Synthesis and characterization of novel tetradentate ruthenium complexes of a pyridine-o-phenylenediamine based chelate ligand

Article abstract of DOI:10.1016/j.ica.2019.119391

The synthesis of the new complexes [cis-Ru(N,N′-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)(DMSO)](Cl), [cis-Ru(N,N′-bis-(2-pyridylmethyl)-o-phenylenediamine)(MeCN)₂](OTf)₂ and [cis-Ru(N,N′-bis-(2-pyridylmethyl)-o-phenylenediamine)

Full text of DOI:10.1016/j.ica.2019.119391

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Research paper
Synthesis and Characterization of Novel Tetradentate Ruthenium Complexes of
a Pyridine-o-phenylenediamine Based Chelate Ligand
Maryanne K. Stones, Ryan J. Sullivan, Dmitriy V. Soldatov, Marcel Schlaf
PII:
S0020-1693(19)31640-8
https://doi.org/10.1016/j.ica.2019.119391
ICA 119391
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
27 October 2019
18 December 2019
19 December 2019
Please cite this article as: M.K. Stones, R.J. Sullivan, D.V. Soldatov, M. Schlaf, Synthesis and Characterization of
Novel Tetradentate Ruthenium Complexes of a Pyridine-o-phenylenediamine Based Chelate Ligand, Inorganica
Chimica Acta (2019), doi: https://doi.org/10.1016/j.ica.2019.119391
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Synthesis and Characterization of Novel Tetradentate Ruthenium Complexes of a Pyridine-
o-phenylenediamine Based Chelate Ligand.
Maryanne K. Stones, Ryan J. Sullivan, Dmitriy V. Soldatov, and Marcel Schlaf*
Department of Chemistry, University of Guelph, The Guelph-Waterloo Centre for Graduate
2
Work in Chemistry (GWC) , 50 Stone Road East, Guelph, Ontario, Canada, N1G 2W1
*
Corresponding author: mschlaf@uoguelph.ca
Highlights



Tetradentate ligands
High-temperature stable ruthenium complexes
Potential Hydrogenation catalysts
1

Abstract
The synthesis of the new complexes
phenylenediamine)(Cl)(DMSO)](Cl),
[cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-
[cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-
[cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-
phenylenediamine)(MeCN) ](OTf)
and
2
2
phenylenediamine)(PhCN) ](OTf) is reported. The ligand, N,N'-bis-(2-pyridylmethyl)-o-
2
2
phenylenediamine, was complexed to ruthenium using the ruthenium precursor, RuCl (DMSO) ,
2
4
to
yield
the
intermediate
complex
[cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-
phenylenediamine)(Cl)(DMSO)](Cl). The metathesis of DMSO and chloride ligands from [cis-
Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)(DMSO)](Cl) was carried out in the
appropriate nitrile solvent with 2 equivalents of AgOTf to yield the complexes [cis-Ru(N,N'-bis-
(
2-pyridylmethyl)-o-phenylenediamine)(MeCN) ](OTf)
and
[cis-Ru(N,N'-bis-(2-
2
2
pyridylmethyl)-o-phenylenediamine)(PhCN) ](OTf) . Both complexes were characterized by
2
2
single crystal XRD. [cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(MeCN) ](OTf)
2
2
and [cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(PhCN) ](OTf) both possess the
2
2
hypothetical characteristics of homogeneous hydrogenation catalysts that are anticipated to be
acid- water- and temperature stable, and have the potential to be tested as such.
Introduction
In recent years there has been significant effort directed towards the development of efficient
catalytic systems to transform and valorize biomass-derived substrates – and even biomass directly
–
to compete with fossil-based carbon sources for the petrochemical industry [1]. This field has
typically been dominated by heterogeneous catalysts [2-7] due to their relative ease of industrial
application. However, biomass-derived substrates pose interesting challenges in heterogeneously
catalyzed conversions such as coking, fouling and – in consequence – deactivation of the solid
2

catalysts through humin formation which is brought about by the high intrinsic self-reactivity of
the sugar substrates [8-10]. An alternative approach is the design and synthesis of molecularly
well-defined homogeneous catalytic systems that in principle can effect the same desired
transformations [11-13].
While homogeneous catalysts can in specific cases offer advantages over heterogeneous catalysts
in the field of biomass conversion, and catalysis generally, there also exist significant barriers and
challenges to their success; notably their temperature stability and recyclability. Through iterative
design and testing, we have, over the past 15 years [14-17], proposed several generations of
homogeneous ruthenium-based catalysts employing chelating pyridine-motif ligands with
increasing water, acid, and temperature stability. In addition, the research groups of Leitner, Miller,
as well as ourselves, have explored the use of Ru-triphos-based catalyst systems for the
hydrodeoxygenation of biomass derived substrates [18-20]. Despite substantial progress, an acid,
water- and high-temperature stable, recyclable and promiscuous homogeneous
hydrodeoxygenation catalyst has however yet to be discovered.
The work described herein describes a further iteration of homogeneous ruthenium-based catalyst
design which was proposed based on the following principles [11]:
(
1) The pairing of a cationic complex with non-coordinating counterions such as triflate, should
impart solubility in polar reaction media, i.e., ideally pure water;
(
2) Based on the chelate effect as the guiding design principle, the increase in ligand denticity
from di- and tri- to tetra-dentate will increase the complex formation constant and ultimately
impart greater complex stability at the elevated temperatures (150 °C or greater) required for
acid-catalyzed dehydration of the substrates; [21]
3

(
3) The metal-ligand system must present at least one labile ligand which, upon dissociation,
will render it capable of the heterolytic activation of dihydrogen to perform ionic
hydrogenation and/or hydrogenolysis reactions; [22, 23]
(
4) Incorporation of an N-H function into the ligand backbone provides the potential for a metal-
ligand bifunctional hydrogenation and/or hydrogenolysis mechanism.
To this end, two novel tetradentate, ruthenium centered complexes employing the known ligand
N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine (1) were synthesized and characterized by single
crystal X-ray diffraction, mass spectrometry and NMR.
Scheme 1 shows the synthetic pathway to the two complexes.
+
2+
N
N
RCN
AgOTf

-2 AgCl
DMSO
2
OH
RuCl2(DMSO)4
KOH
HN
NH
Cl
Cl-
HN
N
NH
N
-
N
(OTf )2
+
2
NH HN
Ru
N
Ru
N
pyridine N-oxide
toluene

Me
Me
-
H N
NH2

S
2
N
N
O
R
R
7
(
6%
1)
95%
(2)
4
% (3), 18% (4)
R = Me (3), Ph (4)
Scheme 1. Synthetic Pathway to [cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(MeCN)
2 2
](OTf) (3) and
[
cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(PhCN) ](OTf) (4).
2
2
To our knowledge, these are the first examples of metal coordination to 1, however, there exist
several previous examples of metal coordination to analogues of 1 that are displayed in Scheme 2.
It shows the only example of coordination of 5 [24] to an iron centre. There are many literature
examples of 6 [25] coordinating to various metal centres (here shown with a Mn centre as an
example) in the presence of secondary ligands. It is interesting to note that in some examples of
metal coordination to analogues of 1, the coordination environment is cis, whereas in other
examples a trans coordination environment is observed. Florián et al. [26] studied the geometric
4

isomerization of 7 between cis and trans coordination environments, which is possible due to the
flexibility of this hexadentate ligand. The only other example of 7 reported in the literature features
3
+
a lanthanum centre (La ) in place of gallium.
Cl
Cl
Cl
Cl
N
England 2008
HN
NH
NH HN
Fe
N
TfO
OTf
N
N
(5)
O
N
O
O
Arafa 2019
HN
H O
NH
NH HN
Mn
N
O
N
N
OH
2
2
(6)
N
HO
OH
O
Florian 2015
O
N
N
N
N
O
Ga
N
N
N
O
O
O
(7)
and geometric isomers
Scheme 2. Literature examples of metal coordination to analogues of 1. [24-26]
Results and Discussion
Ligand 1 was chosen due to the potentially tetradentate binding pocket provided by four nitrogen
atoms, thus increasing the electron density of the metal centre. The phenylene backbone of 1 was
hypothesized to impart rigidity in the ligand and thus postulated to increase the binding energy to
a metal centre. The positively polarized hydrogens bound to the amine nitrogens are anticipated to
act as proton donors in a conceivable ruthenium-hydride/amine mediated metal-ligand bifunctional
5

mechanism, as, e.g., described by Crabtree [27], Noyori [28], Ikariya [29], Morris [30], and
Gordon [31], as well by ourselves, uniquely under aqueous acidic conditions [32].
The synthesis of 1 was carried out according to literature procedures outlined by Miyano et al. [33,
3
4] as already described in Scheme 1 above. Purification of 1 as described in literature – by vacuum
distillation – proved to be difficult as a tacky, viscous, orange liquid was obtained unlike the solid
described in literature. The product would cool to a viscous, honey-like material inside of the
distillation apparatus, and constant heating of the entire apparatus using a heat gun was required
to pass the entirety the material through to the receiving flask. Notably, England et al. [24] also
describe a lack of reproducibility with the original procedure [33, 34] as they only obtained starting
material and no bis(pyridylmethyl) diamine product.
1
13
Despite difficulties with product purification, the H and C NMR spectra of 1 are well defined
and show pure product. (cf. images of spectra supplied in the Supplementary Material).
Coordination reactions of the ligand with ruthenium were therefore successfully carried out with
the viscous liquid product obtained.
1
was reacted with RuCl (DMSO) [35], in 1:1 stoichiometry as a suspension in toluene. This
2 4
reaction produced [cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)(DMSO)](Cl) (2)
in nearly quantitative yield as a dark yellow/brown powder. The identity of 2 was confirmed by
1
13
H, and C NMR as well as MS (cf. Supplementary Material). Although in Scheme 1, 2 has been
drawn with a sulfur coordinated DMSO ligand – postulated based on the assumption that the
oxygen coordinated DMSO would be much more labile than the sulfur coordinated version [35] –
it is also possible that the DMSO ligand is instead oxygen coordinated, or a mixture of both is
present.
6

When 2 was initially synthesized, a trans coordination motif was anticipated, but the NMR spectra
provided direct evidence towards a cis coordination. In a trans coordination, only 8 individual
signals of the 1 backbone would be present due to the compound symmetry, but instead these
signals are split due to the asymmetric environment induced by the cis coordination motif. 2 was
found to be air stable for short periods of time, but the colour of the complex will gradually darken
from yellow to brown upon exposure to air indicating decomposition.
Because of the strong binding properties of chloride and DMSO (and its potential products under
reducing conditions, e.g., dimethyl sulfide) 2 is not suitable as a catalyst for heterolytic hydrogen
activation, which requires the irreversible generation of free coordination sites generated through
loss of labile spectator ligands that cannot impede catalysis by coordinative inhibition. Therefore
complex 3 was synthesized from 2 via a metathesis reaction of the chloride ligands bound to
ruthenium by silver triflate in acetonitrile at elevated temperatures. The concomitant removal of
the DMSO ligand required elevated temperatures, well above the boiling point of acetonitrile.
Therefore, the reaction was carried out at 175 °C in a pressure sealed 316SS Autoclave Engineers
mini-reactor. This reaction yielded 3 as a light brown powder, however only in a 4 % yield
following isolation and purification. It is likely that the low yields are a result of both product loss
during purification, and incomplete conversion to product. Because the DMSO ligand cannot be
scavenged by silver ions, even if it dissociates from the ruthenium centre, it binds much more
strongly to the ruthenium centre than the labile acetonitrile ligands and could re-coordinate. While
the yield of this process is very low, the ability of 3 to survive temperatures of 175 °C shows
promise for 1 as a ligand in biomass conversion chemistry which requires temperatures of >150
°
C.
7

Despite low product yields, a crystal suitable for single crystal X-ray analysis could be obtained
by vapour diffusion of diethyl ether into a saturated product solution of methylene chloride. The
1
13
identity of 3 was confirmed by H NMR, C NMR, MS and single crystal XRD (cf. Supplementary
Material for images of spectra and references to crystal data/CIF in the CCDC) [36]. Figure 1
shows an ORTEP and the asymmetric unit cell of 3, which displayed disorder in two of the triflate
counterions. The crystal structure confirms the cis coordination environment of 1 complexed to
the ruthenium centre, which is expected from 2 also displaying a cis coordination environment.
Figure 1: ORTEP and capped stick rendering of the asymmetric unit cell of 3 (hydrogens and disorder of the triflate
counterions omitted for clarity in the right image).
The low yields of 3 obtained – and the inability to scale up the reaction inside of a limited volume
pressure vessel – prompted a switch in reaction solvent from acetonitrile to the much higher boiling
benzonitrile. The synthesis of 4 was again carried out with silver triflate being used to scavenge
the chloride ligand, but could be performed at ambient pressure at 200 °C. This reaction yielded 4
in an 18 % yield as a pink/red powder, a significant improvement from the reaction carried out in
acetonitrile to yield 3. It is conceivable that the increased temperature of the reaction promoted a
greater dissociation of the DMSO ligand, resulting in an increased yield. The ambient pressure
8

reaction is also more convenient for scale-up as it can be carried out in the appropriate benchtop
glassware and should be amenable to further optimization as a function of reaction temperature,
time, and volume, which was however beyond the scope of this initial study.
As with 3 crystals suitable for single crystal X-ray analysis were grown by vapour diffusion of
diethyl ether into a saturated product solution of methylene chloride. The identity of 4 was
1
13
confirmed by H and C NMR, IR, MS, and single crystal XRD. Figure 2 shows an ORTEP and
the asymmetric unit cell of 4 which, unlike the asymmetric unit cell of 3, only contains one metal
coordinated complex instead of three. 4 also contains a water molecule, which may have either
aided in the crystallization process or been trapped inside the crystal lattice. As Figure 2 illustrates,
4
was also confirmed to exist as a cis coordination environment.
Figure 2: ORTEP and capped stick rendering of the asymmetric unit cell of 4 (hydrogens omitted for clarity).
Table 1 lists and compares the bond distances and angles of the ruthenium coordination
II
environment in 3 and 4. The bond distances fall in the expected ranges for Ru -N bonds with
neutral ligands (~ 2 Å). The bond angles in the planar chelate (N5-Ru-N4) are ~ 83.7 ° and 79.5-
8
1° for the non-planar (N3-Ru-N4 and N6-Ru-N5) 5-membered chelate rings. The former fall in
9

the middle of the range (81.3° and 86.0°) for the only other dicationic ruthenium complexes
reported in the CCDC 2019 database (deposition numbers 1565148 and 1565149) that pair a
neutral phenylene-diamine with pyridine ligands [37].
1
0

Table 1: Bond length and angles of the Ruthenium coordination environment in 3 and 4.a
Bond Length [Å] 3 (R = CH
3
CN)b 4 (R = PhCN)
Ru-N1
Ru-N2
Ru-N3
Ru-N4
Ru-N5
2.021(3)
2.0075(16)
2.0138(17)
2.0658(16)
2.0887(16)
2.0847(15)
2.0735(16)
2.029(3)
2.082(3)
2.087(3)
2.082(3)
2.063(3)
Ru-N6
Bond Angles [°]
N1-Ru1-N2
N1-Ru1-N6
N2-Ru1-N6
N1-Ru1-N3
N2-Ru1-N3
N6-Ru1-N3
N1-Ru1-N5
N2-Ru1-N5
N6-Ru1-N5
N3-Ru1-N5
N1-Ru1-N4
N2-Ru1-N4
N6-Ru1-N4
N3-Ru1-N4
N5-Ru1-N4
91.65(14)
95.37(13)
88.95(12)
88.75(13)
97.65(13)
172.14(13)
173.76(13)
93.33(13)
80.97(12)
94.31(12)
91.89(13)
175.39(13)
93.67(12)
79.48(12)
83.34(12)
87.55(7)
95.17(7)
93.27(6)
92.87(6)
94.38(7)
169.13(6)
174.78(6)
94.21(6)
79.83(6)
91.90(6)
95.00(6)
174.64(7)
91.19(6)
80.80(7)
91.19(6)
a
Complete tables of all structural and data collection parameters for 3 and 4 can be found in the Supplementary Material and in the CIF files
b
deposited with the CCDC (3: #1961063; 4: #1961064). Atoms for 3 labeled as A in the ORTEP in Figure 1 by selection of one of the three
cations in the asymmetric unit cell.
An alternative to the use of monodentate nitrile solvents in the metathesis step, would the use of
bidentate nitrile solvents such as succinonitrile or glutaronitrile. The chloride metathesis is driven
by the precipitation of silver chloride and will yield a free coordination site for coordination of one
nitrogen of the bidentate ligand to coordinate. This could more easily drive the dissociation of the
DMSO ligand due to the formation of a secondary chelate ligand. Further experiments using this
approach should result in optimization of the yields of analogues of 3 and 4 allowing for them to
be tested as catalysts for the hydrodeoxygenation of biomass-derived, substrates in aqueous-acidic
media at temperatures at least equivalent to that of the boiling point of benzonitrile (191 °C).
1
1

Experimental section
General All reagents and solvents were purchased from readily available commercial sources and
used as received unless otherwise specified. The neutral Al O used for column chromatography
2
3
had a Brockmann Activity I. Manipulations performed under inert atmospheric conditions were
carried out using degassed solvents and standard Schlenk vacuum line techniques under an inert
argon atmosphere. All NMR spectra were gathered on a 400 MHz spectrometer and calibrated to
the residual solvent shift. Single crystal X-ray diffraction analysis were carried out on an Agilent
SuperNova Single Crystal X-Ray Diffractometer. Mass spectral data were collected on a Bruker
n
AmaZon SL LC-MS bypassing the LC and instead using direct injection with electrospray
ionization (ESI).
N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine (1). o-phenylenediamine (3.2033 g, 29.62
mmol), 2-pyridinemethanol (7.7447 g, 70.97 mmol), pyridine 1-oxide (0.0295 g, 0.31 mmol) and
KOH (0.6880 g, 12.26 mmol) were combined in a round bottom flask with still head apparatus.
Incremental heating of the flask to 225 ºC resulted in a vigorous boiling reaction with yellow solid
forming in the flask. 1.6 mL of distillate was collected at a vapour temperature of 100 ºC. The
flask was cooled to room temperature. H O (25 mL) was added and neutralized with HCl to pH 7.
2
The product was extracted with CHCl (2 x 25 mL) and the remaining solvent removed under
3
vacuum. A fractional distillation was performed on crude product with yellow oil distilling off at
1
70 ºC, 160 mTorr. Two fractions were collected. Fraction 1 yield: 3.1294 g, 36%. Fraction 2
yield: 2.1688 g, 25%. The first fraction was purified by silica packed column chromatography (30
x 300 mm) with a 20:1 acetonitrile:methanol mobile phase. Two distinct yellow bands passed
through the column, the latter being the product. The product was collected, and solvent removed
1
under vacuum. Column fraction yield: 1.2903 g, 15%. Total yield: 3.4618 g, 40%. H NMR (400
1
2

MHz, CDCl ): δ= 4.46 (s, 6H), 6.66 (m, 2H), 6.75 (m, 2H), 7.18 (tdd, J =6.16 Hz, J =1.12 Hz,
3
1
2
J =1.12 Hz, 2H), 7.36 (d, J=7.84 Hz, 2H), 7.64 (td, J =7.74 Hz, J =1.81 Hz, 2H), 8.59 (dq, J =4.87
3
1
2
1
1
3
Hz, J =0.88 Hz, 2H). C NMR (400 MHz, CDCl ): δ= 49.9 (CH ), 112.2 (CH), 119.4 (CH), 121.7
2
3
2
(CH), 122.1 (CH), 136.6 (CH), 137.0 (C), 149.3 (CH), 158.9 (C).
.
RuCl (DMSO) .[35] RuCl xH O (2.0348 g, 7.78 mmol) was dissolved in ethanol (50 mL) and
2
4
3
2
brought to reflux at 100 ºC with stirring. The solution was refluxed for 4 h and then cooled to room
temperature. The dark green solution was filtered, and the solvent evaporated, leaving a dark green
oil. DMSO (8 mL) was added and the solution submerged in an oil bath pre-heated to 150 ºC,
resulting in a colour change to bright orange with yellow precipitate. The solution was refluxed
for 2 h then cooled to room temperature. Acetone (60 mL) was added to complete precipitation
and the suspension was left to settle overnight. The bright yellow product was collected by vacuum
filtration, washing with acetone. Crude yield: 2.8809 g, 76 %. The product was then recrystallized
from a minimal amount of hot DMSO and collected by vacuum filtration, washing with acetone.
The bright yellow crystals were then dried under vacuum. Yield: 2.3871 g, 63 %.
[cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)(DMSO)](Cl) (2). This reaction
was carried out using standard Schlenk techniques. Toluene (100 mL) was added to a flask
containing N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine (638.2 mg, 2.20 mmol) and
RuCl (DMSO) (1.0719 g, 2.21 mmol). The yellow suspension was heated to reflux with stirring.
2
4
The solution was refluxed at 125 ºC for 20 h. The yellow powder was then vacuum filtered via
Buchner funnel, washing with the mother liquor three times. The product was collected and dried
1
under vacuum. Yield: 1.1352 g, 95%. H NMR (400 MHz, CD CN): δ = 4.50 (d, J=16.24 Hz, 1H),
3
4
.63 (d, J=15.28 Hz, 1H), 4.90 (dd, J =16.28 Hz, J =5.4 Hz, 1H), 5.51 (dd, J =15.16 Hz, J =4.88
1 2 1 2
Hz, 1H), 6.83 (d, J=4.84 Hz, 1H), 7.31 (m, 5H), 7.40 (t, J=6.68 Hz, 1H), 7.50 (dd, J =7.84 Hz,
1
1
3

J =1.44 Hz, 1H), 7.63 (m, 2H), 7.75 (m, 2H), 9.20 (dd, J =6.2 Hz, J =1.52 Hz, 1H), 9.33 (dd,
2
1
2
1
3
J =5.68 Hz, J =0.84 Hz, 1H). C NMR (400 MHz, CD CN): δ = 61.4 (CH ), 64.5 (CH ), 122.3
1
2
3
2
2
(CH), 122.5 (CH), 124.0 (CH), 124.3 (CH), 126.4 (CH), 126.9 (CH), 129.1 (CH), 129.4 (CH),
1
5
36.8 (CH), 137.3 (CH), 143.4 (C), 145.1 (C), 153.6 (CH), 156.2 (CH), 161.2 (C), 161.9 (C). m/z
+
04.99 [C H ClN ORuS] .
2
0
24
4
[
Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(MeCN) ](OTf) (3). Acetonitrile (35
2 2
mL) was added to a flask containing [cis-Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)
DMSO](Cl) (296.6 mg, 0.55 mmol) and AgOTf (297.7 mg, 1.16 mmol). The resulting solution
(
was green with a brown suspension. The solution was heated to 175 ºC with stirring in an Engineers
Autoclave mini-reactor for 20 h. The solution was cooled to room temperature and vacuum filtered
through a frit with Celite® to remove the grey AgCl precipitate. The resulting bright red solution
was evaporated and dried under vacuum resulting in a bright red oil. Crude yield: 546.4 mg, 86 %.
The crude product was then purified on a neutral alumina column (30 x 330 mm) with a 2:1
acetonitrile:toluene mobile phase and the yellow/brown band was collected. The solvent was
removed by rotary evaporation and the dark orange oil was dried under vacuum. The sample was
dissolved in acetonitrile (6 mL) and precipitated with diethyl ether (60 mL) resulting in a light
brown powder which was collected on a frit and dried under vacuum. Yield: 14.9 mg, 4 %. Crystals
suitable for single crystal X-ray diffraction analysis were grown by vapour diffusion of diethyl
1
ether into a saturated solution of methylene chloride. H NMR (400 MHz, CD CN): δ= 4.61 (d,
3
J=16.11 Hz, 2H), 4.87 (dd, J =16.04 Hz, J =5.28 Hz, 2H), 7.11 (d, J=4.96 Hz, 2H), 7.36 (m, 6H),
1
2
1
3
7
.52 (q, J=3.44 Hz, 2H), 7.73 (td, J =7.74 Hz, J =1.48 Hz, 2H), 9.012 (d, J=5.08 Hz, 2H). C
1 2
NMR (400MHz, CD CN): δ= 63.3 (CH ), 122.9 (CH), 124.8 (CH), 126.9 (CH), 130.4 (CH), 138.0
3
2
+
(
CH), 144.9 (C), 154.8 (CH), 161.4 (C). m/z: 623.01 [C H F N O RuS] .
23 24 3 6 3
1
4

[
Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(PhCN) ](OTf) (4). Benzonitrile (20
2 2
mL) was added to [Ru(N,N'-bis-(2-pyridylmethyl)-o-phenylenediamine)(Cl)(DMSO)](Cl) (101.9
mg, 0.19 mmol) and AgOTf (100.3 mg, 0.39 mmol) and the solution was brought to reflux at 200
°
C with stirring for 16 h. The solution was then filtered through a frit with Celite® to remove the
grey AgCl, resulting in a dark red solution. The solvent was distilled off in vacuo, leaving a dark
red oil. The crude product was purified on a neutral alumina column (20 x 200 mm) with a 2:1
acetonitrile:toluene mobile phase and the red band was collected. The solvent was removed by
rotary evaporation. The red solid was dissolved in a minimal amount of acetonitrile and
precipitated with diethyl ether yielding a pink/red powder which was collected on a frit and dried
under vacuum. Yield: 19.9 mg, 18 %. Crystals suitable for single crystal X-ray diffraction analysis
were grown by vapour diffusion of diethyl ether into a saturated solution of methylene chloride.
1
H NMR (400 MHz, CD Cl ): δ= 4.63 (2H, d, J=16.4 Hz), 5.21 (2H, dd, J = 5.6, 16 Hz), 7.26 (2H,
2
2
d, J = 7.6 Hz), 7.31 (2H, dd, J = 2.4, 3.6 Hz), 7.37 (2H, t, J = 5.6 Hz), 7.56 (4H, t, J = 8 Hz), 7.65
1
3
(
6H, m), 7.98 (4H, dd, J = 8.4, 0.1 Hz), 9.18 (2H, d, J = 4.8). C NMR (400 MHz, CD Cl ): δ=
2 2
6
1
1
5
4.1 (CH ), 111.9 (C), 122.3 (CH), 124.7 (CH), 126.4 (CH), 127.3 (C), 129.7 (CH), 130.1 (CH),
2
-1
33.9 (CH), 134.1 (CH), 144.6 (C), 154.7 (CH), 160.8 (C). ATR-IR (solid, cm ): 3096w, 3066w,
596w, 1489s, 1447s, 1262s, 1222s, 1140s, 1029s, 1000w, 934w, 753s, 683s, 635s, 572s, 552s,
+
15s. m/z: 747.07 [C H F N O RuS] .
3
3
28
3
6
3
1
13
Supplementary Material: Details of synthetic procedures, spectral data and images of H/ C
NMR spectra, Tables of crystallographic data and ORTEPs (pdf file 75 pages). CIF files have
been deposited with and are available from the Cambridge Crystallographic Data Centre. CCDC
codes: 3 #1961063; 4 #1961064. The data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures.
1
5

Acknowledgment: This work was supported by the Discovery Grant Program of the Natural
Science and Engineering Research Council of Canada (NSERC) and the Bioeconomy Program
of the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).
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CRediT author statement
Maryanne K. Stones: Investigation, Data Curation, Visualization, Writing - Original Draft
Ryan J. Sullivan: Investigation
Dmitriy V. Soldatov: Investigation, Data Curation, Visualization
Marcel Schlaf: Conceptualization, Supervision, Funding acquisition, Writing - Review &
Editing
Highlights


Tetradentate ligands
High-temperature stable ruthenium complexes

Potential Hydrogenation catalysts
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