An effective diphosphoramidite rhodium catalyst for selective hydroformylation of 1-octene

Article abstract of DOI:10.1016/j.catcom.2018.07.004

A very efficient and highly selective rhodium catalyst with a C₂-symmetric BINOL-derived diphosphoramidite ligand for hydroformylation of 1-octene has been developed. At mild conditions (50 °C and 10 bar H₂/CO) a very active rhodium catalyst has been obtained which produces over 99% of aldehydes with 98.2% n-regioselectivity. The spectroscopic characterization of the hydridorhodium catalytically active species showed that the diphosphoramidite ligand coordinates bis-equatorially in the trigonal bipyramidal rhodium complex, which coupled with its π-acceptor capacity might account for the high catalyst performance.

Full text of DOI:10.1016/j.catcom.2018.07.004

Accepted Manuscript
An effective diphosphoramidite rhodium catalyst for selective
hydroformylation of 1-octene
Dario Drommi, Carmela Grazia Arena
PII:
S1566-7367(18)30248-6
doi:10.1016/j.catcom.2018.07.004
CATCOM 5444
DOI:
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
2 June 2018
27 June 2018
3 July 2018
Please cite this article as: Dario Drommi, Carmela Grazia Arena , An effective
diphosphoramidite rhodium catalyst for selective hydroformylation of 1-octene. Catcom
(2018), doi:10.1016/j.catcom.2018.07.004
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ACCEPTED MANUSCRIPT
An effective diphosphoramidite rhodium catalyst for selective
hydroformylation of 1-octene
*
Dario Drommi and Carmela Grazia Arena arenac@unime.it
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Viale F. Stagno
d’Alcontres 31, 98166 Messina, Italy
*
Corresponding author

ACCEPTED MANUSCRIPT
Abstract
A very efficient and highly selective rhodium catalyst with a C -symmetric BINOL-derived
2
diphosphoramidite ligand for hydroformylation of 1-octene has been developed. At mild
conditions (50 °C and 10 bar H /CO) a very active rhodium catalyst has been obtained which
2
produces over 99% of aldehydes with 98.2% n-regioselectivity. The spectroscopic
characterization of the hydridorhodium catalytically active species showed that the
diphosphoramidite ligand coordinates bis-equatorially in the trigonal bipyramidal rhodium
complex, which coupled with its -acceptor capacity might account for the high catalyst
performance.
Keywords: hydroformylation; diphosphoramidite; regioselectivity; rhodium catalyst;
homogeneous catalysis

ACCEPTED MANUSCRIPT
1
. Introduction
The hydroformylation of unfunctionalized terminal olefins is an important industrial process
for producing aldehydes [1,2].
Rhodium complexes with phosphorus ligands are known to be the most effective
homogeneous catalysts for the hydroformylation of unfunctionalized short-medium chain
olefins [3].
Despite high price of rhodium, P-ligand modified rhodium catalysts are suitable for industrial
applications as they predominantly produce the desired linear aldehyde at low syngas pressure
[
4]. In this context, the electronic [5,6] and steric [7,8,9] properties of the ancillary
phosphorus ligands play a critical role on the activity and selectivity of the rhodium catalyst.
Hence, many efforts have been done to develop P-ligands that improve the catalyst
performance.
The electronic [4,5] and steric [6,7,8] properties of the ancillary phosphorus ligands play a
critical role on the activity and selectivity of the rhodium catalyst. Hence, despite high price
of rhodium, P-ligand modified rhodium catalysts are suitable for industrial applications as
they predominantly produce the desired linear aldehyde at low syngas pressure [9]. Therefore,
several efforts have been done to develop P-ligands that improve the catalyst performance.
In 1968, Pruett and Smith found that the hydroformylation of terminal olefins catalyzed by
rhodium complexes with -acceptor triaryl phosphite ligands gave very high percentage of
linear aldehydes [10]. Since then, several mono [11,12,13] and bidentate [14,15,16,17]
phosphite ligands have been explored and their positive effect on both rate and
regioselectivity has been proved.
In recent years, phosphoramidites have been the subject of growing interest as -acceptor
ligands for rhodium-catalyzed hydroformylation of olefins [2].
Phosphoramidites are an interesting class of ligands because they are synthesized in two steps
from accessible and inexpensive sources [18]. Furthermore, these ligands are quite stable in
air and in some cases are resistant to hydrolysis [19].
In 1996, van Leeuwen et al. first tested a series of mono- and bidentate phosphoramidites in
the rhodium catalyzed hydroformylation of 1-octene [20]. The authors showed that rhodium
catalysts with bis-equatorially coordinating bidentate phosphoramidites produced higher
quantities of linear aldehyde than ones with monodentate phosphoramidites.

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More recently, very high l/b ratios of aldehydes (up to 471) have been obtained using
pyrrolyl-based phosphoramidites, although with high percentages of the isomerized product
2
-octene [6,21,22,23,24].
For several years, our research group has been interested in the design and development of
new bidentate phosphoramidite ligands to be used as auxiliaries in homogeneous catalysis
[
25,26,27,28].
We have recently prepared the bidentate chiral C -symmetric diphosphoroamidite ligand 1
2
(
Fig. 1) having the 1,2-diaminobenzene fragment as the backbone and two (R)-1,1’-
binaphtalene-2,2’-dioxy (Bino) groups. This ligand was readily synthesized, in high yields, by
reaction of 1,2-phenylenediamine with two equivalents of (R)-BINOL-phosphorochloridite. It
easily formed the chelate rhodium(I) complex [Rh(cod)(P,P)]BF (cod = 1,5-cyclooctadiene)
4
useful as pre-catalyst for asymmetric hydrogenation of dimethylitaconate [29].
We then decided to test the BINOL-derived diphosphoroamidite 1 in other catalytic
transformations.
During our research on its possible use as chiral auxiliary in asymmetric catalysis, we found
that Matt and coworkers achieved a high regioselectivity in the rhodium-catalyzed
hydroformylation of 1-octene using C -symmetric 1,3-calix[4]diphosphites with a
2
calix[4]arene backbone and two (S)-BinoP groups at the lower rim [30,31]. The authors
suggested that the steric hindrance of the binaphthyl moieties was relevant for the
regioselectivity.
In view of this findings, we have thought that our bidentate C -symmetric phosphoramidite
2
ligand 1 suitable featured for application in the rhodium-catalyzed hydroformylation because
it contains a flat rigid skeleton and two bulky binaphthyl groups with a defined configuration.
Here we show that the (S,S)-phosphoramidite 1/Rh system is a highly selective catalyst for the
hydroformylation of 1-octene at very mild conditions. The spectroscopic characterization
under atmospheric pressure and room temperature of the trigonal bipyramidal
hydridorhodium catalytically active species with bis-equatorially coordinating ligand 1 is also
reported.
2
. Experimental
2
.1 General remarks
All reagents were purchased from Sigma-Aldrich and used without further purification. All
reactions were performed under a dry argon atmosphere using standard Schlenk techniques.
Solvents were bought in crown cap anhydrous bottles. The nuclear magnetic resonance

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spectra were recorded with a Bruker AMX R-300 spectrometer equipped with a pulsed field
1
13
1
gradient probe. The values of chemical shifts (δ) for H spectra and C{ H} NMR are
measured relative to the solvent peak and are reported in ppm in reference to the value for the
3
1
1
tetramethylsilane (TMS δ = 0 ppm). The chemical shifts for the P{ H} NMR spectra were
measured using aqueous H PO (85% D O) as an external reference (δ = 0 ppm).
3
4
2
Hydroformylation experiments were executed in a 100 mL stainless steel autoclave equipped
with glass reaction vessel. IR spectra were recorded on a Nicolet iS50 FT-IR spectrometer.
1
Conversion and selectivities was determined by H NMR and GC Fisons 8000 ThermoQuest
(
using helium as a carrier gas and a flame ionization detector FID) equipped with a OV1
capillary column. (25m x 0.25mm).
2
.2 General procedure for the Rh(I)-catalyzed hydroformylation.
All hydroformylations were performed in a glass-lined, 100 mL stainless steel autoclave
containing a magnetic stirring bar. In a typical experiment [Rh(acac)(CO) ] (acac =
2
-
3
-2
-3
acetylacetonate) (4×10 mmol) and the ligand (1×10 or 6×10 mmol) were dissolved in 10
mL of toluene under an argon atmosphere in a Schlenk apparatus; 1-octene (10 mmol) was
added resulting in a substrate:Rh ratio of 2500:1. The autoclave was placed under vacuum and
subsequently purged three times using argon gas. The catalyst solution was introduced via a
syringe into the autoclave and was flushed twice with syngas (CO/H 1:1 v/v), after which it
2
was pressurized with syngas to the desired pressure and heated to the required temperature. At
full conversion, the reactor was cooled and carefully vented and then opened. The reaction
1
mixture was filtered through a short pad of silica and analyzed by H NMR and by GC. The
components of the reaction mixture were identified using authentic GC standards (where
available).
2
.3 In situ preparation of [HRh(CO) (1)] complex.
2
The catalytically active hydride complex was prepared by the reaction of [Rh(acac)(CO) ] (8
2
mg, 0.031 mmol) with ligand 1 (25 mg, 0.034 mmol) in benzene-d at 50° C, in autoclave
6
under argon. After half an hour, the autoclave was purged three times using syngas,
pressurized to 10 bar H /CO and heated at 50°C for 3 hours. Upon cooling to room
2
temperature and depressurization, the red-ruby solution was transferred under an argon
atmosphere into a 5 mm NMR tube to be further analyzed. The complex solution remained
stable for several days at room temperature
3
. Results and discussion

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The hydroformylation of 1-octene with the diphosphoramidite ligand (S,S)-1 rhodium catalyst
system was carried out in toluene solution using an equimolar hydrogen/carbon monoxide
mixture and a substrate-to-metal ratio of 2500.
The results obtained with the rhodium catalyst prepared in situ by addition of ligand 1 to
[
Rh(acac)(CO) ] (acac = acetylacetonate) are reported in Table 1.
2
The first test was conducted at 80° C and 20 bar with a ligand: metal ratio of 2.5:1. A 94.8%
conversion of 1-octene was obtained within 6 h. The aldehyde selectivity was very high
(
99.5%) and the regioselectivity reached 91.7 % (Entry 1).
No marked influence of CO/H pressure on catalyst performance was observed. Lowering
2
syngas pressure to 10 bar caused only small decreases in activity and regioselectivity of the
rhodium catalyst (Entry 2).
It is well known that the regioselectivity increases with decreasing temperature at the cost of
the reaction rate. Instead, in our case The conversion remained high (over 90%) when the
reaction temperature was decreased from 80 to 60°C and a significant improvement in the
regioselectivity (90 to 97.8%) was obtained (Entries 3-4).
Interestingly, the selectivity of (S,S)-phosphoramidite 1/Rh catalyst system improved with
increasing of conversion of 1-octene (Entries 4-5).
The effects of ligand: metal ratio on catalyst performance was also evaluated.
Moreover, at a ligand to rhodium ratio of 1.5, the regioselectivity remained high (96.9%)
(
Entry 6).
Given the above, we decided to test our catalytic system at 50° C under 10 bar of CO/H2
pressure.
The results obtained were quite surprising. A 96.3% conversion of 1-octene was obtained in 4
h with a regioselectivity of 98.4% (Entry 7). It is noteworthy that a 91.9% conversion was
reached within 2 h at the same temperature (Entry 8).
Finally, an improvement of the catalyst performance could be obtained by mixing ligand 1
and [Rh(acac)(CO) ] in toluene at 50° C for 30 min in a Schlenk flask before introducing in
2
the autoclave (Entry 9).
Compared with calix[4]arene-based binaphthyl diphosphites modified rhodium catalyst,
BINOL-derived diphosphoramidite ligand 1 formed a more effective hydroformylation
catalyst at lower pressure and temperature. Moreover, for Matt’s ligands large excesses (L/Rh
=
10) were required to attain high regioselectivities.
Compared with bidentate phosphoramidites reported by van Leeuwen [20], BINOL-derived
diphosphoramidite 1 formed a more effective hydroformylation rhodium catalyst at milder

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conditions and lower L/Rh ratios. Probably the rigidity of ligand 1 plays a key role in
determining the high regioselectivity.
In order to get information on the catalytically active hydride complex formed with the
diphosphoramidite 1, we carried out the reaction of [Rh(acac)(CO) ] with ligand 1 in
2
benzene-d at 50° C, in autoclave under argon. After half an hour, the autoclave was purged
6
three times using syngas, pressurized to 10 bar H /CO and heated at 50°C for 3 hours. Upon
2
cooling to room temperature and depressurization, the red-ruby solution was transferred under
an argon atmosphere into a 5 mm NMR tube to be further analyzed. The complex solution
remained stable for several days at room temperature.
In order to get information on the hydridorhodium diphosphoramidite catalyst, we carried out
the reaction of [Rh(acac)(CO) ] with ligand 1 under hydroformylation conditions in benzene-
2
3
1
1
1
d6. The resulting red-ruby solution was immediately analysed by P{ H} and H NMR
spectroscopy under atmospheric conditions.
31
1
The corresponding P{ H} NMR spectrum showed only a doublet at δ 167.66 ppm with the
JRhP coupling constant of 235 Hz (similar value as those found for bidentate phosphite ligands
1
laying in equatorial positions [32]). The H NMR signals support the presence in solution of
the stable hydridorhodium derivative, showing the expected doublet of triplets at δ -10.24
1
2
(
JRhH = 5 Hz, J = 5 Hz), due to the coupling of the hydride with two (time-averaged)
PH
equivalent phosphorus atoms and the rhodium atom. The small JRhH and JPH coupling
constants of 5 Hz are indicative of coordination of both phosphorus atoms in the equatorial
plane of the trigonal bipyramidal rhodium complex (Fig. 2) [20]. On the basis of the above, it
3
1
1
was performed P- H correlation spectroscopy that has revealed the presence of cross peak
between the doublet of phosphorus atoms and the doublet of triplets of the hydride atom
confirming the spin-spin coupling between proton and the two phosphorus atoms. The IR
spectrum, recorded on the NMR solution, showed two absorption bands for the carbonyl
-
1
ligands at 2076 and 2023 cm . The number and position of the carbonyl frequencies confirm
that only the ee isomer is present [23]. This results show, as reported by van Leeuwen [20],
that the bis-equatorial coordination of the bidentate phosphoramidites ligand is one of the
requirements for achieving high l/b ratios.
Although a simple correlation between spectroscopic results and the observed high selectivity
is not possible, we believe that the equatorial-equatorial coordination mode coupled to the -
acid character of the bulky diphosphoramidite ligand 1, determine the outcome of the
hydroformylation reaction.
4
. Conclusions

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In conclusion, we can say that a new effective and highly selective hydroformylation catalyst
operating at very mild conditions has been developed. The spectroscopic data obtained for the
hydride complex [HRh(CO) (1)] pointed out an equatorial-equatorial coordination of the
2
diphosphoramidite ligand in the trigonal bipyramidal catalytically active species.
To our knowledge this is the first phosphoramidite/Rh system that turned out to be a very
efficient catalyst for hydroformylation of 1-octene at low pressure and low temperature.
Finally, we believe that the peculiar steric and electronic properties of the ligand 1 make it
promising for application in industrial hydroformylation reactions of a broad range of olefins.
Acknowledgements
We thank MIUR for financial support. Authors wish to thank Mr. Daniele Cosio of
Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra of
the University of Messina for his technical assistance.

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References
[
[
[
[
1] R. Franke, D. Selent, A. Börner, Applied hydroformylation, Chem. Rev. 112 (2012) 5675-
732.
5
2] A. Börner, R. Franke, Hydroformylations: Fundamentals, Processes and Applications in
Organic Synthesis, Vol. 1-2, Wiley-VCH, Weinheim, 2016.
3] P. W. N. M. van Leeuwen, C. Claver, Rhodium Catalyzed Hydroformylation, Kluwer
Academic Publishers, Dordrecht, Netherlands, 2002.
4] L. A. van der Veen, M. D. K. Boele, F. R. Bregman, P. C. J. Kamer, P. W. N. M. van
Leeuwen, K. Goubitz, J. Fraanje, H. Schenk, C. Bo, Electronic effect on rhodium diphosphine
catalyzed hydroformylation: the bite angle effect reconsidered, J. Am. Chem. Soc. 120 (1998)
1
1616-11626.
[
[
5] S. C. van der Slot, J. Duran, J. Luten, P. C. J. Kamer, P. W. N. M. van Leeuwen, Rhodium-
catalyzed hydroformylation and deuterioformylation with pyrrolyl-based phosphorus amidite
ligands: influence of electronic ligand properties, Organometallics 21 (2002) 3873-3883.
6] P. C. J. Kamer, P. W. N. M. van Leeuwen, J. N. H. Reek, Wide bite angle diphosphines.
Xantphos ligands in transition metal complexes and catalysis, Acc. Chem. Res. 34 (2001)
8
95-904.
[
[
7] M. N. Birkholz, Z. Freixa, P. W. N. M. van Leeuwen, Bite angle effects of diphosphines in C-
C and C-X bond forming cross coupling reactions, Chem. Soc. Rev. 38 (2009) 1099-1118.
8] Y. Jiao, M. S. Torne, J. Gracia, J. W. Niemantsverdriet, P. W. N. M. van Leeuwen, Ligand
effects in rhodium-catalyzed hydroformylation with bisphosphines: steric or electronic? Catal.
Sci. Technol. 7 (2017) 1404-1414.
[
[
[
9] H. W. Bohnen, B. Cornils, Hydroformylation of alkenes: an industrial view of the status and
importance, Adv. Catal. 47 (2002) 1-64.
10] R. L. Pruett, J. A. Smith, A low-pressure system for producing normal aldehydes by
hydroformylation of  olefins, J. Org. Chem. 34 (1969) 327-330.
11] P. W. N. M. van Leeuwen, C. Roobeek, A process for the hydroformylation of olefins, (Shell
International Research Maatschappij B. V.) EP Patent 0054986, 1981.

ACCEPTED MANUSCRIPT
[
12] A. van Rooy, E. N. Orij, P. C. J. Kamer, F. van Den Aardweg, Hydroformylation of oct-1-ene
with extremely high rates using rhodium catalysts containing bulky phosphites, J. Chem. Soc.,
Chem. Commun. (1991) 1096-1097.
[
[
[
13] T. A. Puckette, Y.S. Liu., Phosphite containing catalysts for hydroformylation processes
(
Eastman Chemical Company) WO Patent 2010151285, 2010.
14] E. Billig, A. G. Abatjoglou, D. R. Bryant, Transition metal complex catalyzed processes,
Union Carbide Corporation) US Patent 4769498, 1988.
(
15] R. Paciello, L. Siggel, M. Röper, Chelated bisphosphites with a calix[4]arene backbone: new
ligands for rhodium-catalyzed low-pressure hydroformylation with controlled regioselectivity,
Angew. Chem. Int. Ed. 38 (1999) 1920-1923.
[
[
[
[
16] D. Selent, W. Baumann, K. D. Wiese, A. Börner, Diastereoisomeric bisphosphite ligands in
the hydroformylation of octenes: rhodium catalysis and HP-NMR investigations, Chem.
Commun. (2008) 6203-6205.
17] D. Selent, R. Franke, C. Kubis, A. Spannenberg, W. Baumann, B. Kreidler, A. Börner, A
New Diphosphite Promoting Highly Regioselective rhodium-catalyzed hydroformylation,
Organometallics 3 (2011) 4509-4514.
18] L. Lefort, J. G. de Vries, Phosphoramidite ligands, in: P. C. J.Kamer , P. W. N. M. van
Leeuwen (Eds.), Phosphorus(III) Ligands in Homogeneous Catalysis: Design and Synthesis,
John Wiley and Sons, Chichester, 2012, pp. 133-157.
19] G. Morales Torres, S. Behrens, D. Michalik, D. Selent, A. Spannenberg, S. Lühr, K. M.
Dyballa, R. Franke, A. Börner, Synthesis of C ‐ symmetric diphosphormonoamidites and
2
their use as ligands in Rh‐ catalyzed hydroformylation: relationships between activity and
hydrolysis, ChemistryOpen 6 (2017) 247-253.
[
[
20] A. van Rooy, D. Burgers, P. C. J. Kamer, P. W. N. M. van Leeuwen, Phosphoramidites: novel
modifying ligands in rhodium catalysed hydroformylation, Recl. Trav. Chim. Pays-Bas 115
(
1996) 492-498.
21] Y. Yan, X. Zhang, X. Zhang, A tetraphosphorus ligand for highly regioselective
isomerization−hydroformylation of internal olefins, J. Am. Chem. Soc. 128 (2006) 16058-
1
6061.

ACCEPTED MANUSCRIPT
[
[
[
[
22] S. Yu, Y. M. Chie, Z. H. Guan, X. Zhang, Highly regioselective
isomerization−hydroformylation of internal olefins to linear aldehyde using Rh complexes
with tetraphosphorus ligands, Org. Lett. 10 (2008) 3469-3472.
23] X. Jia, Z. Wang, C. Xia, K. Ding, Spiroketal‐ based phosphorus ligands for highly
regioselective hydroformylation of terminal and internal olefins, Chem. Eur. J. 18 (2012)
1
5288-15295.
24] C. Chen, Y. Qiao, H. Geng, X. Zhang, A novel triphosphoramidite ligand for highly
regioselective linear hydroformylation of terminal and internal olefins, Org. Lett. 15 (2013)
1
048-1051.
25] C. G. Arena, V. Casilli, F. Faraone, New chiral amino-phosphoramidite and
bisphosphoramidite ligands derived from (R,R)-1,2-diaminocyclohexane: application in Cu-
catalyzed asymmetric conjugate addition of diethylzinc to 2-cyclohexenone, Tetrahedron
Asymmetry 14 (2003) 2127-2131.
[
[
26] C. G. Arena, R. Pattacini, Chiral rhodium complexes containing bidentate ligands derived
from (R,R)-1,2-diaminocyclohexane for catalytic enantioselective hydrosilylation of
acetophenone, J. Mol. Cat. A: Chem. 222 (2004) 47-52.
27] C. G. Arena, G. Bruno, F. Nicolò, Chiral cyclopentadienyl ruthenium(II) complexes with P,P-
ligands derived from (1R,2R)-1,2-diaminocyclohexane: Synthesis, crystal structures and
catalytic activity in Diels-Alder reactions, Polyhedron 29 (2010) 2822-2828.
[
[
28] D. Drommi, G. Micalizzi, C. G. Arena, New chiral diphosphoramidite rhodium(I) complexes
for asymmetric hydrogenation, Appl. Organomet. Chem. 28 (2014) 614-619.
29] D. Drommi, C. G. Arena, Rh(I) complexes with new C ‐ symmetric chiral diphosphoramidite
2
ligands: catalytic activity for asymmetric hydrogenation of olefins, Appl. Organomet. Chem.
3
1 (2017) e3837.
[
[
30] D. Sémeril, C. Jeunesse, D. Matt, L. Toupet, Regioselectivity with hemispherical chelators:
increasing the catalytic efficiency of complexes of diphosphanes with large bite angles,
Angew. Chem. Int. Ed. 45 (2006) 5810-5814.
31] D. Sémeril, D. Matt, L. Toupet, Highly regioselective hydroformylation with hemispherical
chelators, Chem. Eur. J. 14 (2008) 7144-7155.

ACCEPTED MANUSCRIPT
[
32] A. van Rooy, P. C. J. Kamer, P. W. N. M. van Leeuwen, K. Goubitz, J. Fraanje, N. Veldman,
A. L. Spek, Bulky diphosphite-modified rhodium catalysts:ꢀ hydroformylation and
characterization, Organometallics 15 (1996) 835-847.
Declarations of Interest
None

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a
Table 1. Hydroformylation of 1-octene catalyzed by [Rh(acac)(CO) ]/1.
2
b
c
d
Conv.
%)
Aldehyde selectivity n-Regioselectivity
Entry
L/Rh
2.5
2.5
2.5
2.5
2.5
1.5
1.5
1.5
1.5
T(°C) P (bar) t (h)
(
(%)
(%)
1
2
3
4
5
6
7
8
80
80
70
60
60
60
50
50
50
20
10
10
10
10
10
10
10
10
6
6
6
6
4
4
4
2
2
94.8
93.3
94.2
93.8
91.6
94.7
96.3
91.9
93.3
99.5
91.7
99.3
99.5
99.4
99.2
99.5
99.6
99.2
99.3
90.9
96.3
97.8
96.9
96.9
98.4
97.9
98.2
e
9
a
-3
Reaction conditions: toluene (10 ml); CO/H = 1/1; [Rh(acac)(CO) ] (4×10 mmol); catalyst:1-
2
2
octene = 1:2500.
b
c
d
e
1
Conversion was determined by H NMR and by GC 8000 ThermoQuest.
Yield (all aldehydes)/Conv.
Yield (linear aldehyde)/Total Yield (all aldehydes).
[
Rh(acac)(CO) ] and ligand 1 were previously mixed at 50° C for 30 minutes.
2

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Figure 1.

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Figure 2

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Figure 1. C -symmetric diphosphoramidite ligands.
2
Figure 2. Trigonal bipyramidal hydridorhodium complex (ee).

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Highlights



Efficient and highly selective hydroformylation catalyst.
High chemo- and regioselectivity at low pressure and temperature.
Use of bulky C -symmetric diphosphoramidite ligand for selective hydroformylation.
2

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Graphical abstract