Synthesis of dimethylmanganese(II) complexes bearing N-heterocyclic carbenes and nucleophilic substitution reaction of tetraalkoxysilanes by diorganomanganese(II) complexes

Article abstract of DOI:10.1016/j.jorganchem.2016.07.025

Reactions of manganese(II) dichlorides bearing a N-heterocyclic carbene ligand (L), [MnCl(μ-Cl)(L)]₂(1a, L?=?1,3-diisopropyl-4,5-dimethylimidazole-2-ylidene (IⁱPr); 1b, L?=?1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene (IMes); 1c, L?=?1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene (IPr)) with MeLi afford the dinuclear dimethylmanganese(II) complexes, [MnMe(μ-Me)(L)]₂(2a, L?=?IⁱPr; 2b, L?=?IMes; 2c, L?=?IPr). Complexes 2a-c achieve nucleophilic substitution of Si(OEt)₄to selectively form MeSi(OEt)₃. Related arylmanganese(II) complexes analogously react with Si(OEt)₄to afford ArSi(OEt)₃and Ar₂Si(OEt)₂(Ar?= Ph, 2,6-Me₂(C₆H₃)). Kinetic studies support an associative mechanism for the observed transformation of Si(OEt)₄, in which both the manganese species and Si(OEt)₄are involved in the rate-limiting step.

Full text of DOI:10.1016/j.jorganchem.2016.07.025

Accepted Manuscript
Synthesis of dimethylmanganese(ii) complexes bearing N-heterocyclic carbenes and
nucleophilic substitution reaction of tetraalkoxysilanes by diorganomanganese(ii)
complexes
Takayoshi Hashimoto, Yuko Kawato, Yumiko Nakajima, Yasuhiro Ohki, Kazuyuki
Tatsumi, Wataru Ando, Kazuhiko Sato, Shigeru Shimada
PII:
S0022-328X(16)30318-7
10.1016/j.jorganchem.2016.07.025
JOM 19576
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 8 April 2016
Revised Date: 27 July 2016
Accepted Date: 29 July 2016
Please cite this article as: T. Hashimoto, Y. Kawato, Y. Nakajima, Y. Ohki, K. Tatsumi, W. Ando, K.
Sato, S. Shimada, Synthesis of dimethylmanganese(ii) complexes bearing N-heterocyclic carbenes and
nucleophilic substitution reaction of tetraalkoxysilanes by diorganomanganese(ii) complexes, Journal of
Organometallic Chemistry (2016), doi: 10.1016/j.jorganchem.2016.07.025.
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Graphical abstract

ACCEPTED MANUSCRIPT
Synthesis of Dimethylmanganese(II) Complexes
Bearing N-heterocyclic Carbenes and Nucleophilic
Substitution Reaction of Tetraalkoxysilanes by
Diorganomanganese(II) Complexes
Takayoshi Hashimoto a, Yuko Kawato b, Yumiko Nakajima a,*, Yasuhiro Ohki b,
Kazuyuki Tatsumi b, Wataru Ando a, Kazuhiko Sato a, Shigeru Shimada a,*
aNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1ꢀ1ꢀ1
Higashi, Tsukuba, Ibaraki 305ꢀ8565, Japan
bDepartment of Chemistry, Graduate School of Science, and Research Center for Materials Science,
Nagoya University, Furoꢀcho, Chikusaꢀku, Nagoya 464ꢀ8602, Japan
Eꢀmail address: sꢀshimada@aist.go.jp (S. Shimada) yumikoꢀnakajima@aist.go.jp (Y. Nakajima)
Abstract
Reactions of manganese(II) dichlorides bearing a
[MnCl(
ꢀCl)(L)]2 (1a, L = 1,3ꢀdiisopropylꢀ4,5ꢀdimethylimidazoleꢀ2ꢀylidene (IiPr); 1b, L =
1,3ꢀbis(2,4,6ꢀtrimethylphenyl)imidazoleꢀ2ꢀylidene (IMes); 1c,
1,3ꢀbis(2,6ꢀdiisopropylphenyl)imidazoleꢀ2ꢀylidene (IPr)) with MeLi afford the dinuclear
dimethylmanganese(II) complexes, [MnMe(
ꢀMe)(L)]2 (2a, L = IiPr; 2b, L = IMes; 2c, L =
Nꢀheterocyclic carbene ligand (L),
µ
L
=
µ
IPr). Complexes 2aꢀc achieve nucleophilic substitution of Si(OEt)4 to selectively form
MeSi(OEt)3. Related arylmanganese(II) complexes analogously react with Si(OEt)4 to afford
ArSi(OEt)3 and Ar2Si(OEt)2 (Ar = Ph, 2,6ꢀMe2(C6H3)). Kinetic studies support an associative
mechanism for the observed transformation of Si(OEt)4, in which both the manganese
species and Si(OEt)4 are involved in the rateꢀlimiting step.
Keywords: Diorganomanganese(II) • Nꢀheterocyclic carbene• Organosilicates • Nucleophilic
substitution
1. Introduction
Manganese(II) complexes possess five unpaired 3d electrons and exhibit strong tendency of being
a high spin state. Owing to this unique electronic structure, manganese(II) complexes are expected to
exhibit characteristic reactivity. Thus, exploration of their reaction chemistry is of great interest in
terms of the investigation of new types of reactions. Since the first discovery of organomanganese
complex in 1937 [1], reactivity of various organomanganese species, such as organomanganese
halides (RMnX), diorganomanganeses (R2Mn), and organomanganates (R3Mn– and R4Mn2-), have
been thus far investigated more than half a century [2][3]. These studies have been performed mainly
using RMnX, R3Mn– and R4Mn2– and examples of detailed study on well-defined

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diorganomanganese(II) complexes were still limited [4], mainly due to their extremely high
instability. In this study, the dinuclear dimethylmanganese(II) complexes bearing N-heterocyclic
carbene ligands have been synthesized. It was also revealed that the nucleophilic character of
diorganomanganese(II) successfully attain nucleophilic substitution of tetraalkoxysilanes to form
organosilicates.
2. Results and discussion
2.1. Synthesis and Structures of Dimethylmanganase(II) Complexes Bearing
Nꢀheterocyclic Carbenes.
Synthesis
of
N
ꢀheterocyclic
carbeneꢀsupported
manganese(II)
dichloride
[MnCl( ꢀCl)(L)]2 (1b, L = 1,3ꢀbis(2,4,6ꢀtrimethylphenyl)imidazoleꢀ2ꢀylidene (IMes); 1c, L
µ
= 1,3ꢀbis(2,6ꢀdiisopropylphenyl)imidazoleꢀ2ꢀylidene (IPr)) were recently reported by
Tonzetich et al. [5]. We also synthesized a manganese(II) dichloride bearing smaller
N
ꢀheterocyclic
1,3ꢀdiisopropylꢀ4,5ꢀdimethylimidazoleꢀ2ꢀylidene (IiPr)) by a similar procedure from
MnCl2 and the corresponding ꢀheterocyclic carbene ligand.
carbene
ligands,
[MnCl(
µ
ꢀCl)(L)]2
(1a,
L
=
N
As reported previously, alkylation of 1c was achieved using Grignard reagents [5]. In
this study, it was found that the alkylation reaction also proceeds via the reaction with
MeLi. Thus, treatment of 1aꢀc with MeLi resulted in the formation of [MnMe(
µꢀMe)(L)]2
(2a, L = IiPr; 2b, L = IMes; 2c, L = IPr) in moderate yields (Scheme 1).
Scheme 1.
Synthesis of [MnMe(µꢀMe)(L)]2 (2aꢀc)
It was also found that a mononuclear manganese(II) precursor [MnCl2(IMes)2] (3),

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which can be prepared by the reaction of 1b with 2 equiv IMes [5], also reacted with
MeLi to give 2b (Scheme 2). Considering the equilibrium between 3 and 1b [5], 2b would
be formed directly from 3 and MeLi and/or through the formation of 1b via dissociation
of one IMes ligand.
Scheme 2.
Synthesis of [MnMe(µꢀMe)(IMes)]2 (2b) from [MnCl2(IMes)2] (3)
Complexes 1 and 2 are paramagnetic and exhibit broad signals in the NMR spectra.
Thus, the complexes were characterized by elemental analysis. The solid state
structures of 1c and 2aꢀc were determined by single crystal Xꢀray diffraction study [6].
Complex 1c exhibits a dinuclear structure composed of two Mn atoms with a distorted
tetrahedral coordination (Figure S1). The bond lengths around the Mn atoms in 1c are
in a typical range of previously reported Mn–C (
bonds [7].
Nꢀheterocyclic carbene) and Mn–Cl
Complexes 2aꢀc also adopt a dinuclear structure. Structure of 2a is shown in Fig. 1.
The Mn…Mn distances of 2aꢀc (2.68 – 2.72 Å) are much shorter than that of 1c
(3.3831(5) Å), probably because of the smaller bridging Me ligands in 2aꢀc. The
Mn2(µꢀMe)2 core is crystallographically planar as observed in the previously reported
alkyl bridged dinuclear manganese(II) complexes [8][9]. The Mn–C1 and Mn–C2 bond
lengths in 2aꢀc (2.13 – 2.14 Å and 2.26 – 2.29 Å, respectively) are comparable to those of
previously reported terminal and bridging Me ligands in manganese(II) complexes [8].

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Fig. 1.
Molecular structure of 2a with 50% probability ellipsoids. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Mn–Mn’ 2.6854(5), Mn–C1
2.1383(17), Mn–C2 2.2969(18), Mn–C2’ 2.2839(17), Mn–C3 2.2153(16), Mn–C2–Mn’
71.78(5), C2–Mn–C2’ 108.22(7), C1–Mn–C2 117.41(7), C1–Mn–C2’ 103.63(7), C1–Mn–
C3 115.32(6).
Manganese(II) alkyl complexes are highly unstable and normally studied using those
with bulky alkyl groups such as CH2SiMe3 and CH2CMe2Ph groups [4a][9]. On the other
hand, complexes 2aꢀc supported by
Nꢀheterocyclic carbenes are stable at room
temperature for at least several months under inert atmosphere. Thus, as far as we
know, complexes 2aꢀc are one of the rare examples of the structurally wellꢀdefined
manganese(II) methyl complexes.
2.2. Reactivity of MnII Complexes Towards Tetraalkoxysilanes.
With the stable dimethyl complexes 2aꢀc in hands, their reactivity towards
tetraalkoxysilanes was surveyed. The reaction of 2a with Si(OEt)4 gradually proceeded
at 80 °C to produce MeSi(OEt)3 in the yield of 43% based on Si(OEt)4. Similarly,
complexes 2b and 2c reacted with Si(OEt)4 at 100 °C to give MeSi(OEt)3 in 47 and 21%
yields, respectively (Eq. 1). In the reaction of 2c, formation of a free
Nꢀheterocyclic
carbene ligand and insoluble metal precipitates were also observed probably due to the
decomposition of 2c at the reaction temperature. The decomposition is also confirmed by
the separate heating reaction of 2c at 80 °C.

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In these reactions, introduction of the Me group successfully proceeded via Si–O bond
cleavage. Such a direct conversion of the Si–O bond to the Si–C bond is known as the
key process for the selective formation of organosilicates RnSi(OR3)4ꢀn, which are the
important starting materials of silicone polymers. It is reported that these reactions has
been thus far involved strong nucleophiles, such as alkyllithium and alkylmagnesium
halide reagents via nucleophilic substitution reaction at the silicon center [10]. We also
found that organomanganese halides (allylMnBr and PhMnBr) [11], which are known
as a soft nucleophile, did not give nucleophilic substitution reaction of Si(OEt)4.
Therefore, potent high reactivity of MnR2 species was indicated.
Motivated by above mentioned results, reactivity investigation towards
tetraalkoxysilanes was further performed using related arylmanganese(II) complexes
[MnAr2]n (4a [12], Ar = phenyl (Ph), n = ∞; 4b, Ar = 2,6ꢀdimethylphenyl (Xyl), n = 3) and
[MnPh2(PCy3)] (5) [4b], in an attempt to perform arylation of tetraalkoxysilanes.
Aryl(trialkoxy)silanes are widely recognized not only as important precursors for the
formation of various silicone products [10c][13] but also as powerful organometallic
nucleophiles in the metalꢀcatalyzed crossꢀcoupling reactions [10g][14].
Although polynuclear 4a exhibited poor solubility towards organic solvents, it
gradually reacted with tetraalkoxysilanes in a turbid toluene solution at elevated
temperature. Reaction of 4a with 1 equiv of Si(OEt)4 proceeded at 100 °C to form
PhSi(OEt)3 as well as Ph2Si(OEt)2 in 80 and 11% yields (the yields are based on
Si(OEt)4), respectively, after 24 h (Eq. 2). Compared to this result, less sterically
hindered Si(OMe)4 was easily phenylated within 2 h at 80 °C to yield PhSi(OMe)3 (12%)
and Ph2Si(OMe)2 (77%). In contrast, reaction of 4b bearing bulky Xyl groups with
Si(OEt)4 was slower and took 96 h at 100 °C to form XylSi(OEt)3 as a sole product in
52% yield (Eq. 3). These results strongly indicate the significant steric effect at the
coordination sphere on the reaction.

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To check the fate of Mn metals in the above reactions, reaction of 4a with 3 equiv of
Si(OEt)4 was performed. The reaction also completed in 24 h at 100 °C, leading to the
quantitative formation of [Mn(OEt)2]n as a white precipitate, which was identified by
elemental analysis as well as by IR [15]. Therefore, it was indicated that two Ph groups
on the Mn atom in 4a were successively consumed for the phenylation reaction.
Similarly, complex 5 supported by PCy3 reacted with Si(OEt)4. The reaction of 5 with
Si(OEt)4 (1 equiv) proceeded at 100 °C for 27 h, resulting in the formation of the mixture
of PhSi(OEt)3 (73%) and Ph2Si(OEt)2 (11%) (Eq. 4). In this reaction, dissociation of PCy3
and formation of [Mn(OEt)2]n were also detected by 31P NMR and IR spectroscopies,
respectively.
2.3. Kinetic study.
To shed light on the further details of the reaction, kinetic studies have been
performed. Since 5 exhibits good solubility in toluene and good stability at elevated
temperature, reaction of 5 with Si(OEt)4 was employed for this study. Complex 5 was
treated with excess Si(OEt)4 (10 equiv) in the presence of icosane as an internal
standard, and the reaction progress at 80 °C was followed by GC analysis. In the
reaction, monophenylated PhSi(OEt)3 was continuously produced as a sole product over
the period of 3 h. It was revealed that the reaction obeyed good pseudoꢀfirstꢀorder
kinetics (Fig. 2a). Moreover, the rate constants observed at three different concentration
of [Si(OEt)4] exhibited a good linear correlation with the [Si(OEt)4]0 value (Fig. 2b).
Therefore, the kinetic data were consistent with the following rate equation: d[5]/dt =
k[5][Si(OEt)4].

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Next, the kinetic parameters were estimated by monitoring the reaction of 5 with
Si(OEt)4 at various temperatures; ∆H S
‡ = 50.9 kJ/mol and ∆ ‡ = –167.3 J/molK. The large
negative values of the activation entropy strongly indicated that the capture of Si(OEt)4
in the reaction site is the most likely the rateꢀdetermining step (vide infra). The result is
consistent with the observed slow reaction rate in the arylation reaction of Si(OEt)4
using [Mn(Xyl)2]3 which possesses bulky Xyl groups.
3
2.5
2
0.5
0
-0.5
-1
1.5
1
0.5
-1.5
0.05
0.1
0.15
0.2
0.25
0
5000
10000
15000
Fig. 2.
(a) Firstꢀorder plot of the reaction of 5 (0.010 M) with Si(OEt)4 (0.10 M) in toluene at
80 °C. (b) Plot of firstꢀorder rate constants (kobsd) against the initial concentrations of
Si(OEt)4 in toluene.
As mentioned above, such a neucleophilic substitution at the silicon atom have also
been reported using organolithium and organomagnesium halide reagents. For these
reactions, two associative mechanisms, SN2, and SNi mechanims, have been proposed
[13a]. It is also known that the substitution reaction of alkoxysilanes preferably
proceeds through SNi mechanism via four centered intermediate with a pentacoordinate
silicon atom, which is stabilized by the coordination of the leaving alkoxy group to the
incoming nucleophile [13a]. Considering these facts, it is likely that phenylation of
Si(OEt)4 by 5 proceeds via SNi mechanism as shown in Scheme 3.
Scheme 3.
Phenylation of alkoxysilane via SNi mechanism.

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3. Conclusions
In this study, dimethylmanganese(II) complexes 2aꢀc supported by
Nꢀheterocyclic
carbene ligand(s) have been synthesized and their structures were fully determined.
Reactivity investigation of 2aꢀc as well as related diarylmanganese(II) complexes
revealed their utility towards the direct conversion of tetraalkoxysilane Si–O bonds to
Si–C bonds to give organosilicates. Kinetic studies supported the associative
mechanism for the reaction of diphenylmanganese complex 5 with Si(OEt)4, in which
both 5 and Si(OEt)4 are involved in the rateꢀlimiting step.
The nucleophilicity of 2aꢀc is not as high as those of organolithium and magnesium
reagents, and 2aꢀc afforded only the monomethylated product in the reaction with
Si(OEt)4. Therefore, these alkylmanganese(II) complexes would be useful as selective
reagents for the direct formation of monoorganosilicates from tetraalkoxysilane Si(OR)4.
4. Experimental
4.1. General procedures
All reactions were carried out using standard Schlenk techniques or a glove box under
a nitrogen atmosphere. Toluene, benzene, diethyl ether, THF, and hexane were purified
by a solvent purification system (MBraun SPSꢀ800). Other solvents were degassed and
distilled from sodium benzophenone ketyl. Si(OEt)4 and Si(OMe)4 were purchased from
commercial sources and distilled prior to use. C6D6 and THFꢀd8 were dried by sodium
and distilled prior to use. MnCl2 was purchased from Kojundo Chemical Laboratory Co.,
Ltd and used without further purification. All other reagents were purchased from
1
commercial sources and used without further purification. The H NMR spectra were
recorded using a Bruker AVANCE 600 spectrometer. The signals were referenced to the
residual peaks of the deuterated solvents. Elemental analyses were performed on a
Thermo Scientific FLASH2000 CHNS analyzer where the samples were sealed into tin
capsules in a glovebox. Gas chromatographic (GC) analyses were conducted on
Shimadzu GCꢀ2014 instrument (FID; CBPꢀ1, 25 m × 0.25 mm). Infrared spectra were
recorded on a Jasco FT/IRꢀ4100 spectrometer. [MnCl2(IMes)2] (3) [5], [MnPh2]∞ (4a) [12],
[MnPh2(PCy3)] (5) [4b] and
N
ꢀheterocyclic carbenes (IMes, IPr, and IiPr) [16] were
prepared according to literature procedures.

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4.2. Synthesis of the Mn complexes
ꢀCl)IiPr]2 (1a). The reaction of MnCl2 (0.30 g, 2.4 mmol) with IiPr (0.43 g, 2.4
[MnCl(
µ
mmol) was performed in THF (30 mL) at room temperature overnight. The resulting
yellow solution was evaporated to dryness, and the residue was washed with hexane (15
mL × 3). After extraction of the residue with THF (10 mL), the extract was filtered
with a syringe filter (0.2
µm) to remove a small amount of insoluble solid and
evaporated under reduced pressure. The residue was washed with hexane (10 mL × 2)
and dried under vacuum to give 1a as a white solid (0.68 g, 1.1 mmol, 93%). Anal. Calcd
1
for C22H40N4Mn2Cl4: C, 43.16; H, 6.59; N, 9.15. Found: C, 43.24; H, 6.82; N, 9.56. H
NMR (600 MHz, THFꢀd8, 298K) 1.95, 2.28, 4.57, 6.91, 8.98.
[MnCl( ꢀCl)IPr]2 (1c). Complex 1c (0.92 g, 0.89 mmol, 75%) was prepared following the
µ
same procedure for 1a using MnCl2 (0.30 g, 2.4 mmol) and IPr (0.92 g, 2.4 mmol). Single
crystals (1c—4C6H6) suitable for crystallography were obtained from a saturated benzene
solution at room temperature.
[MnMe(µ
ꢀMe)IiPr]2 (2a). To a THF (30 mL) solution of complex 1a (0.30 g, 0.49 mmol)
was added an Et2O solution of MeLi (1.11 M, 1.8 mL, 2.00 mmol) at ꢀ78 °C. The mixture
was gradually warmed to room temperature and stirred overnight. The resulting yellow
solution was evaporated to dryness, and the residue was washed with hexane (10 mL ×
3). After extraction of the resulting solid with toluene (20 mL), the extract was filtered
with a celite pad to remove insoluble solid (LiCl). The extract was evaporated under
reduced pressure to afford [MnMe(µ
ꢀMe)IiPr]2 as a yellow powder (0.12 g, 0.23 mmol,
48%). Single crystals suitable for crystallography were obtained from a saturated
benzene solution at room temperature. Anal. Calcd for C26H52N4Mn2: C, 58.85; H, 9.88;
N, 10.56. Found: C, 59.23; H, 10.12; N, 10.91. 1H NMR (600 MHz, C6D6, 298K) 1.20, 1.71,
7.65.
[MnMe(µꢀMe)IMes]2 (2b). (a) Starting from 1b: Complex 2b (0.085 g, 0.11 mmol, 47%)
was prepared following the same procedure for 2a using 1b (0.20 g, 0.23 mmol). Single
crystals suitable for crystallography were obtained from a saturated Et2O solution at
room temperature. Anal. Calcd for C46H60N4Mn2: C, 70.94; H, 7.76; N, 7.19. Found: C,
1
70.65; H, 7.61; N, 7.55. H NMR (600 MHz, C6D6, 298K) 2.19, 3.00, 3.24, 9.35. (b)
Starting from 3: To a THF (25 mL) solution of complex 3 (0.30 g, 0.41 mmol), was added
an Et2O solution of MeLi (1.11 M, 0.75 mL, 0.83 mmol) at ꢀ78 °C. The mixture was
gradually warmed to room temperature and stirred overnight. The resulting yellow
solution was evaporated to dryness, and the residue was washed with hexane (10 mL ×
3). After extraction of the resulting solid with toluene (30 mL), the extract was filtered

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with a celite pad to remove insoluble solid (LiCl). The extract was evaporated under
reduced pressure to afford 2b contaminated with a small amount of the free IMes ligand,
which could not be fully removed by washing with hexane (0.13 g).
[MnMe(µꢀMe)IPr]2 (2c). Complex 2c (0.12 g, 0.13 mmol, 43%) was prepared following
the same procedure for 2a using 1c (0.30 g, 0.29 mmol). Single crystals suitable for
crystallography were obtained from a saturated benzene solution at room temperature.
[Mn3Xyl6] (4b). Complex 4b was synthesized following the similar procedure for
[Mn3Mes6] [4g]. A THF solution of XylMgBr (0.62 M, 30 mL, 18.6 mmol) was added to a
THF (20 mL)/dioxane (20 mL) suspension of MnBr2 (2.00 g, 9.31 mmol) at −78 °C. The
mixture was gradually warmed to room temperature and stirred overnight. The
resulting yellow suspension was filtered with a Celite pad to remove insoluble solid, and
the solution was evaporated to dryness. The residue was washed with hexane (30 mL ×
3). After extraction of the resulting solid with toluene (40 mL), the extract was filtered
with a celite pad to remove a small amount of insoluble solid. The solution was
evaporated under reduced pressure to afford Mn3Xyl6 as a light green powder (1.62 g,
2.04 mmol, 66%). Single crystals suitable for crystallography were obtained from a
saturated toluene solution at room temperature. Anal. Calcd for C48H54Mn3: C, 72.45; H,
6.84. Found: C, 72.40; H, 6.83. 1H NMR (600 MHz, C6D6, 298K) 1.88.
4.3. Reaction with alkoxysilanes
Reaction of 2a with Si(OEt)4. A typical procedure (Eq. 1) is as follows. A 10 mL Schlenk
tube equipped with a Teflon valve was charged with 2a (10.0 mg, 0.019 mmol), icosane
(internal standard; 10.0 mg, 0.035 mmol), and benzene (2.0 mL). After a benzene
solution (1.0 mL) of Si(OEt)4 (8.0 mg, 0.038 mmol) was added, the mixture was stirred
at 80 °C for 60 h. The GC analysis of the solution revealed the formation of MeSi(OEt)3
(0.017 mmol, 43%).
Reaction of 4a with Si(OEt)4. A typical procedure (Eq. 2) is as follows. A 10 mL Schlenk
tube equipped with a Teflon valve was charged with 4a (12.8 mg, 0.061 mmol), icosane
(internal standard; 10.0 mg, 0.035 mmol), and toluene (2.5 mL). After a toluene solution
(1.5 mL) of Si(OEt)4 (12.7 mg, 0.061 mmol) was added, the mixture was stirred at
100 °C for 24 h. The GC analysis of the solution revealed the formation of PhSi(OEt)3
(0.049 mmol, 80%) and Ph2Si(OEt)2 (0.0067 mmol, 11%).
Isolation of [Mn(OEt)2]n by the Reaction of 4a with Si(OEt)4. A 10 mL Schlenk tube
equipped with a Teflon valve was charged with 4a (50.0 mg, 0.239 mmol) and toluene
(2.5 mL). After adding a toluene solution (1.5 mL) of Si(OEt)4 (150 mg, 0.721 mmol), the

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mixture was stirred at 100 °C for 24 h, during which time a white crystalline powder of
[Mn(OEt)2]n appeared. The crystalline powder was separated by decantation, washed
with toluene (15 mL × 2) and hexane (10 mL), and dried under vacuum to give
analytically pure [Mn(OEt)2]n (28 mg, 0.193 mmol, 81%). IR (KBr): 1109 (s, CꢀO) cmꢀ1.
Anal. Calcd for C4H10MnO2: C, 33.12; H, 6.95. Found: C, 32.90; H, 6.78.
Reaction of 5 with Si(OEt)4. A 10 mL Schlenk tube equipped with a Teflon valve was
charged with 5 (30.0 mg, 0.061 mmol), icosane (internal standard; 10.0 mg, 0.035 mmol),
and toluene (2.5 mL). After a toluene solution of Si(OEt)4 (1.5 mL, 0.061 mmol) was
added, the mixture was stirred at 100 °C for 27 h. The GC analysis of the solution
revealed the formation of PhSi(OEt)3 (0.045 mmol, 73%) and Ph2Si(OEt)2 (0.0067 mmol,
11%).
Kinetic Examinations for the Reaction of 5 with Si(OEt)4. Reactions of 5 (20.0 mg,
0.041 mmol) with Si(OEt)4 (in three different concentrations 0.408 mmol, 0.102 M; 0.612
mmol, 0.153 M, 0.817 mmol, 0.204 M) was performed in toluene (4 mL) at 80 °C and
monitored by GC analysis using icosane (10.0 mg, 0.036 mmol) as an internal standard.
The observed rate constant,
where [5] is calculated based on the following equation, [5]0 – [PhSi(OEt)3]. Pseudo first
order rate constants were calculated respectively,
obs (sꢀ1) = 1.18 × 10ꢀ4 (0.102 M), 1.71 ×
kobs, was obtained from plots of ln([5]/[5]0) versus time (s),
k
10ꢀ4 (0.153 M), 2.44 × 10ꢀ4 (0.204 M). The rate constants are found to obey
pseudoꢀfirstꢀorder dependent on [Si(OEt)4].
Calculation of the Activation Parameters for the Phenylation of Si(OEt)4 with 5.
Complex 5 (30.0 mg, 0.061 mmol), icosane (internal standard; 10.0 mg, 0.036 mmol)
were dissolved in toluene (4.0 mL). After Si(OEt)4 (12.8 mg, 0.061 mmol) was added, the
reaction was monitored by GC analysis using icosane as an internal standard. At the
early stage of the reaction, PhSi(OEt)3 was predominantly formed. Thus, the observed
initial rate constant,
time (s), where [Si(OEt)4]o is the initial concentration of Si(OEt)4, at a variety of
temperatures [
obs = 3.99 × 10ꢀ4 (80 °C), 6.68 × 10ꢀ4 (90 °C), 1.16 × 10ꢀ3 (100 °C), 1.61 ×
kobs, was obtained from plots of 1/[Si(OEt)4]ꢀ1/[Si(OEt)4]o versus
k
H S
10ꢀ3 (Mꢀ1sꢀ1) (110 °C)], and the activation parameters (∆ ‡ = 50.9 kJ/mol and ∆ ‡ = ꢀ167.3
J/molK) were determined from an Eyring plot.
4.4. Singleꢀcrystal Xꢀray diffraction studies
The single crystal Xꢀray diffraction measurements of 1c, 2aꢀc, and 4b were performed
at –150 °C under a cold nitrogen stream on a Bruker APEX II diffractometer using
graphite monochromated Mo Kα radiation. The determination of crystal systems and

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unit cell parameters was carried out with the APEX2 program package [17a]. The raw
frame data were processed using SAINT [17b] and SADABS [17c] to yield the reduction
data file. The calculations were performed with the CrystalStructure program package.
All structures were solved by direct methods using SIR97 program [17d], and refined by
fullꢀmatrix least squares. The methyl group of solvent (toluene) in the lattice of 4b is
disordered over two positions in a 1:1 ratio. CCDC 1422052, CCDC 1422053, CCDC
1422054 , CCDC 1422055 and CCDC 1422057 contain supplementary crystallographic
data for 1c, 2a, 2b, 2c and 4b in this paper. These data can be obtained free of charge
from
The
Cambridge
Crystallographic
Data
Center
via
www.ccdc.cam.ac.uk/data_request/cif.
Appendix A. Supplementary material
Crystal structures and crystal data of 1c, 2aꢀc, and 4b; Eyring plot for the reaction of 5
with Si(OEt)4. This material is available free of charge via the Internet.
Acknowledgements
This work was supported by the "Development of Innovative Catalytic Processes for
Organosilicon Functional Materials" project (PL: K.Sato) from the New Energy and Industrial
Technology Development Organization (NEDO).
Notes and references
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National Institute of Advanced Industrial Science
and Technology (AIST)
Central 5-2, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan
Dr. Yumiko NAKAJIMA
Phone: +81-29-861-6707 Fax: +81-29-861-4568
e-mail: yumiko-nakajima@aist.go.jp
Aug 27, 2016
Prof. Raymond W. Y. Wong
The Regional Editor, Journal of Organometallic Chemistry
Department of Chemistry, Hong Kong Baptist University,
Waterloo Road, Kowloon Tong, Hong Kong, China
RE: Manuscript ID: JORGANCHEM-D-16-00206
Title: “Synthesis of Dimethylmanganese(II) Complexes Bearing N-heterocyclic Carbenes and Nucleophilic
Substitution Reaction of Tetraalkoxysilanes by Diorganomanganese(II) Complexes”
Authors: Takayoshi Hashimoto, Yuko Kawato, Yumiko Nakajima, Yasuhiro Ohki, Kazuyuki Tatsumi,
Wataru Ando, Kazuhiko Sato, Shigeru Shimada
Dear Prof. Wong,
Thank you very much for your e-mail on July 21, 2016, regarding the above referred manuscript. The
manuscript has been revised in the light of helpful suggestion of reviewers.
As pointed out by reviewer 1, the synthesis of complexes 1b, 1c, 2c, and 3 has already been reported (ref
5). However, we independently synthesized the manganese complexes and the synthetic procedures are
slightly different from the reported one. Furthermore, complexes 1a, 2a, and 2b are new compounds. These
points are now thoroughly explained in the main text. Some experiments are now explained in more detail as
recommended by reviewer 1.
The structural refinement of 2c was improved based on the reviewer 2’s comment.
A pdf document (“revsdparts.pdf”) has been uploaded as “Other Files for Editors Only” to show what
changes have been made.
We hope that the manuscript has been improved satisfactorily to be acceptable for publication in J.
Organomet. Chem.
Sincerely yours,
Yumiko Nakajima