Ruthenium(II) complexes containing lutidine-derived pincer CNC ligands: Synthesis, structure, and catalytic hydrogenation of C=N bonds

Article abstract of DOI:10.1002/chem.201406040

Abstract A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5e(BF₄) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C=N bond assisted either by the pincer ligand or a second coordinated H₂ molecule. The outer limits: Facially coordinated Ru-CNC complexes, in the presence of tBuOK, are active catalysts in the hydrogenation of a series of substrates containing C=N bonds (see scheme). Intermediate species in the catalytic cycle have been studied by using NMR spectroscopy; DFT calculations support a stepwise outer-sphere mechanism for the hydrogen transfer to the C=N bond assisted by either the pincer ligand or a second coordinated H₂ molecule.

Full text of DOI:10.1002/chem.201406040

DOI: 10.1002/chem.201406040
Full Paper
&
Hydrogenation
Ruthenium(II) Complexes Containing Lutidine-Derived Pincer CNC
Ligands: Synthesis, Structure, and Catalytic Hydrogenation of C=N
bonds
[
b]
[a]
[a]
Martín Hernµndez-Juµrez, Joaquín López-Serrano,* Patricia Lara, Judith P. Morales-
[b]
[a]
[a]
[b]
[a]
Cerón, Mónica Vaquero, Eleuterio lvarez, Verónica Salazar, and AndrØs Suµrez*
Abstract: A series of Ru complexes containing lutidine-de-
rived pincer CNC ligands have been prepared by transmeta-
lation with the corresponding silver-carbene derivatives.
Characterization of these derivatives shows both mer and
fac coordination of the CNC ligands depending on the wing-
tips of the N-heterocyclic carbene fragments. In the pres-
ence of tBuOK, the Ru-CNC complexes are active in the hy-
drogenation of a series of imines. In addition, these com-
plexes catalyze the reversible hydrogenation of phenantri-
dine. Detailed NMR spectroscopic studies have shown the
capability of the CNC ligand to be deprotonated and get in-
volved in ligand-assisted activation of dihydrogen. More in-
terestingly, upon deprotonation, the Ru-CNC complex
5e(BF ) is able to add aldimines to the metal–ligand frame-
4
work to yield an amido complex. Finally, investigation of the
mechanism of the hydrogenation of imines has been carried
out by means of DFT calculations. The calculated mechanism
involves outer-sphere stepwise hydrogen transfer to the C=
N bond assisted either by the pincer ligand or a second co-
ordinated H molecule.
2
Introduction
able, atom-economical catalytic hydrogenation and dehydro-
[6,7]
genation reactions of polar substrates. Examples of these re-
actions include the hydrogenation of carboxylic acid deriva-
tives such as esters, amides, formates, ureas, carbamates and
In the last years, metal–ligand cooperation has become an im-
portant concept in both organometallic chemistry and catalyst
[
1,2]
[6b–f]
[6g]
[6h–j]
development.
Particularly, metal complexes incorporating
organic carbonates,
nitriles,
CO2,
and processes in-
[7]
neutral tridentate PNX (X=phosphane, hemilabile N-donor) li-
gands based on a picolyl fragment and bulky electron-rich
phosphanes are a prominent class of derivatives due to their
volving the acceptorless dehydrogenation of alcohols.
[
2]
ability to activate HÀY (Y=H, O, N, C, S) bonds. In these com-
plexes, deprotonation of the methylene carbons gives dearom-
atized species that are capable of bond activation in a ligand–
metal cooperative process. In addition, the nucleophilic charac-
[
3]
ter of the dearomatized ligands allows MÀPNX to function as
metal-based frustrated Lewis pairs (FLP) in the activation of
[
4]
[5]
electrophiles such as CO , carbonyl compounds, and nitriles.
2
Also, of particular importance, exploration of RuÀPNX com-
plexes by Milstein and co-workers (Figure 1), and their depro-
tonated counterparts, have led to the development of sustain-
[
a] Dr. J. López-Serrano, Dr. P. Lara, Dr. M. Vaquero, Dr. E. lvarez, Dr. A. Suµrez
Instituto de Investigaciones Químicas (IIQ) and Centro de Innovación en
Química Avanzada (ORFEO-CINQA), CSIC and Universidad de Sevilla
Avda AmØrico Vespucio 49, 41092 Sevilla (Spain)
Figure 1. Lutidine-derived pincer ruthenium complexes.
E-mail: joaquin.lopez@iiq.csic.es
andres.suarez@iiq.csic.es
Since substitution of phosphane ligands by N-heterocyclic
[
b] Dr. M. Hernµndez-Juµrez, J. P. Morales-Cerón, Prof. V. Salazar
carbenes (NHC) has resulted in the improvement of several im-
[8]
Centro de Investigaciones Químicas
Universidad Autónoma del Estado de Hidalgo
Carretera Pachuca-Tulacingo Km 4.5
portant catalytic processes, replacement of P-donors in Ru-
PNP and PNN complexes by more electron-donating NHC con-
geners may offer new opportunities for electronic and steric
modification of the metal center, while at the same time main-
taining the acidity of the pyridylic protons. Based on this ap-
4
2184 Mineral de la Reforma, Hidalgo (Mexico)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201406040.
Chem. Eur. J. 2015, 21, 7540 – 7555
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Full Paper
proach, some examples of metal complexes containing CNN-
type pincers derived from lutidine have been reported. For ex-
Results and Discussion
[
9]
[10]
ample, the groups of Song and Milstein have independent-
ly reported Ru-CNN complexes with an hemilabile amine or
pyridine fragment, respectively. These derivatives provide very
active catalysts in the hydrogenation of esters, in some cases
outperforming their Ru-PNN counterparts. Similarly, del Pozo,
Iglesias, and Sµnchez have employed supported Ru-CNN com-
plexes in the dehydrogenation of alcohols and in the transfer
Ru-CNC complexes
Attempted preparation of ruthenium complexes incorporating
CNC ligands was performed by treatment of the imidazolium
salt 1a(Br) with different Ru precursors ([RuHCl(PPh ) ],
3
3
[RuCl (PPh ) ], [RuHCl(CO)(PPh ) ], [RuH (CO)(PPh ) ]) at low
2
3 3
3 3
2
3 3
temperature in the presence of a base (lithium bis(trimethylsi-
lyl)amide (Li(HMDS)), tBuOK, NaH). Contrary to what was previ-
ously observed, this approach did not provide clean reactions,
probably as a consequence of the acidity of the methylene
protons of the CNC ligand. N-Heterocyclic carbene transfer
with Ag-NHC complexes to different metals has developed
into a well-established methodology for the preparation of
[
11]
hydrogenation of ketones. The latter group has also report-
ed the formation of Ru-CNC complexes that exhibit a moderate
[
11]
activity in the dehydrogenation of alcohols. Recently, during
the progress of our work, Pidko and co-workers have described
the use of Ru-CNC complexes in the hydrogenation of CO and
2
[
12]
esters.
[16]
Reduction of imines to their corresponding amines is an im-
portant transformation in organic synthesis. Although a variety
of metal hydrides may be used in this reaction, the use of H2
has a significant interest as a clean and atom-economical re-
metal-NHC complexes under mild conditions. Hence, an al-
ternative procedure based on the transmetalation with Ag-
NHC complexes 2 was sought (Scheme 1). Complexes 2 were
obtained by reaction of bis(imidazolium) salts 1 with Ag O in
2
[
13]
ductant both in laboratory and industrial settings. However,
in comparison with the hydrogenation of other unsaturated
bonds, such as olefins and ketones, there is still a lack of mech-
CH Cl , as noted by the disappearance of the imidazolium
2
2
1
proton signals in the H NMR spectra and appearance of rela-
13
1
tively broad signals at about d=180 ppm in the C{ H} NMR
[
13d]
2
[17]
anistic understanding of these reductions.
Among the cata-
experiments due to the C carbons of the NHC moieties. Ele-
mental analysis and NMR spectroscopy data are in agreement
with the proposed elemental formulation for derivatives 2.
lytic systems that promote the (enantioselective) hydrogena-
tion of C=N bonds, ruthenium(II) catalysts incorporating acid–
base responsive ligands based
on OH and NH functionalities, in-
cluding Shvo- and Noroyi-type
complexes, have been found to
[
14]
be particularly effective. These
catalysts are thought to operate
by H2 activation involving the
metal and the basic ligand frag-
ment, followed by a (concerted)
transfer of the hydridic and
acidic hydrogen atoms to the
iminic carbon and the N atom,
Scheme 1. Synthesis of silver (2) and ruthenium (3) complexes.
[
13d,14a,f,g]
respectively.
Based on these precedents,
we anticipated that lutidine-derived pincer Ru complexes
might provide efficient catalysts for the hydrogenation of sub-
strates containing C=N bonds. Hence, in a previous communi-
cation, we have described the synthesis and acid–base reactivi-
ty of fac-coordinated Ru-CNC complexes, and preliminary stud-
In addition, to confirm the proposed structures in the solid
state, derivatives 2a(Br) and 2d(Cl) have been studied by
using single-crystal X-ray diffraction (Figure 2). The solid-state
structures consist of monomeric units with each NHC fragment
coordinated to an Ag-halogen moiety. The coordination geom-
etry at the metal atom is roughly linear (C-Ag-Br 165.688; C-
Ag-Cl 166.758), with weak AgÀAg intramolecular interactions
of 3.32 (2a(Br)) and 3.24 Š (2d(Cl)) (sum of the van der Waals
radii: 3.44 Š).
[15]
ies of their application in the hydrogenation of imines.
I
I
Herein, we provide a full account of our research on this topic
including a detailed study of the structural features of Ru com-
plexes containing N-heterocyclic carbene pincer CNC ligands,
as well as their catalytic performance in the hydrogenation of
C=N bonds. In addition, insights into the mechanism of this
process have been obtained from the spectroscopic study of
reaction intermediates and DFT calculations.
Ruthenium complexes 3a(Cl) and 3b(Cl) were prepared
from the appropriate silver reagent 2 and [RuHCl(CO)(PPh ) ] in
3
3
THF at 558C (Scheme 1). Similarly, complexes 3a(BF ) and
4
3c(Br) were obtained from the corresponding bromine deriva-
tives 2a(Br) and 2c(Br), after treatment with NaBF or NaBr, re-
4
spectively. Finally, the synthesis of the xilyl-substituted deriva-
tive 3d(Cl) was more conveniently carried out in CH Cl at
2
2
room temperature. Complexes 3 are obtained as yellow solids
after recrystallization from MeOH/toluene solutions. They are
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Figure 3. ORTEP drawing at 30% ellipsoid probability of the cationic compo-
4
nent of complex 3a(BF ). Hydrogen atoms, except for the hydrido ligand,
o
have been omitted for clarity. Selected bond lengths [Š] and angles [ ]:
Ru(1)-C(8) 2.084(19); Ru(1)-C(14) 2.117(19); Ru(1)-N(1) 2.233(16); Ru(1)-C(20)
1.79(2); C(8)-Ru(1)-C(14) 101.3(8).
nation geometry has been further confirmed by a X-ray diffrac-
[15]
tion analysis of derivative 3a(BF ) (Figure 3).
4
To determine the differences in the donor strength of the
different CNC ligands, the CO stretch bands in the IR spectra of
complexes 3 in CH Cl solution have been analyzed. Lower ab-
2
2
À1
sorption energies in the range 1919–1924 cm have been
Figure 2. ORTEP drawings at 30% ellipsoid probability of complexes 2a(Br)
top) and 2d(Cl)·2CHCl (bottom). Hydrogen atoms and solvent molecules
have been omitted for clarity. Selected bond lengths [Š] and angles [ ] for
a(Br): Ag1-Ag2 3.3192(7); Ag1-Br1 2.4478(5); Ag1-C1 2.084(4); Br1-Ag1-C1
found for alkyl-substituted complexes 3a(Cl), 3b(Cl), and
(
3
3
c(Br) in comparison with derivative 3d(Cl) that exhibit the
o
À1
same band at 1934 cm . Therefore a higher basicity of the
alkyl-substituted CNC ligands may be expected.
2
o
1
3
65.68(11). Selected bond lengths [Š] and angles [ ] for 2d(Cl)·2CHCl : Ag1-
Ag2 3.2436(5); Ag1-Cl1 2.3625(11); Ag1-C7 2.080(4); Cl1-Ag1-C7 166.75(13).
The facial coordination of the pincer in complexes 3 is un-
usual in light of previously reported metal complexes contain-
[11,12,18]
[9,10]
ing structurally related CNC
and CNN ligands.
To
stable in the presence of atmospheric agents in the solid state,
although they slowly decompose in chlorinated solvents. Elec-
trospray mass spectroscopy investigation of complexes 3 pro-
compare the structure of the coordinated CNC ligands in com-
plexes 3 with that observed in derivatives with a mer arrange-
ment of the pincer, as well as to have RuÀCNC complexes
+
duces peaks consistent with the expected molecular ion [M] .
without coordinated PPh available for mechanistic studies, we
3
+
Fragmentation of [M] gives rise to peaks assignable to the
have prepared complexes 4d and 4e. Derivative 4e was syn-
+
loss of PPh , [MÀPPh ] . Complexes 3 have been fully charac-
thetized from the treatment of 2e(Cl) with [RuHCl(CO)(PPh ) ]
3
3
3 3
[19]
terized by NMR spectroscopic techniques, and they show very
in CH Cl2 (Scheme 2).
In turn, treatment of [RuHCl
2
1
13
1
similar features. For example, both H- and C{ H} NMR spectra
reflect the non-equivalence of the two halves of the CNC
(CO)(PPh ) ] with 2d(Cl) in THF at 608C provided about a 1:4
3
3
mixture of 4d and the cationic complex 3d(Cl).
ligand. For complex 3a(Cl), the hydrido ligand produces in the
The solution and solid-state structures of mer-coordinated
RuÀCNC complexes were studied in detail. For example, good-
quality crystals for an X-ray diffraction analysis of the mesityl
derivative 4e were grown from CH Cl (Figure 4). The structure
1
H NMR spectrum a doublet centered at d=À7.30 ppm (J
=
HP
3
0.5 Hz), whereas the methylene protons of the CNC ligand
give rise to four different doublet signals in the range d=4.1–
2
2
1
3
1
5
.7 ppm. The C{ H} NMR spectrum contains one doublet
of complex 4e is comprised of a stereogenic Ru atom in an oc-
2
signal for each C carbon atom of the NHC fragment at d=
81.5 (J =81 Hz, trans to PPh ) and 189.0 ppm (J =7 Hz,
tahedral coordination geometry, with the carbene fragments of
2
2
1
the pincer disposed trans to each other (C (NHC)-Ru-C (NHC)=
170.08), and the carbonyl ligand trans to the pyridine. The two
chelate rings of the pincer have boat conformations as deter-
mined by the dihedral angles C(5)-N(1)-Ru(1)-C(20) and C(1)-
N(1)-Ru(1)-C(7) of À35.5 and À34.18, respectively. This causes
a mesityl group to be aligned with the hydrido and the other
with the chloride ligand, and therefore significantly different
CP
3
CP
trans to H), whereas the carbonyl ligand signal appears at d=
31
1
2
09.2 ppm as a doublet (J =15 Hz). Finally, the P{ H} NMR
CP
spectrum of complex 3a(Cl) shows a singlet at d=42.4 ppm.
These data supports a fac coordination of the CNC ligand, for
which one carbene donor is situated trans to the hydrido
[
18]
ligand and the other is trans to the phosphane. This coordi-
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pected from the examination of
the X-ray structure of 4e. In fact,
in the solid-state structure of 4e
there is a very short HÀCl con-
tact (2.42 Š; sum of the van der
Waals radii=2.9–3.0 Š) between
a methylene hydrogen and the
[20]
chloride ligand. At room tem-
1
perature, the H NMR spectrum
of 4e shows significant line
broadening indicative of the ex-
istence of a dynamic behavior in
solution (see below). Similar
NMR spectroscopy features are
found for 4d. Moreover, heating
of a solution of 4e at 608C in
CD OD for 1 h shows partial
3
4
Scheme 2. Synthesis of complexes 4, 5(Cl), and 5(BF ).
deuteration (90%) of the hydrido
ligand, whereas prolonged heat-
ing over 16 h yields full deutera-
tion of RuH and partial deuterium incorporation (75%) in the
CH arms, in line with the expected acidity of the methylene
2
protons.
In the presence of MeCN, chloride ligand decoordination in
complexes 4 occurs, leading to the formation of the cationic
1
complexes 5(Cl) (Scheme 2). H NMR spectra in CD CN of deriv-
3
atives 5(Cl) are characterized by the presence of a singlet reso-
nance at about d=À14 ppm, attributable to the hydrido
ligand, and four broad doublets in the region between d=
5.2–5.7 ppm produced by the methylene-bridge protons. In
CD Cl in the presence of MeCN, complexes 4 and 5(Cl) are in
2
2
equilibrium in a temperature-dependent ratio, and a linear de-
pendence of lnKeq with temperature is evidenced. From the
0
corresponding van’t Hoff plots, values of DH =À8.67 kcal
À1
0
0
À1
mol and DS =À42.1 eu for 4e, and DH =À8.64 kcalmol
0
and DS =À43.9 eu for 4d were calculated (see the Supporting
Information for details). Cleavage of the RuÀCl bond in com-
plexes 4 with NaBF in MeCN yields adducts 5(BF ) (Scheme 2).
4
4
These derivatives have been fully characterized, and their spec-
troscopic data are in accord with a mer arrangement of the
1
Figure 4. ORTEP drawing at 30% ellipsoid probability of complex 4e·CH
2
Cl
2
.
CNC ligands. For example, the H NMR spectrum of 5e(BF )
4
Hydrogen atoms, with exception of the hydrido ligand, and solvent mole-
cule have been omitted for clarity. Selected bond lengths [Š] and angles [ ]:
Ru(1)-C(7) 2.044(7); Ru(1)-C(20) 2.127(6); Ru(1)-N(1) 2.209(8); Ru(1)-C(32)
shows similar features to that of 5e(Cl), including the appear-
ance of the signal of the hydrido ligand as a singlet at d=
o
13
1
2
À14.5 ppm. The C{ H} NMR spectrum exhibits the C carbon
atoms of the NHC fragments at d=190 ppm, whereas the car-
bonyl ligand signal appears at d=206 ppm. Finally, in the IR
1
1
.841(10); Ru(1)-Cl(1) 2.565(2); C(7)-Ru(1)-C(20) 170.0(3); C(32)-Ru(1)-N(1)
75.0(4).
À1
spectrum the CO stretch band appears at 1932 cm .
2
RuÀC (NHC) distances are found (Ru(1)ÀC(7)=2.04 Š; Ru(1)À
C(20)=2.13 Š).
The inferred structure of complexes 5(BF ) has been con-
4
[21]
firmed by a crystal X-ray analysis of 5d(BF ) (Figure 5). Com-
4
1
The H NMR spectrum registered in CD Cl at 238 K of 4e
plex 5d(BF ) exhibits an octahedral coordination around the
2
2
4
shows a singlet signal at d=À16.2 ppm for the hydrido ligand,
Ru atom with the CNC ligand coordinated in a mer fashion
2
2
and four non-equivalent signals for the ortho-CH groups of
(C (NHC)-Ru-C (NHC)=169.38), and the CO ligand situated
trans to the pyridine fragment. Boat conformations of the two
chelate rings of the pincer are defined by torsion angles of
C(5)-N(1)-Ru(1)-C(19)=À31.0 and C(1)-N(1)-Ru(1)-C(8)=À39.28.
3
the mesityl wingtips. Also, the methylene protons produce
three doublets in the range d=4.8–5.4 ppm and a forth dou-
blet significantly shifted downfield at d=7.5 ppm. The signifi-
cant deshielding of the latter signal may be attributed to the
formation of an intramolecular halogen–hydrogen bond, as ex-
2
In addition, Ru-C (NHC) distances of 2.05 (Ru(1)-C(8)) and
2.08 Š (Ru(1)-C(19)) are observed.
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Figure 5. ORTEP drawing at 30% ellipsoid probability of the cationic compo-
nent of complex 5d(BF )·C . Hydrogen atoms, with exception of the hydri-
4
7 8
H
do ligand, and solvent molecule have been omitted for clarity. Selected
o
bond lengths [Š] and angles [ ]: Ru(1)-C(8) 2.055(2); Ru(1)-C(19) 2.083(3);
Ru(1)-N(1) 2.201(2); Ru(1)-C(30) 1.820(3); Ru(1)-N(6) 2.169(2); C(8)-Ru(1)-C(19)
169.33(10); C(30)-Ru(1)-N(1) 174.91(11).
As mentioned above, complexes 4, 5(Cl), and 5(BF ) produce
4
1
broadened signals at room temperature in the H NMR spectra,
indicative of the existence of a dynamic process in solution.
For example, solutions of 5e(BF ) in CD CN show two sets of
4
3
1
signals for the methylene protons in the H NMR spectra regis-
tered at temperatures below 278 K: Two doublets at d=5.13
1
4
Figure 6. Variable temperature (VT)- H NMR spectra of complex 5e(BF ) in
CD CN.
3
2
and 5.38 ppm ( J =14.1 Hz), and two other doublets at d=
HH
2
5
.30 and 5.62 ppm ( J =15.6 Hz) (Figure 6).
HH
A rise in the temperature causes pairwise broadening of the
signals, and their coalescence at 288 and 293 K, respectively.
plexes 4 and 5 containing the same ligand. For the latter com-
plexes, however, no influence of the counteranion was ob-
served in the exchanging process. In addition, the dynamic be-
havior is rather independent of the solvent. Hence, this ex-
change may be accompanied by previous chloride or MeCN
ligand dissociation facilitated by the large trans influence of
Further heating of the sample gives rise to two geminally cou-
2
pled doublets at d=5.28 and 5.54 ppm ( J =15.0 Hz). In
HH
square-planar palladium derivatives incorporating CNC ligands,
a similar dynamic process has been attributed to a slow inter-
conversion between the two twisted conformations adopted
2
[22]
[23]
by both C (NHC)-N(Py)-Pd rings of the pincer ligand. Similar-
ly, the observed dynamic behavior in derivatives 4 and 5 can
be ascribed to the slow exchange between the two limiting
enantiomeric forms (Scheme 3).
the hydrido ligand. Moreover, unlike it was observed with
PdÀCNC complexes, the calculated barriers are consistently
higher for species with xilyl-substituted CNC ligands than for
derivatives containing the more encumbered pincer with mesi-
[24]
tyl groups, reflecting a likely case of “steric assistance”.
°
Table 1. Free energy barriers (DG ) at coalescence temperature for com-
Tc
4
plexes 4, 5(Cl), and 5(BF ).
°
Tc
Complex
Solvent
CD Cl
T
c
DG
À1
[
K]
[kcalmol ]
Scheme 3. Enantiomers interconversion for 4, 5(Cl), and 5(BF
4
) in solution.
4d
288
263
303
278
313
273
308
283
15.1
13.2
15.7
14.0
16.1
13.8
16.4
14.2
2
2
4
5
5
e
d(Cl)
e(Cl)
CD
3
CN
Table 1 collects free energy barriers at the coalescence tem-
perature estimated for the exchange of the environments of
the para-methyl groups of the mesityl substituents for com-
5d(BF4)
5e(BF
2 2
CD Cl
4
)
5
5
d(BF
e(BF
4
)
)
3
CD CN
plexes 4e and 5e, and of the m-CH of the xilyl wingtips for
3
4
4
d and 5d. Similar energy barriers have been found for com-
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Catalytic hydrogenation of C=N bonds
[a]
Table 2. Hydrogenation of aldimines.
Entry Imine
Initial catalytic experiments were carried out with sol-
Cat.
Conv.
TOF
À1
[
%]
[h
]
utions of N-benzylideneaniline (6a) in 2-methyltetra-
[
25]
hydrofuran at 708C under 5 bar of H2 (Table 2).
Under these conditions, complex 3b(Cl), in the pres-
ence of tBuOK, efficiently completes the reaction in
1
3a(Cl)
60
100.0
6
h by using an S/C/B ratio of 1000:1:10 (Table 2,
entry 2). The rest of the series of complexes 3 also
catalyzes the reduction of 6a, although they provide
significantly lower conversions (Table 2, entries 1, 3,
and 4). In addition, the catalyst precursor 4e exhibits
a good catalytic activity for this reaction under the
examined conditions (Table 2, entry 5). Hydrogena-
tion of derivatives bearing electron-releasing and
2
3
4
5
3b(Cl)
3c(Br)
3d(Cl)
4e
100
26
54
166.7
43.3
90.0
98
163.3
6
7
8
9
3b(Cl)
100
80
166.7
133.3
-withdrawing groups can be carried out with com-
plex 3b(Cl), however, a significant influence of the
nature of the substituents in the catalytic activity is
evidenced (Table 2, entries 6–9). Moreover, the hydro-
genation of 6 f, having a hydroxyl group, can be ac-
complished although higher catalyst loadings (S/C=
100) were needed to get acceptable conversions
21
54
81
35.0
90.0
13.5
(Table 2, entry 10). Finally, the hydrogenation of N-
alkyl-substituted aldimines was examined (Table 2,
entries 11 and 12). N-Benzylidenebenzylamine (6g)
was hydrogenated more slowly than its N-phenyl
counterpart, whereas no hydrogenation was ob-
served in the case of N-benzylidene-tert-butylamine
(6h).
Next, to further study the scope of these catalysts,
[b]
10
the hydrogenation of several ketimines with precur-
sor 3b(Cl) was pursued (Table 3). A series of N-aryl ke-
timines (7a–f) was reduced with full conversions by
using an S/C/B ratio of 1000:1:10 (Table 3, entries 1–
[
b]
11
98
0
16.3
0
6). Under the specified conditions, no differences in
reactivity were observed for substrates having elec-
tron-donating or -withdrawing substituents at both
aryl groups. Also, the naphtyl-substituted imine 7g
was hydrogenated with high activity. In contrast, re-
duction of the thionyl-substituted imine 7h was
found to be more sluggish (Table 3, entry 8). The hy-
drogenation of C,C-dialkyl imine 7i was tested with
complex 3b(Cl), yielding the corresponding amine
with good conversion using a S/C ratio of 500
[b]
1
2
2
[a] Reaction conditions, unless otherwise noted: 5 bar H , 708C, 2-methyltetrahydro-
furan, S/C/B=1000:1:10, base: tBuOK, 6 h; [S]=1.4m; conversions were determined
by H NMR spectroscopy; turnover frequency (TOF) values as calculated from conver-
sions; [b] S/C/B=100:1:10.
1
(
Table 3, entry 9). Finally, hydrogenation of the N-
benzyl imine 7j was slower than that of its N-aryl counterparts,
since a lower S/C ratio was required to achieve full conversion
conversions of 94 (3a(Cl)) and 95% (3b(Cl)). Interestingly, the
catalytic system derived from 3b(Cl) efficiently catalyzes the
aceptorless dehydrogenation of 5,6-dihydrophenanthridine in
dioxane heated at reflux with complete conversion (S/C/B=
100:1:10).
(
Table 3, entry 10).
The development of catalytic systems for the (reversible) de-
hydrogenation of N-heterocycles is gaining considerable inter-
[26]
est for applications both in synthesis and H storage. Based
2
on the previous results, we were intrigued by the ability of cat-
alysts 3 to mediate the hydrogenation/dehydrogenation of N-
heterocycles. Hence, we have examined the catalytic activity of
complexes 3a(Cl) and 3b(Cl) in the hydrogenation of phen-
Stoichiometric reactions of RuÀCNC complexes
An important feature of the picolyl-NHC fragment, relevant to
metal–ligand cooperativity, resides in the acidity of the methyl-
[
27]
[1a,2]
anthridine (Scheme 4).
This substrate was hydrogenated
ene protons.
Previously, we and others have studied the
under 10 bar of H at 808C by using a S/C/B=250:1:10 with
deprotonation of RuÀCNC species. For example, selective de-
2
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protonation with tBuOK of the methylene arm of the NHC frag-
ment coordinated trans to the hydrido ligand of fac-complexes
[
a]
Table 3. Hydrogenation of ketimines with 3b(Cl).
Entry Imine
Conv.
%]
TOF
3a(Cl) and 3d(Cl) provides derivatives 8a and 8d, respectively
À1
[
[h
]
[15]
(
Scheme 5). Analysis by NMR spectroscopy of complexes 8
clearly shows the dearomatization of the pyridine fragment
since significant upfield shifts (d=4.6–5.5 ppm) are observed
for the central ring proton resonances. Similarly, mer-coordinat-
ed RuÀCNC complexes react with tBuOK to yield the corre-
1
100
100
100
100
100
166.7
[
11,12]
sponding dearomatized/deprotonated derivatives.
2
3
4
5
166.7
166.7
166.7
166.7
Scheme 5. Deprotonation reactions of complexes 3a(Cl) and 3d(Cl).
We hypothesized that ligand-assisted dihydrogen activation
by complexes 8 should lead to hydrido species capable of hy-
drogenating the imine substrates. Hence, upon exposure of
a [D ]THF solution of 8a to 3 bar of H and subsequent heating
8
2
at 558C for 1.5 h, derivative [RuH (CNC)(CO)] (9a) was cleanly
2
1
obtained (Scheme 6). In the H NMR spectrum of 9a, the hydri-
do ligands produce a singlet peak at d=5.7 ppm, whereas sig-
nals corresponding to the pyridine fragment appear in the
range expected for a rearomatized ring (d=7.1–7.7 ppm). In
6
7
100
166.7
166.7
addition, resonances produced by the methylene protons
2
appear as two doublets at d=5.29 and 5.61 ppm ( J
=
HH
100
44
13.0 Hz), in agreement with a mer arrangement of the CNC
ligand. This coordination mode of the pincer in 9a is further
2
confirmed by the existence of only one peak for the C -NHC
13
1
carbon atoms in the C{ H} NMR spectrum at d=201.3 ppm.
The signal corresponding to the CO ligand appears at d=
[
b]
8
1.8
214.3 ppm. For comparison, under similar reaction conditions
as employed for 9a, mesityl derivative 9e has been prepared
from a suspension of 5e(BF ) in [D ]THF in the presence of
4
8
[
c]
9
89
74.2
tBuOK (Scheme 6). Complex 9e has been recently reported by
[12]
Pidko and co-workers. Spectroscopic features of complexes
a and 9e are very similar.
9
[
c]
10
100
83.3
[a] Reaction conditions, unless otherwise noted: 5 bar H
2
, 708C, 2-methyl-
tetrahydrofuran, S/C/B=1000:1:10, base: tBuOK, 6 h; [S]=1.4m. Conver-
1
sions were determined by using H NMR spectroscopy. TOF values as cal-
culated from conversions; [b] 808C, S/C/B=100:1:10, 24 h; [c] S/C/B=
5
00:1:10.
Scheme 6. Generation of dihydrido complexes 9.
Dihydrido complex 9a readily loses H2 when exposed to
vacuum, leading to the formation of uncharacterized species.
Subsequent heating of the solution at 558C for 15 min under
Scheme 4. Reversible hydrogenation of phenanthridine. Conditions:
a) 3a(Cl) or 3b(Cl), 10 bar H , 2Me-THF, 808C, S/C/tBuOK=250:1:10;
b) 3b(Cl), dioxane, heated at reflux, S/C/tBuOK=100:1:10.
2
.5 bar of H regenerates the dihydrido complex. More interest-
2
2
1
1
ingly, in the H, H- exchange spectroscopy (EXSY) spectrum
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(
mixing time=0.8 s) of 9e registered at 258C under H (3 bar)
2
intense exchange cross-peaks are observed between the signal
corresponding to RuH and those of free H and both methyl-
2
ene protons. These observations suggest the reversible ex-
2
change of free H with a h -H ligand resulting from the intra-
2
2
molecular protonation of RuÀH by protons of the CNC methyl-
[
28]
ene fragment (Scheme 7). To determine the participation of
complexes 9 in the hydrogenation of imines, N-benzylideneani-
line (6a) was added under H to a [D ]THF solution of 9a and
Scheme 8. Synthesis of complexes 10a–d.
2
1
8
the reaction was followed by H NMR spectroscopy. Immediate
disappearance of the RuÀH signal of 9a occurs and two new
peaks in the hydride region at d=À13.14 and À13.27 ppm in
a 1.0:0.2 ratio are observed. Once the imine is hydrogenated
to the corresponding amine, the hydrido ligand signal of 9a is
regenerated.
ment by the presence of an intense cross-peak between the
CHN proton of the amido ligand and the methine carbon of
the pincer.
Interestingly, addition at room temperature of imine 6c to
the adduct 10a gives within minutes a mixture of 10a and
10c, leading to further evidence for the reversibility of the for-
[
31]
mation of the CÀC and NÀRu bonds.
Also, exposing
a sample of 10b to 3 bar of H at 558C for 30 min produces
2
the dihydrido complex 9e along with the hydrogenation of
6
b. Relative thermodynamic stabilities of complexes 10 have
been determined from the equilibria 10+6’$10’+6 by using
H NMR spectroscopy. From the corresponding K , a stability
1
298
eq
order of the adducts 10d>10a>10c>10b has been found
see the Supporting Information for details). This trend agrees
(
Scheme 7. Equilibria involved in the exchange of complex 9e and H
2
.
with the expected electrophilicity of the iminic carbon of the
imines, as well as with the better capability of electron-with-
drawing groups in the ArN fragment to reduce d(p)–p(p) re-
pulsion between the d-electrons of the metal and the nitrogen
Deprotonated metal–PNP complexes have been shown to
exhibit FLP-type reactivity towards small electrophiles such as
[32]
electron pair.
[
5,12]
CO , carbonyl compounds, and nitriles.
In our case, forma-
It is worth mentioning that addition of carbon nucleophiles
to coordinated imines to yield amido complexes has been
2
tion of analogous species with imines may sequester the cata-
lyst and be a catalytic cycle end-off. Generation of these spe-
cies was studied by addition of tBuOK to a suspension of com-
plex 5e(BF ) and imines 6a–d in a 1:1 to 1:1.6 ratio in [D ]THF.
[33]
used only very scarcely, and that adducts 10 represent a rare
II
case of Ru complexes with labile amido ligands with b-hydro-
gens, in which the RuÀN bond breaking takes place in the ab-
4
8
[34,35]
NMR analysis of the obtained solutions shows formation of ad-
ducts 10 resulting from the addition of the imine to the depro-
tonated metal–ligand framework with concomitant formation
sence of protonation or b-hydrogen elimination.
DFT calculations
1
of RuÀN and CÀC bonds (Scheme 8). H NMR spectra of com-
plexes 10 exhibit singlet signals at about d=À14 ppm attrib-
utable to the hydrido ligands. This chemical shift is close to
the value reported by the Milstein’s group for amido RuÀPNP
complexes (d=À12.8 ppm) obtained from the ligand-assisted
DFT calculations (PBE0/6-31g(d,p)+SDD; see the Computation-
al Details) were carried out on two model systems. First, a sim-
plified model (denoted by the subscript Me), in which the R
substituents of the CNC ligands are CH was used for explora-
3
[
29]
NÀH activation of anilines. In addition, the pyridine aromati-
zation in 10 is inferred from the downfield shift of the aromatic
protons appearing in the range d=7.1–7.5 ppm. More interest-
ingly, the formation of the new carbon–carbon bond is ob-
tory calculations. In the second model (denoted by the sub-
script Ph), Ph substituents are placed on the CNC ligand. (E)-N-
methylethanimine (6 ) and (E)-N-benzylideneaniline (6a) were
Me
chosen as substrates. Fac coordination of the CNC ligand was
+
served from the appearance of two doublets at about d=5.8
reproduced in the model complexes 3Me and 8Me by using
3
and 4.4 ppm ( J =5 Hz) corresponding to the methine proton
PMe instead of PPh . Phosphane dissociation free energy was
HH
3
3
À1
of the pincer and the amido CHNÀRu fragment, respectively.
estimated for the latter to be 17.9 kcalmol (DG (dispersion
corrected) in THF). Rearrangement of the CNC ligand coordina-
tion mode, from fac to mer, takes place upon phosphane loss
from 8 , and yields a 16-electron species (A ), which serves
The latter value is significantly shifted upfield with respect to
[
30]
the chemical shift of the free imine. Further confirmation of
the assignation of this signal was obtained from the existence
Me
Me
1
1
of an exchange cross-peak in the H, H-EXSY spectrum with
the signal of the iminic proton of the uncoordinated imine. In
as a model for the dehydrogenated form of the active catalyst.
N-methylethanimine coordination to this intermediate yields
a model for species 10, and is calculated to be thermodynami-
13
1
addition, the C{ H} NMR spectrum contains two signals at
about d=64 and 72 ppm, attributable to the amido carbon
and the methine carbon of the CNC, respectively. Formation of
À1
cally favorable by 12.3 kcalmol . Similarly, coordination of N-
methylethanimine or N-benzylideneaniline (6a) to A , analo-
Ph
1
13
À1
the new bond is further evidenced in the H- C HMBC experi-
gous to A , is exergonic by 11.0 and 20.7 kcalmol , respec-
Me
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tively. These values are consistent with the formation of 10a
from 5e(BF ), tBuOK and 6a, and justify the reversibility of the
4
coordination of imines (see the previous section).
According to the calculations, heterolytic H cleavage from
2
2
the h -H adduct A ·H takes place through a concerted four-
2
Ph
2
membered transition state (TS
a low energy barrier (DE) of 2.9 kcalmol . The hydrogena-
; Figure 7) and has
APh·H2!9Ph
À1 [36]
tion step is energetically favorable, yielding 9 with an energy
Ph
À1
return of 17.0 kcalmol .
Figure 8. Energy profile of the simultaneous transfer of two H atoms to N-
À1
methylethanimine. Zero-point and dispersion-corrected DE [kcalmol ] in
continuum THF (data in parentheses correspond to DG in THF). Inset: DFT-
optimized geometry of the corresponding transition state.
Figure 7. Heterolytic H
2
activation at APh. Data are zero-point- and disper-
À1
sion-corrected DE [kcalmol ] in continuum THF (the dotted line and data in
parentheses correspond to DG in THF). Inset: DFT-optimized geometry of
the corresponding transition state.
Once species 9Ph is formed, the hydrogenation reaction
begins with the formation of a “soft complex” (or loose pre-
complex) between the imine and 9Ph (Figure 8). When the
imine is N-methylethanimine, a transition state was found for
the simultaneous (albeit asynchronous) transfer of two hydro-
gen atoms, one hydrido ligand and one from a CH arm of the
2
Figure 9. Energy profile for the transfer of one hydride from 9Ph to N-benzyli-
deneaniline. Zero-point and dispersion-corrected DE [kcalmol ] in continu-
um THF (data in parentheses correspond to DG in THF). The insets represent
the DFT-optimized geometries of the corresponding transition state and of
the resulting ion pair, B.
À1
CNC ligand, to the C= and =N atoms of the imine linkage, re-
[
37]
spectively. This is a six-membered pericyclic transition state
similar to those proposed for related Noyori- and Shvo-type
[
38]
hydrogenation of ketones.
This individual step is almost
À1
thermoneutral and has an energy barrier of 16.7 kcalmol .
The resulting amine forms another “soft complex”, in this case
with the dehydrogenated active form of the catalyst APh,
which is broken to liberate the amine and regenerate the cata-
lyst. The calculations show that the overall reaction is exergon-
À1
À1
2.7 kcalmol , and is exothermic by 7.7 kcalmol . However,
the calculations show that barrier-less coordination of the
amide nitrogen of the benzyl(phenyl)amide anion to Ru to
À1
ic by 3.9 kcalmol (DG in THF).
give species C may be thermodynamically preferred (DG=
À1
When the imine is N-benzylideneaniline (Figure 9), stepwise
À14.2 kcalmol from B) to the formation of A +benzylani-
Ph
À1
hydrogen transfer takes place instead. First, hydride transfer to
line (DG=À9.6 kcalmol ). N-coordination of an intermediate
[
38a,39]
the C= atom of the soft complex 9 ·imine occurs
with an
amide to Ru to give stable species could account for the hy-
dride resonances seen by NMR spectroscopy in the reaction of
9a and 6a, but according to the results of the calculations de-
scribed to this point, it would represent a thermodynamic sink
Ph
À1
energy barrier of 4.7 kcalmol , to yield an ion pair (DE=
À1
1
.3 kcalmol , relative to 9 ·imine) involving the correspond-
Ph
ing cationic Ru complex and benzyl(phenyl)amide anion. This
[40]
ion pair (B) is further stabilized by CÀH···N (1.88 Š) and CÀ that may halt the catalysis. Alternatively, Dub, Gordon et al.
[5f,6i]
H···Ru (2.02 Š) interactions.
as well as Pidko et al.
have recently proposed a role for the
Following this point, hydrogen transfer from the correspond-
coordination of a second molecule of hydrogen to Ru prior to
a second hydrogen transfer in related asymmetric hydrogena-
tion of ketones and CO2 hydrogenation, respectively
ing CH arm of the CNC ligand of B to the amide nitrogen can
2
occur to generate N-benzylaniline and A , which may then
Ph
react with more H and imine, to turn over the catalytic cycle.
(Figure 10), albeit in those reactions, higher H pressures than
2
2
The second hydrogen transfer from B has a barrier of only
in this work were used. In this case, cleavage of the CÀH···Ru
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silver complexes 2 and [RuHCl(CO)(PPh ) ]. Contrary to previ-
3
3
ously observed meridional coordination of analogous CNC li-
gands, complexes 3 exhibit a fac coordination mode for the
pincer. Derivatives 3, in the presence of tBuOK, catalyze the hy-
drogenation of C=N bonds of imines and phenanthridine with
S/C ratios of up to 1000. Mechanistic insight has been ob-
tained from the NMR study of several derivatives including de-
protonated complexes 8, dihydrido derivatives 9 and imine ad-
ducts 10. In addition, DFT calculations show that stepwise hy-
drogen transfer, initiated by outer-sphere hydride transfer with
formation of ion pairs, may account for the addition of H to
2
the imines.
Experimental Section
General procedures
All reactions and manipulations were performed under nitrogen or
argon, either in a Braun Labmaster 100 glovebox or using standard
Schlenk-type techniques. All solvents were distilled under nitrogen
with the following desiccants: Sodium-benzophenone-ketyl for di-
ethyl ether (Et O) and tetrahydrofuran (THF, [D ]THF), sodium for
Figure 10. Competing protonation of the benzyl(phenyl)amide anion by
2
8
a CH
2
fragment of the ion pair B or by the dihydrogen ligand of ion pair D.
À1
hexane and toluene, CaH2 for dichloromethane and acetonitrile
(CH Cl , CH CN, CD CN), and NaOMe for methanol (MeOH). Imida-
Zero-point- and dispersion-corrected DE [kcalmol ] in continuum THF (data
in parentheses correspond to DG in THF). Insets: DFT-optimized geometries
of the transition state of the hydrogen transfer from B (top) and of the ion
pair D (bottom).
2
2
3
3
zolium salts 1 and silver complexes 2 were prepared as specified in
the Supporting Information. [RuHCl(CO)(PPh ) ] was synthesized ac-
3
3
[41]
cording to a literature procedure. Syntheses of imines 7 were ef-
fected following literature methods (see the Supporting Informa-
tion). All other reagents were purchased from commercial suppliers
and used as received. NMR spectra were obtained on a Bruker
DPX-300, DRX-400, AVANCEIII/ASCEND 400R, or DRX-500 spectrom-
interaction and H coordination to Ru in B is exothermic by
2
À1
À1
0.9 kcalmol (and endergonic by only 5.1 kcalmol ).
The second hydrogen transfer from the new ion pair (D)
13
1
1
eters. C{ H} and H shifts were referenced to the residual signals
may then occur from the coordinated H , which, according to
2
31
1
19
1
of deuterated solvents. P{ H} and F{ H} NMR shifts were refer-
enced to external 85% H PO and CFCl , respectively. All data are
a relaxed potential energy surface scan, may be barrier-less (no
3
4
3
transition state was located for this transformation) yielding
reported in ppm downfield from Me Si. All NMR measurements
4
À1
benzylaniline and 9 , with DG=À20.6 kcalmol , and closing
were carried out at 258C, unless otherwise stated. GC-MS analyses
were performed on a Shimadzu GCMSQP2010-Plus apparatus
Ph
the catalytic cycle. These results, summarized in the free
energy profile depicted in
Scheme 9, suggest that both
stepwise pathways may com-
pete in the catalytic hydrogena-
tion of imines by the Ru-CNC
pincer complexes of this work.
However, the relative stability of
intermediate C (which may map
onto hydride intermediates de-
tected in the reaction of 9a and
6
a), support the mechanism in
which the imide intermediate B
is protonated by a second dihy-
drogen molecule coordinated to
Ru.
Conclusion
A series of new ruthenium com-
plexes 3 incorporating neutral
dicarbene CNC ligands have
Scheme 9. DFT calculated free energy profile of the hydrogenation of N-benzylideneaniline by APh (zero-point cor-
been prepared by reaction of rected energy data are also shown in parenthesis). Note that the origin of energies is APh +2H
2
+imine.
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7549

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+
equipped with a ZB-5MS capillary column (10 m, 0.18 mm i.d.,
.18 mm film thickness). HRMS data were obtained on a JEOL JMS-
[(MÀClÀPPh ) ]); elemental analysis calcd (%) for C H ClN OPRu:
3
38 41
5
0
C 60.75, H 5.50, N 9.32; found: C 60.66, H 5.68, N 9.35.
SX 102 A mass spectrometer at the Instrumental Services of Univer-
sidad de Sevilla (CITIUS). ESI-MS experiments were carried out in
a Bruker 6000 apparatus by the Mass Spectrometry Service of the
Instituto de Investigaciones Químicas. Elemental analyses were run
by the Analytical Service of the Instituto de Investigaciones Quími-
cas in a Leco TruSpec CNH elemental analyzer. IR spectra were ac-
quired on a Bruker Tensor 27 instrument.
Complex 3a(BF ): A mixture of silver complex 2a(Br) (0.050 g,
4
0
.07 mmol) and [RuHCl(CO)(PPh ) ] (0.068 g, 0.07 mmol) in THF
3 3
(2 mL) was heated at 558C for 16 h. The resulting solution was fil-
tered, brought to dryness, and extracted with MeOH (2”2 mL).
The solvent was removed, and the obtained solid was dissolved in
CH Cl (2 mL) and treated with NaBF (0.008 g, 0.07 mmol) for 16 h.
2
2
4
The resulting mixture was filtered through a short pad of Celite,
and solvent was evaporated. Complex 3a(BF ) was isolated as
4
a yellow solid after recrystallization from CH Cl /Et O (0.037 g,
2
2
3
2
X-ray structure analysis
1
6
5%). H NMR (400 MHz, [D ]DMSO): d=7.86 (t, J(H,H)=7.6 Hz,
6
3
CCDC-1027679 [2a(Br)], CCDC-1027680 [2d(Cl)·2CHCl ], CCDC-
1H; H-4 py), 7.66 (m, 2H; H imid+H-3 py), 7.61 (d, J(H,H)=1.6 Hz,
1H; H imid), 7.51 (d, J(H,H)=1.6 Hz, 1H; H imid), 7.46 (d, J(H,H)=
2.0 Hz, 1H; H imid), 7.28 (t, J(H,H)=7.6 Hz, 3H; 3 H arom, PPh ),
7.20 (t, J(H,H)=7.6 Hz, 6H; 6 H arom, PPh ), 7.14 (d, J(H,H)=
3
3
3
1
027681 [4e·CH Cl ] and CCDC-1044008 [5d(BF )·C H ] contain the
2
2
4
7
8
3
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
3
3
3
3
3
3
7.2 Hz, 1H; H-3 py), 7.06 (dd, J(H,P)=9.2 Hz, J(H,H)=9.2 Hz, 6H;
2
6
H arom, PPh ), 5.67 (d, J(H,H)=14.4 Hz, 1H; py-CHH), 5.56 (d,
3
2
3
J(H,H)=13.6 Hz, 1H; py-CHH), 5.31 (h, J(H,H)=6.4 Hz, 1H;
Computational details
2
3
CH(CH ) ), 5.25 (d, J(H,H)=15.6 Hz, 1H; py-CHH), 4.94 (h, J(H,H)=
3
2
2
6
.4 Hz, 1H; CH(CH ) ), 4.18 (d, J(H,H)=15.2 Hz, 1H; py-CHH), 1.57
3
2
Calculations were carried out at the DFT level using the Gaussi-
3
3
[42]
[43]
(d, J(H,H)=6.8 Hz, 3H; CH
1.29 (d, J(H,H)=6.8 Hz, 3H; CH
3
), 1.48 (d, J(H,H)=6.4 Hz, 3H; CH
),
3
an 09 program with the PBE0 functional. All atoms were repre-
3
3
[44]
3
), 1.20 (d, J(H,H)=6.4 Hz, 3H;
sented with the 6-31g(d,p) basis set, except Ru, for which the
Stuttgart/Dresden Effective Core Potential and its associated basis
2
31
1
CH ), À7.38 ppm (d, J(H,P)=30.4 Hz, 1H; RuH); P{ H} NMR
3
13
1
[45]
(162 MHz, [D
6
]DMSO): d=42.9 ppm;
C{ H} NMR (101 MHz,
set SDD was used. All geometry optimizations were performed
in the gas phase without restrictions. Vibrational analysis was used
to characterize the stationary points in the potential energy sur-
face, as well as for calculating the zero-point, enthalpy and Gibbs
energy corrections at 295 K and 1 atm. The nature of the inter-
mediates connected by a given transition state along a reaction
path was proven by intrinsic reaction coordinate (IRC) calculations
or by perturbing the geometry of the TS along the reaction path
eigenvector. Bulk solvent effects were modeled with the SMD con-
2
2
[D ]DMSO): d=209.5 (d, J(C,P)=15 Hz; CO), 187.9 (d, J(C,P)=
6
2
8
1
Hz; C-2 imid), 180.4 (d, J(C,P)=81 Hz; C-2 imid), 157.6 (C-2 py),
1
56.6 (C-2 py), 140.5 (C-4 py), 136.7 (brd, J(C,P)=40 Hz; 3 Cq
3
arom, PPh ), 133.3 (d, J(C,P)=11 Hz; 6 CH arom, PPh ), 130.5 (3 CH
arom, PPh ), 129.1 (d, J(C,P)=9 Hz; 6 CH arom, PPh ), 125.4 (C-3
3
3
4
3
3
py), 125.2 (C-3 py), 124.7 (CH imid), 123.8 (CH imid), 120.0 (CH
imid), 118.7 (CH imid), 58.5 (py-CH ), 55.8 (py-CH ), 52.7 (CH(CH ) ),
2
2
3 2
5
1.9 (CH(CH ) ), 24.9 (CH ), 24.7 (CH ), 24.2 (CH ), 23.2 ppm (CH ); IR
3 2 3 3 3 3
À1
[46]
(Nujol): n˜ =1909, 1878, 1840 cm (CO, RuH); HRMS (FAB): m/z
calcd for C H N OPRu: 716.2029 [(MÀBF ) ]; found: 716.2108.
tinuum model.
+
38
41
5
4
Complex 3b(Cl): This complex was prepared as described for
Synthesis of Ru-CNC complexes 3–5
1
3
a(Cl). Yellow solid (0.056 g, 47%). H NMR (400 MHz, CD Cl ): d=
2 2
3
7
.96 (d, J(H,H)=1.6 Hz, 1H; H imid), 7.85 (brs, 1H; H imid), 7.53 (t,
Complex 3a(Cl): A mixture of silver complex 2a(Cl) (0.150 g,
3
J(H,H)=4.4 Hz, 1H; H-4 py), 7.19–7.29 (m, 17H; 15H arom PPh +
3
0
.25 mmol) and [RuHCl(CO)(PPh ) ] (0.234 g, 0.25 mmol) in THF
3 3
3
2
H-4 py), 7.08 (d, J(H,H)=1.6 Hz, 1H; H imid), 6.95 (brs, 1H; H
(
8 mL) was heated at 558C for 24 h. The resulting solution was fil-
2
imid), 5.95 (d, J(H,H)=14.0 Hz, 1H; py-CHH), 5.76 (m, 2H; 2 py-
CHH), 4.75 (m, 1H; CHH), 4.41 (m, 1H; CHH), 4.26 (d, J(H,H)=
tered, brought to dryness, and extracted with MeOH (2”5 mL).
The solvent was evaporated and the obtained solid was recrystal-
lized from MeOH/toluene. Yellow solid (0.120 g, 65%). H NMR
2
1
15.2 Hz, 1H; py-CHH), 4.06 (m, 2H; 2 CHH), 1.74 (m, 4H; 2 CH
2
),
2
1
2
.36 (m, 12H; 6 CH ), 0.87 (m, 6H; 2CH ), À7.14 ppm (d, J(H,P)=
2
3
3
(
400 MHz, CD Cl ): d=8.05 (s, 1H; H imid), 7.89 (s, 1H; H imid),
2 2
1
1
8.8 Hz, 1H; RuH); P{ H} NMR (162 MHz, CD Cl ): d=43.3 ppm;
2
2
7
.49 (s, 1H; H imid), 7.15 (m, 18H; 15 H arom PPh +2H-3 py+H-4
3
1
3
1
2
2
C{ H} NMR (101 MHz, CD
2
Cl
2
): d=209.4 (d, J(C,P)=15 Hz; CO),
py), 7.01 (s, 1H; H imid), 5.91 (d, J(H,H)=14.0 Hz, 1H; py-CHH),
5
2
2
2
2
189.9 (d, J(C,P)=8 Hz; C-2 imid), 182.3 (d, J(C,P)=81 Hz; C-2
imid), 157.1 (2 C-2 py), 138.6 (C-4 py), 136.6 (d, J(C,P)=39 Hz; 3 C
arom, PPh ), 133.1 (d, J(C,P)=10 Hz; 6CH arom, PPh ), 129.8 (3 CH
.82 (d, J(H,H)=15.5 Hz, 1H; py-CHH), 5.71 (d, J(H,H)=14.0 Hz,
1
3
q
1
H; py-CHH), 5.44 (h, J(H,H)=6.5 Hz, 1H; CH(CH ) ), 5.04 (h,
3
2
3
3
2
3
3
J(H,H)=6.5 Hz, 1H; CH(CH ) ), 4.29 (d, J(H,H)=15.5 Hz, 1H; py-
3
2
4
3
3
arom, PPh ), 128.4 (d, J(C,P)=8 Hz; 6 CH arom, PPh ), 125.0 (C-3
3 3
CHH), 1.61 (d, J(H,H)=6.5 Hz, 3H; CH ), 1.59 (d, J(H,H)=6.5 Hz,
3
6
NMR (202 MHz, CD Cl ): d=42.4 ppm; C{ H} NMR (126 MHz,
CD Cl ): d=209.2 (d, J(C,P)=15 Hz; CO), 189.0 (d, J(C,P)=7 Hz; C-
3
3
3
py), 124.5 (CH imid+C-3 py), 122.8 (CH imid), 121.2 (CH imid),
H; CH ), 1.30 (d, J(H,H)=6.5 Hz, 3H; CH ), 1.22 (d, J(H,H)=
3 3
2
31
1
120.2 (CH imid), 58.6 (py-CH ), 55.6 (py-CH ), 51.7 (CH ), 50.7 (CH ),
2
2
2
2
.5 Hz, 3H; CH ), À7.30 ppm (d, J(H,P)=30.5 Hz, 1H; RuH); P{ H}
3
13
1
31.9 (CH ), 31.7 (2CH ), 31.2 (CH ), 26.9 (CH ), 26.7 (CH ), 22.8 (2
2 2 2 2 2
2
2
À1
2
2
CH ), 14.0 ppm (2CH ); IR (CH Cl ): n˜ =1924 cm (CO); MS (ESI,
2 3 2 2
2
2
+
2
DMSO/MeOH): m/z (%): 800 (100) [(MÀCl) ] (fragmentation of ion
2
2
1
1
imid), 181.5 (d, J(C,P)=81 Hz; C-2 imid), 157.0 (C-2 py), 156.9 (C-
+
1
m/z 800: 538 (100) [(MÀClÀPPh ) ]); elemental analysis calcd (%)
3
py), 138.7 (C-4 py), 136.7 (brd, J(C,P)=39 Hz; 3 C arom, PPh ),
q
3
2
for C H ClN OPRu: C 63.26, H 6.39, N 8.38; found: C 63.25, H 6.39,
44
53
5
33.2 (d, J(C,P)=11 Hz; 6 CH arom, PPh ), 129.9 (3 CH arom, PPh ),
28.5 (d, J(C,P)=9 Hz; 6 CH arom, PPh ), 125.1 (C-3 py), 125.0 (C-3
3
3
4
N 8.34.
3
py), 124.6 (CH imid), 123.5 (CH imid), 117.8 (CH imid), 116.7 (CH
Complex 3c(Br): A mixture of silver complex 2c(Br) (0.175 g,
imid), 58.5 (py-CH ), 55.6 (py-CH ), 52.3 (CH(CH ) ), 51.7 (CH(CH ) ),
0.23 mmol) and [RuHCl(CO)(PPh ) ] (0.233 g, 0.23 mmol) in THF
2
2
3 2
3 2
3 3
2
1
7
4.9 (CH ), 25.0 (CH ), 24.2 (2 CH ), 23.0 ppm (CH ); IR (Nujol): n˜ =
(8 mL) was heated at 558C for 24 h. The resulting solution was fil-
tered, brought to dryness and extracted with MeOH (3”5 mL). The
solvent was evaporated, and the residue was dissolved in THF and
3
3
3
3
À1
921, 1878, 1840 cm (RuH, CO); MS (ESI, DMSO/MeCN): m/z (%):
+
16 (100) [(MÀCl) ] (fragmentation of ion m/z 716: 454 (100)
Chem. Eur. J. 2015, 21, 7540 – 7555
www.chemeurj.org
7550
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
treated with NaBr (0.023 g, 0.23 mmol) for 24 h. Solvent was re-
moved under vacuum, and the solid was extracted in CH Cl (3”
Complex 4d: A mixture of complex 2d(Cl) (0.363 g, 0.49 mmol)
and [RuHCl(CO)(PPh ) ] (0.471 g, 0.49 mmol) in THF (15 mL) was
2
2
3 3
5
mL). The resulting solution was brought to dryness, and the solid
heated at 608C for 24 h. The resulting solution was filtered off, and
the solid was extracted with MeCN (3”5 mL). The solution was
brought to dryness, and the solid was washed with cold THF (2”
5 mL) yielding complex 4d as a yellow solid (0.034 g, 11 %). On the
other hand, the THF solution was evaporated, and the solid was
extracted with MeOH (2”5 mL). Solvent was removed under
vacuum, and the obtained solid was recrystallized from MeOH/tol-
uene. Complex 3d(Cl) was obtained as a brown solid (0.138 g,
33%). Low solubility in common organic solvents of 4d did not
was recrystallized from MeOH/toluene. Yellow solid (0.042 g, 22%).
1
3
H NMR (500 MHz, CD Cl ): d=8.07 (d, J(H,H)=1.6 Hz, 1H; H imid),
2
2
3
3
7
.85 (d, J(H,H)=1.6 Hz, 1H; H imid), 7.39 (d, J(H,H)=7.5 Hz, 1H;
3
H-3 py), 7.26 (m, 9H; 9H arom, PPh ), 7.23 (d, J(H,H)=1.6 Hz, 1H;
H imid), 7.17 (dd, J(H,P)=8.0 Hz, J(H,H)=8.0 Hz, 6H; 6H arom,
PPh ), 7.12 (d, J(H,H)=8.5 Hz, 1H; H-3 py), 7.07 (t, J(H,H)=6.5 Hz,
3
3
3
3
3
3
3
2
1
1
H; H-4 py), 7.05 (d, J(H,H)=1.6 Hz, 1H; H imid), 5.85 (d, J(H,H)=
2
4.0 Hz, 1H; py-CHH), 5.73 (d, J(H,H)=15.0 Hz, 1H; py-CHH), 5.47
2
2
1
(
d, J(H,H)=14.0 Hz, 1H; py-CHH), 5.12 (d, J(H,H)=13.5 Hz, 1H;
permit full spectroscopic characterization. H NMR (500 MHz,
2
3
CHHC(CH )), 4.84 (d, J(H,H)=13.5 Hz, 1H; CHHC(CH )), 4.52 (d,
CD Cl , 278 K): d=7.85 (t, J(H,H)=7.7 Hz, 1H; H-4 py), 7.62 (d,
3
3
2
2
2
2
2
J(H,H)=15.0 Hz, 1H; py-CHH), 3.93 (d, J(H,H)=13.5 Hz, 1H;
J(H,H)=15.5 Hz, 1H; py-CHH), 7.70 (s, 2H; 2H arom), 7.50 (d,
J(H,H)=7.6 Hz, 2H; 2H-3 py), 7.19 (s, 1H; H imid), 7.14 (s, 1H; H
2
3
CHHC(CH )), 3.81 (d, J(H,H)=13.5 Hz, 1H; CHHC(CH )), 1.21 (s, 9H;
3
3
2
C(CH ) ), 1.07 (s, 9H; C(CH ) ), À7.52 ppm (d, J(H,P)=31.5 Hz, 1H;
imid), 7.08 (m, 3H; 3H arom), 6.95 (m, 3H; H arom+2H imid), 5.31
3
3
3 3
3
1
1
13
1
2
2
RuH); P{ H} NMR (202 MHz, CD Cl ): d=44.2 ppm; C{ H} NMR
(d, J(H,H)=14.1 Hz, 1H; py-CHH), 5.13 (d, J(H,H)=14.1 Hz, 1H; py-
2
2
2
2
(
126 MHz, CD Cl ): d=211.0 (d, J(C,P)=16 Hz; CO), 190.3 (brs; C-2
CHH), 4.89 (d, J(H,H)=14.7 Hz, 1H; py-CHH), 2.30 (s, 6H; 2CH ),
2
2
3
2
imid), 185.2 (d, J(C,P)=82 Hz; C-2 imid), 157.3 (C-2 py), 157.0 (C-2
py), 138.7 (C-4 py), 136.5 (brd, J(C,P)=40 Hz; 3 C arom, PPh3),
2.27 (s, 6H; 2CH ), À16.01 (s, 1H; RuH); IR (Nujol): n˜ =1948, 1934,
3
1
À1
1905 cm (RuH, CO); MS (ESI, CH Cl /MeOH): m/z (%): 612 (100)
q
2
2
3
+
+
1
1
33.5 (d, J(C,P)=11 Hz; 6 CH arom, PPh ), 130.0 (3 CH arom, PPh ),
28.5 (d, J(C,P)=9 Hz; 6 CH arom, PPh ), 124.8 (C-3 py), 124.2 (C-3
[(MÀH) ] (fragmentation of ion m/z 612: 584 (100) [(MÀHÀCO) ]);
3
3
4
elemental analysis calcd (%) for C H ClN ORu: C 58.77, H 4.93, N
3
30 30
5
py), 124.1 (CH imid), 123.2 (CH imid), 121.7 (CH imid), 121.2 (CH
11.42; found: C 58.60, H 5.00, N 11.17.
imid), 63.1 (2 CH C(CH ) ), 61.7 (2 CH C(CH ) ), 58.5 (py-CH ), 56.0
2
3 3
2
3 3
2
Complex 4e: A mixture of 2e(Cl) (0.200 g, 0.26 mmol) and [RuHCl-
(
py-CH ), 34.1 (C(CH ) ), 34.0 (C(CH ) ), 29.0 (3 CH ), 28.4 ppm (3
2 3 3 3 3 3
(
CO)(PPh ) ] (0.250 g, 0.26 mmol) in CH Cl (10 mL) was stirred for
3
3
2
2
À1
CH ); IR (CH Cl ): n˜ =1919 cm (CO); MS (ESI, DMSO/MeOH): m/z
3
2
2
2
4 h. The resulting mixture was filtered, and solvent was removed
+
(
[
%): 772 (100) [(MÀBr) ] (fragmentation of ion: m/z 772: 510 (100)
under reduced pressure. The solid was washed with toluene (2”
mL) and Et O (4 mL), and extracted with MeOH (2”5 mL). Recrys-
+
(MÀBrÀPPh ) ]); elemental analysis calcd (%) for C H BrN OPRu:
3
42 49
5
5
2
C 59.22, H 5.80, N 8.22; found: C 59.24, H 5.92, N 8.17.
tallization from MeOH/toluene yields complex 4e as a yellow solid
13
1
(
0.065 g, 39%). A meaningful C{ H} NMR spectrum for 4e in
a non-coordinating solvent could not be obtained due to low solu-
Complex 3d(Cl): A mixture of 2d(Cl) (0.092 g, 0.13 mmol) and
RuHCl(CO)(PPh ) ] (0.120 g, 0.13 mmol) in CH Cl (8 mL) was stirred
1
bility of the product and significant line broadening. H NMR
[
3
3
3
2
2
(
500 MHz, CD Cl , 238 K): d=7.84 (t, J(H,H)=7.6 Hz, 1H; H-4 py),
2
2
for 6 h. The resulting solution was filtered, brought to dryness, and
extracted with MeOH (2”5 mL). The solvent was evaporated and
the obtained solid was recrystallized from MeOH/toluene. Yellow
solid (0.056 g, 51%). Although stable under inert atmosphere in
the solid state, complex 3d(Cl) decomposes in solution (CH Cl ,
7
.49 (m, 3H; 2H-3 py+py-CHH), 7.20 (s, 2H; 2 H imid), 6.93 (s, 1H;
H arom), 6.88 (s, 1H; H arom), 6.85 (s, 2H; 2H arom), 6.69 (s, 1H; H
imid), 6.68 (s, 1H; H imid), 5.33 (m, 1H; py-CHH), 5.10 (d, J(H,H)=
2
2
1
4.0 Hz, 1H; py-CHH), 4.83 (d, J(H,H)=14.5 Hz, 1H; py-CHH), 2.31
2
2
(s, 3H; Ar-CH ), 2.28 (s, 3H; Ar-CH ), 2.11 (s, 3H; Ar-CH ), 2.03 (s,
3 3 3
MeOH, MeCN, THF). Hence, spectroscopically pure samples could
3
H; Ar-CH ), 1.87 (s, 3H; Ar-CH ), 1.81 (s, 3H; Ar-CH ), À16.24 ppm
3
3
3
1
13
1
not be obtained. Signals of the complex in the H and C{ H} NMR
À1
(s, 1H; RuH); IR (Nujol): n˜ =1932 (RuH), 1878 cm (CO); MS (ESI,
1
13
1
13
spectra were assigned with the help of H, C-HMQC and H, C-
+
CH Cl /MeOH): m/z (%): 608 (100) [(M+HÀCl) ] (fragmentation of
2
2
1
HMBC experiments. H NMR (500 MHz, CD Cl ): d=8.11 (s, 1H; H
imid), 7.76 (s, 1H; H imid), 7.67 (d, J(H,H)=6.5 Hz, 1H; H-3 py),
.36 (m, 2H; H-3 py+H-4 py), 7.27 (m, 4H; 3 H arom, PPh +H
+
2
2
ion m/z 608: 578 (100) [(MÀClÀCO) ]); elemental analysis calcd
3
(%) for C H ClN ORu: C 59.94, H 5.34, N 10.92; found: C 59.89, H
32 34 5
7
3
5
.30, N 10.79.
arom), 7.18 (m, 13H; 12 H arom, PPh + H arom), 7.00 (s, 1H; H
3
Complex 5d(Cl): A suspension of 4d (0.015 g, 0.02 mmol) in MeCN
(3 mL) was stirred for 24 h, and volatiles were removed under re-
duced pressure. Complex 5d(Cl) was isolated as a yellow solid
(0.016 g, 94%). A meaningful C{ H} NMR spectrum for 5d(Cl)
could not be obtained due to low solubility of the product in
CD Cl2 and CD CN and significant line broadening. H NMR
(500 MHz, CD CN, 288 K): d=8.00 (t, J(H,H)=7.3 Hz, 1H; H-4 py),
3
7.70 (d, J(H,H)=7.1 Hz, 1H; H-3 py), 7.68 (d, J(H,H)=6.6 Hz, 1H;
H-3 py), 7.16 (s, 1H; H imid), 7.09 (brm, 8H; 6H arom+2H imid),
imid), 6.86 (s, 1H; H arom), 6.75 (s, 1H; H arom), 6.62 (s, 1H; H
2
imid), 6.29 (s, 2H; 2 H arom), 6.14 (d, J(H,H)=14.0 Hz, 1H; py-
2
2
CHH), 5.96 (d, J(H,H)=14.0 Hz, 1H; py-CHH), 5.94 (d, J(H,H)=
1
13
1
2
5.5 Hz, 1H; py-CHH), 4.51 (d, J(H,H)=15.5 Hz, 1H; py-CHH), 2.36
2
(
brs, 6H; 2 Ar-CH ), 2.11 (s, 6H; 2 Ar-CH ), À7.56 ppm (d, J(H,P)=
3
3
1
3
1
1
2
3
2
7.5 Hz, 1H; RuH); P{ H} NMR (202 MHz, CD Cl ): d=43.4 ppm;
2 2
3
1
3
1
2
C{ H} NMR (126 MHz, CD Cl ): d=208.9 (d, J(C,P)=15 Hz; CO),
91.3 (d, J(C,P)=7 Hz; C-2 imid), 182.3 (d, J(C,P)=81 Hz; C-2
2
2
3
3
2
2
1
imid), 158.0 (C-2 py), 157.4 (C-2 py), 140.6 (Cq arom), 140.2 (Cq
arom), 138.7 (C-4 py), 138.4 (brs, CH arom), 137.9 (C-3 py), 136.9 (2
2
7
.06 (s, 1H; H imid), 5.53 (d, J(H,H)=15.6 Hz, 1H; py-CHH), 5.47 (d,
2
2
3
J(H,H)=14.5 Hz, 1H; py-CHH), 5.35 (d, J(H,H)=16.2 Hz, 1H; py-
C arom), 136.6 (2 C arom), 133.2 (d, J(C,P)=10 Hz; 6 CH arom,
q
q
2
CHH), 5.32 (d, J(H,H)=15.2 Hz, 1H; py-CHH), 2.30 (s, 6H; 2 CH ),
3
PPh ), 130.8 (CH arom), 129.8 (3 CH arom, PPh ), 128.8 (CH arom),
3
3
À1
4
2.27 (s, 6H; 2CH ), À13.87 (s, 1H; RuH); IR (Nujol): n˜ =1908 cm
3
1
28.6 (d, J(C,P)=9 Hz; 6 CH arom, PPh ), 125.6 (CH imid), 125.2
3
102
(CO); HRMS (FAB): m/z calcd for C H N O Ru: 577.1416
30
29
5
(
CH imid), 125.0 (CH imid), 124.5 (CH arom), 124.4 (C-3 py), 122.5 (2
+
[(MÀHClÀMeCN) ]; found: 577.1440.
CH arom), 121.9 (CH imid), 59.3 (py-CH ), 56.0 (py-CH ), 21.4 (2 Ar-
2
2
À1
CH ), 21.4 ppm (brs; 2 Ar-CH ); IR (CH Cl ): n˜ =1934 cm (CO); MS
Complex 5e(Cl): This complex was prepared as described for
5d(Cl). Yellow solid (0.021 g, 99%). H NMR (400 MHz, CD CN): d=
7.97 (t, J(H,H)=6.4 Hz, 1H; H-4 py), 7.71 (d, J(H,H)=6.4 Hz, 2H; 2
H-3 py), 7.54 (s, 2H; 2H imid), 6.93 (brs, 4H; 4H arom), 6.88 (s, 2H;
3
3
2
2
+
1
(
ESI, DMSO/MeOH): m/z (%): 840 (100) [(MÀCl) ] (fragmentation of
3
+
3
3
ion m/z 840: 578 (100) [(MÀClÀPPh ) ]); HRMS (FAB): m/z calcd for
3
1
02
+
C H N OP Ru: 840.2405 [(MÀCl) ]; found: 840.2350.
48
45
5
Chem. Eur. J. 2015, 21, 7540 – 7555
www.chemeurj.org
7551
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1
3
1
2
H imid), 5.55 (br, 2H; 2 py-CHH), 5.33 (br, 2H; 2 py-CHH), 2.29
6.5 Hz, 6H; 2 CH ), À5.70 ppm (s, 2H; 2 RuH); C{ H} NMR
3
(
brs, 6H; 2Ar-CH ), 1.88 (brs, 12H; 4Ar-CH ), À14.33 ppm (s, 1H;
(101 MHz, [D ]THF): d=214.3 (CO), 201.3 (2 C-2 imid), 159.1 (2 C-2
py), 135.8 (C-4 py), 121.7 (2 C-3 py), 119.4 (2 CH imid), 114.8 (2 CH
3
3
8
1
3
1
RuH); C{ H} NMR (400 MHz, CD CN): d=206.6 (CO), 190.1 (2 C-2
3
imid), 159.0 (br; 2 C-2 py), 140.4 (C-4 py), 139.6 (C arom), 137.2 (3
imid), 57.4 (2 py-CH ), 51.7 (2 CH(CH ) ), 24.0 (2 CH ), 22.1 ppm (2
q
2
3 2
3
C arom), 129.6 (2 C-3 py), 129.3 (C arom), 129.1 (2CH imid), 125.9
CH3).
q
q
(
1
Cq arom), 125.4 (2 CH imid), 124.3 (Cq arom), 123.4 (Cq arom),
Complex 9d: In a J.-Young valve NMR tube, a solution of 5e(BF4)
23.0 (br; 4CH arom), 56.4 (br; 2 py-CH ), 21.1 (2 Ar-CH ), 18.5 (2
2
3
(0.010 g, 0.01 mmol) in [D ]THF (0.7 mL) was treated with tBuOK
8
À1
Ar-CH ), 18.0 ppm (2 Ar-CH ); IR (Nujol): n˜ =1910 cm (CO); HRMS
(
found: 606.1846.
3
3
(0.002 g, 0.02 mmol). The solution was pressurized with 3 bar of H
2
102
+
FAB): m/z calcd for C H N O Ru: 606.1807 [(MÀClÀMeCN) ];
1
32
34
5
and heated to 508C for 1 h. H NMR spectrum of the resulting
[12] 1
product is in agreement with previously reported data.
H NMR
3
Complex 5d(BF ): A suspension of 4d (0.028 g, 0.05 mmol) in
MeCN (2 mL) was treated with NaBF (0.006 g, 0.05 mmol). The sus-
(500 MHz, [D ]THF): d=7.64 (t, J(H,H)=7.7 Hz, 1H; H-4 py), 7.38
(d, J(H,H)=7.7 Hz, 2H; 2 H-3 py), 7.23 (d, J(H,H)=1.7 Hz, 2H; 2H
4
8
3
3
4
pension was stirred for 4 h, and the solvent was removed under re-
imid), 6.73 (s, 2H; 2 H arom), 6.73 (s, 2H; 2H arom), 6.61 (d,
3
2
duced pressure. CH Cl2 (5 mL) was added to the resulting solid,
J(H,H)=1.7 Hz, 2H; 2H imid), 5.59 (d, J(H,H)=12.5 Hz, 2H; 2 py-
2
2
and the suspension was filtered through a short pad of Celite.
CHH), 5.30 (d, J(H,H)=12.5 Hz, 2H; 2 py-CHH), 2.21 (s, 6H; 2 CH ),
3
Complex 5d was isolated as a yellow solid after solvent evapora-
1.95 (s, 6H; 2CH ), 1.93 (s, 6H; 2CH ), À5.96 ppm (s, 2H; 2RuH).
3
3
1
3
tion (0.020 g, 61%). H NMR (400 MHz; CD Cl ): d=7.89 (t, J(H,H)=
2
2
3
7
.6 Hz, 1H; H-4 py), 7.68 (d, J(H,H)=7.5 Hz, 1H; H-3 py), 7.60 (d,
3
Procedure for the preparation of complexes 10
J(H,H)=7.6 Hz, 1H; H-3 py), 7.34 (s, 2H; 2 H imid), 7.08 (s, 4H; 4 H
arom), 7.04 (s, 1H; H arom), 7.02 (s, 2H; 2 H imid), 6.97 (s, 1H; H
arom), 5.53 (d, J(H,H)=15.0 Hz, 1H; py-CHH), 5.49 (d, J(H,H)=
In a NMR tube, a suspension of 5e(BF ) (0.020 g, 0.03 mmol) and
the corresponding imine (0.03–0.04 mmol, 1.0–1.6 equiv) in
2
2
4
2
1
(
4.4 Hz, 1H; py-CHH), 5.28 (d, J(H,H)=14.8 Hz, 1H; py-CHH), 5.26
[
D ]THF (0.7 mL) was treated with tBuOK (0.003 g, 0.03 mmol). The
2
8
d, J(H,H)=14.0 Hz, 1H; py-CHH), 2.31 (s, 6H; 2 CH ), 2.29 (s, 6H; 2
3
resulting solution was immediately analyzed by using NMR spec-
troscopy. Attempted isolation of complexes 10 led to product de-
composition.
13
1
CH ), 1.81 (s, 3H; MeCN), À13.89 ppm (s, 1H; RuH); C{ H} NMR
3
(
126 MHz, CD Cl , 273 K): d=207.1 (CO), 189.1 (C-2 imid), 188.4
2 2
(
C-2 imid), 157.7 (C-2 py), 157.1 (C-2 py), 140.8 (C arom), 140.4 (Cq
q
1
3
Complex 10a: H NMR (500 MHz, [D ]THF): d=7.45 (d, J(H,H)=
8
arom), 139.4 (C-4 py), 138.8 (2 C arom), 138.7 (2 C arom), 130.3
q
q
3
3
1
.5 Hz, 1H; H imid), 7.40 (dd, J(H,H)=7.5 Hz, J(H,H)=7.5 Hz, 1H;
H-4 py), 7.39 (d, J(H,H)=1.5 Hz, 1H; H imid), 7.33 (d, J(H,H)=
.5 Hz, 1H; H-3 py), 6.84 (s, 1H; H arom, mesityl), 6.79 (m, 8H; H-3
py + 2H arom, mesityl+5 H arom, NPh), 6.74 (d, J(H,H)=1.5 Hz,
1H; H imid), 6.66 (d, J(H,H)=1.5 Hz, 1H; H imid), 6.35 (s, 1H;
Harom, mesityl), 6.18 (dd, J(H,H)=7.5 Hz, J(H,H)=7.5 Hz, 2H; 2H
arom, PhCN), 6.10 (d, J(H,H)=8.0 Hz, 2H; 2 H arom, PhCN), 5.87
d, J(H,H)=5.5 Hz, 1H; py-CH), 5.66 (dd, J(H,H)=6.5 Hz, J(H,H)=
.5 Hz, 1H; H arom, PhCN), 5.49 (d, J(H,H)=13.5 Hz, 1H; py-CHH),
(
1
(
CH arom), 129.9 (CH arom), 125.4 (2 CH arom), 125.1 (C-3 py),
25.0 (2 CH arom+MeCN), 124.4 (C-3 py), 123.3 (CH imid), 122.7
CH imid), 122.0 (CH imid), 121.6 (CH imid), 57.5 (py-CH ), 54.9 (py-
3
3
7
2
3
CH ), 21.2 (4 CH ), 3.5 ppm (br, MeCN); IR (Nujol): n˜ =1967 (RuH),
2
3
3
À1
1
[
5
909 cm
(CO); MS (ESI, CH Cl /MeCN): m/z (%): 578 (100)
2
2
3
3
+
102
(MÀBF ÀMeCN) ]; HRMS (FAB): m/z calcd for C H N O Ru:
4
30 30
5
3
+
78.1494 [(MÀBF ÀMeCN) ]; found: 578.1490.
4
3
3
3
(
6
5
Complex 5e(BF ): This complex was prepared as described for
2
4
1
5
3
7
(
d(BF ). Yellow solid (0.022 g, 97%). H NMR (500 MHz, CD Cl ,
13 K): d=7.91 (t, J(H,H)=7.5 Hz, 1H, H-4 py), 7.69 (d, J(H,H)=
.5 Hz, 2H; 2H-3 py), 7.44 (d, J(H,H)=1.3 Hz, 2H; 2 H imid), 6.94
s, 2H; 2 H arom), 6.89 (s, 2H; 2H arom), 6.78 (d, J(H,H)=1.5 Hz,
H; 2H imid), 5.49 (brs, 2H; 2 py-CHH), 5.37 (d, J(H,H)=15.0 Hz,
H; 2 py-CHH), 2.33 (s, 6H; 2Ar-CH ), 2.02 (s, 3H; MeCN), 1.94 (brs,
2
3
4
2
2
.35 (d, J(H,H)=13.5 Hz, 1H; py-CHH), 4.46 (d, J(H,H)=5.0 Hz, 1H;
3
3
CHNRu), 2.26 (s, 3H; Ar-CH ), 2.25 (s, 3H; Ar-CH ), 2.02 (s, 3H; Ar-
3
3
3
CH ), 1.88 (s, 3H; Ar-CH ), 1.74 (s, 3H; Ar-CH ), 1.42 (s, 3H; Ar-CH ),
3
3
3
3
3
13
1
À13.72 ppm (s, 1H; RuH); C{ H} NMR (126 MHz, [D ]THF): d=
2
8
2
2
6
2
1
1
1
1
10.7 (CO), 197.4 (2 C-2 imid), 162.2 (Cq arom), 160.2 (Cq arom),
3
57.3 (C arom), 149.6 (C arom), 138.4 (C arom), 138.4 (C arom),
38.1 (C arom), 138.0 (C arom), 137.8 (C arom), 137.4 (C arom),
36.8 (C arom), 136.6 (CH arom), 136.0 (C arom), 131.2 (CH arom),
29.4 (2 CH arom), 128.7 (2 CH arom), 128.0 (2 CH arom), 127.9 (2
q
q
q
q
H; 2Ar-CH ), 1.91 (brs, 6H; 2 Ar-CH ), À14.5 ppm (s, 1H; RuH);
3
3
1
3
1
q
q
q
q
C{ H} NMR (CD Cl , 126 MHz, 313 K): d=205.6 (CO), 190.1 (2 C-2
2
2
q
q
imid), 158.0 (br; 2 C-2 py), 139.5 (C-4 py), 139.2 (2 C arom), 136.8
q
(
m; 6 C arom), 129.3 (2 C-3 py), 128.6 (2 CH imid), 124.8 (2 CH
q
CH arom), 127.5 (2 CH arom), 126.0 (CH arom), 124.2 (CH arom),
22.9 (CH imid), 121.9 (CH arom), 121.5 (CH arom), 120.8 (CH
arom), 120.6 (CH imid), 118.1 (2 CH arom), 107.1 (CH arom), 71.9
imid), 122.4 (m; 4 CH arom+MeCN), 56.4 (br; 2 py-CH ), 21.2 (2 Ar-
2
1
CH ), 18.5 (2 Ar-CH ), 18.1 (2 Ar-CH ), 3.9 ppm (MeCN); IR (Nujol):
3
3
3
À1
n˜ =1932 cm (CO); MS (ESI, CH Cl /MeCN): m/z (%): 606 (100)
2
2
(
py-CH), 63.7 (CHNRu), 57.8 (py-CH ), 21.3 (Ar-CH ), 21.2 (Ar-CH ),
+
102
2
3
3
[
6
(MÀHBF ÀMeCN) ]; HRMS (FAB): m/z calcd for C H N O Ru:
4
32 34
5
1
8.7 (2 Ar-CH ), 18.4 (Ar-CH ), 18.3 ppm (Ar-CH ).
+
3
3
3
06.1807 [(MÀHBF ÀMeCN) ]; found: 606.1812.
4
1
3
Complex 10b: H NMR (500 MHz, [D ]THF): d=7.43 (dd, J(H,H)=
8
3
3
7
.5 Hz, J(H,H)=7.5 Hz, 1H; H-4 py), 7.42 (d, J(H,H)=2.0 Hz, 1H; H
imid), 7.38 (d, J(H,H)=1.5 Hz, 1H; H imid), 7.33 (d, J(H,H)=7.5 Hz,
H; H-3 py), 6.85 (s, 1H; H arom, mesityl), 6.82 (d, J(H,H)=7.5 Hz,
3
3
Complexes [RuH (CNC)(CO)] (9)
2
3
1
Complex 9a: In a J.-Young valve NMR tube, a solution of 3a(Cl)
1H; H-3 py), 6.78 (s, 1H; H arom, mesityl), 6.77 (s, 1H; H arom, me-
3
3
(
0.013 g, 0.02 mmol) in [D ]THF (0.7 mL) was treated with tBuOK
sityl), 6.72 (d, J(H,H)=2.0 Hz, 1H; H imid), 6.69 (d, J(H,H)=8.0 Hz,
8
3
(
0.002 g, 0.02 mmol) forming a dark-red solution. The solution was
2H; 2 H arom, N(MeO-Ph)), 6.65 (d, J(H,H)=1.5 Hz, 1H; H imid),
3
pressurized with 3 bar of H and heated to 558C for 1.5 h. Complex
6.38 (s, 1H; H arom), 6.35 (d, J(H,H)=8.5 Hz, 2H; 2 H arom,
2
1
3
9
[
1
a was only stable under a H2 atmosphere. H NMR (500 MHz,
D ]THF): d=7.64 (t, J(H,H)=7.5 Hz, 1H; H-4 py), 7.13–7.40 (m,
9H; 2 H-3 py+2 H imid+free PPh ), 7.01 (d, J(H,H)=1.5 Hz, 2H;
H imid), 5.61 (d, J(H,H)=13.0 Hz, 2H; 2 py-CHH), 5.54 (h,
J(H,H)=6.5 Hz, 2H; 2 CH(CH ) ), 5.29 (d, J(H,H)=13.0 Hz, 2H; 2
py-CHH), 1.49 (d, J(H,H)=6.5 Hz, 6H; 2 CH ), 1.33 (d, J(H,H)=
N(MeO-Ph)), 6.02 (d, J(H,H)=9.5 Hz, 2H; 2 H arom, (MeO-Ph)CN),
3
3
5.91 (d, J(H,H)=9.5 Hz, 2H; 2 H arom, (MeO-Ph)CN), 5.80 (d,
8
3
3
2
J(H,H)=5.5 Hz, 1H; py-CH), 5.48 (d, J(H,H)=13.5 Hz, 1H; py-CHH),
3
2
2
3
2
5.34 (d, J(H,H)=13.5 Hz, 1H; py-CHH), 4.36 (d, J(H,H)=5.0 Hz, 1H;
3
2
CHNRu), 3.55 (s, 3H; Ar-OCH ), 3.51 (s, 3H; Ar-OCH ), 2.29 (s, 3H;
3
2
3
3
3
3
Ar-CH ), 2.24 (s, 3H; Ar-CH ), 2.02 (s, 3H; Ar-CH ), 1.89 (s, 3H; Ar-
3 3 3
3
Chem. Eur. J. 2015, 21, 7540 – 7555
www.chemeurj.org
7552
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
CH ), 1.73 (s, 3H; Ar-CH ), 1.43 (s, 3H; Ar-CH ), À13.65 ppm (s, 1H;
Representative procedure for catalytic hydrogenation reac-
tions of imines
3
3
3
1
3
1
RuH); C{ H} NMR (101 MHz, [D ]THF): d=210.6 (CO), 197.3 (C-2
8
imid), 197.2 (C-2 imid), 160.2 (C arom), 158.5 (C arom), 157.7 (C
q
q
q
q
q
q
In a glovebox, a Fischer–Porter vessel was charged with a solution
of complex 3b(Cl) (1.2 mg, 1.4 mmol), tBuOK (1.6 mg, 14.0 mmol)
and the corresponding imine (1.4 mmol) in 2-methyltetrahydrofur-
arom), 157.0 (C arom), 145.9 (C arom), 141.5 (C arom), 138.4 (C
q
q
q
arom), 138.2 (C arom), 138.0 (C arom), 137.9 (C arom), 137.8 (C
q
q
q
arom), 137.3 (C arom), 136.7 (C arom), 136.4 (CH arom), 135.9 (C
q
q
an (1.0 mL). The reactor was purged three times with H , and finally
arom), 130.9 (CH arom), 130.6 (CH arom), 129.2 (CH arom), 128.6 (2
CH arom), 128.5 (CH arom), 124.1 (CH imid), 122.6 (CH arom), 121.7
2
pressurized to 5 bar and heated to 708C. After 6 h, the reactor was
slowly cooled down to room temperature and depressurized. The
reaction solution was evaporated, and conversion was determined
(
1
CH arom), 121.3 (CH arom), 120.6 (CH imid), 120.3 (CH arom),
15.8 (CH arom), 115.0 (CH arom), 114.7 (CH arom), 114.5 (CH
arom), 114.3 (CH arom), 113.2 (CH arom), 72.1 (py-CH), 63.7
CHNRu), 57.7 (py-CH ), 56.5 (Ar-OCH ), 54.8 (Ar-OCH ), 21.2 (Ar-
1
by H NMR spectroscopy.
(
2
3
3
CH ), 21.0 (Ar-CH ), 18.6 (Ar-CH ), 18.5 (Ar-CH ), 18.2 (Ar-CH ),
3
3
3
3
3
Procedure for the hydrogenation of phenanthridine
1
8.1 ppm (Ar-CH3).
In a glovebox, a Parr-type reactor (40 mL) was charged with a solu-
tion of complex 3b(Cl) (4.2 mg, 5.6 mmol), tBuOK (6.3 mg,
1
3
Complex 10c: H NMR (500 MHz, [D ]THF): d=7.43 (dd, J(H,H)=
8
3
3
7
.5 Hz, J(H,H)=7.5 Hz, 1H; H-4 py), 7.42 (d, J(H,H)=2.0 Hz, 1H; H
imid), 7.39 (d, J(H,H)=2.0 Hz, 1H; H imid), 7.35 (d, J(H,H)=7.5 Hz,
H; H-3 py), 6.86 (s, 1H; H arom, mesityl), 6.81 (d, J(H,H)=7.5 Hz,
H; H-3 py), 6.78 (s, 1H; H arom, mesityl), 6.78 (s, 1H; H arom, me-
sityl), 6.74 (d, J(H,H)=2.0 Hz, 1H; H imid), 6.66 (m, 3H; H imid+2
H arom), 6.36 (m, 3H; 3 H arom), 5.99 (m, 2H; 2 H arom, (F-Ph)CN),
5
6.1 mmol) and phenanthridine (0.251 g, 1.4 mmol) in 2-methylte-
3
3
trahydrofuran (1.5 mL). The reactor was purged three times with
3
1
1
H , and finally pressurized to 10 bar and heated to 808C. After
2
2
4 h, the reactor was slowly cooled down to room temperature
3
and depressurized. The reaction solution was evaporated, and con-
1
version was determined by using H NMR spectroscopy.
3
5
.92 (m, 2H; 2 H arom, (F-Ph)CN), 5.78 (d, J(H,H)=5.0 Hz, 1H; py-
2
2
CH), 5.48 (d, J(H,H)=13.5 Hz, 1H; py-CHH), 5.35 (d, J(H,H)=
3
1
3.5 Hz, 1H; py-CHH), 4.28 (d, J(H,H)=5.5 Hz, 1H; CHNRu), 3.55
Ar-OCH ), 2.27 (s, 3H; Ar-CH ), 2.24 (s, 3H; Ar-CH ), 2.02 (s, 3H; Ar-
Procedure for the dehydrogenation of 5,6-dihydrophenan-
thridine
(
3
3
3
CH ), 1.88 (s, 3H; Ar-CH ), 1.73 (s, 3H; Ar-CH ), 1.43 (s, 3H; Ar-CH ),
3
3
3
3
19
1
A solution of complex 3b(Cl) (1.0 mg, 1.3 mmol), tBuOK (1.5 mg,
13.0 mmol) and 5,6-dihydrophenanthridine (0.024 g, 0.13 mmol) in
dioxane (1.0 mL) was heated at reflux for 24 h. Conversion was de-
À13.78 ppm (s, 1H; RuH); F{ H} NMR (376 MHz, [D ]THF): d=
8
1
3
1
À143.2 ppm; C{ H} NMR (101 MHz, [D ]THF): d=210.5 (CO), 196.9
8
(
2 C-2 imid), 160.1 (Cq arom), 158.8 (Cq arom), 158.6 (Cq arom),
1
termined by using GC-MS and H NMR spectroscopy.
1
1
1
1
57.1 (C arom), 151.1 (d, J(C,F)=222 Hz; C arom), 140.8 (C arom),
q q q
38.4 (C arom), 138.0 (C arom), 137.9 (C arom), 137.8 (C arom),
q
q
q
q
37.6 (CH arom), 136.8 (C arom), 136.6 (CH arom), 135.9 (C arom),
q
q
Acknowledgements
30.8 (CH arom), 129.3 (CH arom), 128.6 (2 CH arom), 128.6 (CH
arom), 124.2 (CH arom), 122.7 (CH arom), 121.8 (CH arom), 121.4
CH arom), 120.7 (CH arom), 120.4 (CH arom), 116.7 (2 CH arom),
13.2 (2 CH arom), 113.0 (CH arom), 112.8 (CH arom), 72.0 (py-CH),
3.7 (CHNRu), 57.7 (py-CH ), 54.8 (Ar-OCH ), 21.0 (2 Ar-CH ), 18.6
(
1
6
Financial support (FEDER contribution) from the Spanish
MINECO (CTQ2009-11867), Consolider-Ingenio 2010 (CSD2007-
00006), and the Junta de Andalucía (2008/FQM-3830, 2009/
FQM-4832) is gratefully acknowledged. M.H.J. thanks CONACYT
for a fellowship (214238). The use of Computational facilities of
the supercomputing Center of Galicia (CESGA) is also acknowl-
edged. J.L.-S. thanks the MICINN and the European Social Fund
for a “Ramón y Cajal” contract. P.L. thanks the Spanish Ministry
of Economy and Competitivity for a Juan de la Cierva contract.
2
3
3
(
Ar-CH ), 18.5 (Ar-CH ), 18.3 (Ar-CH ), 18.0 ppm (Ar-CH ).
3 3 3 3
1
3
Complex 10d: H NMR (500 MHz, [D ]THF): d=7.48 (dd, J(H,H)=
8
3
3
7
.5 Hz, J(H,H)=7.5 Hz, 1H; H-4 py), 7.43 (d, J(H,H)=2.0 Hz, 1H; H
imid), 7.40 (d, J(H,H)=2.0 Hz, 1H; H imid), 7.38 (d, J(H,H)=7.5 Hz,
H; H-3 py), 6.87 (s, 1H; H arom, mesityl), 6.84 (d, J(H,H)=7.5 Hz,
H; H-3 py), 6.77 (m, 7H; 6 H arom+H imid), 6.68 (d, J(H,H)=
.0 Hz, 1H; H imid), 6.51 (d, J(H,H)=8.5 Hz, 2H; 2 H arom), 6.49 (d,
J(H,H)=8.5 Hz, 2H; 2 H arom), 6.39 (s, 1H; H arom, mesityl), 5.95
m, 4H; 4 H arom, (F-Ph)CN), 5.82 (d, J(H,H)=5.1 Hz, 1H; py-CH),
.48 (d, J(H,H)=13.5 Hz, 1H; py-CHH), 5.36 (d, J(H,H)=13.5 Hz,
3
3
3
1
1
3
3
2
3
3
(
5
1
Keywords: carbenes
·
homogeneous
catalysis
·
2
2
hydrogenation · ligands · ruthenium
3
H; py-CHH), 4.35 (d, J(H,H)=5.1 Hz, 1H; CHNRu), 2.28 (s, 3H; Ar-
CH ), 2.25 (s, 3H; Ar-CH ), 2.02 (s, 3H; Ar-CH ), 1.89 (s, 3H; Ar-CH ),
3
3
3
3
[
1] a) J. I. van der Vlugt, J. N. H. Reek, Angew. Chem. Int. Ed. 2009, 48, 8832–
1
.73 (s, 3H; Ar-CH ), 1.41 (s, 3H; Ar-CH ), À13.80 ppm (s, 1H; RuH);
3
3
8846; Angew. Chem. 2009, 121, 8990–9004; b) J. I. van der Vlugt, Eur. J.
1
9
1
13
1
F{ H} NMR (376 MHz, [D ]THF): d=À142.8, À118.8 ppm; C{ H}
8
Inorg. Chem. 2012, 363–375; c) S. Schneider, J. Meiners, B. Askevold,
Eur. J. Inorg. Chem. 2012, 412–429; d) S. E. Clapham, A. Hadzovic, R. H.
Morris, Coord. Chem. Rev. 2004, 248, 2201–2237; e) H. Grützmacher,
Angew. Chem. Int. Ed. 2008, 47, 1814–1818; Angew. Chem. 2008, 120,
1838–1842; f) Top. Organomet. Chem. Vol. 37 (Eds.: T. Ikariya, M. Shiba-
saki), Springer, Heidelberg, 2011.
NMR (101 MHz, [D ]THF): d=210.4 (CO), 196.9 (C-2 imid), 196.7 (C-
8
2
imid), 161.7 (d, J(C,F)=243 Hz; C arom), 159.7 (C arom), 158.6
q q
(
C arom), 157.3 (C arom), 151.2 (d, J(C,F)=223 Hz; C arom), 145.6
q q q
(
C arom), 144.9 (C arom), 138.3 (C arom), 138.0 (C arom), 137.9
q q q q
(
CH arom), 137.6 (C arom), 137.4 (C arom), 136.8 (C arom), 136.7
q q q
[
2] a) C. Gunanathan, D. Milstein, Acc. Chem. Res. 2011, 44, 588–602; b) J. I.
van der Vlugt, M. Lutz, E. A. Pidko, D. Vogt, A. L. Spek, Dalton Trans.
(
C arom), 135.8 (C arom), 130.8 (CH arom), 128.7 (m; 3 CH arom),
q q
1
28.6 (d, J(C,F)=15 Hz, CH arom), 124.1 (CH arom), 122.7 (CH
2
009, 1016–1023; c) J. I. van der Vlugt, E. A. Pidko, R. C. Bauer, Y. Gloa-
arom), 122.1 (CH arom), 121.5 (CH arom), 120.7 (CH arom), 120.4
CH arom), 116.6 (CH arom), 115.5 (d, J(C,F)=23 Hz, CH arom),
15.4 (CH arom), 114.3 (d, J(C,F)=21 Hz, CH arom), 113.0 (d,
J(C,F)=20 Hz, CH arom), 71.5 (py-CH), 63.4 (CHNRu), 57.5 (py-CH2),
guen, M. K. Rong, M. Lutz, Chem. Eur. J. 2011, 17, 3850–3854; d) Y.-H.
Chang, Y. Nakajima, H. Tanaka, K. Yoshizawa, F. Ozawa, J. Am. Chem. Soc.
(
1
2
013, 135, 11791–11794.
[3] J. I. van der Vlugt, E. A. Pidko, D. Vogt, M. Lutz, A. L. Spek, Inorg. Chem.
2009, 48, 7513–7515.
2
1.0 (2 Ar-CH ), 18.5 (2 Ar-CH ), 18.1 (Ar-CH ), 17.9 ppm (Ar-CH ).
3
3
3
3
Chem. Eur. J. 2015, 21, 7540 – 7555
www.chemeurj.org
7553
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
[
4] For leading examples of reactivity of metal complexes as FLP: a) A. M.
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