Cationic η3-allyl sulfide complexes of nickel(II) for the polymerization of butadiene in aqueous emulsion

Article abstract of DOI:10.1016/j.jorganchem.2009.11.041

Reaction of the dimeric allyl-nickel(II) chloro complex [Ni(η³-C₃H₅)(μ-Cl)]₂ (5) with sulfur donor ligands (L = L₁₀-L₁₃) in the presence of NaBAr₄^F (Ar₄

Full text of DOI:10.1016/j.jorganchem.2009.11.041

Journal of Organometallic Chemistry 695 (2010) 673–679
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Cationic
g
3-allyl sulfide complexes of nickel(II) for the polymerization of butadiene
in aqueous emulsion
c
d
Govindaswamy Padavattan a, Christoph Jäkel a,b, , Tobias Steinke , Valentine Reimer ,
*
M. Belén Díaz-Valenzuela a, Patrick Crewdson a, Frank Rominger e
a CaRLa – Catalysis Research Laboratory, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 584, 69120 Heidelberg, Germany
b BASF SE, GCB/C – M313, 67056 Ludwigshafen, Germany
c BASF SE, GKT/P – B008, 67056 Ludwigshafen, Germany
d BASF SE, KT/KE – E100, 67056 Ludwigshafen, Germany
e Organisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, 69120 Heidelberg, Germany
a r t i c l e i n f o
a b s t r a c t
Reaction of the dimeric allyl-nickel(II) chloro complex [Ni(g l-Cl)]2 (5) with sulfur donor ligands
3-C3H5)(
Article history:
Received 21 August 2009
Received in revised form 25 November 2009
Accepted 27 November 2009
Available online 21 December 2009
(L = L10–L13) in the presence of NaBArF (Ar4F = 3,5-(CF3)2C6H3) gives the corresponding cationic mononu-
4
clear complexes of the type [Ni(
g
3-C3H5)(L)2]+ (1–4) [L = L10 = diphenyl sulfide (1); L = L11 = 4,40-thiodi-
phenol (2); L = L12 = 4,40-thio-bis(6-tert-butyl-o-cresol) (3); L = L13 = 4,40-thio-bis (6-tert-butyl-m-cresol)
(4)]. All of these complexes were characterized by elemental analysis and NMR spectroscopy, as well
as the representative complex 3 additionally by single-crystal X-ray analysis. In comparison to the known
Keywords:
Nickel
Sulfur ligands
Butadiene
Emulsion polymerization
Catalytic polymerization
complex [Ni(g g
3-C3H5)( 6-BHT)][BArF4] (BHT = 3,5-di-tert-butyl-4-hydroxytoluene), the herein described
cationic complexes show an increased stability towards water. The activity of the complexes for butadi-
ene polymerization in aqueous emulsions was studied.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
growing polymer chain are the truly active catalysts for 1,4-cis-
polymerization of butadiene [7].
Over the past decades there has been considerable interest in
the development of nickel based polymerization catalysts [1],
and in particular in the ability of certain allyl-nickel(II) complexes
to act as efficient catalysts for the polymerization of dienes [2,3].
Aqueous emulsion polymerization is a widely used industrial
technology for the preparation of polybutadiene dispersions.
Water is a readily available, cheap, non-toxic and non-flammable
solvent with a high heat capacity. It is suitable for the preparation
of polymer latices and is therefore very attractive as a reaction
medium. In today0s industrial applications the emulsion polymeri-
zation is largely centered on radical-initiated reactions. Long cycle
times are a big drawback of this polymerization process. Further-
more, tuning of the polymer microstructure and thus the product
properties is very limited. On the other hand, highly stereoregular
polybutadiene is prepared industrially by catalytic polymerization
in organic solution [8]. Besides the ability to control the polymer
microstructure, short reaction times as well as an enhanced pro-
cess control could be significant advantages of generating the poly-
mers by an insertion-type approach.
Recently, Mecking reported about the aqueous emulsion
polymerization of butadiene in the presence of cationic allyl-nickel
triphenylstibine complexes. Due to the hydrolytic lability found
with these complexes, special precautions are necessary during
polymerization to prevent the pre-catalyst from decomposing pre-
maturely. Despite the potential of industrial application, this work
is to our knowledge the only published work so far on aqueous
Wilke et al. showed that the catalytic activity of
g
3-allyl-nickel
chlorides can be increased dramatically by adding aluminium ha-
lides or organoaluminium halides [4]. Generally, the addition of Le-
wis acids promotes the polymerization of 1,3-dienes such as
butadiene and isoprene [5] as a result of an increase in the cationic
character of the metal center due to halide abstraction. Cationic al-
lyl-nickel(II) complexes are capable of acting as catalysts for the
polymerization of dienes without the use of additional Lewis acids.
The use of cationic allyl-nickel complexes with labile ancillary li-
gands favors the formation of highly stereoregular 1,4-cis-polybu-
tadiene [6]. In fact, work of Taube and recently Brookhart showed
that ‘‘ligand-free” allyl complexes, being only coordinated by the
* Corresponding author. Address: CaRLa – Catalysis Research Laboratory, Rupr-
echt-Karls Universität Heidelberg, Im Neuenheimer Feld 584, 69120 Heidelberg,
Germany. Tel.: +49 06216056351; fax: +49 0621606656351.
E-mail address: christoph.jaekel@basf.com (C. Jäkel).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.11.041

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G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
emulsion polymerization of butadiene with cationic nickel com-
plexes [9].
+
+
H2O
R
hydrolyzed
Ni-compounds
Ni
LnNi
- Ln
Herein we report our independent studies [10] on the serendip-
itous finding, characterization and syntheses of novel, robust thio-
ether-based mononuclear Ni(II) cationic complexes of the type
- Ln
slow
fast
[Ni(g
3-C3H5)(L)2][BArF4] and their ability to catalyze the selective
Scheme 2. Ligand tasks for aqueous emulsion polymerization of butadiene.
1,4-polymerization of butadiene in aqueous emulsion.
the growing polymer chain wrapped around the nickel center
would protect the catalyst from decomposing via hydrolysis.
We studied the catalytic activity with in situ generated catalysts
as emulsions in the presence of water. Interestingly, good polymer-
ization activities were observed with sulfur-substituted arenes like
4,40-thiodiphenol (L11) or 4,40-thio-bis(6-tert-butyl-o-cresol) (L12),
respectively (Scheme 1). To clarify the true coordination mode of
these ligands, we decided to investigate these complexes more clo-
2. Results and discussion
2.1. Initial screening
The objective of our work was to identify a catalyst capable of
1,4-polymerization of butadiene in an aqueous environment,
which would yield a polymer suitable for impact modification of
thermoplastics. Guided by the findings of Taube and others, we fo-
cused on cationic allyl-nickel complexes with easily replaceable
ancillary ligands to favor 1,4-cis-polymerization of butadiene
[3b]. Thus, based on Campora0s report on the use of simple
arene-coordinated, cationic allyl-nickel complexes as precursors
of Taube0s ‘‘ligandless” nickel catalysts [6], we started an extensive
screening of potential arene-type ligands of the general formula
sely. Therefore, selected
g
3-allyl-nickel(II) catalysts have been syn-
thesized, isolated, characterized and subsequently tested for
catalytic activity in the mini-emulsion polymerization of 1,3-buta-
diene [10].
2.2. Synthesis and characterization
[Ni(
g
3-C3H5)(L)n]+ with L being such an arene (Scheme 1).
The
Cl)]2 5 reacts with four equivalents of sulfur donor ligands (L10–L13
in diethyl ether in the presence of NaBArF (ArF = 3,5-(CF3)2C6H3) at
g g l-
3-allyl-nickel(II) bridged-chloro complex [Ni( 3-C3H5)(
With this screening, we hoped to identify suitable ligands that
would merge two properties (Scheme 2). First, the ligand should
provide a sufficient stabilization of the complex against hydrolysis
until the anticipated ‘‘ligandless” nickel catalyst, coiled into the
growing polymer chain, would be formed. Second, the ligand
should be easily replaceable by the olefinic moieties of the growing
polymer chain to allow smooth polymerization, retaining as much
cis-selectivity as possible (Scheme 2).
)
4
4
ꢀ60 °C to give the mononuclear cationic complexes of the type
[Ni(
3-C3H5)(L)2][BArF4] (1–4) in satisfactory yields of 52–60%
(L = diphenyl sulfide (L10), 4,40-thiodiphenol (L11), 4,40-thio-bis (6-
tert-butyl-o-cresol) (L12), 4,40-thio-bis (6-tert-butyl-m-cresol) (L13
g
)
(Scheme 3). The cationic complexes 1–4 are orange-brown in color,
and are isolated as bench-stable crystalline solids, only slightly
sensitive against air and moisture. They are soluble in dichloro-
methane, acetone, chloroform, diethyl ether and insoluble in n-
hexane and n-pentane.
In this regard, our ideal ligand would not take part in catalysis,
but would stabilize the (pre-)catalyst until the catalytic reaction
commences. Once the polymerization proceeds, we speculated that
Scheme 1. Arene-type ligands used in the initial screening for aqueous emulsion polymerization of butadiene.

G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
675
Scheme 3. Synthesis of [Ni(g
3-C3H5)(L)2][BArF4] complexes (1–4).
All the compounds are diamagnetic, and display appropriate
signals in their proton NMR spectra. The 1H NMR spectra of com-
plexes 1–4 exhibit two doublets at around 2.8 and 3.4 ppm which
correspond to the allyl protons of Hsyn and Hanti and the typical
multiplet for the central CH proton appears in the range 5.77–
5.92 ppm. The hydroxyl (–OH) protons of complexes 2–4 appear
as singlets at 5.64, 5.16 and 5.22 ppm, respectively. The methyl
(–CH3) protons of complexes 3 and 4 appear as singlets at 2.12
and 2.05 ppm, respectively. The tert-butyl group (t-CMe3) protons
of complexes 3 and 4 appear as singlets at 1.38 and 1.34 ppm.
The aromatic protons of complexes 1–4 appear in the range of
6.49–7.50 ppm and the [BAr4F ]ꢀ protons appear in the range of
7.52–7.82 ppm.
The 13C{1H} NMR spectrum of complexes 1–4 contain reso-
nances for the allyl CH2 and CH group carbons at around 70 and
117 ppm, respectively. The resonances for the aromatic carbons
of complexes 1–4 appear in the range of 120–160 ppm. 1H NMR
studies in the presence of water were carried out in order to survey
the reactivity of the complexes relative to Campora’s catalyst
[Ni(g g
3-C3H5)( 6-BHT)][BArF4] (BHT = 3,5-Di-tert-butyl-4-hydroxy-
toluene) [6] towards water. Exposure of 1 to 5 equivalents of water
in CD2Cl2 solution at room temperature resulted in decomposition
of Campora’s complex within a few minutes, to form a black solid
and the free arene. During the decomposition, signals of a new
allylic system were observed, which might indicate the formation
of an intermediate aqua complex (Fig. 1) as has been reported also
(c)
(b)
(a)
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
Chemical Shift (ppm)
Fig. 1. 1H NMR spectra (200 MHz, CD2Cl2) of complex [Ni(
g
3-C3H5)( 6-BHT)]+ with (a) no water-d2, (b) water-d2 in 5 min and (c) water-d2 in 10 min.
g

676
G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
(c)
(b)
(a)
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
Chemical Shift (ppm)
Fig. 2. 1H NMR spectra (200 MHz, CD2Cl2) of complex 3 with (a) no water-d2, (b) water-d2 in 20 min and (c) water-d2 in 40 min.
by Mecking in related work [9] When complexes 1–4 were tested
under identical conditions with water they showed no immediate
sign of decomposition, indicating that these complexes are much
more resistant to water hydrolysis (representative spectra of com-
plex 3 shown in Fig. 2).
pseudo square-planar coordination geometry with the terminal
carbons of the allyl group in a cis relationship [C(45)–Ni(1)–
C(47) = 71.5(2)°, C(45)–Ni(1)–S(1) = 97.27(16)°, C(45)–Ni(1)–S(2)
= 161.20(17)°, S(1)–Ni(1)–S(2) = 100.50(4)°]. The allyl group is
almost evenly coordinated as would be expected since both sulfur
ligands are identical [Ni(1)–C(45) = 2.008(5) Å, Ni(1)–C(46) =
2.006(5) Å, Ni(1)–C(47) = 2.049(5) Å, C(45)–C(46) = 1.374(7) Å,
C(46)–C(47) = 1.392(7) Å]. The Ni–S bond distances are compara-
ble to other allyl Ni(II) complexes with sulfur based ligands
[Ni(1)–S(1) = 2.195(1) Å and Ni(1)–S(2) = 2.214(1) Å] [11]. There
2.3. Molecular structure of [Ni(g3-C3H5)(4,40-thio-bis(6-tert-butyl-o-
cresol)2]+
The molecular structure of the mononuclear allyl-nickel-sulfide
complex 3 has been established by single-crystal X-ray structure
analysis (Fig. 3). A summary of the single-crystal X-ray structure
analysis is shown in Table 1. The ORTEP drawing of compound 3
is shown in Fig. 3 with selected bond lengths and angles given in
the caption.
appears to be a p–p stacking interaction between two neighbour-
ing phenyl rings of the sulfur ligands which are in close proximity
to one another [C(1)–C(23) = 3.172(5) Å, C(2)–C(23) = 3.455(5) Å,
C(3)–C(25) = 3.522(5) Å, C(3)–C(26) = 3.700(5) Å]. The dihedral an-
gle formed by the plane containing the atoms S(1)–Ni(1)–S(2) and
that containing C(45)–C(46)–C(47) is 62°.
Compound 3 consists of a cationic Ni(II) allyl complex and an
associated non-coordinating [BArF4]ꢀ anion. The complex crystal-
(II)
ꢀ
lizes in the triclinic space group P1. The Ni center exists in a
Table 1
Crystal data and structure refinement for complex 3.
Empirical formula
Formula weight
T (K)
C79H77BF24NiO4S2
1680.05
200(2)
Wavelength (Å)
Crystal system
Space group
Crystal size (mm3)
a (Å)
0.7107
Triclinic
ꢀ
P1
0.39 ꢁ 0.32 ꢁ 0.09
13.1424(2)
b (Å)
18.1998(1)
c (Å)
19.3080(2)
a
(°)
116.371(1)
b (°)
94.478(1)
c
(°)
95.413(1)
4081.78(8)
2
1.367
1728
0.390
Semi-empirical from equivalents
0.9657 and 0.8627
1.57–24.71
ꢀ15 ꢂ h ꢂ 15, ꢀ21 ꢂ k ꢂ 21, ꢀ22 ꢂ l ꢂ 22
33 734/13 902 [Rint = 0.0759]
13 902/468/1192
1.007
V (Å3)
Z
Dc (g cmꢀ3
F(0 0 0)
)
Absorption coefficient (mmꢀ1
Absorption correction
)
Max. and min. transmission
h Range for data collection (°)
Limiting indices
Reflections collected/unique
Data/restraints/parameters
Goodness-of-fit (GOF)
Fig. 3. ORTEP diagram of cation 3 at 50% probability level. The anion and the
non-allyl H atoms are omitted for clarity. Selected bond lengths (Å) angles (°):
Ni1–C45 = 2.008(5), Ni1–C46 = 2.006(5), Ni1–C47 = 2.049(5), Ni1–S1 = 2.1951(11),
Ni1–S2 = 2.214(1),
S1–C1 = 1.782(4),
S1–C12 = 1.789(4),
S2–C34 = 1.787(4),
S2–C23 = 1.793(4), S1–Ni1–S2 = 100.50(4), C45–Ni1–C47 = 71.5(2), C45–Ni1–
S1 = 97.27(16), C45–Ni1–S2 = 161.84(17), C47–Ni1–S1 = 167.84(16), C47–Ni1–
S2 = 90.27(15).
Final R indices [I > 2
r
(I)]
R1 = 0.0596, wR2 = 0.1252
R1 = 0.1237, wR2 = 0.1530
0.534, ꢀ0.341
R indices (all data)
Max., min.
Dq
(e Å3)

G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
677
Table 2
Polymerization of 1,3-butadiene with Ni catalysts.
Entry
Catalyst
Ratio Bu/Ni-catalyst
Solids content (%)
Yield (%)
PSD (d50) (nm)
Vinyl/cis/trans (%)a
Mw
Mn
Mw/Mn
1
2
3
2
2000
2000
2000
2000
12 200
10.2
12.2
10.4
10.9
n.d.d
50.8
43.0
39.7
41.3
5
221
221
212
185
n.d.d
2/48/50
1/42/57
2/32/65
2/19/79
n.d.d
2.0 ꢁ 104
2.8 ꢁ 104
2.0 ꢁ 104
1.5 ꢁ 104
n.d.d
7.0 ꢁ 103
8.5 ꢁ 103
7.1 ꢁ 103
5.3 ꢁ 103
n.d.d
2.9
3.3
2.8
2.9
n.d.d
In situ 2
3
4
In situ 3
5b
Cat. Ref. [9]c
Polymerization conditions entries 1–4: 40 °C, 4 h, 0.37 mmol Ni complex. Polymerization conditions entry 5: 20 °C, 4 h, 20
l
mol complex, see Ref. [9].
a
Determined from IR spectra.
b
According to Ref. [9] only polymer from pre-polymerization obtained, no catalytic activity after mini-emulsification.
[(allyl)Ni(SbPh3)2]BArF4.
n.d. ‘‘not determined”.
c
d
2.4. Mini-emulsion polymerization of 1,3-butadiene with
[Ni(
3-C3H5)(L)2]+
latices with a high 1,4-trans content (65–79%) (Table 2). Interest-
ingly, when using the in situ generated catalyst an even higher
1,4-trans content is observed [15]. In contrast, polymerization with
the same catalysts in organic solution gives high cis-1,4-PBu selec-
tivity [10,16]. Radical polymerization of 1,3-butadiene via mini-
emulsion yields an almost unselective microstructure containing
14% cis-1,4-PBu, 69% trans-1,4-PBu and 17% 1,2-PBu units [17].
The difference in the microstructure between emulsion and solu-
tion polymerization results most likely from the presence of water,
acting as a trans-regulating ligand for the cationic nickel com-
plexes. The trans-regulating influence of coordinating ligands on
the cationic nickel complexes has been described by Taube in de-
tail [15]. In the report of Mecking et al. a similar polybutadiene
g
Initial experiments showed that pre-polymerization of butadi-
ene is helpful in protecting the active cationic Ni center against
hydrolysis during emulsion polymerization. Therefore, a solution
of complex 2 or 3 in toluene was treated with small amounts of
1,3-butadiene before emulsification with sodium dodecyl sulfate
(SDS), hexadecane and water. For comparison, a pre-polymerized
catalyst emulsion has been synthesized by in situ methods. Here,
[Ni(
g
3-C3H5)Cl]2 was combined with two equivalents of Na[BArF ]
4
and the appropriate aryl sulfide and stirred for 1 h at ꢀ60 °C in tol-
uene, followed by addition of 1,3-butadiene and finally emulsifica-
tion (vide supra).
The polymerization of 1,3-butadiene with 2 and 3 was per-
formed at 40 °C for 4 h. The results of the emulsion polymeriza-
tions are presented in Table 2. The polymer latices have been
studied with GPC, HDF and IR spectroscopy.
microstructure (70–80% of 1,4-trans content) by using [Ni(g3
-
C3H5)(SbPh3)2][BArF ] and [Ni(
g
3-C3H5)(SbPh3)2] [Al(OC(CF3)3)4] is
4
described [9]. The high 1,4-trans content in this work was ascribed
to the coordination of water as a ligand in the active species.
The catalysts show moderate activities with polymer yields
of 30–50% and solid contents of 8–12%. Interestingly, no
further polymerization after emulsification is observed, when
3. Conclusions
We have screened several ligands for the emulsion polymeriza-
[(allyl)Ni(SbPh3)2]BArF is used as a catalyst. Here, fine-tuning of
tion of 1,3-butadiene using [Ni(g
3-C3H5)Cl]2 as a precursor for the
4
the catalyst solubility is necessary to prevent premature decompo-
sition of the catalyst and only a partially insoluble catalyst survives
the vigorous mixing conditions of mini-emulsification [9].
in situ generation of the catalyst in the presence of a ligand and Na-
BArF4. Based on our ligand screening we have isolated a series of
new
g
3-allyl-nickel(II) complexes containing sulfur donor ligands.
No difference in activities was observed between the polymer-
ization of 1,3-butadiene with the isolated Ni(II) catalysts (2 and 3)
or the in situ prepared catalysts. The polymer particles have an
average size (d50) of 210–260 nm. In contrast, the conventional
radical-initiated polymerization yields particles with a d50 of
about 100 nm. The latices have a number average molecular
weight of ca. 7 ꢁ 103 g/mol. This value is lower by an order of mag-
nitude to catalytic polymerizations with Ni(II) systems in organic
solvent and still to low for applications [6,7]. It appears that chain
terminations can occur with our complexes in the aqueous emul-
sion more readily than in organic phase, which is also reflected
in the rather high polydispersity of the obtained polymers. In addi-
tion to catalyst decomposition in the presence of water, mass
transfer limitation may serve as an additional source for the rela-
tively low average molecular weight of the polymer formed in
aqueous emulsion. Once the butadiene of a certain droplet is con-
sumed, additional butadiene has to be transported to the catalyst
by diffusion through the aqueous phase. This would result in a re-
duced effective concentration of butadiene at the catalyst and with
this, the relative rate of insertion will be retarded relatively to
chain termination and chain transfer [12,13]. The general catalyst
efficiencies as measured in turn over numbers (ton) are in a satis-
fying range of 800–1000. The microstructure has been studied by
IR spectroscopy [14]. The emulsion polymers exhibit a relatively
high fraction of trans-1,4-polybutadiene; the cis:trans ratio varies
between 50:50 and 20:80. Particularly, 3 yields polybutadiene
Taking advantage of their good stability towards hydrolysis, these
complexes have been found suitable for the aqueous emulsion
polymerization of butadiene. The isolated complexes and in situ
generated catalysts show similar activities in the aqueous emul-
sion polymerizations. The cis/trans-selectivity of the polymeriza-
tion is affected by the reaction medium and results in aqueous
emulsion in a higher 1,4-trans-content of the polymer. But, in com-
parison to typical radical-initiated emulsion polymerizations of
butadiene, the here described catalysts give polymer particles with
low 1,2-polybutadiene content and, for aqueous emulsion poly-
merization, an unprecedented high 1,4-cis-polybutadiene content
of up to 48%.
4. Experimental
4.1. General remarks
All manipulations were performed under inert atmosphere
using conventional Schlenk technique and a glove box. All reagents
used were purchased from Aldrich, Acros, Fluka, Strem or MCat and
were used without further purification, unless stated. Anhydrous
solvents were dried using a SPS MBSPS-800 system from MBraun
and degassed by the freeze-pump-thaw method. All 1H NMR and
13C{1H} NMR spectra were recorded as CD2Cl2 solutions on a Bru-
ker DPX200 spectrometer (200 MHz). All 13C NMR spectra were

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G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
referenced to CD2Cl2 (q, 53.42 ppm) as the internal standard, and
all 1H NMR spectra referenced to tetramethylsilane (TMS) as the
internal standard with J values given in hertz. Glove box manipu-
lations were carried out in a MB200G (LMF) glove box under an ar-
gon atmosphere. GPC analyses were performed with an Agilent
1100 series instrument in THF at 36 °C against a polybutadiene
standard. IR spectra of the pure polymer were recorded on a BioRad
FTS-175 spectrometer with a DTGS detector (resolution 2 cmꢀ1).
Hydrodynamic chromatography (HDC) was performed with PL-
PSDA (Polymer Laboratories-Particle Size Distribution Analyzer)
and 4,40-thio-bis(6-tert-butyl-m-cresol) (L13) (0.54 g, 1.52 mmol).
Yield 0.75 g (60%). 1H NMR (CD2Cl2, 200 MHz): d = 7.72 (s, 8H,
0
0
CHo-Ar ), 7.56 (s, 4H, CHp-Ar ), 7.47 (s, 4H, CHm-Ar), 6.50 (s, 4H,
CHo-Ar), 5.82 (m, 1H, allyl CHcentral), 5.22 (s, 4H, OH), 3.23 (d, 2H,
3JH–H = 7.40 Hz, allyl CHsyn), 2.80 (d, 2H, 3JH–H = 14.0 Hz, allyl CHanti),
2.05 (s, 12H, CH3), 1.34 (s, 36H, Bu); 13C NMR (CD2Cl2, 75.5 MHz)
t
d = 162.4, 156.3, 138.5, 136.3, 134.9, 129.3, 127.4, 122.0, 120.4,
119.2, 117.0, 68.8, 34.6, 29.1, 19.3; Anal. Calc. for C79H77O4S2-
F24BNi: C, 56.48; H, 4.62. Found: C, 56.53; H, 4.41%.
using a PS cartridge (10–15
tween 10 and 1200 nm can be detected.
lm). By this method particles in be-
4.6. Emulsion polymerization of butadiene with complexes 2 and 3 as
catalyst
4.2. Synthesis of [Ni(
g
3-C3H5)(L10)2][BArF ] 1(L10 = diphenyl sulfide)
For emulsion polymerization, a solution of cationic complexes 2
or 3 (0.37 mmol) in toluene was treated with 6 ml of 1,3-butadiene
at 0 °C. Afterwards 0.8 ml of hexadecane (0.0027 mmol) and a solu-
tion of sodium dodecyl sulfate (SDS) in water (1 g in 80 ml) is
added and subsequently emulsified with an ultrasound sonotrode
for 4 min.
The polymerizations were carried out in a 500 ml steel auto-
clave equipped with a mechanical stirrer (600 rpm) and with a
cooling/heating jacket supplied with a thermostat controlled by a
thermocouple dipping into the polymerization mixture. The reac-
tor was charged with a solution of 1 g SDS in 70 ml water. Then
the catalyst mini-emulsion was added and the reactor was warmed
to 40 °C. Butadiene was added in five portions at intervals of 2 min.
After 4 h the autoclave was cooled to room temperature. Residual
butadiene was removed by applying vacuum for several times.
4
In a Schlenk flask a solution of diphenyl sulfide (L10) (0.28 g,
1.52 mmol) and NaBArF4 (0.67 g, 0.76 mmol) in 10 ml of diethyl
ether was added to a stirred solution of [Ni(g l-Cl)]2 5
3-C3H5)(
(0.1 g, 0.38 mmol) in diethyl ether (20 ml) at ꢀ60 °C. After 2 h,
the cooling bath was removed and the mixture was allowed to stir
at room temperature overnight. The solvent was evaporated under
vacuum, and the residue extracted with dichloromethane (20 ml),
and the resulting solution was filtered and concentrated. The prod-
uct was crystallized twice form CH2Cl2–hexane. Yield 0.51 g (52%).
1H NMR (CD2Cl2, 200 MHz): d = 7.83 (s, 8H CHo-Ar ), 7.61 (s, 4H,
0
0
CHp-Ar ), 7.41 (m, 20H, Ph), 5.92 (m, 1H, allyl CHcentral), 3.48
3
3
(d, JH–H = 5.64 Hz, allyl CHsyn), 2.85 (d, JH–H = 10.08 Hz, 2H, allyl
CHanti); 13C NMR (CD2Cl2, 75.5 MHz) d = 161.7, 159.3, 138.5,
134.2, 129.6, 125.4, 122.3, 121.4, 119.9, 116.6, 70.1; Anal. Calc.
for C59H37S2F24BNi: C, 53.06; H, 2.79. Found: C, 53.23; H, 2.91%.
5. X-ray crystallography
4.3. Synthesis of [Ni(
g
3-C3H5)(L11)2][BArF ] 2 (L11 = 4,40-thiodiphenol)
4
A suitable crystal was selected, mounted on a thin glass fiber
using paraffin oil, and cooled to the data collection temperature.
Data was collected on a Bruker SMART CCD diffractometer using
This compound was prepared by the same procedure described
above for 1 using 5 (0.6 g, 2.22 mmol), NaBArF4 (3.93 g 4.44 mmol)
and 4,40-thiodiphenol (L11) (1.94 g, 8.90 mmol). Yield 3.2 g (53%).
0.3°
x scans at 0°, 90°, 180°, and 270° in u. Initial unit-cell param-
eters were determined from data frames collected at different sec-
tions of the Ewald sphere. Semi-empirical absorption corrections
based on equivalent reflections were applied [18]. The diffraction
data and unit-cell parameters were consistent with the reported
1H NMR (CD2Cl2, 200 MHz): d = 7.82 (s, 8H, CHo-Ar ), 7.74 (s, 4H,
0
3
0
CHp-Ar ), 7.23 (d, 8H, CHAr), 6.79 (d, 8H, JH–H = 8.70 Hz, CHAr),
5.85 (m, 1H, allyl CHcentral), 5.64 (s, 4H, OH), 3.37 (d, 2H,
3JH–H = 7.28 Hz, allyl CHsyn), 2.85 (d, 2H, JH–H = 13.92 Hz, allyl
3
ꢀ
space group P1 for complex 3. No symmetry higher than triclinic
CHanti); 13C NMR (CD2Cl2, 75.5 MHz) d = 162.7, 158.4, 135.3,
133.9, 129.1, 127.8, 122.4, 117.9, 117.5, 117.0, 69.9; Anal. Calc.
for C59H37O4S2F24BNi: C, 50.63; H, 2.66. Found: C, 50.80; H, 2.96%.
was observed, and the solution in the centrosymmetric space
group yielded chemically reasonable and computationally stable
results after refinement. The structure was solved by direct meth-
ods, completed with difference Fourier syntheses, and refined with
full-matrix least-squares procedures based on F2. All non-hydrogen
atoms were refined with anisotropic displacement coefficients. All
hydrogen atoms were treated as idealized contributions. The fluo-
rine atoms of the non-coordinating anion showed considerable
rotation and thus several CF3 groups were anisotropically modeled
in two rotational positions with a total occupancy factor of 1. All
scattering factors are contained in the shelxtl 6.12 program library
[19]. A summary of the crystal data, data collection parameters and
convergence results is compiled in Table 1.
4.4. Synthesis of [Ni(
butyl-o-cresol)
g
3-C3H5)(L12)2][BArF ] 3 (L12 = 4,40-thio-bis(6-tert-
4
This compound was prepared by the same procedure described
above for 1 using 5 (0.6 g, 2.22 mmol), NaBArF4 (3.93 g 4.44 mmol)
and 4,40-Thio-bis(6-tert-butyl-o-cresol) (L12) (3.18 g, 8.90 mmol).
Yield 4.1 g (55%). X-ray quality crystals of the complex 3 were
grown by slow diffusion of hexane into a dichloromethane solution
at ꢀ40 °C. 1H NMR (CD2Cl2, 200 MHz): d = 7.72 (s, 8H, CHo-Ar ), 7.57
0
4
0
(s, 4H, CHp-Ar ), 7.31 (d, 4H, CHo-Ar), 6.84 (d, 4H, JH–H = 2.0 Hz,
CHo-Ar), 5.77 (m, 1H, allyl CHcentral), 5.16 (s, 4H, OH), 3.30 (d, 2H,
3JH–H = 7.40 Hz, allyl CHsyn), 2.80 (d, 2H, 3JH–H = 14.0 Hz, allyl CHanti),
Acknowledgements
t
2.12 (s, 12H, CH3), 1.38 (s, 36H, Bu); 13C NMR (CD2Cl2, 75.5 MHz)
P.G., B.D., P.C. and C.J work at CaRLa of Heidelberg University,
being co-financed by University of Heidelberg, the state of Ba-
den-Württemberg and BASF SE. Support of these institutions is
greatly acknowledged.
d = 162.6, 137.9, 135.0, 131.6, 129.3, 127.5, 125.2, 122.1, 121.4,
117.7, 116.9, 69.5, 34.9, 29.3, 15.8; Anal. Calc. for C79H77O4S2-
F24BNi: C, 56.48; H, 4.62. Found: C, 56.23; H, 4.38%.
4.5. Synthesis of [Ni(
butyl-m-cresol)
g
3-C3H5)(L13)2][BArF ] 4 (L13 = 4,40-thio-bis(6-tert-
4
Appendix A. Supplementary material
This compound was prepared by the same procedure described
CCDC 707916 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
above for 1 using 5 (0.1 g, 0.38 mmol), NaBArF4 (0.67 g 0.76 mmol)

G. Padavattan et al. / Journal of Organometallic Chemistry 695 (2010) 673–679
679
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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.
2009.11.041.
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