Stereoelectronic effects in a homologous series of bidentate cyclic phosphines. A clear correlation of hydroformylation catalyst activity with ring size

Article abstract of DOI:10.1039/b815056g

The homologous series of diphosphines (CH₂) _n-1P(CH₂)₃P(CH₂)_n-1 where n = 5 (L₅), 6 (L₆), or 7 (L₇) have been synthesized from the corresponding PhP(CH

Full text of DOI:10.1039/b815056g

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Stereoelectronic effects in a homologous series of bidentate cyclic phosphines.
A clear correlation of hydroformylation catalyst activity with ring size†
a
a
a
a
b
Mairi F. Haddow, Ann J. Middleton, A. Guy Orpen, Paul G. Pringle* and Rainer Papp
Received 29th August 2008, Accepted 14th October 2008
First published as an Advance Article on the web 25th November 2008
DOI: 10.1039/b815056g
The homologous series of diphosphines (CH
have been synthesized from the corresponding PhP(CH
the 6-membered chelates cis-[PtCl (L5–7)], the crystal structures for which reveal that L5–7 have very
similar steric bulk and bite angles. Treatment of [Rh Cl (CO) ] with L5–7 gave the binuclear
] with syn and anti orientations of the CO and Cl ligands suggested by the
P NMR spectra and the crystal structures of syn–trans-[Rh Cl (CO) (m-L ] and anti–trans-
Rh Cl (CO) (m-L ]. The n(CO) values for trans-[Rh Cl (CO) ] indicate that the donor
< L < L . A study of rhodium-catalysed hydroformylation of
-octene using diphosphines L5–7 is described. The catalyst activity decreases with increasing
2
)
n-1P(CH
2
)
3
P(CH
2
)
n-1 where n = 5 (L
5
), 6 (L
(cod)] with L5–7 gave
6
), or 7 (L
7
)
2
)
n-1. Treatment of [PtCl
2
2
2
2
4
trans-[Rh
2
Cl
2
(CO)
2
(m-L5–7
)
2
3
1
2
2
2
5 2
)
[
2
2
2
7
)
2
2
2
2
(m-L5–7
)
2
strength increases in the order L
5
6
7
1
phosphacycle ring size: L
5
> L
6
7
> L .
Introduction
Monodentate and bidentate phosphacycles of a variety of types
and sizes are excellent ligands for hydroformylation catalysis as
illustrated by the examples LA–H given in Fig. 1.
Phosphacyclic ligands often give more active, selective and
stable catalysts than their linear analogues. Delineating factors
that influence the efficiency of catalysts for hydroformylation
1,2
is apparently easy, understanding them remains a challenge.
In the case of phosphacycles, the features that lead to their
advantages include: (i) the entropic stabilisation of the P–X bonds
in phosphacycles, (ii) the conformational rigidity of the ring and
(
iii) the constraints on the X–P–X angle imposed by the ring. Thus,
3
the kinetic stabilisation of the P–O bonds in cyclic phosphites,
such as L
4
A
or the P–N bonds in cyclic phosphamides, such as L
B
make them less susceptible to hydrolysis than acyclic analogues
and this has greatly contributed to their utility. The rigidity
5
6
7
of ligands such as L
C
, L
D
and L
E
, make the a-substituents
sterically demanding, which may contribute to the high hydro-
formylation catalytic activity of their rhodium complexes. The
ring rigidity in L results in a highly defined chiral space around
F
the metal centre, which may account for the success of L
F
and
8
related ligands in asymmetric hydroformylation. The constrained
C–P–C angle imposed by the phosphacycle influences the frontier
9
orbital energies thereby modulating the s-donor and p-acceptor
Fig. 1 Examples of phosphacyclic ligands used in hydroformylation
characteristics of the ligand and this may partly explain the high
catalysis.
activity of hydroformylation catalysts derived from phosphacycles
1
0
11
such as L
G
and L
H
.
catalysis. We are interested in understanding the effect the size
of the ring has on the coordination chemistry and catalytic
As is evident from the examples in Fig. 1, phosphacycles
with ring sizes from 5–7 are important for hydroformylation
7,12,13
performance of P-ligands.
Recently, we reported a systematic
study of the homologous series of cyclic monophosphines 1a–c and
12
their application in rhodium-catalysed hydroformylation. From
spectroscopic measurements, it was found that the donor order
was 1a < 1b < 1c, which is in line with the prediction that the
more acute the C–P–C angle is made, the lower the HOMO and
a
School of Chemistry, University of Bristol, Cantocks Close, Bristol, UK
BS8 1TS. E-mail: paul.pringle@bristol.ac.uk; Fax: +44 (0)117 929 0509;
Tel: +44 (0)117 928 8114
b
BASF Aktiengesellschaft, D-67056 Ludwigshafen, Germany
9
LUMO energies on the ligand become. The steric properties of
†
CCDC reference numbers 700268–700272. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b815056g
the monophosphacycles (particularly 1c) were shown to depend
2
02 | Dalton Trans., 2009, 202–209
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1
4
critically on the ring conformation but no clear trend emerged
in aqueous sodium hydroxide yielded the phosphine oxides 3a–
c as white waxy solids. The reduction of 3a–c with phenylsilane,
followed by distillation directly from the hot reaction mixture,
from the hydroformylation catalysis study with 1a–c and related
12
ligands. Part of the problem with discerning structure–activity
relationships with monodentate ligands is the variable number
produced L5–7. Diphosphines L
5
6
and L are colourless liquids and
(
between 0 and 3) of ligands that may be coordinated to the metal
L
7
is a low-melting solid (see Experimental for the characterising
15
and the cis/trans/axial/equatorial geometric relationships to each
other that they adopt in the catalytic intermediates. We reasoned
that the number of variables would be reduced, and therefore
data); L
Platinum(II) complexes
The addition of one equivalent of diphosphines L5–7 to [PtCl
5
has been previously reported but L
6
7
and L are new.
clearer trends may emerge, using the cyclic diphosphines L5–7
.
2
(cod)]
in dichloromethane afforded the corresponding complexes cis-
PtCl (L5–7)] (4a–c) as air-stable, white solids in quantitative yields
eqn (1), see Experimental for the characterising data).
[
2
(
(
1)
Results and discussion
Crystal structures for all three chelates 4a–c were obtained (see
Fig. 2–4 and Tables 1–3). The chloroform solvate of 4a crystallises
in the space group P2 from a saturated CHCl solution. The
Ligand synthesis
1
2
1
2
1
3
molecule of 4a (see Fig. 2) has approximate mirror symmetry.
Selected bond lengths and angles are given in Table 1.
The series of bidentate cyclic phosphines L5–7 were synthesised
12
by the route shown in Scheme 1. The phosphacycles 1a–c were
quaternized with 1,3-dibromopropane to give the corresponding
phosphonium salts 2a–c as air-stable solids. Refluxing these salts
Fig. 2 Thermal ellipsoid plot of the structure of 4a in 4a·CHCl
3
.
Displacement ellipsoids are shown at the 50% probability level. All
hydrogen atoms have been removed for clarity.
Fig. 3 Thermal ellipsoid plot of the structure of 4b. Displacement
ellipsoids are shown at the 50% probability level. All hydrogen atoms
have been removed for clarity.
Scheme 1
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◦
◦
a
Table 1 Selected bond distances ( A˚ ) and angles ( ) for 4a·CHCl
Table 3 Selected bond distances ( A˚ ) and angles ( ) for 4c. Parameters
3
for the atoms that were restrained have been omitted
Bond distances/A˚
Bond distances/A˚
Pt1–P1
Pt1–Cl1
P1–C1
P1–C5
P2–C8
2.2143(11)
2.3604(10)
1.835(4)
1.807(4)
1.822(5)
Pt1–P2
Pt1–Cl2
P1–C4
P2–C7
P2–C11
2.2089(11)
2.3533(10)
1.828(4)
1.819(4)
1.838(4)
Pt1–P1
Pt1–P2
2.2275(17) Pt2–P3
2.2330(15) Pt2–P4
2.2258(16) Pt3–P5
2.2293(15) Pt3–P6
2.2303(18)
2.2347(18)
2.3636(18)
2.3921(18)
1.811(7)
Pt1–Cl1 2.3719(16) Pt2–Cl3 2.3740(16) Pt3–Cl5
Pt1–Cl2 2.3884(16) Pt2–Cl4 2.3898(15) Pt3–Cl6
P1–C1
P1–C4
P1–C9
P2–C3
P2–C10
P2–C15
1.837(6)
1.821(6)
1.825(6)
1.818(6)
1.827(6)
1.831(6)
P3–C16
P3–C19
P3–C24
P4–C18
P4–C25
P4–C30
1.835(6)
1.829(6)
1.821(6)
1.810(6)
1.823(6)
1.825(6)
P5–C31
◦
Bond angles/
P6–C33
P6–C40
P6–C45
1.814(6)
1.823(7)
1.827(7)
P1–Pt1–P2
C1–P1–C4
C7–P2–C8
C8–P2–C11
96.02(3)
96.26(19)
104.5(2)
C1–P1–C5
C4–P1–C5
C7–P2–C11
104.1(2)
104.1(2)
103.5(2)
95.81(19)
◦
Bond angles/
◦
Table 2 Selected bond distances ( A˚ ) and angles ( ) for 4b
P1–Pt1–P2
C1–P1–C4
C1–P1–C9
C4–P1–C9
97.09(6) P3–Pt2–P4
97.00(6) P5–Pt3–P6
95.24(6)
102.6(3) C16–P3–C24 102.2(3)
103.3(3) C16–P3–C19 103.5(3)
109.5(3) C19–P3–C24 110.0(3)
Bond distances/A˚
C3–P2–C10 104.1(3) C18–P4–C25 103.4(3) C33–P6–C40 102.6(3)
C3–P2–C15 103.6(3) C18–P4–C30 103.7(3) C33–P6–C45 102.2(3)
C10–P2–C15 110.4(3) C25–P4–C30 110.5(3) C40–P6–C45 108.6(3)
Pt1–P1
Pt1–Cl1
P1–C1
P1–C6
P2–C9
2.2228(12)
2.3716(13)
1.825(5)
1.823(4)
1.827(5)
Pt1–P2
Pt1–Cl2
P1–C5
P2–C8
P2–C13
2.2289(13)
2.3774(13)
1.822(5)
1.817(5)
1.827(5)
a
Equivalent distances for the second and third independent molecules
in the asymmetric unit are given in columns 4 and 6. Atoms which are
disordered are labelled A or B.
◦
Bond angles/
(
asymmetric envelope), (C) both above or both below the plane
P1–Pt1–P2
C8–P2–C13
C1–P1–C5
C5–P1–C6
96.48(5)
104.0(2)
104.5(2)
105.6(2)
C8–P2–C9
C9–P2–C13
C1–P1–C6
104.8(2)
104.0(2)
104.0(2)
(envelope) or (D) one above and one below the plane (twist). In
4
a, both rings adopt an asymmetric envelope conformation, with
◦
the torsion angle C–C–C–C = ± 47.6 .
Crystals of 4b crystallised from a saturated MeOH solution in
the space group Pbca with one molecule in the asymmetric unit.
Selected bond lengths and angles are given in Table 2. The PC
rings adopt a chair conformation with the C chelate backbone and
the metal in axial and equatorial sites, respectively (see Fig. 3).
5
3
Crystals of 4c crystallised from a saturated MeCN solution in
the space group Pc with three molecules in the asymmetric unit.
In two of the molecules, significant disorder is present in the PC
6
rings. The molecular geometry (see Table 3) of the only ordered
molecule in the crystal structure is shown in Fig. 4. The seven-
membered rings in the molecule containing Pt1 adopt twist-chair
and boat conformations. In the molecule containing Pt2 they
adopt chair conformations with the P atom in a different position
in each of the rings and in the molecule containing Pt3 they adopt
Fig. 4 Thermal ellipsoid plot of the ordered molecule (of three) in the
asymmetric unit of the structure of 4c. Displacement ellipsoids are shown
at the 50% probability level. All hydrogen atoms have been removed for
clarity.
12,16
twist-chair, and chair conformations.
From the crystallographic parameters collected in Table 4, it
can be deduced that: (1) the intracyclic C–P–C angles increases
significantly with increasing ring size, (2) the ligand bite angles
increase slightly with increasing ring size and (3) the ligand cone
The five-membered phospholane rings can adopt a range
of conformations of which four idealised forms may usefully
be identified (Fig. 5). If the phosphorus atom and the two
neighbouring carbon atoms are considered to define a reference
plane, the other two carbons in the ring can be: (A) in plane with
these atoms (planar), (B) one in plane and one out of the plane
17
angles (calculated by Tolman’s method ) show that the ligands
have essentially the same bulk.
◦
Table 4 Selected angles ( ) from the crystal structures of 4a–c
◦
Angles/
4a
4b
4c
a
a
b
Intracyclic C–P–C
P–Pt–P
Tolman cone angle
96.0
96.0
228
104.3
96.5
229
109.8a
97.0
225
c
a
b
c
Average of two. Average of five. Average of three.
Fig. 5 Conformations of five-membered phospholane rings.
2
04 | Dalton Trans., 2009, 202–209
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Rhodium(I) complexes
Addition of two equivalents of L5–7 to [Rh
2
Cl
2
(CO)
4
] in CH
2
Cl
2
gave two species in each case, which are assigned to the binuclear
complexes trans-[Rh Cl (CO) ] as a mixture of anti-5a–c
and syn-5a–c isomers (eqn (2), see Experimental for characterising
2
2
2
(m-L5–7
)
2
3
1
data). These structures are assigned on the basis of the P NMR
spectra, which showed, in each case, two doublets with similar
d(P) and J(RhP) having values typical of a trans-RhCl(CO)(PR
3 2
)
18
structure. A similar ligand-bridged binuclear structure has been
19
reported for trans-[Rh
2
Cl
2
(CO)
2
(m-Ph
2
P(CH
2
)
3
PPh ) ].
2
2
Fig. 7 Thermal ellipsoid plot of the structure of anti-5c. Displacement
ellipsoids are shown at the 50% probability level. All hydrogen atoms have
been removed for clarity.
(
2)
◦
Table 5 Selected bond distances ( A˚ ) and angles ( ) for syn-5a
Bond distances/A˚
Rh1–C23
Rh1–P1
Rh2–C24
Rh2–P2
P1–C1
P1–C5
P2–C8
P3–C12
P3–C16
P4–C19
1.805(4)
2.3183(9)
1.811(4)
2.3017(9)
1.839(3)
1.833(4)
1.839(4)
1.838(3)
1.835(3)
1.836(3)
Rh1–Cl1
Rh1–P4
Rh2–Cl2
Rh2–P3
P1–C4
2.3714(9)
2.3049(9)
2.3746(9)
2.3077(9)
1.852(3)
1.831(3)
1.836(4)
1.847(3)
1.838(3)
1.844(3)
The crystal structures of syn-5a and anti-5c have been deter-
mined (see Fig. 6 and 7 and Tables 5 and 6). Crystals of syn-5a
were grown by slow diffusion of diethyl ether into a saturated
P2–C7
P2–C11
P3–C15
P4–C18
P4–C22
CH
2
Cl
2
solution. The crystals form in the space group P2 /c with
1
one binuclear molecule in the asymmetric unit. The phospholane
rings all adopt distorted asymmetric envelope conformations with
four out of five atoms in the ring (including phosphorus) coplanar.
◦
Bond angles/
C1–P1–C4
C4–P1–C5
C7–P2–C8
C12–P3–C15
C15–P3–C16
C18–P4–C19
94.56(16)
103.21(17)
104.57(18)
94.05(16)
104.71(17)
106.55(16)
C1–P1–C5
103.68(17)
104.51(17)
93.59(18)
105.84(16)
103.57(16)
94.05(16)
C7–P2–C11
C8–P2–C11
C12–P3–C16
C18–P4–C22
C19–P4–C22
The angle between the mean planes of Rh1, P1, P4 and Cl1 and
◦
Rh2, P2, P3 and Cl2 is 15.1(1) . Selected geometric parameters
are given in Table 5.
Crystals of anti-5c were grown by slow diffusion of hexane into
a saturated CH
2
Cl
2
solution, and form in the space group P2
1
2 2
1 1
with one binuclear molecule in the asymmetric unit (see, Fig. 7).
There is disorder in one of the seven membered rings (involving
P4) which was modelled as lying over two conformations in the
ratio 0.44 : 0.56. The angle between the mean planes of Rh1, P1,
◦
P3 and Cl1 and Rh2, P2, P4 and Cl2 is 41.0(1) . Selected geometric
parameters are given in Table 6.
The IR spectra of 5a–c showed single absorptions for n(CO) at
-
1
1
968 (5a), 1963 (5b) and 1960 cm (5c), which are consistent
20
with the donor properties of the ligands being in the order
9
L
5
< L
6
< L
7
. This is the trend expected on the basis of the
Fig. 6 Thermal ellipsoid plot of the structure of syn-5a. Displacement
ellipsoids are shown at the 50% probability level. All hydrogen atoms have
been removed for clarity.
crystallographically determined intracyclic C–P–C angles for the
phosphines (see below).
This journal is © The Royal Society of Chemistry 2009
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◦
Table 6 Selected bond distances ( A˚ ) and angles ( ) for anti-5c
(L
), has the smallest bite angle while generally, increasing the
5
◦
ligand bite angle above 90 increases the activity of the derived
hydroformylation catalysts.
Electronegative substituents on the P-donor often increase the
hydroformylation catalytic activity of the Rh complex although
this is not always the case. Therefore, we conclude that the
phosphacycle ring effect observed here is electronic in origin,
confirming the prediction of Orpen and Connelly that reducing
the C–P–C angle has the effect of reducing the s-donor and
increasing the p-acceptor properties of the tertiary phosphine.
Bond distances/A˚
23
Rh1–C31
Rh1–P1
Rh2–C32
Rh2–P2
Rh2–P4B
P1–C1
P1–C9
P2–C10
P3–C16A
P3–C24
P4A–C30A
1.927(9)
2.3200(17)
1.807(8)
2.3111(18)
2.242(9)
1.833(6)
1.833(6)
1.819(6)
1.813(7)
1.826(6)
1.81(3)
Rh1–Cl1
Rh1–P3
Rh2–Cl2
Rh2–P4A
2.381(2)
2.3160(17)
2.376(2)
24
25
2.429(10)
9
P1–C4
P2–C3
1.830(6)
1.836(5)
1.822(6)
1.837(6)
1.812(18)
P2–C15
P3–C19
P4A–C25A
Experimental
◦
General procedures
Bond angles/
Unless otherwise stated, all reactions were carried out under a
dry nitrogen atmosphere using standard Schlenk line techniques.
C1–P1–C4
C4–P1–C9
C3–P2–C15
C16A–P3–C19
C19–P3–C24
C18A–P4A–C30A
C18B–P4B–C25B
C25B–P4B–C30B
104.4(3)
101.8(4)
102.9(3)
102.8(3)
101.5(3)
101.7(13)
104.2(8)
101.8(14)
C1–P1–C9
C3–P2–C10
C10–P2–C15
C16A–P3–C24
C18A–P4A–C25A
C25A–P4A–C30A
C18B–P4B–C30B
99.7(3)
101.8(3)
101.7(4)
101.2(3)
106.5(10)
101.5(19)
101.9(10)
Dry N
2
2
-saturated solvents were collected from a Grubbs solvent
6
system in flame and vacuum dried glassware. MeOH was dried
˚
over 3 A molecular sieves and deoxygenated by N saturation.
2
Commercial reagents were used as supplied unless otherwise
stated. All phosphines were stored under nitrogen at room
temperature. Most complexes were stable to air in the solid state
and were stored in air at room temperature. Starting materials
a
Table 7 Hydroformylation of 1-octene
27
28
[
PtCl
2
(cod)] and [Rh
2
Cl
2
(CO)
4
]
were prepared by literature
Entry
Ligand
% Conversion to nonanals
n : iso
methods. Elemental analyses were carried out by the Microanalyt-
ical Laboratory of the School of Chemistry, University of Bristol.
Electron Impact and Fast Atom Bombardment mass spectra were
recorded by the Mass Spectrometry Service, University of Bristol
on a MD800 and an Autospec. Infrared spectroscopy was carried
out on a Perkin Elmer 1600 Series FTIR. NMR spectra were
measured on a Joel GX 300, Jeol Eclipse 400 or Jeol GX 400.
1
2
3
L
L
L
5
6
7
69
48
3
2.3
2.2
2.0
a
◦
2
Reactions conditions: 90 C, 10 bar CO–H (1 : 1) for 4 h in toluene, L–
Rh = 5 : 1. See Experimental for details. No decomposition to metallic
rhodium was apparent when the autoclaves were opened at the end of a
◦
catalytic run. Under more forcing conditions (140 C, 80 bar), quantitative
conversion to aldehyde was observed for all three ligands. No 2-octene was
detected in the product of any run and under the same conditions (90 C,
3
1
1
13
1
1
P{ H}, C{ H} and H NMR spectra were recorded at ambient
◦
temperature of the probe at 300, 100 and 121 MHz, respectively,
using deuterated solvent to provide the field–frequency lock.
1
0 bar, 4 h) the conversions when 2-octene was the substrate were < 1%.
The conversions of 1-octene to nonanals are the average of 2 or 3 runs; the
differences between individual runs were within 5% for entries 1 and 2 and
within 0.5% for entry 3.
Synthesis of 1,3-bis(phenylphospholanium)propane dibromide
(
2a). 1-Phenylphospholane 1a (2.11 g, 12.9 mmol) and 1,3-
3
dibromopropane (0.65 cm , 1.30 g, 6.45 mmol) in acetonitrile
(20 cm ) were heated at 60 C for 48 h. The solvent was
3
◦
Hydroformylation catalysis
removed under reduced pressure to give 2a as a white solid
Diphosphines with a propane backbone have previously been used
in rhodium-catalysed hydroformylation and it is assumed that
mononuclear 6-membered chelates are involved in the catalysis.
(
3.40 g, 6.45 mmol, 100%). Elemental analysis, found (calcd
31
for C23
(
(
2
1
2
H
32Br
2
P
2
·H
/ppm: 49.7 (s). H NMR (CD
m, 4H, ArH), 7.74–7.58 (m, 6H, ArH), 3.48–3.23 (m, 8H), 2.60–
2
O): C 49.85 (50.38), H 6.28 (6.25). P NMR
21
1
CD
2
Cl
2
) d
P
2
Cl
2
H
) d /ppm: 8.16–8.03
The diphosphines L5–7 were screened for the rhodium-catalysed
hydroformylation of 1-octene and the results are given in Table 7.
The regioselectivity is similar for the three catalysts which is
13
.44 (m, 4H), 2.36–1.94 (m, 10H). C NMR (CD
34.7 (s), 132.6 (m), 130.4 (m), 119.6 (d, ArCipso, J(PC) 77.6 Hz),
6.9 (m), 23.5 (m), 23.5 (d, PCH
2
Cl
2
) d /ppm:
C
1
22
consistent with the ligands having similar steric bulk. The activity
of the catalysts is in the order L > L > L , which parallels the
1
2
, J(PC) 51.5 Hz), 17.6 (t,
5
6
7
2
PCH
2
CH
2
CH P, J(PC) 2.3 Hz).
2
order of increasing electronic donation of the three ligands. Thus
for this series of isosteric diphosphine ligands containing 5-, 6-
or 7-membered phosphacycles, the smaller the ring, the higher
the hydroformylation catalytic activity of the derived rhodium
complex.
1,3-Bis(phenylphosphinanium)propane dibromide (2b). Com-
pound 2b was made in a similar fashion to 2a from 1-
phenylphosphinane 1b in 84% yield. Elemental analysis, found
3
1
(calcd for C25
H
36Br
2
P ): C 53.53 (53.78), H 6.74 (6.50). P NMR
2
1
Diphosphine ligands are widely used for hydroformylation and
it has been shown that the ligand bite angle and the bulk of the
(CD Cl ) d /ppm: 21.9 (s). H NMR (CD
2
2
P
2
Cl
2
) d /ppm: 8.20–
H
8.10 (m, 4H, ArH), 7.73–7.66 (m, 2H, ArH), 7.66–7.58 (m, 4H,
1,23
ligand have a significant effect on the efficiency of the catalyst.
ArH), 3.21–2.94 (m, 12H), 2.24–2.06 (m, 4H), 2.06–1.90 (m,
1
3
However, the crystal structures of 4a–c described above show that
chelated ligands L5–7 are essentially isosteric and have very similar
bite angles. Moreover, the ligand giving the most active catalyst
2H), 1.87–1.72 (m, 2H), 1.70–1.52 (m, 6H). C NMR (CD
2
Cl )
2
1
d
C
/ppm: 134.6 (s), 133.1 (m), 130.4 (m), 117.3 (d, ArCipso, J(PC)
1
79.2 Hz), 24.9 (m), 24.4 (dd, PCH
2
CH
2
CH
2
P, J(PC) 48.4 Hz,
2
06 | Dalton Trans., 2009, 202–209
This journal is © The Royal Society of Chemistry 2009

View Online
3
1
1
J(PC) 16.1 Hz), 21.4 (m), 18.5 (d, PCH
2
, cyclo, J(PC) 47.7 Hz),
(d, J(PC) 2.3 Hz), 24.5 (d, PCH
J(PC) 2.3 Hz), 22.1 (t, PCH CH
2
, cyclo, J(PC) 10.8 Hz), 23.2 (d,
2
2
1
6.1 (t, PCH
2
CH
2
CH
2
P, J(PC) 3.1 Hz).
2
2
CH P, J(PC) 15.4 Hz).
2
1
,3-Bis(phenylphosphepanium)propane dibromide (2c). Com-
1,3-Diphosphepanopropane (L
fashion to L
7
).
L
7
was made in a similar
◦
pound 2c was made in a similar fashion to 2a from 1-
phenylphosphepane 1c in 90% yield. Elemental analysis, found
calcd for C27
CDCl ) d /ppm: 33.9 (s). H NMR (CDCl
m, 4H, ArH), 7.63–7.51 (m, 6H, ArH), 3.27–3.12 (m, 4H), 3.06–
.95 (m, 4H), 2.93–2.79 (m, 4H), 2.17–1.93 (m, 6H), 1.81–1.62 (m,
H), 1.56–1.41 (m, 4H). C NMR (CDCl
31.9 (m), 130.1 (m), 118.7 (d, ArCipso, J(PC) 80.0 Hz), 28.7 (s),
5.0 (m), 21.7 (m), 21.4 (d, J(PC) 46.9 Hz), 16.4 (m).
5
in 78% yield. b.p. = 117–126 C, 0.2 mmHg.
Elemental analysis, found (calcd for C15
H
30
P ): C 66.45 (66.15),
2
3
1
31
1
(
(
(
2
8
1
2
H
40Br
2
P
2
): C 54.71 (55.31), H 7.24 (6.88). P NMR
H 11.10 (11.27). P NMR (CDCl
3
) d /ppm: -33.2 (s). H NMR
P
1
13
3
P
3
) d
H
/ppm: 8.02–7.92
(CDCl
NMR (CDCl
13.1 Hz), 28.3 (d, 4.6 Hz), 25.8 (d, J(PC) 7.7 Hz), 22.6 (t,
3
) d
H
/ppm: 1.90–1.65 (m, 8H), 1.63–1.20 (m, 22H).
C
3
) d /ppm: 31.0 (t, J(PC) 10.7 Hz), 29.0 (d, J(PC)
C
1
3
2
3
) d
C
/ppm: 134.1 (s),
PCH
2
CH
2
CH P, J(PC) 14.6 Hz).
2
1
Synthesis of [PtCl
2
(L
5
)] (4a). To a solution of L
5
(0.090 g,
(cod)]
3
0.416 mmol) in dichloromethane (2 cm ) was added [PtCl
2
Synthesis of 1,3-diphospholanopropane dioxide (3a). To 2a
3.40 g, 6.45 mmol) was added NaOH (50 cm , 20 wt% in
(0.140 g, 0.375 mmol). After stirring the reaction for 12 h, the
solvent was removed and the resulting white solid was washed
with methanol (10 cm ) to give the desired product (0.142 g,
3
(
3
distilled water) and the resulting suspension was heated under
3
reflux for 16 h. The product was extracted into CHCl
and the resulting solution dried over MgSO . The solvents were
removed under reduced pressure to give 3a as a white solid (1.43 g,
3
(3 ¥ 25 cm )
0.294 mmol, 79% yield). Elemental analysis, found (calcd for
3
1
4
C
11
H
22Cl
2
P
2
Pt): C 27.82 (27.40), H 4.56 (4.60). P NMR (CDCl )
3
1
d
P
/ppm: 2.8 (s, J(PtP) 3323 Hz). H NMR (CDCl
3
) d
2.57 (m, 4H), 2.40–1.59 (m, 18H). C NMR (CDCl
27.7 (m), 27.3 (m), 23.8 (m), 20.8 (s). EI mass spectrum: m/z 482
H
/ppm: 2.88–
3
1
1
13
5
(
(
.76 mmol, 90%). P NMR (CDCl
3
) d
P
/ppm: 70.4 (s). H NMR
) d /ppm: 31.5
P, J(PC) 60.7 Hz, J(PC) 11.5 Hz), 26.9 (d,
, cyclo, J(PC) 65.3 Hz), 24.2 (m), 15.7 (t, PCH CH CH P,
J(PC) 3.8 Hz).
3
) d /ppm:
C
1
3
CDCl
dd, PCH
3
) d
H
/ppm: 2.24–1.66 (m). C NMR (CDCl
3
C
1
3
+
+
+
2
CH
2
CH
2
(M ), 446 (M - Cl), 409 (M - 2Cl).
1
PCH
2
2
2
2
2
[PtCl
to 4a from L
Pt): C 30.42 (30.78), H 5.07 (5.14). P NMR (CDCl )
2
(L
6
)] (4b). Compound 4b was made in a similar fashion
6
in 64% yield. Elemental analysis, found (calcd for
3
1
1
,3-Diphosphinanopropane dioxide (3b). Compound 3b was
C
13
H
26Cl
2
P
2
3
3
1
1
made in a similar fashion to 3a from 2b in 100% yield. P NMR
d
P
/ppm: -17.1 (s, J(PtP) 3343 Hz). H NMR (CDCl
3
) d /ppm:
H
1
(
CD
2
Cl
2
) d
P
/ppm: 39.0 (s). H NMR (CD
2
Cl
/ppm: 28.9 (dd, PCH
J(PC) 64.6 Hz, J(PC) 12.3 Hz), 28.0 (d, PCH , cyclo, J(PC)
2
) d
H
/ppm: 1.97–
2.99–2.81 (m, 4H), 2.05–1.76 (m, 14H), 1.75–1.65 (m, 2H), 1.60–
1
3
13
1
.36 (m). C NMR (CD
2
Cl
2
) d
C
2
CH CH P,
2
2
1.38 (m, 6H). C NMR (CDCl
3
) d /ppm: 25.7 (m), 23.2 (m), 22.2
C
1
3
1
+
2
(m), 19.3 (s), 17.8 (m). EI mass spectrum: m/z 474 (M - Cl), 437
2
+
6
3
2.3 Hz), 26.9 (m), 23.1 (m), 14.2 (t, PCH
.9 Hz).
2
CH
2
CH
2
P, J(PC)
(M - 2Cl).
[
PtCl
to 4a from L
Pt): C 33.43 (33.47), H 5.48 (5.62). P NMR (CDCl )
2
(L
7
)] (4c). Compound 4c was made in a similar fashion
1
,3-Diphosphepanopropane dioxide (3c). Compound 3c was
7
in 70% yield. Elemental analysis, found (calcd for
3
1
31
made in a similar fashion to 3a from 2c in 99% yield. P NMR
C
15
H
30Cl
2
P
2
3
1
1
(
CDCl
3
) d
P
/ppm: 52.9 (s). H NMR (CDCl
3
) d
/ppm: 31.1 (dd, PCH
J(PC) 63.68 Hz, J(PC) 11.5 Hz), 29.8 (s) 29.8 (d, PCH
H
/ppm: 2.10–
CH CH P,
, cyclo,
P, J(PC) 3.9 Hz).
d
P
/ppm: -8.3 (s, J(PtP) 3333 Hz). H NMR (CDCl
2.98–2.78 (m, 4H), 2.14–1.73 (m, 14H), 1.72–1.46 (m, 12H).
NMR (CDCl ) d /ppm: 29.3 (s), 28.1 (m), 23.1 (m), 22.1 (m), 18.9
(m). FAB mass spectrum: m/z 501 (M - Cl-1).
3
) d /ppm:
H
1
3
13
1
.52 (m). C NMR (CDCl
3
) d
C
2
2
2
C
1
3
2
3
C
1
2
+
J(PC) 62.3 Hz), 21.1 (m), 14.6 (t, PCH
2
CH
2
CH
2
Synthesis of 1,3-diphospholanopropane (L
5
). A mixture of 3a
Synthesis of [Rh
(0.034 g, 0.157 mmol) in dichloromethane (3 cm ) was added
[RhCl(CO) (0.030 g, 0.079 mmol) as a solid. After stirring
2
Cl
2
(CO)
2
(l-L
5
)
2
] (5a). To a solution of L
5
3
3
(
1.43 g, 5.76 mmol) and phenylsilane (0.98 cm , 0.88 g, 8.1 mmol)
◦
was heated at 100 C for 2 h and the evolution of gas was
observed. The resulting opalescent viscous liquid was distilled
]
2 2
3
the reaction for 1 h, the solvent was reduced to ca. 1 cm and
3
(
1
4
(
0.01 mmHg, fraction collected and boiled over the range 100–
hexane (20 cm ) was added. The resulting precipitate was filtered
◦
40 C) to give L
5
as a clear viscous liquid (0.58 g, 2.69 mmol,
): C 60.78
off, washed with hexane and dried under reduced pressure to
afford the desired product as a light brown powder (0.027 g,
0.071 mmol, 45% yield). Elemental analysis, found (calcd for
6%). Elemental analysis, found (calcd for C11
H
22
P
2
3
1
1
61.10), H 10.02 (10.25). P NMR (CDCl
NMR (CDCl ) d /ppm: 1.89–1.61 (m, 12H), 1.59–1.33 (m, 10H).
C NMR (CDCl
6.6 Hz, J(PC) 10.9 Hz), 27.6 (d, J(PC) 4.2 Hz), 25.7 (d, PCH
cyclo, J(PC) 11.4 Hz), 24.0 (t, PCH
3
) d /ppm: -26.7 (s). H
P
3
1
3
H
C
24
H
44Cl
2
O
2
P
4
Rh
2
): C 37.20 (37.67), H 5.27 (5.80). P NMR
1
3
1
3
) d
C
/ppm: 30.4 (dd, PCH
2
CH
2
CH
2
P, J(PC)
(CD
2
Cl
2
) d
P
/ppm: 27.9 (br d, J(RhP) 108 Hz), 27.0 (d, J(RhP)
3
1
1
2
,
113 Hz). H NMR (CD
2
Cl
2
) d
H
/ppm: 2.50–1.30 (br m, 22H, CH
Cl
2
2
).
):
1
2
13
2
CH
2
CH
2
P, J(PC) 16.6 Hz).
C NMR (CD
2
Cl
2
) d
C
/ppm: 32.0–24.4 (m). IR nCO (CH
2
-
1
+
1968 cm . EI mass spectrum: m/z 708 (M - 2CO).
1
,3-Diphosphinanopropane (L
6
).
L
6
was made in a similar
◦
fashion to L
Elemental analysis, found (calcd for C13
5
in 85% yield. b.p. = 112–113 C, 0.2 mmHg.
[Rh Cl (CO) (l-L ] (5b). Compound 5b was made in a
2
2
2
6
)
2
H
26
P
2
) C 64.38 (63.91),
similar fashion to 5a from L in 64% yield. Elemental analysis,
found (calcd for C28 Rh ): C 41.24 (40.95), H 7.06
/ppm: 6.7 (d, J(RhP) 117 Hz), 6.0
(d, J(RhP) 117 Hz). H NMR (CD Cl ) d /ppm: 2.50–1.10 (m,
/ppm: 188.7–187.6 (m, CO),
6
3
1
1
H 11.05 (10.73). P NMR (CDCl
CDCl ) d /ppm: 1.87–1.73 (m, 14H), 1.73–1.62 (m, 4H), 1.58–
.44 (m, 12H), 1.33–1.17 (m, 6H). C NMR (CDCl
3
) d
P
/ppm: -41.9 (s). H NMR
H
52Cl
2
O
2
P
4
2
3
1
(
1
2
3
H
(6.38). P NMR (CD
2
Cl
2
) d
P
1
3
1
3
) d
C
/ppm:
2
2
H
1
3
13
8.7 (dd, PCH
2
CH
2
CH
2
P, J(PC) 13.1 Hz, J(PC) 11.5 Hz), 27.8
26H, CH
2
). C NMR (CD
2
Cl
2
) d
C
This journal is © The Royal Society of Chemistry 2009
Dalton Trans., 2009, 202–209 | 207

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Table 8 Crystallographic data
Compound
4a·CHCl
3
4b
4c
5a
5c
Colour, habit
Size/mm
Colourless, block
Colourless, plate
Colourless, block
Yellow, block
Yellow, plate
0.40 ¥ 0.26 ¥ 0.02
32 2 2 4 2
C H60Cl O P Rh
0.14 ¥ 0.07 ¥ 0.07
0.25 ¥ 0.07 ¥ 0.03
0.14 ¥ 0.10 ¥ 0.06
0.40 ¥ 0.30 ¥ 0.20
Empirical Formula
C
12
H
23Cl
5
P
2
Pt
C
13
H
26Cl
2
P
2
Pt
C
15
H
30Cl
2
P
2
Pt
C
24
H
44Cl
2
O
2
P
4
Rh
2
-1
M
r
/g mol
601.58
Orthorhombic
P2
510.27
Orthorhombic
Pbca
12.723(3)
11.954(3)
22.007(6)
90.00
3347.0(15)
8
8.878
173
20 486
3843
538.32
Monoclinic
Pc
34.324(7)
6.3850(13)
12.625(3)
92.05(3)
2765.1(10)
6
8.065
173
28 297
12 421
765.19
Monoclinic
P2 /c
877.40
Orthorhombic
P2
Crystal system
Space group
a/A˚
1
2
1
2
1
1
1 1 1
2 2
12.165(2)
12.425(3)
12.614(3)
90.00
1906.4(7)
4
8.217
100
21 202
4334
11.7519(7)
11.9472(7)
22.4102(13)
91.1220(10)
3145.8(3)
4
1.442
173
20 348
7198
11.0204(18)
11.9691(16)
28.877(3)
90.00
3809.0(9)
4
1.202
173
25 010
8754
b/A˚
c/A˚
◦
b/
V/A˚
3
Z
-1
m/mm
T/K
Total reflections
Independent reflections
R
int
0.0291
0.0185
0.0468
1.06, -0.66
2.096
0.0602
0.0292
0.0706
1.65, -1.61
2.025
0.0296
0.0281
0.0693
1.76, -1.57
1.940
-0.001(4)
0.0518
0.0364
0.0795
0.65, -0.65
1.616
0.0811
0.0444
0.1079
0.62, -0.95
1.530
Final R
1
(I > 2s)
2
Final wR
Largest peak, hole (e A˚
-3
)
-3
r
calcd/g cm
Flack parameter
0.461(5)
—
—
-0.01(4)
-
1
29
◦
3
0.9–20.5 (m). IR nCO (CH
2
Cl
2
): 1963 cm . EI mass spectrum:
were integrated from several series of exposures measuring 0.3
in w. Absorption corrections were based on equivalent reflections
+
m/z 764 (M - 2CO).
30
2
using SADABS, and structures were refined against all F
o
[
Rh
2
Cl
2
(CO)
2
(l-L ) ] (5c). Compound 5c was made in a
7
2
data with hydrogen atoms riding in calculated positions using
SHELXTL. Crystal structure and refinement data are given in
similar fashion to 5a from L
7
in 88% yield. Elemental analysis,
Rh ): C 43.75(43.80), H6.98(6.89).
/ppm: 18.5 (d, J(RhP) 115 Hz), 17.0 (d,
Cl ) d /ppm: 2.60–2.29 (m, 2H),
.13–1.36 (m, 28H). C NMR (CD Cl ) d /ppm: 188.8–187.6
m, CO), 32.5–23.9 (m). IR nCO (CH Cl ): 1960 cm . FAB mass
31
found (calcdfor C32
H
60Cl
2
O
2
P
4
2
Table 8. In 4a·CHCl
3
the molecular complex has approximate
3
1
P NMR (CD
2
Cl
2
) d
P
mirror symmetry, as such that the crystal structure may also be
approximately described in the space group Pnma, albeit with
disorder in the chloroform molecule. The crystal structure refines
1
J(RhP) 115 Hz). H NMR (CD
2
(
2
2
H
1
3
2
2
C
-
1
2
2
satisfactorily in P2
1
2
1
2
1
as an inversion twin (Flack parameter =
+
+
spectrum: m/z 877 (M ), 720 (M - 2CO).
0
.461(5)). Coupled with the fact that there are a significant number
of (albeit weak) reflections present in the diffraction data, which
should be systematically absent in Pnma, and that the weighted
R-factor is lower and residual density map is cleaner in the lower
Hydroformylation catalysis. The phosphine (0.060 mmol) and
[
(
Rh(CO)
2
(acac)] (3.0 mg, 0.012 mmol) were dissolved in toluene
10 cm ) under nitrogen in a Schlenk tube. The resulting solution
was transferred by cannula to a 100 mL autoclave, which had been
flushed 3 times with 3 bar CO–H (1 : 1). The autoclave was then
pressurized with 2 bar of CO–H (1 : 1) at room temperature.
3
symmetry space group, this suggests that P2
1
2
1
1
2 is the correct
choice. In 4c, the ring containing P(4) has three of the carbon
atoms disordered over two positions in proportions 0.66/0.34, and
the ring containing P(5) has all of the carbon atoms disordered
over two positions (ration 0.57/0.43). The use of restraints on
carbon–carbon bond lengths was necessary to ensure convergence
of the refinement.
2
2
The reaction mixture was then stirred vigorously with a sparging
◦
stirrer and heated to 90 C over a period of 30 min. After this
pre-activation of the catalyst, the 1-octene (10 g) was introduced
into the autoclave via a lock by means of CO–H pressure. The
2
pressure was then immediately raised to 10 bar and maintained at
this pressure throughout the catalysis by introduction of further
Acknowledgements
CO–H (1 : 1) via a pressure regulator. After running the reactions
2
for 4 h, the autoclave was cooled, vented and emptied. Analysis of
the reaction products was carried out by GC.
We thank BASF and the EPSRC for financial support, Johnson-
Matthey for a loan of precious metal compounds and the
Leverhulme Trust for a Research Fellowship (to PGP).
Crystal structure determinations
X-Ray diffraction experiments of 4b, 4c, syn-5a and anti-5c were
carried out at 173K on a Bruker SMART diffractometer; an
experiment on 4a (as its chloroform solvate) was carried out
at 100K on a Bruker SMART APEX diffractometer, all using
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2
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MoKa radiation (l = 0.71073 A). All data collections were
performed using a CCD area detector from a single crystal coated
in perfluoroalkylether and mounted on a glass fibre. Intensities
2
08 | Dalton Trans., 2009, 202–209
This journal is © The Royal Society of Chemistry 2009

View Online
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