Dual Catalysis of the Selective Polymerization of Biosourced Myrcene and Methyl Methacrylate Promoted by Salicylaldiminato Cobalt(II) Complexes with a Pendant Donor

Article abstract of DOI:10.1021/acs.organomet.8b00708

Cobalt complexes (Co1-Co6) bis-chelated by phenoxy (4,6-di-tert-butyl-2-phenol, naphthalen-2-ol)-imine ligands containing pendant hard oxygen (Co1 and Co4), soft sulfur (Co2 and Co5), or phosphine donors (Co3 and Co6) are reported for dual catalysis of selective polymerization for biosourced myrcene and methyl methacrylate (MMA). X-ray analysis reveals that the complexes features a distorted octahedral coordination of the cobalt center binding with phenolate oxygen, imine nitrogen, and pendant donor (P for Co3 and S for Co5). Activated by MMAO or AlⁱBu₃, all precursors are able to not only convert myrcene to cis-1,4-polymyrence but also polymerize MMA resulting in poly(methyl methacrylate) (PMMA) with moderate syndiotacticity. The introduction of pendant donor concurrently improves activity and stability particularly at 60-80 °C for polymerizations of both monomers. The enhanced activity and selectivity observed in myrcene cis-1,4 polymerization promoted by the sulfur and oxygen containing catalysts may relate to the weak Co-X (X = O, S) interaction, facilitating myrcene coordination. However, the donor effect on MMA polymerization activity is reversed, with phosphine donated catalyst demonstrating remarkably enhanced activity. This study represents the first example of cobalt catalyzed polymerization of both polar and nonpolar functions via possible mechanisms differentiated by pendant donor and also may provide valuable insights into their essential role in mediating the polymerization process.

Full text of DOI:10.1021/acs.organomet.8b00708

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Dual Catalysis of the Selective Polymerization of Biosourced
Myrcene and Methyl Methacrylate Promoted by Salicylaldiminato
Cobalt(II) Complexes with a Pendant Donor
Xiaoyu Jia, Wenxin Li, Junyi Zhao, Feiyan Yi, Yunjie Luo, and Dirong Gong*,†
‡
,§
†
†
†
†
†
Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, P. R. China
‡
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, No.1799, Jimei
Road, Xiamen, Fujian 361021, P. R. China
§
Ningbo Urban Environment Observation and Research Station-NUEORS, Chinese Academy of Sciences, Ningbo, Zhejiang
3
15830, P. R. China
*
S Supporting Information
ABSTRACT: Cobalt complexes (Co1−Co6) bis-chelated by phenoxy
4,6-di-tert-butyl-2-phenol, naphthalen-2-ol)-imine ligands containing
(
pendant hard oxygen (Co1 and Co4), soft sulfur (Co2 and Co5), or
phosphine donors (Co3 and Co6) are reported for dual catalysis of
selective polymerization for biosourced myrcene and methyl meth-
acrylate (MMA). X-ray analysis reveals that the complexes features a
distorted octahedral coordination of the cobalt center binding with
phenolate oxygen, imine nitrogen, and pendant donor (P for Co3 and S
i
for Co5). Activated by MMAO or Al Bu , all precursors are able to not
3
only convert myrcene to cis-1,4-polymyrence but also polymerize MMA
resulting in poly(methyl methacrylate) (PMMA) with moderate
syndiotacticity. The introduction of pendant donor concurrently
improves activity and stability particularly at 60−80 °C for polymer-
izations of both monomers. The enhanced activity and selectivity
observed in myrcene cis-1,4 polymerization promoted by the sulfur and oxygen containing catalysts may relate to the weak Co−
X (X = O, S) interaction, facilitating myrcene coordination. However, the donor effect on MMA polymerization activity is
reversed, with phosphine donated catalyst demonstrating remarkably enhanced activity. This study represents the first example
of cobalt catalyzed polymerization of both polar and nonpolar functions via possible mechanisms differentiated by pendant
donor and also may provide valuable insights into their essential role in mediating the polymerization process.
INTRODUCTION
(CH Si(CH ) ) PNP and LuCH Si(CH ) SNS for 3,4-poly-
2 3 3 2 2 3 3
■
myrcene (PNP, iminophosphonamide; SNS, β-diimidosulfo-
The polymerization of isoprene and butadiene has been one of
the most important industrial processes to access to high
performance rubber; however, the field is encountering the
increased likelihood of gradual exhaustion of petroleum
5
6
nate), Lu(CH Ph) PNP for trans-1,4-polymyrcene, and
2
2
titanium dithiolate (TiOSSO) complexes for polymyrcene
7
with trans-1,4, 3,4, and cis-1,4 mixed structures. In polymer-
1
ization of conjugated dienes, cobalt-based systems have
received the earliest recognition in both academic and
commercial production of polybutadiene due to easy
resources and environment pollution. Motivated by the
surge of sustainability in this field, exploitation of renewable
polymers derived mostly or entirely from biosources that can
resemble and replace the fossil based elastomer has attracted
8
9
preparation, high stability, and versatile selectivities,
particularly, the unique 1,2-stereoselectivities in polymerization
1
c
considerable attention from industry and academic sectors.
10
of some substituted butadienes. Nevertheless, they have been
β-Myrcene (7-methyl-3-methylene-1,6-octadiene), resembling
the chemical structure of many petro-based olefins, can be
found within the essential oil of various plants and can be
produced on a commercial scale by the pyrolysis of β-pinene.
Radical (co)polymerization of myrcene has provided an entry
rarely relevant for syntheses of cis-1,4-polyisoprene and
1
1,12
-polymyrcene,
probably due to steric factors disfavoring
+
2
monomer coordination and insertion to a smaller radius Co .
In the meanwhile, production of functionalized olefinic
polymers with polar groups by direct synthesis has been one of
the most challenging research goals hardly achieved by
3
to a novel type of biosourced elastomer. In the meanwhile,
metal catalyzed highly specific polymerization of myrcene has
been also reported for regular polymyrcene based materials;
however, examples have been limited to the Nd-
Received: September 30, 2018
4
(
BH ) (THF) /BEM complex for cis-1,4-polymyrcene, Lu-
4
3
3
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00708
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Organometallics
Article
1
3
conventional industrial chemical process. In this aspect,
cobalt catalyst has been also attractive due to low oxophilic and
higher tolerance to moisture and oxygen, avoiding masking
polar functionalities. Although many cobalt complexes have
been developed for mediating radical (co)polymerization of
structural and catalytic properties of the ligand-supported
27
transition metal complexes, very little is known about the
structures of their cobalt counterparts and few have been
reported for polymerizations of myrcene or polar mono-
8c,d,28
mers.
In order to gain insight into the polymerizations of
14
15
polar monomers such as MMA, vinyl acetate, acryloni-
both functions by cobalt catalysts, the current work focuses on
syntheses, structure analyses, and dual polymerization catalysis
by a series of cobalt complexes with tridentate salicylaldiminate
paired with oxygen, sulfur, and phosphine donors.
1
6
17
trile, and ethylene, coordinative polymerization of polar
monomers by cobalt metal is still a challenging endeavor,
because simple coordination of the functional group to the
metal may hamper monomer activation. Till now, reported
catalysts have been limited to N,N-di(2-picolyl)amine Co-
RESULTS AND DISCUSSION
■
1
8
19
(
II), bis(salicylaldiminate)-Co(II) complexes, and Co(II)-
20
Synthesis and Characterization of Ligands and
Complexes. Phenoxy imine-thio (S), ester (O), and
phosphine (P) ligands including different combinations of
phenoxy and donor substituents have been designed. Their
phenolate complexes, Co1−Co6, depicted in Scheme 1, have
been prepared by treating cobalt acetate with 2.0 equiv of the
corresponding ligands in refluxed ethanol under a nitrogen
atmosphere.
Pyridyl bis(imine)/MAO for low efficiency MMA polymer-
ization. The strong binding of ester functionality to the metal
center via η -chelation retarding the chain-growth reaction is
responsible for the low activities, and so far there have been no
general ways to improve the catalytic activity and selectivity, as
well as the stability.
4
Generally, the development of coordination catalysts has
met limited monomer versatilities, for example, catalysts
efficient for nonpolar monomers are usually not active for
polar monomers, and vice versa. The discoveries of a handful
of competent polymerization catalysts capable of performing
both polar and nonpolar functions at our disposal seemingly
ease the dilemma, but the mechanism has not yet been
elucidated. On the other hand, it becomes more and more
difficult, as well as costly, to synthesize new catalysts that are
applicable for limited monomers and as a result increasingly
difficult to discover new polymerization strategies or new
materials. Therefore, studies into alternative catalyst design
strategies are important for addressing both functions.
Considering different polymerization mechanisms that could
be operating for different type of monomers, a single catalyst
that is able to polymerize different monomers, namely, “dual
catalysis”, via a switchable mechanism is highly attractive. And,
their potential dual catalysis performance for both functions is
also desirable but still challenging.
Scheme 1. Structures of Cobalt Complexes Studied in the
Work
In the late 1990s, the exploration of catalysts incidentally led
three groups to independently discover that certain salicylaldi-
mine (phenoxy-imine) compounds could serve as excellent
ligands for olefin insertion polymerization catalysts with
2
1
1H NMR spectra were recorded at room temperature, and
those of Co1 and Co3 are displayed in Figure 1 and Figure 2,
respectively. Cobalt(II) complexes Co1, Co2, Co4, and Co5
give rise to paramagnetic NMR spectra with relatively sharp
resonances in the range of −7.76 to 57.12 ppm probably due to
transition metals. These discoveries have invoked renewed
interest in this conventional and yet versatile ligand motif and
spurred intense research into its associated chemistry around
the globe. These ligands benefit from ease of synthesis and
amenability to structural and electronic modifications, which
have resulted in extremely rich and diverse ligand libraries.
Moreover, the phenoxy-imine ligands can act on different
metals over a wide range of the periodic table, resulting in
7
5
2
the rapid electron relaxation of the high spin d (t
e
2
g
g
29
configuration) systems. As shown in Figure 1, the cobalt(II)
complex Co1 displays resonances arising from eight of the nine
nonequivalent H atoms, but one signal is not detected,
presumably due to its close vicinity to the paramagnetic metal
2
2
23
24
25
superb olefin, diene, acrylate, cyclic ester, and alcohol
(
(
co)polymerization catalysts, and a very similar ligand design
position, size, and nature of substituents) has been often used
3
0
center and a resulting substantial dipolar relaxation.
in order to maximize catalytic performance. The phenoxy-
However, 2-D NMR for full assignment for each peak is
discouraging due to its low intensity even if the acquisition
time is prolonged. The isostructural Co2 displays a similar
NMR behavior to that of Co1. As anticipated, the -OMe
imine ligands can be further classified into bridged tetradentate
21
[
O,N,N,O] ligands, including classical salen and salphen, and
tridentate [O,N,X] or [O,N,L] phenoxy-imine ligands that
have pendant donors (X or L) bearing a Lewis base group in
1
complex Co5 shows H NMR spectrum similar to that of the
21,26
addition to an inert fragment.
The tridentate ligands have
-SMe complex Co4. The magnetic measurements calculated by
Evans method for Co1, Co2, Co4, and Co5 lead to effective
magnetic moments between 3.99 and 4.39 μB, which are in the
been attracting substantial interests in olefin polymerization
catalysis, where judiciously designing the pendant donor is able
to delicately tune the electronic and steric environment of the
metal center via proximate and flexible metal-donor coordina-
tion. Despite the wide research work on the syntheses and
7
expected range for Co(II) with octahedral geometry and d
5
2
30
high spin (t e ) configuration. The phosphine donated
2
g
g
complexes Co3 and Co6, however, are fall in the range of
B
DOI: 10.1021/acs.organomet.8b00708
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Article
1
Figure 1. H NMR spectrum of complex Co1.
1
Figure 2. H NMR spectrum of complex Co3.
8
.38−0.76 ppm in 1H NMR spectra with all detectable
protons. As in Figure 2, two tert-butyl proton sets down-shift to
.75 and 1.13 ppm, respectively, and protons in the aromatic
0
region also slightly shift with respect to those of free ligand.
Inferred from the effective magnetic moments valued at 1.99
μB and 2.14 μB, respectively, the Co(II) for Co3 and Co6
7
6
g
1
30
probably adopts d low spin (t2 e ) configuration. The low
g
spin state for both Co3 and Co6 supports that phosphine has
more electron donating capability than oxygen and sulfur
atoms, though steric effect may also play a minor role. The
+
mass spectra display an intact molecule of [M] as the highest
m/z ion peak. The cyclic voltammetry was also applied for
analyzing the electron property which is an important
parameter for evaluating catalysis properties. All the complexes
exhibit two successive anodic irreversible waves, I and II , at
potential ranges of −0.75 to −0.54 V and 0.0 to 0.3 V versus
SCE, respectively (see example in Figure 3 for Co1). The
former wave can be tentatively assigned to the Co(II)
Figure 3. Cyclic voltammetry of complex Co1 (analysis conditions
are included in the Experimental Section).
ox
ox
C
DOI: 10.1021/acs.organomet.8b00708
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Article
conversion to Co(III) and the latter to ligand based oxidation,
which are close to those found for salicylaldimine cobalt(II)
2
9,30
compounds.
Intense, broad, and irreversible cathodic
red
waves (E ) were also detected in the ranges of −0.15 to
0.13 V and −0.75 to −0.55 V versus SCE, which are believed
p
−
to involve the Co(II) to Co(I) and Co(0) conversions. The
cyclic voltammetry, however, does not allow us to distinguish
the complexes supported by different donors. In addition,
crystals of complexes Co3 and Co5 suitable for structure
analyses were developed from dichloromethane solutions. The
complex Co6, however, is cocrystallized with 2-hydroxynaph-
thalene-1-carbaldehyde decomposed from the complex, and its
a
crystal parameters are appended in a footnote. Crystallo-
graphic data for Co3 and Co5 are provided in the Supporting
Information. Selected bond lengths and angles for Co3 and
Co5 are provided in Figures 4 and 5, respectively.
Figure 5. Drawing of complex Co5. Hydrogen atoms are omitted for
clarity. Selected bond length (Å) and angles (deg): Co1−O1
1.907(3), Co1−O1 1.907(3), Co1−N1 1.922(4), Co1−N1
1
.922(4), Co1−S1 2.2186(13), Co1−S2 2.2186(13), O1−Co1−O1
0.00(18), O1−Co1−N1 86.23(12), O1−Co1−N1 94.86(12), O1−
9
Co1−N1 94.86(12), O1−Co1−N1 86.23(12), N1−Co1−N1
1
78.46(16), O1−Co1−S1 175.77(9), O1−Co1−S1 91.92(10), N1−
Co1−S1 89.85(9), N1−Co1−S1 89.03(9), O1−Co1−S1 91.92(10),
O1−Co1−S1 175.77(9), N1−Co1−S1 89.02(9), N1−Co1−S1
89.85(9), S1−Co1−S1 86.42(7).
2
.2053(14) for Co3) are slightly longer than the Co−S (Co1−
S1 2.2186(13) Å, Co5), probably due to the more electronic
23
donating capability of P donor, and this also means Co−S is
more labile. The bond angles sum of C18−S1−Co1 115.6(4)°,
C18−S1−C1 101.6(4)°, and C1−S1−Co1 96.69(14)° is
3
23
313.89°, suggesting that the S atom in Co5 is sp -hybridized.
These results show that the side arm could readily modulate
the spatial and the electronic properties of the metal center and
thus possibly tune the catalytic performance, which will be
discussed in the following sections.
Polymerization of Myrcene. Polymerizations of myrcene
were conducted with variable cocatalysts. MMAO shows the
best cocatalyst activity (entry 1, Table 1), whereas the use of
Figure 4. Drawing of complex Co3. Hydrogen atoms and H O are
omitted for clarity. Selected bond lengths (Å) and angles (deg):
Co1−O2 1.915(4), Co1−O1 1.914(3), Co1−N1 1.923(3), Co1−N2
2
aluminumalkyls proves detrimental to the catalyst, partially
1
8
.934(4), Co1−P2 2.2053(14), Co1−P1 2.2075(14), O2−Co1−O1
5.88(14), O2−Co1−N1 84.85(14), O1−Co1−N1 96.20(15), O2−
i
(
Al Bu , entry 2, Table 1) or completely (AlEt , entry 3, Table
3
3
1
) inhibiting the polymerization activity. Thus, the effects of
Co1−N2 95.91(15), O1−Co1−N2 84.68(15), N1−Co1−N2
1
78.88(16), O2−Co1−P2 172.70(13), O1−Co1−P2 88.00(13),
a
N1−Co1−P2 91.71(15), N2−Co1−P2 87.59(15), O2−Co1−P1
8
Table 1. Myrcene Polymerization by Cobalt Catalysts
8.17(13), O1−Co1−P1 172.68(11), N1−Co1−P1 87.46(12),
d
T
conv
Mn
×
N2−Co1−P1 91.74(12), P2−Co1−P1 98.07(5).
entry complex monomer (°C) (%)
10 4
−
PDI
d
3,4/cis-1,4
e
1
2
3
4
5
6
7
8
9
1
1
1
1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co2
Co3
Co4
Co5
Co6
MY
MY
MY
MY
MY
MY
IP
BD
MY
MY
MY
MY
MY
30
30
30
0
60
90
60
60
60
60
60
60
60
83.2
24.2
5.4
20.8
7.9
f
2.5
3.1
f
4.7/95.3
8.3/91.7
f
As shown in Figures 4 and 5, X-ray crystallographic analyses
of complexes reveal that two ligands are situated perpendic-
ularly to minimize the steric congestion and coordinate the
cobalt atom with phenolate oxygen, imine nitrogen, and
pendant donor (P for Co3 and S for Co5), similar to the
b
c
78.5
89.2
80.4
85.9
86.5
94.3
55.1
90.1
92.1
43.1
22.9
20.4
17.2
15.7
15.6
21.5
25.3
27.2
28.2
31.2
2.1
2.6
3.2
1.9
2.5
2.1
2.3
2.2
2.0
1.8
3.3/96.7
5.6/94.4
9.7/90.3
23.5/76.5
2.8/97.2
8.3/91.7
24.7/75.3
7.9/92.1
9.2/90.8
25.1/74.9
31
titanium analogues. Both complexes feature a distorted
octahedral coordination of the cobalt center in which the five
atoms, that is, Co, O1, O2, and two pendant atoms, are nearly
coplanar, with the sum of four equatorial angles of nearly 360°.
The N atoms occupy at the two axial points via trans-
configuration and form an axial angle N1−Co−N2 of nearly
0
1
2
3
1
1
80° (the angle of N1−Co−N2 is in the range of
78.42(18)°−178.99(19)°). Alternatively, two oxygen anions
and the two pendant atoms are both cis-positioned. Complex
a
Polymerization conditions: isoprene and myrcene, 10.0 mmol;
activator, MMAO, [Al]/[Co] = 300 except as noted; solvent, toluene;
total volume, 10 mL; reaction time, 2 h. T for all polymyrcene was in
the range of −61.3 to −70.3 °C. Al( Bu) . AlEt . Determined by
GPC. Calculated by H NMR. Not determined.
Co3 differs in bond distances Co−O1 vs Co−O2, Co−N1 vs
Co−N2, and Co−P1 vs Co−P2; however, complex Co5 is C
S
g
b
i
c
d
symmetrical, and bond distances for each pair are identical.
3
3
e f
1
The Co−P bond distances (Co1−P1 2.2075(14), Co1−P2
D
DOI: 10.1021/acs.organomet.8b00708
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1
Figure 6. H NMR of polymyrcene obtained from entry 5, Table 1.
cocatalyst loading, reaction temperature, and catalyst were
investigated under activation with MMAO. Varying the
temperature shows that the best activity is reached at 60 °C
resulting in polymyrcene with a much higher M of (2.72−
n
5
3.12) × 10 g/mol and a lower PDI of 1.8−2.2 (entries 11−13,
Table 1). The donor induces the same trend in stereocontrol,
-OMe (Co4, cis-1,4 = 92.1%) > -SMe (Co5, cis-1,4 = 90.8%) >
(
entry 5, Table 1), which provides a polymer yield of 89.2%.
The stereospecificity of Co1 shows little sensitivity to changes
in temperature (entries 1 and 4−6, Table 1), which implies
that conformational dynamics or changes responsible for the
different polymer microstructures are negligible despite the
− PPh (Co6, cis-1,4 = 74.9%). The reason for this reduced
2
activity in phosphine ligated complexes is possibly too strong
binding and too great a steric hindrance that to a certain
degree causes substantially reduced monomer access. The
coordinative flexibility in O and S donors could facilitate
metal−donor dissociation thereby increasing monomer−metal
binding and simultaneously increasing the selectivity. Probably,
in these cases only the P atom remains coordinated to the
cobalt atom, as suggested by production of a polymer with a
1
temperature variation (Figure 6, H NMR of polymer entry 5,
Table 1,). It should be noted that acceptable activity and
selectivity are still maintained at 90 °C (entry 6, Table 1),
suggesting improved stability of the active species possibly via
saturation of the metal coordinative vacancy by the O-donor.
These enhanced performances are consistent with those of
8f,g
higher 1,2 content.
2
5b,26a
titanium and vanadium catalysts
compared to the Schiff-base cobalt analogues without pendant
donors.
and are remarkable
Polymerization of MMA. In order to explore the catalytic
potential of Co1−Co6 for MMA polymerization and on
PMMA properties, the reaction parameters such as Al type,
[Al]/[Co] ratio, reaction temperature, and MMA feed were
systematically modified using Co1 as precatalyst, and the other
complexes were compared at the optimized conditions. As the
data collected in Table 2, when they were associated with an
exogenous organic aluminum compound, all cobalt complexes
are active in the MMA polymerization. Polymerizations by
either metal compounds or MAO alone show no activity,
demonstrating that binary components are necessary to initiate
the polymerization of MMA.
8
c,d
The molecular weight distribution of the polymer
becomes broader but still unimodal in the GPC, in agreement
with the accelerated chain transfer rate diagram. The catalyst is
also efficient for isoprene (entry 7, Table 1) and butadiene
(
entry 8, Table 1) polymerizations, providing essential cis-1,4
polymers known for cobalt catalysts.
To establish the correlation of structural variations in the
precatalysts with their catalytic performances in myrcene
polymerization, all of the remaining cobalt complexes (Co2−
Co6) were also studied under these conditions. Indeed, the
nature of donor on the phenoxy-imine ligand affects the ability
of the catalyst to control monomer enchainment in the
polymerization of myrcene. The complexes Co1 and Co2
MAO (entry 1, Table 2), MMAO (entry 2, Table 2), and
AlEt (entry 3, Table 2) are all efficient in activating Co1 for
3
polymerization with a lower degree of monomer conversion
i
(
entry 9, Table 1) with pendant groups containing oxygen and
and syndiotactic selectivity (rr) than those initiated by Al Bu
3
sulfur donors, respectively, show much higher activity than that
of Co3 (entry 10, Table 1) under comparable conditions. With
respect to the selectivity, it seems to follow grossly the type of
donor, -OMe (Co1, cis-1,4 = 94.7%) > -SMe (Co2, cis-1,4 =
(entry 4, Table 2). The molecular weights of the resultant
i
PMMAs are also lower than that achieved with Al Bu . This
3
may reflect the occurrence of transfer to the MAO, MMAO,
and AlEt side reactions under such conditions, as supported
3
9
1.7%) > -PPh (Co3, cis-1,4 = 75.3%). Compared with Co1,
by the fairly broad dispersity values. Considering the feeding
2
i
Co2 and Co3 give polymers with higher molecular weight and
narrower molecular weight distribution, probably resulting
from synergic effects of steric hindrance and the electronic
properties of the pendant group. We observed comparable
specificity and activity of catalysts of the other series but the
amount and the cost of activator, herein, Al Bu was selected
3
for further study.
Reaction changes in the [Al]/[Co] ratio and temperature
displays a profound effect on the catalytic activities and
characteristic properties of the resultant PMMA. When the
E
DOI: 10.1021/acs.organomet.8b00708
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Article
a
Table 2. MMA Polymerization Results by Cobalt Catalysts
those of salicylaldiminato cobalt complexes without additional
18a
donor.
The reaction proceeded with higher syndiotactic
[
Al]/
T
conv
(%)
M ×
n
−4
selectivity (75%) when it was carried out at a lower
temperature (entry 8, Table 2), indicating that active species
entries complexes [Co] (°C)
10
PDI
mm/mr/rr
b
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co1
Co2
Co3
Co4
Co5
Co6
300
300
60
60
20
40
80
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
0
30
80
100
60
60
60
60
60
43.6
40.6
52.6
59.9
35.1
48.0
56.4
32.4
51.5
47.8
42.6
53.3
75.6
40.3
43.3
72.6
4.44
6.57
8.57
11.57
13.95
10.8
7.45
7.76
8.02
5.84
5.21
8.34
14.8
7.83
8.94
14.1
2.72
2.87
2.38
1.42
1.81
1.60
1.91
1.41
1.50
1.93
2.23
1.67
2.05
1.62
1.99
2.67
8/35/57
9/38/53
4/35/61
5/29/66
8/31/61
2/30/68
2/28/70
4/21/75
8/25/67
16/29/55
16/31/53
6/30/64
2/13/85
5/29/66
7/30/63
6/21/73
c
geometry is more stable. Notably, as the temperature increased
i
d
from 0 to 100 °C or as the molar ratio of [Al]/[Co] of Al Bu
3
increased from 20 to 100, the molecular weight of PMMA
almost monotonously drops and displays a wider molecular
1
8
weight distribution.
literature
These findings agree with the
2
0,21
and can be ascribed to either the higher molar
ratio of [Al]/[Co] or higher temperature increasing the rate of
chain transfer in comparison to chain propagation. However,
all of the polymer samples at different temperatures or molar
ratios of [Al]/[Co] display unimodal and narrow molecular
weight distributions, suggesting that single site active species
are involved throughout the polymerizations. To rule out a
radical mechanism, the reactivity of the propagating polymer
end was examined by highly active monomer acrylonitrile
0
1
2
3
4
5
6
(
AN); however, the reaction of Co1 with an AN/MMA
a
mixture produces PMMA with no AN incorporation. Addi-
tionally, Co1 is unable to homopolymerize AN.
Complex Co2, with a pendant -SMe group, gives increased
activity (53.3% in yield, entry 12, Table 2); nevertheless,
Polymerization conditions: MMA, 10.06 mmol; activator, Al(i-Bu)3
except as noted; solvent, toluene; total volume, 10 mL; reaction time,
b
c
d
4
h. MAO. MMAO. AlEt .
3
complex Co3, bearing -PPh group, produces substantially
2
[
Al]/[Co] ratio was increased from 20 to 80 and the
temperature was kept constant at 60 °C (entries 4−7, Table
), an [Al]/[Co] ratio of 60 was found to be the best; a lower
increased polymer under the same polymerization conditions
(75.6% in yield, entry 13, Table 2). The stereoselectivity also
2
benefits from the -PPh group. The catalytic activity and
2
or higher ratio of cocatalyst shows reduced activities. The
selectivity changed in the same order Co4 < Co5 < Co6, but
their performances are slightly lower than those of the
corresponding 2,4-di-tert-butylsacylialdehyde counterparts
Co1, Co2, and Co3, respectively. These may be related to
the use of donor of stronger binding capability to saturate the
coordination sphere of the metal center, which can retard the
ester group. As a result, formation of thermally stable
syndiotactic selectivity is in the range of 61−70%, and a slightly
beneficial effect from the higher cocatalyst feeding is seen
1
(
typical H NMR of entry 6, Table 2 shown in Figure 7).
When the reaction temperature was increased from 0 to 100
C with the [Al]/[Co] ratio fixed at 60 and the reaction
°
running time at 4 h, the activity gradually increased to a
maximum level of 59.9% (entry 4, Table 2). Above 60 °C, the
catalytic activity was maintained at 47.8% at 80 °C (entry 10,
Table 2), but the selectivity slightly dropped at elevated
temperature. Still, a high activity of 42.6% (entry 11, Table 2)
is maintained at 100 °C; the lack of catalyst decomposition or
change highlights the high thermal stability probably ascribed
to the pendant arms, which are again more pronounced than
4
deactivated η -α,β-unsaturated ester intermediate is avoided,
21,27
which has been revealed in the literature.
This dramatic
switch of catalytic performance on two different monomers is
not fully understood but is potentially related to changes in
monomer−metal coordination mode that are affected by the
character of donor. The results probably support that myrcene
4
is more likely coordinated to metal by η -mode; thus more
1
Figure 7. H NMR of PMMA obtained from entry 6, Table 2.
F
DOI: 10.1021/acs.organomet.8b00708
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
labile O−Co and S−Co binding favors monomer access, while
3423 (broad, −OH), 2948 (Ph−H), 1624 (-CN-), 1245 (−C−
O−).
2
η -mode is possibly favorable for MMA coordination where the
2
-((2′-(Methylthio)phenylimino)methyl)-4,6-di-tert-butylphenol
stronger Co−P interaction is more beneficial. This elucidation
is also good agreement with the distinctive spin configurations
of the two types of complexes as revealed by the Evans
method.
1
(
L2). Yield: 61.3%. H NMR (400 MHz, CDCl , ppm) δ: 8.71 (s, 1H,
3
−
CHN), 7.45 (s, 1H, Ar−H), 7.22−7.00 (m, 5H, Ar−H), 2.52 (s,
13
3
H, S−CH ), 1.50 (s, 9H, −CH ), 1.35 (s, 9H, −CH ). C NMR
3
3
3
(
100 MHz, CDCl , ppm) δ: 164.26 (-CN-), 158.85 (HO-Ar),
3
1
1
1
53.04 (Ar−C), 140.49 (Ar−C), 138.12 (Ar−C), 127.82 (Ar−C),
26.76 (Ar−C), 121.21 (Ar−C), 120.29 (Ar−C), 118.84 (Ar−C),
11.97 (Ar−C), 56.11 (S−CH ), 35.52 (CMe ), 34.19 (CMe ), 31.82
CONCLUSIONS
■
3
3
3
In summary, this paper presents using a series of tridentate
phenoxy-imine ligands with a pendant donor (O, S, and P) for
dual catalysis for polymerization of myrcene and methyl
methacrylate. The catalytic system has enhanced thermal
tolerance in polymerization of two monomers, and cis-1,4-
polymyrcene and syndiotactic poly(methyl mathacrylate)
result with acceptable yields in the range of 0−100 °C. The
nature of donor possibly plays a distinctive role in affecting the
method of monomer insertion, and the stronger binding
capability of the P donor catalyst has pronounced activity
toward MMA, whereas more labile O and S type catalysts are
much more active in myrcene polymerization. This work may
be important for potential dual catalysis processes for both
polar and nonpolar monomers.
−1
(
-C−CH ), 29.71 (-C−CH ). IR (KBr, cm ) ν: 3420 (broad,
3
3
−OH), 2956 (Ph-H), 1625 (-CN-), 1244 (−C−O−).
2-((2′-(Diphenylphosphino)phenylimino)methyl)-4,6-di-tert-bu-
1
tylphenol (L3). Yield: 76.1%. H NMR (400 MHz, CDCl , ppm) δ:
3
8
−
.42(s, 1H, −CHN), 7.29−6.89 (m, 16H, Ar−H), 1.42 (s, 9H,
1
3
CH ), 1.30 (s, 9H, −CH ). C NMR (100 MHz, CDCl , ppm) δ:
3
3
3
1
1
1
1
2
63.73 (-CN-), 158.32 (HO-Ar), 152.11 (Ar−C), 140.36 (Ar−C),
37.33 (Ar−C), 136.14 (Ar−C), 134.42 (Ar−C), 133.10 (Ar−C),
30.20 (Ar−C), 128.61 (Ar−C), 125.44 (Ar−C), 118.31 (Ar−C),
17.65 (Ar−C), 35.25 (-CMe ), 34.33 (-CMe ), 31.69 (-C−CH ),
3
3
3
3
1
9.31 (-C−CH ). P NMR (162 MHz, CDCl , ppm): 13.71. IR
3
3
−
1
(KBr)ν/cm : 3424 (broad, −OH), 3056(Ph−H), 1623(-CN-),
1450(-CC−), 1250(−C−O−).
1-((2′-Methoxylphenylimino)methyl)naphthalen-2-ol (L4). Yield:
1
4
2.6%. H NMR (400 MHz, CDCl , ppm) δ: 9.19 (s, 1H, −CHN-
3
)
, 7.99 (d, 1H, Ar−H), 7.70 (d, 1H, Ar−H), 7.61 (d, 1H, Ar−H),
7
.40−7.22 (m, 2H, Ar−H), 7.13−7.01 (m, 2H, Ar−H), 6.94−6.90
EXPERIMENTAL SECTION
13
(
m, 2H, Ar−H), 3.99 (s, 3H, O−CH ). C NMR (100 MHz, CDCl ,
■
3
3
ppm) δ: 175.33(-CN-), 153.11 (Ar−C), 149.93 (Ar−C), 139.44
Materials and Methods. All reactions sensitive to air and
moisture were performed under a dry and air free argon atmosphere
by means of standard Schlenk technique or under an argon
atmosphere in a glovebox. Myrcene and methyl methacrylate was
(Ar−C), 136.19 (Ar−C), 133.42 (Ar−C), 130.44 (Ar−C), 129.25
(Ar−C), 127.09 (Ar−C), 126.28 (Ar−C), 125.36 (Ar−C), 122.45
(Ar−C), 119.21 (Ar−C), 118.44 (Ar−C), 112.34 (Ar−C), 108.98
(
−1
Ar−C), 57.10 (O−CH ). IR (KBr, cm ) ν: 3433(broad, −OH),
distilled from CaH and stored under nitrogen atmosphere. Toluene
3
2
1621 (-CN-), 1445 (-CC−), 1229 (−C−O−).
and THF were refluxed over sodium and vacuum transferred to flask
1
-((2′-(Methylthio)phenyl)imino)methyl)naphthalen-2-ol (L5).
under N atmosphere prior to use. Tri-isobutyl aluminum, triethyl
2
1
Yield: 41.2%. H NMR (400 MHz, CDCl , ppm) δ: 9.21 (s, 1H,
aluminum, MAO (methylaluminoxane), MMAO (tributylaluminox-
ane modified MAO), and anhydrous cobalt acetate were purchased
from Energy Chemical. 3,5-Di-tert-butyl-2-hydroxybenzaldehyde, 2-
hydroxynaphthalene-1-carbaldehyde, 2-(diphenylphosphino)aniline,
3
−
CHN-), 7.98 (d, 1H, Ar−H), 7.72 (d, 1H, Ar−H), 7.63 (d, 1H,
Ar−H), 7.47−7.27 (m, 2H, Ar−H), 7.23−7.07 (m, 2H, Ar−H),
1
3
6.97−6.93 (m, 2H, Ar−H), 4.02 (s, 3H, S−CH
MHz, CDCl
). C NMR (100
3
2
-methoxyaniline, and 2-(methylthio)aniline were available from
3
, ppm) δ: 178.13(-CN-), 151.06 (Ar−C), 149.21
Alfa Aesar without further purification. Ligands (L1−L6) were
synthesized via salicylaldehyde and aliphatic amine condensation
(Ar−C), 138.52 (Ar−C), 134.29 (Ar−C), 131.12 (Ar−C), 129.67
(Ar−C), 128.21 (Ar−C), 126.89 (Ar−C), 125.18 (Ar−C), 123.86
(Ar−C), 121.35 (Ar−C), 118.18 (Ar−C), 117.12 (Ar−C), 111.97
1
13
31
methods. NMR analyses ( H, 400 MHz; C, 100 MHz; and P, 162
MHz) for ligands and polymers were recorded on a Bruker AV400
spectrometer. Elemental analyses for C, H, N, and Co were carried on
Flash 2000-Thermo Scientific CHNO Analyzer and Inductively
Coupled Plasma Mass Spectrometry (icap Q). Mass spectra of cobalt
complexes were analyzed on LC-MS Xeov GS-2 QTOF in methanol
−
1
(Ar−C), 108.28 (Ar−C), 56.26 (S−CH ). IR (KBr, cm ) ν:
3
3420(broad, −OH), 1625 (-CN-), 1486 (-CC−), 1247 (−C−
O−).
1-((2′-(Diphenylphosphino)phenylimino)methyl)naphthalen-2-
1
ol (L6). Yield: 47.1%. H NMR (400 MHz, CDCl , ppm) δ: 9.11 (s,
3
1
H, -CN-), 7.99−7.41 (m, 2H, Ar−H), 7.34−7.01 (m, 18H, Ar−
solution. The molecular weights (M ) and molecular weight
n
1
3
H). C NMR (100 MHz, CDCl , ppm) δ: 177.54 (-CN-), 154.11
distributions (M /M ) of poly(methyl methacrylate) and poly-
3
w
n
(
(
(
(
(
Ar−C), 149.87 (Ar−C), 139.12 (Ar−C), 135.11 (Ar−C), 131.17
Ar−C), 129.66 (Ar−C), 128.87 (Ar−C), 128.24 (Ar−C), 127.78
Ar−C), 127.11 (Ar−C), 126.24 (Ar−C), 125.78 (Ar−C), 110.15
myrcene were measured at 30 °C by gel permeation chromatography
(
(
GPC) equipped with a Waters 515 HPLC pump, four columns
HMW7 THF, HMW6E THF×2, HMW2 THF), and a Waters 2414
−
1
Ar−C). IR (KBr, cm ) ν: 3420 (broad,−OH), 3045 (Ph-H), 1625
-CN-), 1440 (-CC−), 1250 (−C−O−).
refractive index detector. THF was used as eluent at a flow rate of 1.0
mL/min. The values of M and M /M were determined using the
n
w
n
Complexes. To an anhydrous ethanol solution (10 mL) of ligand
polystyrene calibration.
L1 (0.21 mmol) in a 50 mL round-bottomed flask under nitrogen
atmosphere, was slowly added an anhydrous ethanol solution (20
mL) of cobalt acetate (0.1 mmol). The formed solution was refluxed
overnight. A precipitate then formed, which was filtered, washed with
anhydrous n-hexane (30 mL × 3), and dried under vacuum to furnish
a red solid. Complexes Co2, Co4, and Co5 were prepared with a
similar procedure. No precipitate formed when phosphine donated
complexes Co3 and Co6 were being prepared; therefore, ethanol was
removed under vacuum, and a residue resulted, which was washed
with anhydrous n-hexane (30 mL × 3) and dried under vacuum to
furnish a dark red solid.
Ligand and Complex Synthesis and Characterization.
Ligands. Condensation with salicylaldehydes and aliphatic amines
furnished the desired tridentate phenoxy-imine compound in high
yields. This reaction was fast and proceeded without any problem at
26a
refluxing temperature.
-(-(2′-Methoxyphenylimino)methyl)-4,6-di-tert-butylphenol
2
1
(
L1). Yield: 57.8%. H NMR (400 MHz, CDCl , ppm) δ: 8.69 (s, 1H,
3
−
CHN−), 7.43 (s, 1H, Ar−H), 7.20−6.99 (m, 5H, Ar−H), 3.91
1
3
(
s, 3H, O−CH ), 1.48 (s, 9H, −CH ), 1.31 (s, 9H, −CH ). C NMR
3 3 3
(
100 MHz, CDCl , ppm) δ: 163.27 (−CN−), 158.03 (HO−Ar),
3
1
1
1
3
52.19 (Ar−C), 139.60 (Ar−C), 137.36 (Ar−C), 136.31 (Ar−C),
27.17 (Ar−C), 125.82 (Ar−C), 120.43 (Ar−C), 119.24 (Ar−C),
18.04 (Ar−C), 111.15 (Ar−C), 55.12(O−CH ), 34.45 (CMe ),
Cobalt Bis(1-((E)-(2′-(methoxy)phenylimino)methyl)-2,4-di-tert-
1
butylphenolate) (Co1). Yield: 78.5%, red solid. H NMR (400
3
3
−1
3.40 (CMe ), 31.00 (-C−CH ), 28.61 (C−CH ). IR (KBr, cm ) ν:
MHz, CDCl , ppm) δ: 57.58 (s, 1H, -CNH-), 38.66 (s, 1H, -Ar),
3
3
3
3
G
DOI: 10.1021/acs.organomet.8b00708
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
8.45 (s, 1H, -Ar), 10.82 (s, 1H, -Ar), 8.14 (br, 3H, -SCH ), 7.41 (s,
(DMF) and 0.5 M C H BrN as electrolyte, and potential was
scanned from −1.7 to +0.7 V with a scan rate of 100 mV/s.
3
16 36
9
H, −C(CH ) ), 3.47 (s, 9H, −C(CH ) ), 1.38 (s, 1H, -Ar), −7.83
3
3
3 3
−
1
(s, 1H, -Ar). IR (KBr, cm ): 2927, 2881, 1627 (ν ), 1434, 1190,
X-ray Structure Analysis. Crystal data were collected on a
Bruker SMART APEX diffractometer with a CCD area detector with
a graphite monochromated Mo K radiation (λ = 1.71073 Å). The
SMART program package was used to calculate the crystal class and
unit cell, and the reflection data file was generated from the raw frame
data by SAINT and SADABS. The space group of crystal was
determined by XPREP implemented in APEX2. The structures of
complexes were solved by using software SHELXTL-97 and refined
C=N
9
90. Anal. Calcd for Co1, C H CoN O : C, 71.82; H, 7.67; N, 3.81;
44 56 2 4
Co, 8.01%. Found: C, 71.79; H, 7.79; N, 3.88; Co, 8.01%. UV−
visible: 325 nm; μ = 3.99 μB. EI-MS: required 735.3572, found
eff
+
735.73504 [M] .
Cobalt Bis(1-((E)-(2′-(methylthio)phenylimino)methyl)-2,4-di-
1
tert-butylphenolate) (Co2). Yield: 78.5%, red solid. H NMR (400
MHz, CDCl , ppm) δ: 57.57 (s, 1H, -CNH-), 38.71 (s, 1H, -Ar),
3
2
18.49 (s, 1H, -Ar), 10.81 (s, 1H, -Ar), 8.12 (br, 3H, -SCH ), 7.42 (s,
by using full-matrix least-squares method on F . All the hydrogen
3
H, −C(CH ) ), 3.55 (s, 9H, −C(CH ) ), 1.34 (s, 1H, -Ar), −7.74
atoms were added at the calculated positions after hybridization.
Procedure for Myrcene and MMA Polymerization. Polymer-
ization of MMA and myrcene were handled in a glovebox. A 50 mL
sealed flask was sequentially charged with toluene (10.0 mL),
monomer (2 mmol), and the cobalt complex (10 μmol). The
polymerization was initiated by the addition of aluminum cocatalyst at
a set temperature. After a given time, the polymer was poured into a
0.5 wt % acidified methanol solution with 1.0% 2,6-dibutyl-4-methyl
phenol. The precipitated polymers were suction filtered, washed with
methanol (30 mL × 3), and dried under vacuum to a constant weight.
3
3
3 3
−
1
C=N
4
4
56
2
2
2
eff
+
Cobalt Bis(1-((E)-(2′-(diphenylphosphino)phenylimino)methyl)-
1
,4-di-tert-butylphenolate) (Co3). Yield: 78.5%, dark red solid. H
3
6
.61 (s, 1H, -Ar), 1.14 (s, 18H, −C(CH ) ), 0.75 (s, 18H,
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00708.
3
3
■
−
1
−
C(CH ) ). IR (KBr, cm ): 2935, 2879, 1626 (ν ), 1431, 1090,
3 3 C=N
*
S
6
6
5
1
90 (νP‑Ph). Anal. Calcd for Co3, C H CoN O P : C, 75.92; H,
66 70 2 2 2
.76; N, 2.68; Co, 5.64%. Found: C, 75.77; H, 6.79; N, 2.59; Co,
.80%. UV−visible: 335 nm; μ = 1.99 μB. EI-MS: required
eff
+
039.3932, found 1039.3973 [M] .
Cobalt Bis(1-((E)-(2′-(methoxy)phenylimino)methyl)naphthalen-
Crystallographic data for Co3 and Co5 (PDF)
1
2
-olate) (Co4). Yield: 78.5%, red solid. H NMR (400 MHz, CDCl ,
3
ppm) δ: 53.08 (s, 1H, -CNH-), 23.19 (s, 1H, -Ar), 19.31 (s, 1H,
Accession Codes
-
Ar), 18.31 (m, 3H, -Ar), 7.36 (b, 1H, -Ar), 5.78 (b, 3H, -Ar), 3.76 (s,
CCDC 1849236−1849237 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
−
1
1
1
H, -Ar), −5.48 (s, 3H, -SMe). IR (KBr, cm ): 1621 (νC=N), 1437,
117, 700. Anal. Calcd for Co4, C H CoN O : C, 70.70; H, 4.61;
3
6
28
2
4
N, 4.58; Co, 9.64%. Found: C, 70.77; H, 4.49; N, 4.49; Co, 9.50%.
UV−visible: 321 nm; μ = 4.31 μB. EI-MS: required 611.1381, found
eff
+
6
11.17892 [M] .
Cobalt Bis(1-((E)-(2′-(methylthio)phenylimino)methyl)-
1
naphthalen-2-olate) (Co5). Yield: 78.5%, red solid. H NMR (400
AUTHOR INFORMATION
Corresponding Author
E-mail: gongdirong@nbu.edu.cn.
MHz, CDCl , ppm) δ: 53.06 (s, 1H, -CNH-), 23.10 (s, 1H, -Ar),
3
■
9.41 (s, 1H, -Ar), 18.09 (m, 3H, -Ar), 7.32 (b, 1H, -Ar), 5.73 (b, 3H,
−
1
*
), 1433, 1077, 690 (ν ). Anal. Calcd for Co5,
P‑Ph
ORCID
C H CoN S O : C, 67.17; H, 4.38; N, 4.35; Co, 9.16%. Found:
36
28
2
2
2
Feiyan Yi: 0000-0003-0733-9712
Yunjie Luo: 0000-0002-2480-1385
Dirong Gong: 0000-0002-9791-9261
C, 66.81; H, 4.47; N, 4.27; Co, 9.20%. UV−visible: 323 nm; μ
=
eff
+
4
.39 μB. EI-MS: required 643.0924, found 643.0757 [M] .
Cobalt Bis(1-((E)-(2′-(diphenylphosphino)phenylimino)methyl)-
1
naphthalen-2-olate) (Co6). Yield: 68.5%, dark solid. H NMR
Notes
400 MHz, CDCl , ppm) δ: 8.36 (s, 1H, -CNH-), 8.18 (s, 1H,
3
The authors declare no competing financial interest.
−1
C=N
P‑Ph
Calcd for Co6, C H CoN O P : C, 75.73; H, 4.60; N, 3.05; Co,
ACKNOWLEDGMENTS
58
42
2
2
2
■
6
3
.41%. Found: C, 75.89; H, 4.69; N, 2.99; Co, 6.37%. UV−visible:
This work is supported by the Natural Science Foundation of
Zhejiang (Grant LY17E30002), the Natural Science Founda-
tion of China (Grants 21507126 and 21304050), and the
Natural Science Foundation of Ningbo (Grants 2016A610045,
and 2017A610055). This work is also sponsored by K. C.
Wong Magna Fund in Ningbo University.
32 nm; μ = 2.14 μB. EI-MS: required 920.2104, found 920.9356
eff
+
[
M] .
Magnetic Susceptibility Measurements. Magnetic measure-
1
ments were performed by solution H NMR using the Evans’ method
on a Bruker Avance 400 spectrometer operating at 400.13 MHz at
room temperature. The measurements were performed in a standard
5
mm NMR tube containing the cobalt complex sample dissolved in
DMSO-d (4.1 wt % TMS), against a coaxial reference tube filled with
the same solvents.
ADDITIONAL NOTE
6
■
a
Complex Co6·2C H O (deposited CCDC number
1
1
8
2
Cyclic Voltammetry Studies. The CV measurements were
conducted on a CHI1100A electrochemical workstation (Chenhua
Instrument Company, Shanghai, China) with scan rates of 0.1 V/s.
The electrolytic cell used is a conventional three-electrode system,
which contains a glass carbon electrode (GCE, 3 mm diameter, Gaoss
Union, Wuhan, China) as working electrode, a Ag/AgCl (3 M KCl)
electrode as reference electrode, and a platinum coil as counter
electrode. The electrode was immersed in dimethyl formamide
1
1
1
8
3
849238). Formula: C H CoN O P . Molecular weight:
8
0
58
2
6 2
̅
264.15. Crystal system: triclinic. Space group: P1. a =
3.940(3) (Å). b = 14.879(3) (Å). c = 16.575(3) (Å). α =
5.062(2) (deg). β = 74.111(2)°. γ = 70.772(2)°. V =
3
3
122.1(10)Å . Z = 2. D
= 1.345 Mg/m . Absorp coeff =
calcd
−
1
0.386 mm . F(000) = 1314. Crystal size, 0.14 × 0.13 × 0.11
mm . θ range: 1.6 to 25°. No. of reflns collected: 9513. No. of
3
H
DOI: 10.1021/acs.organomet.8b00708
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
indep reflns: 10953 (R = 0.0291). Selected bond length (Å)
and angles (deg): Co1−O2 1.9138(13), Co1−O1 1.9273(13),
Co1−N1 1.9271(16), Co1−N2 1.9420(15), Co1−P1
(7) Naddeo, M.; Buonerba, A.; Luciano, E.; Grassi, A.; Proto, A.;
Capacchione, C. Stereoselective Polymerization of Biosourced
Terpenes β-Myrcene and β-Ocimene and their Copolymerization
with Styrene Promoted by Titanium Catalysts. Polymer 2017, 131,
int
2
.2024(6), Co1−P2 2.2129(6), O2−Co1−O1 86.73(5),
1
(
51−159.
O2−Co1−N1 84.56(6), O1−Co1−N1 94.57(6), O2−Co1−
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DOI: 10.1021/acs.organomet.8b00708
Organometallics XXXX, XXX, XXX−XXX