Ferrocenyl phosphane nickel carbonyls: Synthesis, solid state structure, and their use as catalysts in the oligomerization of ethylene

Article abstract of DOI:10.1016/j.jorganchem.2010.03.012

The synthesis of diverse ferrocenyl phosphane nickel carbonyls of type (FcPPh₂)Ni(CO)₃ (3), (FcPPh₂)₂Ni(CO)₂ (4), fc(PR₂Ni(CO)₃)₂ (R = Ph (6a), R = p-tolyl (6b)), and (fc(PPh₂)₂)Ni(CO)₂ (7) (Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe, fc = (η⁵-C₅H₄)₂Fe) starting from FcPPh₂ (1), fc(PR₂)₂ (R = Ph (5a); R = p-tolyl (5b)), and Ni(CO)₄ (2) is described. The structures of 3, 4, 6b, and 7 in the solid state are reported, intermolecular interactions by π-π-contacts are discussed. The behavior of 3, 4, 6a, 6b, and 7 towards the oligomerization of ethylene is reported. All compounds, except 4, were found to be inactive in homogeneous ethylene oligomerization, while they exhibit moderate activities (up to 660 kg prod/mol Ni h) in heterogeneous ethylene oligomerization experiments.

Full text of DOI:10.1016/j.jorganchem.2010.03.012

Journal of Organometallic Chemistry 695 (2010) 1541–1549
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Ferrocenyl phosphane nickel carbonyls: Synthesis, solid state structure,
and their use as catalysts in the oligomerization of ethylene
Dieter Schaarschmidt a, Janett Kühnert a, Sascha Tripke a, Helmut G. Alt b, Christian Görl b, Tobias Rüffer a,
Petra Ecorchard a, Bernhard Walfort a, Heinrich Lang a,
*
a Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Lehrstuhl für Anorganische Chemie, Straße der Nationen 62, 09111 Chemnitz, Germany
b Laboratorium für Anorganische Chemie, Universität Bayreuth, Postfach 10 12 51, 95440 Bayreuth, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of diverse ferrocenyl phosphane nickel carbonyls of type (FcPPh2)Ni(CO)3 (3),
(FcPPh2)2Ni(CO)2 (4), fc(PR2Ni(CO)3)2 (R = Ph (6a), R = p-tolyl (6b)), and (fc(PPh2)2)Ni(CO)2 (7) (Fc = (g5
-
Received 15 December 2009
Received in revised form 3 March 2010
Accepted 7 March 2010
C5H5)(
and Ni(CO)4 (2) is described. The structures of 3, 4, 6b, and 7 in the solid state are reported, intermolec-
ular interactions by -contacts are discussed. The behavior of 3, 4, 6a, 6b, and 7 towards the oligomer-
g g
5-C5H4)Fe, fc = ( 5-C5H4)2Fe) starting from FcPPh2 (1), fc(PR2)2 (R = Ph (5a); R = p-tolyl (5b)),
Available online 21 March 2010
p–p
ization of ethylene is reported. All compounds, except 4, were found to be inactive in homogeneous
ethylene oligomerization, while they exhibit moderate activities (up to 660 kg prod/mol Ni h) in hetero-
geneous ethylene oligomerization experiments.
Dedicated to Professor Hubert Schmidbaur
on the occasion of his 75th birthday
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Nickel carbonyls
Ferrocenyl phosphanes
Oligomerization of ethylene
Homogeneous catalysis
Heterogeneous catalysis
1. Introduction
Weng et al. have reported that nickel(0) compounds show high
catalytic activity and selectivity towards a-olefins in ethylene olig-
Nickel phosphanes have attracted considerable interest in re-
cent years because they can be applied successfully in homoge-
neous catalysis including the polymerization of formaldehyde
omerization, although they are more sensitive compared to nickel(II)
compounds [34,36,39,40].
This prompted us to prepare a series of different di- and trime-
tallic ferrocenyl phosphane-based nickel carbonyls and to screen
[1,2], dimerization of propene [3–11], synthesis of
a-olefines
[12–19], asymmetric hydrocyanation of styrene [20,21], hydrogen-
olysis of biphenylene [22,23], and the coupling of Grignard re-
agents with chloropyrimidines [24,25] and aryl chlorides [26,27].
Due to their diverse applications in the field of material sciences,
e.g. the synthesis of semi-conductive nickel phosphane coordina-
tion polymers [28] and the generation of nickel nanoparticles from
nickel carbonyls [29–33], nickel-containing compounds are of top-
ical interest.
their catalytic activities in a-olefin oligomerization reactions.
2. Results and discussion
Complexes (FcPPh2)Ni(CO)3 (3) (Fc = (
and fc(PR2Ni(CO)3)2 (fc = (
5-C5H4)2Fe; R = Ph (6a); R = p-tolyl
g g
5-C5H5)( 5-C5H4)Fe)
g
(6b)) are accessible by treatment of the phosphino ferrocenes
FcPPh2 (1) and fc(PR2)2 (R = Ph (5a); R = p-tolyl (5b)) with an
excess of Ni(CO)4 (2) in petroleum ether at ambient temperature
(Fig. 1). When the stoichiometry of 1 and 2 is changed to 2:1
(FcPPh2)2Ni(CO)2 (4) could be isolated. The introduction of a third
FcPPh2 group was not possible which is attributed to electronic
reasons as outlined elsewhere [41]. The more phosphane ligands
are present, the stronger the Ni–CCO bonds are. Organometallics 3
and 4 are orange solid materials which are stable under inert gas
atmosphere. Under aerobic conditions they slowly decompose to
give elemental nickel and the respective ferrocenyl phosphanes.
In contrast, compounds 6a and 6b gradually decompose even
under inert gas atmosphere within days. Heating 6a in toluene
Focusing on one topic, the oligomerization of
possible by using catalytically active nickel systems, i.e. [((g5
C5H4C(H)@NPh)(
5-C5H4PtBu2)Fe)NiCl] [34], [(1,5-cod)2Ni] (cod =
cyclooctadiene) [35], and [((
5-C5H4C(H)@N(C6F5))( 5-C5H4PPh2)
Fe)2Ni(CO)2] [36]. In 1976, Yoo [37] described the heterogeneous
oligomerization of -olefins catalyzed by triphenylphosphane
a-olefins is
-
g
g
g
a
nickel carbonyls, while Wu [38] demonstrated the oligomerization
potential of the same complexes in homogeneous reactions. Lately,
* Corresponding author. Tel.: +49 371 531 21210; fax: +49 371 531 21219.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.03.012

1542
D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
PPh2
P
Ni(CO)3
P
Ni(CO)2
Ph2
Ph2
Ni(CO)4 (2)
- CO
FcPPh2 (1)
- CO
Fe
Fe
Fe
2
1
3
4
Ph2
P
PR2
PR2
P
Ni(CO)3
Ni(CO)3
R2
2 Ni(CO)4 (2)
- 2 CO
R = Ph (6a), ΔT
Fe
Ni(CO)2
Fe
Fe
- Ni(CO)4
P
P
R2
Ph2
6a, R = Ph
6b, R = Tol
7
5a, R = Ph
5b, R = Tol
Fig. 1. Synthesis of 3, 4, 6a, 6b, and 7 from 1, 5a, 5b, and 2.
gave (fc(PPh2)2)Ni(CO)2 (7) (Fig. 1), firstly synthesized by Vasapollo
et al. [42] and Hamann and Hartwig [43].
The 31P{1H} NMR spectra of 3, 4, 6, and 7 show the expected res-
onances at 23.0 (3), 28.7 (4), 22.6 (6a), 19.7 (6b) and 25.1 ppm (7)
owing to the coordination of the ferrocenyl phosphane moieties to
a Ni(CO)x (x = 2, 3) fragment. Compared to the starting materials
(ꢀ16.8 (1), ꢀ18.2 (5a), ꢀ20.1 (5b)) a shift to lower field is observed.
The largest down-field shifts are found for compounds L2Ni(CO)2
(4, 7), whereas 4 is less shielded.
Compounds 3, 4, 6, and 7 were characterized by NMR (1H and
31P{1H}) and IR spectroscopy proving the formation of ferrocenyl
phosphane nickel carbonyls. Additionally, the structures of 3, 4,
6b, and 7 in the solid state were determined by single crystal X-
ray diffraction analysis.
The 1H NMR spectral properties of 3, 4, 6, and 7 are in accor-
dance with their formulations as ferrocenyl phosphane-substituted
nickel carbonyls showing the respective resonance patterns for the
cyclopentadienyl and phenyl moieties. Most distinctive for 3 and 4
is the appearance of a broadened singlet for the C5H5 protons. All
compounds exhibit broad signals for the C5H4PR2 protons between
3.9 and 4.5 ppm, due to metallic nickel impurities on a sub-micro-
gram scale.
Representative IR absorptions for the Ni(CO)x building blocks in
3, 4, 6, and 7 are found between 1925 and 2070 cmꢀ1 (Table 1),
whereby the nickel carbonyl units display the characteristic CO
absorption patterns according to their C2 or C3 symmetry [43–
v
v
46]. The symmetric CO stretching frequency A1 depends both on
the nature and the number of the coordinated phosphane ligands
[47,48]. From Table 1 it can be seen that the phosphanes exhibit al-
most identical donating properties (3, 6a and 6b), though signifi-
cant differences are found, when mono- and di-substituted
complexes are compared (3 and 6a vs. 4 and 7). Strongest Ni–C
bonds are observed for non-chelating donors as given in 4, which
is more likely attributed to steric than to eletronic reasons (vide
infra).
The structures of 3 (Fig. 2), 4 (Fig. 3), 6b (Fig. 4) and 7 (Fig. 5) in
the solid state were determined by single crystal X-ray diffraction
analysis. Single crystals could be obtained by cooling concentrated
dichloromethane–toluene (3, 6b, 7) or petroleum ether–toluene
mixtures (4) to ꢀ30 °C. Relevant crystallographic and structure
Table 1
IR mCO (KBr) and 31P{1H} NMR (CDCl3) data of 3, 4, 6a, 6b, and 7.
Compd
mCO (cmꢀ1
)
31P{1H} (ppm)
3
4
6a
6b
7
1984, 2066
1927, 1989
1985, 2067
1980, 2066
1943, 2000
23.0
28.7
22.6
19.7
25.1
Fig. 2. Left: ORTEP diagram (50% probability level) of 30 with the atom numbering scheme (hydrogen atoms are omitted for clarity). Right: Graphical representation of the
p–
p
-interactions (dotted lines) between centrosymmetric pairs of 30 (hydrogen atoms are omitted for clarity), where d refers to the center-to-center distance and ° refers to the
inter-planar angle of the cyclopentadienyl C6–C10 and the phenyl ring C17A–C22A. Label ‘A’ refers to atoms of a first symmetry generated molecule of 30. Found
interactions for related planes in 300: d = 5.016 Å, ° ¼ 79:3ꢁ.
p–p-

D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
1543
Fig. 3. Left: ORTEP diagram (50% probability level) of 4 with the atom numbering scheme (hydrogen atoms are omitted for clarity). Right: Graphical representation of the
-interactions (dotted lines) between centrosymmetric pairs of 4 (hydrogen atoms are omitted for clarity), where d refers to the center-to-center distance and ° refers to the
inter-planar angle of the cyclopentadienyl rings of the atoms C1–C5 and C23A–C27A. Label ‘A’ refers to atoms of a first symmetry generated molecule of 4.
p–
p
Organometallics 3, 4, 6b, and 7 show the expected tetrahedral
ligand coordination around the nickel atom (Figs. 2–5). The cyclo-
pentadienyl rings of all ferrocenes exhibit an almost coplanar con-
formation showing dihedral angles of their calculated mean planes
of 2.8(2) (30), 3.2(2) (300), 1.8(3) and 0.3(3) (4), 0.9(2) (6b0), 0.0 (6b00)
and 2.0(4)° (7) not influenced by mono-dentate (3, 4, 6b) or chelat-
ing (7) coordinations. The cyclopentadienyl rings are rotated by
12.3 (30), 12.1 (300), 17.5 (4 with Fe1), and 14.8° (6b0), while the
rotation angle of the second ferrocenyl unit in 4 (1.4° (with Fe2))
reveals an almost eclipsed conformation. Unlike, in 7 and 6b00 rota-
tion angles of 35° and 36° are found, illustrating a staggered con-
formation of the ferrocenes.
Compounds 3, 4, and 7 form centrosymmetric dimers of adja-
cent molecules in the solid state by
p–p-interactions between
one cyclopentadienyl and one phenyl (3), two cyclopentadienyl
(4), or two phenyl rings (7). Geometrical details given in Figs. 2,
3 and 5 are closely related to T-shaped benzene dimers (d = 4.96
Å) [49]. Probably these
p-contacts cause the different twisting of
the two ferrocenyl moieties in 4.
The observed Ni–C and Ni–P bond distances are in the range as
reported for similar phosphane–Ni(CO)x compounds (x = 2, 3), i.e.
[((
Ni–C, 1.747(6), 1.786(7) Å) [50], and [(2, 4, 6-C(CH3)3C6H2P-
2–Me3SiC@CSiMe3))Ni(CO)3] (Ni–P, 2.276(1); Ni–C, 1.783(3),
g g
6-C6H6)( 6-C6H5PMe2)Cr)2Ni(CO)2] (Ni–P, 2.207(2), 2.217(2);
(g
1.798(3), 1.794(3) Å) [51]. Compared with 4 the Ni–P and Ni–C
separations in 30 are slightly longer. This means that the more
phosphane substituents and hence, less CO donors are present
around the nickel atom, the shorter the Ni–C and Ni–P bonds. This
is in full agreement with IR spectroscopy (vide supra).
The steric demand of a phosphane ligand can be expressed with
the commonly used concept of the Tolman cone angle [47,52]. The
Tolman cone angle allows to evaluate the catalytic activity of orga-
nometallics, as described elsewhere [52–54]. The cone angles were
calculated to 167 (30), 169 (300), 180 (4 with P1), 162 (4 with P2),
166 (6b0 with P1), 170 (6b0 with P2), 166 (6b00), 163 (7 with P1),
and 153° (7 with P2) (Table 3) using the program STERIC [55,56]
implying larger cone angles than PPh3 (145°) [47]. Obviously ferr-
ocenyl moieties require more space than phenyl groups. Cone an-
gles of 3, 4 (with P2), and 6 agree well, while the cone angle of 4
Fig. 4. ORTEP diagram (50% probability level) of 6b0 with the atom numbering
scheme (hydrogen atoms are omitted for clarity).
refinement data are summarized in Table 5. Representative bond
distances (Å) and angles (°) are given in Table 2.
The asymmetric unit cell of 3 contains two (molecules 30 and 300)
and that of 6b one and a half crystallographic independent
molecules (molecules 6b0 and 6b00). Molecule 6b00 possesses a
crystallographic imposed inversion symmetry with the inversion
center on Fe2. Related bond distances of the two independent
molecules 30 and 300 as well as 6b0 and 6b00 are identical within their
mean deviations, while apparently differences for the related bond
angles up to 3.5% are found for the independent molecules of 3 and
6 (Tables 2 and S1 (Supplementary material)). Therefore, only the
bond lengths of molecules 30 and 6b0 are discussed, whereas
essential bond angles are disputed for each molecule.
(with P1) deviates more than 10°, which may be attributed to
p-
contacts (vide supra).

1544
D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
Fig. 5. Left: ORTEP diagram (50% probability level) of 7 with the atom numbering scheme (hydrogen atoms and the non-coordinating CH2Cl2 molecule are omitted for clarity).
Right: Graphical representation of the -interactions (dotted lines) between centrosymmetric pairs of 7 (hydrogen atoms are omitted for clarity), where d refers to the
p–p
center-to-center distance and ° refers to the inter-planar angle of the phenyl rings of the atoms C17–C22 and C29A–C34A. Label ‘A’ refers to atoms of a first symmetry
generated molecule of 7.
Table 2
Selected bond distances (Å) and angles (°) for 3, 4, 6b, and 7.a
30
300
4
6b0
6b00
7
Ni–P bond distances
Ni1–P1
2.2260(6)
Ni2–P2
2.2263(6)
Ni1–P1
Ni1–P2
2.2161(12)
2.2204(12)
Ni1–P1
Ni2–P2
2.2234(12)
2.2280(11)
Ni3–P3
2.2266(11)
Ni1–P1
Ni1–P2
2.206(2)
2.211(2)
Ni–C bond distances
Ni1–C23
Ni1–C24
Ni1–C25
1.792(3)
1.802(3)
1.793(3)
Ni2–C48
Ni2–C49
Ni2–C50
1.785(3)
1.796(3)
1.797(3)
Ni1–C45
Ni1–C46
1.780(5)
1.773(5)
Ni1–C25
Ni1–C26
Ni1–C27
Ni1–C42
Ni1–C43
Ni1–C44
1.779(6)
1.773(6)
1.764(6)
1.792(6)
1.755(6)
1.792(5)
Ni3–C64
Ni3–C65
Ni3–C66
1.776(6)
1.765(5)
1.778(6)
Ni1–C35
Ni1–C36
1.756(7)
1.771(7)
Bond angles
P1–Ni1–P2
110.98(4)
P1–Ni1–P2
108.19(8)
a
Standard uncertainties are given in the last significant figure(s) in parenthesis.
Considering the relatively large cone angles of the phosphanes
1, 5a, and 5b as well as the P–Ni–P bite angles of 4 and 7 near to
ideal tetrahedral geometry it is obvious that the nickel carbonyls
form catalysts rather for ethylene oligomerization than for poly-
merization [59].
Table 3
Summary of Tolman cone angles of 3, 4, 6b, and 7.
Compound
Tolman cone angle H
(°)a
3
4
6b
7
167 (30), 169 (300)
180 (with P1), 162 (with P2)
161 (6b0 with P1), 170 (6b0 with P2), 166 (6b00)
163 (with P1), 153 (with P2)
Comparing the Tolman cone angles of 1 and 5a with the P–Ni–P
bite angles of 4 and 7—the bite angle in 4 and 7 (Table 2) is almost
identical whereas FcPPh2 (1) seems to have a distinctively larger
Tolman cone angle than fc(PPh2)2 (5a) (Table 3)—reveals that these
two methods may give different results concerning steric parame-
ters. The question arising from this observation is whether the Tol-
man model or the bite angle concept allows a more serious
prediction of catalytic activity in ethylene oligomerization.
Compounds 3, 4, 6a, and 7 were applied for both, homogeneous
and heterogeneous ethylene oligo-/polymerization experiments.
For blank tests, samples of the appropriate compounds were dis-
solved in a small amount of toluene (5 mL) and n-pentane
(250 mL) and subjected to an ethylene pressure of 10 bar in a 1 L
a
Tolman cone angles have been determined using STERIC.
For chelating ligands P–M–P bite angles are commonly used to
discuss their steric characteristics [57]. There is some evidence that
these angles affect the activity in catalytic reactions [58] including
aminations [43], hydrocyanations [51], and ethylene oligo-/poly-
merizations [59]. For 7, the P1–Ni1–P2 angle is 108.19(8)° (Table
2) which is similar to values observed for related molecules
[60,61] and even non-chelating systems such as 4 (110.98(4)°).

D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
1545
Büchi steel reactor without the addition of a cocatalyst. The reac-
tion temperature was set to 60 °C. As expected, no oligomerization
products were obtained (entries 1–4, Table 4). Due to the excess of
ethylene, the CO ligands at the nickel center may have been re-
placed by ethylene, however, there is no accessible metal–carbon
bond into which the ethylene molecules can be inserted.
aluminoxane (MAO) at a rate of Ni:Al = 1:2500. In contrast to the
activation of metallocenes or other metal halide complexes, it is as-
sumed that MAO attacks one of the CO ligands forming a carbene
type complex [62,63]. A proof for this intermediate carbene com-
plex would be the formation of polyacetylenes after adding acety-
lene. However, an oxidation step is required, since a carbocationic
nickel center is usually proposed as the active species. Another
possible pathway may be the release of both CO ligands followed
For the ethylene oligomerization experiments in homogeneous
reactions the appropriate complexes were activated with methyl-
Table 4
Ethylene oligomerization results for the dinuclear and trinuclear complexes 3, 4, 6a, and 7 (solvent: 250 mL n-pentane, activator: MAO, 10 bar ethylene, 60 °C, 1 h; for
heterogeneous reactions, 2.0 g of silica was applied as support material). The contents of butenes (C4), hexenes (C6) and higher hydrocarbons were calculated from the GC
integrals.
P
P
P
Entry
Complex
Al:Ni
Reaction Type
Activity (kg prod/mol Ni h)
C4 (%)
C6 (%)
P C8 (%)
1
2
3
4
3
4
6a
7
–
–
–
–
blank test
blank test
blank test
blank test
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
5
6
7
8
9
10
3
4
4
4
6a
7
2500
2500
250
homogeneous
homogeneous
homogeneous
homogeneous
homogeneous
homogeneous
–
–
–
–
4
6
7
–
–
290
81
52
–
28
31
45
–
68
63
48
–
250a
2500
2500
–
–
–
11
12
13
14
15
16
17
3
4
4
4
4
6a
7
250
400
250
230
50
heterogeneous
heterogeneous
heterogeneous
heterogeneous
heterogeneous
heterogeneous
heterogeneous
131
206
355
225
129
181
660
67
47
89
69
59
62
54
25
40
10
22
27
24
33
8
13
traces
9
14
250
250
14
12
a
Reaction conducted at 20 °C.
Table 5
Crystal and structure refinement data for complexes 3, 4, 6a, and 7.
3
4
6b
7 ꢂ CH2Cl2
Formula weight
Chemical formula
Crystal system
Space group
a (Å)
512.93
855.11
895.94
C44H36FeNi2O6P2
754.01
C
25H19FeNiO3P
C46H38Fe2NiO2P2
triclinic
C37H30Cl2FeNiO2P2
monoclinic
P21/c
9.1954(10)
18.495(3)
19.327(3)
90
91.900(4)
90
3285.0(7)
1.525
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
9.8541(4)
13.6595(5)
18.2094(7)
95.8440(10)
96.7360(10)
110.4530(10)
2253.64(15)
1.512
10.4428(6)
12.2856(6)
16.8503(9)
70.2800(10)
73.3520(10)
73.4920(10)
1907.15(18)
1.489
13.1526(13)
13.5622(13)
20.297(2)
80.153(2)
85.661(2)
81.632(2)
3524.5(6)
1.266
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
qcalc (g cmꢀ3
F(0 0 0)
)
1048
880
1380
1544
Crystal size dimensions
(mm)
Z
0.3 ꢃ 0.2 ꢃ 0.2
0.2 ꢃ 0.1 ꢃ 0.01
0.3 ꢃ 0.2 ꢃ 0.2
0.4 ꢃ 0.2 ꢃ 0.2
4
2
3
4
Index ranges
ꢀ13 6 h 6 12, ꢀ18 6 k 6 18,
ꢀ12 6 h 6 13, ꢀ14 6 k 6 15,
ꢀ16 6 h 6 16, ꢀ16 6 k 6 16,
ꢀ11 6 h 6 11, 0 6 k 6 23,
0 6 l 6 24
1.574
0 6 l 6 21
1.362
0 6 l 6 25
1.206
0 6 l 6 24
1.308
l
(mmꢀ1
)
T (K)
203
203
293
188
h (°)
1.14–28.30
59483
11138
1.80–26.37
24813
7778
1.54–26.52
41145
14419
1.52–26.44
11733
5951
Total reflections
Unique reflections
Rint (%)
3.90
8.10
4.58
10.30
Data/restraints/
parameters
11138/0/559
7778/0/478
14419/0/751
5951/0/406
R1, wR2 [I P
r
(I)]a
0.0363, 0.0785
0.0573, 0.0864
1.018
0.428, ꢀ0.269
0.0532, 0.1025
0.1038, 0.1181
1.005
0.388, ꢀ0.374
0.0567, 0.1627
0.0986, 0.1875
1.019
1.158, ꢀ0.371
0.0735, 0.1373
0.1561, 0.1647
1.016
0.893, ꢀ0.651
R1, wR2 (all data)a
Godness-of-fit on F2b
D
q
(e Åꢀ3
)
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
P
2
wðF2o ꢀF2c
Þ
maxð0;F2o Þþ2ꢂF2c
hkl jjFojꢀjFc
R1
¼
jj ; wR2
¼
; w ¼
þbꢂP ; P ¼
.
a
1
hkl
P
P
2
2
wðF2o
Þ
r2 ðF2o ÞþðaꢂPÞ
3
hkl jFo
j
hkl
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
2
wðF2o ꢀF2c
Þ
b
hkl mꢀn
GOF ¼
; m ¼ number of reflections;n ¼ parameters used.

1546
D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
by an oxidative addition as described for a series of
a
-nitroketone
Most likely nickel complexes bearing sterically demanding
phosphane ligands may react via tricoordinated species. This
hypothesis would either explain the higher catalytic activity—just
for steric reasons monophosphane nickel complexes favor the
coordination of monomer molecules, the activation barrier for
the insertion of ethylene monomers into the nickel–alkyl bond
should be lower—or the decreasing selectivity towards 1-bu-
tene—a decrease in steric bulk by dissociation of one phosphane
would allow further isomerization steps. Such monophosphane
pathways are well established in homogeneous catalysis, e.g. the
Suzuki coupling [69–75].
At a lower Al:Ni ratio, the activity dropped, while the selectivity
to C4 hydrocarbons remained nearly constant (entries 6–8, Table 4)
and mainly (>60%) hexenes were formed. When the experiment
was performed at room temperature with a low aluminum:nickel
ratio an increase in the formation of butenes was observed.
The inactivity of 3 and 6a is in accordance with the observation
that [Ni(PBu3)(CO)3] does not catalyze either the isomerization nor
the oligomerization of ethylenes in presence of alkylaluminum
reagents [76].
[64] or salicylaldimine nickel catalysts [65] which is formulated to
be the initial reaction sequence in nickel mediated polymerization
of acetylenes [66].
Yellow solutions of 3, 4, 6a, and 7 turn dark red after addition of
MAO (Fig. 6a and b). Homogeneous ethylene oligomerization runs
were performed for one hour under an ethylene pressure of 10 bar
at 60 °C unless otherwise indicated (Table 4).
Complex 4 was the only candidate that showed oligomerization
activity under homogeneous reaction conditions. Its activity was
calculated to 290 kg prod/mol Ni h. The product mixture mainly
consists of C6 isomers and lower amounts of C4 isomers. Higher
olefins were only detected in traces. According to the theoretical
discussion above, the Tolman cone angle seems to be a more reli-
able parameter to predict oligomerization activities than the P–Ni–
P bite angle, as 7 is totally inactive (vide supra).
Previously Kamer and coworkers showed a clear relationship
between the steric bulk of substituted pyridine–phosphane ligands
and their performance in nickel mediated ethylene oligomeriza-
tion—the turnover frequency increases with increasing steric bulk,
as long as the nickel complexes are not overcrowded. Furthermore,
the selectivity to 1-butene dropped significantly [67,68].
For heterogeneous ethylene oligomerization reactions, MAO
was added separately to a suspension of silica (GRACE, Davicat SI
1102, dried at 350 °C) and to a solution of the corresponding nickel
complex. After methane evolution ceased—which was observed,
when MAO was added to the silica suspension—the activated cat-
alyst solution was combined with the silica/MAO mixture. The
resulting heterogenous catalysts were washed and dried in vacuo
to free flowing brownish or reddish powders (Fig. 6c).
Surprisingly, all complexes are potentially suitable as heteroge-
neous ethylene oligomerization catalysts. The highest activity of
660 kg prod /mol Ni h was achieved with 7 (entry 17, Table 4),
while the residual complexes exhibited distinctively lower activi-
ties between 130 and 350 kg prod/mol Ni h, respectively. Interest-
ingly, the selectivities toward C4 or C6 hydrocarbons have changed
dramatically as determined by GC and GC/MS analyses. In all
experiments, the C4 fraction was dominant in the product mix-
tures, and less amounts of hexenes were obtained. The contents
of olefins PC8 in the product mixtures slightly increased in the
heterogeneous oligomerization reactions. At an aluminum:nickel
ratio of 250:1, the best selectivity (89%) toward butenes was real-
ized with complex 4 (entry 13, Table 4). At higher (400:1, entry 12)
or lower (50:1, entry 15, Table 4) Al:Ni ratios, both the activities
Fig. 6. (a) Catalyst solution in toluene. (b) Catalyst activated with MAO for
homogeneous oligomerizations. (c) Heterogenized catalyst on silica (the color of the
solution faded indicating the successful heterogenization). For a colored version of
Fig. 6 see Supplementary material.
Fig. 7. GC spectrum of the C4–C6 region from a product mixture obtained with catalyst 6a.

D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
1547
and selectivities of complex 4 decreased. The most active catalyst 7
showed only moderate selectivity to butenes.
external standard (d = 139.0) rel. to 85% H3PO4 (d = 0.00). Melting
points of analytical pure samples (sealed off in nitrogen purged
capillaries) were determined using a Gallenkamp MFB 595 010 M
melting point apparatus. Microanalyses were performed using a
Thermo FLASHEA 1112 Series instrument.
According to the ‘‘core-shell” model, aluminoxane cages can be
grown on the surfaces of appropriate support materials like silica.
The support acts as a template [77–79] and favors the formation of
MAO cages [80] leading to a distinctively higher number of cages
compared with homogeneous solutions. As result thereof, the re-
quired amount of trimethylaluminum or MAO can be reduced dra-
matically. This effect was also observed for heterogenized
complexes 3, 4, 6a, and 7. Coordination to the support surface
seems to be responsible for the catalytic activity of all nickel car-
bonyls, therefore it is obvious that the Tolman cone angle is not
suitable to predict activities of immobilized catalysts. It has been
found previously that the catalytic productivity can be expressed
by a complex function of e.g. the ligand structure, however those
relationships can be quite different for analogous supported and
unsupported species [81].
4.2. Synthesis of [(FcPPh2)Ni(CO)3] (3)
FcPPh2 (1) (200 mg, 0.540 mmol) was added in a single portion
to a petroleum ether solution (20 mL) containing Ni(CO)4 (2)
(111 mg, 0.650 mmol) at 25 °C. The resulting reaction solution
was stirred for 2.5 h at this temperature and was then filtered
through a pad of celite. Afterward, all volatiles were removed in
oil pump vacuum. Orange single crystals of 3 could be obtained
by cooling a petroleum ether–toluene mixture (ratio 20:1, v/v,
10 mL) containing 3 to ꢀ30 °C. Yield: 221 mg (0.431 mmol, 80%
based on 1).
Fig. 7 shows a GC spectrum (C4/C6 region) obtained from the
product mixture produced with complex 6a (entry 16, Table 4) in
which the peaks for the three butene isomers (1-butene, (Z)-2-bu-
tene, (E)-2-butene) are clearly separated. The ‘‘chain-running”
mechanism can be postulated for these catalysts, since all possible
isomers could be detected by GC or GC/MS (see especially the C6
fraction).
Mp. 103 °C. Anal. Calc. for C25H19FeNiO3P (512.93): C, 58.54; H,
3.73. Found: C, 58.54; H, 4.02%. IR (KBr): 2066 (s,
mCO), 1984 (vs,
m
CO) cmꢀ1 1H NMR (250 MHz; CDCl3; Me4Si): dH 3.98 (bs, 5H,
.
C5H5), 4.31 (bs, 2H, C5H4), 4.49 (bs, 2H, C5H4), 7.00–7.70 (m, 10H,
C6H5) ppm. 31P{1H} NMR (101 MHz; CDCl3; P(OMe)3): dP 23.0 ppm.
4.3. Synthesis of [(FcPPh2)2Ni(CO)2] (4)
3. Conclusions
[(FcPPh2)Ni(CO)3] (3) (50 mg, 0.097 mmol) and FcPPh2 (1)
(36 mg, 0.097 mmol) were dissolved in 10 mL of petroleum ether
and stirred for 2 h at 25 °C. During this time a yellow solid precip-
itated. Decanting the solvent and washing the solid with petro-
leum ether (2 ꢃ 4 mL) gave the title complex. Single crystals of 4
could be obtained by cooling a dichloromethane–toluene mixture
(ratio 20:1, v/v, 10 mL) containing 4 to ꢀ30 °C. Yield: 31 mg
(0.036 mmol, 37% based on 3).
A series of bi- and trimetallic nickel(0) carbonyl complexes of
type [(FcPPh2)xNi(CO)4ꢀx
[fc(PR2Ni(CO)3)2] (R = Ph, p-tolyl; Fc = (
fc = (
5-C5H4)2Fe) have been obtained by the reaction of FcPPh2 or
]
(x = 1, 2), [(fc(PPh2)2)Ni(CO)2], and
g
5-C5H5)( 5-C5H4)Fe;
g
g
fc(PR2)2 (R = Ph, p-tolyl) with Ni(CO)4. All compounds have been
structurally characterized. Significant differences in the structural
parameters of these compounds (e.g. the Tolman cone angles) have
been outlined and discussed with respect to each other. In homoge-
neous ethylene oligomerization reactions it was found that only
[(FcPPh2)2Ni(CO)2] (4) forms an active catalyst. Our investigations
show that the influence of steric characteristics on the activity in
ethylene oligo-/polymerization experiments can more seriously be
predicted by the Tolman model rather than the bite angle concept.
In heterogeneous experiments, chelate complex [(fc(PPh2)2)Ni
(CO)2] (7) revealed the highest oligomerization activity but its selec-
tivity toward C4 or C6 is only moderate. The selectivities to C4 and
C6 were found to be completely different in heterogeneous reac-
tions compared with the results of the homogeneous runs.
Mp: 137 °C. IR (KBr): 1989(s, m), 1927 (vs, m .
CO) cmꢀ1 1H NMR
(250 MHz; CDCl3; Me4Si): dH 4.07–4.47 (m, 18H, C5H5 and C5H4),
7.00–7.77 (m, 20H, C6H5) ppm. 31P{1H} NMR (101 MHz; CDCl3;
P(OMe)3): dP 28.7 ppm.
4.4. Synthesis of [fc(PPh2Ni(CO)3)2] (6a)
fc(PPh2)2 (5a) (100 mg, 0.180 mmol) was added in a single por-
tion to a petroleum ether–toluene solution (ratio 2:1, v/v, 30 mL)
containing 2 (74 mg, 0.433 mmol) at 25 °C. After 30 min of stirring
at this temperature, 10 mL of toluene was added. Stirring was con-
tinued for 18 h. After filtration through a pad of celite, all volatiles
were removed in oil pump vacuum. Orange single crystals of 6a
were obtained by cooling a petroleum ether–toluene mixture (ratio
20:1, v/v, 10 mL) containing 6a to ꢀ30 °C. Yield: 95 mg
(0.113 mmol, 63% based on 5a).
4. Experimental
4.1. General remarks
Mp: 152 °C. Anal. Calc. for C40H28FeNi2O6P2 (839.83): C, 57.21;
H, 3.36. Found: C, 56.84; H, 3.71%. IR (KBr): 2067 (s,
mCO), 1985
All reactions were carried out under an atmosphere of purified
nitrogen (4.6) using standard Schlenk technique. Toluene, n-pen-
tane and petroleum ether were purified by distillation from so-
dium; dichloromethane was purified by distillation from calcium
hydride. Celite (purified and annealed, Erg. B.6, Riedel de Haen)
was used for filtrations. Ni(CO)4 was purchased from Aldrich and
used as received. FcPPh2, [82] fc(PPh2)2, [83] and fc(P(p-tolyl)2)2
[83] were prepared according to published procedures. Infrared
spectra were recorded with a Perkin Elmer FT-IR spectrometer
Spectrum 1000. 1H NMR spectra were recorded with a Bruker
Avance 250 spectrometer operating at 250.130 MHz in the Fourier
transform mode at 298 K. Chemical shifts are reported in d units
(parts per million) down-field from tetramethylsilane with the sol-
vent as reference signal (CDCl3: 1H NMR d = 7.26). 31P{1H} NMR
spectra were recorded at 101.249 MHz in CDCl3 with P(OMe)3 as
(vs,
m
CO) cmꢀ1 1H NMR (250 MHz; CDCl3; Me4Si): dH 3.98 (bs,
.
4H, C5H4), 4.27 (bs, 4H, C5H4), 7.00–7.70 (m, 20H, C6H5) ppm.
31P{1H} NMR (101 MHz; CDCl3; P(OMe)3): dP 22.6 ppm.
4.5. Synthesis of [fc(P(p-tolyl)2Ni(CO)3)2] (6b)
Fc(P(p-tolyl)2)2 (100 mg, 0.164 mmol) (5b) and 2 (67 mg,
0.394 mmol) were reacted under the same reaction conditions as
described for the synthesis of 6a (vide supra). After appropriate
work-up, compound 6b could be isolated as a yellow solid. Yield:
113 mg (0.126 mmol, 77% based on 5b).
Mp: 161 °C. Anal. Calc. for C44H36FeNi2O6P2 (895.93): C, 58.99;
H, 4.05%. Found: C, 58.93; H, 3.91%. IR (KBr): 2066 (s,
mCO), 1980
(vs,
m
CO) cmꢀ1 1H NMR (250 MHz; CDCl3; Me4Si): dH 2.28 (s, 6H,
.

1548
D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
CH3), 3.91–4.50 (m, 8H, C5H4), 6.59–7.66 (m, 16H, C6H5) ppm.
over sodium sulfate. n-Pentane was distilled off using a Vigreux
column. The resulting oligomer mixtures were characterized using
gas chromatography and GC/MS analyses.
31P{1H} NMR (101 MHz; CDCl3; P(OMe)3): dP 19.7 ppm.
4.6. Synthesis of [(fc(PPh2)2)Ni(CO)2] (7)
4.10. Gas chromatography
A new method for the preparation of 7 was developed: complex
[fc(PPh2Ni(CO)3)2] (30 mg, 0.036 mmol) (6a) was dissolved in
10 mL of toluene and heated for 6 h to 40 °C. Afterward, the reac-
tion mixture was filtered through a pad of celite and all volatiles
were removed in oil pump vacuum. Molecule 7 could be obtained
as a yellow solid after crystallization from a dichloromethane tol-
uene mixture (ratio 20:1, v/v, 4 mL) at ꢀ30 °C. Yield: 10 mg
(0.015 mmol, 42% based on 6a).
GC/MS spectra were recorded with
gaschromatograph in combination with a Thermo DSQ mass detec-
tor containing TR-5MS column (5% phenyl(equiv)-poly-
silphenylenesiloxane; length: 30 m; film: 0.25
m; flow: 200 mL/
a
Thermo Focus
a
l
min, split: 200:1). Helium (4.6) was applied as carrier gas. The rou-
tinely used temperature program includes a starting phase (2 min
at 50 °C), a heating phase (24 min; heating rate: 10 K/min; final
temperature: 290 °C) and a plateau phase (15 min at 290 °C).
GC spectra were recorded on a gaschromatograph HP 6890N
(Agilent) equipped with a HP-5 (5% phenyl–methyl–siloxane) col-
IR (KBr): 2000 (s, mCO), 1943 (vs, m .
CO) cmꢀ1 1H NMR (250 MHz;
CDCl3; Me4Si): dH 4.08 (bs, 4H, C5H4), 4.22 (bs, 4H, C5H4), 7.26–7.70
(m, 20H, C6H5) ppm. 31P{1H} NMR (101 MHz; CDCl3; P(OMe)3): dP
25.1 ppm.
umn (length: 30 m; film: 1.5 lm; diameter: 0.53 mm). Using argon
as the carrier gas, the flow was adjusted to 150 mL/min (split 50:1).
The temperature program contains a starting phase (6 min at
35 °C), a heating phase (1 K/min for 10 min, then 20 K/min for
10 min) and the final plateau phase (20 min at 250 °C).
4.7. Single crystal X-ray diffraction analysis
Crystal data for 3, 4, 6a, and 7 are summarized in Table 5. All
data were collected on a Bruker Smart CCD diffractometer at 203
(3, 4), 293 (6b) or 188 K (7) using Mo
Ka radiation
Acknowledgement
(k = 0.71073 Å). The structures were solved by direct methods
using SHEXLS-97 [84] and refined by full-matrix least-square proce-
dures on F2 using SHELXL-97 [85]. All non-hydrogen atoms were re-
fined anisotropically and a riding model was employed in the
refinement of the hydrogen atom positions.
We are grateful to the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie for generous financial support.
Appendix A. Supplementary material
4.8. Homogeneous polymerization of ethylene in a 1 L Büchi autoclave
CCDC 756889, 756890, 756891, and 756892 contain the supple-
mentary crystallographic data for 3, 4, 6a, and 7. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2010.03.012.
An amount of 5–25 mg of the respective complex was dissolved
in 5 mL of toluene. Methylalumoxane (MAO) (10% in toluene) was
added according to the desired Ni:Al ratio resulting in an immedi-
ate color change. The mixture was added to a 1 L Schlenk flask
filled with 250 mL of n-pentane. This mixture was transferred to
a 1 L Büchi laboratory autoclave under inert atmosphere and
thermostated at 60 °C. An ethylene pressure of 10 bar was applied
for 1 h. The reactor was cooled to ambient temperature and the
pressure was released. To the oligomer solutions, diluted hydro-
chloric acid was added. The organic phase was separated and dried
over sodium sulfate. n-Pentane was distilled off using a Vigreux
column. The resulting oligomer mixtures were characterized using
gas chromatography and GC/MS analyses.
References
[1] W. Hodes, L. Meriwether, Patent US 3054775, 1962.
[2] J. Floss, N.v. Kutepow, Patent DE 1153904, 1963.
[3] C. Carlini, M. Marchionna, A. Galletti, G. Sbrana, J. Mol. Catal. A: Chem. 169
(2001) 19.
[4] F. Benvenuti, C. Carlini, M. Marchionna, R. Patrini, A. Galletti, G. Sbrana, Appl.
Catal. A 199 (2000) 123.
[5] F. Benvenuti, C. Carlini, M. Marchionna, R. Patrini, A. Galletti, G. Sbrana, Appl.
Catal. A 204 (2000) 7.
Please, notice that for blank tests, the toluene solutions of the
corresponding complexes were applied without addition of MAO.
[6] S. Wu, S. Lu, Chin. Chem. Lett. 14 (2003) 958.
[7] S. Wu, S. Lu, Appl. Catal. A 246 (2003) 295.
[8] S. Wu, S. Lu, J. Mol. Catal. A: Chem. 198 (2003) 29.
[9] S. Wu, S. Lu, J. Mol. Catal. A: Chem. 197 (2003) 51.
[10] F. Benvenuti, C. Carlini, M. Marchionna, A. Galletti, G. Sbrana, J. Mol. Catal. A:
Chem. 178 (2002) 9.
4.9. Heterogeneous polymerization of ethylene in a 1 L Büchi autoclave
Silica (2.0 g, Davison, GRACE, SI 1102, dried at 350 °C) was sus-
pended in 30 mL toluene. Half of the calculated amount of MAO
was added to the silica suspension resulting in an immediate evo-
lution of methane. An amount of 5–25 mg of the desired complex
was dissolved in 5 mL of toluene and the residual amount of
MAO was added by syringe resulting in a color change from yellow
to dark red. The catalyst solution was combined with the silica/
MAO suspension after methane evolution had ceased. After stirring
for 2 h, the heterogeneous catalyst was filtered over a glass frit,
washed twice with 10 mL portions of toluene and 10 mL of n-pen-
tane and dried in vacuo to give a free flowing powder. Subse-
quently, the polymerization reactor was charged with 250 mL of
n-pentane and the powdered catalyst under inert atmosphere
and thermostated at 60 °C. An ethylene pressure of 10 bar was ap-
plied for 1 h. The reactor was cooled to room temperature and the
pressure was released. To the oligomer solutions, diluted hydro-
chloric acid was added. The organic phase was separated and dried
[11] M. Bluhm, C. Folli, D. Pufky, M. Kröger, O. Walter, M. Döring, Organometallics
24 (2005) 4139.
[12] P. Kuhn, D. Sémeril, D. Matt, M. Chetcuti, P. Lutz, Dalton Trans. 5 (2007) 515.
[13] J. Heinicke, M. Köhler, N. Peulecke, W. Keim, J. Catal. 225 (2004) 16.
[14] F. Speiser, P. Braunstein, L. Saussine, Organometallics 23 (2004) 2625.
[15] C. Carlini, M. Marchionna, R. Patrini, A. Galletti, G. Sbrana, Appl. Catal. A 216
(2001) 1.
[16] J. Pietsch, P. Braunstein, Y. Chauvin, New. J. Chem. 22 (1998) 467.
[17] F. Speiser, P. Braunstein, L. Saussine, Acc. Chem. Res. 38 (2005) 784.
[18] P. Wasserscheid, Synthetic Methods of Organometallic and Inorganic
Chemistry, Thieme, Stuttgart, 2002.
[19] W. Keim, Angew. Chem., Int. Ed. Engl. 29 (1990) 235.
[20] M. Kranenburg, P. Kamer, P. van Leeuwen, D. Vogt, W. Keim, J. Chem. Soc.,
Chem. Commun. (1995) 2177.
[21] W. Goertz, W. Keim, D. Vogt, U. Englert, M. Boele, L. van der Veen, P. Kamer, P.
van Leeuwen, J. Chem. Soc., Dalton Trans. (1998) 2981.
[22] B. Edelbach, D. Vicic, R. Lachicotte, W. Jones, Organometallics 17 (1998) 4784.
[23] C. Perthuisot, B. Edelbach, D. Zubris, N. Simhai, C. Iverson, C. Müller, T. Satoh,
W. Jones, J. Mol. Catal. A: Chem. 189 (2002) 157.
[24] H. Yamanaka, K. Edo, F. Shoji, S. Konno, T. Sakamoto, M. Mizugaki, Chem.
Pharm. Bull. 26 (1978) 2160.
[25] M. Elmoghayar, K. Undheim, Acta Chem. Scand. B37 (1983) 160.

D. Schaarschmidt et al. / Journal of Organometallic Chemistry 695 (2010) 1541–1549
1549
[26] K. Tamao, J. Organomet. Chem. 653 (2002) 23.
[58] P.W.N.M. van Leeuwen, P.C.J. Kamer, J.N.H. Reek, P. Dierkes, Chem. Rev. 100
(2000) 2741.
[59] I. Albers, E. Álvarez, J. Cámpora, C.M. Maya, P. Palma, L.J. Sánchez, E. Passaglia, J.
Organomet. Chem. 689 (2004) 833.
[27] M. Uemura, H. Yorimitsu, K. Oshima, Chem. Commun. (2006) 4726.
[28] M. Fox, D. Chandler, Adv. Mater. 3 (1991) 381.
[29] R. Mercury, Patent WO 2007142662, 2007.
[30] L. Zhou, A. Rai, N. Piekiel, X. Ma, M. Zachariah, Chem. Phys. Process. Combust.
(2007) C14.
[60] I.R. Butler, W.R. Cullen, T.-J. Kim, S.J. Rettig, J. Trotter, Organometallics 4 (1985)
972.
[31] R. Mercury, Patent US 2007034050, 2007.
[61] W.H. Watson, A. Nagl, M.-J. Don, M.G. Richmond, J. Chem. Cryst. 29 (1999) 871.
[62] P.C. Casey, C.R. Cyr, R.A. Boggs, Synth. Inorg. Metal–Org. Chem. 3 (1973) 249.
[63] C.T. Lam, C.D. Malkiewich, C.V. Senoff, Inorg. Synth. (1977) 95.
[64] C. Carlini, M. Marchionna, A.M.R. Galletti, G. Sbrana, Appl. Catal. A 210 (2001)
173.
[65] C. Carlini, A.M.R. Galletti, G. Sbrana, Polymer 44 (2003) 1995.
[66] L.S. Meriwether, M.F. Leto, E.C. Colthup, G.W. Kennerly, J. Org. Chem. 27 (1962)
3930.
[67] J. Flapper, P.W.N.M. van Leeuwen, C.J. Elsevier, P.C.J. Kamer, Organometallics
28 (2009) 3264.
[68] J. Flapper, H. Kooijman, M. Lutz, A.L. Spek, P.W.N.M. van Leeuwen, C.J. Elsevier,
P.C.J. Kamer, Organometallics 28 (2009) 3272.
[69] Z. Li, Y. Fu, Q.-X. Guo, L. Liu, Organometallics 27 (2008) 4043.
[70] E. Galardon, S. Ramdeehul, J.M. Brown, A. Cowley, K.K.M. Hii, A. Jutand, Angew.
Chem., Int. Ed. 41 (2002) 1760.
[71] F. Barrios-Landeros, J.F. Hartwig, J. Am. Chem. Soc. 127 (2005) 6944.
[72] J.P. Stambuli, M. Bühl, J.F. Hartwig, J. Am. Chem. Soc. 124 (2002) 9346.
[73] J.P. Stambuli, C.D. Incarvito, M. Bühl, J.F. Hartwig, J. Am. Chem. Soc. 126 (2004)
1184.
[32] E. Kauffeldt, T. Kauffeldt, J. Nanopart. Res. 8 (2006) 477.
[33] Y. He, X. Li, M. Swihart, Chem. Mater. 17 (2005) 1017.
[34] Z. Weng, S. Teo, L. Koh, T. Hor, Angew. Chem., Int. Ed. 44 (2005) 7560.
[35] K. Barnett, Patent US 4628139 A 19861209, 1986.
[36] Z. Weng, S. Teo, T. Hor, Organometallics 25 (2006) 4878.
[37] J. Yoo, Patent US 3992470 19761116, 1976.
[38] A.-H. Wu, Patent US 5237118 A 19930817, 1993.
[39] Z. Weng, S. Teo, Z.-P. Liu, T. Hor, Organometallics 26 (2007) 2950.
[40] S. Shimizu, A. Osuka, Chem. Commun. (2006) 1319.
[41] C. Tolman, J. Am. Chem. Soc. 92 (1970) 2956.
[42] G. Vasapollo, L. Toniolo, G. Cavinato, F. Bigoli, M. Lanfranchi, M. Pellinghelli, J.
Organomet. Chem. 481 (1994) 173.
[43] B. Hamann, J. Hartwig, J. Am. Chem. Soc. 120 (1998) 3694.
[44] C. Elschenbroich, A. Salzer, Organometallchemie, Teubner, Studienbücher,
Stuttgart, 1993.
[45] C. Tolman, J. Am. Chem. Soc. 92 (1970) 2953.
[46] H. Lang, B. Lühmann, R. Buschbeck, J. Organomet. Chem. 689 (2004) 3598.
[47] C. Tolman, Chem. Rev. 77 (1977) 313.
[48] H. Han, M. Elsmaili, S.A. Johnson, Inorg. Chem. 45 (2006) 7435.
[49] M.O. Sinnokrot, E.F. Valeev, C.D. Sherrill, J. Am. Chem. Soc. 124 (2002) 10887.
[50] C. Elschenbroich, M. Wünsch, A. Behrend, B. Metz, B. Neumüller, K. Harms,
Organometallics 24 (2005) 5509.
[51] T. Baumgartner, P. Moors, M. Nieger, H. Hupfer, E. Niecke, Organometallics 21
(2002) 4919.
[52] A. Jakob, B. Milde, P. Ecorchard, C. Schreiner, H. Lang, J. Organomet. Chem. 693
(2008) 3821.
[53] R.B. DeVasher, J.M. Spruell, D.A. Dixon, G.A. Broker, S.T. Griffin, R.D. Rogers,
K.H. Shaughnessy, Organometallics 24 (2005) 962.
[54] J.W. Gosselink, H. Bulthuis, G. van Koten, J. Chem. Soc., Dalton Trans. 6 (1981)
1342.
[55] B.C. Taverner, J. Comput. Chem. 17 (1996) 1612.
[56] B.C. Taverner, Steric, 1.11, 1995 <http://www.ccl.net/cca/software/SOURCES/
C/steric/index.shtml>.
[74] T.E. Barder, S.D. Walker, J.R. Martinelli, S.L. Buchwald, J. Am. Chem. Soc. 127
(2005) 4685.
[75] T.E. Barder, M.R. Biscoe, S.L. Buchwald, Organometallics 26 (2007) 2183.
[76] L.M. Clutterbuck, L.D. Field, G.B. Humphries, A.F. Masters, M.A. Williams, Appl.
Organomet. Chem. 4 (1990) 507.
[77] M. Helldörfer, H.G. Alt, J. Ebenhoch, J. Appl. Polym. Sci. 86 (2002) 3021.
[78] W.-R. Schmeal, J.-R. Street, AlChE J. 17 (1971) 1188.
[79] E.J. Nagel, V.A. Kirillov, W.H. Ray, Ind. Eng. Chem. Prod. Res. Dev. 19 (1980)
372.
[80] E. Zurek, T.K. Woo, T.K. Firman, T. Ziegler, Inorg. Chem. 40 (2001) 3619.
[81] S.D. Ittel, L.K. Johnson, Chem. Rev. 100 (2000) 1169.
[82] G.P. Sollott, H.E. Mertwoy, S. Portnoy, J.L. Snead, J. Org. Chem. 28 (1963) 1090.
[83] J.J. Bishop, A. Davidson, M.L. Katcher, D.W. Lichtenberg, R.E. Merrill, J.C. Smart,
J. Organomet. Chem. 27 (1971) 241.
[84] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[85] G.M. Sheldrick, SHELXL-97 Program for Crystal Structure Refinement, Universität
Göttingen, 1997.
[57] G. Wilkinson, R.D. Gillard, J.A. McCleverty, Comprehensive Coordination
Chemistry, second ed., Pergamon Press, Oxford, 1987.