A simple procedure for the separation of the catalytically important phosphabicyclononane isomers

Article abstract of DOI:10.1039/a703204h

The isomeric [3.3.1]- and [4.2.1]-phosphabicyclononanes are readily separated by a sequence of hydrophosphination/ dehydrophosphination steps; new diphosphine ligands derived from the [3.3.1] isomer are described.

Full text of DOI:10.1039/a703204h

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A simple procedure for the separation of the catalytically important
phosphabicyclononane isomers
Joanne H. Downing, Victoria Gee and Paul G. Pringle*
School of Chemistry, University of Bristol, Cantocks Close, Bristol, UK BS8 1TS
The isomeric [3.3.1]- and [4.2.1]-phosphabicyclononanes are
readily separated by a sequence of hydrophosphination/
H
I
I
P
i
P
P
dehydrophosphination steps; new diphosphine ligands de-
rived from the [3.3.1] isomer are described.
ii NEt3
1a
4
overall yield 17%
Phosphine (PH
3
) adds to cycloocta-1,5-diene to give a mixture
Br
Br
i
of the bicyclic secondary phosphines 1a and 1b, sometimes
referred to as ‘phobane’.1 Tertiary phosphines made from this
mixture are ligands for the cobalt-catalysed hydroformylation
ii NEt3
,2
3
4
process currently carried out on a large scale industrially.
Recently derivatives of 1a and 1b have attracted attention as
P
Br
LiPPh2
P
PPh2
5
6
ligands for hydroformylation, carbonylation, and asymmetric
catalysis.2 To date there have been no reports of the separation
of the isomers 1a and 1b although, by exploiting the difference
in reactivity between the isomers, ligands derived from the
,7
6
5
Scheme 2 (Overall yield 50%)
2,8
symmetrical isomer 1a have been isolated. Here we report an
easy method for separating 1a and 1b and the use of pure 1a in
further ligand synthesis.
suggests that it is the hydroxymethyl group lying over the
seven-membered ring that is the reactive one.8
Treatment of an aqueous solution of 2a with NaOH and
NaHSO (to trap the generated CH O) gave the symmetrical
3 2
secondary phosphine 1a which was then extracted into pentane.
Similarly the unsymmetrical isomer 1b was made by treatment
The reactions which form the basis for the separation are
summarised in Scheme 1. The crystalline, air-stable phospho-
nium salts 2a and 2b are readily made from the mixture of 1a
and 1b with CH
a/b is promoted by NaOH but we have found that one
2 2
O in the presence of HCl. Loss of CH O from
2
3
of a pentane solution of 3b with aqueous NaOH and NaHSO .
hydroxymethyl group in 2b is much more reactive than any of
the others. Thus an aqueous solution of a 2a/b mixture reacted
selectively with NaOH to give neutral phosphine 3b which was
then extracted into pentane to leave pure 2a in the aqueous
The separation can be carried out efficiently on a multigram
scale† and both 1a and 1b have been isolated and fully
characterised.‡
Access to 1a has allowed us to synthesise the diphosphine
derivatives 4 and 5 by the routes shown in Scheme 2; the modest
overall yields reported reflect the small scale (0.1–1 g) of these
2 2
layer. The crystal structure of the complex cis-[PtCl (3b) ]
H
2 3
preliminary reactions. Treatment of 1a with I(CH ) I followed
H
P
P
gave 45 exclusively in contrast to the mixture of
P(CH PH adds to cycloocta-
Br gave the inter-
by NEt
isomers formed when H
,5-diene. Treatment of 1a with Br(CH
mediate 6 which reacts with LiPPh to give the unsymmetrical
3
2
2
)
3
2
1
2 3
)
1a
1b
2
CH2O, HCl
diphosphine 5. The application of these new ligands in
coordination chemistry and catalysis is in progress.
We thank EPSRC and Albright and Wilson for supporting
this work.
HOCH2
HOCH2
CH2OH
CH2OH
HOCH2
CH2OH
CH2OH
P
P
Cl
Cl
Cl
Footnotes and References
2
a
2b
NaOH
*
†
E-mail: paul.pringle@bristol.ac.uk
The separation of 1a and 1b was carried out as follows (under nitrogen
except where specified). To a stirred solution of a crude mixture of 1a and
1b supplied by Albright and Wilson Ltd (77 g, ca. 60% 1a/b by P NMR
P
P
31
3
with the ratio of 1a to 1b of ca. 1.1 :1) in aqueous CH
2
O (95 cm , 35% m/m,
.20 mol) was added aqueous HCl (120 cm , 5 m, 0.60 mol) dropwise over
0 min. After 1 h, the volatiles were removed on a rotary evaporator in air
3
1
3
2a
3b
aqueous layer
pentane layer
3
to give a viscous white oil. In air, trituration with propan-2-ol (400 cm )
gave a white solid which was filtered off, washed with cold propan-2-ol (50
cm ) and diethyl ether (50 cm ); the yield of salts 2a and 2b was 56 g which
represents ca. 72% yield. The solid was dissolved in hot (ca. 60 °C) water
(ca. 20 cm ) and then when the solution had cooled to ca. 40 °C, acetone
was added until the solution turned cloudy (ca. 50 cm ). Then the mixture
NaOH /
NaOH /
3
3
NaHSO3
NaHSO3
3
H
P
H
P
3
was refrigerated (0 °C) for 16 h to give crystalline 2a/b in > 80% recovery.
3
To a rapidly stirred solution of 2a/b (8.5 g, 36 mmol) in water (20 cm ) with
3
3
1b
a layer of pentane (35 cm ), was added aqueous NaOH (16 cm , 1 m, 16
mmol) dropwise by syringe over 5 min. After a further 10 min, the pentane
layer was separated and the aqueous layer washed with pentane (2 3 10
1a
Scheme 1
Chem. Commun., 1997
1527

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3
3
cm ). To the aqueous layer, more aqueous NaOH (1 m, 1 cm ) was added (to
remove the final traces of 2b) and then in a separating funnel (in air), the
(162 MHz): 2a (D
(CDCl ) d 4.3; 4 (C
PPh ); 6 (C ) d 237.8.
2
O) d +23.1; 2b (D
2
O) d 55.4; 3a (CDCl ) d 231.7; 3b
8
) d 238.1 (s, PC H14), 217.2 (s,
3
3
6 6
D ) d 237.6; 5 (C
6
D
6
3
aqueous layer was washed with pentane (2 3 30 cm ) and then separated.
The aqueous layer was then deaerated, pentane (50 cm ) was added, then
aqueous NaOH (37.6 cm , 1 m, 37.6 mmol) added dropwise over 5 min and
finally solid NaHSO
2
6 6
D
3
3
1
2
3
R. F. Mason and J. L. Van Winkle, US Pat., 3 400 163, 1968, to Shell Oil
Co.
H. C. L. Abbenhuis, U. Burckhardt, V. Gramlich, C. K o¨ llner, P. S.
Pregosin, R. Salzmann and A. Togni, Organometallics, 1995, 14, 759.
Shell International Research, Chem. Abstr., 1967, 66, 65101r; Neth. Pat.,
3
(7.8 g, 75 mmol) was added and the mixture stirred for
1
h. Then the pentane layer was separated and the aqueous layer washed
3
with pentane (2 3 20 cm ). The pentane extracts were combined, dried over
MgSO , filtered and then evaporated to dryness to give a white solid 1a
2.32 g, 87%) which was 99.5% pure 1a (by P NMR).
In a separate experiment a pentane solution (ca. 30 cm ) of 3b (obtained
as described above but from 1.78 g of 2a/b, 7.5 mmol) was treated with
water (20 cm ) and NaOH (3.25 cm , 1 m, 3.25 mmol) followed by solid
NaHSO (3.44 g, 33 mmol) and the mixture rapidly stirred for 44 h. Then
the pentane layer was separated and the aqueous layer washed with pentane
4
3
1
(
6
9
604 094, 1966; Mitsubishi Petrochemical Co. Ltd., Chem. Abstr., 1981,
5, 186 627z; Jpn. Kokai Tokkyo Koho, JP 80 113 731, 1980.
3
4
5
6
7
K. Weisselmel and H-J. Arpe, Industrial Organic Chemistry, VCH, New
York, 1993.
E. Drent, D. H. L. Pello, J. C. L. J. Suykerbuyk and J. Van Gogh, World
Pat., 5354, 1995, to Shell International Research.
R. P. Tooze, World Pat., 15 938, 1995, to ICI; S. T. Howard, J. P.
Foreman and P. G. Edwards, Inorg. Chem., 1996, 35, 5805.
H. C. L. Abbenhuis, U. Burckhardt, V. Gramlich, A. Martelletti, J.
Spencer, I. Steiner and A. Togni, Organometallics, 1996, 15, 1614;
H. C. L. Abbenhuis, U. Burckhardt, V. Gramlich, A. Togni, A. Albinati
and B. M u¨ ller, Organometallics, 1994, 13, 4481.
3
3
3
3
(
3 3 10 cm ). The pentane extracts were combined, dried over MgSO
filtered and then evaporated to dryness to give a white solid 1b (0.26 g,
5%) which was 99% pure 1b (by P NMR).
4
,
3
1
5
‡
[
3
1
Selected spectroscopic data. 1a: P NMR (CDCl , 162 MHz) d 254.1
3
1
1
1
J(PH) 192.1 Hz]; H (CDCl
.55–2.55 (br m, 14 H); 13C (CDCl
0.0 [d, J(PC) 9.2 Hz], 22.6 (s), 22.4 [d, J(PC) 42.7 Hz], 22.1 (s); mass
3
, 400 MHz) d 3.20 [d, 1 H, J(PH) 192.1 Hz],
1
3
3
, 100 MHz) d 33.9 [d, J(PC) 6.1 Hz],
8
9
J. Fawcett, P. A. T. Hoye, R. D. W. Kemmitt, D. J. Law and D. R. Russell,
J. Chem. Soc., Dalton Trans., 1993, 2563.
J. H. Downing, PhD thesis, University of Bristol, 1992.
+
31
spectrum (EI) m/z 142 (M ). 1b: P NMR (CDCl
J(PH) 188.1 Hz]; H (CDCl
.59 (br s, 2 H), 2.06 (m, 2 H), 1.35–1.82 (m, 10 H). C (CDCl , 100 MHz)
3
, 162 MHz) d 248.4
3
, 400 MHz) d 2.70 [d, 1H, J(PH) 188.0 Hz],
1
1
1
[
1
3
2
3
d 37.1 [d, J(PC) 7.6 Hz], 35.5 [d, J(PC) 7.6 Hz], 35.3 [d, J(PC) 15.3 Hz],
+
31
2
5.8 [d, J(PC) 7.6 Hz]; mass spectrum (EI) m/z 142 (M ). P NMR data
Received in Cambridge, UK, 9th May 1997; 7/03204H
1528
Chem. Commun., 1997