Complexation associated rearrangement of iminobiphosphines to diphosphinoamines

Article abstract of DOI:10.1016/j.ica.2005.09.058

The reaction of the iminobiphosphines RN{double bond, long}PPh₂-PPh₂, where R = C₆H₄(p-CN), C₆H₄(m-CN), C₆H₄(o-C₆H₅), C₆F₅ or C₆H₄(o-CF₃), with one molecular equivalent of M(cod)Cl₂ (M = Pd or Pt) results in a rearrangement of the N{double bond, long}P{single bond}P unit to the more commonly encountered P-N-P unit, forming mono-chelating complexes of general formula M{RN(PPh₂)₂}Cl₂. The related reaction of the same range of iminobiphosphines with Pt(cod)Cl₂ (but not Pd(cod)Cl₂) in 2:1 ratio affords complexes of general formula [Pt{RN(PPh₂)₂}₂]2Cl. All 15 complexes are isolated in moderate to high yield and they have been fully characterised by spectroscopic methods. Six complexes, viz. [M{C₆H₄(p-CN)N(PPh₂)₂}Cl₂], [M{C₆H₄(m-CN)N(PPh₂)₂}Cl₂] and [M{C₆H₄(o-C₆H₅)N(PPh₂)₂}Cl₂] (M = Pd and Pt), have been characterised in the solid state by single crystal X-ray diffraction analysis.

Full text of DOI:10.1016/j.ica.2005.09.058

Inorganica Chimica Acta 359 (2006) 2635–2643
www.elsevier.com/locate/ica
Complexation associated rearrangement of iminobiphosphines to
diphosphinoamines
*
Zhaofu Fei, Wee Han Ang, Dongbin Zhao, Rosario Scopelliti, Paul J. Dyson
Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
Received 16 August 2005; accepted 24 September 2005
Available online 23 November 2005
Dedicated to Professor Brian R. James on the occasion of his 70th birthday.
Abstract
The reaction of the iminobiphosphines RN@PPh2–PPh2, where R = C6H4(p-CN), C6H4(m-CN), C6H4(o-C6H5), C6F5 or C6H4(o-
CF3), with one molecular equivalent of M(cod)Cl2 (M = Pd or Pt) results in a rearrangement of the N@PAP unit to the more commonly
encountered P–N–P unit, forming mono-chelating complexes of general formula M{RN(PPh2)2}Cl2. The related reaction of the same
range of iminobiphosphines with Pt(cod)Cl2 (but not Pd(cod)Cl2) in 2:1 ratio affords complexes of general formula [Pt{RN(PPh2)2}2]2Cl.
All 15 complexes are isolated in moderate to high yield and they have been fully characterised by spectroscopic methods. Six complexes,
viz. [M{C6H4(p-CN)N(PPh2)2}Cl2], [M{C6H4(m-CN)N(PPh2)2}Cl2] and [M{C6H4(o-C6H5)N(PPh2)2}Cl2] (M = Pd and Pt), have been
characterised in the solid state by single crystal X-ray diffraction analysis.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: P-Ligands; Diphosphinoamines; Iminophosphines; X-ray crystal structures; Palladium complexes; Platinum complexes
1. Introduction
nation and hydroformylation reactions [7]. Much of the
recent research has focused on chiral systems [8], and func-
tionalised diphosphinoamines with, for example, addi-
tional nitrogen and oxygen donor centres [9].
Iminobiphosphines with PR2–PR2@NR0 backbones (I
in Chart 1) are isoelectronic to the oxobiphosphines with
PR2–PR2@O skeletons (II). They are also isomers of the
more commonly encountered diphosphinoamines (III) with
R2P–NR0–PR2 skeletons, and the transformation has been
shown to take place on coordination to transition metals
[1]. Similarly, oxobiphosphines can also rearrange on coor-
dination to a number of transition metals to give diphos-
phoxanes PR2–O–PR2 (IV), which act as bidentate
ligands [2]. Diphosphinoamines are widely used as ligands
[3], with the ability to chelate to various transition metal
centres [4,5], and such compounds have been reviewed in
detail [6]. Some diphosphinoamine complexes have been
evaluated as catalysts in, for example, asymmetric hydroge-
Although iminobiphosphines have also been known for
many years [10], they have not been studied to the same
extent as oxobiphosphines or diphosphinoamines, presum-
ably because they are generally less stable – some iminobi-
phosphines are even pyrophoric [11]. However, a series of
iminobiphosphines RN@PPh2–PPh2 (R = substituted phe-
nyl) recently prepared in our laboratory proved to be stable
[12,13], although the cleavage of the P–P bond takes place
in the presence of water, leading to the formation of
aminophosphines RNHPPh2 and the oxide derivative
RNH–P(O)Ph2 [1]. Since iminobiphosphines contain a
phosphorus(III) centre with a free lone pair of electrons
they should be able to complex to transition metal centres.
As yet, however, no such compounds have been isolated,
although recently, we reported a transition metal associ-
ated-rearrangement reaction from iminobiphosphine to
*
Corresponding author.
E-mail address: paul.dyson@epfl.ch (P.J. Dyson).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.09.058

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Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
Ph
Ph
Ph
Ph
N
R
P
R
R
R
P
R
R
N
M(cod)Cl2
- cod
Cl
Cl
P
P
M
R
P
P
R
P
N
R'
P
O
Ph Ph
Ph
Ph
R
I
R
II
R'
N
6 R = C6H4(p-CN), a M = Pd, b M = Pt
7 R = C6H4(m-CN), a M = Pd, b M = Pt
8 R = C6H4(o-Ph), a M = Pd, b M = Pt
9 R = C6F5, a M = Pd, b M = Pt
O
R
P
P
R
R
P
P
R
R
R
R
R
III
IV
Chart 1.
10 R = C6H4(o-CF3), a M = Pd, b M = Pt
Scheme 1. Reaction of iminobiphosphines 1–5 with M(cod)Cl2 (M = Pd
or Pt) in equimolar quantities.
diphosphinoamine [1]. In continuation of our ongoing pro-
gram in developing and exploring P–N based ligands and
their coordination chemistry [14], we report herein a series
of reactions between iminobiphosphines and palladium(II)
and platinum(II) complexes in which conversion to diph-
osphinoamines takes place. Based on spectroscopic studies,
we are able to comment further on the mechanism of the
N@PAP ! P–N–P rearrangement.
indicated by 31P NMR spectroscopy. The formation of
P–NH products and Ph2PCl during the reaction suggests
that on coordination of the iminobiphosphine to metal cen-
tre (Pd or Pt), an intermediate in which the intact iminobi-
phosphine coordinates to the Pd or Pt centre (labelled X in
Scheme 2) forms initially. This intermediate is presumably
short-lived, and rapidly rearranges to the diphosphino-
amine, which initially coordinates through just one phos-
phorus centre (Y in the Scheme) before yielding the final
product. Cleavage of the P–P bond in intermediate X
would lead to the formation of radicals, which could react
to form RN(PPh2)2, RHNPPh2 and Ph2PCl, as indicated
by the presence of signals at 65, 30 and 82 ppm in the 31P
NMR spectrum. In order to establish the source of the
chloride, all the reactions were repeated in a non-chlori-
nated solvent (thf) but Ph2PCl is always observed, indicat-
ing that the source of the chloride is most probably from
the transition metal–chloride starting material. Attempts
to quench the reaction in order to analyse the intermediates
in more detail failed.
2. Results and discussion
The reaction of the iminobiphosphines PPh2–PPh2@NR,
where R = C6H4(p-CN) (1), C6H4(m-CN) (2), C6H4(o-Ph)
(3), C6F5 (4) or C6H4(o-CF3) (5), with M(cod)Cl2 (M = Pd
or Pt, cod = cycloocta-1,5-diene) in equimolar quantities
affords compounds of formula [M{C6H4(p-CN)N(PPh2)2}-
Cl2] (Pd = 6a, Pt = 6b), [M{C6H4(m-CN)N(PPh2)2}Cl2]
(Pd = 7a, Pt = 7b), [M{C6H4(o-Ph)N(PPh2)2}Cl2] (Pd =
8a, Pt = 8b), [M{C6F5N(PPh2)2}Cl2] (Pd = 9a, Pt = 9b)
and [M{C6H4(o-CF3)N(PPh2)2}Cl2] (Pd = 10a, Pt = 10b),
(see Scheme 1).
All reactions were followed in situ by 31P NMR spectros-
copy, and in the case of the reactions with the palladium(II)
complex, the reaction takes place instantaneously at room
temperature in dichloromethane, and no evidence for the
formation of P–P–Pd intermediates was observed, even on
reducing the temperature to ca. ꢀ20 ꢁC. As an illustrative
example, the reaction of C6H4(p-CN)N@PPh2–PPh2 (1)
with Pd(cod)Cl2 in dichloromethane affords, apart from
the main signal at 36.0 ppm, corresponding to the forma-
tion of [Pd{C6H4(p-CN)N(PPh2)2}Cl2] (6a), three other sig-
nals at 68.5, 30.5 and 82.0 ppm with low relative intensities.
The former two signals probably correspond to the forma-
tion of the free ligands C6H4(p-CN)N(PPh2)2 and C6H4(p-
CN)NHPPh2, respectively, but due to the low quantity
present it was not possible to isolate the compounds respon-
sible for these signals. However, the frequencies of structur-
ally related compounds are similar (cf. C6H4(o-R)N(PPh2)2
64.0–69.0 ppm [13,15] and C6H4(o-R)NHPPh2 26.0–
31.0 ppm [13,16]). The signal at 82.0 ppm is tentatively
assigned to Ph2PCl [17].
The 31P NMR chemical shifts of the compounds 6–10
are in keeping with structurally related complexes [4,9],
and there does not appear to be a significant effect of the
substituent on the chemical shift. The JP–Pt values in com-
plexes 6b–10b are also normal, with only minor variations
compared to the structurally similar compounds [4,9].
The solubility of complexes 6–10 is generally quite poor
in common solvents such as diethyl ether, dichloromethane
or chloroform. However, six of the complexes, [M{C6H4(p-
CN)N(PPh2)2}Cl2] (Pd = 6a, Pt = 6b), [M{C6H4(m-CN)-
N(PPh2)2}Cl2] (Pd = 7a, Pt = 7b), [M{C6H4(o-Ph)-
N(PPh2)2}Cl2] (Pd = 8a, Pt = 8b), afford crystals from
solutions of dichloromethane–diethyl ether or chloro-
form–diethyl ether (whereas the other complexes form
powders under similar conditions). Complexes 9a, 9b, 10a
and 10b do not re-dissolve in CHCl3 or CH2Cl2 and are
only sparingly soluble in CH3CN. It is possible that the flu-
orous-groups are involved in strong hydrogen bonding
interactions in the solid state which hinders re-dissolution.
The solid state structures of 6a, 6b, 7a, 7b, 8a and 8b
have been established by single crystal X-ray diffraction.
The analogous reactions with Pt(cod)Cl2 result in same
by-products, viz. RN(PPh2)2, RNHPPh2 and Ph2PCl, as

Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
2637
R
N
R
Ph
Ph
Ph
Ph
Ph
M
Ph Ph
P
Ph
P
N
Cl
Cl
Cl
Cl
Cl
Cl
P
P
P
Ph
M
M
R
N
Ph
- cod
P
Ph Ph
X
Y
Ph
P.
Ph
P
[H, Cl]
+ Ph2P.
RN(PPh2)2 + RNHPPh2 + Ph2PCl
N.
R
N
R
Ph
Ph
Scheme 2. Proposed reaction mechanism of 1–5 with M(cod)Cl2 (M = Pd or Pt).
Table 1
Crystallographic data for 6a, 6b, 7a, 7b, 8a and 8b
6a
6b
7a
7b
8a
8b
Chemical formula
Fw
C33H28Cl6N2P2Pd C33H28Cl6N2P2Pt C32H26Cl4N2P2Pd C32H26Cl4N2P2Pt C36H29Cl2NP2Pd C39H32Cl11NP2Pt
833.61
orthorhombic
Pbcn
922.30
orthorhombic
Pbcn
748.69
monoclinic
P21/n
837.38
monoclinic
P21/n
714.84
triclinic
1161.64
triclinic
Crystal system
Space group
ꢀ
ꢀ
P1
P1
˚
a (A)
11.4007(8)
21.1544(14)
14.7294(10)
90
90
90
11.318(3)
21.213(3)
14.7099(9)
90
90
90
12.990(3)
14.7846(14)
17.130(3)
90
103.657(19)
90
12.9553(7)
14.8941(5)
17.2375(9)
90
104.105(5)
90
10.4419(6)
11.9054(9)
13.3373(10)
91.543(6)
109.875(6)
91.405(6)
1557.71(18)
2
12.0399(5)
13.8676(10)
13.9204(10)
82.787(6)
87.218(5)
77.646(5)
2251.9(3)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
3552.4(4)
4
3534.7(10)
4
3196.6(11)
4
3225.8(3)
4
Z
Dcalc (g cmꢀ3
F(000)
)
1.559
1.733
1.556
1.724
1.524
1.713
1672
1800
1504
1632
724
1136
l (mmꢀ1
)
1.090
4.541
1.041
4.806
0.897
3.869
Temperature (K)
140(2)
0.71073
20449
2995
140(2)
0.71073
19912
3030
140(2)
0.71073
18710
140(2)
0.71073
18234
140(2)
0.71073
9518
140(2)
0.71073
13484
˚
Wavelength (A)
Measured reflections
Unique reflections
5653
5382
4830
6992
Unique reflections [I > 2r(I)] 2466
2565
4086
4484
3844
6184
Number of data/restraints/
parameters
2995/6/221
3030/0/222
5653/0/371
5382/0/371
4830/0/380
6992/18/487
Ra [I > 2r(I)]
0.0379
0.0846
1.117
0.0808
0.1858
1.333
0.0591
0.1826
1.085
0.0224
0.0550
0.972
0.0288
0.0541
0.947
0.0485
0.1275
1.040
a
wR2 (all data)
Goodness-of-fitb
P
P
P
P
2
2
1=2
a
R = ||Fo| ꢀ |Fc||/ |Fo|, wR2 ¼ f ½wðF 2o ꢀ F c2Þ ꢁ= ½wðF o2Þ ꢁg
.
P
2
1=2
b
Goodness-of-fit ¼ f ½wðF 2o ꢀ F 2c Þ ꢁ=ðn ꢀ pÞg where n is the number of data and p is the number of parameters refined.
Crystal data and details of the structure determination are
summarised in Table 1 and their structures are shown in
Figs. 1–3 together with key bond parameters summarised
in Tables 2 and 3.
There are close similarities between the solid state
structures of 6–8 with all the compounds having the same
overall features, viz. a chelating P–N–P ligand and two
chloride ligands forming a square planar geometry. The
M–P bond distances and M–Cl bond distances are typical
for such compounds [4,9]. Notably, larger P1–M–P2
angles are observed in the platinum complexes compared
to the palladium complexes, while smaller Cl1–M–Cl2
angles are found for each pair of the diphosphinoamine–
metal complexes. The larger P1–M–P2 angles required
for the platinum complexes originate from the greater size
of the platinum centre, as compared to palladium. Conse-
quently, the phenyl groups on the diphosphinoamine
ligands bonded to the platinum centres are spread out
more widely, resulting in greater steric interactions with
the chloro ligands and smaller Cl–M–Cl angles. The
metal–ligand bond parameters for the complexes are com-
pared in Table 2.
The different substituents on the amino-phenyl rings
also affect the planarity of the trigonal P1–N1–(C13)–P2

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Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
Fig. 1. ORTEP representation of 6a (left) and 6b (right); thermal ellipsoids are drawn at 50% equiprobability envelopes, with hydrogen atoms as spheres
of arbitrary diameter. C and H atoms are not labelled for clarity and solvent molecules are also omitted.
Fig. 2. ORTEP representation of 7a (left) and 7b (right); thermal ellipsoids are drawn at 50% equiprobability envelopes, with hydrogen atoms as spheres
of arbitrary diameter. C and H atoms are not labelled for clarity and solvent molecules are also omitted.
Fig. 3. ORTEP representation of 8a (left) and 8b (right); thermal ellipsoids are drawn at 50% equiprobability envelopes, with hydrogen atoms as spheres
of arbitrary diameter. C and H atoms are not labelled for clarity and solvent molecules are also omitted.

Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
2639
Table 2
Key metal–ligand bond parameters in 6a, 6b, 7a, 7b, 8a and 8b
˚
˚
Ligand
M–Pave (A)
M–C1ave (A)
P1–M–P2 (ꢁ)
Cl1–M–Cl2 (ꢁ)
6a
6b
C6H4(p-CN)N(PPh2)2
2.2211(8)
2.201(3)
2.3667(8)
2.352(3)
72.62(4)
73.38(14)
95.18(4)
91.23(15)
7a
7b
C6H4(m-CN)N(PPh2)2
2.219(3)
2.212(2)
2.355(3)
2.360(2)
72.29(5)
72.77(3)
95.31(5)
92.03(3)
8a
8b
C6H4(o-phenyl)N(PPh2)2
2.216(2)
2.117(4)
2.360(2)
2.353(4)
72.23(3)
72.95(7)
92.39(3)
91.84(7)
Table 3
Key bond parameters of iminophosphine ligands in 6a, 6b, 7a, 7b, 8a and 8b
N1–C13a (A)
˚
P1–N1–P2 (ꢁ)
P1ꢂ ꢂ ꢂP2 (A)
d(N1)b (A)
R(N1)c (ꢁ)
˚
˚
˚
P–Nave (A)
1
1.727(6)
1.715(2)
1.733(10)
1.434(4)
1.434(5)
1.400(19)
114.49(14)
100.1(2)
98.7(7)
6a
6b
2.631
2.630
0.000
0.000
359.96
360.10
2
1.746(2)
1.706(8)
1.713(6)
1.449(6)
1.440(7)
1.445(4)
112.7(2)
100.2(2)
99.99(13)
7a
7b
2.618
2.625
0.076
0.093
359.30
358.99
8a
8b
a
1.735(5)
1.712(12)
1.458(4)
1.460(10)
97.70(13)
99.9(3)
2.613
2.621
0.311
0.156
348.60
357.10
C13 refers to the C-atom on the phenyl ring adjacent to the N1-atom.
d(N1) refers to the perpendicular distance of the N1-atom from the plane formed by P1, P2 and C13 atoms. The distances were measured using CCDC
b
Mercury 1.4 [18].
c
R(N1) refers to the total angular displacement about the N1-atom subtended by the P1, P2 and C13 atoms.
moieties in the coordinated diphosphinoamine complexes
(Table 3). This is in keeping with our previous observations
based on complexes derived from C6H4(o-CN)N@PPh2–
PPh2 [1a], and other functionalised diphosphinoamine
complexes [4,9]. In a planar environment, N1 would lie
within the plane formed by P1, P2 and C13 and the angles
subtended at N1 by P1, P2 and C13 should sum up to 360ꢁ,
as observed in 6a and 6b. In 7a and 7b, the displacement
distances of N1 from planarity are significantly larger,
Since all the complexes discussed here are derived from
N@P–P ligands following a rearrangement reaction, it
makes little sense to compare the structural features
between the complexes and the N@P–P ligands before
and after coordination. However, since the P–N–P ligands
[C6H4(p-CN)N(PPh2)2, C6H4(m-CN)N(PPh2)2] have also
been analysed by X-ray [13], it is worth comparing the
effect of coordination on the structural features on the
P–N–P ligand. The bond lengths of the C„N group are
only marginally different from the parent ligand. Notably,
the average P–N distances in complexes 6a, 7a and 7b are
˚
0.076 and 0.093 A, respectively, and the total angular dis-
placements about N1 are slightly lower than 360ꢁ, i.e.,
359.30ꢁ and 358.99ꢁ, respectively. However, the largest
deviations were observed in complexes derived from imino-
phosphine, 3. In 8a and 8b, the displacement distances are
˚
1.715(2), 1.706(8) and 1.713(6) A, respectively, which are
somewhat shorter than in the free diphosphinoamine
˚
ligands derived from 1 and 2 [1.727(6) and 1.746(2) A,
˚
0.311 and 0.156 A, respectively, while the total angular dis-
respectively]. In addition, despite coordination of the phos-
phorus centres to the transition metal, the N1–C13 distance
placements about N1 are only 348.60ꢁ and 357.10ꢁ, indicat-
ing significant deviation from planarity. A plausible
explanation for these structural differences is the participa-
tion of the amino-phenyl group in the p-delocalisation
framework between the P1–N1–P2 atoms. For 6a and 6b,
the amino-phenyl rings were oriented such that they are
coplanar to the trigonal P1–N1–(C13)–P2 moieties, while
in 7a, 7b, 8a and 8b, the amino-phenyl rings are almost per-
pendicular. Therefore, it is possible that in 6a and 6b,
extended delocalisation within the P1–N1–[C6H4(p-CN)]–
P2 system is present, stabilising the planar framework,
which is not present in 7a, 7b, 8a and 8b. In addition for
8a and 8b, the bulky o-phenyl groups create further steric
hindrances resulting in greater deviations.
˚
˚
˚
in 6a 1.434(5) A, 7a 1.440(7) A and 7b 1.445(4) A, remains
essentially unchanged compared to the corresponding par-
˚
ent ligands, i.e., 1.434(4) and 1.449(6) A. In 6b, however,
the reverse was observed, i.e., the average P–N distance
˚
[1.733(10) A] remains unchanged while the N1–C13 dis-
˚
tance [1.400(19) A] is significantly smaller. The most signif-
icant changes are observed in the P–N–P angles. In the
diphosphinoamine ligands derived from 1 and 2, the
P–N–P angles are 114.49(14)ꢁ and 112.70(2)ꢁ, respectively.
In order to accommodate the transition metal centres,
these angles are reduced to between 98ꢁ and 100ꢁ in 6a,
6b, 7a and 7b, corresponding to a 10% decrease in angular
displacement between the P1–N1 and P2–N1 bonds.

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Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
Not surprisingly, the nature of the crystal packing of 6a,
are air stable in the solid state and in solution, the cationic
complexes 6c–10c are very sensitive to moisture, decompos-
ing to the mono-chelating complexes 6b–10b. The other
components from the decomposition are the appropriate
aminophosphine RNHPPh2 and Ph2P(O)H, as evidenced
by 31P NMR spectroscopy. Complexes 6c–10c are reason-
ably soluble in common solvents such as dichloromethane,
chloroform and acetonitrile. Crystals of 6c and 7c have
been obtained from a dichloromethane–diethyl ether solu-
tion upon cooling to 0 ꢁC, unfortunately the quality of the
crystals was not adequate for single crystal X-ray diffrac-
tion analysis.
6b, 7a, 7b, 8a and 8b in the solid state is strongly dependent
on the nature of the substituent attached to the diphosph-
inoamine ligand, rather than transition metal. For 6a and
6b, both complexes are packed into the orthorhombic lat-
tice with the Pbcn space group, for 7a and 7b the mono-
clinic lattice with the P21/n space group, and 8a and 8b
the triclinic lattice with the P1 space group (Table 1).
The presence of the dichloromethane (or chloroform) sol-
vate appears to have little influence on the structural motif
and such solvates in related molecules are not uncommon
[14,19].
The reaction of [Pt(cod)Cl2] with two equivalents of the
iminobiphosphines 1–5 affords the cationic platinum com-
plexes [Pt{C6H4(p-CN)N(PPh2)2}2]2Cl (6c), [Pt{C6H4(m-
CN)N(PPh2)2}2]2Cl (7c), [Pt{C6H4(o-Ph)N(PPh2)2}2]2Cl
(8c), [Pt{C6F5N(PPh2)2}2]2Cl (9c) and [Pt{C6H4(o-
CF3)N(PPh2)2}2]2Cl (10c), as the major products (Scheme
3). The analogous reaction with [Pd(cod)Cl2] leads to the
formation of 6a–10a and unreacted starting materials
along with some impurities. Cationic platinum(II) com-
plexes with two diphosphinoamine ligands have been pre-
pared previously from diphosphinoamine ligands [20].
The reaction of [Pt(cod)Cl2] with two molar equivalents
Unlike the reaction of 1–5 with [Pt(cod)2Cl2] in 2:1 ratio,
by which the bis-chelating complexes are formed as main
products, the 2:1 reaction with [Pd(cod)2Cl2] is somewhat
more complicated. The 31P NMR spectra of all the reaction
mixtures in dichloromethane contain several signals in the
ranges 25.0–45.0 and 64.0–67.0 ppm as well as a peak at
81 ppm. Following recrystallization, only the mono-chelat-
ing products 6a–10a could be isolated in low yield.
2.1. Concluding remarks
The transition metal mediated rearrangement of imino-
biphosphines (N@P–P) to diphosphinoamines (P–N–P) has
been described in some detail. This kind of rearrangement
is analogous to the transformation from O@P–P to P–O–P,
and has potential use in synthesis of chelating and bis-che-
lating transition metal complexes, since not all diphosphi-
noamines are available [13] using the commonly used
synthetic methods.
of
the
diphosphinoamines
C6H4(p-CN)N(PPh2)2,
C6H4(m-CN)N(PPh2)2 or C6H4(p-Ph)N(PPh2)2 in dichloro-
methane gave quantitatively the bis-chelating complexes
6c–8c. In each case, the 31P NMR spectrum of the reaction
mixture gave rise to only a singlet with characteristic P–Pt
satellites. The products isolated from the reaction using
iminobiphosphines 1, 2 or 3 as starting materials gave iden-
tical signals, however, impurities similar to those observed
in the 1:1 reactions were also present. The yield is thus
correspondingly lower compared to the reaction with the
P–N–P ligands, even when the reaction is conducted in a
non-chlorinated solvent such as thf. It is not unreasonable
to assume that the formation of 6c–10c follows a similar
mechanism as illustrated above in Scheme 2.
3. Experimental
All manipulations were performed under an inert atmo-
sphere of dry nitrogen using standard Schlenk techniques
using solvents dried using the appropriate reagents and dis-
tilled prior to use. Iminobiphosphines 1–5 were prepared
according to the previously published method [13]. NMR
spectra were obtained at 20 ꢁC on a Bruker DMX 200
The d 31P chemical shift of complexes 6c–10c lies within
the range of related known complexes [1a,20], with similar
JP–Pt values. Compared to 6(a and b)–10(a and b), which
1
instrument using SiMe4 for H and 85% H3PO4 for 31P
as external standards. ESI-MS spectra were recorded on
a ThermoFinnigan LCQꢂ Deca XP Plus quadrupole ion
trap instrument using the literature procedure [21]. Samples
were infused directly into the source at 5 lL minꢀ1 using a
syringe pump. The spray voltage was set at 5 kV and the
capillary temperature at 50 ꢁC. Elemental analysis was car-
ried out at the EPFL.
2+
Ph Ph
P
Ph
Ph
Ph
Ph
Ph
N
N
M(cod)Cl2
- cod
P
P
Pt
N
R
2Cl-
2
R
P
P
R
P
Ph Ph
Ph
Ph
Ph
1 - 5
6c: C6H4(p-CN)
7c: C6H4(m-CN)
8c: C6H4(o-Ph)
9c: C6F5
3.1. Reaction of 1–5 with Pd(cod)Cl2 in a 1:1 mole ratio,
synthesis of 6a–10a
A typical procedure. Pd(cod)Cl2 (14.3 mg, 0.05 mmol) in
dichloromethane (5.0 ml) was added to a solution of 1–5
(0.05 mmol) in dichloromethane (5.0 ml) at 0 ꢁC. After
the addition was complete, the reaction mixture was
allowed to warm to room temperature. The reaction was
10c: C6H4(o-CF3)
Scheme 3. Reaction of iminobiphosphine 1–5 with Pt(cod)Cl2 in 2:1 ratio.

Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
2641
followed by 31P NMR spectroscopy which showed that the
starting material had been consumed after 5 min. After this
time the reaction was stopped, the solvent was removed
under reduced pressure and thf or diethyl ether (2.0 ml)
was added and the sample was stored at 2 ꢁC. After 24 h
the precipitate that had formed was collected by filtration.
Crystals of 6a, 7a and 8a suitable for X-ray diffraction
analysis were grown from a solution of dichloromethane–
diethyl ether at ꢀ21 ꢁC.
formed after cooling the sample at 0 ꢁC for 1–2 days was
collected by filtration and washed with diethyl ether
(2 · 2.0 ml). Crystals of 6b and 7b suitable for X-ray dif-
fraction analysis were grown from a solution of dichloro-
methane–diethyl ether solution at ꢀ21 ꢁC, and crystals of
8b were grown from a solution of chloroform–diethyl
ether.
3.2.1. [Pt{C6H4(p-CN)N(PPh2)2}Cl2] (6b)
Yield: 72%; m.p. 249 ꢁC. 1H NMR (ppm in CDCl3): 6.60–
8.10 (m, aromatic H); 31P NMR (ppm in CDCl3): 22.41 (s,
1J(PPt) = 3342.82 Hz), ESI-MS m/z: 751 [M + H]+. Anal.
Calcd for C31H24Cl2N2P2Pt: H 3.21, C 49.48, N 3.72; Found:
H 3.28, C 49.64, N 3.66%.
3.1.1. [Pd{C6H4(p-CN)N(PPh2)2}Cl2] (6a)
Yield: 70%; m.p. > 285 ꢁC (decomp.). 1H NMR (ppm in
CD2Cl2): 6.65–8.15 (m, aromatic H); 31P NMR (ppm in
CD2Cl2): 36.07 (s), ESI-MS m/z: 662 [M + H]+, Anal. Calc.
for C31H24Cl2N2P2Pd: H, 3.64; C, 56.09; N, 4.22. Found:
H, 3.67; C, 56.50; N, 4.18%.
3.2.2. [Pt{C6H4(m-CN)N(PPh2)2}Cl2] (7b)
Yield: 69%; m.p. 270 ꢁC. 1H NMR (ppm in CDCl3): 6.65–
8.15 (m, aromatic H); 31P NMR (ppm in CDCl3): 23.69 (s,
1J(PPt) = 3350.25 Hz), ESI-MS m/z: 751 [M + H]+. Anal.
Calc. for C31H24Cl2N2P2Pt: H, 3.21; C, 49.48; N, 3.72.
Found: H, 3.26; C, 49.59; N, 3.67%.
3.1.2. [Pd{C6H4(m-CN)N(PPh2)2}Cl2] (7a)
1
Yield: 61%; m.p. > 285 ꢁC. H NMR (ppm in CD2Cl2):
6.65–8.20 (m, aromatic H); 31P NMR (ppm in CD2Cl2):
37.85 (s), ESI-MS m/z: 662 [M + H]+. Anal. Calc. for
C31H24Cl2N2P2Pd: H, 3.64; C, 56.09; N, 4.22. Found: H,
3.66; C, 56.41; N, 4.15%.
3.2.3. [Pt{C6H4(o-C6H5)N(PPh2)2}Cl2] (8b)
1
Yield: 71%; m.p. > 285 ꢁC. H NMR (ppm in CD2Cl2):
3.1.3. [Pd{C6H4(o-C6H5)N(PPh2)2}Cl2] (8a)
1
6.65–8.15 (m, aromatic H); 31P NMR (ppm in CD2Cl2):
26.52 (s, 1J(PPt) = 3371.04 Hz), ESI-MS m/z: 801
[M + H]+. Anal. Calc. for C36H29Cl2NP2Pt: H, 3.64; C,
53.81; N, 1.74. Found: H, 3.73; C, 53.92; N, 1.76%.
Yield: 75%; m.p. 275 ꢁC (decomp.). H NMR (ppm in
CDCl3): 6.60–8.25 (m, aromatic H); 31P NMR (ppm in
CDCl3): 39.99 (s), ESI-MS m/z: 712 [M + 1]+. Anal. Calc.
for C36H29Cl2NP2Pd: H, 4.09; C, 60.48; N, 1.96. Found: H,
4.13; C, 60.53; N, 1.91%.
3.2.4. [Pt{C6F5N(PPh2)2}Cl2] (9b)
1
Yield: 52%; m.p. > 285 ꢁC. H NMR (ppm in CD2Cl2):
3.1.4. [Pd{C6F5N(PPh2)2}Cl2] (9a)
1
6.65–8.15 (m, aromatic H); 31P NMR (ppm in CD2Cl2):
31.14 (s, 1J(PPt) = 3392.61 Hz), ESI-MS m/z: 815
[M + H]+. Anal. Calc. for C30H20Cl2F5NP2Pt: H, 2.47; C,
44.08; N, 1.71. Found: H, 2.74; C, 44.21; N, 1.69%.
Yield: 62%; m.p. > 285 ꢁC. H NMR (ppm in CDCl3):
6.80–8.30 (m, aromatic H); 31P NMR (ppm in CDCl3):
45.0 (s), ESI-MS m/z: 727 [M + 1]+. Anal. Calc. for
C30H20Cl2F5NP2Pd: H, 2.77; C, 49.44; N, 1.92. Found:
H, 2.80; C, 49.53; N, 1.89%.
3.2.5. [Pt{C6H4(o-CF3)N(PPh2)2}Cl2] (10b)
Yield: 58%; m.p. > 285 ꢁC.1H NMR (ppm in CDCl3):
3.1.5. [Pd{C6H4(o-CF3)N(PPh2)2}Cl2] (10a)
1
6.65–8.15 (several multiples, aromatic H); 31P NMR
1
Yield: 61%; m.p. 220 ꢁC. H NMR (ppm in CD3CN):
(ppm in CDCl3): 25.50 (s, J(PPt) = 3350.0 Hz), ESI-MS
6.65–8.15 (m, aromatic H); 31P NMR (ppm in CD3CN):
44.80 (s), ESI-MS m/z: 703 [M + 1]+. Anal. Calc. for
C31H24Cl2F3NP2Pd: H 3.42, C 52.68, N 1.98; Found: H
3.49, C 52.73, N 2.00%.
m/z: 793 [M + H]+. Anal. Calc. for C31H24Cl2F3NP2Pt:
H, 3.04; C, 46.81; N, 1.76. Found: H, 3.08; C, 46.92; N,
1.73%.
3.3. Reaction of 1–5 with Pt(cod)Cl2 in a 2:1 mole ratio,
synthesis of 6c–10c
3.2. Reaction of 1–5 with Pt(cod)Cl2 in a 1:1 mole ratio,
synthesis of 6b–10b
A typical procedure. Pt(cod)Cl2 (18.7 mg, 0.05 mmol) in
dichloromethane (5.0 ml) was added to a solution of 1–5
(0.10 mmol) in dichloromethane (5.0 ml) at 0 ꢁC. After
the addition was complete, the reaction mixture was
allowed to warm to room temperature and stirred for
4 h. The 31P NMR spectra of the reaction mixture showed
that the starting materials have been consumed. The sol-
vent was then removed under reduced pressure and the
remaining solid was washed with diethyl ether
(3 · 5.0 ml). The collected solid was suspended in diethyl
A typical procedure. Pt(cod)Cl2 (17.2 mg, 0.05 mmol) in
dichloromethane (5.0 ml) was added to a solution of 1–5
(0.05 mmol) in dichloromethane (5.0 ml) at 0 ꢁC. After
the addition was complete, the reaction mixture was
allowed to warm to room temperature and stirred for
30 min. The solvent was removed under reduced pressure
and the solid residue was washed with diethyl ether
(2 · 5.0 ml). To the solid, dichloromethane (2.0 ml) and
diethyl ether (10.0 ml) were added. The precipitate that

2642
Z. Fei et al. / Inorganica Chimica Acta 359 (2006) 2635–2643
ether (10.0 ml) and dichloromethane (2.0 ml) was added.
The samples were placed in a freezer at ꢀ21 ꢁC. The solid
formed after 1–2 days was collected by filtration.
3. The CIF files have been deposited with the Cambridge
Crystallographic Data Centre, CCDC Nos. 281091–
281096. Copies of these information may be obtained free
of charge via www.ccdc.cam.ac.uk/data_request/cif.
3.3.1. [Pt{C6H4(p-CN)N(PPh2)2}2 Æ 2Cl] (6c)
1
Yield: 63%; m.p. > 285 ꢁC. H NMR (ppm in CDCl3):
Acknowledgement
6.60–8.10 (m, aromatic H); 31P NMR (ppm in CDCl3):
1
34.73 (s, J(PPt) = 2438.43 Hz); ESI-MS+ m/z 1166 [cat-
We thank the EPFL, Roche Research Foundation and
the Swiss National Science Foundation for financial
support.
ion]+. Anal. Calc. for C62H48Cl2N4P4Pt: H, 3.90; C,
60.10; N, 4.52. Found: H, 3.95; C, 60.14; N, 4.46%.
3.3.2. [Pt{C6H4(m-CN)N(PPh2)2}2 Æ 2Cl] (7c)
1
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