Bis(allyl)ruthenium(rV) complexes containing water-soluble phosphane ligands: Synthesis, structure, and application as catalysts in the Selective hydration of organonitriles into amides

Article abstract of DOI:10.1002/chem.201001152

The novel mononuclear ruthenium(IV) complexes [RuCl₂(η ³: η³-C₁₀H₁₆)(L)] [L = (meta-sulfonatophenyl)diphenylphosphane sodium salt (TPPMS) (2a), 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane (PTA) (2b), 1-benzyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1^3,7]decane chloride (PTABn) (2c), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) (2d), and 2,4,10-trimethyl-1,2,4,5,7,10-hexaaza-3-phosphatricyclo[3.3.1. 1^3,7]decane (THPA) (2e)] have been synthesized by treatment of the dimeric precursor [{RuCl(μ-Cl)((η³: η³-C ₁₀H₁₆)}₂] (C₁₀H₁₆ = 2,7-dimethylocta-2,6-diene-1,8-diyl) (1) with two equivalents of the corresponding water-soluble phosphane. Reaction of 1 with one equivalent of the cage-type diphosphane ligand 2,3,5,6,7,8-hexamethyl-2,3,5,6,7,8-hexaaza-1,4- diphosphabicyclo[2.2.2]octane (THDP) allowed also the high-yield preparation of the dinuclear derivative [[RuCl₂(η³: η³-C₁₀H₁₆)}₂(μ-THDP)] (2f). All these new complexes have been analytically and spectroscopically (IR and multinuclear NMR) characterized. In addition, the structure of 2b, 2c, 2d, and 2 f was unequivocally confirmed by X-ray diffraction methods. Complexes 2a-f are active catalysts for the selective hydration of nitriles to amides in pure aqueous medium under neutral conditions. The wide scope of this catalytic transformation has been evaluated by using the most active catalysts [RuCl ₂(η³: η³-C₁₀H ₁₆)(THPA)] (2e) and [{RuCl₂(η³: η³-C₁₀H₁₆)}₂(μ-THDP)] (2f). Advantages of using MW versus conventional thermal heating are also discussed.

Full text of DOI:10.1002/chem.201001152

DOI: 10.1002/chem.201001152
BisACHTUNGTRENNUNG(allyl)ruthenium(IV) Complexes Containing Water-Soluble Phosphane
Ligands: Synthesis, Structure, and Application as Catalysts in the Selective
Hydration of Organonitriles into Amides
Victorio Cadierno,* Josefina Dꢀez, Javier Francos, and Josꢁ Gimeno*[a]
Dedicated to Professor Josꢀ Barluenga on the occasion of his 70th birthday
Abstract: The novel mononuclear ruth-
enium(IV) complexes [RuCl2(h3:h3-
thylocta-2,6-diene-1,8-diyl) (1) with
two equivalents of the corresponding
water-soluble phosphane. Reaction of 1
with one equivalent of the cage-type
diphosphane ligand 2,3,5,6,7,8-hexa-
alytically and spectroscopically (IR and
multinuclear NMR) characterized. In
addition, the structure of 2b, 2c, 2d,
and 2 f was unequivocally confirmed by
X-ray diffraction methods. Complexes
2a–f are active catalysts for the selec-
tive hydration of nitriles to amides in
pure aqueous medium under neutral
conditions. The wide scope of this cata-
lytic transformation has been evaluated
by using the most active catalysts
C10H16)(L)]
[L=(meta-sulfonatophe-
nyl)diphenylphosphane sodium salt
(TPPMS) (2a), 1,3,5-triaza-7-phospha-
tricyclo[3.3.1.13,7]decane (PTA) (2b), 1-
benzyl-3,5-diaza-1-azonia-7-phosphatri-
cyclo[3.3.1.13,7]decane chloride (PTA-
Bn) (2c), 3,7-diacetyl-1,3,7-triaza-5-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
phosphabicyclo
N
CHTUNGTRENNUNG
(2d), and 2,4,10-trimethyl-1,2,4,5,7,10-
hexaaza-3-phosphatricy-
All these new complexes have been an-
[RuCl2(h3:h3-C10H16)
ACHTUNGTRENNUNG
clo[3.3.1.13,7]decane (THPA) (2e)]
have been synthesized by treatment of
[{RuCl2(h3:h3-C10H16)}
CHTUNGTRENNUNG
Keywords: amides · homogeneous
Advantages of using MW versus con-
ventional thermal heating are also dis-
cussed.
catalysis
· hydration · nitriles ·
the dimeric precursor [{RuClACTHNUTRGNEUG(N m-
ruthenium
Cl)(h3:h3-C10H16)}2] (C10H16 =2,7-dime-
Introduction
Scheme 1).[2] Moreover, from an industrial perspective, the
final neutralization step required either in the acid- or base-
catalyzed reactions leads to extensive salt formation with in-
convenient product contamination and pollution effects.
Hydration of nitriles to access amides is a process of great
significance, because amides are versatile intermediates used
in the production of pharmacological products, polymers,
detergents, lubricants, and drug stabilizers.[1] Traditionally,
this reaction is catalyzed by strong acids and bases under
harsh conditions, methods which are not compatible with
many sensitive functional groups and usually cause over-hy-
drolysis of the amides into the corresponding carboxylic
acids, a faster reaction specially under basic conditions (see
Scheme 1. Nitrile hydration and amide hydrolysis reactions.
To overcome these limitations, different methods based
on the use of enzymes,[3] heterogeneous catalysts,[4] and tran-
sition-metal complexes[5] have been developed. In particular,
a variety of homogeneous catalysts, mainly of Group 8–12
metals, operating in organic media and showing a high selec-
tivity to the amide, have been described in the literature.[5,6]
From a mechanistic point of view, although several reaction
pathways have been proposed for these metal-catalyzed
transformations, coordination of the nitrile to the metal is a
[a] Dr. V. Cadierno, Dr. J. Dꢀez, J. Francos, Prof. Dr. J. Gimeno
Departamento de Quꢀmica Orgꢁnica e Inorgꢁnica
Instituto Universitario de Quꢀmica Organometꢁlica
“Enrique Moles” (Unidad Asociada al CSIC)
Universidad de Oviedo
Juliꢁn Claverꢀa 8, 33006 Oviedo (Spain)
Fax : (+34)98-510-3446
E-mail: vcm@uniovi.es
jgh@uniovi.es
9808
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Chem. Eur. J. 2010, 16, 9808 – 9817

FULL PAPER
ꢀ
common prerequisite for most of them. In this way, the C
the activity of these bifunctional systems. Our attention was
N bond is activated towards the nucleophilic addition of
water, or the hydroxyl group if basic conditions are used,
thus improving the kinetics of the hydration process versus
the hydrolysis (see Scheme 1).
then turned to the chloro-bridged bis
ACHTUNGERTN(NUNG allyl)-ruthenium(IV)
dimer [{RuCl
AHCTUNGTRENNUNG
locta-2,6-diene-1,8-diyl; 1 in Scheme 3). Although compara-
tively much less developed,[15]
Owing to practical and environmental concerns, current
research has focused on the search of catalytic systems able
to operate directly in water under neutral conditions.[7]
However, few promising methodologies have been proposed
to date.[8,9] In this context, in the course of our current stud-
ies directed to the application of ruthenium complexes in
catalytic aqueous organic synthesis,[10] we have recently re-
the reactivity of complex 1 is
closely related to that of the
more classical arene–rutheniu-
(h6-
m(II) species [{RuClACTHNUTRGENNUG(m-Cl)AHCTUNGTRENNGUN
arene)}2], thus allowing the
easy preparation of mononu-
clear derivatives [RuCl2(h3:h3-
C10H16)(L)] by simple cleavage
of the chloride bridges with ap-
propriate two-electron donor li-
Scheme 3. Structure of the bis-
AHCTUNGTERG(NNUN allyl)ruthenium(IV) dimer 1.
ported that half-sandwich ruthenium(II) species [RuCl2ACTHNUTRGNEUNG
(h6-
arene)(L)], containing the hydrosoluble P-donor ligands
PTA (1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane), PTA-
Bn
(1-benzyl-3,5-diaza-1-azonia-7-phosphatricy-
gands. Thus, herein we report on the reactivity of [{RuClACHTUNGTRENNUNG(m-
clo[3.3.1.13,7]decane chloride) and DAPTA (3,7-diacetyl-
Cl)(h3:h3-C10H16)}2] (1) towards the hydrophilic phosphanes
depicted in Scheme 2, as well as an evaluation of the ability
of the resulting ruthenium(IV) complexes to catalyze the se-
lective hydration of organonitriles into the corresponding
amides in pure aqueous medium at neutral pH.
1,3,7-triaza-5-phosphabicyclo
[3.3.1]nonane)
(see
Scheme 2),[11,12] are excellent precatalysts for the selective
Results and Discussion
Synthesis and characterization of the bisACTHNUTRGNE(NUG allyl)-rutheniu-
m(IV) complexes [RuCl2(h3:h3-C10H16)(L)] (L=TPPMS,
PTA, PTA-Bn, DAPTA, THPA) and [{RuCl2(h3:h3-
C10H16)}
AHCTUNGTRENNUNG
2ACHTUNGTRENUN(NG m-THDP)]: Treatment of the purple dimer [{RuCl-
(m-Cl)(h3:h3-C10H16)}2] (1) with two equivalents of the mono-
Scheme 2. Structure of the water-soluble phosphanes PTA, PTA-Bn,
DAPTA, TPPMS, THPA, and THDP.
dentate P-donor ligands TPPMS, PTA, PTA-Bn, DAPTA,
and THPA (2,4,10-trimethyl-1,2,4,5,7,10-hexaaza-3-phospha-
tricyclo[3.3.1.13,7]decane),[16] in dichloromethane at room
temperature, results in the formation of bright orange solu-
tions from which the mononuclear complexes [RuCl2(h3:h3-
C10H16)(L)] (L=TPPMS (2a), PTA (2b), PTA-Bn (2c),
DAPTA (2d), THPA (2e)) could be isolated, as air-stable
solids in 67–90% yield, after partial removal of the solvent
in vacuo and subsequent precipitation with hexane
(Scheme 4).
The new compounds 2a–e were fully characterized by
means of elemental analyses and multinuclear NMR spec-
troscopy (details are given in the Experimental Section).
Complexes 2a–c and 2e showed a singlet resonance in their
31P{1H} NMR spectra, strongly deshielded with respect to
that of the corresponding free phosphane (Dd=30–50 ppm),
hydration of organonitriles to amides under these challeng-
ing conditions.[13] Interestingly, the presence of the nitrogen-
containing phosphanes PTA, PTA-Bn, and DAPTA turned
out to be key to attain good conversions, as related (h6-are-
ne)ruthenium(II) complexes bearing the sulfonated phos-
phane TPPMS ((meta-sulfonatophenyl)diphenylphosphane
sodium salt) proved much less effective.[13] This fact strongly
suggests that the hydration process occurs through a bifunc-
tional catalysis mechanism,[14] that is, the metal acts as a
Lewis acid activating the nitrile and the nitrogen-containing
ligand acts as a Lewis base directing the attack of water
through hydrogen bonding. Such a cooperative effect, also
proposed by Oshiki and Breit and their co-workers in relat-
ed RuII-catalyzed nitrile hydration reactions,[6a,m,o] has been
largely exploited in homogeneous catalysis during the last
years. In this sense, the transfer hydrogenation processes
through an outer-sphere mechanism, described by Noyori
and co-workers, and the selective hydration of alkynes to al-
dehydes (anti-Markovnikov addition), developed by Grot-
jahnꢃs group, are probably the most illustrative and success-
ful examples of this concept.[14]
With the aim of finding more efficient catalysts for this
relevant transformation, we wondered about the effect of an
increase in the Lewis acid character of the metal center in
Scheme 4. Synthesis of the mononuclear bisACTHNUTRGNE(NUG allyl)ruthenium(IV) com-
plexes 2a–e.
Chem. Eur. J. 2010, 16, 9808 – 9817
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9809

V. Cadierno, J. Gimeno et al.
Table 1. Selected bond lengths [ꢄ] and angles [8] for compounds 2b, 2c,
2d, and 2 f.
thus supporting the selective P-coordination of the ligands.
In addition, both 1H and 13C{1H} NMR spectra showed a
single set of signals for the two allylic moieties suggesting
that the two halves of the 2,7-dimethylocta-2,6-diene-1,8-
diyl skeleton are in equivalent environments, as expected
for the formation of a simple equatorial adduct. In contrast,
2b
2c
2d
2f
bond lengths
2.4307(9)
2.4218(9)
2.3421(9)
2.204(4)
2.255(4)
2.264(4)
2.257(4)
2.259(4)
2.243(4)
1.412(7)
1.399(6)
1.399(8)
1.402(8)
bond angles
166.44(4)
85.94(3)
94.92(3)
90.03(3)
80.68(3)
89.31(3)
97.16(3)
117.25(2)
112.96(2)
129.767(13)
115.6(4)
115.1(5)
ꢁ
Ru Cl1
2.483(3)
2.372(4)
2.3779(13)
2.268(10)
2.312(8)
2.275(8)
2.229(8)
2.125(8)
2.147(12)
1.398(13)
1.429(14)
1.397(14)
1.440(15)
2.4081(9)
2.4362(9)
2.3516(9)
2.235(4)
2.276(4)
2.283(4)
2.284(4)
2.281(4)
2.237(4)
1.418(6)
1.405(6)
1.405(6)
1.406(6)
2.502(2)
2.331(3)
2.3945(9)
2.104(8)
2.186(7)
2.179(7)
2.312(7)
2.379(6)
2.381(9)
1.434(11)
1.423(15)
1.411(10)
1.409(11)
ꢁ
Ru Cl2
ꢁ
Ru P1
for complex [RuCl2(h3:h3-C10H16)
ACTHNUTRGNEUNG(DAPTA)] (2d), two sin-
ꢁ
Ru C1
glets were observed at room temperature in its
31P{1H} NMR spectrum (approximately in a 1.2:1 ratio).
Similarly, a doubling on the number of signals expected for
ꢁ
Ru C2
ꢁ
Ru C4
ꢁ
Ru C7
ꢁ
Ru C8
the bisACHTUNGTRENNUNG
(allyl) moiety was also observed in the 1H and
ꢁ
Ru C10
13C{1H} NMR spectra. Variable-temperature 31P{1H} NMR
measurements showed that the two singlets observed at
room temperature converge to a single signal at tempera-
tures above 353 K, indicating that they correspond to con-
formational isomers. These isomers are most likely owed to
the syn and anti conformations adopted by the acyl groups
of the DAPTA ligand (see Scheme 5), a fact that has already
been observed both within the free phosphane[17] and in
some of its metal-complexes.[18]
ꢁ
C1 C2
ꢁ
C2 C4
ꢁ
C7 C8
ꢁ
C8 C10
Cl1-Ru-Cl2
Cl1-Ru-P1
162.94(13)
80.11(8)
92.37(8)
91.12(10)
83.70(8)
90.27(8)
100.48(10)
117.12(1)
114.50(1)
128.09(2)
113.2(9)
116.3(9)
171.10(3)
89.54(3)
93.41(3)
88.82(3)
81.56(3)
90.24(3)
94.87(3)
112.95(3)
115.74(3)
131.273(13)
117.3(4)
117.1(4)
172.87(9)
91.16(5)
92.03(5)
Cl1-Ru-C*[a]
Cl1-Ru-C**[a]
Cl2-Ru-P1
82.51(5)
83.41(10)
94.50(13)
94.88(14)
117.86(3)
109.01(2)
132.906(13)
114.7(9)
Cl2-Ru-C*[a]
Cl2-Ru-C**[a]
P1-Ru-C*[a]
P1-Ru-C**[a]
C*-Ru-C**[a]
C1-C2-C4
C7-C8-C10
116.7(8)
[a] C* and C** denote the centroids of the allyl units (C1, C2, C4, and
C7, C8, C10, respectively).
Scheme 5. syn and anti conformations of the DAPTA ligand in complex
2d.
The proposed structures for complexes 2b, 2c, and 2d
were unequivocally confirmed by means of X-ray diffraction
methods. Single crystals suitable for X-ray analysis were ob-
tained by slow diffusion of hexane into saturated solutions
of these compounds in dichloromethane. ORTEP plots of
the molecular structures are shown in Figures 1–3, whereas
selected bonding parameters are listed in Table 1.
Figure 2. ORTEP-type view of the structure of compound 2c showing the
crystallographic labeling scheme. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are drawn at the 10% probability level.
The geometry about the respective ruthenium(IV) atoms
is best described as a distorted trigonal bipyramid by consid-
ering the allyl groups as monodentate ligands bound to the
metal through their centers of mass (C* and C**; see foot-
note of Table 1). In all cases, the chloride ligands occupy the
Figure 1. ORTEP-type view of the structure of compound 2b showing
the crystallographic labeling scheme. Atoms labeled with an “a” are re-
lated to those indicated by a crystallographic plane of symmetry. Hydro-
gen atoms have been omitted for clarity. Thermal ellipsoids are drawn at
the 10% probability level.
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Ruthenium(IV) Complexes
FULL PAPER
characterized by using elemental analyses and IR and NMR
1
(31P{1H}, H, and 13C{1H}) spectroscopy (details are given in
the Experimental Section). The dinuclear nature of 2 f was
confirmed by comparing the relative intensities of the octa-
1
dienediyl and diphosphane resonances (2:1) in the H NMR
spectrum. However, a closer examination of the NMR data
revealed the presence of two different isomers in solution in
an approximate 5:1 ratio. This is evidenced by: i) the appear-
ance of one singlet (dP =135.9 ppm; major) and two dou-
blets (AB system; dP =132.8 and 135.7 ppm (3J
ACHTUNGTRENNUNG(P,P)=
102.1 Hz); minor) in the 31P{1H} NMR spectrum, and ii) the
doubling of some proton and carbon resonances for the or-
ganic octadienediyl unit. No interconversion was observed
by variable-temperature 31P{1H} NMR experiments suggest-
ing that, contrary to 2d, conformational issues are not re-
sponsible of the mixture observed in solution. Taking into
account the chirality associated to the metal coordinated
2,7-dimethylocta-2,6-diene-1,8-diyl unit (in solution dimer 1
itself exits in two diasteromeric forms),[15,20] two diastereo-
isomers with overall Ci (meso) and C2 (rac) symmetry are
possible for 2 f (see Scheme 6). Thus, although the meso
Figure 3. ORTEP-type view of the structure of compound 2d showing
the crystallographic labeling scheme. Hydrogen atoms have been omitted
for clarity. Thermal ellipsoids are drawn at the 10% probability level.
axial positions (Cl1-Ru-Cl2 bond angles ranging from
162.94(13) to 171.10(3)8), whereas the octadienediyl moiety
and the P-donor ligand are located at the equatorial sites.
Both allyl groups of the organic C10H16 fragment are h3-
ꢁ
ꢁ
bound to the ruthenium atom with Ru C and C C distances
in the ranges 2.147(12)–2.312(8) ꢄ and 1.397(14)–
1.440(15) ꢄ, respectively (Table 1). These values, together
with the internal allylic C-C-C angles (113.2(9)–117.3(4)8),
compare well with those observed in other structures con-
taining the “Ru(h3:h3-C10H16)” unit.[19] Concerning the struc-
ture of the DAPTA complex 2d (Figure 3), the COCH3
groups of the ligand are anti with respect to each other, as
they are in solid state structure of the free phosphane.[17]
Quite recently, Majoral and ourselves, have studied the
suitability of the almost unexplored cage-type ligand
tris(1,2-dimethylhydrazino)diphosphane
PACTHNGUTERU(NNG NMeNMe)3P
Scheme 6. The meso and rac forms of the dinuclear complex 2 f.
(THDP in Scheme 2) to design water-tolerant transition-
metal catalysts.[10j] To gain a deeper knowledge on the po-
tentiality of this ligand in aqueous catalysis, the reactivity of
form could account for the singlet signal observed in the
31P{1H} NMR spectrum, the absence of an inversion center
in the rac one makes the two phosphorus atoms of the
bridging THDP ligand inequivalents, and therefore an AB
system should be expected, as observed experimentally.[21]
To establish conclusively the structure of the product
formed we carried out a single-crystal structural analysis.
The X-ray study (see Figure 4 and Table 1) showed that in
the crystalline material only one of the isomers is present.
That isomer has overall overall Ci symmetry (meso form),
whereas the organic octadienediyl units have the expected
local C2 symmetry. The geometry about the crystallographi-
cally unique metal ion is that of a distorted trigonal bipyra-
mid, with the chloride ligands occupying again the axial po-
sitions and the bis-allyl chain and THDP located at the
equatorial sites.
THDP towards [{RuClACTHNUTRGNEUNG
(m-Cl)(h3:h3-C10H16)}2] (1) was also
explored. Thus, as shown in Equation (1), we have found
that 1 readily reacts with one equivalent of THDP, in di-
chloromethane at room temperature, to generate the dinu-
clear derivative [{RuCl2(h3:h3-C10H16)}
2ACHTNUTRGNEUNG(m-THDP)] (2 f) in
which the cage-like diphosphane is acting as a bridging
ligand. All attempts to generate the mononuclear derivative
ACHTUNGTRENNUNG
[RuCl2(h3:h3-C10H16){k1-(P)-THDP}] by using excess of
THDP (up to 15 equiv) failed, the reactions leading to mix-
tures containing the dinuclear complex 2 f and the unreacted
diphosphane. This coordination feature was also found start-
ing from the RuII dimer [{RuCl
(m-Cl)(h6-p-cymene)}2].[10j]
ACHTUNGTRENNUNG
CH2Cl2
RT
1 þ THDP
! ½fRuCl2ðh3 : h3-C10H16Þg2ðm-THDPÞꢂ ð2 fÞ
ð1Þ
As previously observed in the solid-state structure of the
2A
(NMe)3 units of the bridged THDP ligand in 2 f do
not adopt an eclipsed orientation. As shown in Figure 5,
Compound 2 f, isolated in 71% yield, is an air-stable
yellow solid soluble in common polar solvents. It has been
the two PACHUTNGTRENNUNG
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V. Cadierno, J. Gimeno et al.
bisACHTNUTGRNEUNG
(allyl) ligand.[21d,e,22] Finally, it must be noted that the sol-
ubility of these complexes in water is only modest (0.5–
5.0 mgmLꢁ1), with the TPPMS derivative 2a showing the
highest value at room temperature (see Table 2).
Catalytic hydration of nitriles: To prove the catalytic poten-
tial of the novel bisACTHNUTRGNEUNG(allyl)-ruthenium(IV) complexes 2a–f,
we first carried out the hydration of benzonitrile into benza-
mide, as a model reaction using a ruthenium loading of
5 mol% of Ru. Thus, as shown in Table 3, performing the
Figure 4. ORTEP-type view of the structure of compound 2 f showing the
crystallographic labeling scheme. Atoms labeled with an “a” are related
Table 3. Ruthenium(IV)-catalyzed hydration of benzonitrile.[a]
to those indicated by
a crystallographic inversion center. Hydrogen
atoms have been omitted for clarity. Thermal ellipsoids are drawn at the
10% probability level.
Entry
Catalyst
[{RuCl
(m-Cl)(h3:h3-C10H16)}2] (1)
[RuCl2(h3:h3-C10H16)
(TPPMS)] (2a)
[RuCl2(h3:h3-C10H16)
(PTA)] (2b)
[RuCl2(h3:h3-C10H16)
(PTA-Bn)] (2c)
[RuCl2(h3:h3-C10H16)
(DAPTA)] (2d)
[RuCl2(h3:h3-C10H16)
(THPA)] (2e)
[{RuCl2(h3:h3-C10H16)}
2A(m-THDP)] (2f)
t [h]
Yield [%][b]
1
2
3
4
5
6
7
G
G
24
24
24
24
24
2
18
42
94
97
97
99
98 (92)
R
N
E
E
N
N
G
T
G
A
A
G
4 (2)
[a] Reactions were performed under N2 atmosphere at 1008C using
1 mmol of benzonitrile (0.33m in water). Substrate/Ru ratio: 100/5.
[b] Determined by GC.
catalytic reactions at 1008C in pure aqueous medium, all the
complexes synthesized were able to provide benzamide as
the unique reaction product (benzoic acid was not detected
by GC/MSD in the crude reaction mixtures). However,
marked differences in activity were observed depending of
the nature of hydrosoluble ligand attached to ruthenium.
Thus, as observed in our previous work,[13] good conversions
(ꢃ94%) could only be attained with those catalysts bearing
the nitrogen-containing phosphanes, complexes 2b–f
(Table 3, entries 3–7), the use of the TPPMS complex 2a
(Table 3, entry 2) or the dimeric precursor 1 (Table 3,
entry 1) leading to remarkably lower conversions (up to
42% GC-yield) after 24 h of heating. This fact, along with
the absence of direct relationships between the measured
Epc potentials and solubilities in water, supports the pro-
posed cooperative effect of the ligand through a bifunctional
catalysis mechanism. Interestingly, the catalytic activity of
2b–d was lower than those previously reported for their
ꢁ
Figure 5. Partial view of the THDP-ligand skeleton along the P1 P1a
axis in complex 2 f.
they are rotated relative to each other by 18.68 (torsion
angle N2-P1-P1a-N1a).
Mononuclear 2a–d and dinuclear 2 f complexes were fur-
ther studied by means of cyclic voltammetry. In all cases a
single irreversible reduction (Epc values are given in Table 2)
was observed over a variety of scan speeds (0.1–1.5 Vsꢁ1),
indicating that the electron-transfer reactions are followed
by rapid chemical decomposition of the complexes. As pre-
viously observed by other authors, such a decomposition
process most probably involves the irreversible loss of the
2ACTHNUTRGNEUNG
RuII counterparts [RuCl (h6-arene)(L)] (arene=benzene,
mesitylene, p-cymene, hexamethylbenzene; L=PTA, PTA-
Bn, DAPTA), which, under the same reaction conditions,
were able to generate benzamide in almost quantitative
yields after only 2–19 h (versus 24 h using 2b–d).[13] This
seems to indicate that the nucleophilic addition of water on
the coordinated nitrile is not the rate-limiting step of these
catalytic reactions, otherwise the higher Lewis acid character
of the ruthenium(IV) centers should favor the addition. In
contrast, complexes 2e–f, containing the more sterically con-
gested phosphanes THPA and THDP, proved to be as com-
petitive as the arene-ruthenium(II) catalysts, leading to the
Table 2. Electrochemical data and solubility in water values for com-
plexes 2a–f.
Complex
Epc
S
A
Complex
Epc
S
[b]
[b]
[V][a]
[mgmLꢁ1
]
[V][a]
[mgmLꢁ1
ACHTUNGTERNNUNG ]
2a
2b
2c
ꢁ1.82
ꢁ1.37
ꢁ1.50
5.0
0.5
2.5
2d
2e
2f
ꢁ2.05
ꢁ2.00
ꢁ2.32
1.0
2.5
1.0
[a] Measured at 0.1 Vsꢁ1 in dichloromethane with a 0.03m solution of
[(nBu)4N]ACHTUNGTRENNUNG[PF6] as the supporting electrolyte. Indicated potentials are ref-
erenced relative to the potential of the [Cp2Fe]/ACHTNUGRTNEUNG
[Cp2Fe]+ couple. [b] Solu-
bility in water at 208C.
9812
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ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 9808 – 9817

Ruthenium(IV) Complexes
FULL PAPER
desired benzamide in 98–99% yield after only 2–4 h of heat-
ing (Table 3, entries 6 and 7).
tography on silica gel provided analytically pure samples of
the amides in 75–90% isolated yield.
Complexes 2e–f were also effective in the selective hydra-
tion of a variety of other aromatic and aliphatic nitriles, thus
confirming their potential for practical applications (see
Table 4). Thus, as observed for benzonitrile (Table 4,
entry 1), other aromatic (Table 4, entries 2–14) and heteroar-
omatic (Table 4, entries 15 and 16) substrates could be selec-
tively converted into the corresponding amides (94–99%
GC-yields) in short reaction times, with no remarkable influ-
ence of the position and electronic nature of the substituents
being observed. Subsequent purification by column chroma-
The presence of common functional groups, such as
halide (Table 4, entries 2–5), nitro (Table 4, entries 6 and 7),
ketone (Table 4, entry 8), amino (Table 4, entry 10), hydroxy
(Table 4, entry 11), ether (Table 4, entries 12 and 14), or thi-
oether (Table 4, entry 13), were tolerated regardless of the
catalyst employed. Interestingly, starting from these aromat-
ic and heteroaromatic substrates, the use of the mononu-
clear complex [RuCl2(h3:h3-C10H16)
ACTHNUTRGNE(UNG THPA)] (2e) resulted in
all cases more advantageous in terms of both reaction rates
and yields. In contrast, the dinuclear species [{RuCl2(h3:h3-
C10H16)}2ACTHNUGTRNEUG(N m-THDP)] (2 f) was more active in the hydration
of the aliphatic derivatives hexanenitrile (94 versus 63%;
Table 4, entry 17) and cyclohexanecarbonitrile (83 versus
57%; Table 4, entry 18). However, these particular sub-
strates required longer reaction times (24 h) and produced
the corresponding amides in lower yields as compared to
the aromatic ones. Sulfonyl-substituted (Table 4, entry 20),
as well as a,b-unsaturated (Table 4, entry 22), nitriles were
also tolerated confirming the wide scope of this catalytic
transformation.
The combined use of microwaves (MWs), as a nonclassi-
cal low-energy-consuming heating source, and water, as an
environmentally friendly solvent, to perform organic reac-
tions has recently emerged as a promising new field of re-
search within the “Green Chemistry” context.[23] In this
sense, as shown in Table 5, our catalytic hydration reactions
can be conveniently performed in water under MW-irradia-
tion. The working conditions employed (80 W/1508C) al-
lowed to reduce considerably the reaction times, as clearly
exemplified in the hydration of the aliphatic derivatives hex-
anenitrile (Table 5, entry 10) and cyclohexanecarbonitrile
(Table 5, entry 11) by the dinuclear complex 2 f, which re-
Table 4. Catalytic hydration of nitriles by complexes 2e,f.[a]
Entry
1
Substrate
Catalyst
t [h]
Yield [%][b]
R=Ph
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2e
2f
2
4
2
5
3
6
1
3
2
2
2
3
1
4
1
2
3
3
1
3
2
3
2
6
2
4
1
4
1
2
2
3
24
24
24
24
4
3
2
5
3
4
7
7
99 (88)
98 (85)
99 (84)
96 (80)
99 (89)
98 (88)
99 (87)
99 (89)
99 (90)
97 (88)
99 (89)
98 (86)
98 (83)
97 (80)
99 (93)
98 (91)
98 (88)
94 (86)
96 (79)
99 (80)
99 (81)
99 (79)
96 (84)
96 (87)
99 (77)
96 (75)
98 (83)
97 (80)
99 (90)
98 (90)
99 (93)
99 (92)
63(50)
2
R=2-C6H4F
3
R=4-C6H4F
4
R=3-C6H4Cl
5
R=4-C6H4Br
6
R=3-C6H4NO2
R=2-Me-4-C6H3NO2
R=4-C6H4C(=O)Et
R=4-C6H4Me
R=3-C6H4NH2
R=2-C6H4OH
R=4-C6H4OMe
R=4-C6H4SMe
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Table 5. Catalytic hydration of nitriles by complex 2 f under MW irradia-
tion.[a]
R=benzoACHTUNGTRENNUNG[1,3]dioxole-5-yl
Entry
Substrate
t [min]
Yield [%][b]
R=3-C5H4N
1
R=Ph
R=Ph
35
90
20
30
30
30
60
30
96
95
98
97
95
99
96
99
95
98
99
95
90
R=5-Me-2-furyl
R=n-C5H11
2[c]
3
R=3-C6H4Cl
R=4-C6H4F
R=3-C6H4NO2
R=2-C6H4OH
R=4-C6H4OMe
R=4-C6H4SMe
R=benzo
R=n-C5H11
R=Cy
R=CH2SO2Ph
R=(E)-CH=CHPh
4
5
6
7
8
9
10
11
12
13
94 (83)
57 (44)
83 (69)
97 (88)
99 (90)
97 (85)
96 (83)
96 (79)
96 (78)
95 (83)
98 (88)
R=Cy
R=CH2-4-C6H4Cl
R=CH2SO2Ph
R=CH2CH2OPh
R=(E)-CH=CHPh
[1,3]dioxole-5-yl
45
420
420
45
180
[a] Reactions were performed under N2 atmosphere at 1008C using
1 mmol of the corresponding nitrile (0.33m in water). Substrate/Ru ratio:
100/5. A CEM Discover S-Class microwave was used (80 W, 1508C, with
cooling to optimize the power). [b] Determined by GC. [c] Reaction per-
formed with a [Substrate]:[Ru] ratio=100:2.
[a] Reactions were performed under N2 atmosphere at 1008C using
1 mmol of the corresponding nitrile (0.33m in water). Substrate/Ru ratio:
100/5. [b] Determined by GC (isolated yields are given in parentheses).
Chem. Eur. J. 2010, 16, 9808 – 9817
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9813

V. Cadierno, J. Gimeno et al.
General procedure for the preparation of mononuclear complexes
[RuCl2(h3:h3-C10H16)(L)] (L=TPPMS (2a), PTA (2b), PTA-Bn (2c),
DAPTA (2d), THPA (2e)): A solution of the dimeric precursor [{RuCl-
quired only 7 h of irradiation to be almost quantitatively
transformed into the corresponding amides (98–99% GC
yield). Finally, it is also important to note that, in contrast to
the classical thermal conditions, a reduction of the catalysts
loading is not associated with a dramatic increase in the re-
action times. As an example, using only 1 mol% of 2 f
(2 mol% of Ru instead of 5 mol%), benzamide is formed in
95% yield after irradiation for only 90 min.
AHCTUNGTRENNUNG
(m-Cl)(h3:h3-C10H16)}2] (1) (0.308 g, 0.5 mmol) and the appropriate mono-
dentate phosphane (1 mmol) in dichloromethane (30 mL) was stirred at
room temperature for 3 h. Concentration to approximately 5 mL fol-
lowed by the addition of hexane (50 mL) led to the precipitation of a
yellow solid, which was washed with hexane (3ꢅ10 mL) and vacuum-
dried. Characterization data are as follows:
ACHUTNGERNNUG AHCUTNGTREN(NUGN TPPMS)] (2a): Yield: 67% (0.450 g); IR (KBr):
[RuCl2(h3:h3-C10H16)
n˜ =523 (w), 618 (m), 677 (m), 694 (s), 746 (m), 786 (m), 861 (w), 994 (m),
1034 (s), 1097 (s), 1141 (s), 1190 (vs), 1310 (w), 1346 (w), 1382 (m), 1433
(m), 1481 (m), 1630 (m), 2852 (w), 2910 (w), 3058 cmꢁ1 (w);
Conclusion
1
31P{1H} NMR (C6D6): d=26.8 ppm (s); H NMR (C6D6): d=2.17 (m, 2H,
H4 and H6), 2.25 (s, 6H, Me), 3.15–3.27 (m, 4H, H2, H10, H5 and H7), 4.60
We have developed new ruthenium-based catalytic systems
that efficiently catalyze, in a neutral aqueous media, the se-
lective hydration of a broad scope of nitriles, including aro-
matic, heteroaromatic and aliphatic substrates. To the best
of our knowledge, these systems constituted by rutheniu-
m(IV) complexes [RuCl2(h3:h3-C10H16)(L)] (L=hydrosolu-
ble phosphane ligand), along with the ruthenium(II) exam-
3
(d, 2H, J
N
(m, 12H, CH of TPPMS), 8.00, 8.85 ppm (br, 1 H each, CH of TPPMS);
13C{1H} NMR (C6D6): d=20.9 (s, Me), 37.0 (s, C4 and C5), 67.8 (d, 2J-
ACHUTNRGENUNG ACHUTGNTRNE(NUGN C,P)=10.9 Hz, C3 and C6), 125.1
(C,P)=8.6 Hz, C1 and C8), 108.5 (d, 2J
(s, C2 and C7), 127.2–135.3 ppm (m, C and CH of TPPMS); elemental
analysis calcd (%) for RuC28H30O3Cl2PSNa: C 50.00, H 4.50; found: C
49.86, H 4.62; solubility in water at 208C: 5 mgmLꢁ1
.
ACHUTNGERNNUG AHCUTNGTREN(NUGN PTA)] (2b): Yield: 86% (0.401 g); IR (KBr): n˜ =
[RuCl2(h3:h3-C10H16)
ples [RuCl2ACHTUNGTRENNUNG
(h6-arene)(L)] previously reported by us,[13] are
473 (m), 572 (m), 582 (s), 727 (w), 745 (m), 814 (m), 896 (w), 947 (s), 974
(vs), 1019 (s), 1098 (m), 1244 (m), 1282 (w), 1380 (w), 1418 (m), 1445
(w), 2893 (w), 2913 (w), 3026 cmꢁ1 (w); 31P{1H} NMR (CDCl3): d=
the most efficient catalysts for this transformation in aque-
ous media. In addition, the high tolerance towards function-
al groups and their accessibility (easily prepared from com-
ꢁ56.1 ppm (s); 1H NMR (CDCl3): d=2.23 (s, 6H, Me), 2.39 (m, 2H, H4
3
and H6), 2.97 (d, 2H, J
G
mercially available metal precursors [{RuCl
(m-Cl)(h3:h3-
ACHTUNGTRENNUNG
3
H7), 3.96 (d, 2H, J(HP)=8.0 Hz, H1 and H9), 4.12–4.42 (m, 12H, PCH2N
and NCH2N), 4.91 ppm (m, 2H, H3 and H8); 13C{1H} NMR (CDCl3): d=
C10H16)}2] and [{RuCl(m-Cl)
N
ACHTUNGTRENNUNG
20.6 (s, Me), 36.4 (s, C4 and C5), 52.6 (d, 1J
ACHTUNGTRENNUNG
tive and efficient synthetic approach of amides genuine po-
tential for practical application avoiding the use of classical
organic solvents.
(d, 2J
(C,P)=7.0 Hz, C1 and C8), 73.1 (d, 3J
2
(d, J
A
ysis calcd (%) for RuC16H28N3Cl2P: C 41.29, H 6.06, N 9.03; found: C
41.50, H 5.91, N 9.23; solubility in water at 208C: 0.5 mgmLꢁ1
[RuCl2(h3:h3-C10H16)
(PTA-Bn)] (2c): Yield: 92% (0.544 g); IR (KBr):
.
A
ACHTUNGTRENNUNG
n˜ =486 (m), 551 (w), 571 (m), 608 (w), 709 (w), 732 (vs), 756 (s), 820 (m),
902 (w), 991 (w), 1035 (s), 1071 (m), 1124 (m), 1266 (w), 1312 (m), 1383
(w), 1485 (m), 2854 (w), 2922 (w), 2977 (w), 3059 cmꢁ1 (w); 31P{1H} NMR
Experimental Section
1
General: Synthetic procedures were performed under an atmosphere of
dry nitrogen by using vacuum-line and standard Schlenk techniques. Sol-
vents were dried by standard methods and distilled under nitrogen
before use. All reagents were obtained from commercial suppliers and
used without further purification with the exception of compounds
(CDCl3): d=ꢁ29.8 ppm (s); H NMR (CDCl3): d=2.15 (s, 6H, Me), 2.78
(m, 2H, H4 and H6), 2.89 (d, 2H, 3J
ACTHUNRGTNEUGN(H,P)=4.0 Hz, H2 and H10), 3.39 (m,
2H, H5 and H7), 4.21–4.39 (m, 4H, PCH2N), 4.49 (d, 2H, 3J
ACHTUNGTRENNUNG(H,P)=
8.8 Hz, H1 and H9), 4.84–5.48 (m, 10H, PCH2N, NCH2Ph, H3, H8 and
NCH2N), 5.94 (m, 2H, NCH2N), 7.38–7.64 ppm (m, 5H, Ph);
13C{1H} NMR (CDCl3): d=20.5 (s, Me), 36.4 (s, C4 and C5), 49.4 (d, 1J-
[{RuClACHTUNGTRENNUNG
(m-Cl)(h3:h3-C10H16)}2] (1),[24] TPPMS,[25] PTA,[26] PTA-Bn,[27]
DAPTA,[17] THPA,[28] and THDP,[29] which were prepared by following
methods reported in the literature. Infrared spectra were recorded by
using a Perkin–Elmer 1720-XFT spectrometer. The C, H, and N analyses
were carried out by using a Perkin–Elmer 2400 microanalyzer. CV meas-
urements (258C) were carried out by using a three-electrode system. The
working electrode was a platinum disk electrode, the counter electrode
was a platinum spiral, and the reference electrode was an aqueous satu-
rated calomel electrode (SCE) separated from the solution by a porous
septum. Current and voltage parameters were controlled using a PAR
system M273. GC/MSD measurements were performed by using a Agi-
lent 6890N equipment coupled to a 5973 mass detector (70 eV electron
impact ionization) using a HP-1MS column. NMR spectra were recorded
on a Bruker DPX300 instrument at 300 MHz (1H), 121.5 MHz (31P) or
75.4 MHz (13C) using SiMe4 or 85% H3PO4 as standards. DEPT experi-
ments have been carried out for all the compounds reported in this
paper. The numbering for protons and carbons of the 2,7-dimethylocta-
2,6-diene-1,8-diyl skeleton is as follows:
ACHUTNGRENNUG CAHTUNGTRENNUGN
(C,P)=18.4 Hz, PCH2N), 49.9 (d, 1J(C,P)=15.9 Hz, PCH2N), 53.4 (d, 1J-
AHCTUNGTERNNG(UN C,P)=14.3 Hz, PCH2N), 60.6 (br, C1 and C8), 64.7 (s, NCH2Ph), 70.0,
2
78.5 and 78.8 (s, NCH2N), 110.5 (d, JACHTNUGTRNEUNG(C,P)=9.5 Hz, C3 and C6), 122.0 (s,
C2 and C7), 125.0 (s, C of Ph), 129.3, 130.6, 133.1 ppm (s, CH of Ph); ele-
mental analysis calcd (%) for RuC23H35Cl3N3P: C 46.67, H 5.96, N 7.10;
found: C 46.90, H 6.12, N 7.24; solubility in water at 208C: 2.5 mgmLꢁ1
.
ACHUTNGERNNUG AHCUTNGTREN(NUGN DAPTA)] (2d): Two conformers were observed in
[RuCl2(h3:h3-C10H16)
solution for this complex (ꢄ1.2:1 ratio). Yield: 90% (0.483 g); IR (KBr):
n˜ =469 (w), 532 (w), 564 (w), 626 (m), 699 (w), 799 (m), 868 (m), 891 (s),
999 (s), 1048 (s), 1100 (m), 1208 (m), 1238 (s), 1332 (s), 1356 (m), 1418
(s),
1651
(vs),
2857
(w),
2898
(w),
2972 cmꢁ1
(w);
NMR data for the major conformer: 31P{1H} NMR (CDCl3): d=
ꢁ30.9 ppm (s); 1H NMR (CDCl3): d=2.11–2.20 (m, 12H, Me and
COMe), 2.79 (m, 2H, H4 and H6), 2.98 (d, 2H, 3J
ACTHNUGTRNE(NUG H,P)=5.1 Hz, H2 and
H10), 3.43 (m, 2H, H5 and H7), 3.70–4.19 (m, 5H, PCH2N and NCH2N),
4.21 (d, 2H, 3J
(H,P)=8.0 Hz, H1 and H9), 4.74–5.00 (m, 5H, PCH2N,
AHCTUNGTRENNUNG
NCH2N, H3 and H8), 5.79 ppm (m, 2H, PCH2N and NCH2N);
13C{1H} NMR (CDCl3): d=20.7 (s, Me), 21.5 (s, COMe), 36.5 (s, C4 and
C5), 39.6 (d, 1J
PCH2N), 49.5 (d, 1J
and C8), 62.0 (br, NCH2N), 110.3 (d, 2J
(s, C2 and C7), 169.5,
NMR data for the minor conformer: 31P{1H} NMR (CDCl3): d=
(C,P)=20.3 Hz, PCH2N), 44.4 (d, 1J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
ACHUTNGRENNUG CAHTUNGTRENNUNG
(C,P)=24.7 Hz, PCH2N), 59.9 (d, 2J
AHCTUNGTRENNUNG
9814
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ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 9808 – 9817

Ruthenium(IV) Complexes
FULL PAPER
ꢁ31.2 ppm (s); 1H NMR (CDCl3): d=2.11–2.20 (m, 12H, Me and
glass microwave reactor vial was charged with the corresponding nitrile
(1 mmol), water (3 mL), complex 2 f (21 mg, 0.025 mmol; 5 mol% of Ru)
and a magnetic stirring bar. The vial was then placed inside the cavity of
a CEM Discover S-Class microwave synthesizer and power was held at
80 W until the desired temperature was reached (1508C). Microwave
power was automatically regulated for the remainder of the experiment
to maintain the temperature (monitored by a built-in infrared sensor;
COMe), 2.79 (m, 2H, H4 and H6), 3.01 (d, 2H, 3J
ACTHNUGTRNE(NUG H,P)=5.1 Hz, H2 and
H10), 3.43 (m, 2H, H5 and H7), 3.70–4.19 (m, 5H, PCH2N and NCH2N),
4.21 (d, 2H, 3J
(H,P)=8.0 Hz, H1 and H9), 4.74–5.00 (m, 5H, PCH2N,
ACHTUNGTRENNUNG
NCH2N, H3 and H8), 5.79 ppm (m, 2H, PCH2N and NCH2N);
13C{1H} NMR (CDCl3): d=20.7 (s, Me), 21.7 (s, COMe), 36.4 (s, C4 and
C5), 38.9 (d, 1J
PCH2N), 49.7 (d, 1J
and C8), 67.0 (br, NCH2N), 110.5 (d, 2J
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(C,P)=19.7 Hz, PCH2N), 44.2 (d, 1J
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(C,P)=25.2 Hz, PCH2N), 60.1 (d, 2J
P
max =20 psi). The course of the reaction was monitored by regular sam-
pling and analysis by GC/MSD.
(s, C2 and C7), 169.6, 170.3 ppm (s, COMe); elemental analysis calcd (%)
X-ray crystal structure determinations: Crystals suitable for X-ray diffrac-
tion analysis were obtained by slow diffusion of hexane (2b, 2c, and 2d)
or pentane (2 f) into a saturated solution of the complexes in dichlorome-
thane. In all cases, data collection was performed by using a Oxford Dif-
fraction Xcalibur Nova single crystal diffractometer, using CuKa radiation
(l =1.5418 ꢄ). Images were collected at a 65 mm fixed crystal-detector
distance, using the oscillation method, with 18 oscillation and variable ex-
posure time per image (3–40 s). Data collection strategy was calculated
with the program CrysAlis Pro CCD.[30] Data reduction and cell refine-
ment was performed with the program CrysAlis Pro RED.[30] An empiri-
cal absorption correction was applied using the SCALE3 ABSPACK al-
gorithm as implemented in the program CrysAlis Pro RED.[26] The soft-
ware package WINGX[31] was used for space group determination, struc-
ture solution and refinement. The structure for the complexes 2c and 2d
were solved Patterson interpretation and phase expansion using
DIRDIF.[32] For 2b and 2 f the structures were solved by direct methods
using SIR2004.[33] In the crystal of 2b a CH2Cl2 solvent molecule per unit
formula of the complex is present. This molecule, along with the octadie-
nediyl chain, is disordered in two positions with an occupancy factor of
0.5. Similarly, in the crystal of 2 f, with the exception of the Ru and P
atoms, and the methyl groups, the rest of atoms are also disordered in
two positions with an occupancy factor of ca. 0.5. Isotropic least-squares
refinement on F2 using SHELXL97[34] was performed. During the final
stages of the refinements, all the positional parameters and the anisotrop-
ic temperature factors of all the non-H atoms were refined. For 2b, 2c,
and 2 f the H atoms were geometrically located and their coordinates
were refined riding on their parent atoms. For 2d, the coordinates of H
atoms were found from different Fourier maps and included in a refine-
ment with isotropic parameters. In all cases the maximum residual elec-
tron density is located near heavy atoms.
for RuC19H32N3Cl2O2P: C 42.46, H 6.00, N 7.82; found: C 42.19, H 6.21,
N 7.82; solubility in water at 208C: 1 mgmLꢁ1
.
ACHTUNGTRENNUNG ACHTUNGTRENNUNG(THPA)] (2e): Yield: 67% (0.342 g); IR (KBr): n˜ =
[RuCl2(h3:h3-C10H16)
468 (m), 583 (w), 613 (s), 629 (s), 645 (m), 671 (w), 789 (w), 803 (m), 887
(s), 922 (s), 940 (m), 982 (w), 1027 (w), 1072 (m), 1130 (w), 1158 (m),
1384 (m), 1426 (m), 1499 (w), 2913 (w), 2927 (w), 3025 cmꢁ1 (w);
31P{1H} NMR (CDCl3): d=135.4 ppm (s); 1H NMR (CDCl3): d=2.15 (s,
3
6H, Me), 2.63 (m, 2H, H4 and H6), 3.14 (d, 3H, J
N
3.17 (d, 3H, 3J
H10), 4.36 (d, 2H, 3J
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
H8), 5.21 (br, 2H, NCH2N), 5.55–5.92 ppm (m, 4H, NCH2N);
13C{1H} NMR (CDCl3): d=20.3 (s, Me), 36.3 (s, C4 and C5), 41.0 (br,
NMe), 46.8 (s, NMe), 62.8 (d, 2J
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
126.7 ppm (s, C2 and C7); elemental analysis calcd (%) for
RuC16H31N6Cl2P: C 37.65, H 6.12, N 16.47; found: C 37.78, H 6.00, N
16.31; solubility in water at 208C: 2.5 mgmLꢁ1
.
Preparation of the dinuclear complex [{RuCl2(h3:h3-C10H16)}
2ACHTUNGTRENN(UNG m-THDP)]
(2 f): A solution of complex [{RuCl
AHCTUNGTRENNUNG
0.5 mmol) and the diphosphine THDP (0.118 g, 0.5 mmol) in dichlorome-
thane (30 mL) was stirred at room temperature for 2 h. Concentration to
ꢄ5 mL followed by the addition of hexane (50 mL) led to the precipita-
tion of a yellow solid, which was washed with hexane (3ꢅ10 mL) and
vacuum-dried. Complex 2 f is formed as a nonseparable mixture of two
diastereoisomers (meso and rac forms) in ꢄ5:1 ratio. Yield: 71%
(0.303 g); IR (KBr): n˜ =466 (w), 492 (m), 594 (s), 613 (s), 744 (s), 759 (s),
820 (w), 861 (m), 915 (m), 937 (m), 1020 (m), 1053 (m), 1138 (w), 1182
(w), 1231 (w), 1308 (w), 1383 (m), 1443 (m), 2849 (w), 2898 (w),
3004 cmꢁ1 (w);
Crystal data for 2b: RuC16H28N3Cl2P·CH2Cl2, M=550.28 gmolꢁ1, T=
120(2) K, orthorhombic, Pnma, crystal size 0.26ꢅ0.08ꢅ0.08 mm, a=
29.6657(5), b=10.0708(2), c=7.1548(1) ꢄ, Z=4, V=2137.55(6) ꢄ3,
NMR data for the major diastereoisomer (meso form): 31P{1H} NMR
(CDCl3): d=135.9 ppm (s); 1H NMR (CDCl3): d=2.20 (br, 6H, Me),
2.64 (br, 2H, H4 and H6), 3.14–3.23 (m, 22H, NMe, H2, H10, H5 and H7),
3.52 (br, 2H, H1 and H9), 4.68 (br, 2H, H3 and H8) ppm; 13C{1H} NMR
(CDCl3): d=20.1 (s, Me), 36.4 (s, C4 and C5), 41.3 (s, NMe), 64.5 (br, C1
and C8), 109.8 (br, C3 and C6), 126.8 ppm (s, C2 and C7);
NMR data for the minor diastereoisomer (rac form): 31P{1H} NMR
1calcd =1.710 gcmꢁ3 m=11.304 mmꢁ1
, , final R1=0.0436 [I>2s(I)] and
0.0481 (all data), and wR2=0.1040 [I>2s(I)] and 0.1088 (all data).
Crystal data for 2c: RuC23H35Cl3N3P, M=591.93 gmolꢁ1, T=293(2) K,
monoclinic, P21/c, crystal size 0.028ꢅ0.083ꢅ0.117 mm, a=12.9696(4), b=
14.4861(3), c=14.0113(4) ꢄ, b=107.552(3)8, Z=4, V=2509.87(3) ꢄ3,
ACTHNUTRGNEUNG
(CDCl3): d=132.8, 135.7 ppm (d, 3J(P,P)=102.1 Hz); 1H NMR (CDCl3):
1calcd =1.566 gcmꢁ3
, , final R1=0.0417 [I>2s(I)] and
m=8.719 mmꢁ1
d=2.20 (br, 6H, Me), 2.64 (br, 2H, H4 and H6), 3.14–3.23 (m, 22H,
NMe, H2, H10, H5 and H7), 3.52 (br, 2H, H1 and H9), 4.68 ppm (br, 2H,
H3 and H8); 13C{1H} NMR (CDCl3): d=20.5 (s, Me), 36.1 (s, C4 and C5),
41.7 (s, NMe), 66.2 (br, C1 and C8), 109.8 (br, C3 and C6), 125.9 ppm (s,
C2 and C7); elemental analysis calcd (%) for Ru2C26H50N6Cl4P2: C 36.63,
H 5.91, N 9.86; found: C 36.79, H 6.08, N 10.01; solubility in water at
0.0452 (all data), and wR2=0.1126 [I>2s(I)] and 0.1149 (all data).
Crystal data for 2d: RuC19H32N3Cl2O2P, M=537.42 gmolꢁ1, T=120(2) K,
monoclinic, P21/c, crystal size 0.13ꢅ0.11ꢅ0.05 mm, a=20.0690(2), b=
8.9949(1), c=12.3476(1) ꢄ, b=94.903(1)8, Z=4, V=2220.82(4) ꢄ3,
1calcd =1.607 gcmꢁ3
, , final R1=0.0270 [I>2s(I)] and
m=8.774 mmꢁ1
208C: 1 mgmLꢁ1
.
0.0347 (all data), and wR2=0.0698 [I>2s(I)] and 0.0785 (all data).
Crystal data for 2 f: Ru2C26H50N6Cl4P2, M=852.60 gmolꢁ1, T=100(2) K,
monoclinic, P21/c, crystal size 0.022ꢅ0.087ꢅ0.137 mm, a=13.9680(2), b=
8.3530(1), c=14.2890(2) ꢄ, b=93.4870(1)8, Z=2, V=1664.08(4) ꢄ3,
General procedure for the catalytic hydration of nitriles under thermal
conditions: Under nitrogen atmosphere, the corresponding nitrile
(1 mmol), water (3 mL), and the appropriate ruthenium catalyst (5
mol% of Ru) were introduced into a sealed tube and the reaction mix-
ture stirred at 1008C for the indicated time (see Tables 3 and 4). The
course of the reaction was monitored by regular sampling and analysis by
GC/MSD. After elimination of the solvent after reduced pressure, the
crude reaction mixture was purified by column chromatography over
silica gel using diethyl ether as eluent. The identity of the resulting
amides was assessed by comparison of their 1H and 13C{1H} NMR spec-
troscopic data with those reported in the literature and by their fragmen-
tation in GC/MSD.
1calcd =1.702 gcmꢁ3 m=11.433 mmꢁ1
, , final R1=0.0371 [I>2s(I)] and
0.0415 (all data), and wR2=0.0958 [I>2s(I)] and 0.0995 (all data).
CCDC-773996 (2b), CCDC-773997 (2c) CCDC-773998 (2d) CCDC-
773999 (2 f) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
General procedure for the catalytic hydration of nitriles under MW irra-
diation: Under nitrogen atmosphere, a pressure-resistant septum-sealed
Chem. Eur. J. 2010, 16, 9808 – 9817
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9815

V. Cadierno, J. Gimeno et al.
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Acknowledgements
Financial support from the Spanish MICINN (Projects CTQ2006-08485/
BQU and Consolider Ingenio 2010 (CSD2007-00006)) and the Gobierno
del Principado de Asturias (FICYT Project IB08-036) is acknowledged.
J.F. thanks MICINN and the European Social Fund for the award of a
Ph.D. grant.
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9816
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 9808 – 9817

Ruthenium(IV) Complexes
FULL PAPER
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Received: April 30, 2010
Published online: June 28, 2010
Chem. Eur. J. 2010, 16, 9808 – 9817
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9817