The relative stabilities of cyclic dicationic derivatives of diphosphanes with three (3P) or four (4P) linked phosphorus atoms

Article abstract of DOI:10.1039/c1dt11549a

Reaction of a diphosphane with a chlorophosphane in the presence of SnCl₂ or AlCl₃ leads to the formation of dicationic heterocycles with three (3P) or four (4P) linked phosphorus atoms. Some 3P derivatives with small alkyl substituents may also be prepared by direct alkylation of cyclic triphosphenium ions. Several new species were prepared in solution, some of which were isolated and characterised by single-crystal X-ray diffraction. Investigations into the factors favouring formation of 3P or 4P species are described.

Full text of DOI:10.1039/c1dt11549a

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PAPER
The relative stabilities of cyclic dicationic derivatives of diphosphanes with
three (3P) or four (4P) linked phosphorus atoms†
Rachel Bashforth,a Alice J. Boyall,a Philippa K. Coffer (ne´e Monks),a Keith B. Dillon,*a Andre´s E. Goeta,a
Judith A. K. Howard,a Alan M. Kenwright,a Michael R. Probert,a Helena J. Shepherda,b and
Amber L. Thompsona,c
Received 17th August 2011, Accepted 13th October 2011
DOI: 10.1039/c1dt11549a
Reaction of a diphosphane with a chlorophosphane in the presence of SnCl2 or AlCl3 leads to the
formation of dicationic heterocycles with three (3P) or four (4P) linked phosphorus atoms. Some 3P
derivatives with small alkyl substituents may also be prepared by direct alkylation of cyclic
triphosphenium ions. Several new species were prepared in solution, some of which were isolated and
characterised by single-crystal X-ray diffraction. Investigations into the factors favouring formation of
3P or 4P species are described.
We have also shown in a preliminary communication that it
Introduction
is sometimes possible to add a second R¢PCl2 molecule to a
The synthesis of the first two dicationic phosphorus heterocycles
diphosphane to yield a cyclic tetraphosphonium dication with
with three linked phosphorus atoms (3P) was described by
four linked phosphorus atoms (4P), Scheme 3; the crystal and
molecular structures of two of these compounds were determined.4
These reactions were initially carried out in the presence of SnCl2,
since a redox reaction is a necessary stage in the process. A further
reaction leading to both 3P and 4P products has subsequently been
described by Weigand, Burford and co-workers, and the molecular
structure of their 3P dication was elucidated.5 In all instances, for
both 3P and 4P species, the P–P bond distances are as expected
for single bonds.
Schmidpeter and co-workers, by reaction of a diphosphane with
a halophosphane in the presence of AlCl3 (Scheme 1).1 These
compounds may also be prepared by direct alkylation of cyclic
triphosphenium ions (CTIs) on the central (bare) phosphorus
atom, at least for small R¢ groups (Scheme 2).2,3 In a recent paper,
we described the synthesis by these two routes of several new 3P
compounds, five of which were characterised by single-crystal X-
ray diffraction.3
Scheme 1 The synthesis of P-alkylated cyclic triphosphenium ions (3P).
Scheme 3 The synthesis of cyclic tetraphosphonium ions (4P) with SnCl2.
In the present work, the syntheses of several new 3P and
4P dications are described, some of which were characterised
crystallographically. The factors favouring formation of 3P or 4P
species in these often competing reactions are discussed.
Scheme 2 Direct alkylation of a CTI.
aChemistry Department, University of Durham, South Road, Durham, DH1
3LE, UK. E-mail: k.b.dillon@durham.ac.uk; Fax: +44 (0)191 384 4737;
Tel: +44 (0)191 334 2092
Results and discussion
(a) New 3P dications
bPresent address: Laboratoire de Chimie de Coordination, 205, route de
Narbonne, 31077, Toulouse cedex 04, France
The 31P solution-state NMR data for the new 3P species, Fig. 1,
are shown in Table 1, including examples of ring sizes from 4–8.
Compounds 1–7 (Fig. 1) were synthesised by the route shown in
Scheme 1 in the presence of AlCl3 or SnCl2,1,3 whereas dications
cPresent address: Chemical Crystallography, Chemistry Research Labora-
tory, University of Oxford, Oxford, OX1 3TA, England
† CCDC reference numbers 840422–840425. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt11549a
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Table 1 31P NMR data for P-alkylated cyclic triphosphenium ions
Diphosphane
R¢
Ring size
PB, ppm
PC, ppm
PA, ppm
1JP–P, Hz
Counter-ion
-
dcypm (1)
nPr
Ph
Et
4
5
6
7
7
7
7
7
8
41.4
46.6
28.7
17.3
25.2
25.5
25.2
24.1
21.8
—
—
—
12.5
24.3
24.7
24.3
20.2
—
-64.0
-76.4
-92.4
-12.2
-7.6
159
290
303
310, 324
296, 317
296, 319
297, 318
292, 301
362
AlCl4
AlCl4
-
dmpe (2)
dcypp (3)
[Al2O4Cl10]2-
2-
biphep (4)
cybiphep (5)
cybiphep (6)
cybiphep (7)
cybiphep (8)
dppdmx (9)
iPr
Et
SnCl6
SnCl6
SnCl6
SnCl6
2-
2-
nPr
iPr
Me
Me
-13.5
-7.3
2-
-24.9
-10.1
SnCl62-/triflate
SnCl62-/triflate
Table 2 Selected bond distances and angles for compounds 3 and 6
3
6
˚
P1–P2 (A)
2.199(2)
2.202(2)
102.95(8)
1.807(6)
2.231(2)
2.208(2)
97.72(8)
1.863(6)
˚
P1–P3 ◦(A)
PŸPŸP( )
˚
P1–C (A)
Fig. 1 The 3P dications synthesised (all carry a 2+ charge).
8 and 9 were prepared by direct methylation using methyl triflate
of the corresponding cyclic triphosphenium ion (Scheme 2).2,3 For
biphep and cybiphep derivatives only, the outer phosphorus atoms
PB and PC are inequivalent, so the PA resonance appeared as a
doublet of doublets (Table 1). In all instances, the JPP values
are appreciably smaller than those in the corresponding cyclic
triphosphenium ions, with no substituent on PA.2–4,6–17
Fig. 2 The molecular structure of dication 3, showing the numbering
scheme for the key atoms (only the major component is shown and
the counter-ions have been omitted for clarity). Atomic Displacement
Parameters (ADPs) are drawn at 50% probability.
1
Dications 1, 3 and 6 were isolated in crystalline form with
counter-ions AlCl4 , [Al4O2Cl10]2-18–24 and SnCl3
+ ,
1 SnCl6
-
-
2-
2
respectively, and were studied by low-temperature single-crystal X-
ray diffraction. Unfortunately, due to the very air-sensitive nature
of 1, the quality of the data obtained was such that while the
connectivities and basic structure could be ascertained, reliable
bond length and bond angle values could not be determined.
Nevertheless, the four-membered ring structure was unequivocally
confirmed. 3 represents the first example of a six-membered ring
dication of this type to be structurally characterised; its molecular
structure is shown in Fig. 2. As found previously in both larger
and smaller rings,3 the P–P distances (Table 2) are entirely as
expected for single bonds, while the PB–PA–PB bond angle is larger
at 102.95(8)◦ than in either the 5- or 7-membered ring examples.3
6 is a new type of 7-membered ring system and its molecular
and 1 SnCl6 and there are also four CDCl3 molecules in the
2-
2
asymmetric unit, two of which show some disorder. P–P bond
distances (Table 2) are again entirely compatible with single bonds,
while the PB–PA–PC bond angle of 97.72(8)◦ is comparable to that
of 96.59(13)◦ found in the only previous structurally characterised
7-membered ring dication of this type.3
Table 3 contains the 31P solution-state NMR spectroscopic data
for five examples of 3P dications with a different counter-ion
from those described in earlier work.2,3 In all instances, there is
good agreement between the sets of NMR parameters for each
of the dications, showing that a change of anion is not a major
influence on these values. This parallels the behaviour of cyclic
triphosphenium ions, where a change of anion has little effect on
the 31P chemical shifts of the cation.2,6,7,10–16,25
-
structure is illustrated in Fig. 3. The counter-ions are SnCl3
1166 | Dalton Trans., 2012, 41, 1165–1172
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triphosphenium ions.7,10 Either the diphosphane tetrachloride
(Scheme 4a) or dichloride (Scheme 4b) is a possible oxidation
product; these may be readily distinguished by 31P NMR spec-
troscopy, since the dichloride will give rise to a pair of doublets,
whereas the tetrachloride will yield a single peak only.
Compounds 15–25 (Fig. 4) were synthesised by the route shown
in Scheme 3, using either AlCl3 or SnCl2. As we have previously
reported, these 4P systems are readily identifiable by 31P NMR
spectroscopy, as they give rise to an AA¢XX¢ pattern.4 The 31P
NMR spectroscopic data for compounds 15–25 were analysed
directly from the spectra, as described by Gu¨nther,26 and the
results are presented in Table 4. The coupling constants for these
systems are in good agreement with those previously reported for
4P systems4,5 and for other compounds containing four- or six-
linked phosphorus atoms.27,28 In a few instances (15b, 17b, 19a,
Fig. 3 The molecular structure of the dication 6, showing the numbering
scheme for the key atoms (the counter-ions have been omitted for clarity).
ADPs are drawn at 50% probability.
Table 3 31P NMR spectroscopic data for alkylated cyclic triphosphenium
ions with different counter-ions to those described previously2,3
1
Diphosphane R Ring size PB, ppm PA, ppm JP–P, Hz Counter-ion
2-
dcypm (10) Et
4
5
39.5
53.6
50.2
52.8
29.3
-62.8
-96.2
-54.2
-79.2
-81.9
157
299
336
293
303
SnCl6
SnCl6
SnCl6
SnCl6
SnCl6
2-
2-
2-
2-
dppe (11)
dppe (12)
dppe (13)
depp (14)
Et
tBu 5
Ph
Et
5
6
(b) New 4P dications
Previously, we reported that for the 4P product to be formed,
a diphosphane, a chlorophosphane and tin(II) chloride were
necessary, as without any one of these components no reaction
takes place.4 Here, we show that in the synthesis of 4P systems
tin(II) chloride can be replaced with aluminium trichloride, with
the diphosphane now acting as the reducing agent to allow
formation of the 4P product. Use of diphosphanes as reducing
agents has previously been demonstrated in the synthesis of cyclic
Fig. 4 The 4P dications synthesised (all carry a 2+ charge; counter-ions:
a denotes SnCl62-; b denotes AlCl4-).
Table 4 31P NMR spectroscopic data for 4P systemsa
Diphosphane
R
Ring size
PB, ppm
PA, ppm
1JAB, Hz
1JBB¢, Hz
2JAB¢, Hz
3JAA¢, Hz
Counter-ion
-
dmpm (15b)
dcypm (16a)
dcypm (16b)
dcypm (17a)
dcypm (17b)
dcypm (18b)
dppm (19a)
dppm (19b)
dppm (20a)
dppm (21a)
dppm (21b)
dppm (22a)
depe (23b)
Et
Et
5
5
5
5
5
5
5
5
5
5
5
5
6
8
8
-38.3
-51.6
-51.9
-49.2
-48.5
-37.9
-40.8
-41.9
-48.7
-26.2
~ -31
4.2
62.1
54.4
54.4
54.0
57.2
51.8
57.5
55.3
58.1
51.7
~ 40
44.7
31.5
30.8
30.3
—
290
288
241
—
306
357
384
—
—
—
339
307
318
321
—
203
202
241
—
306
175
280
—
—
—
287
140
125
141
—
-36
-36
-49
—
-41
-30
-56
—
—
—
-9
-30
-80
-88
—
36
34
8
AlCl4
2-
SnCl6
-
Et
AlCl4
nPr
nPr
iPr
Et
SnCl6
2-
-
—
46
74
58
—
—
—
15
-3
11
15
AlCl4
AlCl4
-
2-
SnCl6
-
Et
AlCl4
nPr
iPr
iPr
tBu
Ph
nPr
iPr
SnCl6
SnCl6
2-
2-
-
AlCl4
2-
SnCl6
-
-71.1
-59.8
-41.8
AlCl4
2-
biphep (24a)
biphep (25a)
SnCl6
SnCl6
2-
a Labels A and B relate to the structures in Fig. 4 and have no relation to the description of the spin system as AA¢XX¢.
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Table 5 31P NMR spectroscopic data for diphosphane dichlorides and related compounds
Diphosphane dichloride
PA, ppm
PB, ppm
2JP–P, Hz
Chloro-cation
P, ppm
Ref.
Diphosphane
P, ppm
Ref.
Me2PA(Cl)CH2PBMe2
Cy2PA(Cl)CH2PBCy2
Ph2PA(Cl)CH2PBPh2
96.5
108.0
73.5
-47.6
-9.7
-26.2
72
59
79
Me3PCl+
Cy3PCl+
90.0
104.2
78.1
29
30
30
Me2PCH2PMe2
Cy2PCH2PCy2
Ph2PCH2PPh2
-53.5
-8.9
-20.4
2
2
Ph2EtPCl+
Scheme 4 The synthesis of cyclic tetraphosphonium ions (4P) with AlCl3.
20a, 21a and 21b) the spectra were insufficiently well-resolved for
a full analysis to be carried out.
In the AlCl3 reactions, the formation of 15b, 16b, 17b, 18b,
19b and 21b was accompanied by the diphosphane dichloride
(Scheme 4b), since pairs of doublets were apparent in the 31P
NMR spectra, one at a higher frequency for the phosphorus
bound to chlorine and one at a lower frequency near to the
shift of the diphosphane itself. The results are given in Table
5, with average shifts and coupling constants for each of the
diphosphane dichlorides. Data for similar species, both chloro-
cations and diphosphanes, are included for comparison. For
23b only, the tetrachloride formed (Scheme 4a), as shown by
a single 31P resonance at 108.2 ppm; this compares well with
the value of 109.9 ppm reported previously for this compound.7
We therefore conclude that under our conditions the preferred
oxidation product of the diphosphane is the dichloride, except
for depe, which may well be the most readily oxidised of these
diphosphanes and leads to the tetrachloride.
Fig. 5 The crystal and molecular structure of the dication 16b. The two
AlCl4 counter-ions and CHCl3 molecule have been omitted for clarity.
-
Crystals suitable for X-ray diffraction of the dications 16b and
19a were obtained and their molecular structures determined at
low temperature (Fig. 5 and 6, respectively). For each compound,
selected bond distances and angles are presented in Table 6. The
ADPs are drawn at 50% probability.
Table 6 Selected bond distances and angles for compounds 16b and 19a
16b
19a
-
molecular structure of 16b contains two AlCl4 counter-ions and
one molecule of CHCl3 within the unit cell, whereas within the unit
cell of 19a there are two half molecules of SnCl6 as counter-ions
for the dication and no solvent.
˚
P1–P2 (A)
2.2055(17)
2.2045(18)
2.1904(17)
1.790(5)
1.855(5)
99.23(7)
2.2056(14)
2.2044(15)
2.1907(15)
1.854(5)
1.872(5)
99.27(6)
2-
˚
P2–P3 (A)
˚
P3–P4 (A)
˚
˚
P2–C (A)
The molecular structure of a 4P dication derived from dppm,
EtPCl2 and SnCl2 has previously been reported, where the unit
P3–C (A)
P1ŸP2ŸP3(◦◦)
2-
P2ŸP3ŸP4( )
96.68(6)
96.69(5)
cell contains one SnCl6 counter-ion for the dication and two
molecules of CHCl3.4 19a is a solvatomorph of this literature com-
pound, without the two CHCl3 molecules; they show differences in
the orientations of the substituents on the four phosphorus atoms,
Fig. 7.
The P–P bond lengths in both 16b and 19a are typical values
for normal P–P single bonds (Table 6) and are similar to
those found in the 3P dications,3 other 4P dications4 and those
reported for other compounds containing four linked phosphorus
atoms.31–37
(c) Investigating the relative stabilities of 3P and 4P dications
3P and 4P dications are often formed in competing reactions. The
proposed mechanism of formation for both 3P and 4P dications
is shown in Scheme 5. The first step, attack of a phosphorus atom
of the diphosphane on one R¢PCl2 molecule, is assumed to be
identical for the formation of both 3P and 4P rings. For the
3P species to form, ring closure must then occur. Alternatively,
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Table 8 Preferential formation of a 3P or 4P product
Diphosphane
R2P(CH2)nPR2
3P ring size
4P ring size
Product
n = 1
n = 2
n = 3
n = 4
4
5
6
7
5
6
7
8
4P preferred
3P, 4P
3P only
3P, 4P
parameters are very similar to those reported previously for the
acyclic intermediate in the formation of a 3P species,7 though in
the present case the 4P dication is preferentially formed. The main
difference, however, is that 2J and 3J coupling are apparent in this
instance because of the close proximity of the phosphorus atoms.
A marked preference is observed for formation of a 3P or
4P product, depending on relative ring size (Table 8). For a
diphosphane where n = 1, giving rise to a 4-membered ring for
the 3P dication or a 5-membered ring for the 4P dication, the
latter is preferred, which is in keeping with normal stabilities for
aliphatic or alicyclic rings. Where n = 2, both possible products are
frequently seen, showing that both 5- and 6-membered rings are
stable. When n = 3, we have never detected a 4P product under our
experimental conditions, the 3P 6-membered ring clearly being
more stable than the potential 4P 7-membered ring. With larger
rings, however, a mixture of 3P and 4P dications is again found,
suggesting that there is little difference in stability between 7- and
8-membered rings.
Fig. 6 The crystal and molecular structure of the dication 19a. Only
the major component is shown and the two half molecules of SnCl6
as counter-ions have been omitted for clarity. ADPs are drawn at 50%
probability.
2-
Conclusions
We have shown that the formation of new cyclic dications
with three (3P) or four (4P) linked phosphorus atoms and a
hydrocarbon backbone is possible in several systems, from reaction
of a diphosphane R2P(CH2)nPR2 with one or two moles of a
chlorophosphane R¢PCl2, in the presence of either AlCl3 or SnCl2
to act as a halide acceptor. Although the synthesis of 4P species
involves a redox step, the presence of an additional reducing agent,
such as SnCl2, is not essential, since the diphosphane starting
material may itself act as a reducing agent.
Fig. 7 Overlap of the dications 19a and the previously reported
solvatomorph.
Formation of the 3P dication is favoured when a six-membered
ring results and the corresponding 4P species has not been
observed under our experimental conditions. The 4P derivative
is favoured when its ring is five-membered, although some 3P
analogues were detected under favourable conditions. For the cases
where the 3P species is a five- or seven-membered ring, both 3P
and 4P dications were detected in most instances, showing that
their rings are of comparable stability. Direct alkylation of cyclic
triphosphenium ions to form 3P dications is a feasible preparative
route for small R¢ groups only.
addition of a second molecule of R¢PCl2 can take place (redox
step) at the previously added phosphorus atom to afford an
unsymmetrical monocationic intermediate, as shown previously
by NMR studies.4 Ring closure can then occur to afford the 4P
dication.
In support of the proposed mechanism, the first intermediate
I (Scheme 5) was detected by 31P NMR spectroscopy from the
reactions of dppm with EtPCl2 and iPrPCl2 (Table 7). The NMR
Table 7 31P NMR spectroscopic data for dppm intermediates (I) where R¢ = Et or iPr
R¢
PA, ppm
PB, ppm
PC, ppm
1JP–P, Hz
2JP–P, Hz
3JP–P, Hz
Et
68.6
79.4
26.6
25.2
-27.8
-28.2
329
345
66
68
87
66
iPr
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Table 9 Quantities of reagents used
Quantity of
diphoshane
Quantity of
R¢PCl2
Quantity of
SnCl2
Quantity of
AlCl3
Compound
number
Diphosphane
R¢ =
g
mmol
mL
mmol
g
mmol
g
mmol
1
dcypm
dmpe
nPr
Ph
Et
0.0394
0.0460
0.0286
0.0183
0.0092
0.0139
0.0196
0.0242
0.0300
0.0497
0.1372
0.0657
0.3306
0.0228
0.0268
0.0497
0.0419
0.0360
0.0394
0.0402
0.0503
0.0645
0.0577
0.0462
0.0493
0.0307
0.4037
0.0183
0.0183
0.10
0.30
0.07
0.035
0.017
0.025
0.036
0.044
0.052
0.12
0.34
0.17
0.83
0.07
0.20
0.12
0.10
0.09
0.10
0.10
0.13
0.17
0.15
0.12
0.13
0.08
1.96
0.035
0.035
0.013
0.18
0.10
0.29
0.10
0.071
0.038
0.051
0.032
0.046
0.22
0.28
0.68
0.33
1.69
0.19
0.22
0.28
0.10
0.27
0.10
0.10
0.28
0.51
0.30
0.33
0.39
0.16
1.96
0.069
0.071
—
—
—
—
—
—
0.0267
0.0816
0.0187
0.20
0.61
0.14
—
—
—
2
3
dcypp
biphep
cybiphep
cybiphep
cybiphep
cybiphep
dppdmx
dcypm
dppe
dppe
dppe
depp
dmpm
dcypm
dcypm
dcypm
dcypm
dcypm
dppm
dppm
dppm
dppm
dppm
dppm
depe
biphep
biphep
0.010
0.009
0.004
0.007
0.004
0.004c
0.020c
0.030
0.070
0.053
0.230
0.020
0.020
0.030
0.010
0.028
0.013
0.012
0.030
0.050
0.040
0.030
0.050
0.0257a
0.270
0.009
0.009
4
iPr
Et
0.0113
0.0064
0.0120
0.0254
0.014
0.040
0.0455
0.0906
0.0449
0.3204
0.0265
—
0.0325
—
0.0341
—
—
0.0512
—
0.060
0.034
0.063
0.134
0.073
0.21
0.24
0.68
0.34
1.69
0.14
—
0.24
—
0.18
—
—
0.27
—
—
—
—
—
5
6
nPr
iPr
Me
Me
Et
7
—
8
0.020b
0.020b
0.18b
0.18b
—
9
10
—
11
Et
—
—
—
—
0.0533
—
0.0267
—
0.0267
0.0267
—
0.0476
—
—
0.0356
—
0.5220
—
—
—
—
—
—
0.40
—
0.20
—
0.20
0.20
—
0.35
—
—
0.26
—
3.91
—
—
12
tBu
Ph
Et
13
14
15b
16a
16b
17a
17b
18b
19a
19b
20a
21a
21b
22a
23b
24a
25a
Et
Et
Et
nPr
nPr
iPr
Et
Et
nPr
iPr
iPr
tBu
Ph
nPr
iPr
0.0569
0.0460
—
0.0306
—
0.0137
0.0113
0.42
0.34
—
0.16
—
0.072
0.060
a RPCl2 is a solid so the quantity is in g. b Quantity of methyl triflate used, not AlCl3. c PCl3 used, not R¢PCl2.
Scheme 5 The proposed mechanism of formation for 3P and 4P dications.
grade were used, in general without further purification. The
31P NMR spectra of all phosphorus-containing starting materials
were recorded to verify that no impurities were present. 31P NMR
spectra were obtained on a Varian Mercury 400 Fourier-transform
spectrometer at 161.91 MHz; chemical shifts are referenced
to 85% H3PO4, with the high frequency direction taken as
positive.
Experimental
Synthesis
All manipulations, including NMR sample preparation, were
carried out either under an inert atmosphere of dry nitrogen
or in vacuo, using standard Schlenk line or glovebox (Saffron
Scientific) techniques. Chemicals of the best available commercial
1170 | Dalton Trans., 2012, 41, 1165–1172
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Table 10 Crystallographic data
3
6
16b
19a
Chemical formula
C29 H55 P3,
2(Al2 Cl5 O)
991.06
2(C39 H59 P3), Cl6 Sn,
8(C H Cl3), 2(Cl3 Sn)
2975.87
C29 H56 P4, C H Cl3,
2(Al Cl4)
985.55
monoclinic
C2/c
38.5425(12)
11.8925(4)
26.5378(9)
90
130.3910(10)
90
C29 H32 P4, Cl6 Sn
Formula weight
Crystal system
Space group
835.82
triclinic
triclinic
triclinic
¯
¯
¯
P1
P1
P1
˚
a/A
10.6187(5)
10.6364(5)
21.8815(11)
91.914(2)
94.314(2)
111.132(2)
2293.80(19)
2
10.5087(6)
15.1261(8)
20.8450(10)
72.928(2)
87.477(2)
72.386(2)
3015.3(3)
1
10.5532(8)
11.0978(8)
16.1102(12)
104.3190(10)
92.3670(10)
100.4550(10)
1790.4(2)
2
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
Volume/A
Z
9264.6(5)
8
Crystal size
Density/g cm-3
m/mm-1
0.06 ¥ 0.12 ¥ 0.14
0.17 ¥ 0.17 ¥ 0.19
0.27 ¥ 0.38 ¥ 0.42
0.15 ¥ 0.15 ¥ 0.20
1.435
1.638
1.413
1.550
0.816
0.0778
8111/1531/790
1.534
0.0894
12391/6/607
0.858
0.0760
12468/15/432
1.360
0.0379
8782/0/375
Rint
Data/restraints/
parameters
R1 [I > 2s(I)]
wR2 [I > 2s(I)]
R1 (all data)
wR2 (all data)
Goodness of fit
0.0463
0.1031
0.0810
0.1143
0.944
-0.775,0.763
0.0520
0.1090
0.1113
0.1301
0.981
-0.947,1.415
0.0348
0.0882
0.0472
0.0953
1.017
-0.860,0.966
0.0466
0.1009
0.0666
0.1085
1.037
-0.891,3.757
-3
˚
Drmin,max/e A
Example reactions are described below. All other reactions were
carried out using similar methods. The quantities of reagents used
are shown in Table 9. Crystals of 3, 6, 16b and 19a were obtained
by slow evaporation of solvent in an inert atmosphere.
flow N2 Cryostream cooling device.38 In each case, a series of
narrow w-scans (0.3◦) was performed at several j-settings to
maximise data coverage. Cell parameters were determined and
refined using the SMART software39 and raw frame data were
integrated using the SAINT program.40 The structures were solved
using direct methods41 and refined by full-matrix least-squares on
F2 using SHELXTL41 and the graphical user interface Olex2.42
Crystallographic data for compounds 3, 6, 16b and 19a are
listed in Table 10. Details of each refinement are given in the
crystallographic information file, including treatment of disorder
in compounds 3 and 19a.
Example reactions
Synthesis of 3. EtPCl2 (0.01 mL, 0.10 mmol) was added via
syringe to a solution of dcypp (0.0286 g, 0.07 mmol) and AlCl3
(0.018 g, 0.14 mmol) under a nitrogen atmosphere. A 31P NMR
spectrum was recorded soon after mixing.
Synthesis of 6. EtPCl2 (0.007 mL, 0.051 mmol) was added via
syringe to a solution of dcypm (0.0139 g, 0.025 mmol) and SnCl2
(0.0120 g, 0.063 mmol) under a nitrogen atmosphere. A 31P NMR
spectrum was recorded soon after mixing.
Acknowledgements
We would like to thank the EPSRC (UK) for research grant
EP/C536436/1 (MRP), and for a research studentship (HJS),
and the Maria da Grac¸a Memorial Fund/Chemistry Department,
University of Durham (PKC), for financial support. We also thank
I. H. McKeag and C. F. Heffernan for their invaluable assistance
in recording some of the NMR spectra.
Synthesis of 16b. EtPCl2 (0.03 mL, 0.28 mmol) was added via
syringe to a solution of dcypm (0.0419 g, 0.10 mmol) and AlCl3
(0.026 g, 0.20 mmol) under a nitrogen atmosphere. A 31P NMR
spectrum was recorded soon after mixing.
Synthesis of 19a. 19a was isolated from the attempted syn-
thesis of a ‘mixed’ cyclic tetraphosphonium ion from reaction of
i
dppm, EtPCl2, PrPCl2 and SnCl2. EtPCl2 (0.01 mL, 0.11 mmol)
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