Synthesis, structure, and polymerization activity of cyclopentadienylnickel(II) N-heterocyclic carbene complexes: Selective cross-metathesis in metal coordination spheres

Article abstract of DOI:10.1002/ejic.200900843

The N-heterocyclic carbene (NHC) complexes [(RC₅H ⁴)Ni(X)(NHC)] (2-5) have been prepared by treating nickelocene [or 1, 1′-bis(alkenyl)nickelocene] with a suitable carbene precursor. The alkenylcyclopentadienido complexes 4 and 5 und

Full text of DOI:10.1002/ejic.200900843

FULL PAPER
DOI: 10.1002/ejic.200900843
Synthesis, Structure, and Polymerization Activity of Cyclopentadienylnickel(II)
N-Heterocyclic Carbene Complexes: Selective Cross-Metathesis in Metal
Coordination Spheres
Włodzimierz Buchowicz,*[a] Wioleta Wojtczak,[a] Antoni Pietrzykowski,[a] Anna Lupa,[a]
[b]
[c]
[c]
´
Lucjan B. Jerzykiewicz, Anna Makal, and Krzysztof Wozniak
Keywords: Nickel / Carbene ligands / Metathesis / Homogeneous catalysis / Polymerization
¯
The N-heterocyclic carbene (NHC) complexes [(RC5H4)Ni-
(X)(NHC)] (2–5) have been prepared by treating nickelocene
[or 1,1Ј-bis(alkenyl)nickelocene] with a suitable carbene pre-
cursor. The alkenylcyclopentadienido complexes 4 and 5 un-
dergo chemoselective cross-metathesis with methyl acrylate
or methyl vinyl ketone in the presence of the seocnd-genera-
P21/n, Ni–Ccarbene 1.879(3) Å] and 7 [triclinic, P1, Ni–Ccarbene
1.8874(6) Å] reveal undistorted trigonal-planar Ni coordina-
tion. VT-NMR studies of complexes 2 and 3, which possess
an N-alkyl substituent, show hindered rotation of the car-
bene ligand. Complexes [(RC5H4)Ni(X)(NHC)], in the pres-
ence of an excess of MAO, display high activity in the poly-
tion Grubbs catalyst to yield complexes 6–8, which bear an merization of styrene and moderate activity in the oligomer-
α,β-unsaturated carbonyl substituent on the cyclopentadien-
ido ligand. The X-ray crystal structure of 2 [monoclinic,
ization of phenylacetylene.
Introduction
The complex [CpNi(Cl)(IMes)] (1; IMes = 1,3-dimes-
itylimidazol-2-ylidene; see Scheme 1) was synthesized for
the first time by Abernethy et al. from nickelocene and 1,3-
dimesitylimidazolium chloride.[1] A number of complexes of
the general formula [(RC5H4)Ni(X)(NHC)] (X = Cl, Br, I;
NHC = N-heterocyclic carbene) have since been prepared
by us[2] and others[3] in a similar fashion since this seminal
publication. Complexes of this type display catalytic activity
in aryl dehalogenation and aryl amination,[3a] styrene poly-
merization in the presence of MAO,[2] and hydrothiolation
of alkynes.[4] The related indenyl complexes [(η3-C9H7)-
Ni(X)(NHC)] are moderately active in the oligomerization
of ethylene[5] and styrene polymerization[6] in the presence
of MAO or NaBPh4, respectively. Other NHC-supported
NiII complexes have also been tested for olefin polymeriza-
tion[7] and carbon–carbon coupling reactions.[8]
Compound
[CpNi(Cl)(H2IMes)] (H2IMes
1
and its saturated counterpart
1,3-dimesityl-4,5-di-
=
hydroimidazol-2-ylidene) display the highest activity in sty-
rene polymerization. The polystyrenes obtained are atactic,
Scheme 1. NHC ligands discussed in this manuscript. The values
[a] Warsaw University of Technology, Faculty of Chemistry,
Koszykowa 75, 00-662 Warszawa, Poland
Fax: +48-22-234-5462
of the steric parameter %Vbur are taken from ref.[9a]
E-mail: wbuch@ch.pw.edu.pl
[b] University of Wrocław, Faculty of Chemistry,
Joliot-Curie 14, 50-353 Wrocław, Poland
[c] Chemistry Department, Warsaw University,
Pasteura 1, 02-093 Warszawa, Poland
and a cationic mechanism has been proposed to explain the
observed reactivity.[2] We reasoned that judicious modifica-
tion of the ligands may lead to the discovery of more ef-
ficient and stereospecific polymerization catalysts, and re-
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900843.
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Cyclopentadienylnickel(II) N-Heterocyclic Carbene Complexes
port herein the synthesis of novel complexes of this type Complex Synthesis
bearing two different substituents in the carbene ligand
Complexes 2–5 were synthesized by treating nickelocene
(Scheme 4). Moreover, α,β-unsaturated carbonyl moieties
have been attached to the cyclopentadienido ligand by
means of selective cross-metathesis (Scheme 5). The activity
of these new complexes in the polymerization of styrene or
phenylacetylene is explored under optimized conditions.
or 1,1Ј-disubstituted nickelocene with an appropriate imid-
azolium or dihydroimidazolium halide in refluxing thf
(Scheme 4). A prolonged reaction time (11–13 h) was
needed to complete the reaction for compounds containing
a substituted cyclopentadienido ligand (4, 5), as well as for
the bromide 3. Complexes 2–5 were isolated as red solids in
good to moderate yields (52–33%).
Results and Discussion
Ligand Synthesis
The electronic and steric (%Vbur) properties of NHC li-
gands (see Scheme 1) have been studied in detail,[9] and it
is now widely accepted that the differences in the electronic
parameters of known NHC ligands are relatively small. Sig-
nificant differences in the chemical behavior of NHC com-
plexes are therefore more likely to arise from steric factors.
Accordingly, carbene precursors bearing two different sub-
stituents on the N atoms have been considered in an at-
tempt to enhance the polymerization activity, in particular
to observe a possible tacticity in the resulting polystyrene.
We have previously established that increased steric bulk
(2,6-diisopropylphenyl vs. 2,4,6-trimethylphenyl) of the
NHC ligand results in a decrease of the polymerization
yield,[2] therefore a cyclohexyl group was chosen to replace
one 2,4,6-trimethylphenyl group. The saturated carbene pre-
cursor [HL1]Cl was synthesized analogously to the method
developed by Mol and co-workers[10] for an adamantyl-sub-
stituted ligand (Scheme 2).
Scheme 4. Synthesis of complexes 2–5 (Mes = 2,4,6-trimeth-
ylphenyl).
Whilst NMR characterization of 4 and 5 was straightfor-
1
ward, the room-temperature H NMR spectra of 2 and 3
feature a number of broad signals. For example, the aro-
matic singlet at δ = 7.07 ppm for complex 3 (Figure 1) is
somewhat broad, and the multiplets assigned to the methyl-
ene groups of the n-butyl substituent are not resolved.
Interestingly, only one singlet of the mesitylene methyl
groups is observed, and no signal could be assigned to the
NCH2 group (Figure 1b). The NCH2 signal appears at
50 °C as a broad singlet centered at δ = 5.02 ppm (Fig-
ure 1a).
The low-temperature spectra of 3 (–50 °C, Figure 1c) re-
veal all expected signals, especially three singlets for the me-
sitylene methyl groups at δ = 1.71, 2.41, and 2.47 ppm. The
three methylene groups of the n-butyl moiety appear as
pairs of non-equivalent multiplets, thus indicating that these
protons are diastereotopic. Noticeably, the NCH2 signals
are 1.15 ppm apart (δ = 4.39 and 5.54 ppm). This large dif-
ference in the values of the chemical shift suggests that one
of the protons interacts with the bromide. Moreover, the
13C NMR spectrum of 3 at –50 °C features six aromatic
carbon resonances and three signals for the mesitylene
methyl groups. We can therefore conclude that at low tem-
perature complex 3 exists as a single rotamer with hindered
rotation around the Ni–Ccarbene and N–CAr bonds.
A similar behavior was observed for complex 2, with all
aromatic and cyclohexyl signals being non-equivalent at
low temperature (see Supporting Information). It is also
interesting to note the low-field signal (δ = 6.07 ppm) for
the proton bonded to C1 of the cyclohexyl ring. This phen-
omenon could be explained by an interaction of this hydro-
gen atom with the halogen atom. Indeed, the solid-state
structure of 2 (see below) provides support for the presence
of an interaction between this proton and the chloride
Scheme 2. Synthesis of ligand precursor [HL1]Cl. Reagents and
conditions: (a) MesNH2, CH2Cl2, 0 °C to room temp. 12 h (ref.[10]);
(b) CyNH2, Et3N, CH2Cl2, 0 °C to room temp. 2 h; (c) (i)
BH3·SMe2, toluene, reflux, 3 h, (ii) aq. HCl; (d) HC(OEt)3,
HCOOH, 130 °C, 3 h.
We also prepared the unsaturated carbene precursor
[HL2]Br, which contains a primary alkyl group, in one
step from N-mesitylimidazole and 1-bromobutane
(Scheme 3)[11]
.
Scheme 3. Synthesis of ligand precursor [HL2]Br.
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1
Figure 1. VT H NMR spectra of complex 3 in CDCl3: (a) 400 MHz; (b) and (c) 700 MHz.
[H···Cl 2.84(4), C···Cl 3.566(4) Å]. In this context, we note bearing an alkyl substituent with a restricted metal–carbene
that an extensive search of crystallographic data showed bond rotation have already been reported,[3b,13] although no
that transition metal–Cl moieties are good hydrogen-bond comprehensive explanation of this phenomenon was
acceptors.[12] Moreover, published data indicate that L1 is given.[3b]
smaller than IMes [%Vbur = 23 for 1,3-dicyclohexylimid-
The solid-state structure of 2 was unambiguously con-
azol-2-ylidene (ICy) and 26 for IMes; see Scheme 1].[9] Tak- firmed by single-crystal X-ray diffraction (Figure 2). Com-
ing into account that IMes rotates freely in complex 1, the plex 2 crystallizes in the monoclinic crystal system (space
hindered rotation of carbene L1 in complex 2 cannot be group P21/n). The nickel coordination is trigonal-planar
explained on the grounds of steric hindrance. Thus, we at- (considering the Cp centroid), with Ni–Ccarbene 1.879(3),
tribute the restricted rotation in 2 to the presence of an N– Ni–Cl 2.1934(11), and Ni–Cp(c) 1.768(6) Å. The presence
CH···Cl–Ni interaction. Likewise, we assume that electronic of ligand L1 does not produce a significant distortion in
effects are also a plausible explanation for the observed be- the Ni coordination sphere when compared with related
havior of 3 in solution. Some examples of NHC complexes complexes.[1–3]
Figure 2. Molecular structure of complex 2. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths [Å] and
angles [°]: Ni–C(1) 1.879(3), Ni–Cl 2.1934(11), Ni–Cp(c) 1.768(6), N(1)–C(1) 1.346(4), C(1)–N(2) 1.325(3), C(2)–C(3) 1.522(5); Cp(c)–
Ni–Cl 131.6(1), C(1)–Ni–Cp(c) 131.0(2), C(1)–Ni–Cl 97.14(8); H(10A)···Cl 2.84(4), C(10)–Cl 3.566(4).
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Cyclopentadienylnickel(II) N-Heterocyclic Carbene Complexes
Figure 3. Molecular structure of complex 7. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths [Å] and
angles [°]: Ni(2)–C(1) 1.8874(6), Ni(2)–Cl(1) 2.1941(2), Ni(2)–Cp(c) 1.778(1), C(3)–C(2) 1.5273(11), N(2)–C(1) 1.3419(9), N(1)–C(1)
1.3391(8); Cp(c)–Ni–Cl 126.32(3), C(1)–Ni(2)–Cl(1) 98.67(2), C1–Ni(2)-Cp(c) 134.65(3). Hydrogen atoms have been omitted for clarity.
Selective Cross-Metathesis in Metal Coordination Spheres
Complexes 6–8 were obtained in high yields (78–51%) by
refluxing complex 4 or 5 with an α,β-unsaturated carbonyl
compound (methyl acrylate, methyl vinyl ketone) in CH2Cl2
in the presence of [RuCl2(=CHPh)(PCy3)(H2IMes)].[21] The
1H NMR spectra of the crude reaction mixtures showed
that a single organometallic product had formed. Large
coupling constants for the olefinic protons (3JH,H = 15–
16 Hz) indicated an (E) configuration for the double bonds.
The structure of complex 7 was confirmed by X-ray crystal-
lographic analysis (Figure 3).
A pronounced influence of the cyclopentadienido ligand
on the reaction outcome could be expected if the styrene
polymerization proceeds by
a
coordination/insertion
mechanism. Thus, we sought to synthesize complexes
[(RC5H4)Ni(X)(NHC)] with a cyclopentadienido ligand
bearing a functional group. Because such complexes are ob-
tained from nickelocene (Scheme 4), their synthesis is re-
stricted by the availability of substituted nickelocenes. In
particular, polar functional groups (e.g. carbonyl) are not
compatible with the lithium or sodium cyclopentadienide
derivatives used in the metallocene synthesis.[14] Unlike fer-
rocene, nickelocene is not stable to lithiation,[15] and func-
tionalization of the cyclopentadienido ligand in nickelocene
has not been reported.[16] On the other hand, olefin metath-
esis has been used successfully to synthesize a number of
organometallic compounds, most often as a ring-closing re-
action between two ligands at a coordination centre.[17] Sev-
eral examples of a cross-metathesis between two transition
metal complexes,[18] or between a complex and an organic
molecule,[18b,18c,19] have also been reported. Therefore, we
decided to apply selective cross-metathesis[20] to attach a
carbonyl group to complexes 4 and 5 (Scheme 5).
¯
Complex 7 crystallizes in the P1 space group of the tri-
clinic crystal system. The nickel coordination is trigonal-
planar (considering the Cp centroid), with an Ni–Ccarbene
bond length of 1.8874(6) Å. Whereas the two methylene
bridging groups are coplanar with the cyclopentadienido
ring, the plane of the α,β-unsaturated carbonyl system is
nearly perpendicular to the cyclopentadienido ring plane.
Polymerization
The activity of complexes 1–8 in styrene polymerization
was investigated under conditions similar to those in our
previous report.[2]
The most active complex polymerized up to 15000 equiv.
of styrene at 50 °C in 3 h (Table 1, Entry 1). Substitution of
one mesitylene group in 1 for an alkyl group (cyclohexyl or
n-butyl) resulted in a significantly lower activity (Table 1,
Entries 2 and 3). Similarly, the allylcyclopentadienido and
butenylcyclopentadienido complexes 4 and 5 were less ef-
ficient than 1. The presence of a carbonyl group had a bene-
ficial effect on the activity (Table 1, Entries 6–8). However,
addition of MAO in these runs resulted in precipitation of
a dark solid that remained insoluble during the entire reac-
tion, in other words these polymerizations appeared to pro-
ceed under heterogeneous conditions. GPC analysis of the
Scheme 5. Selective cross-metathesis for complexes 4 and 5 (Ar =
2,4,6-trimethylphenyl).
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Table 1. Styrene polymerization with complexes 1–8 in the presence of an excess of MAO.[a]
Entry
Complex
Yield [%]
Mn
Mw/Mn
1
2
3
4
5
6
7
8
[CpNi(Cl)(IMes)] (1)
98
49
52
72
42
90
94
92
11100
12550
12100
13000
13200
13400
12300
13300
1.8
1.8
1.9
1.8
1.8
1.9
1.9
1.9
[CpNi(Cl)(L1)] (2)
[CpNi(Br)(L2)] (3)
[(C5H4CH2CH=CH2)Ni(Cl)(H2IMes)] (4)
[{C5H4(CH2)2CH=CH2}Ni(Cl)(H2IMes)] (5)
[{C5H4CH2CH=CHC(O)CH3}Ni(Cl)(H2IMes)] (6)
[{C5H4(CH2)2CH=CHC(O)CH3}Ni(Cl)(H2IMes)] (7)
[{C5H4(CH2)2CH=CHC(O)OCH3}Ni(Cl)(H2IMes)] (8)
[a] All runs in duplicate. Conditions: styrene/Ni = 15000:1, Al/Ni = 300:1, [Ni] = 4.0 m in toluene, 50 °C, 3 h; L1 = 1-cyclohexyl-3-
mesityl-4,5-dihydroimidazol-2-ylidene; L2 = 1-(n-butyl)-3-mesitylimidazol-2-ylidene; IMes = 1,3-dimesitylimidazol-2-ylidene; H2IMes =
1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (see Scheme 1).
resulting polystyrenes showed similar results (Mn = 11100–
13400 Da, DP = 110–130, Mw/Mn = 1.8–1.9) for all the
Conclusions
complexes studied. The 13C NMR spectra indicated that the
obtained polymers were isotactic-rich atactic.[22] The
MALDI-TOF mass spectra of the polymer produced with
complex 2 featured peaks corresponding to the molecular
formula [(C8H8)nAg]+ (e.g. for n = 16 peak centered at m/z
= 1774). Accordingly, we conclude that the methyl groups
from MAO were not incorporated into the polymer chains.
The results presented in Table 1 show that the structure
of the Ni complex significantly affects the polymerization
yield, although it has very little or no effect on the structure
of the polystyrene produced. These observations are in
agreement with a cationic mechanism for styrene polymeri-
zation,[2,23] although a coordination/insertion mechanism
involving an Ni–H species cannot be ruled out.[22,24]
We have synthesized and fully characterized seven new
[(RC5H4)Ni(X)(NHC)] complexes. Complexes 2 and 3,
which bear an alkyl substituent in the NHC ligand (L1 and
L2, respectively), display restricted rotation of this ligand
in solution due to the presence of an N–CH···Cl–N interac-
tion rather than to steric hindrance. The studied complexes,
in the presence of an excess of MAO, efficiently polymerize
styrene with an activity up to 8700 gPS/gNih. The polyme-
rization yield depends strongly on the composition of both
the cyclopentadienido and NHC ligands, whereas the tac-
ticity of the resulting polystyrenes is not affected by the
structure of the nickel complexes.
Selected complexes were also tested in the polymerization Experimental Section
of phenylacetylene in the presence of an excess of MAO
General: All manipulations involving organometallic complexes
(Table 2). Moderate activities (TONs up to 600) were ob-
tained under conditions similar to those for styrene. The
presence of an alkyl substituent in the NHC moiety
(Table 2, Entry 3) resulted in a significantly lower activity
than for the bis(aryl) counterparts. Phenylacetylene oligo-
mers (Mn = 1200–1600 Da) were obtained in most runs
with the exception of [CpNi(Cl)(H2IPr)] (Table 2, Entry 4),
where a bimodal distribution was detected with a high mo-
lecular weight fraction (Mn = 13600 Da). Accordingly, we
conclude that the increased steric bulk in the NHC ligand
(H2IPr vs. H2IMes) affects the course of the polymerization.
were performed by using standard Schlenk techniques under argon.
All solvents were purified by appropriate methods.[25] A commer-
cial solution of MAO in toluene (10 wt.-%) from Aldrich was used
in all experiments. Styrene, phenylacetylene, methyl vinyl ketone,
and methyl acrylate (Aldrich) were dried with CaH2 and distilled
under reduced pressure. Cyclohexylamine (Aldrich) and 1-bromo-
butane (POCh) were distilled under argon. Nickelocene,[14] 1,1Ј-
bis(allyl)nickelocene and 1,1Ј-bis(but-3-enyl)nickelocene,[17i] pre-
viously described ligands,[26] NHC complexes,[1–3] and N-mesityl-
imidazole[27] were synthesized according to reported methods. All
other reagents were purchased from commercial sources (Aldrich,
POCh) and used as received. EI (70 eV) mass spectra were recorded
with an AMD-604 spectrometer and ESI mass spectra with an ESI
Mariner spectrometer. Unless otherwise noted, NMR spectra were
recorded at ambient temperature with a Mercury 400BB spectrom-
eter at 400 MHz for 1H and at 101 MHz for 13C with chemical
shifts reported relative to the residual deuterated solvent. Mw and
Mn of polymers were determined with a LabAlliance liquid chro-
matograph equipped with a Jorgi Gel DVB Mixed Bed column
(250 mmϫ10 m) with thf (polystyrenes) or CHCl3 (polyphenyl-
acetylenes) as the mobile phase. MALDI TOF mass spectra of the
polymers were recorded with a Kratos Kompakt 4 V 5.2.1 instru-
ment by using the DHB/THF (30 mg/mL) matrix (CF3COOAg was
added).
Table 2. Phenylacetylene polymerization with selected complexes in
the presence of an excess of MAO.[a]
Entry
Complex
Yield [%]
Mn
Mw/Mn
1
2
3
4
[CpNi(Cl)(IMes)] (1)
[CpNi(Cl)(H2IMes)]
[CpNi(Br)(L2)] (3)
[CpNi(Cl)(H2IPr)]
60
56
23
50
1200
1600
1.2
1.1
1.1
1.2
1.4
1400
1200[b]
13600
[a] All runs in duplicate. Conditions: phenylacetylene/Ni = 1000:1,
Al/Ni = 300:1, [Ni] = 2.7 m in toluene, 75 °C, 5 h. IMes = 1,3-
dimesitylimidazol-2-ylidene; H2IMes = 1,3-dimesityl-4,5-dihydro-
imidazol-2-ylidene; L2 = 1-(n-butyl)-3-mesitylimidazol-2-ylidene;
H2IPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylid-
ene (see Scheme 1). [b] Bimodal distribution.
Ligand Synthesis.
N-Cyclohexyl-NЈ-(2,4,6-trimethylphenyl)oxalamide (B): A solution
of cyclohexylamine (4.0 mL, 36.7 mmol) and triethylamine
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Cyclopentadienylnickel(II) N-Heterocyclic Carbene Complexes
(5.0 mL, 35.8 mmol) in CH2Cl2 (40 mL) was added dropwise to a
CH2Cl2 (200 mL) solution of oxo(2,4,6-trimethylphenylamino)ace-
tyl chloride[10] (A; 8.131 g, 36.3 mmol) at 0 °C and the resulting
yellow mixture stirred at room temp. for an additional 1.5 h. Water
(200 mL) was added, and the organic layer was separated and dried
with MgSO4. The solvent was removed under reduced pressure to
afford a yellow residue, which was crystallized from CH2Cl2
(50 mL) and Et2O (12 mL) to give the title compound as a white
(2,4,6-Trimethylphenyl)N(CHO)CH2CH2N(CHO)Cy was also iso-
lated as a yellow solid (0.693 g). H NMR (400 MHz, CDCl3): δ =
1
1.32–1.90 (m, 10 H, Cy), 2.19 (s, 6 H, o-CH3), 2.28 (s, 3 H, p-CH3),
3.29 (m, 1 H, 1-H of Cy), 3.52 (m, J = 4.0 Hz, 2 H, NCH2CH2N),
3.60 (m, J = 4.0 Hz, 2 H, NCH2CH2N), 6.92 (s, 2 H, Ar), 8.00 (m,
1 H, CHO), 8.10 (m, 1 H, CHO) ppm. 13C NMR (101 MHz,
CDCl3): δ = 18.39 (o-CH3), 20.87 (p-CH3), 24.96, 25.73, 32.42,
38.67 (Cy), 45.06, 58.53 (NCH2CH2N), 129.63, 135.98, 136.08,
138.30 (Ar), 162.58 (CHO), 164.03 (CHO) ppm. ESI MS: m/z =
1
solid (6.63 g, 23.0 mmol, 63%). H NMR (400 MHz, CDCl3): δ =
1.25–1.98 (m, 10 H, Cy), 2.19 (s, 6 H, o-CH3), 2.28 (s, 3 H, p-CH3),
339 [M + Na]+. IR (KBr): ν = 2931 (Cy), 2856 [C(O)–N], 1672
˜
3.78 (m, 1 H, 1-H of Cy), 6.91 (s, 2 H, Ar), 7.48 (d, J = 8.8 Hz, 1 (C=O) cm–1. C19H28N2O2 (316.45): calcd. C 72.12, H 8.92, N 8.85;
H, NH-Cy), 8.77 (s, 1 H, NH-Ar) ppm. 13C NMR (101 MHz,
CDCl3): δ = 18.33 (o-CH3), 20.92 (p-CH3), 24.75, 25.28, 32.63,
49.08 (Cy), 129.00, 129.75, 134.71, 137.46 (Ar), 158.44, 158.80
(C=O) ppm. ESI MS: m/z = 289 [M + H]+, 311 [M + Na]+, 599
found C 71.92, H 8.87, N 8.90.
1-Butyl-3-(2,4,6-trimethylphenyl)imidazolium Bromide ([HL2]Br):
N-Mesitylimidazole[27] (1.984 g, 10. 6 mmol) and 1-bromobutane
(1.15 mL, 10.7 mmol) were heated at reflux in toluene (30 mL) for
16 h. Et2O (60 mL) was then added and the resulting suspension
filtered to afford the title compound (1.169 g, 34%) as a white so-
lid. 1H NMR (400 MHz, [D6]DMSO): δ = 0.92 (t, J = 7.2 Hz, 3
H, CH3), 1.27 (sext, J = 8.0 Hz, 2 H, CH2), 1.87 (quint, J = 7.2 Hz,
2 H, CH2), 2.00 (s, 6 H, o-CH3), 2.32 (s, 3 H, p-CH3), 4.28 (t, J =
7.2 Hz, 2 H, N-CH2), 7.14 (s, 2 H, Ar), 7.94 (t, J = 1.6 Hz, 1 H,
imidazole), 8.11 (t, J = 1.6 Hz, 1 H, imidazole), 9.47 (d, J = 6.8 Hz,
1 H, NCHN) ppm. 13C NMR (101 MHz, [D6]DMSO): δ = 13.28
(CH3), 16.87 (CH2), 18.75 (o-CH3), 20.59 (p-CH3), 21.06 (CH2),
49.02 (NCH2), 123.17, 123.94, 129.25 (imidazole), 131.16, 134.28,
137.26, 140.24 (Ar) ppm. ESI MS: m/z = 243 [M – Br]+.
C16H23BrN2·0.4H2O (330.48): calcd. C 58.15, H 7.26, N 8.48;
found C 58.42, H 6.66, N 8.52.
[2M + Na]+. IR (KBr): ν = 1656 (C=O), 1505 (N–H), 1448 (CH ),
˜
2
1375 (CH3), 1230 [C(O)–N], 844, 746, 710 (2,4,6-C–H) cm–1.
C17H24N2O2 (288.39): calcd. C 70.80, H 8.39, N 9.72; found C
70.77, H 8.36, N 9.78.
N-Cyclohexyl-NЈ-(2,4,6-trimethylphenyl)ethane-1,2-diamine Dihydro-
chloride (C): BH3·SMe2 (46.5 mL, 2.0  solution in toluene,
93 mmol) was added to a solution of B (6.54 g, 22.68 mmol) in
toluene (165 mL) and the resulting mixture heated at reflux for 4 h.
After cooling to room temp., 1  aq. HCl (ca. 200 mL) was added
until the solution became acidic, then 10% aq. NaOH (ca. 150 mL)
until it became basic. The mixture was transferred to a separating
funnel and the organic layer separated. The aqueous layer was ex-
tracted with CH2Cl2 (2ϫ50 mL), and the combined organic ex-
tracts were reduced to about 1/4 of the original volume. Acetone
(40 mL) was added to the yellow solution followed by 12  aq. HCl
until a white solid appeared. This mixture was stirred at room temp.
for 12 h. The resulting solid was collected by filtration, washed with
diethyl ether, and dried in air to give the title compound as a white,
crystalline solid (5.45 g, 20.97 mmol, 89%). 1H NMR (400 MHz,
[D6]DMSO): δ = 1.23–1.78 (m, 10 H, Cy), 2.07 (s, 6 H, o-CH3),
2.21 (s, 3 H, p-CH3), 3.06 (br. t, J = 10 Hz, 1 H, 1-H of Cy), 3.36
(br. s, 2 H, CH2NHCy), 3.55 (br. s, 2 H, CH2NHAr), 6.95 (s, 2 H,
Ar), 9.62 (br. s, 2 H, both NH) ppm. 13C NMR (101 MHz, [D6]-
DMSO): δ = 18.00 (o-CH3), 20.26 (p-CH3), 23.78, 24.72, 28.46,
30.71 (Cy), 45.66, 56.02 (NCH2CH2N), 130.27, 131.60, 137.26 (br.,
Synthesis of [(RC5H4)Ni(X)(NHC)] Complexes
[CpNi(Cl){1-cyclohexyl-3-(2,4,6-trimethylphenyl)-4,5-dihydroimid-
azol-2-ylidene}] (2): Nickelocene (0.229 g, 1.21 mmol) and [HL1]Cl
(0.385 g, 1.26 mmol) were refluxed in thf (12 mL) for 2.5 h. The
usual workup[1] provided 0.279 g (0.652 mmol, 52%) of complex 2
1
as a red solid. H NMR (400 MHz, CDCl3, 20 °C): δ = 1.61–1.80
(m, 10 H, Cy), 1.98 (br. s, 3 H, o-CH3), 2.37 (s, 3 H, p-CH3), 2.61
(br. s, 3 H, o-CH3), 3.67 (s, 4 H, NCH2CH2N), 4.73 (s, 5 H, Cp),
6.07 (br., 1 H, 1-H of Cy), 6.94 and 7.11 (2 overlapping br. s, 2 H,
Ar) ppm. 13C NMR (101 MHz, CDCl3, 20 °C): δ = 17.61 (br., o-
CH3), 19.22 (br., o-CH3), 21.09 (p-CH3), 25.54 (Cy), 31.16 (br.,
Cy), 43.72 (NCH2CH2N), 50.09 (NCH2CH2N), 60.16 (Cy), 91.57
(Cp), 128.59 (b), 130.00 (b), 137.12, 138.05 (Ar), 196.00 (NCN)
Ar) ppm. ESI MS: m/z = 261 [M + H]+. IR (KBr): ν = 3304 (N–
˜
H), 2938 (Cy), 1021 (C–N) cm–1. C17H28N2·2HCl·2H2O (369.39):
1
ppm. H NMR (500 MHz, CDCl3, –60 °C): δ = 1.47–1.99 (m, 10
calcd. C 55.28, H 9.28, N 7.58; found C 56.67, H 8.81, N 7.77.
H, Cy), 1.84 (s, 3 H, o-CH3), 2.37 (s, 3 H, p-CH3), 2.60 (s, 3 H, o-
CH3), 3.70 (br. s, 4 H, NCH2CH2N), 4.72 (s, 5 H, Cp), 6.00 (br. s,
1 H, 1-H of Cy), 6.96 (s, 1 H, Ar), 7.12 (s, 1 H, Ar) ppm. 13C NMR
(126 MHz, CDCl3, –60 °C): δ = 17.50 (o-CH3), 19.10 (o-CH3),
21.16 (p-CH3), 25.02, 25.20, 25.44, 30.69, 31.11 (Cy), 43.53, 49.75
(NCH2CH2N), 59.80 (Cy), 91.20 (Cp), 128.38, 129.69, 134.90,
136.63, 137.99, 138.60 (Ar), 194.10 (NCN) ppm. 1H NMR
(400 MHz, CDCl3, 40 °C): δ = 1.53–2.40 (m, 16 H, Cy and o-CH3),
2.37 (s, 3 H, p-CH3), 3.67 (s, 4 H, NCH2CH2N), 4.73 (s, 5 H, Cp),
6.11 (t, J = 3.2 Hz, 1 H, 1-H of Cy), 7.03 (br.s, 2 H, Ar) ppm. EI
MS (70V): m/z (%) [58Ni, 35Cl] = 428 (64) [M+], 392 (83) [M –
HCl]+, 335 (70) [C23H31N2]+, 323 (55) [NiC18H21N2]+, 269 (88)
[L1 – H]+, 245 (43) [NiC12H15N2]+, 187 (100) [C12H15N2]+, 123
(8) [NiCp]+, 65 (16) Cp. HR EI MS: calcd. for C23H31N235Cl58Ni
428.15292; found 428.15384. Complex decomposes at 180 °C.
C23H31ClN2Ni (429.66): calcd. C 64.29, H 7.27, N 6.52; found C
63.92, H 7.17, N 6.51. Crystals suitable for X-ray analyses were
obtained by slow concentration of a hexane solution at room temp.
1-Cyclohexyl-3-(2,4,6-trimethylphenyl)-4,5-dihydroimidazolinium
Chloride ([HL1]Cl): A suspension of C (5.254 g, 20.21 mmol) in
triethyl orthoformate (80 mL) with a few drops of formic acid was
heated at reflux for 3 h. During this time the white solid dissolved,
and the solution turned orange. After cooling to room temp., the
volatiles were removed under reduced pressure. The brown residue
was treated with CH2Cl2 (10 mL) and hexane (25 mL). Two phases
separated; the upper layer was collected, and the solvents were
evaporated to dryness to yield a yellow solid that was crystallized
twice from thf to give the title compound as a white solid (0.385 g,
1
1.25 mmol, 6%). H NMR (400 MHz, CDCl3): δ = 1.14–1.86 (m,
10 H, Cy), 2.26 (s, 3 H, p-CH3), 2.30 (s, 6 H, o-CH3), 4.16 (m, J =
4.4 Hz, 2 H, NCH2CH2N), 4.19 (m, J = 4.2 Hz, 2 H, NCH2CH2N),
4.34 (m, 1 H, 1-H of Cy), 6.91 (s, 2 H, Ar), 9.77 (s, 1 H, NCHN)
ppm. 13C NMR (101 MHz, CDCl3): δ = 18.03 (o-CH3), 20.97 (p-
CH3), 24.59, 24.80, 31.17, 45.82 (Cy), 50.43, 57.56 (NCH2CH2N),
129.95, 130.73, 135.19, 140.16 (Ar), 158.79 (NCN) ppm. ESI MS:
m/z = 271 [M – Cl]+. This compound was used in the next step
without further purification.
[CpNi(Br){1-butyl-3-(2,4,6-trimethylphenyl)imidazol-2-ylidene}] (3):
Nickelocene (0.51 g, 2.70 mmol) and [HL2]Br (0.90 g, 2.78 mmol)
Eur. J. Inorg. Chem. 2010, 648–656
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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653

W. Buchowicz et la.
FULL PAPER
were stirred at reflux in thf (25 mL) for 12 h and then at room temp.
for 2 d. The usual workup[1] provided 0.53 g (1.19 mmol, 44%) of
complex 3 as a red, microcrystalline solid. 1H NMR (400 MHz,
CDCl3, 20 °C): δ = 1.07 (t, J = 7.2 Hz, 3 H, CH3), 1.51 (m, J =
H, =CH2), 5.71 (m, 1 H, =CH), 7.06 (s, 4 H, Ar) ppm. 13C NMR
(101 MHz, CDCl3): δ = 18.57, 21.12 (o- and p-CH3), 26.40
(C5H4CH2CH2), 31.57 (C5H4CH2CH2), 50.92 (NCH2CH2N),
82.86, 97.56 (C5H4CH2), 113.95 (=CH2), 115.57 (C5H4CH2),
7.6 Hz, 2 H, CH2), 2.03 (br.m, 2 H, CH2), 2.42 (s, 3 H, p-CH3), 129.37, 136.9 (br.), 136.98, 138.15 (Ar), 139.04 (=CH), 202.59
4.78 (s, 5 H, Cp), 6.84 (d, J = 1.6 Hz, 1 H, imidazole), 7.07 (br. s,
(NCN) ppm. EI MS (70 eV): m/z (%) [58Ni, 35Cl] = 518 (19) [M+],
2 H, Ar), 7.15 (d, J = 2.0 Hz, 1 H, imidazole) ppm. 1H NMR 482 (47) [M – HCl]+, 364 (20) [Ni(L)]+, 305 (100) [L – H]+, 304
(400 MHz, CDCl3, 50 °C): δ = 1.08 (t, J = 7.4 Hz, 3 H, CH3), 1.54
(sext, J = 7.6 Hz, 2 H, CH2), 2.06 (m, overlapped with a br. s
centered at δ = 2.1 ppm, 8 H, CH2 and o-CH3), 2.42 (s, 3 H, p-
CH3), 4.78 (s, 5 H, Cp), 5.02 (br., 2 H, N-CH2), 6.83 (d, J = 1.6 Hz,
1 H, imidazole), 7.07 (br. s, 2 H, Ar), 7.14 (d, J = 2.0 Hz, 1 H,
(35) [L – 2H]+, 303 (54) [L – 3 H]+, 146 (24), 117 (6), 91 (12),
77 (9). HR EI MS: calcd. for C30H3735ClN258Ni 518.19987; found
518.19887. C30H37ClN2Ni (519.79): calcd. C 69.32, H 7.17, N 5.39;
found C 68.92, H 7.06, N 5.46.
Selective Cross-Metathesis
1
imidazole) ppm. H NMR (700 MHz, CDCl3, –50 °C): δ = 1.03 (t,
J = 7.7 Hz, 3 H, CH3), 1.39 and 1.48 (2 m, 2 H, CH2), 1.71 (s, 3
H, o-CH3), 1.91 and 2.01 (2 m, 2 H, CH2), 2.41 (s, 3 H, p-CH3),
2.47 (s, 3 H, o-CH3), 4.39 (m, 1 H, NCH2), 4.76 (s, 5 H, Cp), 5.54
(dt, J = 13.3, 7.7 Hz, 1 H, NCH2), 6.85 (d, J = 1.4 Hz, 1 H, imid-
azole), 6.98 (s, 1 H, Ar), 7.16 (d, J = 1.4 Hz, 1 H, imidazole), 7.17
(s, 1 H, Ar) ppm. 13C NMR (101 MHz, CDCl3, 20 °C): δ = 13.99
(CH3), 18.5 (br., o-CH3), 19.97 (CH2), 21.14 (p-CH3), 33.34 (CH2),
52.34 (NCH2), 91.56 (Cp), 122.41, 123.68 (imidazole), 129.0 (br.,
m-Ar), 136.74, 138.99 (Ar), 163.19 (NCN) ppm. 13C NMR
(176 MHz, CDCl3, –50 °C): δ = 14.49 (CH3), 17.85 (o-CH3), 19.97
(CH2), 20.14 (o-CH3), 21.54 (p-CH3), 33.42 (CH2), 52.37 (NCH2),
91.59 (Cp), 122.67, 123.94 (imidazole), 128.59, 129.76, 134.34,
136.60, 137.73, 139.19 (Ar), 161.50 (NCN) ppm. EI MS (70 eV):
m/z (%) [58Ni, 79Br] = 444 (32) [M+], 364 (28) [M – HBr]+, 307
(100) [M – NiBr]+, 295 (20) [C10H10BrN2Ni]+, 242 (19) [L2]+, 185
(17) [L2 – C4H9]+, 123 (4) [NiCp]+, 91 (11) [C7H7]+, 65 (7) [Cp+].
HR EI MS: calcd. for C21H2779BrN258Ni 444.07111; found
444.07265. C21H27BrN2Ni (446.05): calcd. C 56.55, H 6.10, N 6.28;
found C 56.61, H 5.65, N 6.51.
[(C5H4CH2CH=CHC(O)CH3]Ni(Cl){1,3-bis(2,4,6-trimethylphen-
yl)-4,5-dihydroimidazol-2-ylidene}] (6): Neat methyl vinyl ketone
(100 µL, 0.086 g, 1.23 mmol) was added to a solution of complex
4 (0.20 g, 0.39 mmol) and [RuCl2(=CHPh)(PCy3)(H2IMes)]
(0.0161 g, 0.0190 mmol) in CH2Cl2 (10 mL). The resulting solution
was stirred at reflux for 3 h after which time the reaction was in-
complete as judged by 1H NMR spectroscopy. Further methyl vinyl
ketone (100 µL) and catalyst (0.0111 g) were added and the reac-
tion mixture was refluxed for a further 3.5 h. The volatiles were
removed under vacuum to yield a red solid, which was redissolved
in toluene (15 mL). This solution was filtered through a pad of
Celite, and the solvents were evaporated to dryness. This crude
product was washed several times with hexane at –78 °C and crys-
tallized from CH2Cl2/hexane. Yield: 0.11 g (0.20 mmol, 51%), red
solid. 1H NMR (400 MHz, CDCl3): δ = 2.20 [s, 3 H, C(O)CH3],
2.32 (d, J = 6.8 Hz, 2 H, C5H4CH2), 2.37 and 2.38 (2 overlapped
s, 18 H, o- and p-CH3), 3.90 (s, 4 H, NCH2CH2N), 4.26 (t, J =
2.4 Hz, 2 H, C5H4CH2), 4.53 (t, J = 2.4 Hz, 2 H, C5H4CH2), 5.92
[d, J = 16 Hz, 1 H, =CHC(O)], 6.64 (dt, J = 16, J = 7.2 Hz, 1 H,
CH2CH=), 7.06 (s, 4 H, Ar) ppm. 13C NMR (101 MHz, CDCl3):
δ = 18.52 (o-CH3), 21.12 (p-CH3), 26.51 [C(O)CH3], 30.69
(C5H4CH2), 50.97 (NCH2CH2N), 83.65, 98.08, 109.95 (C5H4CH2),
129.41, 129.74, 136.7 (br.), 136.86, 138.25, 145.83 (Ar and C=C),
[(C5H4CH2CH=CH2)Ni(Cl){1,3-bis(2,4,6-trimethylphenyl)-4,5-di-
hydroimidazol-2-ylidene}] (4): 1,1Ј-Bis(allyl)nickelocene[17i] (0.90 g,
3.34 mmol) and 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimid-
azolinium chloride[26] (1.15 g, 3.35 mmol) were stirred at reflux in
thf (35 mL) for 13 h and then at room temp. for 3 d. The usual
workup provided 0.85 g (1.68 mmol, 50%) of complex 4 as a red,
crystalline solid. 1H NMR (400 MHz, CDCl3): δ = 2.14 (d, J =
6.8 Hz, 2 H, C5H4CH2), 2.38 (s, 18 H, o- and p-CH3), 3.92 (s, 4 H,
NCH2CH2N), 4.26 (t, J = 2.4 Hz, 2 H, C5H4), 4.47 (m, J = 2.2 Hz,
2 H, C5H4), 4.83, 4.85, 4.90 (m, 2 H, =CH2), 5.85 (m, 1 H, =CH),
7.06 (s, 4 H, Ar) ppm. 13C NMR (101 MHz, CDCl3): δ = 18.54 (o-
CH3), 21.10 (p-CH3), 31.61 (C5H4CH2), 50.89 (NCH2CH2N),
83.03, 97.91, 113.35 (C5H4CH2), 115.05 (=CH2), 129.36 (m-Ar),
135.95 (=CH), 136.91 (o or p-Ar), 136.9 (br., ipso-Ar), 138.11 (o or
p-Ar), 202.25 (NCN) ppm. EI MS (70 eV): m/z (%) [58Ni, 35Cl] =
504 (12) [M+], 468 (59) [M – HCl]+, 364 (27) [NiL]+, 305 (100) [L –
H]+, 304 (69) [L – 2 H]+, 303 (82) [L – 3 H]+, 146 (40), 103 (15)
[C8H7]+, 91 (21) [C7H7]+, 77 (18) [C6H5]+. HR EI MS: calcd. for
C29H3535ClN258Ni 504.18422; found 504.18263. C29H35ClN2Ni
(505.76): calcd. C 68.87, H 6.97, N 5.54; found C 68.90, H 6.88, N
5.45.
199.05 (C=O), 200.84 (NCN) ppm. IR (KBr): ν = 2919, 1671, 1486,
˜
1433, 1256, 1019, 984, 852, 795 cm–1. EI MS (70 eV): m/z [58Ni,
35Cl] = 546 [M+], 510 [M – HCl]+. C31H37ClN2NiO (547.80): calcd.
C 67.97, H 6.81, N 5.11; found C 67.79, H 6.66, N 5.16.
[(C5H4(CH2)2CH=CHC(O)CH3]Ni(Cl){1,3-bis(2,4,6-trimethyl-
phenyl)-4,5-dihydroimidazol-2-ylidene}] (7): Complex 5 (0.21 g,
0.40 mmol) and [RuCl2(=CHPh)(PCy3)(H2IMes)] (0.0192 g,
0.0226 mmol, 5.6 mol-%) were dissolved in CH2Cl2 (11 mL).
Freshly distilled methyl vinyl ketone (100 µL, 1.23 mmol,
3.1 equiv.) was added and the resulting solution stirred at reflux for
3 h, after which time the volatiles were removed under vacuum to
yield a red solid. This was redissolved in toluene (20 mL), the solu-
tion filtered through a short pad of Celite, and the solvents were
evaporated to dryness. The residue was washed with hexane
(2 ϫ 3 mL) at –78 °C and crystallized from CH2Cl2/hexane at
–78 °C. Yield: 0.17 g (0.30 mmol, 75%). M.p. 137–140 °C (CH2Cl2/
hexane). 1H NMR (400 MHz, CDCl3): δ = 1.58 (t, J = 8.0 Hz,
[(C5H4(CH2)2CH=CH2)Ni(Cl){1,3-bis(2,4,6-trimethylphenyl)-4,5-di- 2 H, C5H4CH2CH2), 2.17 (m, 2 H, C5H4CH2CH2), 2.20 [s, 3 H, C(O)-
hydroimidazol-2-ylidene}] (5): 1,1Ј-Bis(but-3-enyl)nickelocene[17i]
(2.23 g, 7.51 mmol) and 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihy-
droimidazolinium chloride[26] (3.22 g, 9.39 mmol) were stirred at
reflux in thf (70 mL) for 11 h. The usual workup provided 1.28 g
(2.47 mmol, 33%) of complex 5 as a red, crystalline solid. 1H NMR
CH3], 2.38 (s, 18 H, o- and p-CH3), 3.92 (s, 4 H, NCH2CH2N),
4.27 (t, J = 2.4 Hz, 2 H, C5H4CH2), 4.48 (t, J = 2.4 Hz, 2 H,
C5H4CH2), 5.96 [dt, J = 16 Hz, 1 H, =CHC(O)], 6.70 (dt, J = 16,
J = 7.2 Hz, 1 H, CH2CH=), 7.06 (s, 4 H, Ar) ppm. 13C NMR
(101 MHz, CDCl3): δ = 18.52 (o-CH3), 21.11 (p-CH3), 26.60 [C(O)-
(400 MHz, CDCl3): δ = 1.51 (t, J = 7.8 Hz, 2 H, C5H4CH2CH2), CH3], 25.51 (C5H4CH2CH2), 30.30 (C5H4CH2CH2), 50.88
2.00 (m, J = 7.8, J = 1.2 Hz, 2 H, C5H4CH2CH2), 2.38 (s, 18 H, o-
and p-CH3), 3.91 (s, 4 H, NCH2CH2N), 4.25 (t, J = 2.4 Hz, 2 H,
C5H4), 4.46 (t, J = 2.2 Hz, 2 H, C5H4), 4.83, 4.85, 4.88, 4.93 (m, 2
(NCH2CH2N), 83.08, 97.47, 113.88 (C5H4CH2), 129.34 (Ar),
131.13 [=CHC(O)], 136.89, 138.20, 145.43 (Ar), 148.90 (CH2CH=),
198.97 (C=O), 201.85 (NCN) ppm. IR (KBr): ν = 2919, 1671, 1487,
˜
654
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 648–656

Cyclopentadienylnickel(II) N-Heterocyclic Carbene Complexes
1435, 1267, 976, 852, 793 cm–1. EI MS (70 eV): m/z [58Ni, 35Cl] =
of complex 5 (0.00165 g, 0.00317 mmol) in toluene (0.16 mL) and
the resulting mixture stirred at room temp. for 30 min. During this
time the color of the solution changed from red to green (for com-
plexes 6–8 a dark precipitate formed instantly after MAO was
added). Styrene (neat, 5.50 mL, 48.0 mmol) was added and the re-
action mixture placed in an oil bath maintained at 50 °C. The reac-
tion mixture was stirred at this temperature for 3 h. After cooling
to room temp., 9% aq. HCl (20 mL) was cautiously added to de-
compose the excess MAO. The organic layer was separated and
poured into methanol (200 mL). The precipitated polymer was fil-
tered off, washed with methanol, and dried under high vacuum.
Yield: 2.47 g (49%). The reproducibility was within 5%.
560 [M+], 524 [M – HCl]+. HR EI MS: calcd. for C32H3935ClN2
-
58
NiO 560.21044; found 560.20949. C32H39ClN2NiO (561.84): calcd.
C 68.34, H 7.00, N 4.99; found C 67.82, H 7.21, N 5.20. Crystals
suitable for X-ray measurement were grown from a CH2Cl2/hexane
solution at room temp.
[(C5H4(CH2)2CH=CHC(O)OCH3)Ni(Cl){1,3-bis(2,4,6-trimethyl-
phenyl)-4,5-dihydroimidazol-2-ylidene}] (8): Complex
5 (0.16 g,
0.31 mmol) and [RuCl2(=CHPh)(PCy3)(H2IMes)] (0.0140 g,
0.0165 mmol, 5.3 mol-%) were dissolved in CH2Cl2 (8.0 mL).
Freshly distilled methyl acrylate (90 µL, 1.00 mmol, 3.2 equiv.) was
added and the resulting solution stirred at reflux for 3.5 h, after
which time the volatiles were removed under vacuum to yield a red
solid. This was redissolved in toluene (20 mL), the solution filtered
through a short pad of Celite, and the solvents were evaporated to
dryness. The residue was washed several times with hexane at 0 °C
and at room temp. to obtain a bright-red solid. Yield: 0.14 g
Typical Procedure for the Polymerization of Phenylacetylene: A tol-
uene solution of MAO was added to a toluene (2.0 mL) solution
of complex 1 (0.0050 g). The resulting solution was stirred at room
temp. for 30 min. An appropriate volume of neat phenylacetylene
was added and the reaction mixture placed in an oil bath main-
tained at 75 °C. The reaction mixture was stirred at this tempera-
ture for 5 h. The resulting polymer was isolated as a yellow solid
as described above for polystyrene.
1
(0.24 mmol, 78%). H NMR (400 MHz, CDCl3): δ = 1.58 (t, J =
7.6 Hz, 2 H, C5H4CH2CH2), 2.14 (m, 2 H, C5H4CH2CH2), 2.38 (s,
18 H, o- and p-CH3), 3.70 (s, 3 H, OCH3), 3.92 (s, 4 H,
NCH2CH2N), 4.27 (t, J = 2.4 Hz, 2 H, C5H4CH2), 4.46 (t, J =
2.4 Hz, 2 H, C5H4CH2), 5.72 [dt, J = 15.6, J = 1.6 Hz, 1 H,
=CHC(O)], 6.70 (dt, J = 15.6, J = 6.8 Hz, 1 H, CH2CH=), 7.06 (s,
4 H, Ar) ppm. 13C NMR (101 MHz, CDCl3): δ = 18.52 (o-CH3),
21.09 (p-CH3), 25.29 (C5H4CH2CH2), 29.95 (C5H4CH2CH2), 50.88
(NCH2CH2N), 51.29 (O-CH3), 83.12, 97.36, 114.14 (C5H4CH2),
120.50 [=CHC(O)OCH3], 129.34 (m-Ar), 136.90, 138.20 (Ar),
149.79 (CH2CH=), 167.18 [C(O)OCH3], 202.02 (NCN) ppm. IR
Crystal Structure Determination: Crystal data collection and refine-
ment parameters for complexes 2 and 7 are summarized in Table 3.
Preliminary examination and intensity data were carried out with
a Kuma KM4 κ-axis diffractometer with graphite-monochromated
Mo-Kα radiation (λ = 0.71073 Å). Lorentz, polarization and ab-
sorption corrections were applied for all collected reflections. The
structures were solved by direct methods and refined by the full-
matrix least-squares method on all F2 data by using the SHELXTL
6.14 program.[28] CCDC-745005 (for 2) and -745006 (for 7) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(KBr): ν = 2919, 1719, 1787, 1439, 1267, 1032, 855, 789 cm–1. EI
˜
MS (70 eV): m/z [58Ni, 35Cl] = 576 [M+], 540 [M – HCl]+. HR EI
MS: calcd. for C32H3935ClN258NiO2 576.20535; found 576.20450.
C32H39ClN2NiO2 (577.83): calcd. C 66.52, H 6.80, N 4.85; found
C 65.97, H 6.66, N 4.86.
Supporting Information (see footnote on the first page of this arti-
1
1
Typical Procedure for the Polymerization of Styrene: A toluene
solution of MAO (0.63 mL, 0.952 mmol) was added to a solution
cle): H-13C HMBC spectrum of complex 2, VT H NMR spectra
of complex 2, and VT 13C NMR spectra of complex 2.
Table 3. Crystallographi data for complexes 2 and 7.
2
7
Empirical formula
Mr
Cell setting, space group
C23H31ClN2Ni
429.66
monoclinic, P21/n
C32H39ClN2NiO
561.81
triclinic, P1
¯
Temperature [K]
a [Å]
b [Å]
c [Å]
α [°]
β [°]
100(2)
11.405 (5)
12.047 (5)
16.244 (6)
90
9.9453(3)
9.9480(3)
15.7420(4)
91.404(2)
106.358(1)
103.509(2)
1446.24(7)
2
90
105.77 (1)
90
2147.9 (15)
4
γ [°]
V [Å3]
Z
Radiation type
Mo-Kα
1.04
Mo-Kα
0.790
µ [mm–1]
Crystal size [mm]
Diffractometer
Absorption correction
0.18ϫ0.18ϫ0.11
Kuma KM-4 CCD kappa-axis diffractometer
analytical CrysAlis CCD, Version 1.171.31, Oxford Diffraction Ltd., 2006; analytical numeric absorp-
tion correction using a multifaceted crystal model based on expressions derived by R. C. Clark, J. S.
Reid, Comput. Phys. Commun. 1998, 111, 243
0.862, 0.914
0.028
0.0566, 0.1036, 1.501
0.0570, 0.1037, 1.501
5170
263
0.53, –0.39
0.09ϫ0.18ϫ0.22
Tmin, Tmax
Rint
0.889, 0.959
0.0339
0.0309, 0.0815, 1.072
0.0426, 0.0873, 1.072
17809
341
0.846, –0.364
R[F2 Ͼ 2σ(F2)], wR(F2), S
Rall, wR(F2), Sall
No. of independent reflections
No. of parameters
∆ρmax, ∆ρmin [eÅ–3]
Eur. J. Inorg. Chem. 2010, 648–656
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
655

W. Buchowicz et la.
FULL PAPER
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C. P. Newman, R. J. Deeth, G. J. Clarkson, J. P. Rourke, Orga-
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This work was financially supported by the Polish Ministry of Sci-
ence and Higher Education (grant no. PBZ-KBN-118/T09/03). Sin-
gle-crystal X-ray measurements for 7 were obtained at the Struc-
tural Research Laboratory of the Chemistry Department, Warsaw
University, Poland. S. R. L. was supported financially by the Euro-
pean Regional Development Found in the Sectoral Operational
Programme “Improvement of the Competitiveness of Enterprises,
years 2004–2006” (Project no. WKP_1/1.4.3./1/2004/72/72/165/
2005/U). A. M. thanks the Polish Ministry of Science and Higher
Education for a doctoral grant (NN204030233), and additional
support from the Foundation for the Polish Science (2008 grant for
young researchers). K. W. and A. M. thank the Foundation for the
Polish Science for a Masters Award.
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Received: August 26, 2009
Published Online: December 18, 2009
656
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Eur. J. Inorg. Chem. 2010, 648–656