Ruthenium complexes bearing N-H acidic pyrazole ligands

Article abstract of DOI:10.1002/ejic.201000802

Chelate ligands containing at least one pyrazole group were treated with RuCl₂(PPh₃)₃, RuHCl(CO)(PPh₃) ₃ and RuH₂(CO)(PPh₃)₃ to form ruthenium complexes bearing protic N-H groups in close proximity to the catalytically active ruthenium centre. In the case of the hydridoruthenium complex RuHCl(CO)(PPh₃)₃ the resulting complexes also contain abasic hydrido ligand. The combination of acidic and basic hydrogen species in one molecule and the arising two-site reactivity was thoroughly investigated spectroscopically and by DFT calculations. Catalytic tests on the hydrogenation and transfer hydrogenation of acetophenone showed a general activity of these systems. Novel ruthenium complexes with protic N-H and hydridic Ru-H units can efficiently be obtained by combining hydridoruthenium precursors with pyrazole-derived ligands.

Full text of DOI:10.1002/ejic.201000802

FULL PAPER
DOI: 10.1002/ejic.201000802
Ruthenium Complexes Bearing N–H Acidic Pyrazole Ligands
Thomas Jozak,[a] Dirk Zabel,[a] Anett Schubert,[a] Yu Sun,[a] and Werner R. Thiel*[a]
Keywords: Ruthenium / Pyrazole / Hydrogenation / Ligand effects
Chelate ligands containing at least one pyrazole group were
treated with RuCl2(PPh3)3, RuHCl(CO)(PPh3)3 and RuH2(CO)-
(PPh3)3 to form ruthenium complexes bearing protic N–H
groups in close proximity to the catalytically active ruthe-
nium centre. In the case of the hydridoruthenium complex
RuHCl(CO)(PPh3)3 the resulting complexes also contain a
basic hydrido ligand. The combination of acidic and basic
hydrogen species in one molecule and the arising two-site
reactivity was thoroughly investigated spectroscopically and
by DFT calculations. Catalytic tests on the hydrogenation
and transfer hydrogenation of acetophenone showed a gene-
ral activity of these systems.
for the formation of strong hydrogen bonds.[3] This effect
should also be beneficial for an improved catalyst–substrate
interaction according to the metal–ligand-bifunctional hy-
drogenation pathway (Scheme 1).
Introduction
Ruthenium(II) complexes play a dominant role in the
catalytic (asymmetric) hydrogenation of carbonyl com-
pounds. Depending on the ligands coordinated to the cen-
tral metal and on the substrates, different mechanistic
routes of hydrogen transfer are possible: (A) direct acti-
vation of dihydrogen, (B) transfer hydrogenation with
alcohols (e.g. 2-propanol) as the hydrogen source or (C)
metal–ligand-bifunctional hydrogenation. Whereas the sub-
strate has to bind directly to the metal centre in (A) and
(B),[1] the hydrogen transfer is performed differently in
metal–ligand-bifunctional hydrogenation. Here, a parallel
transfer of a hydrido ligand coordinated to the metal site
and a proton derived from a protic group of one of the
donor ligands occurs, which, in an ideal case, enhances the
reaction rate significantly. Such protic groups can either be
alcohols or amines or amine derivatives like sulfonamides,
etc. Noyori et al. and others described a series of chiral
ruthenium-based catalysts following these requirements and
showing high activity and enantioselectivity in the hydro-
genation of ketones and other substrates with polar C=E
double bonds.[2]
In the present work ruthenium complexes of bi- (N,N-)
or tridentate (N,N,N-) donors have been investigated, which
include at least one pyrazole fragment with a protic NH
group. Coordination of these ligands brings this NH group
in close proximity to the metal site, and it becomes even
more acidic due to the coordination of the Lewis-acidic
metal site to the pyrazole moiety. We recently could show
that such a coordination motif provides a proton donor site
Scheme 1. Postulated reaction mechanism for the metal–ligand-bi-
functional hydrogenation with pyrazole-based ligands.
Results and Discussion
Ligand Synthesis
During the last decade, a series of pyrazole-based ligands
have been introduced for catalytic applications.[4] However,
pyrazoles coordinated to ruthenium(II) catalysts have rarely
been reported.[5] For investigations described in this article
the pyrazole-derived ligands 1–3 (Scheme 2), all bearing
NH groups at a pyrazole ring, were used to generate a series
of novel ruthenium(II) complexes.
[a] Fachbereich Chemie, Technische Universität Kaiserslautern
Erwin-Schrödinger-Str. Geb. 54, 67663 Kaiserslautern,
Germany
Fax: +49-631-2054676
E-mail: thiel@chemie.uni-kl.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000802.
View this journal online at
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Scheme 2. Pyrazole ligands used for the synthesis of ruthenium(II)
complexes.
The syntheses of the tridentate 2,6-bis(5-butylpyrazol-3-
yl)pyridine (1), a structural analogue of the well-known
2,2Ј:6Ј6ЈЈ-terpyridine ligand, the bidentate 2-[3(5)-pyrazol-
yl]pyridines (2a, 2b) and the bidentate 3,3Ј-bi(1H-pyrazole)
(3a) were carried out according to published procedures.[6–8]
Butyl side chains attached to the pyrazole ring were em-
ployed to enhance the solubility of the derived ruthenium
complexes in organic solvents. The novel 3,3Ј-bi(1H-pyr-
azole) ligand 3b was synthesized by performing a double
Claisen condensation between diethyl oxalate and hexan-2-
one in the presence of sodium methoxide (Scheme 3). The
intermediate tetraketone was characterized solely by NMR
spectroscopy. It undergoes keto/enol tautomerism where the
enol form is the major isomer. The desired bipyrazole 3b
was obtained from the tetraketone by ring closure with hy-
drazine and purified by recrystallization from ethyl acetate.
Figure 1. Top: molecular structure of 3b in the solid state. Charac-
teristic hydrogen-bond parameters: N1–H1 0.88 Å, H1···N2 2.02 Å,
N1···N2 2.8728(17) Å; N1–H1···N2 163.00°. Centre: views of the
linking pyrazole tetramers; the hydrogen atoms are omitted for
clarity. Bottom: 3D-network structure (perpendicular to the ac
plane) formed by the 3,3Ј-bi(1H-pyrazole) cores; the butyl side
chains are omitted for clarity.
In its solid-state structure, 3b includes a centre of sym-
metry at its central C–C bond (Figure 1, top). Both pyr-
azole rings act as proton-donating (N1) and -accepting
(N2) sites for intermolecular hydrogen bonds. This results
in the formation of a complex three-dimensional network
structure, wherein pyrazole tetramers[3,9d,10] are involved as
the linking centres (Figure 1, centre). The network contains
three-dimensional pores, filled by the butyl chains.
Scheme 3. (i) NaOMe, Et2O, room temp., 45 h, 45%. (ii) N2H4,
EtOH, 80 °C, 4.5 h, 42%.
The bipyrazole 3b exhibits a sharp absorption for the N–
H stretching vibration at 3400 cm–1 in the IR spectrum
(KBr) that is typical for pyrazoles with N–H···N hydrogen
bonds in the solid state.[9] Single crystals suitable for X-ray
diffraction were grown by diffusion of pentane into a solu-
Ruthenium Complexes
Three different ruthenium precursors, RuCl2(PPh3)3
tion of 3b in MeOH. The bipyrazole 3b crystallizes in the (4),[11] RuHCl(CO)(PPh3)3 (5)[12] and RuH2(CO)(PPh3)3
tetragonal space group I41/a. Figure 1 shows the molecular (6),[12] were treated with the ligands 1–3, which lead to dif-
structure of 3b.
ferent products as described below. Treatment of the
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Ruthenium Complexes Bearing N-H Acidic Pyrazole Ligands
dichloridoruthenium complex RuCl2(PPh3)3 (4) with the
tridentate ligand 1 in dichloromethane yields the orange-
coloured cationic species 7 with chloride as the counterion
(Scheme 4).
Scheme 4. Synthesis of the 2,6-bis(5-butylpyrazol-3-yl)pyridine
complexes 7 and 8.
The occurrence of the ligand N–H groups in 7 can clearly
be seen by the N–H stretching absorption in the IR spec-
trum (3438 cm–1). There is only one singlet at δ = 25.5 ppm
in the 31P{1H} NMR spectrum and one resonance in the
1H and 13C{1H} NMR spectra for each chemically different
proton and carbon atom of the ligand. This proves, in com-
bination with a single-crystal X-ray structure analysis, that
the ruthenium centre has an octahedral coordination with
a trans orientation of the phosphane ligands. Single crystals
suitable for X-ray diffraction were grown by diffusion of
pentane into a solution of 7 in MeOH. Compound 7 crys-
tallizes in the monoclinic space group P21/a. Figure 2 shows
the molecular structure of 7 in the solid state.
The structure of 7 is distinguished by the trans orienta-
tion of the phosphane ligands and by two different N–
H···Cl hydrogen bonds. One of the N–H protons binds to
the chlorido ligand coordinated to the ruthenium centre
leading to a centrosymmetric dimer, the second N–H unit
interacts with the chloride anion. There are several cationic
ruthenium complexes with a similar set of ligands.[13] How-
ever, none of them provides protic N–H units for dimeriza-
tion through hydrogen binding. The meridional coordina-
tion of the nitrogen donors seems to be favourable even if
monodentate ligands like acetonitrile are used.[14] There are
only a few examples of tridentate N,N,N-donors per-
forming facial coordination as long as meridional coordina-
tion is sterically possible.[15] Additionally, only bidentate
Figure 2. Top: molecular structure of 7 in the solid state; character-
istic bond lengths [Å], angles [°] and torsion angles [°]: Ru1–Cl1
2.4605(8), Ru1–P1 2.3909(9), Ru1–P2 2.3897(10), Ru1–N2
2.056(3), Ru1–N3 1.983(3), Ru1–N4 2.118(3), N1–H1 0.88,
H1···Cl1 2.41, N1···Cl1 3.242(3), N5–H5 0.88, H5···Cl2 2.25,
N5···Cl2 3.104(4); Cl1–Ru1–P1 90.17(3), Cl1–Ru1–P2 89.69(3),
Cl1–Ru1–N2 92.44(9), Cl1–Ru1–N3 170.56(9), Cl1–Ru1–N4
111.80(9), P1–Ru1–P2 176.62(4), P1–Ru1–N2 92.29(7), P1–Ru1–
N3 90.09(8), P1–Ru1–N4 89.50(7), P2–Ru1–N2 91.09(7), P2–Ru1–
N3 90.61(8), P2–Ru1–N4 87.42(7), N2–Ru1–N3 78.12(13), N2–
Ru1–N4 155.70(12), N3–Ru1–N4 77.64(12), N1–H1···Cl1 159.00,
N5–H5···Cl2 3.104(4); N3–C1–C6–N2 3.4(5), N3–C5–C9–N4–
5.4(5). Bottom: dimeric structure of 7.
To obtain models for metal–ligand-bifunctional hydro-
phosphanes are found to coordinate to ruthenium in a cis genation catalysts bearing hydrido ligands at the ruthenium
configuration.[10,16] The bond parameters around the ruthe- centre and protic N–H groups in close proximity, hydrido-
nium centre in compound 7 are in complete agreement with ruthenium precursors were treated with the ligands 1–3. If
similar complexes in the literature. The Ru–N3 (pyridine) 1 is treated with the dihydrido complex 6, the dipyrazolido-
bond length is shorter than the other two Ru–N bond ruthenium(II) complex 8 is formed in 15–20% spectro-
lengths due to the steric restrictions of the tridentate ligand scopic yield (Scheme 4). It seems that in this case the basic-
and the weak chlorido ligand in the trans position to pyr- ity of the hydrido ligands is sufficient for a complete NH
idine. Ru–N4 is about 6 pm longer than Ru–N2, probably deprotonation of the N,N,N-chelate ligand. This is sup-
due to the different hydrogen-bond motifs at the neighbour- ported by an alternative access to 8, which was opened up
ing nitrogen atoms.
by bubbling CO through a solution of 7 in the presence of
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T. Jozak, D. Zabel, A. Schubert, Y. Sun, W. R. Thiel
FULL PAPER
KOtBu (yield 59%). The IR spectrum of 8 is dominated by
There are just two examples of ruthenium(II) complexes
an intense band of the C=O stretching vibration at where two phosphane centres, one carbonyl ligand and
1961 cm–1. The signals for the N–H vibration observed in three nitrogen donors coordinate the metal site:
the IR spectrum of 7 have vanished. As compared to 7, the [TpRu(PPh3)2(CO)]+ and [(dppe)Ru(CO)(MeCN)3]2+ [17]
.
31P resonance (δ = 32.0 ppm) is shifted by almost 6 ppm Furthermore only a few structurally characterized rutheni-
1
downfield. All H NMR resonances of the N,N,N-chelate um(II) complexes bearing anionic N-donors have been de-
ligand are shifted upfield compared to those of 7; whereas scribed up to now: three complexes with bridging imid-
the 13C NMR resonances remain almost unaffected.
azolido ligands,[18] one example wherein an aliphatic amido
Crystals suitable for X-ray diffraction were obtained by ligand is involved[19] and only two compounds where at le-
slow diffusion of pentane into a concentrated solution of 8 ast one deprotonated pyrazole coordinates to rutheni-
in toluene. The compound crystallizes in the monoclinic um(II).[20] This is quite astonishing, since similar amides
space group P21/a. Figure 3 shows the molecular structure have been postulated as intermediates in ruthenium-cata-
of 8 in the solid state.
lyzed hydrogenation reactions. The structural parameters of
7 and 8 can be compared directly: as expected, the Ru–P
bond lengths are almost identical for both compounds. Af-
ter the weak chlorido ligand in 7 is exchanged with the
strong σ-donor CO group, the Ru–pyridine bond length be-
comes about 8 pm longer in 8. The two Ru–pyrazole bond
lengths are now almost identical. Despite the anionic nature
of the pyrazoles in 8, there is no significant change in the
Ru–pyrazole bond lengths compared to those in 7, probably
because of the steric restrictions resulting from the triden-
tate ligand.
Treatment of 1 with the monohydrido complex 5 gives a
complex mixture of products, which as yet have not been
completely isolated and characterized. Addition of sodium
perchlorate led to just a few crystals (yield Ͻ 5%) of a cat-
ionic
carbonyl(hydrido)bis(triphenylphosphane)rutheni-
um(II) complex, wherein 2,6-bis(5-butylpyrazol-3-yl)pyr-
idine acts as a bidentate donor (for structure see Supporting
Information). One of the pyrazole units remains uncoordi-
nated, both pyrazole N–H groups undergo hydrogen bind-
ing to the perchlorate anion. Here, the hydrido ligand of
the starting material 5 seems to be unable to deprotonate
the pyrazole.
We therefore extended our investigation to the bidentate
ligands 2 and 3, which gave, by treatment with the monohy-
drido complex 5, the desired carbonyl(hydrido)bis(triphen-
ylphosphane)ruthenium(II) complexes 9 and 10 in 65–85%
yields (Scheme 5).
Complex 9a was obtained in crystalline form by slow dif-
fusion of n-pentane into a chloroform solution. It crys-
tallizes with two crystallographically independent molecules
and one molecule of chloroform per formula unit in the
unit cell. Figure 4 shows the molecular structure of one of
these molecules in the solid state. For the complete solid-
state structure see the Supporting Information
Since pyridine is a stronger σ-donor than pyrazole, the
hydrido ligand is found oriented in the trans position to the
pyrazole unit (see below for spectroscopic discussion) and
thus in an unfavourable position for a metal–ligand-bifunc-
tional hydrogenation. The only way to overcome this prob-
lem is to change from pyrazolylpyridine to a bipyrazol li-
gand. Complex 10b could be crystallized by slow diffusion
of n-pentane into a solution of this compound in ethanol.
The solvent is included in the crystalline material. Figure 5
shows the molecular structure of one of these molecules in
the solid state.
Figure 3. Molecular structure of 8 in the solid state; characteristic
bond lengths [Å], angles [°] and torsion angles [°]: Ru1–P1
2.3828(17), Ru1–P2 2.3866(19), Ru1–N1 2.062(6), Ru1–N2
2.084(6), Ru1–N4 2.069(6), Ru1–C20 1.862(8), O1–C20 1.150(10);
P1–Ru1–P2 178.14(7), P1–Ru1–N1 90.49(17), P1–Ru1–N2
86.72(17), P1–Ru1–N4 92.90(16), P1–Ru1–C20 89.3(3), P2–Ru1–
N1 90.77(17), P2–Ru1–N2 94.91(17), P2–Ru1–N4 86.03(16), P2–
Ru1–C20 89.5(3), N1–Ru1–N2 76.6(2), N1–Ru1–N4 77.8(2), N1–
Ru1–C20 179.3(3), N2–Ru1–N4 154.4(2), N2–Ru1–C20 104.1(3),
N4–Ru1–C20 101.5(3), Ru1–C20–O1 177.8(7); N1–C1–C6–N2
2.5(10), N1–C5–C9–N4 2.5(9).
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Ruthenium Complexes Bearing N-H Acidic Pyrazole Ligands
Scheme 5. Synthesis of the hydridocarbonylruthenium complexes 9
and 10.
Figure 5. Molecular structure of 10b in the solid state; characteris-
tic bond lengths [Å], angles [°] and torsion angles [°]: Ru1–P1
2.3552(11), Ru1–P2 2.3542(10), Ru1–N1 2.119(3), Ru1–N3
2.183(3), Ru1–C1 1.813(4), Ru1–H1 1.60(4), N2–H2N 0.86(2),
H2N···O2 1.86(2), N2···O2 2.710(6), O2–H2O 0.77(2), H2O···Cl1
2.25(2), O2···Cl1 3.013(3), N4–H4N 0.85(3), H4N···Cl1 2.25(3),
N4···Cl1 3.082(3); P1–Ru1–P2 172.85(4), P1–Ru1–N1 90.19(9), P1–
Ru1–N3 93.27(9), P1–Ru1–C1 88.87(13), P2–Ru1–N1 90.78(9), P2–
Ru1–N3 93.80(9), P2–Ru1–C1 90.29(13), N1–Ru1–N3 73.60(11),
N1–Ru1–C1 178.58(14), N3–Ru1–C1 105.41(15), C1–Ru1–H1
84.1(13), P1–Ru1–H1 85.8(13), P2–Ru1–H1 87.0(13), N1–Ru1–H1
96.9(13), N3–Ru1–H1 170.5(13), N2–H2N···O2 177(3), O2–
H2O···Cl1 172(3), N4–H4N···Cl1 166(3); N1–C2–C5–N3 0.5(5).
the trans position (H– and CO). This becomes clear when
the Ru–N bond lengths of complex 10b are discussed: here
the strong σ-donating hydrido ligand leads to a pronounced
increase of the Ru–N bond length in the trans position. Ac-
cordingly, the bond length between the ruthenium centre
and the carbonyl carbon atom is slightly shorter in 10b,
reflecting the poorer σ-donor strength of pyrazole. The hyd-
rido ligands in 9a and 10b could be located in the difference
Fourier map. However, the Ru–H bond lengths differ
largely [9a: 1.77(3) Å; 10b: 1.60(4) Å], probably due to gene-
ral problems with the exact location of the hydrido ligands
in close proximity to the electron-rich metal sites, which is
always subject to errors. In 10b the hydrido ligand is located
in the “correct” position to an N–H unit of one of the pyr-
azole moieties. The corresponding distance H1–H2N is
3.16(4) Å, which is rather ideal for the concerted Ru–
Figure 4. Molecular structure of 9a in the solid state; characteristic
bond lengths [Å], angles [°] and torsion angles [°]: Ru1–P1
2.3849(12), Ru1–P2 2.3453(12), Ru1–N1 2.159(3), Ru1–N2
2.180(3), Ru1–C9 1.835(4), Ru1–H1 1.77(3), N3–H3A 0.88,
H3A···Cl2 2.19, N3···Cl2 3.066(3); P1–Ru1–P2 176.51(4), P1–Ru1–
N1 87.43(8), P1–Ru1–N2 90.35(7), P1–Ru1–C9 93.00(12), P2–Ru1–
N1 91.06(8), P2–Ru1–N2 92.29(7), P2–Ru1–C9 88.29(12), N1–
Ru1–N2 74.78(11), N1–Ru1–C9 176.09(14), N2–Ru1–C9
109.10(14), P2–Ru1–H1 85.9(9), N1–Ru1–H1 94.7(10), P1–Ru1–
H1 91.1(10), C9–Ru1–H1 81.4(10), N2–Ru1–H1 169.4(10), N3–
H3A···Cl2 3.066(3); N1–C1–C6–N2 0.6(4).
In the solid state, the six-coordinate cationic ruthenium H···C=O···H–N interaction with the carbonyl group of a
complexes 9a and 10b undergo hydrogen bonding to the substrate.
chloride anion, leading to isolated ion pairs in the case of
Complexes 9a,b and 10a,b were additionally charac-
9a. Compound 10b forms a one-dimensional hydrogen- terized by elemental analysis, IR and NMR spectroscopy.
bonded polymer structure, wherein both N–H units, the The C=O stretching frequencies were found between 1952
chloride anion and one additional molecule of ethanol are and 1941 cm–1; the Ru–H stretching vibrations could not
included. In 9a, the Ru–N distances differ by about 2 pm be assigned. They are reported in the literature to appear at
due to a balance between the donor strengths of pyrazole 1980–1950 cm–1,[12,17a,21] which is close to the intense C=O
versus pyridine and the donor strengths of the ligands in absorption, or to be unobservable because of their low in-
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T. Jozak, D. Zabel, A. Schubert, Y. Sun, W. R. Thiel
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tensities.[22] The 31P{1H} NMR resonances of 9a,b (δ = are not due to the different ligands but to the different sol-
46.3, 46.4 ppm) and 10a,b (δ = 44.9, 43.9 ppm) are shifted vents used for NMR spectroscopy. For compounds 10a and
by about 50 ppm downfield with respect to those of free 10b two different N–H resonances are found since the two
1
triphenylphosphane. The H NMR resonances of the hy- pyrazolyl units occupy chemically different coordination
drido ligands are found as triplets, shifted remarkably up- sites at the ruthenium centre.
field (9a: δ = –12.50 ppm; 9b: δ = –12.66 ppm; 10a: δ =
Analogous reactions between the bidentate ligands 2a,b
–12.19 ppm; 10b: δ = –12.10 ppm) with coupling constants and the dihydrido precursor RuH2(CO)(PPh3)3 (6) give the
2JPH = 19.8–20.4 Hz. In contrast, the resonances of the pro- corresponding neutral carbonylhydridopyrazolido com-
tic N–H units are shifted downfield (9a: δ = 16.41 ppm; 9b: plexes 11a,b in high yields (Scheme 6). However, treatment
δ = 13.61 ppm; 10a: δ = 12.82, 14.13 ppm; 10b: δ = 12.26, of 3a,b with RuH2(CO)(PPh3)3 (6) did not result in the for-
13.60 ppm). The differences between compounds 9 and 10 mation of the corresponding complexes 12 bearing a mono-
deprotonated bipyrazole ligand. The additional hydrido li-
gand should undergo reaction with the remaining N–H
unit, similar to the formation of compound 8. This will
yield a pentacoordinate ruthenium(II) complex, which
probably decomposes in solution.
Theory
The metal–ligand-bifunctional hydrogenation of carb-
onyl compounds with such cationic ruthenium(II) com-
plexes was calculated with a model system similar to com-
pound 7, wherein the chlorido ligand was replaced by a
hydrido ligand, and the P(C6H5)3 ligands were replaced by
PMe3. Formaldehyde was employed as the substrate. We
used the DFT functional B3LYP[23] in combination with
the 6-31G* basis set[24] for C, H, N, O, P and the
LANL2DZ (ECP) basis set for Ru[25] (for details see Exper-
imental Section and Supporting Information). The results
are summarized in Figure 6 and Table 1.
Scheme 6. Synthesis of the carbonylhydridoruthenium complexes
11.
Figure 6. Results of the DFT calculation on the mechanism of the hydrogenation of formaldehyde catalyzed by a cationic ruthenium(II)
complex with an N,N,N-donor ligand. ∆HR and ∆GR are given in kcalmol–1.
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Ruthenium Complexes Bearing N-H Acidic Pyrazole Ligands
Table 1. Results of the DFT calculations with B3LYP/6- Catalysis
31G*(LANL2DZ).
According to the results of the quantum chemical calcu-
lations, the barriers for the correlated proton and hydride
transfer as well as for the hydrogen uptake by the ruthe-
nium complex should be low. We therefore investigated the
hydrogenation and transfer hydrogenation of acetophenone
catalyzed by the ruthenium complexes mentioned above.
The results are summarized in Table 2.
Compound
Hf, Gf
[hartrees]
∆Hf, ∆Gf
∆Hf, ∆Gf
[kcalmol–1] [kJmol–1]
H2
–1.162036
–1.176828
CH2O
–114.469832
–114.495307
–1793.037347
–1793.133610
–1908.669215
–1908.805745
–1907.519167
–1907.626542
–1908.681203
–1908.803370
–1907.510028
–1907.610546
–1908.672064
A
A + H2 + CH2O
0.0
0.0
0.0
0.0
Table 2. Hydrogenation (h.) and transfer hydrogenation (t.h.) of
acetophenone with a series of ruthenium complexes bearing pyr-
azole-based ligands.
B
Entry
Cata-
T
Time
[h]
Yield
[%][b]
B + H2
–7.5
+1.5
–31.8
+6.2
lyst Hydrogen source[a] [°C]
TS(BC)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
7
7
7
7
7
8
8
8
9b
9b
10b
10b
10b
10b
11b
11b
h.
h.
t.h.
t.h.
t.h.
h.
h.
h.
h.
h.
h.
h.
t.h.
t.h.
h.
21
80
21
80
80
21
80
80
21
80
21
80
20
80
21
80
2
2
2
2
6
2
2
21
2
2
2
2
2
2
2
2
0
Ͼ 99
0
39
95
0
16
96
0
18
0
79
0
3
0
19
TS1 + H2
–1.8
–7.5
+48.2
–1908.787374 +11.5
–1907.522995
–1907.623711
C
C + H2
–1908.685031
–1908.800539
–1908.683531
–1908.793190
–1908.703865 –21.7
–1908.811741 –3.8
–1908.696767 –17.3
–1908.802115 +2.3
–1908.718532 –30.9
–1908.824868 –12.0
–115.658700
–115.685656
–0.026832
–0.013521
–9.9
+3.3
–9.0
+7.9
–41.5
+3.7
TS(CD)
–37.6
+33.0
–91.0
–15.7
–72.3
+9.5
D
TS(DE)
E
–129.5
–50.2
h.
CH3OH
[a] Hydrogenation (h.): PH2 = 40 bar; transfer hydrogenation (t.h.):
with 2-propanol. [b] Yields determined by GC–MS.
H2 + CH2O Ǟ CH3OH
16.8
–8.5
–70.5
–35.5
Table 2 clearly shows that all the ruthenium complexes
investigated show only moderate activity. At room tempera-
The calculations, which were carried out without any ad- ture they are almost inactive. Compound 7 (cationic chlor-
ditional solvent models, show that in the first step of the idoruthenium complex with a tridentate N,N,N-donor)
reaction (A Ǟ B) H2C=O forms an adduct to the catalyst shows good activity at 80 °C under hydrogenation condi-
by an N–H···O=C hydrogen bond with one of the two pyr- tions (Entry 2: PH2 = 40 bar) and reduced activity under
azole NH groups and a weak Ru–H···H–C interaction. This transfer hydrogenation conditions (Entries 4 and 5: 39 and
adduct formation is exothermic as expected, but slightly 95% conversion after 2 and 6 h, respectively). This is in
endergonic. Then a concerted transfer of the NH proton contrast to the behaviour of compound 8, where the ruthe-
and the Ru–hydrido ligand takes place via a first transition nium centre is coordinated with the same ligand in its two-
state (TS1). This is quite low in energy and leads to a depro- fold deprotonated state. However, here a carbonyl ligand
tonated pyrazole unit and a methanol molecule in the coor- is coordinated to the ruthenium atom, which is probably
dination sphere of the ruthenium centre bound by an responsible for a strong decrease in hydrogenation activity
N···H–O–C and a (weak) Ru···H–C interaction (C). Com- (Entries 7 and 8: 16 and 96% conversion after 2 and 21 h,
pared to the starting material B, this hydrogen-transfer step respectively).
is almost thermoneutral, probably because the coordination
Compounds 9b and 11b differ slightly in their hydrogena-
number of the ruthenium(II) centre is reduced from six to tion activity (Entries 10 and 16: 18 and 19% conversion af-
five. This is supported by the very small barrier for the ad- ter 2 h), which is not surprising since 11b should be formed
dition of dihydrogen (∆H‡ = +0.9 kcalmol–1) in the follow- from 9b in the presence of a base (here: KOtBu). In con-
ing reaction (TS2) and the pronounced stabilization of the trast, compound 10b (Entry 12: 79% conversion after 2 h) is
resulting six-coordinate non-classical hydrogen complex D. much more active than compound 9b. These two complexes
Now a retransfer of the proton to the deprotonated pyr- differ solely in the nature of the N,N-chelate ligand (pyraz-
azole site occurs simultaneously with a splitting of the dihy- olylpyridine versus bipyrazol). The difference in the hydro-
drogen ligand into a ruthenium-bound hydrido ligand and genation activity can be explained by the different electronic
an oxygen-bound proton (D Ǟ TS3 Ǟ E). The reaction is influence of either the pyridine or the pyrazole moiety. To
finished by an endothermic elimination of the methanol elucidate this, in the future we will investigate ligands
from the coordination sphere of the catalyst. Details on the equipped with electron-donating and -withdrawing groups
calculations can be found in the Supporting Information.
at the pyrazole ring.[7] On the other hand, the difference
Eur. J. Inorg. Chem. 2010, 5135–5145
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5141

T. Jozak, D. Zabel, A. Schubert, Y. Sun, W. R. Thiel
FULL PAPER
3
NMR (400 MHz, CD3OD): δ = 6.39 (s, 2 H, HPz), 2.66 (t, JHH
=
might be explained by the orientation of the hydrido ligand
with respect to the acidic pyrazole unit. As already men-
tioned above, the hydrido ligand in 9a is located in the trans
position to the pyrazole ligand, we expect a similar situa-
tion for 9b. In 10b, which is the best catalyst in our series
bearing a carbonyl ligand, the hydrido ligand comes close
to the protic N–H unit of a pyrazole moiety, which should
be ideal for metal–ligand-bifunctional hydrogenation.
In summary, it has to be mentioned here that the cata-
lytic activities of the (pyrazole)ruthenium complexes are not
as high as suggested by the low barriers of activation de-
rived from DFT calculations (see Figure 6). We assign this
disagreement to the choice of our model system. We have
employed formaldehyde as the substrate, the smallest alde-
hyde molecule, which additionally possesses a strongly elec-
trophilic carbonyl carbon atom. Furthermore, we have
found that switching from triphenylphosphane to trimeth-
ylphosphane largely enhances the catalytic activity of re-
lated ruthenium complexes in hydrogenation reactions,
probably because of steric effects.
7.4 Hz, 4 H, HBu), 1.69–1.62 (m, 4 H, HBu), 1.39 (m, 4 H, HBu),
0.95 (t, 3JHH = 7.4 Hz, 6 H, HBu) ppm. 13C NMR (101 MHz, [D6]-
DMSO): δ = 143.8, 100.10, 30.9, 24.4, 21.6, 13.5 ppm.
[2,6-Bis(5-butyl-1H-pyrazol-3-yl)pyridine]chloridobis(triphenylphos-
phane)ruthenium Chloride (7): Ligand 1 (119 mg, 0.37 mmol) and
(PPh3)3RuCl2 (355 mg, 0.37 mmol) were dissolved in dry CH2Cl2
(10 mL) and stirred at 25 °C for 2 h. The solvent was removed, and
the remaining solid was washed twice with diethyl ether (15 mL).
Yield 302 mg (80%), orange-coloured solid. IR (KBr): ν = 3438 (w,
˜
N–H), 2927 (m), 2360 (w), 1635 (m), 1558 (m), 1433 (m), 1221
1
(w), 1093 (m), 748 (m), 699 (s), 517 (s) cm–1. H NMR (600 MHz,
3
CD3OD): δ = 7.28–7.12 (m, 31 H, HPh, HPy), 6.97 (d, JHH
=
3
7.9 Hz, 2 H, Hpy), 6.40 (s, 2 H, HPz), 2.54 (t, JHH = 7.3 Hz, 4 H,
HBu), 1.43–1.38 (m, 4 H, HBu), 1.13–1.07 (m, 4 H, HBu), 0.83 (t,
3JHH = 7.3 Hz, 6 H, HBu) ppm. 13C NMR (150.09 MHz, CD3OD):
1
δ = 154.9, 154.1, 149.6, 134.7–134.6 (m), 132.4 (t, JCP = 19.2 Hz),
2
130.6, 129.0 (t, JCP = 4.8 Hz), 119.5, 104.0, 32.5, 26.2, 22.7,
14.1 ppm. 31P NMR (242.9 MHz, CD3OD): δ = 24.13 (s) ppm.
C55H55Cl2N5P2Ru (1019.98): calcd. C 64.76, H 5.44, N 6.86; found
C 61.85, H 5.42, N 6.70.
Carbonylbis(triphenylphosphane)[5,5Ј-pyridine-2,6-diylbis(3-butyl-
pyrazol-1-ido)]ruthenium (8). Method A: [RuH2(CO)(PPh3)3]
(50 mg, 72.0 µmol) and ligand 1 (29.4 mg, 90 µmol) were dissolved
in dry toluene (10 mL) and heated to reflux for 5 h. The solvent
Conclusions
Reaction of pyrazole-containing bi- and tridentate che- was removed, and the raw product was purified by column
chromatography (Al2O3/ethyl acetate) to give a yellow solid in 20%
yield. Method B: Compound 7 (250 mg 0.25 mmol) was dissolved
in dry toluene (20 mL). Carbon monoxide was bubbled through
the solution, KOtBu (84.1 mg, 0.75 mmol) was added, and the mix-
ture was heated to reflux for 5 h. After the solvent was removed,
the raw product was purified by column chromatography (Al2O3/
late ligands with the ruthenium precursors RuCl2(PPh3)3,
RuHCl(CO)(PPh3)3 and RuH2(CO)(PPh3)3 resulted in the
formation of the corresponding chelate complexes. De-
pending on the nature of the ruthenium precursor, depro-
tonation of the acidic pyrazole N–H groups can occur. On
the other hand ruthenium complexes possessing both an
acidic N–H unit and a hydridic Ru–H moiety can be gener-
ated. DFT calculations on a model system with a tridentate
ligand show relatively low activation barriers for the metal–
ethyl acetate). Yield 160 mg (59%), yellow solid. IR (KBr): ν =
˜
2928 (m), 1961 (s, C=O), 2954 (s), 1605 (m), 1555 (m), 1480 (m),
1433 (m), 1358 (w), 1321 (w), 1181 (w), 1153 (w), 1093 (m), 1022
1
(w), 742 (m), 694 (s), 590 (w), 518 (s) cm–1. H NMR (400 MHz,
ligand-bifunctional hydrogenation of formaldehyde. Cata- C6D6): δ = 7.60–7.55 (m, 12 H, HPh), 7.2–6.9 (m, 18 H, HPh), 6.78
3
3
(t, JHH = 7.7 Hz, 1 H, HPy), 6.24 (d, JHH = 7.7 Hz, 2 H, HPy),
lytic studies prove the activity of these complexes in the
hydrogenation and transfer hydrogenation of acetophenone.
The activity of the complexes investigated can be related to
the ligand pattern and be explained with the influence of
the other ligands and the electronic and structural situation
of the N–H and the Ru–H units.
In the future we will investigate the electronic influence
of a series of functionalized pyrazolylpyridines, which can
be done without changing steric factors. A further task will
be the application of chiral pyrazole-derived ligands for
enantioselective hydrogenation reactions.
6.03 (s, 2 H, HPz), 2.99 (t, 3JHH = 7.3 Hz, 4 H, HBu), 1.82–1.75 (m,
3
4 H, HBu), 1.47–1.41 (m, 4 H, HBu), 1.10 (t, JHH = 7.3 Hz, 4 H,
HBu) ppm. 13C NMR (150.92 MHz, C6D6): δ = 206.3 (t, JCP
=
2
2
15.2 Hz, CO), 155.0, 152.9, 149.8, 136.6, 134.7 (t, JCP = 5.5 Hz),
1
131.1 (t, JCP = 22.2 Hz), 129.6, 111.8, 102.1, 33.4, 29.3, 22.9,
14.4 ppm. 31P NMR (161.97 MHz, CDCl3): δ = 32.00 (s) ppm.
C56H53N5OP2Ru (975.07): calcd. C 68.98, H 5.48, N 7.18; found C
68.29, H 5.40, N 7.24.
General Procedure for the Synthesis of Ruthenium Complexes of the
Type [LRuH(CO)(PPh3)2]Cl (9, 10): [RuHCl(CO)(PPh3)3]
(0.16 mmol) was dissolved in dry THF (15 mL). The corresponding
pyrazole (0.16 mmol) was added, and the mixture was heated to
reflux for 2 h. After cooling to room temperature the resulting solid
was filtered off and washed thoroughly with diethyl ether.
Experimental Section
5,5Ј-Dibutyl-1H,1ЈH-3,3Ј-bipyrazole (3b): 5,7,8,10-Tetraoxotetrade-
cane (7.00 g, 27.5 mmol) was dissolved in EtOH (130 mL) and
heated to 60 °C. Hydrazine hydrate (3.70 g, 74.0 mmol) was then
added slowly, and the mixture was heated under reflux for 4.5 h.
The solvent was removed under reduced pressure, and the pale-
yellow solid was recrystallized from ethyl acetate. Yield 2.85 g
(Carbonyl)(hydrido)[2-(1H-pyrazol-3-yl)pyridine]bis(triphenylphos-
phane)ruthenium Chloride (9a): Yield 81 %, colourless solid. IR
(KBr): ν = 3430 (m, NH), 1949 (s, C=O), 1610 (w), 1480 (w), 1433
˜
1
(m), 1092 (m), 750 (w), 696 (m), 521 (s), 496 (w) cm–1. H NMR
(600 MHz, CDCl3): δ = 15.42 (s, 1 H, NH), 7.38 (d, 3JHH = 2.2 Hz,
1 H, HPz), 7.20–7.06 (m, 32 H, HPh, HPy), 6.26 (d, JHH = 2.1 Hz,
3
3
2
(42%). IR (KBr): ν = 3180 (s), 3144 (s), 3087 (s), 3034 (s), 2960 1 H, HPz), 6.00 (t, JHH = 6.4 Hz, 1 H, HPy), –12.50 (t, JHP
=
˜
(s), 2930 (s), 2872 (s), 2858 (s), 1577 (s), 1464 (m), 1435 (m), 1409
19.1 Hz, 1 H, Ru-H) ppm. 31P NMR (242.92 MHz, CDCl3): δ =
(m), 1379 (w), 1347 (w), 1305 (w), 1270 (m), 1197 (w), 1137 (m), 46.24 (s) ppm. C45H38ClN3OP2Ru (835.27): calcd. C 64.71, H 4.58,
1
1061 (w), 1036 (m), 947 (m), 847 (m), 781 (m), 729 (w) cm–1. H N 5.03; found C 63.86, H 4.55, N 4.86.
5142
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 5135–5145

Ruthenium Complexes Bearing N-H Acidic Pyrazole Ligands
[2-(5-tert-Butyl-1H-pyrazol-3-yl)pyridine](carbonyl)(hydrido)bis(tri-
13.60 (s, 1 H, NHЈ), 12.27 (s, 1 H, NH), 7.43–7.42 (m, 30 H, HPh),
3
phenylphosphane)ruthenium Chloride (9b): Yield 66%, colourless so- 6.20 (s, 1 H, HPzЈ), 6.07 (s, 1 H, HPz), 2.03 (t, JHH = 7.5, 4 H,
lid. IR (KBr): ν = 3421 (m, NH), 1952 (s, C=O), 1740 (w), 1610
HBu), 1.48–1.40 (m, 4 H, HBu), 1.27–1.04 (m, 8 H, HBu), 0.87–0.82
˜
(w), 1480 (w), 1433 (m), 1212 (w), 1092 (m), 747 (m), 697 (m), 520 (m, 6 H, HBu), –12.10 (t, 2JH-P = 20.4, 1 H, H-Ru) ppm. 13C NMR
(s), 497 (w) cm–1. 1H NMR (600 MHz, CDCl3/[D6]DMSO): δ = (150.91 MHz, MeOD): δ = 205.6–205.3 (m, CO), 150.4, 149.6,
13.61 (s, 1 H, NH), 7.14–7.10 (m, 2 H, HPy), 7.05–6.95 (m, 18 H, 146.4, 134.8–134.7 (m), 134.6, 134.5, 131.0, 129.2 (t, 2JPC = 4.6 Hz),
3
HPh), 6.94–6.91 (m, 12 H, HPh), 6.82 (d, JHH = 5.6 Hz, 1 H, HPy),
101.9, 101.6, 32.6, 31.87, 26.3, 23.0, 14.1, 14.0 ppm. 31P NMR
3
5.98 (s, 1 H, HPz), 5.73 (t, JHH = 5.6 Hz, 1 H, HPy), 0.96 (s, 9 (242.94 MHz, MeOD): δ = 43.91 (s) ppm. C51H53ClN4OP2Ru
2
H, HtBu), –12.66 (t, JHP = 20.2 Hz, 1 H, Ru-H) ppm. 13C NMR
(936.46): calcd. C 65.41, H 5.71, N 5.98; found C 65.55, H 5.84, N
(150.92 MHz, CDCl3/[D6]DMSO): δ = 203.6–203.3 (m, CO), 156.9, 5.52.
153.73, 149.6, 147.5, 135.8, 132.8–132.7 (m), 131.6–131.3 (m),
(Carbonyl)(hydrido)[5-(pyridin-2-yl)pyrazol-1-ido]bis(triphenylphos-
129.3, 127.7–127.6 (m), 123.3, 119.8, 99.0, 30.65, 29.3 ppm. 31P
NMR (242.93 MHz, CDCl3/[D6]DMSO): δ = 46.36 (s) ppm.
C49H46ClN3OP2Ru (891.38): calcd. C 66.02, H 5.20, N 4.71; found
C 65.97, H 5.44, N 4.45.
phane)ruthenium (11a): [RuH2(CO)(PPh3)3] (140 mg, 0.15 mmol)
and 2-(1H-pyrazol-3-yl)pyridine (22 mg, 0.15 mmol) were dissolved
in dry toluene (10 mL) and stirred under reflux for 2 h. The re-
sulting colourless solid was filtered off and washed thoroughly with
(1H,1ЈH-3,3Ј-Bipyrazole)(carbonyl)(hydrido)bis(triphenylphosphane)- toluene and diethyl ether. Yield 101 mg (87%). IR (KBr): ν = 3051
˜
ruthenium Chloride (10a): Yield 75%, colourless solid. IR (KBr): ν
= 3429 (m, NH), 3053 (w), 2853 (w), 2825 (w), 1941 (s, C=O), 1622
(w), 1923 (s, CO), 1602 (w), 1529 (w), 1480 (w), 1447 (m), 1434
˜
(m), 1094 (w), 742 (w), 695 (m), 517 (m) cm–1. 1H NMR (400 MHz,
3
(w), 1480 (w), 1433 (m), 1093 (m), 749 (w), 695 (m), 521 (m), 495 CDCl3): δ = 7.94 (d, JHH = 5.3 Hz, 1 H, HPy), 7.45–7.41 (m, 2 H,
(w) cm–1. 1H NMR (400 MHz, [D6]DMSO): δ = 14.13 (s, 1 H, HPy, HPz), 7.36–7.30 (m, 12 H, HPh), 7.23–7.13 (m, 18 H, HPh),
3
3
NHЈ), 12.82 (s, 1 H, NH), 7.77 (s, 1 H, HPzЈ), 7.49–7.25 (m, 31 H, 6.89 (d, JHH = 7.9 Hz, 1 H, HPy), 6.40 (t, JHH = 5.9 Hz, 1 H,
2
HPh, HPz), 6.47 (s, 1 H, HPzЈ), 6.33 (s, 1 H, HPz), –12.19 (t, JH–P HPy), 6.15 (d, 3JHH = 1.5 Hz, 1 H, HPz), –10.37 (t, 2JHP = 20.2 Hz,
= 20.3 Hz, 1 H, Ru-H) ppm. 13C NMR (150.9, [D6]DMSO): δ = 1 H, RuH) ppm. 31P NMR (161.9 MHz, CDCl3): δ = 45.66 (s)
204.2–203.9 (m, CO), 144.3, 143.9, 133.1 (t, JPC = 5.7 Hz), 132.8– ppm. C45H37N3OP2Ru (798.82): calcd. C 67.66, H 4.67, N 5.26;
132.5 (m), 129.9, 128.3, 102.3, 102 ppm. 31P NMR (161.9 MHz, found C 66.74, H 4.56, N 5.10. The solubility of this compound is
CDCl3): δ = 44.97 (s) ppm. C43H37ClN4OP2Ru (824.25): calcd. C too low to record a 13C NMR spectrum.
62.66, H 4.52, N 6.80; found C 62.08, H 4.70, N 7.31.
[3-tert-Butyl-5-(pyridin-2-yl)pyrazol-1-ido](carbonyl)(hydrido)bis(tri-
(5,5Ј-Dibutyl-1H,1ЈH-3,3Ј-bipyrazole)(carbonyl)(hydrido)bis(triphen- phenylphosphane)ruthenium (11b): [RuH2(CO)(PPh3)3] (50 mg,
ylphosphane)ruthenium Chloride (10b): Yield 68%, colourless solid.
72.0 µmol) and 2-(5-tert-butyl-1H-pyrazol-3-yl)pyridine (18.2 mg,
90 µmol were dissolved in dry toluene (10 mL) and heated to reflux
for 72 h. After cooling to room temperature, pentane (10 mL) was
IR (KBr): ν = 3429 (m, NH), 2927 (m), 1948 (s), 1625 (w), 1570
˜
(w), 1497 (w), 1433 (m), 1092 (m), 808 (w), 743 (w), 695 (s), 595
1
(w), 518 (s), 497 (w) cm–1. H NMR (400 MHz, [D6]DMSO): δ = added. The precipitated colourless solid was filtered off and washed
Table 3. Summary of the crystallographic data and details of data collection and refinement for compounds 3b, 7, 8, 9a and 10b.
3b
7
8
9a
10b
Empirical formula
Mr [gmol–1]
Crystal size [mm]
T [K]
C14H22N4
246.36
0.40ϫ0.28ϫ0.10
150(2)
1.54184
tetragonal
I41/a
12.5762(2)
12.5762(2)
18.2475(5)
90
C55H55Cl2N5P2Ru
1019.95
0.14ϫ0.11ϫ0.08
150(2)
0.71073
monoclinic
P21/c
12.3066(2)
16.6012(3)
25.5794(4)
90
91.136(2)
90
5224.96(15)
4
1.297
0.504
2.45–32.48
71068
C56H53N5OP2Ru
975.04
0.12ϫ0.06ϫ0.04
150(2)
1.54184
monoclinic
P21/n
14.4507(2)
21.4693(3)
15.4743(2)
90
98.5410(10)
90
4747.60(11)
4
1.364
3.665
C46H39Cl4N3OP2Ru C53H59ClN4O2P2Ru
954.61
0.14ϫ0.07ϫ0.04
150(2)
982.50
0.28ϫ0.26ϫ0.12
293(2)
λ [Å]
1.54184
0.71073
monoclinic
Cc
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
triclinic
¯
P1
9.295(3)
19.736(8)
25.897(8)
68.40(3)
88.11(2)
81.37(3)
4366(3)
4
24.6004(16)
9.8153(5)
23.5948(14)
90
117.497(7)
90
5053.6(5)
4
1.291
90
90
γ [°]
V [Å3]
2886.04(10)
8
1.134
0.545
6.95–62.66
3324
Z
ρcalcd. [gcm–3]
µ [mm–1]
θ range [°]
Measured reflections
1.452
6.158
3.67–62.50
34979
0.469
2.30–28.17
30310
3.91–62.64
23051
Independent reflections 1137 [Rint = 0.0267] 17334 [Rint = 0.1069] 7487 [Rint = 0.0275] 13540 [Rint = 0.0344] 12257 [Rint = 0.0405]
Data/restraints/param.
Final R indices
[IϾ2σ(I)][a]
1137/0/83
17334/0/586
7487/0/586
13540/0/1033
12257/2/576
0.0435, 0.1252
0.0631, 0.1250
0.0247, 0.0533
0.0264, 0.0638
0.0322, 0.0592
R indices
(all data)[b]
0.0495, 0.1276
1.123
0.1443, 0.1522
0.964
0.0374, 0.0567
0.925
0.0393, 0.0782
1.051
0.0535, 0.0630
0.843
GoF[c]
Flack parameter
–
–
–
–
0.271(18)
0.414/–0.441
∆ρmax/ρmin [eÅ–3]
0.175/–0.186
0.961/–0.616
0.222/–0.425
0.619/–0.605
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}1/2. [c] GoF = {Σ[w(Fo – Fc ) ]/(n – p)}1/2
.
2
2 2
2
2 2
Eur. J. Inorg. Chem. 2010, 5135–5145
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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T. Jozak, D. Zabel, A. Schubert, Y. Sun, W. R. Thiel
FULL PAPER
6780–6785; Angew. Chem. Int. Ed. 2005, 44, 6622–6627; c) S. E.
Clapham, A. Hadzovic, R. H. Morris, Coord. Chem. Rev. 2004,
248, 2201–2237; d) M. Yamakawa, H. Ito, R. Noyori, J. Am.
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thoroughly with pentane. Yield 44.5 mg (70%). IR (KBr): ν = 3054
˜
(w), 2957 (w), 1917 (s, CO), 1604 (w), 1481 (w), 1434 (m), 1260
(w), 1093 (m), 804 (w), 744 (w), 695 (m), 517 (s) cm–1. 1H NMR
(600 MHz, [D6]DMSO): δ = 7.84 (br. s, 1 H), 7.4–7.1 (m, 31 H),
6.89 (br. s, 1 H), 6.47 (br. s, 1 H), 5.95 (br. s, 1 H), 1.04 (br. s, 9
H), –10.49 (br. s, 1 H, RuH) ppm. 31P NMR (242.94 MHz, [D6]-
DMSO): δ = 46.49 (s) ppm. C49H45N3OP2Ru (854.93): calcd. C
68.84, H 5.30, N 4.91; found C 69.32, H 5.41, N 4.83. The solubility
of this compound is too low to record a 13C NMR spectrum.
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corresponding CIF file. CCDC-786064 (3b), -786065 (7), -786066
(8), -786063 (9a) and -786067 (10b) contain the supplementary
crystallographic data for this paper. These data can be obtained
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