Geometric isomerization and geometry controlled catalytic alcohol aminations of ruthenium hydride compounds containing bidentate pyrrolyl-imines

Article abstract of DOI:10.1016/j.jorganchem.2019.120957

A series of ruthenium hydride compounds containing bidentate pyrrole-imine ligands were synthesized and characterized and their properties were fully studied. Reacting [C₄H₃NH-(2-CH=N-R) (L₁H, R = CH₂-2-furanyl; L₂H, R = CH₂-morpholine; L₃H, R = CH₂-2-pyridyl) with one equivalent of n-BuLi afforded the corresponding lithium reagents (LiL₁～LiL₃). Combining RuHCl(CO)(PPh₃)₂ with LiL₁～LiL₃ in THF at 0 °C with stirring at room temperature for 12 h generated pure trans-Pyr-Ru-H 1–3 in moderate yields after repeated fractional recrystallization. When the reactions were performed at reflux temperature, pure cis-Pyr-Ru-H 1–3 were obtained by fractional recrystallization in relatively high yields. A thermal isomerization study showed that pure cis-Pyr-Ru-H 1–3 and trans-Pyr-Ru-H 1–3 can be interconverted in THF after refluxing and equilibrium was attained. Reacting a bulkier ligand [C₄H₃NLi-(2-CH=N-^tBu)] (LiL₄) with one equivalent RuHCl(CO)(PPh₃)₃ at room temperature afforded only cis-Pyr-Ru-H 4 after purification. No trans-Pyr-Ru-H 4 was observed, indicating the bulkier t-butyl group of the L₄ ligand altered the stability of cis- and trans-Pyr-Ru-H 4. A catalytic alcohol amination study showed the cis forms of Pyr-Ru-H were the active catalysts for converting benzyl alcohol to N-benzylaniline.

Full text of DOI:10.1016/j.jorganchem.2019.120957

Journal of Organometallic Chemistry 902 (2019) 120957
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Geometric isomerization and geometry controlled catalytic alcohol
aminations of ruthenium hydride compounds containing bidentate
pyrrolyl-imines
Yong-Jie Li a, Hsuan-Ting Lai a, Ching-Han Hu a, Jie-Hong Chen a, Chia-Her Lin b,
,
*
Jui-Hsien Huang a
a Department of Chemistry, National Changhua University of Education, Changhua, Taiwan, 50058
b Department of Chemistry, Chung-Yuan Christian University, Chun-Li, 320, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of ruthenium hydride compounds containing bidentate pyrrole-imine ligands were synthesized
and characterized and their properties were fully studied. Reacting [C4H3NH-(2-CH¼N-R) (L1H, R ¼ CH2-
2-furanyl; L2H, R ¼ CH2-morpholine; L3H, R ¼ CH2-2-pyridyl) with one equivalent of n-BuLi afforded the
corresponding lithium reagents (LiL1~LiL3). Combining RuHCl(CO)(PPh3)2 with LiL1~LiL3 in THF at 0 ꢀC
with stirring at room temperature for 12 h generated pure trans-Pyr-Ru-H 1e3 in moderate yields after
repeated fractional recrystallization. When the reactions were performed at reflux temperature, pure cis-
Pyr-Ru-H 1e3 were obtained by fractional recrystallization in relatively high yields. A thermal isomer-
ization study showed that pure cis-Pyr-Ru-H 1e3 and trans-Pyr-Ru-H 1e3 can be interconverted in THF
after refluxing and equilibrium was attained. Reacting a bulkier ligand [C4H3NLi-(2-CH¼N-tBu)] (LiL4)
with one equivalent RuHCl(CO)(PPh3)3 at room temperature afforded only cis-Pyr-Ru-H 4 after purifi-
cation. No trans-Pyr-Ru-H 4 was observed, indicating the bulkier t-butyl group of the L4 ligand altered
the stability of cis- and trans-Pyr-Ru-H 4. A catalytic alcohol amination study showed the cis forms of
Pyr-Ru-H were the active catalysts for converting benzyl alcohol to N-benzylaniline.
Received 24 April 2019
Received in revised form
19 September 2019
Accepted 25 September 2019
Available online 8 October 2019
Keywords:
Ruthenium
Pyrrole-imine
cis-trans isomerization
Hydrido
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
RuHCl(CO)(PPh3)3 (1) [9] is a common starting material for
synthesizing corresponding compounds with ancillary ligands.
Ruthenium compounds are widely used as catalysts for dehy-
drogenation [1], arylation [2], transfer hydrogenation [3], alcohol
amination [4], geometry isomerization [5], and for cancer cell
growth inhibition reagents [6], etc. Among these ruthenium com-
pounds, octahedral geometries of ruthenium complexes containing
hydride, carbonyl, and varieties of ligands represent an important
series of catalysts and several review papers regarding the corre-
sponding ruthenium hydride compounds have been published [7].
The relative positions of ancillary ligands and hydride on the
ruthenium atom may confer different catalytic activities to these
ruthenium compounds. Therefore, the geometries and thermal
stability of ruthenium hydride [8] compounds are important factors
in the study of catalytic reactions using these ruthenium hydride
compounds.
Reacting 1 with asymmetric bidentate C~N, N~N, N~O ligands (L~L0)
generated RuH(L~L0)(CO)(PPh3)2 which may contain trans- and cis-
P-Ru-P [10] types of geometries as shown in Scheme 1. In searching
the Cambridge Crystal Structure Database, we found most of the
related geometries of RuH(L~L0)(CO)(PPh3)2 are the trans-P-Ru-P
type and only a few are the cis-P-Ru-P type [11]. Among the trans-P-
Ru-P type of RuH(L~L0)(CO)(PPh3)2 compounds, some asymmetrical
bidentate N~N0 ligands were used to generate
a series of
RuH(N~N0)(CO)(PPh3)2 compounds [12]. It is known that the hy-
dride group of these ruthenium compounds may be arranged in
either trans or cis position relative to one of the nitrogen atoms of
the N~N’ ligand and sometimes both geometries can be obtained
simultaneously, as shown in Scheme 1(a). These observations led us
to examine the questions: (i) can the two isomers be separated; (ii)
can the two isomers be interconverted to each other; and (iii)
which isomer is the active form for catalytic alcohol amination?
Here we report the synthesis of a series of ruthenium hydride
* Corresponding author.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
https://doi.org/10.1016/j.jorganchem.2019.120957
0022-328X/© 2019 Elsevier B.V. All rights reserved.

2
Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
Scheme 1. Possible geometries of Ru(L~L0)HCl(CO)(PPh3)2 where the two PPh3 fragments are arranged as (a) trans and (b) cis form.
compounds containing asymmetrical bidentate pyrrole-imine li-
gands. We discuss their geometries, thermal isomerization, and
their abilities to catalyze alcohol aminations.
defined based on the relative position of the hydride and pyrrolyl
fragments.
The 1H, 13C and 31P NMR and IR spectra of trans-Pyr-Ru-H 1e3
were measured. The signals of ruthenium hydride for compounds
trans-Pyr-Ru-H 1e3 appeared as a triplet at ca.
d
ꢁ11.3 with 2JPH at
2. Results and discussion
ca. 19 Hz, representing the two PPh3 ligands located cis to the Ru-H
[4c,12,14]. The 13C NMR spectra of all compounds showed a triplet
2
2.1. Synthesis and characterization of compounds trans- and cis-
at ca.
d
206 for the CO group [15] with JC-P coupling constants at
Pyr-Ru-H 1e3 and cis-Pyr-Ru-H 4
14e17 Hz. The phenyl Cipso carbon of PPh3 showed typical virtual
coupling [16] with the 1JP-C at ca. 20 Hz. The 1H NMR and 13C NMR
signal for the methine of imine CH¼N fragment showed a single
The bidentate pyrrole-imine ligands L1H~L4H (L1H, R ¼ -CH2-20-
furanyl; L2H, R ¼ -CH2CH2-morpholine; L3H, R ¼ -CH2-20-pyridinyl,
L4H, R ¼ -tBu) were prepared easily according to the published
procedures [13] by reacting pyrrole-2-carboxaldehyde with an
equimolar amount of amines in methanol. The pyrrole-imine li-
gands L1H~L3H were converted to their corresponding lithium salts
(LiL1~LiL3) with n-BuLi in THF and with the consecutive addition of
those lithium salts toTHF solutions of RuH(CO)Cl(PPh3)3 at 0 ꢀC. The
solutions were stirred at room temperature under nitrogen for 12 h
generating RuH(CO)(PPh3)2[C4H3N(2-CH¼NR)] (trans-Pyr-Ru-H 1,
R ¼ -CH2-20-furanyl; trans-Pyr-Ru-H 2, R ¼ -CH2CH2-morpholine;
trans-Pyr-Ru-H 3, R ¼ -CH2-20-pyridinyl) in moderate yields after
filtration through Celite to remove LiCl, washing with heptane to
remove excess PPh3, and repeated fractional recrystallization
(Scheme 2). Here the trans-Pyr-Ru-H and cis-Pyr-Ru-H were
resonance in the range of
d 7.52e6.29 and d 159.6e153.7, respec-
tively. The results were confirmed by 1H-13C NMR 2D NMR spec-
troscopy (see supporting information, shows only the NMR spectra
of trans-Pyr-Ru-H 1).
It is worth noting that adding LiL1-LiL3/THF solutions to
RuH(CO)Cl(PPh3)3/THF solution under nitrogen and heating at
70 ꢀC for 24 h afforded RuH(CO)(PPh3)2[C4H3N(2-CH¼NR)] (cis-
Pyr-Ru-H 1, R ¼ -CH2-20-furanyl; cis-Pyr-Ru-H 2, R ¼ -CH2CH2-
morpholine; cis-Pyr-Ru-H 3, R ¼ -CH2-20-pyridinyl) in moderate
yields after filtration and recrystallization as shown for the syn-
thesis of trans-Pyr-Ru-H 1e3. The 1H, 13C, and 31P NMR resonance
patterns of cis-Pyr-Ru-H 1e3 were very similar to those of trans-
Pyr-Ru-H 1e3. The ruthenium hydride chemical shifts in CDCl3 for
compounds cis-Pyr-Ru-H 1e3 appeared at ca.
d
ꢁ10.74 ~ ꢁ10.93
with JPH at ca. 22 Hz, and the 31P NMR showed resonance at ca.
47.0.
2
d
2.2. Thermal isomerization of trans- and cis-Pyr-Ru-H compounds
The geometries of ruthenium hydrides containing multidentate
ligands can affect their catalytic activity toward reactants. This is
due to different ligands restrict the reactants approaching the metal
centers. Therefore, many ruthenium hydrides have been structur-
ally characterized. Among these compounds, only limit examples
show the interconversion of their geometries under certain con-
ditions [17]. Interestingly, the pure trans- and cis-Pyr-Ru-H 1e3
can interconvert thermodynamically. When solutions of trans-Pyr-
Ru-H 1 (Fig. 1a) and cis-Pyr-Ru-H 1 (Fig. 1c) in C6D6 were heated in
J-Young NMR tubes for 8 h at 70 ꢀC, both solutions reached equi-
librium with the Keq, (298K) at 12.8 (Fig. 1b and d). The conversion
rates of trans-Pyr-Ru-H 1 to cis-Pyr-Ru-H 1 were measured by
using 1H NMR spectra for recording the conversion rates. The kobs
were obtained from the plot of time (sec) vs conversion. By using
kobs vs temperature, we can calculate the 1/T and ln(kobs/T) (Table 1)
and generate an Erying plot as shown in Fig. 2. The
D D
HŦ and SŦ
were estimated at 29.5 kcal/mol and 8.86 cal K/mol, respectively.
Theoretical calculations of the relative energy (in terms of total
enthalpy at 298 K) of trans- and cis-Pyr-Ru-H 1e3 were obtained
with the M06-2X functional [18], along with 6-31G(d)-basis set for
C, H, O, N, and LANL2DZ for Ru. Solvation effects of THF were
included using the conductor-like polarizable continuum model
Scheme 2. Synthesis of complexes cis-Pyr-Ru-H 1e3 and cis-Pyr-Ru-H 1e3.

Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
3
Fig. 1. Thermal interconversion of compounds trans-Pyr-Ru-H 1 and cis-Pyr-Ru-H 1. (a) and (c): 1H NMR spectra of hydride region of pure compounds trans-Pyr-Ru-H 1 and cis-
Pyr-Ru-H 1, respectively; (b) and (d), after heating at 70 ꢀC for 8 h in C6D6.
Table 1
2.3. Molecular geometries of trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H
1-3
The Eyring plot of thermal conversion of compound trans-Pyr-Ru-H 1 to cis-Pyr-Ru-
H 1 in C6D6.
Temp (K)
kobs
1/T
Ln(kobs/T)
Even though the compounds trans- and cis-Pyr-Ru-H 1e3 were
characterized by NMR spectroscopy, the relative positions of the
pyrrole, imine, hydride, carbonyl and two PPh3 were still unclear.
Structure determination was quite important to understand their
geometries, thermal stabilities, and reactivities. The crystals of
trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H 2e3 were obtained by
dissolving these compounds in methylene chloride and with
careful layering with dimethylsulfoxide. The crystals of cis-Pyr-Ru-
H 1 were obtained from a methylene chloride/heptane mixed so-
lution. The geometries of trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H
1e3 are shown in Figs. 3e7 and their data collection and selected
bond lengths and angles are listed in Tables 3 and 4, respectively. All
the geometries of trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H 1e3
displayed an octahedral geometry. The geometries of trans-Pyr-
Ru-H 1e2 showed that the two nitrogen atoms of bidentate
pyrrole-imine took the cis positions in an equatorial plane where
the pyrrole fragment was trans to the hydride and the imine frag-
ment was trans to the carbonyl group. The remaining two PPh3 li-
gands mutually occupied the trans positions. The geometries of cis-
Pyr-Ru-H 1e3 were very like the geometries of trans-Pyr-Ru-H
isomers except the pyrrole fragment was trans to the carbonyl and
the imine fragment was trans to the hydride, resulting in the pyr-
role fragment being cis to the hydride. The bond lengths of Ru to
pyrrolyl and imine were all very similar to those of trans-Pyr-Ru-H
1e2 and cis-Pyr-Ru-H 1e3, consistent with the results reported in
the literature [21]. However, our findings revealed some important
information regarding these structures: (i) the trans form has a
lower C-O stretching frequency than the cis form, it seems that the
imine group is a better donor than the pyrrolyl and (ii) the linearity
of P-Ru-P was highly dependent on the geometries of the bidentate
pyrrole-imine verses the hydride and the CO groups where the
trans-Pyr-Ru-H 1e2 presented a larger bonding angle (>170ꢀ) than
those of the cis-Pyr-Ru-H 1e3 variant (<170ꢀ).
328
333
338
343
348
1.34 ꢂ 10ꢁ5
3.00 ꢂ 10ꢁ5
6.27 ꢂ 10ꢁ5
9.92 ꢂ 10ꢁ5
2.04 ꢂ 10ꢁ4
3.05 ꢂ 10ꢁ3
3.00 ꢂ 10ꢁ3
2.96 ꢂ 10ꢁ3
2.92 ꢂ 10ꢁ3
2.87 ꢂ 10ꢁ3
ꢁ17.01
ꢁ16.22
ꢁ15.50
ꢁ15.06
ꢁ14.35
Fig. 2. The Eyring plot for the conversions of trans-Pyr-Ru-H 1 to cis-Pyr-Ru-H 1. X
axis, the values of 1/T; Y, the values of ln(kobs/T).
(CPCM) approach [19]. The Gaussian 09 suite of programs was used
in our studies [20]. Geometry optimizations and harmonic vibra-
tional frequencies were performed using the CPCM analytic gra-
dients. The vibrational frequencies were utilized to compute
thermodynamic corrections to enthalpies at 298 K. The relative
energies of cis Pyr-Ru-H 1e3 were all lower than those of their
trans-Pyr-Ru-H 1e3 counterparts (Table 2). The results were
consistent with the experimental data showing that the cis Pyr-Ru-
H form is much more stable than the trans- ones. Presumably, the
stereo geometry arrangement of cis form has less steric hindrance
and lower the energy.

4
Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
Table 2
Theoretical calculation of formation energy of cis- and trans-Pyr-Ru-H 1e4.
compound
Formation energy (hartrees)
DH
Formation energy (KJ/mol)
cis-Pyr-Ru-H 1
trans-Pyr-Ru-H 1
cis-Pyr-Ru-H 2 trans-Pyr-Ru-H 2
ꢁ2849.8303
ꢁ2849.8292
ꢁ2946.7609
ꢁ2946.7585
ꢁ2868.0638
ꢁ2868.0550
ꢁ2738.9348
ꢁ2738.9322
2.28
6.30
cis-Pyr-Ru-H 3 trans-Pyr-Ru-H 3
23.10
16.28
cis-Pyr-Ru-H 4
trans-Pyr-Ru-H 4
*A hartree is equal to 2625.5 kJ/mol.
Fig. 5. Molecular geometry of cis-Pyr-Ru-H 1. The hydrogen atoms except the hydride
were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.
Fig. 3. Molecular geometry of trans-Pyr-Ru-H 1. The hydrogen atoms except the hy-
dride were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.
Fig. 4. Molecular geometry of trans-Pyr-Ru-H 2. The hydrogen atoms except the hy-
dride were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.
Fig. 6. Molecular geometry of cis-Pyr-Ru-H 2. The hydrogen atoms except the hydride
were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.
2.4. The effect of a bulky imine substituent–synthesis and
characterization of cis-Pyr-Ru-H 4
relation to this, the greater steric hindrance of t-butyl amine was
used to form a bidentate pyrrole-imine ligand L4H and to synthe-
size its corresponding ruthenium compound as shown in Scheme 3.
When L4H was used to react with n-BuLi in THF and with consec-
utive addition of the LiL4/THF solution to a THF solution of RuH(CO)
Cl(PPh3)3 at 0 ꢀC with stirring at room temperature under nitrogen
for 12 h, only RuH(CO)(PPh3)2[C4H3N(2-CH¼NtBu)] (cis-Pyr-Ru-H
4) was isolated in 74% yield (Scheme 3). No trans-Pyr-Ru-H 4 was
found in the reaction products. These results indicated that the
bulky imine substituent raised the formation energy of trans-Pry-
Ru-H 4 and lowered the formation energy of cis-Pyr-Ru-H 4 as
In the beginning of this research, only primary amines were
used for the ligand synthesis, i.e., only L1H~L3H were used. From the
experimental data, we learned that the cis-Pyr-Ru-H 1e3 isomers
were more thermally stable than the trans-Pyr-Ru-H 1e3 isomers.
Even though their bond angles and lengths were quite similar, after
carefully comparing these geometries, we noted that the bond
angles of P-Ru-P for the cis-Pyr-Ru-H 1e3 (ca.169ꢀ) were smaller
than those of trans-Pyr-Ru-H 1e2 (ca. 173-176ꢀ). Presumably, the
steric hindrance of the imine substituents affected the geometry
arrangement of trans-Pyr-Ru-H and cis-Pyr-Ru-H isomers. With

Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
5
shown in Table 2. The 1H NMR spectra of cis-Pyr-Ru-H 4 showed a
2
triplet at ꢁ12.08 with JP-H at 23 Hz assigned as the Ru-H. The 13C
NMR spectrum of cis-Pyr-Ru-H 4 showed a triplet at ca
d 207.6 for
the CO group with 2JC-P coupling constant at 13 Hz. Heating cis-Pyr-
Ru-H 4 in C6D6 in a J-Young NMR tube at elevated temperature did
not establish an equilibrium between trans- and cis-Pyr-Ru-H 4 in
the solution. The yellowish crystals of cis-Pyr-Ru-H 4 were ob-
tained from a THF and heptane mixed solvent at ꢁ20 ꢀC. Crystal
data and selected bond lengths and angles are listed in Tables 3 and
4 and its molecular geometry is shown in Fig. 8. The geometry of
cis-Pyr-Ru-H 4 is similar to cis-Pyr-Ru-H 1e3 and can be described
as a distorted octahedral. Their bond lengths and angles were quite
similar. However, while comparing the geometry and bonding an-
gles of cis-Pyr-Ru-H 4 with cis-Pyr-Ru-H 1e3, we found that the
P(1)-Ru(1)-P(2) is at 161.71(5)º, much smaller than those for cis-
Pyr-Ru-H 1e3. The results further proved the previous assumption
that the steric bulkiness of the substituted imine R group may alter
Fig. 7. Molecular geometry of cis-Pyr-Ru-H 3. The hydrogen atoms except the hydride
were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.
Table 3
Summary of crystallographic data for trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H 1~4.
trans-Pyr-Ru-H 1
trans-Pyr-Ru-H 2
cis-Pyr-Ru-H 1
formula
FW
C47H40N2O2P2Ru
827.82
C49H49Cl2N3O2P2Ru
945.82
C47H40N2O2P2Ru
827.82
T [K]
150
100
150
Crystal system
space group
a [Å]
b [Å]
c [Å]
Triclinic
P-1
Triclinic
P-1
Triclinic
P-1
11.720(3)
12.369(3)
16.202(4)
73.898(12)
75.231(12)
62.691(10)
1982.5(8)
2
10.1825(11)
12.0355(13)
18.613(2)
89.713(6)
77.152(6)
82.980(6)
2206.7(4)
2
10.4546(6)
12.3797(7)
17.0623(10)
106.398(3)
97.897(3)
108.112(3)
1951.1(2)
2
a
b
g
[º]
[º]
[º]
V [Å3]
Z
rc [Mg mꢁ3
m
]
1.385
0.517
1.423
0.592
1.409
0.526
[mm-1]
F(000)
850
976
852
rflns collected
34518
32029
39152
independent rflns
10174 [Rint ¼ 0.0415]
10174/0/491
0.888
10924 [Rint ¼ 0.0538]
10924/0/536
1.037
10093 [Rint ¼ 0.0467]
10093/0/491
0.887
data/restraints/parameters
goodness-of-fit on F2
R1, wR2 (I > 2
s
(I))
R1 ¼ 0.0367, wR2 ¼ 0.1117
R1 ¼ 0.0502, wR2 ¼ 0.1317
0.479/-1.466
R1 ¼ 0.0384, wR2 ¼ 0.0917
R1 ¼ 0.0482, wR2 ¼ 0.0979
0.944/-0.899
R1 ¼ 0.0376, wR2 ¼ 0.1128
R1 ¼ 0.0486, wR2 ¼ 0.1256
0.741/-0.958
R1, wR2(all data)
largest diff. peak, hole [eÅꢁ3
]
cis-Pyr-Ru-H 2
cis-Pyr-Ru-H 3
cis-Pyr-Ru-H 4
formula
FW
C48H47N3O2P2Ru
860.89
C48H41N3OP2Ru
838.84
C46H44N2OP2Ru
803.89
T [K]
100(2)
150(2)
100(2)
Crystal system
space group
a [Å]
b [Å]
c [Å]
Monoclinic
P21/n
12.758(3)
23.499(5)
14.075(3)
90
90.796(15)
90
4219.3(16)
4
1.355
0.490
Triclinic
P-1
Monoclinic
P21/c
18.041(10)
12.436(7)
18.913(9)
90
112.28(3)
90
3927(4)
4
1.358
0.518
10.5045(4)
12.4650(5)
16.9596(6)
106.029(2)
97.669(2)
109.256(2)
1952.27(14)
2
a
b
g
[º]
[º]
[º]
V [Å3]
Z
rc [Mg mꢁ3
m
]
1.425
0.525
[mm-1]
F(000)
1784
862
1660
rflns collected
39929
38134
55156
independent rflns
9843 [Rint ¼ 0.1282]
10114 [Rint ¼ 0.0503]
10114/0/500
0.864
10018 [Rint ¼ 0.1770]
10018/0/476
0.962
data/restraints/parameters
9843/0/505
goodness-of-fit on F2
0.785
R1, wR2 (I > 2
s
(I))
R1 ¼ 0.0564, wR2 ¼ 0.1022
R1 ¼ 0.1174, wR2 ¼ 0.1180
0.849/-0.605
R1 ¼ 0.0384, wR2 ¼ 0.1128
R1 ¼ 0.0509, wR2 ¼ 0.1265
0.826/-0.686
R1 ¼ 0.0686, wR2 ¼ 0.1631
R1 ¼ 0.1349, wR2 ¼ 0.2001
1.314/-2.174
R1, wR2(all data)
largest diff. peak, hole [eÅꢁ3
]

6
Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
Table 4
Selected Bond lengths (Å) and angles (º) for compounds trans-Pyr-Ru-H 1e2 and cis-Pyr-Ru-H 1~4.
trans-Pyr-Ru-H 1
Ru(1)-C(11)
Ru(1)-N(1)
Ru(1)-P(2)
O(2)-C(11)
1.837(3)
Ru(1)-N(2)
Ru(1)-P(1)
Ru(1)-H(100)
2.138(2)
2.3422(7)
1.63(2)
2.1894(19)
2.3435(7)
1.161(3)
C(11)-Ru(1)-N(2)
P(1)-Ru(1)-P(2)
trans-Pyr-Ru-H 2
Ru(1)-C(48)
Ru(1)-N(1)
Ru(1)-P(2)
177.96(8)
173.31(2)
N(2)-Ru(1)-N(1)
N(1)-Ru(1)-H(100)
76.11(8)
164.7(9)
1.837(2)
Ru(1)-N(2)
Ru(1)-P(1)
Ru(1)-H(100)
2.1521(19)
2.3417(6)
1.53(2)
2.1591(19)
2.3545(6)
1.162(3)
O(1)-C(48)
C(48)-Ru(1)-N(2)
P(1)-Ru(1)-P(2)
cis-Pyr-Ru-H 2
Ru(1)-C(60)
Ru(1)-N(2)
Ru(1)-P(1)
Ru(1)-H(101)
C(60)-Ru(1)-N(1)
P(2)-Ru(1)-P(1)
cis-Pyr-Ru-H 3
Ru(1)-C(12)
Ru(1)-N(2)
Ru(1)-P(1)
O(1)-C(12)
C(12)-Ru(1)-N(1)
P(2)-Ru(1)-P(1)
cis-Pyr-Ru-H 4
Ru(1)-C(10)
Ru(1)-N(2)
Ru(1)-P(1)
175.92(9)
176.33(2)
N(2)-Ru(1)-N(1)
N(1)-Ru(1)-H(100)
76.45(7)
164.4(10)
1.837(5)
2.169(3)
2.3624(11)
1.6040
173.32(16)
168.70(4)
Ru(1)-N(1)
Ru(1)-P(2)
O(1)-C(60)
2.123(3)
2.3362(11)
1.159(4)
N(1)-Ru(1)-N(2)
N(2)-Ru(1)-H(101)
76.96(12)
166.7
1.845(2)
2.185(2)
2.3575(6)
1.154(3)
176.79(9)
169.15(2)
Ru(1)-N(1)
Ru(1)-P(2)
Ru(1)-H(41)
2.1178(19)
2.3438(6)
1.57(3)
N(1)-Ru(1)-N(2)
N(2)-Ru(1)-H(41)
76.18(8)
169.2(10)
1.826(5)
2.241(4)
2.3577(16)
1.170(6)
Ru(1)-N(1)
Ru(1)-P(2)
Ru(1)-H(44)
2.155(4)
2.3439(16)
1.53(4)
O(1)-C(10)
C(10)-Ru(1)-N(1)
P(2)-Ru(1)-P(1)
175.35(19)
161.71(5)
N(1)-Ru(1)-N(2)
N(2)-Ru(1)-H(44)
76.63(14)
172.2(15)
Scheme 3. Synthesis of complex cis-Pyr-Ru-H 4.
the geometries of ruthenium complexes and their relative stabil-
ities. The question of which geometry is the real active form for
catalytic reactions remains to be answered.
2.5. Catalytic alcohol amination
Secondary and tertiary amines, obtained from the reactions of
imine condensation and reductive hydrogenation or from the reac-
tion of amines with alkyl halides, are important in organic synthesis
and the pharmaceutical industry [22]. Finding a “green method” for
generating substituted amines with higher atom economy and lower
energy consumption is a general trend in the current chemistry
community. Using organometallic catalysts to catalyze the reaction
of alcohol aminations forming substituted amines is under investi-
gation by many research groups and among these studies,
ruthenium-based catalysts are quite important [23]. It is believed
that the mechanism of alcohol amination is achieved through (a)
dehydrogenation of alcohol by ruthenium compounds, (b) imine
condensation with amine substrates, and (c) hydrogenation via the
Fig. 8. Molecular geometry of cis-Pyr-Ru-H 4. The hydrogen atoms except the hydride
were omitted for clarity. Thermal ellipsoids were drawn at 30% probabilities.

Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
7
borrowing hydrogen methodology (Scheme 4).
Avance 300 spectrometer and the chemical shifts were recorded in
We first tried to understand the relationship between geome-
tries and the catalytic activity. Therefore, we chose to use the
thermally stable cis-Pyr-Ru-H 4 as the catalyst for the reaction of
benzyl alcohol with aniline. The possible products, N-benzylide-
neaniline and N-benzylaniline, were detected and conversion rates
were calculated by using 1H NMR spectra. The results showed that
cis-Pyr-Ru-H 4 cannot catalyze the amination of benzyl alcohol
with aniline even after exposure at 110 ꢀC overnight (as shown in
Table 5, Entry 9). When the pure cis- and trans-Pyr-Ru-H 1e3 were
used as catalysts, the results in Table 5 showed all the conversions
are at ca. 97% after 24 h, according to the 1H NMR spectra. These
results imply that pre-heating the cis- and trans-Pyr-Ru-H 1e3
compounds induced geometry isomerization of these compounds
and they reached an equilibrium before the benzyl alcohol and
aniline were added. The trans form of the catalysts are the active
catalysts. Reaction time affected the final products of the alcohol
amination (Entries 5 and 6). Benzyl alcohol was first dehydro-
genated by the catalysts forming benzaldehyde which then reacted
with aniline to from N-benzylideneaniline via imine condensation.
The N-benzylideneaniline then was hydrogenated to yield N-ben-
zylaniline in the presence of the metal hydride catalysts as shown
in Scheme 4(c).
ppm relative to the residual protons of CDCl3
(
d
¼ 7.24, 77.0 ppm).
External standard of 85% H3PO4 was used for 31P NMR chemical
shift. Elemental analyses were performed using a Heraeus CHN-OS
Rapid Elemental Analyzer at the Instrument Center of the NCHU.
Ligands
C4H3NH(2-CH¼NCH2-20-furanyl)
(L1H)
C4H3NH(2-
CH¼NCH2CH2-morpholine) (L2H), C4H3NH(2-CH¼NCH2-20-pyr-
idinyl) (L3H) [13], and [RuHCl(CO)(PPh3)3] [9] are synthesized by
modifying the published procedures.
4.2. Synthesis of compounds
4.2.1. Synthesis of trans-Pyr-Ru-H 1
A Schlenk flask containing L1H (0.40 g, 2.3 mmol) and THF
(50 mL) was added 2.5 M of n-BuLi (1.01 mL, 2.53 mmol) at ꢁ78 ꢀC.
The solution was stirred for 4 h at room temperature and added
dropwise at 0 ꢀC to another flask which contains RuHCl(CO)(PPh3)3
(2.18 g, 2.3 mmol) and THF (30 mL). The mixture was stirred at
room temperature for 12 h and volatiles were removed under
vacuum. The residue was extracted with methylene chloride and
filtered through celite. The filtrate was dried again under vacuum
and the solid was washed with heptane to remove excess of tri-
phenylphosphine. The remaining solid was recrystallized from a
methylene chloride solution at ꢁ20 ꢀC to give 0.59 g of final product
(31% yield). 1H NMR (CDCl3): 7.27e7.49 (m, 30H, PPh3), 7.12 (s, 1H,
CH furan), 6.95 (s, 1H, CH pyrrole), 6.48 (s, 1H, CH imine), 6.23 (m,
1H, CH pyrrole), 6.08 (s, 1H, CH furan), 5.92 (m, 1H, CH pyrrole), 5.32
3. Conclusions
Steric hindrance of substituents on the imine group of bidentate
pyrrole-imine ligands affected the geometries of ruthenium com-
pounds which also contained hydride and carbonyl groups. When
the bulky t-butyl group was used as the imine substituent, only cis-
Pyr-Ru-H 4 was isolated and no trans-Pyr-Ru-H 4 was observed. In
contrast, with smaller imine substituents such as -CH2-20-furanyl,
-CH2CH2-morpholine, and -CH2-20-pyridinyl, trans and cis -Pyr-
Ru-H 1e3 were observed and isolated. These trans and cis -Pyr-Ru-
H forms could be interconverted to each other thermodynamically
and reached an equilibrium. Catalytic alcohol aminations using
these ruthenium compounds showed that only the trans form of
the ruthenium hydride compounds could catalyze these reactions
actively. Presumably, the geometries of ruthenium catalysts
blocked the entrances of alcohol to the ruthenium center to form
ruthenium alkoxide and the successive steps. These results indicate
the importance of geometry of the catalyst.
2
(m, 1H, CH furan), 3.64 (s, 2H, CH2), ꢁ11.34 (t, JHP ¼ 19.5 Hz, 1H,
RuH). 13C{1H} NMR (CDCl3): 206.2 (t, JCP ¼ 16.0 Hz, CO), 157.1 (CH
imine), 150.9 (C furan), 142.1 (CH furan), 140.5 (C pyrrole), 139.5 (CH
pyrrole), 134.5 (t, JCP ¼ 5.9 Hz, CH PPh3), 134.1 (vt, JCP ¼ 20.4 Hz, C
PPh3), 129.5 (CH PPh3), 127.9 (t, JCP ¼ 4.5 Hz, CH PPh3), 115.1 (CH
pyrrole), 111.1 (CH pyrrole), 110.6 (CH furan), 110.1 (CH furan), 55.5
2
(CH2). 31P NMR (CDCl3): 46.5 (d, JHP ¼ 19.5 Hz, PPh3). IR (KBr,
cmꢁ1):
n
¼ 1901 (CO). Anal. Calcd. for RuC47H40N2O2P2: Calcd.: C:
68.19, H: 4.87, N: 3.38. Found: C: 68.04, H: 4.94, N: 3.54.
4.2.2. Synthesis of cis-Pyr-Ru-H 1
Same procedures used as for synthesizing trans-Pyr-Ru-H 1 are
adopted except the solution of RuHCl(CO)(PPh3)3 and the lithium
reagent of L1H was refluxed for 24 h. Successively purification
procedures are same as that for purifying compound 1. White
crystals of cis-Pyr-Ru-H 1 was obtained from a saturated methy-
lene chloride/heptane solution at ꢁ20 ꢀC (0.86 g, 45%). 1H NMR
(CDCl3): 7.22e7.31 (m, 30H, PPh3), 7.14 (s, 1H, CH furan), 6.89 (s, 1H,
CH imine), 6.29 (s, 1H, CH pyrrole), 6.18 (m, 1H, CH furan), 5.94 (s,
1H, CH pyrrole), 5.69 (mz, 1H, CH pyrrole), 5.68 (m, 1H, CH furan),
4. Experimental section
4.1. Materials and physical techniques
2
4.11 (s, 2H, CH2), ꢁ10.74 (t, JHP ¼ 21.6 Hz, 1H, RuH). 13C{1H} NMR
The 1H and 13C NMR spectra were recorded using a Bruker
(CDCl3): 206.1 (t, JCP ¼ 14.0 Hz, CO),155.8 (CH imine),151.8 (C furan),
142.3 (CH furan), 141.2 (C pyrrole), 138.6 (CH pyrrole), 134.4 (vt,
JCP ¼ 20.5 Hz, CH PPh3), 134.0 (t, JCP ¼ 6.0 Hz, C PPh3), 129.2 (CH
PPh3), 127.9 (t, JCP ¼ 4.4 Hz, CH PPh3), 114.5 (CH pyrrole), 111.5 (CH
pyrrole), 110.2 (CH furan), 109.7 (CH furan), 55.8 (CH2). 31P NMR
(CDCl3): 47.5 (d, 2JHP ¼ 21.6 Hz, PPh3). IR (KBr, cmꢁ1):
¼ 1916 (CO).
n
Anal. Calcd. for RuC47H40N2O2P2: Calcd.: C: 68.19, H: 4.87, N: 3.38.
Found: C: 68.09, H: 4.39, N: 3.42.
4.2.3. Synthesis of trans-Pyr-Ru-H 2
Similar procedures used as for synthesizing trans-Pyr-Ru-H 1
are adopted. Reactants L2H (0.40 g, 1.93 mmol), 2.5 M of n-BuLi
(0.85 mL, 2.12 mmol), RuHCl(CO)(PPh3)3 (1.84 g, 1.93 mmol) were
used. Compound trans-Pyr-Ru-H
2 was recrystallized from
dichloromethane/DMSO solution in 39% yield (0.654 g). 1H NMR
(CDCl3): 7.24e7.45 (m, 30H, PPh3), 6.96 (s,1H, CH imine), 6.77 (s,1H,
CH pyrrole), 6.43 (m, 1H, CH pyrrole), 5.94 (m, 1H, CH pyrrole),
Scheme 4. The plausible mechanism for alcohol amination.

8
Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
Table 5
Catalytic amination of benzyl alcohol with anilinea.
Entry
Cat.
mol%
Time (h)
Conv. (%)
PhCH ¼ NPh: PhCH2NHPh
1
2
3
4
5
6
7
8
9
‒
12
24
24
24
12
24
24
24
24
trace
97
97
97
97
97
97
97
0
trans-Pyr-Ru-H 1
cis-Pyr-Ru-H 1
trans-Pyr-Ru-H 2
cis-Pyr-Ru-H 2
cis-Pyr-Ru-H 2
trans-Pyr-Ru-H 3
cis-Pyr-Ru-H 3
cis-Pyr-Ru-H 4
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
3:97
12:88
10:90
32:68
20:80
8:92
6:94
0
a
Reaction condition: aniline (4 mmol)/benzyl alcohol (4 mmol)/catalyst/KOH (8 mmol) in toluene at 110 ꢀC.
3.50e3.53 (m, 4H, CH2O morpholine), 2.51e2.57 (m, 2H, CH2),
1.91e1.94 (m, 4H, CH2N morpholine), 1.39e1.45 (m, 2H,
CH2), ꢁ11.43 (t, 2JHP ¼ 18.9 Hz,1H, RuH). 13C{1H} NMR (CDCl3): 206.0
(t, JCP ¼ 16.5 Hz, CO), 158.7 (CH imine), 140.3 (C pyrrole), 139.6 (CH
pyrrole), 134.5 (t, JCP ¼ 5.8 Hz, CH PPh3), 134.0 (vt, JCP ¼ 20.6 Hz, C
PPh3), 129.5 (CH PPh3), 127.8 (t, JCP ¼ 4.5 Hz, CH PPh3), 114.8 (CH
pyrrole), 111.2 (CH pyrrole), 66.9 (CH2 morpholine), 57.7 (CH2), 57.4
(CH2), 53.8 (CH2 morpholine). 31P NMR (CDCl3): 46.8 (d,
(vt, JCP ¼ 20.6 Hz, C PPh3), 129.4 (CH PPh3), 127.8 (t, JCP ¼ 4.5 Hz, CH
PPh3), 124.8 (CH pyridine), 122.1 (CH pyridine), 115.4 (CH pyrrole),
111.3 (CH pyrrole), 66.8 (CH2). 31P NMR (CDCl3): 45.5 (d,
2JHP ¼ 18.9 Hz, PPh3). IR (KBr, cmꢁ1):
¼ 1901 (CO). Anal. Calcd. for
n
RuC48H41N3OP2: Calcd.: C: 68.72, H: 4.93, N: 5.01. Found: C: 66.92,
H: 4.67, N: 4.94. Small amount of solvent was packed in crystals
resulting inaccurate for the elemental analysis.
2JHP ¼ 18.9 Hz, PPh3). IR (KBr, cmꢁ1):
¼ 1905 (CO). Small amount of
n
methylene chloride was packed in crystals resulting inaccurate for
the elemental analysis.
4.2.6. Synthesis of cis-Pyr-Ru-H 3
Similar procedures used as for synthesizing cis-Pyr-Ru-H 1 are
adopted. Reactants L3H (0.40 g, 2.16 mmol), 2.5 M of n-BuLi
(0.95 mL, 2.38 mmol), RuHCl(CO)(PPh3)3 (2.06 g, 2.16 mmol) were
used. Compound cis-Pyr-Ru-H 3 was obtained in 46% yield (0.83 g).
1H NMR (CDCl3): 8.41 (m, 1H, CH pyridine), 7.25 (s, CH imine),
7.16e7.30 (m, 31H, pyridineþPPh3), 7.00 (m, 1H, CH pyridine), 6.40
(m, 1H, CH pyrrole), 6.31 (m, 1H, CH pyridine), 5.90 (m, 1H, CH
pyrrole), 5.72 (m, 1H, CH pyrrole), 4.39 (s, 2H, CH2), ꢁ10.93 (t,
2JHP ¼ 22.2 Hz, 1H, RuH). 13C{1H} NMR (CDCl3): 205.9 (t,
JCP ¼ 13.7 Hz, CO), 158.6 (C pyridine), 158.2 (CH imine), 149.2 (CH
pyridine), 141.4 (C pyrrole), 138.6 (CH pyrrole), 136.4 (CH pyridine),
134.4 (vt, JCP ¼ 20.6 Hz, C PPh3), 134.0 (t, JCP ¼ 5.8 Hz, CH PPh3),
129.2 (CH PPh3), 127.8 (t, JCP ¼ 4.5 Hz, CH PPh3), 123.2 (CH pyridine),
121.8 (CH pyridine), 114.8 (CH pyrrole), 111.6 (CH pyrrole), 67.3
4.2.4. Synthesis of cis-Pyr-Ru-H 2
Similar procedures used as for synthesizing cis-Pyr-Ru-H 1 are
adopted. Reactants L2H (0.40 g, 1.93 mmol), 2.5 M of n-BuLi
(0.85 mL, 2.12 mmol), RuHCl(CO)(PPh3)3 (1.84 g, 1.93 mmol) were
used. Compound cis-Pyr-Ru-H
2
was recrystallized from
dichloromethane/DMSO solution in 42% yield (0.70 g). 1H NMR
(CDCl3): 7.19e7.34 (m, 30H, PPh3), 7.18 (s, 1H, CH imine), 6.35 (s, 1H,
CH pyrrole), 5.82 (m, 1H, CH pyrrole), 5.66 (m, 1H, CH pyrrole),
3.59e3.62 (m, 4H, CH2O morpholine), 3.07e3.12 (m, 2H, CH2), 2.16
(m, 4H, CH2N morpholine), 1.74e1.79 (m, 2H, CH2), ꢁ10.80 (t,
2JHP ¼ 21.9 Hz, 1H, RuH). 13C{1H} NMR (CDCl3): 206.5 (t,
JCP ¼ 13.8 Hz, CO), 157.1 (CH imine), 141.3 (C pyrrole), 138.6 (CH
pyrrole), 134.3 (vt, JCP ¼ 20.6 Hz, C PPh3), 134.0 (t, JCP ¼ 5.9 Hz, CH
PPh3), 129.2 (CH PPh3), 127.8 (t, JCP ¼ 4.5 Hz, CH PPh3), 113.9 (CH
pyrrole), 111.1 (CH pyrrole), 67.0 (CH2 morpholine), 59.0 (CH2), 57.8
(CH2), 53.9 (CH2 morpholine). 31P NMR (CDCl3): 47.5 (d,
2
(CH2). 31P NMR (CDCl3): 46.5 (d, JHP ¼ 22.2 Hz, PPh3). IR (KBr,
cmꢁ1):
n
¼ 1914 (CO), 1940 (Ru-H). Small amount of solvent was
packed in crystals resulting inaccurate for the elemental analysis.
2JHP ¼ 21.9 Hz, PPh3). IR (KBr, cmꢁ1):
¼ 1913 (CO). Anal. Calcd. for
n
RuC49H47N3O2P2: Calcd.: C: 66.89, H: 5.61, N: 4.88. Found: C: 65.72,
H: 5.26, N: 4.80. Small amount of solvent was packed in crystals
resulting inaccurate for the elemental analysis.
4.2.7. Synthesis of cis-Pyr-Ru-H 4
Similar procedures used as for synthesizing cis-Pyr-Ru-H 1 are
adopted. Reactants L4H (0.10 g, 0.67 mmol), 2.5 M of n-BuLi
(0.32 mL, 0.80 mmol), RuHCl(CO)(PPh3)3 (0.64 g, 0.57 mmol) were
used. Compound cis-Pyr-Ru-H 4 was obtained in 74% yield (0.34 g).
1H NMR (CDCl3): 7.52 (s, CH imine), 7.20e7.33 (m, 30H, PPh3), 6.47
(m, 1H, CH pyrrole), 5.63 (m, 1H, CH pyrrole), 5.60 (m, 1H, CH pyr-
4.2.5. Synthesis of trans-Pyr-Ru-H 3
Similar procedures used as for synthesizing trans-Pyr-Ru-H 1
are adopted. Reactants L3H (0.40 g, 2.16 mmol), 2.5 M of n-BuLi
(0.95 mL, 2.38 mmol), RuHCl(CO)(PPh3)3 (2.06 g, 2.16 mmol) were
used. Compound trans-Pyr-Ru-H 3 was obtained in 36% yield
(0.64 g). 1H NMR (CDCl3): 8.33 (s, 1H, CH pyridine), 7.22e8.31 (m,
30H, PPh3), 6.89e7.08 (m, 3H, CH pyridineþpyrrole), 6.87 (s, 1H, CH
imine), 6.31 (m, 1H, CH pyridine), 6.22 (s, 1H, CH pyrrole), 5.95 (m,
1H, CH pyrrole), 3.88 (s, 2H, CH2), ꢁ11.31 (t, 2JHP ¼ 18.9 Hz, 1H, RuH).
13C{1H} NMR (CDCl3): 206.2 (t, JCP ¼ 16.8 Hz, CO), 159.6 (CH imine),
156.9 (C pyridine), 149.1 (CH pyridine), 140.7 (C pyrrole), 139.3 (CH
pyrrole), 135.6 (CH pyridine), 134.5 (t, JCP ¼ 6.1 Hz, CH PPh3), 134.1
t
2
role), 0.89 (s, 9H, Bu), ꢁ12.08 (t, JHP ¼ 24 Hz, 1H, RuH). 13C{1H}
NMR (CDCl3): 153.7 (CH imine), 142.4 (C pyrrole), 138.0 (CH pyr-
role), 134.4 (vt, JCP ¼ 20.6 Hz, C PPh3), 134.0 (t, JCP ¼ 6 Hz, CH PPh3),
129.3 (CH PPh3), 127.8 (t, JCP ¼ 4.5 Hz, CH PPh3), 114.1 (CH pyrrole),
110.6 (CH pyrrole), 59.2 (C tBu), 31.5 (Me tBu). 31P NMR (CDCl3): 44.5
2
(d, JHP ¼ 24 Hz, PPh3). IR (KBr, cmꢁ1):
n
¼ 1924 (CO), 2109 (Ru-H).
Small amount of solvent was packed in crystals resulting inaccurate
for the elemental analysis.

Y.-J. Li et al. / Journal of Organometallic Chemistry 902 (2019) 120957
9
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R.M. Waymouth, C.E.D. Chidsey, Inorg. Chem. 55 (2016) 1623e1632;
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44 (2005) 2483e2492;
4.3. General procedure for catalytic alcohol amination
Under nitrogen atmosphere, a mixture of KOH (8.0 mmol) and
catalyst in toluene (10 mL) was heated at 110 ꢀC for 2hr in order to
reach equilibrium for the cis and trans forms of the complexes. A
toluene solution (10 ml) of benzyl alcohol (4.0 mmol) and aniline
(4.0 mmol) was added. The mixture was heated at 110 ꢀC for a
period of time. Small amount of samples (ca. 0.5 mL) were drawn
from the reaction flask via syringe during the reactions. The
products were analyzed by 1HNMR spectra using the integrations of
methylene protons of N-benzylideneaniline, N-benzylaniline, and
(d) W. Xu, R. Langer, Dalton Trans. 44 (2015) 16785e16790.
[4] (a) N. Nakagawa, E.J. Derrah, M. Schelwies, F. Rominger, O. Trapp, T. Schaub,
Dalton Trans. 45 (2016) 6856e6865;
(b) D. Pingen, M. Lutz, D. Vogt, Organometallics 33 (2014) 1623e1629;
(c) D. Pingen, J.H. Choi, H. Allen, G. Murray, P. Ganji, P.W.N.M. Van Leeuwen,
M.H.G. Prechtl, D. Vogt, Catal. Sci. Technol. 8 (2018) 3969e3976;
(d) G. Choi, S.H. Hing, Angew. Chem. Int. Ed. 57 (2018) 6166e6170;
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S. Nikolaou, E. Tfouni, Inorg. Chem. Commun. 15 (2012) 93e96;
(b) A. Gavriluta, G.E. Büchel, L. Freitag, G. Novitchi, J.B. Tommasino,
N-benzylaniline (d 8.45, 4.32, 4.60) for calculating the conversions.
ꢀ
E. Jeanneau, P.-S. Kuhn, L. Gonzalez, V.B. Arion, D. Luneau, Inorg. Chem. 52
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Chem. 41 (2002) 2960e2970.
4.4. X-ray structure determination
[6] (a) A. Merlino, Coord. Chem. Rev. 326 (2016) 111e134;
(b) P. Kumar, R.K. Gupta, D.S. Pandey, Chem. Soc. Rev. 43 (2014) 707e733;
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5805e5821.
All of the crystals were mounted on a glass fiber using epoxy
resin and transferred to a goniostat. The data were collected on a
Bruker SMART CCD diffractometer using graphite monochromated
Mo-Ka radiation. The data were corrected for absorption empiri-
[7] (a) J.-P. Djukic, J.-B. Sortais, L. Barloy, M. Pfeffer, Eur. J. Inorg. Chem. (2009)
817e853;
cally via
j scans. All non-hydrogen atoms were refined using
anisotropic displacement parameters. For all of the structures, the
hydrogen atom positions were calculated, and they were con-
strained to idealized geometries and treated as riding where the H
atom displacement parameter was calculated from the equivalent
isotropic displacement parameter of the bound atom. The struc-
tures were determined using direct-method procedures in SHELXS
[24] and refined using full-matrix least-squares methods on F2's in
SHELXL [25]. All the relevant crystallographic data and structure
refinement parameters are summarized in Table 1. The crystallo-
graphic data for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publications nos. CCDC-1845663 (trans-Pyr-Ru-H
1), CCDC- 1873675 (trans-Pyr-Ru-H 2), CCDC-1873939 (cis-Pyr-
Ru-H 1), CCDC-1873940 (cis-Pyr-Ru-H 2), CCDC-1873941 (cis-Pyr-
Ru-H 3), and CCDC-1873942 (cis-Pyr-Ru-H 4). These data can be
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This work is supported by the Ministry of Science and Tech-
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