Coordination properties of novel hemilabile acetamide-derived P,O phosphine ligands. Crystal structures of Ph2PNHC(O)Me and [PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][O3SCF 3]

Article abstract of DOI:10.1039/b002386h

Cationic methyl Pd(n) complexes are described in which the new heterofunctional phosphine ligands Ph₂PNHC(O)Me 1 or Ph₂PN(Me)C(O)Me 3 behave as rigid and/or hemilabile P,O chelates. The chelating ability of 3 is higher than that of 1 and both are compared to that of other P,O ligands, such as the keto- and amido-phosphines Ph₂PCH₂C(O)Ph and Ph₂PCH₂C(O)NPh₂, respectively. The crystal structure of 1 reveals the presence in the solid-state of an intermolecular hydrogen-bonded network N-H ... O and that of [PdMe{PPh₂NHC(O)Me} {PPh₂NHC(O)Me}][O₃SCF₃] 12b establishes the presence of both a chelating and a monodentate ligand 1 in the same complex. Carbonylation of the cationic methyl complexes 8a, 17, 18a and 20a afforded the corresponding acetyl complexes in which this ligand occupies a position cis to phosphorus, irrespective of that of the alkyl ligand in the precursor complex. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b002386h

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Coordination properties of novel hemilabile acetamide-derived P,O
phosphine ligands. Crystal structures of Ph2PNHC(O)Me and
[PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][O3SCF3]†
Pierre Braunstein,a Céline Frison,a Xavier Morisea and Richard D. Adamsb
a Laboratoire de Chimie de Coordination (UMR CNRS 7513), Université Louis Pasteur,
4 rue Blaise Pascal, F-67070 Strasbourg Cédex, France
b Department of Chemistry and Biochemistry, University of South Carolina, Columbia,
South Carolina 29208
Received 27th March 2000, Accepted 10th May 2000
Published on the Web 14th June 2000
Cationic methyl Pd() complexes are described in which the new heterofunctional phosphine ligands
Ph2PNHC(O)Me 1 or Ph2PN(Me)C(O)Me 3 behave as rigid and/or hemilabile P,O chelates. The chelating
ability of 3 is higher than that of 1 and both are compared to that of other P, O ligands, such as the keto- and
amido-phosphines Ph2PCH2C(O)Ph and Ph2PCH2C(O)NPh2, respectively. The crystal structure of 1 reveals
the presence in the solid-state of an intermolecular hydrogen-bonded network N–H ؒ ؒ ؒ O and that of
[PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][O3SCF3] 12b establishes the presence of both a chelating and
a monodentate ligand 1 in the same complex. Carbonylation of the cationic methyl complexes 8a, 17, 18a and
20a afforded the corresponding acetyl complexes in which this ligand occupies a position cis to phosphorus,
irrespective of that of the alkyl ligand in the precursor complex.
Ϫ
…
…
ligand [Ph2PN—C(—NPh)Ph] which is isoelectronic with the
Introduction
Ϫ 17
…
…
phosphino enolate [Ph2PCH—C(—O)Ph] .
Since ligands largely govern the stoichiometric and catalytic
reactivity of metal complexes, the continuing interest in the
design of new functional ligands is not surprising and applies in
particular to phosphines, which are ubiquitous in coordination
and organometallic chemistry, and various P,O systems have
been studied, which combine a soft phosphine moiety with a
hard oxygen functionality.1,2 Their chelating ability confers
additional stability during catalysis, whereas their dissym-
metrical nature may be of interest for a stereo-electronic control
of the active metal centre. For example, anionic P,O ligands
have been shown to play a key role in the nickel-catalyzed
ethene oligomerization into linear α-olefins (Shell Higher Olefin
Process), where subtle ligand variations strongly influence the
reactivity and/or the selectivity of the active metal centre,3–5 in
the rhodium-catalyzed activation of alkanes6 or in the revers-
ible CO2 fixation and catalytic lactone synthesis by palladium
complexes.7 Furthermore, neutral P,O ligands may display a
hemilabile behaviour, involving the weak donor functionality,
which leads to the storage of a potential vacant coordination
site suitable for substrate activation.1,2,8–11
We report here investigations on the coordination properties
of the new acetamido derived phosphine ligand Ph2PNHC-
(O)Me 1 and its N-methyl derivative Ph2PN(Me)C(O)Me 3.
Cationic Pd() complexes in which 1 or 3 act as rigid P,O
chelate and/or a hemilabile ligand are described. The chelating
ability of these ligands is compared to that of other potential
P,O chelates, such as the keto- and amido-phosphines Ph2-
PCH2C(O)Ph18 and Ph2PCH2C(O)NPh2,19 respectively. The
crystal structures of 1 and [PdMe{PPh2NHC(O)Me}{PPh2-
NHC(O)Me}][O3SCF3] 12b are also reported.
Results
Synthesis and characterization of the ligands
The new acetamido phosphine Ph2PNHC(O)Me 1 was pre-
pared by condensation of N-trimethylsilylacetamide with
Ph2PCl in toluene (Scheme 1). The reaction did not proceed
By analogy with the interesting properties brought about
by the NH group of dppa (bis(diphenylphosphino)amine)
compared with the CH2 group of dppm (bis(diphenylphos-
phino)methane),12–15 it appeared interesting to investigate the
corresponding effect on heteroditopic P,O ligands. We therefore
set out to study the coordination properties of ligands of the
type PhnP{NHC(O)CH3}3 Ϫ n (n = 1, 2), i.e. acetamido ano-
logues of the ketophosphines PhnP{CH2C(O)R}3 Ϫ n. Modifi-
cations of the chelating ability and of the hemilabile behaviour
were anticipated, owing to the different electronic influences
of the NH and CH2 groups and to changes in the P–N–C vs.
P–C–C bond angle in α position to the P atom,16 which could
influence the reactivity of the corresponding complexes. We
have recently reported Ni complexes with the anionic chelating
† Part of the Doctoral Thesis of C. F.
DOI: 10.1039/b002386h
Scheme 1
J. Chem. Soc., Dalton Trans., 2000, 2205–2214
This journal is © The Royal Society of Chemistry 2000
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Table 1 Selected IR and NMR data for compounds 1–20
1H NMR,b δ (ppm), J (Hz)
IRa/cmϪ1
31P{1H}NMR,b
Complex
ν(C᎐O)
Ligand 1 or 3
Other
δ (ppm), J (Hz)
᎐
1
1Ј
2
1715s
1672m
1669s
1698s
2.13 [s, 3H, C(O)Me], 6.15 (br, 1H, NH)
2.30 [s, 3H, C(O)Me], OH not observed
2.18 [d, 3H, 4JPH = 3, C(O)Me], 2.24
(d, 3H, 2JPH = 13, PMe)
21.6
31.1
19.8
3
4
2.54 (d, 3H, 3JPH = 4.8, NMe), 2.74 [s, 3H,
C(O)Me]
55.1
2.10 [s, 3H, C(O)Me], 9.7 (br, 1H, NH)
(298 K); 2.06 [s, 3H, C(O)Me], 9.2 (d, 1H,
2JPH = 16, NH) (220 K)
2.87 (d, 6H, 4JPH = 2.8, NMe2), 3.99
(d, 2H, 4JPH = 6.9, NCH2) (298 K);
2.87 (s, br, 6H, NMe2), 3.98 (s, br, 2H,
NCH2) (220 K)
61.8 (br) (298 K)
60.7 (220 K)
4Ј
5
2.52 [s, 3H, C(O)Me], 12.9 (br, 1H, NH)
(220 K)
2.93 (s, br, 6H, NMe2), 4.07 (s, br, 2H,
NCH2) (220 K)
79.7 (220 K)
79.0c
1604s
1672s
1584s
2.43 [s, 3H, C(O)Me], 10.74 (br, 1H, NH)c
2.93 (d, 6H, 4JPH = 2.8, NMe2), 4.06
(d, 4JPH = 2.1, NCH2)c
6
2.38 [s, 3H, C(O)Me], 2.99 (d, 3H,
3JPH = 6.6, NMe)
2.85 (d, 6H, 4JPH = 3.0, NMe2), 4.03
(d, 2H, 4JPH = 2.4, NCH2)
85.8
7
2.56 [s, 3H, C(O)Me], 3.11 (d, 3H,
2.92 (d, 6H, 4JPH = 3.0, NMe2), 4.03
(d, 2H, 4JPH = 2.4, NCH2)
97.8
3JPH = 5.4, NMe)
8a
8b
9
1614s
1602s
2.40 [s, 3H, C(O)Me], 10.06 (br, 1H, NH)c
2.35 [s, 3H, C(O)Me], 10.23 (br, 1H, NH)
2.37 [s, 3H, C(O)Me], 8.88 (br, 1H, NH)
0.74 (s, 3H, PdMe), 2.27 (s, 3H, NCMe)c
0.76 (s, 3H, PdMe), 2.31 (s, 3H, NCMe)
0.65 (dd, 3H, 3JPH = 6.0, 5.9, PdMe), 4.27
(dd, 2H, 2JPH = 9.3, 3JPH = 1.6, CH2)
0.62 (dd, 3H, 3JPH = 6.3, 6.0, PdMe), 3.60
(d, 2H, 2JPH = 9.0, CH2)
79.8c
79.3
1675m,d
1606me
1659m,d
1604me
1611s
14.0 (d, 1P, CP), 70.1 (d, 1P,
2JPP = 417, NP)
10
2.34 [s, 3H, C(O)Me], 9.55 (br, 1H, NH)
17.2 (d, 1P, CP), 69.0 (d, 1P,
2JPP = 418, NP)
11
—
0.83 (s, 3H, PdMe), 2.31 (s, 3H, MeCN),
4.48 (d, 2H, 2JPH = 11.4, CH2)
0.59 (t, 3H, 3JPH = 5.7, PdMe)
36.0
12a
12b
13
1687,
1611f
1689s,
1612sf
1674s,
1607s
1591s
2.27 [s, 6H, C(O)Me], 8.07 (br, 2H, NH)
2.33 [s, 6H, C(O)Me], 9.08 (br, 2H, NH)
—
60.2
59.0
20.9
0.64 (m, 3H, PdMe)
0.73 (br, 3H, PdMe), 4.48 (s, br, 2H, CH2)
14
2.37 [s, 3H, C(O)Me], 2.98 (d, 3H,
3JPH = 5.4, NMe)g
0.60 (d, 3H, 3JPH = 2.4, PdMe), 2.04 (s, 3H, 98.0g
MeCN)g
15
1665m,
1582sb
1701m,
1589s
2.37 [s, 6H, C(O)Me], 2.95 (virtual t, 6H,
0.47 (t, 3H, 3JPH = 6.0, PdMe)g
77.7g
|3JPH ϩ 5JPH| = 6.0, NMe)g
16
2.20 [s, 3H, C(O)Me], 2.44 [s, 3H,
C(O)Me], 3.06 (br, 3H, NMe), 8.33 (br,
1H, NH)g
0.46 (br, 3H, PdMe)g
49.6 (d, 1P, HNP), 90.7 (d, 1P,
2JPP = 444, MeNP)g
17
1604s
1596s
2.38 [s, 3H, C(O)Me], 10.71 (s, 1H, NH)
0.61 (dd, 3H, 3JPH = 6.5, 5.6, PdMe)
24.8 (d, 1P, PPh3), 70.7 (d, 1P,
2JPP = 405, NP)
cis-18a
2.49 [s, 3H, C(O)Me], 8.75 (br, 1H, NH)
2.45 [s, 3H, C(O)Me], 8.72 (br, 1H, NH)
2.23 [s, 3H, C(O)Me], 10.27 (br, 1H, NH)
2.18 [s, 3H, C(O)Me], 10.01 (br, 1H, NH)
2.51 [s, 3H, C(O)Me], 10.72 (br, 1H, NH)
1.07 (d, 3H, 3JPH = 7.7, PdMe), 3.62 [d, 9H,
3JPH = 13.3, P(OMe)3]
67.8 (d, 1P, NP), 121.3 [d, 1P,
2JPP = 43, P(OMe)3]
trans-18a 1652m
cis-18b 1589s
trans-18b 1608s
cis-19b 1592m
0.86 (dd, 3H, 3JPH = 6.1, 5.9, PdMe), 3.81
[d, 9H, 3JPH = 12.2, P(OMe)3]
0.76 (d, 3H, 3JPH = 7.5, PdMe), 3.43 [d, 9H,
3JPH = 13.3, P(OMe)3]c
68.7 (d, 1P, NP), 119.0 [d, 1P,
2JPP = 603, P(OMe)3]
67.3 (d, 1P, NP), 121.2 [d, 1P,
2JPP = 46, P(OMe)3]c
0.68 (br, 3H, PdMe), 3.54 [d, 9H,
68.3 (d, 1P, NP), 119.7 [d, 1P,
2JPP = 607, P(OMe)3]c
3JPH = 11.4, P(OMe)3]
1.00 (d, 3H, 3JPH = 7.62, PdMe), 1.17
[d, 6H, 3JHH = 3.0, CH(CH3)2], 4.68 [M,
1H, CH((CH3)2)]
67.7 (d, 1P, NP), 111.4 [d, 1P,
2JPP = 36, P(OiPr)3]
trans-19b 1610m
2.44 [s, 3H, C(O)Me], NH not identified
0.88 (dd, 3H, 3JPH = 7.2, 6.6, PdMe), 1.27
[d, 6H, 3JHH = 3.2, CH(CH3)2], 4.68 [m,
1H, CH((CH3)2)]
68.3 (d, 1P, NP), 110.8 [d, 1P,
2JPP = 598, P(OiPr)3]
cis-20b
1589m
2.46 [s, 3H, C(O)Me], 10.74 (br, 1H, NH)
2.26 [s, 3H, C(O)Me], 10.47 (br, 1H, NH)
0.93 (d, 3H, 3JPH = 7.7, PdMe)
69.3 (d, 1P, NP), 110.2 [d, 1P,
2JPP = 46, P(OPh)3]
trans-20b 1613m
0.68 (dd, 3H, 3JPH = 6.7, 5.6, PdMe)
70.5 (d, 1P, NP), 107.5 [d, 1P,
2JPP = 593, P(OPh)3]
a Recorded in CH2Cl2 unless otherwise stated. b Recorded in CDCl3 unless otherwise stated. c Recorded in CD3C(O)CD3. d νCO of Ph2PCH2C(O)R.
e νCO of Ph2PNHC(O)Me. f Recorded as KBr disk. g Recorded in CD2Cl2.
until the temperature of the mixture was raised to 60 ЊC. Then
the solution became cloudy and vapours of chlorotrimethyl-
silane were noticed, which were evacuated under reduced pres-
sure. Upon slow cooling, 1 deposited as a colourless crystalline
material which was recovered by decantation. Its 31P{1H} NMR
(CDCl3) spectrum consisted of two signals at δ 21.6 and 31.1
(ratio 60/40). This could be explained by a tautomeric equi-
librium between the acetamido and the iminol forms 1 and 1Ј,
respectively (Scheme 1), which is supressed in the correspond-
a deshielding effect on the nearby atoms, the 31P{1H} signal of
1Ј is expected to occur at lower field than that of 1. We therefore
assign the signal at δ 21.6 (major tautomer) to the acetamido
ligand 1. In the 1H NMR spectrum the signals due to the CH3
protons of 1 and 1Ј occurred at δ 2.13 and δ 2.30, respectively
(Table 1). The 13C signal of the HN–C᎐O moiety in 1 was
᎐
observed at δ 173.31 and that of N᎐C–OH in 1Ј at δ 174.33, the
᎐
latter showing a 2JPC value of 13 Hz. The suggested tautomeric
equilibrium 1 1Ј appears solvent dependent: in CD2Cl2, the
acetamido form 1 represents more than 75% (60% in CDCl3),
ing N-methyl derivative (see below). The N᎐C bond having
᎐
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J. Chem. Soc., Dalton Trans., 2000, 2205–2214

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whereas in acetone-d6 the iminol form 1Ј was not detected.
Alternatively, the second isomer could have a structure such
as 1ЈЈ formed by rotation about the partial C–N double bond.
We cannot distinguish between these two possibilities with
the available data. The crystal structure of 1 has been deter-
mined by X-ray diffraction (vide infra). Interestingly, N-
methylation of 1 did not occur upon treatment with KH
followed by addition of MeI. Instead, the phosphorus ylide 2
was formed (Scheme 1, Table 1). Its 31P{1H} NMR spectrum
consisted of a singlet at δ 19.8, whereas in the 1H NMR
spectrum two doublets at δ 2.18 (4JPH = 3 Hz) and 2.24
(2JPH = 13 Hz) were ascribed to the C(O)Me and PMe protons,
respectively. In the IR spectrum the ν(CO) vibration was
that 4Ј was not detected when the NMR spectra were run
in toluene-d8. This solvent dependence of the equilibrium
4Ј is consistent with the ionic nature of 4Ј. Addition of
Ag(O3SCF3) to a 4/4Ј mixture led to anion metathesis and
induced a shift of the equilibrium towards the cationic species
4
which afforded [(dmba)Pd{PPh2NHC(O)Me}[O3SCF3] 5 in
quantitative yield (Scheme 2). Reaction of the more electron
donating ligand 3 with [Pd(dmba)(µ-Cl)]2 gave a single product.
This was evidenced by the presence of a sharp 31P{1H} NMR
1
signal at δ 85.8 and of only one set of signals in the H NMR
spectrum. No additional resonances were observed upon cool-
ing. The IR spectrum showed a ν(CO) vibration at 1672 cmϪ1
,
which indicates that the amide oxygen atom is not coordinated
to the Pd centre. These data are in agreement with the form-
ation of [(dmba)PdCl{PPh2N(Me)C(O)Me}] 6 in which 3 acts
as a monodentate phosphine ligand (Scheme 3). For com-
observed at 1672 cmϪ1
.
The N-methyl acetamido phosphine 3 could, however, be
prepared from Me3SiN(Me)C(O)Me and Ph2PCl (eqn. 1). The
parison, the cationic complex [(dmba)Pd{PPh2N(Me)C(O)-
Me}][O3SCF3] 7 was prepared from 3, [Pd(dmba)(µ-Cl)]2 and
Ag(O3SCF3). Its spectroscopic data are clearly different from
those of 6 (Scheme 3, Table 1).
(1)
reaction proceeded at ambient temperature in CH2Cl2, whereas
in toluene, thermal activation was needed, which led to the
formation of by-products such as Ph2PP(O)Ph2 (δ Ϫ21.4 and
1
35.3, JPP = 228 Hz). In contrast to the case of 1, only one
1
species was detected in the H and 31P{1H} NMR spectra of 3
(Table 1), which would be in accord with the involvement of the
NH proton in the equilibrium shown in Scheme 1.
Cationic Pd complexes
Reaction of [Pd(dmba)(µ-Cl)]2 (dmba-H = N,N-dimethyl-
benzylamine) with 2 molar equiv. of 1 afforded [(dmba)PdCl{P-
Ph2NHC(O)Me}] 4 as a pale green solid. At room temperature
its 31P{1H} NMR spectrum (CDCl3) consisted of a broad signal
at δ 61.8, a feature which suggested the occurence of a dynamic
behaviour. Indeed, at 220 K two 31P{1H} resonances are
observed at δ 79.7 and 60.7 (ratio: 45/55). The presence of two
Scheme 3
The reaction of 1, [PdCl(Me)(COD)] (COD = 1,5-cyclo-
octadiene) and TlPF6 in acetonitrile afforded the cationic
complex [PdMe{PPh2NHC(O)Me}(NCMe)][PF6] 8a in 90%
yield (Scheme 4) in which chelation of 1 to the electron deficient
Pd() centre has occurred (31P{1H} NMR: δ 79.8, IR (CH2Cl2):
ν(CO) 1614 cmϪ1). The Pd-bound methyl resides in cis posi-
tion to the P atom, as indicated by the absence of any detect-
1
species, in this temperature range, was confirmed by H NMR
spectroscopy (Table 1). These observations suggest the exist-
ence in solution of an equilibrium between 4 and 4Ј resulting
from the hemilability of coordinated 1 (Scheme 2).
3
able JPH coupling (Table 1). The triflate analogue of 8a
[PdMe{PPh2NHC(O)Me}(NCMe)][O3SCF3] 8b, was pre-
pared in a similar manner by use of Ag(O3SCF3) instead of
TlPF6.
Treatment of 8a with 1 molar equiv. of Ph2PCH2C(O)R
afforded almost quantitatively [PdMe{PPh2NHC(O)Me}-
{PPh2CH2C(O)R}][PF6]
9 (R = Ph) and 10 (R = NPh2)
(Scheme 4). In these complexes the added P,O phosphine
behaves as a monodentate ligand whereas 1 remains chelated to
the Pd centre. Both 31P{1H} NMR spectra showed an AX
2
pattern with a large JPP value of ca. 420 Hz, indicative of a
trans arrangement of the two P nuclei with respect to the metal
centre (Table 1). Complex 9 was also obtained by addition of 1
molar equiv. of 1 to [PdMe{PPh2CH2C(O)Ph}(NCMe)][PF6]
11 (Scheme 4). The latter was prepared in a similar manner to
8a, from [PdCl(Me)(COD)], Ph2PCH2C(O)Ph and TlPF6 in
acetonitrile (see Experimental section and Table 1). However,
it appeared less stable in solution than 8a (31P{1H} NMR
monitoring).
Complex 12a was obtained by reaction of 8a with 1 molar
equiv. of 1 and showed only a broad 31P{1H} NMR signal at
δ 60.2 (Scheme 4). This value is intermediate between the chem-
ical shifts observed for 1 when it behaves as a chelate (δ ca. 80)
or a monodentate ligand (δ ca. 45) in other cationic Pd() com-
plexes (see below). This indicates the occurrence in solution of a
fast equilibrium on the NMR time scale 12a 12aЈ in which
Scheme 2
Formation of the ionic species 4Ј resulted from chelation of
1 and concomittant displacement of ClϪ. We assigned to this
complex the 31P{1H} NMR signal at lower field (δ 79.7). Note
J. Chem. Soc., Dalton Trans., 2000, 2205–2214
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chelate around the Pd centre resulted in the occurrence of the
ν(CO) vibration at 1591 cmϪ1 (1669 cmϪ1 in the case of
uncoordinated 3) and a low field 31P{1H} NMR resonance at
δ 98.0. Addition of a second molar equiv. of 3 led to the form-
ation of 15 in which a dynamic behaviour similar to that
described above in 12a (see 15 15Ј, Scheme 5) also occurs
and only a broad 31P{1H} NMR resonance was observed
(δ 77.7).
To compare the chelating ability of 1 with that of 3, complex
8a was reacted with 1 molar equiv. of 3. Although the new,
mixed phosphine complex 16 was obtained as the main prod-
uct, formation of 12a and 15 was also observed (Scheme 6).
Spectroscopic data support the structure proposed for 16. The
31P{1H} NMR spectrum showed two doublets at δ 90.7 and
49.6, whose values are characteristic for the P atom of 3 being
part of a chelate ring in contrast to that of 1, respectively.
Furthermore, the large 2JPP value of 444 Hz indicates a mutual
trans arrangement of these nuclei.
Interestingly, when complex 14 was treated with 1 molar
equiv. of 1 or when stoichiometric amounts of 12a and 15 were
reacted together, the same reaction mixture as that obtained in
the reaction between 8a and 3 was obtained (Scheme 6). This
suggests the rapid establishment of a thermodynamic equi-
librium (Scheme 6) between 16 and 12a and 15 and in situ
31P{1H} NMR spectroscopy gave a relative ratio of 3:1:1,
respectively. Note that in the mass spectrum, the molecular
peaks of 12a, 15 and 16 were also observed, with their expected
isotopic pattern.
No ligand redistribution was observed with mono-
dentate phosphorus ligands but cis–trans isomerizations
were evidenced. Thus, whereas reaction of the cation
[PdMe{PPh2NHC(O)Me}(NCMe)]ϩ with PPh3 afforded
[PdMe{PPh2NHC(O)Me}(PPh3)]ϩ (see 17) in which the P
atoms are in mutual trans position (2JPP = 405 Hz) (Table 1),
reaction with P(OMe)3, P(OiPr)3 or P(OPh)3 yielded an iso-
meric mixture, 18–20, respectively, in which the cis isomer was
always the major species (see Experimental section). This gives
rise in their 31P{1H} NMR spectrum to two independent AX
patterns with 2JPP values of ca. 45 Hz or 595 Hz for the cis and
trans isomers, respectively. The ratio between the two isomers
was not sensitive to the nature of the counter ion but to that of
the solvent, as shown by 31P{1H} NMR: the cis/trans ratio
varies from 90:10 in CDCl3 to 70:30 in acetone-d6 in the case
of cis-18a. The existence of such isomers allowed the study of
the possible influence of the trans ligand on the reactivity of the
Pd–Me bond towards e.g. carbonylation.
Scheme 4
each phosphine ligand alternatively acts in a chelate or mono-
dentate manner (Scheme 4). The 1H NMR data were consistent
with the proposed structure (Table 1). Low temperature NMR
experiments did not slow the exchange rate sufficiently to show
separate resonances. However, the fact that each phosphine
ligand adopts a different coordination mode in 12a was clearly
evidenced in the solid state IR spectrum (KBr), which showed
two ν(CO) vibrations at 1687 cmϪ1 (free C᎐O) and 1611 cmϪ1
(coordinated C᎐O), and was further confirmed by a crystal
᎐
᎐
structure determination of the triflate salt 12b (see below). Note
that a similar hemilabile behaviour was found for the ketophos-
phine ligands Ph2PCH2C(O)Ph in complex 13 which was pre-
pared from 11 and Ph2PCH2C(O)Ph (Scheme 4). Interestingly,
when 12a was reacted with 13 in a 1:1 ratio, a ligand redistribu-
tion was observed and the mixed phosphine complex 9 was
formed quantitatively (Scheme 4).
Carbonylation reactions. Carbonylation of the methyl deriv-
atives 8a, 17, 18a and 20a in CH2Cl2 was monitored by 31P{1H}
NMR and IR spectroscopies. In all cases, only one isomer of
the acetyl derivatives is observed, in which the C(O)Me group is
in the cis position to the P donor atom of coordinated 1. This is
established by a characteristic upfield shift of ca. 20 for its
resonance20 and the high value of the 2JPP coupling constant in
22–24. Two νCO absorptions are observed, at ca. 1611 cmϪ1 for
the coordinated amide and ca. 1710 cmϪ1 for the acyl ligand
(see Experimental section).
Complex 14 was obtained in a similar manner to 7, from 3,
[PdCl(Me)(COD] and TlPF6 (Scheme 5). Formation of a P,O
Crystal structures of 1 and 12b
Selected bond distances and angles for 1 are given in Table 2.
An ORTEP representation of two adjacent molecules of 1 is
presented in Fig. 1. Bond distances and angles are within the
range of those reported for related amide and phosphine
derivatives. Note, however, that the P–N bond (1.728(2) Å) is
longer than that found in PhP(O)(OMe)NHC(O)Ph (1.674 Å)21
and in (MeO)P(O)(SMe)NHC(O)Me (1.641 Å)22 and similar to
that of Ph2P(S)NHC(O)Ph (1.72(1)Å).23 The P–N–C(13) bond
angle (122.3(1)Њ) is more obtuse than the P–C–C angle found in
Ph2PCH2CO2Et (113.24Њ)24 and Ph2PCH2CO2H (110.188Њ).25
Scheme 5
2208
J. Chem. Soc., Dalton Trans., 2000, 2205–2214

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Scheme 6
Fig. 1 View of the molecular structure of Ph2PNHC(O)Me 1 showing
the dimeric unit resulting from intermolecular hydrogen bonding
N–H ؒ ؒ ؒ O. Hydrogen H(14) is bonded to N.
Table 3 Selected intramolecular distances (Å) and angles (Њ) for 12b
Table 2 Selected intramolecular distances (Å) and angles (Њ) for
Ph2PNHC(O)Me 1
Pd(1)–P(1)
Pd(1)–O(2)
P(1)–N(1)
P(1)–C(7)
P(2)–C(13)
O(1)–C(31)
N(1)–C(31)
C(31)–C(32)
2.307(2)
2.181(4)
1.700(5)
1.813(6)
1.807(6)
1.198(8)
1.379(8)
1.51(1)
Pd(1)–P(2)
Pd(1)–C(50)
P(1)–C(1)
2.265(2)
2.022(7)
1.810(6)
1.718(5)
1.808(7)
1.244(7)
1.353(8)
1.492(9)
P(1)–C(1)
P(1)–C(7)
P(1)–N(1)
1.836(2)
1.828(2)
1.728(2)
N(1)–C(13)
C(13)–O(1)
1.346(3)
1.218(3)
P(2)–N(2)
P(2)–C(19)
O(2)–C(41)
N(2)–C(41)
C(41)–C(42)
C(1)–P(1)–C(7)
C(1)–P(1)–N(1)
C(7)–P(1)–N(1)
101.71(9)
98.33(8)
101.66(9)
P(1)–N(1)–C(13)
N(1)–C(13)–O(1)
N(1)–C(13)–C(14)
122.3(1)
120.8(2)
117.1(2)
P(1)–Pd(1)–P(2)
P(1)–Pd(1)–O(2)
P(2)–Pd(1)–O(2)
O(2)–Pd(1)–C(50)
Pd(1)–P(2)–N(2)
P(1)–N(1)–C(31)
O(1)–C(31)–C(32)
O(2)–C(41)–N(2)
N(2)–C(41)–C(42)
178.20(6)
98.0(1)
80.5(1)
172.4(2)
99.8(2)
122.3(5)
123.6(7)
122.4(5)
117.4(6)
P(2)–N(2)–C(41)
P(1)–Pd(1)–C(50)
P(2)–PD(1)–C(50)
Pd(1)–P(1)–N(1)
Pd(1)–O(2)–C(41)
O(1)–C(31)–N(1)
118.3(4)
89.0(2)
92.5(2)
114.4(2)
116.9(4)
122.3(6)
Estimated standard deviations in the least significant figure are given in
parentheses.
The most notable feature is the fact that molecules pack to form
H-bonded chains due to strong intermolecular N–H(14) ؒ ؒ ؒ
O᎐C hydrogen bonding [N ؒ ؒ ؒ O 2.828 Å, H(14) ؒ ؒ ؒ O 1.882 Å;
᎐
N(1)–C(31)–C(32) 114.1(6)
O(2)–C(41)–C(42) 120.1(6)
N–H ؒ ؒ ؒ O 173.68Њ]. A view along the y axis shows a head to tail
disposition for adjacent molecules, with the P, N, C(13), O,
H(14) and C(14) atoms being coplanar, thus giving the
arrangement pictured in Fig. 2a. A view along the z axis shows
the layer stacking due to hydrogen bonding (Fig. 2b).
Selected bond distances and angles for 12b are given in Table
3. An ORTEP representation of the cation of 12b is presented
in Fig. 3. It clearly evidences the different coordination modes
of the two phosphine ligands. The Pd–P bond distance of the
monodentate phosphine (2.307(2) Å) is slightly longer than that
Estimated standard deviations in the least significant figure are given in
parentheses.
of the chelate (2.265(2) Å). The bond distances within the
coordinated phosphine ligands are similar to those observed for
free 1. Note that the C(41)–O(2) distance (1.244(7) Å) is slightly
longer than C(31)–O(1) (1.198(8) Å) as a result of the
coordination of the O(2) atom to the Pd centre. The Pd–O(2)
distance of 2.181(4) Å is in the expected range for the carbonyl
J. Chem. Soc., Dalton Trans., 2000, 2205–2214
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Fig. 3 View of the molecular structure of [PdMe{PPh2NHC(O)Me}-
{PPh2NHC(O)Me}][O3SCF3] 12b.
Discussion
In spite of the extensive studies carried out during the past
decade on organophosphorus compounds containing a P–N
bond, such as dppa and its oxidized derivatives,29–31 the chem-
istry of amido derived phosphine ligands remains relatively
unexplored. To the best of our knowledge, phosphine 1 repre-
sents one of the rare examples of an acetamido-derived phos-
phine. During the course of our work, Woollins et al. have
reported a 34% yield synthesis of Ph2P(S)NHC(O)Ph from the
benzamide phosphine Ph2PNHC(O)Ph, which was not isol-
ated but reacted in situ with sulfur.23 Our synthesis of ligand 1,
from N-trimethylsilylacetamide and Ph2PCl, is straightforward
and almost quantitative. The driving force for the reaction is
the formation of chlorotrimethylsilane. This approach is
related to that described by Schmutzler et al. for the prepar-
ation of urea- and thiourea-derived phosphines.32 It is interest-
ing to note that treatment of 1 with KH and MeI only
gave the phosphorus ylide derivative 2 (Scheme 1), a similar
observation was reported for the alkylation of dppa
(Ph2PNHPPh2).33
The hemilabile properties of 1 and 3 were evidenced by their
dynamic behaviour in complexes 4 and 12a and in complex 15,
respectively. Yet, the situation in 4 was quite unexpected, since it
has been observed that the reaction of [Pd(dmba)(µ-Cl)]2 with
P,O phosphines, such as Ph2PCH2C(O)R (R = Ph, NPh2, etc.),
only gave neutral species in which the latter acted as a mono-
dentate ligand.30 The existence of the equilibrium between 4
and 4Ј revealed a certain propensity of 1 to chelate metal
centres (Scheme 2). The reaction of 3 with [Pd(dmba)(µ-Cl)]2
only produced 6, in which the P,O ligand acts as a monodentate
phosphine. This observation is quite surprising since 3 dis-
plays an increased chelating ability with respect to 1 due to
N-methylation, as evidenced in the structure of complex 16.
Interaction between the N–H proton and ClϪ in 4Ј, which can-
not occur in 6, may be invoked in order to account for the
existence of the equilibrium 4 4Ј. It became therefore of
interest to evaluate the chelating ability of 1 by introducing in
the coordination sphere of the Pd centre a second, potentially
competing P,O chelate. This was achieved by substitution of
the labile acetonitrile ligand in 8a with the desired P,O phos-
phine. In the presence of the ketophosphine Ph2PCH2C(O)Ph,
or its amido analogue Ph2PCH2C(O)NPh2, the P–N–C–O–Pd
five membered ring present in 8a was retained and complexes 9
and 10 were obtained, respectively (Scheme 4). Furthermore,
the displacement by 1 of the pre-existent P,O chelate in 11 and
the ligand exchange reaction, which occurred between 12a
and 13, confirmed the higher chelating ability of 1 than Ph2-
PCH2C(O)Ph. Both reactions led to 9 as a sole product (Scheme
4). It is interesting to note that the chelation of 1 or 3 in 8a or
14, respectively, gives rise to more stable complexes than that
of Ph2PCH2C(O)Ph in 11.
Fig. 2 Views of the packing of 1: (a) along the y axis and (b) along the
z axis. Colour code: P red, O blue, N green and H (NH) pink.
group of a P,O chelate coordinated to a Pd centre.26–28 The
latter has a square planar geometry, with a trans arrangement
of the P atoms (P(1)–Pd–P(2) 178.20(6)Њ) and of the methyl
group and the O atom of the chelating P,O ligand (O(2)–Pd–
C(50) 172.4(2)Њ). As a result of the occurence of the P(2)–N(2)–
C(41)–O(2)–Pd(1) five-membered ring, the P(2)–N(2)–C(41)
angle (118.3(4)Њ) is more acute than the P(1)–N(1)–C(31)
angle (122.3(5)Њ) and the P(1)–N(1)–C(13) angle of the free
phosphine 1 (122.3(1)Њ). There are no other significant differ-
ences in the bond angle values between coordinated phosphines
and free 1.
2210
J. Chem. Soc., Dalton Trans., 2000, 2205–2214

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When the two acetamido derived phosphine ligands 1 and 3
are present in the same complex, as in 16, chelation of the
N-methyl derivative 3 is preferred over that of 1. It is, however,
interesting to note that ligand redistribution occurs in solution
since a mixture of the bis(acetamido-phosphine) complex 12a
and the bis(N-methylacetamido-phosphine) complex 15 is
in equilibrium with 16. It is interesting to note that these 3
species could also be identified in the solid state by mass
spectroscopy.
Ϫ20 ЊC for 48 h, affording a second crop of 1. Overall yield:
16.96 g (84%). 13C{1H} NMR (CDCl3, 298 K): δ 22.35 [s,
C(O)Me], 24.18 [s, C(O)Me of 1Ј], 128.43–138.19 (aromatics),
173.31 (s, C᎐O), 174.33 (d, N᎐C–OH of 1Ј, 2JPC = 13 Hz). Calc.
᎐
᎐
for C14H14NOP: C, 69.13; H, 5.80; N, 5.76. Found: C, 69.28; H,
5.92; N, 5.85%.
(Me)Ph P᎐NC(O)Me 2. The ligand Ph PNHC(O)Me 1
᎐
2
2
(0.395 g, 1.612 mmol) was dissolved in THF (30 mL) and KH
(0.065 g, 1.612 mmol) was added at Ϫ30 ЊC. The solution was
stirred for 1 h at this temperature before excess MeI (2 mL) was
added. The mixture was allowed to warm to ambient temper-
ature. The solution was filtered and volatiles were removed
under vacuum, giving 2 as a white powder which was washed
with diethyl ether (15 mL) and pentane (15 mL) and dried in
vacuo. Yield: 0.310 g (75%). 13C{1H} NMR (CDCl3, 298 K):
The cationic methyl complexes 17–20 did not give rise to
redistribution reactions between the monodentate phosphines,
in contrast to the situation observed with 16 or in related work
between Ph2PCH2C(O)NPh2 and PCy3.34 Whereas in such
Pd() complexes with P,O or P,N chelates the alkyl ligand tends
to avoid the position trans to phosphorus,35 as also observed
with the PPh3 derivative 17, the phosphite derivatives 18–20
exist as a mixture of the cis (major) and trans (minor) isomers
which does not appear to be dependent on the counter ion. The
availability of two isomeric alkyls in the case of the phosphite
derivatives suggested the study of their reactivity towards CO
insertion to see whether one isomer would react preferentially.
Such studies are relevant to current interest in CO/olefin coup-
ling reactions.36,37 We found that only one isomer is produced,
which suggests that either one of the isomeric precursors has
reacted faster, leading to a displacement of its equilibrium with
the other isomer, or that a very fast isomerization between two
isomeric acetyl derivatives leads to the observed one. Low
energy processes are readily available for ligand isomerization in
penta-coordinated Pd() intermediates. In situ experiments only
showed the presence of one acetyl isomer throughout carbon-
ylation. The preference for a soft carbon ligand (either alkyl or
acyl) to avoid a position trans to phosphorus is consistent with
Pearsons antisymbiotic effect.38–40
1
3
δ 13.00 (d, JPC = 64 Hz, PMe), 27.45 [d, JPC = 18.4 Hz,
C(O)Me], 183.52 (d, 2JPC = 9.7 Hz, C᎐O). Calc. for C H NOP:
᎐
15 16
C, 70.03; H, 6.27; N, 5.44. Found: C, 70.04; H, 6.27; N,
5.27%.
Ph2PN(Me)C(O)Me 3. The compound MeC(O)NMeSiMe3
(475 µL, 2.950 mmol) was dissolved in CH2Cl2 (15 mL). Pure
Ph2PCl (530 µL, 2.950 mmol) was added to the solution and the
mixture was stirred for 15 min. The volatiles were removed
under reduced pressure, giving 3 as a white powder which was
washed with diethyl ether (15 mL) and dried in vacuo. Yield:
0.540 g (71%). 13C{1H} NMR (CDCl3, 298 K): δ 23.61 (d,
3
2JPC = 64 Hz, NMe), 31.82 [d, JPC = 6.5 Hz, C(O)Me], 176.4
2
(d, JPC = 6.0 Hz, C᎐O). Calc. for C H NOP: C, 70.03; H,
᎐
15 16
6.27; N, 5.44. Found: C, 69.86; H, 6.38; N, 4.80%.
[(dmba)PdCl{PPh2NHC(O)Me}] 4. Solid 1 (0.976 g, 3.984
mmol) was added to a solution of [Pd(dmba)(µ-Cl)]2 (1.100 g,
1.991 mmol) in CH2Cl2 (100 mL) at ambient temperature. The
mixture was stirred for 20 min. The solution was filtered and the
volatiles were evaporated to leave a pale green powder, which
was washed with diethyl ether (20 mL) and pentane (2 × 20 mL)
and dried under vacuum. Yield: 1.856 g (90%). Calc. for
C23H26ClN2OPPd: C, 53.20; H, 5.05; N, 5.39. Found: C, 53.37;
H, 5.04; N, 5.50%.
Experimental
All reactions were performed using Schlenk-tube techniques
under dry nitrogen. Solvents were dried and distilled prior to
use under nitrogen. The 1H, 31P{1H} and 13C{1H} NMR spectra
were recorded at 300.1, 121.5 and 50.0 MHz, respectively, on a
FT Bruker AC 300 instrument. Chemical shifts are positive
1
downfield from external tetramethylsilane (TMS) for H and
13C, and from H3PO4 (85% in H2O) for 31P. IR spectra were
recorded in the 4000–400 cmϪ1 range on a Bruker IFS66 FT
spectrometer. Elemental C, H and N analyses were performed
by the service de microanalyse du CNRS (ULP) and at the
University of Saarbrücken (Germany). Electrospray mass spec-
tra were run on a HP 1100 series LC/MSD spectrometer.
[(dmba)Pd{PPh2NHC(O)Me}][O3SCF3] 5. Complex 4 (0.160
g, 0.308 mmol) was treated with Ag(O3SCF3) (0.079 g, 0.308
mmol) in CH2Cl2 (200 mL) at ambient temperature. The solu-
tion was filtered and the solvent was removed under reduced
pressure. The residue was washed with pentane (10 mL) and 5
was obtained as a pale yellow-green solid. Yield: 0.179 g (92%).
Calc. for C24H26F3N2O4PPdS: C, 45.55; H, 4.14; N, 4.43.
Found: C, 45.26; H, 4.02; N, 4.35%.
Syntheses
The complexes [PdCl(Me)COD],41 [Pd(dmba)(µ-Cl)]242 and the
19
ligands Ph2PCH2C(O)Ph18 and Ph2PCH2C(O)NPh2 were
[(dmba)PdCl{PPh2N(Me)C(O)Me}] 6. Ligand 3 (0.058 g,
0.225 mmol) was added to a solution of [Pd(dmba)(µ-Cl)]2
(0.062 g, 0.113 mmol) in CH2Cl2 (15 mL). The mixture was
stirred for 20 min at ambient temperature. The solution was
filtered and the solvent was evaporated to leave a white powder,
which was washed with diethyl ether (10 mL) and pentane (10
mL) and dried under vacuum. Yield: 0.112 g (93%). Calc. for
C24H28ClN2OPPd: C, 53.95; H, 5.47; N, 5.24. Found: C, 53.86;
H, 5.28; N, 5.00%.
prepared according to published procedures. Ph2PCl, TlPF6
(Strem), MeC(O)NHSiMe3, AgBF4 and KPF6 (Aldrich) were
purchased and used as received.
Ph2PNHC(O)Me 1. The compound MeC(O)NHSiMe3
(10.893 g, 0.083 mmol) was dissolved in toluene (150 mL),
Ph2PCl (15 mL, 0.083 mmol) was added to the solution and the
mixture was placed under vacuum for 30 s, before being heated
to 60 ЊC. The mixture was placed under vacuum for 10 s every 5
min in order to eliminate ClSiMe3 which was formed. After 30
min, the solution was allowed to cool to ambient temperature,
during which 1 deposited as a colourless crystalline material.
The solution was filtered and 1 was dried under vacuum. Suit-
able crystals for X-ray diffraction were obtained by allowing the
reaction mixture to cool from 60 ЊC to room temperature by
keeping the Schlenk tube in the oil bath. Then, hexane (100 mL)
was added to the filtrate and the resulting mixture was placed at
[(dmba)Pd{PPh2N(Me)C(O)Me}][O3SCF3] 7. Complex 6
(0.160 g, 0.299 mmol) was treated with Ag(O3SCF3) (0.077 g,
0.299 mmol) in CH2Cl2 (50 mL) at ambient temperature. The
solution was filtered and the solvent was removed under
reduced pressure. The residue was washed with pentane (10
mL) and 7 was obtained as a pale yellow-green solid. Yield:
0.170 g (88%). Calc. for C25H28F3N2O4PPdS: C, 46.42; H, 4.36;
N, 4.33. Found: C, 46.22 ; H, 4.34; N, 4.18%.
J. Chem. Soc., Dalton Trans., 2000, 2205–2214
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0.149 mmol) were placed in a Schlenk flask and CH2Cl2 (10 mL)
[PdMe{PPh2NHC(O)Me}(NCMe)][PF6] 8a. Solid [PdCl-
(Me)(COD)] (1.086 g, 4.098 mmol) was added to a solution of
1 (0.996 g, 4.098 mmol) in MeCN (300 mL). The mixture was
stirred for 30 min, before TlPF6 (1.432 g, 4.098 mmol) was
added. The solution was then stirred for 30 min. The white
suspension was filtered and the solvent was evaporated under
vacuum to leave a beige solid which was washed with diethyl
ether (15 mL) and dried in vacuo. Yield: 2.03 g (90%). Calc. for
C17H20F6N2OP2Pd: C, 37.08; H, 3.66; N, 5.09. Found: C, 36.86;
H, 3.61; N, 4.83%.
was added. The solution was stirred for 5 min before solid
Ag(O3SCF3) (0.038 g, 0.149 mmol) was added in one portion.
The mixture was stirred for 30 min. After filtration, the solvent
was evaporated under vacuum to leave 12b as a pale yellow
sticky material. Crystallization from CH2Cl2/pentane afforded
yellow crystals suitable for X-ray diffraction study. Yield: 0.083
g (74%). Calc. for C30H31F3N2O5P2PdS: C, 47.60; H, 4.13; N,
3.70. Found: C, 47.61; H, 4.28; N, 3.40%.
[PdMe{PPh2CH2C(O)Ph}{PPh2CH2C(O)Ph}][PF6]
13.
Solid Ph2PCH2C(O)Ph (0.054 g, 0.178 mmol) was added to a
solution of 11 (0.110 g, 0.178 mmol) in CH2Cl2 (10 mL) at
ambient temperature. The solution was stirred for 30 min, fil-
tered and the solvent was evaporated under reduced pressure,
affording 13 as a beige powder. It was washed with diethyl ether
(20 mL) and hexane (20 mL) and dried under vacuum. Yield:
0.129 g (82%). Calc. for C41H37F6O2P3Pd: C, 56.28; H, 4.26.
Found: C, 56.49; H, 4.36%.
[PdMe{PPh2NHC(O)Me}(NCMe)][O3SCF3]
8b.
Solid
[PdCl(Me)(COD)] (0.506 g, 1.909 mmol) was added to a solu-
tion of 1 (0.468 g, 1.909 mmol) in MeCN (200 mL). The mix-
ture was stirred for 30 min, before Ag(O3SCF3) (0.491 g, 1.909
mmol) was added. The solution was then stirred for 30 min. The
white suspension was filtered and the solvent was evaporated
in vacuo to leave a beige solid which was washed with diethyl
ether (15 mL) and dried in vacuo. Yield: 0.974 g (92%). Calc. for
C18H20F3N2O4PPdSؒ0.5Et2O: C, 40.59; H, 4.26; N, 4.73. Found:
C, 40.24; H, 3.50; N, 4.36%.
[PdMe{PPh2N(Me)C(O)Me}(NCMe)][PF6] 14. Solid [PdCl-
(Me)(COD)] (0.277 g, 1.045 mmol) was added to a solution of
Ph2PN(Me)C(O)Me (0.268 g, 1.045 mmol) in MeCN (40 mL) at
ambient temperature. The mixture was stirred for 30 min,
before solid TlPF6 (0.365 g, 1.045 mmol) was added. The
solution was then stirred for 30 min before it was filtered. The
solvent was evaporated under vacuum to leave an orange solid
which was washed with diethyl ether (15 mL) and dried under
vacuum. Yield: 0.530 g (90%). Calc. for C18H22F6N2OP2Pd: C,
38.28; H, 3.93; N, 4.96. Found: C, 38.52; H, 4.08; N, 4.94%.
[PdMe{PPh2NHC(O)Me}{PPh2CH2C(O)Ph}][PF6]
9.
Method (a). Solid Ph2PCH2C(O)Ph (0.033 g, 0.108 mmol) was
added at ambient temperature to a solution of 8a (0.060 g,
0.108 mmol) in CH2Cl2 (15 mL). The mixture was stirred for 30
min. The solvent was evaporated under reduced pressure to
leave a brown oil which was washed with diethyl ether (20 mL)
and pentane (20 mL) and dried to give 9 as a beige powder.
Yield: 0.072 g (82%). Calc. for C35H34F6NO2P3Pdؒ0.5MeCN: C,
51.81; H, 4.29; N, 2.52. Found: C, 51.77; H, 4.34; N, 2.55%.
Method (b). In a NMR tube were placed 11 (see below, 0.010
g, 0.016 mmol) and 1 (0.004 g, 0.016 mmol) in CDCl3. The
spectroscopic data obtained were identical to those of complex
9 prepared using method (a).
[PdMe{PPh2N(Me)C(O)Me}{PPh2N(Me)C(O)Me}][PF6]
15. Solid 3 (0.050 g, 0.194 mmol) was added to a solution of 14
(0.110 g, 0.194 mmol) in CH2Cl2 (15 mL) at ambient temper-
ature. After being stirred for 30 min, the solution was filtered,
and the solvent was evaporated under reduced pressure, giving
15 as a yellow powder which was washed with diethyl ether
(15 mL) and pentane (15 mL). Yield: 0.120 g (80%). Calc. for
C31H35F6N2O2P3Pd: C, 47.68; H, 4.52; N, 3.59. Found: C, 47.83;
H, 4.56; N, 2.90%.
Method (c). In a NMR tube were placed 12a (see below,
0.015 g, 0.020 mmol) and 13 (see below) (0.017 g, 0.020 mmol)
in CDCl3. The spectroscopic data obtained were similar to
those of complex 9 prepared using method (a).
[PdMe{PPh2NHC(O)Me}{PPh2CH2C(O)NPh2}][PF6]
10.
[PdMe{PPh2N(Me)C(O)Me}{PPh2NHC(O)Me}][PF6] 16.
Method (a). Solid 3 (0.051 g, 0.198 mmol) was added to a
solution of 8a (0.110 g, 0.198 mmol) in CH2Cl2 (10 mL) at
ambient temperature. The solution was stirred for 30 min,
filtered and the solvent was evaporated under vacuum to leave
a beige powder which was washed with pentane (10 mL) and
dried under vacuum. Compound 16 could not be separated
from 12a and 15 which were formed in lower yields (see text). A
mass spectrum of the mixture contained the molecular peaks of
each complex, with the expected isotopic pattern. ES-MS: m/z:
[Mϩ]: 635 (15), 623 (16), 607 (12a).
Method (b). Solid 1 (0.029 g, 0.120 mmol) was added to a
solution of 14 (0.068 g, 0.120 mmol) in CH2Cl2 (10 mL) at
ambient temperature. The solution was stirred for 30 min, fil-
tered and the solvent was evaporated under vacuum to leave a
yellow powder which was washed with pentane (10 mL) and
dried under vacuum. The spectroscopic data obtained were
identical to those of complex 16 prepared using method (a).
The presence of 12a and 15 was also observed, in an identical
ratio to that obtained using method (a).
In a NMR tube were placed 8a (0.017 g, 0.031 mmol) and solid
Ph2PCH2C(O)Ph (0.012 g, 0.030 mmol) in CDCl3. Complex 10
was characterized by comparison of its spectroscopic data with
those of 9 (see Table 1).
[PdMe{PPh2CH2C(O)Ph}(NCMe)][PF6] 11. Solid [PdCl-
(Me)(COD)] (0.385 g, 1.453 mmol) was added to a solution of
Ph2PCH2C(O)Ph (0.442 g, 1.453 mmol) in MeCN (100 mL) at
ambient temperature. The mixture was stirred for 30 min,
before solid TlPF6 (0.507 g, 1.453 mmol) was added. The
solution was then stirred for 30 min before it was filtered. The
solvent was evaporated under vacuum to leave a beige solid
which was washed with diethyl ether (15 mL) and dried under
vacuum. Yield: 0.765 g (86%). Calc. for C23H23F6NOP2Pd: C,
45.16; H, 3.79; N, 2.29. Found: C, 45.44; H, 3.71; N, 2.21%.
[PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][PF6]
12a.
Solid 1 (0.051 g, 0.208 mmol) was added to a solution of 8a
(0.115 g, 0.208 mmol) in CH2Cl2 (15 mL) at ambient temper-
ature. After being stirred for 30 min, the solution was filtered,
and the solvent was evaporated under vacuum to leave 12a as a
yellow oil which was washed with diethyl ether (15 mL) and
pentane (15 mL). Yield: 0.154 g (97%). Calc. for C29H31F6-
N2O2P3Pd: C, 46.26; H, 4.15; N, 3.72. Found: C, 46.07; H, 3.98;
N, 3.54%.
Method (c). Solid 12a (0.026 g, 0.033 mmol) and 15 (0.027 g,
0.033 mmol) were mixed together in CD2Cl2 (2 mL) at ambient
temperature. The spectroscopic data obtained were identical to
those of complex 16 prepared using method (a). Compounds
12a and 15 were also observed, in an identical ratio to that
observed using method (a).
[PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][O3SCF3] 12b.
Solid 1 (0.073 g, 0.298 mmol) and [PdCl(Me)(COD)] (0.039 g,
[PdMe{PPh2NHC(O)Me}(PPh3)][O3SCF3] 17. Solid PPh3
(0.236 g, 0.901 mmol) was added to a solution of 8b (0.500 g,
2212
J. Chem. Soc., Dalton Trans., 2000, 2205–2214

View Article Online
Crystallographic data of Ph2PNHC(O)Me and
[PdMe{PPh2NHC(O)Me}{PPh2NHC(O)Me}][O3SCF3] 12b
Table
4
1
0.901 mmol) in CH2Cl2 (100 mL). After the solution was stirred
for 30 min, it was filtered and the solvent was removed under
reduced pressure to leave a white powder which was washed
with diethyl ether (30 mL) and pentane (30 mL) and dried
under vacuum. Yield 0.615 g (88%). Calc. for C34H32F3NO4P2-
SPd: C, 52.62; H, 4.16; N, 1.80. Found: C, 52.44; H, 4.30; N,
1.85%.
1
12b
Formula
M
C14H14NOP
243.25
C30H31F3N2O5P2PdS
756.99
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/n
[PdMe{PPh2NHC(O)Me}{P(OMe)3}][PF6] 18a. Using
a
T/K
294
294
similar procedure to that detailed below for 20a, 8a (0.202 g,
0.367 mmol) was treated with pure P(OMe)3 (43 µL, 0.367
mmol) in CH2Cl2 (75 mL). Complexes cis- and trans-18a were
obtained as a brown powder in a 90:10 ratio. Yield 0.203 g
(87%). Calc. for C18H26F6NO4P3Pd: C, 34.12; H, 4.14; N, 2.21.
Found: C, 34.37; H, 4.11; N, 2.08%.
a/Å
b/Å
c/Å
8.094(1)
9.5744(5)
17.020(1)
97.513(7)
1307.5(3)
4
9.542(1)
15.538(4)
22.717(3)
92.21(1)
33.65.8(9)
4
β/Њ
V/Å3
Z
ρ (calcd)/g cmϪ3
1.24
1.49
Radiation, λ Mo-Kα/Å 0.71073
0.71073
0.765
4623
µ/mmϪ1
0.187
3021
[PdMe{PPh2NHC(O)Me}{P(OMe)3}][O3SCF3] 18b. In a
similar manner, but using 8b instead of 8a, complexes cis- and
trans-18b were obtained in a 90:10 ratio (80% yield). Since the
spectroscopic data obtained were identical to those of cis- and
trans-18a, no further analysis was performed.
No. of reflcns
measured
No. of reflcns
Residuals
1725
2951
0.042; 0.063 (R; Rw)
0.042; 0.051 (R; Rw)
[PdMe{PPh2NHC(O)Me}{P(OiPr)3}][O3SCF3] 19b. Pure
P(OiPr)3 (71.4 µL, 0.289 mmol) was added to a solution of 8b
(0.160 g, 0.289 mmol) in CH2Cl2 (40 mL). After being stirred
for 30 min, the solution was filtered, and the solvent was
removed under vacuum to leave a white residue which was
washed with diethyl ether (15 mL) and pentane (15 mL) and
dried under vacuum to give a white powder. Yield 0.185 g
(89%). Complexes cis- and trans-19b were obtained in a 85:15
ratio. Calc. for C34H32F3NO7P2SPd: C, 49.56; H, 3.91; N, 1.70.
Found: C, 49.51; H, 4.07; N, 1.51%.
[s, 3H, PdC(O)Me], 2.35 [s, 3H, C(O)Me], 10.64 (s, 1H, NH);
31P{1H} NMR (CDCl3): δ 18.2 (d, 1P, PPh3), 52.8 (d, 1P,
JPP = 270 Hz, NP).
[Pd{C(O)Me}{PPh2NHC(O)Me}{P(OMe)3}][PF6] 23. IR
(CH2Cl2, cmϪ1): νCO = 1712s, 1611w; 31P{1H} NMR (CDCl3):
δ 53.0 (d, 1P, NP), 115.4 [d, 1P, JPP = 411 Hz, P(OMe)3].
[Pd{C(O)Me}{PPh2NHC(O)Me}{P(OPh)3}][PF6] 24. IR
1
(CH2Cl2, cmϪ1): νCO = 1719s, 1613w; H NMR (CDCl3): δ 2.00
[s, 3H, PdC(O)Me], 2.17 [s, 3H, C(O)Me], 8.57 (s, 1H, NH);
31P{1H} NMR (CDCl3): δ = 53.9 (d, 1P, NP), 106.0 [d, 1P,
JPP = 392 Hz, P(OPh)3].
[PdMe{PPh2NHC(O)Me}{P(OPh)3}][PF6]
20a.
Pure
P(OPh)3 (210 µL, 0.809 mmol) was added to a solution of 8a
(0.446 g, 0.809 mmol) in CH2Cl2 (100 mL). After being stirred
for 30 min, the solution was filtered, and the solvent was evap-
orated under reduced pressure to leave a brown oil which was
washed with diethyl ether (15 mL) and pentane (15 mL) and
dried under vacuum to give a brown powder. Complexes cis-
and trans-20a were obtained as a brown powder in a 60:40
X-Ray crystallographic analyses
The relevant data for 1 and 12b are summarized in Table 4. For
1 all non-hydrogen atoms were refined anisotropically. The
hydrogen atoms were calculated and fixed in idealized positions
(dC-H = 0.95 Å, BH = 1.3Bequiv for the carbon to which it was
attached), except for the NH proton which was located in the
difference Fourier map and refined with a fixed isotropic B = 4
Å2. For 12b all non-hydrogen atoms were refined anisotropic-
ally. The hydrogen atoms were calculated and fixed in idealized
positions (dC-H = 0.95 Å). Fig. 1 and 3 were generated using
ORTEP.43
ratio. Yield: 0.498 g (75%). cis-20a: IR (CH2Cl2, cmϪ1): νCO
=
1586s; 31P{1H} NMR (acetone-d6): δ 69.7 (d, 1P, NP), 109.9 [d,
1P, JPP = 46 Hz, P(OPh)3]. trans-20a: IR (CH2Cl2, cmϪ1): νCO
=
1641m; 31P{1H} NMR (acetone-d6): δ 71.0 (d, 1P, NP), 107.3
[d, 1P, JPP = 595 Hz, P(OPh)3]. Calc. for C33H32F6NO4P3Pd: C,
48.34; H, 3.93; N, 1.71. Found: C, 48.54; H, 3.89; N, 1.52%.
CCDC reference number 186/1980.
See http://www.rsc.org/suppdata/dt/b0/b002386h/ for crystal-
lographic files in .cif format.
[PdMe{PPh2NHC(O)Me}{P(OPh)3}][O3SCF3] 20b. A pro-
cedure similar to that used for 20a starting from 8b (0.118 g,
0.210 mmol) in CH2Cl2 (40 mL) and P(OPh)3 (55.7 µL, 0.210
mmol) yielded cis- and trans-20b in a 60:40 ratio. Yield 0.129 g
(75%). Calc. for C34H32F3NO7P2SPd: C, 49.56; H, 3.91; N, 1.70.
Found: C, 49.51; H, 4.07; N, 1.51%.
Acknowledgements
We are grateful to Professor J. Fischer, Dr A. DeCian and
N. Gruber (Strasbourg) for the crystal structure determination
of 1. This work was supported by the Centre National de la
Recherche Scientifique and the Ministère de l’Education
Nationale, de l’Enseignement Supérieur et de la Recherche
(PhD grant to CF). We are grateful to NATO (research grant
CRG 920073) for financial support and to Johnson Matthey
PLC for a generous loan of PdCl2.
Carbonylation reactions
A solution of the appropriate monocationic methyl complex
(8a, 17, 18a or 20a) in CH2Cl2 (20 mL) was treated with CO at
room temperature to give the acetyl complexes 21–24 which
were characterized by spectroscopic methods.
[Pd{C(O)Me}{PPh2NHC(O)Me}(NCMe)][PF6]
21.
IR
(CH2Cl2, cmϪ1):νCO = 1716s, 1618w; 1H NMR (acetone-d6):
δ 2.27 [s, 3H, PdC(O)Me], 2.30 (s, 3H, NCMe), 2.35 [s,
3H, C(O)Me], 8.79 (s, 1H, NH); 31P{1H} NMR (acetone-d6):
δ 58.95.
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1
(CH2Cl2, cmϪ1): νCO = 1705s, 1608w; H NMR (CDCl3): δ 1.64
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