A phosphino-oxazoline ligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: Catalytic ethylene oligomerization

Article abstract of DOI:10.1039/c1dt11352f

The Pd(ii) complex [PdCl₂(1)] [1 = ({oxazolin-2-yl}methyl) diphenylphosphine] was obtained by the 1:1 reaction of 1 with [PdCl ₂(NCPh)₂]. Although this neutral complex is stable in the solid-state and in solution, it react

Full text of DOI:10.1039/c1dt11352f

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PAPER
A phosphino-oxazoline ligand as a P,N-bridge in palladium/cobalt or
P,N-chelate in nickel complexes: catalytic ethylene oligomerization†
Shuanming Zhang,a Roberto Pattacini,a Suyun Jiea,b and Pierre Braunstein*a
Received 18th July 2011, Accepted 21st September 2011
DOI: 10.1039/c1dt11352f
The Pd(II) complex [PdCl2(1)] [1 = ({oxazolin-2-yl}methyl)diphenylphosphine] was obtained by the 1 : 1
reaction of 1 with [PdCl2(NCPh)2]. Although this neutral complex is stable in the solid-state and in
solution, it reacts with the dinuclear complex [CoCl2(m-1)]2 to afford the heterometallic zwitterionic
+
complex [{PdCl(1)} (m-1)(CoCl3)-] (2). Under inert atmosphere, two equivalents of 1 reacted with
[NiCl2(dme)] to give trans-[NiCl2(1)2] (3) in CH2Cl2 but cis-[NiCl2(1)2] (4) in CHCl3. When the latter
reaction was performed in air, trans-[NiCl2(5)2] (6) [5 = ({oxazolin-2-yl}methyl)diphenylphosphine
oxide] was obtained. All metal complexes, 2, 3, 4 and 6, have been structurally characterized by X-ray
diffraction. Complexes 3, 4 and 6 have been evaluated as precatalysts for ethylene oligomerisation in the
presence of AlEtCl2 as cocatalyst. Complexes 3 and 6 yielded a turnover frequency (TOF) of 60 700 and
62 600 mol of C2H4/((mol of Ni)·h), respectively, in the presence of 10 equiv. of AlEtCl2. In the presence
of only 6 equiv. of cocatalyst, these Ni complexes yielded TOF values of 41 500 and 58 000 mol of
C2H4/((mol of Ni)·h), respectively.
Introduction
Transition metal complexes bearing functional P,N-type ligands
attract much attention because they combine hard nitrogen
donor(s) and soft phosphorus donor(s) and offer considerable
chemical and structural diversity.1 They may also display hemil-
abile behaviour resulting in enhanced or unique reactivity.2 Among
the diverse N-functions encountered in P,N-ligands, the oxazoline
heterocycle and its derivatives have enjoyed special attention.3
We have been interested in the coordination chemistry of the P,N
ligand ({oxazolin-2-yl}methyl)diphenylphosphine (1), and found
that although it usually behaves as a P,N-chelate, the nuclearity
of its metal complexes may be different from that anticipated, as
observed with the unusual, tetranuclear complex [NiCl2(1)]4 which
transforms under pressure into the corresponding mononuclear
Ni(II) complex [NiCl2(1)] (Scheme 1).4
Scheme 1
When 1 was substituted at the 4-position by a phenyl or methyl
group, several dichloride-bridged dinuclear Ni(II) complexes were
obtained and the coordination geometry of the Ni centers was
established to be trigonal-bipyramidal in the case of the gem-
dimethyl-substituted oxazoline and X = Br (Scheme 2).5
Scheme 2
aLaboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177
CNRS), Universite´ de Strasbourg, 4 rue Blaise Pascal, CS 90032, F-67081,
Strasbourg Cedex, France. E-mail: braunstein@unistra.fr; Fax: +33 (0)3
68 85 13 22; Tel: +33 (0)3 68 85 13 08
A cationic, single chloride-bridged dinuclear Pt(II) complex
bearing ligand 1 could also be structurally characterized (Scheme
3),6 as well as Pd(II) complexes containing two chelating ligands.7
In Ru(II) chemistry, two isomeric complexes [RuCl2(1)2] possess-
ing an all-cis or all-trans ligand arrangement have been obtained
(Scheme 4).8 Here, we report the synthesis of a heterodinuclear
Pd/Co complex which displays a rare m-P,N bridging mode for
bCurrent address: State Key Laboratory of Chemical Engineering, Depart-
ment of Chemical and Biological Engineering, Zhejiang University, 38 Zheda
Road, Hangzhou, 310027, China
† CCDC reference numbers 831824–831827. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt11352f
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Scheme 3
Fig. 1 ORTEP of the molecular structure of 2 in 2·MeCN. Hydrogen
atoms and solvent molecules omitted for clarity. Ellipsoids include 30%
◦
˚
of the electron density. Selected distances (A) and angles ( ): Pd1–N1
2.090(3), Pd1–P1 2.2523(8), Pd1–P2 2.2592(9), Pd1–Cl1 2.3442(8),
Co1–N2 2.060(3), Co1–Cl3 2.2459(11), Co1–Cl2 2.2537(10), Co1–Cl4
2.2604(10), N1–C3 1.274(4), N2–C19 1.273(4); N1–Pd1–P1 81.55(7),
N1–Pd1–P2 176.10(7), P1–Pd1–P2 99.77(3), N1–Pd1–Cl1 92.17(7),
P1–Pd1–Cl1 173.71(3), P2–Pd1–Cl1 86.49(3), N2–Co1–Cl3 105.86(8),
N2–Co1–Cl2 110.55(8), Cl3–Co1–Cl2 114.01(4), N2–Co1–Cl4 105.27(8),
Cl3–Co1–Cl4 109.57(5), Cl2–Co1–Cl4 111.11(4).
Scheme 4
ligand 1 and of Ni complexes of general formula [NiCl2(1)2], which
share similarities with the [RuCl2(1)2] complexes,8 and contain
the chelating P,N ligands in a all-cis or all-trans arrangement,
depending on the solvent used. We shall also briefly examine their
sensitivity towards air and oxygen.
In the molecular structure of zwitterionic 2 in 2·MeCN, the Pd
centre is P,N-chelated by ligand 1. The palladium coordination
sphere is completed by a terminal chloride and the P donor of
a second ligand 1, which acts as a bridge between the formally
cationic palladium centre and a formally negatively charged
[CoCl3]- moiety. The coordination geometries of the Pd(II) and
Co(II) metal centres are slightly distorted square planar and
tetrahedral, respectively. The P2–Pd1 and Co1–N2 lines form an
angle of 68.10(7)◦. Surprisingly, to the best of our knowledge,
only one example of a P,N-bridged Pd/Co complex has been
reported before12 and there are only three precedents for a
bridging behaviour of ligand 1, in a Fe/Co,13 Fe/Cu14 and
Co/Co complex.11 The reaction leading to 2 features (i) the
cleavage of the parent dinuclear cobalt complex, (ii) a chloride
transfer from Pd to Co, and (iii) P-migration from cobalt to
palladium. This complex thus prefers to adopt a zwitterionic
structure rather than that of the hypothetical formula isomers
[Pd(1)2]2+[CoCl4]2- or [Pd2Co2Cl8(1)4], analogous to [NiCl2(1)]4.
NMR studies were hampered by the paramagnetic nature of
the complex but the similarity of its colour in solution and
in the solid-state suggests that the solid-state structure of 2 is
retained in solution. Although in solution equilibria between 2 and
[Pd(1)2]2+[CoCl4]2- are conceivable, in view of the ligand lability
observed even with chelating ligands,15 we have no indication that
this is the case.
Results and discussion
The Pd(II) complex [PdCl2(1)] was obtained by the 1 : 1
reaction between
1 and [PdCl2(NCPh)2] in CH2Cl2, and
its spectroscopic data are comparable with those of
the related complexes [PdCl2{(4-phenyl-{oxazolin-2-yl}methyl)-
diphenyl phosphine}]9 and [PdCl2{(4,4-dimethyl-{oxazolin-2-yl}
methyl)diphenylphosphine}2].10 On the basis of the observations
made earlier with related Ni(II) complexes (see above) and its
formulation, we wondered whether it could associate with another
divalent transition metal complex of the type [MCl2(1)] to form a
heterometallic di- or tetranuclear complex (Schemes 1 and 2). We
thus reacted [PdCl2(1)] with the dinuclear complex [CoCl2(1)]2,11
in a 2 : 1 stoichiometry. Although a heterometallic complex indeed
resulted, whose composition corresponds to the formal association
of [PdCl2(1)] with “[CoCl2(1)]”, the formation of the zwitterion
+
[{PdCl(1)} (m-1)(CoCl3)-] (2) was unexpected (Scheme 5). Its
molecular structure was determined by X-ray diffraction methods
and is shown in Fig. 1.
The coordination chemistry of ligand 1 towards Ni(II) precur-
sors was further investigated by reacting two equivalents of ligand
1 with [NiCl2(dme)] (dme = 1,2-dimethoxyethane) in CH2Cl2.
This led to the complex all-trans-[NiCl2(1)2] (3, Scheme 6, Fig.
2) while in CHCl3, all-cis-[NiCl2(1)2] was obtained quantitatively
(4, Scheme 6, Fig. 3).
In the molecular structure of 3, the metal centre shows an
octahedral coordination geometry. The nickel atom is chelated
Scheme 5
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Scheme 6
Fig. 3 ORTEP of the molecular structure of 4 in 4·2CHCl3. Hydrogen
atoms and solvent molecules omitted for clarity. Ellipsoids include 30%
◦
˚
of the electron density. Selected distances (A) and angles ( ): Ni1–N1
2.083(14), Ni1–N2 2.098(14), Ni1–Cl1 2.402(5), Ni1–P1 2.439(5), Ni1–Cl2
2.444(5), Ni1–P2 2.499(5), P1–C1 1.845(19), C1–C2 1.52(2), C2–N1
1.26(2), P2–C17 1.858(17), C17–C18 1.44(3), C18–N2 1.29(2); N1–Ni1–N2
91.8(6), N1–Ni1–Cl1 177.5(5), N2–Ni1–Cl1 90.6(4), N1–Ni1–P1 78.0(5),
N2–Ni1–P1 169.7(4), Cl1–Ni1–P1 99.56(17), N1–Ni1–Cl2 88.6(4),
N2–Ni1–Cl2 92.6(4), Cl1–Ni1–Cl2 90.73(16), P1–Ni1–Cl2 88.95(16),
N1–Ni1–P2 93.8(4), N2–Ni1–P2 78.4(4), Cl1–Ni1–P2 87.28(16),
P1–Ni1–P2 100.26(16).
˚
long [Ni1–P1 2.439(5) and Ni1–P2 2.499(5) A] when compared to
those typically observed in Ni(II) chemistry.
Fig.
2
An ORTEP of the molecular structure of 3. Hydrogen
Whereas taking to dryness a CH2Cl2 solution of 3 or a
CHCl3 solution of 4, 3 and 4 were fully recovered, respectively,
isomerization of 3 to 4 was observed when a CHCl3 solution of 3
was evaporated to dryness. Conversely, evaporation of a CH2Cl2
solution of 4 afforded solid 3 (Scheme 7). These transformations
are thus fully reversible, depending on the solvent used and appear
to be related to the polarity of the solvent, which is a better
criterion than its dielectric constant.18 The more polar solvent
CHCl3 (polarity index 4.1) favors the cis isomer 4 and the less
polar solvent CH2Cl2 (polarity index 3.1) favors 3 where the
trans arrangement of the ligands results in cancellation of the
dipole moments. Related observations have been reported for
square-planar Ni(II) complexes.19 Owing to the paramagnetism of
these complexes, NMR spectroscopy could not be used for their
atoms omitted for clarity. Ellipsoids include 30% of the electron
density. Selected distances (A) and angles (◦): Ni1–N1 2.052(2),
˚
Ni1–P1 2.5249(9), Ni1–Cl1 2.4045(8), P1–C4 1.843(3), C4–C3 1.490(5),
C3–N1 1.264(4), C3–O1 1.345(4); N1–Ni1–P1 78.18(8), Ni1–P1–C4
93.96(11), P1–C4–C3 106.5(2), C4–C3–N1 124.2(3), C3–N1–Ni1 121.9(2),
N1–Ni1–Cl1 88.53(8), P1–Ni1–Cl1 86.66(3).
by two mutually trans ligands 1 (through P1 and N1) and by
two trans chlorides. The bonding parameters within the P1–C4–
C3–N1 group in 3 are very close to those of the corresponding
ligand in the related complex [NiBr2(1)],4 while the Ni–P and Ni–
N bonds in 3 are significantly longer than the corresponding bonds
˚
in [NiBr2(1)]. In particular, the Ni–P distances [2.5249(9) A] are re-
markably long for Ni(II)–P bonds. Only two structures were found
in the CSD (Cambridge Structural Database) that display longer
P–Ni separations,16 both showing trans P donors coordinated to
octahedral Ni(II) centres (median on 2188 structures containing
˚
tertiary phosphine-Ni bonds: 2.191 A; median on octahedral Ni
17
˚
centres: 2.206 A ).
Since no repulsive steric interactions can be invoked from the
crystal structure, it was concluded that the reason for such long
Ni–P interactions is of electronic origin.
In the molecular structure of 4 in 4·2CHCl3, the metal centre
shows a slightly distorted octahedral coordination geometry and
is chelated by two ligands 1 in a mutual cis-P,P and cis-N,N
arrangement. Two cis terminal chloride ligands complete the
coordination sphere around the Ni(II) centre. Although the P
donors are not mutually trans as in 3, the Ni–P bonds remain very
Scheme 7
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characterization in solution, while FTIR spectroscopy provided
an informative comparison. The MID-FTIR spectrum showed
almost no difference, while in the far infrared spectrum, the
different Ni–Cl arrangements in these octahedral complexes led to
different absorptions, especially in the 200–300 cm-1 region (Fig.
4).20 The assignments of the n(Ni–Cl) stretching modes (289 cm-1
for 3, 262 cm-1 and 277 cm-1 for 4) were further verified by the
disappearance of these bands after reaction with NaI, as a result
of an anion exchange between Cl- and I-.
Fig. 5 ORTEP of the molecular structure of 6 in 6·4CHCl3. Hydrogen
atoms and solvent molecules omitted for clarity. Ellipsoids include 30% of
◦
˚
the electron density. Selected distances (A) and angles ( ): Ni1–N1 2.049(2),
Ni1–O1 2.0827(19), Ni1–Cl1 2.4553(7), O1–P1 1.495(2), P1–C4 1.827(3),
C4–C1 1.481(4), C1–N1 1.271(3), C1–O2 1.349(3); N1–Ni1–O1 91.69(8),
Ni1–O1–P1 126.15(11), O1–P1–C4 111.82(12), P1–C4–C1 113.49(19),
C4–C1–N1 125.7(2), C1–N1–Ni1 127.62(19), N1–Ni1–Cl1 91.73(7),
O1–Ni1–Cl1 90.58(6).
Fig. 4 Comparison between the far infrared spectra of 3 (bottom line)
and 4 (top line), emphasizing the spectroscopic differences between the
two complexes (reflectance mode, 600–100 cm-1 region).
The synthesis of 4 in CHCl3 according to Scheme 6 was
carried out under inert atmosphere but when it was per-
formed in air, the complex [NiCl2(5)2] [5 = {(oxazolin-2-
yl)methyl}diphenylphosphine oxide] (6) was obtained quantita-
tively (Scheme 8, Fig. 5). This complex was also obtained when
the synthesis of 4 under air was performed in CH2Cl2, as a result
of direct ligand oxidation at phosphorus. This leads to a six-
1
membered N,O chelate. The reaction was monitored by 31P{ H}
NMR (CDCl3) where the phosphorus nucleus of ligand 5 resonates
at a lower field (28 ppm) than that of ligand 1 (-17 ppm).
Fig. 6 Comparison between the FTIR spectra of 6 (bottom line) and 3
(top line), emphasizing the n(P O) stretching vibration band at 1040 cm-1
(reflectance mode, 1800–700 cm-1 region).
6. This is thus different from the situation encount-
ered with a related dinuclear Co(II) complex bearing two
N,O bridging ligands, [CoCl2{m-OPPh2CH2 C N CMe2CH2O ,
k-O,N}]2
(Scheme
accidental air-oxidation of
9),
which
a
was
obtained
by
P,N-chelated complex
[CoCl2{PPh2CH2 C N CMe2CH2O }] in CH2Cl2 bearing a li-
gand very similar to 1.11 The complex [NiCl{PhB(CH2PPh2)3}]
was also found to be oxidized at two phosphine donor sites to
give [NiCl{PhB(CH2P(O)Ph2)2(CH2PPh2)}].21
Scheme 8
In the centrosymmetric structure of 6 in 6·4CHCl3, two N,O
ligands 5 chelate the metal centre through their nitrogen and
oxygen atoms to form two six-membered chelate rings. This
structure shares analogies with that of 3, displaying a similar
arrangement, with trans oxygen (and N) donors and trans terminal
chlorides. The Ni–N and Ni–Cl distances compare well with
those found in 3. Complex 6 was also characterized by FTIR
spectroscopy and its spectrum is comparable to that of 3, except
for the n(P O) stretching vibration band which appears at 1040
cm-1 (Fig. 6).
Further experiments showed that exposing to air
a
solution of 3 in CH2Cl2 or of 4 in CHCl3 did not give
Scheme 9
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Table 1 Catalytic data for complexes 3, 4 and 6 in ethylene oligomerization with AlEtCl2 as cocatalysta
Selectivity (mass%)
AlEtCl2
(equiv.)
Activity [g C2H4/
(g Ni h-1)]
TOF [mol C2H4/
(mol Ni h-1)]
Selectivity for
b
precatalyst
C4
C6
C8
1-butene (mol%)c
3
3
6
10
10
6
78
51
58
49
56
51
19
41
36
43
38
41
2
7
5
7
5
6
3600
7600
17
4
6
3
4
19 800
29 000
21 000
27 700
29 900
41 500
60 700
44 000
58 000
62 600
4
6
10
8
a Conditions: T = 303 K, 10 bar of C2H4, 35 min, 4 ¥ 10-5 mol of complex; solvent: 13.5, 12, and 10 mL of chlorobenzene for 3, 6, 10 equiv. of AlEtCl2,
respectively (1.5, 3, and 5 mL of AlEtCl2 solution in toluene). b The selectivity for 1-hexene was ca. 0.4% of the C6 fraction. c Within the C4 fraction.
Catalytic oligomerization of ethylene
phosphine oxide complexes in ethylene oligomerization and we are
therefore cautious about the reasons for the better performances
of 6 vs. 3 in our case since both the nature of the donor atom
and the chelate ring size are varied. Finally, when the number
of equivalents of AlEtCl2 used was reduced to 3, the activity
of complex 3 dropped significantly [3600 g C2H4/(g Ni·h)] but
the selectivity was slightly higher for 1-butene (17%), which
could be consistent with a less exothermic reaction. We have no
direct information on the nature of the active species generated
after reaction of the Ni(II) complex with AlEtCl2 and various
possibilities exist to generate a coordinatively unsaturated and
catalytically active complex. Alkylation followed by cationization
of the complex is certainly one of them, possibly involving
(reversible) decoordination of a phosphorus donor atom in the
case of 3 and 4, consistent with the long Ni–P distances in these
complexes, or migration of the oxygen donor atom from Ni to Al
in the case of 6.
Catalytic ethylene oligomerization continues to represent a topic
of considerable academic and industrial interest, in particular
for the production of linear a-olefins in the C4–C10 range whose
demand is growing fast. Ni(II) complexes with a range of chelating
ligands have been successfully used but identifying and controlling
the parameters which influence the activity and selectivity of
the catalyst still represent major challenges at the interface
between coordination/organometallic chemistry and homoge-
neous catalysis.22 In addition, using the least possible amount of
cocatalyst is of obvious economic interest. Complexes 3, 4 and 6
have been tested as precatalysts in the oligomerization of ethylene
with variable amounts of AlEtCl2 as cocatalyst (Table 1), which
has often been found to be a better choice than methylalumoxane
(MAO) for such types of complexes.22 Under conditions similar
to those previously used for other Ni(II) complexes with P,N
chelating ligands,22 we observed that all three complexes exhibit
good activity in the presence of only 10 equiv. of AlEtCl2, in
the range 20 000–30 000 g C2H4/(g Ni·h). Mostly dimers and
trimers were formed. The selectivity for 1-butene is lower than with
[NiCl2(1¢)] which contains only one P,N-chelating ligand 1¢ (1¢ =
(4,4-dimethyl-{oxazolin-2-yl}methyl)diphenyl phosphine), which
only differs from 1 by the presence of two gem-Me groups at
the 4-position of the oxazoline.5 The reasons for the enhanced
isomerization ability of the nickel species formed in situ in the
case of [NiCl2(1)] have not been further investigated. High activity
was still observed in the case of 3 and 6 when only 6 equivalents
of AlEtCl2 were used, with 6 being again more active [27 700 g
C2H4/(g Ni·h)] than 3 [19 800 g C2H4/(g Ni·h)]. The comparison
between the performances of 3 and 6 illustrates the combined
influence of a different donor atom (P vs. O) and different ring
size (5 vs. 6) of the metal chelates. Increasing the ring size from
5 to 6 upon replacement of a phosphine donor by a phosphinite
donor associated with an oxazoline moiety has been previously
found to also lead to an increase in catalytic activity for the
corresponding Ni(II) complexes.22,23 A similar trend was noticed
when the oxazoline donor was replaced with a pyridine.22,24 In the
latter case, a positive ring size effect was also noticed when two
CH2 groups were present as spacers between the phosphine donors
and the pyridine ring instead of one.24 However, a comparison
between Co(II) complexes, one bearing ligand 1¢ and the other the
corresponding phosphinito-oxazoline, revealed an opposite trend,
but these complexes displayed relatively low activity.11 We did not
find comparative data in the literature between phosphine and
Conclusion
Phosphine 1 has proven to be an efficient and versatile
bidentate ligand. As seen in this and previous works, it can
readily form stable monochelated nickel(II),4 palladium(II),9
platinum(II)6 and molybdenum(III)25 complexes, bischelated oc-
tahedral ruthenium(II)8 or nickel(II) complexes, such as 3 and 4,
and much more rarely, act as a bridging ligand. To the best of
our knowledge, this situation has only been encountered in a
+
Fe–Co,13 Fe–Cu14 and Co–Co11 complex and in [{PdCl(1)} (m-
1)(CoCl3)-] (2) which contains in addition a P,N-chelating ligand
1. This zwitterionic complex was obtained by reaction of [PdCl2(1)]
with [CoCl2(1)]2, which involves opening of the P,N chelate at Pd.
Interconversion between the all-trans and all-cis isomeric com-
plexes 3 and 4, respectively, was found to be solvent-dependent.
Complex 6 contains the oxidized ligand 5 while direct oxidation
of complex 3 did not give 6. By comparison with related Ni(II)
complexes containing similar P,N chelates,22 these complexes were
found to be very active for ethylene oligomerisation and afforded
mostly butenes and hexenes.
X-ray data collection, structure solution and refinement for all
compounds
Suitable crystals for the X-ray analysis of all compounds were
obtained as described above. The intensity data were collected
on a Kappa CCD diffractometer26 (graphite monochromated
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Table 2 X-ray data collection and refinement parameters
Compound
2·MeCN
3
4·2CHCl3
6·4CHCl3
Chemical formula
Formula mass
C32H32Cl4CoN2O2P2Pd·MeCN
C32H32Cl2N2NiO2P2
668.15
Orthorhombic
8.2701(2)
15.3634(7)
24.168(1)
90.00
90.00
90.00
3070.7(2)
173(2)
C32H32Cl2N2NiO2P2·2CHCl3
C32H32Cl2N2NiO4P2·4CHCl3
886.72
906.88
1177.69
Crystal system
Triclinic
Triclinic
9.7779(6)
11.0881(5)
18.3495(11)
88.468(4)
83.143(3)
78.299(4)
Triclinic
˚
a/A
12.5554(4)
12.9516(5)
13.0189(5)
81.649(2)
88.148(2)
63.361(2)
10.2269(4)
10.5261(4)
13.0935(6)
66.761(2)
69.761(2)
80.429(2)
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
1870.96(12)
173(2)
1934.14(19)
173(2)
1214.46(9)
173(2)
T/K
¯
¯
¯
Space group
Z
P1
Pbca
4
0.943
6317
P1
P1
2
2
1
m/mm-1
1.330
18204
9506
0.0455
0.0401
0.0898
0.0728
0.0999
1.012
425
1.172
9816
6657
0.0388
0.1615
0.3896
0.1823
0.3959
1.131
442
1.274
7694
5547
0.0183
0.0475
0.1153
0.0664
0.1279
1.060
268
Measd reflect.
Indep. reflect.
Rint
3502
0.0445
0.0440
0.1092
0.0958
0.1487
1.065
R1 (I > 2s(I))
wR(F2) (I > 2s(I))
R1 (all data)
wR(F2) (all data)
S on F2
No. of parameters
187
˚
Mo-Ka radiation, l = 0.71073 A) at 173(2) K for all compounds.
Crystallographic and experimental details for the structures are
summarized in Table 2. The structures were solved by direct
methods (SHELXS-97) and refined by full-matrix least-squares
procedures (based on F2, SHELXL-97)27 with anisotropic ther-
mal parameters for all the non-hydrogen atoms. The hydrogen
atoms were introduced into the geometrically calculated positions
(SHELXL-97 procedures) and refined riding on the corresponding
parent atoms. CCDC 831824 (2·MeCN), 831825 (3), 831826
(4·2CHCl3), 831827 (6·4CHCl3) contain the supplementary crys-
tallographic data for this paper that can be obtained free of
charge from the Cambridge Crystallographic Data Center via
www.ccdc.cam.ac.uk/data_request/cif.†
solution of 1 (0.255 g, 0.95 mmol) in CH2Cl2 (5 mL). The reaction
mixture was stirred at room temperature for 24 h, whereupon
a yellow precipitate formed. The volatiles were removed under
reduced pressure. The yellow residue was washed with diethyl ether
(2 ¥ 15 mL), pentane (15 mL) and dried under vacuum. Complex
[PdCl2(1)] was obtained as a yellow powder (Yield: 0.365 g, 96%).
3
1H NMR (DMSO): d = 3.88 (t, 2H, J(H,H) = 9.6 Hz, NCH2),
4.01 (d, 2H, 2J(P,H) = 11.6 Hz, PCH2), 4.71 (t, 2H, 3J(H,H) = 9.6
1
Hz, OCH2), 7.57–7.97 (m, 10H, Ph); 31P{ H} NMR (DMSO): d =
1
1
22.5 (s); 13C{ H} NMR (DMSO): d = 29.9 (d, J(C,P) = 36 Hz,
PCH2), 53.2 (s, NCH2), 73.1 (s, OCH2), 127.3–133.9 (m, Ph), 177.0
(d, 2J(C,P) = 24.1 Hz, N CO). Anal. Calcd for C16H16Cl2NOPPd
(446.60): C 43.03, H 3.61, N 3.14. Found: C 42.97, H 3.76, N 2.94.
Preparation and spectroscopic data for 2. Solid [PdCl2(1)]
(0.100 g, 0.22 mmol) and [CoCl2(1)]2 (0.088 g, 0.11 mmol) were
mixed in MeCN (10 mL). The resulting green reaction mixture
was stirred for 1 h and the solution was layered with diethyl
ether, which afforded green-blue crystals of 2·CH3CN (Yield:
0.134 g, 71%). FTIR: 689vs, 727w, 745s, 803m, 833w, 935m,
998m, 1045m, 1103m, 1186w, 1232w, 1256m, 1274m, 1335w,
1375s, 1398w, 1435sh, 1478w, 1630vs [n(C N)], 1648s [n(C N)],
2920m, 2970m, 3062w. Anal. Calcd for C34H35Cl4CoN3O2P2Pd
(886.77): C 46.05, H 3.98, N 4.74. Found: C 46.44, H 4.13, N 4.54.
General considerations
All manipulations were carried out under argon atmosphere, using
standard Schlenk-line techniques and dried and freshly distilled
solvents. Unless otherwise stated, the H, 13C{ H}, and 31P{ H}
NMR spectra were recorded on a Bruker Avance 300 instrument
at 300.13, 75.47 and 121.49 MHz, respectively, using TMS or
H3PO4 (85% in D2O) as external standards, with downfield shifts
reported as positive. All NMR spectra were measured at 298 K,
unless otherwise specified. The assignment of the signals was
1
1
1
1
1
1
made by H, H-COSY, and H, 13C-HMQC experiments. The
FTIR spectra reported below were collected on a Thermo-Nicolet
6700 spectrometer, equipped with a diamond crystal SMART
ORBIT accessory. Elemental C, H, and N analyses were performed
by the “Service de microanalyses”, Universite´ de Strasbourg.
[PdCl2(NCPh)2],28 [NiCl2(dme)] (dme = dimethoxyethane)24 and
ligand 1 were prepared according to literature procedures.10
Ph2PCl and NEt3 were freshly distilled before use. Other chemicals
were commercially available and were used as received.
Preparation and spectroscopic data for 3. Solid [NiCl2(dme)]
(0.082 g, 0.37 mmol) was added under argon to a solution
of 1 (0.200 g, 0.74 mmol) in CH2Cl2 (10 mL). The reaction
mixture was stirred at room temperature for 10 min, whereupon a
purple solution formed. The volatiles were removed under reduced
pressure. The pale-blue residue was washed with diethyl ether
(2 ¥ 10 mL) and dried under vacuum. The resulting solid was
dissolved in a minimum amount of CH2Cl2 and the solution
was layered with pentane, which afforded blue-green crystals of
3 (Yield: 0.182 g, 73%). (Redissolution of these crystals into
CH2Cl2 gives again a purple solution when diluted, which becomes
Preparation and spectroscopic data for [PdCl2(1)]. Solid
[PdCl2(NCPh)2] (0.327 g, 0.85 mmol) was added under argon to a
384 | Dalton Trans., 2012, 41, 379–386
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green when more concentrated). FTIR: 690vs, 740s, 823m, 927m,
970w, 997m, 1028m, 1097m, 1131w, 1186w, 1263s, 1330w, 1367m,
1398m, 1433s, 1482m, 1644s, 2910m, 2981w, 3046w. Anal. Calcd
for C32H32Cl2N2NiO2P2 (668.16): C 57.52, H 4.83, N 4.19. Found:
C 57.40, H 4.91, N 3.98.
monitoring of the ethylene uptake. At the end of each test (35 min)
a dry ice bath was used to rapidly cool the reactor. When the inner
temperature reached 0 ◦C, the ice bath was removed, allowing the
temperature to slowly rise to 18 ◦C. The gaseous phase was then
transferred into a 10 L polyethylene tank filled with water. An
aliquot of this gaseous phase was transferred into a Schlenk flask,
previously evacuated, for GC analysis. The amount of ethylene
not consumed was thus determined. Although this method is of
limited accuracy, it was used throughout and gave satisfactory
reproducibility. The reaction mixture in the reactor was quenched
in situ by the addition of ethanol (1 mL), transferred into a
Schlenk flask, and separated from the metal complexes by trap-
to-trap evaporation (20 ◦C, 0.8 mbar) into a second Schlenk flask
previously immersed in liquid nitrogen in order to avoid loss of
product.
Preparation and spectroscopic data for 4. Solid [NiCl2(dme)]
(0.082 g, 0.37 mmol) was added under argon to a solution
of 1 (0.200 g, 0.74 mmol) in CHCl3 (10 mL). The reaction
mixture was stirred at room temperature for 10 min, whereupon a
green solution formed. The volatiles were removed under reduced
pressure. The pale-blue residue was washed with diethyl ether (2
¥ 10 mL) and dried under vacuum. The resulting residue was
dissolved in a minimum amount of CHCl3 and the solution
was layered with pentane, which afforded blue-green crystals of
4·2CHCl3 (Yield: 0.166 g, 67%). FTIR: 661m, 691s, 735s, 827s,
922s, 965w, 990w, 1026s, 1095m, 1129m, 1171w, 1199w, 1239w,
1262s, 1332m, 1365s, 1433s, 1483s, 1644vs, 2945m, 3053w. Anal.
Calcd for C34H34Cl8N2NiO2P2 (4·2CHCl3) (906.91): C 45.03, H
3.78, N 3.09. Found: C 45.16, H 3.85, N 3.06.
Acknowledgements
The work was supported by the CNRS, the Ministe`re de
l’Enseignement Supe´rieur et de la Recherche, and the Institut
Franc¸ais du Pe´trole, Energies Nouvelles (IFPEN). We are grateful
to the French Embassy in Beijing for a doctoral grant to S. J.
to perform research in Strasbourg in the context of the Franco-
Chinese Laboratory for Catalysis, in cotutelle with Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
We thank Me´lanie Boucher and Marc Mermillon-Fournier for
experimental assistance.
Solvent-dependent isomerizations between 3 and 4. Solid 3
(0.100 g, 0.15 mmol) was dissolved in CHCl3 (20 mL), and
evaporation of the solvent gave 4 as a pale-blue powder quan-
titatively. Likewise, 3 was obtained quantitatively by evaporation
of a solution of 4 (0.100 g, 0.15 mmol) in CH2Cl2 (20 mL).
Preparation and spectroscopic data for 6. A solution of 1 (0.200
g, 0.74 mmol) in CHCl3 (10 mL) was stirred for 30 min in air.
Solid [NiCl2(dme)] (0.082 g, 0.37 mmol) was then added to this
solution. The reaction mixture was stirred at room temperature
for 10 min, whereupon a red solution formed. The volatiles were
removed under reduced pressure. The pale-green residue was
washed with diethyl ether (2 ¥ 10 mL) and dried under vacuum.
The resulting residue was dissolved in a minimum amount of
CHCl3 and the solution was layered with pentane, which afforded
blue-greencrystals of 6·4CHCl3 (Yield: 0.190 g, 73%). FTIR: 696w,
746m, 824m, 864w, 928m, 968w, 999m, 1027m, 1040s, 1095m,
1133s, 1181m, 1196w, 1266s, 1329m, 1373s, 1400m, 1434s, 1481m,
1647s, 2910m, 2981w, 3044m. Anal. Calcd for C32H32Cl2N2NiO4P2
(700.15): C 54.89, H 4.61, N 4.00. Found: C 55.09, H 5.05, N 3.86.
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©