Influence of the functional group on the synthesis of aminophosphines, diphosphinoamines and iminobiphosphines

Article abstract of DOI:10.1039/b303645f

The reaction of the anilines RNH₂ [R = C₆H₄(o-CN), C₆H₄(p-CN), C₆H₄(m-CN), C₆H₄(o-C₆H₅), C₆F₅ and C₆H₄(o-CF₃)] with Ph₂PCl and inorganic or organic bases in differing stoichiometry and in different solvents has been studied. The electronic properties and steric effects of the substituent groups, the base employed, the stoichiometry and the solvent all influence the outcome of the reaction and a series of aminophosphines, diphosphinoamines and iminobiphosphines have been isolated and characterised. The structures of three diphosphinoamines and three iminobiphosphines have been established using single-crystal X-ray diffraction.

Full text of DOI:10.1039/b303645f

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Influence of the functional group on the synthesis of
aminophosphines, diphosphinoamines and iminobiphosphines
Zhaofu Fei, Rosario Scopelliti and Paul J. Dyson*
Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne,
EPFL-BCH, CH-1015 Lausanne, Switzerland. E-mail: paul.dyson@epfl.ch
Received 1st April 2003, Accepted 21st May 2003
First published as an Advance Article on the web 6th June 2003
The reaction of the anilines RNH2 [R = C6H4(o-CN), C6H4(p-CN), C6H4(m-CN), C6H4(o-C6H5), C6F5 and C6H4-
(o-CF3)] with Ph2PCl and inorganic or organic bases in differing stoichiometry and in different solvents has been
studied. The electronic properties and steric effects of the substituent groups, the base employed, the stoichiometry
and the solvent all influence the outcome of the reaction and a series of aminophosphines, diphosphinoamines and
iminobiphosphines have been isolated and characterised. The structures of three diphosphinoamines and three
iminobiphosphines have been established using single-crystal X-ray diffraction.
functionalised aminophosphines are mostly limited to ether
Introduction
and pyridyl derivatives.1 Since both steric and electronic effects
exerted by a functional group on the amine play a significant
role on the outcome of the reaction it is important to study
their effect in more detail. Recently, we described how the lithi-
ation of the functionalised amine C6H4(o-CN)NH2 1a, followed
by addition of Ph2PCl, afforded the aminophosphine C6H4-
(o-CN)NHPPh2 2a in high yield.11 During the course of our
research, we found in the same reaction the iminobiphosphine
While phosphine ligands with exclusively P–C bonds are the
most widely studied, aminophosphines, diphosphinoamines
and iminobiphosphines (Chart 1) have also attracted increasing
considerable attention. Interest in phosphines with P–N bonds
arises from the different electronic properties transferred by the
nitrogen centre to the phosphorus centre(s).1,2 A review describ-
ing the coordination chemistry of diphosphinoamines reveals a
burgeoning and exciting field,3 and further possibilities are
highlighted in a very recent review that describes diphosphines
with inorganic backbones more generally.4 Although imino-
biphosphines have also been known for many years,5 they have
not been studied to the same extent as aminophosphines and
diphosphinoamines, due to, at least in part, their relative instabil-
ity compared to aminophosphines and diphosphinoamines.6
C H (o-CN)N᎐PPh PPh 4a is also formed and it was possible
᎐
6
4
2
2
to isolate it. Compared to other anilines, the CN group exerts a
determining effect on the reactivity of the aminophosphine, as
evident from the reaction of the 2a with another equivalent of
Ph2PCl in the presence of triethylamine which gives the imino-
biphosphine 4a in nearly quantitative yield, instead of the
diphosphinoamine C6H4(o-CN)N(PPh)2 3a. The analogous
reaction of Ph2PCl with PhNHPPh2 gave only the diphos-
phinoamine PhN(PPh2)2. In this paper we expand on our earlier
studies by examining how both electronic and steric effects
influence the formation of aminophosphines, diphosphino-
amines and iminobiphosphines.
Results and discussion
In phosphorus chemistry, 31P NMR spectroscopy has been
widely used to monitor reactions, which allows the rapid
identification of products based on characteristic signals in the
spectrum.12 In general, arylaminodiphenylphosphines C6H4-
(o-R)NHPPh2 give rise to singlet resonances between 25 and 35
ppm [cf. 29.4 ppm in PhNH–PPh2,13 26.4 ppm in PyNH–PPh2
(Py = 2-pyridyl),1a 27.2 ppm in C6H4(o-OCH3)NH–PPh2,14 29.6
ppm in C6H4(o-PPh2)NH–PPh2 15]. Diphenylphosphinoamines
also exhibit a singlet resonance, but at higher frequency, typi-
cally around 64–70 ppm [cf. 67.7 ppm in PhN(PPh2)2,16 65.6
ppm in C6H4(o-OCH3)N(PPh2)2 17]. Iminobiphosphines display
Chart 1
Among the routes used to prepare aminophosphines and
diphosphinoamines, the most frequently used method involves
aminolysis of a phosphine chloride.7 The reaction of phosphine
chloride and the amine usually provides the target compound,
RNHPRЈ2 or RN(PRЈ2)2, in high yield. The HCl liberated from
the reaction forms a salt with an organic base, for example
triethylamine, which is insoluble in the reaction solvent, typi-
cally diethyl ether or thf, and therefore leads to facile separation
and purification of the product. It is possible to replace the
organic base with an inorganic base such as BunLi, Na or K,
which leads to deprotonation of the amine and formation of an
amide anion. The anion can subsequently be converted into an
aminophosphine8 or iminobiphosphine9 by reaction with a
phosphine chloride. In contrast to the aminolysis method, this
latter procedure using alkali bases has received little attention,
presumably due to the sensitivity of the intermediate and the
additional costs associated with such bases.
1
a distinctive AB system with a characteristic JP–P value of
ca. 220–290 Hz.5,9 Using these data, it is possible to rapidly
evaluate the products obtained from the reactions described
herein.
Reaction of the anilines 1(a–f) with BunLi and Ph2PCl in diethyl
ether
Alkali-metalated amide anions of type RNHM (R = alkyl, aryl,
M = Li, Na, K) are important precursors in organic synthesis.
Lithiated amines are the most common and many structures
have been elucidated by X-ray crystallography.18–20 However,
since many lithiated species are not very stable, even at low
temperature, the amide anions are often generated in situ and
The solid-state structures of aminophosphines and diphos-
phinoamines have been extensively studied.10 In contrast, full
structural characterisation of iminobiphosphine compounds is
rare.11 In addition, despite the availability of a wide range
of functionalised amine and related phosphorus compounds,
D a l t o n T r a n s . , 2 0 0 3 , 2 7 7 2 – 2 7 7 9
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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Table 1 Relative ratio of the products from the reaction of the anilines 1(a–f) with BunLi and Ph2PCl in 1 : 1 : 1 ratio in diethyl ether based on 31
NMR spectroscopy
P
1: RNH2
2: RNHPPh2 (%)
3: RN(PPh2)2 (%)
4: RN᎐P(PPh2)–PPh2 (%)
᎐
1a: C6H4(o-CN)NH2
1b: C6H4(p-CN)NH2
1c: C6H4(m-CN)NH2
1d: C6H4(o-Ph)NH2
1e: C6F5NH2
2a: 85
2b: 45
2c: 30
2d: 95
2e: 0
3a: < 1
3b: ∼5
3c: ∼ 5
3d: 0
4a: 15
4b: 50
4c: 65
4d: ∼5
4e: 100
4f: 35
3e: 0
1f: C6H4(o-CF3)NH2
2f: 65
3f: 0
converted into the desired product. Lithiation of the functional-
ised aniline C6H4(o-CN)NH2 1a using BunLi in diethyl ether
resulted in the precipitation of a solid, which was then reacted
with Ph2PCl. When no further reaction takes place, as evi-
denced by 31P NMR spectroscopy, the solvent and volatile
components were removed under vacuum. The resulting solid
was dissolved in thf and analysed by 31P NMR spectroscopy
which showed the presence of three compounds. A signal at
29.0 ppm with a relative intensity of ca. 85% can be assigned to
the aminophosphine C6H4(o-CN)NHPPh2 2a. About 15% of
4e was detected as the single phosphorus-containing product,
the aminophosphine C6F5NHPPh2 2e and the diphosphino-
amine C6F5N(PPh2)2 3e were not formed. Using the aniline
C6H4(o-CF3)NH2 1f the result is similar as from the reaction
from 1a, a high yield of the aminophosphine C6H4(o-CF3)-
NHPPh2 2f was found, whereas C H (o-CF )N᎐PPh –PPh
᎐
6
4
3
2
2
4f was formed in relatively low yield and the formation of
C6H4(o-CF3)N(PPh2)2 3f was not observed.
The diphosphinoamines 3 and iminobiphosphines 4 are pre-
sumably derived from aminophosphine anions (2X in Scheme
2), generated by deprotonation of the newly formed amino-
phosphine with the lithiated amine RNHLi. In the solution, 2X
can undergo a metatropism reaction into 2Y. There is a prece-
dent for this type of reaction and such intermediates have been
proposed previously.10b,21,22 It is not unreasonable to assume
that reaction of the 2X-type anion with Ph2PCl will give the
P–N–P product, whereas reaction of the 2Y-type anion with
the iminobiphosphine C H (o-CN)N᎐PPh –PPh 4a is present;
᎐
6
4
2
2
it gives rise to two sets of doublets at 7.5 ppm and Ϫ15.5 ppm
1
with a JP–P value of 262 Hz. There are also traces of the
diphosphinoamine C6H4(o-CN)N(PPh2)2 3a, tentatively charac-
terised on the basis of a singlet at 67.0 ppm, with a very low
relative intensity (less than 1%).
In an analogous reaction using the para-isomer C6H4-
(p-CN)NH2 1b, which exhibits a very similar electron with-
drawing effect, but is clearly of less steric hindrance than the
ortho-isomer 1a, the formation of the aminophosphine C6H4-
(p-CN)NHPPh2 2b is lower (ca. 45%), and the formation of the
Ph PCl will give the N᎐P–P product. Based on this hypothesis
᎐
2
the ratio of 2X and 2Y is clearly dependant on the substituent,
with electron withdrawing groups at the ortho-position stabilis-
ing the 2Y-type anion, thereby increasing ratio of the N᎐P–P
᎐
iminobiphosphine C H (p-CN)N᎐PPh –PPh 4b and diphos-
product, for example, C6F5NH2 affords exclusively the imino-
biphosphines product. It is also possible that the solubility of the
lithiated anilines contribute to the outcome of the reactions.
Addition of BunLi to the anilines 1a, 1b, 1c, 1d and 1f in diethyl
ether gives a suspension. The lithaited anilines are clearly
poorly soluble in diethyl ether. Only in the case of 1e a clear
᎐
6
4
2
2
phinoamine C6H4(p-CN)N(PPh2)2 3b is significantly higher
(ca. 50 and 5%, respectively). Using the meta-isomer C6H4-
(m-CN)NH2 1c as the starting material the amount of the
aminophosphine C6H4(m-CN)NHPPh2 2c decreased further to
about 30% and the quantity of the iminobiphosphine C6H4-
(m-CN)N᎐PPh –PPh 4c increased to ca. 65% compared to the
solution is formed, which gives the highest yield of the N᎐P–P
᎐
᎐
2
2
other isomers. Diphosphinoamine C6H4(p-CN)N(PPh2)2 3c is
formed in low yield. These reactions are summarised in Scheme
1 and the relative amounts of each product are listed in Table 1.
product 4e. A comparison of the reaction of 1a, 1b and 1c
indicates that steric influences also play a role. Steric hindrance
of the CN group at the ortho-position prevents further de-
protonation of the formed aminophosphine 2a; so that 2a is the
main product. A similar result is found for 1f. In the case of 1d,
the yield of N᎐P–P product is very low, maybe the electron
᎐
withdrawing effect is not appreciable and the steric hindrance
of the more bulky phenyl group is much higher than the smaller
CN group, so that the phenyl group prevents the deprotonation
at the nitrogen. In the case of 1e, there is no steric hinderance
and the electron withdrawing effect of the C6F5 group plays a
Scheme 1 Reactions of the anilines 1 with BunLi and Ph2PCl (1:1:1) in
diethyl ether.
dominant role, so that only N᎐P–P formation was observed.
᎐
Replacing the ortho-nitrile substituent by a phenyl group in
the starting material, viz. C6H4(o-C6H5)NH2 1d, results in the
formation of almost exclusively the aminophosphine C6H4-
In all cases, iminobiphosphines 4(a–f) could be isolated in
pure form with low-to-moderate yield, due to differences in
solubility of the other compounds. After removal of the solvent
from the reaction mixture, the solid residue is copiously washed
with diethyl ether removing both the aminophosphine, diphos-
phinoamine and any unreacted amine. The remaining solid con-
tains the iminobiphosphine 4(a–f) and LiCl, the latter of which
(o-C H )NHPPh 2d, only about 5% of C H (o-C H )N᎐PPh –
᎐
6
5
2
6
4
6
5
2
PPh2 4d is found and the formation of the diphosphinoamine
C6H4(o-C6H5)N(PPh2)2 3d is not observed. Starting from the
aniline 1e C F NH , the iminobiphosphine C F N᎐PPh –PPh
2
᎐
6
5
2
6
5
2
Scheme 2 Proposed intermediates leading to the formation of 3 and 4.
D a l t o n T r a n s . , 2 0 0 3 , 2 7 7 2 – 2 7 7 9
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Table 2 Relative ratio of the products from the reaction of the anilines 1(a–f) with Ph2PCl and Et3N in 1 : 1 : 1 ratio in dichloromethane based on
31P NMR spectroscopy
1: RNH2
2: RNHPPh2 (%)
3: RN(PPh2)2 (%)
4: RN᎐PPh2–PPh2 (%)
᎐
1a: C6H4(o-CN)NH2
1b: C6H4(p-CN)NH2
1c: C6H4(m-CN)NH2
1d: C6H4(o-Ph)NH2
1e: C6F5NH2
2a: ∼5
2b: 65
2e: 90
2d: 100
2e: 0
3a: 10
3b: 35
3c: 10
3d: 0
3e: 25
3f: 0
4a: 85
4b: 0
4c: 0
4d: 0
4e: 75
4f: 100
1f: C6H4(o-CF3)NH2
2f: 0
Table 3 Relative ratio of the products from the reaction of the anilines
1(a–f) with Ph2PCl and Et3N in 1 : 2 : 2 ratio in dichloromethane based
on 31P NMR spectroscopy
could be isolated with CH2Cl2, affording a highly pure product.
Among the iminobiphosphines 4(a–f), only 4e is highly soluble
in diethyl ether, and separation from the free amine is possible
by recrystallisation at low temperature with 4e crystallising first
from the solution. Only the aminophosphine products 2a and
2d could be isolated in high yield. Recrystallisation of 2b results
in a pure product, but the yield is low. However, isolation of the
other aminophosphines 2c and 2f is not straightforward as the
reaction product also contains unreacted anilines which have
similar solubilities to aminophosphines in common solvents. It
was not possible to isolate any of the diphosphinoamines 3a, 3b
and 3c in pure form, and 3b and 3c are better prepared by the
reaction of the anilines with two equivalents of Ph2PCl in the
presence of two equivalents of triethylamine (see below).
1: RNH2
3: RN(PPh2)2 (%)
4: RN᎐PPh2–PPh2 (%)
᎐
1a: C6H4(o-CN)NH2
1b: C6H4(p-CN)NH2
1c: C6H4(m-CN)NH2
1d: C6H4(o-Ph)NH2
1e: C6F5NH2
3a: ∼5
3b: 98
3c: 100
3d: 98
3e: 20
3f: 0
4a: 95
4b: ∼2
4c: 0
4d: ∼2
4e: 80
4f: 100
1f: C6H4(o-CF3)NH2
Reaction of anilines 1(a–f) with Ph2PCl in the presence of Et3N
in a 1 : 1 : 1 ratio in dichloromethane
In dichloromethane the reaction between the anilines 1(a–f)
and Ph2PCl in the presence of triethylamine is fast and all the
reaction products are soluble. Again, the relative percentage of
the various products was estimated using 31P NMR spectro-
scopy and the results are summarized in Table 2.
Reaction of C6H4(o-C6H5)NH2 1d with Ph2PCl in the presence of
Et3N in 1 : 1 : 1 and 1 : 2 : 2 ratio in diethyl ether
Aminolysis is the standard method used to prepare amino-
phosphines and diphosphinoamines. For example, the ether
functionalized aniline C6H4(o-OCH3)NH2 reacts with Ph2PCl
in the presence of triethylamine to give C6H4(o-OCH3)-
Reaction of 1a with one equivalent of Ph2PCl in the presence
of one equivalent of triethylamine affords the iminophosphine
4a as the main product, although both 2a and 3a are also
formed in low yield. Interestingly, with 1b and 1c, formation of
iminobiphosphines 4b and 4c was not observed, whereas for 1d,
formation of the aminophosphine 2d, is quantitative, and 3d
and 4d were not observed. Under the same conditions, 1e gave
both 3e and 4e, with 4e being the main product. In the case of
1f, the iminobiphosphine 4f is the only phosphorus containing
product, formation of 2f and 3f was not observed. In general,
isolation of the products is difficult since the 1 : 1 : 1 reaction
does not give high selectivity and some unreacted amine con-
taminates the reaction mixture. The only synthetically useful
reaction is that of 1d which affords 2d in quantitative yield.
Although isolation of 4a, 4e and 4f is also possible, they can be
prepared in higher yield in a 1 : 2 : 2 reaction with Ph2PCl and
Et3N in dichloromethane (see below).
14
17
NHPPh2 or C6H4(o-OCH3)N(PPh2)2 in high yield, depend-
ing on stoichiometry. However, the method cannot be
generalised for all anilines as our earlier results show that
iminobiphosphines can be obtained as the major product, if an
appropriate functional group is present. Additionally, the
choice of solvent is also very important in determining the
outcome of the reaction.
In diethyl ether the reaction of the anilines 1(a–f) with
Ph2PCl in the presence of triethylamine (1 : 1 : 1 molar ratio) is
very slow. The reaction of C6F5NH2 1e with Ph2PCl was moni-
tored by 31P NMR spectroscopy at room temperature which
showed that less than 10% of Ph2PCl had reacted after one
week. The resulting spectrum also showed that apart from the
formation of the aminophosphine 2e, the diphosphinoamine 3e
and iminobiphosphine 4e were also present. The only syn-
thetically useful reaction is that of 1d with Ph2PCl, since this
reaction gave the iminobiphosphine 4d in higher yield in a
reasonable time.
Reaction of anilines 1(a–f) with Ph2PCl in the presence of Et3N
in a 1 : 2 : 2 ratio in dichloromethane
If 1d is allowed to react with Ph2PCl in the presence of tri-
ethylamine in a 1 : 1 : 1 ratio in diethyl ether, all three products
2d, 3d and 4d form, as evidenced by two singlet resonances at
29.95 and 67.0 ppm representing 2d and 3d, respectively, and
In dichloromethane, the products from the reaction of the
analines 1(a–f) with two equivalents of Ph2PCl in the presence
of two equivalent triethylamine are simpler than in the 1 : 1 : 1
reaction. While the formation of aminophosphines 2 can be
avoided, there is still competition between the formation of
diphosphinoamines 3 and iminobiphosphines 4. In the case of
1a, the iminobiphosphine 4a is formed as the main product,
with 3a formed in very low yield. In contrast, 1b and 1d react to
form the diphosphinoamines 3b and 3d as the major products,
with 4b and 4d observed only in low yield. Starting with 1c
under the same condition, diphosphinoamine 3c was obtained
in quantitative yield. In the case of 1e, both 3e and 4e are
formed, with the 4e being the main product, which can be
isolated by recrystallisation. In the case of 1f the imino-
biphosphine 4f is obtained in near quantitative yield. These
results are summarised in Table 3.
1
two doublets at 1.60 and Ϫ14.00 ppm with a J(P–P) value
260.0 Hz which correspond to 4d. Isolation of 4d is possible.
After washing the reaction mixture with a large amount of di-
ethyl ether, 4d can be isolated in ca. 35% yield by washing the
remaining solid with thf. When the ratio of 1d : Ph2PCl : NEt3
is changed from 1 : 1 : 1 to 1 : 2 : 2, 4d is obtained in higher
yield, ca. 65%, but 3d can also be isolated in about 35% yield.
Separation of 3d and 4d is relatively facile since 3d is soluble in
diethyl ether whereas 4d is essentially insoluble. After washing
the reaction mixture with diethyl ether, the remaining yellow
solid contains triethylamine hydrochloride and the imino-
biphosphine 4d. The iminobiphosphine 4d could be isolated in
pure form following washing with thf. Reactions of other
anilines under the same conditions were too slow and not
investigated further.
From the above results, it is clear that reaction of aniline with
Ph2PCl using triethylamine as base is very different to that
using the inorganic base. Since triethylamine is a much weaker
D a l t o n T r a n s . , 2 0 0 3 , 2 7 7 2 – 2 7 7 9
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base than the lithiated aniline, deprotonation of the amino-
phosphine is less efficient, so that the formation of the
diphosphinoamine 3 or iminobiphosphine 4 takes place via the
aminophosphine 2. However, aminophosphines can undergo
prototropism reactions,9a,23 so that in solution 2 can exist
in equilibrium together with the iminophosphine isomer 2Ј as
shown in Scheme 3. Reaction of 2 with Ph2PCl gives the
diphosphinoamine 3, whereas reaction of 2Ј with Ph2PCl
affords the iminobiphosphine 4.
Scheme 3 Prototropism of aminophosphine 2.
The aminolysis route is synthetically useful when carried
out in dichloromethane, affording diphosphinoamines 3 and
iminobiphosphine 4, when the appropriate stoichiometry of
reagents is used. The formation of the two different products is
determined by the steric and electronic properties of the func-
tional group. Essentially, the greater the steric hindrance and
the greater the electron-withdrawing effect of the substituent at
the ortho-position of the aniline, the greater the yield of the
iminobiphosphine 4. This is clearly demonstrated by the reac-
tion of 1a and 1f (both ortho-substituted) with two equivalents
of Ph2PCl and triethylamine, which both gave near quantitative
yields of iminobiphosphines 4a and 4f, respectively. In contrast,
in 1b and 1c, the meta- and para-isomers of 1a, the diphos-
phinoamines 3b and 3c are the major products. The electron-
withdrawing effect of the phenyl group in 1d is comparatively
weak, despite the bulky phenyl ring at the ortho-position, and
the diphosphinoamine 3d is still the main product. In the case
of 1e, although the C6F5 is a very strong electron-withdrawing
group there is no steric hindrance, so both 3e and 4e are formed.
The new bidentate diphosphinoamines 3b, 3c and 3d and the
iminobiphosphines 4e and 4f can be isolated in high yield,
whereas 3a and 3e are formed in very low yield and are their
synthesis is not viable by this route.
Fig. 1 Molecular structure of 3b in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–N1, 1.732(3); P2–N1, 1.723(3), N1–C1,
1.434(4); N2–C7, 1.151(5); P2–N1–P1, 114.49(14).
Fig. 2 Molecular structure of 3c in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–N1, 1.746(2); N1–P1A, 1.746(2), N1–C1,
1.449(6); N2–C7, 1.138(8); P1–N1–P1A, 112.7(2). Letter A indicates
the following symmetry transformation: x, Ϫy Ϫ 1/2, z.
Structural characterisation of the diphosphinoamines 3b, 3c, 5
and aminobiphosphines 4b, 4e and 4f
Both 3b and 3c form good quality crystals from diethyl ether at
room temperature suitable for X-ray determination. In the case
of compound 3d we have been able to determine the connec-
tivity, though the refinement of the structure is of low quality
and therefore not reported. Crystals of iminobiphosphines 4b
and 4f suitable for X-ray determination were obtained from
dichloromethane and diethyl ether; the latter crystallised with
a CH2Cl2 solvate. Crystals of 4e were obtained by cooling a
diethyl ether solution at Ϫ22 ЊC. In addition, the structure of
the known diphosphinoamine PhN(PPh2)2,16 the prototype of
the series of compounds described herein, is reported for
comparison purposes.
There are surprisingly very few X-ray structures of free
diphosphinoamines known, compared to their transition metal
complexes. Even the structure of the well studied ligand
PhN(PPh2)2 5 has not been structurally investigated (Fig. 3). We
therefore synthesised this diphosphinoamine according to the
literature method,16 to study the X-ray structure. The solid state
structures of 3b, 3c and 5 are shown in Figs. 1–3 with key
parameters given in the captions. The molecular symmetry for
3b, 3c and 5 is different, 3b shows no symmetry, 3c lies on a
crystallographic mirror plane and it has Cs symmetry, whereas 5
lies on two-fold axis showing then a C2 symmetry. In 3b, 3c and
5 the two lone electron pairs point to the same direction. The
P(1)–N(1)–P(2) angles in all the three compounds are slightly
different with 5 having the longest C1–N1 distance. The C1–N1
Fig. 3 Molecular structure of 5 in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–N1, 1.7315(15); N1–P1A, 1.7315(15);
N1–C1, 1.455(4); P1–N1–P1A, 113.37(14). Letter A indicates the
following symmetry transformation: Ϫx, y, Ϫz ϩ 1/2.
distances in 3b and 3c are only marginally different to 5 despite
the electron-withdrawing effect of CN group at the para and
meta position on the phenyl ring.
D a l t o n T r a n s . , 2 0 0 3 , 2 7 7 2 – 2 7 7 9
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Although many N᎐P–P compounds are known, the first
together with key parameters listed in the caption. There are
᎐
structure, 4a, of this family was published only recently.11 The
solid-state structures of 4b, 4e and 4f of are shown in Figs. 4–6
close similarities in the solid structures of 4b, 4e and 4f with 4a.
In all cases, the two Ph2P group bonded to P1 are trans to those
on P2. All the P1–N1, P1–P2 and N1–C1 distances in 4b, 4e and
4f are very close to that found in 4a. The difference of the
different steric and electron-withdrawing effect seems to have
only minimum effect on the structural parameters in the solid
state. Additionally, the C1–N1–P1 and N1–P1–P2 angles in 4b
and 4f are also within the range found in 4a. However, in 4e,
there is π–π interaction between C6F5 ring and one of the
phenyl rings bonded to P2 (C19 ؒ ؒ ؒ C24), the distance between
the two centroids is 3.628(3) Å. As the result, the C1–N1–P1
angle is larger and the N1–P1–P2 angle is smaller than in 4a, 4b
and 4f.
Concluding remarks
We have studied the reaction of a series of functionalised
anilines with Ph2PCl using different bases, stoichiometries and
solvents. A series of aminophosphines, diphosphinoamines and
iminobiphosphines were isolated. In all the reactions, the out-
come of the final products strongly depends on the steric and
electronic effect of the functional group attached to the aniline
starting material. All the functionalised iminobiphosphine
ligands show somewhat unusual properties towards small mole-
cules, such as H2O, H2O2, S8, and transition metal complexes
leading to cleavage of the P–P bond or rearrangement from
Fig. 4 Molecular structure of 4b in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–P2, 2.2451(16); P1–N1, 1.572(5); N1–C1,
1.382(7); N2–C31, 1.140(7); C4–C31, 1.446(8); N1–P1–C7, 115.1(3);
N1–P1–P2, 121.68(17); C1–N1–P1, 131.3(4).
N᎐P–P to P–NH or P–N–P. These results will be reported in
᎐
due course.
Experimental
All manipulations were performed under an inert atmosphere
of dry nitrogen using standard Schlenk techniques. Anilines
1(a–f), BunLi, Ph2PCl and Et3N were purchased from Aldrich
chemicals and used as received. Solvents were dried using the
appropriate reagents and distilled prior to use. NMR spectra
were obtained at 20 ЊC with a Bruker DMX 200 instrument
1
using SiMe4 for H and 85% H3PO4 for 31P as external stand-
ards. For the 31P NMR spectra of the reaction mixture, a C6D6
capillary was used as a lock. With the reaction of lithiated
anilines with Ph2PCl, the 31P NMR spectra were recorded
after removal of all the solvents and re-dissolving the resulting
solid in a large amount of thf until a clear solution formed. For
the final identification, CDCl3 was used as the NMR solvent.
ESI-MS spectra were recorded on a ThermoFinnigan LCQ
Deca XP Plus quadrupole ion trap instrument.24 Samples were
infused directly into the source at 5 µL minϪ1 using a syringe
pump. The spray voltage was set at 5 kV and the capillary tem-
perature at 50 ЊC. The MS detector was tuned automatically on
the base peak, which optimized the remaining parameters.
Elemental analysis was carried out by the Institute of Molec-
ular and Biological Chemistry at the EPFL.
Fig. 5 Molecular structure of 4e in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–P2, 2.2379(16); P1–N1, 1.571(3); N1–C1,
1.371(4); N1–P1–C7, 118.17(14); N1–P1–P2, 117.82(11); C1–N1–P1,
135.2(2).
Reaction of aniline C6H4(o-CN)NH2 1a with BunLi and Ph2PCl,
synthesis of 2a and 4a
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol)
was added slowly to a solution of C6H4(o-CN)NH2 1a (2.36 g,
20.0 mmol) in 50 ml of diethyl ether at Ϫ78 ЊC. The resulting
suspension was allowed to warm to Ϫ20 ЊC over 30 min and
Ph2PCl (4.41 g, 20.0 mmol) was added. The reaction mixture
was stirred at room temperature for 30 min and then filtered
and washed with diethyl ether (3 × 20 ml). From the diethyl
ether filtrate large crystals of 2a were obtained on cooling to
Ϫ22 ЊC. The solid was washed with dichloromethane (3 ×
30 ml). The dichloromethane filtrates were collected and the
solvent was removed in vacuum. The resulting solid was
recrystallised from dichloromethane and diethyl ether to give
the product 4a. Yield: 0.24 g, 5% (based on Ph2PCl). For
spectroscopic chracterisation of 1a and 4a see ref. 11.
Fig. 6 Molecular structure of 4f in the solid-state. Key bond lengths
(Å) and angles (Њ) include: P1–P2, 2.2498(18); P1–N1, 1.578(3); N1–C1,
1.385(5); N1–P1–C7, 113.98(17); N1–P1–P2, 122.49(14); C1–N1–P1,
132.2(3).
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Reaction of aniline C6H4(p-CN)NH2 1b with BunLi and Ph2PCl,
synthesis of 2b and 4b
Reaction of aniline C6F5NH2 1e with BunLi and Ph2PCl,
synthesis of 4e
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol) was
slowly added to a solution of C6F5NH2 1e (3.66 g, 20.0 mmol)
in 50 ml of diethyl ether at Ϫ78 ЊC. The resulting solution was
allowed to warm to Ϫ20 ЊC over 30 min and Ph2PCl (4.41 g,
20.0 mmol) was added. The reaction mixture was stirred at
room temperature for 30 min and then filtered and washed with
diethyl ether (3 × 20 ml). The combined ether filtrates were
concentrated to about its ¼ volume and cooled at Ϫ22 ЊC
overnight. Crystals formed from the solution and were collected
by filtration to give the product 4e. Yield: 3.03 g, 55%. Mp 122
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol)
was slowly added to a solution of C6H4(p-CN)NH2 1b (2.36 g,
20.0 mmol) in 50 ml of diethyl ether at Ϫ78 ЊC. The result-
ing suspension was allowed to warm to Ϫ20 ЊC over 30 min
and Ph2PCl (4.41 g, 20.0 mmol) was added. The reaction
mixture was stirred at room temperature for 30 min and then
filtered and washed with diethyl ether (3 × 20 ml). From
the diethyl ether filtrates 2b was obtained on repeated recrystal-
lisation in diethyl ether (three times). Yield: 0.60 g, 10%. Mp
142 ЊC. 1H NMR: δ 8.00–6.90 (m, 14H, aromatic H), 4.90
(br signal, 1H, NH), ppm. 31P NMR: δ 29.30 (s) ppm. ESI-MSϩ:
m/z 303 [M ϩ H]ϩ. Anal. Calc. for C19H15N2P: H, 5.00; C 75.49;
N, 9.27. Found: H, 5.09, C, 75.58, N, 9.25%. The remaining
solid was then washed with dichloromethane (3 × 30 ml). The
dichloromethane filtrates were collected and solvent was
removed in vacuum. The solid was recrystallised from di-
chloromethane and diethyl ether to give the product 4b as
1
ЊC. H NMR: δ 8.25–7.15 (m, aromatic H) ppm; 31P NMR:
1
δ 10.05 (d), Ϫ14.50 (d, JP–P = 266.5 Hz) ppm. ESI-MSϩ: m/z
552 [M ϩ H]ϩ. Anal. Calc. for C30H20F5NP2: H 3.66, C 65.34, N
2.54. Found H 3.68, C 65.42, N 2.53%.
Reaction of aniline C6H4(o-CF3)NH2 1f with BunLi and Ph2PCl,
synthesis of 4f
1
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol)
was slowly added to a solution of C6H4(o-CF3)NH2 1f (3.22 g,
20.0 mmol) in 50 ml of diethyl ether at Ϫ78 ЊC. The resulting
suspension was allowed to warm to Ϫ20 ЊC over 30 min and
Ph2PCl (4.41 g, 20.0 mmol) was added. The reaction mixture
was stirred at room temperature for 30 min and then filtered
and washed with diethyl ether (3 × 10 ml). The remaining solid
was washed with dichloromethane (3 × 30 ml). The dichloro-
methane filtrates were collected and solvent was removed in
vacuum The solid was washed again with diethyl ether (3 ×
10 ml) and then recrystallised from dichloromethane and di-
ethyl ether to give the product 4f. Yield: 2.38 g, 45%. Mp 126
colourless crystals. Yield: 1.70 g, 35%. H NMR: δ 8.05–6.85
1
(m, aromatic H) ppm; 31P NMR: δ 7.50 (d), Ϫ15.65 (d, JP–P
=
264.0 Hz) ppm ESI-MSϩ: m/z 487 [M ϩ H]ϩ. Anal. Calc. for
C31H24N2P2: H 4.97, C 76.54, N 5.76. Found H 5.01, C 76.60, N
5.61%.
Reaction of aniline C6H4(m-CN)NH2 1c with BunLi and Ph2PCl,
synthesis of 4c
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol)
was slowly added to a solution of C6H4(m-CN)NH2 1c (2.36 g,
20.0 mmol) in 50 ml of diethyl ether at Ϫ78 ЊC. The resulting
suspension was allowed to warm to Ϫ20 ЊC over 30 min and
Ph2PCl (4.41 g, 20.0 mmol) was added. The reaction mixture
was stirred at room temperature for 30 min and then filtered
and washed with diethyl ether (3 × 20 ml). The remaining solid
was washed with dichloromethane (3 × 30 ml). The dichloro-
methane filtrates were collected and solvent was removed in
vacuum. The resulting solid was recrystallised from dichloro-
methane and thf to give the product 4c. Yield: 2.48 g, 51%. Mp
143 ЊC. 1H NMR: δ 8.10–6.80 (m, aromatic H) ppm; 31P NMR:
δ 7.50 (d), Ϫ15.00 (d, 1JP–P = 263.0 Hz) ppm. ESI-MSϩ: m/z 487
[M ϩ H]ϩ. Anal. Calc. for C31H24N2P2: H 4.97, C 76.54, N 5.76.
Found: H 5.03, C 76.62, N 5.55%.
1
ЊC. H NMR: δ 8.05–6.65 (m, aromatic H) ppm; 31P NMR:
δ 5.35 (d), Ϫ17.20 (d, 1JP–P = 265.5 Hz) ppm. ESI-MSϩ: m/z 530
[M ϩ H]ϩ. Anal. Calc. for C31H24F3NP2: H 4.57, C 70.32, N
2.65. Found H 4.59, C 70.43, N 2.64%.
The 1 : 1 : 1 reaction of aniline 1d with Ph2PCl/Et3N in diethyl
ether, synthesis of 4d
To a solution of C6H4(o-C6H5)NH2 1d (1.69 g, 10.0 mmol) and
triethylamine (1.02 g, 10.0 mmol) in 50 ml diethyl ether Ph2PCl
(2.21 g, 10.0 mmol) was added at room temperature in one
portion. The reaction mixture was stirred 4 days and then
filtered. The yellow solid was washed firstly with diethyl ether
(3 × 20 ml) and then thf (3 × 20 ml). The thf filtrates were
collected. Removal of the solvent gave the compound 4d. Yield:
0.94 g, 35% (based on Ph2PCl).
Reaction of aniline C6H4(o-C6H5)NH2 1d with BunLi and
Ph2PCl, synthesis of 2d and 4d
The reagent BunLi (12.5 ml, 1.6 M in hexane, 20.0 mmol)
was slowly added to a solution of C6H4(o-C6H5)NH2 1d (3.38 g,
20.0 mmol) in 50 ml of diethyl ether at Ϫ78 ЊC. The result-
ing suspension was allowed to warm to Ϫ20 ЊC over 30 min
and Ph2PCl (4.41 g, 20.0 mmol) was added. The reaction
mixture was stirred at room temperature for 30 min and then
filtered and washed with diethyl ether (3 × 20 ml). The diethyl
ether filtrates were collected and the solvent was removed
in vacuum. The resulting oil was washed with cold diethyl
ether (3 × 5 ml) at Ϫ22 ЊC to give the product of 2d as an
off-white oil. Yield: 5.30 g, 75%. 1H NMR: δ 5.80 (br
signal, 1H, NH), 8.00–7.40 (m, aromatic H) ppm. 31P NMR:
δ 30.5(s) ppm. ESI-MSϩ: m/z 354 [M ϩ H]ϩ. Anal. Calc.
for C24H20NP: H 5.70; C 81.57; N 3.96. Found: H 5.75, C
81.68, N 3.91%. The remaining solid was washed with di-
chloromethane (3 × 10 ml). The dichloromethane filtrates
were collected and solvent was removed in vacuum to give a
yellow solid. Washing this solid with diethyl ether (2 × 5 ml)
Under the same condition, the 1 : 1 : 1 reaction of 1a, 1b, 1c,
1e and 1f with Ph2PCl/Et3N in diethyl ether is too slow and was
not investigated further.
The 1 : 2 : 2 reaction of aniline 1d with Ph2PCl/Et3N in diethyl
ether, synthesis of 3d and 4d
To a solution of C6H4(o-C6H5)NH2 1d (1.69 g, 10.0 mmol) and
triethylamine (2.03 g, 20.0 mmol) in 50 ml diethyl ether Ph2PCl
(4.42 g, 20.0 mmol) was added at room temperature in one
portion. The reaction mixture was stirred one week and then
filtered. The yellow solid was washed firstly with diethyl ether
(3 × 20 ml) and then thf (3 × 20 ml). From the diethyl ether
filtrates 3d was obtained after removal of the solvent. Yield:
1.86 g, 35%. Mp 158 ЊC. 1H NMR: δ 8.35–7.35 (m, aromatic H)
ppm; 31P NMR: δ 68.20 (s) ppm. ESI-MSϩ: m/z 538 [M ϩ H]ϩ.
Anal. Calc. for C36H29NP2: H 5.44, C 80.43, N 2.61. Found H
5.48, C 80.47, N 2.59%. From the thf filtrate the compound 4d
was obtained after removal of the solvent. Yield: 3.48 g, 65%.
1
gave the product 4d. Yield: 0.10 g, 2%. Mp 148 ЊC. H NMR:
The 1 : 1 : 1 reaction of aniline 1d with Ph2PCl/Et3N in
dichloromethane, synthesis of 2d
δ 8.15–7.40 (m, aromatic H) ppm; 31P NMR: δ 1.60 (d), Ϫ14.00
(d, 1JP–P = 261.0) ppm. ESI-MSϩ: m/z 538 [M ϩ H]ϩ. Anal. Calc.
for C36H29NP2: H 5.44, C 80.43, N 2.61. Found: H 5.45, C
80.51, N 2.59%.
To a solution of 1d (1.69 g, 10.0 mmol) and triethylamine
(1.01 g, 10.0 mmol) in 50 ml dichloromethane Ph2PCl (2.21 g,
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Table 4 Crystal data and details of the structure determination for 3b, 3c, 4b, 4e, 4f and 5
3b
3c
4b
4e
4f
5
Chemical formula
Formula weight
Crystal system
Space group
C31H24N2P2
486.46
Monoclinic
P21/c
C31H24N2P2
486.46
Orthorhombic
Pnma
C31H24N2P2
486.46
Monoclinic
Cc
C30H20F5NP2
551.41
C32H26Cl2F3NP2
614.38
C30H25NP2
461.45
Monoclinic
C2/c
Triclinic
Triclinic
¯
¯
P1
P1
a/Å
b/Å
c/Å
α/Њ
11.397(4)
11.702(4)
18.829(3)
90
91.048(19)
90
2510.7(12)
4
1.287
16.8591(16)
17.3905(12)
8.7547(7)
90
90
90
2566.8(4)
4
1.259
15.778(3)
11.6783(16)
15.070(2)
90
112.375(15)
90
2567.8(7)
4
1.258
10.322(6)
10.871(4)
13.079(6)
108.49(4)
95.79(4)
110.44(4)
1266.7(10)
2
10.087(2)
10.647(5)
15.187(7)
82.05(4)
74.46(3)
67.64(3)
1452.0(10)
2
18.5448(16)
12.7369(11)
10.4063(8)
90
100.092(7)
90
2420.0(3)
4
1.267
β/Њ
γ/Њ
V/Å3
Z
Dc/g cmϪ3
1.446
1.405
F(000)
1016
0.196
1016
0.192
1016
0.192
564
0.230
632
0.377
968
0.198
µ/mmϪ1
T /K
λ/Å
140
0.71070
13933
4318
3263
4318/317
0.0708
0.2181
1.165
140
0.71073
14985
2343
1999
2343/172
0.0784
0.1488
1.292
140
0.71073
7264
3951
2905
3951/317
0.0663
0.1787
0.973
140
0.71070
7700
4197
2862
4197/344
0.0477
0.1373
1.004
140
0.71070
9435
4805
3330
4805/390
0.0748
0.2295
1.096
140
0.71073
6712
2017
1745
2017/151
0.0391
0.0959
1.147
Measured reflections
Unique reflections
Unique reflections [I > 2σ(I )]
Data/parameters
Ra [I > 2σ(I )]
wR2a (all data)
GoFb
2
a R = Σ||Fo| Ϫ |Fc||/Σ|Fo|, wR2 = {Σ[w(Fo2 Ϫ Fc2)2]/Σ[w(Fo )2]}1/2
.
b GoF = {Σ[w(Fo2 Ϫ Fc2)2]/(n Ϫ p)}1/2 where n is the number of data and p is the number
of parameters refined.
10.0 mmol) was added at 0 ЊC within 15 min. The reaction
mixture was then stirred for 30 min at r.t. and examined by 31
Ph2PCl (4.42 g, 20.0 mmol) at 0 ЊC within 15 min. The reaction
mixture was then stirred at room temperature for 30 min. After
removal of the dichloromethane solvents the remaining solid
was washed with diethyl ether (4 × 30 ml). All the filtrates were
collected and concentrated to about its ¼ volume. At Ϫ22Њ,
crystals formed and collected by filtration to give the product
4e. Yield: 2.75 g, 50%.
P
NMR spectroscopy which shows that the signals of Ph2PCl
disappeared and only one singlet at 30.20 ppm indicating 2d
had formed. After removal of the solvent the residue was
washed with diethyl ether (3 × 20 ml). Removal of the diethyl
ether gave the product 2d as greyish oil in pure form. Yield 3.47
g, 98%.
Under the same condition, the 1 : 1 : 1 reaction of 1a, 1b, 1c,
1e and 1f with Ph2PCl/Et3N in dichloromethane gave mixtures
and only investigated by 31P NMR spectra. Attempts to isolate
a pure product were not made.
The 1 : 2 : 2 reactions of 1a and 1f with Ph2PCl/Et3N in dichloro-
methane, synthesis of 4a and 4f
To a solution of C6H4(o-CN)NH2 1a (1.18 g, 10.0 mmol) and
triethylamine (2.02 g, 20.0 mmol) in dichloromethane (50 ml),
Ph2PCl (4.42 g, 20.0 mmol) was added at 0 ЊC over 15 min.
The reaction mixture was then stirred at room temperature for
30 min. After removal of the dichloromethane solvents the
resulting solid was washed with diethyl ether (3 × 10 ml). The
remaining solid was washed again with thf (4 × 30 ml). The thf
filtrates were collected. Removal of the thf gave the product 4a.
Yield: 4.52 g, 93%.
Starting from 1f C6H4(o-CF3)NH2 (1.61 g, 10.0 mmol)
and triethylamine (2.02 g, 20.0 mmol) and Ph2PCl (4.42 g,
20.0 mmol) in 50 ml dichloromethane following the same pro-
cedure as described above, 4f was obtained. Yield: 5.24 g, 99%.
The 1 : 2 : 2 reaction of anilines 1b, 1c and 1d with Ph2PCl/Et3N
in dichloromethane, synthesis of 3b, 3c and 3d
To a solution of C6H4(p-CN)NH2 1b (1.18 g, 10.0 mmol) and
triethylamine (2.02 g, 20.0 mmol) in dichloromethane (50 ml),
Ph2PCl (4.42 g, 20.0 mmol) was added at 0 ЊC within 15 min.
The reaction mixture was stirred 30 min at r.t.. After removal of
the dichloromethane solvents the residue was washed with di-
ethyl ether (4 × 30 ml). Removal of the solvent gave the product
3b as colourless solid. Yield 4.69 g. 96%. Mp 109 ЊC. 1H NMR:
δ 8.0–6.6 (m, aromatic H) ppm; 31P NMR: δ 68.50 (s) ppm
ESI-MSϩ: m/z 487 [M ϩ H]ϩ. Anal. Calc. for C31H24N2P2: H
4.97, C 76.54, N 5.76. Found H 4.99, C 76.58, N 5.61%.
Structural characterisation
Using the same procedure as described above, C6H4(m-
CN)NH2 1c (1.18 g, 10.0 mmol), triethylamine (2.02 g, 20.0
mmol) and Ph2PCl (4.42 g, 20.0 mmol) in 50 ml dichloro-
X-Ray measurements were performed on a 4-circle kappa
goniometer equipped with an Oxford Diffraction KM4
Sapphire CCD (3c, 4b, 5) and on a marresearch mar345 IPDS
(3b, 4e, 4f ) at 140 K. A summary of the crystallographic data
and the structure refinements is listed in Table 4 and relevant
geometrical parameters, including bond lengths and angles are
included into the figure captions. Data reduction was carried
out with CrysAlis RED, release 1.6.9.25 Absorption correc-
tion26 was applied to all data sets except for 3c. Structure
solution and refinement as well as molecular graphics and geo-
metrical calculations were performed for all structures with the
SHELXTL software package, release 5.1.27 The structures were
refined using the full-matrix least-squares on F 2 with all non-H
atoms anisotropically defined. H atoms were placed in calcu-
lated positions using the “riding model”. Some disorder prob-
lems have been encountered during the refinement of 4f. In this
1
methane yielded 3c. Yield: 4.81 g, 99%. Mp 99 ЊC. H NMR:
δ 8.05–6.60 (m, aromatic H) ppm; 31P NMR: δ 69.50 (s) ppm
ESI-MSϩ: m/z 487 [M ϩ H]ϩ. Anal. Calc. for C31H24N2P2: H
4.97, C 76.54, N 5.76. Found H 4.98, C 76.59, N 5.59%.
Using the same procedure as described above, C6H4(o-C6H5)-
NH2 1d (1.69 g, 10.0 mmol), triethylamine (2.02 g, 20.0 mmol)
and Ph2PCl (4.42 g, 20.0 mmol) in 50 ml dichloromethane
yielded 3d. Yield: 5.10 g, 95%.
The 1 : 2 : 2 reaction of aniline 1e with Ph2PCl/Et3N in
dichloromethane, synthesis of 4e
To a solution of C6F5NH2 1e (1.83 g, 10.0 mmol) and triethyl-
amine (2.02 g, 20.0 mmol) in 50 ml dichloromethane added
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7 (a) G. Ewart, A. P. Lane, J. McKechnie and D. S. Payne, J. Chem.
Soc. A, 1964, 1543; (b) A. P. Lane, D. A. Morton-Blake and
D. S. Payne, J. Chem. Soc. A, 1967, 1492.
8 D. Fenske, B. Maczek and K. Maczek, Z. Anorg. Allg. Chem., 1997,
623, 1113.
9 (a) H. Rossknecht and A. Schmidtpeter, Z. Naturforsch., Teil B,
1971, 26, 81; (b) H. Rossknecht, W. P. Lehman and A. Schmidtpeter,
Phosphorus, 1975, 5, 195.
case a disordered CH2Cl2 has been solved using the split model
[occupancy factor for site A = 0.763(5)] and fixing geometrical
parameters.
CCDC reference numbers 207371–207376.
See http://www.rsc.org/suppdata/dt/b3/b303645f/ for crystal-
lographic data in CIF or other electronic format.
10 For X-ray structures of aminophosphines in the solid state see ref. 1
and: (a) T. G. Wetzel, S. Dehnen and P. W. Roesky, Angew. Chem.,
Int. Ed., 1999, 38, 1086; (b) B. Eichhorn, H. Nöth and T. Seifert, Eur.
J. Inorg. Chem., 1999, 12, 2355.
Acknowledgements
We would like to thank the EPFL and the Swiss National
11 Z. Fei, R. Scopelliti and P. J. Dyson, Inorg. Chem., 2003, 42, 2125.
12 S. Berger, S. Braun and H.-O. Kalinowski, NMR-Spektroskopie von
Nichtmetallen, Band 3, 31P-NMR-Spektroskopie, Georg Thieme
Verlag, Stuttgart, New York, 1993.
13 W. Wiegräbe and H. Bock, Chem. Ber., 1968, 101, 1414.
14 A. D. Burrows, M. F. Mahon and M. T. Palmer, J. Chem. Soc.,
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