Ru(II) complexes containing (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole: Synthesis, solid-state structure, computational study and catalysis in N-alkylation reactions

Article abstract of DOI:10.1016/j.ica.2020.119864

Reactions of (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole (L) with ruthenium(II) prefabricated precursors [RuHCl(CO)(EPh₃)₃] and [RuH₂(CO)(EPh₃)₃] (E = P or As) afforded new Ru(II) complexes [RuCl(CO)(EPh₃)₂(L)] and [RuH(CO)(EPh₃)₂(L)] (E = P or As) (1–4). All the Ru(II) complexes (1–4) were characterized by IR, NMR spectroscopies, ESI-mass spectrometry and elemental analyses. The solid-state structures of Ru(II) complexes (2 and 3) were established by single crystal X-ray analyses and revealed distorted octahedral geometries around the ruthenium(II) ion and mono anionic bidentate N^N coordination mode for hydrazine ligand. The Ru(II) complexes 2 and 3 were also analyzed using Hirshfeld surface analysis and DFT calculations. Moreover, all the complexes (1–4) were utilized in the N-alkylation reactions of amines using alcohol. Complex 3 was found to be highly active towards N-alkylation of different aromatic amines with alcohol.

Full text of DOI:10.1016/j.ica.2020.119864

Journal Pre-proofs
Research paper
Ru(II) complexes containing (2-(pyren-1-ylmethylene)hydrazinyl)benzothia‐
zole: Synthesis, solid-state structure, computational study and catalysis in N-
alkylation reactions
Kaliyappan Murugan, Subbarayan Vijayapritha, Periasamy
Viswanathamurthi, Kandasamy Saravanan, Paranthaman Vijayan, Stephen O.
Ojwach
PII:
DOI:
Reference:
S0020-1693(20)31063-X
https://doi.org/10.1016/j.ica.2020.119864
ICA 119864
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Inorganica Chimica Acta
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Revised Date:
Accepted Date:
14 January 2020
29 June 2020
29 June 2020
Please cite this article as: K. Murugan, S. Vijayapritha, P. Viswanathamurthi, K. Saravanan, P. Vijayan, S.O.
Ojwach, Ru(II) complexes containing (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole: Synthesis, solid-state
structure, computational study and catalysis in N-alkylation reactions, Inorganica Chimica Acta (2020), doi:
https://doi.org/10.1016/j.ica.2020.119864
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Ru(II)complexescontaining(2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole:
Synthesis,solid-statestructure,computationalstudyandcatalysisinN-alkylation
reactions
a
a
a
Kaliyappan Murugan , Subbarayan Vijayapritha , Periasamy Viswanathamurthi *, Kandasamy
b
c
c
Saravanan , Paranthaman Vijayan , Stephen O. Ojwach
aDepartment of Chemistry, Periyar University, Salem-636 011, India.
bDepartment of Physics, Periyar University, Salem-636 011, India.
cSchool of Chemistry and Physics, Pietermaritzburg Campus, University of KwaZulu-Natal,
Private Bag X01, Scottsville 3209, South Africa.
Corresponding Author:
E-mail: viswanathamurthi@gmail.com
Fax: +91 427 2345124

Abstract
Reactions of (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole (L) with ruthenium(II)
prefabricated precursors [RuHCl(CO)(EPh ) ] and [RuH (CO)(EPh ) ] (E= P or As) afforded
3
3
2
3 3
new Ru(II) complexes [RuCl(CO)(EPh ) (L)] and [RuH(CO)(EPh ) (L)] (E= P or As) (1-4). All
3
2
3 2
the Ru(II) complexes (1-4) were characterized by IR, NMR spectroscopies, ESI-mass
spectrometry and elemental analyses. The solid-state structures of Ru(II) complexes (2 and 3)
were established by single crystal X-ray analyses and revealed distorted octahedral geometries
around the ruthenium(II) ion and mono anionic bidentate N^N coordination mode for hydrazine
ligand. The Ru(II) complexes 2 and 3 were also analyzed using Hirshfeld surface analysis and
DFT calculations. Moreover, all the complexes (1-4) were utilized in the N-alkylation reactions
of amines using alcohol. Complex 3 was found to be highly active towards N-alkylation of
different aromatic amines with alcohol.
Key words: Ru(II) complexes, π-π interaction, DFT calculations, Catalytic activity.

1
. Introduction
Synthesis of compounds with C-N bond has occupied a special place in synthetic organic
chemistry since nitrogen functionalities occur in various compounds of synthetic and
pharmaceutical significance as well as in important biologically active molecules [1].
Conventionally, transition-metal-catalyzed methodologies such as amination of arylhalides [2],
reductive amination of carbonyl compounds [3] or the hydroamination [4] and hydroamino-
methylation [5] of C–C multiple bonds, etc., have been used for synthesis of compounds
containing C-N bond. However, pre-functionalization step and stoichiometric excess amount of
base have required for above methods which generates equivalent amount of salt as waste [6].
These drawbacks prompted to develop an alternative protocol to achieve the related objective. In
recent years N-alkylation of amines with alcohols catalyzed by transition-metal catalysts by
borrowing hydrogen methodology (BH) becomes eminent [7]. Such reactions release water as
the only byproduct and hence environmentally benign in addition to highly atom economical
[8,9].
Among transition metal homogeneous catalysts, iridium and ruthenium metal complexes
have gained escalating attention due to their high catalytic performance with high product
selectivity. Beller's group used a dimeric Shvo's ruthenium catalyst system [10] and realized the
alkylation of indoles using alcohols, while Williams and co-workers have used ruthenium dimer
catalyst [11] to achieve good results. Koten, Milstein and co-workers have obtained good yields
in the N-alkylation of aromatic amines with diols using 0.1–1 mol% of the PNP pincer type
○
ruthenium catalyst [12,13] at high temperature (130–180 C). Also, Yamaguchi and co-workers
reported an elegant synthesis of N-alkyl substituted amines using readily available [Cp*IrCl ] (1
2
2
○
mol%) at 110 C [14]. Kempe also reported that small loadings of [IrCl(PN)COD] afford
excellent results in the N-alkylation of amines, forming selective mono- and dialkylated products
[15]. Two very recently reported compounds of Ru(II)CNN [16] and IrPNP [17] pincer type
catalyst from Matute, Ozawa and co-workers, are the first selective C–N bond formation reaction
catalyst for the synthesis of N-alkylated amines with excellent results. Our own group has also
successful in applying the ruthenium carbonyl complexes [18] to couple a wide range of amines,
diamines and alcohols together.

Generally, in the area of development of transition metal catalysts for a specific process,
besides choosing the right metal ion, the design of ligand is also very important. Since nature of
the ligand has a profound effect on the coordination chemistry of a metal complex, the designing
and “tailoring” of ligand properties can lead to complexes with efficient homogeneous catalytic
activities. In this regard, in recent years, the Schiff base ligands have been enticed as an
outstanding toolbox, not only due to its usefulness in controlling the performance of catalysts but
also for the reason that it has enhanced co-ordination with the metal atom [19-21]. The main
advantages of these ligands are great availability, inexpensiveness, easy synthesis, tunability, and
stability. The resulting complexes exhibit numerous applications in pharmaceutical chemistry
[22] and luminescent magnetic materials besides catalysis [23,24]. Generally, Schiff base ligands
having both hard and soft donor atoms (e.g. NS or XNS, X = N, O, and S) are considered
eminent because of their coordination versatility [19] and remarkable applications in catalytic
[20] and biological sciences [21]. Vast number of researchers has paid considerable interest in
the development of new such compounds. The recent report shows that hydrazino
benzothiazole framework functionalized with suitable groups attract considerable attention as
versatile ligands with respect to their variable coordination behavior [25]. Pyrene or its
analogues are selected for functionalization of benzothiazole hydrazone due to their strong
electron donor properties bestows electron donor-acceptor systems which can influence the
catalytic or biological properties. Many researchers have synthesized transition metal
complexes containing a variety of these compounds and evaluated their biological activities
[26]. However, limited reports were documented regarding catalytic activities of these
compounds [27].
Based on the above facts and in continuing our efforts to study the coordination behavior
of complexes and exploit new catalytic system, this work describes synthesis of new Schiff base
from hydrazino benzothiazole and pyrene carbaldehyde and its ruthenium(II) complexes (1-4).
The chelating behavior of ligand with ruthenium ion was extensively investigated using various
spectroscopy techniques and their solid-state structures were corroborated by single-crystal
XRD. The catalytic properties of the new Ru(II) complexes (1-4) have been studied for N-
alkylation of various amines with benzyl alcohol.

2
. Experimental
2
.1. Materials and methods
All the chemicals used in the reactions were pure and AR grade. The starting complexes
[
RuHCl(CO)(EPh ) ], [RuH (CO)(EPh ) ] (E
=
P
or As) and (2-(pyren-1-
ylmethylene)hydrazinyl)benzothiazole (L) were prepared according to previous procedures [28-
0]. Thin layer chromatography (TLC) (Merck 1.05554 aluminum sheets precoated with silica
gel 60 F254) was used to monitor the reactions and the spots were visualized with UV light at
54 nm. Column chromatography purifications were performed by silica mesh (200-400). The C,
3
3
2
3 3
3
2
H, N and S analyses were carried out with a Vario EL III Elemental analyzer. Mass spectra were
measured on a Q ToF Micro hybrid quadrupole time flight spectrometer, using electrospray
1
13
ionization (ESI) mode. The H and C NMR spectra were measured by Avance III HD Nanobay
00 MHz instrument using CDCl as solvent. Tetramethylsilane (TMS) was used as reference for
4
3
measuring the chemical shifts (in ppm). Infrared spectra of the ligands and the metal complexes
-1
were recorded in the range of 4000-600 cm using a Bruker FT-IR spectrophotometer. The
melting points were checked with a Lab India melting point apparatus.
2
.2. Synthesis of ruthenium(II) hydrazine complexes (1-4)
All the complexes were synthesized by the following common procedure. To an ethanol-
chloroform (1:1) solution of (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole ligand (L), prefabricated
ruthenium(II) precursors were dissolved and reacted under reflux for 12 h. Initially, the reaction
mixtures turned orange to red color and the reaction was monitored by TLC. After completion of
the reaction, the solvent was evaporated under vacuum and the resulting red color compound was
purified by column chromatography (silica mesh 200-400) using ethyl acetate and petroleum
ether (9:1) mixture as eluent.
2
.2.1. Synthesis of [RuCl(CO)(PPh ) (L)] (1)
3 2
The ligand L (0.0377 g, 0.1 mmol) was reacted with [RuHCl(CO)(PPh ) ] (0.0952 g, 0.1
3
3
o
mmol) to form complex 1. Yield: (80 %). Mp: 220 C. Anal. Calc. for C H N OP RuClS: C,
6
1
43
3
2
6
8.76; H, 4.16; N, 3.01; S, 3.94 %. Found: C, 68.82; H, 4.24; N, 3.07; S, 3.97 %. FTIR (ATR
-1
1
cm ): 1941 (CO), 1665 (C=N). H NMR (CDCl , 400 MHz, ppm): 8.83 (s, 1H, HC=N); 8.47 (d,
3
2
H, J = 7.8 Hz, ArH), 8.17 (d, 2H, J = 6.8 Hz, ArH), 8.03-7.95 (m, 30H), 7.78-7.67 (m, 4H,
ArH), 7.30 (d, 2H, J = 5.12 Hz, ArH), 7.13 (d, 2H, J = 7.16 Hz, ArH), 6.99 (d, 2H, J = 6.8 Hz,
1
3
ArH), 6.95 (d, 2H, J = 8Hz, ArH), 6.85 (t, 1H, J = 6.2 Hz, ArH). C NMR (CDCl , 100 MHz,
3

y
q
r
s
x
ppm): 203.35 (C , CO), 166.12 (C , -HC=N), 151.65 (C , N=C-N) 147.64 (C , ArC), 145.64 (C ,
a
b
c
d
e
ArC), 137.16 (C , ArC), 133.85 (C , ArC), 133.73 (C , ArC), 133.66 (C , ArC), 133.62 (C , ArC),
f
g
h
i
j
1
1
1
33.44 ( C , ArC), 133.23 (C , ArC), 133.01 (C , ArC), 132.08 (C , ArC), 131.97 (C , ArC),
k
l
m
n
o
31.33 (C , ArC), 130.08 (C , ArC), 129.29 (C , ArC), 128.72 (C , ArC), 128.54 (C , ArC),
t
u
v
w
28.47 (C , ArC), 128.17 (C , ArC), 127.91 (C , ArC), 127.87(C , ArC), 127.67-117.81 (ArC of
+
PPh ). MS (ESI, m/z) 1031.1 [M-Cl+H] was in accordance with the calculated molecular mass
3
1
065.1.
2
.2.2. Synthesis of [RuCl(CO)(AsPh ) (L)] (2)
3
2
The ligand L (0.0377 g, 0.1 mmol) was reacted with [RuHCl(CO)(AsPh ) ] (0.1082 g,
3
3
o
0
.1 mmol) to form complex 2. Yield: (65%). Mp: 210 C. Anal. Calc. for C H N OAs RuClS:
61 44 3 2
C, 63.52; H, 3.84; N, 3.64; S, 2.75 %. Found: C, 63.58; H, 3.86; N, 3.73; S, 2.79 %; IR (ATR
-1
1
cm ): 1943 (CO), 1660 (C=N). H NMR (CDCl , 400 MHz, ppm): 8.79 (s, 1H, HC=N), 8.71 (d,
3
1
H, J = 9 Hz, ArH), 8.62 (d, 2H, J = 8.7.Hz, ArH), 8.23 (d, 2H, J = 7.8 Hz, ArH), 8.15 (d, 1H, J
8.2 Hz, ArH), 8.10 (d, 2H, J = 5 Hz, ArH), 8.03-7.74 (m, 30H, ArH), 7.66 -7.60 (m, 4H, ArH),
=
1
3
6
2
1
1
1
1
.89 (d, 2H, J = 7.2 Hz, ArH), 6.50 (t, 1H, J = 7.2 Hz, ArH). C NMR (CDCl , 100 MHz, ppm):
3
y
q
r
y
x
01.03 (C , CO), 162.76 (C , C=N), 154.95 (C , N=C-N), 146.30 (C , ArC), 143.99 (C , ArC),
a
b
c
d
e
39.74 (C , ArC), 136.54 (C , ArC), 134.94 (C , ArC), 134.34 (C , ArC), 134.17 (C , ArC),
f
g
h
i
j
33.95 (C , ArC), 133.66 (C , ArC), 133.01 (C , ArC), 132.93 (C , ArC), 132.55 (C , ArC),
k
l
m
n
o
30.81 (C , ArC), 130.43 (C , ArC), 130.18 (C , ArC), 129.99 (C , ArC), 129.69 (C , ArC),
t
u
v
w
29.35 (C , ArC), 129.11 (C , ArC), 128.90 (C , ArC), 128.74 (C , ArC), 128.65-119.31 (ArC of
+
AsPh ). MS (ESI, m/z) 1153.8 [M] was in accordance with the calculated molecular mass
3
1
154.0. Single crystals of suitable for X-ray determination were grown by slow evaporation of
dichloromethane-methanol (1:1) solution of 2 at room temperature.
.2.3. Synthesis of [RuH(CO)(PPh ) (L)] (3)
2
3
2
The ligand L (0.0377 g, 0.1 mmol) was reacted with [RuH (CO)(PPh ) ] (0.0918 g,0.1
2
3 3
o
mmol) to form complex 3. Yield: (76%). Mp: 232 C. Anal. Calc. for C H N OP RuS: C,
6
1
45
3
2
-
1
6
1
5.45; H, 4.05; N, 3.76; S, 2.87%. Found: 65.07; H, 4.12; N, 3.81; S, 2.92 %. FT-IR (ATR cm ):
1
946 (CO), 1662 (C=N). H NMR (CDCl , 400 MHz, ppm): -12.36 (t, Ru-H), 8.87 (s, 1H,
3
HC=N), 8.47 (t, 1H, J = 5.6.Hz, ArH), 8.41 (d, 2H, J = 8.Hz, ArH), 8.23 (d, 2H, J = 5.Hz, ArH),
.13 (d, 2H, J = 8.4.Hz, ArH), 7.98 (d, 2H, J = 6.2 Hz, ArH), 7.77-7.50 (m, 30H, ArH), 7.43-7.31
8
1
3
(
m, 4H, ArH), 7.06 (d, 2H, J = 8.1 Hz, ArH), 6.97 (d, 1H, J = 6.7.Hz, ArH). C NMR (CDCl ,
3
y
q
r
s
1
00 MHz, ppm): 201.04 (C , CO), 163.10 (C , C=N), 154.54 (C , N=C-N), 134.39 (C , ArC),

x
a
b
c
d
1
1
1
1
1
34.34 (C , ArC), 134.28 (C , ArC), 134.09 (C , ArC), 133.23 (C , ArC), 133.17. (C , ArC),
e
f
g
h
i
33.11 (C , ArC), 132.84 (C , ArC), 132.59 (C , ArC), 132.38 (C , ArC), 132.15 (C , ArC),
j
k
l
m
n
32.05 (C , ArC), 132.02 (C , ArC), 131.80 (C , ArC), 130.58 (C , ArC), 130.06 (C , ArC),
o
p
t
u
v
29.46 (C , ArC), 128.61 (C , ArC), 128.48 (C , ArC), 128.41 (C , ArC), 128.36 (C , ArC),
w
+
28.25 (C , ArC), 128.22-118.14 (ArC of PPh ). MS (ESI, m/z) 1032.1 [M+H] was in
3
accordance with the calculated molecular mass 1031.1. Single crystals of suitable for an X-ray
determination were grown by slow evaporation of acetonitrile solution of 3 at room temperature.
2
.2.4. Synthesis of [RuH(CO)AsPh ) (L)] (4)
3 2
The ligand L (0.0377 g, 0.1 mmol) was reacted with [RuH (CO)(AsPh ) ] (0.1050 g, 0.1
2
3 3
o
mmol) to form complex 4. Yield: 60%. Mp: 242 C. Anal. Calc. for C H N OAs RuS: C,
6
1
45
3
2
6
5.47; H, 4.05; N, 3.76; S, 2.87 %. Found: C, 65.56; H, 4.08; N, 3.81; S, 2.89 %. FT-IR (ATR
-1
1
cm ): 1943 (CO); 1664 (C=N). H NMR (CDCl , 400 MHz, ppm): -11.12 (s, Ru-H), 8.94 (s, 1H,
3
HC=N), 8.75 (d, 2H, J = 8.72 Hz ArH), 8.64-8.32 (m, 30H. ArH), 7.54 (d, 1H, J = 7.4 Hz ArH),
7
.45 (d, 2H, J = 7Hz, ArH), 7.33-7.04 (m, 3H, ArH), 6.97 (d, 1H, J = 7.28 Hz, ArH), 6.87-6.60
1
3
y
(
m, 3H, ArH), 6.40 (t, 1H, J = 9Hz, ArH). C NMR (CDCl , 100 MHz, ppm): 205.16 ( C , -CO),
3
q
r
s
x
a
1
1
1
1
1
1
61.27 C -C=N), 155.82 (C , -N=C-N), 134.04 (C , ArC), 133.76 (C , ArC), 133.57 (C , ArC),
b
c
d
e
f
33.40 (C , ArC), 133.24 (C , ArC), 131.97 (C , ArC), 131.87 (C , ArC), 131.39 (C , ArC),
g
h
i
j
k
31.17 (C , ArC), 130.36 (C , ArC), 129.96 (C , ArC), 128.76 (C , ArC), 128.66 (C , ArC),
l
m
n
o
p
27.56 (C , ArC), 125.94 (C , ArC), 125.75(C , ArC), 125.63 (C , ArC), 125.63 (C , ArC),
t
t
u
v
w
24.30 (C , ArC), 123.82 (C , ArC), 123.23 (C , ArC), 120.27 (C , ArC), 118.45 (C , ArC),
28.65-119.31 (ArC of AsPh3).
2
.3. X-ray crystallography
To collect the data of the crystals obtained for complexes 2 and 3, it should be mounted
on glass fiber and then used for further analysis using monochromatic Mo–Kα radiation (λ
=
0.71073 Å) in a single crystal X‒ray diffractometer known as Bruker AXS Kappa APEX II at
ο
2
96 (2) K. By using SADABS software with multi-scan features, the absorption corrections
were done due to Lorentz and polarization effects [31]. To solve the structures of the crystal and
2
the least square on F full-matrix was refined by using SHELXS-2018 method [31]. The
2
anisotropic property having least squares on F in the weighted full matrix was used to refine the
non-hydrogen atoms. The computer programming was already incorporated by the atomic
scattering factors.

2
2
.4. Computational studies
.4.1. Hirshfeld surface analysis
A necessary complete structural description is done by Hirshfeld Surface Analysis (HSA)
which is used to visualize and quantify the individual types of intermolecular contacts and their
impact on crystal packing in the crystal environment. Furthermore, HSA helps to define the
occupied space by molecule and partitioning electron density of the crystal into molecular
fragments [32,33]. The Crystal Explorer 17.5 software [34] was used to calculate the HSA and
their respective fingerprint plots at very high resolution for the two coordination complexes with
the aid of Crystallographic Information File (CIF). The dnorm plot indicates the distances from
outside nuclei surface (de) and inside the surface (di), the color scale for dnorm plot were fixed for
compound 2 and 3, -0.15 – 1.58 and -0.19 – 3.21 Å respectively. The shape index plot is mapped
in the color range -1.0 − 1.0 au. In the dnorm surface, the sum of vdw radii was indicated by white
surface, the short contact distances than vdw radii was displayed by blue surface and the close-
contact interactions (hydrogen bond contacts) was shown in red surface on the three-dimensional
(3D) Hirshfeld surfaces. In the shape index, the blue and red color reflects the cycle stacking
(C−H∙∙∙π and π∙∙∙π interactions). Moreover, the 2D fingerprint plots help to summarize contact
distances to HSA (di, de) which have shown the range from 0.6 to 2.8 Å including reciprocal
contacts in which, the different type of intermolecular interactions of the molecule in the crystal
can be characterized by the shapes of fingerprint plots.
2
.4.2. Density functional theory
Full geometry optimizations of the newly synthesized complexes (2 and 3) were carried
out by Becke’s three parameter hybrid exchange functional (B3LYP) level of density functional
theory (DFT). To get more accurate energy optimization of organometallic complexes, the metal
atoms with Lee–Yang–Parr nonlocal correlation functional (LANL2DZ) basis set and all the
non-metal atoms were described using the 6-311G** basis set [35]. All the gas phase structural
optimization was performed by using Gaussian03 software package [38]. The Mullikan
population analysis of atomic charges (MPA), higher occupied molecular orbital (HOMO), lower
unoccupied molecular orbital (LUMO) and electrostatic potential map have been analyzed from
Gauss view [36] and 3D plot [37] software packages [39].

2
.5. Typical procedure for catalytic N-alkylation of amines with alcohols
Primary amine (1 mmol), aromatic alcohol (1 mmol), catalyst (1 mol %), potassium
hydroxide (30 mol %) and toluene (5 mL) were placed in a Schlenk tube and stirred under reflux
for 12 h. Upon completion of the reaction, examined by TLC, water was added and the organic
layer was extracted with CH Cl (3 × 10 mL). The combined organic layers were dried with
2
2
sodium sulfate and concentrated. The crude products were purified by column chromatography
with petroleum ether-ethyl acetate (9:3) as eluent and analyzed by spectral methods.
3
. Results and discussion
3
.1. Synthesis and spectroscopic characterization of ruthenium(II) complexes
New ruthenium(II) complexes were obtained by the reaction of L with ruthenium(II)
precursors such as [RuHCl(CO)(EPh ) ] or [RuH (CO)(EPh ) ] (E= P or As) in CHCl -C H OH
3
3
2
3 3
3
2
5
medium under reflux condition (Scheme 1). All the complexes are air stable for extended periods
and remarkably soluble in methanol, ethanol, dichloromethane, chloroform, THF, CH CN, DMF
3
and DMSO. The micro analyses (C, H, N and S) of the Ru(II) complexes (1-4) were in good
agreement with the proposed molecular formulae. The ESI mass spectra of complexes 1, 2 and 3
(Figs. S1-S3 in the supporting information) show the molecular ion peak (m/z) at 1031.0 [M-
+
+
+
Cl+H], 1153.8 [M] and 1032.1 [M+H] , respectively, which are in good agreement with their
molecular masses of the complexes.

c
r
b
H
S
x
t
N
E
w
e
q
d
a
N
N
o
v
f
[
RuHCl(CO)(E)3]
n
s
y
C
Ru
E
g
p
m
Cl
u
h
O
k
l
E= PPh (1), AsPh (2)
3
3
i
j
CHCl -C H OH
3
2
5
N
N
HN
Reflux
H
S
S
N
E
N
N
H
[
RuH (CO)(E) ]
2 3
Ru
E
C
O
E= PPh (3), AsPh (4)
3
3
Scheme 1. Synthetic route of ruthenium(II) complexes 1-4.
3
.2. IR spectra
The IR spectral data of the ligand precursor and its complexes show significant details
-1
about the metal ligand coordination. In free ligand, NH peak appeared at 3367 cm , upon
complexation the peak disappeared in all the complexes suggests the amine–imine tautomerism
followed by deprotonation in hydrazino benzothiazole moiety. A sharp band was observed at
-1
1
670 cm in the spectrum of ligand corresponding to imine which was slightly red shifted and
-1
appeared at 1665-1660 cm for all new complexes. Such a fact suggested the involvement of
imine nitrogen in coordination. Moreover, strong band was observed in the region 1946-1941
-1
cm for coordinated terminal carbonyl and is observed slightly higher frequency than the
precursor complexes [40].
3
.3. NMR spectra
1
The H NMR spectral data of ligand precursor and its ruthenium complexes provide
further information to confirm coordination mode (Figs. S4-S10 in the supporting information).
The NH signal appeared at 9.16 ppm in the spectrum of ligand was disappeared upon
complexation confirmed amine–imine tautomerism followed by deprotonation of benzothiazole
secondary amine proton prior to coordination with ruthenium ion. The azomethine proton

appeared as singlets in the region at 8.94-8.82 ppm for complexes. The peak shows slightly
downfield shift compared with the free ligand at 8.96 ppm, implying coordination of azomethine
nitrogen to ruthenium. The aromatic protons appeared region at 8.06-6.99 ppm as multiplets for
all the complexes. In addition, for complexes 3 and 4, the Ru-H signal appeared in the region -
1
3
1
2.36 to -11.12 ppm. In C NMR spectra (Figs. S11-S15 in the supporting information) carbonyl
(C≡O) carbon appears in the region 203.35-201.03 ppm, azomethine (C=N) and N=C-N carbons
exhibit peak in the region 166.12-161.52 and 155.82-151-65 ppm respectively for all complexes.
The aromatic carbons show peak in the region 138.39-117.16 ppm [41].
3
.4. Molecular structures of complexes 2 and 3
The solid-state structures of the complexes 2 and 3 have been determined by single
crystal X-ray diffraction to confirm the exact bidentate N^N coordination mode of the ligand and
geometry around ruthenium atom. The crystal data and structure refinement parameters for
complexes 2 and 3 are summarized in Table 1 and selected bond lengths and bond angles are
depicted in Table 2. The ORTEP view of complexes 2 and 3 along with the atomic numbering
scheme are given in Figs. 1–2. The single-crystal X-ray studies reveal that complex 2 crystallized
in a monoclinic system with the space group P2 /c, whereas complex 3 crystallized in a triclinic
1
system with the space group Pī. All the Ru(II) complexes described distorted octahedral
geometry where in a bidentate mode creating a five-membered chelate ring involving Nimine and
Namine. The remaining apical sites are filled up by carbonyl, chloride or hydride ion and a pair of
PPh or AsPh co-ligands based on CN P Cl or CN As H coordination environment. Typically,
3
3
2
2
2
2
the PPh or AsPh co-ligands normally desire to occupy equally cis position for an enhanced π-
3
3
interaction, however in presence of CO, a stronger π-acidic ligand might have forced the bulky
PPh /AsPh ligands to take trans position for steric reasons [41, 42].
3
3
In complex 2, Ru1-N1imine bond length was 2.132 Å shorter than complex 3 bond length
2
.180 Å which is evident N1imine atom trans to carbonyl group with bite angle 175.04(4) C(25)-
Ru(1)-N(1) (complex 2) whereas complex 3 trans to hydride atom with the bite angle 170.99(2)
N(1)-Ru(1)-H(1A). The Ru-CO distance of complex 2 1.934(13) was longer than that of
complex 3 1.840(7). Ru1-N3amine bond lengths 2.088-2.099 Å are more or less equal to both
complexes 2 and 3. Interestingly, complex 2, AsPh groups slightly bent towards bulky pyrene
3
rings due to π-π interaction distances 4.330 Å between one of phenyl ring from AsPh and
3
pyrene ring. In complex 3, PPh groups bent towards benzothiazole ring due to π-π interaction
3

distances 3.798 Å between one of phenyl ring from PPh and benzothiazole ring (Fig. S16 in the
3
supportive information). Ru-As/P distances displayed 2.473(12)- 2.491(12) (complex 2) and
2
.361(15)- 2.357(16) (complex 3) trans positioned AsPh /PPh groups and are slightly bent due to
3 3
π-π interaction, causing a slight deviation from a linear trans arrangement, which is evident from the
bond angle of As(2)-Ru(1)-As(1) 173.15(5) (complex 2) and P(1)-Ru(1)-P(2) 173.27(5) (complex
3
). The observed bond distances and bond lengths of Ru-As/P were comparable with reported
earlier ruthenium complexes [43]. Finally, the bite angle () for the five membered chelate ring
involving N(3)-Ru(1)-N(1) is 77.02(3) (2) and 75.19(19) (3).
Table 1 Crystal data and structural refinement parameters for complexes 2 and 3.
2
3
CCDC Number
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
Unit cell dimensions
a(Å)
1964286
1964287
C H N OAs RuClS
C H N OP RuS
6
1
44
3
2
61 45
3
2
1153.42
1031.07
293(2) K
0.71073 Å
Monoclinic
P 21/c
296(2) K
0.71073 Å
Triclinic
P -1
11.7685(6) Å
38.622(2) Å
10.6204(10) Å
13.8955(12) Å
17.3879(16) Å
96.369(4)°
b(Å)
c(Å)
12.0399(6) Å
90°
α
β
90.980(3)°
90°
104.386(4)°
96.658(4)°
γ
Volume
3
3
5
4
471.6(5) Å
2442.6(4) Å
Z
2
Density (calculated)
3
3
1
1
.400 Mg/m
1.402 Mg/m
Absorption
coefficient
-1
.616 mm
-1
0.476 mm
F(000)
2328
1060

Theta range for data 1.054 to 29.077
collection
1.222 to 29.206
Index ranges
-14<=h<=14,
-14<=h<=14,
-18<=k<=18,
-23<=l<=23
-
52<=k<=52
16<=l<=16
-
Reflections collected 54246
40281
Independent
reflections
14459 [R(int) = 0.1115]
13012 [R(int) = 0.0787]
Completeness
theta = 25.242°
Absorption
to 99.6 %
None
99.3 %
None
correction
Refinement method
2
2
Full-matrix least-squares on F Full-matrix least-squares on F
Data/restraints/
parameters
14459 / 0 / 631
13012 / 0 / 626
Goodness-of-fit
1.109
1.081
2
on F
Final R indices
I >2sigma(I)]
R indices (all data)
R1 = 0.1103, wR2 = 0.2706
R1 = 0.1849, wR2 = 0.3109
R1 = 0.0852, wR2 = 0.2693
R1 = 0.1253, wR2 = 0.3009
[
Table 2 Selected bond length and bond angle in complexes 2 and 3.
2
3
Inter atomic distance (Å)
Ru(1)-C(25)
Ru(1)-N(3)
Ru(1)-N(1)
Ru(1)-Cl(1)
1.934(13)
Ru(1)-C(25)
Ru(1)-N(3)
Ru(1)-N(1)
Ru(1)-P(1)
1.840(7)
2.099(5)
2.179(5)
2.357(16)
2.088(8)
2.132(8)
2.413(3)

Ru(1)-As(2)
2.473(12)
2.491(12)
Ru(1)-P(2)
2.361(15)
1.506(5)
Ru(1)-As(1)
Ru(1)-H(1A)
Bond angles ()
C(25)-Ru(1)-N(3)
C(25)-Ru(1)-N(1)
N(3)-Ru(1)-N(1)
C(25)-Ru(1)-Cl(1)
N(3)-Ru(1)-Cl(1)
N(1)-Ru(1)-Cl(1)
C(25)-Ru(1)-As(2)
N(3)-Ru(1)-As(2)
N(1)-Ru(1)-As(2)
Cl(1)-Ru(1)-As(2)
C(25)-Ru(1)-As(1)
N(3)-Ru(1)-As(1)
N(1)-Ru(1)-As(1)
Cl(1)-Ru(1)-As(1)
As(2)-Ru(1)-As(1)
98.14(4)
175.06(4)
77.02(3)
92.23(3)
169.58(2)
92.63(2)
90.46(3)
90.94(2)
88.67(2)
89.97(8)
94.13(3)
93.44(2)
87.18(2)
84.77(8)
173.15(5)
C(25)-Ru(1)-N(3)
C(25)-Ru(1)-N(1)
N(3)-Ru(1)-N(1)
C(25)-Ru(1)-P(1)
N(3)-Ru(1)-P(1)
N(1)-Ru(1)-P(1)
C(25)-Ru(1)-P(2)
N(3)-Ru(1)-P(2)
N(1)-Ru(1)-P(2)
P(1)-Ru(1)-P(2)
C(25)-Ru(1)-H(1A)
N(3)-Ru(1)-H(1A)
N(1)-Ru(1)-H(1A)
P(1)-Ru(1)-H(1A)
P(2)-Ru(1)-H(1A)
178.16(3)
103.51(3)
75.19(19)
90.35(2)
91.03(13)
93.63(15)
90.63(2)
88.14(13)
92.61(15)
173.27(5)
85.48(2)
95.84(2)
170.99(2)
85.53(19)
87.90(19)

Fig. 1. Perspective view (30 % probability ellipsoids) of complex 2.
Fig. 2. Perspective view (30 % probability ellipsoids) of complex 3.

3
.5. Hirshfeld surface analysis
The main purpose of Hirshfeld surface analysis is exactly used to study the different type
of intermolecular interactions in the crystal structure and it plays most important role in the
formation of supramolecular compounds. Fig. 3 shows the dnorm and shape index of the
coordination compounds 2 and 3. As shown in Fig. 3, the compound 3 shows blue surface higher
than compound 2 and compound 2 displays white surface higher than compound 3. This is
clearly attributed due to hydrophobic cyclic rings around the metal atoms. However, the metal
region shows large red surfaces which confirm that metal atoms are forming strong coordination
bond with neighboring atoms present in both complexes 2 and 3. In the shape index, the dark red
and blue surfaces indicate that the molecules are forming C−H∙∙∙π interactions with surrounding
molecules in the crystal. Fig. 4 displays the fingerprint plot and percentage graph, which are
useful to quantify the contribution of different type of interactions in the solid state. On
comparing with compound 2 and 3, the fingerprint plot is almost similar. The H∙∙∙H and C∙∙∙H
type of interactions are highly presented in the both molecules which also confirm that the
Vander Walls and C−H∙∙∙π interactions play the major role in the crystal environment. The
contribution of H∙∙∙H and C∙∙∙H values of the both molecules are 57.8/62.2 and 24.7/26.4%
respectively. The C∙∙∙H and S∙∙∙H fingerprint plots show similar symmetrically wing shape, the
O∙∙∙H and Cl∙∙∙H plots looks like sharp spikes and the H∙∙∙H plot is overlapped in full fingerprint
plots that would commonly separate from each other. The compound 2 exhibits slightly higher
H∙∙∙H and C∙∙∙H contributions than compound 3. Whereas, the O∙∙∙H and S∙∙∙H contribution
values are high in compound 2 [O∙∙∙H: 3.3/3.0 % and S∙∙∙H: 5.1/2.2 %]. The C∙∙∙C contribution of
compound 2 is slightly lower than compound 3 which indicates that compound 3 has high π∙∙∙π
accumulation than compound 2. Therefore, this fingerprint plot clearly confirms that the
existence of weaker hydrogen bonding which leads to stability of the coordination compounds.

Fig. 3. Hirshfeld surface analysis mapped with dnorm and shaped index for complexes 2 and 3.

Fig. 4. Fingerprint plot of the complexes 2 and 3. Close contacts are labeled as O∙∙∙H, C∙∙∙H and
H∙∙∙H contacts showing the percentages (%) of contacts contributed to the total Hirshfeld surface
area of molecule
3
3
.6. Density functional theory
.6.1. Atomic charges, MEP, HOMO and LUMO
By using Gaussian03 software, the Mulliken atomic charges (MPA) for the two
coordination compounds (2 and 3) were calculated [37]. Fig. S17 in the supporting information
predicts the variation on the MPA charges of the atoms in the complexes. The MPA charge of
ruthenium atom in complexes 2 and 3 are -0.177e and -0.052e and these values are mainly
attributed due to the bonding of different atoms (arsenic, phosphorus, chlorine, nitrogen,
sulphur). The arsenic, phosphorus and sulphur atoms are carrying high positive charges due to
bonding with ruthenium [As: ~0.85e, P: ~0.70e, S: ~0.43e]. The charges on the nitrogen atoms in
the complexes 2 and 3 (N2: -0.34/-0.37e; N3: -0.19/-0.15e) show the delocalization of double
bond and location of negative charge on ring nitrogen. The carbon atoms [C(8), C(20), C(32),

C(44), C(81), C(83), C(20), C(37), C(47), C(66), C(83), C(87), C(91)] in complexes 2 and 3
exhibit higher negative charges (-0.5e) than the nitrogen and oxygen (-0.02e). The carbon atoms
C(60), C(66) (complex 2) and C(7), C(23) (complex 3) carries high positive charges (~0.5e). The
data show that the MPA charge is almost same for all the atoms in the two complexes (2 and 3).
Interestingly, the electrostatic potential (ESP) is used to predict the possible reactive sites
of the complexes with the presence of nucleophilic (attracted to regions with positive potential)
and electrophilic (attracted towards the regions with negative potential) regions in the
complexes. Fig. S18 in the supporting information shows the isosurface representation of the
molecular electrostatic potential (MSP) of the metal coordination complexes (2 and 3). In both
molecules, the large electronegative regions are found in the surface of metal coordination
region.
The essential quantum chemical descriptors such as HOMO and LUMO were calculated
for the two metal coordination complexes (2 and 3) and are highly related to the chemical
activities. The molecular surface of HOMO and LUMO maps of the both complexes were drawn
at 0.2 au and shown in Fig. 5 in which, the HOMO and LUMO energy surface of the both
molecules were found over the metal and functional group regions. The HOMO is highly
localized on the metal surrounding (Ru, As, P, N, S atom) and other regions are very low
whereas in the LUMO, major contributions on phenyl rings and minor contribution on metal
surrounding. The positive and negative regions are shown in green and red colors respectively. In
order to understand the charge injection and transporting properties of metal coordination
molecules, the global reactivity descriptors were calculated. The HOMO and LUMO energies are
reason for the transfer of charge in a reaction [44]. Thus the calculated values for the HOMO and
LUMO energies are found to be -4.87/-4.67 eV and -2.12/-1.96 eV respectively [Table S1 in the
supporting infomation]. The band gap of both molecules are -2.76/-2.72 eV. The predicted
electron affinity, ionization potential and electronegativity of the complexes 2 and 3 are
2
.12/1.96, 4.88/4.67 and 3.5/3.32 eV. Thus the electron affinity and electronegativity values are
low when compared to the ionization potential [45] which suggests high reactivity.

Fig. 5. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular
orbital (LUMO) of complexes 2 and 3. The HOMO and LUMO are drawn at 0.02 au level.
3
.7. N-alkylation of amines catalyzed by ruthenium complexes (1-4)
There are several reports on the use of Ru(II) complexes as catalysts in N-alkylation
reactions [46]. From the results, it has been recognized that the introduction of suitable ligand to
the ruthenium complexes plays a significant role in controlling the catalytic activities of these
Ru(II) complexes. Hence, new Schiff base ligands have been used to syntheses Ru(II) complexes
not only due to its usefulness in controlling the performance of catalytic but also for the reason
that it has enhanced co-ordination with the metal atom. To explore the catalytic activities of
synthesized ruthenium complexes (1-4), initial screening was performed to optimize the reaction
parameters such as solvent, base, time and the effect of catalyst loading on the yield using the
substrates benzyl alcohol and 1-naphthylamine. The solvent-dependent differences in the
activities of catalysts were explored by carrying out the model reaction using toluene, benzene,
1
,4-dioxane, acetonitrile, ethanol, methanol, THF, DMF and DMSO (Table 3). Aromatic
solvents such as toluene and benzene (Table 3, entries, 8 and 9) afford better yield than polar
aprotic and polar protic solvents (DMF, DMSO, acetonitrile, ethanol and methanol (Table 3,
entries 12–16), particularly toluene bestow excellent yield up to 93%. Cyclic ether solvents such
as 1, 4-dioxane and THF (Table 3, entries 10 and 11) give moderate yields (60% and 50%). After

select the solvent, screen was done to assess the crucial role of bases such as NaHCO , Na CO ,
3
2
3
K CO , NaOtBu, KOtBu, NaNH , NaOH, and KOH in promoting the generation of metal
2
3
2
intermediates all along the catalytic cycle. Moderate bases such as NaHCO , Na CO , and
3
2
3
K CO were less reactive (Table 3, entries 1-3). The reaction was accelerated by the addition of
2
3
strong bases such as NaOtBu, KOtBu, NaNH , and NaOH (Table 3, entries 4–7). When the
2
reaction was carried out in the presence of KOH, formation of N-alkylated amine was excellent
(Table 3, entry 8 up to 93%). As a result, KOH was chosen as the ultimate choice of base for all
the reactions. Control experiments were performed for extended time without solvent, base and
catalyst give products with low yield (Table 3, entries 17-19) confirm the necessity of solvent,
base and catalyst in N-alkylation reaction.
Table 3 Screening of various conditions for N–alkylation reactiona.
H
N
Ru(II) catalyst 3
NH2
HO
Solvent, base
H O
2
o
110 C
Entry
Solvent
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Benzene
1,4 Dioxane
THF
Base
Time (h)
12
Yield (%)b
1
2
3
4
5
6
7
8
9
NaHCO3
Na CO
63
67
70
80
82
87
75
93
85
60
50
59
10
42
56
12
2
3
K CO
2
12
3
NaOtBu
KOtBu
NaNH2
NaOH
KOH
KOH
12
12
12
12
12
12
1
1
1
1
1
1
0
1
2
3
4
5
KOH
12
KOH
12
DMF
KOH
12
DMSO
KOH
12
Acetonitrile
Ethanol
KOH
12
KOH
12

1
1
1
6
7
8
9
Methanol
_
KOH
KOH
_
12
24
24
24
35
25c
15d
10e
Toluene
Toluene
1
KOH
a
o
Reactions were carried out at 110 C for 12 h under argon atmosphere using 1-naphthylamine
(
1mmol), benzyl alcohol (1 mmol), catalyst 3 (1 mol %) and base (30 mol%) in solvent (5mL).
b
c
Isolated yields.
Solvent-free.
Base-free.
d
e
Without catalyst.
Using the best base in the N-alkylation reaction, we then investigated the optimum catalyst. The
results show that the catalyst 3 on low mol% (Table 4, entries 1-3) gives moderate yield and by
taking 1 mol% the yield obtained was about 93% (Table 4, entry 4). However, the catalyst 1, 2
and 4 afford lower yield under same conditions (Table 4 entries 5-7). The results show that the
Ru(II) catalyst 3 containing benzothizole, PPh and hydride ligands completes the N-alkylation
3
process efficiently under optimized conditions with good yield compared to catalyst 1, 2 and 4.
Table 4 Effect of catalyst loading on N-alkylation of 1-naphthylamine with benzyl alcohol
catalyzed by Ru(II) catalyst.
H
NH2
N
Ru(II) catalyst
Toluene, KOH, 110 C
HO
o
H O
2
Entry
Catalyst
Amount of catalyst
Time (h)
Yieldb
(mol %)
1
2
3
4
5
6
7
3
3
0.1
12
12
81
83
0.25
3
3
1
2
4
0.5
1
12
12
12
12
12
87
93
80
85
79
1
1
1

a
o
Reactions were carried out at 110 C for 12 h under argon atmosphere using 1-naphthylamine
(1 mmol), benzyl alcohol (1 mmol), catalyst and KOH (30 mol%) in toluene 5mL.
b
Isolated yields.
After optimization of conditions for the catalytic of N-alkylation, diverse amines were
reacted with benzyl alcohol to prove the general applicability of the new catalytic system.
Initially, we observed that the N-alkylation of electron donating substrates (aniline with benzyl
alcohol) gives superior yield upto 96% (Table 5, 5a-5e) and electron-withdrawing substrates
(
substituted aniline) give N-monoalkylated anilines with moderate yield upto 78% (Table 5, 5f,
g and 5h). The sterically hindered 2,4,6-methyl aniline, 2,6 isopropyl aniline and 2,6-di ethyl
aniline provide corresponding mono alkylated amines with moderate yield (Table 5, 5i, 5j and
k, 82, 77 and 79% respectively). Notably, hetero aromatic amines such as 8-amino quinoline
5
5
and 2-picoliamine produce the compounds such as 5l and 5m with better yields of 83% and 89%
respectively. By treating cyclohexylamine and aniline with benzyl alcohol results the superior
yield upto 87% (Table 5, 5o and 5n). We also optimized the reaction of aliphatic amines such as
propyl amine, tertiary butylamine with benzyl alcohol, which also results in the formation of
desired product with good yield of 81 and 86% respectively (Table 5, 5q and 5r). In addition, the
reaction of 2-amino benzothiazole with benzyl alcohol leads corresponding product with 90%
yield (Table 5, 5p) and the formed product has good pharmaceutical application. The reaction of
benzylamine with benzyl alcohol give alkylated product with 91% yield (Table 5, 5s). Moreover,
the synthetic utility of this method was demonstrated by the alkylation of 1-naphthylamine with
benzyl alcohol and the yield obtained was about 93% (Table 5, 5t). When compared to
previously reported catalysts for N alkylation reactions, the present catalyst required lower
amount (1 mol % catalyst loading) for effective formation of alkylated products. Moreover, the
catalyst can be applied to a wide range of substrates including various amines and primary
alcohols that were scarcely addressed by previously reported catalysts for N alkylation reactions.
[47].

Table 5 N-alkylation different amines with benzyl alcohola.
Ru(II) catalyst 3
H
NH2
HO
N
H O
2
R
Toluene, KOH
R
o
1
10 C
H
N
H
N
H
H
N
Me
N
Br
H CO
Cl
3
5
a, 89%
5b, 92%
5
c, 96%
5
d, 85%
H
N
H
N
H
N
H
N
O N
2
Cl
e, 81
NO2
g, 78%
O N
2
5
5h, 65%
5
5f, 75%
H
N
H
N
H
N
H
N
N
5i, 79%
5j, 82%
5l, 83%
5k, 77%
H
H
N
H
N
N
S
H
N
N
N
5n, 87%
5m, 89%
5o, 80%
5p, 90%
H
H
N
N
N
N
H
H
5q, 81%
5r, 79%
5s, 91%
5t, 93%
a
o
Reactions were carried out at 110 C for 12 h, amine (1mmol), benzyl alcohol (1 mmol),
catalyst 3 (1 mol%) and KOH (30 mol %) in toluene (5mL).
Isolated yields.
b
4
. Conclusions
A new series of Ru(II) complexes (1-4) were synthesized by the reaction of
[
RuHCl(CO)(EPh ) ] or [RuH (CO)(EPh ) ] (E
=
P
or As) with (2-(pyren-1-
3
3
2
3 3
ylmethylene)hydrazinyl)benzothiazole (L). The formation of the complexes was established by
spectroscopic methods including single crystal XRD. The solid-state structures reveal a distorted
octahedral geometry around the ruthenium ion with the ligand acts as mono anionic bidentate
(N^N) donor manner via imine nitrogen and benzothiazole nitrogen. Hirshfeld surface analysis
has showed that the crystal lattices of complexes (2 and 3) are influenced by the presence of
several intermolecular interactions. The catalytic screening of the complexes shows that the

complex 3 acts as an efficient catalyst towards N-alkylation of a wide range of substituted
aromatic amines with alcohol.
Declaration of Competing Interest
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.
Appendix A. Supplementary data
CCDC 1964286 and 1964287 contain the supplementary crystallographic data for complexes 2
and
3.
This
data
can
be
obtained
free
of
charge
via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or email:
deposit@ccdc.cam.ac.uk. Supplementary data to this article can be found online at https://

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