Arene-ruthenium(II) and bis(allyl)-ruthenium(IV) complexes containing 2-(diphenylphosphanyl)pyridine ligands: Potential catalysts for nitrile hydration reactions?

Article abstract of DOI:10.1002/ejic.201200592

Neutral arene-ruthenium(II) complexes [RuCl₂(η⁶- arene){κ¹-(P)-PPh₂py}] and [RuCl₂(η ⁶-arene){κ¹-(P)-PPh₂(py-4-NMe ₂)}] (arene = benzene, p-cymene, mesityle

Full text of DOI:10.1002/ejic.201200592

FULL PAPER
DOI: 10.1002/ejic.201200592
Arene-Ruthenium(II) and Bis(allyl)-Ruthenium(IV) Complexes Containing
2-(Diphenylphosphanyl)pyridine Ligands: Potential Catalysts for Nitrile
Hydration Reactions?
Rocío García-Álvarez,[a] Sergio E. García-Garrido,[a] Josefina Díez,[a] Pascale Crochet,*[a]
and Victorio Cadierno*[a]
Keywords: Homogeneous catalysis / Ruthenium / N,P ligands / Amides / Hydration
Neutral arene-ruthenium(II) complexes [RuCl2(η6-arene){κ1-
(P)-PPh2py}] and [RuCl2(η6-arene){κ1-(P)-PPh2(py-4-NMe2)}]
(arene = benzene, p-cymene, mesitylene, hexamethylbenz-
ene) have been synthesized and studied as potential catalysts
for the selective hydration of nitriles to amides using benzo-
nitrile as a model substrate. The effectiveness of these com-
plexes was low due to the high tendency of the 2-(diphenyl-
phosphanyl)pyridine ligands to form stable κ2-(P,N)-chelate
rings, as demonstrated by NMR spectroscopy and catalytic
experiments performed with the isolated cationic derivatives
[RuCl(η6-arene){κ2-(P,N)-PN}][SbF6] [PN = PPh2py, PPh2(py-
4-NMe2)]. Despite its reluctance to adopt a chelating κ2-(P,N)
coordination mode, cooperative effects of the bulky 2-(di-
phenylphosphanyl)pyridine ligand PPh2(py-6-tert-amyl)
were not observed in complexes [RuCl2(η6-arene)-
{κ1-(P)-PPh2(py-6-tert-amyl)}] (arene = benzene, p-cymene).
The novel bis(allyl)-ruthenium(IV) derivatives [RuCl(η3:η3-
C10H16){κ2-(P,N)-PN}][SbF6] [PN
NMe2)] and
=
PPh2py, PPh2(py-4-
[RuCl2(η3:η3-C10H16){κ1-(P)-PPh2(py-6-tert-
amyl)}] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl) were
also synthesized and fully characterized, and again led to
modest conversions in the benzonitrile hydration reaction.
Improvements in the catalytic activities of complexes
[RuCl2(η6-p-cymene){κ1-(P)-PPh2py}], [RuCl(η6-p-cymene)-
{κ2-(P,N)-PPh2py}][SbF6] and [RuCl(η3:η3-C10H16){κ2-(P,N)-
PPh2py}][SbF6] were observed in the presence of excess
PPh2py due to the in situ formation of the catalytically more
active dication [Ru{κ2-(P,N)-PPh2py}3]2+
.
powerful alternatives to carry out these transformations.[5]
Several homogeneous[4] and heterogeneous[6] systems have
been described with the former showing greater synthetic
applicability. Among them, MurahashiЈs ruthenium[7] and
ParkinsЈ platinum[8] complexes, [RuH2(PPh3)4] and
[PtH(PMe2OH){(PMe2O)2H}], respectively, are the most
widely employed due to their remarkable activity and excel-
lent functional group tolerance. The RhI-based systems
[{Rh(μ-OMe)(cod)}2]/PCy3 (cod = 1,5-cyclooctadiene)[9]
and [RhBr(pin)(cod)] [pin = 1-isopropyl-3-(5,7-dimethyl-
1,8-naphthyrid-2-yl)imidazol-2-ylidene][10] also deserve to
be highlighted due to their effectiveness under ambient con-
ditions.
Introduction
The hydration of nitriles is an important transformation
because the resulting amides present a huge number of ap-
plications in synthetic organic chemistry, as well as indus-
trial and pharmaceutical interest.[1] For example, the large-
scale production of acrylamide, nicotinamide and 5-cyano-
valeramide is currently based on this reaction.[2] In addition
to a higher chemoselectivity, that is, amides are not further
hydrolysed to the corresponding carboxylic acids (see
Scheme 1), transition-metal catalysed nitrile hydration reac-
tions offer other advantages over the conventional acid- and
base-promoted transformations,[3] such as milder reaction
conditions and higher tolerance to other functional
groups.[4] Moreover, despite the significant progress
achieved in enzymatic nitrile hydration reactions and their
commercial success,[2] the narrow substrate specificity and
high isolation costs of the currently available enzymes make
the metal-based methodologies the simplest and most
Scheme 1. Nitrile hydration and amide hydrolysis reactions.
[a] Laboratorio de Compuestos Organometálicos y Catálisis
(Unidad Asociada al CSIC), Departamento de Química
Orgánica e Inorgánica, Instituto Universitario de Química
Organometálica “Enrique Moles“, Universidad de Oviedo,
Julián Clavería 8, 33006 Oviedo, Spain
Although different reaction pathways have been pro-
posed for the metal-catalysed nitrile hydration processes,
coordination of the nitrile to the metal is a common pre-
requisite for most of them.[4] Through this coordination, the
CϵN unit becomes more electrophilic and susceptible to
nucleophilic attack by water, thus improving the kinetics of
Fax: +34-985-103-446
E-mail: crochetpascale@uniovi.es
vcm@uniovi.es
Homepage: http://www.unioviedo.es/comorca
4218
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
the hydration process in comparison with hydrolysis phanyl)pyridine ligands 1–3 (Figure 2) to assess whether
(Scheme 1). Recent works have also suggested that this key cooperative effects also operate in these systems. The results
nucleophilic addition step can be facilitated by the presence of this study are presented herein.
of functionalized ligands able to activate the water molecule
through a secondary hydrogen-bond interaction (Fig-
ure 1).[10,11] Such a cooperative effect of the ligand repre-
sents a new example of the so-called “bifunctional cataly-
sis”, that is, the metal ion acts as a Lewis acid and the
ligand as a Lewis base, a concept widely exploited in homo-
geneous catalysis during recent years.[12]
Figure 1. Simplified representation of the cooperative effect of the
ligand.
In this context, Oshiki and co-workers reported that the
ruthenium(II) complex cis-[Ru(acac)2{κ1-(P)-PPh2py}2]
(acac = acetylacetonate), which contains the well-known
and commercially available heteroditopic phosphane 2-(di-
phenylphosphanyl)pyridine (PPh2py, 1; Figure 2),[13] is an
excellent bifunctional catalyst for the selective hydration of
nitriles to amides under neutral conditions.[11b,11h] The di-
Figure 3. Structures of some RuII and RuIV catalysts previously de-
recting effect of the uncoordinated pyridyl unit of the
PPh2py ligands allowed impressive turnover frequency
(TOF) values of up to 20900 h–1 to be obtained with this
complex. Further studies by the same group employing
[Ru(η3-2-methylallyl)2(cod)]/PR3 systems also indicated the
greater effectiveness of the related ligand PPh2(py-4-NMe2)
(2; Figure 2) over the unsubstituted PPh2py (1) due to the
increased electron density on the nitrogen atom of the pyr-
idyl unit generated by the presence of the electron-donating
dimethylamino group (i.e., greater hydrogen-bond acceptor
character).[11k]
scribed by us.
Results and Discussion
Our investigations started with the preparation of the
neutral complexes [RuCl2(η6-arene){κ1-(P)-PPh2py}] [arene
= benzene (5a), p-cymene (5b), mesitylene (5c), hexameth-
ylbenzene (5d)] and [RuCl2(η6-arene){κ1-(P)-PPh2(py-4-
NMe2)}] [arene = benzene (6a), p-cymene (6b), mesitylene
(6c)] through the classical cleavage of the chloride bridges
in the dimeric precursors [{RuCl(μ-Cl)(η6-arene)}2] (4a–d)
with 2.4 equiv. of the corresponding 2-(diphenylphos-
phanyl)pyridine ligand 1 or 2 (Scheme 2). The reactions,
which were conducted in tetrahydrofuran at room tempera-
ture, delivered the desired complexes 5a–d and 6a–c in high
yields (81–88%). In contrast, all attempts to generate the
neutral complex [RuCl2(η6-hexamethylbenzene){κ1-(P)-
PPh2(py-4-NMe2)}] (6d) by the reaction of dimer 4d with
phosphane 2 in different solvents (THF, CH2Cl2, 1,2-di-
chloroethane or methanol) failed, the reactions leading in-
stead to the rapid and selective formation of the cationic
Figure 2. Structure of the 2-(diphenylphosphanyl)pyridine ligands
1–3.
In recent years our group has been active in this field, species [RuCl(η6-hexamethylbenzene){κ2-(P,N)-PPh2(py-4-
describing different series of arene-ruthenium(II) (A–C; NMe2)}][Cl] by direct chelation of the ligand. This complex
Figure 3) and bis(allyl)-ruthenium(IV) complexes (D,E; Fig- was isolated as the corresponding hexafluoroantimonate
ure 3), all containing potential hydrogen-bond acceptor salt 8d after Cl–/SbF6– counter-anion exchange with a meth-
phosphane ligands that are able to promote efficiently the anolic solution of NaSbF6 at room temperature. The related
selective hydration of nitriles to amides.[11e–11g,11i–11j] As an cationic complexes [RuCl(η6-arene){κ2-(P,N)-PPh2py}]-
extension of these studies, and inspired by the work of [SbF6] [arene = benzene (7a), p-cymene (7b), mesitylene
Oshiki,[11b,11h,11k] we decided to investigate the catalytic ac- (7c), hexamethylbenzene (7d)] and [RuCl(η6-arene){κ2-
tivities of related arene-ruthenium(II)[14] and bis(allyl)-ru- (P,N)-PPh2(py-4-NMe2)}][SbF6] [arene = benzene (8a), p-
thenium(IV) complexes derived from the 2-(diphenylphos- cymene (8b), mesitylene (8c)] were also synthesized in high
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4219

P. Crochet, V. Cadierno et al.
FULL PAPER
yields (75–80%) by treatment of the isolated complexes 5a– 39.6 ppm. In addition, the structure of the cationic complex
d and 6a–c, respectively, with NaSbF6 in methanol [RuCl(η6-mesitylene){κ2-(P,N)-PPh2(py-4-NMe2)}][SbF6]
(Scheme 2).
(8c) was unambiguously confirmed by X-ray diffraction
analysis. X-ray quality crystals were obtained by slow dif-
fusion of diethyl ether into a saturated solution of 8c in
acetone. An ORTEP view of the molecule, along with se-
lected structural parameters, is shown in Figure 4.[18] The
expected pseudo-octahedral three-legged piano-stool geom-
etry around the ruthenium atom was observed, with the
interligand angles P(1)–Ru(1)–Cl(1), P(1)–Ru(1)–N(1) and
Cl(1)–Ru(1)–N(1) and those between the centroid of the
mesitylene ring C* and the legs typical of a pseudo-octa-
hedron. Remarkably, the bond lengths and angles found
within the four-membered ruthenacycle [Ru(1)–P(1)–C(10)–
N(1)] are almost identical (Ϯ0.03 Å or Ϯ0.1°) to those pre-
viously observed in the solid-state crystal structures of
the complexes [RuCl2(η6-p-cymene){κ2-(P,N)-PPh2py}]+
(7b)[15a,15d] and [RuCl2(η6-hexamethylbenzene){κ2-(P,N)-
PPh2py}]+ (7d),[15c] which indicates a negligible structural
effect of the dimethylamino substituent on the 2-(diphenyl-
phosphanyl)pyridine ligand.
Scheme 2. Synthesis of the (η6-arene)ruthenium(II) complexes 5–
8a–d containing the 2-(diphenylphosphanyl)pyridine ligands 1 or 2
coordinated in a κ1-(P) or κ2-(P,N) manner.
Complexes 5a,b,d and 7a,b,d containing the more classi-
cal Ph2Ppy ligand 1 have previously been reported in the
literature.[15] The spectroscopic data obtained for the new
mesitylene analogues 5c and 7c are comparable to those
described for 5a,b,d and 7a,b,d and deserve no further com-
ment. For compounds 6a–c and 8a–d, which represent rare
examples of isolated metal complexes containing the di-
methylamino-substituted 2-(diphenylphosphanyl)pyridine
ligand 2,[16] characterization was straightforward from their
analytical and spectroscopic data (see the Exp. Sect.). In
particular, the 31P{1H} NMR spectra are very informative,
showing for the neutral complexes 6a–c a strong downfield
shift of the Ph2P signal (δP = 21.9–28.3 ppm) with respect
to that shown by the free phosphane 2 (δP = –2.8 ppm) as
a consequence of the coordination of this group to ruthe-
nium. In contrast, important shielding was observed for the
Ph2P resonances when moving from 6a–c to 8a–d (δP from
Figure 4. ORTEP-type view of the structure of [RuCl(η6-
mesitylene){κ2-(P,N)-PPh2(py-4-NMe2)}][SbF6] (8c) showing the
–
crystallographic labeling scheme. Hydrogen atoms and the SbF6
anion have been omitted for clarity. Thermal ellipsoids are drawn
at the 10% probability level. Selected bond lengths [Å] and angles
[°]: Ru(1)–P(1) 2.332(2), Ru(1)–Cl(1) 2.405(2), Ru(1)–N(1) 2.146(5),
Ru(1)–C* 1.720(4), P(1)–C(10) 1.820(5), P(1)–C(17) 1.813(7), P(1)–
C(23) 1.805(6), C(10)–N(1) 1.371(7), C(12)–N(2) 1.361(8), C(15)–
N(2) 1.435(2), C(16)–N(2) 1.47(1), C*–Ru(1)–P(1) 135.2(1), C*–
Ru(1)–N(1) 136.5(3), C*–Ru(1)–Cl(1) 128.2(3), P(1)–Ru(1)–Cl(1)
86.27(6), P(1)–Ru(1)–N(1) 66.3(1), Cl(1)–Ru(1)–N(1) 81.6(1),
Ru(1)–P(1)–C(10) 85.7(2), P(1)–C(10)–N(1) 99.6(4), C(10)–N(1)–
Ru(1) 106.0(3). C* denotes the centroid of the mesitylene ring
[C(1)–C(2)–C(3)–C(4)–C(5)–C(6)].
–19.3 to –13.2 ppm for 8a–d), in agreement with the forma-
The catalytic potential of the synthesized complexes for
tion of a strained four-membered chelate ring.[17] The H nitrile hydration reactions was investigated by using benzo-
and 13C{1H} NMR spectra also show the signals expected nitrile as the model substrate. In a typical experiment, the
for η6-coordinated arene groups and the PPh2(py-4-NMe2) corresponding ruthenium catalyst (5 mol-%) was added to
ligand. For the latter, characteristic NMe2 singlet reso- a 0.33 m aqueous solution of benzonitrile and the mixture
nances were observed at δH = 2.78–3.08 ppm and δC = 38.6– was heated in an oil bath at 100 °C for 24 h.
1
4220
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
As shown in Table 1, the effectiveness of the neutral de- der identical reaction conditions (entries 8–15; conversions
rivatives [RuCl2(η6-arene){κ1-(P)-PPh2py}] (5a–d; en- Յ37% after 24 h of heating). We must also note that, de-
tries 1–4) and [RuCl2(η6-arene){κ1-(P)-PPh2(py-4-NMe2)}] spite the hemilabile character usually associated with phos-
(6a–c; entries 5–8), potential candidates to operate through phanylpyridine ligands,[13,22] all attempts to generate the
a bifunctional mechanism, was very low.[19] Thus, in the compounds
[RuCl(η6-p-cymene)(NϵCPh){κ1-(P)-
best case, a maximum conversion of 69% was reached with PPh2py}][SbF6] and [RuCl(η6-p-cymene)(NϵCPh){κ1-(P)-
complex [RuCl2(η6-C6Me6){κ1-(P)-PPh2py}] (5d; en- PPh2(py-4-NMe2)}][SbF6] by treating complexes 7,8b with
try 4).[20] In contrast to the observations made by Oshiki excess benzonitrile (up to 50 equiv.) were unsuccessful.[23]
and co-workers,[11k] the presence of the dimethylamino sub- Consequently, the low reactivity observed for 5a–c and 6a–
stituent on the pyridyl ring does not exert any beneficial c can be attributed to the stability of the four-membered
effect as no marked differences in reactivity were found be- chelate rings generated by κ2-(P,N) coordination of the li-
tween complexes 5a–c and 6a–c (entries 1–3 vs. 5–7). Note gands, a process thermodynamically favoured by the high
also that the catalytic activities of 5a–d and 6a–c were only polarity of the catalytic reaction media.[24]
slightly higher than those shown by the analogous com-
To avoid the chelation of the pyridyl unit, we decided to
plexes [RuCl2(η6-arene)(PPh3)] (9a–d; entries 16–19), in explore related arene-ruthenium(II) complexes with the 2-
which the presence of the triphenylphosphane ligand elim- (diphenylphosphanyl)pyridine ligand PPh2(py-6-tert-amyl)
inates the possibility of secondary hydrogen-bond interac- (3; Figure 2). This commercially available phosphane, devel-
tions with the nucleophilic water molecules. This indicates oped by Hintermann and co-workers, previously proved
that cooperative effects of the 2-(diphenylphosphanyl)pyr- useful in the ruthenium-catalysed anti-Markovnikov hy-
idine ligands are negligible in our complexes.[21] Interest- dration of terminal alkynes through bifunctional reaction
ingly, inspection of the crude reaction mixtures by 31P{1H} pathways.[25] The presence of the bulky tert-amyl substitu-
NMR spectroscopy showed, in all cases, the major presence ent adjacent to the nitrogen atom was expected to suppress
of the corresponding cationic species [RuCl(η6-arene){κ2- the coordination ability of its now sterically shielded lone
(P,N)-PPh2py}]+ (7a–d) and [RuCl(η6-arene){κ2-(P,N)- pair. As shown in Scheme 3, treatment of THF solutions of
PPh2(py-4-NMe2)}]+ (8a–c) in solution. These complexes dimers [{RuCl(μ-Cl)(η6-arene)}2] [arene = benzene (4a), p-
are less active than 5a–d and 6a–c, as assessed by per- cymene (4b)] with 2.4 equiv. of 3 at room temperature deliv-
forming the catalytic hydration of benzonitrile with the iso- ered the expected mononuclear κ1-(P) complexes 10a,b,
lated hexafluoroantimonate salts of 7,8a–d (Scheme 2) un- which were isolated as air-stable orange solids in high yields
(85–89%).[26]
Table 1. Catalytic hydration of benzonitrile using the arene-ruthe-
nium(II) complexes 5–10a–d.[a]
Entry Catalyst
Yield[b]
[%]
1
2
3
4
5
6
7
8
[RuCl2(η6-C6H6){κ1-(P)-PPh2py}] (5a)
55
57
67
69
45
65
60
7
[RuCl2(η6-p-cym){κ1-(P)-PPh2py}] (5b)
[RuCl2(η6-mes){κ1-(P)-PPh2py}] (5c)
Scheme 3. Synthesis of the (η6-arene)ruthenium(II) complexes
10a,b containing the 2-(diphenylphosphanyl)pyridine ligand 3.
[RuCl2(η6-C6Me6){κ1-(P)-PPh2py}] (5d)
[RuCl2(η6-C6H6){κ1-(P)-PPh2(py-4-NMe2)}] (6a)
[RuCl2(η6-p-cym){κ1-(P)-PPh2(py-4-NMe2)}] (6b)
[RuCl2(η6-mes){κ1-(P)-PPh2(py-4-NMe2)}] (6c)
[RuCl(η6-C6H6){κ2-(P,N)-PPh2py}]+ (7a)
[RuCl(η6-p-cym){κ2-(P,N)-PPh2py}]+ (7b)
[RuCl(η6-mes){κ2-(P,N)-PPh2py}]+ (7c)
[RuCl(η6-C6Me6){κ2-(P,N)-PPh2py}]+ (7d)
[RuCl(η6-C6H6){κ2-(P,N)-PPh2(py-4-NMe2)}]+ (8a)
[RuCl(η6-p-cym){κ2-(P,N)-PPh2(py-4-NMe2)}]+ (8b)
[RuCl(η6-mes){κ2-(P,N)-PPh2(py-4-NMe2)}]+ (8c)
[RuCl(η6-C6Me6){κ2-(P,N)-PPh2(py-4-NMe2)}]+ (8d)
[RuCl2(η6-C6H6)(PPh3)] (9a)
Complexes 10a,b were characterized by elemental analy-
ses and multinuclear NMR (1H, 31P{1H} and 13C{1H})
spectroscopy, the data obtained being fully consistent with
the structural proposals (see the Exp. Sect. for details). In
particular, the monodentate κ1-(P) coordination of the
phosphane ligand 3 is reflected in the 31P{1H} NMR spec-
tra by the appearance of a singlet signal at δP = 20.1–
25.0 ppm, a chemical shift range that fits well with that ob-
served for compounds 5a–d and 6a–c. The structure of the
benzene complex [RuCl2(η6-benzene){κ1-(P)-PPh2(py-6-
tert-amyl)}] (10a) was also unambiguously confirmed by
single-crystal X-ray diffraction. An ORTEP-type drawing
of the molecule is depicted in Figure 5; selected bond
lengths and angles are listed in the caption. The ruthenium
atom is coordinated to two terminal chlorides, the η6-benz-
ene ligand and the phosphorus atom of 3, all arranged in a
9
16
11
2
10
11
12
13
14
15
16[c]
17[c]
18[c]
19[c]
20
21
28
37
32
22
45
45
21
48
28
37
[RuCl2(η6-p-cym)(PPh3)] (9b)
[RuCl2(η6-mes)(PPh3)] (9c)
[RuCl2(η6-C6Me6)(PPh3)] (9d)
[RuCl2(η6-C6H6){κ1-(P)-PPh2(py-6-tert-amyl)}] (10a)
[RuCl2(η6-p-cym){κ1-(P)-PPh2(py-6-tert-amyl)}] (10b)
[a] Reactions performed under N2 at 100 °C with 1 mmol of benzo-
nitrile (0.33 m in water). Substrate/Ru ratio: 100:5. [b] Yield of
benzamide determined by GC. [c] Data taken from ref.[11f]
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4221

P. Crochet, V. Cadierno et al.
FULL PAPER
typical pseudo-octahedral three-legged piano-stool geome- be reached with 5 mol-% of these complexes after 24 h of
try. The Ru(1)–Cl(1) [2.389(1) Å], Ru(1)–Cl(2) [2.407(1) Å] heating at 100 °C. These results, which are worse than those
and Ru(1)–P(1) [2.3521(9) Å] bond lengths observed are obtained with complexes [RuCl2(η6-arene){κ1-(P)-PPh2py}]
very similar (Ϯ0.03 Å) to those described previously for (5a–d; entries 1–4), [RuCl2(η6-arene){κ1-(P)-PPh2(py-4-
[RuCl2(η6-p-cymene){κ1-(P)-PPh2py}] (5b)[15a,15d] and NMe2)}] (6a–c; entries 5–7) and [RuCl2(η6-arene)(PPh3)]
[RuCl2(η6-hexamethylbenzene){κ1-(P)-PPh2py}] (5d),[15c] (9a–d; entries 16–19), rule out any cooperative effect of the
which again suggests negligible effects of the pyridyl substit- phosphane ligand 3. Steric congestion around the Lewis
uent on the structure of this family of arene-ruthenium acid metal centre, which prevents the approach of the ben-
complexes. On the other hand, we would also like to note zonitrile molecule, may be responsible for the low catalytic
that, to the best of our knowledge, 10a is the first structur- activities shown by 10a,b.
ally characterized complex containing the bulky 2-(di-
As commented in the introduction to this article, pre-
vious studies from our group have demonstrated the high
potential of catalytic systems consisting of bis(allyl)-ruthe-
phenylphosphanyl)pyridine ligand 3.[27]
nium(IV) complexes [RuCl2(η3:η3-C10H16)(L)] (C10H16
=
2,7-dimethylocta-2,6-diene-1,8-diyl; L = phosphane ligand)
for nitrile hydration processes (e.g., compound D in Fig-
ure 3).[11g] That is why we also decided to explore the reac-
tivity of dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (11) towards
phosphanes 1–3 and the catalytic behaviour of the resulting
complexes.[28] As shown in Scheme 4, although the treat-
ment of 11 with a two-fold excess of ligand 1 or 2 resulted
in the rapid and direct formation of the corresponding cat-
ionic chelate complexes, isolated as the hexafluoroantimon-
ate salts [RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2py}][SbF6] (12)
and
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2(py-4-NMe2)}]-
[SbF6] (13), the neutral derivative [RuCl2(η3:η3-C10H16){κ1-
(P)-PPh2(py-6-tert-amyl)}] (14) was cleanly obtained by
using the bulky phosphane 3. As previously observed with
Figure 5. ORTEP-type view of the structure of [RuCl2(η6-
benzene){κ1-(P)-PPh2(py-6-tert-amyl)}] (10a) showing the crystal-
lographic labeling scheme. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are drawn at the 10% probability level.
Selected bond lengths [Å] and angles [°]: Ru(1)–P(1) 2.3521(9),
Ru(1)–Cl(1) 2.389(1), Ru(1)–Cl(2) 2.407(1), Ru(1)–C* 1.6928(3),
P(1)–C(7) 1.843(4), P(1)–C(17) 1.828(4), P(1)–C(23) 1.819(4), C(7)–
N(1) 1.339(5), C*–Ru(1)–P(1) 128.82(2), C*–Ru(1)–Cl(1) 126.07(3),
C*–Ru(1)–Cl(2) 124.70(3), P(1)–Ru(1)–Cl(1) 86.99(4), P(1)–Ru(1)–
Cl(2) 87.83(3), Cl(1)–Ru(1)–Cl(2) 89.79(4), Ru(1)–P(1)–C(7)
114.4(1), P(1)–C(7)–N(1) 115.7(3). C* = centroid of the benzene
ring [C(1)–C(2)–C(3)–C(4)–C(5)–C(6)].
To determine whether the chelation of 3 could interfere
during catalysis, the reactivities of complexes [RuCl2(η6-
arene){κ1-(P)-PPh2(py-6-tert-amyl)}]
(10a,b)
towards
NaSbF6 were first explored. In contrast to the behaviour
shown by 5a–d and 6a–c (Scheme 2), complexes 10a,b re-
mained unchanged when methanolic solutions were treated
with a large excess (10 equiv.) of NaSbF6, even after pro-
longed periods at reflux. This clearly indicates that, in solu-
tion, the equilibrium [RuCl2(η6-arene){κ1-(P)-PPh2(py-6-
tert-amyl)}] h [RuCl(η6-arene){κ2-(P,N)-PPh2(py-6-tert-
amyl)}][Cl] is completely displaced to the left. However, de-
spite the reluctance of PPh2(py-6-tert-amyl) to adopt a che-
lating κ2-(P,N) coordination mode, the catalytic activities
of complexes 10a,b in the hydration of benzonitrile were
unexpectedly disappointing. Thus, as shown in Table 1 (en-
tries 20 and 21), only yields of 28–37% of benzamide could 14.
Scheme 4. Synthesis of the bis(allyl)-ruthenium(IV) complexes 12–
4222
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
its arene-ruthenium(II) counterparts 10a,b, methanolic
solutions of complex 14 did not react with NaSbF6, which
confirms the reluctance of 3 to undergo κ2-(P,N) coordina-
tion. In addition, similarly to 7,8b, no chelate ring opening
occurred when 12 or 13 was treated with benzonitrile.
The new compounds 12–14, isolated as air-stable yellow
solids in yields of 86–91%, were characterized by elemental
analyses and multinuclear NMR spectroscopy (see the Exp.
Sect.). The different coordination adopted by the 2-(di-
phenylphosphanyl)pyridine ligands 1–3 was readily evi-
denced in the 31P{1H} NMR spectra, which show for 12
and 13 singlet signals (δP = –39.1 and –38.3 ppm) at much
1
higher fields than observed for 14 (δP = 25.8 ppm). The H
and 13C{1H} NMR spectra of these compounds are also
very informative. Thus, as expected for the formation of a
simple equatorial adduct, a unique set of signals for the two
allylic moieties of 14 was observed, which suggests that the
two halves of the 2,7-dimethylocta-2,6-diene-1,8-diyl skel-
eton are in equivalent environments. In contrast, for 12 and
13, the two halves of the 2,7-dimethylocta-2,6-diene-1,8-diyl
ligand are inequivalent, as clearly reflected by the appear-
ance 10 different signals in the 13C{1H} NMR spectra.
Figure 6. ORTEP-type view of the structure of [RuCl(η3:η3-
C10H16){κ2-(P,N)-PPh2py}][SbF6] (12) showing the crystallographic
–
labeling scheme. Hydrogen atoms and the SbF6 anion have been
omitted for clarity. Thermal ellipsoids are drawn at the 10% prob-
ability level. Selected bond lengths [Å] and angles [°]: Ru(1)–Cl(1)
2.414(1), Ru(1)–P(1) 2.364(1), Ru(1)–N(1) 2.130(4), Ru(1)–C*
1.9729(4), Ru(1)–C** 1.9674(4), Ru(1)–C(1) 2.199(6), Ru(1)–C(2)
2.231(7), Ru(1)–C(4) 2.249(6), Ru(1)–C(7) 2.229(5), Ru(1)–C(8)
Doubling of the allylic resonances for 12 and 13 is in com- 2.216(5), Ru(1)–C(10) 2.211(6), C(1)–C(2) 1.40(1), C(2)–C(4)
1.41(1), C(7)–C(8) 1.408(9), C(8)–C(10) 1.405(9), P(1)–C(11)
1.816(5), P(1)–C(16) 1.825(5), P(1)–C(22) 1.802(6), C(11)–N(1)
1.359(7), Cl(1)–Ru(1)–N(1) 154.9(1), Cl(1)–Ru(1)–P(1) 87.43(5),
Cl(1)–Ru(1)–C* 90.92(4), Cl(1)–Ru(1)–Cl** 97.39(4), P(1)–Ru(1)–
plete accord with the loss of C2 symmetry in these chelate
complexes. The structure of [RuCl(η3:η3-C10H16){κ2-(P,N)-
PPh2py}][SbF6] (12) was fully confirmed by X-ray crystallo-
graphic studies (Figure 6). The geometry about the ruthe-
nium atom in 12 is best described as a highly distorted tri-
gonal bipyramid by considering the allyl groups as mono-
dentate ligands bound to the metal through their centres of
mass (C* and C**; see caption to Figure 6). The chloride
ligand and pyridyl nitrogen atom occupy the axial positions
[Cl(1)–Ru–N(1) bond angle of 154.9(1)°], whereas the oc-
tadienediyl and diphenylphosphanyl units are located at
equatorial sites. Both allyl groups of the organic C10H16
fragment are η3-bound to the ruthenium atom with Ru–
C and C–C distances in the ranges 2.199(6)–2.249(6) and
1.40(1)–1.41(1) Å, respectively. These values, together with
the internal allylic C(1)–C(2)–C(4) and C(7)–C(8)–C(10)
angles [115.1(7) and 113.2(6)°, respectively], compare well
with those observed in other structures containing the
“Ru(η3:η3-C10H16)” unit.[29]
When applied to the catalytic hydration of benzonitrile
under conditions identical to those employed with 5–10a–d
(Table 1), the RuIV derivatives 12–14 also showed very low
activities (Table 2). In contrast to the former cases, the best
result was obtained with the neutral complex [RuCl2(η3:η3-
C10H16){κ1-(P)-PPh2(py-6-tert-amyl)}] (14), which led to
the selective formation of benzamide in 62% yield after 24 h
N(1) 67.4(1), P(1)–Ru(1)–C* 117.52(4), P(1)–Ru(1)–C** 115.08(4),
N(1)–Ru(1)–C* 100.1(1), N(1)–Ru(1)–C** 93.9(1), C*–Ru–C**
127.02(2), Ru(1)–P(1)–C(11) 83.8(2), P(1)–C(11)–N(1) 103.0(4),
C(1)–C(2)–C(4) 115.1(7), C(7)–C(8)–C(10) 113.2(6). C* and C**
denote the centroids of the allyl units [C(1)–C(2)–C(4), and C(7)–
C(8)–C(10), respectively].
Table 2. Catalytic hydration of benzonitrile using the bis(allyl)-ru-
thenium(IV) complexes 12–15.[a]
Entry Catalyst
Yield[b]
[%]
1
2
3
4
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2py}]+ (12)
7
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2(py-4-NMe2)}]+ (13)
[RuCl2(η3:η3-C10H16){κ1-(P)-PPh2(py-6-tert-amyl)}] (14)
[RuCl2(η3:η3-C10H16)(PPh3)] (15)
34
62
56
[a] Reactions performed under N2 at 100 °C with 1 mmol of benzo-
nitrile (0.33 m in water). Substrate/Ru ratio: 100:5. [b] Yield of
benzamide determined by GC.
of heating (entry 3). However, this yield does not differ resentative models (see Table 3). We observed that the per-
much from that reached with [RuCl2(η3:η3-C10H16)(PPh3)] formances shown by the arene derivatives 5b and 7b were
(15; entry 4), which again suggests a lack of a cooperative reduced when benzonitrile was hydrated in the presence of
effect of ligand 3 during the catalytic event.
50 equiv. (per Ru) of free p-cymene (entry 2 vs. 1, and 7 vs.
To gain more information on the catalytic behaviour of 6). These observations suggest that the vacant sites required
our systems, some additional experiments were performed for the coordination of the substrate may be generated
with complexes [RuCl2(η6-p-cymene){κ1-(P)-PPh2py}] (5b), through the dissociation of the arene ligand. On the other
[RuCl(η6-p-cymene){κ2-(P,N)-PPh2py}][SbF6] (7b) and hand, remarkable improvements in the catalytic activities of
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2py}][SbF6] (12) as rep- these complexes occurred when 1 or 2 equiv. (per Ru) of the
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4223

P. Crochet, V. Cadierno et al.
FULL PAPER
free 2-(diphenylphosphanyl)pyridine ligand 1 were intro-
duced into the reaction media (entries 3 and 4 vs. 1, and 8
and 9 vs. 6). A beneficial effect of the addition of free phos-
phane was also observed with the bis(allyl)-ruthenium(IV)
derivative 12 (entries 12 and 13 vs. 11). In particular, in the
presence of 2 equiv. of PPh2py, the quantitative formation
of benzamide could be reached after 24 h of heating with
the three complexes 5b, 7b and 12 (entries 4, 9 and 13). The
role of the free phosphane as a simple base was discarded
because the activities shown by 5b and 7b remained almost
unaltered in the presence of 2 equiv. (per Ru) of pyridine
(entries 5 vs. 1, and 10 vs. 6).
Table 3. Catalytic hydration of benzonitrile with complexes 5b, 7b
and 12 in the presence of different additives.[a]
Entry
Catalyst
Additive
Yield[b] [%]
1
2
3
4
5
6
7
8
5b
5b
5b
5b
5b
7b
7b
7b
7b
7b
12
12
12
none
57
21
99
Ͼ99
58
16
2
89
Ͼ99
15
7
p-cymene (250 mol-%)
PPh2py (1; 5 mol-%)
PPh2py (1; 10 mol-%)
py (10 mol-%)
Scheme 5. Synthesis and behaviour in solution of the octahedral
ruthenium(II) complex 16.
none
p-cymene (250 mol-%)
PPh2py (1; 5 mol-%)
PPh2py (1; 10 mol-%)
py (10 mol-%)
9
Interestingly, when the dicationic complex 16 was dis-
solved in non-polar solvents, such as dichloromethane or
tetrahydrofuran, it readily evolved into the known mono-
cationic derivative fac-[RuCl{κ1-(P)-PPh2py}{κ2-(P,N)-
PPh2py}2][Cl] (17) by coordination of one of the chloride
counter-anions to ruthenium (Scheme 5).[31] This is clearly
evidenced in the 31P{1H} NMR spectra in which the singlet
at –4.1 ppm splits into three new signals at –8.0 [dd, 2J(P,P)
10
11
12
13
none
PPh2py (1; 5 mol-%)
PPh2py (1; 10 mol-%)
61
Ͼ99
[a] Reactions performed under N2 at 100 °C with 1 mmol of benzo-
nitrile (0.33 m in water). Substrate/Ru ratio: 100:5. [b] Yield of
benzamide determined by GC.
2
= 33.1, 27.7 Hz], –6.4 (dd, JP,P = 27.7, 27.7 Hz) and 47.5
For a better understanding of the role of the PPh2py li- (dd, 2JP,P = 33.1, 27.7 Hz) ppm. Remarkably, such a chelate
gand 1 added during the catalysis, the reactivity of complex ring-opening process is reversible and 16 was instantane-
[RuCl2(η6-p-cymene){κ1-(P)-PPh2py}] (5b) towards 1 was ously recovered when 17 was dissolved in polar media
explored. As shown in Scheme 5, treatment of a methanolic (methanol or water). Hemilabile behaviour was also ob-
solution of 5b with 2.2 equiv. of 1 at reflux resulted in the served for 16 when a dichloromethane solution of this com-
clean formation of the new octahedral derivative [Ru{κ2- plex was treated with excess benzonitrile, the 31P{1H} NMR
(P,N)-PPh2py}3][Cl]2 (16) by displacement of the p-cymene spectrum of the mixture showing, after 5 h at room temp.,
ligand. Complex 16 was isolated as an air-stable yellow so- the formation of mer-[Ru(NCPh){κ1-(P)-PPh2py}{κ2-
lid in 85% yield and characterized by elemental analysis (P,N)-PPh2py}2][Cl]2 (18) as the major product [a character-
and multinuclear NMR spectroscopy (see the Exp. Sect.). istic ABX spin system is observed with signals at –7.5 (m)
In accord with the chemical equivalence of the three PPh2 and 47.3 (t) ppm].[32] Work up of the mixture regenerated
units, a unique singlet resonance is observed in the 31P{1H} 16 quantitatively (Scheme 5).
NMR spectrum of this complex, the chemical shift ob-
In complete accord with the catalytic results collected in
served (δP = –4.1 ppm) being coherent with κ2-(P,N) coordi- Table 3, the dicationic complex [Ru{κ2-(P,N)-PPh2py}3]-
nation. As shown by 31P{1H} NMR spectroscopy, the [Cl]2 (16) proved effective in the hydration of benzonitrile,
[Ru{κ2-(P,N)-PPh2py}3]2+ dication was also formed as the leading to the quantitative formation of benzamide after
major species when methanolic solutions of [RuCl(η6-p- 24 h.[33] The higher reactivity of 16 in comparison with the
cymene){κ2-(P,N)-PPh2py}][SbF6] (7b) and [RuCl(η3:η3- other complexes containing κ2-(P,N)-coordinated 2-(di-
C10H16){κ2-(P,N)-PPh2py}][SbF6] (12) were heated at reflux phenylphosphanyl)pyridines studied in this work most
with an excess of PPh2py.[30] However, in these cases, other probably stems from its hemilabile character. However, we
byproducts were also generated, which prevented its isola- must note that the activity of this complex was still far from
tion in pure form.
that previously reported by us with the ruthenium catalysts
4224
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
A–E depicted in Figure 3,[11e–11g,11i–11j] which were able to
effect the complete hydration of benzonitrile in only 1–5 h
under identical reaction conditions (a conversion of only
36% after 7 h was observed for 16).
experiments were carried out for all the compounds reported in
this paper. The numbering of the H and C atoms of the 2,7-dimeth-
ylocta-2,6-diene-1,8-diyl skeleton is given below.
Conclusions
In the search for cooperative effects of ligands, several
arene-ruthenium(II) and bis(allyl)-ruthenium(IV) com-
plexes with electronically and sterically varied 2-(diphenyl-
phosphanyl)pyridines have been synthesized, structurally
characterized and investigated as potential catalysts for the
selective hydration of nitriles to amides. In contrast to the
previous work of Oshiki and co-workers with this type of
phosphane ligands,[11b,11h,11k] our results from the hydration
[RuCl2(η6-mesitylene){κ1-(P)-PPh2py}] (5c): A solution of dimer
[{RuCl(μ-Cl)(η6-mesitylene)}2] (4c) (0.292 g, 0.5 mmol) in tetra-
hydrofuran (40 mL) was treated with the phosphane ligand 1
(0.316 g, 1.2 mmol) at room temperature for 3 h. The solvent was
of the benzonitrile model substrate ruled out the involve- then removed under reduced pressure to give an orange solid,
which was washed with hexanes (3ϫ20 mL) and dried in vacuo.
Yield 0.461 g (83%). 31P{1H} NMR (CDCl3): δ = 29.4 (s) ppm. 1H
NMR (CDCl3): δ = 1.90 (s, 9 H, C6H3Me3), 4.91 (s, 3 H,
ment of bifunctional pathways during the catalytic events.
In fact, the high tendency of PPh2py (1) and PPh2(py-4-
NMe2) (2) to adopt chelating coordination results in the
formation of species with very low activity, whereas in the
case of PPh2(py-6-tert-amyl) (3) the presence of the bulky
tert-amyl substituent seems to prevent the approach of the
substrate to the Lewis acid metal centre, also leading to
poor results in the catalysis. Although improvements in the
catalytic activities of complexes [RuCl2(η6-p-cymene){κ1-
3
C6H3Me3), 7.25–7.96 (m, 13 H, CHarom), 8.70 (d, JH,H = 8.0 Hz,
1
H, CHarom) ppm. 13C{1H} NMR (CD2Cl2):
δ = 18.0 (s,
C6H3Me3), 86.1 (s, CH of mes), 103.7 (s, C of mes), 123.8 and 130.2
(s, CHarom), 127.6 (br., CHarom), 131.7 (d, 3JP,C = 23.1 Hz, CHarom),
133.0 (d, 1JP,C = 45.3 Hz, Carom), 135.1 (d, 2JP,C = 8.0 Hz, CHarom),
3
1
148.5 (d, JP,C = 15.1 Hz, CHarom), 158.8 (d, JP,C = 68.4 Hz,
Carom) ppm. C26H26Cl2NPRu (555.45): calcd. C 56.22, H 4.72, N
(P)-PPh2py}],
[RuCl(η6-p-cymene){κ2-(P,N)-PPh2py}]- 2.52; found C 56.34, H 4.77, N 2.69.
[SbF6] and [RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2py}][SbF6]
were observed in the presence of excess PPh2py due to the
in situ formation of the more active dication [Ru{κ2-(P,N)-
PPh2py}3]2+, the results obtained are still far from the
benchmarks already described in the literature for this cata-
lytic transformation. Overall, the results described herein
demonstrate that cooperative effects of ligands in homogen-
eous catalysis depend not only on the ligand structure, but
also on the metal fragment to which they are attached. For
the particular case of 2-(diphenylphosphanyl)pyridine li-
gands, hemilability seems to be a key factor that must be
taken into account when designing catalysts with these li-
gands.
[RuCl2(η6-arene){κ1-(P)-PPh2(py-4-NMe2)}] [arene = benzene (6a),
p-cymene (6b), mesitylene (6c)]: A solution of the appropriate dimer
[{RuCl(μ-Cl)(η6-arene)}2] (4a–c) (0.5 mmol) in tetrahydrofuran
(40 mL) was treated with the phosphane ligand 2 (0.367 g,
1.2 mmol) at room temperature for 2 (6b,c) or 6 h (6a). The solvent
was then removed under reduced pressure to give an orange solid,
which was washed with hexanes (3ϫ20 mL) and dried in vacuo.
6a: Yield 0.467 g (84%). 31P{1H} NMR (CDCl3): δ = 26.5 (s) ppm.
1H NMR (CDCl3): δ = 2.78 [s, 6 H, N(CH3)2], 5.57 (s, 6 H, C6H6),
6.43 (m, 2 H, CHarom), 7.35 (m, 6 H, CHarom), 7.90 (m, 4 H,
3
CHarom), 8.37 (d, JH,H = 6.0 Hz, 1 H, CHarom) ppm. 13C{1H}
2
NMR (CD2Cl2): δ = 38.6 [s, N(CH3)2], 89.1 (d, JP,C = 3.0 Hz,
2
C6H6), 106.4 and 130.3 (s, CHarom), 114.1 (d, JP,C = 22.1 Hz,
3
1
CHarom), 127.8 (d, JP,C = 12.0 Hz, CHarom), 133.2 (d, JP,C
=
2
3
46.2 Hz, Carom), 134.7 (d, JP,C = 8.0 Hz, CHarom), 149.3 (d, JP,C
3
= 16.0 Hz, CHarom), 153.6 (d, JP,C = 11.1 Hz, Carom), 156.8 (d,
1JP,C = 69.4 Hz, Carom) ppm. C25H25Cl2N2PRu (556.44): calcd. C
Experimental Section
53.96, H 4.53, N 5.03; found C 54.15, H 4.44, N 5.21.
General: Synthetic procedures were performed under dry nitrogen
using vacuum-line and standard Schlenk techniques. Solvents were
dried by standard methods and distilled under nitrogen before use.
The phosphane ligand 2[34] and the ruthenium(II) complexes
6b: Yield 0.496 g (81%). 31P{1H} NMR (CDCl3): δ = 21.9 (s) ppm.
3
1H NMR (CDCl3): δ = 0.97 [d, JH,H = 6.9 Hz, 6 H, CH(CH3)2],
3
1.75 (s, 3 H, CH3), 2.64 [sept., JH,H = 6.9 Hz, 1 H, CH(CH3)2],
[{RuCl(μ-Cl)(η6-arene)}2] (4a–d),[35] [RuCl2(η6-arene){κ1-(P)- 2.80 [s, 6 H, N(CH3)2], 5.36 and 5.48 (d, 3JH,H = 6.3 Hz, 2 H each,
PPh2py}] (5a,b,d),[15] [RuCl(η6-arene){κ2-(P,N)-PPh2py}][SbF6]
(7a,b,d),[15] [RuCl2(η6-arene)(PPh3)] (9a–d),[35a,36] [{RuCl(μ-
CH of cym), 6.50 (m, 2 H, CHarom), 7.36 (m, 6 H, CHarom), 8.04
3
(m, 4 H, CHarom), 8.40 (d, JH,H = 6.1 Hz, 1 H, CHarom) ppm.
Cl)(η3:η3-C10H16)}2] (11),[37] and [RuCl2(η3:η3-C10H16)(PPh3)] (15) 13C{1H} NMR (CD2Cl2): δ = 16.9 (s, CH3), 21.5 [s, CH(CH3)2],
[38]
2
were prepared by following the methods reported in the litera-
30.1 [s, CH(CH3)2], 38.6 [s, N(CH3)2], 85.4 (d, JP,C = 5.0 Hz, CH
2
ture. The rest of the reagents employed in this work were obtained
from commercial suppliers and used as received. C, H and N analy-
ses were carried out with a Perkin–Elmer 2400 microanalyser.
NMR spectra were recorded with Bruker DPX300 or AV400 in-
struments. Chemical shifts are given in ppm, relative to internal
tetramethylsilane (1H and 13C), and external 85% aqueous H3PO4
solutions (31P). The coupling constants J are given in Hz. DEPT
of cym), 91.0 (d, JP,C = 3.0 Hz, CH of cym), 94.8 and 109.0 (s, C
2
of cym), 106.3 and 130.0 (s, CHarom), 114.3 (d, JP,C = 19.1 Hz,
3
1
CHarom), 127.5 (d, JP,C = 11.0 Hz, CHarom), 132.4 (d, JP,C
=
2
3
43.7 Hz, Carom), 134.9 (d, JP,C = 8.0 Hz, CHarom), 148.8 (d, JP,C
3
= 18.1 Hz, CHarom), 153.4 (d, JP,C = 11.7 Hz, Carom), 157.8 (d,
1JP,C = 74.4 Hz, Carom) ppm. C29H33Cl2N2PRu (612.54): calcd. C
56.86, H 5.43, N 4.57; found C 56.93, H 5.32, N 4.71.
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4225

P. Crochet, V. Cadierno et al.
FULL PAPER
6c: Yield 0.526 g (88%). 31P{1H} NMR (CDCl3): δ = 28.3 (s) ppm.
3
= 45.2 Hz, Carom), 129.5 and 130.0 (d, JP,C = 11.1 Hz, CHarom),
1
2
1H NMR (CDCl3): δ = 1.90 (s, 9 H, C6H3Me3), 2.89 [s, 6 H, 129.8 (d, JP,C = 47.5 Hz, Carom), 131.4 and 134.9 (d, JP,C
=
4
N(CH3)2], 4.90 (s, 3 H, C6H3Me3), 6.40 (m, 2 H, CHarom), 7.36 (m, 10.0 Hz, CHarom), 132.1 and 132.8 (d, JP,C = 3.0 Hz, CHarom),
6 H, CHarom), 8.03 (m, 4 H, CHarom), 8.31 (d, JH,H = 6.0 Hz, 1 151.5 (d, 3JP,C = 18.1 Hz, CHarom), 154.4 (d, 3JP,C = 5.0 Hz, Carom),
3
H, CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 18.0 (s, C6H3Me3),
166.6 (d, JP,C
=
59.0 Hz, Carom) ppm. C29H33ClF6N2PRuSb
1
38.9 [s, N(CH3)2], 85.9 (s, CH of mes), 105.6 (s, C of mes), 106.4 (812.83): calcd. C 42.85, H 4.09, N 3.45; found C 42.70, H 4.18, N
and 129.9 (s, CHarom), 115.8 (d, 2JP,C = 28.2 Hz, CHarom), 127.4 (d,
3.66.
1
3JP,C = 13.0 Hz, CHarom), 133.8 (d, JP,C = 45.3 Hz, Carom), 135.0
8c: Yield 0.311 g (78%). 31P{1H} NMR (CDCl3): δ = –13.2
(s) ppm. H NMR (CDCl3): δ = 2.17 (s, 9 H, C6H3Me3), 3.08 [s, 6
H, N(CH3)2], 5.08 (s, 3 H, C6H3Me3), 6.50 and 6.78 (m, 1 H each,
2
3
(d, JP,C = 9.0 Hz, CHarom), 148.7 (d, JP,C = 16.1 Hz, CHarom),
1
3
1
153.4 (d, JP,C = 14.1 Hz, Carom), 157.5 (d, JP,C = 62.8 Hz,
Carom) ppm. C28H31Cl2N2PRu (598.52): calcd. C 56.19, H 5.22, N
4.68; found C 55.92, H 5.40, N 4.60.
3
CHarom), 7.45–7.91 (m, 10 H, CHarom), 8.11 (d, JH,H = 6.4 Hz, 1
H, CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 18.9 (s, C6H3Me3),
39.5 [s, N(CH3)2], 82.3 (s, CH of mes), 105.9 (s, C of mes), 110.7
(d, 2JP,C = 4.5 Hz, CHarom), 111.6 (d, 4JP,C = 3.0 Hz, CHarom), 121.5
[RuCl(η6-mesitylene){κ2-(P,N)-PPh2py}][SbF6] (7c): An orange
solution of complex 5c (0.278 g, 0.5 mmol) in methanol (20 mL)
was treated with NaSbF6 (0.194 g, 0.75 mmol) at room temperature
for 4 h. The solvent was then removed under reduced pressure to
give a yellow solid, which was dissolved in CH2Cl2 (10 mL), filtered
through Kieselguhr and the filtrate concentrated to around 3 mL.
Addition of hexanes (30 mL) led to the precipitation of a yellow
microcrystalline solid, which was washed with hexanes (3ϫ20 mL)
and vacuum-dried. Yield 0.287 g (76%). 31P{1H} NMR (CDCl3):
1
3
(d, JP,C = 46.0 Hz, Carom), 129.2 and 129.7 (d, JP,C = 12.1 Hz,
CHarom), 130.0 (d, 1JP,C = 49.1 Hz, Carom), 131.9 and 135.0 (d, 2JP,C
4
= 10.3 Hz, CHarom), 132.3 and 132.9 (d, JP,C = 3.0 Hz, CHarom),
151.0 (d, 3JP,C = 18.2 Hz, CHarom), 154.4 (d, 3JP,C = 5.3 Hz, Carom),
1
166.8 (d, JP,C
= 63.4 Hz, Carom) ppm. C28H31ClF6N2PRuSb
(798.80): calcd. C 42.10, H 3.91, N 3.51; found C 42.23, H 3.86, N
3.69.
1
δ = –12.3 (s) ppm. H NMR (CDCl3): δ = 2.20 (s, 9 H, C6H3Me3),
[RuCl(η6-hexamethylbenzene){κ2-(P,N)-PPh2(py-4-NMe2)}][SbF6]
(8d): A solution of dimer [{RuCl(μ-Cl)(η6-hexamethylbenzene)}2]
(4d; 0.334 g, 0.5 mmol) in tetrahydrofuran (40 mL) was treated with
the phosphane ligand 2 (0.367 g, 1.2 mmol) at room temperature
for 2 h. Methanol (10 mL) and NaSbF6 (0.388 g, 1.5 mmol) were
then added and the resulting mixture was stirred at room tempera-
ture for 1 h. After this time, solvents were removed under reduced
pressure and CH2Cl2 (10 mL) was added. The resulting suspension
was filtered through Kieselguhr and the filtrate concentrated to
around 3 mL. Addition of hexanes (30 mL) led to the precipitation
of a yellow microcrystalline solid, which was washed with diethyl
ether (3ϫ10 mL) and vacuum-dried. Yield 0.647 g (77%). 31P{1H}
5.22 (s, 3 H, C6H3Me3), 7.15–8.04 (m, 13 H, CHarom), 8.78 (d, 3JH,H
= 8.1 Hz, 1 H, CHarom) ppm. 13C{1H} NMR ([D6]acetone): δ =
18.3 (s, C6H3Me3), 82.6 (s, CH of mes), 107.5 (s, C of mes), 121.6
1
3
(d, JP,C = 48.3 Hz, Carom), 129.1 and 129.8 (d, JP,C = 11.1 Hz,
2
CHarom), 129.3 and 139.6 (d, JP,C = 4.0 Hz, CHarom), 130.1 (d,
1JP,C = 55.3 Hz, Carom), 130.4, 132.3 and 132.9 (s, CHarom), 132.2
3
2
(d, JP,C = 11.5 Hz, CHarom), 135.3 (d, JP,C = 7.1 Hz, CHarom),
3
1
153.9 (d, JP,C = 14.0 Hz, CHarom), 168.3 (d, JP,C = 63.4 Hz,
arom) ppm. C26H26ClF6NPRuSb (755.73): calcd. C 41.32, H 3.47,
C
N 1.85; found C 41.46, H 3.39, N 2.01.
[RuCl(η6-arene){κ2-(P,N)-PPh2(py-4-NMe2)}][SbF6] [arene = benz-
ene (8a), p-cymene (8b), mesitylene (8c)]: Compounds 8a–c, isolated
as air-stable yellow solids, were prepared as described for 7c start-
ing from the appropriate neutral complex [RuCl2(η6-arene){κ1-(P)-
PPh2(py-4-NMe2)}] (6a–c) (0.5 mmol) and NaSbF6 (0.194 g,
0.75 mmol).
1
NMR (CDCl3): δ = –8.5 (s) ppm. H NMR (CDCl3): δ = 2.05 (s,
18 H, C6Me6), 3.01 [s, 6 H, N(CH3)2], 6.46 and 6.79 (m, 1 H each,
CHarom), 7.19 (m, 2 H, CHarom), 7.54–7.79 (m, 8 H, CHarom), 7.92
3
(d, JH,H = 6.5 Hz, 1 H, CHarom) ppm. 13C{1H} NMR (CD2Cl2):
1
δ = 15.6 (s, C6Me6), 39.4 [s, N(CH3)2], 96.9 (d, JP,C = 3.0 Hz,
8a: Yield 0.284 g (75%). 31P{1H} NMR (CDCl3): δ = –18.6
C6Me6), 110.4 (d, 2JP,C = 5.0 Hz, CHarom), 111.0 (d, 4JP,C = 3.0 Hz,
1
1
1
(s) ppm. H NMR (CDCl3): δ = 2.97 [s, 6 H, N(CH3)2], 5.75 (s, 6
CHarom), 123.6 (d, JP,C = 44.2 Hz, Carom), 128.4 (d, JP,C
=
48.2 Hz, Carom), 129.0 and 129.8 (d, 3JP,C = 11.1 Hz, CHarom), 132.0
H, C6H6), 6.57 and 6.78 (m, 1 H each, CHarom), 7.39–7.92 (m, 10
3
H, CHarom), 8.28 (d, JH,H = 5.5 Hz, 1 H, CHarom) ppm. 13C{1H}
4
2
and 132.7 (d, JP,C = 3.0 Hz, CHarom), 132.2 and 135.1 (d, JP,C
=
9.5 Hz, CHarom), 148.0 (d, 3JP,C = 18.1 Hz, CHarom), 154.5 (d, 3JP,C
NMR (CD2Cl2): δ = 39.6 [s, N(CH3)2], 87.4 (s, C6H6), 111.5 (br.,
3
1
2 C, CHarom), 129.6 and 130.0 (d, JP,C = 15.0 Hz, CHarom), 130.2
=
5.0 Hz, Carom), 167.4 (d, JP,C
=
62.4 Hz, Carom) ppm.
1
2
(d, JP,C = 58.3 Hz, Carom), 131.4 and 134.9 (d, JP,C = 9.0 Hz,
C31H37ClF6N2PRuSb (840.88): calcd. C 44.28, H 4.44, N 3.33;
found C 44.36, H 4.29, N 3.45.
1
CHarom), 132.2 and 133.0 (s, CHarom), 133.6 (d, JP,C = 57.6 Hz,
Carom), 152.4 (d, JP,C = 12.1 Hz, CHarom), 154.4 (d, JP,C
4.0 Hz, Carom), 166.1 (d, JP,C
3
3
=
[RuCl2(η6-arene){κ1-(P)-PPh2(py-6-tert-amyl)}] [arene = benzene
(10a), p-cymene (10b)]: Complexes 10a,b, isolated as air-stable
orange solids, were prepared as described for 6a,b starting from the
appropriate dimer [{RuCl(μ-Cl)(η6-arene)}2] (4a,b) (0.5 mmol) and
the phosphane ligand 3 (0.400 g, 1.2 mmol).
1
=
40.2 Hz, Carom) ppm.
C25H25ClF6N2PRuSb (756.72): calcd. C 39.68, H 3.33, N 3.70;
found C 39.54, H 3.42, N 3.83.
8b: Yield 0.325 g (80%). 31P{1H} NMR (CDCl3): δ = –19.3
3
(s) ppm. 1H NMR (CDCl3): δ = 1.18 [d, JH,H = 6.6 Hz, 3 H,
3
CH(CH3)2], 1.26 [d, JH,H = 7.1 Hz, 3 H, CH(CH3)2], 2.03 (s, 3 H,
10a: Yield 0.519 g (89%). 31P{1H} NMR (CDCl3): δ = 25.0
3
CH3), 2.63 [m, 1 H, CH(CH3)2], 2.92 [s, 6 H, N(CH3)2], 5.18 and
(s) ppm. 1H NMR (CDCl3): δ = 0.79 (t, JH,H = 8.0 Hz, 3 H,
3
3
5.73 (d, JH,H = 6.0 Hz, 1 H each, CH of cym), 5.50 and 5.61 (d,
CH2CH3), 1.41 [s, 6 H, C(CH3)2], 1.83 (q, JH,H = 8.0 Hz, 2 H,
CH2CH3), 5.55 (s, 6 H, C6H6), 7.12–7.60 (m, 9 H, CHarom), 7.92
3JH,H = 5.5 Hz, 1 H each, CH of cym), 6.57 and 6.80 (m, 1 H each,
3
CHarom), 7.42–7.90 (m, 10 H, CHarom), 8.17 (d, JH,H = 6.6 Hz, 1 (m, 4 H, CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 9.0 (s,
H, CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 18.2 (s, CH3), 21.8 CH2CH3), 27.2 [s, C(CH3)2], 35.9 (s, CH2CH3), 41.3 [s, C(CH3)2],
2
and 22.7 [s, CH(CH3)2], 30.9 [s, CH(CH3)2], 39.5 [s, N(CH3)2], 83.9
89.0 (d, JP,C = 3.0 Hz, C6H6), 120.9 and 130.4 (s, CHarom), 127.7
2
2
3
3
and 87.1 (d, JP,C = 3.0 Hz, CH of cym), 85.8 and 89.5 (d, JP,C
=
(d, JP,C = 12.0 Hz, CHarom), 127.8 (d, JP,C = 22.9 Hz, CHarom),
133.0 (d, 1JP,C = 48.3 Hz, Carom), 134.8 (d, 2JP,C = 9.0 Hz, CHarom),
135.8 (d, 2JP,C = 8.0 Hz, CHarom), 156.8 (d, 1JP,C = 71.4 Hz, Carom),
2
5.0 Hz, CH of cym), 101.8 and 107.6 (s, C of cym), 111.4 (d, JP,C
= 4.8 Hz, CHarom), 111.6 (d, 4JP,C = 3.0 Hz, CHarom), 129.3 (d, 1JP,C
4226
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
3
4
168.0 (d, JP,C = 15.1 Hz, Carom) ppm. C28H30Cl2NPRu (583.50): 112.2 (d, JP,C = 1.5 Hz, CHarom), 113.4 (d, 2JP,C = 11.8 Hz, C-3 or
2
2
calcd. C 57.64, H 5.18, N 2.40; found C 57.50, H 5.31, N 2.59.
C-6), 114.4 (d, JP,C = 4.4 Hz, CHarom), 116.8 (d, JP,C = 2.2 Hz,
C-2 or C-7), 118.6 (d, JP,C = 1.5 Hz, C-2 or C-7), 128.7 (d, JP,C
2
1
10b: Yield 0.544 g (85%). 31P{1H} NMR (CDCl3): δ = 20.1
1
= 47.4 Hz, Carom), 128.9 (d, JP,C = 48.1 Hz, Carom), 129.6 and
(s) ppm. 1H NMR (CDCl3): δ = 0.79 (t, JH,H = 8.6 Hz, 3 H,
3
129.9 (d, 3JP,C = 12.4 Hz, CHarom), 131.8–132.4 (m, CHarom), 149.3
3
CH2CH3), 0.92 [d, JH,H = 6.2 Hz, 6 H, CH(CH3)2], 1.43 [s, 6 H,
C(CH3)2], 1.63 (s, 3 H, CH3), 1.85 (q, JH,H = 8.6 Hz, 2 H,
(d, 3JP,C = 14.8 Hz, CHarom), 155.0 (d, 3JP,C = 5.1 Hz, Carom), 162.3
3
1
(d, JP,C = 59.2 Hz, Carom) ppm. C29H35ClF6N2PRuSb (814.84):
calcd. C 42.75, H 4.33, N 3.44; found C 42.84, H 4.21, N 3.62.
3
CH2CH3), 2.62 [sept., JH,H = 6.2 Hz, 1 H, CH(CH3)2], 5.21 (d,
3JH,H = 6.5 Hz, 2 H, CH of cym), 5.45 (dd, JH,H = 6.5, JP,H
=
3
3
2.0 Hz, 2 H, CH of cym), 7.25–7.54 (m, 9 H, CHarom), 8.11 (m, 4
[RuCl2(η3:η3-C10H16){κ1-(P)-PPh2(py-6-tert-amyl)}] (14): A solu-
H, CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 9.1 (s, CH2CH3), tion of dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (11; 0.308 g,
16.8 (s, CH3), 21.3 [s, CH(CH3)2], 27.2 [s, C(CH3)2], 30.0 [s, 0.5 mmol) in dichloromethane (40 mL) was treated with the phos-
2
CH(CH3)2], 35.9 (s, CH2CH3), 41.3 [s, C(CH3)2], 85.1 (d, JP,C
=
phane ligand 3 (0.400 g, 1.2 mmol) at room temperature for 15 min.
5.0 Hz, CH of cym), 90.9 (s, CH of cym), 94.5 and 110.2 (s, C of
cym), 120.6 and 130.0 (s, CHarom), 127.4 (d, JP,C = 12.1 Hz, yellow solid, which was washed with hexanes (3ϫ20 mL) and dried
The solvent was then removed under reduced pressure to give a
3
3
1
CHarom), 128.2 (d, JP,C = 24.1 Hz, CHarom), 134.3 (d, JP,C
=
in vacuo. Yield 0.583 g (91%). 31P{1H} NMR (CD2Cl2): δ = 25.8
44.3 Hz, Carom), 135.0 (d, JP,C = 10.0 Hz, CHarom), 135.6 (d, JP,C (s) ppm. 1H NMR (CD2Cl2): δ = 0.75 (t, JH,H = 7.5 Hz, 3 H,
2
2
3
= 8.0 Hz, CHarom), 158.3 (d, 1JP,C = 67.4 Hz, Carom), 167.3 (d, 3JP,C
= 13.1 Hz, Carom) ppm. C32H38Cl2NPRu (639.61): calcd. C 60.09,
H 5.99, N 2.19; found C 60.20, H 5.87, N 2.34.
CH2CH3), 1.41 and 1.42 [s, 3 H each, C(CH3)2], 1.87 (q, JH,H
=
3
7.5 Hz, 2 H, CH2CH3), 2.24 (s, 6 H, CH3), 2.64 (m, 2 H, 4-H and
3
6-H), 2.91 (d, JP,H = 3.3 Hz, 2 H, 2-H and 10-H), 3.46 (m, 2 H,
5-H and 7-H), 4.70 (d, 3JP,H = 8.9 Hz, 2 H, 1-H and 9-H), 5.16 (m,
2 H, 3-H and 8-H), 7.10–7.44 (m, 9 H, CHarom), 8.03 (m, 4 H,
CHarom) ppm. 13C{1H} NMR (CD2Cl2): δ = 9.5 (s, CH2CH3), 20.8
(s, CH3), 27.6 and 27.8 [s, C(CH3)2], 36.3 (s, CH2CH3), 37.2 (s, C-
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2py}][SbF6]
[RuCl(η3:η3-C10H16){κ2-(P,N)-PPh2(py-4-NMe2)}][SbF6] (13):
(12)
and
A
solution of dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (11; 0.308 g,
0.5 mmol) in dichloromethane (40 mL) was treated with the appro-
priate phosphane ligand 1 or 2 (1.2 mmol) at room temperature for
15 min. The solvent was then removed under reduced pressure to
give a yellow solid, which was washed with hexanes (3ϫ20 mL)
and dried in vacuo. The resulting solid was dissolved in CH2Cl2/
MeOH (20 mL, 1:1, v/v) and treated with NaSbF6 (0.776 g,
3 mmol) at room temperature. After stirring for 1 h, the solvents
were removed under reduced pressure and CH2Cl2 (10 mL) was
added. The resulting suspension was filtered through Kieselguhr
and the filtrate concentrated to around 3 mL. The addition of hex-
anes (30 mL) led to the precipitation of a yellow microcrystalline
solid, which was washed with diethyl ether (3ϫ10 mL) and vac-
uum-dried.
2
4 and C-5), 41.7 [s, C(CH3)2], 67.0 (d, JP,C = 5.2 Hz, C-1 and C-
2
8), 108.8 (d, JP,C = 9.8 Hz, C-3 and C-6), 119.8 and 127.7 (s,
CHarom), 125.8 (s, C-2 and C-7), 127.0 (d, 3JP,C = 10.3 Hz, CHarom),
3
4
127.7 (d, JP,C = 10.6 Hz, CHarom), 129.6 and 130.1 (d, JP,C
=
1
3
1.8 Hz, CHarom), 134.3 (d, JP,C = 44.4 Hz, Carom), 135.1 (d, JP,C
1
= 14.1 Hz, CHarom), 135.8 (d, JP,C = 46.3 Hz, Carom), 136.2 (d,
2JP,C = 7.4 Hz, CHarom), 137.3 (d, JP,C = 8.0 Hz, CHarom), 160.0
2
1
3
(d, JP,C = 65.2 Hz, Carom), 167.1 (d, JP,C = 13.4 Hz, Carom) ppm.
C32H40Cl2NPRu (641.62): calcd. C 59.90, H 6.28, N 2.18; found C
60.03, H 6.16, N 2.25.
[Ru{κ2-(P,N)-PPh2py}3][Cl]2 (16): A solution of complex [RuCl2(η6-
p-cymene){κ1-(P)-PPh2py}] (5b; 0.285 g, 0.5 mmol) and the phos-
phane ligand 1 (0.290 g, 1.1 mmol) was heated at reflux in meth-
anol (30 mL) for 8 h. The colour of the solution progressively
changed from orange to yellow. After cooling the mixture, the sol-
vent was removed under vacuum and the solid residue was washed
with hexanes (3ϫ20 mL) and diethyl ether (10 mL) and dried in
vacuo. Yield 0.409 g (85%). 31P{1H} NMR (CD3OD): δ = –4.1
(s) ppm. 1H NMR (CD3OD): δ = 6.71 (br., 6 H, CHarom), 7.12–
7.91 (m, 30 H, CHarom), 8.19–8.35 (m, 6 H, CHarom) ppm. 13C{1H}
NMR (CD3OD): δ = 126.7 (m, Carom), 128.9 (m, CHarom), 129.4
(m, CHarom), 130.1 (s, CHarom), 131.6 (s, CHarom), 132.2 (m,
CHarom), 132.6 (s, CHarom), 132.9 (m, CHarom), 139.9 (s, CHarom),
151.6 (m, CHarom), 171.0 (s, Carom) ppm. C51H42Cl2N3P3Ru
(961.81): calcd. C 63.69, H 4.40, N 4.37; found C 63.55, H 4.28, N
4.56.
12: Yield 0.663 g (86%). 31P{1H} NMR (CD2Cl2): δ = –39.1
(s) ppm. 1H NMR (CD2Cl2): δ = 1.99 and 2.35 (s, 3 H each, CH3),
3
2.33 (d, JP,H = 7.9 Hz, 1 H, 2-H or 2-H), 2.98 (m, 2 H, 4-H and
3
6-H), 3.29 (m, 2 H, 5-H and 7-H), 3.44 (d, JP,H = 5.1 Hz, 1 H, 2-
3
H or 10-H), 3.70 (d, JP,H = 8.3 Hz, 1 H, 1-H or 9-H), 3.75 and
3
4.73 (m, 1 H each, 3-H and 8-H), 3.83 (d, JP,H = 6.8 Hz, 1 H,
1-H or 9-H), 7.51–8.25 (m, 14 H, CHarom) ppm. 13C{1H} NMR
(CD2Cl2): δ = 19.7 (s, 2 C, CH3), 33.8 and 37.1 (s, C-4 and C-5),
2
71.2 (d, 2JP,C = 3.1 Hz, C-1 or C-8), 71.5 (d, JP,C = 4.1 Hz, C-1 or
2
2
C-8), 102.9 (d, JP,C = 5.6 Hz, C-3 or C-6), 115.7 (d, JP,C
=
11.2 Hz, C-3 or C-6), 119.0 and 119.3 (s, C-2 and C-7), 128.3 (d,
3
1JP,C = 49.7 Hz, Carom), 129.9 and 130.1 (d, JP,C = 11.0 Hz,
CHarom), 131.3 (s, CHarom), 131.7–132.7 (m, Carom and CHarom),
2
3
141.0 (d, JP,C = 3.5 Hz, CHarom), 153.6 (d, JP,C = 13.3 Hz,
CHarom), 164.2 (d, 57.8 Hz, Carom) ppm.
1JP,C
=
General Procedure for the Catalytic Hydration of Benzonitrile: Un-
der nitrogen, benzonitrile (0.103 g, 1 mmol), water (3 mL), the cor-
responding ruthenium complex (0.05 mmol; 5 mol-% of Ru) and
additive (when indicated) were introduced into a sealed tube and
the reaction mixture was stirred at 100 °C for 24 h. Conversion was
determined by GC, analysing a sample of around 20 μL of the
crude reaction mixture, which was extracted with CH2Cl2 (3 mL).
The identity of the resulting benzamide was assessed by compari-
son with a commercially available pure sample.
C27H30ClF6NPRuSb (771.78): calcd. C 42.02, H 3.92, N 1.81;
found C 42.06, H 4.13, N 2.01.
13: Yield 0.733 g (90%). 31P{1H} NMR (CD2Cl2): δ = –38.3
(s) ppm. 1H NMR (CD2Cl2): δ = 2.01 and 2.33 (s, 3 H each, CH3),
2.95–3.29 (m, 6 H, 2-H, 4-H, 5-H, 6-H, 7-H and 10-H), 3.15 (s, 6
H, N(CH3)2), 3.49 and 4.52 (m, 1 H each, 3-H and 8-H), 3.67 (d,
3
3JP,H = 7.9 Hz, 1 H, 1-H or 9-H), 3.72 (d, JP,H = 6.4 Hz, 1 H, 1-
H or 9-H), 6.70, 6.94 and 7.15 (m, 1 H each, CHarom), 7.47–7.71
(m, 8 H, CHarom), 8.11 (m, 2 H, CHarom) ppm. 13C{1H} NMR X-ray Crystal Structure Determinations of Complexes 8c, 10a and
(CD2Cl2): δ = 19.3 and 19.7 (s, CH3), 33.3 and 36.5 (s, C-4 and C-
12: Crystals of 8c and 12 suitable for X-ray diffraction analysis
were obtained by the slow diffusion of diethyl ether into saturated
solutions of the complexes in acetone or dichloromethane, respec-
2
5), 40.0 [s, N(CH3)2], 71.2 (d, JP,C = 3.7 Hz, C-1 or C-8), 71.6 (d,
2
2JP,C = 4.4 Hz, C-1 or C-8), 101.1 (d, JP,C = 5.9 Hz, C-3 or C-6),
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4227

P. Crochet, V. Cadierno et al.
FULL PAPER
Table 4. Crystal data and structure refinement details for 8c, 10a and 12.
8c
10a
12
Chemical formula
Molecular mass
T [°K]
Wavelength [Å]
Crystal system
Space group
Crystal size [mm]
a [Å]
Ru2C56H62F12N4Cl2P2Sb2
1597.58
293(2)
1.5418
orthorhombic
Pca21
0.196ϫ0.057ϫ0.031
25.393(5)
15.340(5)
16.063(5)
90
RuC28H30Cl2NP
583.47
293(2)
1.5418
monoclinic
P21/c
0.32ϫ0.20ϫ0.18
10.0028(3)
11.8993(3)
22.2935(4)
90
RuC27H30F6ClNPSb
771.76
293(2)
1.5418
monoclinic
P21/c
0.254ϫ0.204ϫ0.093
10.4788(2)
16.0744(2)
18.0987(3)
90
b [Å]
c [Å]
α [°]
β [°]
γ [°]
90
90
97.803(2)
90
105.461(2)
90
Z
4
4
4
V [Å3]
6257(3)
1.696
12.529
2628.9(2)
1.474
7.390
2938.23(8)
1.745
13.304
ρcalcd. [gcm–3]
μ [mm–1]
F(000)
3152
1192
1520
θ range [°]
Index ranges
2.88–74.75
–31ՅhՅ31
–18ՅkՅ13
–19ՅlՅ13
98.0
29535
9878 (Rint = 0.0286)
731/0
4.00–74.77
–11ՅhՅ11
–14ՅkՅ14
–27ՅlՅ27
96.7
3.74–74.73
–8ՅhՅ13
–19ՅkՅ18
–22ՅlՅ22
95.6
13656
5757 (Rint = 0.0418)
361/0
Completeness to θmax [%]
No. of data collected
No. of unique data
19302
5218 (Rint = 0.0432)
280/0
No. parameters/restraints
Refinement method
full-matrix least-squares on F2
1.077
Goodness of fit on F2
Weight function (a, b)
1.063
0.0783, 0.5490
0.0395
1.013
0.1138, 0.0000
0.0549
0.0990, 3.1526
0.0555
0.1495
[a]
R1 [IϾ3σ(I)]
[a]
wR2 [IϾ3σ(I)]
0.1058
0.1484
R1 (all data)
0.0414
0.1093
0.0568
0.1517
1.365 and –2.424
0.0632
0.1624
1.715 and –1.009
wR2 (all data)
Largest diff peak and hole [eÅ–3] 0.474 and –0.723
2
2 2
[a] R1 = Σ(|Fo| – |Fc|)/Σ|Fo|; wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}1/2
.
tively. Crystals of 10a were grown by the slow diffusion of n-pent- are given in Table 4) with σ(Fo2) from counting statistics and P =
2
ane into a saturated solution of the complex in tetrahydrofuran. [Max (Fo2,0) + 2Fc ]/3. Atomic scattering factors were taken from
For all crystals, data collection was performed with a Oxford Dif- the International Tables for X-ray Crystallography.[44] Geometrical
fraction Xcalibur Nova single-crystal diffractometer using Cu-Kα calculations were performed with PARST.[45] The crystallographic
radiation (λ = 1.5418 Å). Images were collected at a fixed crystal- plots were prepared by using PLATON.[46] Selected crystal and re-
detector distance of 63 mm by using the oscillation method with finement data are presented in Table 4.
1° oscillation and variable exposure time per image (2–8 s for 8c,
CCDC-884153 (for 8c), -884154 (for 10a) and -884155 (for 12) con-
tain the supplementary crystallographic data for this paper. These
8–30 s for 10a and 1.5–2.5 s for 12). The data collection strategy
was calculated with the program CrysAlis Pro CCD.[39] Data re-
data can be obtained free of charge from The Cambridge Crystallo-
duction and cell refinement was performed with the program Crys-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Alis Pro RED.[39] An empirical absorption correction was applied
by using the SCALE3 ABSPACK algorithm as implemented in the
program CrysAlis Pro RED.[39] The software package WINGX[40]
Acknowledgments
was used for space group determination, structure solution and
refinement. The structures of complexes 8c and 12 were solved by
Patterson interpretation and phase expansion by using SIR92.[41]
The structure of 10a was solved by direct methods using
DIRDIF.[42] Isotropic least-squares refinement on F2 was per-
formed by using SHELXL97.[43] During the final stages of the re-
finements, all the positional parameters and the anisotropic tem-
perature factors of all the non-hydrogen atoms were refined. The
coordinates of the hydrogen atoms were geometrically located and
their coordinates were refined riding on their parent atoms (except
for H1A, H1B, H10A and H10B for 12, which were found from
different Fourier maps and included in a refinement with isotropic
Financial support by the Spanish Ministerio de Ciencia e Innova-
ción (MICINN) (project numbers CTQ2010-14796/BQU,
CTQ2009-08746/BQU and CSD2007-00006) and the Gobierno del
Principado de Asturias (FICYT project FC-11-COF11-13) is grate-
fully acknowledged. S.E.G.-G. also thanks the MICINN and the
European Social Fund for the award of a “Ramón y Cajal“ con-
tract.
[1] See, for example: a) J. Zabicky (Ed.), The Chemistry of Amides,
Wiley, New York, 1970; b) A. Greenberg, C. M. Breneman,
J. F. Liebman (Eds.), The Amide Linkage: Structural Signifi-
cance in Chemistry, Biochemistry and Materials Science, Wiley,
New York, 2000; c) B. L. Deopura, B. Gupta, M. Joshi, R.
2
2
parameters). The function minimized was [Σw(Fo
– Fc )/
Σw(Fo2)]1/2 in which w = 1/[σ2(Fo2) + (aP)2 + bP] (a and b values
4228
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230

Ruthenium Catalysts for Nitrile Hydration Reactions
Alagirusami (Eds.), Polyesters and Polyamides, CRC Press,
Boca Raton, 2008; d) I. Johansson, Kirk-Othmer Encyclopedia
of Chemical Technology, Wiley, New York, 2004, vol. 2, pp.
442–463.
Sammons, T. Sammakia, Angew. Chem. 2010, 122, 2447–2450;
Angew. Chem. Int. Ed. 2010, 49, 2397–2400.
A. Goto, K. Endo, S. Saito, Angew. Chem. 2008, 120, 3663–
3665; Angew. Chem. Int. Ed. 2008, 47, 3607–3609.
[9]
[2]
See, for example: a) H. Yamada, M. Kobayashi, Biosci. Bi-
otechnol. Biochem. 1996, 60, 1391–1400; b) S. van Pelt, F.
van Rantwijk, R. A. Sheldon, Focus in Catalysis Applications
(supplement to Chimica Oggi/Chemistry Today), Teknoscienze
Srl, Milano, Italy, 2008, vol. 26, pp. 2–4; c) S. Sanchez, A. L.
Demain, Org. Process Res. Dev. 2011, 15, 224–230; d) B. Li, J.
Su, J. Tao, Org. Process Res. Dev. 2011, 15, 291–293.
a) P. D. Bailey, T. J. Mills, R. Pettecrew, R. A. Price, in: Com-
prehensive Organic Functional Group Transformations II (Eds.:
A. R. Katritzky, R. J. K. Taylor), Elsevier, Oxford, 2005, vol.
5, pp. 201–294; b) D. Döpp, H. Döpp (Eds.), Methoden Org.
Chem. Houben Weyl, Thieme, Stuttgart, Germany, 1985, vol.
E5(2), pp. 1024–1031.
For reviews on the metal-catalysed hydration of nitriles, see: a)
A. W. Parkins, Platinum Met. Rev. 1996, 40, 169–174; b) V. Y.
Kukushkin, A. J. L. Pombeiro, Chem. Rev. 2002, 102, 1771–
1802; c) N. A. Bokach, V. Y. Kukushkin, Russ. Chem. Bull.
2005, 74, 153–170; d) V. Y. Kukushkin, A. J. L. Pombeiro, In-
org. Chim. Acta 2005, 358, 1–21; e) T. J. Ahmed, S. M. M.
Knapp, D. R. Tyler, Coord. Chem. Rev. 2011, 255, 949–974.
a) C. L. Allen, J. M. J. Williams, Chem. Soc. Rev. 2011, 40,
3405–3415; b) D. J. C. Constable, P. J. Dunn, J. D. Hayler, G. R.
Humphrey, J. L. Laezer Jr, R. J. Linderman, K. Lorenz, J.
Manley, B. A. Pearlman, A. Wells, A. Zaks, T. Y. Zhang, Green
Chem. 2007, 9, 411–420; c) J. S. Carey, D. Laffan, C. Thomson,
M. T. Williams, Org. Biomol. Chem. 2006, 4, 2337–2347.
For selected examples, see: a) K. Mori, K. Yamaguchi, T. Mi-
zugaki, K. Ebitani, K. Kaneda, Chem. Commun. 2001, 461–
462; b) K. Yamaguchi, M. Matsushita, N. Mizuno, Angew.
Chem. 2004, 116, 1602–1606; Angew. Chem. Int. Ed. 2004, 43,
1576–1580; c) T. Mitsudome, Y. Mikami, H. Mori, S. Arita, T.
Mizugaki, K. Jitsukawa, K. Kaneda, Chem. Commun. 2009,
3258–3260; d) V. Polshettiwar, R. S. Varma, Chem. Eur. J. 2009,
15, 1582–1586; e) M. Tamura, H. Wakasugi, K.-I. Shimizu, A.
Satsuma, Chem. Eur. J. 2011, 17, 11428–11431; f) S. E. García-
Garrido, J. Francos, V. Cadierno, J. M. Basset, V. Polshettiwar,
ChemSusChem 2011, 4, 104–111; g) A. Y. Kim, H. S. Bae, S.
Park, S. Park, S. H. Park, Catal. Lett. 2011, 141, 685–690; h)
K.-I. Shimizu, N. Imaiida, K. Sawabe, A. Satsuma, Appl. Ca-
tal. A 2012, 421–422, 114–120; i) Y. Gangarajula, B. Gopal,
Chem. Lett. 2012, 41, 101–103; j) R. B. N. Baig, R. S. Varma,
Chem. Commun. 2012, 48, 6220–6222.
See, for example: a) S.-I. Murahashi, T. Naota, E. Saito, J. Am.
Chem. Soc. 1986, 108, 7846–7847; b) S.-I. Murahashi, S. Sasao,
E. Saito, T. Naota, J. Org. Chem. 1992, 57, 2521–2523; c) S.-I.
Murahashi, S. Sasao, E. Saito, T. Naota, Tetrahedron 1993, 49,
8805–8826; d) S.-I. Murahashi, T. Naota, Bull. Chem. Soc. Jpn.
1996, 69, 1805–1824; e) A. J. M. van Dijk, T. Heyligen, R. Du-
chateau, J. Meuldijk, C. E. Koning, Chem. Eur. J. 2007, 13,
7664–7672.
See, for example: a) T. Ghaffar, A. W. Parkins, Tetrahedron
Lett. 1995, 36, 8657–8660; b) J. Akinsaya, A. W. Parkins, J. W.
Steed, Org. Process Res. Dev. 1998, 2, 274–276; c) T. Ghaffar,
A. W. Parkins, J. Mol. Catal. A 2000, 160, 249–261; d) A. Pa-
pakyprianou, A. W. Parkins, P. D. Prince, J. W. Steed, Org.
Prep. Proced. Int. 2002, 34, 436–440; e) X.-B. Jiang, A. J. Min-
naard, B. L. Feringa, J. G. de Vries, J. Org. Chem. 2004, 69,
2327–2331; f) M. North, A. W. Parkins, A. N. Shariff, Tetrahe-
dron Lett. 2004, 45, 7625–7627; g) T. J. Greshock, R. L. Funk,
Org. Lett. 2006, 8, 2643–2645; h) X. Jiang, N. Williams, J. K.
De Brabander, Org. Lett. 2007, 9, 227–230; i) T. Kan, Y. Kawa-
moto, T. Asakawa, T. Furuta, T. Fukuyama, Org. Lett. 2008,
10, 169–171; j) R. A. Jones, M. J. Krische, Org. Lett. 2009, 11,
1849–1851; k) L. E. Brown, Y. R. Landaverry, J. R. Davies,
K. A. Milinkevich, S. Ast, J. S. Carlson, A. G. Oliver, J. P. Kon-
opelski, J. Org. Chem. 2009, 74, 5405–5410; l) C.-K. Mai, M. F.
[10]
[11]
P. Daw, A. Sinha, S. M. W. Rahaman, S. Dinda, J. K. Bera,
Organometallics 2012, 31, 3790–3797.
a) W. K. Fung, X. Huang, M. L. Man, S. M. Ng, M. Y. Hung,
Z. Lin, C. P. Lau, J. Am. Chem. Soc. 2003, 125, 11539–11544;
b) T. Oshiki, H. Yamashita, K. Sawada, M. Utsunomiya, K.
Takahashi, K. Takai, Organometallics 2005, 24, 6287–6290; c)
C. W. Leung, W. Zheng, D. Wang, S. M. Ng, C. H. Yeung, Z.
Zhou, Z. Lin, C. P. Lau, Organometallics 2007, 26, 1924–1933;
[3]
[4]
ˇ
d) T. Smejkal, B. Breit, Organometallics 2007, 26, 2461–2464;
e) V. Cadierno, J. Francos, J. Gimeno, Chem. Eur. J. 2008, 14,
6601–6605; f) R. García-Álvarez, J. Díez, P. Crochet, V. Cadi-
erno, Organometallics 2010, 29, 3955–3965; g) V. Cadierno, J.
Díez, J. Francos, J. Gimeno, Chem. Eur. J. 2010, 16, 9808–9817;
h) T. Oshiki, I. Hyodo, A. Ishizuka, J. Synth. Org. Chem. Jpn.
2010, 68, 41–51; i) R. García-Álvarez, P. Crochet, V. Cadierno,
Tetrahedron Lett. 2011, 52, 4218–4220; j) R. García-Álvarez, J.
Díez, P. Crochet, V. Cadierno, Organometallics 2011, 30, 5442–
5451; k) M. Muranaka, I. Hyodo, W. Okumura, T. Oshiki, Ca-
tal. Today 2011, 164, 552–555; l) W.-C. Lee, B. J. Frost, Green
Chem. 2012, 14, 62–66; m) S. M. M. Knapp, T. J. Sherbow, J. J.
Juliette, D. R. Tyler, Organometallics 2012, 31, 2941–2944.
[5]
[6]
[12]
For leading accounts and reviews on bifunctional catalysts, see:
a) D. B. Grotjahn, Chem. Eur. J. 2005, 11, 7146–7153; b) A. S.
Borovik, Acc. Chem. Res. 2005, 38, 54–61; c) T. Ikariya, K.
Murata, R. Noyori, Org. Biomol. Chem. 2006, 4, 393–406; d)
T. Ikariya, A. J. Blacker, Acc. Chem. Res. 2007, 40, 1300–1308;
e) D. B. Grotjahn, Dalton Trans. 2008, 6497–6508; f) D. B.
Grotjahn, Chem. Lett. 2010, 39, 908–914; g) D. B. Grotjahn,
Pure Appl. Chem. 2010, 82, 635–647; h) T. Ikariya, I. D. Grid-
nev, Top. Catal. 2010, 53, 894–901; i) D. B. Grotjahn, Top. Ca-
tal. 2010, 53, 1009–1014.
For reviews on the coordination chemistry of phosphanylpyrid-
ine ligands, see: a) G. R. Newkome, Chem. Rev. 1993, 93, 2067–
2089; b) Z.-Z. Zhang, H. Cheng, Coord. Chem. Rev. 1996, 147,
1–39; c) P. Espinet, K. Soulantica, Coord. Chem. Rev. 1999,
193–195, 499–556; d) A. P. Sadimenko, Adv. Heterocycl. Chem.
2011, 104, 391–475.
In addition to our work, arene-ruthenium(II) catalysts for ni-
trile hydration reactions have also been described in: a) S. M.
Ashraf, I. Berger, A. A. Nazarov, C. G. Hartinger, M. P. Koro-
teev, E. E. NifantЈev, B. K. Keppler, Chem. Biodiversity 2008,
5, 1640–1644; b) S. M. Ashraf, W. Kandioller, M.-G. Mendoza-
Ferri, A. A. Nazarov, C. G. Hartinger, B. K. Keppler, Chem.
Biodiversity 2008, 5, 2060–2066; c) A. Cavarzan, A. Scarso, G.
Strukul, Green Chem. 2010, 12, 790–794; d) H. B. Ammar, X.
Miao, C. Fischmeister, L. Toupet, P. H. Dixneuf, Organometal-
lics 2010, 29, 4234–4238; e) S. Kamezaki, S. Akiyama, Y.
Kayaki, S. Kuwata, T. Ikariya, Tetrahedron: Asymmetry 2010,
21, 1169–1172.
[13]
[14]
[7]
[8]
[15]
[16]
a) I. Moldes, E. de la Encarnación, J. Ros, A. Alvarez-Larena,
J. F. Piniella, J. Organomet. Chem. 1998, 566, 165–174; b) D.
Drommi, C. G. Arena, F. Nicolò, G. Bruno, F. Faraone, J. Or-
ganomet. Chem. 1995, 485, 115–121; c) P. Govindaswamy, Y. A.
Mozharivskyj, M. R. Kollipara, Polyhedron 2004, 23, 3115–
3123; d) R. Lalrempuia, P. J. Carroll, M. R. Kollipara, J. Chem.
Sci. 2004, 116, 21–27.
I
To the best of our knowledge only a dinuclear Cu complex,
namely [Cu2I2{PPh2(py-4-NMe2)}3], has previously been iso-
lated in the context of a patented work directed towards the
design of copper complexes for optoelectronic applications: U.
Monkowius, T. Scher, T. Hofbeck, T. Baumann, T. Grab, PCT
Int. Appl. WO2010/149748, 2010.
P. E. Garrou, Chem. Rev. 1981, 81, 229–266.
The crystals measured contain two independent molecules in
the asymmetric unit with very similar structural parameters.
[17]
[18]
Eur. J. Inorg. Chem. 2012, 4218–4230
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4229

P. Crochet, V. Cadierno et al.
FULL PAPER
For brevity, only one conformer is represented in Figure 4, and
only its bond lengths and angles are presented.
J. Gimeno, I. Merino, E. Rubio, F. J. Suárez, Inorg. Chem. 2011,
50, 4868–4881; f) L. Bellarosa, J. Díez, J. Gimeno, A. Lledós,
F. J. Suárez, G. Ujaque, C. Vicent, Chem. Eur. J. 2012, 18,
7749–7765.
[19]
Complexes 5a–d and 6a–c are poorly soluble in water. However,
reasons of solubility cannot be evoked to explain the modest
activities of these complexes because reactions performed in
the presence of the surfactants sodium dodecyl sulfate (SDS)
and cetyltrimethylammonium bromide (CTABr) did not lead
to an improvement in the benzamide yields.
The hydrolysis of benzamide to benzoic acid was not observed
in any of the catalytic reactions listed in Tables 1–3.
This contrasts with the dramatic rate acceleration observed by
Oshiki et al. in the hydration of nitriles catalysed by the octahe-
dral RuII complexes cis-[Ru(acac)2(PR3)2] when moving from
PPh3 to PPh2py; see ref.[11b]
For general reviews on hemilabile coordination complexes, see:
a) C. S. Slone, D. A. Weinberger, C. A. Mirkin, Prog. Inorg.
Chem. 1999, 48, 233–250; b) S. E. Angell, C. W. Rogers, Y.
Zhang, M. O. Wolf, W. E. Jones Jr, Coord. Chem. Rev. 2006,
250, 1829–1841; c) M. Bassetti, Eur. J. Inorg. Chem. 2006,
4473–4482.
a) Complexes 7–8b were recovered unchanged when the reac-
tions were performed at room temp. in different solvents (THF,
CH2Cl2 or MeOH). In refluxing methanol, after prolonged re-
action periods, partial decomposition was observed by release
of the p-cymene ligand; b) variable-temperature 31P{1H} NMR
experiments in CD3CN were also performed with complexes 7–
8b. No chelate ring opening was observed over the 293–353 K
temperature range.
[30] In the case of 12, a RuIV/RuII reduction takes place, the excess
of the phosphane ligand 1 probably acting as the reducing
agent. We note that such a redox chemistry is well documented
for [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (11) and its derivatives (see
ref.[28]). For selected examples, see: a) V. Cadierno, S. E.
García-Garrido, J. Gimeno, J. Am. Chem. Soc. 2006, 128,
15094–15095; b) S. Y. Ng, G. K. Tan, L. L. Koh, W. K. Leong,
L. Y. Goh, Organometallics 2007, 26, 3352–3361; c) V. Cadi-
erno, J. Francos, J. Gimeno, Chem. Commun. 2010, 46, 4175–
4177; d) V. Cadierno, J. Francos, S. E. García-Garrido, J. Gi-
meno, Green Chem. Lett. Rev. 2011, 4, 55–61.
[20]
[21]
[22]
[23]
[31] a) The preparation of complex 17 by the reaction of
[RuCl2(cod)]n with 3 equiv. of PPh2py in refluxing methanol
has been described in: D. Drommi, F. Nicolò, C. G. Arena, G.
Bruno, F. Faraone, R. Gobetto, Inorg. Chim. Acta 1994, 221,
109–116; b) the X-ray crystal structure of this compound has
also been determined: K. Wajda-Hermanowicz, Z. Ciunik, A.
Kochel, Inorg. Chem. 2006, 45, 3369–3377.
[32] Simulation of this spectrum by using the gNMR v.4.1 software
2
(Adept Scientific plc) led to JP,P coupling constants of 250
(trans) and 30 Hz (cis).
[33] a) High conversions (90–99%) were also attained in the hy-
dration of 4-fluorobenzonitrile, 4-chlorobenzonitrile and 4-
methylbenzonitrile with complex 16 (5 mol-%) after heating for
24 h at 100 °C; b) for comparative purposes, the hydration of
benzonitrile (0.33 m solutions) by complex 16 (5 mol-%) was
also studied in iPrOH/H2O (2:1, v/v) and 1,2-dichloroethane/
H2O (2:1, v/v). In these organic media the conversions to
benzamide were remarkably lower than that reached in pure
water (23–35% after 24 h at 100 °C).
[34] D. Cuperly, P. Gros, Y. Fort, J. Org. Chem. 2002, 67, 238–241.
[35] a) M. A. Bennett, A. K. Smith, J. Chem. Soc., Dalton Trans.
1974, 233–241; b) M. A. Bennett, T.-N. Huang, T. W. Mathe-
son, A. K. Smith, Inorg. Synth. 1982, 21, 74–78; c) J. W. Hull,
W. L. Gladfelter, Organometallics 1984, 3, 605–613.
[36] a) H. Werner, H. Kletzin, J. Organomet. Chem. 1982, 228, 289–
300; b) D. L. Davies, J. Fawcett, R. Krafczyk, D. R. Russell, K.
Singh, J. Chem. Soc., Dalton Trans. 1998, 2349–2352.
[37] a) L. Porri, M. C. Gallazzi, A. Colombo, G. Allegra, Tetrahe-
dron Lett. 1965, 47, 4187–4189; b) A. Salzer, A. Bauer, S. Gey-
ser, F. Podewils, G. C. Turpin, R. D. Ernst, Inorg. Synth. 2004,
34, 59–65.
[24] Disappointing results have recently been reported from a study
of the alkyne hydration processes with bifunctional CpRuII cat-
alysts containing imidazole-based P,N ligands due to their high
tendency to block the metal by chelation: P. C. Kunz, I. Thiel,
A. L. Noffke, G. J. Reib, F. Mohr, B. Spingler, J. Organomet.
Chem. 2012, 697, 33–40.
[25] a) T. Kribber, A. Labonne, L. Hintermann, Synthesis 2007,
2809–2818; b) A. Labonne, L. Zani, L. Hintermann, C. Bolm,
J. Org. Chem. 2007, 72, 5704–5708; c) L. Hintermann, L. Xiao,
A. Labonne, Angew. Chem. 2008, 120, 8370–8374; Angew.
Chem. Int. Ed. 2008, 47, 8246–8250; d) L. Hintermann, T. T.
Dang, A. Labonne, T. Kribber, L. Xiao, P. Naumov, Chem.
Eur. J. 2009, 15, 7167–7179; e) F. Boeck, T. Kribber, L. Xiao,
L. Hintermann, J. Am. Chem. Soc. 2011, 133, 8138–8141.
[26] Attempts to generate related complexes starting from dimers
[{RuCl(μ-Cl)(η6-arene)}2] [arene = mesitylene (4c), hexameth-
ylbenzene (4d)] failed. The starting materials were recovered
untouched, even after 24 h of heating at reflux in THF. The
steric repulsion between the tert-amyl group of the phosphane
and the methyl substituents in the η6-coordinated arenes may
be behind this lack of reactivity.
[38] R. A. Head, J. F. Nixon, J. R. Swain, C. M. Woodard, J. Or-
ganomet. Chem. 1974, 76, 393–400.
[39] CrysAlisPro CCD, CrysAlisPro RED, Oxford Diffraction Ltd.,
Abingdon, 2008.
[27] In fact, despite its commented utility in catalysis, the coordina-
tion chemistry of this phosphane remains unexplored because
only the cyclopentadienyl-ruthenium(II) complex [RuCp-
(NϵCMe){κ1-(P)-PPh2(py-6-tert-amyl)}2][PF6] has previously
been isolated. See the Supporting Information of ref.[25e]
[28] For reviews on the coordination chemistry of this dimer and
catalytic applications of its derivatives, see: a) V. Cadierno, P.
Crochet, S. E. García-Garrido, J. Gimeno, Curr. Org. Chem.
2006, 10, 165–183; b) C. Bruneau, M. Achard, Coord. Chem.
Rev. 2012, 256, 525–536.
[29] See, for example: a) V. Cadierno, P. Crochet, J. Díez, J. García-
Álvarez, S. E. García-Garrido, J. Gimeno, S. García-Granda,
M. A. Rodríguez, Inorg. Chem. 2003, 42, 3293–3307; b) V. Cad-
ierno, P. Crochet, J. Díez, J. García-Álvarez, S. E. García-Gar-
rido, S. García-Granda, J. Gimeno, M. A. Rodríguez, Dalton
Trans. 2003, 3240–3249; c) C. Xu, S. A. Pullarkat, L. Y. Goh,
Aust. J. Chem. 2009, 62, 1537–1543; d) R. K. Gupta, A. K.
Singh, M. Yadav, P. Kumar, S. K. Singh, P. Li, Q. Xu, D. S.
Pandey, J. Organomet. Chem. 2010, 695, 1924–1931; e) J. Díez,
[40] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837–838.
[41] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
1994, 27, 435–436.
[42] P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman, S.
García-Granda, R. O. Gould, J. M. M. Smits, C. Smykalla, The
DIRDIF Program System, Technical Report of the Crystallo-
graphic Laboratory, University of Nijmegen, The Netherlands,
1999.
[43] G. M. Sheldrick, SHELXL97: Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
[44] Tables for X-ray Crystallography, Kynoch Press, Birmingham,
1974, vol. IV (present distributor: Kluwer Academic Publish-
ers, Dordrecht, The Netherlands).
[45] M. Nardelli, Comput. Chem. 1983, 7, 95–97.
[46] A. L. Spek, PLATON: A Multipurpose Crystallographic Tool,
University of Utrecht, The Netherlands, 2007.
Received: May 30, 2012
Published Online: August 3, 2012
4230
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 4218–4230