Coordinatively Labile 18-Electron Arene Ruthenium Iminophosphonamide Complexes

Article abstract of DOI:10.1002/chem.201702862

The thermodynamics of chloride dissociation from the 18e arene ruthenium iminophosphonamides [(η⁶-arene)RuCl{(R′N)₂PR₂}] (1 a–d) [previously known with arene=C₆Me₆, R=Ph, R′=p-Tol (a); R=Et, R′=p-Tol (b); R=Ph, R′=Me (c); and new with arene=p-cymene, R=Ph, R′=p-Tol (d)] was assessed in both polar and apolar solvents by variable-temperature UV/Vis, NMR, and 2D EXSY ¹H NMR methods, which highlighted the influence of the NPN ligand on the equilibrium parameters. The dissociation enthalpy ΔH_d decreases with increasing electron-donating ability of the N- and P-substituents (1 a, 1 d>1 b>1 c) and solvent polarity, and this results in exothermic spontaneous dissociation of 1 c in polar solvents. The coordination of neutral ligands (MeCN, pyridine, CO) to the corresponding 16e complexes [(η⁶-arene)Ru{(R′N)₂PR₂}]⁺PF₆^? (2 a–d) is reversible; the stability of the 2?L adducts depends on the π-accepting ability of L. Carbonylation of 2 a and 2 d resulted in rare examples of cationic arene ruthenium carbonyl complexes (3 a, 3 d), while the monocarbonyl adduct derived from 2 c reacts further with a second equivalent of CO with conversion to carbonyl-carbamoyl complex 3 c, in which one CO molecule is inserted into the Ru?N bond. The new complexes 1 d, 2 d, 3 a, 3 c, and 3 d were isolated and structurally characterized.

Full text of DOI:10.1002/chem.201702862

A Journal of
Accepted Article
Title: Coordinatively labile 18-electron arene ruthenium
iminophosphonamide complexes
Authors: Iana S. Sinoplanikova, Tat'yana A. Peganova, Valentin
V. Novikov, Ivan V. Fedyanin, Oleg A. Filippov, Natalia V.
Belkova, Elena S. Shubina, Rinaldo Poli, and Alexander M.
Kalsin
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Chemistry - A European Journal
10.1002/chem.201702862
FULL PAPER
Coordinatively labile 18-electron arene ruthenium
iminophosphonamide complexes
Iana S. Sinopalnikova,[a,b] Tat'yana A. Peganova, Valentin V. Novikov, Ivan V. Fedyanin, Oleg A.
[a]
[a]
[a]
Filippov, Natalia V. Belkova, Elena S. Shubina, Rinaldo Poli, Alexander M. Kalsin*[a]
[
a]
[a]
[a]
[b,c]
Dedication ((optional))
Abstract: The thermodynamics of chloride dissociation from the 18ē
catalyst must be tolerant. The reactivity of the unsaturated
species thus should be fine-tuned by reducing the electrophilicity
of the ruthenium center with the ligand environment. Ligands
having extra lone pair at the coordinated heteroatom are capable
to partially compensate the electron deficiency of the metal via π-
6
arene ruthenium iminophosphonamides [(η -arene)RuCl{(R’N)
2 2
PR }]
6 6
(1a-d) (previously known systems with arene = C Me , R = Ph, R’ =
p-Tol (a); R = Et, R’ = p-Tol (b); R = Ph, R’ = Me (c); and new ones
with arene = p-cymene, R = Ph, R’ = p-Tol (d)) has been assessed in
both polar and apolar solvents, using variable-temperature UV-visible,
[
2]
donation. O- and N-ligands usually provide significantly greater
stabilization than halides, e.g. following the order OSiMe Ph >
NHPh > OSiPh > OCH CF >> Cl > Br > I for half-sandwich
[Cp*Ru(X)(PR
)] complexes. Among the chelating anionic κ2-
1
NMR and 2D EXSY H NMR methods, highlighting the NPN ligand
2
influence on the equilibrium parameters. The dissociation enthalpy
3
2
3
[
3]
∆
H
d
decreases upon increasing the electron-donating ability of the
3
N-,P- substituents (1a, 1d > 1b > 1c) and the solvent polarity, resulting
in the exothermic spontaneous dissociation of 1c in polar solvents.
The coordination of neutral ligands (MeCN, pyridine, CO) to the
N,N-ligands, strongly electron-donating β-diketiminate and
zwitterionic bis(imidazoline-2-imine) ligands were found to
generate either 18ē complexes with weakened Ru–Cl bonds,[
or very stable 16ē half-sandwich ruthenium complexes that do not
4-6]
6
+
-
2 2 6
corresponding 16ē complexes [(η -arene)Ru{(R’N) PR }] (PF ) (2a-
[
7,8]
d) is reversible; the stability of the 2·L adducts depends on the L π-
accepting ability. Carbonylation of 2a and 2d results rare examples of
cationic arene ruthenium carbonyl complexes (3a, 3d), while the
monocarbonyl adduct derived from 2c reacts further with a second
CO molecule, rapidly converting to the carbonyl-carbamoyl complex
coordinate the chloride ion at all.
The π-donation of the lone
electronic pairs at the nitrogen atoms in ruthenium amidinates is
limited because of symmetry reasons; it occurs only in the
unfavorable conformation with a bent metallacycle and thus the
[
9-13]
stabilization effect is less pronounced.
We have recently
3
c, where one CO molecule is inserted into the Ru–N bond. The new
proposed that structurally similar iminophosphonamide ligands
-
complexes 1d, 2d, 3a, 3c and 3d were isolated and structurally
[R
2
P(NR’)
2
] can efficiently stabilize the coordinatively unsaturated
[
14]
characterized.
ruthenium complexes, thanks to their zwitterionic structure and
therefore to the absence of symmetry restrictions for π-
donation.[15] The observation of elongated Ru–Cl bonds (2.44–
2
.45 Å) in 18ē complexes [(C
6 6 2 2
Me )RuCl{(RN) PR’ }] and
Introduction
shortened Ru–N bonds (average 2.01–2.04 Å) in the
corresponding 16ē complexes [(C Me )Ru{(RN) PR’ }] (X )
6 6 2 2
supports this hypothesis. In 1998 Parsons et al. reported the
first 16ē ruthenium iminophosphonamide complex [(p-
Cymene)Ru{(PrN)
and inert to the addition of Cl , PPh
adduct could not be isolated due to intrinsic instability. Since
2 2
then, no 18ē cationic NPN complexes [(arene)Ru(L){(RN) PR’
+
-
Coordinatively unsaturated complexes are often considered as
intermediates in various metal-catalyzed organic transformations.
Generally the stability of these species correlates with their
activity in catalysis, i.e. the more unsaturated species are more
reactive, however at the expense of selectivity. Ruthenium
complexes are known to catalyze numerous organic reactions[1]
of substrates bearing various functional groups, to which a
[15]
i
i
2
PPh(NHPr)}](BPh
4
) to be extremely stable
-
3
and P(OEt)
3
; even the CO
[16]
}]+
could be isolated, suggesting that the σ,π-donor character of the
NPN ligand is too strong to allow stability for such adducts.
Here we report a comprehensive quantitative exploration of
reversible coordination of neutral ligands with various π-acceptor
capabilities (MeCN, pyridine and CO) to cationic 16ē arene
ruthenium iminophosphonamides 2a-d, and the chloride
dissociation from the 18ē complexes 1a-d (Chart 1), aiming to
determine the influence of the arene nature and of the N-, P-
substituents in the NPN-ligand on the thermodynamics of ligand
coordination/dissociation. These data on the coordination
behavior of ruthenium iminophosphonamides are particularly
important in view of their potential use in catalysis.
[
a]
Ms. Iana S. Sinopalnikova, Dr. Tat'yana A. Peganova, Dr. Valentin
V. Novikov, Dr. Ivan V. Fedyanin, Dr. Oleg A. Filippov, Prof. Natalia
V. Belkova, Prof. Elena S. Shubina, and Dr. Alexander M. Kalsin*
A.N. Nesmeyanov Institute of Organoelement Compounds
Russian Academy of Sciences
28 Vavilov str., 119991 Moscow, Russia
E-mail: kalsin@ineos.ac.ru
[
b]
c]
Ms. Iana S. Sinopalnikova and Prof. Rinaldo Poli
Laboratoire de Chimie de Coordination CNRS
Université de Toulouse, UPS, INPT
205 Route de Narbonne, 31077 Toulouse Cedex 4, France
[
Prof. Rinaldo Poli
Institut Universitaire de France
1, rue Descartes, 75231 Paris Cedex 05, France
Supporting information for this article is given via a link at the end of
the document.
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Chart 1.
Results and Discussion
Synthesis and characterization of the complexes 1d and 2d.
The new p-cymene ruthenium NPN-complexes (1d, 2d) were
synthesized similarly to their hexamethylbenzene analogues 1a
and 2a,[15] i.e. by reacting [(p-cymene)RuCl
]
with
2
2
iminophosphonamide A after deprotonation with 1 equiv. of
NaHMDS to obtain 1d and further abstraction of the chloride
ligand with AgPF
6
to yield the corresponding 16ē cationic complex
Figure 2. ORTEP diagram of the cation 2d. Ellipsoids are shown at the 50%
probability level; hydrogen atoms and the anion are omitted for clarity. Selected
bond lengths (Å) and angles (°): Ru···Arene(centroid) 1.659(1), Ru–N1 2.031(2),
Ru–N2 2.017(3), N1–Ru–N2 72.42(10), Ru–N1–P–N2 174.27(15), Σ(N1)
2d (Scheme 1). The isolated products were fully characterized by
NMR spectroscopy and elemental analysis, and their molecular
structures were confirmed by single crystal X-ray diffraction
studies (Figures 1 and 2, Table S6 in ESI).
360.0(6), Σ(N2) 358.9(5).
The 18ē complex 1d exhibits a three-legged piano stool
geometry with a pseudo octahedral configuration of the ligands
around the ruthenium atom. The structural parameters of 1d are
6 6
similar to those of its C Me analogues 1a-c, except for the Ru–N
and Ru–Cl distances that are about 0.02 Å shorter (the average
Ru–N and Ru–Cl bond lengths in 1a-c are 2.148–2.156(4) Å and
2
.437–2.445(4) Å, respectively).[15] The p-cymene ligand is a
Scheme 1. Synthesis of the complexes 1d, 2d.
6 6
weaker donor and has lower steric requirements than C Me ,
hence the lack of electron density on the ruthenium atom in 1d is
compensated by shortening the bonds with the NPN and Cl
ligands. The pyramidalization of the nitrogen atoms, as indicated
by Σ(N), is small like for the complexes 1a,b. This is a result of the
ability of the N-tolyl substituents in 1a,b,d to delocalize the
unshared electron density of the nitrogen atoms, in sharp contrast
with the severe pyramidalization of one of the nitrogen atoms in
1c (Σ(N1) = 344.4°), for which such delocalization is impossible.
The 16ē cationic complex 2d exhibits a two-legged piano-
stool geometry with the chelating NPN-ligand positioned nearly
perpendicular to the p-cymene ligand. Most of the structural
parameters of 2d are similar to those of its C
a,b, besides less significant distortion of the arene ligand. The
p-cymene ligand in 2d is almost planar (Ru–C(arene) bonds in the
6 6
Me counterparts
2
6 6
2.159–2.204(3) Å range) compared to the C Me ring in 2a and
2b, which is bent towards a boat conformation with two
considerably longer Ru–C(arene) bonds (trans to Ru–N; 2.228-
[
15]
2
.275(2) Å) vs. the other four (2.143-2.201(2) Å). This structural
peculiarity may result from weaker back-bonding from the
ruthenium atom to the arene ligand in 2d.
Figure 1. ORTEP diagram of 1d. Ellipsoids are shown at the 50% probability
level; hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (°): Ru···Arene(centroid) 1.667(1), Ru–Cl 2.415(1), Ru–N1 2.145(2),
Ru–N2 2.126(3), N1–Ru–N2 68.24(9), Ru–N1–P–N2 178.43(16), Σ(N1)
6 6
The geometrical differences observed for the C Me and p-
cymene complexes were reproduced by the density functional
theory (DFT) calculation performed for 1a, 1d, 2a and 2d in the
gas phase with PBE functional and def2-TZVP basis set. The
optimized structures differ from the experimentally determined
357.2(6), Σ(N2) 358.2(6).
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ones by <0.03 Å for the distances and <2° for the bond angles
bonding of chlorine atom in the p-cymene complex vs those
(
ESI, Tables S7 and S8). It is noteworthy that the DFT calculations
also predict the arene orientation relative to the Cl,N,N atoms in
a and 1d (the dihedral angle Cl–Ru–Centroid-C5 differs by <3°).
Coordination of the arene ligand in the 16ē complexes 2a and 2d
6 6
containing C Me , as reflected by the computed and measured
Ru–Cl bond lengths (Tables S7 and S8).
1
Coordination lability of complexes 1a-d
2
2
has a well-pronounced η -η character, with the Ru–C1 and Ru–
C4 bonds being ca. 0.04 Å (2d) or 0.09 Å (2a) longer than the
other four Ru–C bonds, which also indicates a stronger distortion
of the planar arene ring towards a boat conformation for 2a than
for 2d. This pattern can be explained by the symmetry of the
ruthenium orbitals interacting with the arene ring (see below).
The 16ē complexes 2a-c exhibit a moderate intensity band in
the UV-vis spectra centered at 540-550 nm,[15] which was
supposed to belong to a d-d* transition. The UV-Vis spectra of 2d
exhibit a similar band, although surprisingly shifted to longer
wavelengths (λmax = 590 nm). According to the calculated orbital
pattern of 2a and 2d, the highest occupied molecular orbitals
Despite the low symmetry (C
two doublets at δ 5.05 and 4.87 (C
1
) of 1d in the solid state, only
) were observed for the
6
D
6
coordinated arene in the 1H NMR spectrum, as well as two
singlets at δ 79.4, 80.7 in the 13C NMR spectrum, because of
facile rotation of the p-cymene ring around the Ru–Arene axis
s
yielding an effective C symmetry in solution. The NMR spectral
feature of 2d are equally in accord with C
s
-symmetry. On the other
hand, the H and 13C NMR spectra for the P-phenyl substituents
1
6 6
of 1d exhibit the expected two sets of signals in C D but only one
in CDCl , suggesting an even higher (effective C2v) point group
3
symmetry in the latter solvent. This can be rationalized, in addition
to the rapid p-cymene ring rotation around the Ru–Arene axis, by
the reversible dissociation of the Ru–Cl bond that yields an
equilibrium mixture of the effectively C2v-symmetric intermediate
(
HOMO) (ESI, Fig. S10) of both cations are assigned to the
antibonding combination of the ruthenium dxy orbital with the A
symmetric group orbital of the NPN ligand (linear combination of
the nitrogen atoms p orbitals) and are located at very close
energies (-7.4 eV in the gas phase and -5.1 eV in CH Cl solution,
2
-
+
-
[2] Cl and undissociated 1, as has been previously proposed for
1c.[15] However, whether this process may occur in apolar
solvents and what is the dissociation enthalpy as a function of
solvent, NPN substituents and type of arene ligand is still open to
question. The additional studies detailed below have brought light
on this point.
y
2
2
Table 1). In both 2a and 2d, the lowest unoccupied molecular
orbital (LUMO) (ESI, Fig. S11) is a combination of the ruthenium
unoccupied dyz orbital and occupied B
2
π-orbital of the arene
ligand. Lowering the energy of the corresponding bonding orbital
UV-vis spectroscopic studies of 1b and 1c in polar solvents.
As we have previously reported,[15] complex 1c bearing the most
electron-releasing N-Me groups partially dissociates in the
relatively polar solutions to give the corresponding cationic
species [2c] Cl (Scheme 2), as revealed by the strong downfield
shift of its 31P NMR resonance in dichloromethane compared to
(
HOMO-14, see ESI, Fig. S12) is responsible for the elongation of
6
two C-C bonds (C2–C3 and C5–C6) of the η -arene ligand. The
greater electron-donating ability of C
LUMO by 0.4 eV in 2a (Table 1). Hence the bands observed at
40 nm (2a) and 590 nm (2d) in the UV-vis spectra appear
6 6
Me leads to a higher energy
+
-
5
consistent with a ligand-to-metal charge-transfer transition, as in
6 6
C D . The detailed study by means of UV-vis spectroscopy
revealed the distinct absorption bands in toluene for 1c (at 430
nm) and 2c (at 550 nm; ESI, Fig. S1A,B). The spectrum of 1c in
the 16ē arene ruthenium dithiolate complexes.[17] The HOMO-
LUMO gap for 2a and 2d are calculated in CH
.65 eV (Table 1), respectively, thus reflecting a significant red
shift for the absorption of 2d compared to 2a.
2 2
Cl as 2.05 and
1
2 2
CH Cl shows a very broad absorption band located in-between
these bands (at 520 nm; Fig. 3), thus suggesting the coexistence
of the dissociated and undissociated forms. The spectra are
temperature dependent in the range 190-290 K, showing
reversible changes with an isosbestic point at λ = 480 nm (Fig. 3).
The standard enthalpy and entropy for the dissociation process
Table 1. The HOMO, LUMO energies and the HOMO-LUMO gap for 2a and
d calculated in the gas phase and CH Cl solution in comparison to the
energy of the experimentally observed band (all in eV).
2
2
2
(
Scheme 2) were calculated from the Van‘t Hoff equation using
the T-dependent molar extinction coefficient of 2c at λ = 600 nm.
The dissociation process is exothermic (∆H = -5.0±0.2 kcal/mol),
with the cationic form dominating at low temperatures. The
unexpectedly large negative entropy change (∆S = -27.0±0.7
2a
2d
d
Gas phase
-7.45
CH
2
Cl
2
Gas phase
-7.37
2 2
CH Cl
d
HOMO
LUMO
Gap
-5.06
-3.01
2.05
2.32
-5.05
-3.40
1.65
2.10
cal/(mol·K)) for the dissociation process is attributed to the need
to re-organize the solvent dipoles around the charged species[
formed upon dissociation of 1c.
18]
-5.50
-5.92
1.95
1.45
Expt
It should be noted that the LUMO in complexes 2 is the orbital
available to accept the electron pair donated by the external
ligand (L or Cl) upon formation of the 18ē adduct. Hence, the
lower energy of the LUMO in 2d is responsible for the stronger
Scheme 2. Chloride dissociation from complex 1c.
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Chemistry - A European Journal
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suggested by the absorption band at 450 nm in their visible
spectra, even though the insufficient solubility of both compounds
did not allow verification of the temperature independence of
these spectra.
NMR study of 1a-d in apolar solvents. The chloride complexes
1
a-c show two inequivalent P-Ph groups in their RT-NMR spectra
in apolar solvents (benzene, toluene), meaning they exist as C
symmetric 18ē complexes on the NMR timescale.[15] We now
report that heating the solution of 1c in C to 338 K gives one
s
-
6
D
6
set of signals for these groups, which is indicative of exchange.
The coalescence of the two ortho-protons signals at δ 7.70 and
c
7.98 is observed at 323±5 K (T ) (ESI, Fig. S3). From this
temperature and from the chemical shift difference, the rate
-1
≠
Figure 3. UV-vis spectra of 1c in CH
2
Cl
2
at 190-298 K. The insert shows the
constant (kex = 380 s ) and activation free energy (∆Gex =
d
Van’t Hoff plot of RlnK vs 1/T.
1
5.2±0.3 kcal/mol) for the degenerative exchange process can be
[
19]
calculated.
For complex 1b with a less donor NPN-ligand,
coalescence for the P-Et methyl resonances at δ 0.40 and 1.39
could not be reached below the boiling point of toluene-d (ESI,
Fig. S4). However, we observed slow exchange of the ethyl
8
groups for this compound in C
6
[20]
D
6
and in toluene-d
8
by the 2D
1
EXSY H NMR method (Fig. 5), yielding the rate constants of
1
.8 s-1 and 1.4 s-1 at 293 K, respectively (Table 2, lines 3,7). The
activation parameters for the exchange process were obtained
from the temperature dependence of the exchange rate constants
≠
(
k
ex) in toluene-d
8
≠
in the range 230–315 K: ∆Hex = 8.4±0.2
kcal/mol and ∆Sex = -29.2±0.7 cal/(mol·K) (ESI, Fig. S5, Table
S1).
2
Figure 4. UV-vis spectra of 1b in MeNO at 250-310 K. The insert shows the
Van’t Hoff plot of RlnK vs 1/T.
d
Complex 1b
releasing p-tolyl substituents on the nitrogen atoms, does not
show any evidence of chloride dissociation in CH Cl . The UV-vis
,
bearing an NPN-ligand with the less electron-
2
2
spectrum is T-independent and only the undissociated 18ē
complexes is present in solution as shown by the band centered
at 450 nm (ESI, Fig. S2). However, the compound predominantly
+
-
exists as cationic complex [2b] Cl in solution of the highly polar
MeNO solvent, exhibiting a band with λmax = 515 nm (Fig. 4).
Analysis of the temperature dependence of this band in the range
50-310 K gave ∆H = 3.5±0.2 kcal/mol and ∆S = +0.3±0.6
cal/(mol·K). Compared to the dissociation of 1c in CH Cl , the
more positive dissociation entropy of 1b in MeNO is attributed to
a more efficient solvation of the charged species by MeNO . On
the other hand, both 1a and 1d, which contain the least donating
NPN-ligand, do not noticeably dissociate even in MeNO as
2
2
d
d
2
2
2
2
1
Figure 5. 2D EXSY H NMR of 1b in toluene-d
200 ms.
8
at 291K and the mixing time of
2
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-
1
≠
1
Table 2. Exchange rate constant kex (s ) and activation free energy ∆Gex (kcal/mol) for the P-bound substituent exchange in 1a, 1b and 1d from the 2D EXSY H
NMR investigations.
Complex
1a
Solvent
Additives
-
C(Ru), mM
C(add), mM
T, K
293
294
293
295
295
295
293
293
293
293
292
k
ex, s-1
∆Gex≠, kcal/mol
>18.5
17.4
1
2
3
4
5
6
7
8
9
1
1
C
C
C
C
6
D
6
D
6
D
6
D
6
6
6
6
10
10
20
20
40
8
<0.1
0.79
1.8
1a
H
-
2
O
10
5
1b
16.8
1b
H
-
2
O
>15
1.6
<15.7
17.0
1b
Toluene
Toluene
Toluene
1b
-
1.6
17.0
1b
-
46
10
10
10
10
1.4
17.0
1d
C
C
C
C
6
D
6
D
6
D
6
D
6
6
6
6
<0.1
0.72
2.6
>18.5
17.3
1d
H
H
2
O
O
0.7
2.4
0.7
0
1
1d
2
16.6
+
N Cl-
1d
Et
4
>11
<15.7
A large negative value of the activation entropy evidences a
highly ordered transition state in the exchange process. The
exchange between R’ and R’ substituents occurs via a
carried out in non-coordinating solvents and coordinating ligands
L are not present, the exchange in 1b most likely takes place via
+
-
a
b
the dissociated complex [2b] Cl , which requires an entropically
configuration inversion at the Ru atom, which can most easily be
envisaged by moving the chloride ligand from one coordination
unfavorable solvation of the chloride-ion by apolar molecules (Fig.
6A), similarly to the dissociation of 1c in CH Cl described above.
2 2
side to the opposite one by ligand exchange processes. Generally, We have further confirmed that the exchange rates are
-1
such ligand exchange may proceed either via a dissociative
mechanism with a cationic 16ē intermediate (pathway A in Fig.
independent on the concentration of 1b (1.6 s in both 40 mM and
8 mM toluene-d solutions at 295 K, Table 2, lines 5,6). The P-
8
6
A) or via a S
transition state (pathway B in Fig. 6B). In the latter case, however,
configuration inversion with exchange of the phosphorus R’ and
substituents could take place only when the entering ligand is
N
2-like associative mechanism through a 20e
substituent exchange for complexes 1a and 1d, which bear the
least electron-donating NPN-ligand, is not observed by 2D EXSY
1H NMR even at t = 1 s, hence the rates are slower than 0.1 s-1
a
m
R’
b
-
and the activation free energies (∆Gex≠) are greater than 18.5
Cl . Given that the NMR and UV studies outlined above were
kcal/mol.
a b
Figure 6. Dissociative (A) and associative (B) mechanisms for the exchange of the R’ and R’ groups in 1.
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In principle, addition of Cl- should either slow down or
accelerate the exchange depending on whether the mechanism
increase with the increase of the water content (Table 2, lines
9,10; ESI, Fig. S7). For the 1d sample with [H O] = 0.7 mM (0.07
2
+
-
is A or B, respectively. Addition of 0.07 equiv. of Et
4
N Cl to 1d
equiv.), the activation parameters could be derived from the
temperature dependence (291-335 K) of kex (ESI, Fig. S8, Table
S2). The calculated activation enthalpy[21] ∆Hex = 11.8±0.2
kcal/mol of the associative exchange can be used as a lower limit
-1
strongly enhances the exchange process (kex > 11 s ). This result
strongly suggests that the exchange occurs by the associative
mechanism B under these conditions (Table 2, line 11, and ESI,
Fig. S6). Therefore, it seems that both mechanisms A and B are
≠
≠
for the ∆Hex in dissociative exchange of 1d in the absence of
-
possible, the former in the absence of added Cl and the latter in
external ligands. It is pertinent to underline that water may have a
double role in the promotion of the associative chloride exchange:
its presence.
-
-
Assistance by an external ligand L may also result in Cl release.
as a ligand to replace Cl in the coordination sphere of the Ru
While the subsequent attack of the same Ru-L intermediate by Cl-
would not result in any P substituent exchange, attack of another
Ru-Cl complex achieves a degenerative self-exchange with
configuration inversion and P substituent exchange (Fig. 7). Thus,
the P-phenyl group exchange for these compounds becomes
atom, and as a proton donor to stabilize the dissociated Cl by H-
-
bonding. Interestingly, the effect of water for 1a is much smaller;
a rate constant of 0.79 s-1 is achieved only in the presence of an
equimolar amount of H
Me
2
O in C
6
D
6
. Perhaps the sterically bulky
-
C
6
6
ligand hampers the Cl or external ligand coordination thus
observable after adding water to the C
6
D
6
solutions (cf. lines 1,2
increasing the activation free energy.
for 1a and lines 8,9 for 1d) and the rate constants are found to
Figure 7. Associative exchange promoted by water-induced chloride dissociation.
We would like to underline that the activation enthalpy ∆Hex≠
for the exchange process in dissociative mechanism A should be
very close to the Ru–Cl bond dissociation enthalpy, ∆H
d
. The
latter depends predominantly on the Ru–Cl bond strength and on
the solvent polarity. Hence, the ∆H
d
value for complex 1c may be
≠
≠
≠
≠
estimated from its ∆G at 323 K as ∆H
d
~ ∆Hex = ∆Gex + T∆Sex
,
≠
where ∆Sex can be assumed to be close to that for 1b (-29.2
cal/(mol·K)). This gives an estimate for the ∆H
kcal/mol. Analogously, the ∆H of 1a and 1d can be estimated as
10 kcal/mol. Thus, we have proved that the Ru–Cl bond in 18ē
arene ruthenium iminophosphonamide complexes can dissociate
even in apolar solvents. The ∆H for 1a-d expectedly lowers with
an increase of the ligand donating ability: over 10 kcal/mol (1a,
d) > 8.4 kcal/mol (1b) > 5.7 kcal/mol (1c).
d
of 1c as ca. 5.7
d
>
Scheme 3.
d
2 2
The titration of 2a with MeCN in CH Cl at 296 K with UV-Vis
1
monitoring shows that the intensity of the 535 nm band does not
significantly change until >100 equiv. of MeCN are added (ESI,
Fig. S9A), while a similar amount of pyridine significantly
extinguishes this band to give rise a new band of the pyridine
adduct at 445 nm (ESI, Fig S9B). The estimated equilibrium
Coordination of ligands to the 16e cationic complexes 2
We have previously mentioned that the 16ē cationic complex
2a interacts with MeCN and CO, but failed to isolate these
unstable adducts.[15] We have now studied the activity of the 16ē
complexes 2 towards coordination of external ligands L (MeCN,
pyridine, CO) in detail by means of UV-Vis and NMR
spectroscopies (Scheme 3) to determine the thermodynamics of
the process and with regard to the conditions allowing isolation.
Since 1a is, among the 18ē chloride complexes 1, the least prone
to chloride dissociation, the corresponding 16ē complex 2a is
expected to display the highest affinity toward saturation by
coordination of L ligands. Hence, the coordination of relatively
weak donors MeCN and Py was studied for 2a only.
constants K
c
are <2 M-1 for 2a·MeCN and 32±7 M-1 (from UV-vis),
-1
3
7±1 M (from NMR, ESI, Fig. S9C) for 2a·Py, (ESI, Tables S3-
S5). The UV-vis measurements carried out for the 1:2 mixture of
a:Py in the temperature range 200-296 K show that 2a
2
dominates at room temperature, while the equilibrium shifts
towards formation of the 18ē adduct 2a·Py at lower temperatures.
The conversion becomes essentially complete below 220 K (Fig.
8
). The analysis of the Van’t Hoff’s plot yields ∆H
kcal/mol and ∆S = -36±2 cal/(mol·K). Thus, pyridine coordination
is moderately exothermic, but a large excess of pyridine is
c
= -12.4±0.5
c
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Chemistry - A European Journal
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required to observe coordination at room temperature because of
high association entropy. This is in sharp contrast with the
previously reported irreversible coordination of pyridine to the 16ē
t
arene ruthenium amidinate complex [(C
6
H
6
)Ru( BuN-C(Ph)-
N Bu}](BAr
4
).10
t
F
Figure 9. ORTEP diagram of the cation 3a. Ellipsoids are shown at the 50%
probability level. The hydrogen atoms and the anion are omitted for clarity.
Selected bond lengths (Å) and angles (°): Ru···Arene(centroid) 1.769(1), Ru–
C(O) 1.871(3), Ru–N1 2.112(2), Ru–N2 2.116(2), C–O 1.145(3), N1–Ru–N2
69.20(9), Ru–N1–P–N2 164.60(15), Σ(N1) 348.3(5), Σ(N2) 359.3(5).
Figure 8. UV-vis spectra of reversible coordination of pyridine to 2a in CH
at 200-296K. The insert shows the Van’t Hoff dependence of RlnK vs 1/T.
2 2
Cl
c
In comparison with acetonitrile and pyridine, carbon monoxide
is a stronger π-acceptor and reacts readily with 2a to give the CO
adduct 3a. However, the reaction is reversible and facile CO
decoordination occurs upon solvent evaporation to give back 2a.
2 2
Nevertheless, 3a could be isolated by precipitation from its CH Cl
solution upon addition of excess diethyl ether. Analogously, the
reaction of 2d with CO resulted in formation of 3d, which is stable
only under a CO atmosphere. This product was isolated, like 3a,
2 2
by using CO-saturated CH Cl solution and diethyl ether.
Although 3a and 3d slowly evolve CO in the solid state under
vacuum, satisfactory elemental analyses were obtained for both.
It should be noted that 3a is stable in a CO-saturated solution,
whereas 3d degrades within days to unknown arene-free
carbonyl complexes, perhaps similar to the previously observed
ones
resulting
from
the
decomposition
of
[(p-
Figure 10. ORTEP diagram of the cation 3d. Ellipsoids are shown at the 50%
probability level. The hydrogen atoms and the anion are omitted for clarity.
Selected averaged bond lengths (Å) and angles (°): Ru···Arene(centroid)
].[22] The molecular structures of 3a,d
Cymene)Ru(CO)(SXyl)
2
were determined by single crystal X-ray diffraction (ESI, Table S6).
Selected structural parameters and views of the molecules are
shown in Figures 9 and 10.
1.768(3), Ru–C(O) 1.879(9), Ru–N1 2.095(7), Ru–N2 2.120(6), C–O 1.145(10),
N1–Ru–N2 68.9(3), Ru–N1–P–N2 165.8(4), Σ(N1) 353.7(13), Σ(N2) 355.3(14).
Complexes 3a and 3d are the first crystallographically
2
characterized arene ruthenium carbonyl derivatives with any κ -
N,N-anionic chelate ligand. The asymmetric unit of 3d contains
two independent molecules, which exhibit identical metric
parameters within experimental error. Both complexes exhibit a
three-legged piano stool geometry with a pseudo octahedral
configuration of the ligands around the ruthenium atom. The
coordinated arene adopts a nearly staggered (3a) or eclipsed (3d)
conformation relative to the Ru-CO axis, with C4–
Arene(centroid)–Ru–CO angles of 25.7° and 5.9–6.4°,
respectively. The presence of the CO ligand significantly
increases the Ru–Arene(centroid) distance by ~0.1 Å in both 3a
and 3d relative to 2a (1.662(2) Å) and 2d. The Ru–C(arene)
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Chemistry - A European Journal
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distances vary in the range 2.208–2.333(3) Å with the longest
bonds being trans to the CO ligand. The C–C bonds length
(
1.389(12)–1.452(4) Å) in the coordinated arene slightly alternate
with the shortest C–C bond (1.389–1.403 Å) located trans to the
CO ligand. A similar Ru–Arene(centroid) (1.810 Å), Ru–C(O)
(
1.846(4) Å) and carbonyl C–O (1.133(7) Å) distances, as well as
elongations for the two Ru–C(arene) bonds trans to CO (2.389–
2
.396 Å) were previously reported for the arene ruthenium
6
)] (4).[17]
dithiolate carbonyl complex [(η -C
6
Me
6
)Ru(CO)(S
2
C
6
H
4
The Ru–N bonds are shorter than those in the neutral 18ē
complexes 1a-d by ca. 0.04 Å, reflecting the presence of the
positive charge, but longer (by 0.05-0.08 Å) than in the 16ē
complexes 2a-d, in which they are strengthened by π-donation
from the NPN-ligand. The chelate N1–Ru–N2 angles in 3a and 3d
are similar to those of the other 18ē NPN-complexes 1a-d.
However, unlike in the related chloride complexes 1a and 1d, the
Ru–N1–P–N2 metallacycles in 3a and 3d are folded by 13–15.6°
from planarity at the N1···N2 hinge and the nitrogen atoms (N1 in
3a; N1 and N2 in 3d) are noticeably pyramidalized as shown by
the Σ(N) parameter. There are several close H···F contacts
-
between the cation and the PF
6
anion in both structures, although
none of these is shorter than the sum of the van der Waals radii
of H and F (2.56 Å).[23]
Figure 11. ORTEP diagram of the cation 3c. Ellipsoids are shown at 30%
probability level. The hydrogen atoms and the anion are omitted for clarity.
Selected bond lengths (Å) and angles (°): Ru···Arene(centroid) 1.828(1), Ru–
N1 2.107(2), Ru–C(O)N 2.042(3), C=O 1.211(4), N–C(O) 1.414(3), Ru–C(O)
Complexes 3a and 3d are sufficiently stable in concentrated
solutions to allow recording their NMR spectra, although the
fraction of the corresponding 16ē complexes increases with time.
The 31P NMR resonance (δ 61.7 for 3a and δ 60.2 for 3d) is
downfield shifted by ca. 10 ppm relative to the corresponding 16ē
1.859(3), C–O 1.143(4), N1–Ru–C(O) 83.15(10), Σ(N1) 349.7(5), Σ(N2)
359.3(6).
cationic complexes 2a and 2d. In the H and 13C{ H} NMR spectra
recorded in CDCl there are two sets of signals for the
magnetically inequivalent phenyl groups at the phosphorus atom,
as expected for the -symmetric complexes, hence the
1
1
The overall geometry of 3c is similar to that of 3a,d except for
3
the expanded metallacycle with a CO group. The addition of two
CO molecules leads to a significant increase of the Ru–
Arene(centroid) distance relative to 2c by ca. 0.18 Å as a result of
elongation of the Ru–C(arene) bonds trans to the terminal CO
(2.299–2.312(3) Å) and to the carbamoyl C=O group (2.373–
2.381(3) Å). The arene C–C bonds trans to the terminal CO
C
s
decoordination of CO is a slow process with a relatively high
activation barrier. The resonance of the coordinated CO ligand in
the 13C NMR spectra is observed at high field (δ 199.2, 193.8), as
is typical of terminal linear coordinated CO ligands (cf. to δ 197.8
for 4[17] and δ 203-208 reported for the cyclopentadienyl
ruthenium complexes with N,N-ligands).[9, 24]
(
1.404(6) Å) and to C=O group (1.392(5) Å) are shorter than the
other four bonds (1.417–1.438(5) Å). Similarly to 3a and 3d, the
terminal carbonyl group is linear. The carbamoyl C=O and C–N
bonds have similar length to or are slightly longer than those in
organic amides. The carbamoyl N2 atom is planar, while N1 is
considerably pyramidalized as in the corresponding 18ē chloride
complex 1c. There are two intermolecular close contacts in the
Both carbonyl adducts 3a and 3d exhibit strong CO stretching
-
1
-
vibration band in the IR spectrum at 1984 cm (3a) and 2012 cm
(
1
3d). The higher νCO in 3d evidences weaker Ru-CO π-back-
Me
bonding relative to 3a that possesses the electron-richer C
6
6
arene. These frequencies are substantially lower than those of the
more electron-deficient arene ruthenium amidinate carbonylic
structure of 3c that fall below the sum of the van der Waals
[23]
radii, implicating hydrogen atoms of the C
6
Me
6
ligand and either
6
t
}](BArF
) (νCO = 2050 cm-
complex [(η -C
1),[10] but closer to those of the arene ruthenium complex with
dianionic ditiolate ligands
Me )Ru(CO)(SXyl)
6
H
6
)Ru(CO){PhC(N Bu)
2
4
-
a PF
6
F atom or the carbamoyl oxygen atom, H(8A)···F (2.269 Å)
and H(10B)···O(2)C (2.418 Å), respectively.
-
1
[17]
[(η6-
13
1
4
=
(νCO
1965 cm )
=
1951 cm ),
The C{ H} NMR spectrum of 3c reveals two signals
-
1 [22]
C
6
6
2
]
(νCO
and of the
corresponding to carbonyl C nuclei: a singlet at δ 198.2 and a
doublet at δ 192.8 (2JСР = 19.6 Hz). All the N- and P-substituents
in 3c are inequivalent and give rise to two sets of signals for both
cyclopentadienyl complex with neutral κ -N,N-ligand [(η5-
2
-1 [24]
C
5
H
5
)Ru(CO)(TMEDA)](BAr
4
) (νCO = 1968 cm ).
1
13
1
Surprisingly, bubbling CO into the solution of 2c yielded a
methyl and phenyl groups in the H and C{ H} spectra. In the IR
stable product, 3c, resulting from the addition of two CO
molecules, one of which has inserted into one of the two Ru–N
bonds. The product has been fully characterized, including by
single crystal X-ray diffractometry (Figure 11, Table S6 in ESI).
spectra 3c shows two strong carbonyl bands νCO at 1984 cm-1
metal bound CO) and at 1644 cm-1 (carbamoyl C=O), the latter
(
frequency being typical of organic amides.
Apparently, the carbonylation of 2c is a two-step reaction
involving: 1) coordination of a first CO molecule to give an
intermediate C, which is structurally similar to 3a,d; and 2)
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insertion of the terminal CO into a Ru–N bond and subsequent
occupation of the resulting vacant site at the ruthenium atom by a
second CO molecule (Scheme 4). This conclusion is further
supported by the results of an IR spectroscopic monitoring at low
temperatures (Fig. 12). Bubbling CO at -40°C for 10 s fully
converts 2c to an orange complex characterized by a strong CO
The latter is unstable: even at -40°C and in the absence of
additional CO it slowly disappears to be replaced by 3c. The
coordination of the first CO molecule is reversible, hence
dissociation from the mono-adduct C provides the needed CO for
the second carbonylation step. The rearrangement is complete
within a few minutes at low temperatures and yields a 1:1 mixture
of 2c and 3c, which were isolated upon evaporation of the solvent.
-1
band at 1975 cm , which can be attributed to the mono-adduct C.
Scheme 4.
C–O is 170.2°), and the Ru–CO and C–O bond lengths are 1.836
Å and 1.159 Å, respectively.
Conclusions
Our detailed spectroscopic study has allowed to investigate
the stabilization of the coordinative unsaturation in half-sandwich
ruthenium iminophosphonamide complexes depending on the
1
N-,P-substituents, arene and other co-ligands. By 2D EXSY H
NMR spectroscopy we have proven that the dynamic exchange
process observed for chlorides 1a-d is attributed to the
dissociation of the chloride ligand via a 16ē intermediate in both
polar and apolar solvents. The chloride dissociation enthalpy
Figure 12. The reaction of 2c with CO monitored by IR. The sample was
(∆H
coordination enthalpy (∆H
d
) determined for the 18ē chloride complexes 1a-d and the Cl-
) to the 16ē complex 2a quantitatively
dissolved in CH
recorded (a) immediately after the preparation, (b) after 40
temperature, (c) after 5 min of keeping (a) at -40°C, (d) after evaporation of (c)
and redissolution in CH Cl
2
Cl
2
at -40°C and CO was bubbled for 10 s. The spectra were
c
s
at room
estimate the stabilization effect of the NPN ligand, which is mostly
provided by highly localized negative charges at the nitrogen
atoms via additional π-donation. Hence the NPN ligands with N-
alkyl groups destabilize the 18ē complexes and compensate the
metal electron deficiency much more effectively than the NPN
ligands with N-aryl groups. Thus, the N-Me chloride complex 1c
dissociates exothermically (∆H = -5.0 kcal/mol) even in CH Cl ,
d 2 2
whereas the dissociation is always endothermic for the N-Tol
complexes (1a, 1b and 2d), even in polar nitromethane. On the
other hand, the less donating arene ligand (p-cymene vs C Me )
6 6
2
2
.
The peculiarity of the mono-carbonyl intermediate C is the
high nucleophilicity of the nitrogen atoms, which is related to the
presence of more electron-donating alkyl substituents. Although
facile CO-insertion into M–N bonds is a known phenomenon for
certain metal aminopyridinates,[25] triazenides,[26] amidinates,[27-30]
and aminophosphines[31] this reaction has not been previously
affects the stability of the 18ē complexes counterintuitively: it
destabilizes the carbonyl adducts due to the lack of electron
density provided for π-backdonation (3d vs 3a), but enhances the
stability of the chloride complex (1d vs 1a) due to lower energy of
the orbital corresponding to Ru-Cl bond. The coordination of
ligands to 16ē complexes 2 appears to be unambiguously
exothermic, while the highly negative association entropy makes
the 18ē complexes stable only at low temperatures. Nevertheless,
stronger π-acceptors (CO > pyridine > MeCN) give more stable
adducts due to significant contribution of π-backdonation to Ru-L
bonding; this fact allowed us to isolate and structurally
reported to the best of our knowledge for arene ruthenium
complexes. The process that most resembles the formation of 3c
involves a carbene insertion into a Ru–N bond in the arene
i
ruthenium amidinate complex [(C
6
Me
6
)Ru{(PrN)
2
CMe}](PF
6
),
i
followed by CO coordination to give [(C
6
Me
6
)Ru(CO){(PrN)-
i
) (5).[32] The spectral and structural data
CMe(NPr)CHSiMe }](PF
3 6
of 5 are similar to those of 3c: the νCO is observed at 1963 cm-1
and the carbonyl resonance appears at δ 203 in the 13C NMR
spectrum; the Ru–Arene(centroid) distance is 1.828 Å with the
elongation of the Ru–C(arene) bonds trans to CO and to the
inserted carbene to 2.320–2.362 Å; the CO ligand is linear (Ru–
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Chemistry - A European Journal
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FULL PAPER
6
characterize complexes 3a and 3d, which are rare examples of
cationic 18ē arene ruthenium carbonyl complexes. The
unexpectedly facile insertion of CO into the Ru–N bond observed
in the 18ē adduct 2c·CO to give the carbonyl-carbamoyl complex
Synthesis of [(η -p-Cymene)Ru{Ph
solution of 1d (0.39 g, 0.59 mmol) in CH
.62 mmol) was added, causing the color to immediately change from red
2
P(N-p-Tol)
2
}](PF
6
)
(2d)
.
To
(0.16 g,
a
2
Cl (15 ml), solid AgPF
2
6
0
to deep violet. The reaction mixture was stirred for 2 h and then filtered
through a bed of Celite. The solvent was removed under reduced pressure,
and the residue was dried in vacuo to give violet-black 2d. Yield 0.41 g
3c proves that arene ruthenium iminophosphonamide complexes
can react in diverse manners and suggests that they have
potential for application in organic synthesis and (bifunctional)
catalysis. Further investigation of these complexes in catalytic
transfer hydrogenation is in progress and will be reported soon.
(
91%). Anal. calcd for C36
55.47; H, 4.99%. 31P NMR (CDCl ): δ 71.3 (s, PPh ), -144.1 (sept, J
PF
=
38 6 2 2
H F N P Ru: C, 55.74; H, 4.94%. Found: C,
3
2
712, PF -
7.47 (m, 4H, o-HPh), 7.02 (d, 3
1
6
3
). H NMR (CDCl ): δ 7.65 (m, 2H, p-HPh), 7.52 (m, 4H, m-HPh),
J
HH = 8.0, 4H, C
6
H
4
), 6.84 (dd, 3
J
HH = 8.0,
4JHP = 1.2, 4H, C
.8, 2H, C
(Cym)), 2.68 (sept, 3JHH = 6.8, 1H, CHMe
MeCym), 2.25 (s, 6H, MeTol), 1.31 (d, 3JHH = 6.8, 6H, CHMe
H
6 4
), 5.88 (d, JHH = 6.8, 2H, C
3
(Cym)), 5.84 (d, JHH
3
=
6
H
4
6
H
6 4
2
), 2.26 (s, 3H,
). 13C NMR
): δ 144.1 (d, 2JСР = 3.6, i-CTol(N)), 134.4 (d, 4JCP = 2.2, p-CPh), 134.1
s, i-CTol(Me)), 132.4 (d, 2
CP = 10.3, о-CPh), 130.2 (s, β-CHTol), 129.5 (d,
2
Experimental Section
(CDCl
3
(
J
General procedures. All manipulations were carried out using standard
Schlenk techniques under an atmosphere of dry argon. Absolute solvents
3
СР = 12.5, m-CPh), 124.7 (d, JCP = 89.4, i-CPh), 123.7 (d, 3
1
J
J
СР = 8.0, α-
CHTol), 99.6 (s, i-CCym), 89.6 (s, i-CCym), 81.0 (s, CHCym), 78.7 (s, CHCym),
1.8 (s, CHMe ), 22.8 (s, СHMe ), 20.9 (s, MeTol), 19.7 (s, MeCym). UV-vis
; λmax, nm; ε, M-1 cm ): 590 (1880).
CH Cl
were used for both synthesis and spectroscopic studies; solvents were
3
(
2
2
purified by standard methods and distilled prior to use. The H, 31P and 13
1
C
-1
2
2
NMR spectra were obtained on Bruker Avance 600 or Bruker Avance 400
spectrometers and referenced to the residual signals of deuterated solvent
Reaction of 2a,2c,2d with CO. General procedure. A stream of CO was
slowly bubbled through a stirred solution of 2a (0.12 g, 0.15 mmol) in
(1
were recorded on a Varian Cary 50 WinUV spectrometer in quartz cells (l
2.2 mm or 10 mm). The IR spectra were obtained on a Fourier
H and 13C), and to 85% H (31P, external standard). The UV spectra
3 4
PO
CH
orange. The product was precipitated with Et
crystalline solid, which was filtered off and dried in vacuo for 1 hr. Yield
Cl
2 2
(5 mL) for 10 min. The color quickly changed from deep violet to
=
2
O (20 ml) as a yellow-orange
spectrometer Nicolet 6700 in KBr cells (l = 0.514 mm). The elemental
analyses were carried out on a Carlo Erba 1106 CHN analyzer. The
0
.12 g (96%). Anal. calcd for C39
H
42
F
6
N
2
OP
2
Ru: C, 56.32; H, 5.09%.
following compounds were prepared according to described procedures:
31
Found: C, 56.34; H, 4.95%. P NMR (СD
Cl
2 2
2
): δ 61.7 (s, PPh ), -144.5
6
,[33] Ph
P(N-p-Tol)(NH-p-Tol) (A),[15] 1a-c, 2a-c.[15]
[
(η -p-Cymene)RuCl
2
]
2
2
sept, 1JPF = 713, PF -
1
3
(
6
). H NMR (СD
2
Cl
2
): δ 7.84 (t, JHH = 8.6, 1H, p-HPh),
7
2
J
.81 (dd, 3JHP = 12.8, 3JHH = 8.0, 2H, o-HPh), 7.69 (dt, 3JHH = 7.2, 4JHP = 3.2,
H, m-HPh), 7.48 (dt, 3JHH = 7.2, 5JHP = 1.6, 1H, p-HPh’), 7.24 (dt, 3JHH = 8.0,
6
Synthesis of [(η -p-Cymene)RuCl{Ph
2
P(N-p-Tol)
2
}] (1d). To a solution
of A (0.79 g, 2.00 mmol) in benzene (60 mL) a 2.0 M solution of NaHMDS
in THF (1.10 mL, 2.20 mmol) was added and the resulting solution was
stirred for 2 h. Then solid [(η -p-Cymene)RuCl
added and the reaction mixture was stirred overnight. The reaction mixture
was filtered and the solvent from the filtrate was removed under reduced
4
HP = 3.2, 2H, m-HPh’), 7.19 (dd, 3JHP = 10.8, 3JHH = 8.0, 2H, o-HPh’), 6.90
d, 3JHH = 8.0, 4H, C
(Tol)), 6.46 (dd, 3
HH = 8.0, 4
(
H
6 4
J
JHP = 2.0, 4H,
6
2
]
2
(0.61 g, 1.00 mmol) was
). 13C NMR (СD
C
H
6 4
(Tol)), 2.21 (s, 6H, MeTol), 2.11 (s, 18H, C
6
Me
6
2 2
Cl ): δ
2
1
199.2 (s, Ru-CO), 140.8 (d, JСР = 2.2, i-CTol(N)), 135.8 (d, JСР = 97.2, i-
Ph), 134.9 (d, 4
СР = 2.6, p-CPh), 133.6 (d, 4JСР = 2.7, p-CPh’), 132.9 (d,
C
J
pressure. The residue was washed with hexane (2x10 mL), Et
and then recrystallized from hot benzene (20 ml). The dark-red crystalline
was filtered off, washed with Et O (5 mL) and dried in vacuo. Yield 1.00 g
88%). Anal. calcd for C36
2
O (2x5 mL),
2
2
J
СР = 9.3, o-CPh), 132.7 (d, JСР = 11.0, o-CPh’), 132.8 (s, i-CTol(Me)), 130.4
4
d, JСР = 1.3, β-CHTol), 130.0 (d, 3JСР = 12.1, m-CPh), 128.9 (d, 3JСР = 11.4,
(
2
m-CPh’), 128.3 (d, JСР = 83.3, i-CPh’), 126.0 (d, JСР = 7.0, α-CHTol), 110.3
1
3
(
2
H38ClN PRu: C, 64.90; H, 5.75%. Found: C,
; λmax, nm; ε, M-
, ν, cm ): 1984 (RuСO).
(
s, C
6
Me
6
), 20.8 (s, MeTol), 17.1 (s, C
6
Me
6
). UV-vis (CH
Cl
2 2
4.85; H, 5.84%. 31P NMR (CDCl
): δ 43.8 (s, PPh
). H NMR (CDCl
1
6
7
4
3
2
3
): δ
1
-1
-1
cm ): 450 (100, shoulder). IR (CH Cl
2
2
.87 (dd, 3JHP = 10.8, 3JHH = 8.0, 4H, o-HPh), 7.50 (m, 2H, p-HPh), 7.39 (m,
H, m-HPh), 6.90 (d, 3
J
HH = 8.0, 4H, C
H
(Tol)), 6.82 (d, 3
(Cym)), 5.41 (d, 3
JHH = 8.4, 4H,
6
4
Analogously, from 2c (0.10 g, 0.15 mmol) in CH
was obtained as a stable yellow crystalline solid. Yield 0.10 g (95%). Anal.
calcd for C28
2 2
Cl (3 ml), complex 3c
C
C
6
H
4
(Tol)), 6.31 (d, 3
J
HH = 5.6, 2H, C
6
H
4
J
HH = 5.6, 2H,
3
H
6 4
(Cym)), 2.89 (sept, JHH = 6.8, 1H, CHMe
2
), 2.19 (s, 6H, MeTol), 2.11
H
34
F
6
N
2
O
2
P
2
Ru•H
2
O: C, 46.35; H, 5.00%. Found: C, 46.49; H,
(
s, 3H, MeCym), 1.21 (d, 3JHH = 6.8, 6H, CHMe
2
). 31P NMR (C
6 6
D ): δ 42.9.
.00%. 31P NMR (CD
H NMR (CD
), -144.5 (sept, 1JPF = 713, PF
-).
5
1
2
Cl
2
): δ 55.2 (s, PPh
2
6
1
3
H NMR (C D
6 6
): δ 8.03 (m, 4H, o-HPh), 7.27 (d, JHH = 7.8, 4H, C
(m+p)-HPh), 6.93 (d, 3JHH = 7.8, 4H, C
m+p)-HPh’), 5.05 (d, JHH = 6.0, 2H, C
6 4
H (Tol)),
): δ 7.83 (ttd, JHH = 7.8, 4JHH = 1.8, 5JHP = 1.2, 1H, p-HPh),
3
2
Cl
2
7
(
.22 (m, 3H
,
6
H
4
(Tol)), 6.75 (m, 3H,
.75 (ttd, 3JHH = 7.8, 4JHH = 1.2, 5JHP = 1.2, 1H, p-HPh’), 7.71 (dt, 3JHH = 7.8,
J
7
4
3
3
6
H
4
(Cym)), 4.87 (d, JHH = 6.0, 2H,
HP = 3.6, 2H, m-HPh), 7.63 (ddd, 3JHP = 12.6, 3JHH = 7.8, 4JHH = 1.2, 2H,
3
C H
6 4
(Cym)), 2.88 (sept, JHH = 6.6, 1H, CHMe
2
), 2.15 (s, 6H, MeTol), 1.86
). 13C NMR (CDCl
): δ 145.8
СР = 4.4, i-CTol(N)), 133.4 (br.s, о-CPh), 131.9 (d, 4JСР = 2.7, p-CPh),
29.0 (s, β-CHTol), 128.2 (d, 3
СР = 11.2, m-CPh), 127.5 (s, i-CTol(Me)),
22.9 (d, 3
СР = 9.7, α-CHTol), 102.0 (s, i-CCym), 94.8 (s, i-CCym), 80.5 (s,
o-HPh), 7.60 (dt, 3JHH = 7.8, 4JHP = 3.6, 2H, m-HPh’), 7.42 (ddd, 3JHP = 12.6,
3JHH = 7.8, 4JHH = 1.2, 2H, o-HPh’), 2.73 (d, 3JHP = 8.4, 3H, NMe(CO)), 2.64
(
(
s, 3H, MeCym), 1.05 (d, 3JHH = 6.8, 6H, CHMe
d, 2
2
3
J
d, 3JHP = 17.4, 3H, NMe), 2.24 (s, 18H, C
). 13C NMR (CD
(
(
1
1
1
6 6 2 2
Me Cl ): δ 198.2
1
1
J
s, Ru-CO), 192.8 (d, 2JСР = 19.6, NC=O), 135.1 (d, 4JСР = 2.4, p-CPh),
J
35.0 (d, 4JСР = 2.4, p-CPh’), 133.6 (d, 2JСР = 10.6, o-CPh’), 132.6 (d, 2JСР
0.6, o-CPh), 130.3 (d, JCP = 12.8, m-CPh), 130.2 (d, JСР = 12.6, m-CPh’),
24.2 (d, 1JCP = 112.2, i-CPh), 122.2 (d, 1
CP = 98.6, i-CPh’), 113.4 (s, i-
=
CHCym), 79.6 (s, CHCym), 30.9 (s, CHMe
8.9 (s, MeCym). 13C NMR (C
2
), 22.5 (s, СHMe
2
), 20.5 (s, MeTol),
3
3
1
(
6
D
6
): δ 146.9 (s, 2JСР = 4.2, i-CTol(N)), 136.5
J
d, 1JCP = 95.1, i-CPh), 135.0 (d, JCP = 11.0, o-CPh), 132.6 (d, JСР = 9.8, o-
2
2
), 39.3 (d, 3JСР = 4.2, NMe), 29.3 (d, JСР = 8.4, NMe(CO)), 17.0 (s,
3
C
C
6
Me
6
C
Ph’), 132.0 (d, 4
J
СР = 2.7, p-CPh), 131.8 (d, 4
J
СР = 2.9, p-CPh’), 130.2 (d,
3
-1
6
Me
6 2 2
),. IR (CH Cl , ν, cm ): 1983 (RuCO), 1644 (RuC(O)N).
1
J
CP = 84.0, i-CPh’), 129.4 (s, β-CHTol), 128.6 (d, JСР = 12.5, m-CPh), 128.5
s, i-CTol(Me)), ~127.7 (overlapped, m-CPh’), 123.9 (d, 3JСР = 9.7, α-CHTol),
02.4 (s, i-CCym), 94.8 (s, i-CCym), 80.7 (s, CHCym), 79.4 (s, CHCym), 31.2 (s,
), 22.5 (s, СHMe
max, nm; ε, M-1 cm ): 450 (450, shoulder).
(
1
Analogously, carbonylation of 2d (0.11 g, 0.14 mmol) gave a red solution
of 3d. The product was precipitated by Et O (20 ml) saturated with CO,
filtered and dried in vacuo for 30 min. Yield 0.09 g (82%). Anal. calcd for
2
CHMe
λ
2
2
), 20.7 (s, MeTol), 18.8 (s, MeCym). UV-vis (CH
2 2
Cl ;
-1
C
37
H
38
F
6
N
2
OP
NMR (CDCl
CDCl
2
Ru: C, 55.29; H, 4.77%. Found: C, 55.05; H, 4.86%. 31P
-
). 1H NMR
3
): δ 60.2 (s, PPh
2
), -144.2 (sept, 1
J
PF = 713, PF
6
): δ 7.93 (dd, 3JHP = 12.4, 3JHP = 7.2 , 2H, o-HPh), 7.80 (t, JHH = 7.2,
3
(
3
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Chemistry - A European Journal
10.1002/chem.201702862
FULL PAPER
ꢟ
ꢓꢥꢦ
ꢟ
ꢧꢕꢨ
1
1
H, p-HPh), 7.73 (dt, 3JHH = 7.6, 4JHP = 2.8, 2H, m-HPh), 7.50 (t, 3JHH = 7.2,
ꢣꢤ
ꢁ
(5)
ꢟ
ꢓꢥꢧꢕ
H, p-HPh’), 7.35 (dd, 3JHP = 10.2, 3JHH = 7.2, 2H, o-HPh’), 7.30 (dt, 3JHH
=
.6, 3
HH = 8.0, 4H, C
HH = 3.2, 2H, m-HPh’), 6.87 (d, 3
(Tol)), 6.29 (br. s, 4H, C
ꢟ
ꢓꢥꢩꢦ
7
J
6 4
JHH = 8.0, 4H, C H (Tol)), 6.51 (d,
ꢣ ꢁ ꢟ
(6)
ꢟ
ꢓꢥꢦ ꢩ
ꢟ
3
3
J
H
6 4
6 4
H
(Cym)), 2.65 (sept, JHH
=
=
=
3
6
6
3
1
=
.8, 1H, CHMe
.8, 6H, CHMe
.4, i-CTol(N)), 134.5 (d, 4JСР = 2.6, p-CPh), 133.7 (d, 4
32.7 (d, JCP = 10.3, o-CPh), 132.2 (d, JСР = 11.3, o-CPh’), 131.1 (d, JСР
0.8, i-CTol-Me), 130.0 (s, ββ CHTol), 129.9 (d, 3JСР = 12.3, m-CPh), 129.0 (d,
2
), 2.18 (s, 6H, MeTol), 2.11 (s, 3H, MeCym), 1.22 (d, JHH
ꢪꢈꢫ ꢌ ꢁ ꢢ ꢈꢫ ꢌꢟꢂꢠēꢕ ꢝ ꢢꢂꢡēꢈꢫ ꢌꢟꢂꢡēꢕ (7)
ꢬ
ꢂꢠē
ꢬ
ꢬ
). 13C NMR (CDCl
2
2
3
): δ 193.8 (s, Ru-CO), 143.1 (d, JСР
J
СР = 2.4, p-CPh’),
ꢪꢈꢫꢠꢭꢭ
ꢌ
2
2
5
ꢟ
ꢂꢠē~ꢢ
(8)
ꢂꢠēꢈꢫꢠꢭꢭꢌꢕ
In the titration of 2a with L, the initial concentrations c016ē of 2a for every i-
titration point was corrected for the dilution factor (ꢟ ꢭꢂ ꢠēꢈꢬꢌ) according to
Equation (9).
3
СР = 11.7, m-CPh’), 128.6 (d, 1JCP = 105.2, i-CPh), 126.8 (d, 1JCP = 80.6, i-
J
3
C
Ph’), 123.4 (d, JСР = 8.6, α-CHTol), 121.2 (s, i-CCym), 119.5 (s, i-CCym), 97.8
(s, CHCym), 95.2 (s, CHCym), 32.1 (s, СHMe
2
), 22.7 (s, СHMe
, ν, cm ): 2012 (RuCO). UV-vis (CH
2
), 20.6 (s,
-1
MeTol), 19.5 (s, MeCym). IR (CH
Cl
2 2
2 2
Cl ;
ꢭ
ꢮ
λ
max, nm; ε, M-1 cm ): 480 (140).
-1
ꢟ
ꢭ
ꢈꢬꢌ ꢁ ꢟꢭ
ꢂꢠē
(9)
ꢂꢠē
ꢂꢠē
ꢭ
ꢮ
ꢊꢮ
ꢩ
ꢂꢠē
EXSY 1H NMR. 2D 1H- H EXSY spectra were collected on a Bruker
Avance 600 spectrometer at 25°С using the standard Bruker library
noesygpph pulse program. At least three experiments with different values
1
where ꢮꢭ and ꢮꢩ are the initial volume of 2a solution and the added
volume of L, correspondingly.
ꢂꢠē
of the mixing time t
resulting in sufficiently large exchange cross-peaks without significant
relaxation contribution. The rate constants k = kAB + kBA for the A ↔ B
exchange reactions were calculated using simple two-site model using
Equations (1), (2), where kAB and kBA are the rate constants of the direct
and inverse reactions, IAB, IBA and IAA, IBB are the cross-peak and the
diagonal peak integral intensities, respectively. In case of exchange
between equally populated states (kAB = kBA), the exchange rate constant
is kex = k/2.
m
were performed to find an optimum mixing time,
Computational details. The geometry optimizations were carried out with
the PBE functional and def2-TZVP[34] basis set for all atoms without any
symmetry restrictions in the gas phase using the Gaussian09 package.[35]
The obtained stationary points were confirmed to have no imaginary
frequencies. The orbital energies were computed with the SMD[36] solvent
[
19]
model using the gas phase optimized geometry.
X-ray crystal structure determination. Single crystals 1d, 2d, 3a, 3c, 3d
were obtained by slow diffusion of Et
of 3d the solution was saturated with CO. The data collection for samples
d and 2d were performed on a Bruker APEX DUO diffractometer, and
2 2 2
O into CH Cl solutions; in the case
ꢂ
ꢉꢊꢂ
ꢉꢋꢂ
ꢀ
ꢁ ꢃ ꢅꢆꢇꢈ
ꢌ
(1)
1
ꢄ
those for 3a, 3c and 3d on a Bruker SMART APEX II diffractometer, both
equipped with an Apex II CCD detector and operating with MoKα radiation
ꢍ
ꢎꢎꢊꢍꢏꢏ
ꢉ ꢁ
(2)
ꢍꢎꢏꢊꢍꢏꢎ
(
λ = 0.71073 Å). Frames were integrated using the Bruker SAINT software
[
37]
The activation free energy ∆G≠ was calculated from the Eyring equation
package
by a narrow-frame algorithm. A semiempirical absorption
[
38]
≠
≠
correction was applied with the SADABS program using the intensity
data of equivalent reflections. The structures were solved with direct
methods and refined by the full-matrix least-squares technique against
F2hkl in anisotropic approximation with the SHELX[39] software package.
The positions of the hydrogen atoms were calculated, and all hydrogen
atoms were refined using the riding model with 1.5Ueq(Cm) and
1.2Ueq(Ci), where Ueq(Cm) and 1.2Ueq(Ci) are respectively the
equivalent thermal parameters of methyl and all other carbon atoms to
which corresponding H atoms are bonded. The structure of 1d contains an
(3) and the activation enthalpy ∆H and entropy ∆S were derived by linear
fitting of Rln(kex/T) plotted vs. 1/T according to the equation (4).
ꢐꢑ ꢁ ꢒꢓꢔꢕꢖꢀ
ꢗꢘ
ꢙ
∆
(3)
ꢀ ꢔ
ꢚ
ꢜ
ꢀ
ꢗꢘ
∆ꢛ
ꢔ
ꢀ
ꢚ
ꢓꢕꢖ ꢔ ꢁ ꢒ
ꢝ ∆ꢞꢑ ꢝ ꢓꢕꢖ ꢙ (4)
UV-Vis spectroscopic study. The UV-vis monitored titrations were
performed in a 10 mm quartz cell, while the spectra at low temperatures
were recorded in a 2.2 mm quartz cell. In most experiments the initial
concentrations of ruthenium complex (c0Ru) were 2.5×10-3 M, while in other
cases c0Ru was in the range 5–8×10-4 M. Neat MeCN and pyridine were
2 2
interstitial CH Cl molecule, which is disordered about an inversion center.
In the structure of 3d two crystallographically independent cations and
anions are related by an approximate non-crystallographic inversion
center. Detailed crystallographic information is given in Table 4.
Crystallographic data have been deposited to the Cambridge
Crystallographic Data Centre, CCDC numbers 1536180-1536184. Copies
used for the titrations. To calculate the dissociation constants K
d
for 1b,c
(
Eq. 5) and the constant K for the ligand coordination to 2a (Eq. 6), the
c
equilibrium concentrations of the 16ē (ꢟꢂꢠē) and 18ē (ꢟꢂꢡē) complexes were
obtained from the UV-vis spectra according to the Beer-Lambert law. The
of
the
data
can
be
obtained
free
or
of
charge
via
http://www.ccdc.cam.ac.uk/data_request/cif,
by
e-mailing
absorption of the equilibrium mixture D(λ
i
) was measured at a wavelength
(Eq. 7), at which the absorption coefficient ꢢꢂꢡē for 18ē complexes (1 or
a(L)) is close to zero, while the ꢢꢂꢠē for 16ē species (2a-c) is still high
data_request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: +44(0)1223-336033.
λ
i
2
enough. Particularly, at the chosen λ
i
= 600 nm, ꢢ is in the range 550 –
ꢂꢠē
50 M-1 cm , whereas ꢢ is < 30 M-1 cm . Therefore, the equilibrium
-1
-1
6
ꢂꢡē
concentration ꢟꢂꢠē can be approximated as in Equation (8).
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Chemistry - A European Journal
10.1002/chem.201702862
FULL PAPER
Table 3. Crystal data and structure refinement parameters for 1d, 2d, 3a, 3c, 3d.
1d
2d
3a
3c
3d
Formula
Formula weight
T, K
C
36.50
H
39Cl
2
N
2
PRu
C
36
H
38
6
F N
2
P
2
Ru
C
39
H
42
6
F N
2
OP
2
Ru
C
28
H
34
6
F N
2 2
O P
2
Ru
37 38 6 2 2
C H F N OP Ru
708.63
120
775.69
120
831.75
100
707.58
120
803.70
120
Crystal system
Space group
Z / Z'
monoclinic
P2 /c
monoclinic
P2 /c
monoclinic
P2 /n
monoclinic
P2 /n
monoclinic
Pn
1
1
1
1
4 / 1
4 / 1
4 / 1
4 / 1
4 / 2
a, Å
9.4575(3)
9.4269(5)
9.6577(7)
14.1458(9)
12.0157(8)
10.2091(7)
10.0913(8)
34.401(3)
96.029(2)
3524.5(4)
1.515
b, Å
23.0562(8)
14.5931(5)
98.659(2)
19.0924(11)
19.2392(11)
92.5880(10)
3459.2(3)
1.489
20.7348(15)
18.7465(14)
94.0820(16)
3744.5(5)
1.475
c, Å
18.3241(12)
99.2530(10)
3074.1(3)
1.529
β, °
V, Å3
3145.81(18)
1.496
7.49
d
calc, g cm-3
µ, cm-1
6.07
5.68
6.79
6.00
2θmax, °
60
54
60
60
58
Reflns. collected / independent
64054 / 9170
6614
47949 / 7492
6101
38229 / 10895
7163
38560 / 8962
7722
27738 / 14871
11444
Observed reflections [I>2σ(I)]
R
1
0.0461
0.1077
1.052
0.0455
0.0475
0.0438
0.0514
wR
2
0.0918
0.1039
0.1182
0.0829
GOF
1.085
1.015
1.079
1.014
Residual density, e Å-3 (dmax/dmin ) 0.515/-0.916
0.880/-0.646
0.845/-0.563
1.593/-0.750
0.724/-0.695
[
7]
T. Matthias, Eur. J. Inorg. Chem. 2007, 3472-3475.
[8] T. Glöge, D. Petrovic, C. Hrib, P.G. Jones, M. Tamm, Eur. J. Inorg.
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9] Y. Yamaguchi, H. Nagashima, Organometallics 2000, 19, 725-727.
[10] T. Hayashida, Y. Yamaguchi, K. Kirchner, H. Nagashima, Chem. Lett.
001, 954-955.
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00-501.
P. Dejan, G. Thomas, B. Thomas, G.H. Cristian, R. Sören, G.J. Peter,
Acknowledgements
[
The authors thank the Russian Science Foundation (grant no. 14-
3-00801) for financial support. I.S. thanks the French Ministry of
2
[
5
1
Foreign Affairs for a Ph.D. scholarship through the French
Embassy in Moscow.
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Nagashima, Organometallics 2005, 24, 2713-2721.
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[
14] T.A. Peganova, A.V. Valyaeva, A.M. Kalsin, P.V. Petrovskii, A.O.
Borissova, K.A. Lyssenko, N.A. Ustynyuk, Organometallics 2009, 28, 3021-
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15] T.A. Peganova, I.S. Sinopalnikova, A.S. Peregudov, I.V. Fedyanin, A.
Demonceau, N.A. Ustynyuk, A.M. Kalsin, Dalton Trans. 2016, 45, 17030-
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[
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1
[16] P.J. Bailey, K.J. Grant, S. Parsons, Organometallics 1998, 17, 551-555.
[17] S. Tsukada, T. Sagawa, T. Gunji, Chem. Asian J. 2015, 10, 1881-1883.
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Jackson, O. Eisenstein, K.G. Caulton, Inorg. Chem. 1995, 34, 488-499.
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[
2
[
3555-3565.
[
[
[
19] A.D. Bain, Prog. Nucl. Magn. Reson. Spectrosc. 2003, 43, 63-103.
20] C.L. Perrin, T.J. Dwyer, Chem. Rev. 1990, 90, 935-967.
21] Although the Van’t Hoff plot for 1d allowed us to find the entropy term
[
∆
S = -18.7±0.4 cal/(mol•K), it requires correction for chloride concentration. In
This article is protected by copyright. All rights reserved.

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