3e, 4e, 5e, and 6e have obtained as a non-sep-
arable mixture of two diastereoisomers in ca. 1:1 ratio.
Compound 3b: Yield: 97% (0.837 g). Anal. Calc. for
FeRuC42H39Cl2P2NO (863.53 g molꢀ1): C, 58.42; H, 4.55;
1
N, 1.62. Found: C, 58.76; H, 4.36; N, 1.57%; H NMR
(CD2Cl2): d 1.26–1.81 (m, 10H, CH2), 3.64 (m, 1H,
NCH), 4.19, 4.25, 4.29 and 4.58 (br, 2H each, C5H4),

5240
J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
7.28–8.31 (m, 20H, Ph) ppm; 13C{1H} NMR (CD2Cl2)
7.34–8.27 (m, 20H, Ph) ppm; 13C{1H} NMR (CD2Cl2)
d = 21.8, 24.3 and 31.4 (s, CH2), 54.1 (s, NCH), 70.9,
d = 23.3, 25.6 and 33.2 (s, CH2), 55.8 (s, NCH), 71.7,
2
2
71.4, 71.6 and 76.3 (d, JCP = 5.5 Hz, CH of C5H4), 74.1,
71.8, 72.3 and 76.9 (d, JCP = 5.3 Hz, CH of C5H4), 74.4,
3
3
74.6, 76.9 and 77.7 (d, JCP = 8.6 Hz, CH of C5H4), 78.5
74.7, 77.4 and 78.6 (d, JCP = 8.1 Hz, CH of C5H4), 80.2
1
1
and 79.1 (d, JCP = 52.8 Hz, C of C5H4), 126.4–136.3 (m,
and 80.9 (d, JCP = 52.9 Hz, C of C5H4), 127.4–137.2
2
2
Ph and RuCN), 197.4 (dd, JCP = 12.9 and 12.9 Hz, CO)
(m, Ph and RuCN), 198.7 (dd, JCP = 12.1 and 12.1 Hz,
ppm.
CO) ppm.
Compound 3c: Yield: 93% (0.779 g). Anal. Calc. for
FeRuC40H37Cl2P2NO (837.50 g molꢀ1): C, 57.36; H, 4.45;
N, 1.67. Found: C, 57.54; H, 4.21; N, 1.70%; H NMR
Compound 4c: Yield: 86% (0.797 g). Anal. Calc. for
FeRuC40H37Br2P2NO (926.40 g molꢀ1): C, 51.86; H, 4.03;
N, 1.51. Found: C, 52.08; H, 3.77; N, 1.52%; H NMR
1
1
(CD2Cl2) d = 1.25 (s, 9H, CH3), 4.20, 4.26, 4.29 and 4.56
(br, 2H each, C5H4), 7.23–8.30 (m, 20H, Ph) ppm;
13C{1H} NMR (CD2Cl2) d = 30.3 (s, CH3), 58.2 (s,
(CD2Cl2) d = 1.26 (s, 9H, CH3), 4.26, 4.29, 4.54 and 4.63
(br, 2H each, C5H4), 7.25–8.28 (m, 20H, Ph) ppm;
13C{1H} NMR (CD2Cl2) d = 30.2 (s, CH3), 58.3
2
2
C(CH3)3), 71.3, 71.7, 71.9 and 76.6 (d, JCP = 5.9 Hz, CH
(s, C(CH3)3), 71.6, 71.7, 72.1 and 76.6 (d, JCP = 5.2 Hz,
3
3
of C5H4), 74.4, 74.7, 77.2 and 77.9 (d, JCP = 8.5 Hz, CH
CH of C5H4), 74.2, 74.4, 77.2 and 78.1 (d, JCP = 8.7 Hz,
1
1
of C5H4), 79.4 and 80.1 (d, JCP = 52.1 Hz, C of C5H4),
CH of C5H4), 80.2 and 80.8 (d, JCP = 55.1 Hz, C of
2
127.3–137.5 (m, Ph and RuCN), 198.3 (dd, JCP = 13.2
C5H4), 127.1–137.0 (m, Ph and RuCN), 198.3 (dd,
2JCP = 12.1 and 12.1 Hz, CO) ppm.
and 13.2 Hz, CO) ppm.
Compound 3d: Yield: 92% (0.815 g). Anal. Calc. for
FeRuC44H37Cl2P2NO (885.54 g molꢀ1): C, 59.68; H, 4.21;
N, 1.58. Found: C, 59.93; H, 3.97; N, 1.62%; H NMR
Compound 4d: Yield: 84% (0.818 g). Anal. Calc. for
FeRuC44H37Br2P2NO (974.44 g molꢀ1): C, 54.23; H, 3.83;
N, 1.44. Found: C, 54.56; H, 3.61; N, 1.46%; H NMR
1
1
(CD2Cl2) d = 2.13 (s, 6H, CH3), 4.16, 4.26, 4.31 and 4.63
(br, 2H each, C5H4), 6.99–8.42 (m, 23H, Ph) ppm;
13C{1H} NMR (CD2Cl2) d = 18.7 (s, CH3), 71.2, 71.8,
(CD2Cl2) d = 2.15 (s, 6H, CH3), 4.24, 4.29, 4.36 and 4.59
(br, 2H each, C5H4), 6.99–8.33 (m, 23H, Ph) ppm;
13C{1H} NMR (CD2Cl2) d = 18.8 (s, CH3), 71.3, 71.6,
2
2
72.1 and 76.8 (d, JCP = 5.4 Hz, CH of C5H4), 74.5, 75.1,
72.0 and 76.8 (d, JCP = 5.5 Hz, CH of C5H4), 74.4, 74.7,
3
3
77.2 and 78.2 (d, JCP = 8.7 Hz, CH of C5H4), 79.4 and
77.2 and 78.6 (d, JCP = 8.2 Hz, CH of C5H4), 79.8 and
1
1
79.6 (d, JCP = 53.6 Hz, C of C5H4), 127.4–137.6 (m, Ph
80.9 (d, JCP = 52.9 Hz, C of C5H4), 127.2–136.6 (m, Ph
and RuCN), 198.1 (dd, 2JCP = 13.1 and 13.1 Hz, CO) ppm.
Compound 3e: Yield: 94% (0.832 g). Anal. Calc. for
FeRuC44H37Cl2P2NO (885.54 g molꢀ1): C, 59.68; H, 4.21;
and RuCN), 198.1 (dd, 2JCP = 12.1 and 12.1 Hz, CO) ppm.
Compound 4e: Yield: 90% (0.877 g). Anal. Calc. for
FeRuC44H37Br2P2NO (974.44 g molꢀ1): C, 54.23; H, 3.83;
1
1
N, 1.58. Found: C, 59.82; H, 4.48; N, 1.61%; H NMR
N, 1.44. Found: C, 54.45; H, 3.90; N, 1.40%; H NMR
3
3
(CD2Cl2) d = 1.39 and 1.52 (d, 3H each, JHH = 6.8 Hz,
(CD2Cl2) d = 1.41 and 1.55 (d, 3H each, JHH = 6.7 Hz,
CH3), 4.18, 4.19, 4.21, 4.25, 4.29, 4.32, 4.56 and 4.58
(br, 2H each, C5H4), 4.59 and 4.73 (q, 1H each,
3JHH = 6.8 Hz, NCH), 7.15–8.37 (m, 50H, Ph) ppm;
13C{1H} NMR (CD2Cl2) d = 25.0 and 25.4 (s, CH3), 56.6
and 56.7 (s, NCH), 71.2, 71.3, 71.6, 71.7, 71.8, 72.0, 76.5
CH3), 4.23, 4.26, 4.29, 4.42, 4.49, 4.53, 4.57 and 4.60 (br,
2H each, C5H4), 4.69 and 4.76 (q, 1H each, 3JHH = 6.7 Hz,
NCH), 7.16–8.36 (m, 50H, Ph) ppm; 13C{1H} NMR
(CD2Cl2) d = 25.4 and 25.6 (s, CH3), 57.0 and 57.2
(s, NCH), 71.6, 71.7, 71.9, 72.0, 72.2, 72.4, 76.8 and 77.0
2
2
and 76.7 (d, JCP = 5.7 Hz, CH of C5H4), 74.4, 74.5,
(d, JCP = 5.2 Hz, CH of C5H4), 74.6, 74.7, 74.8, 74.9,
3
3
74.8, 74.9, 77.1, 77.2, 77.5 and 78.0 (d, JCP = 8.4 Hz,
77.4, 77.5, 77.6 and 77.7 (d, JCP = 8.8 Hz, CH of C5H4),
1
1
CH of C5H4), 78.1, 78.7, 79.3 and 79.9 (d, JCP = 52.4 Hz,
78.5, 78.6, 79.3 and 80.1 (d, JCP = 53.6 Hz, C of C5H4),
C of C5H4), 126.0–139.0 (m, Ph and RuCN), 198.1 and
198.5 (dd, JCP = 12.4 and 12.4 Hz, CO) ppm.
126.2–139.0 (m, Ph and RuCN), 197.9 and 198.6 (dd,
2JCP = 13.6 and 13.6 Hz, CO) ppm.
2
Compound 4a: Yield: 85% (0.816 g). Anal. Calc. for
Compound 5a: Yield: 85% (0.625 g). Anal. Calc. for
FeRuC31H43Cl2P2NO (735.45 g molꢀ1): C, 50.63; H, 5.89;
N, 1.90. Found: C, 50.94; H, 5.53; N, 2.01%; H NMR
FeRuC43H35Br2P2NO (960.41 g molꢀ1): C, 53.77; H, 3.67;
1
1
N, 1.46. Found: C, 54.09; H, 3.41; N, 1.51%; H NMR
(CD2Cl2) d = 4.24, 4.29, 4.41, 4.55 and 4.60 (br, 2H each,
C5H4 and NCH2), 7.24–8.37 (m, 25H, Ph) ppm; 13C{1H}
NMR (CD2Cl2) d = 48.4 (s, NCH2), 71.6, 71.9, 72.2 and
(CD2Cl2) d = 1.27 (m, 24H, CH(CH3)2), 2.36, 2.58, 2.92
and 3.11 (m, 1H each, CH(CH3)2), 4.36, 4.51, 4.69, 4.77
and 4.91 (br, 2H each, C5H4 and NCH2), 7.36–7.52
(m, 5H, Ph) ppm; 13C{1H} NMR (CD2Cl2) d = 19.2,
19.6, 20.0, 20.2, 20.3, 20.4, 20.5 and 20.9 (s, CH(CH3)2),
2
76.9 (d, JCP = 5.7 Hz, CH of C5H4), 74.7, 74.9, 77.4 and
3
78.7 (d, JCP = 8.8 Hz, CH of C5H4), 80.0 and 81.3
1
1
(d, JCP = 52.0 Hz, C of C5H4), 127.3–136.9 (m, Ph and
25.9, 26.3, 30.2 and 31.6 (d, JCP = 23.4 Hz, CH(CH3)2),
2
RuCN), 198.5 (d, JCP = 12.3 and 12.3 Hz, CO) ppm.
49.0 (s, NCH2), 71.2, 71.7, 72.0 and 76.7 (d, 2JCP = 5.1 Hz,
3
Compound 4b: Yield: 89% (0.848 g). Anal. Calc. for
CH of C5H4), 72.4, 75.0, 77.2 and 78.2 (d, JCP = 8.7 Hz,
FeRuC42H39Br2P2NO (952.44 g molꢀ1): C, 52.96; H, 4.13;
CH of C5H4), 79.1 and 79.7 (d, JCP = 41.5 Hz, C of
1
1
2
N, 1.47. Found: C, 53.18; H, 3.86; N, 1.49%; H NMR
C5H4), 127.2–132.3 (m, Ph), 147.2 (dd, JCP = 120.7 and
2
(CD2Cl2) d = 1.34–1.86 (m, 10H, CH2), 3.68 (m, 1H,
21.8 Hz, RuCN), 199.9 (dd, JCP = 13.6 and 13.6 Hz,
NCH), 4.25, 4.28, 4.41 and 4.55 (br, 2H each, C5H4),
CO) ppm.

J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
5241
Compound 5b: Yield: 82% (0.596 g). Anal. Calc. for
57.9 (s, NCH), 71.2, 71.5, 71.6, 71.7, 71.8, 71.9, 75.4 and
2
FeRuC30H47Cl2P2NO (727.47 g molꢀ1): C, 49.53; H, 6.51;
75.5 (d, JCP = 5.6 Hz, CH of C5H4), 72.0, 72.1, 73.9,
1
3
N, 1.93. Found: C, 49.78; H, 6.32; N, 1.89%; H NMR
74.1, 75.6, 75.8, 76.0 and 76.1 (d, JCP = 7.7 Hz, CH of
1
(CD2Cl2) d = 1.65 (m, 34H, CH(CH3)2 and CH2), 2.48,
2.71, 2.89 and 3.18 (m, 1H each, CH(CH3)2), 3.89
(m, 1H, NCH), 4.38, 4.47, 4.67 and 4.80 (br, 2H each,
C5H4) ppm; 13C{1H} NMR (CD2Cl2) d = 19.0, 20.0,
20.3, 20.4, 20.5, 20.6, 21.3 and 22.7 (s, CH(CH3)2), 23.4,
25.3 and 32.4 (s, CH2), 25.8, 26.3, 30.2 and 31.6
C5H4), 78.9, 79.1, 80.2 and 80.4 (d, JCP = 43.3 Hz, C of
2
C5H4), 126.2–132.1 (m, Ph), 139.2 and 140.1 (dd, JCP
=
=
2
119.8 and 21.6 Hz, RuCN), 199.5 and 200.2 (dd, JCP
12.4 and 12.4 Hz, CO) ppm.
Compound 6a: Yield: 87% (0.717 g). Anal. Calc. for
FeRuC31H43Br2P2NO (824.35 g molꢀ1): C, 45.17; H, 5.26;
1
1
(d, JCP = 25.4 Hz, CH(CH3)2), 55.4 (s, NCH), 71.2, 71.5,
N, 1.70. Found: C, 45.32; H, 5.06; N, 1.81%; H NMR
2
71.6 and 75.1 (d, JCP = 5.3 Hz, CH of C5H4), 71.9, 73.6,
(CD2Cl2) d = 1.36 (m, 24H, CH(CH3)2), 2.44, 2.71, 2.78
and 3.23 (m, 1H each, CH(CH3)2), 4.35, 4.38, 4.42, 4.70
and 4.97 (br, 2H each, C5H4 and NCH2), 7.28–7.54 (m,
5H, Ph) ppm; 13C{1H} NMR (CD2Cl2) d = 19.5, 19.8,
20.2, 20.3, 20.6, 20.7, 20.8 and 21.2 (s, CH(CH3)2), 26.8,
3
75.6 and 75.8 (d, JCP = 8.4 Hz, CH of C5H4), 79.4 and
1
2
79.9 (d, JCP = 42.7 Hz, C of C5H4), 143.4 (dd, JCP
=
2
119.3 and 22.4 Hz, RuCN), 200.1 (dd, JCP = 12.1 and
12.1 Hz, CO) ppm.
1
Compound 5c: Yield: 80% (0.561 g). Anal. Calc. for
FeRuC28H45Cl2P2NO (701.43 g molꢀ1): C, 47.94; H, 6.47;
27.9, 30.9 and 33.8 (d, JCP = 21.8 Hz, CH(CH3)2), 49.1
2
(s, NCH2), 70.9, 71.3, 71.6 and 75.5 (d, JCP = 5.8 Hz,
1
3
N, 2.00. Found: C, 47.95; H, 6.43; N, 2.11%; H NMR
CH of C5H4), 72.3, 74.0, 75.9 and 76.0 (d, JCP = 8.3 Hz,
1
(CD2Cl2) d = 1.32 (m, 24H, CH(CH3)2), 1.54 (s, 9H,
C(CH3)), 2.49, 2.74, 2.91 and 3.19 (m, 1H each,
CH(CH3)2), 4.39, 4.47, 4.69 and 4.81 (br, 2H each, C5H4)
ppm; 13C{1H} NMR (CD2Cl2) d = 19.5, 19.6, 19.7, 19.7,
19.9, 20.2, 20.5 and 20.6 (s, CH(CH3)2), 25.8, 26.3,
CH of C5H4), 79.6 and 80.2 (d, JCP = 42.7 Hz, C of
2
C5H4), 127.8–138.8 (m, Ph), 145.4 (dd, JCP = 121.5 and
2
23.1 Hz, RuCN), 199.6 (dd, JCP = 12.8 and 12.8 Hz,
CO) ppm.
Compound 6b: Yield: 88% (0.718 g). Anal. Calc. for
FeRuC30H47Br2P2NO (816.37 g molꢀ1): C, 44.14; H, 5.80;
1
30.2 and 31.8 (d, JCP = 23.1 Hz, CH(CH3)2), 30.5
1
(s, C(CH3)3), 58.3 (s, C(CH3)3), 71.2, 71.4, 72.1 and 76.6
N, 1.72. Found: C, 44.31; H, 5.53; N, 1.80%; H NMR
2
(d, JCP = 5.9 Hz, CH of C5H4), 74.4, 75.2, 77.1 and 78.3
(CD2Cl2) d = 1.57 (m, 34H, CH(CH3)2 and CH2), 2.57,
2.87, 2.94 and 3.24 (m, 1H each, CH(CH3)2), 4.01 (m,
1H, NCH), 4.39, 4.51, 4.70 and 4.98 (br, 2H each, C5H4)
ppm; 13C{1H} NMR (CD2Cl2) d = 18.9, 19.3, 19.9, 20.5,
20.6, 20.7, 20.8 and 21.3 (s, CH(CH3)2), 23.0, 24.9 and
3
1
(d, JCP = 7.5 Hz, CH of C5H4), 79.5 and 80.1 (d, JCP
=
2
40.9 Hz,
C of C5H4), 142.6 (dd, JCP = 121.8 and
2
24.1 Hz, RuCN), 200.1 (dd, JCP = 14.0 and 14.0 Hz,
CO) ppm.
1
Compound 5d: Yield: 81% (0.607 g). Anal. Calc. for
FeRuC32H45Cl2P2NO (749.47 g molꢀ1): C, 51.28; H, 6.05;
32.4 (s, CH2), 26.3, 27.5, 30.4 and 33.6 (d, JCP = 22.7 Hz,
CH(CH3)2), 55.4 (s, NCH), 70.5, 70.8, 71.0 and 74.7
1
2
N, 1.87. Found: C, 51.53; H, 5.84; N, 1.98%; H NMR
(d, JCP = 5.9 Hz, CH of C5H4), 71.9, 73.6, 75.5 and 75.7
3
1
(CD2Cl2) d = 1.38 (m, 24H, CH(CH3)2), 2.31, 2.79, 2.96
and 3.28 (m, 1H each, CH(CH3)2), 2.56 (s, 6H, CH3),
4.42, 4.46, 4.75 and 4.85 (br, 2H each, C5H4), 7.03–7.36
(m, 3H, Ph) ppm; 13C{1H} NMR (CD2Cl2) d = 18.9,
19.1, 19.6, 19.7, 20.0, 20.5, 20.7 and 21.1 (s, CH(CH3)2),
(d, JCP = 8.9 Hz, CH of C5H4), 78.5 and 80.2 (d, JCP =
2
43.4 Hz,
C of C5H4), 138.2 (dd, JCP = 122.5 and
2
25.1 Hz, RuCN), 199.7 (dd, JCP = 13.4 and 13.4 Hz,
CO) ppm.
Compound 6c: Yield: 93% (0.735 g). Anal. Calc. for
FeRuC28H45Br2P2NO (790.33 g molꢀ1): C, 42.55; H, 5.74;
1
19.4 (s, CH3), 26.3, 26.4, 30.4 and 31.7 (d, JCP = 25.7 Hz,
CH(CH3)2), 71.4, 71.4, 71.8 and 73.9 (d, 2JCP = 5.2 Hz, CH
of C5H4), 71.9, 75.2, 75.5 and 75.9 (d, 3JCP = 8.1 Hz, CH of
N, 1.77. Found: C, 42.81; H, 5.63; N, 1.92%; H NMR
1
(CD2Cl2) d = 1.29 (m, 24H, CH(CH3)2), 1.57 (s, 9H,
C(CH3)), 2.58, 2.85, 2.98 and 3.24 (m, 1H each,
CH(CH3)2), 4.35, 4.39, 4.68 and 4.98 (br, 2H each, C5H4)
ppm; 13C{1H} NMR (CD2Cl2) d = 19.7, 20.1, 20.2, 20.3,
20.7, 20.8, 20.9 and 21.8 (s, CH(CH3)2), 26.7, 27.9,
1
C5H4), 78.8 and 79.4 (d, JCP = 41.8 Hz, C of C5H4),
2
128.4–136.6 (m, Ph), 147.2 (dd, JCP = 122.3 and 23.2 Hz,
2
RuCN), 199.9 (dd, JCP = 13.6 and 13.6 Hz, CO) ppm.
Compound 5e: Yield: 75% (0.562 g). Anal. Calc. for
FeRuC32H45Cl2P2NO (749.47 g molꢀ1): C, 51.28; H, 6.05;
31.2 and 34.2 (d, JCP = 25.6 Hz, CH(CH3)2), 30.4
1
1
N, 1.87. Found: C, 51.41; H, 6.34; N, 1.94%; H NMR
(s, C(CH3)3), 58.6 (s, C(CH3)3), 70.9, 71.4, 71.6 and 74.0
2
(CD2Cl2) d = 1.36 (m, 48H, CH(CH3)2), 1.47 and 1.81 (d,
(d, JCP = 5.3 Hz, CH of C5H4), 72.3, 75.4, 75.9 and 76.1
3
3
1
3H each, JHH = 6.9 Hz, CH3), 2.37, 2.51, 2.69, 2.72,
(d, JCP = 9.0 Hz, CH of C5H4), 79.9 and 80.4 (d, JCP =
2
2.82, 2.85, 3.23 and 3.34 (m, 1H each, CH(CH3)2), 4.27,
40.5 Hz, C of C5H4), 141.6 (dd, JCP = 122.6 and
22.7 Hz, RuCN), 199.8 (dd, JCP = 12.8 and 12.8 Hz,
CO) ppm.
2
4.32, 4.39, 4.48, 4.61, 4.67, 4.73 and 4.81 (br, 2H each,
3
C5H4), 4.95 and 5.23 (q, 1H each, JHH = 6.9 Hz, NCH),
7.27–7.61 (m, 10H, Ph) ppm; 13C{1H} NMR (CD2Cl2)
d = 18.9, 19.1, 19.3, 19.5, 19.8, 19.9, 20.0, 20.2, 20.3,
20.4, 20.5, 20.7, 20.8, 20.9, 21.1 and 21.3 (s, CH(CH3)2),
24.3 and 25.4 (s, CH3), 24.6, 24.8, 26.5, 26.7, 30.2, 30.3,
Compound 6d: Yield: 96% (0.805 g). Anal. Calc. for
FeRuC32H45Br2P2NO (838.38 g molꢀ1): C, 45.84; H, 5.41;
1
N, 1.67. Found: C, 46.08; H, 5.23; N, 1.68%; H NMR
(CD2Cl2) d = 1.26 (m, 24H, CH(CH3)2), 2.54, 2.87, 2.95
and 3.27 (m, 1H each, CH(CH3)2), 2.59 (s, 6H, CH3),
1
32.2 and 32.8 (d, JCP = 23.9 Hz, CH(CH3)2), 57.4 and

5242
J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
4.41, 4.46, 4.78 and 5.07 (br, 2H each, C5H4), 7.11–7.21 (m,
3H, Ph) ppm; 13C{1H} NMR (CD2Cl2) d = 19.1, 19.7,
20.3, 20.4, 20.5, 20.9, 21.0 and 21.5 (s, CH(CH3)2), 19.5
CH(CH3)2), 4.28, 4.34, 4.56 and 4.82 (br, 2H each, C5H4)
ppm; 13C{1H} NMR (CD2Cl2) d = 18.4, 18.5, 18.6, 18.7,
19.3, 19.4, 19.8 and 20.2 (s, CH(CH3)2), 24.7, 25.4, 29.9
1
1
(s, CH3), 26.8, 27.9, 31.3 and 33.9 (d, JCP = 22.8 Hz,
and 31.6 (d, JCP = 25.7 Hz, CH(CH3)2), 70.7, 71.2, 71.3
2
2
CH(CH3)2), 70.9, 71.0, 71.6 and 74.1 (d, JCP = 5.9 Hz,
and 73.1 (d, JCP = 5.5 Hz, CH of C5H4), 71.8, 74.3,
3
3
CH of C5H4), 72.4, 75.6, 75.7 and 76.1 (d, JCP = 8.7 Hz,
75.2 and 75.3 (d, JCP = 8.6 Hz, CH of C5H4), 76.8 and
1
1
2
CH of C5H4), 79.6 and 80.2 (d, JCP = 42.2 Hz, C of
77.4 (d, JCP = 43.5 Hz, C of C5H4), 191.3 (dd, JCP =
2
2
C5H4), 128.0–136.1 (m, Ph), 156.0 (dd, JCP = 119.9 and
113.3 and 12.8 Hz, CO), 196.0 (dd, JCP = 14.4 and
12.1 Hz, CO) ppm.
2
21.9 Hz, RuCN), 199.6 (dd, JCP = 12.8 and 12.8 Hz,
CO) ppm.
Compound 8b: Yield: 87% (0.639 g). Anal. Calc. for
FeRuC24H36Br2O2P2 (735.21 g molꢀ1): C, 39.21; H, 4.94.
Found: C, 39.07; H, 5.13%; H NMR (CD2Cl2) d = 1.32
Compound 6e: Yield: 86% (0.721 g). Anal. Calc. for
FeRuC32H45Br2P2NO (838.38 g molꢀ1): C, 45.84; H, 5.41;
N, 1.67. Found: C, 46.11; H, 5.27; N, 1.85%; H NMR
(CD2Cl2) d = 1.28 (m, 48H, CH(CH3)2), 1.44 and 1.80
(d, 3H each, JHH = 6.2 Hz, CH3), 2.48, 2.50, 2.83, 2.86,
1
1
(m, 24H, CH(CH3)2), 2.61, 2.89, 2.97 and 3.30 (m, 1H each,
CH(CH3)2), 4.39, 4.43, 4.47 and 4.70 (br, 2H each, C5H4)
ppm; 13C{1H} NMR (CD2Cl2) d = 19.4, 19.5, 20.5, 20.6,
20.9, 21.2, 21.4 and 21.9 (s, CH(CH3)2), 26.6, 28.1, 32.2
3
2.90, 2.94, 3.21 and 3.30 (m, 1H each, CH(CH3)2), 4.34,
4.36, 4.39, 4.42, 4.63, 4.69, 4.94 and 4.98 (br, 2H each,
1
and 34.9 (d, JCP = 26.4 Hz, CH(CH3)2), 71.9, 72.2, 72.4
3
2
C5H4), 5.20 and 5.24 (q, 1H each, JHH = 6.2 Hz, NCH),
and 74.8 (d, JCP = 5.3 Hz, CH of C5H4), 73.5, 75.8,
7.32–7.54 (m, 10H, Ph) ppm; 13C{1H} NMR (CD2Cl2)
d = 19.8 (2C), 19.9 (2C), 20.0, 20.1, 20.2, 20.3 (2C), 20.4,
20.5, 20.7, 20.8 (2C), 21.4 and 21.4 (s, CH(CH3)2), 24.5
and 24.7 (s, CH3), 26.7, 26.8, 27.9, 28.0, 31.0, 31.1, 33.7
76.6 and 76.7 (d, JCP = 8.3 Hz, CH of C5H4), 78.5 and
3
1
2
79.0 (d, JCP = 44.7 Hz, C of C5H4), 192.5 (dd, JCP
=
2
110.3 and 12.1 Hz, CO), 196.5 (dd, JCP = 14.3 and
11.3 Hz, CO) ppm.
1
and 34.1 (d, JCP = 22.3 Hz, CH(CH3)2), 57.2 and 57.3
(s, NCH), 71.0, 71.1, 71.3 (2C), 71.6 (2C) and 74.0 (2C)
4.4. General procedure for the catalytic transfer
hydrogenation of acetophenone
2
(d, JCP = 5.3 Hz, CH of C5H4), 72.3 (2C), 75.5 (2C),
3
75.8 (2C) and 76.0 (2C) (d, JCP = 8.2 Hz, CH of C5H4),
1
79.7, 79.8, 80.2 and 80.3 (d, JCP = 42.7 Hz, C of C5H4),
Under inert atmosphere, acetophenone (5 mmol), the
ruthenium catalyst precursor (0.02 mmol; 0.4 mol% of
Ru), and 45 ml of propan-2-ol were introduced into a
Schlenk tube fitted with a condenser and heated at 82 ꢂC
for 10 min. NaOH was then added (5 ml of a 0.096 M solu-
tion in propan-2-ol; 9.6 mol%). The course of the reaction
was monitored by regular sampling and analysis by gas
chromatography. 1-Phenylethanol and acetophenone were
the only products detected in all cases. The identity of the
resulting 1-phenylethanol was assessed by comparison with
commercially available pure sample.
2
125.7–138.7 (m, Ph), 144.1 and 144.4 (dd, JCP = 121.3
2
and 23.1 Hz, RuCN), 199.6 and 199.9 (dd, JCP = 13.0
and 13.0 Hz, CO) ppm.
4.3. Synthesis of dicarbonyl complexes cis,cis,cis-
[RuX2(CO)2(PꢀP)] (PꢀP = dppf, X = Br (7b);
PꢀP = dippf, X = Cl (8a), Br (8b))
Carbon monoxide was bubbled at 65 ꢂC through a
solution of the corresponding dimeric species [{RuX-
(l-X)(CO)(PꢀP)}2] (1–2a–b; 0.5 mmol) in 70 ml of THF
for 5 h (7b) or 15 min (8a–b). After removing the solvent
under reduced pressure, diethyl ether (50 ml) was added
to the residue, yielding the precipitation of a yellow solid,
which was filtered off, washed with diethyl ether
(2 · 50 ml), and vacuum-dried.
4.5. General procedure for the catalytic cycloisomerization
of (Z)-3-methyl-2-penten-4-yn-1-ol
(Z)-3-Methylpent-2-en-4-yn-1-ol (5 mmol) and the cor-
responding ruthenium catalyst precursor (0.05 mmol;
1.0 mol% of Ru) were introduced into a sealed tube under
inert atmosphere. The reaction mixture was then heated at
75 ꢂC for the indicated time (see Table 4). The course of the
reaction was monitored by regular sampling and analysis
by gas chromatography. 2,3-Dimethylfuran and (Z)-3-
methylpent-2-en-4-yn-1-ol were the only products detected
in all cases. The identity of the resulting 2,3-dimethylfuran
was assessed by comparison with a commercially available
pure sample.
Compound 7b: Yield: 84% (0.732 g). Anal. Calc. for
FeRuC36H28Br2O2P2 (871.28 g molꢀ1): C, 49.63; H, 3.24.
1
Found: C, 49.87; H, 3.13%; H NMR (CD2Cl2) d = 4.28,
4.40, 4.63 and 4.66 (br, 2H each, C5H4), 7.29–8.30
(m, 20H, Ph) ppm; 13C{1H} NMR (CD2Cl2) d = 71.7,
2
72.4, 72.5 and 77.2 (d, JCP = 5.3 Hz, CH of C5H4), 74.4,
3
75.4, 77.3 and 78.4 (d, JCP = 8.3 Hz, CH of C5H4), 77.9
1
and 79.1 (d, JCP = 45.3 Hz, C of C5H4), 127.3–136.5 (m,
2
Ph), 189.7 (dd, JCP = 120.5 and 9.8 Hz, CO), 195.1 (dd,
2JCP = 13.6 and 11.3 Hz, CO) ppm.
Compound 8a: Yield: 79% (0.510 g). Anal. Calc. for
FeRuC24H36Cl2O2P2 (646.31 g molꢀ1): C, 44.60; H, 5.61.
Found: C, 44.42; H, 5.87%; H NMR (CD2Cl2) d = 1.24
Acknowledgments
1
This work was supported by the Ministerio de Educa-
´
cion y Ciencia (MEC) of Spain (Project CTQ2006-08485/
(m, 24H, CH(CH3)2), 2.41, 2.73, 2.91 and 3.12 (m, 1H each,

J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
5243
[9] (a) Examples of highly efficient ruthenium precatalysts lacking Ru–
NH2R units can be found in: H. Yang, M. Alvarez-Gressier, N.
Lugan, R. Mathieu, Organometallics 16 (1997) 1401;
(b) P. Braunstein, M.D. Fryzuk, F. Naud, S.J. Rettig, J. Chem. Soc.,
Dalton Trans. (1999) 589;
BQU and Consolider Ingenio 2010 (CSD2007-00006)) and
the Gobierno del Principado de Asturias (FICYT project
IB05-035). S.E.G.G. and V.C. thank MEC and the Euro-
pean Social Fund for the award of a Ph.D. grant and a
´
‘‘Ramon y Cajal’’ contract, respectively. J.A. (from the
(c) Y. Nishibayashi, I. Takei, S. Uemura, M. Hidai, Organometallics
18 (1999) 2291;
(d) P. Dani, T. Karlen, R.A. Gossage, S. Gladiali, G. van Koten,
Angew. Chem., Int. Ed. 39 (2000) 743;
University of Hamburg, Germany) thanks the Erasmus
Program.
´
(e) P. Crochet, J. Gimeno, S. Garcıa-Granda, J. Borge, Organomet-
allics 20 (2001) 4369;
References
(f) D. Cuervo, M.P. Gamasa, J. Gimeno, Chem. Eur. J. 10 (2004)
425;
(g) M.T. Reetz, X. Li, J. Am. Chem. Soc. 128 (2006) 1044;
(h) R.J. Lundgren, M.A. Rankin, R. McDonald, G. Schatte, M.
Stradiotto, Angew. Chem., Int. Ed. 46 (2007) 4732.
[1] (a) For reviews covering this field, see: C. Bruneau, P.H. Dixneuf,
Chem. Commun. (1997) 507;
(b) T. Naota, H. Takaya, S.-I. Murahashi, Chem. Rev. 98 (1998)
2599;
(c) B.M. Trost, F.D. Toste, A.B. Pinkerton, Chem. Rev. 101 (2001)
2067;
(d) T.M. Trnka, R.H. Grubbs, Acc. Chem. Res. 34 (2001) 18;
(e) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev. 102 (2002) 1731;
(f) B.M. Trost, M.U. Fredericksen, M.T. Rudd, Angew. Chem., Int.
Ed. 44 (2005) 6630;
[10] (a) For reviews on the coordination chemistry of dppf and related
ferrocenyl-diphosphines, see: K.S. Gan, T.S.A. Hor, in: A. Togni, T.
Hayashi (Eds.), Ferrocenes: Homogeneous Catalysis, Organic Syn-
thesis and Material Science, Wiley–VCH, Weinheim, 1995, p. 3;
(b) G. Bandoli, A. Dolmella, Coord. Chem. Rev. 209 (2000) 161;
(c) T.J. Colacot, Platinum Metals Rev. 45 (2001) 22.
[11] We note that the dimeric precursors 1–2a–b are also active precat-
alysts for transfer hydrogenation reactions. V. Cadierno, P. Crochet,
(g) C. Bruneau, P.H. Dixneuf, Angew. Chem., Int. Ed. 45 (2006)
2176.
[2] (a) For books covering this field, see: S.-I. Murahashi (Ed.),
Ruthenium in Organic Synthesis, Wiley–VCH, Weinheim, 2004;
(b) C. Bruneau, P.H. Dixneuf (Eds.), Ruthenium Catalysts and Fine
Chemistry, Topics in Organometallic Chemistry, vol. 11, Springer,
Berlin, 2004.
´
´
´
J. Dıez, S.E. Garcıa-Garrido, J. Gimeno, S. Garcıa-Granda, Organo-
metallics 22 (2003) 5226.
´
´
´
[12] (a) V. Cadierno, P. Crochet, J. Garcıa-Alvarez, S.E. Garcıa-Garrido,
J. Gimeno, J. Organomet. Chem. 663 (2002) 32;
(b) P. Crochet, J. Gimeno, J. Borge, S. Garcıa-Granda, New J.
´
[3] J. Gimeno (Guest Ed.), Ruthenium catalyzed processes, Curr. Org.
Chem. 10 (2006) 113–225 (a thematic issue devoted to this topic).
[4] (a) For reviews and accounts on transition-metal-catalyzed transfer
hydrogenation of ketones, see: G. Zassinovich, G. Mestroni, S.
Gladiali, Chem. Rev. 92 (1992) 1051;
Chem. 27 (2003) 414;
(c) P. Crochet, M.A. Fernandez-Zumel, C. Beauquis, J. Gimeno,
´
Inorg. Chim. Acta 356 (2003) 114;
´
´
´
´
(d) V. Cadierno, P. Crochet, J. Dıez, J. Garcıa-Alvarez, S.E. Garcıa-
Garrido, J. Gimeno, S. Garc´ıa-Granda, M.A. Rodr´ıguez, Inorg.
(b) R. Noyori, S. Hashiguchi, Acc. Chem. Res. 30 (1997) 97;
(c) M.J. Palmer, M. Wills, Tetrahedron: Asymmetry 10 (1999) 2045;
(d) R. Noyori, M. Yamakawa, S. Hashiguchi, J. Org. Chem. 66
(2001) 7931;
Chem. 42 (2003) 3293;
´
´
´
´
(e) V. Cadierno, P. Crochet, J. Dıez, J. Garcıa-Alvarez, S.E. Garcıa-
´
´
Garrido, S. Garcıa-Granda, J. Gimeno, M.A. Rodrıguez, Dalton
Trans. (2003) 3240;
(e) J.E. Ba¨ckvall, J. Organomet. Chem. 652 (2002) 105;
(f) D. Carmona, M.P. Lamata, L.A. Oro, Eur. J. Inorg. Chem. (2002)
2239;
(g) R. Noyori, Angew. Chem., Int. Ed. 41 (2002) 2008;
(h) K. Everaere, A. Mortreux, J.F. Carpentier, Adv. Synth. Catal.
345 (2003) 67;
(i) S.E. Clapham, A. Hadzovic, R.H. Morris, Coord. Chem. Rev. 248
(2004) 2201;
(j) S. Gladiali, A. Alberico, Chem. Soc. Rev. 35 (2006) 226;
(k) J.S.M. Samec, J.E. Ba¨ckvall, P.G. Andersson, P. Brandt, Chem.
Soc. Rev. 35 (2006) 237.
´
(f) G.A. Carriedo, P. Crochet, F.J. Garcıa-Alonso, J. Gimeno, A.
Presa-Soto, Eur. J. Inorg. Chem. (2004) 3668;
(g) V. Cadierno, J. Francos, J. Gimeno, N. Nebra, Chem. Commun.
(2007) 2536.
[13] On the basis of our previous work (see Ref. [6]), we assume that the
present catalytic TH reactions proceed via dihydride intermediates
cis,cis-[RuH2(CNR)(CO)(PꢀP)]. Although these species can be gen-
erated by treatment of ethanolic solutions of the corresponding halide
precursors 2–6a–e with two equivalents of NaOEt under refluxing
conditions, they are not stable enough to be isolated in pure form. It
should be also noted that the catalytic activity of complexes 2–6a–e is
completely inhibited when the reactions are performed under CO
atmosphere (1 atm) or in the presence of free isocyanide (isocyanide/
Ru ratio=50:1). This is consistent either with the dissociation of CO
or CNR, which provide the required vacant site on the metal for
coordination of the acetophenone.
[5] In classical hydrogenations very large substrate to catalyst ratios can
be reached, allowing their application to large-scale preparations (the
highest ratio is about 2 · 106; more than 103–104 times higher than in
the transfer hydrogenations). See for example: H. Doucet, T.
Ohkuma, K. Murata, T. Yokozawa, M. Kozawa, E. Katayama,
A.F. England, T. Ikariya, R. Noyori, Angew. Chem., Int. Ed. 37
(1998) 1703.
[14] (a) For recent reviews on the synthesis of furans, see: X.L. Hou, H.Y.
Cheung, T.Y. Hon, P.L. Kwan, T.H. Lo, S.Y. Tong, H.N.C. Wong,
Tetrahedron 54 (1998) 1955;
´
´
[6] V. Cadierno, P. Crochet, J. Dıez, S.E. Garcıa-Garrido, J. Gimeno,
Organometallics 23 (2004) 4836.
(b) B.A. Keay, Chem. Soc. Rev. 28 (1999) 209;
[7] (a) Outstanding contributions to this field can be found in: W.
Baratta, P. Da Ros, A. Del Zotto, A. Sechi, E. Zangrando, P. Rigo,
Angew. Chem., Int. Ed. 43 (2004) 3584;
(c) A. Jeevanandam, A. Ghule, Y.-G. Ling, Curr. Org. Chem. 6
(2002) 841;
(d) R.C.D. Brown, Angew. Chem., Int. Ed. 44 (2005) 850;
(e) S.F. Kirsch, Org. Biomol. Chem. 4 (2006) 2076.
(b) W. Baratta, G. Chelucci, S. Gladiali, K. Siega, M. Toniutti, M.
Zanette, E. Zangrando, P. Rigo, Angew. Chem., Int. Ed. 44 (2005)
6214;
[15] (a) See for example: B.H. Lipshutz, Chem. Rev. 86 (1986) 795;
(b) H. Heaney, J.S. Ahn, in: A.R. Katritzky, C.W. Rees, E.F.V.
Scriven (Eds.), Comprehensive Heterocyclic Chemistry II, vol. 2,
Pergamon Press, Oxford, 1996, p. 297;
(c) W. Baratta, M. Bosco, G. Chelucci, A. Del Zotto, K. Siega, M.
Toniutti, E. Zangrando, P. Rigo, Organometallics 25 (2006) 4611.
[8] R. Noyori, T. Ohkuma, Angew. Chem., Int. Ed. 40 (2001) 40, and
references cited therein. See also Refs. [4g,i,k].
(c) H.N.C. Wong, P. Yu, C.-Y. Yick, Pure Appl. Chem. 71 (1999)
1041;

5244
J. Albers et al. / Journal of Organometallic Chemistry 692 (2007) 5234–5244
¨
¨
(d) H.-K. Lee, K.-F. Chan, C.-W. Hui, H.-K. Yim, X.-W. Wu,
H.N.C. Wong, Pure Appl. Chem. 77 (2005) 139.
(g) I. Ozdemir, B. Yig˘it, B. C¸ etinkaya, D. Ulku, M.N. Tahir, C.
¨
Arici, J. Organomet. Chem. 633 (2001) 27;
¨
[16] (a) B. Seiller, C. Bruneau, P.H. Dixneuf, Tetrahedron 51 (1995)
13089;
(h) T. Sec¸kin, I. Ozdemir, B. C¸ etinkaya, J. Appl. Polym. Sci. 80
(2001) 1329;
¨
(i) B. C¸ etinkaya, N. Gurbuz, T. Sec¸kin, I. Ozdemir, J. Mol. Catal. A
¨ ¨
(b) B. Gabriele, G. Salerno, Chem. Commun. (1997) 1083;
(c) B. Gabriele, G. Salerno, E. Lauria, J. Org. Chem. 64 (1999) 7687;
(d) B. Gabriele, G. Salerno, M. Costa, Synlett (2004) 2468;
184 (2002) 31;
(j) T. Seckin, S. Koytepe, I. Ozdemir, N. Gurbuz, B. C¸ etinkaya, J.
¨
¨
¨
´
(e) V. Cadierno, J. D´ıez, J. Garc´ıa-Alvarez, J. Gimeno, N. Nebra, J.
Inorg. Organomet. Polym. 14 (2004) 177.
´
Rubio-Garcıa, Dalton Trans. (2006) 5593.
[22] (a) Solvent-free chemistry has received a great deal of attention in
recent years due to the many advantages that presents: reducing
pollution, low costs and simplicity in process and handling, all these
characteristics fulfilling the Green Chemistry’s principles. See for
example: P.T. Anastas, J.C. Warner, in: Green Chemistry Theory
and Practice, Oxford University Press, Oxford, 1998;
(b) K. Tanaka, F. Toda, Chem. Rev. 100 (2000) 1025;
(c) A.C. Matlack, in: Introduction to Green Chemistry, Marcel
Dekker, New York, 2001;
´
´ˇ
[17] D. Vegh, P. Zalupsky, J. Kovac, Synth. Commun. 20 (1990) 1113.
[18] (a) J.A. Marshall, C.A. Sehon, J. Org. Chem. 60 (1995) 5966;
(b) P. Pale, J. Chuche, Eur. J. Org. Chem. (2000) 1019.
[19] (a) A.S.K. Hashmi, L. Schwarz, J.-H. Choi, T.M. Frost, Angew.
Chem., Int. Ed. 39 (2000) 2285;
(b) Y. Liu, F. Song, Z. Song, M. Liu, B. Yan, Org. Lett. 7 (2005)
5409.
[20] (a) S. Elgafi, L.D. Field, B.A. Messerle, J. Organomet. Chem. 607
(2000) 97;
(d) M. Lancaster, in: J.H. Clark, D.J. Macquarrie (Eds.), Handbook
of Green Chemistry and Technology, Blackwell Publishing, Abing-
ton, 2002;
´
(b) A.E. D´ıaz-Alvarez, P. Crochet, M. Zablocka, C. Duhayon, V.
Cadierno, J. Gimeno, J.-P. Majoral, Adv. Synth. Catal. 348 (2006)
1671.
(e) M. Lancaster, Green Chemistry: An Introductory Text, RSC
Editions, Cambridge, 2002;
(f) J. Xiao, Environ. Catal. (2005) 547.
[21] (a) B. Seiller, C. Bruneau, P.H. Dixneuf, J. Chem. Soc., Chem.
Commun. (1994) 493;
(b) H. Kucukbay, B. Cetinkaya, S. Guesmi, P.H. Dixneuf, Organo-
¨ ¨
metallics 15 (1996) 2434;
[23] Representative examples of TOF values attained by ruthenium
complexes are as follows: [RuCl2(g6-p-cymene)(PPh3)] (TOF = 50 hꢀ1
Ref. [16a]), [RuCl2(g6-p-cymene)(benzimidazole)] (TOF = 90 hꢀ1
;
;
¨
(c) B. C¸ etinkaya, I. Ozdemir, C. Bruneau, P.H. Dixneuf, J. Mol.
Catal. A 118 (1997) L1;
Ref. [21f]), [RuCl2(g6-C6Me6)(1-methyl-1,4,5,6-tetrahydropyrimi-
(d) B. C¸ etinkaya, T. Sec¸kin, I. Ozdemir, B. Alici, J. Mater. Chem. 8
dine)] (TOF = 49 hꢀ1
;
Ref. [21e]), [{Ru(O2CH)(CO)2(PPh3)}2]
¨
(1998) 1835;
(TOF = 50 hꢀ1; Ref. [16a]) and [RuCl2(g6-arene)(NHC)] (arene =
p-cymene, C6Me6, 1,3,5-C6H3Me3; NHC = N-heterocyclic carbene
ligand; TOF = 22–400 hꢀ1; Refs. [21b,c,g,i]).
¨
(e) B. C¸ etinkaya, B. Alici, I. Ozdemir, C. Bruneau, P.H. Dixneuf, J.
Organomet. Chem. 575 (1999) 187;
¨
(f) B. C¸ etinkaya, I. Ozdemir, C. Bruneau, P.H. Dixneuf, Eur. J.
Inorg. Chem. (2000) 29;