N-phosphanylamidine ligands and their catalytic activity in the hydroformylation of 1-octene and styrene

Article abstract of DOI:10.1016/j.jorganchem.2010.10.030

Pyridine-based N-phosphanylamidine ligands i-Pr₂N-C(pyr)N- PR₂ (R = Ph (3), i-Pr (4)) were synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Mononuclear rhodium complexes 7 and 8 were obtained in one

Full text of DOI:10.1016/j.jorganchem.2010.10.030

Journal of Organometallic Chemistry 696 (2011) 897e904
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
N-phosphanylamidine ligands and their catalytic activity in the hydroformylation
of 1-octene and styrene
,
,
,
,
,b
Régis Maura a b, Jennifer Steele a b, Laure Vendier a b, Damien Arquier a b, Stéphanie Bastin a
,
Martine Urrutigoïty a , Philippe Kalck b, Alain Igau a
,
b,
a,
,b,
*
*
a CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France
b Université de Toulouse, UPS, INPT, LCC, F–31077 Toulouse, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Pyridine-based N-phosphanylamidine ligands i-Pr2NeC(pyr)]NePR2 (R ¼ Ph (3), i-Pr (4)) were
synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Mononuclear
rhodium complexes 7 and 8 were obtained in one step from the [RhCl(COD)]2 dimer and the mono-
dentate ligands 1 and 2. Their single-crystal X-ray diffraction studies revealed the structural adaptive
behavior of the monodentate N-phosphanylamidine ligands 1 and 2 upon k1-P coordination mode in
rhodium(I) complexes with the imino nitrogen atom of the amidine function which behaves as
a “universal joint”. Compounds 1e4 were evaluated as ligands in the 1-octene and styrene hydro-
formylation reactions. The results obtained are encouraging and represent the first report on the use of
N-phosphanylamidine ligands of the type R002NeC(R0)]NePR2 in catalytic reactions.
Received 10 October 2010
Accepted 12 October 2010
Available online 23 October 2010
Keywords:
Amidines
Phosphanes
Rhodium
Hydroformylation
Pyridine
Ó 2010 Elsevier B.V. All rights reserved.
X-ray diffraction
1. Introduction
R1R2C]NePR2 have been tested in catalytic chemical trans-
formations [12,13].
Hydroformylation is a straightforward synthetic methodology
affording aldehydes by creating a CeC bond in only one step from
quite inexpensive feedstock. It represents one of the most impor-
tant homogeneous catalytic processes applied on an industrial
scale [1,2]. A large number of ligands have been developed and
applied to this reaction [3e8] and there is continued interest in the
development of new mono- and heteroditopic bidentate phos-
phane ligands to increase the efficiency and selectivity of this
chemical transformation. The straightforward formation of PeN
bonds from halophosphanes is a method of choice to prepare easily
a large scope of phosphane ligands. This synthetic methodology
allows a fine tuning of the steric and electronic properties of the
phosphane moiety [9,10]. This high versatility is one of the reasons
why, for example, aminophosphane R2PeNR02 [10] and phosphor-
amidite (RO)2PeNR02 [11] ligands are extensively studied for their
applications in catalysis. It is noteworthy that very few examples of
methylenaminophosphine-type ligands of the general formula
“Hybrid” ligands, such as bifunctional P,N-ligands bearing two
chemically different donor atoms, are of particular interest in
catalytic reactions since they can reversibly adopt either a
2-P,N coordination mode along the catalytic cycle and therefore
modify the catalytic properties of the metallic center. Even though
the
1-P and 2-P,N coordination modes to Rh(I) have been identi-
fied with P,N hybrid ligands, very few experimental data have
evidenced the
2-P,N chelating mode under hydroformylation
k
1-P or
a
k
k
k
k
conditions [14]. Nevertheless, the results recorded up to now with
these P,N hybrid ligands highlight the beneficial effect of the
presence of the non-coordinated nitrogen function in the catalytic
activity [14,15].
On the basis of these considerations, we were interested in
developing a class of hybrid P,N-ligands incorporating PeN bonds.
We have a strong experience in the ligand design of monodentate
N-phosphanylamidine of the general formula R002NeC(R0)]NePR2
(R0 ¼ H, Ph). We have previously reported their reactivity towards
Brönsted acids [16], phospheniums [17] and initiated their coordi-
nation chemistry with ruthenium metal fragment [18]. Complexes
with N-phosphanylamidines as ligands have been reported in the
literature before our studies [19,20] but as far as we know, this class
of ligands has never been tested in catalysis. In this paper, we report
the coordination behavior of monodentate N-phosphanylamidine
* Corresponding authors. CNRS, LCC (Laboratoire de Chimie de Coordination),
205, route de Narbonne, F-31077 Toulouse, France.
E-mail address: alain.igau@lcc-toulouse.fr (A. Igau).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.10.030

898
R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
ligands i-Pr2NeC(Ph)]NePR2 (R ¼ Ph, i-Pr) towards rhodium
precursors and the synthesis of their corresponding bidentate
pyridine-based ligands i-Pr2NeC(pyr)]NePR2 (R ¼ Ph, i-Pr). Both
monodentate and bidentate ligands were applied to the catalytic
hydroformylation reaction of 1-octene and styrene.
compound but to a mixture of complexes as evidenced by the 31P
NMR spectra. After treatment of the different crude reaction
mixtures, we could not obtain X-ray quality crystals which could
have allowed us to state on the coordination mode of ligands 1 and 3
with [Rh(acac)(CO)2]. Nevertheless, we ascertained the compati-
bility of ligands 1 and 2 with rhodium(I) by reacting two equivalents
of 1 and 2 with the rhodium dimer [Rh(COD)Cl]2 affording the
corresponding complexes 7 and 8 in 79% and 83% yield, respectively,
as outlined in Scheme 3. The 31P NMR spectra exhibit a doublet at
58.3 ppm for compound 7 (JRhP ¼ 154.2 Hz) and at 74.0 ppm for
compound 8 (JRhP ¼ 147.0 Hz) which clearly indicates the P-coordi-
nation of the N-phosphanylamidine ligands. In 13C NMR, complexes
7 and 8 exhibit a resonance at 164.1 and 161.8 ppm, respectively,
assigned to the carbon of the imino C]N moiety. For 7, the low 2JCP
coupling constant value (2JCP ¼ 8.6 Hz) is consistent with the
P-coordination mode of the ligand. In complex 8, the corresponding
2JCP coupling constant value was too low to be observed. As
expected, proton NMR spectra show two sets of signals for the CH
protons of the cyclooctadiene resulting from the two different trans
substituents at the metallic center [21,22]: signals at 5.26 (7) and
5.70 (8) ppm are assigned to the trans P-CH protons and signals at
3.18 (7) and 3.62 (8) ppm to the trans CleCH protons which fall in
the range of chemical shifts observed for these protons in [RhCl
(COD)(PR3)] type complexes [23].
2. Results and discussion
2.1. Synthesis of the N-phosphanylamidine ligands 1e4
As previously described [18], the monodentate N-phosphany-
lamidine ligands 1 and 2 were isolated in good yields (82% and 85%,
respectively) by successive addition of phenyllithium and the cor-
responding chlorophosphane R2PCl onto the N,N-diisopropylcya-
namide (Scheme 1).
By introducing a pyridine fragment into the amidine organic
framework, we prepared the bidentate N-phosphanylamidine ligand 3
by successive addition of the N,N-diisopropylcyanamide onto the
lithiated pyridine, obtained by lithiation of 2-bromopyridine using
butyllithium, and Ph2PCl. The 31P NMR analysis of the crude reaction
mixture revealed the presence of the expected product at 43.4 ppm
along with two side products at 112.5 and ꢀ14.6 ppm. In order to
facilitate the purification of 3, addition of the BH3$THF adduct was
performed and afforded the phosphorus borane-protected compound
5in 20%yield after purificationbycolumn chromatography (Scheme 2,
pathway A). Compound 6 resulting from the coordination of the BH3
moiety onto the phosphorus and the nitrogen atom of the pyridyl
group was also isolated in 7% yield (Scheme 2, pathway A). In order to
improve the reaction yield, we investigated another way of synthe-
sizing ligand 3 starting from 2-cyanopyridine. Successive addition of
lithiumdiisopropylamide (LDA) freshly prepared and Ph2PCl onto 2-
cyanopyridine afforded the bidentate ligand 3 in good yield (82%).
Following the same reaction sequence, ligand 4 was isolated in 60%
yield (Scheme 2, pathway B). Compounds 3e6 were fully character-
ized by mass spectrometry and 1H, 31P and 13C NMR spectroscopy. The
1H NMR spectra of compounds 3e6 showed the characteristic proton
chemical shifts of the isopropyl groups. In 31P NMR, 3 and 4 exhibited
signals at 43.4 and 69.4 ppm, respectively; the spectra of 5 and 6
showedthepresenceofabroaddoubletat45.9(JPB ¼ 74.8 Hz) and 45.2
(JPB ¼ 85.4 Hz) ppm, respectively, characteristic of a phosphorus atom
bearing a BH3 moiety. In 13C NMR spectra, the 2JCP imino carbon >C]
NeP coupling constants [30.9 Hz (3), 29.0 Hz (4), 7.2 Hz (5) and 4.1 Hz
(6)] confirmed the presence of the phosphanyl group attached to the
amidine pattern. The low 2JCP imino carbon coupling constant values
2.3. Single-crystal X-ray studies of compounds 3 and 5e8
X-ray quality crystals were obtained from a saturated solution of
3 in diethylether at ꢀ20 ꢁC and by slow evaporation of a saturated
Et2O/pentane solution at room temperature of each compound 5
and 6. Monocrystals of rhodium complexes 7 and 8 were grown by
slow evaporation of a saturated diethylether solution of each
complex at room temperature. Selected geometric data for all
structures are reported in Table 1.
The structures of 3, 5 and 6 revealed an E-stereoisomer which is
consistent with the other three structurally characterized N-phospha-
nylamidines i-Pr2NeC(Ph)]NePR2 (R ¼ Ph, i-Pr) [18], (Me3Si)2NeC
(Ph)]NePPh2 [24] and i-Pr2NeC(H)]NePPh2 [16]. As expected, the
amino nitrogen atom i-Pr2Ne is planar and the phosphorus atom
exhibits a pyramidal geometry in all compounds (Figs. 1e3). The
difference of 0.06 Å between the C1eN1 and C1eN2 bond lengths in
the ligand 3 is more significant than in compounds 5 (0.035 Å) and 6
(0.045 Å), which may be due to a stronger localisation of the >C1]N1e
double bond in 3. The coordination of the BH3 moiety is trans to the
electronic lone pair of the imino nitrogen atom in both N-phosphany-
lamidines 5 and 6. Moreover the P1eB1 bond lengths, 1.908(2) Å in (5)
and 1.922(2) Å in (6), and the N3eB2 bond length of 1.596(3) Å in
compound 6, are in the range of those reported in literature for ami-
nophosphine borane [25e28] and pyridine-borane [29] complexes,
respectively.
observed for 5 and 6 are consistent with a tetracoordinated
phosphorus fragment [16e18].
s
4-P
2.2. Synthesis of the rhodium complexes 7 and 8
In order to get a better insight into the coordination mode of the
N-phosphanylamidine ligands with the catalytic rhodium precursor
[Rh(acac)(CO)2], we reacted this latter with one or two equivalents
of ligand 1 and 3. Unfortunately, the reactions did not lead to a single
The molecular structures of complexes 7 and 8 depicted in Figs.
4 and 5 assessed the P-coordination of ligands 1 and 2 and confirm
the conclusions deduced from the spectroscopic data recorded in
solution.
The metallic center displays a slightly distorted square-planar
geometry with the four coordination positions being defined by the
chloride ligand, the phosphorus atom of the k
1-PN-phosphanyla-
midine ligand and the centroids of the two cyclooctadiene (COD)
olefin bonds. The COD ligand adopts a “tub” conformation with
both CeC double bonds being approximately normal to the coor-
dination plane. In complexes 7 and 8, the P-trans RheCH(COD)
distances are ca 0.1 Å longer than the Cl-trans RheCH(COD)
distances due to a strong trans influence of the phosphane ligand.
As it was already observed for N-phosphanylamidine ligands 1 and
2 upon P-coordination to ruthenium metal fragment [18], in
Scheme 1. Synthesis of the N-phosphanylamidines 1 and 2.

R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
899
Scheme 2. Synthesis of the N-phosphanylamidines 3 and 4.
complexes 7 and 8, the N2eC1eN1 bond angle value does not
change to any great extent compared to the corresponding free
ligands and a shortening of the N1eP1 bond length is observed. The
C1eN1eP1 bond angle value of 143.1(3) Å in 8 is the largest
recorded to date for N-phosphanylamidine ligands. This dramatic
opening of the C1eN1eP1 bond angle reflects the ability of these
ligands to adapt their geometry to minimize the steric constraints.
In marked contrast to what was expected, the C1eN1eP1 bond
angle of ligand 1 remains almost unchanged in complex 7 with
into the structure of ligand 1 which results in a higher steric
constraint around the metal fragment compared to ligand 2. It is
then not surprising to observe that the distortion from the square
planar geometry is more pronounced in complex 7 than in complex
8. This is reflected by the position of the centers of the CeC double
bonds of COD which are displaced by 0.118 and 0.408 Å with respect
to the plane defined by the P1, Rh1 and Cl1 atoms.
2.4. Catalytic activity of {[Rh(acac)(CO)2/1e4} systems in
hydroformylation reactions
a value of 123.9(3) Å. The N-phosphanylamidine ligand 1 in the
rhodium complex 7 adopts a stacking arrangement between
k
1-P
pep
the phenyl ring linked to the carbon atom of the methylene >C
(Ph)]Ne fragment and one of the two phenyl substituents on the
phosphorus atom defined by the C8eC13 and C14eC19 carbon
atoms, respectively. This interaction is characterized by a cen-
It is known [3a,30] that the [Rh(H)(CO)2L2] catalyst precursor,
which usually provides the active species by dissociation of a CO
ligand [31], is instantaneously and selectively produced by addition
of the L phosphine ligand to [Rh(acac)(CO)2] under typical hydro-
formylation conditions. Thus, N-phosphanylamidine ligands 1e4
have been introduced in the coordination sphere of [Rh(acac)(CO)2]
troidecentroid distance of 3.849 Å and an offset angle
intramolecular interaction in complex 7 induces some rigidity
a
of 32ꢁ. This
pep
Scheme 3. Synthesis of the N-phosphanylamidines rhodium complexes 7 and 8.

900
R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
Table 1
Selected bond lengths (Å) and angles (ꢁ) for compounds 3, 5, 6e8.
3
5
6
7
8
C1eN1
C1eN2
N1eP1
B1eP1
Rh1eP1
Rh1eCl1
1.301(2)
1.360(2)
1.309(2)
1.343(2)
1.297(2)
1.341(2)
1.301(5)
1.357(5)
1.674(3)
1.284(4)
1.369(5)
1.653(3)
1.7098(16) 1.6427(15) 1.6681(14)
/
/
/
1.908(2)
1.922(2)
/
/
/
/
/
/
2.3030(10) 2.3077(9)
2.3777(10) 2.3676(9)
N2eC1eN1 121.59(16) 120.93(16) 121.07(14)
C1eN1eP1 118.98(13) 130.51(13) 128.32(12)
120.1(4)
123.9(3)
119.8(3)
143.1(3)
N1eP1eB1
/
113.63(10) 124.11(8)
/
/
in order to evaluate their catalytic activity in the hydroformylation
reaction of 1-octene (Scheme 4) and styrene (Scheme 5). The
hydroformylation reactions were carried out at 60 ꢁC and 30 bar of
syngas CO/H2 (1:1) using a stock solution of the rhodium pre-
catalyst (1.0 mM in toluene) prepared in situ from [Rh(acac)(CO)2]
and the corresponding ligands 1e4. The production of all deriva-
tives generated during the reaction (products and side products)
was monitored by gas chromatography.
Fig. 2. Molecular structure of N-phosphanylamidine 5. Hydrogen atoms have been
omitted for clarity.
2.4.1. Hydroformylation of 1-octene
The hydroformylation results with the N-phosphanylamidine
ligands 1e4 are displayed in Table 2.
conditions, ligands 1 (entry 3) and 4 (entry 13) induce a significant
isomerization reaction, respectively, 15% and 9% of formation of
internal octenes, than ligands 2, 3 and PPh3 (entries 1, 6 and 7)
In a first approach, the catalytic experiments were conducted
under mild conditions of temperature (60 ꢁC) and pressure (30 bar)
with a molar ratio ligand/Rh of 5:1 and a molar ratio 1-octene/Rh of
510:1. Conversions and selectivities were determined after 6 h of
reaction by GC. High conversions near to 99% were reached, either
for 1 and 3 which compare quite well with that obtained with PPh3
(entries 1, 3 and 7). The reaction rate is somewhat lower with ligand
2 since in 6 h the conversion is 84% (entry 6). Increasing the
substrate to catalyst ratio from 510 to 832 does not significantly
affect the conversion (entries 4, 5, 7, 9 and 10). However, this
conversion is dramatically reduced to 49% (entry 12) when this
ratio is increased to 1020. A comparison of results of entries 3, 6, 7
and 13 performed with the four ligands 1e4 reveal that ligand 3
displays a better chemoselectivity towards aldehydes (>99%) and
a better regioselectivity for the linear aldehyde with a linear to
branched ratio of 2.22 (entry 7). Under the same catalytic
which suggests a higher b-H elimination reaction rate. This isom-
erization process increases also in varying the catalytic conditions
(entries 7e12), especially when the ligand to rhodium ratio is only
equal to 1 (entry 11), when the temperature is reduced to 45 ꢁC
(entry 8), or when the substrate to rhodium ratio reaches the 1020
value (entry 12). We can note that high conversion rates can be
reached with however lower l/br ratios than for PPh3.
2.4.2. Hydroformylation of styrene
Similarly, we compared the activities and selectivities of the
N-phosphanylamidine ligands 1 and 3. The hydroformylation
results are displayed in Table 3. The corresponding complexes
formed in situ are good precursors to catalyze the hydroformylation
of styrene, under the same experimental conditions of 30 bar of
CO/H2 syngas (CO/H2:1/1) at 60 ꢁC. We choose to keep a ligand to
rhodium ratio of 3.3 and a substrate to rhodium ratio of 832. After
6 h, conversions up to 85e94% are reached (entries 3, 4), 1 and 3
Fig. 1. Molecular structure of N-phosphanylamidine 3. Hydrogen atoms have been
Fig. 3. Molecular structure of N-phosphanylamidine 6. Hydrogen atoms have been
omitted for clarity.
omitted for clarity.

R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
901
ray diffraction analyses of the resulting complexes [RhCl(COD)(1)] 7
and [RhCl(COD)(2)] 8 revealed that the monodentate N-phospha-
nylamidine ligands 1 and 2 are able to adapt to a large extent their
molecular structure with a significant amplitude of 20ꢁ for the
C1eN1eP1 bond angle value depending on the steric hindrance
around the metal center or the formation of an intramolecular pep
interaction in the amidine organic function. To conclude on this
preliminary approach in hydroformylation of 1-octene and styrene,
the reactivity induced by the present new ligands 1e4 is consistent
with the coordination of two phosphorus atoms on the rhodium
metal center, since we did not detect sufficient differences to state
the bidentate coordination of pyridine-based N-phosphanylamidine
ligands 3 and 4. The better regioselectivity observed in the hydro-
formylation reaction of styrene with ligands 1 and 3 prompt us to
study further the influence of the electronic and steric properties of
the N-amidine moiety on the catalytic activity and regioselectivity of
carbonylation reactions. Moreover, the synthesis of this class of N-
phosphanylamidine ligands enables a large variation of the alkyl/
aryl groups on the phosphorus atom which is essential for further
catalytic investigations. Particularly, we are currently exploring the
introduction of a chiral backbone on the phosphorus atom for
applications in asymmetric hydroformylation reactions.
Fig. 4. Molecular structure of
h
1-P N-phosphanylamidine rhodium complex 7.
Hydrogen atoms have been omitted for clarity.
4. Experimental
4.1. General
comparing well to PPh3 ligand. Satisfactory turnovers (TON) are
gained to around 750. No loss of chemioselectivity was observed
when using ligands 1 and 3 in place of Ph3P (no ethylbenzene as
styrene hydrogenation product was detected by GC analysis).
Moreover, regarding the regioselectivity, a comparison of the b/l
ratio obtained with the ligands 1 and 3 (b/l ¼ 15.7) with the one
obtained with Ph3P (entry 2) (b/l ¼ 5.7) evidences the beneficial
effect of the amidine moiety in the hydroformylation reaction of
styrene. At this stage of the study, it is difficult to attribute this
encouraging result to the electronic and/or steric properties of the
N-phosphanylamidine ligands.
All reactions were conducted under an inert atmosphere of dry
argon using standard Schlenk-line techniques. Solvents were dried
and degassed by standard methods before use. NMR spectra were
recorded on a Bruker AV 500, AV 300, DPX 300 or AC200 spec-
trometer. Chemicals shifts for 1H and 13C are referenced to residual
solvent resonances used as an internal standard and reported
relative to SiMe4. 31P NMR chemical shifts are reported relative to
external aqueous 85% H3PO4. Mass spectra were recorded on a TSQ
7000 Thermo Electron mass spectrometer. Melting points were
obtained using an Electrothermal Digital Melting Point apparatus
and are uncorrected. The synthesis of ligands 1 and 2 has previously
been described [18]. GC chromatograms were recorded on a Per-
kineElmer Clarus 500 apparatus equipped with a flame ionization
detector and a 30 m DB-5GC capillary column (0.25 mm i.d.,
3. Conclusions
The new bidentate pyridine-based N-phosphanylamidine
ligands i-Pr2NeC(pyr)]NePR2 3 (R ¼ Ph) and 4 (R ¼ i-Pr) were
synthesized and fully characterized. The coordination chemistry of
the monodentate ligands 1 and 2 with rhodium was studied. The X-
0,25 mm film thickness).
4.2. Preparation of N-phosphanylamidines 3 and 4
Six millilitres of n-BuLi (1.6 mol Lꢀ1, 9.60 mmol) were added to
a solution of N,N-diisopropylamine (1.35 mL, 9.6 mmol) in 8 mL of
THF at 0 ꢁC. The solution was stirred for 10 min and then cooled
down to ꢀ78 ꢁC. A solution of 2-cyanopyridine (1.0 g, 9.60 mmol) in
6 mL of THF was added dropwise and the mixture was stirred for 1 h
before the addition of the corresponding chlorophosphane R2PCl
(9.6 mmol). After 1 h stirring at room temperature the solution was
concentrated down to 5 mL before the addition of 10 mL of degassed
Et2O, LiCl was removed by filtration. The solvent was removed and
the reaction product was extracted with Et2O (3 ꢂ10 mL) to give 3 in
82% (3.06 g, 7.87 mmol) yield and 4 in 60% yield (1.85 g, 5.76 mmol).
d
Compound 3: 31P{1H} NMR (121.5 MHz, C6D6): [ /ppm] 43.4 (s). 1H
NMR (300.1 MHz, C6D6): [ /ppm] 8.48e8.45 (m, 1H, Ar), 7.95e7.90
d
(m, 4H, Ar), 7.32e7.27 (m, 5H, Ar), 7.19e7.05 (m, 2H, Ar), 6.96e6.94
3
(m, 1H, Ar), 6.67e6.64 (m, 1H, Ar), 3.52 (h, JHH ¼ 6.7 Hz, 2H, NCH
(CH3)2),1.41 (br s,12H, NCH(CH3)2).13C{1H} NMR (62.9 MHz, CDCl3):
2
[d
/ppm] 164.6 (d, JCP ¼ 30.9 Hz, C]N), 156.1 (d, JCP ¼ 7.0 Hz, Ar),
149.5 (s, Ar), 145.2 (d, JCP ¼ 12.0 Hz, Ar), 136.0 (s, Ar), 131.2 (d,
JCP ¼ 19.7 Hz, Ar), 127.7 (d, JCP ¼ 7.9 Hz, Ar), 122.9 (s, Ar), 122.0 (d,
JCP ¼ 5.7 Hz, Ar), 48.8 (br s, NCH(CH3)2), 20.8 (s, NCH(CH3)2). DCI
Fig. 5. Molecular structure of
Hydrogen atoms have been omitted for clarity.
h
1-P N-phosphanylamidine rhodium complex 8.

902
R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
CHO
[Rh(acac)(CO)2]/1,3
CHO
+
+
+
H2
R
R
R
CO
R = C6H13
Scheme 4. The hydroformylation of 1-octene.
[NH3] MS m/z: 390 [M þ H]þ. Compound 4: 31P{1H} NMR
13C{1H} NMR (75.5 MHz, CDCl3): [
d
/ppm] 156.9 (d, 2JCP ¼ 4.1 Hz, C]
(121.5 MHz, C6D6): [
d
/ppm] 69.4 (s). 1H NMR (300.1 MHz, C6D6): [
d/
N), 150.3 (d, JCP ¼ 7.5 Hz, Ar), 148.5 (s, Ar), 139.5 (s, Ar), 135.9 (d,
JCP ¼ 78.9 Hz, Ar), 133.6 (d, JCP ¼ 52.1 Hz, Ar), 132.6 (d, JCP ¼ 10.5 Hz,
Ar), 131.4 (d, JCP ¼ 10.6 Hz, Ar), 130.1 (d, JCP ¼ 2.4 Hz, Ar), 129.9 (d,
JCP ¼ 2.3 Hz, Ar),128.1 (d, JCP ¼ 10.8 Hz, Ar),127.7 (d, JCP ¼ 9.7 Hz, Ar),
125.3 (s, Ar), 124.9 (s, Ar), 123.5 (s, Ar), 122.7 (s, Ar), 52.1 (d,
4JCP ¼ 1.0 Hz, NCH(CH3)2), 47.4 (s, NCH(CH3)2), 20.7 (s, NCH(CH3)2),
20.6 (s, NCH(CH3)2), 20.5 (s, NCH(CH3)2), 20.0 (s, NCH(CH3)2). DCI
[NH3] MS m/z: 418 [M þ H]þ. Mp: 160e164 ꢁC (dec.).
ppm] 8.58 (br d, JHH ¼ 4.8 Hz, 1H, Ar), 7.21 (ddd, JHH ¼ 7.8 Hz,
JHH ¼ 7.8 Hz, JHH ¼ 1.8 Hz,1H, Ar), 7.01 (brd, JHH ¼ 7.8 Hz,1H, Ar), 6.70
(ddd, JHH ¼ 7.5 Hz, JHH ¼ 4.8 Hz, JHH ¼ 0.9 Hz, 1H, Ar), 3.49 (h,
3JHH ¼ 6.9 Hz, 2H, NCH(CH3)2),1.94 (h, 3JHH ¼ 6.9 Hz, 2H, PCH(CH3)2),
3
3
1.40 (dd, JHH ¼ 6.9 Hz, JHP ¼ 10.0 Hz, 6H, PCH(CH3)2), 1.22 (dd,
3JHH ¼ 7.2 Hz, 3JHP ¼ 14.5 Hz, 6H, PCH(CH3)2),1.43e1.21 (m,12H, NCH
(CH3)2). RMN 13C{1H} (75.5 MHz, C6D6):
[d/ppm] 165.6 (d,
2JCP ¼ 29.0 Hz, C]N),157.1 (d, JCP ¼ 6.6 Hz, Ar),149.1 (d, JCP ¼ 0.6 Hz,
Ar), 135.0 (d, JCP ¼ 1.4 Hz, Ar), 122.6 (d, JCP ¼ 5.7 Hz, Ar), 121.9 (s, Ar),
48.0 (br s, NCH(CH3)2), 27.4 (d, 1JCP ¼ 12.7 Hz, PCH(CH3)2), 20.6 (s,
NCH(CH3)2),18.9 (d, 2JCP ¼ 19.5 Hz, PCH(CH3)2),18.2 (d, 2JCP ¼ 8.9 Hz,
PCH(CH3)2). DCI[NH3] MS m/z: 322 [M þ H]þ.
4.4. Preparation of N-phosphino amidines rhodium complexes 7
and 8
To a solution of [Rh(COD)Cl]2 (0.10 g, 0.20 mmol) in CH2Cl2
(4 mL) was added a solution of 0.40 mmol of ligand (1, 155 mg; 2,
128 mg) in CH2Cl2 (4 mL). The reaction mixture was stirred at room
temperature for 2 h. The solvent was removed and the resulting
yellow powder was washed with n-pentane (3 ꢂ 3 mL) to give 7 in
79% (200 mg, 0.32 mmol) yield and 8 in 83% yield (188 mg,
4.3. Preparation of N-phosphanylamidines 5 and 6
The 8.30 mL of n-BuLi (1.6 mol Lꢀ1, 13.30 mmol) were added
slowly at ꢀ78 ꢁC to
a solution of 2-bromopyridine (2.10 g,
13.30 mmol) in 20 mL of Et2O. The mixture was stirred for 1 h and
a solution of iPr2CN (2.02 mL, 13.30 mmol) in 8 mL of Et2O was
added. After 1 h at ꢀ40 ꢁC, Ph2PCl (2.40 mL,13.30 mmol) was added.
The reaction mixture was stirred for 1 h at ꢀ40 ꢁC and then allowed
to reach 0 ꢁC before the addition of BH3$THF (1.0 mol Lꢀ1, 13.30 mL,
13.30 mmol). The reaction mixture was stirred overnight at room
temperature. LiCl formed during the reaction was removed by
filtration and the crude product was then purified by column chro-
0.33 mmol). Compound 7: 31P{1H} NMR (121.5 MHz, CDCl3):
1
[
d
/ppm] 58.3 (d, JPRh ¼ 154.2 Hz). 1H NMR (200.1 MHz, CDCl3):
[d
/ppm] 7.64e7.53 (m, 5H, Ar), 7.34e7.14 (m, 10H, Ar), 5.26 (br s, 2H,
3
olefinic HCOD), 3.69 (m, 1H, NCH(CH3)2), 3.40 (h, JHH ¼ 6.7 Hz, 1H,
NCH(CH3)2), 3.18 (br s, 2H, olefinic HCOD), 2.35e2.06 (m, 4H,
aliphatic HCOD), 1.94e1.76 (m, 4H, aliphatic HCOD), 1.61 (d,
3JHH ¼ 6.9 Hz, 6H, NCH(CH3)2), 0.99 (d, JHH ¼ 6.7 Hz, 6H, NCH
3
(CH3)2). 13C{1H} NMR (50.3 MHz, CDCl3):
[d/ppm] 164.1 (d,
matography (eluent Et2O/pentane: 20/80). Compound
5
was
2JCP ¼ 8.6 Hz, C]N), 138.5 (d, J ¼ 46.0 Hz, Ar), 132.9 (d, J ¼ 11.9 Hz,
Ar), 128.5 (d, J ¼ 2.0 Hz, Ar), 128.4 (s, Ar), 127.2 (d, J ¼ 10.0 Hz, Ar),
126.8 (s, Ar),103.9 (dd, 1JCRh ¼ 6.2 Hz, 2JCP ¼ 12.9 Hz, CHCOD), 69.4 (d,
1JCRh ¼ 14.5 Hz, CHCOD), 51.3 (s, NCH(CH3)2), 46.6 (s, NCH(CH3)2),
32.7 (s, CH2COD), 28.4 (s, CH2COD), 20.6 (s, NCH(CH3)2), 20.1 (s, NCH
(CH3)2). DCI[CH4] MS m/z: 635 [M þ H]þ, 634 [M]þ. Compound 8:
obtained in 20% yield as a white powder. The side product 6 was
isolated in 7% yield. Compound 5: 31P{1H} NMR (121.5 MHz, CDCl3):
1
[
[
d
/ppm] 45.9 (br d, JPB ¼ 74.8 Hz). 1H NMR (200.1 MHz, CDCl3):
d
/ppm] 8.21 (d, JHH ¼ 5.1 Hz,1H, Ar), 7.81e7.04 (m,13H, Ar), 3.75 (m,
1H, NCH(CH3)2), 3.43 (m, 1H, NCH(CH3)2), 1.73 (d, 3JHH ¼ 6.6 Hz, 6H,
NCH(CH3)2), 1.13 (br s, 6H, NCH(CH3)2). 13C{1H} NMR (75.5 MHz,
31P{1H} NMR (121.5 MHz, C6D6): [
d
/ppm] 74.0 (d, 1JPRh ¼ 147.0 Hz).
CDCl3): [
d
/ppm] 163.6 (d, 2JCP ¼ 7.2 Hz, C]N), 153.3 (d, JCP ¼ 7.6 Hz,
1H NMR (300.1 MHz, C6D6): [
d/ppm] 7.62e7.60 (m, 2H, Ar),
Ar), 149.2 (s, Ar), 136.2 (s, Ar), 131.8 (br s, Ar), 129.7 (s, Ar), 127.8 (d,
JCP ¼ 10.1 Hz, Ar), 123.5 (s, Ar), 122.6 (s, Ar), 51.6 (s, NCH(CH3)2), 47.0
(s, NCH(CH3)2), 20.4 (s, NCH(CH3)2). DCI[NH3] MS m/z: 404 [M þ H]þ.
7.29e7.18 (m, 3H, Ar), 5.70 (br s, 2H, olefinic HCOD), 3.62 (br s and m,
3H, olefinic HCOD and NCH(CH3)2), 3.38e3.36 (m, 1H, NCH(CH3)2),
2.42 (hd, 3JHH ¼ 7.2 Hz, 2JPH ¼ 7.2 Hz, 2H, PCH(CH3)2), 2.31e2.24 (m,
4H, aliphatic HCOD), 1.88e1.82 (m, 4H, aliphatic HCOD), 1.66e1.56 (m,
Mp: 154e156 ꢁC (dec.). Compound 6: 31P{1H} NMR (121.5 MHz,
1
3
3
CDCl3): [
CDCl3): [
d
/ppm] 45.2 (br d, JPB ¼ 85.4 Hz). 1H NMR (300.1 MHz,
6H, NCH(CH3)2), 1.52 (dd, JHH ¼ 7.2 Hz, JPH ¼ 12.9 Hz, 6H, PCH
3 3
d
/ppm] 8.18 (d, JHH ¼ 5.8 Hz, 1H, Ar), 7.84e7.78 (m, 3H, Ar),
(CH3)2), 1.36 (dd, JHH ¼ 7.2 Hz, JPH ¼ 14.7 Hz, 6H, PCH(CH3)2),
0.79e0.77 (m, 6H, NCH(CH3)2). 13C{1H} NMR (75.5 MHz, C6D6): [
d/
7.57e7.52 (m, 2H, Ar), 7.44e7.39 (m, 4H, Ar), 7.21e7.15 (m, 4H, Ar),
3.78 (h, 3JHH ¼ 6.8 Hz,1H, NCH(CH3)2), 3.22 (h, 3JHH ¼ 6.5 Hz,1H, NCH
ppm] 161.8 (s, C]N),139.6 (d, JCP ¼ 6.7 Hz, Ar),128.4 (s, Ar),128.1 (s,
3
1
2
(CH3)2), 2.4 (br s, 3H, BH3), 1.75 (d, JHH ¼ 6.8 Hz, 3H, NCH(CH3)2),
Ar), 127.8 (s, Ar), 101.4 (dd, JCRh ¼ 6.8 Hz, JCP ¼ 12.8 Hz, CHCOD),
66.1 (d, 1JCRh ¼ 14.2 Hz, CHCOD), 50.4 (br s, NCH(CH3)2), 46.3 (s, NCH
1.68 (d, 3JHH ¼ 6.8 Hz, 3H, NCH(CH3)2),1.41 (d, 3JHH ¼ 6.5 Hz, 3H, NCH
(CH3)2), 1.02 (d, 3JHH ¼ 6.5 Hz, 3H, NCH(CH3)2), 0.50 (br s, 3H, BH3).
3
(CH3)2), 33.3 (d, JCP ¼ 2.6 Hz, CH2COD), 29.7 (d, 1JCP ¼ 25.2 Hz, PCH
CHO
CHO
[Rh(acac)(CO)2]/1,3
+
+
+
H2
CO
Scheme 5. The hydroformylation of styrene.

R. Maura et al. / Journal of Organometallic Chemistry 696 (2011) 897e904
903
Table 2
Rh-catalyzed hydroformylation of 1-octene.
Entry
Ligand
Ligand/Rh ratio
Substrate/Rh ratio
Conversion [%]
l/br ratio
Isomerization [%]
Selectivity [%]
TONa
1
2
3
4
5
6
7
8
PPh3
PPh3
1
1
1
2
3
3
3
3
3
3
4
5
3.3
5
3.3
3.3
5
5
5
5
3.3
1
510
510
510
510
832
510
510
510
832
832
510
1020
510
>99
>99
99
96
99
3.00
2.12
1.67
1.83
1.67
1.32
2.22
2.12
2.22
2.13
2.03
2.12
1.70
<1
<1
15
14
12
1
<1
15
12
27
39
23
9
>99
>99
85
82
88
99
>99
85
88
73
505
505
429
401
725
424
505
88
725
601
258
255
455
84
>99
20b
99
99
83
9
10
11
12
13
61
51
91
5
5
49
98
a
Defined as mol of aldehydes (l þ br)/mol of Rh.
b
45 ꢁC.
(CH3)2), 28.3 (d, 3JCP ¼ 1.3 Hz, CH2COD), 20.5 (br s, NCH(CH3)2), 20.1
(s, NCH(CH3)2), 19.6 (d, 2JCP ¼ 2.9 Hz, PCH(CH3)2). DCI[CH4] MS m/z:
567 [M þ H]þ, 566 [M]þ. Mp: 129e131 ꢁC.
autoclave was pressurized at 30 bar, and the reaction mixture was
stirred at 1200 rpm for the desired time. The autoclave was then
cooled and slowly depressurized. A sample was analysed by GC.
4.5. Structure determination and refinement for compounds 3, 5e8
Acknowledgements
Data of the structures 5, 6, and 7 were collected at low
temperature (180 K) on an Xcalibur Oxford Diffraction diffractom-
We thank the Institut National Polytechnique de Toulouse
(ENSIACET) and the CNRS for financial support. D.A. thanks the
European Community for a post-doctoral fellowship (FSE). We
acknowledge Johnson Matthey for a gift of the rhodium precursor
[Rh(COD)Cl]2.
eter using
a
graphite-monochromated Mo-K
a
radiation
(l
¼ 0.71073 Å) and equipped with an Oxford Instrument Cooler
Device. Data of the structures 3 and 8 were collected at low
temperature (180 k) on an IPDS STOE diffractometer using
a graphite-monochromated Mo-K
a
radiation (
l
¼ 0.71073 Å) and
Appendix A. Supplementary data
equipped with an Oxford Cryosystems Cryostream Cooler Device.
The final unit cell parameters have been obtained by means of
a least-squares refinement. The structures have been solved by
Direct Methods using SIR92 [32], and refined by means of least-
squares procedures on a F2 with the aid of the program SHELXL97
[33] included in the software package WinGX version 1.63 [34]. The
Atomic Scattering Factors were taken from International Tables for
X-Ray Crystallography [35]. All hydrogen atoms were geometrically
placed and refined by using a riding model. All non-hydrogen
atoms were anisotropically refined, and in the last cycles of
refinement a weighting scheme was used, where weights are
CCDC-786352e786356 contains the supplementary crystallo-
graphic data for compounds 3, 5e8. These data can be obtained free
of charge from the Cambridge Crystallographic Data Center via
www.ccdc.cam.ac.uk/data_request/cif.
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Entry
Liganda, b
Time (h)
Conv. (%)
br/l ratio
TONc
1
2
3
4
PPh3
PPh3
1
3
6
6
6
95d
94
94
85
4.0
5.7
15.7
15.7
790
782
782
707
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3
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a
Ligand/Rh ratio ¼ 3.3.
b
c
Substrate/Rh ratio ¼ 832.
defined as mol of aldehydes (l þ br)/mol of Rh.
d
80 ꢁC.

904
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