Rhodium complexes containing the hybrid P, O ligand PPh2NHC(O)Me or its anion, [PPh2N...C(...O)Me]-

Article abstract of DOI:10.1039/b208735a

The coordination behaviour of the heterofunctional phosphine ligand PPh₂NHC(O)Me towards Rh(I) is reported and examples of neutral and cationic complexes containing mono- or bi-dentate modes of coordination are found. The X-ray structure of [Rh{PPh₂NHC(O)Me}(CO)Cl]·CH ₂Cl₂ (1·CH₂Cl₂) shows that the P,O-chelate is almost planar and coplanar with the Rh(I) square-plane. An unusual example of coordination is found in the dimmer [Rh{μ-PPh ₂Ni...C(...O)Me}(CO)]₂ (2), which contains the bidentate, anionic ligand that bridges two rhodium atoms via the oxygen; it is probable that the neutral ligand can form similar complexes, such as 11 and 12. Displacement of the P,O ligand by CO or RNC ligands occurs in 1 but not in 2.

Full text of DOI:10.1039/b208735a

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Rhodium complexes containing the hybrid P,O ligand
؊
ؒ ؒ ؒ
ؒ ؒ ؒ
PPh2NHC(O)Me or its anion, [PPh2N––C(––O)Me] †
Pierre Braunstein,a Brian T. Heaton,b Chacko Jacob,b Lucia Manzib and Xavier Morisea
a Laboratoire de Chimie de Coordination, UMR 7513 CNRS, Université Louis Pasteur,
4 rue Blaise Pascal, Strasbourg Cedex, France. E-mail: braunst@chimie.u-strasbg.fr
b Department of Chemistry, University of Liverpool, Liverpool, UK L69 3BX
Received 6th September 2002, Accepted 10th January 2003
First published as an Advance Article on the web 19th February 2003
The coordination behaviour of the heterofunctional phosphine ligand PPh2NHC(O)Me towards Rh() is reported
and examples of neutral and cationic complexes containing mono- or bi-dentate modes of coordination are found.
The X-ray structure of [Rh{PPh2NHC(O)Me}(CO)Cl]ؒCH2Cl2 (1ؒCH2Cl2) shows that the P,O-chelate is almost
planar and coplanar with the Rh() square-plane. An unusual example of coordination is found in the dimer
ؒ ؒ ؒ
ؒ ؒ ؒ
[Rh{µ-PPh N C( O)Me}(CO)] (2), which contains the bidentate, anionic ligand that bridges two rhodium atoms
–– ––
2
2
via the oxygen; it is probable that the neutral ligand can form similar complexes, such as 11 and 12. Displacement of
the P,O ligand by CO or RNC ligands occurs in 1 but not in 2.
of the phosphorus resonance from that of the free phosphine
Introduction
(∆δP ca. ϩ80 ppm) is consistent with the formation of a five-
The continuing interest in the coordination behaviour of new
membered chelate ring. The IR spectrum supports the presence
functional ligands applies in particular to phosphines, which
are ubiquitous in coordination and organometallic chemistry,
and various systems have been studied, in particular those
Ϫ1
of a carbonyl group [ν(C᎐O) 1997 cm (CH2Cl2); 1990 cmϪ1
᎐
᎐
(KBr)]. Chelation of the amide group via the oxygen atom
results in a shift of ν(C᎐O) from 1714 cmϪ1 (free ligand) to 1579
᎐
which combine a soft phosphine moiety with a hard oxygen
cmϪ1
.
functionality.1–3 Their asymmetry may be of interest for the
occurrence of hemilability and for allowing a stereo-electronic
control of the active metal centre. For example, the ketophos-
phine ligand PPh2CH2C(O)Ph readily displays hemilabile
behaviour in Ru() and Rh() complexes.4,5 We recently began
to study the coordination properties of ligands of the type
In order to confirm the structure of 1 in solution, the reaction
in eqn. (1) was carried out with [Rh(µ-Cl)(13CO)2]2 (100%
13CO). In this case, the 31P{1H} NMR shows additional coup-
ling (2JPC 17.9 Hz) and the carbonyl resonance in the 13C{1H}
1
NMR spectrum is a doublet of doublets (δC 187, JRhC 77.4,
2JPC 18 Hz); the low value of 2JPC is entirely consistent with CO
being cis to the phosphorus. The broad (in CDCl3) N–H reson-
ance (δH 10.5) at room temperature is 4 ppm downfield from the
free ligand and in the range observed for Pd() complexes con-
taining this chelating ligand.6 This is consistent with electron
withdrawal from the ligand on coordination.
PPhn{NHC(O)CH3}3Ϫn (n = 1, 2),6 i.e. acetamido anologues of
7
the ketophosphines PPhn{CH2C(O)RЈ}3Ϫn
.
Modifications 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 versus
P–C–C bond angle in the α-position to the P atom.8 Further-
more, deprotonation of the NH group should be easy and
lead to anionic chelating ligands related to the phosphino-
enolates obtained from the corresponding ketophosphines,
whose square-planar Rh() complexes catalyse the activation
of alkanes by transfer-hydrogenation.9 We report here investi-
gations on the coordination properties of the acetamide-
derived ligand PPh2NHC(O)Me in Rh() complexes.
Single crystals of 1ؒCH2Cl2, suitable for X-ray analysis, were
grown by slow diffusion of THF/diethyl ether (1 : 3) into a
solution of 1 in dichloromethane. A view of the structure is
shown in Fig. 1 and is entirely consistent with the solution
Results and discussion
Slow addition of a dichloromethane solution of PPh2NH-
C(O)Me (P,O)‡ to a solution of [Rh(µ-Cl)(CO)2]2 in dichloro-
methane results in CO evolution and formation of 1, [eqn. (1)].
(1)
The 31P{1H} NMR spectrum of 1 in dichloromethane is
unchanged over the temperature range 293–193 K and consists
1
of a doublet (δP 104.8, JRhP 174 Hz); the large downfield shift
† Dedicated to Dr Jean-Marie Basset on the occasion of his 60th birth-
day, with our congratulations and best wishes.
‡ Abbreviations used: free ligand, P,O; monodentate coordination
through P: P,O; bidentate coordination through P and O: P,O.
Fig. 1 Molecular geometry of [Rh(P,O)(CO)Cl] (1). The H atoms,
including the NH atom, are not shown for clarity. Thermal ellipsoids
correspond to 50% probability.
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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 Selected intramolecular bond distances (Å) and angles (Њ) for
[Rh(P,O)(CO)Cl]ؒCH2Cl2 (1ؒCH2Cl2)
Table 2 31P{1H} NMR data (CD2Cl2 unless otherwise stated) for
PPh2NHC(O)Me and related Rh() complexes
Rh–Cl
Rh–P
C(1)–O(1)
N–C(14)
2.372(1)
2.180(1)
1.155(7)
1.337(6)
Rh–C(1)
Rh–O(2)
C(14)–O(2)
1.794(7)
2.094(4)
1.265(6)
Compound
Free P,O
δP (ppm)
1JRhP/Hz
Trans-group
30.4 (minor)
22.3 (major)a
Cl–Rh–C(1)
Cl–Rh–O(2)
C(1)–Rh–O(2)
N–C(14)–O(2)
95.6(2)
88.2(1)
176.2(2)
120.9(5)
Cl–Rh–P
170.88(6)
93.1(2)
83.1(1)
Monodentate P,O
C(1)–Rh–P
P–Rh–O(2)
P–N–C(14)
6
7
8
9
49.5
49.7
53.3
55.1
127
126
128
130
CO
PPh3
CNR
CNR
118.0(4)
structure. The chelating ligand forms a five-membered ring with
the metal in which the P–N–C–O moiety is almost planar and
coplanar with rhodium, which adopts a slightly distorted
square-planar geometry. The bite angle of 83.1Њ is comparable
to those found for other Rh() complexes containing the chelat-
ing ketophosphine PPh2CH2C(O)Ph.9 The O(2)–C(14) bond
distance in the chelate ring [1.265(6) Å] is shorter than a single
C–O bond distance. These values also compare with those
found in the Pd() complexes 80.5(1) and 1.244(7) Å, respect-
ively.6 The values of the bond distances around the Rh centre
are in agreement with those found for analogous neutral Rh()
carbonyl complexes and selected bond distances and angles are
given in Table 1.
Bidentate P,O/neutral
1
2
104.8
114.2
174
153
Cl
O-bridge
Chelating P,O/cationic
11
12
13
14
15
109.2
109.0
94.6
93.3
81.9
181
184
156
129
122
O-bridge
O-bridge
PPh3
PPh3
P (P,O)
a At room temperature, there are two resonances due to the keto/iminol
equilibrium.
The N–H proton in 1 can be removed by addition of a source
of hydride. Thus, on addition of a suspension of 1 in THF to a
suspension of KH or NaH in THF, the colour changes from
orange to give a new brown/black complex, 2. In the 1H NMR
spectrum of 2, there is no evidence for the N–H proton and
elemental analysis shows the absence of chloride. The form-
ation of 2 is completely reversible and addition of HCl to a
solution of 2 in CH2Cl2 results in reformation of 1. The mass
spectrum (FAB) of 2 suggests a dimeric formulation [eqn. (2)]
but all attempts to obtain crystals of 2, suitable for X-ray
analysis, failed.
SCH2CH2PPh2), analogous to 1, is likely to be involved but
catalytic experiments using 1 have not yet been carried out.
The reaction of 1 with CO to give 6 is completely reversible
[eqn. (3)]. The IR spectrum of 6 in CH2Cl2 solution, under an
᎐
atmosphere of CO, shows two strong ν(C᎐O) bands (2020 and
᎐
1996 cmϪ1), consistent with the proposed cis-geometry. The
value of ν(C᎐O) for the amide group (1708 cmϪ1) is close to that
᎐
of the free ligand, in-keeping with monodentate coordination
of the ligand. Consistent with the opening of the chelate ligand
in 1, there is a large high field shift (∆δP ca. Ϫ55 ppm) of the
phosphorus resonance for 6 (δP 49.5, 1JRhP = 127 Hz).
(2)
Spectroscopic data (Table 2) are entirely in agreement with
the above formulation of 2. The 31P{1H} NMR spectrum of 2 in
1
CH2Cl2 consists of a doublet (δP 114.2, JRhP 153 Hz) and
103Rh{31P} HMQC measurements show only one 103Rh reson-
ance (δRh Ϫ68). Consistent with the presence of the anionic
᎐
ligand, the value of ν(C᎐O), compared to 1, shifts to lower
The structure of 6 in solution has been unambiguously estab-
lished by carrying out the reaction of 1 with 13CO (100% 13CO).
The 31P{1H} NMR spectrum of 6 (100% 13CO) at 193 K shows
᎐
frequency, 1965 cmϪ1, and this increased electron density is also
ؒ ؒ ؒ
delocalised over the coordinated amidate group [ν(C N) ϩ
––
Ϫ1
2
ν(C O) 1465 cm ].
additional couplings, (2JPCtrans ca. 122, JPCcis ca. 7 Hz) and, on
ؒ ؒ ؒ
––
These spectroscopic data are in agreement with the values
found for related rhodium carbonyl dimers containing phos-
phinothiolate ligands e.g. [Rh(SC6H4PPh2-κ2P,S)(CO)]2 (3)
increasing the temperature, the resonance broadens (coales-
cence temperature 213 K, ∆G# = 41.6 KJ molϪ1) but there is
little change in the chemical shift. It is thus unlikely that this
broadening results from an equilibrium involving a mono-/
bi-dentate interconversion of the P,O ligand and we presently
favour an equilibrium involving a monomer/chloro-bridged
dimer, through loss of CO, with retention of the monodentate
P,O ligand [eqn. (4)].
1
Ϫ1
᎐
(δP 60.5, JRhP 158 Hz, ν(C᎐O) 1946 cm ) and [Rh(SCH -
᎐
2
1
CH2PPh2-κ2P,S)(CO)]2 4 (δP 63.7, JRhP 158 Hz, ν(C᎐O) 1947
᎐
᎐
cmϪ1). The methods of preparation of 2, 3 and 4 are similar
and involve the reaction of the appropriate ligand with [Rh-
(µ-Cl)(CO)2]2 in the presence of a base. It should be noted that
3 and 4 have been shown to be four times more active in
catalysing the carbonylation of MeOH than the well-known
catalyst [RhI2(CO)2]Ϫ.10
Although the exact catalytic mechanism for the carbonyl-
ation of MeOH by 3 and 4 is still unclear, the formation of a
mononuclear species [Rh(P,S)(CO)I], (5) (P,S = SC6H4PPh2 or
Reaction of 1 with other ligands, such as PPh3, RNC (R =
2,6-Me2C6H4), is related but different to that observed with CO
(see Scheme 1). The 31P{1H} NMR spectrum of 7 shows two sets
of doublets of doublets due to the inequivalent P atoms, P,O
1
2
(δP(A) 49.7, JRhP(A) 126, JP(A)P(B) 356 Hz) and PPh3 (δP(B) 27.4,
1JRhP(B) 122, JP(A)P(B) 356 Hz); the large value of JP(A)P(B)
2
2
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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Scheme 2
Scheme 1
unambiguously confirms the trans arrangement of the two
phosphine groups and the shift to high field (compared to 1) is
consistent with a monodentate P,O ligand.
Further addition of PPh3 to 7 results in displacement of the
P,O ligand and formation of trans-[Rh(PPh3)2(CO)Cl]; this
reaction can be reversed, but in order to completely reverse the
reaction, it is necessary to add excess P,O ligand.
Complex 8 is formed on addition of RNC to 1 (Scheme 1)
and the 31P{1H} NMR data (δP 53.3, 1JRhP 128 Hz) are similar to
those found for 6 and 7. The low value of 1JRhP thus appears to
be typical of phosphorus trans to π-acceptor ligands such as
PPh3, CO or RNC.
The IR spectrum of 8 (CH2Cl2) shows two absorptions at
2001 and 2158 cmϪ1 ascribed to ν(C᎐O) and ν(C᎐N), respect-
᎐
᎐
᎐
᎐
Scheme 3
ively. Further addition of one molar equivalent of RNC to 8
results in the formation of 9 with the disappearance of the
(4 h) at room temperature (see Scheme 3). However, the best
synthetic route to 13 is via the addition of P,O (1 equiv.) to
a solution of [Rh(PPh3)2(nbd)]ClO4 in CH2Cl2 under an
atmosphere of H2.
᎐
ν(C᎐O) band and the phosphorus resonance remains in the
᎐
1
monodentate P-bonded region (δP 55.1, JRhP 130 Hz); the IR
᎐
spectrum (KBr) has two strong ν(C᎐N) bands at 2126 and 2098
᎐
cmϪ1, consistent with the cis-arrangement of the RNC ligands.
Complex 9 is not stable in CHCl3 or CH2Cl2 solution and, after
The 31P{1H} NMR spectrum of 13 (see Fig. 2) consists of
three sets of resonances which unambiguously establishes the
structure; the P,O resonance is a doublet of doublets of
1 day, a new complex is formed, [δP 88.7, 1JRhP 91.5 Hz; ν(C᎐N)
᎐
᎐
2150 cmϪ1], which is formulated as 10 (Scheme 1). However, we
1
2
2
doublets [δP(A) 94.6, JRhP(A) 156, JP(A)P(B) 38, JP(A)P(C) 310 Hz],
have not been able to isolate a pure complex from these
solutions.
Halide abstraction and formation of the cationic dimeric
complexes 11 and 12 occurs on addition of AgClO4 and AgBF4
to a solution of 1 in CH2Cl2 and THF, respectively (Scheme 2).
Elemental analysis and spectroscopic data are consistent with
the formulations of 11 and 12; both the 31P{1H} NMR spec-
1
trum (δP 109.2, JRhP 181 Hz) and the IR spectrum (KBr)
Ϫ1
᎐
[ν(C᎐O) 2006; ν(C᎐O) 1653 cm ] of 11 are consistent with
᎐
᎐
coordination of the P,O ligand shown in Scheme 2.
The tetrafluoborate complex 12 is almost insoluble in
CH2Cl2, CHCl3, THF and MeOH. However, in acetone it is
1
possible to obtain the 31P{1H} NMR spectrum (δP 109, JRhP
184 Hz), which is similar to that of 11. For both 11 and 12
(CDCl3) the N–H resonances (δ 10.5) are coincident and broad.
Addition of KH to a solution/suspension of 11 or 12 in THF
results in deprotonation of the P,O ligand and formation of 2,
vide supra.
The cationic Rh() chelate complex [Rh(P,O)(PPh3)2]ClO4
(13) can be synthesised by addition of P,O (1 equiv.) to a MeOH
solution of [Rh(PPh3)2(η6-toluene)]ClO4 followed by stirring
Fig. 2 31P{1H} NMR spectrum of [Rh(P,O)(PPh3)2]ClO4 (13) in
CH2Cl2 at room temperature. The starred peaks correspond to
impurities.
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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the PPh3 resonance trans to the oxygen is a doublet of triplets
(3 equiv.) to an acetone solution of 14 gives the bis-chelate
1
2
2
[δP(B) 50, JRhP(B) 177, JP(B)P(A) 38, JP(B)P(C) 38 Hz] and the
resonance due to PPh3 trans to phosphorus is also a doublet
cationic complex [Rh(P,O)2]ClO4 (15) as a yellow precipitate
and the neutral complex trans-[Rh(PPh3)2(CO)Cl], remains in
solution.
1
2
of doublets of doublets [δP(C) 28.8, JRhP(C) 140, JP(C)P(B) 38,
2JP(C)P(A) 310 Hz] (see Fig. 2 for labelling scheme).
Complex 15 is soluble in polar solvents such as MeOH and
The synthesis of the related cationic, Rh() carbonyl com-
plex [Rh(P,O)(CO)(PPh3)]ClO4 (14) has been achieved by the
slow addition of PPh3 and AgClO4 to a MeOH solution of
[Rh(µ-Cl)(CO)2]2 followed by addition of the P,O ligand
(Rh : P,O = 1 : 1) [eqn. (5)].
EtOH and the 31P{1H} NMR spectrum consists of one doublet
1
(δP 81.9, JRhP 122 Hz); in the IR spectrum (KBr), the ν(CO)
band due to the amide group occurs at 1593 cmϪ1. Although
bis-chelate Rh() complexes, such as [Rh(PPh2CH2py-κ2P,N)2]-
14
ClO4,13 [Rh{PPh2(CH2)2py-κ2P,N}2]PF6 or [Rh{PPh2CH2C-
(O)Ph-κ2P,O}2]PF6,9 prefer to adopt a cis geometry, the small
value of 1JRhP for 15 (122 Hz compared to ca. 170 Hz) suggests
that in this case the trans-configuration is adopted. This is
1
consistent with the change in JRhP observed on going from
cis-[Rh{PPh2(CH2)2py-κ2P,N}2]PF6 (171 Hz) to trans-[Rh-
{PPh2(CH2)2py-κ2P,N}2(CO)] (125 Hz).14
(5)
In their recent studies of the coordination properties of the
related ligand PPh2NHC(O)Ph,15a Woollins et al. have observed
P-monodentate behaviour with Pt(), Rh() and Ru() and
P,O-chelation with Ni().15b
The 31P{1H} NMR spectrum of 14 is temperature-independ-
ent over the range 193–293 K and consists of two resonances
1
2
due to the P,O ligand [δP(A) 93.3, JRhP(A) 129, JP(A)P(B) 315 Hz]
1
2
and PPh3 [δP(B) 27.7, JRhP(B) 132, JP(A)P(B) 315 Hz]. In the IR
᎐
spectrum (KBr) the ν(C᎐O) and ν(C᎐O) vibrations occur at
Experimental
᎐
᎐
1989 and 1576 cmϪ1, respectively. Both sets of data are entirely
consistent with the structure shown in eqn. (5).
All operations were carried out under a nitrogen atmosphere.
Solvents were distilled and dried using published methods. The
13C{1H} and 31P{1H} NMR spectra were recorded on a Bruker
AMX-200 or AMX-400 spectrometer. The 31P{103Rh} HMQC
measurements were carried out on a Bruker AMX-200
spectrometer using a 10 mm probe, as described previously.16
Chemical shifts are referenced to SiMe4 (δC = 0) external 85%
H3PO4 in D2O (δP = 0) and 3.14 MHz at such a magnetic field
that the protons in SiMe4 resonate at exactly 100 MHz (δRh = 0).
IR spectra were recorded in solution, using CaF2 cells previ-
ously purged with nitrogen, or as a KBr disc on a Perkin-Elmer
257 FTIR spectrometer. Elemental analyses were carried out by
the microanalytical staff at the Universities of Liverpool and
Strasbourg.
It is of interest to compare the different reactivities of 13 and
14. Complex 13 is stable for several weeks in CH2Cl2 solution
and, as found for the related complex [Rh{PPh2CH2C(O)-
Ph-κ2P,O}(PPh3)2]ϩ, there is no reaction with H2 or with an
excess of PPh3 and no dissociation of PPh3 occurs. However,
the chelate P,O ligand is replaced by the more strongly coordin-
ating bidentate ligand 2-(diphenylphosphino)methylpyridine,
1
to give [Rh(PPh2CH2py-κ2P,N)2]ClO4 (δP 60.4, JRhP 168.5 Hz)
(Scheme 4).
Syntheses
Literature methods were used to prepare PPh2NHC(O)Me6
(abbreviated as P,O), [Rh(µ-Cl)(CO)2]2 17 and [Rh(nbd)(PPh3)2]-
ClO4.18
2-(Diphenylphosphinomethyl)pyridine (PPh2CH2py)
A solution of n-butyllithium (15.6 mL of a 1.6 M solution in
hexane, 25 mmol) was added to 2-picoline (2.33 g, 25 mmol) in
dry THF (20 mL) at 253 K over 20 min. After stirring (1 h), the
mixture was added to a solution of chlorodiphenylphosphine
(5.5 g, 25 mmol) in dry THF (25 mL) at 213 K over 30 min
followed by warming to 253 K over 45 min. The mixture was
then cooled to 248 K and water (50 mL) added over 10 min,
followed by stirring for 30 min. The product was obtained by
extraction with an HCl solution (2 × 250 mL, 0.3 M), followed
by neutralisation with a NaHCO3 solution, and extraction with
dichloromethane (3 × 100 mL). The solvent and any unreacted
2-picoline were removed in vacuo. The yield of crude product
was 4.7 g (75%). The latter was dissolved in warm EtOH
(50 mL) followed by addition of water (50 mL). Storing over-
night at 243 K gave a cream coloured precipitate of the product.
This was filtered off and dried in vacuo, yield 3.8 g, 60%.
(Found: C, 77.80; H, 5.75; N, 5.00%. C18H16NP requires C,
77.94; H, 5.82; N, 5.05%.) δP (CH2Cl2): Ϫ11.6. Other spectro-
scopic data are consistent with literature values.19
Scheme 4
When CO was bubbled through a solution of 13 in CH2Cl2,
displacement of the P,O ligand occurred to give [Rh(CO)2-
(PPh3)2]ClO4 (δP 22.3, 1JRhP 114 Hz),11 which readily reacts fur-
ther with CO to give the more stable five-coordinate complex
[Rh(CO)3(PPh3)2]ClO4 (δP 32.2, 1JRhP 72 Hz).12
Unlike 13, 14 does not react with CO at atmospheric pressure
nor with other potentially bidentate P,N ligands. There is also
no reaction of 14 with even a large excess of HBF4 or HSO3Me
in acetone or CH2Cl2 solution; however, addition of HCl
[Rh(P,O)(CO)Cl] (1)
A solution of P,O (0.27 g, 1.11 mmol) in CH2Cl2 (5 mL) was
added dropwise to a solution of [Rh(µ-Cl)(CO)2]2 (0.22 g, 0.56
mmol) in CH2Cl2 (5 mL) at room temperature. The resulting
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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Table 3 X-Ray experimental data for complex 1ؒCH2Cl2
orange solution was stirred (2 h), evaporated to dryness and the
residue washed with pentane to give the crude product as an
orange powder, (yield 0.37 g, 80%). Yellow crystals of 1ؒ
CH2Cl2, suitable for X-ray analysis, were obtained by slow
diffusion of THF/Et2O (1 : 3) into a dichloromethane solution
of the crude product. (Found: C, 44.00; H, 3.45; N, 3.43%.
Calc. for C15H14ClNO2PRh: C, 43.95; H, 3.48; N, 3.42%.)
δP (CD2Cl2): 104.8 (d, 1JRhP 174 Hz); δC (CD2Cl2): 187 (dd, CO,
Formula
Molecular weight
C16H16NO2PCl3Rh
494.55
Crystal system
a/Å
b/Å
c/Å
monoclinic
9.5442(2)
16.4222(4)
13.2981(2)
102.916(9)
2031.6(2)
173
P21/n
4
1.311
β/Њ
2
V/Å3
1JRhC 77.4, JPC 18 Hz); δH (CDCl3): 10.5 (br, NH); IR (KBr)
Temperature/K
Space group
Z
ν(CO): 1997, 1579 cmϪ1, ν(Rh–Cl) 283 cmϪ1.
µ/mmϪ1
ؒ ؒ ؒ
ؒ ؒ ؒ
[Rh{ꢀ-PPh N C( O)Me}(CO)] (2)
–– ––
2
2
Number of data meas.
Number of data
R, Rw
17433
3550 with I > 3 σ(I )
0.053; 0.070
A suspension of 1 in THF was added dropwise to a suspen-
sion of KH (KH : 1 = ca. 10 : 1) in THF at room temperature.
After stirring (1 h), the colour changed from yellow/orange to
brown/green. The suspension was filtered and the filtrate dried
in vacuo; the residue was washed with pentane to give 2 as a
brown/black powder, typical yield 65%. (Found: C, 48.30; H,
3.52; N, 3.76%. Calc. for C30H26N2O4P2Rh2: C, 48.28; H, 3.51;
N, 3.75%.) δP (CD2Cl2): 114.2 (1JRhP 153 Hz); δRh Ϫ68; IR (KBr)
ν(CO): 1965, 1465 cmϪ1.
a
a R = Σhkl(||Fobs| Ϫ |Fcalc||)/Σhkl|Fobs|; Rw = [Σhklw(|Fobs| Ϫ |Fcalc|)2/Σhklw-
2
1/2
Fobs
] .
[Rh(P,O)2]ClO4 (15)
HCl in Et2O (2 × 75 mL, 1 M) was added to a solution of
[Rh(P,O)(PPh3)(CO)]ClO4 (0.5 g, 0.68 mmol) in acetone
(10 mL) at room temperature. A yellow precipitate of the prod-
uct was formed immediately; the complex 15 was filtered off,
washed with hexane and dried in vacuo, yield 0.34 g, 75%.
(Found: C, 48.85; H, 4.30; N, 4.10%. Calc. for C28H28ClN2O6-
P2Rh: C, 48.82; H, 4.10; N, 4.09%.) δP (CD2Cl2): 81.9 (d,
1JRhP 122 Hz); IR (KBr) ν(CO): 1593 cmϪ1.
[Rh(ꢀ-P,O)(CO)]2[ClO4]2 (11)
To a solution of 1 (0.06 g, 0.15 mmol) in THF (10 mL) was
added AgClO4 (0.03 g, 0.15 mmol). After stirring at room tem-
perature (2 h), the colour of the reaction mixture became green/
brown. The resulting suspension was filtered; the product 11
was obtained by concentrating the filtrate in vacuo followed by
washing with pentane, yield 0.05 g, 70%. (Found: C, 38.06; H,
3.00; N, 2.97%. Calc. for C30H28Cl2N2O12P2Rh2: C, 38.04; H,
2.98; N, 2.96%.) δP (CD2Cl2): 109.2 (1JRhP 181 Hz); δH (CD2Cl2):
10.5; IR (KBr) ν(CO): 2006, 1653 cmϪ1.
X-Ray diffraction study
Yellow, single crystals of 1ؒCH2Cl2 suitable for X-ray diffrac-
tion were grown by slow diffusion of THF/Et2O (1 : 3) into a
dichloromethane solution of the crude product. The X-ray
experimental data are given in Table 3. 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.
A similar procedure was followed for the synthesis of the
[BF4]Ϫ salt, 12, using AgBF4 instead of AgClO4. However, in
this case, the yield was usually lower (ca. 60%).
[Rh(P,O)(PPh3)2]ClO4 (13)
CCDC reference number 192615.
See http://www.rsc.org/suppdata/dt/b2/b208735a/ for crystal-
lographic data in CIF or other electronic format.
Hydrogen was bubbled through a solution containing [Rh(nbd)-
(PPh3)2]ClO4 (0.10 g, 0.12 mmol) and P,O (0.03 g, 0.12 mmol)
in dichloromethane (5 mL) for 5 min; the colour of the solu-
tion immediately changed from yellow/orange to deep red.
Addition of petroleum ether (40–60) (10 mL) gave, after 3 days
in the refrigerator, deep red needles of 13, which were filtered
off, washed with petroleum ether (40–60) (3 × 10 mL)
and dried in vacuo, yield 0.09 g, 80%. (Found: C, 62.00; H,
4.58; N, 1.90%. Calc. for C50H44ClNO5P3Rh: C, 61.90; H,
Acknowledgements
This work was supported by the Centre National de la
Recherche Scientifique (Paris), the Ministère de la Recherche
(Paris) and the EC (Contract No. CHRX-CT93-0277). We
are grateful to the Erasmus mobility scheme for support to
L. M. during her stay in Strasbourg and to EPSRC for the
NMR equipment. We thank Dr. A. DeCian and N. Kyritsakis
(Strasbourg) for the X-ray structure determination.
1
4.57; N, 1.44%.) δP (CD2Cl2): 94.6 (ddd, P(A), JRhP(A) 156 Hz,
2
1
2JP(A)P(C) 310 Hz, JP(A)P(B) 38 Hz), 50 (dt, P(B), JRhP(B) 177 Hz,
2JP(A)P(B) = JP(B)P(C) 38 Hz), 28.8 (ddd, P(C), JRhP(C) 140 Hz,
2
1
2JP(A)P(C) 310 Hz, JP(B)P(C) 38 Hz) (see Fig. 2 for labelling
2
scheme).
References
[Rh(P,O)(PPh3)(CO)]ClO4 (14)
1 A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108, 27.
2 C. S. Slone, D. A. Weinberger and C. A. Mirkin, Prog. Inorg. Chem.,
1999, 48, 233.
3 P. Braunstein and F. Naud, Angew. Chem., Int. Ed., 2001, 40,
680.
4 P. Braunstein, Y. Chauvin, J. Nähring, Y. Dusausoy, D. Bayeul,
A. Tiripicchio and F. Ugozzoli, J. Chem. Soc., Dalton Trans., 1995,
851.
5 P. Braunstein, Y. Chauvin, J. Nähring, A. DeCian and J. Fischer,
J. Chem. Soc., Dalton Trans., 1995, 863.
6 P. Braunstein, C. Frison, X. Morise and R. D. Adams, J. Chem. Soc.,
Dalton Trans., 2000, 2205.
7 S.-E. Bouaoud, P. Braunstein, D. Grandjean, D. Matt and D. Nobel,
Inorg. Chem., 1986, 25, 3765.
8 P. Braunstein, J. Pietsch, Y. Chauvin, S. Mercier, L. Saussine,
A. DeCian and J. Fischer, J. Chem. Soc., Dalton Trans., 1996,
3571.
To a solution of [Rh(µ-Cl)(CO)2]2 (0.163 g, 0.415 mmol) in
MeOH (10 mL) was added slowly a suspension of PPh3 (0.218
g, 0.83 mmol) in MeOH (20 mL); AgClO4 (0.172 g, 0.83 mmol)
was then added and the solution left to stir overnight. The sus-
pension of AgCl was filtered off and a solution of P,O (0.204 g,
0.83 mmol) in MeOH (5 mL) was slowly added to the filtrate
with stirring. Effervescence due to the evolution of CO was
observed and concentration gave the product 14 as yellow crys-
tals which were filtered off, washed with Et2O (2 × 5 mL) and
dried in vacuo, yield 0.49 g, 80%. (Found: C, 53.88; H, 3.81; N,
2.00%. Calc. for C33H29ClNO6P2Rh: C, 53.86; H, 3.97; N,
1.90%.) δP (CD2Cl2): 93.3 (dd, 1JRhP 129 Hz, 2JPP 315 Hz), 27.7
(dd, PPh3, 1JRhP 132 Hz, 2JPP 315 Hz); δH (CDCl3): 10.8 (b, NH);
IR (KBr): ν(CO) 1989, 1576 cmϪ1.
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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View Article Online
9 P. Braunstein, Y. Chauvin, J. Nähring, A. DeCian, J. Fischer,
A. Tiripicchio and F. Ugozzoli, Organometallics, 1996, 15, 5551.
10 J. R. Dilworth, J. R. Miller, N. Wheatley, M. J. Baker and J. G.
Sunley, J. Chem. Soc., Chem. Commun., 1995, 1579.
11 A. R. Siedle, R. A. Newmark and R. D. Howells, Inorg. Chem., 1988,
27, 2473.
15 (a) T. Q. Ly, A. M. Z. Slawin and J. D. Woollins, Polyhedron, 1999,
18, 1761; (b) P. Bhattacharyya, T. Q. Ly, A. M. Z. Slawin and
J. D. Woollins, Polyhedron, 2001, 20, 1803.
16 E. V. Grachova, B. T. Heaton, J. A. Iggo, I. S. Podkorytov,
D. J. Smawfield, S. P. Tunik and R. Whyman, J. Chem. Soc.,
Dalton Trans., 2001, 3303 and references therein.
12 G. A. Long, T. B. Marder, P. E. Behnken and M. F. Hawthorne,
J. Am. Chem. Soc., 1984, 106, 2979.
13 L. Manzi, PhD Thesis, University of Liverpool, 2000.
14 M. P. Anderson, A. L. Casalnuovo, B. J. Johnson, B. M. Mattson,
A. M. Mueting and L. H. Pignolet, Inorg. Chem., 1988, 27, 1649.
17 J. A. McCleverty and G. Wilkinson, Inorg. Synth., 1966, 8, 211.
18 R. R. Schrock and J. A. Osborn, J. Am. Chem. Soc., 1971, 93,
2397.
19 B. Åkermark, B. Krakenberger, S. Hansson and A. Vitagliano,
Organometallics, 1987, 6, 620.
D a l t o n T r a n s . , 2 0 0 3 , 1 3 9 6 – 1 4 0 1
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