Iminophosphorane-based [P2N2] rhodium complexes: Synthesis, reactivity, and application in catalysed transfer hydrogenation of polar bonds

Article abstract of DOI:10.1039/c0nj00299b

[Rh(P₂N₂)X] complexes (2-X, X = Cl, BF₄) featuring a tetradentate iminophosphorane phosphine ligand were synthesised and characterised. X-Ray analysis provides evidence for a square planar geometry without coordination of the chloride anion. These complexes proved to be air-sensitive, and their oxidation to Rh(iii) complexes 3-X was observed in air. The controlled reaction of 2-BF₄ with one equivalent of hexachloroethane yielded [Rh(P₂N₂)Cl₂(BF ₄)] (3-BF₄). Direct synthesis of 3-Cl can also be achieved by coordination of the [P₂N₂] ligand to [RhCl(THT) ₃] (THT = tetrahydrothiophene). The reactivity of Rh(i) complexes 2 was further investigated, and no reaction was observed with silanes, aryl halides, or pinacolborane, although decomposition was observed under 1 atm of H₂ upon prolonged heating. Interestingly, reduction of complex 3-Cl was observed by NMR upon treatment with silanes or sodium isopropoxide. Therefore, complex 3-Cl was used for catalytic transfer hydrogenation of polar bonds. The reduction of aromatic and aliphatic ketones can be carried out using 1% catalyst and 10% sodium isopropoxide, while imines are partially reduced under these conditions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/c0nj00299b

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
Iminophosphorane-based [P2N2] rhodium complexes: synthesis, reactivity,
and application in catalysed transfer hydrogenation of polar bondsw
Antoine Buchard, Elina Payet, Audrey Auffrant,* Xavier Le Goff and
Pascal Le Floch*z
Received (in Montpellier, France) 20th April 2010, Accepted 9th July 2010
DOI: 10.1039/c0nj00299b
[Rh(P2N2)X] complexes (2-X, X = Cl, BF4) featuring a tetradentate iminophosphorane
phosphine ligand were synthesised and characterised. X-Ray analysis provides evidence for a
square planar geometry without coordination of the chloride anion. These complexes proved to
be air-sensitive, and their oxidation to Rh(III) complexes 3-X was observed in air. The controlled
reaction of 2-BF4 with one equivalent of hexachloroethane yielded [Rh(P2N2)Cl2(BF4)] (3-BF4).
Direct synthesis of 3-Cl can also be achieved by coordination of the [P2N2] ligand to
[RhCl(THT)3] (THT = tetrahydrothiophene). The reactivity of Rh(I) complexes 2 was further
investigated, and no reaction was observed with silanes, aryl halides, or pinacolborane, although
decomposition was observed under 1 atm of H2 upon prolonged heating. Interestingly, reduction
of complex 3-Cl was observed by NMR upon treatment with silanes or sodium isopropoxide.
Therefore, complex 3-Cl was used for catalytic transfer hydrogenation of polar bonds.
The reduction of aromatic and aliphatic ketones can be carried out using 1% catalyst
and 10% sodium isopropoxide, while imines are partially reduced under these
conditions.
and they have been successfully employed in a number of
different catalytic processes.7
Introduction
Tetradentate ligand systems featuring two phosphines and two
It is noteworthy that most iminophosphorane-based ligand
nitrogen donors (either amine or amide functions) have been
preparations rely on the Staudinger reaction involving the
widely studied for almost 30 years (Chart 1).1 Furthermore,
addition of an azide to a phosphine.8 This methodology,
efficient enantioselective catalysts have been developed by the
though very clean, induces severe limitations concerning the
introduction of chirality to their carbon backbone, the main
substitution pattern at the nitrogen atom, because of the
successes having been obtained with iridium,2 palladium,3 and
limited availability of azides. We have favoured synthetic
ruthenium4 complexes. More recently, Morris and coworkers
strategies involving the Kirsanov reaction, which allows the
use of amines as the nitrogen source.9 This has allowed a high-
have developed iron-based systems able to achieve the efficient
asymmetric transfer hydrogenation of polar bonds.5 Motivated
yielding two-step synthesis of tetradentate mixed phosphine-
by these results, we have recently started to investigate their
iminophosphorane [P2N2] ligands, which were first coordinated
phosphorus analogues, namely [P2N2] ligands exhibiting
to group 10 metal centers (Pd, Ni). The complexes obtained
an iminophosphorane group instead of amine or imine
were shown to be extremely stable and were able to catalyze
Suzuki couplings in aqueous biphasic media.7m Then, a series
functionalities (Chart 1). We anticipated that the electronic and
steric properties of these new ligands would markedly differ from
of iron(II) complexes was synthesised from tetradentate ligands
those of classical imine derivatives. Indeed, iminophosphoranes
combining iminophosphorane with phosphine, thiophosphine,
behave as strong s and p donors because of the presence of two
catalytic transfer hydrogenation of acetophenone.7p Pursuing
lone pairs at the nitrogen atom. Moreover, they do not present
or phosphine oxide groups, and these were used for the
any p acceptor character because of the absence of a true p
system. Although iminophosphorane-based ligands are much
our investigations concerning this tetradentate mixed phosphine-
iminophosphorane ligand, we report here its coordination to
less exploited in catalysis than their carbon analogues, their
Rh(I) and Rh(III) centers. The reactivity of these complexes is
potential in coordination chemistry is now well established,6
investigated and their catalytic performance in the catalysed
transfer hydrogenation of polar bonds is presented.
´ ´ ´ ´
Ecole Polytechnique, Laboratoire Heteroelements et Coordination,
CNRS UMR7653, route de Saclay, 91128 Palaiseau Cedex, France.
E-mail: audrey.auffrant@polytechnique.edu; Fax: +33 (0)169334440
w Electronic supplementary information (ESI) available: CIF files,
ORTEP plot and tables giving crystallographic data for 2-BF4 and 3-Cl,
including atomic coordinates, bond lengths, angles, and anisotropic
displacement parameters. CCDC reference numbers 772851–772854.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c0nj00299b
Results and discussion
Coordination and reactivity studies
All coordination experiments were carried out by addition of a
rhodium precursor to a THF solution of ligand 1, which was
obtained by in situ deprotonation of bis(aminophosphonium)
adduct 1-(HCl)2 using 2 equivalents of MeLi (Scheme 1).
z Deceased.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2943–2949 2943

View Article Online
Chart 1 Tetradentate [P2N2] ligands.
To synthesise the Rh(I) complexes, different metal precursors
were employed. [(P2N2)RhCl] complex 2-Cl was synthesised
by addition of half an equivalent of the [Rh(COD)Cl]2 or the
[Rh(COE)2Cl]2) precursors. After elimination of the lithium
salts, and washing with diethyl ether, complex 2-Cl was
isolated in 84% yield. However, the reaction conditions were
found to be highly dependent on the nature of the precursor.
Thus, with the cyclooctadiene dimer 6 h of heating at 60 1C
was required, whereas with cyclooctene complex the reaction
occurred smoothly and was achieved within 6 h at room
temperature, or 2 h at 60 1C. The coordination of the
phosphine and iminophosphorane arms could be inferred
from the AA0BB0 signal pattern observed in the 31P{1H}
NMR spectrum. This complex 2-Cl indeed logically appears
Fig. 1 Molecular structure of complex 2-Cl. Thermal ellipsoids
drawn at the 50% probability level. Hydrogen atoms have been
omitted for clarity. Selected distances (A) and angles (1): P2–Rh1
2.1935(6), N1–Rh1 2.075(2), N2–Rh1 2.082(2), P4–Rh1 2.1896(6),
Rh1–Cl1 6.434, P1–N1 1.604(2), P3–N2 1.603(2), P1–C15 1.805(3),
P2–C15 1.873(2), P3–C40 1.805(3), P4–C40 1.879(2); P4–Rh1–P2
100.40(2), N1–Rh1–N2 80.39(8), P4–Rh1–N2 89.66(6), P2–Rh1–N1
89.55(6), P1–N1–Rh1118.2(1), N1–P1–C15 105.1(1), P1–C15–P2
107.4(1),
C15–P2–Rh1
105.57(8),
C40–P4–Rh1
105.21(8),
P4–C40–P3 106.4(1), C40–P3–N2 105.1(1), P3–N2–Rh1 117.4(1),
N1–P2–P4–N2 ꢀ0.78(9), P1–P2–P4–P3 ꢀ17.72(4), P2–N1–N2–P4
ꢀ0.98(11), P2–P1–P3–P4 ꢀ10.36(4).
as a doublet (2JRhP = 18.5 Hz) of virtual triplets (2JPP = 3JPP
=
13.0 Hz) centred at dp(THF) = 38.2 ppm, corresponding to
the PQN groups and a doublet of doublet of doublets centred
from 1-(HBF4)2, with one equivalent of [Rh(COD)2](BF4)
(Scheme 1). This way, complex 2-BF4 was isolated as a yellow
powder in 75% yield after standard work-up. Its NMR data
are similar to those of 2-Cl, and its X-ray structure (see ESIw)
is almost identical to that of 2-Cl, apart from that tetrafluoro-
borate replaces chloride.
2
at dp(THF) = 41.5 ppm (2JPP = 19.5 Hz, JPP = 13.0 Hz,
1JRhP = 171.0 Hz) for the phosphines. This new complex
was further characterised by multinuclear NMR spectroscopy
(31P, 1H, 13C) and elemental analyses. Moreover, single crystals
suitable for X-ray analysis were obtained by slow diffusion of
hexanes into a concentrated dichloromethane solution of 2-Cl.
An ORTEP view of one molecule is presented in Fig. 1.
As can be seen, complex 2-Cl is a cationic species which
adopts a square planar geometry, as expected for a d8 complex,
with the chloride anion being more than 4 A away from the
metal centre. The deviation from planarity is very small – only
0.98(11)1 for the P2–N1–N2–P4 dihedral angle. The two five-
membered Rh–N–P–C–P metallacycles have similar bond
lengths and angles. Moreover, the observed structural para-
meters are in the range of those measured by Cavell and
coworkers for Rh(I) complexes bearing bidentate phosphine-
iminophosphorane (PPh2CH2PPh2QNR) ligand.10 In particular,
the N–Rh and P–Rh bond distances in 2-Cl were on average
2.079 and 2.1915 A, respectively – only slightly shorter than
those observed by Cavell.
Finally, we found that syntheses of both complexes could be
conveniently carried out in dichloromethane using 1 and the
required rhodium precursor, a procedure which avoids solvent
exchange to remove the lithium salts. In this case, overnight
stirring at room temperature was necessary to drive the
reaction to completion. Note that iminophosphorane derivatives
usually decompose when standing in dichloromethane, which
emphasises the particular stability of the [P2N2] ligand.
Complexes 2-Cl and 2-BF4 were found to be oxygen-sensitive.
When exposed to air, CH2Cl2 solutions of 2-Cl and 2-BF4 with
traces of chloride salts underwent transformation to a new
complex, 3. In the 31P{H} NMR, this new species also exhibits
a AA0BB0 spin system, in which the chemical shifts of the
coordinated phosphine ligand P(III) and the iminophosphorane
P(V) are inverted. Thus in 3, the signal corresponding to the
coordinated phosphine group is centred at dp(THF) = 19.4 ppm
and appears as a doublet (1JRhP = 104.0 Hz) of virtual triplets
The tetrafluoroborate derivative of complex 2 was also
synthesised by reacting ligand 1 (free of LiCl salt or prepared
Scheme 1 Synthesis of complexes 2-X.
c
2944 New J. Chem., 2010, 34, 2943–2949 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
Scheme 3 Synthesis of complex 3-Cl.
Scheme 2 Oxidation of complex 2-BF4.
apical positions. The deviation from planarity is slightly more
pronounced than in 2 (N1–P2–P4–N2 7.31(5)). The oxidation
is accompanied by a decrease of most of the inner angles in the
five-membered metallacycle; in particular, the average
C–P–Rh and N–Rh–P angles change from 105.391 and
89.611 (respectively) in 2-Cl to 100.81 and 86.771 in 3-BF4.
Only the P–C–P angle widens after oxidation (from 107.4(1)1
in 2-Cl to 109.2(1) in 3-BF4). This accompanies an elongation
of the P–Rh bond lengths (from 2.19 A on average in 2 versus
2.30 A on average in 3), and a shortening of the P(III)–C bonds
(from 1.876 A in the Rh(I) complex to 1.850 A on average in
the Rh(III) derivative). No substantial change is observed for
the N–Rh and P–N bond lengths.
(2JPP = 3JPP = 15.0 Hz). The P(V) atoms resonate at dp(THF) =
41.2 ppm, and (logically) the signal appears as a virtual triplet
(JPP = 15.5 Hz) of doublets (2JRhP = 6.5 Hz). It is noteworthy
that the coupling constant between the phosphine ligand and
the rhodium (1JRhP) is lower in 3 (1JRhP = 104 Hz) than in 2
(1JRhP = 171 Hz), which may be attributed to the oxidation of
the rhodium centre, according to the literature.11
This hypothesis was confirmed by parallel experiments
aimed at the synthesis of complexes 3 through a controlled
oxidation process (Scheme 2). Reactions of 2-BF4 with one
equivalent of hexachloroethane in dichloromethane cleanly
yielded the expected complex 3-BF4 in good yield (96%).
Definitive evidence concerning the structure of 3-BF4 was
obtained by X-ray analysis. An ORTEP view of the molecular
structure is presented in Fig. 2 together with the most relevant
structural parameters.
Interestingly, complex 3-Cl was directly obtained by reacting
ligand 1 with one equivalent of [RhCl3(THT)3] (THT: tetra-
hydrothiophene) complex (Scheme 3). In this case heating
overnight at 80 1C was required to complete the reaction.
Complex 3-Cl precipitated from the reaction mixture and was
isolated in 90% yield after washing with diethyl ether. This
complex proved to be poorly soluble in most organic solvents
(toluene, THF, CH2Cl2, or CDCl3), but complete NMR
characterisation was achieved using a saturated solution of
the compound in CD2Cl2. These NMR data are identical to
those of 3-BF4. X-Ray diffraction analysis revealed that the
molecular structure of 3-Cl is also very similar to that of 3-BF4
(see ESIw). In contrast to complexes 2, which are rather
sensitive to air and moisture, complexes 3 can be handled
and stored without particular precautions.
The resulting complex is cationic and features an octahedral
geometry around the metal center, with coordination of the
[P2N2] in the median plane and two chlorine atoms in the
The reactivity of Rh(I) complexes 2 towards aryl halides,
pinacolborane, and silanes (Et3SiH, Ph2SiH2) was investigated,
but no reaction was observed even at high temperature. Under
H2 atmospher (1 atm), decomposition was observed upon
prolonged heating (501 C). Ultimately, as mentioned above,
only the oxidation to the Rh(III) species could be cleanly
performed.
More significant results were obtained by reacting a suspen-
sion of 3-Cl in THF with one equivalent of silane (PhSiH3 or
EtSiH3). After 8 h heating at reflux, a colour change of the
reaction mixture from yellow to brown-green was observed.
The 31P{1H} NMR spectrum of the crude mixture showed a
signal pattern similar to that observed for 2-Cl and 2-BF4,
suggesting that a reduction to Rh(I) had occurred. Impor-
tantly, the 1H NMR spectrum of the reaction mixture
(in d3-acetonitrile) revealed the presence of a hydride which
appears as a complicated multiplet centred at dp(CD3CN) =
ꢀ16.18 ppm). In the 1H{31P} spectrum, this hydride appears as
a (broad doublet, JRhH = 19.0 Hz), thus confirming the
presence of a Rh–H bond. Unfortunately, the poor solubility
of this complex in acetonitrile or THF, combined with its
instability, precluded the recording of its 13C NMR spectrum
Fig. 2 Molecular structure of complex 3-BF4. Thermal ellipsoids
drawn at the 50% probability level. Hydrogen atoms have been
omitted for clarity. Selected distances (A) and angles (1): P2–Rh1
2.2974(7), N1–Rh1 2.077(2), N2–Rh1 2.080(2), P4–Rh1 2.3097(7),
Rh1–Cl1 2.3653(7), Rh1–Cl2 2.3616(7), Rh1–B1 7.040, P1–N1
1.591(2), P3–N2 1.585(2), P1–C15 1.803(3), P2–C15 1.848(3),
P3-C40 1.806(3), P4–C40 1.851(3), P4–Rh1–P2 106.56(3),
N1–Rh1–N2 80.5(1), P4–Rh1–N2 86.67(7), P2–Rh1–N1 86.85(7),
Cl1–Rh1–Cl2 173.23(3), Cl1–Rh1–P2 98.02(2), Cl1–Rh1–P4
85.73(3), P(3)–N(2)–Rh(1) 123.3(1), N(2)–P(3)–C(40) 103.4(1),
C(40)–P(4)–Rh(1)
100.3(1),
C(15)–P(2)–Rh(1)
101.3(1),
N(1)–P(1)–C(15) 104.3(1), P(1)–N(1)–Rh(1) 122.9(1), P1–C15–P2
109.2(1), P4–C40–P3 109.3(1), N1–P2–P4–N2 7.31(5), P1–P2–P4–P3
7.77(3), P2–N1–N2–P4 10.03(14), P2–P1–P3–P4 4.93(3).
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2943–2949 2945

View Article Online
half-conversion was achieved after 18 h in the absence of any
catalyst.12 Because Rh(III) complex 3-Cl gave satisfactory
results and was by far easier to handle than complex 2-Cl, it
was used for the rest of the study. With 1% of 3-Cl catalyst
loading, hydrogenation of para-substituted acetophenone was
also achieved efficiently (entries 3–5), the reaction being most
rapid for 4-methylacetophenone (99% conversion after 8 h).
Isobutyrophenone was also hydrogenated, but only 71%
conversion was observed after 18 h (entry 6). These perfor-
mances compare favorably with those reported by Gao
for Rh(I) complexes bearing tetradentate aminophosphine
ligands. Indeed, with these carbon-based ligands 86%, 49%,
and 38% conversions were observed for acetophenone,
4-methoxylacetophenone and isobutyrophenone respectively
(conditions: 22 h in isopropanol at reflux with 1% catalyst and
1% potassium isopropoxide).13 Nevertheless, other rhodium-
based catalytic systems have been shown to efficiently catalyse
the reduction of aromatic ketones under milder conditions.14
Interestingly, complex 3-Cl is also able to catalyse the
transfer hydrogenation of 3-methylbut-2-one, providing 94%
conversion after 1 day reaction (entry 7). Moreover the
reduction of N-benzylideneaniline can be also performed,
yielding 67% of amine after 24 h.
Scheme 4 Reduction of 3-Cl.
and a full characterisation. Several crystallization attempts
were also made, but suitable crystals for an X-ray structural
analysis could not be obtained. Based on these NMR indica-
tions, we nevertheless propose that this complex is the hydride
derivative 4 (Scheme 4).
Importantly, when reacting the Rh(III) complex 3 with two
equivalents of sodium isopropoxide in a mixture of isopropanol–
THF (1 : 1) (for solubility purposes) at 60 1C for some hours,
the 31P NMR of the crude mixture indicated the formation of
a Rh(I) complex, since signals similar to those of 2 were
observed (d 38.4 (vtd, JRhP = 18.5.0 Hz, JPP = JPP = 12.5 Hz);
41.5 (ddd, JRhP = 170.0 Hz, JPP = 14.0 Hz, JPP = 19.5 Hz)
ppm). Unfortunately, this Rh(I) complex could not be isolated.
This last observation prompted us to investigate the reactivity
of these rhodium complexes in the catalysed transfer hydro-
genation of polar bonds.
Regarding the mechanism of the catalytic reaction, the reduc-
tion of 3-Cl by isopropoxide was established independently by
NMR experiments. In addition, the monitoring of a catalytic
test by 31P{1H} NMR spectroscopy confirmed the presence of
a [P2N2] rhodium(I) complex. Despite this evidence, the
formation of a hypothetical hydride active species remains
difficult to explain, since no vacant site is available to allow the
transfer of a hydride on the rhodium. An active role of the
ligand can not be ruled out, as the iminophosphorane function
could act as a masked amide through the nitrogen or as an
electrophilic site through the phosphorus. Another possibility
would be the liberation of one coordination site by a transitory
phosphine decoordination. A stoichiometric reaction between
complex 2-Cl and one equivalent of isopropoxide was carried
out in d8-THF at room temperature and then at 60 1C to shed
light on this question. Unfortunately, the analysis of the crude
mixture by 31P{1H} and 1H NMR spectroscopy was rather
difficult, but no free phosphine or hydride was seen. Several
signals with complicated coupling patterns were observed,
which may indicate a desymmetrization of the complex. The
elucidation of this mechanism may therefore benefit from a
complete theoretical study.
Catalytic transfer hydrogenation experiments
Reactions were conducted using 1% of complex 3-Cl as the
catalyst, and 10% isopropoxide as the base, in refluxing
isopropanol (reactions were very sluggish at room temperature
or even at 50 1C). The progress of the reaction was monitored
by 1H NMR, and these data are gathered in Table 1. For
example, acetophenone was reduced in 90% yield after 4 h
(entry 1) using complex 3-Cl as the catalyst, with full conver-
sion being achieved after 18 h. As expected, the same reac-
tion carried out with Rh(I) complex 2-Cl was more rapid,
leading to total conversion after 4 h (entry 2). Note that
under the employed conditions ([iPrONa] B0.03 mol Lꢀ1), only
Table 1 Catalytic transfer hydrogenationa
Conversion (%)b
4 h
8 h
18 h
24 h
Entry
X
R
R0
Conclusion
1
2
3
4
5
6
7
8
O
Ph
Ph
Me
Me
Me
Me
Me
iPr
iPr
H
90
100
44
98
74
51
47
22
97
—
51
99
86
55
65
32
99
—
99
—
96
71
85
58
—
—
—
—
—
—
94
67
Oc
O
In conclusion, we have synthesised rhodium(I) and rhodium
(III) complexes 2 and 3 respectively, featuring tetradentate
iminophosphorane-based ligands. The reactivity of these com-
plexes was investigated. Complex 2 did not react with aryl
halides, silanes, or pinacolborane. Under 1 atm of H2 and high
temperature, decomposition of the complex was observed.
Only the oxidation of Rh(I) derivatives into the corresponding
Rh(III) complexes proceeded smoothly. The reduction of
complex 3 using silanes or isopropoxide was inferred from
in situ NMR spectroscopy analysis, which prompted us to
investigate the transfer hydrogenation of polar bonds using
p-Cl–C6H4
p-Me–C6H4
p-MeO–C6H4
Ph
Me
Ph
O
O
O
O
NPh
a
Typical catalyst runs were performed with 1.4 mmol of substrate, 1%
of 3-Cl as catalyst, 10% iPrONa (0.03 mol Lꢀ1), iPrOH (5 mL) at
b
reflux (82 1C). Conversion into reduction product determined by
1H NMR, average of two runs. Same conditions, except complex
2-Cl was used as the catalyst in place of 3-Cl.
c
c
2946 New J. Chem., 2010, 34, 2943–2949 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
3
2
the stable Rh(III) complex 3. Transfer hydrogenations of
substituted aromatic ketones and an alkyl-substituted ketone
were achieved. Partial hydrogenation of N-benzylideneaniline
was also achieved. Additional experiments could not fully
explain the observed hydride formation and the hydrogen
transfer, but a complete theoretical study may cast some light
on these aspects.
(d, JPC = 6.5 Hz, m-CH–(Ph2P(V))), 132.1 (d, JPC = 13.0 Hz,
o-CH–(Ph2P(V))), 134.6 (CIV(Ph2P(V)), J not measurable).
C52H48ClN2P4Rh, calcd: C 64.84, H 5.02, N 2.91; found:
C 65.08, H 4.86, N 2.64.
2-BF4. This complex was obtained by a similar procedure,
using [Rh(COD)2BF4] (45 mg, 0.111 mmol) as the rhodium(I)
precursor and either 1-(HBF4)2 or 1-(HCl)2 as the reagent.
When using 1-(HCl)2, the lithium salts have to be removed
before the addition of the metal precursor. 2-BF4 was obtained
as a yellow solid (89 mg, 75%) and had NMR data similar
to those of 2-Cl. C52H48BF4RhN2P4, calcd: C 61.56, H 4.77,
N 2.76; found: C 61.71, H 4.63, N 2.54.
Experimental
Synthesis
All experiments were performed under an atmosphere of dry
nitrogen or argon using standard Schlenk and glove-box
techniques. Solvents were freshly distilled under dry nitrogen
from Na/benzophenone (THF, diethyl ether, petroleum ether),
from P2O5 (dichloromethane). Aminophosphonium salt 1-(HCl)2,9
[Rh(COD)Cl]2 (COD = cyclooctadiene),15 [Rh(COE)2Cl]2
(COE = cyclooctene),16 [Rh(COD)2BF4],17 and RhCl3(THT)3]
(THT = tetrahydrothiophene),18 were prepared according to
literature procedures. All other reagents and chemicals were
obtained commercially and used without further purification,
except for isopropanol which was distilled under dry nitrogen
from calcium hydride. Nuclear magnetic resonance spectra
were recorded on Bruker Avance 300 spectrometer operating
at 300 MHz for 1H, 75.5 MHz for 13C and 121.5 MHz for 31P.
Solvent peaks were used as internal references for 1H and
13C chemical shifts (ppm). 31P are relative to a 85% H3PO4
external reference. Coupling constants are expressed in hertz.
The following abbreviations are used: b, broad; s, singlet; d,
doublet; dd, doublet of doublets; t, triplet; m, multiplet; v,
virtual. Elemental analyses were performed by the ‘‘Service
d’analyse du CNRS’’, at Gif sur Yvette, France.
For both compounds, crystals suitable for X-ray diffraction
analysis were grown by diffusion of hexanes into a concen-
trated dichloromethane of the complex (see ESIw).
Synthesis of complex 3
3-BF4. C2Cl6 (23 mg, 0.099 mmol) was added to a solution
of 2-BF4 (100 mg, 0.099 mmol) in dichloromethane (5 mL).
After 3 h stirring at room temperature, solvents were removed
in vacuo and the obtained solid was washed with hexanes
(3 ꢁ 5 mL) to give 3-BF4 as a yellow solid (103 mg, 96%).
1
31P {1H} NMR (CD2Cl2) d 19.4 (dvt, JRhP = 104.0 Hz,
2
2JPP
=
2JPP = 15.5 Hz, P(III)), 41.2 (vtd, JPP
=
3JPP
=
15.5 Hz, 2JRhP = 6.5 Hz, P(V)) ppm. 1H NMR (CD2Cl2) d 3.15
(4H, vt, JPH = 5.5 Hz, N–CH2), 4.23 (4H, td, JPH =
3
2
4
11.5 Hz, JPH = 1.0 Hz, PCH2P), 7.10 (4H, t, JHH = 7.5 Hz,
3
3
4
p-H Ph2P(V)) 7.19 (8H, vt, JHH = 7.5 Hz, JPH = 7.5 Hz,
o-H (Ph2 P(III))), 7.36 (4H, t, 3JHH = 7.5 Hz, p-H (Ph2 P(III))),
7.56 (8H, td, JHH = 7.5 Hz, JPH = 2.5 Hz, m-H Ph2P(V)),
3
3
7.67 (8H, td, 3JHH = 7.5 Hz, 4JPH = 1.5 Hz, m-H (Ph2 P(III))),
7.96 (8H, dd, 3JHH = 7.5 Hz, 3JPH = 12.5 Hz, o-H (Ph2P(V))).
13C {1H} NMR (CD2Cl2) d 52.0 (s, NCH2), 105.2 (t, JPC
=
1
Synthesis of complex 2
38.0 Hz, PCH2P), 128.1 (vt, 4JPC = 5.0 Hz, p-CH (Ph2 P(V))),
128.8 (CIV(Ph2P(III), J not measurable), 129.4 (d, 3JPC = 12.0 Hz,
m-CH (Ph2P(V))), 131.2 (CIV(Ph2P(V)), J not measurable),
2-Cl. MeLi (140 mL, 0.223 mmol) was added to a suspension
of 1-(HCl)2 (100 mg, 0.111 mmol) in THF (5 mL) cooled to
ꢀ78 1C, and the suspension was stirred at room temperature
for 15 min. [Rh(COE)Cl]2 (40 mg, 0.056 mmol) was added,
and the solution turned yellow. After heating for 2 h at 60 1C,
all volatiles were removed in vacuo and dichloromethane was
added to filter off precipitated LiCl salts. After evaporation of
CH2Cl2, the obtained solid was washed with petroleum ether
(3 ꢁ 10 mL) to deliver 2-Cl as a yellow solid (90 mg, 84%).
131.4 (s, p-CH-(Ph2P(III))), 133.4 (d, JPC = 11.5 Hz,
2
o-CH–(Ph2P(V))), 133.7 (d, 2JPC = 10.0 Hz, o-CH–(Ph2P(III))),
133.9 (bs, m-CH–(Ph2P(III))). C52H48Cl2BF4RhN2P4, calcd: C
57.54, H 4.46, N 2.58; found: C 57.37, H 4.68, N 2.73.
3-Cl. MeLi (140 mL, 0.223 mmol) was added to a suspension
of 1-(HCl)2 (100 mg, 0.111 mmol) in toluene (5 mL) cooled to
ꢀ78 1C. After warming to room temperature, stirring was
continued for 15 min, and then the lithium salts were filtered
off. [RhCl3(THT)3] (52 mg, 0.110 mmol) was subsequently
added to the ligand solution, inducing a red coloration. After
heating 12 h at 80 1C, the complex which precipitated from the
reaction mixture was filtered and washed with hexanes (3 ꢁ 5 mL).
3-Cl was obtained as an orange solid after drying in vacuo
(100 mg, 90%). Single crystals were grown by diffusion of
diethyl ether into an acetonitrile solution of the complex.
NMR data are similar to those of 3-BF4. C52H48Cl3N2P4Rh,
calcd: C 60.40, H 4.68, N 2.71; found: C 60.27, H 4.92, N 2.51.
31P {1H} NMR (CD2Cl2) d 37.8 (dvt, 2JRhP = 31.5 Hz, 2JPP
=
=
1
2
3JPP = 13.0 Hz, P(V)), 41.5 (ddd, JRhP = 170.0 Hz, JPP
2
13.0 Hz, JPP = 19.0 Hz, P(III)) ppm. 1H NMR (CD2Cl2)
3
2
d 3.20 (4H, t, JPH = 4.5 Hz, N-CH2), 3.53 (4H, dd, JPH
=
2
3
3.5 Hz, JPH = 8.5 Hz, PCH2P), 6.94 (4H, t, JHH = 7.5 Hz,
p-H (Ph2P(III))) 7.07 (8H, dd, 3JHH = 7.5 Hz, 4JPH = 8.5 Hz,
m-H (Ph2P(III))), 7.14 (8H, dd, 3JHH = 7.5 Hz, 3JPH = 11.0 Hz,
o-H (Ph2P(III))), 7.34 (12H, vtd, JHH = 7.5 Hz, JPH
3
4
=
2.0 Hz, p-H, m-H (Ph2P(V))), 7.50 (8H, dd, JPH = 11.5 Hz,
3JHH = 7.5 Hz, o-H (Ph2P(V))) ppm. 13C {1H} NMR (CD2Cl2)
d = 39.8 (dd, 1JPC = 4.5 Hz, 2JPC = 87.0 Hz, PCH2P), 53.5 (d,
2JPC = 14.0 Hz, NCH2), 126.0 (d, JPC = 83.5 Hz, CIV
General procedure for the transfer hydrogenation of polar bonds
4
Ph2P(III)), 127.1 (vt, JPC = 5 Hz, p-CH–(Ph2P(III))), 128.3
(d, 2JPC = 12.0 Hz, o-CH–(Ph2P(III))), 129.0 (s, p-CH–(Ph2P(V))),
A Schlenk flask was charged under nitrogen atmosphere
3
131.5 (d, JPC
=
9.5 Hz, m-CH–(Ph2P(III))), 132.0
with 3-Cl (8.0 mg, 0.007 mmol) and sodium isopropoxide
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2943–2949 2947

View Article Online
Table 2 Crystal data and structural refinement details for complexes 2-Cl and 3-BF4
Compound
2-Cl
3-BF4
Molecular formula
Molecular weight
Crystal system
Space group
C52H48N2P4Rh, 4(CH2Cl2), Cl
C52H48Cl2N2P4Rh, 3(CHCl3), BF4
1302.87
Monoclinic
P21/c
1443.53
Monoclinic
P21/c
a (A)
b (A)
c (A)
a (1)
11.715(1)
21.218(1)
23.598(1)
90.00
10.806(1)
35.589(1)
16.434(1)
90.00
b (1)
91.563(1)
90.00
5863.5(6)
4
13346
100.108(1)
90.00
6222.0(7)
4
40501
17688
0.0373
0.0476
772853
g (1)
V (A3)
Z
Reflections measured
Unique data
Rint
R1
CCDC number
13346
0.0329
0.0376
772851
(6.3 mg, 0.07 mmol). Isopropanol (2.5 mL) and ketone or
imine (0.7 mmol) were then added, and the reaction mixture
was vigorously stirred under reflux (82 1C). The progress of the
reaction was monitored by 1H NMR. At the appropriate time,
an aliquot was taken from the reaction mixture, dried under
vacuum, flushed through a short silica column with CDCl3
to remove the rhodium complexes, and then analysed by
1H NMR. For the transfer hydrogenation of 3-methylbut-2-one,
the progress of the reaction was monitored on the crude mixture
without any evaporation due to the low boiling point of the
substrate.
G. A. Odoherty, J. Am. Chem. Soc., 1995, 117, 9662–9670;
(e) B. M. Trost, C. B. Lee and J. M. Weiss, J. Am. Chem. Soc.,
1995, 117, 7247–7248; (f) B. M. Trost and R. C. Bunt, Angew.
Chem. Int. Ed. Engl., 1996, 35, 99–102; (g) B. M. Trost and
D. L. VanVranken, Chem. Rev., 1996, 96, 395–422;
(h) B. M. Trost, M. J. Krische, R. Radinov and G. Zanoni,
J. Am. Chem. Soc., 1996, 118, 6297–6298; (i) B. M. Trost,
R. Radinov and E. M. Grenzer, J. Am. Chem. Soc., 1997, 119,
7879–7880; (j) B. M. Trost and F. D. Toste, J. Am. Chem. Soc.,
1998, 120, 815–816; (k) B. M. Trost and D. E. Patterson, J. Org.
Chem., 1998, 63, 1339–1341.
4 (a) J. X. Gao, T. Ikariya and R. Noyori, Organometallics, 1996, 15,
1087–1089; (b) J. X. Gao, H. L. Wan, W. K. Wong, M. C. Tse and
W. T. Wong, Polyhedron, 1996, 15, 1241–1251; (c) J. X. Gao,
P. P. Xu, X. D. Yi, C. B. Yang, H. Zhang, S. H. Cheng, H. L. Wan,
K. R. Tsai and T. Ikariya, J. Mol. Catal. A: Chem., 1999, 147,
105–111; (d) R. M. Stoop, S. Bachmann, M. Valentini and
A. Mezzetti, Organometallics, 2000, 19, 4117–4126; (e) J. X. Gao,
H. Zhang, X. D. Yi, P. P. Xu, C. L. Tang, H. L. Wan, K. R. Tsai
and T. Ikariya, Chirality, 2000, 12, 383–388; (f) S. Bachmann,
M. Furler and A. Mezzetti, Organometallics, 2001, 20, 2102–2108;
(g) C. Bonaccorsi, S. Bachmann and A. Mezzetti, Tetrahedron:
Asymmetry, 2003, 14, 845–854; (h) W. K. Wong, X. P. Chen,
T. W. Chik, W. Y. Wong, J. P. Guo and F. W. Lee, Eur. J. Inorg.
Chem., 2003, 3539–3546; (i) T. S. Li, R. Churlaud, A. J. Lough,
K. Abdur-Rashid and R. H. Morris, Organometallics, 2004, 23,
6239–6247; (j) C. Bonaccorsi and A. Mezzetti, Organometallics,
2005, 24, 4953–4960; (k) C. Bonaccorsi and A. Mezzetti, Curr. Org.
Chem., 2006, 10, 225–240; (l) T. Li, I. Bergner, F. N. Haque, M. Z.
D. Iuliis, D. Song and R. H. Morris, Organometallics, 2007, 26,
5940–5949; (m) M. Althaus, C. Becker, A. Togni and A. Mezzetti,
Organometallics, 2007, 26, 5902–5911; (n) F. Santoro, M. Althaus,
C. Bonaccorsi, S. Gischig and A. Mezzetti, Organometallics, 2008,
27, 3866–3878; (o) M. Ranocchiari and A. Mezzetti, Organo-
metallics, 2009, 28, 3611–3613; (p) C. Schotes and A. Mezzetti,
J. Am. Chem. Soc., 2010, 132, 3652–3653.
X-Ray crystallography
Data were collected on a Nonius Kappa CCD diffractometer
using a Mo Ka (l = 0.71073 A) X-ray source and a graphite
monochromator. Crystal data and structural refinement
details are gathered in Table 2 and in Table S1w. CCDC
772851–772854 contain the supplementary crystallographic
data for this paperw. The crystal structure was solved using
SIR 9719 and Shelxl-97.20 ORTEP drawings were created using
ORTEP III for Windows.21
Acknowledgements
We thank the CNRS, the Ecole Polytechnique and the ANR
(Projet Blanc ANR-06-BLAN-0060-01) for financial support
of this work. Rhodium(III) chloride hydrate was generously
donated by Johnson Matthey.
5 (a) A. A. Mikhailine, E. Kim, C. Dingels, A. J. Lough and
R. H. Morris, Inorg. Chem., 2008, 47, 6587–6589; (b) C. Sui-Seng,
F. Freutel, A. J. Lough and R. H. Morris, Angew. Chem. Int. Ed.,
2008, 47, 7360–7363; (c) N. Meyer, A. J. Lough and R. H. Morris,
Chem. Eur. J., 2009, 15, 5605–5610; (d) A. Mikhailine, A. J. Lough
and R. H. Morris, J. Am. Chem. Soc., 2009, 131, 1394–1395;
(e) R. H. Morris, Chem. Soc. Rev., 2009, 38, 2282–2291;
(f) P. O. Lagaditis, A. A. Mikhailine, A. J. Lough and
R. H. Morris, Inorg. Chem., 2010, 49, 1094–1102.
6 (a) K. Aparna, R. P. K. Babu, R. McDonald and R. G. Cavell,
Angew. Chem. Int. Ed., 1999, 38, 1483–1484; (b) R. P. K. Babu,
R. McDonald, S. A. Decker, M. Klobukowski and R. G. Cavell,
Organometallics, 1999, 18, 4226–4229; (c) R. G. Cavell, R. P. K.
Babu, A. Kasani and R. McDonald, J. Am. Chem. Soc., 1999, 121,
5805–5806; (d) K. Aparna, R. G. Cavell and M. Ferguson, J. Am.
Chem. Soc., 2000, 122, 726–727; (e) R. P. K. Babu, R. McDonald
References
1 (a) J. C. Jeffery, T. B. Rauchfuss and P. A. Tucker, Inorg. Chem.,
1980, 19, 3306–3316; (b) R. Noyori and S. Hashiguchi, Acc.
Chem. Res., 1997, 30, 97–102; (c) B. M. Trost and M. L. Crawley,
Chem. Rev., 2003, 103, 2921–2943.
2 (a) Y. Y. Li, X. Q. Zhang, Z. R. Dong, W. Y. Shen, G. Chen and
J. X. Gao, Org. Lett., 2006, 8, 5565–5567; (b) Y. Xing, J. S. Chen,
Z. R. Dong, Y. Y. Li and J. X. Gao, Tetrahedron Lett., 2006, 47,
4501–4503.
3 (a) B. M. Trost and D. L. v. Vrancken, Angew. Chem. Int. Ed.,
1992, 31, 228–230; (b) B. M. Trost, B. Breit, S. Peukert,
J. Zambrano and J. W. Ziller, Angew. Chem. Int. Ed., 1995, 34,
2386–2388; (c) B. M. Trost and M. G. Organ, J. Am. Chem. Soc.,
1994, 116, 10320–10321; (d) B. M. Trost, M. G. Organ and
c
2948 New J. Chem., 2010, 34, 2943–2949 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
and R. G. Cavell, Organometallics, 2000, 19, 3462–3465; (f) R. P. K.
Babu, K. Aparna, R. McDonald and R. G. Cavell, Inorg. Chem.,
2000, 39, 4981–4984; (g) K. Aparna, R. McDonald, R. P. K. Babu
and R. G. Cavell, Angew. Chem. Int. Ed. Engl., 2001, 40, 4400–4401;
(h) R. G. Cavell, R. P. K. Babu and K. Aparna, J. Organomet.
Chem., 2001, 617–618, 158–169; (i) V. Cadierno, J. Diez, P. Crochet,
S. E. Garcia-Garrido, S. Garcia-Granda and J. Gimeno, Dalton
Trans., 2002, 1465–1472; (j) N. D. Jones, G. Lin, R. A. Gossage,
R. MacDonald and R. G. Cavell, Organometallics, 2003, 22,
2832–2841; (k) G. Lin, N. D. Jones, R. McDonald and
R. G. Cavell, Angew. Chem. Int. Ed., 2003, 42, 4054–4057;
(l) V. Cadierno, J. Diez and J. Gimeno, Chem. Commun., 2004,
Chim. Acta, 1919, 2, 619–635; (b) Y. G. Gololobov, I. N. Zhmurova
and L. F. Kasukhin, Tetrahedron, 1981, 37, 437–472;
(c) Y. G. Gololobov and L. F. Kasukhin, Tetrahedron, 1992, 48,
1353–1406; (d) Ylides and Imines of Phosphorus, ed. A. W. Johnson,
Wiley, New York, 1993.
9 (a) A. V. Kirsanov, Izv. Akad. Nauk SSSR, 1950, 426;
(b) M. Sauthier, J. Fornie
Organometallics, 2000, 19, 553–562; (c) L. Boubekeur, L. Ricard,
N. Mezailles and P. L. Floch, Organometallics, 2005, 24,
s-Camer, L. Toupet and R. Reau,
´ ´
´
1065–1074; (d) M. Demange, L. Boubekeur, A. Auffrant,
N. Mezailles, L. Ricard, X. Le Goff and P. Le Floch, New
J. Chem., 2006, 30, 1745–1754; (e) T. Cantat, N. Mezailles,
´
2716–2717; (m) L. Boubekeur, L. Ricard, N. Me
P. L. Floch, Organometallics, 2005, 24, 1065–1074;
(n) L. Boubekeur, L. Ricard, N. Mezailles, M. Demange,
A. Auffrant and P. L. Floch, Organometallics, 2006, 25,
3091–3094; (o) L. Boubekeur, S. Ulmer, L. Ricard, N. Mezailles
´
zailles and
A. Auffrant and P. Le Floch, Dalton Trans., 2008, 1957–1972.
10 (a) K. V. Katti, B. D. Santarsiero, A. A. Pinkerton and
R. G. Cavell, Inorg. Chem., 1993, 32, 5919–5925; (b) J. Li,
R. McDonald and R. G. Cavell, Organometallics, 1996, 15,
1033–1041.
´
´
and P. L. Floch, Organometallics, 2006, 25, 315–317;
(p) V. Cadierno, J. Diez, J. Garcia-Alvarez and J. Gimeno, Organo-
metallics, 2008, 27, 1809–1822; (q) P. Oulie, C. Freund, N. Saffon,
´
B. Martin-Vaca, L. Maron and D. Bourissou, Organometallics,
2007, 26, 6793–6804; (r) M. S. Hill and P. B. Hitchcock, Polyhedron,
2007, 26, 1245–1250; (s) T. K. Panda and P. W. Roesky, Chem. Soc.
Rev., 2009, 38, 2782–2804; (t) A. Buchard, A. Auffrant, L. Ricard,
X. F. Le Goff, R. H. Platel, C. K. Williams and P. Le Floch, Dalton
Trans., 2009, 1659–1667.
11 See for examples: (a) J. Duran, D. Oliver, A. Polo, J. Real,
J. Benet-Buchholz and X. Fontrodona, Tetrahedron: Asymmetry,
2003, 14, 2529–2538; (b) G. Canepa, C. D. Brandt and H. Werner,
Organometallics, 2004, 23, 1140–1152; (c) M. Douglas,
A. B. Chaplin and A. S. Weller, Organometallics, 2008, 27,
2918–2921.
12 See for examples: (a) M. C. Carrion, F. A. Jalon, B. R. Manzano,
A. M. Rodriguez, F. Sepulveda and M. Maestro, Eur. J. Inorg.
Chem., 2007, 3961–3973; (b) L. Yang, A. Kruger, A. Neels and
7 (a) R. G. Cavell, K. Aparna, R. P. K. Babu and Q. Y. Wang,
J. Mol. Catal. A: Chem., 2002, 189, 137–143; (b) V. Cadierno,
P. Crochet, J. Garcia-Alvarez, S. E. Garcia-Garrido and
J. Gimeno, J. Organomet. Chem., 2002, 663, 32–39;
(c) V. Cadierno, P. Crochet, J. Diez, J. Garcia-Alvarez,
S. E. Garcia-Garrido, S. Garcia-Granda, J. Gimeno and
M. A. Rodriguez, Dalton Trans., 2003, 3240–3249;
(d) V. Cadierno, J. Diez, J. Garcia-Alvarez and J. Gimeno, Organo-
M.
Albrecht,
Organometallics,
2008,
27,
3161–3171;
(c) C. Ganesamoorthy, M. S. Balakrishna and J. T. Mague, Dalton
Trans., 2009, 1984–1990.
13 (a) J. X. Gao, X. D. Yi, P. P. Xu, C. L. Tang, H. L. Wan and
T. Ikariya, J. Organomet. Chem., 1999, 592, 290–295; (b) J. X. Gao,
X. D. Yi, P. P. Xu, C. L. Tang, H. Zhang, H. L. Wan and
T. Ikariya, J. Mol. Catal. A: Chem., 2000, 159, 3–9.
14 (a) K. Murata and T. Ikariya, J. Org. Chem., 1999, 64, 2186–2187;
(b) M. Albrecht, R. H. Crabtree, J. Matab and E. Peris, Chem.
Commun., 2002, 32–33; (c) D. S. Matharu, D. J. Morris,
A. M. Kawamoto, G. J. Clarkson and M. Wills, Org. Lett.,
metallics, 2005, 24, 2801–2810; (e) M. T. Gamer, M. Rastatter,
¨
P. W. Roesky, A. Steffens and M. Glanz, Chem. Eur. J., 2005, 11,
3165–3172; (f) T. K. Panda, A. Zulys, M. T. Gamer and
P. W. Roesky, Organometallics, 2005, 24, 2197–2202;
2005, 7, 5489–5491; (d) P. Maire, T. Buttner, Fr. Breher, P. Le
¨
Floch and H. Grutzmacher, Angew. Chem. Int. Ed., 2005, 44,
¨
(g) M. Rastatter, A. Zulys and P. W. Roesky, Chem. Commun.,
¨
2006, 874–876; (h) M. Rastatter, A. Zulys and P. W. Roesky, Chem.
Eur. J., 2007, 13, 3606–3616; (i) B. Liu, D. Cui, J. Ma, X. Chen and
X. Jing, Chem. Eur. J., 2007, 13, 834–845; (j) M. Wiecko,
P. W. Roesky, V. V. Burlakov and A. Spannen, Eur. J. Inorg.
Chem., 2007, 876–881; (k) M. T. Gamer, P. W. Roesky, I. Palard,
M. Le Hellaye and S. M. Guillaume, Organometallics, 2007, 26,
651–657; (l) A. Buchard, A. Auffrant, C. Klemps, L. Vu-Do,
L. Boubekeur, X. F. Le Goff and P. Le Floch, Chem. Commun.,
2007, 1502–1504; (m) A. Buchard, B. Komly, A. Auffrant, X. F. Le
Goff and P. Le Floch, Organometallics, 2008, 27, 4380–4385;
(n) C. Klemps, A. Buchard, R. Houdard, A. Auffrant,
N. Mezailles, X. F. Le Goff, L. Ricard, L. Saussine, L. Magna
and P. Le Floch, New J. Chem., 2009, 33, 1748–1752; (o) K. Yadav,
J. S. J. McCahill, G. Bai and D. W. Stephan, Dalton Trans., 2009,
1636–1643; (p) A. Buchard, H. Heuclin, A. Auffrant, X. F. Le Goff
and P. Le Floch, Dalton Trans., 2009, 1659–1667; (q) A. Buchard,
R. H. Platel, A. Auffrant, X. F. Le Goff, P. Le Floch and
C. K. Williams, Organometallics, 2010, in press.
6318–6323; (e) J. Wettergren, A. B. Zaitsev and H. Adolfsson, Adv.
Synth. Catal., 2007, 349, 2556–2562; (f) X. F. Wu, X. H. Li,
A. Zanotti-Gerosa, A. Pettman, J. K. Liu, A. J. Mills and
J. L. Xiao, Chem. Eur. J., 2008, 14, 2209–2222; (g) G. Dyson,
J. C. Frison, A. C. Whitwood and R. E. Douthwaite, Dalton
Trans., 2009, 7141–7151.
15 A. Vanderent and A. L. Onderdelinden, Inorg. Synth., 1990, 28,
90–92.
16 G. Giordano and R. H. Crabtree, Inorg. Synth., 1990, 28,
88–90.
17 H. Qiu, Y. Inoue and S. Che, Angew. Chem. Int. Ed., 2009, 48,
3069–3072.
18 E. A. Allen and W. Wilkinso, J. Chem. Soc., Dalton Trans., 1972,
613–617.
19 A. Altomare, M. C. Burla, M. Camalli, G. Cascarano,
C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori
and R. Spagna, J. Appl. Cryst., 1999, 32, 115–119.
20 G. M. Sheldrick, SHELXS-96, Program for the Solution of Crystal
8 For the synthesis of iminophosphosphorane by the Staudinger
reaction, see for example: (a) H. Staudinger and J. Meyer, Helv.
Structures, University of Gottingen, Gottingen, Germany, 1996.
¨ ¨
21 L. J. Farrugia, ORTEP-3, J. Appl. Cryst., 1997, 32, 565.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2943–2949 2949