Room Temperature Activation of Aromatic C-H Bonds by Non-Classical Ruthenium Hydride Complexes Containing Carbene Ligands

Article abstract of DOI:10.1002/adsc.200303091

Non-classical ruthenium hydride complexes are promising lead structures for the C-H bond activation and functionalization of aromatic compounds. In the present paper, the preparation and crystallographic characterisation of the first organo-metallic complexes bearing dihydrogen ligands and N-heterocyclic carbene ligands in the same coordination sphere are described. The mixed phosphine/ carbene complex [(IMes)Ru(H)₂(H₂) ₂(PCy₃)] (IMes = 1,3-dimesityl-1,3-dihydro-2H-imidazol-2- ylidene; 3a) shows a unique reactivity pattern in the inter- and intramolecular activation of C-H bonds. In particular, complex 3a effects a rapid and remarkably selective intermolecular activation of sp² C-H bonds in simple aromatic compounds at room temperature.

Full text of DOI:10.1002/adsc.200303091

FULL PAPERS
À
Room Temperature Activation of Aromatic C H Bonds by Non-
Classical Ruthenium Hydride Complexes Containing Carbene
Ligands
Daniela Giunta,a Markus Hˆlscher,a Christian W. Lehmann,b Richard Mynott,b
Cornelia Wirtz,b Walter Leitnera,*
a
Institut f¸r Technische Chemie und Makromolekulare Chemie, Rheinisch-Westf‰lische Technische Hochschule Aachen,
Worringer Weg 1, 52074 Aachen, Germany
Fax: ( ‡ 49)-241-8022177, e-mail: leitner@itmc.rwth-aachen.de
b
Max-Planck-Institut f¸r Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 M¸lheim an der Ruhr, Germany
Received: May 9, 2003; Accepted: July 4, 2003
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de or from the author.
th
Dedicated to Prof. Manfred T. Reetz on the occasion of his 60 birthday.
Abstract: Non-classical ruthenium hydride complexes 3a) shows a unique reactivity pattern in the inter- and
À
À
are promising lead structures for the C H bond intramolecular activation ofC H bonds. In particu-
activation and functionalization of aromatic com- lar, complex 3a effects a rapid and remarkably
2
À
pounds. In the present paper, the preparation and selective intermolecular activation of sp C H bonds
crystallographic characterisation ofthe ifrst organo-
metallic complexes bearing dihydrogen ligands and
N-heterocyclic carbene ligands in the same coordina-
tion sphere are described. The mixed phosphine/ Keywords: C H bond activation; deuterium ex-
carbene complex [(IMes)Ru(H)2(H2)2(PCy3)] (IM- change; homogeneous catalysis; N-heterocyclic car-
in simple aromatic compounds at room temperature.
À
es ˆ 1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene;
benes; hydrido complexes; ruthenium complexes
Introduction
coupling ofacetophenone and ethylene even at room
temperature.[6] We found that the scope of the two types
The functionalization of aromatic compounds by direct ofcatalysts is complementary in certain cases, ofr
À
À
À
conversion ofC H to C C or C X (X ˆ N, O) bonds example, with electron-poor acetophenones being
can open new sustainable pathways for the synthesis of more reactive with 2 as compared to 1.[7] Unfortunately,
substituted aromatics.[1] In 1993, Murai first reported on catalyst 2 has a very limited lifetime under catalytic
the ruthenium-catalyzed coupling ofaromatic com-
conditions resulting from a rapid deactivation process
pounds with unsaturated substrates such as olefins or and loss ofPCy 3 from the catalytically active ruthenium
carbon monoxide.[2] The Murai reaction shows a broad centre.[8]
scope for both coupling partners and provides a
The substitution ofPCy 3 for strongly bulky and basic
promising synthetic approach to the waste-free con- N-heterocyclic carbene ligands[9] has been proven a
struction ofstructurally diverse C C skeletons.[3] Cleav- successful approach to generate active and stable
À
2
age ofan aromatic sp C H bond in ortho-position to a ruthenium catalysts, e.g., for olefin metathesis.[10] How-
À
ˆ
ˆ
suitable anchoring group (e.g., C O or C NR) consti- ever, there are currently no examples for organometallic
tutes a key step in the catalytic cycle.[3b,4]
compounds containing a basic carbene ligand in the
The first and still widely used generation of catalysts vicinity ofthe strongly acidic M-H moiety.[11,12] This
2
consists ofruthenium carbonyl hydride complexes such
as [(PPh3)3Ru(CO)(H)2] (1).[3] Generally, these com- analogues ofChaudret×s complex, [(IMes) xRu(H)2(H2)2-
plexes require high reaction temperatures ( ꢀ 1108C) (PCy3)2 x (IMes ˆ1,3-dimesityl-1,3-dihydro-2H-imid-
prompted us to target the synthesis ofthe carbene
]
and high catalyst loadings ( ꢀ 10 mol %). More recently, azol-2-ylidene; 3a: x ˆ1; 3b: x ˆ2).
Chaudret reported that his non-classical ruthenium
In the present paper, we report on the preparation and
hydride complex [(PCy3)2Ru(H)2(H2)2] (PCy3 ˆ tricy- X-ray crystallographic characterization of 3a and 3b.
clohexylphosphine, 2)[5] is able to initiate the Murai-type Furthermore, we describe that 3a is able to activate C H
À
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DOI: 10.1002/adsc.200303091
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Daniela Giunta et al.
FULL PAPERS
Table 1. Optimized conditions for the synthesis of 3a.
bonds in simple aromatic compounds very efficiently. In
particular, this is evidenced by a rapid and selective H/D
exchange process at room temperature. The intermo-
lecular exchange process is accompanied by two differ-
ent modes of sp C H bond activation in the coordina-
tion sphere ofthe ligand.
IMes/Ru
H2
[bar]
Solvent
Time
[h]
Temp.
[ 8C]
Yield
[%]
3
1.1/1
1.1/1
2.8/1
1/1
4
5
4
5
5
Toluene
Toluene
Hexane
Hexane
Hexane
3
19
3
3
6
RT
55
50
55
55
0
0
30
20
65
À
1/1
Results and Discussion
Initial attempts to prepare complexes 3 via the direct
hydrogenation route[7] starting from [(cod)Ru(h3- 0.84(5) and 0.67(6) ä, and they are interpreted as
C4H7)2] and free IMes were unsuccessful, most likely dihydrogen ligands. One ofthese H ligands (H4,H5)
2
due to a surprising lack ofreactivity ofthe carbene
resides on the same plane as the two hydrides (H8,H9)
ligand with the ruthenium precursor. Fortunately, we whereas the shorter H2 moiety (H6,H7) is almost
found that the mixed carbene/phosphine complex 3a is perpendicular to it. Despite some variation in the
obtained readily by treatment ofChaudret×s complex 2 individual values, the X-ray data suggest that the
-
À
with IMes under H2 atmosphere in hydrocarbon sol- Ru H distance is longer for the dihydrogen ligands [d
vents (Scheme 1). Under optimized conditions, 3a was
-
ˆ 1.69(5) ä] than for the classical hydrides [d ˆ
isolated in good yield directly from the reaction mixture 1.52(3) ä].
as a dark brown powder upon cooling and filtration
A small amount ofcrystalline 3b was isolated upon
(Table 1). Double substitution to give the bis-carbene cooling from a reaction mixture containing IMes and 2
hydride [(IMes)2Ru(H)2(H2)2] 3b was observed only in in a 4:1 ratio after 19 h at 558C. In the crystal lattice 20%
very small amounts even after prolonged treatment of 2 ofthe sites were occupied by the dinitrogen complex
with IMes in excess.
[(IMes)2Ru(H2)(N2)(H)2] (4) (Figure 2). Complex 4 is
Crystals of 3a suitable for X-ray diffraction were most likely formed from 3b by incorporation ofadven-
obtained by slow crystallisation from a dilute mother titious nitrogen during the preparation and mounting of
liquor at 08C.[13] The molecular structure reveals a trans the crystals. In addition to the end-on dinitrogen ligand,
arrangement ofthe two bulky ligands, as expected
(Figure 1). The C Ru P angle amounts to 165.98(7)8 map in the coordination sphere ofruthenium. They were
four peaks were located from the difference Fourier
À
À
À
indicating a significant deviation from linearity, which is interpreted as hydrogen atoms resulting in Ru H
in contrast to the linear arrangement in the complex 2.[14] distances in the range from 1.39(6) and 1.66(3) ä. Two
À
À
The Ru C and Ru P distances are in the typical range
observed for complexes containing the two different
ligand types.[10a] The mesitylene rings ofthe carbene
ligand are rotated relative to each other by 68.
For complex 3a, a total ofsix peaks were located from
the difference Fourier map in the coordination sphere of
ruthenium. These peaks were interpreted as hydrogen
atoms with distances from the central ruthenium
atom ranging between 1.44(3) and 1.82(5) ä. Two
hydrogen atoms (H8 and H9) have no close neighbours
and can be considered as hydride ligands positioned
cis to each other. The remaining four hydrogen atoms
are arranged in pairs with interatomic distances of
Figure 1. Molecular structure of 3a as determined by single
crystal X-ray diffraction. Selected atom distances [ä] and
angles [8] (thermal ellipsoids are given on the 50% proba-
bility level): Ru1 C1 2.055(2), Ru1 P1 2.317(7), Ru1 H4
1.82(5), Ru1 H5 1.60(4), Ru1 H6 1.69(4), Ru1 H7 1.63(5),
Ru1 H8 1.60(3), Ru1 H9 1.44(3); C1 Ru1 P1 165.98(7),
H8 Ru1 H9 81.0(18), H9 Ru1 H5 79.9(19), H8 Ru1
H6 88.7(19).
Scheme 1. Formation of 3a and 3b from 2 and IMes (IMes ˆ
1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene;
Mesityl ˆ 2,4,6-trimethylphenyl).
Mes ˆ
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Room Temperature Activation ofAromatic C H Bonds
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Figure 2. Molecular structure of 4 as determined by single
crystal X-ray diffraction. Selected atom distances [ä] and
angles [8] (thermal ellipsoids are given on the 50% proba-
bility level): H2 H3 0.90(8), C1' Ru1 2.050(4), C1 Ru1
2.057(4), C1 Ru1 C1' 166.54(16), H2 Ru1 H3 34.0(3).
1
Figure 4. Significant parts of the H NMR spectra for the H/
D exchange in 3a: a) averaged signal for the classical and
non-classical hydride ligands; b) CH3 groups in the IMes
ligand.
indicated at this theoretical level. The calculated (CDA
analysis,[15] B3LYP/B2) dissociation energies for the
IMes ( À 48.4 kcal/mol) and the PCy3 ( À 29.0 kcal/mol)
ligands are in agreement with a stronger Ru-carbene
interaction.[10b,10c]
1H, 13C{1H}, and 31P{1H} NMR spectroscopic studies
demonstrate that the molecular core of 3a is retained in
toluene-d8 solution. In a freshly prepared sample, the six
hydrogens in the coordination sphere ofruthenium give
rise to an averaged signal at room temperature, appear-
ing as a doublet (2JHP ˆ 8.32 Hz) ofbroad signals centred
at d ˆÀ 7.35. However, the intensity ofthis signal
decreases quickly to only 10% ofits original strength
after 5 hours at room temperature (Figure 4a). The
signals ofthe ortho-methyl groups in the IMes ligand
(d ˆ 2.17) disappear practically at the same rate (Figure
Figure 3. Comparison ofcalculated and crystallographically
determined atom distances [ä] and angles [8] of 3a (for
clarity only the core ofthe complex is shown). Geometries
were calculated on the BP86(RI)/TZVP level (details see
ref.[15]), figures in brackets denote the crystallographically
determined values).
ofthe hydrogen atoms are at adistance of0.90(8) ä from
À
À
each other [the H Ru H angle is 34(3)8] and have been 4b). This decay ofsignal intensities is accompanied by a
assigned as a dihydrogen ligand. The other two hydro- concurrent increase in the solvent resonances.
gen atoms are trans to each other. The angle between the
Detailed analysis ofthe time-resolved
1H and
two least squares planes formed by the five-membered 13C{1H} NMR spectra reveals that these changes result
rings ofthe two N-heterocyclic carbene ligands is 37.58. from a rapid H/D exchange between the meta-position
À
Key features of the experimentally determined mo- ofthe deuterated aromatic solvent, the Ru H moieties,
lecular structure of 3a are reflected in a theoretical and the ortho-methyl groups ofthe IMes ligand
analysis by DFT calculations (Figure 3).[15] Although the (Scheme 2, Figure 5). The incorporation ofdeuterium
metal hydrogen distances are somewhat overestimated at the metal centre and the methyl positions was
in the calculations, the ruthenium hydride distances are unambiguously demonstrated by deuterium NMR spec-
predicted to be significantly shorter (1.62 ä) than the troscopy and by the characteristic coupling pattern in
Ru H distances in the non-classical binding mode the 13C{H} NMR spectra. This activity of 3a for the
À
À
(1.75 1.87 ä) at several levels ofcomputation. The
activation ofsimple aromatic C H bonds is in remark-
distances and angles within the in-plane dihydrogen able contrast to Chaudret×s complex 2, which did not
ligand are also very similar. The out-of-plane co- show any significant exchange with toluene-d8 under the
ordination ofthe second H ligand is, however, not present conditions.
2
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Daniela Giunta et al.
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Scheme 2. H/D exchange process between 3a and toluene-d8.
Figure 5. Time-dependent evolution ofthe 1H NMR inten-
sities I (arbitrary scale) of 3a and toluene during the H/D
exchange with 3a in toluene-d8 (see text for details).
Despite the rapid incorporation ofdeuterium in the
ortho-methyl ofthe IMes ligand, [16] the methyl groups in
para-position and in toluene are not involved in the
exchange process to a significant extent even after
prolonged reaction times. There is, however, a slow
Scheme 3. Incorporation ofdeuterium in aromatic com-
pounds in benzene-d6 solutions containing 3a'. The style of
the arrows indicates the relative reactivity ofthe individual
positions (full arrow: fast exchange; dashed arrow: slow
secondary exchange process leading to incorporation of exchange).
deuterium in the cyclohexyl ring ofthe PCy ligand.[17]
3
After several weeks, approximately 75% of the hydro-
gens in the cyclohexyl rings were replaced with deute- various aromatic compounds is summarized in
rium whereby the exchange occurred preferentially at Scheme 3.
C3, C4 and to a lesser extent C1.
In order to get further insight into the sp C H bond benzene is very fast. Similarly, 3a' exchanges readily with
activation by complex 3a, we investigated the H/D biphenyl whereby the incorporation occurs mainly in
As mentioned above, the H/D exchange of 3a with
2
À
exchange with a series ofother aromatic compounds.
meta and para positions as further demonstrated in
Upon dissolving 3a in benzene-d6, the exchange be- Figure 7. It seems tempting to assign the lower reactivity
tween the complex and the solvent was even faster than in ortho-position to steric hindrance, but more complex
with toluene-d8, leading to complete deuteration at the control mechanisms seem to be operating as indicated by
metal centre and the ortho-methyl groups within 5 the strong meta preference of the exchange with toluene.
minutes at ambient conditions. Solutions ofthe deuter-
ated ruthenium complex 3a' obtained by this method substituents such as Cl and CN are not activated under
were treated with 10 equivalents ofanother aromatic the present conditions. Anisol is deuterated with
Aromatic compounds with strongly electronegative
compound (relative ratios: benzene-d6:3a':substrate ˆ moderate activity at the aromatic core with a slight
1000:1:10) and analyzed for decay of the substrate ortho/para preference. Deuterium incorporation in the
1
signals as a function of time by H NMR at room OCH3 group is also noticeable, amounting to approx-
temperature. Figure 6 shows the results ofa typical
imately 20% OCH2D after 14 hours. Phenol, however,
experiment as exemplified for aniline as the aromatic exchanges only at the protic position with no detectable
substrate. The disappearance ofthe signals arising from
the ortho protons upon incorporation ofdeuterium in
incorporation ofdeuterium in the aromatic positions. In
contrast, aniline shows a fast exchange in the NH2 group
the aromatic compound is accompanied by a concurrent and simultaneous incorporation ofdeuterium almost
increase ofthe signal intensity ofthe solvent. The overall exclusively in the ortho position ofthe aromatic ring
reactivity pattern resulting from these investigations for (Figures 6 and 8).
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Room Temperature Activation ofAromatic C H Bonds
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In summary, we have prepared the first organometal-
lic compounds containing N-heterocyclic carbene li-
gands and dihydrogen ligands in the same coordination
sphere. The non-classical ruthenium hydride [(IMes)-
Ru(H)2(H2)2(PCy3)] 3a exhibits a unique reactivity
pattern for intra- and intermolecular activation of
À
C H bonds. In particular, complex 3a effects a rapid
and remarkably selective intermolecular activation of
2
À
sp C H bonds in simple aromatic compounds at room
temperature. This reactivity appears to be directly
related to the presence ofthe IMes ligand in the
coordination sphere of 3a, as the related bisphosphine
complex 2 does not show a similar reactivity under
identical conditions. Substituents at the aromatic core of
the substrate have a decisive influence on the reactivity
ofthe exchange process, exhibiting a complex interplay
of electronic and steric effects. Further studies to
Figure 6. Staggered plot ofthe time dependent 1H NMR
spectra during the H/D exchange ofaniline in benzene- d6 in
the presence of 3a' (every second spectrum ofthe monitoring
process is shown for clarity).
À
elucidate the mechanism ofthe C H activation process
and to evaluate the catalytic properties of 3a are
currently under way.
Figure 7. Time-dependent evolution ofthe 1H NMR intensities I (arbitrary scale) ofbiphenyl in a benzene- d6 solution of 3a'
(see text for details).
Figure 8. Time-dependent evolution ofthe 1H NMR intensities I (arbitrary scale) ofaniline in a benzene- d6 solution of 3a'
(details see text).
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Daniela Giunta et al.
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1H NMR in intervals of 1 h for one day (see Figure 6 for
details). The H/D exchange experiments with other aromatic
substrates were performed in the same way.
Experimental Section
General Procedures
Reactions were conducted under Ar or H2 atmospheres.
Solvents and substrates were purchased from Aldrich and
Acros and purified according to standard procedures. Prepa-
ration ofthe IMes ligand was carried out following a modified
literature procedure.[18] Chaudret×s complex was obtained
according to the direct hydrogenation route.[7] 1H NMR,
13C NMR and 31P NMR spectra were recorded in deuterated
Acknowledgements
This work was supported bythe Bundesministerium f¸r Bildung
und Forschung as part of the lighthouse project ∫Nachhaltige
Aromatenchemie (03C0342F)∫.
2
solvents on a Bruker DPX 300 spectrometer. D NMR and
13C NMR spectra of3a were perofrmed in non-deuterated
solvents on a Bruker DMX 600 spectrometer.
References and Notes
[1] a) J. A. Davies, P. C. Watson, J. F. Liebman, A. Green-
berg, Selective Hydrocarbon Activation, VCH, Wein-
heim, 1990; b) A. D. Ryabov, Chem. Rev. 1990, 90, 91;
c) G. Dyker, Angew. Chem. Int. Ed. 1999, 38, 1698 1712;
d) Y. Guari, S. Sabo-Etienne, B. Chaudret, Eur. J. Inorg.
Chem. 1999, 1047 1055.
[2] S. Murai, F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani,
M. Sonoda, N. Chatani Nature 1993, 366, 529 531.
[3] a) F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani, M.
Sonoda, N. Chatani, S. Murai, Bull Chem. Soc. Jpn. 1995,
68, 62 83; b) M. Sonoda, F. Kakiuchi, N. Chatani, S.
Murai, Bull Chem. Soc. Jpn. 1997, 70, 3117 3128; c) K.
Fumitoshi, S. Murai, Acc. Chem. Res. 2002, 35, 826 834.
[4] T. Matsubara, N. Koga, D. G. Musaev, K. Morokuma,
Organometallics 2000, 19, 2318 2329.
[5] a) B. Chaudret, G. Commenges, R. Poilblanc, J. Chem.
Soc. Chem. Commun. 1983, 641 643; b) B. Chaudret, R.
Poilblanc, Organometallics 1985, 4, 1722 1726.
[6] a) Y. Guari, S. Sabo-Etienne, B. Chaudret, J. Am. Chem.
Soc. 1998, 120, 4228 4229; b) Y. Guari, S. Sabo-Etienne,
B. Chaudret, Eur. J. Inorg. Chem. 1999, 1047 1055.
[7] S. Busch, W. Leitner, Chem. Commun. 1999, 2305 2306.
[8] S. Busch, W. Leitner, Adv. Synth. Catal. 2001, 343, 192
195.
Preparation of the Complex
(IMes)Ru(H)2(H2)2(PCy3) 3 a
Compound 2 (258 mg, 0.38 mmol), IMes (133 mg, 0.43 mmol)
and hexane (15 mL) were introduced in a thick-walled glass
reactor which was subsequently charged with H2 (5 bar). The
white suspension was heated under stirring to 558C for 6 h after
which the solution had turned dark orange. After cooling to
room temperature, the solution was transferred to a Schlenk
tube. Complex 3a was obtained as a dark brown powder by
cooling to À 208C for several days followed by filtration and
drying under H2 atmosphere; Yield: 157 mg (0.23 mmol,
60.5%); 1H NMR (300 MHz, toluene-d8, 258C): d ˆÀ 7.35 (d,
2
6H ofRu-H, JH,P ˆ 8.32 Hz), 1.0 2.0 (m, 33H ofPCy 3), 2.17 (s,
12H, o-CH3 ofIMes), 2.19 (s, 6H, p-CH3 ofIMes), 6.36 (s, 2H,
NCHCHN), 6.85 (s, 4H, m-CH ofIMes); 31P NMR (121 MHz,
toluene-d8, 258C): d ˆ 78.09 (s); 13C NMR (150 MHz, toluene,
258C): d ˆ 199 (NCN, JP, C ˆ 74.4 Hz), 140.3 (NC1 ofthe
mesitylene ring), 137.4 (p-C-CH3 ofIMes), 136.2 ( o-C-CH3 of
IMes), 129.1 (m-CH ofthe IMes), 120.0 (CH ofthe imidazo-
lium ring, JP, C ˆ 2.3 Hz), 38.2 (PCH ofthe Cy, J ˆ 16.8 Hz),
P, C
30.6 (o-CH2 ofthe Cy), 28.4 ( m-CH2 ofthe Cy, J P, C ˆ 9.7 Hz),
d ˆ 27.4 (p-CH2 ofthe Cy), 21.2 ( p-CH3 ofthe IMes), 18.8 ( o-
CH3 ofthe IMes).
[9] a) W. A. Herrmann, C. Kˆcher, Angew. Chem. Int. Ed.
Engl. 1997, 36, 2162 2187; b) W. A. Herrmann, Angew.
Chem. Int. Ed. 2002, 41, 1290 1309.
[10] a) T. Weskamp, W. C. Schattenmann, M. Spiegler, W. A.
Herrmann, Angew. Chem. Int. Ed. 1998, 37, 2490 2492;
b) J. Huang, E. D. Stevens, S. P. Nolan, J. L. Petersen, J.
Am. Chem. Soc. 1999, 121, 2674 2678; c) M. S. Sanford,
J. A. Love, R. H. Grubbs, J. Am. Chem. Soc. 2001, 123,
6543 6554.
[11] G. J. Kubas, Metal Dihydrogen and s-Bond Complexes,
Kluver Academic/Plenum Publishers, New York, 2001;
b) P. J. Jessop, R. H. Morris, Coord. Chem. Rev. 1992,
121, 155 284.
H/D-Exchange Experiments with 3a and Deuterated
Aromatic Compounds
Complex 3a (13 mg; 0.018 mmol) and toluene-d8 (0.6 mL) were
introduced in a NMR tube under argon. The solution was
analysed by 1H NMR in intervals of1 h ofr one day (see
Figure 4 for details). The 2D NMR (92 MHz, toluene-d8, 258C)
after 3 h showed resonances at d ˆ 2.13 (o-Me ofthe mesity-
lene groups), 1.65 and 1.06 (Cy groups), and À 7.3 (Ru-D). The
same methodology was applied with benzene-d6 as the solvent.
[12] For the stability ofcoordinated carbenes in the presence
ofacidic groups see also: A. Fuerstner, H. Krause, L.
Ackermann, C. W. Lehmann, Chem. Commun. 2001, 21,
2240 2241.
[13] Crystal structure analyses. 3a: brown crystals with
dimensions 0.32  0.20  0.12 mm3, l ˆ 0.71073 ä, Tˆ
100 K, monoclinic, P21/n (No. 14), a ˆ 12.1460(7), b ˆ
18.9333(11), c ˆ 17.2816(10) ä, b ˆ 106.291(2)8, Vˆ
H/D-Exchange with 3a'and Non-Deuterated Aromatic
Compounds
Complex 3a (5.4 mg; 0.0078 mmol) and benzene-d6 (0.7 mL)
were introduced in a NMR tube under argon. The solution was
kept at room temperature for 24 hours and checked by
1H NMR for full deuteration of 3a to 3a'. Then, aniline (7.2 mg;
0.078 mmol) was introduced and the solution was analysed by
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Room Temperature Activation ofAromatic C H Bonds
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3
1
3814.6(4) ä3, Z ˆ 4, rcalc. ˆ 1.205 Mg m , m ˆ 0.480 mm ,
from reaction with adventitious N2 during the set up of
the diffraction experiment.
F(000) ˆ 1480, 13993 independent reflections of which
7807 with I > 2s I (total reflections 41072), 2qmax
ˆ
[14] A. F. Borowski, B. Donnadieu, J.-C. Daran, S. Sabo-
Etienne, B. Chaudret, Chem. Commun. 2000, 543 544.
[15] Calculations on 3a were carried out using the Gaussian98
and the Turbomole5.5 suite ofprograms. Gaussian98
calculations which were used as input for CDA-analysis
were done on the B3LYP level oftheory using the 6
31G(d) basis set for C, H, N and P and a (441/2111/31/1)
valence basis for Ru associated with a non relativistic
small core ECP. Turbomole calculations were carried out
on the BP86 level oftheory taking advantage ofthe RI-
DFT method using the TZVP basis set together with a
quasirelativistic ECP for Ru. All geometry optimisations
were carried out with no constraints and all geometries
were checked to be minima on the hypersurface by
frequency calculations (zero imaginary frequencies).
Further details and the full references for the computa-
tional methods are compiled in the Supplementary
Material.
[16] For metallation ofthe ortho-methyl groups in Ru-IMes
complexes under much more forcing conditions, see:
R. F. R. Jazzar, S. A. Macgregor, M. F. Mahon, S. P.
Richards, M. K. Whittlesey, J. Am. Chem. Soc. 2002,
124, 4944 4945.
[17] For precedence ofexchange processes in cyclohexyl
groups attached to ruthenium phosphine groups see: C.
Six, K. Beck, A. Wegner, W. Leitner, Organometallics
2000, 19, 4639 4642 and references cited therein.
[18] A. J. Arduengo III, R. Krafczyk, R. Schmutzler, H. A.
Craig, J. R. Goerlich, W. J. Marshall, M. Unverzagt,
Tetrahedron 1999, 55, 14523 14534.
66.348. Structure solution by Patterson method
(SHELXS-97). Full matrix least squares refinement
(SHELXL-97) versus F2. Data/restraints/parameters
13993/0/416. GOF on F2 ˆ 0.92, R1[I > 2s (I)] ˆ 0.058,
wR2 (all data) ˆ 0.125. Max./min. residual electron den-
3
sity: 0.7/ 0.7 e A . Six hydrogen atoms at the ruthenium
centre were located from the difference Fourier map and
their positions and isotropic displacement parameters
were refined. All other hydrogen atoms were forced to
ride on the attached carbon atoms in geometrically
idealised positions. CCDC-202653 contains the supple-
mentary crystallographic data for this paper. These data
can be obtained online free of charge (or from the
Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: ( ‡ 44) 1223-336-
033 or deposit@ccdc.cam.ac.uk). 3b/4: pale yellow crystal
3
with dimensions 0.39  0.18  0.18 mm , l ˆ 0.71073 ä,
Tˆ 100 K, monoclinic, P21/n (No. 14), a ˆ 14.2338(7),
b ˆ 11.2474(5), c ˆ 24.3152(11) ä, b ˆ 92.095(2)8, Vˆ
3
3890.1(3)
ä3,
Z ˆ 4,
rcalc. ˆ 1.216
Mg m , m ˆ
1
0.435 mm , F(000) ˆ 1496, 8489 independent reflections
ofwhich 5916 with I > 2s(I) (total reflections 32528)
2qmax ˆ 548. Structure solution with Patterson method.
Full matrix least squares refinement versus F2. Data/
restraints/parameters 8489/0/423. GOF on F2 ˆ 1.04,
R1[I > 2s(I)] ˆ 0.056, wR2 ˆ 0.1440. Max./min. residual
3
electron density: 1.6/ 0.8 e A . Approximately 20% of
the lattice sites in 3b were occupied by the corresponding
N2-complex [Ru(H)2(N2)2(IMes)2] 4, presumably formed
Adv. Synth. Catal. 2003, 345, 1139 1145
asc.wiley-vch.de
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1145