1,3,4-Oxadiazole-functionalizedα-amino-phosphonates as ligands for the ruthenium-catalyzed reduction of ketones

Article abstract of DOI:10.1039/d1nj01861b

Threeα-aminophosphonates, namely diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-trifluoromethylphenyl) methyl]phosphonate (3a), diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(2-methoxyphenyl)methyl]phosphonate (3b) and diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-nitrophenyl)methyl]phosphonate (3c), were synthetizedviathe Pudovik-type reaction between diethyl phosphite and imines, obtained from 5-phenyl-1,2,4-oxadiazol-2-amine and aromatic aldehydes, under microwave irradiation. Compounds3a-cunderwent complexation with a ruthenium(ii) precursor, selectively at the more basic nitrogen atom of the oxadiazole ring, leading to the corresponding ruthenium complexes4a-cof the formula [RuCl₂(L)(p-cymene)] (L= α-aminophosphonates3a-c). Complexes4a-cproved to be efficient catalysts for the transfer hydrogenation of ketones to alcohols. All new compounds were fully characterised by elemental analysis, infrared, mass and NMR spectroscopy. An X-ray structure of the α-aminophosphonate3bwas obtained and revealed the presence, in the solid state, of an infinite chain of3bunits supramolecularly interlinked. Two X-ray diffraction studies carried out on ruthenium complexes confirm the specific coordination of the electron-enricher nitrogen atom of the oxadiazole ring.

Full text of DOI:10.1039/d1nj01861b

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1,3,4-Oxadiazole-functionalized
a-amino-phosphonates as ligands for the
ruthenium-catalyzed reduction of ketones†‡
Cite this: New J. Chem., 2021,
45, 11327
c
b
b
Shaima Hkiri,ab Christophe Gourlaouen,
Soufiane Touil,
Ali Samarat
and
a
David Semeril
*
´
Three a-aminophosphonates, namely diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-trifluoromethylphenyl)
methyl]phosphonate (3a), diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(2-methoxyphenyl)methyl]phosphonate
(3b) and diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-nitrophenyl)methyl]phosphonate (3c), were synthetized
via the Pudovik-type reaction between diethyl phosphite and imines, obtained from 5-phenyl-1,2,4-oxadiazol-
2-amine and aromatic aldehydes, under microwave irradiation. Compounds 3a–c underwent complexation
with a ruthenium(II) precursor, selectively at the more basic nitrogen atom of the oxadiazole ring,
leading to the corresponding ruthenium complexes 4a–c of the formula [RuCl2(L)(p-cymene)] (L =
a-aminophosphonates 3a–c). Complexes 4a–c proved to be efficient catalysts for the transfer hydro-
genation of ketones to alcohols. All new compounds were fully characterised by elemental analysis,
infrared, mass and NMR spectroscopy. An X-ray structure of the a-aminophosphonate 3b was obtained
and revealed the presence, in the solid state, of an infinite chain of 3b units supramolecularly interlinked.
Two X-ray diffraction studies carried out on ruthenium complexes confirm the specific coordination of
the electron-enricher nitrogen atom of the oxadiazole ring.
Received 16th April 2021,
Accepted 19th May 2021
DOI: 10.1039/d1nj01861b
rsc.li/njc
piperazine,2a quinoline3 and imidazole4 have demonstrated good
abilities for their coordination to transition metals.
Introduction
a-Aminophosphonates, which are structural analogues of
Oxadiazole derivatives, especially the 1,3,4-oxadiazole isomer,
natural a-amino acids, have elicited considerable interest from have wide pharmacological applications5 and coordination
chemists due to their wide-range of useful properties. In addition properties.6 Although the 1,3,4-oxadiazole moiety is present in
to their well-known biological activities,1 these phosphorus many ruthenium complexes,7 there are only a few examples in
compounds have gradually developed from a synthetic challenge which the 1,3,4-oxadiazole ring is directly coordinated to the
to a directed and rational design of novel molecular ligands with ruthenium atom.8
outstanding metal-complexing properties. For instance, many
In the present investigation, we describe the synthesis and
a-aminophosphonate ligands bearing nitrogenated heterocyclic characterization of three a-aminophosphonates (L) incorporating
donor atoms, i.e. a-aminophosphonate derivatives of pyridine,2
a 1,3,4-oxadiazole ring, which could coordinate, via their
electron-enriched nitrogen atom, to a ruthenium(II) precursor.
The resulting ruthenium complexes of the general formula
[RuCl2(L)(Z6-p-cymene)]9 (Fig. 1) could be applied as catalysts for
the reduction of ketones into alcohols using the transfer
hydrogenation strategy, which is selective, efficient, safe and
compatible with green chemistry principles.10
a
`
´
University of Strasbourg, Synthese Organometallique et Catalyse,
UMR-CNRS 7177, 4 rue Blaise Pascal, 67008 Strasbourg, France.
E-mail: dsemeril@unistra.fr
b University of Carthage, Faculty of Sciences of Bizerte, LR18ES11,
Laboratory of Hetero-Organic Compounds and Nanostructured Materials, 7021,
Bizerte, Tunisia
c University of Strasbourg, Laboratoire de Chimie Quantique, UMR-CNRS 7177,
4 rue Blaise Pascal, 67008 Strasbourg, France
† Dedicated to Prof. Christian Bruneau for his outstanding contribution to
catalysis.
‡ Electronic supplementary information (ESI) available: Computational details
and characteristic data for the compounds. CCDC 2076185–2076187. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/
d1nj01861b
Fig. 1 Targeted [RuCl2(L)(Z6-p-cymene)] complexes.
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Results and discussion
Preparation of a-aminophosphonates
The synthesis of ruthenium complexes 4a–c required, firstly,
the preparation of the a-aminophosphonate ligands 3a–c,
respectively (Scheme 1). Precursor 1, which was conveniently
prepared according to a method earlier reported,11 was condensed
with three aromatic aldehydes, namely 4-trifluoromethyl-
benzaldehyde, 2-methoxybenzaldehyde and 4-nitrobenzaldehyde
in order to obtain the corresponding imines 2a–c in 87–93%
yields. The Pudovik-type reaction12 of these imine intermediates
with diethyl phosphite under microwave irradiation13 in neat
conditions (115 1C and 300 W) for 10 min led to the formation
of the desired a-aminophosphonates 3a–c in 76–93% yields. The
advantages of the procedure are short reaction time, high yields,
and simple work up. The structures of 1,3,4-oxadiazole derivatives
3a–c were firmly established by well-defined infrared, multi-
nucleus NMR spectroscopy (1H, 13C, 31P and 19F), mass spectro-
metry and elemental analysis (see the Experimental section). Their
31P{1H} NMR spectra in DMSO-d6 show a quadruplet at 19.4 ppm
for 3a, due to phosphorus/fluorine coupling (7JPF = 2.2 Hz), and
singlets at 20.7 and 18.8 ppm, for 3b and 3c, respectively. The
1H NMR spectra revealed for the NH signals (d = 8.87–9.18 ppm) a
doublet of doublets due to a proton/proton (3JHH = 6.0–10.2 Hz)
and a phosphorus/proton (3JPH = 1.5–3.9 Hz) vicinal coupling. The
mass spectra analyses display peaks at 456.13, 418.15 and 433.13,
for 3a, 3b and 3c, respectively, corresponding to their [M + H]+
cations with the expected isotopic profiles.
Fig. 2 ORTEP drawing of 3b, 50% probability thermal ellipsoids, showing the
two enantiomers. Important bond lengths (Å) and angles (1): N1–N2 1.419(5),
N2–C8 1.304(5), C8–O1 1.365(5), O1–C7 1.385(5), C7–N1 1.275(6),
C8–N3 1.341(5), N4–N5 1.419(5), N5–C28 1.297(5), C28–O6 1.365(5),
O6–C27 1.384(5), C27–N4 1.281(6), C28–N6 1.347(5), C7–N1–N2 107.1(3),
N1–N2–C8 104.9(3), N2–C8–O1 113.6(3), C8–O1–C7 101.5(3), O1–C7–N1
112.9(3), C27–N4–N5 106.9(3), N4–N5–C28 105.0(3), N5–C28–O6 113.8(4),
C28–O6–C27 101.5(3), O6–C27–N4 112.7(4).
turn self-organises via p–p interactions between the oxadiazole
and the phenyl rings (O-phenyl centroid 3.369 Å and between
the centroid of oxadiazole and the centroid of phenyl 3.621 Å)15
(Fig. 3).
Preparation of ruthenium(II) complexes
The natural bond orbital charge analysis carried out on 3a (see
ESI‡) reveals that the presence of the amine moieties polarises the
oxadiazole ring. If the nitrogen at position 4 in the oxadiazole ring
(N1 in Fig. 2) is slightly affected, there is a strong polarisation of
the nitrogen at position 3 in the oxadiazole ring (N2 in Fig. 2),
which becomes more basic. Consequently, the latter nitrogen
atom should be preferentially coordinated to a metal cation.
The a-aminophosphonates 3a–c readily formed complexes with
the ruthenium(II) precursor. Thus by using a Ru/L stoichiometry of
1:1, the reaction of 3a–c (1 equivalent) with [RuCl2(p-cymene)]2
(0.5 equivalent) in CH2Cl2 at room temperature for 4 h led to the
The a-aminophosphonate 3b crystallises in the triclinic
%
asymmetric space group P1 with two distinct enantiomeric
molecules (A and B molecules in which C9 and C29 have an
R and an S configuration, respectively; Fig. 2). The oxadiazole
and phenyl aromatic rings are almost planar with dihedral
angles of 1.271 in B and 4.471 in A. The study revealed the
presence in the solid state of an infinite chain of 3b units
supramolecularly interlinked. An (R)- and an (S)-molecule of 3b
dimerise via hydrogen bonds between their N–H and PQO
moieties (Hꢀ ꢀ ꢀO 2.007 Å)14 to form a racemic dimer, which in
formation of complexes 4a–c in 81–92% yields (Scheme 1). The 31
NMR spectra of the obtained complexes display slight
P
a
upfield shift (around 3.5 ppm) with regard to the free a-
aminophosphonates. Infrared measurements show that the band
at B1600 cmꢁ1 for free ligands (n(CQN) stretching vibrations
of the oxadiazole ring) shifts towards higher wave numbers by
5–10 cmꢁ1 in the complexes,8c which confirms the coordination of
a nitrogen atom to the metal centre. The mass spectra analyses,
which show peaks corresponding to [M ꢁ Cl]+, [M + Na]+ and [M +
K]+ cations with the expected isotopic profiles, unambiguously
confirm the coordination of the a-aminophosphonates to the
ruthenium precursor. The formation of the complexes coordinated
by the nitrogen in position 3 of the oxadiazole ring (noted N1 in the
X-ray structures (Fig. 4 and 6)) was confirmed by single X-ray
diffraction studies. The complexes crystallise in the monoclinic
form with the P21/n space group. Four molecules of complexes
are present in the racemic unit cell, two ruthenium atoms are
coordinated to an (S)-a-aminophosphonate and the two others to
Scheme 1 Synthesis of a-aminophosphonates 3a–c and the corres-
ponding ruthenium complexes 4a–c.
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Fig. 3 Self-organised structure of 3b via hydrogen bonds (magenta) and p–p (blue) interactions.
an (R)-a-aminophosphonate. The ruthenium atom has a typical was confirmed by the noncovalent interaction (NCI) analysis of the
pseudooctahedral geometry with the p-cymene occupying three density functional theory (DFT)-optimised structure carried out on
adjacent sites of the octahedron (Ru-centroid of p-cymene = 1.663 the ruthenium complex 4a (Fig. 5). Furthermore, the calculations
and 1.656 Å in complexes 4a and 4b, respectively).16 The three reveal that coordination of the oxadiazole ring by its nitrogen in
others sites are occupied with two chloride atoms and the a-amino- position 3 (noted N1 in the X-ray structures) is favored due to
phosphonate coodinated by its oxadiazole ring, which is almost higher basicity of this nitrogen atom, lower steric constraints and
orthogonal to the coordinated p-cymene (dihedral angle of 80.51 presence of the NHꢀꢀꢀCl hydrogen bond (see the ESI‡).
and 86.291 in complexes 4a and 4b, respectively). The bond lengths
of Ru–Cl and Ru–N were found to be 2.432, 2.432 and 2.137 Å,
respectively in complex 4a and 2.429, 2.433 and 2.125 Å, respec-
Reduction of ketones
The ruthenium complexes 4a–c were evaluated as catalysts for
reduction of ketones. The corresponding tests were performed
in the presence of a base in iso-propyl alcohol (iPrOH)
(Scheme 2).
In order to determine the optimum catalytic conditions, the
ruthenium complex 4a (1 mol%) was used as a model catalyst in
the reduction of acetophenone in iPrOH as a solvent. The reaction
was studied with various bases under different conditions.
Initially, the reaction was performed with K3PO4 as base at
80 1C for 2 h. Thus, a conversion of 67% was measured based
on 1H NMR analysis (Table 1, entry 1). As control experiments, no
products were observed without the addition of the ruthenium
complex 4a or base. In the first series of tests, we determined the
tively in complex 4b. In the solid state, complex 4b formation of
dimers was observed, formed from a (R)- and a (S)-3b. The two
complexes were supramolecularly linked via four hydrogen bonds
between aromatic CH of p-cymene and chloride atoms (CHꢀꢀꢀCl
2.757 and 2.806 and Å; Fig. 7). The most striking feature is the
presence of a hydrogen bond involving a chlorine atom and the NH
(length NHꢀꢀꢀCl 2.280 and 2.371 Å in complexes 4a and 4b,
respectively). The presence of a strong NHꢀꢀꢀCl hydrogen bond
Fig. 4 ORTEP drawing of the ruthenium complex 4a showing 50%
probability thermal ellipsoids. For clarity reason, only one of the four
molecules present in the unit cell is shown. Important bond lengths (Å)
and angles (1): Ru1–Cl1 2.4320(5), Ru1–Cl2 2.4322(5), Ru1–N1 2.1369(15),
N1–N2 1.413(2), N2–C1 1.283(2), C1–O1 1.381(2), O1–C2 1.355(2),
C2–N1 1.313(2), Cl1–Ru1–N1 83.99(4), Cl1–Ru1–Cl2 87.880(18), Cl2–Ru1–
N1 89.45(4) C1–N2–N1 106.25(14), N2–N1–C2 106.29(14), N1–C2–O1
111.92(15), C2–O1–C1 102.97(14), O1–C1–N2 112.58(15).
Fig. 5 Visualising the noncovalent interactions in complex 4a with attrac-
tive electrostatic interactions in blue, attractive dispersion forces in green
and steric repulsions in red.
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Table 1 Ruthenium-catalyzed reduction of acetophenone – screening of
catalytic conditionsa
Entry
[Ru]
Base
Time (h)
Hg
T (1C)
Conv. (%)
1
2
3
4
5
6
7
8
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
4b
4c
K3PO4
NaOEt
NaOAc
KOAc
Cs2CO3
K2CO3
KOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
No
No
No
No
No
No
No
No
No
No
Yes
Yes
No
No
No
80
80
80
80
80
67
41
31
28
16
12
76
95
17
100
62
97
59
57
38
80
80
80
60
100
80
100
80
80
80
9
10
11
12
13
14
15
Fig. 6 ORTEP drawing of the ruthenium complex 4b showing 50%
probability level of thermal ellipsoids. For clarity reason, only one of the
four molecules present in the unit cell is shown. Important bond lengths
(Å) and angles (1): Ru1–Cl1 2.4330(7), Ru1–Cl2 2.4293(7), Ru1–N1 2.125(2),
N1–N2 1.410(3), N2–C12 1.282(4), C12–O1 1.376(4), O1–C11 1.350(3),
C11–N1 1.315(4), Cl1–Ru1–N1 84.03(7), Cl1–Ru1–Cl2 89.54(3), Cl2–Ru1–N1
87.21(7) C12–N2–N1 105.9(3), N2–N1–C11 106.5(2), N1–C11–O1 111.7(3),
C11–O1–C12 103.0(2), O1–C12–N2 112.9(3).
a
Reagents and conditions: ruthenium complex (1 mol%), acetophe-
none (1.0 mmol), base (0.25 mmol), iPrOH (5 mL). The conversions were
determined by 1H NMR spectroscopy by integrating the CH3 signals.
with a bulkier aromatic substituent on the ruthenium, complex
4b, slightly reduced the effectiveness of the catalyst, conversions
of 59 and 57% were measured using 4a and 4b, respectively
(Table 1, entries 13 and 14). Note that, under our catalytic
conditions, tests realised in the presence of
a drop of
mercury,18 no significant change in activities were observed
(Table 1, entries 11 and 12), suggesting that no ruthenium
nanoparticles were present.19
Applying these optimised conditions (NaOH as base at
100 1C) for 2 h, the precatalyst 4a was assigned to hydride
transfer of several ketones. Seven aryl methyl ketones, namely
acetophenone, 40-chloroacetophenone, 40-bromoacetophenone,
40-nitroaceto-phenone, 40-methoxyacetophenone, 20,40-dichloro-
acetophenone and 20-bromoacetophenone, were tested.
Conversions higher than 93% were observed in the cases of
acetophenone and halogenated acetophenones. For example,
conversions of 97% and 93% were measured for the reduction
of 40-chloroacetophenone and 20,40-dichloroacetophenone or
20-bromoacetophenone, respectively. The presence of a nitro or
a methoxy substituent on the aromatic moiety led to low
or moderated conversions, in fact, only 7% and 66% of 40-
nitroacetophenone and 40-methoxyacetophenone, respectively,
were reduced into the corresponding alcohol. The precatalyst
4a efficiently carried out the hydride transfer on dialkyl and
cyclic ketones, and conversions of 77%, 61% and 93% were
measured starting from 3,3-dimethylbutan-2-one, cyclopentanone
and cyclohexanone, respectively (Fig. 8).
Fig. 7 Self-organised structure of 4b via hydrogen bonds (magenta)
interactions.
optimal base by employing NaOEt, NaOAc, KOAc, Cs2CO3, K2CO3,
KOH or NaOH. As can be inferred from the results (Table 1,
entries 2–8), the most efficient base was NaOH, which led to a
conversion of 95% (Table 1, entry 8). Operating at lower
temperature (60 1C) led to a lower conversion (17%; Table 1,
entry 9). In contrast, carrying out the reaction at 100 1C
increased the catalysis, and a full conversion was observed in
only one hour (Table 1, entry 10). It is well established that
modification of the ruthenium coordination sphere, sterically
and/or electronically, has a direct effect on the catalytic
outcome.17 In fact, substitution of the CF3 moiety by a NO2
function on the ruthenium complex, the use of precatalyst 4c,
drastically reduced the formation of alcohol (conversion of
38%; Table 1, entry 15). Interestingly, carrying out the catalysis
Conclusions
We have shown that the synthesis of three a-aminophosphonates,
in their racemic form, incorporating a 1,3,4-oxadiazole moiety, in
which the nitrogen atom closer to the amine group is electrically
richer than the second one. The more basic nitrogen could easily
react with a ruthenium(II) precursor leading to the formation of the
corresponding [RuCl2(L)(p-cymene)] (L = a-aminophosphonate)
Scheme 2 Ruthenium-catalyzed reduction of ketones.
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(E)-1-(4-Trifluoromethylphenyl)-N-(5-phenyl-1,3,4-oxadiazol-2-yl)-
methanimine (2a). White solid, yield 90%. 1H NMR (300 MHz,
DMSO-d6): d = 9.47 (s, 1H, NQCH), 8.33 (d, 2H, arom. CH of
C6H4CF3, 3JHH = 8.4 Hz), 8.09 (dd, 2H, arom. CH of C6H5, 3JHH
7.2 Hz, 4JHH = 1.8 Hz), 7.99 (d, 2H, arom. CH of C6H4CF3, 3JHH
=
=
8.4 Hz), 7.68–7.60 (m, 3H, arom. CH of C6H5) ppm; 13C{1H}
NMR (126 MHz, DMSO-d6): d = 169.48 (s, NQCH), 166.26
(s, arom. Cquat C(N)QN), 163.57 (s, arom. Cquat C(Ph)QN),
138.29 (s, arom. Cquat of C6H4CF3), 133.46 (q, arom. Cquat
Fig. 8 Formation of alcohols, reagents and conditions: ruthenium
complex 4a (1 mol %), ketone (1.0 mmol), base (0.25 mmol), iPrOH
(5 mL), 100 1C, 2 h. The conversions were determined by 1H NMR
spectroscopy.
2
CCF3, JCF = 31.9 Hz), 132.68 (s, arom. CH), 131.31 (s, arom.
CH), 129.96 (s, arom. CH), 126.98 (s, arom. CH), 126.64 (d,
arom. CH, 3JCF = 3.4 Hz), 124.25 (q, CF3, 1JCF = 273.2 Hz), 123.88
(s, arom. Cquat of C6H5) ppm; 19F{1H} NMR (282 MHz, DMSO-
d6): d = ꢁ61.61 (s, CF3) ppm. Elemental analysis calcd (%) for
complexes. Two X-ray diffraction studies confirm the specific
coordination of the electronic richer nitrogen atom of the
oxadiazole ring. The latter ruthenium(II) complexes were
assigned in the transfer hydrogenation of ketones. To the best
of our knowledge, the present work represents the first examples
of ruthenium catalysts coordinated to a 1,3,4-oxadiazole ring.
Further work is aimed at exploiting the potential chirality of
a-aminophosphonates and their application as ligands in the
ruthenium-catalyzed asymmetric reduction of CQO and
CQN bonds.
C
16H10ON3F3 (317.27): C 60.57, H 3.18, N 13.24; found C 60.62,
H 3.22, N 13.18.
(E)-1-(2-Methoxyphenyl)-N-(5-phenyl-1,3,4-oxadiazol-2-yl)-
1
methanimine (2b). White solid, yield 93%. H NMR (300 MHz,
DMSO-d6): d = 9.53 (s, 1H, NQCH), 8.12 (dd, 1H, arom. CH,
3JHH = 7.8 Hz, 4JHH = 1.5 Hz), 8.06–8.02 (m, 2H, arom. CH), 7.69
3
4
(td, 1H, arom. CH, JHH = 7.6 Hz, JHH = 1.5 Hz), 7.65–7.59 (m,
3
3H, arom. CH), 7.25 (d, 1H, arom. CH, JHH = 8.4 Hz), 7.14
3
(t, 1H, arom. CH, JHH = 7.5 Hz), 3.96 (s, 3H, OCH3) ppm;
13C{1H} NMR (126 MHz, DMSO-d6): d = 166.67 (s, arom. Cquat
ortho of OCH3), 164.34 (s, NQCH), 162.75 (s, arom. Cquat
C(Ph)QN), 160.96 (s, arom. Cquat C(N)QN), 136.53 (s, arom.
CH), 131.95 (s, arom. CH), 129.44 (s, arom. CH), 127.63 (s,
arom. CH), 126.36 (s, arom. CH), 123.59 (s, arom. Cquat),
122.10 (s, arom. Cquat), 121.11 (s, arom. CH), 112.58 (s, arom.
CH), 56.13 (s, OCH3) ppm. Elemental analysis calcd (%) for
Experimental part
All manipulations involving phosphorus derivatives were carried
out under dry argon. Solvents were dried using conventional
methods and were distilled immediately before use. Routine 1H,
13C{1H}, 31P{1H} and 19F{1H} spectra were recorded on Bruker FT
instruments (AC 300 and 500). 1H NMR spectra were referenced
to residual protonated solvents (d = 2.50 ppm for DMSO-d6 and
d = 7.26 ppm for CDCl3). 13C NMR chemical shifts are reported
relative to deuterated solvents (d = 39.52 ppm for DMSO-d6 and
d = 77.16 ppm for CDCl3). 31P and 19F NMR spectroscopic data
are given relative to external H3PO4 and CCl3F, respectively.
Chemical shifts and coupling constants are reported in ppm
and Hz, respectively. Infrared spectra were recorded on a Bruker
FT-IR Alpha-P spectrometer. Microwave irradiation was carried
out using a CEM Discover microwave synthesis system equipped
C
16H13O2N3 (279.29): C 68.81, H 4.69, N 15.04; found C 68.84, H
4.73, N 14.99.
(E)-1-(4-Nitrophenyl)-N-(5-phenyl-1,3,4-oxadiazol-2-yl)-
methanimine (2c). Yellow solid, yield 87%. 1H NMR (300 MHz,
DMSO-d6): d = 9.51 (s, 1H, NQCH), 8.44 (d, 2H, arom. CH of
3
C6H4NO2, JHH = 9.0 Hz), 8.37 (d, 2H, arom. CH of C6H4NO2,
3
3JHH = 9.0 Hz), 8.09 (d, 2H, arom. CH of C6H5, JHH = 8.1 Hz),
7.68–7.62 (m, 3H, arom. CH of C6H5) ppm; 13C{1H} NMR
(126 MHz, DMSO-d6): d = 168.44 (s, NQCH), 165.69 (s, arom.
Cquat C(N)QN), 163.21 (s, arom. Cquat C(Ph)QN), 150.27 (q,
arom. Cquat CNO2), 139.60 (s, arom. Cquat of C6H4NO2), 132.31
(s, arom. CH), 131.31 (s, arom. CH), 129.54 (s, arom. CH),
126.57 (s, arom. CH), 124.34 (s, arom. CH), 123.38 (s, arom.
Cquat of C6H5) ppm. Elemental analysis calcd (%) for
with
a pressure controller (17 bar). Elemental analyses
were carried out using the Service de Microanalyse, Institut de
´
Chimie, Universite de Strasbourg. 5-Phenyl-1,3,4-oxadiazol-2-
C
15H10O3N4 (294.27): C 61.22, H 3.43, N 19.04; found C 61.18,
amine (1) was prepared by literature procedure.11
H 3.35, N 18.97.
General procedure for the synthesis of (E)-1-(aryl)-N-(5-phenyl- General procedure for the synthesis of diethyl[(5-phenyl-1,3,4-
1,3,4-oxadiazol-2-yl)methanimine 2a–c oxadiazol-2-ylamino)(aryl)methyl]phosphonate 3a–c
In a round bottom flask equipped with a Dean Stark apparatus, In a round bottom flask, a mixture of (E)-1-(aryl)-N-(5-phenyl-
a mixture of phenyl-1,3,4-oxadiazol-2-amine (1) (2.0 mmol) and 1,3,4-oxadiazol-2-yl)methanimine (2) (1.0 mmol) and diethyl
aryl aldehyde (3.0 mmol) in toluene (20 mL) was refluxed for phosphite (0.25 mL, 2.0 mmol) was added and irradiated under
48 h. After cooling to room temperature, the solvent was microwave under neat conditions at 115 1C for 10 min at 300 W.
evaporated and the crude product was washed with cool After cooling to room temperature, the crude product was
ethanol (15 mL), filtered and dried under a vacuum to afford washed with EtO2 (3 ꢂ 10 mL), filtered and dried under a
the desired imine.
vacuum to afford a white solid. In the case of 3c, the crude
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product was purified by column chromatography (EtOAc/Et2O, Cquat C(Ph)QN), 147.16 (d, arom. Cquat C(NH)QN, 3JCP = 2.4 Hz),
50 : 50, v/v) to afford a white solid. 143.36 (s, arom. Cquat CNO2), 130.87 (s, arom. CH), 129.39
Diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-trifluoromethyl- (s, arom. CH), 129.33 (s, arom. CH), 125.35 (s, arom. CH), 123.91
1
phenyl)methyl]phosphonate (3a). Yield 90%. H NMR (300 MHz, (s, arom. Cquat of C6H5), 123.39 (s, arom. CH), 63.08 (d, OCH2CH3,
DMSO-d6): d = 9.14 (dd, 1H, NH, 3JHH = 6.0 Hz, 3JPH = 1.5 Hz), 7.85– 2JCP = 22.7 Hz), 63.03 (d, OCH2CH3, 2JCP = 22.6 Hz), 54.11 (d, CHP,
3
7.77 (m, 6H, arom. CH), 7.56–7.51 (m, 3H, arom. CH), 5.38 (dd, 1JCP = 152.5 Hz), 16.20 (d, OCH2CH3, JCP = 15.5 Hz), 16.16
2
3
3
1H, CHP, JPH = 13.5 Hz, JHH = 5.7 Hz), 4.08–3.88 (m, 4H, (d, OCH2CH3, JCP = 15.7 Hz) ppm; 31P{1H} NMR (121 MHz,
OCH2CH3), 1.18 (t, 3H, OCH2CH3, JHH = 4.2 Hz), 1.10 (t, 3H, DMSO-d6): d = 18.8 (s, P(O)) ppm. IR: n = 1601 cmꢁ1 (CQN). MS
3
3
OCH2CH3, JHH = 4.2 Hz) ppm; 13C{1H} NMR (126 MHz, DMSO- (ESI-TOF): m/z = 433.13 [M + H]+, 455.11 [M + Na]+, 471.08 [M + K]+
d6): d = 162.95 (d, arom. Cquat para of CF3, 2JCP = 11.2 Hz), 158.41 (expected isotopic profiles). Elemental analysis calcd (%) for
(s, arom. Cquat C(Ph)QN), 140.37 (s, arom. Cquat C(NH)QN), C19H21O6N4P (432.37): C 52.78, H 4.90, N 12.96; found C 52.84, H
130.80 (s, arom. CH), 129.30 (s, arom. CH), 128.92 (d, arom. CH, 4.94, N 12.91.
3JCP = 4.6 Hz), 128.43 (q, arom. Cquat CCF3, 2JCF = 32.8 Hz), 125.30
(s, arom. CH), 125.14 (s, arom. CH), 124.20 (q, CF3, JCF
1
General procedure for the synthesis of the ruthenium(II)
complexes 4a–c
=
272.5 Hz), 123.94 (s, arom. Cquat of C6H5), 62.91 (d, OCH2CH3,
2JCP = 23.1 Hz), 62.86 (d, OCH2CH3, 2JCP = 22.9 Hz), 54.10 (d, CHP, To a stirred solution (CH2Cl2, 15 mL) of diethyl[(5-phenyl-1,3,4-
1JCP = 153.3 Hz), 16.16 (d, OCH2CH3, JCP = 19.1 Hz), 16.12 oxadiazol-2-ylamino)(aryl)methyl] phosphonate (3a–c) (1.00 mmol)
3
(d, OCH2CH3, JCP = 19.3 Hz) ppm; 31P{1H} NMR (121 MHz, was added a solution of [RuCl2(p-cymene)]2 (0.306 g, 0.05 mmol)
3
DMSO-d6): d = 19.4 (q, P(O), JPF = 2.2 Hz) ppm; 19F{1H} NMR in CH2Cl2 (15 mL). After stirring at room temperature for 4 h,
7
(282 MHz, DMSO-d6): d = ꢁ60.97 (d, CF3, 7JPF = 2.0 Hz) ppm. IR: the reaction mixture was concentrated to ca. 1 mL, upon which
n = 1600 cmꢁ1 (CQN). MS (ESI-TOF): m/z = 456.13 [M + H]+, 478.11 n-hexane (50 mL) was added. The orange/red precipitate was
[M + Na]+, 494.09 [M + K]+ (expected isotopic profiles). Elemental separated by filtration and dried under a vacuum.
analysis calcd (%) for C20H21O4N3F3P (455.37): C 52.75, H 4.65, N
9.23; found C 52.71, H 4.59, N 9.20.
Dichloro-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)-
(4-trifluoro-methylphenyl)methyl]phosphonate}(p-cymene)-
1
Diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(2-methoxyphenyl)- ruthenium(II) (4a). Yield 92%. H NMR (500 MHz, CDCl3): d =
methyl]phosphonate (3b). Yield 93%. 1H NMR (300 MHz, DMSO- 8.46 (dd, 1H, NH, 3JHH = 9.0 Hz, 3JPH = 8.0 Hz), 7.73–7.71 (m, 4H,
d6): d = 8.87 (dd, 1H, NH, 3JHH = 10.2 Hz, 3JPH = 2.7 Hz), 7.81–7.78 arom. CH), 7.60 (d, 2H, arom. CH, 3JHH = 8.0 Hz), 7.52–7.45 (m,
(m, 2H, arom. CH), 7.62 (dt, 1H, arom. CH, 3JHH = 7.8 Hz, 4JHH
=
3H, arom. CH), 5.67 and 5.40 (AA0BB0 spin system, 2H, arom.
3
2.0 Hz), 7.56–7.52 (m, 3H, arom. CH), 7.34–7.28 (m, 1H, arom. CH of p-cymene, JHH = 6.0 Hz), 5.65 and 5.38 (AA0BB0 spin
CH), 7.03 (d, 1H, arom. CH, 3JHH = 8.1 Hz), 6.98 (t, 1H, arom. CH, system, 2H, arom. CH of p-cymene, 3JHH = 5.5 Hz), 5.00 (dd, 1H,
3JHH = 7.5 Hz), 5.69 (dd, 1H, CHP, 2JPH = 21.3 Hz, 3JHH = 10.2 Hz), CHP, JPH = 23.0 Hz, JHH = 9.0 Hz), 4.28–4.16 (m, 2H,
2
3
4.09–3.99 (m, 2H, OCH2CH3), 3.95–3.83 (m, 1H, OCH2CH3), 3.86 OCH2CH3), 4.03–3.91 (m, 2H, OCH2CH3), 3.14 (hept, 1H,
3
3
(s, 3H, OCH3), 3.82–3.69 (m, 1H, OCH2CH3), 1.18 (t, 3H, JHH
=
CH(CH3)2, JHH = 6.7 Hz), 2.33 (s, 3H, CH3 of p-cymene), 1.32
7.1 Hz, OCH2CH3), 1.04 (t, 3H, JHH = 7.1 Hz, OCH2CH3) ppm; (d, 3H, CH(CH3)2, 3JHH = 6.7 Hz), 1.31 (d, 3H, CH(CH3)2, 3JHH
=
3
13C{1H} NMR (126 MHz, DMSO-d6): d = 163.08 (d, arom. Cquat 6.7 Hz), 1.30 (t, 3H, OCH2CH3, JHH = 6.5 Hz), 1.20 (t, 3H,
ortho of OCH3, 2JCP = 10.1 Hz), 158.12 (s, arom. Cquat C(Ph)QN), OCH2CH3, 3JHH = 7.0 Hz) ppm; 13C{1H} NMR (126 MHz, CDCl3):
156.37 (d, arom. Cquat C(NH)QN, 3JCP = 5.7 Hz), 130.69 (s, arom. d = 162.20 (d, arom. Cquat para of CF3, 2JCP = 11.8 Hz), 156.67 (s,
3
3
CH), 129.32 (s, arom. CH), 128.74 (d, arom. CH, JCP = 3.5 Hz), arom. Cquat C(Ph)QN), 138.47 (s, arom. Cquat C(NH)QN),
125.17 (s, arom. CH), 124.03 (s, arom. Cquat of C6H5), 123.67 (s, 131.69 (s, arom. CH), 129.26 (s, arom. CH), 128.37 (d, arom. CH,
2
arom. Cquat COCH3), 120.34 (s, arom. CH), 110.99 (s, arom. CH), 3JCP = 4.5 Hz), 130.42 (q, arom. Cquat CCF3, JCF = 30.5 Hz),
62.49 (d, OCH2CH3, 2JCP = 5.8 Hz), 55.83 (s, OCH3), 47.17 (d, CHP, 125.91 (s, arom. CH), 125.67 (s, arom. CH), 124.08 (q, CF3, 1JCF
=
1JCP = 158.3 Hz), 16.24 (d, OCH2CH3, JCP = 5.4 Hz), 16.01 (d, 273.2 Hz), 122.98 (s, arom. Cquat of C6H5), 103.14 (s, arom.
OCH2CH3, 3JCP = 5.4 Hz) ppm; 31P{1H} NMR (121 MHz, DMSO-d6): Cquat of p-cymene), 98.97 (s, arom. Cquat of p-cymene), 83.91
d = 20.7 (s, P(O)) ppm. IR: n = 1604 cmꢁ1 (CQN). MS (ESI-TOF): m/ (s, arom. CH of p-cymene), 83.82 (s, arom. CH of p-cymene),
z = 418.15 [M + H]+, 440.13 [M + Na]+, 456.11 [M + K]+ (expected 81.49 (s, arom. CH of p-cymene), 81.37 (s, arom. CH of p-cymene),
3
2
2
isotopic profiles). Elemental analysis calcd (%) for C20H24O5N3P 64.72 (d, OCH2CH3, JCP = 7.1 Hz), 64.33 (d, OCH2CH3, JCP
=
(417.40): C 57.55, H 5.80, N 10.07; found C 57.45, H 5.72, N 10.01. 7.3 Hz), 55.68 (d, CHP, 1JCP = 152.5 Hz), 30.78 (s, CH(CH3)2), 22.45
Diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-nitrophenyl)- (s, CH(CH3)2), 22.41 (s, CH(CH3)2), 19.00 (s, CH3 of p-cymene),
3
3
methyl]phosphonate (3c). Yield 76%. 1H NMR (300 MHz, 16.61 (d, OCH2CH3, JCP = 5.3 Hz), 16.58 (d, OCH2CH3, JCP
=
DMSO-d6): d = 9.18 (dd, 1H, NH, JHH = 9.9 Hz, JPH = 3.9 Hz), 4.6 Hz) ppm; 31P{1H} NMR (121 MHz, CDCl3): d = 15.8 (q, P(O),
3
3
8.27 (d, 2H, arom. CH, JHH = 8.4 Hz), 7.86–7.82 (m, 4H, arom. 7JPF = 2.2 Hz) ppm; 19F{1H} NMR (282 MHz, CDCl3): d = ꢁ62.68
3
2
CH), 7.55–7.53 (m, 3H, arom. CH), 5.46 (dd, 1H, CHP, JPH
=
(d, CF3, 7JPF = 2.2 Hz) ppm. IR: n = 1650 cmꢁ1 (CQN). MS (ESI-
23.1 Hz, JHH = 9.9 Hz), 4.12–3.89 (m, 4H, OCH2CH3), 1.18 TOF): m/z = 726.10 [M ꢁ Cl]+, 784.06 [M + Na]+, 800.04 [M + K]+
3
3
3
(t, 3H, OCH2CH3, JHH = 7.1 Hz), 1.12 (t, 3H, OCH2CH3, JHH
=
(expected isotopic profiles). Elemental analysis calcd (%) for
7.1 Hz) ppm; 13C{1H} NMR (126 MHz, DMSO-d6): d = 162.90
C30H35O4N3F3PCl2Ru (761.56): C 47.31, H 4.63, N 5.52; found C
2
(d, arom. Cquat para of NO2, JCP = 11.1 Hz), 158.50 (s, arom. 47.24, H 4.55, N 5.48.
11332
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Dichloro-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)- CH of p-cymene), 83.74 (s, arom. CH of p-cymene), 81.50 (s, arom.
(2-methoxyphenyl)methyl]phosphonate}(p-cymene)ruthenium(II) (4b). CH of p-cymene), 81.31 (s, arom. CH of p-cymene), 64.76
1
2
2
Yield 81%. H NMR (500 MHz, CDCl3): d = 8.37 (dd, 1H, NH, (d, OCH2CH3, JCP = 7.3 Hz), 64.48 (d, OCH2CH3, JCP = 7.3 Hz),
3JHH = 6.0 Hz, JPH = 9.0 Hz), 7.78 (d, 2H, arom. CH, JHH
=
55.68 (d, CHP, JCP = 151.4 Hz), 30.81 (s, CH(CH3)2), 22.46
3
3
1
6.5 Hz), 7.55 (d, 1H, arom. CH, 3JHH = 7.5 Hz), 7.51–7.47 (m, 3H, (s, CH(CH3)2), 22.40 (s, CH(CH3)2), 18.99 (s, CH3 of p-cymene),
3
3
3
arom. CH), 7.21 (t, 1H, arom. CH, JHH = 7.7 Hz), 6.94 (t, 1H, 16.61 (d, OCH2CH3, JCP = 5.0 Hz), 16.58 (d, OCH2CH3, JCP
=
arom. CH, 3JHH = 7.5 Hz), 6.84 (d, 1H, arom. CH, 3JHH = 8.0 Hz), 4.4 Hz) ppm; 31P{1H} NMR (121 MHz, CDCl3): d = 15.1 (s, P(O))
5.63 and 5.36 (AA0BB0 spin system, 2H, arom. CH of p-cymene, ppm. IR: n = 1650 cmꢁ1 (CQN). MS (ESI-TOF): m/z = 703.10 [M ꢁ
3JHH = 6.0 Hz), 5.61 and 5.34 (AA0BB0 spin system, 2H, arom. CH Cl]+, 761.06 [M + Na]+, 777.04 [M + K]+ (expected isotopic profiles).
3
2
of p-cymene, JHH = 6.0 Hz), 5.54 (dd, 1H, CHP, JPH = 22.0 Hz, Elemental analysis calcd (%) for C29H35O6N4PCl2Ru (738.56): C
3JHH = 9.0 Hz), 4.23–4.13 (m, 2H, OCH2CH3), 4.07–3.01 (m, 2H, 47.16, H 4.78, N 7.59; found C 47.08, H 4.66, N 7.54.
OCH2CH3), 3.90 (s, 3H, OCH3), 3.12 (hept, 1H, CH(CH3)2, 3JHH
=
General procedure for the ruthenium-catalyzed reduction of
ketones
6.7 Hz), 2.30 (s, 3H, CH3 of p-cymene), 1.29 (d, 3H, CH(CH3)2,
3JHH = 6.7 Hz), 1.28 (d, 3H, CH(CH3)2, 3JHH = 6.7 Hz), 1.26 (t, 3H,
OCH2CH3, 3JHH = 6.5 Hz), 1.24 (t, 3H, OCH2CH3, 3JHH = 7.5 Hz) A 10 mL-Schlenk tube was filled with the ruthenium precursor
ppm; 13C{1H} NMR (126 MHz, CDCl3): d = 162.26 (d, arom. (1.0 mol %), NaOH (0.25 mol) and ketone (1.0 mmol). PrOH
i
2
Cquat ortho of OCH3, JCP = 10.6 Hz), 156.77 (d, arom. Cquat (5 mL) was then added. The reaction mixture was stirred at
3
C(NH)QN, JCP = 5.6 Hz), 156.30 (s, arom. Cquat C(Ph)QN), 100 1C for 2 h. An aliquot (0.25 mL) of the resulting solution
131.35 (s, arom. CH), 129.54 (d, arom. CH, 4JCP = 5.1 Hz), 129.51 was then passed through a Millipore filter, the solvent was then
3
(d, arom. CH, JCP = 7.5 Hz), 129.11 (s, arom. CH), 125.86 (s, removed under a vacuum and the resulting crude solution was
arom. CH), 123.38 (s, arom. Cquat COCH3), 122.73 (s, arom. analyzed by H NMR spectroscopy.
1
Cquat of C6H5), 121.17 (s, arom. CH), 110.63 (s, arom. CH),
103.00 (s, arom. Cquat of p-cymene), 98.67 (s, arom. Cquat of
X-Ray crystal structure analysis
p-cymene), 83.74 (s, arom. CH of p-cymene), 83.72 (s, arom. CH Single crystals of 3b suitable for X-ray analysis were obtained by
of p-cymene), 81.45 (s, arom. CH of p-cymene), 81.42 (s, arom. slow evaporation of a diethyl ether solution of the crude reaction
2
CH of p-cymene), 64.05 (d, OCH2CH3, JCP = 7.1 Hz), 63.81 (d, mixture. Crystal data: C20H24N3O5P, Mr = 417.40 g molꢁ1, triclinic,
OCH2CH3, 2JCP = 7.3 Hz), 55.96 (s, OCH3), 49.39 (d, CHP, 1JCP
=
space group P1, a = 8.8977(11) Å, b = 12.5369(14) Å, c = 19.5140(20)
%
158.3 Hz), 30.71 (s, CH(CH3)2), 22.42 (s, CH(CH3)2), 22.38 Å, a = 90.816(4)1, b = 94.235(4)1, g = 103.384(4)1, V = 2110.8(4) Å3,
(s, CH(CH3)2), 18.93 (s, CH3 of p-cymene), 16.63 (d, OCH2CH3, Z = 4, D = 1.313 g cmꢁ3, m = 0.166 mmꢁ1, F(000) = 880, T = 120(2) K.
3
3JCP = 4.4 Hz), 16.60 (d, OCH2CH3, JCP = 5.0 Hz) ppm; 31P{1H} The sample (0.220 ꢂ 0.200 ꢂ 0.180) was studied on a Bruker
NMR (121 MHz, CDCl3): d = 17.5 (s, P(O)) ppm. IR: n = PHOTON-III CPAD using Mo-Ka radiation (l = 0.71073 Å). The
1644 cmꢁ1 (CQN). MS (ESI-TOF): m/z = 688.13 [M ꢁ Cl]+, data collection (2ymax = 28.0121, omega scan frames by using 0.71
746.09 [M + Na]+, 762.06 [M + K]+ (expected isotopic profiles). omega rotation and 30 s per frame, range hkl: h ꢁ11,11 k ꢁ16,16
Elemental analysis calcd (%) for C30H38O5N3PCl2Ru (723.59): C l ꢁ25,25) gave 95 599 reflections. The structure was solved with
49.80, H 5.29, N 5.81; found C 49.73, H 5.19, N 5.76.
SHELXT-2014/5,20 which revealed the non-hydrogen atoms of the
Dichloro-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)- molecule. After anisotropic refinement, all of the hydrogen atoms
(4-nitrophenyl)methyl]phosphonate}(p-cymene)ruthenium(II) (4c). were found with a Fourier difference map. The structure was
Yield 82%. 1H NMR (500 MHz, CDCl3): d = 8.53 (dd, 1H, NH, refined with SHELXL-2014/721 by the full-matrix least-square
3
3JHH = 8.5 Hz, JPH = 8.0 Hz), 8.19 (d, 2H, arom. CH of O2NC6H4, techniques (the use of F square magnitude; x, y, z, bij for C, N,
3JHH = 8.0 Hz), 7.81 (d, 2H, arom. CH, 3JHH = 7.5 Hz), 7.72 (d, 2H, O and P atoms; x, y, z in riding mode for H atoms); 538 variables
2
arom. CH of O2NC6H4, 3JHH = 8.0 Hz), 7.53–7.45 (m, 3H, arom. CH), and 8283 observations with I 4 2.0 s(I); calcd w = 1/[s2(Fo ) +
2
2
5.68 and 5.40 (AA0BB0 spin system, 2H, arom. CH of p-cymene, (0.0942P)2 + 8.1397P] where P = (Fo + 2Fc )/3, with the resulting
3JHH = 5.5 Hz), 5.65 and 5.39 (AA0BB0 spin system, 2H, arom. CH of R = 0.0823, RW = 0.2412 and SW = 1.036, Dr o 0.677 e Åꢁ3
.
p-cymene, 3JHH = 6.0 Hz), 5.05 (dd, 1H, CHP, 2JPH = 23.5 Hz, 3JHH
=
Single crystals of 4a suitable for X-ray analysis were obtained
8.5 Hz), 4.28–4.19 (m, 2H, OCH2CH3), 4.04–3.95 (m, 2H, OCH2CH3), by slow diffusion of n-hexane into a dichloromethane solution
3
3.14 (hept, 1H, CH(CH3)2, JHH = 6.7 Hz), 2.33 (s, 3H, CH3 of of the complex. Crystal data: C30H35Cl2F3N3O4PRu, Mr
=
p-cymene), 1.32 (d, 3H, CH(CH3)2, JHH = 6.7 Hz), 1.31 (d, 3H, 761.56 g molꢁ1, monoclinic, space group P21/n, a = 15.3065(6) Å,
3
CH(CH3)2, 3JHH = 6.7 Hz), 1.30 (t, 3H, OCH2CH3, 3JHH = 7.2 Hz), 1.21 b = 13.8547(5) Å, c = 15.6247(6) Å, b = 94.198(2)1, V = 3304.6(2) Å3,
(t, 3H, OCH2CH3, JHH = 7.0 Hz) ppm; 13C{1H} NMR (126 MHz, Z = 4, Dx = 1.531 g cmꢁ3, m = 0.740 mmꢁ1, F(000) = 1552, T = 120(2)
3
2
CDCl3): d = 162.19 (d, arom. Cquat para of NO2, JCP = 11.5 Hz), K. The sample (0.080 ꢂ 0.100 ꢂ 0.100 mm) was studied on a
156.79 (s, arom. Cquat C(Ph)QN), 147.89 (d, arom. Cquat Bruker APEX-II CCD using Mo-Ka radiation (l = 0.71073 Å). The
3
5
C(NH)QN, JCP = 2.8 Hz), 141.91 (d, arom. Cquat CNO2, JCP
=
data collection (2ymax = 27.9211, omega scan frames by using 0.71
2.1 Hz), 131.81 (s, arom. CH), 129.31 (s, arom. CH), 128.99 (d, arom. omega rotation and 30 s per frame, range hkl: h ꢁ20,20 k ꢁ18,18 l
3
CH, JCP = 4.4 Hz), 125.91 (s, arom. CH), 123.88 (s, arom. CH), ꢁ20,20) gave 98 790 reflections. The structure was solved with
122.89 (s, arom. Cquat of C6H5), 103.24 (s, arom. Cquat of SHELXT-2014/5,20 which revealed the non-hydrogen atoms of the
p-cymene), 99.05 (s, arom. Cquat of p-cymene), 83.92 (s, arom. molecule. After anisotropic refinement, all of the hydrogen atoms
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were found with a Fourier difference map. The structure was Notes and references
refined with SHELXL-2018/321 using the full-matrix least-square
1 (a) J. H. Meyer and P. A. Bartlett, J. Am. Chem. Soc., 1998,
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Huang, Y.-J. Li, Y.-M. Pan, Q. Xu, Z.-X. Liao and H.-S.
Wang, Bioorg. Med. Chem. Lett., 2014, 24, 501–507;
( f ) S. A. R. Mulla, M. Y. Pathan, S. P. Gample and
D. Sarkar, RSC Adv., 2014, 4, 7666–7672; (g) R. Damiche
and S. Chafaa, J. Mol. Struct., 2017, 1130, 1009–1017; (h)
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Silicon Relat. Elem., 2019, 194, 426–437.
techniques (the use of F square magnitude; x, y, z, bij for C, Cl, F,
N, O, P and Ru atoms; x, y, z in riding mode for H atoms);
402 variables and 7227 observations with I 4 2.0s(I); calcd
w = 1/[s2(Fo ) + (0.0278P)2 + 3.8006P] where P = (Fo + 2Fc )/3,
with the resulting R = 0.0282, RW = 0.0692 and SW = 1.048, Dr o
2
2
2
0.926 e Åꢁ3
.
Single crystals of 4b suitable for X-ray analysis were obtained
by slow diffusion of n-hexane into dichloromethane
a
solution of the complex. Crystal data: C30H38Cl2N3O5PRu,
Mr = 723.57 g molꢁ1, monoclinic, space group P21/n, a =
11.2342(6) Å, b = 17.0441(10) Å, c = 16.4074(8) Å, b =
92.713(2)1, V = 3138.1(3) Å3, Z = 4, Dx = 1.532 g cmꢁ3
,
m = 0.764 mmꢁ1, F(000) = 1488, T = 120(2) K. The sample
(0.180 ꢂ 0.150 ꢂ 0.120 mm) was studied on a Bruker PHOTON-
III CPAD using Mo-Ka radiation (l = 0.71073 Å). The data
collection (2ymax = 27.9321, omega scan frames by using 0.71
omega rotation and 30 s per frame, range hkl: h ꢁ14,14 k
ꢁ22,22 l ꢁ21,21) gave 99 843 reflections. The structure was
solved with SHELXT-2014/5,20 which revealed the non-
hydrogen atoms of the molecule. After anisotropic refinement,
all of the hydrogen atoms were found with a Fourier difference
map. The structure was refined with SHELXL-2018/321 by the
full-matrix least-square techniques (the use of F square
magnitude; x, y, z, bij for C, Cl, N, O, P and Ru atoms; x, y, z in
riding mode for H atoms); 392 variables and 6696 observations
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ˇ ´
ˇ
´
´
3 (a) M. Juribasic, K. Molcanov, B. Kojic-Prodic, L. Bellotto,
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2
with I 4 2.0s(I); calcd w = 1/[s2(Fo ) + (0.0252P)2 + 8.1733P] where
5 (a) G. A. Pinna, G. Murineddu, C. Murruzzu, V. Zuco,
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2
P = (Fo2 + 2Fc )/3, with the resulting R = 0.0417, RW = 0.0948 and
SW = 1.081, Dr o 1.565 e Åꢁ3
.
CCDC 2076187 (3b), 2076185 (4a) and 2076186 (4b).‡
Computational details
All calculations were performed using the Gaussian 09
program,22 using the functional oB97XD. Dispersion
corrections were included.23 All atoms were described using
the 6-31+G** basis set except the ruthenium atom described by
the SDD basis set and the associated pseudopotential. The
structure was fully optimised and the wavefunction saved.
The free enthalpy was extracted from the frequency calculations
performed on this geometry. The weak interactions were
studied through the NCI analysis24 of the Gaussian wavefunction.
All calculations were performed in the gas phase.
ˇ
ˇ
´ˇ
´
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A. Carazo, K. Konecna, J. Stolarıkova, A. Hrabalek, O. Pavlis,
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Conflicts of interest
There are no conflicts to declare.
Acknowledgements
We gratefully acknowledge the University of Carthage and the
Tunisian Ministry of Higher Education and Scientific Research
for the financial support (grant for S. H.).
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