Ruthenium carbene complexes featuring a tridentate pincer-type ligand

Article abstract of DOI:10.1021/om0501780

Ruthenium carbene complexes featuring the bulky tridentate N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamido pincer-type ligand and different stabilizing phosphine ligands were synthesized and characterized. Preliminary results for the application to ring-closing metathesis show low activity for the cyclization of 1,7-octadiene with benzylidene(triphenylphosphine)[N,N′-bis(2,6-diisopropylphenyl)-2, 6-pyridinedicarboxamido-_κ³O,N,O/O,N,N]ruthenium(II) (4a,b). Benzylidene(tricyclohexylphosphine)[N,N′-bis(2,6-diisopropylphenyl) -2,6-pyridinedicarboxamido-_κ³3O,N,O]ruthenmm(II) (5) successfully transformed 1,7-octadiene to cyclohexene and ethylene in good yields at room temperature or 80°C.

Full text of DOI:10.1021/om0501780

Organometallics 2005, 24, 4289-4297
4289
Ruthenium Carbene Complexes Featuring a Tridentate
Pincer-type Ligand
Julia-Christina Wasilke,†,‡ Guang Wu,†,§ Xianhui Bu,†,§ Gerald Kehr,‡ and
Gerhard Erker*,‡
Department of Chemistry and Biochemistry, Institute for Polymers and Organic Solids,
University of California, Santa Barbara, California 93106, and Organisch-Chemisches Institut
der Universita¨t Mu¨nster, Corrensstrasse 40, D-48149 Mu¨nster, Germany
Received March 10, 2005
Ruthenium carbene complexes featuring the bulky tridentate N,N′-bis(2,6-diisopropylphen-
yl)-2,6-pyridinedicarboxamido pincer-type ligand and different stabilizing phosphine ligands
were synthesized and characterized. Preliminary results for the application to ring-closing
metathesis show low activity for the cyclization of 1,7-octadiene with benzylidene(triphen-
ylphosphine)[N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamido-κ3O,N,O/O,N,N]-
ruthenium(II) (4a,b). Benzylidene(tricyclohexylphosphine)[N,N′-bis(2,6-diisopropylphenyl)-
2,6-pyridinedicarboxamido-κ3O,N,O]ruthenium(II) (5) successfully transformed 1,7-octadiene
to cyclohexene and ethylene in good yields at room temperature or 80 °C.
Chart 1. Catalysts for Olefin Metathesis
Introduction
Olefin metathesis catalyzed by middle-1 and late-
transition-metal2 carbene complexes has become an
important tool in organic synthesis as well as polymer
chemistry.3 Various catalyst modifications have been
made improving catalyst activity and sensitivity, reac-
tion conditions, and range of tolerance toward functional
groups (Chart 1).4 One or both phosphine ligands have
been replaced by other ligands, such as N-heterocyclic
carbenes,5 showing increased reactivities with various
olefinic substrates. Catalyst immobilization has led to
recyclable systems.6
Recent development of the [Ru]dCHR type catalysts
include structures that contain various connections
between the supporting N-heterocyclic carbene ligand
and the active alkylidene group at ruthenium7 as well
as variations of donor groups and functionalities at the
dCHR end of the Ru-carbene complex.8 Halide-free
systems have found an increasing interest,9 and the use
of small chelate phosphine ligands has sometimes been
* To whom correspondence should be addressed. E-mail: erker@
uni-muenster.de.
† University of California.
‡ Universita¨t Mu¨nster.
§ X-ray crystal structure determinations.
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10.1021/om0501780 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 07/15/2005

4290 Organometallics, Vol. 24, No. 17, 2005
Wasilke et al.
Chart 2. Ru Metathesis Catalysts with N-Donor
Ligands
material for the carbene complex synthesis, tris(tri-
phenylphosphine)ruthenium dichloride was reacted with
2 to give [N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedi-
carboxamido-κ3O,O,N]bis(triphenylphosphine)ruthenium-
(II) (3; (lig)Ru(PPh3)2) as a red crystalline material
(Scheme 1). The compound was fully characterized by
elemental analysis and NMR spectroscopy. The 1H NMR
spectrum shows one septet for the isopropyl CH groups
and two broad singlets for the methyl groups, indicating
that the coordination modes of both sides of the metal
are the same and one isomer is formed. This is sup-
ported by the 31P NMR spectrum of 3, showing one peak
at δ 60.2 ppm.
Scheme 1
Reaction of 3 with phenyldiazomethane in dichlo-
romethane at -35 °C led to replacement of one PPh3
ligand to yield the product 4 as a mixture of two isomers
in an overall yield of 91% (Scheme 2). The metal center
can be coordinated by the ligand in an O∧N∧O or
O∧N∧N fashion (ratio ∼4:7). Each isomer could be
isolated from the red-brown solid. Crystallization from
dichloromethane by pentane diffusion at -35 °C gave
the O∧N∧O isomer 4a as dark red crystals suitable for
X-ray diffraction. Crystallization from toluene by pen-
tane diffusion at room temperature gave the O∧N∧N
advantageous.10 Replacement of the labile phosphine at
ruthenium by pyridine or pyridine derivates (see Chart
2) has led to very reactive olefin metathesis catalysts.11
Similarly, the attachment of monoanionic salicylaldi-
mine-type chelate ligands (see Chart 2) has sometimes
resulted in improved catalytic features.12 We want to
present the first examples of a new ligand and catalyst
development where we have combined the essential
features of the latter systems and attached a dianionic
tridentate 2,6-disubstituted pyridine pincer-type ligand
to [Ru]dCHR to form a new halide-free [(lig)(PR3)Rud
CHR] olefin metathesis catalyst system.
1
isomer 4b as a red crystalline material. H NMR data
confirmed the installation of the carbene moiety at δ
18.21 (4a) and δ 18.24 (4b) for the two isomers,
respectively. Due to the electronic influences of the
different ligand coordination environments, the 31P
NMR spectra display two distinct signals at δ 49.2 (4a)
and δ 38.2 (4b) for the two isomers, respectively.
Attempts were directed toward the replacement of the
triphenylphosphine ligand of the compounds 4 with
tricyclohexylphosphine. Prolonged reaction with tri-
cyclohexylphosphine, as previously reported for other
compounds,13 did not result in phosphine exchange.
Therefore, we reacted the dianionic ligand 2 with
benzylidenebis(tricyclohexylphosphine)ruthenium (II)
dichloride in dichloromethane at room temperature
overnight (Scheme 3). After purification the product 5
was isolated as a brown powder in 93% yield. Single
crystals could not be obtained, but NMR spectroscopy
indicates only O∧N∧N coordination of the ligand in
comparison to the triphenylphosphine derivatives.
Nickel Complexes. The system was carried forward
to nickel compounds, since only a limited number of
nickel carbene complexes are known.14 To obtain the
nickel precursor material for the carbene compound
synthesis, (dimethoxyethane)nickel dichloride was re-
acted with 2. At room temperature over 3 h, potassium
[N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxa-
Results and Discussion
Synthesis of the Ligand System and Ru Com-
plexes. The new carbene complexes were derived from
the tridentate ligand 1, which is easily synthesized from
2,6-pyridinedicarboxylic acid chloride and 2,6-diisopro-
pylaniline (Scheme 1). Deprotonation proceeded most
reliably and reproducibly with KH in THF to yield the
potassium salt 2. To obtain the ruthenium precursor
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Ruthenium Complexes Featuring a Pincer-Type Ligand
Scheme 2
Organometallics, Vol. 24, No. 17, 2005 4291
Scheme 3
analysis (Figure 1). Suitable single crystals were grown
from a methanol solution by evaporation in air. A
conformation is found where all three nitrogens are
oriented toward the “inside” of the chelate framework.
mido-κ3N,N,N]nickel(II) chloride (6) was obtained as a
polymeric material with loss of 1 equiv of potassium
chloride. Reaction at 80 °C over 5 days yielded [N,N′-
bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamido-
κ3N,N,N]nickel(II) as a poorly soluble orange powder.
Crystallization from polar solvents provided X-ray
structures of the solvent adducts 7 and 8. The reaction
was repeated in the presence of trimethylphosphine to
give [N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicar-
boxamido-κ3O,N,N′](trimethylphosphine)nickel(II) (9;
(lig)NiPMe3) as a red crystalline material after workup
(Scheme 4). Compound 9 is more soluble than com-
pounds 7 and 8 and was characterized by elemental
analysis, NMR spectroscopy, and X-ray diffraction.
Reaction of (lig)NiPMe3 (9) with phenyldiazomethane
in dichloromethane at -35 °C gave an orange powder
Figure 1. Molecular structure of the ligand system 1.
Thermal ellipsoids are shown at the 50% probability level;
hydrogen atoms have been omitted for clarity.
Single crystals of the potassium salt 2 were grown
from hot THF. The compound revealed a complex
crystallization pattern. The ratio of potassium to ligand
is 2:1, q.e.d. Two ligands are facing each other, and the
four oxygen and the two pyridine nitrogen centers are
coordinating three potassium atoms. The central potas-
sium is further coordinated by two molecules of THF.
Each dimeric set of ligands is connected via a fourth
potassium binding a nitrogen from each set in such a
way that the individual dimers are shifted against each
other (Figure 2).
1
after workup. Two isomers were observed by H NMR
spectroscopy, both containing a signal at low field for
the carbene proton, but the compounds were otherwise
1
ill defined. Comparison of the H NMR spectrum (for
details see the Experimental Section) with the ruthe-
nium derivatives suggests O∧N∧O and O∧N∧N coor-
dination at nickel in a 3:7 ratio.
X-ray Crystal Structure Analyses. Some of the
compounds synthesized in the course of this study were
characterized by X-ray diffraction. First, we investigated
the free ligand system 1 by an X-ray crystal structure
Pentane diffusion into a solution of the compound 3
in toluene at room temperature gave a red crystalline
material suitable for X-ray crystal structure analysis
Scheme 4

4292 Organometallics, Vol. 24, No. 17, 2005
Wasilke et al.
Figure 2. Drawing and X-ray structure of the ligand potassium salt 2.
(Figure 3). The structure reveals O∧N∧O coordination
of the ligand. The ruthenium is surrounded by its
ligands in a distorted-square-pyramidal fashion with the
two phosphines and the coordinating oxygen atoms in
the plane and the coordinating pyridine ring perpen-
dicular to it.
Crystallographic analysis of compounds 4a,b show a
square-pyramidal arrangement of the ligand coordinat-
ing to the metal center for both isomers (Figure 4). In
each case the tridentate ligand and phosphine form a
square-planar arrangement around the metal center
while the carbene carbon builds the tip of the pyramid.
In the triclinic O∧N∧O isomer (4a) the ruthenium atom
is slightly pushed out of the plane toward the carbene
carbon and the metal center is less sterically hindered
than in the monoclinic O∧N∧N isomer (4b). The nitro-
gen coordination by one of the amidate functionalities
renders the isopropyl groups of the amide in closer
proximity to the ruthenium-carbene carbon bond. The
coordinating oxygen is slightly distorted out of the plane
away from the carbene carbon, and ruthenium is equally
pushed out of the plane toward the carbene carbon.
Selected bond lengths for both isomers are shown in
Table 1. The C(7)-N(1) bonds (4a, 1.275(4) Å; 4b, 1.269-
(5) Å) show double-bond character, and the C(7)-O(1)
bonds (1.329(3), 1.326(4) Å) show single-bond character
in both isomers, as expected. The C(13)-N(3) bonds
(1.283(4), 1.359(5) Å) show double-bond character in the

Ruthenium Complexes Featuring a Pincer-Type Ligand
Organometallics, Vol. 24, No. 17, 2005 4293
angles exceed a perpendicular arrangement, while the
C(32)-Ru-P (88.43(10), 90.74(12)°) angles match a
perpendicular alignment. The angles formed by the
tridentate ligand with the ruthenium center fall short
of 90° angles, while the bond angles formed by the
tridentate ligand, ruthenium, and the phosphine ligand
exceed perpendicular alignment (see Table 1).
Single crystals of the nickel complex 6 were obtained
from hot THF, and the structure incorporates three
additional molecules of THF (Figure 5). The nickel
center is surrounded by the N∧N∧N-coordinating tri-
dentate ligand and chloride in a square-planar arrange-
ment. Potassium coordinates to oxygen and one phenyl
ring in an η6 fashion. The structure is polymeric,
forming a chain with potassium linking the monomeric
subunits (K(1)-O(11) ) 2.716(4) Å; e.g. K(1)-C(13) )
3.255(6) Å). As expected, the carboxamido C-N bonds
are rather long (N(11)-C(57) ) 1.354(7) Å, N(21)-C(58)
) 1.352(7) Å), whereas the adjacent CdO bonds are
short (O(11)-C(57) ) 1.241(6) Å, O(21)-C(58) ) 1.230-
(6) Å).
Figure 3. View of the molecular structure of (lig)Ru-
(PPh3)2 (3). Thermal ellipsoids are shown at the 50%
probability level; hydrogen atoms have been omitted for
clarity.
Single crystals of compound 7 were obtained from wet
hexane (Figure 6). The structure reveals N∧N∧N coor-
dination of the ligand to the metal center. Crystalliza-
tion from methanol gives the according structure where
the water ligand is replaced by methanol (8) (for details
see the Supporting Information).
Single crystals of compound 9 were grown from THF
or from toluene by pentane diffusion at -35 °C (Figure
7). The nickel center is surrounded by the O∧N∧N-
O∧N∧O isomer (4a) and single-bond character in the
O∧N∧N isomer, while the C(13)-O(2) bond of 4a shows
single-bond character (1.324(4) Å) and that of 4b double-
bond character (1.230(4) Å). The C(32)-Ru bonds (4a,
1.853(3) Å; 4b, 1.846(4) Å) show the expected bond
lengths for a ruthenium-carbene bond (1.77-1.90 Å).15
Bond angles are similar in both isomers. The C(32)-
Ru-N(2) (105.71(12), 102.23(14)°), -O(2) (102.89(11)°),
-N(3) (103.37(14)°), and -O(1) (102.70(11), 98.19(14)°)
Figure 4. ORTEP drawings of (lig)Ru(PPh3)CHPh (4a) (O∧N∧O) (left) and (lig)Ru(PPh3)CHPh (4b) (O∧N∧N) (right).
Thermal ellipsoids are shown at the 50% probability level; hydrogen atoms have been omitted for clarity.
Table 1. Selected Bond Lengths for Both Isomers of (lig)Ru(PPh3)CHPh (4)
bond length (Å)
O∧N∧O (4a)
O∧N∧N (4b)
bond angle (deg)
O∧N∧O (4a)
O∧N∧N (4b)
C(6)-N(1)
C(7)-N(1)
C(7)-O(1)
C(13)-N(3)
C(13)-O(2)
C(14)-N(3)
C(32)-C(33)
C(32)-Ru
N(2)-Ru
1.425(4)
1.275(4)
1.329(3)
1.283(4)
1.324(4)
1.430(4)
1.469(4)
1.853(3)
2.029(2)
2.0369(19)
2.037(2)
1.426(4)
1.269(5)
1.326(4)
1.359(5)
1.230(4)
1.451(5)
1.450(5)
1.846(4)
2.009(3)
2.060(3)
C(33)-C(32)-Ru
C(32)-Ru-N(2)
C(32)-Ru-O(2)
N(2)-Ru-O(2)
C(32)-Ru-N(3)
N(2)-Ru-N(3)
C(32)-Ru-(O1)
N(2)-Ru-O(1)
C(32)-Ru-P
131.9(2)
132.3(3)
105.71(12)
102.89(11)
78.29(9)
102.23(14)
103.37(14)
77.55(12)
98.19(14)
78.23(11)
90.74(12)
102.70(11)
78.64(9)
88.43(10)
97.10(6)
165.75(7)
100.32(6)
O(1)-Ru
O(2)-Ru-P
O(2)-Ru
N(2)-Ru-P
164.76(9)
92.16(7)
N(3)-Ru
2.077(3)
2.3273(10)
O(1)-Ru-P
P-Ru
2.2975(8)

4294 Organometallics, Vol. 24, No. 17, 2005
Wasilke et al.
Scheme 5. RCM of 1,7-Octadiene to Cyclohexene
and Ethylene
Ring-Closing Metathesis: Preliminary Results.
To investigate the activity of the ruthenium and nickel
carbene complexes for RCM, 1,7-octadiene was chosen
as a simple and straightforward example known from
the literature.16 The main products are expected to be
cyclohexene and 1 equiv of ethylene (Scheme 5). Possible
side products are mainly double-bond isomers of the
diene.
Reactions were run in deuterated benzene inside
Young NMR tubes at room temperature or 80 °C and
monitored by 1H NMR spectroscopy. Alternatively,
reactions were run more dilute in toluene and aliquots
were analyzed by GC. Commercially available samples
served as reference for the product. Commercially
available Cl2Ru(PCy3)2dCHPh, Cl2Ru(PCy3)2dCHCHd
CMe2, and Cl2Ru(PCy3)dCH(o-C6H4OiPr) were tested
for comparison. Table 2 summarizes the results.
The triphenylphosphine-stabilized O∧N∧O-coordi-
nated ruthenium carbene complex 4a displays relatively
low conversion of 1,7-octadiene to cyclohexene. After
3 h at 80 °C 76% product is observed, as well as 24%
isomers. Prolonged reaction time up to 27 h yields
conversion up to 98% product. The presence of the
Figure 5. X-ray structure analysis of (lig)NiKCl (6): view
of the repetitive unit in the coordination polymer. Thermal
ellipsoids are shown at the 50% probability level; hydrogen
atoms have been omitted for clarity.
17
proton source (2H-pyrrole)B(C6F5)3 did not markedly
change the catalyst performance. Activation with Lewis
acids reduced the product yield drastically along with
increased amounts of isomers.18 Addition of 3 equiv of
B(C6F5)3 reduced the yield to 40% after 3 days at 80 °C.
The N∧N∧O isomer 4b showed no activity with or
without B(C6F5)3 activation under the applied reaction
conditions.
Replacement of the triphenylphosphine moiety by
tricyclohexylphosphine provides a catalyst (5) with
activities comparable to Grubbs analogues at 80 °C as
well as at room temperature. Product yields varied in
the range of 83-95% with negligible amounts of iso-
mers. Overall the concentration did not play as signifi-
cant a role as reported for commonly used ruthenium
carbene catalysts. Within the range of 1.6-6 mM
catalyst in deuterated benzene or toluene, yields did not
vary significantly.
Figure 6. X-ray structure analysis of (lig)Ni(H2O) (7).
Thermal ellipsoids are shown at the 50% probability level;
hydrogen atoms have been omitted for clarity.
Conclusions
Two ruthenium carbene complexes (4 and 5) with a
bulky tridentate ligand were synthesized and character-
ized. NMR spectroscopy and X-ray crystallography
allowed for characterization of the coordination mode
of the ligand in compound 4. Compound 5 shows
activities comparable to that of previously reported
catalysts for RCM of 1,7-octadiene, while the nickel
compound has not shown any activity so far. The Ru
Figure 7. X-ray structure analysis of (lig)NiPMe3 (9).
Thermal ellipsoids are shown at the 50% probability level;
hydrogen atoms have been omitted for clarity.
coordinating tridentate ligand and trimethylphosphine
in a square-planar fashion. It seems that the steric
demand of the phosphine is sufficient to change one
coordination site of the ligand from N to O coordination.
(16) For examples see: (a) Fu¨rstner, A.; Thiel, O. R.; Ackermann,
L.; Schanz, H.-J.; Nolan, S. P. J. Org. Chem. 2000, 65, 204-227. (b)
Opstal, T.; Verpoort, F. J. Mol. Catal. 2003, 200, 49-61.
(17) Kleingrewe, N.; Kehr, G.; Roesmann, R.; Fro¨hlich, R.; Holst,
C.; Erker, G. Eur. J. Inorg. Chem. 2001, 2, 535-538.
(18) (a) Romero, P. E.; Piers, W. E.; McDonald, R. Angew. Chem.
2004, 116, 6287-6291; Angew. Chem., Int. Ed. Engl. 2004, 43, 6161-
6165. (b) Yang, L.; Mayr, M.; Wurst, K.; Buchmeiser, M. R. Chem. Eur.
J. 2004, 10, 5761-5770.
(15) Ru-C bond compared to: Li, Y.; Huang, J.-S.; Xu, G.-B.; Zhu,
N.; Zhou, Z.-Y.; Che, C.-M.; Wong, K.-Y. Chem. Eur. J. 2004, 10, 3486-
3502.

Ruthenium Complexes Featuring a Pincer-Type Ligand
Organometallics, Vol. 24, No. 17, 2005 4295
Table 2. [Ru]dCHR-Catalyzed RCM of 1,7-Octadiene
yield, %
catalyst
cocatalyst
time
temp
product
isomers
(lig)Ru(PPh3)dCHPh(O∧N∧O) (4a)
(lig)Ru(PPh3)dCHPh(O∧N∧O) (4a)
(lig)Ru(PPh3)dCHPh(O∧N∧O) (4a)
(lig)Ru(PPh3)dCHPh(N∧N∧O) (4b)
(lig)Ru(PPh3)dCHPh(N∧N∧O) (4b)
(lig)Ru(PCy3)dCHPh (5)
3 h
3 h
3 d
9 h
9 h
1 h
3 h
5 h
1 h
1 h
1 h
1 h
1 h
1 h
1 day
80 °C
76
70
40
21
0
95
94
83
93
24
20
12
17
PyrB(C6F5)3
B(C6F5)3
B(C6F5)3
80 °C
80 °C
80 °C
80 °C
80 °C
5
6
(lig)Ru(PCy3)dCHPh (5)
room temp
room temp
room temp
80 °C
(lig)Ru(PCy3)dCHPh (5)
Cl2Ru(PCy3)2dCHPh
7
Cl2Ru(PCy3)2dCHPh
quantitative
96
quantitative
95
quantitative
minimal
4
Cl2Ru(PCy3)2dCHCHdCMe2
Cl2Ru(PCy3)2dCHCHdCMe2
Cl2Ru(PCy3)dCH(o-C6H4OiPr)
Cl2Ru(PCy3)dCH(o-C6H4OiPr)
(lig)Ni(PMe3)CHPh (10)
room temp
80 °C
room temp
80 °C
80 °C
minimal
5
minimal
the product as a white solid, which was dried in DCM over
magnesium sulfate. Single crystals were grown from methanol
at room temperature through solvent evaporation. Yield: 1.05
g, 88%. Mp: 210 °C. MS-EI (m/z): calcd 485.3042, found
485.3050. Anal. Calcd for C31H39N3O2 (mol wt 485.65): C,
catalyst system 5 proved to be relatively insensitive to
changes of concentration and temperature.
Experimental Section
1
76.66; H, 8.09; N, 8.65. Found: C, 76.56; H, 8.14; N, 8.75. H
General Procedures. Reactions with organometallic sub-
strates or reagents were carried out in an inert atmosphere
using Schlenk-type glassware or in a glovebox. Solvents were
dried and distilled under argon prior to use. NMR spectra were
recorded with Varian UNITY INOVA 500 MHz (499.9 MHz)
and Varian UNITY INOVA 400 MHz instruments (1H, 399.9
MHz; 13C, 100.6 MHz; 31P, 161.9 MHz). The following instru-
ments were used for additional physical characterization:
melting points, DSC 2010 TA instruments; elemental analysis,
Leeman Labs Inc. CE440 elemental analyzer or a Control
Equipment Corp. 440 elemental analyzer. 2H-Pyrrole-N-tris-
(pentafluorophenyl)borane (PyrB(C6F5)3) was synthesized ac-
cording to literature procedures.17
For X-ray crystal structure analysis, the single crystal was
mounted on a glass fiber and transferred to a Bruker CCD
platform diffractometer. The SMART program package (SMART
Software Users Guide, Version 5.1, Bruker Analytical X-ray
Systems, Inc., Madison, WI, 1999) was used to determine the
unit-cell parameters and for data collection (25 s/frame scan
time for a sphere of diffraction data). The raw frame data were
processed using SAINT20 and SADABS21 to yield the reflection
data file. Subsequent calculations were carried out using the
SHELXTL22 program. The structure was solved by direct
methods and refined on F2 by full-matrix least-squares tech-
niques. Analytical scattering factors23 for neutral atoms were
used throughout the analysis.
NMR (chloroform-d, 298 K): δ 9.05 (br s, 2H, NH), 8.58 (d,
2H, H-3, H-5), 8.20 (t, 1H, H-4), 7.36 (t, 2H, H-11), 7.25 (d,
4H, H-10), 3.16 (s, 4H, 3JH-12,H-13 ) 6.87 Hz, CH), 1.24 (d, 24H,
3JH-12,H-13 ) 6.87 Hz, CH3). 1H NMR (methanol-d4, 298 K): δ
9.99 (br s, 2H, NH), 8.46 (d, 2H, H-3, H-5), 8.22 (t, 1H, H-4),
7.28 (t, 2H, H-11), 7.20 (d, 4H, H-10), 3.22 (sep., 2H, 3JH-1,2H-13
3
1
) 6.86 Hz, CH), 1.20 (d, 24H, JH-12,H-13 ) 6.86 Hz, CH3). H
NMR (benzene-d6, 298 K): δ 9.12 (br s, 2H, NH), 9.32 (d, 2H,
H-3, H-5), 7.23 (t, 1H, H-11), 7.13 (d, 4H, H-10), 7.04 (t, 1H,
3
H-4), 3.28 (s, 2H, JH-12,H-13 ) 6.94 Hz, CH), 1.20 (d, 24H,
3JH-12,H-13 ) 6.94 Hz, CH3). 13C{1H} NMR (benzene-d6, 298
K): δ 163.0 (C-7), 149.8 (C-2, C-6), 146.9 (C-9), 140.0 (C-4),
132.2 (C-8), 129.1 (C-3, C-5), 126.2 (C-10), 124.3 (C-11), 29.9
(C-CH), 24.1 (C-CH3).
X-ray crystal structure analysis of 1: formula C33H47N3O4,
Mr ) 549.74, colorless crystals, 0.30 × 0.30 × 0.30 mm, a )
9.510(3) Å, b ) 12.530(4) Å, c ) 14.021(5) Å, R ) 82.479(6)°, â
) 85.019(6)°, γ ) 72.137(6)°, V ) 1574.6(9) Å3, Fcalcd ) 1.159
Mg m-3, µ ) 0.076 mm-1, Z ) 2, triclinic, space group P1h, λ )
0.710 73 Å, T ) 150 K, 13 442 reflections collected, 5524
independent (I > 2σ(I)), 381 refined parameters, R1 ) 0.0583,
wR2 ) 0.1536, hydrogen atoms added to calculated positions.
Dipotassium N,N′-Bis(2,6-diisopropylphenyl)-2,6-py-
ridinedicarboxamidate (2). N,N′-Bis(2,6-diisopropylphenyl)-
2,6-pyridinedicarboxamide (1; 500 mg, 1.03 × 10-3 mol) and
potassium hydride (83 mg, 2.06 × 10-3 mol) were stirred in
THF (60 mL) overnight. A rapid, strong gas development
indicates the side product hydrogen. The solvent was reduced
to precipitate the product. Single crystals were obtained from
hot THF. Yield: 554 mg, 96%. MS-EI (m/z): (m - 2‚K + H)-
in MeOH calcd 484.2964, found 484.2986, Anal. Calcd for
C31H37K2N3O2 (mol wt 561.83): C, 66.27; H, 6.64; N 7.48.
Found: C, 64.76; H, 6.29; N, 7.09. 1H NMR (chloroform-d, 298
K): δ 8.57 (d, 2H, H-3, H-5), 8.20 (t, 1H, H-4), 7.37 (t, 2H,
H-11), 7.25 (d, 4H, H-10), 3.15 (sep, 4H, 3JH-12,H-13 ) 6.96 Hz,
N,N′-Bis(2,6-diisopropylphenyl)-2,6-pyridinedicarbox-
amide (1). 2,6-Pyridinedicarboxylic acid chloride (500 mg, 2.45
3
CH), 1.24 (d, 24H, JH-12,H-13 ) 6.96 Hz, CH3). 13C{1H} NMR
× 10-3 mol) was dissolved in 15-20 mL of dry THF. Diiso-
propylaniline (924 mL, 4.90 × 10-3 mol) and triethylamine (683
mL, 4.90 × 10-3 mol), dried over molecular sieves (4 Å), were
added at 0 °C. The reaction mixture was stirred at room
temperature for 2 h. The precipitated Et3N‚HCl was filtered
off and the solvent of the filtrate removed under vacuum. The
crude material was triturated with boiling hexane to provide
(chloroform-d, 298 K): δ 162.7 (C-7), 149.1 (C-2, C-6), 146.3
(C-9), 139.8 (C-4), 130.7 (C-8), 128.9 (C-3, C-5), 126.1 (C-10),
123.9 (C-11), 29.3 (CH), 24.8 (CH3).
X-ray crystal structure analysis of 2: formula C43H61N3O5K2,
Mr ) 778.15, colorless crystals, 0.2 × 0.10 × 0.05 mm, a )
(21) Sheldrick, G. M. SADABS, Version 2.05; Bruker Analytical
X-ray Systems, Inc., Madison, WI, 2001.
(22) Sheldrick, G. M. SHELXTL, Version 6.12; Bruker Analytical
X-ray Systems, Inc., Madison, WI, 2001.
(19) Analogous to ref 2b,c.
(20) SAINT Software Users Guide, Version 6.0; Bruker Analytical
X-ray Systems, Inc., Madison, WI, 1999.
(23) International Tables for X-ray Crystallography; Kluwer Aca-
demic: Dordrecht, The Netherlands, 1992; Vol. C.

4296 Organometallics, Vol. 24, No. 17, 2005
Wasilke et al.
32.017(3) Å, b ) 11.4707(10) Å, c ) 26.801(2) Å, R ) 90°, â )
13.3971(12) Å, R ) 101.828(2)°, â ) 112.436(2)°, γ ) 105.383-
119.704(2)°, γ ) 90°, V ) 8549.6(12) Å3, Fcalcd ) 1.209 g cm-3
,
(2)°, V ) 2753.0(4) Å3, Fcalcd ) 1.269 g cm-3, µ ) 0.407 mm-1
,
µ ) 0.267 mm-1, Z ) 8, monoclinic, space group C2/c, λ )
0.710 73 Å, T ) 117(1) K, 20 177 reflections collected, 6780
independent (I > 2σ(I)), 510 refined parameters, R1 ) 0.0587,
wR2 ) 0.1605, hydrogen atoms added to calculated positions.
[N,N′-Bis(2,6-diisopropylphenyl)-2,6-pyridinedicarbox-
amido-K3O,O,N]bis(triphenylphosphine)ruthenium(II) (3;
(lig)Ru(PPh3)2). Tris(triphenylphosphine)ruthenium dichlo-
ride (500 mg, 5.21 × 10-4 mol) in THF (50 mL) was added to
dipotassium N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicar-
boxamidate (2; 293 mg, 5.21 × 10-4 mol) in THF (30 mL). The
reaction mixture turned dark red and was stirred overnight.
All volatiles were removed under vacuum. The dark red crude
material was extracted with toluene, filtered, and triturated
with pentane. Further purification by dissolving the red
powder in toluene and pentane diffusion at room temperature
provided dark red crystals, suitable for X-ray crystallography.
Yield: 437 mg, 76%. Anal. Calcd for C37H37N3O2P2Ru (mol wt
1109.24): C, 72.54; H, 6.09; N, 3.79. Found: C, 73.14; H, 6.43;
Z ) 2, triclinic, space group P1h, λ ) 0.710 73 Å, T ) 117(1) K,
16 969 reflections collected, 9573 independent (Rint ) 0.0192)
(I > 2σ(I)), 651 refined parameters, R1 ) 0.0464, wR2 )
0.1159, hydrogen atom of the carbene ligand located from the
difference map, other hydrogen atoms added to calculated
positions.
X-ray crystal structure analysis of 4b (O∧N∧N): formula
C61H70N3O2PRu, Mr ) 1009.24, dark red crystals, 0.2 × 0.2 ×
0.1 mm, a ) 13.3875(11) Å, b ) 29.217(2) Å, c ) 14.0010(12)
Å, R ) 90°, â ) 97.765(3)°, γ ) 90°, V ) 2753.0(4) Å3, Fcalcd
)
1.269 g cm-3, µ ) 0.407 mm-1, Z ) 2, triclinic, space group
P1h, λ ) 0.710 73 Å, T ) 117(1) K, 35 017 reflections collected,
11 945 independent (I > 2σ(I)), 639 refined parameters, R1 )
0.0643, wR2 ) 0.1420, hydrogen atom of the carbene ligand
located from the difference map, other hydrogen atoms added
to calculated positions.
(Benzylidene)(tricyclohexylphosphine)[N,N′-bis(2,6-
diisopropylphenyl)-2,6-pyridinedicarboxamido-K3O,N,O]-
ruthenium(II) (5; (lig)Ru(PCy3)dCHPh). Dipotassium N,N′-
bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamidate (2; 227
mg, 4.05 × 10-4 mol) and (benzylidene)bis(tricyclohexyl-
phosphine)ruthenium(II) dichloride (333 mg, 4.05 × 10-4 mol)
were added in dichloromethane (50 mL) at room temperature
and stirred overnight. All volatiles were removed under
vacuum, and the residue was dissolved in toluene and filtered
over Celite. Toluene was removed under vacuum, and the
crude material was triturated with pentane overnight. The
product was isolated as a brown powder by filtration and dried
under vacuum. Temperature-dependent 1H NMR spectroscopy
showed limited reversible isomerization. Yield: 355 mg, 93%.
Anal. Calcd for C56H76N3O2PRu (mol wt 944.14): C, 71.24; H,
8.11; N, 4.45. Found: C, 70.10; H, 7.96; N, 3.34. 1H NMR
(benzene-d6, 298 K): δ 20.62 (s, 1H, dCHPh), 8.73, 7.80-6.40
(14H, H Ph), 3.8-2.8 (m, 4H, CH), 2.88 (br t, 33H, PCy), 1.97
1
N, 3.26. H NMR (benzene-d6, 298 K): δ 8.03 (d, 2H, H Ph),
7.33 (m, 8H, H Ph), 7.21 (m, 11H, H Ph), 6.86 (t, 9H, H-Ph),
6.74 (t, 9H, H Ph), 3.32 (sep., 4H, 3JHH ) 6.9 Hz, CH), 1.42 (br
s, 12H, CH3), 1.10 (br s, 12H, CH3). 31P{1H} NMR (benzene-
d6, 298 K, relative to H3PO4): δ 60.2 (ν1/2 ) 3.6 Hz).
X-ray crystal structure analysis of 3: formula C67H67N3O2P2-
Ru, Mr ) 1109.25, dark red crystals, 0.30 × 0.16 × 0.08 mm,
a ) 11.724(3) Å, b ) 14.298(3) Å, c ) 19.268(4) Å, R ) 89.156-
(4)°, â ) 80.866(4)°, γ ) 77.064(4)°, V ) 3107.3(12) Å3, Fcalcd
)
1.186 Mg m-3, µ ) 0.347 mm-1, Z ) 2, triclinic, space group
P1h, λ ) 0.710 73 Å, T ) 150 K, 28 168 reflections collected,
10 908 independent (I > 2σ(I)), 689 refined parameters, R1 )
0.0396, wR2 ) 0.1192, hydrogen atoms added to calculated
positions.
(Benzylidene)(triphenylphosphine)[N,N′-bis(2,6-diiso-
propylphenyl)-2,6-pyridinedicarboxamido-K3O,N,O/O,
N,N]ruthenium(II) (4; (lig)Ru(PPh3)dCHPh).19 Phenyldi-
azomethane (107 mg, 9.02 × 10-4 mol) in dichloromethane was
added to [N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicar-
boxamido-κ3-O,N,O]bis(triphenylphosphine)ruthenium(II) (3;
(lig)Ru(PPh3)2; 500 mg, 4.51 × 10-4 mol) in dichloromethane
(60 mL) at -35 °C. The reaction mixture turned from brown-
red to dark red with vigorous gas development and was stirred
for 5 min. All volatiles were removed in vacuo to give a dark
red solid, which was washed with pentane. The resulting
brown-red solid was dried in vacuo. The crude material
consists of two isomers, which coordinate to the ruthenium in
an O∧N∧O and O∧N∧N fashion, respectively. The O∧N∧O
isomer was isolated by crystallization from a dichloromethane
solution by pentane diffusion at -35 °C to yield the product
as dark red crystals suitable for X-ray crystallography. The
O∧N∧N isomer 4b was isolated from a toluene solution by
pentane diffusion at room temperature. Yield: 382 mg, 91%,
Anal. Calcd for C56H58N3O2PRu (mol wt 937.09): C, 71.77; H,
3
3
(d, 3H, JHH ) 11.8 Hz, CH3), 1.68 (d, 3H, JHH ) 11.8 Hz,
3
3
CH3), 1.61 (d, 3H, JHH ) 11.8 Hz, CH3), 1.57 (d, 3H, JHH
)
11.8 Hz, CH3), 1.23 (m, 12 H, CH3). 13C{1H} NMR (benzene-
d6, 298 K): δ 295.4 (dCHPh), 163.1, 153.7, 150.0, 147.5, 146.9,
139.9, 138.6, 132.4, 131.8, 129.7, 129.6, 126.1, 124.2, 36.4, 35.9,
32.8, 32.0, 30.5, 29.9, 29.3, 28.5, 27.3, 25.9, 25.2, 24.5, 24.2,
23.1, 22.7, 14.6. 31P{1H} NMR (benzene-d6, 298 K, relative to
H3PO4): δ 34.6 (ν1/2 ) 7 Hz).
Potassium [N,N′-Bis(2,6-diisopropylphenyl)-2,6-py-
ridinedicarboxamido-K3N,N,N]nickel(II) Chloride-Tris-
(tetrahydrofuran) (6; (lig)NiKCl). A slurry of nickel dichlo-
ride-dimethoxyethane (39 mg, 1.78 × 10-4 mol) in THF (4
mL) was added to dipotassium N,N′-bis(2,6-diisopropylphenyl)-
2,6-pyridinedicarboxamidate (2; 100 mg, 1.78 × 10-4 mol) in
THF (10 mL). The reaction mixture turned red instantaneously
and was stirred for 3 h. The product was filtered and dried
under vacuum, to give an orange powder. NMR spectroscopic
characterization was limited, due to low solubility of the
product. Single crystals were obtained by dissolving the
product in hot THF and slowly cooling it to room temperature.
Yield: 123 mg, 83%. Anal. Calcd for C31H37ClKN3NiO2 (mol
wt 616.87): C, 60.35; H, 6.05; N, 6.81. Found: C, 58.82; H,
5.75; N, 6.06. 1H NMR (benzene-d6, 298 K): δ 8.05 (t, 1H, 3JHH
) 7.7 Hz, Ph-pyr), 7.61 (d, 2H, 3JHH ) 7.7 Hz, Ph-pyr), 7.04
(m, 6 H, Ph), 4.16 (sep, 4H, 3JHH ) 6.8 Hz, CH), 3.66 (m, 12H,
6.24; N, 4.49. Found: C, 71.76; H, 5.98; N, 3.89. O∧N∧O
3
isomer: 1H NMR (benzene-d6, 298 K) δ 18.21 (d, 1H, JHP
)
27.3 Hz, dHPh), 7.85, 7.53, 7.16, 6.98, 6.86, 6.77 (29H, H Ph),
3.47 (br m, 1H, CH), 3.34 (br m, 2H, CH), 3.01 (br m, 1H, CH),
1.23 (br s, 12H, CH3), 1.12 (br s, 12H, CH3); 31P{1H} NMR
(benzene-d6, 298 K, relative to H3PO4) δ 49.2 (ν1/2 ) 11.9 Hz).
O∧N∧N isomer: 1H NMR (benzene-d6, 298 K) δ 18.24 (d, 1H,
3JHP ) 28.6 Hz, dHPh), 7.82, 7.80, 7.11, 6.90, 6.86 (29H, H
Ph), 3.56 (sep., 1H, 3JHH ) 6.8 Hz, CH), 3.26 (br sep, 1H, 3JHH
) 6.4 Hz, CH), 2.95 (br sep, 1H, 3JHH ) 6.4 Hz, CH), 2.32 (sep,
1H, 3JHH ) 6.8 Hz, CH), 1.27 (m, 15H, CH3), 1.08 (d, 3H, 3JHH
) 6.8 Hz, CH3), 0.51 (d, 3H, 3JHH ) 6.8 Hz, CH3), 0.15 (d, 3H,
3JHH ) 6.8 Hz, CH3); 31P{1H} NMR (benzene-d6, 298 K, relative
to H3PO4) δ 38.2 (ν1/2 ) 2.4 Hz).
3
THF), 1.80 (m, 12H, THF), 1.41 (d, 6H, JHH ) 6.8 Hz, CH3),
1.38 (br s, 6H, CH3), 1.17 (d, 6H, 3JHH ) 6.8 Hz, CH3), 1.10 (br
s, 6H, CH3).
X-ray crystal structure analysis of 6: formula C43H61ClKN3-
NiO5, Mr ) 833.21, red crystals, 0.22 × 0.10 × 0.08 mm, a )
21.067(6) Å, b ) 11.926(4) Å, c ) 19.209(6) Å, R ) 90°, â )
115.991(6)°, γ ) 90°, V ) 4338(2) Å3, Fcalcd ) 1.276 Mg m-3, µ
) 0.650 mm-1, Z ) 4, monoclinic, space group P21/c, λ )
0.710 73 Å, T ) 150 K, 17 663 reflections collected, 5671
X-ray crystal structure analysis of 4a (O∧N∧O): formula
C
61.5H71ClN3O2PRu, Mr ) 1051.70, dark red crystals, 0.18 ×
0.15 × 0.08 mm, a ) 14.9888(14) Å, b ) 16.3811(15) Å, c )

Ruthenium Complexes Featuring a Pincer-Type Ligand
Organometallics, Vol. 24, No. 17, 2005 4297
independent (R(int) ) 0.0814), 474 refined parameters, R1 )
0.0579, wR2 ) 0.1416, hydrogen atoms added to calculated
positions.
145.0, 144.9 (C-10, C-14), 140.2 (C-4), 139.3, 138.3 (C-24, C-28),
125.5 (C Ph-12), 123.6 (C-5), 123.4 (C Ph-11, C Ph-13), 123.1
(C Ph-26), 122.9 (C-3), 122.5 (C Ph-25, C Ph-27), 29.4 (CH-15,
CH-18), 29.1 (CH-29, CH-32), 25.6, 24.9 (CH3-16/17), 23.6
(CH3-30, CH3-31, CH3-33, CH3-34), 23.1 (CH3-19/20), 10.0 (d,
P(CH3)3). C-7/9/21 were not identified. Some additional signals
may be due to isomers. 31P{1H} NMR (benzene-d6, 298 K,
relative to H3PO4): δ -10.0 (ν1/2 ) 2.0 Hz).
[N,N′-Bis(2,6-diisopropylphenyl)-2,6-pyridinedicarbox-
amido-K3N,N,N]nickel(II)-Bis(potassium chloride) (L )
H2O (7), MeOH (8); (lig)NiL). Dipotassium N,N′-bis(2,6-
diisopropylphenyl)-2,6-pyridinedicarboxamidate (2; 300 mg,
5.34 × 10-4 mol) and nickel dichloride-dimethoxyethane (117
mg, 5.34 × 10-4 mol) were added in THF (40 mL). The reaction
mixture turned into a red suspension and was heated to 80
°C for 5 days. The red suspension was isolated by filtration
and the solid washed with toluene and pentane and dried
under vacuum to give the product as an orange powder. Red
single crystals were obtained by crystallization from wet
hexane or slow evaporation of methanol. Yield: 334 mg, 91%.
Anal. Calcd for C31H37Cl2K2N3NiO2‚H2O (mol wt 667.41): C,
52.48; H, 5.54; N, 5.92. Found: C, 52.44; H, 5.41; N, 4.61.
X-ray crystal structure analysis of 7: formula C67H91Cl3N6-
Ni2O10, M ) 1364.23, red crystals 0.2 × 0.15 × 0.06 mm, a )
18.606(4) Å, b ) 15.396(3) Å, c ) 26.072(6) Å, R ) 90°, â )
106.239(4)°, γ ) 90°, V ) 7170(3) Å3, Fcalcd ) 1.264 Mg m-3, µ
) 0.694 mm-1, Z ) 4, monoclinic, space group P21/n, λ )
0.710 73 Å, T ) 117(1) K, 23 332 reflections collected, 9645
independent (R(int) ) 0.0496), 811 refined parameters, R1 )
0.0868, wR2 ) 0.2369, hydrogen atoms added to calculated
positions.
X-ray crystal structure analysis of 9: formula C42H64N3-
NiO4P, Mr ) 764.64, red crystals, 0.32 × 0.24 × 0.20 mm, a )
10.306(2) Å, b ) 29.396(6) Å, c ) 16.036(4) Å, R ) 90°, â )
100.884(4)°, γ ) 90°, V ) 4770.7(19) Å3, Fcalcd ) 1.065 Mg m-3
,
µ ) 0.477 mm-1, Z ) 4, monoclinic, space group P21/n, λ )
0.717 03 Å, T ) 150 K, 19 124 reflections collected, 5841
independent (I > 2σ(I)), 450 refined parameters, R1 ) 0.0960,
wR2 ) 0.2805, hydrogen atoms added to calculated positions.
(Benzylidene)(trimethylphosphine)[N,N′-bis(2,6-diiso-
propylphenyl)-2,6-pyridinedicarboxamido-K3O,N,O/N]-
nickel(II) (10; (lig)Ni(PMe3)dCHPh). N,N′-Bis(2,6-diiso-
propylphenyl)-2,6-pyridinedicarboxamido-κ3O,N,N](trimeth-
ylphosphine)nickel(II) (6; 86 mg, 1.39 × 10-4 mol) and phen-
yldiazomethane (33 mg, 2.78 × 10-4 mol) were added in
dichloromethane (15 mL) at -35 °C. The red reaction mixture
was stirred for 5 min, and all volatiles were removed under
vacuum. The crude material was triturated with pentane
overnight and the product isolated by filtration as an orange
powder, which was dried under vacuum. The product consists
[N,N′-Bis(2,6-diisopropylphenyl)-2,6-pyridinedicarbox-
amido-K3O,N,N′](trimethylphosphine)nickel(II) (9; (lig)-
NiPMe3). Dipotassium N,N′-bis(2,6-diisopropylphenyl)-2,6-
1
of two isomers in a ratio of 3:7. Yield: 91 mg, 92%. H NMR
3
(dichloromethane-d2, 298 K): δ 12.74 (d, 1H, JHP ) 1.9 Hz,
dCHPh), 11.08 (d, 1H, 3JHP ) 2.7 Hz, dCHPh), 8.16-6.79 (m,
3
28 H, H Ph), 4.91 (sep, 1H, JHH ) 6.8 Hz, CH-b), 3.88 (br
3
sep., 2H, CH-a), 3.66 (sep., 1H, JHH ) 6.8 Hz, CH-b), 3.55
3
3
(sep, 1H, JHH ) 6.8 Hz, CH-b), 3.07 (sep, 1H, JHH ) 6.8 Hz,
3
CH-b), 2.95 (br sep, 2H, JHH ) 6.8 Hz, CH-a), 1.61 (d, 3H,
3JHH ) 6.8 Hz, CH3-b), 1.49 (d, 9H, JHH ) 13.0 Hz, PMe3),
3
1.39 (d, 3H, 3JHH ) 6.8 Hz, CH3-b), 1.16-1.02 (m, 36 H, CH3-
3
3
a/-b), 0.94 (d, 3H, JHH ) 6.8 Hz, CH3-b), 0.79 (d, 9H, JHH
)
13.0 Hz, PMe3), 0.64 (d, 3H, JHH ) 6.8 Hz, CH3-b). 31P{1H}
3
NMR (benzene-d6, 298 K, relative to H3PO4): δ 47.2 (ν1/2
3.2 Hz), 44.5 (ν1/2 ) 2.8 Hz).
)
pyridinedicarboxamidate (2; 500 mg, 1.78 × 10-3 mol), NiCl2
(115 mg, 1.78 × 10-3 mol), and trimethylphosphine (68 mg,
1.78 × 10-3 mol) were added in diethyl ether/THF (1:1) or THF
only (100 mL). The yellow suspension turned orange and was
stirred for two nights. The suspension was filtered to give a
red solution. All volatiles were evaporated under vacuum to
give the product as a red powder. A THF/Et2O solution was
cooled to -35 °C to give red crystals overnight, suitable for
X-ray crystal structure analysis. Alternatively, monocrystalline
material can be obtained from a toluene solution at -35 °C.
Yield: 510 mg, 93%. Anal. Calcd for C34H46N3NiO2P (mol wt
618.39): C, 66.03; H, 7.50; N, 6.80. Found: C, 64.89; H, 7.51;
N, 6.22. 1H NMR (benzene-d6, 298 K): δ 7.61 (d, 1H, H-5),
7.49 (d, 1H, H-3), 7.22 (d, 1H, Ph-25, Ph-27), 7.13 (m, 1H, Ph-
26), 7.05 (m, 1H, Ph-12), 6.97 (d, 2H, Ph-11, Ph-13), 6.84 (dd,
1H, H-4), 3.84 (sept., 2H, 3JiPr ) 6.95 Hz, CH-15, CH-18), 3.30
Ring-Closing Metathesis: General Procedure. The
appropriate catalyst ((4.75-4.90) × 10-6 mol) was dissolved
in deuterated benzene (800 µL, 6 mM) or toluene (3 mL, 1.6
mM), and 1,7-octadiene (9.50 × 10-5 mol) was added. The
reaction mixture was stirred at room temperature or 80 °C
1
and monitored by H NMR spectroscopy or GC.
Acknowledgment. Financial support from the DOE
(Grant No. DE-FG03098ER 14910) is gratefully ac-
knowledged by J.C.W. We thank Professor Guillermo
C. Bazan for his support and for many helpful discus-
sions.
Supporting Information Available: Text giving ad-
ditional spectroscopic data and details of the catalytic reactions
and tables giving additional information about the X-ray
crystal structure analyses; X-ray data are also available in CIF
format. This material is available free of charge via the
Internet at http://pubs.acs.org.
3
3
(sept., 2H, JiPr ) 6.95 Hz, CH-29, CH-32), 1.34 (d, 12H, JiPr
) 6.95 Hz, CH3-30, CH3-31, CH3-33, CH3-34), 1.29 (d, 6H, 3JiPr
3
) 6.95 Hz, CH3-16/19), 1.27 (d, 6H, JiPr ) 6.95 Hz, CH3-17/
1
20), 0.27 (d, 9H, JHP ) 10.53 Hz, PMe3). 13C{1H} NMR
(benzene-d6, 298 K): δ 153.5 (C-6), 149.1 (C-2), 145.6 (C-23),
OM0501780