Synthesis and characterization of N,N-chelate manganese complexes and applications in C[sbnd]N coupling reactions

Article abstract of DOI:10.1016/j.ica.2019.119358

Bidentate NN-ligands have been derived from the reaction between aldehydes and 2-(aminomethyl)pyridine. The treatment of these ligands with Mn(CO)₅Br gave complexes that are highly bench stable. The complexes were characterized by various analytical and spectral methods. Single-crystal XRD of complex Mn-2 was performed, which indicates an octahedral geometry around the metal center. The complexes efficiently catalyze the N-alkylation of anilines with alcohols under optimized reaction conditions.

Full text of DOI:10.1016/j.ica.2019.119358

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Research paper
Synthesis and characterization of N,N-chelate manganese complexes and ap-
plications in C–N coupling reactions
Kuhali Das, Amol Kumar, Akash Jana, Biplab Maji
PII:
S0020-1693(19)31479-3
https://doi.org/10.1016/j.ica.2019.119358
ICA 119358
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Inorganica Chimica Acta
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11 December 2019
12 December 2019
Please cite this article as: K. Das, A. Kumar, A. Jana, B. Maji, Synthesis and characterization of N,N-chelate
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Synthesis and characterization of N,N-chelate manganese complexes and
applications in C–N coupling reactions
a
a
a
a,
Kuhali Das , Amol Kumar , Akash Jana , and Biplab Maji *
aDepartment of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
⁎
Corresponding author. E-mail address: bm@iiserkol.ac.in
Abstract Bidentate NN-ligands have been derived from the reaction between aldehydes and 2-
aminomethyl)pyridine. The treatment of these ligands with Mn(CO) Br gave complexes that are highly bench
(
5
stable. The complexes were characterized by various analytical and spectral methods. Single-crystal XRD of
complex Mn-2 was performed, which indicates an octahedral geometry around the metal center. The complexes
efficiently catalyze the N-alkylation of anilines with alcohols under optimized reaction conditions.
Keywords: Manganese; Non-pincer ligand; C–N Coupling reactions; Phosphine free; Amines; X-Ray structure
o
1
. Introduction:
under such harsh conditions (≥ 180 C). Over the past few
decades, a diverse range of homogeneous and heterogeneous
catalysts based on noble metals Ru[4a, 4c, 7], Rh[7s], Ir[7m,
Nitrogen-containing compounds such as amines and imines
are important building constituents for bioactive molecules,
pharmaceuticals, herbicides, and dyestuffs[1]. The
development of sustainable routes for the construction of C-
N bonds is of substantial interest for synthetic chemists. The
traditional methods for their synthesis involve the
substitution of alkyl halides, triflates, tosylates, and
mesylates with amines[2]. However, over-alkylation, as well
as the formation of copious waste, limits the applicability of
these methods. An alternate pathway employs the reductive
amination with aldehydes, ketones, and carboxylic acids[1e,
8
], Pd[7m, 9], Pt[4d, 10], Ta[11], Au[12] have been
synthesized and utilized efficiently for C-N bond formation.
However, due to the toxicity, sparse availability, and high-
cost, numerous efforts have been made for the replacement
of these precious metals by their lower congeners. Indeed,
significant progress has been achieved with Fe[13], Co[7m,
1
4], Ni[4d, 7m, 15] and Mn[4e, 16], Cu[17] based catalysts
for C–N bond formation reactions. In this context, the groups
of Feringa[13a], Barta[13a, 13c, 15c], Saito (Fe catalyst),
Beller[4e, 16a], Milstein[4e, 18] (Mn catalyst), Zheng[14a],
Kempe[14b, 16d] (Co, Mn catalyst) have made prominent
contribution.
After iron and titanium, manganese is the third most
abundant transition metal in Earth’s crust and is less toxic
and economically amiable. It envisioned as a potential
replacement for its higher congeners. Milstein[18] and co-
workers utilized a PNP-pincer based manganese catalyst for
coupling of amines with alcohols which yielded aldimines.
Pioneering work in the field of N-alkylation with manganese
catalyst was demonstrated by Beller[16a] and co-workers,
using an Mn(I)-PNP pincer based catalyst. After that, in
3] in the presence of stoichiometric hydride transfer agents.
However, this also suffers from low functional group
tolerance and generation of substantial metal waste.
Of late, the borrowing hydrogen (BH) methodology, also
known as hydrogen auto-transfer[2a, 4] employing suitable
metal catalyst, have been developed as a greener and atom
economical way to synthesize alkylated amines. This three-
step technique can be achieved in one pot utilizing the
readily available, cheap and less noxious alcohols as starting
materials and therefore gained recognition in the perspective
of sustainable development. In this process, initially, the
alcohol is dehydrogenated to aldehyde, followed by
condensation with an amine to generate the imine.
Hydrogenation of the imine by the hydrogen borrowed in the
preliminary step yields the saturated amine. In 1981,
Grigg[5] and Watanabe[6] group individually reported Rh-
and Ru- catalyzed synthesis of N-alkylated amines based on
this borrowing hydrogen strategy for the first time.
Nevertheless, the methods suffered from the lack of product
selectivity as both secondary and tertiary amines formed
2
017, Kirchner[19] and Sortais[16b] groups also reported
phosphine based PNP-pincer manganese complexes for N-
alkylation of primary amines. Although these phosphine-
based catalyst systems have achieved immense success in
this field, the toxicity, high cost, and operational difficulties
demand other alternative ligand systems. In 2018, Balaraman
et al.[16e] reported in-situ generated manganese catalyst with
pincer NNN and salen based ligands for this transformation.

Srimani et al. have developed NNS-Mn complexes for the C– non-hydrogen atoms were refined anisotropically, using
2
N bond formation reaction [16f]. Very recently, Ke et weighted full-matrix least-squares on F . Atomic scattering
al.[16h] developed N-heterocyclic carbene based Mn catalyst factors were incorporated in the computer programs.
for N-alkylation of anilines with alcohols.
2
.2. Synthesis of ligands
Our group also reported manganese catalyzed olefination of
heteroaryl moieties[20], and sulfones[21], α-alkylation of
ketones[22], and nitriles[23], and hydroboration of
carboxylic acids[24] with different homogeneous manganese
catalysts. Maintaining our focus on homogeneous manganese
catalysis, herein, we are reporting the synthesis of two
phosphine-free bidentate non-pincer manganese complexes
and their applications in selective N-alkylation of amines
with alcohols. The developed method requires very low
catalyst loading (2 mol%) to achieve the complete
conversion to the product without the necessity for functional
group manipulations. In the viewpoint of environmental
concern, this method is sustainable as water is forming as the
only byproduct.
L1-3: [25] The ligands were prepared according to the
following modified procedures. Aldehyde (2.0 mmol) and 2-
(aminomethyl)pyridine (2.1 mmol) are mixed in methanol,
and then sodium sulfate (2.5 mmol) was added. The reaction
mixture was stirred at 35 C for 12 h and then filtered. To the
filtrate was added NaBH (4.0 mmol) and heated at 45 C for
1
white paste. The organic part was extracted with DCM and
purified using flash column chromatography. The ligands
were obtained as a yellow oil. The spectral data resembles
that reported in the literature[25].
o
o
4
h. The solvent was removed under vacuum resulting in a
L4: A solution of N-(2-(methylthio)benzyl)-1-(pyridin-2-
yl)methanamine (L1) (0.5 mmol) in dry THF (3 ml) was
cooled to 0 C and NaH (1.5 equiv.) was added in one
2. Experimental
o
portion. The resulting mixture was stirred at that temperature
for 30 mins and methyl iodide (1.5 equiv.) was added
2.1. General
All commercially available chemicals were purchased from dropwise. The solution was warmed to room temperature and
Sigma-Aldrich, Alfa-Aesar, TCI, and Avra Synthesis and stirred overnight during which the color changed from
used without further purification. Non-halogen containing yellow to orange. The reaction was quenched with water, the
solvents were dried over calcium hydride. THF was dried organic part was extracted with EtOAc and purified using
over sodium/benzophenone and distilled under argon flash column chromatography. Yield: 65%. Selected IR
-1
atmosphere. The solvents were degassed with argon and (ATR, cm ): 1568, 1550, 1450, 1416, 1226, 1055, 1016,
1
stored over activated 4 Å molecular sieves. Merck pre-coated 957, 863, 736, 669. H NMR (500 MHz, CDCl ) δ 8.51 (d, J
3
TLC plates (silica gel 60 F254 0.25mm) were used for thin- = 4.8 Hz, 1H), 7.64 (td, J = 7.7, 1.7 Hz, 1H), 7.57 (d, J = 7.8
layer chromatographic (TLC) analysis and spots were Hz, 1H), 7.39 (d, J = 7.4 Hz, 1H), 7.25 (d, J = 3.8 Hz, 2H),
visualized by UV light (254nm), KMnO , and under I . FT- 7.15 – 7.06 (m, 2H), 3.73 (s, 2H), 3.68 (s, 2H), 2.47 (s, 3H),
4
2
1
3
IR spectra were collected on Bruker ATR and Perkin-Elmer 2.21 (s, 3H). C NMR (126 MHz, CDCl ) δ 160.1, 148.9,
3
FT-IR spectrometer. High-resolution mass spectra (HRMS) 139.0, 137.2, 136.6, 129.8, 127.8, 125.7, 124.6, 123.3, 122.0,
1
13
+
were recorded using Bruker mass spectrometer. H, C, and 63.7, 60.5, 42.2, 16.2. HRMS: Calculated for [C H N S ;
1
5
19
2
1
9
1
+
F NMR spectra were obtained using Bruker ( H: 500 MHz, [M+H] ] 259.1263, found 259.1264.
C: 126 MHz) and JEOL ( H: 400 MHz, C: 100 MHz)
spectrometer employing CDCl as solvent and peaks are
1
3
1
13
2
.3. Synthesis of manganese (I) complexes
3
reported as δ (ppm) with reference to the resonance of the
solvent. Coupling constant (J) values are reported in Hz.
Multiplicity patterns are stated as follows: br (broad), s
Mn 1 and Mn-2: To a solution of the ligand (1 equiv.) in dry
THF (0.05 M) was added Mn(CO) Br (1.05 equiv.) under
5
argon atmosphere. The resulting yellow colored solution was
(singlet), d (doublet), t (triplet), q (quartet), dd (doublet of
o
heated at 90 C for 3h, during which time the color changes
doublet), m (multiplet).
to dark orange or brown. The solution was cooled to ambient
Crystal of Mn-2 was mounted on glass fibers and data were temperature, and the solvent was removed under vacuum.
collected at 100 K using an AGILENT SUPERNOVA The resulting orange or yellow residue was washed with
hexane and dried under vacuum to yield the complexes as
orange or yellow-colored solid. Single crystals for the
complexes were obtained by slow diffusion of diethyl ether
into a saturated solution of the complex in THF.
SINGLE CRYSTAL XRD diffractometer. Graphite
monochromated Cu-Kα radiation (λ = 1.54184 Å) was used
throughout. The absorption corrections were done by the
multi-scan method. Corrections were made for Lorentz and
polarization effects. The structure was solved by direct
methods using the program SHELXS. Refinements and all
other calculations were carried out using SHELXL-97. The
H atoms were included in calculated positions and treated as
riding atoms using the SHELXL default parameters. The
Mn-4: Following the procedure described for Mn-1 to 2 a
orange colored solid was formed. THF (0.05 M) was added
to the orange solid and the light-yellow precipitate was
formed. The aliquot was decanted, and the precipitate was
washed with THF (2 times), dried under vacuum.

Mn-1 The complex was synthesized following the above- The ligand L4 was synthesized by the substitution of N-H
mentioned procedure in 90% yield as yellow solid. Mp: 76- proton by a methyl group using methyl iodide. The N,N-
o
-1
7
(
6
7
8 C, Selected IR (CH Cl cm ): 3045, 2928, 2860, 2025
2 2,
chelate Mn(I) complexes (Mn-1, Mn-2 and Mn-4) were
s, ν ), 1962 (ν ), 1913 (ν ), 1605, 1478, 1429, 1088, 751,
CO
CO
CO
synthesized by treating a solution of amine-based ligands in
1
97. H NMR (500 MHz, CDCl ) δ 9.00 (s, o-H of Py 1H),
.73 (br s, 1H), 7.53 – 6.93 (m, 6H), 5.10 – 4.72 (m,-
NHCH Py, 1H), 4.69 – 4.35 (m, -NHCH Py, 1H), 4.17 [br
s,-NHCH (o-SMeC H ), 1H], 3.97 [s, -NHCH (o-SMeC H ),
H], 2.53 (s,-SCH 3H). [Py = Pyridyl]. C NMR (126
MHz, CDCl ) δ 222.9, 221.4, 221.1, 158.9, 153.8, 138.4,
38.2, 133.6, 130.8, 129.8, 127.1, 125.7, 124.7, 121.3, 58.6,
0
3
THF with MnBr(CO) at 90 C for 3 h in 1:1.05 M ratio
5
(
9
Scheme 1). The manganese complexes were obtained in 90,
1 and 97% yields, respectively and are highly stable in air.
For characterization of these complexes, analytical,
2
2
2
6
4
2
3
6
4
1
1
3,
1
13
spectroscopic methods (IR, H, C NMR, and HRMS) were
3
employed. X-ray crystallography for Mn-1 and Mn-2 are
1
5
described below. The reaction of L3 with Mn(CO) Br
6.9, 16.2. HRMS: Calculated for [C H MnN O S; [M –
5
1
1
7
16
2
3
+
resulted in a mixture of compounds, which shows broad H
Br] ] 383.0262, found 383.0188.
NMR spectra. At present, we are unable to purify and
Mn-2 The complex was synthesized following the procedure characterize it.
mentioned above in 91% yield as orange solid. Mp: 140 –
o
-1
3.2. Spectroscopy studies
1
42 C. Selected IR (ATR, cm ): 3190, 2888, 1991 (s, ν ),
CO
1
903 (s, ν ), 1852 (s, ν ), 1589, 1427, 1048, 971, 763, 681.
CO
CO
In the IR spectra of the manganese(I) complexes three bands
characteristic to terminal νCO was observed. For Mn-1, three
1
H NMR (500 MHz, CDCl ) δ 8.99 (br s, o-H of Py, 1H),
3
7.78 (br s, 1H), 7.36 (br s, 2H), 4.43 (s, -NHCH Py, 1H),
2
-
1
strong bands distinctive to ν appeared at 2025 cm , 1962
CO
3.96 (s, -NHCH Py, 1H), 3.75 (s, -NHCH Cy, 1H), 3.22 (s, -
2
2
-1
and 1913 cm . However, for Mn-2, one of the three bands
corresponding to νCO was observed at 2023 cm and the
NHCH Cy, 1H), 2.99 (s,-NH, 1H), 1.79 (br s, 6H), 1.45 –
2
-1
0
(
.74 (m, 7H). [Py = Pyridyl, Cy = Cyclohexyl]. 13C NMR
-1
126 MHz, CDCl ) δ 222.8, 221.3, 221.1, 158.9, 153.8, other two bands observed at 1926, and 1907 cm overlapped
3
1
2
3
38.2, 124.8, 121.2, 63.4, 58.1, 35.5, 31.2, 29.9, 26.2, 25.7, with each other. The three carbonyl stretching frequencies
+
-1
5.55. HRMS: Calculated for [C H MnN O ; [M – Br] ] for Mn-4 were observed at 2001, 1909, 1897 cm .
1
6
20
2
3
43.0854, found 343.0836.
Vibrations corresponding to the presence of aliphatic and
aromatic bonds also appeared in normal positions. The IR
spectra of the three complexes thus confirm the bidentate
binding mode of the secondary amine-based ligands to the
metal center.
The H NMR spectra of the complexes show downfield
chemical shifts in comparison to the free ligand. The singlets
that observed at 3.91 and 3.93 ppm corresponding to the -
Mn-4 The complex was synthesized following the procedure
mentioned above in 70% yield as yellow solid. Selected IR
-1
(
ATR, cm ): 2001 (ν ), 1909 (ν ), 1897 (ν ), 1591, 1446,
CO CO CO
1427, 1283, 946, 846, 761, 747, 669. HRMS: Calculated for
1
+
[
C H MnN O S; [M – Br] ] 397.0419, found 397.0420.
18 18 2 3
2.4. Synthetic procedure for N-alkylation of amines with
CH -NH-CH - protons in L1 shifted to downfield 5.10 –
alcohols
2
2
4
1
.72 (m, 1H), 4.69 – 4.35 (m, 1H), 4.17 (br s, 1H), 3.97 (s,
H) ppm in the complex (Mn-1) due to the coordination of
In a 10 mL screw-capped vial was placed 2.0 mol% of
manganese(I) catalyst, 40 mol% of the base, 0.1 mL of
toluene, 0.4 mmol of alcohol and 0.2 mmol of amine under
the nitrogen atom to Mn(I), also their splitting pattern is
changed due to the presence of diastereotopic -CH - protons
2
o
argon atmosphere. The reaction mixture was heated at 140 C
in the complex. Signals characteristic to the aromatic proton
of pyridine ring at 8.55 ppm also shifted to 9.00 ppm
suggesting deshielding upon the coordination of pyridine
for 24 h in an oil bath. The reaction mixture was then cooled
at ambient temperature, quenched with water, and the
organic layers were extracted with ethyl acetate. The
combined organic layers were dried over sodium sulfate and
concentrated. The product was purified by silica gel column
chromatography using the mixture of ethyl acetate and
hexane as eluent.
13
nitrogen to Mn(I). The C NMR spectra are also conclusive
about the composition of the complex. For the uncoordinated
ligands, the peaks corresponding to -CH -NH-CH - were
2
2
observed at 54.8 and 51.5 ppm. Upon coordination and
complex formation, these signals showed a downfield shift to
5
8.6 and 56.9 ppm. The signals due to the aromatic carbons
also changed considerably from that of free ligand. These
.1. Synthesis and characterization of manganese(I) shifts are very much conclusive about the coordination of
3
. Results and discussions
3
complexes
ligands and the formation of the complex. The signals for
terminal C≡O carbon atoms for Mn-1.was observed at 222.9,
The secondary amine-based ligands (L1-3) were prepared by
the reductive amination of 2-(aminomethyl)pyridine with
2
21.4, and 221.1ppm.
For Mn-2, similar shifts and change in splitting patterns
aldehydes,
2-(methylthio)benzaldehyde,
cyclohexyl
1
observed in the H NMR spectra. For free ligands the signal
carboxaldehyde, and benzaldehyde, respectively (Scheme 1).

due to the presence of -CH -NH-CH - protons were shifted exhibited signals at 56.5 and 55.5 ppm in the free ligand,
2
2
from 3.87 (s, 2H) and 2.47 (d, J = 6.6 Hz, 2H) to 3.96 (s, whereas in the complex they shifted at 63.4 and 58.1 ppm,
H), 3.75 (s, 1H), 3.22 (s, 1H), 2.99 (s, 1H) indicative of respectively due to deshielding upon coordination of
1
nitrogen coordination. Signals due to the coordination of the nitrogen. Aromatic carbons also showed considerable shift
pyridine nitrogen atom also shifted to downfield 8.98 ppm upon complex formation.
1
3
from 8.53 ppm. In C NMR spectra, the expected signals for All these spectral data are indicative of coordination of
three-terminal C≡O bonds observed at 222.8, 221.3, and nitrogens in bidentate fashion to manganese(I) center and
221.1 ppm. The two carbon atoms adjacent to nitrogen formation of distinct complexes.
NH2
i) Na SO , MeOH
2
4
N
Br
o
35 C, 12 h
N
R
Mn(CO)5Br
HN
OC
N
R
H
o
Mn
ii) NaBH , MeOH
N
THF, 90 C, 3 h
4
R
O
o
CO
45 C, 1h
R= o-SMeC H (L1) 90%
6
4
CO
Cy
Ph
(L2) 55%
(L3) 50%
Br
N
R
N
MeI (1.5 equiv.)
N
R
Mn(CO)5Br
N
R
H
N
o
Mn
N
THF, 90 C, 3 h
NaH (1.5 equiv.)
OC
CO
o
R= o-SMeC H (L1) THF, 0 C - rt
L4
6
4
CO
overnight
SMe
N
SMe
HN
Br
Br
Br
N
HN
OC
N
N
Mn
Mn
Mn
CO
CO
OC
CO
CO
OC
CO
CO
Mn-1 (90%)
Mn-2 (91%)
Mn-4 (70%)
Scheme 1 Synthesis of manganese (I) complexes

3.3. Crystal structure of manganese(I) complexes
The crystals of Mn-1 & Mn-2 suitable for X-ray
diffraction were obtained by the slow diffusion of diethyl
ether into a saturated solution of the complexes in THF.
The Mn-1 complex was crystallized as a monoclinic
crystal system with space group P2 /c. The single crystal
1
X-ray diffraction experiment was performed at 293K. The
ORTEP diagram is given in Figure 1. A five-membered
ring formed from the coordination of Mn(I) to the nitrogen
atoms of the L1 ligand and the nitrogen atoms occupy two
equatorial sites around Mn(I). The geometry of the
complex around the Mn(I) ion is distorted octahedron.
Two terminal carbonyl groups are occupying the two other
equatorial site trans to the nitrogen atoms. Other carbonyl
and the bromide coordinates Mn(I) linearly, perpendicular
to the equatorial plane.
Figure 2 ORTEP diagram of Mn-2[27]
Table 1 Crystal data and structure refinement parameters
for Mn-1
Dark orange crystals of Mn-2 approximate dimensions
Complex Mn-1
0
.5×0.5×0.3 mm were isolated, and the single-crystal X-
Empirical formula
17 2 3
C H16BrMnN O S
Formula weight
463.23
ray diffraction experiment was performed at 100 K. The
ORTEP diagram is given in Figure 2. The complex was
crystallized in a monoclinic system with space group
Temperature(K)
293(2)
Crystal system
monoclinic
Space group
1
P2 /c
P2 /c. The structure resembles with that of Mn-1.
1
a(Å)
10.7643(2)
13.4050(3)
13.3946(2)
96.471(2)
1920.47(6)
4
b(Å)
The structure refinement parameters selected bond angles,
and bond lengths are summarized in Table 1 to 4.
c(Å)
β(°)
Volume(Å)3
Z
Density (calculated) (g/cm3)
1.602
-1
Absorption coefficient (mm )
9.199
F(000)
928.0
Scan range for data collection(°)
Index ranges
8.26 to 132.86
-12 ≤ h ≤ 12,
-15 ≤ k ≤ 15,
1
5 ≤ l ≤ 12
Reflections collected
17531
3360 [Rint = 0.0430,
sigma = 0.0249]
Independent reflections
R
Data/restraints/parameters
Goodness-of-fit on F2
3360/0/227
1.028
Final R indexes [I>=2σ (I)]
1
R = 0.0308,
wR
2
= 0.0846
Final R indexes [all data]
1
R = 0.0339,
2
wR = 0.0878
Figure 1 ORTEP diagram of Mn-1[26]
Table 2 Selected bond lengths and bond angles of Mn-2.
Interatomic distances (Å)
Mn(1)-Br(1)
Mn(1)-N(1)
Mn(1)-N(2)
2.5232(5)
2.099(2)
2.059(2)
Mn(1)-C(15)
Mn(1)-C(16)
Mn(1)-C(17)
1.798(3)
1.803(3)
1.812(4)
Bond angles(o)
N(2)-Mn(1)-Br(1)
N(1)-Mn(1)-Br(1)
86.16(6)
85.88(6)
C(16)-Mn(1)-N(1)
C(16)-Mn(1)-C(15)
94.59(12)
90.05(15)

N(1)-Mn(1)-N(2)
C(15)-Mn(1)-Br(1)
C(15)-Mn(1)-N(2)
C(15)-Mn(1)-N(1)
C(16)-Mn(1)-Br(1)
C(16)-Mn(1)-N(2)
79.31(8)
89.46(11)
95.65(14)
C(16)-Mn(1)-C(17)
C(17)-Mn(1)-Br(1)
C(17)-Mn(1)-N(2)
91.68(19)
88.55(13)
173.54(14)
96.62(13)
88.00(16)
Decreasing the amount of alcohol, however, decreases the
yield of 3a (Table 3, entry 2). The catalytic activity of the
catalyst Mn-2 was found to be significantly lower than
that of Mn-1 under the same condition, and 40% 3a was
obtained (Table 3, entry 3). Interestingly, the use of Mn-4
as a catalyst resulted in 18% yield of the desired product
173.34(13) C(17)-Mn(1)-N(1)
179.45(13) C(17)-Mn(1)-C(15)
93.64(15)
(Table 3, entry-4). This indicated the operation of N-H
proton assisted bifunctional mechanism. Utilization of
more polar solvents such as t-AmOH, THF, or under neat
condition greatly affects the reaction outcome (Table 3,
entry 5-7). The reaction was also found sensitive to the
nature of base. The use of t-BuONa, t-BuOLi, KOH, and
Cs CO resulted in lower yields of 3a under identical
conditions (Table 3, entry 8-11). Decreasing the base
loading, reaction time, and reaction temperature decreases
the yield (Table 3, entry 12-15). Notably, the N,N-
dialkylation was not observed during the reaction. The
control experiment demonstrated that in the absence of
Mn-catalyst or base only traces of the desired product was
obtained (Table 3, entry 16-17).
Table 3 Crystal data and structure refinement parameters
for Mn-2.
Complex Mn-2
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
β (°)
Volume (Å)3
16 2 3
C H20BrMnN O
2
3
423.19
100.00(10)
monoclinic
1
P2 /c
18.2446(3)
7.42000(10)
13.1500(2)
96.652(2)
1768.20(5)
4
Z
3
Density (calculated) (g/cm )
Absorption coefficient (mm )
1.590
8.847
Table 3 Reaction optimization
-1
F(000)
856.0
12.9 to 133.08
-21 ≤ h ≤ 18,
H
[
Mn] (2 mol%)
Scan range for data collection (°)
Index ranges
NH2
N
OH
Base (x mol%)
o
Solvent, 140 C
-8 ≤ k ≤ 8,
-15 ≤ l ≤ 15
1a
2a
24 h
3a
Reflections collected/ unique, Rint
15731
090, 0.0401, 0.0260
3090/0/208
1.061
3
Entry
Catalyst
Mn-1
Mn-1
Mn-2
Mn-4
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
Mn-1
-
Solvent
Toluene
Toluene
Toluene
Toluene
t-AmOH
THF
Base (mol%)
3a
b
(%)
Data/restraints/parameters
Goodness-of-fit on F2
Final R indexes [I>=2σ (I)]
1
2c
3
4
5
6
7
8
9
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
t-BuONa (40 mol%)
t-BuOLi (40 mol%)
KOH (40 mol%)
91
37d
R
1
= 0.0283,
wR = 0.0735
= 0.0294,
wR = 0.0743
40d
2
Final R indexes [all data]
R
1
18d
55d
2
Traced
12d
Table 4 Selected bond lengths and bond angles of Mn-2.
Neat
Interatomic distances (Å)
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
37d
Mn(1)-Br(1)
Mn(1)-N(1)
Mn(1)-N(2)
2.5243(5)
2.046(2)
2.090(2)
Mn(1)-C(15)
Mn(1)-C(16)
Mn(1)-C(14)
1.853(3)
1.797(3)
1.819(3)
Traced
55d
1
1
0
1
Bond angles(o)
Cs
2
CO
3
(40 mol%)
Traced
45d
N(2)-Mn(1)-Br(1)
N(1)-Mn(1)-Br(1)
N(1)-Mn(1)-N(2)
C(15)-Mn(1)-Br(1)
C(15)-Mn(1)-N(2)
C(15)-Mn(1)-N(1)
C(16)-Mn(1)-Br(1)
C(16)-Mn(1)-N(2)
85.63(6)
88.29(6)
79.07(8)
176.37(7)
90.75(9)
91.15(9)
90.53(8)
173.38(10)
C(16)-Mn(1)-N(1)
C(16)-Mn(1)-C(15)
C(16)-Mn(1)-C(14)
C(14)-Mn(1)-Br(1)
C(14)-Mn(1)-N(2)
C(14)-Mn(1)-N(1)
C(14)-Mn(1)-C(15)
95.45(10)
93.10(11)
88.51(11)
88.96(8)
96.80(10)
175.20(10)
91.34(11)
12
t-BuOK (20 mol%)
t-BuOK (10 mol%)
t-BuOK (40 mol%)
t-BuOK (40 mol%)
-
1
3
20d
14e
5f
16
67d
1
25d
Traced
Traced
1
7
t-BuOK (40 mol%)
3
.4. Catalytic N-alkylation of amines
a
Reaction conditions: catalyst (2 mol%), Base (x mol%), Solvent (2M),
The preliminary catalytic exploration started using aniline
o
alcohol (0.4 mmol), amine (0.2 mmol) at 140 C for 24 h under argon.
1
a and benzyl alcohol 2a as the model substrate and Mn-1
b
c
d
1
Isolated yields. alcohol (1.5 equiv.). Yields determined by H NMR
e
f
o
as the catalyst (Table 3). The treatment of aniline (2
equiv.) with benzyl alcohol (1 equiv.) in the presence of 2
using 1,3,5-trimethoxybenzene as an internal standard. 18 h. 120 C.
To check the applicability of the developed manganese
catalyzed C-N bond-forming protocol, we have tested N-
alkylation of different substituted amines with differently
substituted alcohols employing Mn-1 as the model
o
mol% Mn-1 and 40 mol% of t-BuOK as a base at 140 C
resulted in full conversion of benzyl alcohol and after
aqueous workup and column chromatography we have
isolated 91% yield of the desired amine (Table 3, entry 1).

catalyst, and the results are summarized in Table 4.
Initially, the N-alkylation of substituted aniline with
substituted alcohols was inspected. Electron-rich aromatic
alcohols such as 4-methoxybenzyl alcohol (2b), and
piperonyl alcohol (2c) reacted smoothly with aniline 1a
under the standard reaction condition to deliver the
corresponding secondary amines 3b,c in 65% and 70%
yields, respectively. Benzylic alcohols containing halogens
such as chloro (2d), and bromo (2e) were also found to be
suitable coupling partner delivering the products 3d,e in
good yields with the complete retention of the halogen
H
R2
Mn-1 (2 mol%)
t-BuOK (x mol%)
NH2
N
R2
OH
R1
R1
Toluene, 140 o
24 h
C
1
2
3
N-alkylated aminea,b
Entry
1
Amine
Alcohol
OH
NH2
H
N
1
a
2a
3a, 91%
OMe
NH2
H
OH
2
3
N
MeO
1a
2b
2c
3b, 65%
O
O
functionality
thus
enabling
potential
future
NH2
O
O
H
OH
N
functionalization. Interesting, the steric effect of the ortho-
substituted impart negligible effect on the reaction
outcome. Likewise, biphenyl methanol (2f) yielded the
adduct 3f in 80% yield. Substrate containing strongly
electron-withdrawing trifluoromethyl group (2g) was also
well-tolerated, and the alkylated amine 3g was isolated in
3c, 70%c
1a
OH
NH2
H
N
4
Cl
Br
Cl
3d, 98%
1a
2d
2e
MeO
H
N
NH2
OH
OMe
5
6
60% yield. Pyridine containing heteroaromatic alcohol
Br
(2h) was also found to be a viable coupling partner
1a
NH2
3e
72%c
,
Ph
delivering the adduct 3h 60% yield. Anilines with
electron-donating as well as withdrawing substituents (1b-
d) could also be converted to the N-benzylated amines 3i-k
with similar efficiency.
OH
OH
H
N
Ph
3f, 80%c
1a
2f
CF3
NH2
H
7
N
F3C
Table 4 Coupling of anilines with alcohols
3g, 60%c
1
a
2g
2h
NH2
H
N
OH
N
8
9
N
1a
h, 60%c
3
NH2
H
N
OH
OH
3i, 72%c
1
b
c
2a
2a
Cl
NH2
H
N
Cl
1
0
1
1
j, 74%c
3
NH2
H
N
OH
1
Cl
Cl
3k, 50%c
1d
2a
a
Reaction conditions: Mn-1 (2 mol%), t-BuOK (40 mol%), toluene (2 M), alcohol (0.4
o
b
c
mmol), amine (0.2 mmol) at 140 C under argon. Isolated yields. 1 equiv. base is
used.
4
. Conclusion
We report the synthesis of three new manganese
complexes Mn-1-3 by the reaction of commercially
available precursor MnBr(CO) and readily made bidentate
5
amine-based ligands. The complexes were well
characterized using IR, NMR, and mass spectroscopic
method. The molecular structure of the complexes Mn-1,2
were determined by X-ray crystallography, which revealed
that the complexes exists as a distorted octahedron around

manganese ion where the ligand binds the Mn center
through bidentate fashion. The catalysts are highly air-
stable and easily handleable. The manganese complexes
were established for catalytic N-alkylation of amines. The
reaction parameters were optimized, and Mn-1 was found
to be most effective. The developed method showed
excellent functional group tolerance and is a sustainable
and atom economical way to secondary amines.
1853-1864; (c) Q. Yang, Q. Wang, Z. Yu, Chem. Soc. Rev.,
44 (2015) 2305-2329; (d) K.-i. Shimizu, Catal. Sci. Tech., 5
(2015) 1412-1427; (e) B. Maji, M.K. Barman, Synthesis, 49
(2017) 3377-3393; (f) A. Corma, J. Navas, M.J. Sabater,
Chem. Rev., 118 (2018) 1410-1459; (g) M. Xiao, X. Yue, R.
Xu, W. Tang, D. Xue, C. Li, M. Lei, J. Xiao, C. Wang, Angew.
Chem. Int. Ed., 58 (2019) 10528-10536; (h) Y. Liu, A.
Afanasenko, S. Elangovan, Z. Sun, K. Barta, ACS
Sustainable Chem. Eng., 7 (2019) 11267-11274; (i) T.
Irrgang, R. Kempe, Chem. Rev., 119 (2019) 2524-2549.
Declaration of Competing Interest
There are no conflicts to declare.
Acknowledgment:
[
5] R. Grigg, T.R.B. Mitchell, S. Sutthivaiyakit, N.
Tongpenyai, J. Chem. Soc. Chem. Commun., (1981) 611-
612.
[
(
[
6] Y. Watanabe, Y. Tsuji, Y. Ohsugi, Tetrahedron Lett., 22
1981) 2667-2670.
7] (a) S. Demir, F. Coşkun, İ. Özdemir, J. Organomet.
B.M.
thanks
IISER
Kolkata
and
SERB
(ECR/2016/001654) for financial support. K.D. and A.J.
thanks CSIR and A.K. thanks INSPIRE for fellowship.
Dedicated to Professor Dr. Goutam Kumar Lahiri on the
occasion of his 60th birthday.
Chem., 755 (2014) 134-140; (b) A.B. Enyong, B. Moasser,
J. Org. Chem., 79 (2014) 7553-7563; (c) R. Ramachandran,
G. Prakash, S. Selvamurugan, P. Viswanathamurthi, J.G.
Malecki, V. Ramkumar, Dalton Trans., 43 (2014) 7889-
Appendix A: Supplementary materials
7
902; (d) G. Prakash, R. Ramachandran, M. Nirmala, P.
Viswanathamurthi, J. Sanmartin, Inorg. Chim. Acta, 427
2015) 203-210; (e) R. Ramachandran, G. Prakash, M.
Electronic supplementary information (ESI) available:
Detailed experimental procedures, analytical data, and
NMR spectra of compounds and complexes.
Crystallographic data for Mn-1, CCDC1948389 and Mn-
(
Nirmala, P. Viswanathamurthi, J.G. Malecki, J. Organomet.
Chem., 791 (2015) 130-140; (f) R. Ramachandran, G.
Prakash, S. Selvamurugan, P. Viswanathamurthi, J.G.
Malecki, W. Linert, A. Gusev, RSC Adv., 5 (2015) 11405-
11422; (g) Z. Şahin, N. Gürbüz, İ. Özdemir, O. Şahin, O.
Büyükgüngör, M. Achard, C. Bruneau, Organometallics, 34
2, CCDC 1948387 can be obtained free of charge from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223–336-033; or e-
mail: deposit@ccdc.cam.ac.uk.
(2015) 2296-2304; (h) S.P. Shan, X. Xiaoke, B.
References:
Gnanaprakasam, T.T. Dang, B. Ramalingam, H.V. Huynh,
A.M. Seayad, RSC Adv., 5 (2015) 4434-4442; (i) I. Sorribes,
J.R. Cabrero-Antonino, C. Vicent, K. Junge, M. Beller, J.
Am. Chem. Soc., 137 (2015) 13580-13587; (j) X. Xie, H.V.
Huynh, ACS Catal., 5 (2015) 4143-4151; (k) R. Adam, J.R.
Cabrero-Antonino, K. Junge, R. Jackstell, M. Beller, Angew.
Chem. Int. Ed., 55 (2016) 11049-11053; (l) N. Kaloglu, I.
Özdemir, N. Gürbüz, M. Achard, C. Bruneau, Catal.
Commun., 74 (2016) 33-38; (m) X. Ma, C. Su, Q. Xu, Top
Curr Chem (Cham), 374 (2016) 27; (n) J.J.A. Celaje, X.
Zhang, F. Zhang, L. Kam, J.R. Herron, T.J. Williams, ACS
Catal., 7 (2017) 1136-1142; (o) X.-J. Yu, H.-Y. He, L. Yang,
H.-Y. Fu, X.-L. Zheng, H. Chen, R.-X. Li, Catal. Commun., 95
[
1] (a) G. Zweifel, K. Nagase, H.C. Brown, J. Am. Chem.
Soc., 84 (1962) 190-195; (b) S. Kobayashi, H. Ishitani,
Chem. Rev., 99 (1999) 1069-1094; (c) J.A. Ellman, T.D.
Owens, T.P. Tang, Acc. Chem. Res., 35 (2002) 984-995; (d)
T.E. Müller, K.C. Hultzsch, M. Yus, F. Foubelo, M. Tada,
Chem. Rev., 108 (2008) 3795-3892; (e) T.C. Nugent, M. El-
Shazly, Adv. Synth. Catal., 352 (2010) 753-819; (f) E.
Vitaku, D.T. Smith, J.T. Njardarson, J. Med. Chem., 57
(
[
(
2014) 10257-10274.
2] (a) L. Legnani, B.N. Bhawal, B. Morandi, Synthesis, 49
2017) 776-789; (b) R.N. Salvatore, C.H. Yoon, K.W. Jung,
Tetrahedron, 57 (2001) 7785-7811.
3] (a) M.-C. Fu, R. Shang, W.-M. Cheng, Y. Fu, Angew.
(2017) 54-57; (p) M. Kaloğlu, N. Gürbüz, D. Sémeril, İ.
[
Özdemir, Eur. J. Inorg. Chem., 2018 (2018) 1236-1243; (q)
M. Maji, K. Chakrabarti, B. Paul, B.C. Roy, S. Kundu, Adv.
Synth. Catal., 360 (2018) 722-729; (r) R. Ramachandran, G.
Prakash, P. Viswanathamurthi, J.G. Malecki, Inorg. Chim.
Acta, 477 (2018) 122-129; (s) P. Dubey, S. Gupta, A.K.
Singh, Organometallics, 38 (2019) 944-961; (t) N. Kaloğlu,
M. Achard, C. Bruneau, İ. Özdemir, Eur. J. Inorg. Chem.,
Chem. Int. Ed., 54 (2015) 9042-9046; (b) B. Li, J.-B. Sortais,
C. Darcel, RSC Adv., 6 (2016) 57603-57625; (c) X.-F. Liu, X.-
Y. Li, C. Qiao, L.-N. He, Synlett, 29 (2018) 548-555; (d) J.R.
Cabrero-Antonino, R. Adam, M. Beller, Angew. Chem. Int.
Ed., 58 (2019) 12820-12838; (e) Y. Hoshimoto, S. Ogoshi,
ACS Catal., 9 (2019) 5439-5444; (f) P. Trillo, H. Adolfsson,
ACS Catal., 9 (2019) 7588-7595.
2
019 (2019) 2598-2606; (u) M. Yiğit, E.Ö. Karaca, B. Yiğit,
[
4] (a) T.D. Nixon, M.K. Whittlesey, J.M.J. Williams, Dalton
N. Gürbüz, İ. Özdemir, Transit. Met. Chem., (2019).
Trans., (2009) 753-762; (b) S. Bähn, S. Imm, L. Neubert, M.
Zhang, H. Neumann, M. Beller, ChemCatChem, 3 (2011)

[
2
3
8] (a) T.D. Apsunde, M.L. Trudell, Synthesis, 46 (2014)
30-234; (b) P. Qu, C. Sun, J. Ma, F. Li, Adv. Synth. Catal.,
56 (2014) 447-459; (c) S. Ruch, T. Irrgang, R. Kempe,
83 (2018) 3378-3384; (e) A.K. Bains, A. Kundu, S. Yadav, D.
Adhikari, ACS Catal., (2019) 9051-9059.
[16] (a) S. Elangovan, J. Neumann, J.-B. Sortais, K. Junge,
C. Darcel, M. Beller, Nat. Commun., 7 (2016) 12641; (b) A.
Bruneau-Voisine, D. Wang, V. Dorcet, T. Roisnel, C. Darcel,
J.-B. Sortais, J. Catal., 347 (2017) 57-62; (c) M. Mastalir, E.
Pittenauer, G. Allmaier, K. Kirchner, J. Am. Chem. Soc.,
139 (2017) 8812-8815; (d) R. Fertig, T. Irrgang, F. Freitag,
J. Zander, R. Kempe, ACS Catal., 8 (2018) 8525-8530; (e)
V.G. Landge, A. Mondal, V. Kumar, A. Nandakumar, E.
Balaraman, Org. Biomol. Chem., 16 (2018) 8175-8180; (f)
K. Das, A. Mondal, D. Pal, H.K. Srivastava, D. Srimani,
Organometallics, 38 (2019) 1815-1825; (g) L. Homberg, A.
Roller, K.C. Hultzsch, Org. Lett., 21 (2019) 3142-3147; (h)
M. Huang, Y. Li, Y. Li, J. Liu, S. Shu, Y. Liu, Z. Ke, Chem.
Commun., 55 (2019) 6213-6216.
[17] (a) P. Xu, F.-L. Qi, F.-S. Han, Y.-H. Wang, Chem. Asian
J., 11 (2016) 2030-2034; (b) S. Gupta, P. Chaudhary, N.
Muniyappan, S. Sabiah, J. Kandasamy, Org. Biomol.
Chem., 15 (2017) 8493-8498; (c) R. Ramachandran, G.
Prakash, P. Vijayan, P. Viswanathamurthi, J. Grzegorz
Malecki, Inorg. Chim. Acta, 464 (2017) 88-93; (d) R.
Sakamoto, S. Sakurai, K. Maruoka, Chem. Eur. J., 23 (2017)
9030-9033; (e) A.R. Bayguzina, C.F. Musina, R.I.
Khusnutdinov, Russ. J. Org. Chem., 54 (2019) 1652-1659.
[18] A. Mukherjee, A. Nerush, G. Leitus, L.J.W. Shimon, Y.
Ben David, N.A. Espinosa Jalapa, D. Milstein, J. Am. Chem.
Soc., 138 (2016) 4298-4301.
Chem. Eur. J., 20 (2014) 13279-13285; (d) J. Wu, H. Jiang,
D. Chen, J. Shen, D. Zhao, J. Xiang, Q. Zhou, Synlett, 25
(
(
2014) 539-542; (e) K. Kim, S.H. Hong, J. Org. Chem., 80
2015) 4152-4156; (f) Y.-H. Chang, I. Tanigawa, H.-o.
Taguchi, K. Takeuchi, F. Ozawa, Eur. J. Inorg. Chem., 2016
2016) 754-760; (g) H. Liu, D.-L. Wang, X. Chen, Y. Lu, X.-L.
(
Zhao, Y. Liu, Green Chem., 19 (2017) 1109-1116; (h) P. Liu,
R. Liang, L. Lu, Z. Yu, F. Li, J. Org. Chem., 82 (2017) 1943-
1
950; (i) K.-i. Fujita, S. Furukawa, N. Morishima, M.
Shimizu, R. Yamaguchi, ChemCatChem, 10 (2018) 1993-
997.
9] (a) X. Liu, P. Hermange, J. Ruiz, D. Astruc,
1
[
ChemCatChem, 8 (2016) 1043-1045; (b) L. Yan, X.-X. Liu, Y.
Fu, RSC Adv., 6 (2016) 109702-109705; (c) R. Mamidala,
M.S. Subramani, S. Samser, P. Biswal, K. Venkatasubbaiah,
Eur. J. Org. Chem., 2018 (2018) 6286-6296; (d) M. Zhang,
S. Wu, L. Bian, Q. Cao, W. Fang, Catal. Sci. Tech., 9 (2019)
2
86-301.
[
(
10] (a) K. Wu, W. He, C. Sun, Z. Yu, Tetrahedron, 72
2016) 8516-8521; (b) F. De Schouwer, S. Adriaansen, L.
Claes, D.E. De Vos, Green Chem., 19 (2017) 4919-4929.
11] S. Gangaram, C.S. Adimulam, R.K. Akula, R. Kengiri,
S.R. Pamulaparthy, S. Madabhushi, N. Banda, Chem. Lett.,
2 (2013) 1522-1524.
12] H. Yang, R. Mao, C. Luo, C. Lu, G. Cheng, Tetrahedron,
0 (2014) 8829-8835.
[
4
[
7
[19] M. Mastalir, M. Glatz, N. Gorgas, B. Stöger, E.
Pittenauer, G. Allmaier, L.F. Veiros, K. Kirchner, Chem.
Eur. J., 22 (2016) 12316-12320.
[
(
13] (a) T. Yan, B.L. Feringa, K. Barta, Nat. Commun., 5
2014) 5602; (b) M. Minakawa, M. Okubo, M. Kawatsura,
Bulletin of the Chemical Society of Japan, 88 (2015) 1680-
682; (c) T. Yan, B.L. Feringa, K. Barta, Sci. Adv., 3 (2017)
[20] M.K. Barman, S. Waiba, B. Maji, Angew. Chem. Int.
Ed., 130 (2018) 9264-9268.
1
eaao6494; (d) C. Qiao, X.-Y. Yao, X.-F. Liu, H.-R. Li, L.-N.
He, Asian J. Org. Chem., 7 (2018) 1815-1818; (e) N.
Hofmann, K.C. Hultzsch, Eur. J. Org. Chem., 2019 (2019)
[21] S. Waiba, A. Das, M.K. Barman, B. Maji, ACS Omega, 4
(2019) 7082-7087.
[22] M.K. Barman, A. Jana, B. Maji, Adv. Synth. Catal., 360
(2018) 3233-3238.
[23] A. Jana, C.B. Reddy, B. Maji, ACS Catal., 8 (2018)
9226-9231.
3
105-3111.
14] (a) G. Zhang, Z. Yin, S. Zheng, Org. Lett., 18 (2016)
00-303; (b) S. Rösler, M. Ertl, T. Irrgang, R. Kempe,
[
3
Angew. Chem. Int. Ed., 54 (2015) 15046-15050; (c) S.P.
Midya, A. Mondal, A. Begum, E. Balaraman, Synthesis, 49
[24] M.K. Barman, K. Das, B. Maji, J. Org. Chem., 84 (2019)
1570-1579.
(
8
2017) 3957-3961; (d) H. Chung, Y.K. Chung, J. Org. Chem.,
3 (2018) 8533-8542; (e) S.P. Midya, J. Pitchaimani, V.G.
Landge, V. Madhu, E. Balaraman, Catal. Sci. Tech., 8
2018) 3469-3473; (f) B. Emayavaramban, P. Chakraborty,
E. Manoury, R. Poli, B. Sundararaju, Org. Chem. Front, 6
[25] (a) W. Rammal, H. Jamet, C. Philouze, J.-L. Pierre, E.
Saint-Aman, C. Belle, Inorg. Chim. Acta, 362 (2009) 2321-
2326; (b) S. Bhattacharyya, J.W. Labadie, O.W. Gooding, S.
Rana Compositions for reductive aminations utilizing
supported tricarboxyborohydride reagents and methods
of using the reductive amination procedure.
US7985882B1, 2011.
[26] CCDC-1948389. Contains the supplementary
crystallographic data.
[27] CCDC-1948387. Contains the supplementary
crystallographic data.
(
(
[
(
2019) 852-857.
15] (a) M. Vellakkaran, K. Singh, D. Banerjee, ACS Catal., 7
2017) 8152-8158; (b) P. Yang, C. Zhang, Y. Ma, C. Zhang,
A. Li, B. Tang, J.S. Zhou, Angew. Chem. Int. Ed., 56 (2017)
4702-14706; (c) A. Afanasenko, S. Elangovan, M.C.A.
Stuart, G. Bonura, F. Frusteri, K. Barta, Catal. Sci. Tech., 8
2018) 5498-5505; (d) J. Das, D. Banerjee, J. Org. Chem.,
1
(

Author statement
Kuhali Das: Conceptualization, Methodology,
Investigation,
Writing-
Original
draft
preparation, Amol Kumar: Investigation,
Methodology. Akash Jana: Investigation,
Methodology. Biplab Maji: Conceptualization,
Supervision, Writing- Original draft preparation,
Writing- Reviewing and Editing, Funding
acquisition

Declaration of interests
☒
The authors declare that they have no
known competing financial interests or personal
relationships that could have appeared to
influence the work reported in this paper.
☐
The authors declare the following financial
interests/personal relationships which may be
considered as potential competing interests:

OH
Ar1
Br
SMe
HN
Ar1
N
N
Ar1
Mn
H
OC
CO
CO
NH2
H2O
Ar1

Highlights:

Highly
bench
stable
phosphine free N,N-chelate
Mn(I) complexes have been
synthesized.

Characterization
by
analytical and spectral
methods propose distorted
octahedral geometry around
manganese.


The single-crystal XRD
experiment confirms the
proposed geometry.
N-alkylation
reactions
could
be
performed
efficiently
with
the
phosphine-free
manganese(I) catalyst.

Good functional group
tolerance observed for the
C-N coupling reactions.