Straightforward synthesis of donor-stabilised phosphenium adducts from imidazolium-2-carboxylate and their electronic properties

Article abstract of DOI:10.1002/ejic.200700590

Cationic imidazolium-2-phosphanes were obtained by the addition of a chlorophosphane (R₂PCl, R = Ph, iPr or Cy) to 1,3- dimethylimidazolium-2-carboxylate without the need for a purification step. An additional anion exchange reaction with KPF

Full text of DOI:10.1002/ejic.200700590

FULL PAPER
DOI: 10.1002/ejic.200700590
Straightforward Synthesis of Donor-Stabilised Phosphenium Adducts from
Imidazolium-2-carboxylate and Their Electronic Properties
Michèle Azouri,[a] Jacques Andrieu,*[a] Michel Picquet,[a] Philippe Richard,[a]
Bernard Hanquet,[a] and Igor Tkatchenko[a]
Keywords: Carboxylates / Phosphanes / Electronic properties / Synthesis / Coordination modes
Cationic imidazolium-2-phosphanes were obtained by the
addition of a chlorophosphane (R2PCl, R = Ph, iPr or Cy) to
1,3-dimethylimidazolium-2-carboxylate without the need for
a purification step. An additional anion exchange reaction
with KPF6 led to the corresponding halide-free ligands in ex-
cellent yields. The molecular structure of one of them was
examined both in the solid state and in solution. The lone
pair of electrons on the phosphorus atom is not delocalised
to the imidazolium fragment and thus remains available for
ceptor phosphorus centre was evaluated upon nickel tricar-
bonyl coordination, and the properties are surprisingly sim-
ilar to those found for phosphites. The stronger π-acceptor
character of these imidazolium-2-phosphanes relative to that
of neutral tertiary phosphanes can thus explain the higher
catalytic activities observed with the corresponding rhodium
complexes in styrene hydroformylation reactions. Addition-
ally, a preliminary study of platinum coordination chemistry
indicated that the steric demand of 1,3-dimethylimidazolium-
further metal coordination. As such compounds can be de- 2-phosphanes is comparable to mixed arylalkylphosphanes.
scribed as phosphenium cations stabilised by a N-heterocar- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
bene donor base, the electronic properties of the Lewis ac-
Germany, 2007)
in the presence of a strong base.[1] However, all these prepa-
rations require several steps, most of which are quite diffi-
cult due to the air-sensitive phosphorus intermediates or
the use of strong alkyllithium bases. Thus, we developed a
short and easy synthetic method allowing the obtention of
the expected products on a large scale. Our synthetic ap-
proach is thus based on the use of 1,3-dimethylimid-
azolium-2-carboxylate (1) as a N heterocarbene source,[12]
as it was reported in the preparation of N heterocarbene
metal complexes[13,14] or ionic liquids,[15,16] as well as in the
study of its reactivity towards several chlorophosphanes.
Introduction
Imidazolium-functionalised phosphanes, when compared
to neutral phosphane ligands, represent an interesting op-
portunity to decrease strongly the metal leaching in homo-
geneous polyphasic catalysis, especially with the use of an
ionic liquid phase.[1–3] However, if the C-2 position of the
imidazolium ring is unprotected, this type of cationic ligand
can sometimes decrease the activity of the catalyst and/or
the enantioselectivity of the reaction because of the pro-
duction of zerovalent metals[4,5] induced by the formation
of the corresponding chelating N-heterocarbene phos-
phane.[6] To overcome such a limitation, we thus focused
our investigations on imidazolium-2-phosphanes. More-
over, these particular structures represent rare examples of
“base donor, P acceptor complexes” involving an electron
rich PIII centre as the Lewis acceptor.[7] It is also noteworthy
that a simple change in the substituent on the nitrogen atom
can easily tune their electronic and steric properties.
Results and Discussion
Synthesis and Characterisation of Imidazolium-2-
phosphanes
The chlorophosphanes Ph2PCl and iPr2PCl react
smoothly with 1 to afford pure imidazolium-2-phosphanes
2a and 2b, respectively (see Experimental Section) after 4 h
(Scheme 1). When the more sterically hindered chloroalk-
ylphosphane Cy2PCl was used, complete conversion leading
to cationic ligand 2c was achieved after a longer period (ca.
8 h), which also favoured the formation of small amounts
of 1,3-dimethylimidazolium chloride [MMIM]Cl as a result
of the competitive hydrolysis of the chlorophosphane by
trace amounts of water in the solution and the subsequent
protonation–decarboxylation of 1 with HCl.[15,16] This side
reaction is, however, inhibited by the addition of molecular
There are few examples of imidazolium-2-phosphanes in
the literature.[8] They are obtained either by selective N al-
kylation of the corresponding free[9] or metal-coordi-
nated[10] neutral imidazolyl-2-phosphane or by the addition
of chlorodiphenylphosphane to isolated[11] or in situ gener-
ated imidazol-2-ylidenes from the related imidazolium salts
[a] Institut de Chimie Moléculaire de l’Université de Bourgogne
(ICMUB) – UMR 5260 CNRS,
9, av. Alain Savary 21078 Dijon
E-mail: Jacques.Andrieu@u-bourgogne.fr
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M. Azouri, J. Andrieu M. Picquet, P. Richard, B. Hanquet, I. Tkatchenko
FULL PAPER
sieves. It is noteworthy that the bulky chlorodialkylphos- therefore unsuitable for crystallographic studies. However,
phane tBu2PCl does not react with imidazolium-2-carbox- suitable crystals for X-ray structure determination were ob-
ylate at room temperature even after 24 h.
tained for compound 3b (Figure 1) from the same mixture
of solvents.
The ORTEP view shows that the P(1)–C(1) bond length
of 1.840(3) Å (Table 1) is similar to that found in the
1,3-diisopropyl-4,5-dimethylimidazolium-2-phosphane ana-
logue (1.813 Å)[11] obtained from the reaction of Ph2PCl
and the corresponding imidazol-2-ylidene.
Table 1. Selected bond lengths [Å] and bond angles [°] for 3b.
P(1)–C(1)
P(1)–C(9)
C(1)–N(2)
C(5)–N(2)
N(1)–C(1)–N(2)
N(2)–C(1)–P(1)
C(1)–P(1)–C(6)
1.840(3)
1.855(3)
1.354(4)
1.474(4)
105.6(3)
133.0(2)
P(1)–C(6)
C(1)–N(1)
C(4)–N(1)
C(2)–C(3)
N(1)–C(1)–P(1)
C(1)–P(1)–C(9)
1.859(3)
1.344(4)
1.476(4)
1.341(5)
121.3(2)
Scheme 1.
An anion exchange reaction of 2a–c with KPF6 in
CH2Cl2, which can be done in a one-pot synthesis, led to
the corresponding halide free ligands 3a–c in excellent
yields. Compounds 3a and 3c could be crystallised from
dichloromethane/pentane as white plates in poor quality
and as a white crystalline powder, respectively, which were
102.47(15)
105.58(16)
98.96(15) C(9)–P(1)–C(6)
C(9)–P(1)–C(1)–N(2) 51.8(4)
C(6)–P(1)–C(1)–N(2) –56.5(4)
The imidazolium heterocycle is in the bisector plan of
the C(9)–P(1)–C(6) angle [dihedral angles C(6,9)–P(1)–
C(1)–N(2), Table 1], analogously to the structure of the
above-mentioned cationic compound, possibly because of
the strong steric hindrance of the methyl groups in the solid
state. In CDCl3 solution, we observed two different signals
for the C(6,9)–CH3 methyl groups. To obtain more infor-
mation, an additional 1D-NMR NOE experiment was re-
corded at 298 K. Figure 2 shows a strong Overhauser effect
of 2.5% between the irradiated N–Me groups and the
C(6,9)H protons. This effect decreases from 1 to Ͻ0.2% for
the C(6,9)Meendo and C(6,9)Meexo methyl groups, respec-
tively. Such a difference in the Overhauser effect observed
for the latter fragments proves that the spatial organisation
of the isopropyl groups observed in the solid state is main-
tained in solution. However, the unique signals obtained at
Figure 1. Molecular structure of 3b with thermal ellipsoids pre-
–
sented at the 50% probability level. The PF6 anion is omitted for
clarity.
1
Figure 2. (a) H NMR spectrum and (b) NOE difference spectrum of 3b in CDCl3 at room temperature.
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Straightforward Synthesis of Donor-Stabilised Phosphenium Adducts
298 K for the N–Me group and for the olefinic CH moiety experiment based on the direct addition of Ph2PCl to the
1
of compound 2 in the H and 13C NMR spectra (for exam- pure carboxylic acid form [MMIM-2-CO2H](BF4)[15,17] of
ple Figure 2, spectrum a) seemed to indicate free rotation 1 in a CH2Cl2/C6D6 mixture did not proceed even after 18 h
of the imidazolium ring. Indeed, VT-NMR spectroscopic at room temperature. Both observations exclude the pos-
experiments in CD2Cl2 solutions were investigated at lower sibility of an acid-catalysed phosphorylation reaction.
temperature and differentiation between the two N–Me sig-
Notably, a mechanism involving the formation of a P–O
nals and between the two olefinic CH was found at 193 K bond followed by P migration to the N–C–N carbon atom
in the 1H and 13C NMR for 2a, whereas the same phenom- can also be excluded, as no adduct was observed after the
ena was observed at 273 K for 2b. These observations show addition of tBu2PCl to the imidazolium-2-carboxylate.
unambiguously that the cationic fragment rotates around Therefore, two alternative mechanisms both involving the
the P(1)–C(1) bond at room temperature, whereas the iso- direct addition of R2PCl were examined (Scheme 2, paths 2
propyl groups do not rotate around the P–C(6,9) bonds. In and 3); these mechanisms differ in their nucleophilic and
addition, and in line with previous calculations,[7] this easy electrophilic nature. To distinguish between them, we envi-
rotation of the imidazolium ring confirms that the lone pair sioned the use of a chlorophosphane reagent in which the
of electrons on the P centre remains selectively localised on nucleophilic character would be masked by metal coordina-
the phosphorus atom, which thus makes it available for fur- tion. The reactivity of imidazolium-2-carboxylate towards
ther metal coordination.
cis-PtCl2(PPh2Cl)2 was then investigated in CD2Cl2 solu-
tion. 31P NMR spectroscopic analysis of the crude product
performed after 2 d showed the absence of a signal at δ =
71.4 ppm, which is due to the platinum starting material,
and the presence of two new peaks at δ = –26.9 and
Mechanistic Aspects in the Formation of Imidazolium-2-
phosphane
1
2.2 ppm; the latter peak showed a JPt,P value of 3420 Hz.
As our phosphorylation reaction contrasts other prepa- This spectrum indicates that the cis-PtCl2(PPh2Cl)2 com-
rations of imidazolium-2-phosphanes because it does not plex had totally disappeared while free ligand 2a and a new
involve the use of additional alkyllithium for the formation monophosphane platinum complex were formed. The latter
of the N heterocyclic carbene intermediate, different mech- complex was assigned to the [PtCl3(2a)] complex 4, which
anistic pathways can reasonably be proposed to explain the was independently prepared by treating [PtCl2(NCPh)2]
formation of 2 (Scheme 2).
with one equivalent of compound 2a (Scheme 3), and by
using reaction conditions similar to those described for a
platinum analogue complex.[18] Because the imidazolium-2-
phosphane was formed in the above experiment in spite of
the platinum coordination, which masks the lone pair of
electrons on the phosphorus atom in chlorodiphenylphos-
phane, we can suggest that PR2Cl likely reacts as an electro-
philic reagent[19] toward imidazolium-2-carboxylate
(Scheme 2, path 3). This assumption is supported by the
lack of reactivity when the less electron rich carboxylic acid
[MMIM-2-CO2H](BF4) is used under the conditions de-
scribed for imidazolium-2-carboxylate (Scheme 2, path 1).
Nevertheless, the presence of free ligand 2a could also be
the result of the direct addition of imidazolium-2-carboxyl-
ate to free PPh2Cl, which thus illustrates the electrophilic
character of compound 1. However, the release of Ph2PCl
Scheme 2. Possible phosphorylation mechanisms of the imid-
azolium-2-carboxylate.
A first kinetic experiment in CH2Cl2 solution with
Ph2PCl showed that the addition of a stoichiometric
amount of K2CO3 did not prevent the formation of 2a, al-
though an increased reaction time from 4 to 14 h was
needed to reach complete conversion. This observation is
more consistent with the strong stabilizing interaction ob-
served in our laboratory between 1 and alkali metals[17]
rather than with an acid-catalysed mechanism. A second Scheme 3.
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M. Azouri, J. Andrieu M. Picquet, P. Richard, B. Hanquet, I. Tkatchenko
FULL PAPER
from cis-PtCl2(PPh2Cl)2 is unlikely at room temperature, as
the reaction would then induce cis/trans-PtCl2(PPh2Cl)2 iso-
merisation, which was shown to require higher tempera-
tures.[20] Therefore, in our case the presence of free ligand
2a in solution seems to be the consequence of imidazolium-
2-phosphane displacement by a chloride anion, which leads
to more stable complex 4.
Electronic Properties of the Ligands and Catalytic
Properties
As mentioned in the introduction, there is only one re-
port of the use of imidazolium-2-phosphanes in homogen-
eous catalysis.[1] In that paper, the authors observed that the
presence of a para-phenylene spacer between the phospho-
rus atom and the imidazolium fragment decreased the TOF
from 552 to 51 h–1 for rhodium catalysts in hydrofor-
mylation reactions of 1-octene and also decreased the n:i
aldehyde ratio.[1] Besides, terminal alkenes are hydroformyl-
ated at higher rates when bulky phosphites[21] or arylphos-
Scheme 4.
phanes containing electron-withdrawing substituents[22] are replacement of the aryl groups by isopropyl or cyclohexyl
used instead of triphenylphosphane. All results agree with substituents in imidazolium-2-phophanes 2b and 2c led to
the fact that the nature of the phosphorus ligand plays an new stretching frequencies at 2075 and 2078 cm–1, respec-
important role in the stabilisation of the active species in tively, in the infrared spectra for the corresponding phos-
hydroformylation reactions and the associated kinetic be- phane–nickel tricarbonyl complexes. The latter values are
haviour (alkene coordination vs. hydrogenolysis step), slightly shifted to lower frequencies owing to the presence
which drastically modify the conversion rate and selectivity of better electron-donating alkyl groups. Nevertheless, the
in the catalytic reaction.[23] However, recent calculations electronic parameters of compounds 2a–c are wedged in the
performed on imidazolium-2-phosphanes describe these range of strong π-acceptor ligands such as phosphites, from
compounds as nonmetal complexes with a coordination P(OiPr)3 [with νCO(A1) = 2076 cm–1] and P(OPh)3 ligands
bond between the electron rich N–C–N carbon and the P [with νCO(A1) = 2085 cm–1][24] and clearly illustrate the
acceptor centre instead of a P–C covalent bond.[7] There- strong acceptor properties of a donor-stabilised phosphen-
fore, we thought that the different hydroformylation experi- ium cation reinforced by the presence of its positive charge
ments performed with an imidazolium-2-phosphane could (Scheme 4).
be correlated with its specific σ-donor/π-acceptor character,
In addition to the above electronic properties studied, a
which should certainly be different to those of the unmodi- preliminary determination of the steric demands of imid-
fied PPh3, although the lone pair of electrons on the phos- azolium-2-phosphanes was investigated in platinum dichlo-
phorus atom is not delocalised (see above). The electronic/ ride complexes with the smallest ligand. So, the addition of
donor properties of the P atom was then evaluated by mea- one (or two) equivalent(s) of ligand 2a to PtCl2(NCPh)2 in
surement of the A1 symmetric stretching frequency of nickel CH2Cl2 solution at room temperature led selectively to the
complexes prepared in situ by replacement of a CO group formation of [PtCl3(2a)] complex 4. When the same reac-
in [Ni(CO)]4 by phosphane 2a. Although less-toxic com- tion was performed under similar conditions with two
pounds than Ni(CO)4 {prepared in situ from [Ni(cod)2]} equivalents of related halide-free ligand 3a, the selective for-
are now more commonly used to characterise the electronic mation of new [PtCl2(3a)2] complex 5 was observed with a
1
properties of phosphanes {for example, the [Rh(CO)2Cl]2 typical JPt,P value of 2785 Hz for a P trans geometry
dimer}, we opted to prepare a nickel–carbonyl complex to around the metal centre (Scheme 3). Additionally, the
compare easily the imidazolium-2-phosphane complex pa- 31P{1H} NMR spectrum of 5 recorded in CH2Cl2/C6D6 af-
rameters directly with the large database tabulated by Tol- ter introduction of KCl in a 1:1 ratio showed the presence
man for adducts of the Ni(CO)3 moiety.[24] We thus reacted of complex 4 and free ligand 2a. This observation confirms
2a with an equimolar amount of Ni(CO)4 to afford [Ni- the higher stability of the latter platinum trichloride com-
(CO)3(2a)] (Scheme 4).
The new nickel complex was not isolated but was recog- from the platinum centre by halide addition (Scheme 3).
nised by its characteristic νCO(A1) carbonyl stretching mode It is interesting to note that the nature of the counter
plex 4, and noteworthy is the phosphane decoordination
in the infrared spectrum of the crude mixture, which was anion perfectly controls the metal/ligand ratio in the metal–
found at 2082 cm–1 in a toluene/CH2Cl2 solution. This imidazoliumphosphane complexes. Nevertheless, the latter
value classifies 2a as less electron-donating than the com- reaction contrasts those with other tertiary phosphanes
mon arylphosphanes [νCO(A1) = 2069 cm–1 with PPh3]. The Ph2PR (R = Ph, Cl, OMe or NEt2[20]), which selectively
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Straightforward Synthesis of Donor-Stabilised Phosphenium Adducts
vacuum to afford a white powder (359 mg, 97%) that was dried for
lead, under similar mild conditions, to the corresponding
cis-[PtCl2(Ph2PR)2] isomers. The results seem to indicate
that compound 2a behaves as a bulky phosphane like the
mixed arylalkylphosphanes. Other investigations on the
electronic and steric properties of the cationic imidazolium-
2-phosphanes, as well as their catalytic properties, are cur-
rently in progress.
3 h under vacuum. M.p. 200 °C. 1H NMR (300 MHz, CDCl3): δ =
8.46 (s, 2 H, CH=), 7.42–7.23 (m, 10 H, aromatics), 3.78 (d, JP,H
=
7.2 Hz, 6 H, NCH3) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ =
142.24 (d, JP,C = 52.1 Hz, 1 C, NCN), 132.74–130.95 (m, 12 C,
3
aromatics), 128.52 (s, 2 C, CH=), 37.71 (d, JP,C = 9.1 Hz, 2 C,
NCH3) ppm. 31P{1H} NMR (121 MHz, CDCl3): δ = –27.31 (s)
ppm. C17H18N2PCl (316.76): calcd. C 64.46, H 5.73, N 8.84; found
C 64.23, H 5.78, N 8.84.
Compound 2b: Prepared in an analogous manner to 2a and ob-
tained as white powder (250 mg, 86%). M.p. 133 °C. 1H NMR
(300 MHz, CDCl3): δ = 8.50 (s, 2 H, CH=), 4.18 (s, 6 H, NCH3),
Conclusions
3
3
2.62 (hept., JH,H = 6.6 Hz, 2 H, PCH), 1.23 (dd, JH,H = 6.6 Hz,
In this paper, we report that imidazolium-2-carboxylate
is an interesting starting material in the simple and straight-
forward synthesis of imidazolium-2-phosphanes, and the re-
action could easily be extended to large-scale preparation.
The synthesis of other base-stabilised phosphenium cation
complexes, in addition to their optically pure forms, are cur-
rently in progress in our laboratory. Moreover, the measure-
ments of the A1 symmetric stretching frequency of related
Ni(CO)3(imidazolium-2-phosphane) complexes have shown
that such compounds behave as stronger π-acceptor ligands
like phosphites. The result seems to be the consequence of
the CǞP bond present in imidazolium-2-phosphanes,
which displaces the positive charge from the imidazolium
ring to the phosphorus centre. This electronic property
combined with the ionic nature of the compounds renders
these ligands very promising in the development of new
continuous-flow catalytic processes that are currently being
investigated.
3
3JP,H = 12.6 Hz, 6 H, CCH3 exo), 0.83 (dd, 3JH,H = 6.9 Hz, JP,H
=
7.2 Hz, 6 H, CCH3 endo) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ
= 145.07 (d, JP,C = 60.4 Hz, 1 C, NCN), 127.17 (s, 2 C, CH=),
37.86 (d, JP,C = 9.1 Hz, 2 C, NCH3), 24.07 (d, JP,C = 10.6 Hz, 2
C, PCH), 21.33 (d, JP,C = 27.2 Hz, 4 C, CH3 exo), 20.75 (d, JP,C
= 9.1 Hz, 4 C, CH3 endo) ppm. 31P{1H} NMR (121 MHz, CDCl3):
δ = –9.44 (s) ppm. C11H22N2PCl (248.73): calcd. C 53.12, H 8.91,
N 11.26; found C 53.05, H 8.71, N 11.70.
3
3
3
3
Compound 2c: Prepared in an analogous manner to 2a over molecu-
lar sieves and obtained as a white powder (277 mg, 72%). 1H NMR
(300 MHz, CDCl3): δ = 8.61 (s, 2 H, CH=), 4.14 (s, 6 H, NCH3),
2.33 (m, 1 H, PCH), 1.77 (m, 8 H, CH2), 1.24 (m, 10 H, CH2) ppm.
13C{1H} NMR (75 MHz, CDCl3): δ = 144.5 (d, JP,C = 60.4 Hz, 1
C, NCN), 127.4 (s, 2 C, CH=), 37.79 (s, 2 C, NCH3), 33.99 (d, JP,C
2
= 11.3 Hz, 2 C, PCH), 31.85 (d, JP,C = 24.2 Hz, 2 C, CH2), 30.39
2
3
(d, JP,C = 6.0 Hz, 2 C, CH2), 26.33 (d, JP,C = 8.3 Hz, 2 C, CH2),
3
26.08 (d, JP,C = 15.1 Hz, 2 C, CH2), 25.51 (s, 2 C, CH2) ppm.
31P{1H} NMR (121 MHz, CDCl3):
δ = –19.77 (s) ppm.
C17H30N2PCl (328.86): No satisfactory elemental analysis was ob-
tained for 2a owing to its strong hygroscopic character.
Compound 3a: To a solution of 2a (0.380 g, 1.20 mmol) in acetone
(5 mL) was added KPF6 (0.277 g, 1.50 mmol), and the resulting
suspension was stirred for 2 d at room temp. The solvent was re-
moved under vacuum at 50 °C for 2 h. The residue was dissolved
in CH2Cl2 (5 mL), and the resulting solution was filtered. Evapora-
tion of solvent under vacuum afforded compound 3a, which was
crystallised from CH2Cl2/pentane as white plates (481 mg, 94%).
M.p. 176 °C. 1H NMR (300 MHz, CDCl3): δ = 7.49 (s, 2 H, CH=),
7.45–7.24 (m, 10 H, aromatics), 3.57 (s, 6 H, NCH3) ppm. 13C{1H}
NMR (75 MHz, CDCl3): δ = 143.08 (d, JP,C = 54.3 Hz, 1 C, NCN),
133.06–130.07 (m, 12 C, aromatics), 127.00 (s, 2 C, CH=), 37.65
Experimental Section
General Procedures: All reactions were performed in Schlenk-type
flasks under an argon atmosphere. Solvents were purified and dried
by conventional methods and distilled under an argon atmosphere.
With the exception of compound 1 and the trans-PtCl2(3a)2 com-
plex, all 1H, 31P{1H} and 13C{1H} NMR spectra were recorded
with a Bruker Avance 300 instrument at 298 K. Complete assign-
ment was achieved by COSY, DEPT and HMQC experiments. All
chemical shifts are reported relative to SiMe4 (1H and 13C NMR)
and 85% H3PO4 (31P NMR) and are given in ppm. Electrospray
spectra were performed with a Bruker micrOTOF-Q instrument.
The IR instrument was calibrated with solutions of Ni(CO)3(PPh3),
for which the A1 νCO stretching band was reported to be
2068.9 cm–1.[24] Elemental analyses were performed with a Fisons
EA 1108 apparatus at the ICMUB in Dijon. The chlorophosphanes
Ph2PCl, iPr2PCl and Cy2PCl were commercial products from Ald-
rich and Ni(1,5-cod)2 was a commercial product from Strem, and
all were used as received. 1,3-Dimethylimidazolium-2-carboxylate
(1) and the PtCl2(NCPh)2 complex were prepared according to the
literature.[15,17,25] Nickel tetracarbonyl Ni(CO)4 was prepared from
Ni(1,5-cod)2 and CO according to the literature;[26] however, owing
to its highly toxic nature, this preparation was handled with ex-
treme care in a dedicated facility (CECUB, Université de Bour-
gogne).
3
(d, JP,C = 7.6 Hz, 2 C, NCH3) ppm. 31P{1H} NMR (121 MHz,
CDCl3): δ = –25.89 (s, Pphosphane), –144.14 (hept., JP,F = 712 Hz,
–
PF6 ) ppm. C17H18N2P2F6 (426.27): calcd. C 47.90, H 4.25, N 6.57;
found C 47.80, H 4.08, N 6.49.
Compound 3b: Prepared in an analogous manner to 3a and ob-
tained as white solid (374 mg, 87%). M.p. 154 °C. 1H NMR
(300 MHz, CDCl3): δ = 7.46 (s, 2 H, CH=), 3.96 (s, 6 H, NCH3),
3
3
2.60 (hept., JH,H = 6.9 Hz, 2 H, PCH), 1.20 (dd, JH,H = 6.9 Hz,
3JP,H = 12.3 Hz, 6 H, CCH3 exo), 0.82 (dd, JH,H = 6.9 Hz, JP,H
3
3
= 7.20 Hz, 6 H, CCH3 endo) ppm. 13C{1H} NMR (75 MHz,
CDCl3): δ = 145.89 (d, JP,C = 62.4 Hz, 1 C, NCN), 126.14 (s, 2 C,
3
CH=), 37.35 (d, JP,C = 9.8 Hz, 2C, NCH3), 23.88 (d, JC,P
=
10.5 Hz, 2 C, PCH), 21.16 (d, 3JP,C = 27.2 Hz, 4 C, CH3 exo), 20.46
(d, 3JP,C = 9.8 Hz, 4 C, CH3 endo) ppm. 31P{1H} NMR (121 MHz,
Compound 2a: To a mixture of 1 (0.164 g, 1.17 mmol) and Ph2PCl
(0.258 g, 1.17 mmol) was added CH2Cl2 (5 mL). The mixture was PF6 ) ppm. C11H22N2P2F6 (358.24): calcd. C 36.88, H 6.19, N 7.82;
CDCl3): δ = –8.57 (s, Pphosphane), –144.40 (hept., JP,F = 712 Hz,
–
stirred for 4 h at room temp. The solvent was then removed under
found C 36.39, H 6.08, N 7.54.
Eur. J. Inorg. Chem. 2007, 4877–4883
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4881

M. Azouri, J. Andrieu M. Picquet, P. Richard, B. Hanquet, I. Tkatchenko
FULL PAPER
Compound 3c: Prepared in an analogous manner to 3a and ob-
tained as white solid (421 mg; 80%). M.p. 193 °C. 1H NMR
(300 MHz, CDCl3): δ = 7.51 (s, 2 H, CH=), 3.95 (s, 6 H, NCH3),
2.37 (m, 2 H, PCH), 1.75 (m, 8 H, CH2), 1.23 (m, 10 H, CH2) ppm.
13C{1H} NMR (75 MHz, CDCl3): δ = 144.53 (d, JP,C = 62.6 Hz, 1
C, NCN), 125.6 (s, 2 C, CH=), 36.57 (s, 2 C, NCH3), 32.86 (d, JP,C
Table 2. Crystallographic and refinement data for complex 3b.
Formula
M
T [K]
C11H22F6N2P2
358.25
110(2)
Crystal system
Space group
a [Å]
monoclinic
P21/c
12.5537(4)
11.1571(4)
2
= 11.3 Hz, 2 C, PCH), 30.87 (d, JP,C = 24.2 Hz, 2 C, CH2), 29.33
2
3
b [Å]
(d, JP,C = 6.8 Hz, 2 C, CH2), 25.22 (d, JP,C = 8.3 Hz, 2 C, CH2),
3
c [Å]
13.0473(6)
90
112.897(1)
1683.45(11)
25.02 (d, JP,C = 15.1 Hz, 2 C, CH2), 24.56 (s, 2 C, CH2) ppm.
31P{1H} NMR (121 MHz, CDCl3): δ = –18.89 (s, Pphosphane),
α = γ [°]
β [°]
–
–144.33 (hept., JP,F = 712 Hz, PF6 ) ppm. C17H30N2P2F6 (438.37):
V [Å3]
calcd. C 46.58, H 6.90, N 6.39; found C 44.99, H 7.54, N 6.05.
Z
4
F(000)
744
1.413
Formation of [Ni(CO)3(2a–c)]: Ni(CO)4 was prepared by treating a
solution of [Ni(1,5-cod)2] (50.1 mg, 0.182 mmol) in toluene (1 mL)
with CO at 0 °C for 5 min, followed by the addition of 2a
(0.0545 mg, 0.172 mmol) in CH2Cl2 (1 mL). The mixture was
stirred for 15 min. A light-green solution was obtained, which was
Dcalcd. [gcm–3]
Diffractometer
Scan type
Enraf–Nonius KappaCCD
mixture: φ rotations and ω
scans
0.71073
0.311
0.25ϫ0.07ϫ0.01
0.65
h –16; 16
k –14; 9
λ [Å]
µ [mm–1]
analysed by infrared spectroscopy. IR (toluene/CH2Cl2): νCO
=
Crystal size [mm]
sin(θ)/λ max [Å–1]
Index ranges
2082 (A1), 2013 cm–1 (E). The formation of the analogous [Ni-
(CO)3(2b)] and [Ni(CO)3(2c)] complexes was performed under
similar conditions. IR (toluene/CH2Cl2): νCO
= 2075 (A1),
2051 cm–1(E) for [Ni(CO)3(2b)] and νCO = 2078 (A1), 2005 cm–1 (E)
for [Ni(CO)3(2c)].
l –16; 16
5899
RC = refl. collected
IRC = independent RC
IRCGT = IRC and [IϾ2σ(I)]
Refinement method
Data/restraints/parameters
R for IRCGT
3831 [R(int) = 0.0414]
2580
Platinum Complex 4: To a mixture of 2a (60.1 mg, 0.19 mmol) was
added PtCl2(PhCN)2 (86.6 mg, 0.19 mmol) in CH2Cl2 (2 mL), and
the mixture was stirred for 7 h. A yellow suspension was obtained.
The suspension was filtered off, and the yellow solid was washed
with diethyl ether and dried under vacuum to afford PtCl3(2a)
full-matrix L.S. on F2
3831/0/192
[a]
[b]
R1[a] = 0.064, wR2[b] = 0.137
R1 = 0.105, wR2 = 0.159
1.024
R for IRC
Goodness-of-fit[c]
1
(94 mg, 85%). M.p. Ͼ200 °C (dec.). H NMR (300 MHz, [D6]ace-
Largest diff. peak and hole [eÅ–3] 0.758 and –0.446
tone): δ = 7.56–7.78 (m, 12 H, aromatics and CH=), 2.03 (s, 6 H,
NCH3) ppm. 31P{1H} NMR (121 MHz, [D6]acetone): δ = 2.24 (s,
JPt,P = 3425 Hz, Pphosphane) ppm. MS: m/z = 510.060 [M – Cl –
HCl]+. C17H18Cl3N2PPt (582.76): calcd. C 35.04, H 3.11, N 4.81;
found C 35.51, H 2.78, N 4.26.
[a] R1 = Σ(||Fo| – |Fc||)/Σ|Fo|. [b] wR2 = {Σw(Fo2–Fc ) /Σ[w(Fo2)2]}1/2
2 2
where w = 1/[σ2(Fo2)+(0.049P)2+3.10P] where P = [max(Fo2,0)
+2·Fc ]/3. [c] Goodness of fit = [Σw(Fo2–Fc ) /(No – Nv)]1/2
.
2
2 2
Platinum Complex 5: To a mixture of 3a (0.0396 mg, 0.093 mmol)
was added PtCl2(PhCN)2 (0.0224 mg, 0.049 mmol) in CH2Cl2
(1.5 mL), and the mixture was stirred for 12 h. A yellow suspension
was obtained. The suspension was filtered off, and the yellow solid
was dried under vacuum to afford trans-PtCl2(3a)2 (100 mg, 95%).
Acknowledgments
We wish to acknowledge the Ministère de la Recherche for support
and for a PhD fellowship to M. A. We also thank the Université
de Bourgogne, the Centre National de la Recherche Scientifique
and the Conseil Régional de Bourgogne for financial support of
this work.
1
M.p. 216 °C. H NMR (300 MHz, [D6]acetone): δ = 8.43–7.80 (m,
20 H, aromatics), 7.97 (s, 4 H, CH=), 3.75 (s, 12 H, NCH3) ppm.
13C{1H} NMR (75 MHz, [D6]acetone): δ = 141.64 (d, JP,C
=
7.5 Hz, 2 C, NCN), 139.51–127.09 (m, 24 C, aromatics), 126.68 (s,
4 C, CH=), 44.04 (s, 4 C, NCH3) ppm. 31P{1H} NMR (121 MHz,
[D6]acetone): δ = 17.83 (s, JPt,P = 2785 Hz, Pphosphane), –139.08
(hept, JP,F = 712 Hz, PF6 ) ppm. C34H48Cl2F12N4P4Pt (1130.64):
calcd. C 36.12, H 4.28, N 4.96; found C 36.30, H 3.86, N 4.66.
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www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: June 7, 2007
Published Online: August 23, 2007
Eur. J. Inorg. Chem. 2007, 4877–4883
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4883