Phosphinooxazolines as assembling ligands in heterometallic complexes

Article abstract of DOI:10.1039/b300277m

It is shown that phosphinooxazolines such as (2-oxazoline-2-ylmethyl) diphenylphosphine 1 can be used as P,N assembling ligands for the synthesis of heterometallic complexes. These were obtained in a stepwise manner from the iron carbonyl complexes containing one, [Fe(CO)₄(PCH₂- oxazoline-P)]₂, or two, trans-[Fe(CO)₃(PCH ₂-oxazoline-P)₂] 6, P-bound phosphinooxazoline ligands. These metalloligands were then reacted with metal complexes. With 2, complete ligand transfer from Fe to the second metal (Pd) was sometimes observed. The metal-metal bonded complex [(OC)₄Fe(μ-PCH₂-oxazoline-P, N)PdCl₂]3 was of limited stability, whereas the trinuclear complex trans-[{(OC)₄Fe(μ-PCH₂-oxazoline-P,N)} ₂CoCl₂] 4, in which 2 functions as a N-donor metalloligand toward the tetrahedral Co(II) centre, was stable and could be fully characterised by X-ray diffraction. This complex catalyses the oligomerization of ethylene to give linear α-olefins in the range C₄-C ₂₆, with a maximum of the Schulz-Flory distribution around C ₆. The complex [{(OC)₄Fe(μ-PCH₂-oxazoline-P, N)}₂HgI₂] 5 was also prepared from 6. With the metalloligand 6, the Fe→Pd and Fe→Co metal-metal bonded compounds trans-[(OC)₃Fe(μ-PCH₂-oxazoline-P,N) ₂Pd(NCMe)](BF₄)₂ 8 and trans-[(OC) ₃Fe(μ-PCH₂-oxazoline-P,N)₂CoCl₂] 9 were obtained. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b300277m

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Phosphinooxazolines as assembling ligands in heterometallic
complexes
Pierre Braunstein,*a Guislaine Clerc,a Xavier Morise,a Richard Welterb and
Giuseppe Mantovanic
a Laboratoire de Chimie de Coordination, UMR CNRS 7513, Université Louis Pasteur,
4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France. E-mail: braunst@chimie.u-strasbg.fr
b Laboratoire DECMET, UMR CNRS 7513, Université Louis Pasteur, 4 rue Blaise Pascal,
F-67070 Strasbourg Cedex, France
c Institute of Chemistry of Organometallic Compounds, ICCOM-CNR, Via Jacopo Nardi, 39,
50132 – Firenze, Italy
Received 8th January 2003, Accepted 21st February 2003
First published as an Advance Article on the web 10th March 2003
It is shown that phosphinooxazolines such as (2-oxazoline-2-ylmethyl)diphenylphosphine 1 can be used as P,N
assembling ligands for the synthesis of heterometallic complexes. These were obtained in a stepwise manner from the
iron carbonyl complexes containing one, [Fe(CO)4(PCH2-oxazoline-P)] 2, or two, trans-[Fe(CO)3(PCH2-oxazoline-
P)2] 6, P-bound phosphinooxazoline ligands. These metalloligands were then reacted with metal complexes. With
2, complete ligand transfer from Fe to the second metal (Pd) was sometimes observed. The metal–metal bonded
complex [(OC)4Fe(µ-PCH2-oxazoline-P,N)PdCl2] 3 was of limited stability, whereas the trinuclear complex trans-
[{(OC)4Fe(µ-PCH2-oxazoline-P,N)}2CoCl2] 4, in which 2 functions as a N-donor metalloligand toward the
tetrahedral Co() centre, was stable and could be fully characterised by X-ray diffraction. This complex catalyses
the oligomerization of ethylene to give linear α-olefins in the range C4–C26, with a maximum of the Schulz-Flory
distribution around C6. The complex [{(OC)4Fe(µ-PCH2-oxazoline-P,N)}2HgI2] 5 was also prepared from 6.
With the metalloligand 6, the Fe Pd and Fe Co metal–metal bonded compounds trans-[(OC)3Fe(µ-PCH2-
oxazoline-P,N)2Pd(NCMe)](BF4)2 8 and trans-[(OC)3Fe(µ-PCH2-oxazoline-P,N)2CoCl2] 9 were obtained.
Such small-bite bridging ligands are more rarely involved in
Introduction
six-membered ring structures.5c,7,8 A metal-induced opening
One of the major motivations for using assembling ligands in
coordination and organometallic chemistry is to allow or
of a stable, five-membered ring mononuclear chelate to form
a metal–metal bonded six-membered structure is thermo-
facilitate the synthesis of complex molecules with strong, weak
dynamically much less attractive than the above transformation
or no metal–metal bonding whereas in cluster chemistry, the
from a four-membered chelate to a five-membered, metal–metal
molecular stability is mainly due to metal–metal bonding.1,2
bonded system (Scheme 1).
Assembling ligands may thus allow greater flexibility in the
Functional phosphine ligands (i.e. phosphine ligands bearing
bonding/non-bonding separation between the metal centres
at least one additional, chemically different function) have been
much used as assembling ligands between two or more metal
atoms, in particular but not exclusively in the context of early–
and lead to systems displaying reversible metal–metal bond
breaking/formation under mild conditions.3 This is of consider-
able relevance to the occurrence of synergistic and bimetallic
effects in stoichiometric or catalytic reactivity where irreversible
late chemistry where the different electronic properties of the
donor groups can lead to very selective binding processes.9
breaking of
a polymetallic structure into mononuclear
When metal–metal bonding is present, mostly five-membered
metallocycles have been reported,1 larger bimetallic cycles being
less frequent. In the case of (P,O) ligands, we reported some
examples of six-membered ring metal–metal bonded systems,10
and with (P,N) ligands, we reported recently the first six-
membered ring metal–metal bonded system.11 Only one seven-
membered cycle has been very recently reported.12
Our interest in phosphinooxazoline ligands, which behave
either as P-monodentate or P,N-donors in five-membered ring
chelate structures (rigid or hemilabile),13 has led us to explore
their potential as bridging ligands, a situation which, to the best
of our knowledge, had not been reported before, and examine
their ability to support a metal–metal bond in a six-membered
ring structure. Preliminary results have been obtained with a
Fe–Cu system.11
fragments is undesirable.4
Among the most often used assembling ligands, one finds
small-bite ligands which by supporting a metal–metal bond
lead to the formation of stabilised five-membered ring struc-
tures, as exemplified with the well-known ligands Ph2PCH2PPh2
(dppm), 2-(diphenylphosphino)pyridine (P–Py) or, more
recently, Ph2PNHPPh2 (dppa).1,5 An efficient method to access
these dimetallic five-membered ring structures consists of start-
ing from a thermodynamically less favourable four-membered
chelate that will insert the second metal into a metal–phos-
phorus bond (metal-induced chelate ring opening) (Scheme 1).6
Results and discussion
Following our studies on heterobimetallic systems involving
the precursors [Fe(CO)4(dppm-P)], [Fe(CO)4(dppa-P)] or
[Fe{Si(OMe)3}(CO)3(dppm-P)]Ϫ,1e,14 we first prepared the
metalloligand [Fe(CO)4(PCH2-oxazoline-P)] 2 by reaction of
[Fe(CO)5] in THF with the ligand (2-oxazoline-2-ylmethyl)-
diphenylphosphine 1 (abbreviated PCH2-oxazoline in the
Scheme 1 Formation of dinuclear, metal–metal bonded complexes by
metal-induced chelate opening (D = donor atom).
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
D a l t o n T r a n s . , 2 0 0 3 , 1 6 0 1 – 1 6 0 5
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following) in the presence of a catalytic amount of CoCl2.15 Its
reaction with [PdCl2(cod)] or [PdCl2(NCPh)2] resulted in the
formation of the desired complex [(OC)4Fe(µ-PCH2-oxazoline-
P,N)PdCl2] 3 which was however too unstable to be fully char-
acterised in the solid-state (eqn. (1)). Its formation was moni-
tored in situ by 31P{1H} NMR spectroscopy (δ 64.0 ppm) and
IR in the ν(CO) (2021 (vs), 1996 (vs), 1934 (w) cmϪ1) and ν(CN)
(1632 (m) cmϪ1) regions.
(1)
This complex rapidly transforms in solution with complete
ligand transfer from Fe to Pd and formation of the mono-
nuclear complex [PdCl2(PCH2-oxazoline-P,N)].16,17a Similarly,
[PdCl(Me)(PCH2-oxazoline-P,N)] was formed in the reaction
of 2 with [PdCl(Me)(cod)]. Obviously, the phosphine-oxazoline
ligand 1 is less suitable than dppm or dppa for the stabilisation
of complexes with a dative Fe Pd metal–metal bond.14
Reaction of two equiv. of 2 with anhydrous CoCl2 afforded a
trinuclear complex trans-[(OC)4Fe(µ-PCH2-oxazoline-P,N)2-
CoCl2] 4 in which 2 functions only as a N-donor metalloligand
Fig. 1 ORTEP view of the crystal structure of complex 4. Ellipsoids
are shown at the 50% probability level.
toward the tetrahedral Co() centre, as indicated by a ν(C᎐N)
᎐
section. It was found to oligomerise ethylene to give linear
α-olefins in the range C4–C26, with a maximum of the Schulz–
Flory distribution around C6. The turnover frequency of 341
(mol C2H4 mol CoϪ1 minϪ1) is much lower than those observed
by Brookhart and co-workers and Gibson and co-workers,19
although our experiments have not been optimized.
absorption at 1630 (w) cmϪ1
.
Similarly to the synthesis of 4, the complex [{(OC)4-
Fe(µ-PCH2-oxazoline-P,N)}2HgI2] 5 was prepared by reaction
of HgI2 with two equiv. of 2 in CH2Cl2. The spectroscopic data
are consistent with the P,N-bridging mode of ligand 1 (see
Experimental section).
In view of the very modest stabilization brought about by the
bridging ligand 1 in a metal–metal bonded complex of type 3,
and its facile, complete transfer from Fe to Pd, we envisaged to
use an iron synthon containing two P,N ligands 1 that could act
as a chelating system, trans-[Fe(CO)3(PCH2-oxazoline-P)2] 6.11
It was obtained by reaction of [Fe(CO)5] with two equiv. of 1 in
1-butanol, using the NaBH4 activation procedure (eqn. (2)),20
whereas addition of one equiv. of 1 to a solution of 2 in CH2Cl2
in the presence of Me3NO led to a mixture of products.
The geometry of this complex was established by X-ray dif-
fraction and confirmed the bridging behaviour of each phos-
phinooxazoline ligand. A view of the crystal structure is shown
in Fig. 1 and selected bond distances and angles are given in
Table 1.
The metals are far apart [Fe(1)–Co and Fe(2)–Co separations
of 5.111(1) and 5.324(1) Å] and each metal centre is found in its
usual coordination environment, trigonal bipyramidal for Fe(0)
and tetrahedral for Co(). The bonding parameters are in the
expected range. The Co–Cl distances of 2.232(3) and 2.261(3) Å
and the Co–N distances of 2.032(8) and 2.044(7) Å are similar
to those found in cobalt oxazoline complexes where the oxazol-
ine moiety is part of a N,N, O,N or P,N chelate,18 taken for
comparison in the absence, to the best of our knowledge, of
structural data on Co() complexes with monohapto or bridg-
ing oxazoline ligands. The Fe–P distances of 2.223(4) and
2.232(3) Å and the ligand arrangement around the Fe centre are
similar to those in the mononuclear complex trans-[Fe(CO)3-
(PCH2-oxazoline-P)2] 6 (see below). In view of the catalytic per-
formances of Fe() and Co() diimine complexes for the
oligomerisation of ethylene,19a,b preliminary experiments were
carried out with 4. The details are given in the Experimental
(2)
The trans-arrangement of the P donors gives rise to a singlet
at δ 77.7 ppm in the 31P{1H} NMR spectrum and it was con-
firmed in the solid-state by an X-ray diffraction study.11
D a l t o n T r a n s . , 2 0 0 3 , 1 6 0 1 – 1 6 0 5
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Table 1 Selected bond distances (Å) and angles (Њ) in 4
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(4)
Fe(1)–P(1)
Fe(2)–C(21)
Fe(2)–C(22)
Fe(2)–C(23)
Fe(2)–C(24)
Fe(2)–P(2)
Co–N(1)
Co–N(2)
Co–Cl(1)
Co–Cl(2)
P(1)–C(5)
P(1)–C(11)
P(1)–C(17)
P(2)–C(28)
P(2)–C(29)
P(2)–C(35)
1.807(9)
1.791(11)
1.816(11)
1.755(11)
2.223(3)
1.799(10)
1.786(9)
1.776(10)
1.804(10)
2.232(3)
2.032(8)
2.044(7)
2.232(3)
2.261(3)
1.808(8)
1.835(9)
1.866(9)
1.860(8)
1.827(9)
1.825(8)
N(1)–C(18)
N(1)–C(20)
N(2)–C(25)
N(2)–C(27)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
1.286(11)
1.487(10)
1.444(11)
1.287(10)
1.136(12)
1.148(12)
1.121(12)
1.149(12)
1.471(12)
1.338(10)
1.435(13)
1.483(14)
1.145(11)
1.140(11)
1.146(11)
1.121(12)
1.563(13)
1.445(11)
1.324(10)
1.482(11)
C(4)–O(4)
C(17)–C(18)
C(18)–O(5)
C(19)–O(5)
C(19)–C(20)
C(21)–O(6)
C(22)–O(7)
C(23)–O(8)
C(24)–O(9)
C(25)–C(26)
C(26)–O(10)
C(27)–O(10)
C(27)–C(28)
centre, signals were observed at: δ 50.5 (vbr), 32.6 (br), 15.2,
Ϫ17.7; 31P{1H} NMR (CD2Cl2, 298 K): δ 72 (br, w1/2 = 51 Hz)),
although no satisfactory elemental analysis could be obtained
for this product. When 2 was reacted with [PdCl2(cod)], [PdCl-
(Me)(cod)] or [PtCl2(cod)], no dinuclear complex could be iso-
lated and complete tranfer of the phosphinooxazoline ligand
occurred to give the known complexes [PdCl2(PCH2-oxazoline-
P)], [PdCl(Me)(PCH2-oxazoline-P)] or [PtCl2(PCH2-oxazoline-
P)], respectively, which were identified by comparison with
authentic samples.17
C(4)–Fe(1)–C(1)
C(4)–Fe(1)–C(2)
C(4)–Fe(1)–C(3)
C(2)–Fe(1)–C(1)
C(2)–Fe(1)–C(3)
C(1)–Fe(1)–C(3)
C(1)–Fe(1)–P(1)
C(2)–Fe(1)–P(1)
C(3)–Fe(1)–P(1)
C(4)–Fe(1)–P(1)
C(21)–Fe(2)–C(22)
C(22)–Fe(2)–C(24)
91.4(5)
91.8(5)
90.3(5)
114.7(5)
124.2(5)
121.0(5)
90.1(3)
91.6(3)
85.0(3)
175.2(4)
87.9(4)
91.5(5)
C(29)–P(2)–C(35)
C(28)–P(2)–C(35)
C(28)–P(2)–Fe(2)
C(29)–P(2)–Fe(2)
C(35)–P(2)–Fe(2)
C(18)–N(1)–C(20)
C(18)–N(1)–Co
C(20)–N(1)–Co
C(25)–N(2)–C(27)
C(25)–N(2)–Co
101.6(4)
104.9(4)
114.0(3)
112.7(3)
118.3(3)
107.0(7)
135.5(6)
117.3(6)
107.9(7)
116.9(5)
134.2(6)
178.1(10)
179.1(9)
178.6(9)
176.5(12)
113.9(6)
116.2(8)
128.0(8)
115.8(8)
105.5(8)
103.9(8)
176.5(9)
179.3(10)
177.8(8)
176.4(9)
103.9(7)
101.4(7)
116.4(8)
127.4(8)
116.2(7)
111.9(6)
107.2(7)
108.6(6)
Conclusion
C(27)–N(2)–Co
O(1)–C(1)–Fe(1)
O(2)–C(2)–Fe(1)
O(3)–C(3)–Fe(1)
O(4)–C(4)–Fe(1)
C(18)–C(17)–P(1)
N(1)–C(18)–O(5)
N(1)–C(18)–C(17)
O(5)–C(18)–C(17)
O(5)–C(19)–C(20)
N(1)–C(20)–C(19)
O(6)–C(21)–Fe(2)
O(7)–C(22)–Fe(2)
O(8)–C(23)–Fe(2)
O(9)–C(24)–Fe(2)
N(2)–C(25)–C(26)
O(10)–C(26)–C(25)
N(2)–C(27)–O(10)
N(2)–C(27)–C(28)
O(10)–C(27)–C(28)
C(27)–C(28)–P(2)
C(18)–O(5)–C(19)
C(26)–O(10)–C(27)
We have shown that the phosphinooxazoline ligand 1 can be
used as an assembling ligand for the synthesis of heterometallic
complexes. This was demonstrated here by a stepwise approach
based on iron carbonyl complexes containing one (2) or two (6)
P-bound phosphinooxazoline ligands as building blocks. These
were subsequently reacted with complexes of a second metal. In
addition to the nitrogen atom of the pendent oxazoline(s) being
available for coordination to a second metal, the filled d orbitals
of the Fe centre can participate in dative metal–metal bonding,
which results in these metalloligands behaving as bidentate or
tridentate donors, respectively. In the former case, complete
ligand transfer from Fe to the second metal was sometimes
observed. The metal–metal bonded Fe Pd complex 3 was of
limited stability, whereas the stable, trinuclear Co/Fe2 complex 4
was fully characterised by X-ray diffraction. This latter complex
catalyses the oligomerisation of ethylene to give linear α-olefins
in the range C4–C26, with a maximum of the Schulz–Flory
distribution around C6. With the metalloligand 6, the Fe Pd
and Fe Co metal–metal bonded compounds 8 and 9 were
obtained, respectively.
C(23)–Fe(2)–C(21) 127.0(4)
C(23)–Fe(2)–C(22) 91.2(4)
C(23)–Fe(2)–C(24) 115.3(4)
C(24)–Fe(2)–C(21) 117.7(4)
C(21)–Fe(2)–P(2)
C(22)–Fe(2)–P(2)
C(23)–Fe(2)–P(2)
C(24)–Fe(2)–P(2)
N(1)–Co–N(2)
N(1)–Co–Cl(1)
N(2)–Co–Cl(1)
N(1)–Co–Cl(2)
N(2)–Co–Cl(2)
Cl(1)–Co–Cl(2)
C(5)–P(1)–C(11)
C(5)–P(1)–C(17)
C(11)–P(1)–C(17)
C(5)–P(1)–Fe(1)
C(11)–P(1)–Fe(1)
C(17)–P(1)–Fe(1)
C(28)–P(2)–C(29)
92.2(3)
176.4(4)
85.8(3)
91.7(3)
113.5(3)
103.4(2)
110.4(2)
107.2(2)
105.7(2)
116.8(1)
102.3(4)
102.1(4)
103.4(4)
112.8(3)
119.2(3)
115.0(3)
103.8(4)
We have recently shown that 6 can indeed function as a chel-
ating metallodiphosphine since its reaction with [Cu(NCMe)4]-
BF4 in CH2Cl2 afforded [(OC)3Fe(µ-PCH2-oxazoline-P,N)2Cu]-
BF4 7, which has been characterised by X-ray diffraction and
shown to contain a dative Fe Cu bond [2.544(7) Å].11 Reac-
tion of 6 with [Pd(NCMe)4](BF4)2 in MeCN afforded an orange
compound, trans-[(OC)3Fe(µ-PCH2-oxazoline-P,N)2Pd(NC-
Me)](BF4)2 8, which could only be characterised spectro-
scopically owing to its limited stability. The latter most likely
results from the geometrical constraints imposed by the bridg-
ing ligands on the Pd() coordination geometry. The N–Pd–N
angle has to severely depart from the usual 180Њ, as suggested
by the corresponding N–Cu–N angle of 132.7(1)Њ in 7.11
Experimental
All the reactions were performed using Schlenk tube techniques
under an inert atmosphere of purified nitrogen. Solvents were
freshly distilled under nitrogen from the usual drying
agent prior to use. Nitrogen was passed through BASF R3–11
catalyst and molecular sieves columns to remove residual
oxygen and water. The 1H and 31P{1H} NMR spectra were
recorded at 300.13 and 121.5 MHz, respectively, on a FT
Bruker AC 300 instrument. Infrared spectra were recorded in
the 4000–400 cmϪ1 range on a IFS-66 FTIR Bruker spectro-
meter. Samples were prepared as KBr pellets or in solutions
using CaF2 cells. The synthesis of the ligand (2-oxazoline-2-
ylmethyl)diphenylphosphine 1 was carried out as described
previously.19a
Reaction of 6 with one equiv. of CoCl2 afforded the para-
magnetic complex trans-[(OC)3Fe(µ-PCH2-oxazoline-P,N)2-
CoCl2] 9 and with [Co(NCMe)6](BF4)2 a red, paramagnetic
compound, formulated as trans-[(OC)3Fe(µ-PCH2-oxazoline-
P,N)2Co(NCMe)](BF4)2 (IR (MeCN): ν(CO) 1970 (w), 1901
Synthesis of the complexes
(vs), 1878 (vs); ν(C᎐N) 1638 (br, m) cmϪ1; 1H NMR (acetone-d6,
Synthesis of [Fe(CO)4(PCH2-oxazoline-P}] 2. A toluene solu-
tion (30 ml) of the PCH2-oxazoline ligand 1 (2.70 g, 10 mmol)
᎐
298 K): consistent with the paramagnetic nature of the Co()
D a l t o n T r a n s . , 2 0 0 3 , 1 6 0 1 – 1 6 0 5
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Table 2 Crystal data and data collection parameters for 4
and a catalytic amount of anhydrous CoCl2 (0.05 g, 0.385
mmol) were refluxed before [Fe(CO)5] (2.63 ml, 20 mmol) was
added. The reaction was monitored by IR in the ν(CO) region.
Reflux was continued until the spectrum remained invariant
with time. After cooling to room temperature, the reaction
mixture was eluted with toluene through a column containing
CoCl2ؒ6H2O (5 g)/neutral alumina (20 g)/silica gel (20 g) dis-
posed in three layers from top to bottom, respectively.15 Solvent
and excess [Fe(CO)5] were then removed under reduced pres-
sure and the product was recrystallized from CH2Cl2–hexane.
The product was isolated as ochre crystals (3.00 g, 70%). IR
Formula
Molecular weight
C40H32Cl2CoFe2N2O10P2
1004.19
Colour
Crystal system
Blue
Monoclinic
Space group
T /K
P21/n
173(2)
a/Å
b/Å
9.619(5)
14.350(5)
c/Å
30.846(5)
92.441(5)
4254(3)
β/Њ
V/Å3
(CH Cl ): ν(CO) 2051 (s), 1975 (m), 1939 (vs); ν(C᎐N) 1662 (w)
Z
4
᎐
2
2
Dc/g cmϪ3
1.568
1.317
1
cmϪ1. H NMR (CDCl3, 298 K): δ 7.71–7.33 (m, 10H, aro-
µ/mmϪ1
3
matics), 4.13 (t, 2H, JHH = 9.8 Hz, OCH2), 3.80 (dt, 2H,
5
2
Radiation
λ/Å
Mo-Kα graphite-monochromated
0.71069
3JHH = 9.8, JPH = 4.4 Hz, NCH2), 3.54 (d, 2H, JPH = 10.6 Hz,
PCH2). 13C{1H} NMR (CD2Cl2): δ 213.5 (d, JPC = 19.5 Hz,
2
hkl Limits
θ Limit/Њ
F(000)
Ϫ12 to 12, 0–18, 0–40
CO), 161.9 (s, C᎐N), 132.7–127.9 (aromatics), 68.2 (s, OCH ),
᎐
2
27.485
2036
9638
7470
55.1 (s, NCH2), 33.5 (d, PCH2, 2JPC = 25.7 Hz). 31P{1H} NMR
(C6D6, 298 K): δ 68.2 (s). Anal. Calc. for C20H16FeNO5P: C,
54.95; H, 3.69; N, 3.20. Found: C, 54.72; H, 3.56; N, 3.00%.
Number of measured data
Number of data (I > 2σ(I ))
Weighting scheme
Ra
2
2
4
4Fo /(σ2(Fo ) ϩ 0.0064Fo )
0.1220
0.2314
1.257
Synthesis of [{(OC)4Fe(ꢀ-PCH2-oxazoline-P,N)}2CoCl2] 4.
Dried CoCl2 (0.043 g, 0.335 mmol) was added to a dichloro-
methane solution (100 ml) of [Fe(CO)4(PCH2-oxazoline-P)] 2
(0.292 g, 0.667 mmol) at room temperature. After a few minutes
of vigorous stirring, the colour of the initial green solution
turned sea-blue. The solution was concentrated to half of its
volume under reduced pressure. Overnight, blue crystals
a
Rw
GOF
a R = Σ||Fo| Ϫ |Fc||/Σ|Fo|; Rw = [Σw(|Fo| Ϫ |Fc|)2/Σw(|Fo|2]1/2
.
precipitate upon cooling. The mixture was concentrated to half
of its volume and the solvent was removed under N2 via canula.
The solid was washed with pentane (3 × 50 ml) and dried under
appeared (0.256 g, 77%). IR (CH2Cl2): ν(CO) 2052 (s), 1978
1
(m), 1945 (vs), 1933 (sh); ν(C᎐N) 1630 (w) cmϪ1. H NMR
vacuum (0.460 g, 39%). IR (CH2Cl2): ν(CO) 1979 (w), 1903 (s),
᎐
1
(CDCl3, 298 K): consistent with the paramagnetic nature of the
Co() centre, signals were observed at: δ 28.66 (br), 9.9 (br),
8.47–7.25 (aromatics), 3.98 (br), 3.74 (br), 3.48 (br). 31P{1H}
NMR (CDCl3, 298 K): δ 61.7 (br, w1/2 = 263 Hz). Anal. Calc. for
C40H32CoCl2Fe2N2O10P2ؒ1.5CH2Cl2: C, 44.05; H, 3.12; N, 2.48.
Found: C, 44.17; H, 2.95; N, 2.47%.
1876 (vs); ν(C᎐N) 1642 (m) cmϪ1. H NMR (CDCl3, 298 K):
᎐
consistent with the paramagnetic nature of the Co() centre,
signals were observed at: δ 55.6 (vbr), 41.9 (vbr), 23.8 (br), 16.9,
15.8, Ϫ5.5 (vbr). 31P{1H} NMR (CDCl3, 298 K): δ 66.4 (br, w1/2
= 130 Hz). Anal. Calc. for C35H32CoCl2FeN2O5P2: C, 52.01; H,
3.99; N, 3.47. Found: C, 50.72; H, 4.00; N, 3.07%.
Synthesis of [{(OC)4Fe(ꢀ-PCH2-oxazoline-P,N)}2HgI2] 5.
Dried HgI2 (0.137 g, 0.30 mmol) was added to a dichloro-
methane solution (100 ml) of [Fe(CO)4(PCH2-oxazoline-P)]
(0.264 g, 0.60 mmol) at room temperature. After a few minutes
of vigorous stirring, the colour of the initial orange solution
turned deep orange. The solution was concentrated to half of
its volume under reduced pressure. Overnight, an orange pre-
cipitate appeared which was collected by filtration (0.32 g,
Catalysis
A mechanically stirred 1000 mL Parr autoclave was heated
overnight to 100 ЊC under vacuum and then cooled to 30 ЊC
under an ethylene atmosphere. The autoclave was charged with
200 mL of degased toluene and 5 mL MAO. The autoclave was
sealed, and ethylene was added (100 psig). The solution was
stirred for 10 min, during which time the desired reaction tem-
perature was established. The ethylene pressure was then
released, and a suspension of [(OC)4Fe(µ-PCH2-oxazoline-
P,N)2CoCl2] 4 (0.1 mmol, 0.081 g in 2 mL of toluene) was
added to the reaction mixture via canula. The reactor was then
sealed and pressurised with ethylene to the desired reaction
pressure. The reaction mixture was stirred under constant
ethylene pressure for 1 h, after which time the reactor was
placed in an ice-bath and the pressure was released. After addi-
tion of 200 µL of n-heptane, an aliquot of the reaction mixture
was analyzed by GC–mass spectroscopy to determine the
Schulz–Flory α constant. The integrated areas of the C12 and
C14 oligomers were used to calculate the α constant. The GLC
conditions used are as follows: injector and detector temper-
atures, 250 ЊC; oven temperature program, 100 ЊC for 4 min, 8
ЊC minϪ1 ramp, 250 ЊC/ for 70 min. Oligomer peaks in the range
C4–C26 were resolved under these analytical conditions.
80%). IR (CH Cl ): ν(CO) 2085 (s), 2002 (vs), 1940 (s), ν(C᎐N)
᎐
2
2
1653 (w) cmϪ1. 1H NMR (CDCl3, 298 K): 7.40–7.70 (m, 20 H,
aromatics), 4.21 (m, 4H, OCH2), 3.83 (m, 4H, NCH2), 3.50 (m,
4H, PCH2). 31P{1H} NMR (CDCl3, 298 K): δ 65.07.
Synthesis of trans-[(OC)3Fe(ꢀ-PCH2-oxazoline-P,N)2Pd-
(NCMe)](BF4)2 8. Solid [Pd(NCMe)4](BF4)2 (0.058 g, 0.13
mmol) was added to a solution of trans-[Fe(CO)3(PCH2-oxazo-
line-P)2] 6 (0.089 g, 0.13 mmol) in MeCN at Ϫ78 ЊC. After a few
minutes of vigorous stirring, the colour of the initial yellow
solution turned orange. The solvent was rapidly evaporated
under reduced pressure. Owing to its observed instability, a cor-
rect elemental analysis could not be obtained for this complex.
IR (CH Cl ): ν(CO) 2018 (s), 1967 (vs), 1943 (ms); ν(C᎐N) 1653
᎐
2
2
(s) cmϪ1. H NMR (acetone-d6, 298 K): δ 8.15–7.46 (m, 20H,
aromatics), 4.75 (m, 4H, PCH2), 4.47 (pseudo t, 4H, 3JHH ≈ 9.35
Hz, OCH2), 3.95 (pseudo t, 4H, 3JHH ≈ 9.35 Hz, NCH2), 2.25 (s,
3 H, CH3CN). 31P{1H} NMR (acetone-d6, 298 K): δ 71.8 (s).
1
X-Ray crystallography
We succeeded in selecting an almost not-twinned crystal, but of
sufficient quality for an unambiguous molecular structure reso-
lution. This factor should explain the relative high R values. It
was mounted on a Kappa CCD diffractometer. The relevant
data are summarized in Table 2. Data were collected using
phi-scans and the structure was solved using direct methods
and refined against F 2 using SHELX 97 software.21,22 No
Synthesis of trans-[(OC)3Fe(ꢀ-PCH2-oxazoline-P,N)2CoCl2]
9. Dried CoCl2 (0.191 g, 1.47 mmol) was added to a solution of
trans-[Fe(CO)3(PCH2-oxazoline-P)2] 6 (1.00 g, 1.47 mmol) dis-
solved in 30 ml of previously degassed 1-butanol. The reaction
mixture was refluxed for 1 h. The colour of the initial yellow
solution turned to pastel green with formation of a pastel green
D a l t o n T r a n s . , 2 0 0 3 , 1 6 0 1 – 1 6 0 5
1604

View Article Online
8 P. Braunstein, M. A. Luke, A. Tiripicchio and M. Tiripicchio
absorption correction was used. All non-hydrogen atoms
were refined anisotropically with H atoms introduced as fixed
contributors (dC–H = 0.95 Å, U11 = 0.04).
CCDC reference number 192296.
See http://www.rsc.org/suppdata/dt/b3/b300277m/ for crys-
tallographic data in CIF or other electronic format.
Camellini, Angew. Chem., Int. Ed. Engl., 1987, 26, 768.
9 (a) D. W. Stephan, Coord. Chem. Rev., 1989, 95, 41; (b) N. Wheatley
and P. Kalck, Chem. Rev., 1999, 99, 3379 and references therein;
(c) P. Braunstein, X. Morise, M. Bénard, M.-M. Rohmer and
W. Welter, Chem. Commun., 2003, 610.
10 (a) P. Braunstein, L. Douce, M. Knorr, M. Strampfer,
M. Lanfranchi and A. Tiripicchio, J. Chem. Soc., Dalton Trans.,
1992, 331; (b) F. Balegroune, P. Braunstein, L. Douce, Y. Dusausoy,
D. Grandjean, M. Knorr and M. Strampfer, J. Cluster Sci., 1992, 3,
275; (c) P. Braunstein, C. Charles, A. Tiripicchio and F. Ugozzoli,
J. Chem. Soc., Dalton Trans., 1996, 4365.
11 P. Braunstein, G. Clerc and X. Morise, New. J. Chem., 2003, 27, 68.
12 D.-J. Cui, Q.-S. Li, F.-B. Xu, X.-B. Leng and Z.-Z. Zhang,
Organometallics, 2001, 20, 4126.
13 (a) M. Gomez, G. Muller and M. Rocamora, Coord. Chem. Rev.,
1999, 193–195, 769; (b) G. Helmchen and A. Pfalz, Acc. Chem. Res.,
2000, 33, 336; (c) P. Braunstein and F. Naud, Angew. Chem., Int. Ed.,
2001, 40, 680.
Acknowledgements
We are grateful to the Centre National de la Recherche
Scientifique (Paris), the Ministère de l’Enseignement Supérieur
et de la Recherche (Paris) and the COST D-17/0002/00 action
of the European Commission for support. G.C. is particularly
grateful to Prof. C. Bianchini for his hospitality and Dr. W.
Oberhauser for assitance during her research stay in Florence.
14 P. Braunstein, J. Durand, M. Knorr and C. Strohmann,
Chem. Commun., 2001, 211.
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