Water-soluble NNN-pincer complexes of cobalt, nickel and palladium: Solid-state structures and catalytic activity

Article abstract of DOI:10.1016/j.poly.2017.09.027

Neutral NNN-pincer ligand 1 based on a pyridyl core and cyclic amidine pendant arms was synthesized via a straightforward condensation reaction. Its square-planar palladium acetate complex 2 was prepared in methanol and featured a cyclic, hexameric solid-state structure assembled through moderately strong N?H?O hydrogen bonds involving the ligand backbone and the non-coordinated acetate group. The octahedral, diamagnetic Co(III) complex 3 was prepared via in-situ air oxidation of its Co(II) analog. Its solid-state structure confirmed the oxidation state of the metal and revealed the presence of weak bridging and terminal N–H?Cl hydrogen bonds. Paramagnetic nickel complex 4 was prepared in a similar fashion to 1 and was postulated to have a covalent attachment of the acetate moieties to the metal. Derivatives 2 and 3 had excellent water solubility and stability while 4 was sparingly soluble in water. Cyclic voltammetry revealed electrochemically reversible electron transfer steps corresponding to the Co(II)/Co(III) and Ni(II)/Ni(III) redox couples at ?0.31 V and 1.04 V versus SHE, respectively. Complex 4 displayed catalytic competency towards the thiolation of iodobenzene with dimethyldisulfide and zinc in DMF. In water, 4 was able to catalyze the Negishi cross-coupling of iodobenzene.

Full text of DOI:10.1016/j.poly.2017.09.027

Accepted Manuscript
Water-soluble NNN-pincer complexes of cobalt, nickel and palladium: Solid-
state structures and catalytic activity
Joshua Heidebrecht, Chris Gendy, Benjamin Gelfand, Roland Roesler
PII:
S0277-5387(17)30604-6
https://doi.org/10.1016/j.poly.2017.09.027
POLY 12837
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
29 July 2017
13 September 2017
15 September 2017
Please cite this article as: J. Heidebrecht, C. Gendy, B. Gelfand, R. Roesler, Water-soluble NNN-pincer complexes
of cobalt, nickel and palladium: Solid-state structures and catalytic activity, Polyhedron (2017), doi: https://doi.org/
1
0.1016/j.poly.2017.09.027
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Water-soluble NNN-pincer complexes of cobalt, nickel and palladium: Solid-state
structures and catalytic activity
Joshua Heidebrecht, Chris Gendy, Benjamin Gelfand, Roland Roesler*
Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4 Canada
Abstract. Neutral NNN-pincer ligand 1 based on a pyridyl core and cyclic amidine pendant arms
was synthesized via a straightforward condensation reaction. Its square-planar palladium acetate
complex 2 was prepared in methanol and featured a cyclic, hexameric solid-state structure
assembled through moderately strong N···H···O hydrogen bonds involving the ligand backbone
and the non-coordinated acetate group. The octahedral, diamagnetic Co(III) complex 3 was
prepared via in-situ air oxidation of its Co(II) analog. Its solid-state structure confirmed the
oxidation state of the metal and revealed the presence of weak bridging and terminal N-H···Cl
hydrogen bonds. Paramagnetic nickel complex 4 was prepared in a similar fashion to 1 and was
postulated to have a covalent attachment of the acetate moieties to the metal. Derivatives 2 and 3
had excellent water solubility and stability while 4 was sparingly soluble in water. Cyclic
voltammetry revealed electrochemically reversible electron transfer steps corresponding to the
Co(II)/Co(III) and Ni(II)/Ni(III) redox couples at -0.31 V and 1.04 V vs. SHE, respectively.
Complex 4 displayed catalytic competency towards the thiolation of iodobenzene with
dimethyldisulfide and zinc in DMF. In water, 4 was able to catalyze the Negishi cross-coupling
of iodobenzene.
1
. Introduction
Following the remarkable success of 2,2’:6’,6”-terpyridine ligands I (terpy or tpy) in
1
,2,3,4
coordination chemistry and catalysis (Chart 1),
other symmetric, neutral NNN-pincer
ligands with pyridine central moieties and unsaturated nitrogen pendant donors have been
pursued. An obvious further development was the replacement of the pyridine side arms with
5
,6
5,7
other aromatic six-membered nitrogen heterocycles such as pyrazine (II), pyrimidine (III),
8
9,10,11
12,13,14,15
1
,3,5- and 1,2,4-triazine (IV and V,
respectively) and 1,2,4,5-tetrazine (VI).
Ligand
1
6
scaffolds having five-membered nitrogen heterocycles such as imidazole (VII), pyrazole
1
7,18,19,20,21
22
23
24,25
(
VIII),
as well as 1,2,4- and 1,2,3-triazole (IX, X, and XI,
respectively) as
pendant arms have been employed extensively, with VIII proving to be a particularly popular
2
6,
27
28
29
choice. Ligands XII, XIII, and XV featuring oxazolyl, thiazolyl and thiazolinyl pendant

arms, respectively, have been reported as well, although their applications are dwarfed by those
3
0,31,32,33
34
of their oxazolinyl analogs XIV (PyBOX).
1-pyrroline (XVI),
2-imidazoline
3
5,36
37
(
XVII),
and 5,6-dihydro-4H-1,3-oxazine (XIX) have also been incorporated in pyridyl-
based NNN-pincer ligands, while the chemistry of ligands XVIII with acyclic imine pendant
3
8
arms has been explored extensively.
Chart 1. Selected symmetric, neutral NNN-pincer ligands with pyridine central moieties and
unsaturated nitrogen pendant donors.
Complexes incorporating the basic ligand frameworks shown in Chart 1 benefit from good
ligand properties, easy access via modular synthesis, and superior oxidative stability, and they
3
9,40,41
42
have been used extensively in homogeneous catalysis,
including olefin polymerization,
3
1
transfer hydrogenation and enantioselective hydrosilylation. Continuing our investigations into
4
3,44
the chemistry of pincer ligands,
we identified scaffold XX as potential candidates for in or on
water homogeneous catalysis. Ligand 1 was deemed accessible via one straightforward synthetic
step from commercially available starting materials, and its complexes were expected to be
soluble in both water and organic solvents. The presence of nitrogen atoms capable to both
accept and donate protons in the ligand framework of 1 was expected to enhance the water
4
5,46,47,48,49
solubility of its complexes, to provide opportunities for ligand-assisted reactivity,
to offer the possibility for variable coordination modes as a neutral (diiminopyridine), mono-
amidoiminopyridine) and dianionic ligand (diamidopyridine). In and on water homogeneous
and
(

catalysis has been widely employed in laboratory and industrial scale organic chemistry, owing
to improved safety and environmental aspects, decreased cost, ease in separating the catalyst
5
0,51,52,53,54
from reaction products, and enhanced reaction rates.
2
. Results and Discussion
Scheme 1. Synthesis of ligand 1.
The synthesis of the NNN-pincer ligand 1 was carried out via a simple condensation reaction,
following the modification of a procedure reported for an anionic phenylene analog (Scheme
5
5
1
). The crude product was obtained by refluxing dipicolinic acid and 2,2-dimethylpropane-1,3-
diamine in ethylene glycol, using p-toluenesulfonic acid as a catalyst. The neutral diamine was
used instead of the reported hydrochloride acid salt, in order to simplify the synthesis. The crude
product precipitated upon cooling and was collected, washed, dried and subsequently used
without further purification for the synthesis of metal complexes.
Scheme 2. Synthesis of Pd(II) complex 2.
The palladium acetate complex, 2, was obtained by refluxing the ligand with the corresponding
metal salt in methanol overnight (Scheme 2). Removing the solvent in vacuo left behind the
crude product as a yellow solid that was washed with small quantities of acetone and dried.
Complex 2 was well soluble in protic solvents such as water and methanol, with no noticeable
1
degradation of the solutions upon exposure to air over one month. The H NMR spectrum was
recorded in D
to the two methylene groups rendered inequivalent upon coordination. As expected for a C
symmetric product, only one signal was observed for the methyl groups of the pincer ligand, at
.07 ppm. The broad resonances corresponding to the inequivalent acetate groups at 2.12 and
2
O and featured two resonances in a 1 : 1 ratio at 3.00 and 3.24 ppm, corresponding
s
1

1
.96 ppm suggest an exchange between free and bound acetate in solution. The signals
1
3
corresponding to the acetate groups were barely visible in the C NMR spectrum, indicating that
coalescence occurred very close to room temperature.
Fig. 1. Supramolecular association of 2 in the solid state via N-H···O hydrogen bonds. Left, ball-
and-stick model with all hydrogen atoms that are not involved in hydrogen bonding removed for
clarity. Right, space filling model including all atoms.
Single crystals suitable for X-ray crystallography were grown at room temperature over a period
of two weeks from a concentrated solution of 2 in dimethylsufoxide. The solid-state structure
revealed the formation of cyclic, hexameric associates with D3d symmetry, described as formally
+
featuring cationic palladium pincer complexes [(1)PdOAc] connected by the acetate counterions
(
Figure 1). These non-coordinated acetate groups form moderately strong N···H···O hydrogen
bonds (N2···O distance 2.717(5) Å) with the pendant amines in the pincer ligand framework.
The supramolecular associates have an internal diameter of ca. 20 Å and an external diameter of
ca. 30 Å; however, due to packing this does not translate into voids in the crystal structure. The
expected NNN-pincer coordination with one bonded acetate group is observed in the
+
[
(1)PdOAc] ions, generating a distorted square-planar geometry at the metal (Figure 2). The
N1-Pd1-N1’ angle of 161.24(9)º is slightly wider than in NNN-palladium pincer complexes with
imine side arms (155-160º), and much more typical of 2,2’:6’,6”-terpyridine complexes (e.g.
+
56
1
62.0(1)º in [Pd(terpy)(OH)] ). Both pendant rings adopt a half-chair conformation in the solid
state, displaying a cisoid arrangement with respect to the palladium-coordinated acetate moiety.
The N1-C6 and N2-C6 bonds are very similar in length (1.312(3) and 1.330(3) Å, respectively),

indicating extensive electron delocalization, as outlined in Scheme 2. Typical of NNN pincer
architectures, the central Pd-N bond is 0.1 Å shorter than the Pd-N bonds involving the pendant
arms. This reflects geometric constrains, rather than electronic effects, as illustrated by the
5
7
structure of [(terpy)PdPy](ClO
4
2
) .
Fig. 2. Solid state structure of the cation in 2 with thermal ellipsoids drawn at 50% probability
level. Selected bond lengths (Å) and angles (deg): Pd1-N1 = 2.0237(18), Pd1-N3 = 1.922(2),
Pd1-O1 = 2.015(2), N3-C7 = 1.338(2), N1-C6 = 1.312(3); N2-C6 = 1.330(3), C6-C7 = 1.484(3);
N1-Pd1-N1’ = 161.24(9), N3-Pd1-O1 = 176.35(10), C7-N3-C7’ = 123.7(2), N1-C6-N2 =
1
25.01(19), N1-C6-C7 = 115.64(18)
Complex 3 was synthesized by refluxing two equivalents of 1 with cobalt (II) chloride
hexahydrate in air overnight (Scheme 3). The dark precipitate was filtered off and the solvent
was removed in vacuo, leaving behind the product as a dark yellow-green solid. Under exclusion
of air, the reaction failed to produce the desired compound, confirming that atmospheric oxygen
was responsible for the oxidation of Co(II) to Co(III). The oxidation of Co(II) to Co(III) in
complexes with nitrogen-based ligands with either air or hydrogen peroxide has been
5
8
6
described. Diamagnetic complex 3, having a low spin d electronic configuration, is soluble
and stable in protic solvents (i.e. water and methanol) and was characterized by NMR using D
2
O
as a solvent. Resonances corresponding to the chemically inequivalent methylene groups were
1
observed at 1.97 and 3.17 ppm in the H NMR spectrum. Only one resonance was observed at
0
.81 ppm for all methyl groups of the ligand, as expected for time-averaged D2d symmetry.

Scheme 3. Synthesis of Co(III) complex 3.
Single crystals suitable for X-ray crystallography were obtained by slow evaporation of a
concentrated solution of 3 in a methanol-toluene mixture. The solid-state structure revealed that
3
+
the trication [(1) Co] crystallized with three chloride anions, instead of the stoichiometric
2
product featuring two chloride ions and one hydroxide (Figure 3). The presence of a small
proportion of disordered hydroxide ions on the site of the chlorides can however not be excluded.
Two of the chloride ions are weakly hydrogen bonded to the cation (Cl1···N2 = 3.177(4) Å)
while the third bridges the cations via weak hydrogen bonds, forming a linear supramolecular
arrangement (Cl2···N4 = 3.208(4) Å).
Figure 3. Fragment from the solid-state structure of pseudo-octahedral complex 3 in a
combination of thermal ellipsoids drawn at 50% probability level and wireframe. All hydrogen
atoms that are not involved in hydrogen bonding have been removed for clarity. Selected bond
lengths (Å) and angles (deg): Co1-N3 = 1.861(2), Co1-N1 = 1.936(2), Co1-N5 = 1.937(2), N3-
C7 = 1.330(4), N3-C11 = 1.343(4), N1-C6 = 1.312(4), N2-C6 = 1.331(4), N5-C12 = 1.311(4),
N4-C12 = 1.330(4); N1-Co1-N5 = 163.68(9), N3-Co1-N3’ = 178.96(15).

Figure 4. Cyclic voltammogram 3 (top) and 4 (bottom) (1 mmol solution in water with 0.1 M
Na SO as supporting electrolyte, 3 mm diameter glassy carbon working electrode, scan rate
.025 (3) and 0.05 Vs (4), Ag/AgCl reference electrode).
2
4
−
1
0
The structure of the cation is unremarkable, with a pseudo-octahedral geometry at the metal (N1-
Co1-N5 = 163.68(9)º, N3-Co1-N3’ = 178.96(15)º) and shorter Co-N bonds involving the pyridyl
nitrogen, N3, than those with the amidine nitrogens, N1 and N5. Cyclic voltammetry showed an
electrochemically-reversible reduction attributed to the Co(II)/Co(III) redox couple at -0.31 V vs.
SHE (Figure 4). This value is similar to those observed for comparable octahedral cobalt
5
9
complexes with nitrogen ligands, which fall between 0.1 and -0.6 V.

Nickel acetate complex 4 was synthesized through a synthetic route similar to the one used for
the palladium and cobalt complexes, by simple coordination of 1 to hydrated nickel acetate in
methanol (Scheme 4). The resulting dark solution was evaporated to dryness in vacuo, and the
remaining dark red-brown solid was collected and used without further purification. The
paramagnetic nickel complex is soluble in alcohols, especially methanol, and air stable, but only
moderately soluble in water. A high-resolution ESI-MS spectrum showed a signal corresponding
+
to the m/z ratio and isotopic distribution of the [(1)Ni(OAc)] ion. Based on this and its
paramagnetic nature, we proposed the structure [(1)Ni(OAc) ] for 4, as shown in Scheme 4,
2
6
0
which has been proven by means of X-ray crystallograpy for [(terpy)Ni(OCOtBu)
2
]. Solution
+
+
equilibria involving species such as [(1)Ni(OAc)] (OAc)¯, {[(1)Ni(OAc)]
2
(µ-OAc)
2
]
and
2
+
[
(1) Ni] 2(OAc)¯ are possible but the limited solubility of 4 in water in comparison to 2 and 3
2
supports a monomeric or dimeric molecular structure with both acetate groups covalently bonded
to the metal, over an ionic structure. Cyclic voltammetry showed one electrochemically-
reversible electron transfer within the solvent window of water at 1.04 V vs. SHE, corresponding
to the Ni(II)/Ni(III) redox couple (Figure 3). No reduction to metallic nickel, which is
6
1
characteristic of nickel acetate, was observed, and no attempts have been made to isolate the
oxidized Ni(III) species via chemical or electrochemical means.
Scheme 4. Synthesis of Ni(II) complex 4
NNN- and PCP-Ni pincer complexes have been shown to selectively catalyze the thiolation of
aryl halides in a one-pot reaction involving disulfides and elemental zinc as a reducing
6
2,63,64
agent.
reaction monitoring by GC-MS showed the expected cross-coupled product in low yields
Scheme 5). A control experiment using hydrated nickel acetate was also performed under
A preliminary assessment of 4 using a 5 mol % catalyst loading in DMF and
(
similar conditions with limited success (Table 1). Using water as a solvent, a preference for the
formation of biphenyl via Negishi coupling instead of carbon-chalcogen coupling was observed.
This line of investigation was pursued with a 2.5 mol % catalyst loading, leading to turnover

numbers of 10 towards the coupled product (Scheme 6). No catalytic activity was observed in a
6
5
control experiment using 5 mol % nickel acetate hydrate under similar conditions. Both Ni(0)
6
3
and Ni(I) intermediates have been postulated for similar transformations in organic solvents.
Proficient palladium-based catalysts for the Negishi coupling in water in the presence of
6
6,67,68
polyoxyethanyl α-tocopheryl sebacate as surfactant have been reported,
but to our
knowledge this is the first report of nickel-catalyzed Negishi coupling in water. Preliminary
experiments using 2 showed that this catalyzed the Negishi cross-coupling in water, but also the
subsequent partial hydrogenation of the resulting biphenyl.
Scheme 5. Thiolation of iodobenzene in the presence of 4.
Scheme 6. Negishi coupling in the presence of 4.
Table 1: Exploratory catalysis with complex 4 compared to Ni(OAc)
2
(H
2
O)
4
a
Reaction
Catalyst
Catalyst loading (mol %)
Product yield (%)
Thiolation
4
5
24
8
Thiolation Ni(OAc)
2
(H
2
2
O)
O)
4
4
6
Negishi
4
2.5
4.5
28
0
Negishi Ni(OAc)
2
(H
a
Yields were determined by GC-MS relative to iodobenzene
3
. Conclusions
Neutral pincer ligand 1 was accessed via a facile condensation reaction starting from
commercially available starting materials. Its metal complexes were obtained by heating the
ligand with the appropriate metal salt in methanol. The water soluble, square-planar palladium
acetate NNN-pincer complex 2 was characterized by NMR, ESI-MS, and elemental analysis. X-
ray crystallography revealed a cyclic, hexameric structure in the solid state, with the non-

coordinated acetate group bridging the cationic metal complexes. Diamagnetic cobalt complex 3
was obtained via in-situ oxidation of its in-situ obtained Co(II) analog with atmospheric oxygen
and was characterized by NMR, ESI-MS and cyclic voltammetry. X-ray crystallography
revealed an octahedral, homoleptic metal complex with three non-coordinated chlorides engaged
in weak hydrogen bonding with the cationic cobalt complex. Paramagnetic Ni(II) NNN-pincer
complex 4 was characterized by ESI-MS and cyclic voltammetry, and its catalytic application
toward thiolation and Negishi coupling were investigated on an exploratory basis. As postulated,
ligand 1 proved to be able to form stable metal complexes that were soluble in both water and
organic solvents. Aside from enhancing the solubility of the complexes in protic solvents,
hydrogen bonding involving the protons on the ligand backbone was responsible for forming
supramolecular associates in the solid state. Nickel complex 4 displayed catalytic activity
towards the reductive thiolation of iodobenzene with dimethyldisulfide in DMF in the presence
of zinc. More significantly, 4 is to our knowledge the first example of a nickel catalyst that
promotes the Negishi coupling in water. Further studies towards in- and on-water catalysis
pertaining to complexes 2 and 4 are in progress.
4
. Associated Content:
Supporting Information: Complete NMR spectra for all new diamagnetic compounds, GC-MS
spectra as well as the relevant crystallography tables and cif files are provided in the Supporting
Information. CCDC 1565556 and 1565557 contains the supplementary crystallographic data for
2
and
3.
These
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 e-mail:
deposit@ccdc.cam.ac.uk.
5
. Author Information
Corresponding Author
*
roesler@ucalgary.ca.
6
. Acknowledgment
Financial support for this work was provided by the Natural Sciences and Engineering Research
Council of Canada in the form of a Discovery Grant to R.R.

7
. Experimental
General Considerations
All reagents were purchased from chemical suppliers and used as received. Unless specified
otherwise, the synthesis and handling of compounds was carried out without rigorous exclusion
1
13
of air and moisture. H and C NMR spectra were acquired on a Bruker Avance 400
1
spectrometer and internally referenced relative to D
2
O ( H, 4.79 ppm) or deuterated methanol
1
13
13
(
H, 3.31 ppm; C, 49.15 ppm). The C NMR spectra recorded in D
2
O were calibrated using
1
3
CH
3
CN as an internal standard ( C, 1.47 ppm). Coupling constants (J) are reported as absolute
values. Combustion analyses were performed on a Perkin Elmer 2400 Series II CHNS Analyzer.
All chromatograms were collected on an Agilent model 5975 GC-MSD using a method with
injection temperature of 250 ºC, initial temperature of 50 ºC, in increments of 10 ºC per minute.
ESI-MS was performed with an Agilent 6520 ESI QTOF instrument. Samples were injected in
MeOH solution with a flow rate of 0.2 mL per minute, the source was held at 200 ºC, the drying
gas has a pressure of 12 psi and a flow rate of 7 L /minute, and the fragmentor voltage was set to
8
0V. Cyclic voltammetry was performed using a PARSTAT 2273 potentiostat, a glassy carbon
working electrode (d = 3 mm), a saturated Ag/AgCl reference electrode and a platinum counter-
electrode. X-ray crystallographic analyses were performed on suitable single crystals coated in
Paratone oil and mounted on a glass fiber. Measurements were collected on either a Nonius
KappaCCD or a Bruker APEX II CCD diffractometer; full details can be found in the
independently deposited crystallography information file (cif).
7
.1. Synthesis of 2,6-bis(5,5-dimethyl-tetrahydropyrimidine)pyridine 1
Pyridine-2,6-dicarboxylic acid (4.820 g, 28.8 mmol), 2,2-dimethylpropane diamine (8.00 mL,
6.6 mmol) and p-toluenesulfonic acid (0.445 g, 2.3 mmol) were placed in a 100 mL round
6
bottom flask equipped with magnetic stirrer and refluxed overnight in 50 mL of ethylene glycol.
After cooling the resulting solution in an ice bath, the white solid that precipitated was collected
by filtration and washed with water (20 mL) in an ultrasonic bath in order to remove residual
glycol. The suspension was filtered and washed with acetone to afford 1 (4.012 g, 47% yield) as
1
a white powder. H NMR (400 MHz, methanol-d
4
): δ 1.00 (s, 12 H, CH
3
), 3.14 (s, 8 H, CH ),
2
1
3
7
.92 (t, 1H, J = 7.9 Hz, p-CH), 8.11 (d, J = 7.9 Hz, 2 H, m-CH). C NMR (101 MHz, methanol-

d
4
) δ 25.3 (CH
3
), 27.0 (C(CH
3
)
2
), 54.6 (CH ), 122.8 (m-CH), 138.9 (p-CH), 151.2 (o-CH), 153.7
2
(
CN ).
2
7
.2. Synthesis of Pd(II) complex 2
Ligand 1 (100 mg, 0.33 mmol) and anhydrous palladium (II) acetate (74 mg, 0.33 mmol) were
stirred overnight at 60 ºC in methanol (15 mL). The solvent was subsequently removed in vacuo
and the yellow-orange solid residue was washed with small quantities of acetone, yielding
1
1
10mg of complex (64% yield). H NMR (400 MHz, D
2
O): δ 1.07 (s, 12 H, CH
), 3.24 (s, 4 H, CH ), 7.98 (d, J = 8.2 Hz, 2
H, m-CH), 8.43 (t, 1H, J = 8.2 Hz, p-CH). C NMR (101 MHz, D O) δ 24.0 (CH ), 27.0
C(CH ), 50.1 (CH ), 57.7 (CH ), 124.3 (m-CH), 142.5 (p-CH), 152.3 (o-CH), 159.3 (CN ).
Elemental analysis (%): Calcd for C21 Pd: C 48.14, H 5.96, N 13.37; Found: C 46.95, H
3
), 1.96 (s, 3 H,
CH
3
COO), 2.12 (s, 3 H, CH
3
COO), 3.00 (s, 4 H, CH
2
2
1
3
2
3
(
3
)
2
2
2
2
H
31
N
5
O
4
+
6
4
.07, N 12.99. HRMS (ESI): m/z calcd for C19
H
28
N
5
O Pd, [(1)PdOAc] : 464.1278, found:
2
64.1280.
7
.3. Synthesis of Co(III) complex 3
Ligand 1 (450 mg, 1.51 mmol) and cobalt (II) chloride hexahydrate (180 mg, 0.75 mmol) were
refluxed overnight in methanol (15 mL) in air. The black precipitate was subsequently filtered
off and the solution was evaporated to dryness in vacuo. The product was isolated as a yellow-
1
green solid. (402mg, 73% yield). H NMR (400 MHz, D
2
O): δ 0.81 (s, 12 H, CH ), 1.97 (s, 4 H,
3
1
3
CH
NMR (101 MHz, D
43.8 (p-CH), 153.7 (o-CH), 157.2 (CN
2
), 3.17 (s, 4 H, CH
2
), 8.52 (d, J = 7.9 Hz, 2 H, m-CH), 8.79 (t, 1H, J = 8.1 Hz, p-CH). C
), 27.8 (C(CH ), 49.9 (CH ), 54.3 (CH ), 126.0 (m-CH),
). HRMS (ESI): m/z calcd for C34
CoCl - H ] : 691.3162, found: 691.3138.
2
O) δ 24.2 (CH
3
3
)
2
2
2
1
2
H N10CoCl,
49
2
+
+ +
[
(1)
2
7
.4. Synthesis of Ni(II) complex 4
Ligand 1 (204 mg, 0.68 mmol) and nickel (II) acetate tetrahydrate (166 mg, 0.67 mmol) were
stirred overnight at 60 ºC in methanol (25 mL). The solvent was subsequently removed in vacuo
and the product was isolated as a red-brown solid (253 mg, 78% yield). HRMS (ESI): m/z calcd
+
for C19
H
28
N
5
O
2
Ni, [(1)NiOAc] : 416.1597, found: 416.1585.

7
.5. Thiolation of iodobenzene in the presence of 4
Iodobenzene (34 µL, 0.3 mmol), zinc powder (20 mg, 0.3 mmol), dimethyldisulfide (13µL, 0.15
mmol) and 4 (7 mg, 0.015 mmol) were heated in DMF at 110 ºC overnight A small portion of the
mother liquor was diluted in chloroform and analyzed by GC-MS. The peak at 8.7 min.
correlated to iodobenzene and the peak 14.1 minutes corresponded to thioanisole.
7
2 2 4
.6. Thiolation of iodobenzene in the presence of Ni(OAc) (H O)
Iodobenzene (34 µL, 0.3 mmol), zinc powder (20 mg, 0.3 mmol), dimethyldisulfide (13 µL, 0.15
mmol) and nickel acetate tetrahydrate (5 mg, 0.02 mmol) were heated in DMF at 110 ºC
overnight. A small portion of the mother liquor was diluted in chloroform and analyzed by GC-
MS. The peak at 8.7 min. correlated to iodobenzene and the peak 14.1 min. corresponded to
thioanisole.
7
.7. Negishi coupling in the presence of 4
Iodobenzene (51 µL, 0.45 mmol), zinc powder (30 mg, 0.46 mmol) and 4 (5 mg, 0.01 mmol)
were heated in water at 100 ºC overnight. A chloroform extract of the sample was diluted and
analyzed by GC-MS. The peak at 8.7 minutes correlated to iodobenzene and the peak 14.1
minutes corresponded to biphenyl.
7
.8. Negishi coupling in the presence of Ni(OAc)
Iodobenzene (51 µL, 0.45 mmol), zinc powder (30 mg, 0.46 mmol) and Ni(OAc)
.02 mmol) were heated in water at 100 ºC overnight. A chloroform extract of the sample was
2 2 4
(H O)
2
(H
2
O) (5 mg,
4
0
diluted and analyzed by GC-MS. The peak at 8.7 minutes corresponded to iodobenzene.
References
[
[
[
[
1] E.C. Constable, Adv. Inorg. Chem. Radiochem. 30 (1986) 69.
2] M. Heller, U.S. Schubert, Eur. J. Org. Chem. (2003) 947
3] H. Hofmeier, U.S. Schubert, Chem. Soc. Rev. 33 (2004) 373. (d)
4] U. S. Schubert, A. Winter, G. R. Newkome, Terpyridine-based Materials: For Catalytic,
Optoelectronic and Life Science Applications; Wiley: Hoboken, NJ, (2011).
5] U. Ziener, E. Breuning, J.-M. Lehn, E. Wegelius, K. Rissanen, G. Baum, D. Fenske, G.
Vaughan, Chem. Eur. J. 6 (2000) 4132.
[
[
6] R. Liegghio, P.G. Potvin, A.B.P. Lever, Inorg. Chem. 40 (2001) 5485.

[
[
[
[
[
7] H. Ali-Haddou, S.L. Wiskur, V.M. Lynch, E.V. Anslyn, J. Am. Chem. Soc. 123 (2001)
1296.
8] M.G.B. Drew, C. Hill, M.J. Hudson, P.B. Iveson, C. Madic, T.G.A. Youngs, Dalton Trans.
2004) 244.
9] M.G.B. Drew, D. Guillaneux, M.J. Hudson, P.B. Iveson, C. Madic, Inorg. Chem. Commun.
(2001) 462.
1
(
4
10] P.B. Iveson, C. Rivière, D. Guillaneux, M. Nierlich, P. Thuéry, M. Ephritikhine, C. Madic,
Chem. Commun. (2001) 1512.
11] M.G.B. Drew, D. Guillaneux, M.J. Hudson, P.B. Iveson, M.L. Russell, C. Madic, Inorg.
Chem. Commun. 4 (2001) 12.
[
[
12] A.K. Hui, B.J. Cook, D.J. Mindiola, K.G. Caulton, Inorg. Chem. 53 (2014) 3307.
13] C.R. Benson, A.K. Hui, K. Parimal, B.J. Cook, C.-H. Chen, R.L. Lord, A.H. Flood, K.G.
Caulton, Dalton Trans. 43 (2014) 6513.
[
[
[
[
[
[
[
[
[
14] A.K. Hui, Y. Losovyj, R.L. Lord, K.G. Caulton, Inorg. Chem. 53 (2014), 3039.
15] A.K. Hui, R.L. Lord, K.G. Caulton, Dalton Trans. 43 (2014), 7958.
16] G. Stupka, L. Gremaud, G. Bernardinelli, A.F. Williams, Dalton Trans. (2004) 407.
17] Y.I. Lin, S.A. Lang, J. Heterocyclic Chem. 14 (1977) 345.
18] K.H. Sugiyarto, H.A. Goodwin, Aust. J. Chem. 41 (1988) 1645.
19] K.H. Sugiyarto, D.C. Craig, A.D. Rae, H.A. Goodwin, Aust. J. Chem. 47 (1994) 869.
20] A. Yoshinari, A. Tazawa, S. Kuwata, T. Ikariya, Chem. Asian J. 7 (2012) 1417.
21] K. Umehara, S. Kuwata, T. Ikariya, J. Am. Chem. Soc. 135 (2013), 6754.
22] P. Yang, M.-X. Li, M. Shao, M.-S. Wang, S.-X. Cao, J.-C. Zhang, H.-H. Zhang, Cryst.
Growth. Des. 13 (2013) 4305.
[
[
23] K.H. Sugiyarto, D.C. Craig, A.D. Rae, H.A. Goodwin, Aust. J. Chem. 46 (1993) 1269.
24] R.M. Meudtner, M. Ostermeier, R. Goddard, C. Limberg, S. Hecht, Chem. Eur. J. 13
(
2007) 9834.
[
[
[
25] Y. Li, J.C. Huffman, A.H. Flood, Chem. Commun. (2007) 2692.
26] M. Halcrow, New J. Chem. 38 (2014) 1868.
27] M. Felsmann, J. Hübscher, F. Eißmann, W. Seichter, E. Weber, Z. Naturforsch. B 66
(
2011) 197.
28] C.R. Rice, C.J. Baylies, L.P. Harding, J.C. Jeffery, R.L. Paul, M.D. Ward, Polyhedron 22
2003) 755.
[
[
[
(
29] J.D. Nobbs, A.K. Tomov, R. Cariou, V.C. Gibson, A.J.P. White, G.J.P. Britovsek, Dalton
Trans. 41 (2012) 5949.
30] H. Nishiyama, H. Sakaguchi, T. Nakamura, M. Horihata, M. Kondo, K. Itoh,
Organometallics 8 (1989) 846.
[
[
[
[
31] H. Nishiyama, S.-B. Park, K. Itoh, Tetrahedron: Asymmetry 3 (1992) 1029.
32] G. Desimoni, G. Faita, P. Quadrelli, Chem. Rev. 103 (2003) 3119.
33] J. Fraile, J.García, J. Mayoral, Coord. Chem. Rev. 252 (2008) 624.
34] A. Cabort, B. Therrien, H. Stoeckli-Evans, K. Bernauer, G. Süss-Fink, Inorg. Chem.
Commun.
[
[
[
35] A.T. Baker, P. Singh, V. Vignevich, Aust. J. Chem. 44 (1991) 1041.
36] A.T. Baker, D. C. Craig, P. Singh, Aust. J. Chem. 44 (1991) 1659.
37] M.K. Tse, S. Bhor, M. Klawonn, G. Anilkumar, H. Jiao, C. Döbler, A. Spannenberg, W.
Mägerlein, H. Hugl, M. Beller, Chem. Eur. J. 12 (2006) 1855.

[
[
[
38] V. Gibson, C. Redshaw, G. Solan, Chem. Rev. 107 (2007) 1745.
39] G. Chelucci, R. P. Thummel, Chem. Rev. 102 (2002) 3129.
40] H.-L. Kwong, H.-L. Yeung, C.-T. Yeung, W.-S. Lee, C.-S. Lee, W.-L. Wong, Coord.
Chem. Rev. 251 (2007) 2188.
[
[
41] A. Winter, G.R. Newkome, U.S. Schubert, ChemCatChem 3 (2011) 1384.
42] G.J.P. Britovsek, M. Bruce, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S. Mastroianni,
S.J. McTavish, C. Redshaw, G.A. Solan, S. Stromberg, A.J.P. White, D.J. Williams, J. Am.
Chem. Soc. 121 (1999) 8728.
[
[
43] R.M. Brown, J. Borau Garcia, J. Valjus, C.J. Roberts, H. M. Tuononen, M. Parvez, R.
Roesler, Angew. Chem., Int. Ed. 54 (2015) 6274.
44] B.M. Puerta Lombardi, R.M. Braun, C. Gendy, C.Y. Chang, T. Chivers, R. Roesler,
Organometallics 36 (2017) submitted.
[
[
[
[
[
[
[
45] H. Grützmacher, Angew. Chem., Int. Ed. 47 (2008) 1814.
46] C. Gunanathan, D. Milstein, Acc. Chem. Res. 44 (2011) 588.
47] T. Zell, D. Milstein, Acc. Chem. Res. 48 (2015) 1979.
48] J.R. Khusnutdinova, D. Milstein, Angew. Chem., Int. Ed. 54 (2015) 12236.
49] D. Milstein, Phil. Trans. R. Soc. A 373 (2015) 20140189.
50] K.H. Shaughnessy, Chem. Rev. 109 (2009) 643.
51] B. Cornils, W.A. Herrmann, Eds., Aqueous-phase organometallics catalysis, Wiley-VCH
(
2004).
[
[
[
[
[
[
[
52] P. Dixneuf, V. Cadierno, Metal-Catalyzed Reactions in Water. Somerset. (2013).
53] M.-O. Simon, C.-J. Li, Chem. Soc. Rev. 41 (2012) 1415.
54] A. Casalnuovo, J. Calabrese, J. Am. Chem. Soc. 112 (1990) 4324.
55] A. Kraft, A. Reichert. Tetrahedron 55 (1999) 3923.
56] P. Castan, F. Dahan, S. Wimmer, Dalton Trans. (1990) 2679.
57] Ž.D. Bugarčić, B. Petrović, E. Zangrando, Inorg. Chim. Acta 357 (2004) 2650.
58] D. Nicholls. Elsevier, 2013 The Chemistry of Iron, Cobalt and Nickel: Comprehensive
Inorganic Chemistry, pp. 1095-1097.
[
[
59] P. Comba, F. Sickmüller, Inorg. Chem. 36 (1997) 4500.
60] I.L. Eremenko, S.E. Nefedov, A.A. Sidorov, M.A. Golubnichaya, P.V. Danilov, V.N.
Ikorskii, Y.G. Shvedenkov, V.M. Novotortsev, I.I. Moiseev, Inorg. Chem. 38 (1999) 3764.
61] R. Srinivasan, G. Ramesh Bapu, T. I. Met. Finish. 91 (2013) 52.
62] O. Baldovino-Pantaleón, S. Hernández-Ortega, D. Morales-Morales, Inorg. Chem.
Commun. 8 (2005) 955.
[
[
[
63] V. Gómez-Benítez, O. Baldovino-Pantaleón, C. Herrera-Álvarez, R. Toscano, D. Morales-
Morales, Tetrahedron Lett. 47 (2006) 5059.
[
[
[
[
[
64] C. Eichman, J. Stambuli, Molecules 16 (2011) 590.
65] J. Zhang, C.M. Medley, J.A. Krause, H. Guan, Organometallics 29 (2010) 6393.
66] A. Krasovskiy, C. Duplais, B. H. Lipshutz, J. Am. Chem. Soc. 131 (2009) 15592.
67] A. Krasovskiy, C. Duplais, B. H. Lipshutz, Org. Lett. 12 (2010) 4742.
68] A. Krasovskiy, C. Duplais, B. H. Lipshutz, Organometallics 30 (2011) 6090.

Palladium, cobalt and nickel complex of a neutral NNN-pincer ligand based on a pyridyl core and
cyclic amidine pendant arms were prepared. The palladium and cobalt complexes formed
hydrogen-bonded supramolecular associations in the solid state, while the nickel analog displayed
catalytic activity towards the Negishi coupling of iodobenzene in water.