Ruthenium metathesis catalysts containing chelating aryloxide ligands

Article abstract of DOI:10.1021/om050952j

Olefin metathesis catalysts containing chelating aryloxide donors, RuXX′(IMes)(py)(=CHPh) (5, XX′ = 3,5-dichloro-2-oxidobenzenesulfonate; 6, XX′ = catecholate), are accessible in high yield by reaction of o-sulfonato aryloxide or catecholate salts, respec

Full text of DOI:10.1021/om050952j

1940
Organometallics 2006, 25, 1940-1944
Ruthenium Metathesis Catalysts Containing Chelating Aryloxide
Ligands
Sebastien Monfette and Deryn E. Fogg*
Center for Catalysis Research and InnoVation, Department of Chemistry, UniVersity of Ottawa,
10 Marie Curie, Ottawa, Ontario, Canada, K1N 6N5
ReceiVed NoVember 4, 2005
Olefin metathesis catalysts containing chelating aryloxide donors, RuXX′(IMes)(py)(dCHPh) (5, XX′
) 3,5-dichloro-2-oxidobenzenesulfonate; 6, XX′ ) catecholate), are accessible in high yield by reaction
of o-sulfonato aryloxide or catecholate salts, respectively, with RuCl2(IMes)(py)2(dCHPh). Isomerization
to π-bound aryloxides, as found with phenoxide ion or 2′-(diphenylphosphino)-1,1′-binaphthyl-2-olate,
is suppressed by use of these smaller, more rigid, chelate rings. Preliminary investigations indicate that
the catecholato derivative exhibits metathesis activity approaching that of the recently reported, highly
active catalyst RuCl(OC6Br5)(IMes)(py)(dCHPh).
a
Chart 1
Introduction
Substituted aryloxide ligands offer considerable promise as
sterically and electronically tunable anionic donors in transition
metal catalysis. In the area of olefin metathesis, remarkable
activity and selectivity are exhibited by group 6 complexes
containing alkoxide, biphenolate, and binaphtholate ligands.1,2
We recently demonstrated that ruthenium alkylidene complexes
bearing monodentate, electron-deficient aryloxides (Chart 1)
exhibit metathesis efficiencies comparable or superior to those
of the “second-generation” catalysts 1 and 2, in some cases at
significantly lower catalyst loadings.3 Our motivation for use
of perhaloaryloxide ligands in 3 and 4 stems from insights
obtained from model reactions of RuXCl(PPh3)3 (X ) H, Cl)
with phenoxide ion, which afforded only piano-stool, π-phe-
noxide complexes (Scheme 1).4 While we were able to curb
the tendency toward σ f π isomerization of the aryloxide ligand
by depleting the electron-donor ability of the aromatic ring,3,5
this appears to exact a price in terms of the lability of the
pyridine donor (and hence initiation efficiency)6 and severely
restricts one of the major potential assets of the aryloxide
platform, its ease of electronic and steric tuning.
a IMes ) N,N′-bis(mesityl)imidazol-2-ylidene.
ylphosphino)-1,1′-binaphthyl-2-ol (NaO-MOP; Scheme 1).7 In
the present study, we explored the potential of smaller, less
flexible chelate rings. We now report that stable, five-coordinate
Ru(σ-XX′)(IMes)(py)(dCHPh) complexes are accessible on
incorporation of the aryloxide donor into a five- or six-
membered chelate ring, irrespective (for the smaller ring) of
the electron-deficiency of the aryloxide ligand.
Scheme 1
In seeking alternatives to electronic stabilization of the Ru-
(σ-OAr) bond, we had considered the possibility that isomer-
ization could be restricted through the chelate effect. (As an
ancillary advantage, we anticipated that catalytic activity might
be enhanced by the reduced steric congestion at the metal.)
However, chelation of the aryloxide donor within a seven-
membered ring proved insufficient to prevent isomerization, as
indicated by reaction of RuXCl(PPh3)3 with sodium 2′-(diphen-
* Corresponding author. Fax: (613) 562-5170. E-mail: dfogg@
science.uottawa.ca.
(1) Hoveyda, A. H.; Schrock, R. R. Chem. Eur. J. 2001, 7, 945-950.
(2) Tsang, W. C. P.; Hultzsch, K. C.; Alexander, J. B.; Bonitatebus, P.
J.; Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2003, 125, 2652-
2666.
Results and Discussion
(3) Conrad, J. C.; Parnas, H. H.; Snelgrove, J. L.; Fogg, D. E. J. Am.
Chem. Soc. 2005, 127, 11882-11883.
Ruthenium complexes in which the sulfonate group functions
as a robust donor ligand are well established. Most common
are simple monodentate tosylate8-11 or triflate12-15 derivatives;
(4) Snelgrove, J. L.; Conrad, J. C.; Yap, G. P. A.; Fogg, D. E. Inorg.
Chim. Acta 2003, 345, 268-278.
(5) Conrad, J. C.; Amoroso, D.; Czechura, P.; Yap, G. P. A.; Fogg, D.
E. Organometallics 2003, 22, 3634-3636.
(6) Conrad, J. C.; Camm, K.; Fogg, D. E. Inorg. Chim. Acta 2006, 359,
in press.
(7) Snelgrove, J. L.; Conrad, J. C.; Eelman, M. D.; Moriarty, M. M.;
Yap, G. P. A.; Fogg, D. E. Organometallics 2005, 24, 103-109.
10.1021/om050952j CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/07/2006

Ruthenium Metathesis Catalysts
Organometallics, Vol. 25, No. 8, 2006 1941
more rarely, sulfonate-bridged complexes have been ob-
tained.16,17 Ortho-sulfonato aryloxide derivatives are thus po-
tentially attractive as precursors to six-membered chelate
complexes. Among five-membered chelates, catecholates are
attractive as planar, tunable ligands. A number of octahedral
Ru-catecholato complexes have been reported, including Ru-
(σ-cat)(ER3)2(CO)2 (ER3 ) AsPh3,18 PiPr3;19 cat ) catecholate).
Although coordinatively unsaturated examples containing labile
ligands have not previously been synthesized, we hoped that
the small ring size might stabilize such species. The following
describes the successful synthesis of both catecholato and
o-sulfonato aryloxide derivatives of the second-generation
Grubbs catalysts, and preliminary explorations of their metath-
esis activity.
Chelating Sulfonato-aryloxide Derivative. Commercially
available sodium 3,5-dichloro-2-hydroxybenzenesulfonate was
converted into its thallium salt (in DMF, as the parent phenol
was insoluble in aromatic solvents) and reacted with 2 in
benzene at 22 °C (Scheme 2). Reaction times could be reduced
from >7 days to 2 h by use of degassed water as cosolvent:
the dibasic anion is slightly soluble in water, though completely
insoluble in organic solvents. The product was isolated as a
blue-green precipitate in 72% yield. Complete conversion to 5
was indicated by inert-atmosphere MALDI-TOF MS analysis.
A mass ion corresponding to [M - py]+• was observed (Figure
1a): the molecular ion could not be observed, but the isotope
pattern confirms complete exchange of the chloride ligands.
Figure 1. Inert-atmosphere MALDI-TOF mass spectra of [M -
py]+• region for (a) 5 (pyrene matrix); (b) 6 (anthracene matrix).
(in which the sample is incompletely soluble) reveals one new
alkylidene singlet at 17.68 ppm. However, two such signals (δH
17.68, 18.51 ppm; ratio 1:1) are observed in CDCl3. These are
assigned to 5a and 5b, although we are unable to distinguish
which singlet is due to which isomer. In view of the complexity
of the overlapping patterns for the two complexes in CDCl3,
we highlight the characterization data obtained in C6D6. Owing
to the low solubility of the complex in this solvent, carbon
signals were most conveniently located by HMQC and HMBC
correlation experiments. The singlet due to the alkylidene proton
at 17.68 ppm correlates with singlets due to the alkylidene
carbon (321 ppm, HMQC) and the IMes carbene carbon (182
ppm, HMBC). The HMBC experiment also permitted location
of the ortho protons of the benzylidene phenyl group (7.83 ppm),
via their correlation with the alkylidene carbon. The meta and
para protons could then be located by a 1H-1H COSY
experiment. The singlet for the imidazole ring proton at 6.06
ppm correlates with 13C NMR singlets due to the “olefinic” IMes
carbon atoms (124.6 ppm, HMQC) and the carbene carbon (182
ppm, HMBC). The aromatic protons of the IMes ligand (6.77,
6.60 ppm) could be assigned on the basis of an HMBC
correlation with the methyl carbon signals and their mutual
correlation by 1H-1H-COSY. The pyridine and aryloxide
protons were distinguished on the basis of the number of 1H-
1H-COSY correlations observed for each. The aryloxide signals
Assignment of the product as 5 is supported by spectroscopic
data and microanalysis. A strong infrared band at 1262 cm-1 is
assigned to the ν(SdO) stretch. The 1H NMR spectrum in C6D6
Scheme 2
(8) Justice, A. K.; Linck, R. C.; Rauchfuss, T. B.; Wilson, S. R. J. Am.
Chem. Soc. 2004, 126, 13214-13215.
4
exhibit the expected two doublets (8.14, 7.53 ppm; JHH ) 3
(9) Harding, P. A.; Preece, M.; Robinson, S. D.; Henrick, K. Inorg. Chim.
Acta 1986, 118, L31-L33.
Hz), each integrating 1:1 relative to the singlet for the alkylidene
proton, in the 1H NMR spectrum. These signals correlate with
13C NMR singlets at 126.0 and 132.5 ppm, respectively, in
HMQC experiments. However, the weakness of the HMBC
correlations prevents location of the signals due to the quaternary
(10) Harding, P. A.; Robinson, S. D.; Henrick, K. J. Chem. Soc., Dalton
Trans. 1988, 415-420.
(11) Fachinetti, G.; Funaioli, T.; Marchetti, F. J. Organomet. Chem. 1995,
498, C20-C22.
(12) Pavlik, S.; Mereiter, K.; Puchberger, M.; Kirchner, K. Organome-
tallics 2005, 24, 3561-3575.
2
aryloxide carbons. While the absence of the JHC correlations
(13) Rowsell, B. D.; McDonald, R.; Cowie, M. Organometallics 2004,
23, 3873-3883.
was expected, given the small size of the 2JHC coupling constants
in aromatic rings (often on the order of 1 Hz),20 failure to
observe the 3JCH coupling, which should be on the order of 4-7
Hz,20 was somewhat surprising. This is probably an artifact of
the low solubility of the complex, which results in poor signal-
to-noise ratios in the HMBC spectrum.
(14) Krause, J. O.; Nuyken, O.; Wurst, K.; Buchmeiser, M. R. Chem.
Eur. J. 2004, 10, 777-784.
(15) Volland, M. A. O.; Hansen, S. M.; Rominger, F.; Hofmann, P.
Organometallics 2004, 23, 800-816.
(16) Takai, Y.; Kitaura, R.; Nakatani, E.; Onishi, T.; Kurosawa, H.
Organometallics 2005, 24, 4729-4733.
(17) Goicoechea, J. M.; Mahon, M. F.; Whittlesey, M. K.; Kumar, P. G.
A.; Pregosin, P. S. Dalton Trans. 2005, 588-597.
(18) Bohle, D. S.; Carron, K. T.; Christensen, A. N.; Goodson, P. A.;
Powell, A. K. Organometallics 1994, 13, 1355-73.
(19) Ferrando-Miguel, G.; Wu, P.; Huffman, J. C.; Caulton, K. G. New
J. Chem. 2005, 29, 193-204.
The two isomers of 5 equilibrate on the NMR time scale, as
indicated by EXSY studies. Unexpectedly, however, isomer-
(20) Kalinowski, H.-O.; Berger, S.; Braun, S. Carbon-13 NMR Spec-
troscopy; Wiley: Toronto, 1988.

1942 Organometallics, Vol. 25, No. 8, 2006
Monfette and Fogg
ization does not involve loss and recoordination of the pyridine
ligand, as exchange is not suppressed by addition of free
pyridine. This treatment gives rise to a new singlet at 18.7 ppm,
presumably due to a pyridine adduct, which correlates (EXSY)
with the singlet at 18.5 ppm; the 5a-5b correlation is also
retained. Similar behavior resulted from addition of acetonitrile;
importantly, the pyridine ligand is not displaced, suggesting that
this ligand is very nonlabile, as also borne out by the metathesis
data (vide infra). Taken together, these data suggest that
isomerization involves decoordination of the sulfonate group,
rather than pyridine, but that chelation is thermodynamically
favored. Given the established correlation between M-OR bond
strengths and H-OR bond energies,21 we presume that the
exchange proceeds via cleavage of the Ru-OSO2R bond. The
relative polarity of the charge-separated intermediate may
account for the failure to observe the isomerization in benzene.
The possibility of selective dissolution of one isomer in benzene
was eliminated on the basis of an experiment in which we
extracted a sample of solid 5 with benzene and then took the
residue up in CDCl3: the 1:1 ratio of isomers was unperturbed,
indicating that the sample was not enriched in a benzene-
insoluble constituent.
are upfield shifts of 0.5-3 ppm for 1H nuclei and up to 30 ppm
for 13C nuclei.7,26-28 The ortho and meta nuclei for the
catecholate ligand in 6 show a very minor coordination shift to
higher field, relative to the free ligand (0.15-0.5 ppm, 1H NMR;
2-6 ppm, 13C NMR). The ipso carbons exhibit a significant
downfield shift of ca. 20 ppm, as also reported for the
six-coordinate catecholato complexes Ru(σ-cat)(ER3)2(CO)2
described above,18,19 in which only a Ru(σ-OAr) bond is present.
The “normal”, aromatic location of the signals for the catecho-
late ligand in 6 is unequivocal evidence for the proposed κ2-
O,O-C6H4 structure, versus a piano-stool complex. The small
size and rigidity of the chelate ring in 6 is evidently sufficient
to inhibit σ f π isomerization, despite the reservoir of electron
density in the aromatic ring. The implication that electron
deficiency is not essential to stabilize the Ru-aryloxide bond
significantly expands the range of (chelating) aryloxide ligands
that can potentially be deployed in Ru-catalyzed olefin metath-
esis, a finding that will facilitate tuning of catalyst properties.
Screening for Metathesis Activity. Complexes 5 and 6 were
tested for ring-closing metathesis (RCM) activity using the
benchmark substrate diethyl diallylmalonate (DEDAM), as well
as more challenging disulfide29 and ene-yne substrates. The low
lability of the pyridine ligand at room temperature is implied
by the requirement for elevated temperatures in order to achieve
high activity, as we earlier found for pseudohalide catalysts 3
and 4.3,5 Catalyst 5 is lower in activity than either 6 or
perfluorophenoxide catalyst 3, the latter of which is the least
reactive of the aryloxide catalysts previously studied. It achieves
95% RCM of diethyldiallyl malonate 7 within 15 min under
our standard conditions (refluxing CDCl3, 0.5 mol % Ru; Table
1), while catalysts 1-4 and 6 effect complete RCM within this
period. However, a much greater discrimination in activity is
found in RCM of diallyl sulfide 9, toward which 5 and 3 exhibit
very low activity, while 6 (and 4b) effect quantitative RCM
within 15 min. We speculate that the near-zero activity of 5 is
due to poisoning by coordination of the sulfide to the metal
center: the electron-deficiency suggested by the low pKa of the
parent SO3H group (Table 2) may enhance binding of the sulfur
donor. Consistent with this interpretation is the strong binding
of the pyridine ligand suggested by the characterization data
discussed above and inferred from the generally lower reactivity
of 5. Finally, while 5 exhibits modest activity for RCM of ene-
yne substrate 11, the activity of catalyst 6 approaches that of
43 and significantly exceeds that found for either 3 or the second-
generation catalyst 1, for which conversions of 85% were
achieved after heating at 80 °C for 1 h, at a catalyst loading of
5 mol %.30
Catecholato Derivative. Reaction of 2 with 1 equiv of Tl2-
(o-O2C6H4) in benzene effected complete conversion to 6 within
2 h at 22 °C (Scheme 3). The identity of the compound is
supported by inert-atmosphere MALDI-TOF mass spectrometry
(Figure 1b), NMR, and elemental analysis. As with 5, only the
[M - py]+• radical cation is evident in the MALDI mass
spectrum. NMR analysis reveals singlets for the benzylidene
proton and carbon at 16.99 and 287 ppm, respectively,
significantly further upfield (2.5-3 ppm (1H); ca. 25 ppm (13C))
than the corresponding signals for RuCl2(PCy3)2(dCHPh),22
RuCl2(NHC)(PCy3)(dCHPh),23,24 or RuCl2(NHC)(py)2(d
CHPh)3,25 (NHC ) IMes, H2IMes). The “olefinic” singlet for
the IMes ring protons is shifted downfield by nearly 1 ppm,
relative to 2:3 it appears in the aromatic region, but is located
from its long-range coupling with the singlet for the carbene
carbon at 189.0 ppm (HMBC). Signals for the pyridine and
benzylidene phenyl protons are readily differentiated on the basis
of the three-bond coupling between the phenyl ortho protons
and the benzylidene carbon. The remaining aromatic signals
1
are assigned on the basis of H-1H COSY analysis, enabling
full assignment of the signals due to the catecholate ring.
Scheme 3
Conclusions
The foregoing demonstrates that incorporating aryloxide
donors into small, rigid chelate rings can be a successful strategy
for formation of stable, coordinatively unsaturated Ru(σ-OAr)
structures, irrespective of the electron-deficiency of the aryloxide
Unambiguous identification of the catecholate signals is
important in confirming the coordination mode of this potentially
π-coordinating ligand. Diagnostic for π-bound aryloxide rings
(26) Geldbach, T. J.; Breher, F.; Gramlich, V.; Kumar, P. G. A.; Pregosin,
P. S. Inorg. Chem. 2004, 43, 1920-1928.
(21) (a) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw,
J. E. J. Am. Chem. Soc. 1987, 109, 1444-1446. (b) Bryndza, H. E.; Tam,
W. Chem. ReV. 1988, 88, 1163-1188.
(27) Geldbach, T. J.; Pregosin, P. S.; Albinati, A. Organometallics 2003,
22, 1443-1451.
(22) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996,
118, 100-10.
(28) Geldbach, T. J.; Pregosin, P. S.; Bassetti, M. Organometallics 2001,
20, 2990-2997.
(23) Huang, J.; Stevens, E. D.; Nolan, S. P.; Petersen, J. L. J. Am. Chem.
Soc. 1999, 121, 2674-2678.
(29) (a) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003,
42, 4592-4633. (b) Armstrong, S. K. J. Chem. Soc., Perkin Trans. 1998,
371-388.
(24) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron
Lett. 1999, 40, 2247-2250.
(30) Fu¨rstner, A.; Ackermann, L.; Gabor, B.; Goddard, R.; Lehmann,
C. W.; Mynott, R.; Stelzer, F.; Thiel, O. R. Chem. Eur. J. 2001, 7, 3236-
3253.
(25) Sanford, M. S.; Love, J. A.; Grubbs, R. H. Organometallics 2001,
20, 5314-5318.

Ruthenium Metathesis Catalysts
Organometallics, Vol. 25, No. 8, 2006 1943
Table 1. Benchmarking RCM Activity of 5 and 6a
findings point toward a correlation between high catalyst
activity, and minimal electron deficiency within the pseudohalide
ligand. The high activity of the catecholato derivative 6 is
noteworthy in this context: this ligand class offers considerable
opportunity for modification of catalyst properties, including
modulation of the electronic properties of the catecholate ligand
itself, without necessarily perturbing the steric characteristics
of the catalyst. Such studies are presently under way and will
be reported in due course.
Experimental Section
General Procedures. Reactions were carried out at room
temperature (RT, 22 °C) under N2 using standard Schlenk or drybox
techniques. Dry, oxygen-free solvents were obtained using a Glass
Contour or Anhydrous Engineering solvent purification system and
stored over Linde 4 Å molecular sieves. Pyridine and acetonitrile
were distilled from CaH2. CDCl3 and C6D6 were dried over activated
sieves (Linde 4 Å) and degassed by consecutive freeze/pump/thaw
cycles. Water was degassed by multiple freeze/pump/thaw cycles.
Anhydrous N,N-dimethylformamide, sodium-3,5-dichloro-2-hy-
droxybenzosulfonate, catechol, and thallium ethoxide (Aldrich) were
used without purification. Complex 2 was prepared as previously
described.3 1H NMR (300 or 500 MHz) and 13C (75 MHz) spectra
were recorded on a Bruker Avance-300 or Avance-500 spectrom-
eter. NMR spectra are reported relative to TMS (1H, 13C) at 0 ppm.
IR spectra were measured on a Bomem MB100 IR spectrometer.
Inert-atmosphere MALDI-TOF MS analyses were performed using
a Bruker OmniFlex MALDI-TOF mass spectrometer equipped with
a nitrogen laser (337 nm) and interfaced to an MBraun glovebox.
Data were collected in positive reflectron mode, with the accelerat-
ing voltage held at 20 kV. Matrix (anthracene or pyrene) and analyte
solutions were prepared in CH2Cl2 at concentrations of 20 and 1
mg/mL, respectively. Samples were mixed in a matrix:analyte ratio
of 20:1. Microanalyses were carried out by Guelph Chemical
Laboratories Ltd., Guelph, Ontario.
a Conditions: 0.5 mol % Ru, CDCl3, ∆, 15 min. Conversions determined
by GC-FID and confirmed by NMR; (2% in replicate runs.
Table 2. Relative Acidity of Protonated Aryloxide Ligands
Note: The toxicity of thallium (particularly in the +1 oxidation
state) is well established, and the subject has been recently
reviewed.36 Care must be taken to prevent introduction into the
body by inhalation, by ingestion via contaminated hands or gloves,
or through the skin. All thallium reagents and wastes, including
contaminated solvents, were handled using double-glove and
secondary containment procedures, with separate disposal of all
wastes in accordance with government regulations.
Representative Procedure for Synthesis of Catecholate Salts.
Tl2(o-O2C6H4). Addition of a solution of thallium ethoxide (1.14
g, 4.6 mmol) in 3 mL of diethyl ether to a solution of catechol
(251 mg, 2.3 mmol) in 10 mL of diethyl ether resulted in an
instantaneous precipitation of an orange solid. The suspension was
stirred at RT for 7 h, following which the product was collected
by filtration, washed with diethyl ether (15 mL), then hexanes (10
mL), and dried under vacuum. Yield: 1.1 g (93%).
[C6H2(3,5-Cl2)(2-OTl)(SO3Na)]. The thallium salt was prepared
in DMF, owing to the low solubility of the ligand precursor in all
other solvents except water, which would decompose the TlOEt
reagent. Addition of TlOEt (0.954 g, 3.82 mmol) to a rapidly stirred,
colorless solution of [C6H2(3,5-Cl2)(2-OH)(SO3Na)] (1.00 g, 3.77
mmol) in 20 mL of DMF caused a white powder to deposit within
ring. Five- and six-membered chelate complexes were prepared
in which the aryloxide donor formed part of a O,OSO2-bound
or O,O-bound aromatic ring, respectively. The stability of these
new complexes, and particularly that of the comparatively
electron-rich catecholate derivative, has important implications
for the range of phenols that can be considered as candidate
ligands for new Ru-pseudohalide catalysts. Of interest is the
low lability of the pyridine ligand within the sulfonato-aryloxide
derivative, which significantly depresses catalyst activity. If, as
this finding suggests, the sulfonato group enhances the binding
affinity of other donor groups present on the metal center,
pseudohalide ligands incorporating this group may be of limited
utility for the purpose of olefin metathesis. More generally, these
(31) Aptula, A. O.; Netzeva, T. I.; Valkova, I. V.; Cronin, M. T. D.;
Schultz, T. W.; Kuhne, R.; Schuurmann, G. Quant. Struct.-Act. Relat. 2002,
21, 12-22.
(32) Calculated using Advanced Chemistry Development (ACD/Labs)
Software V8.14 for Solaris (1994-2005 ACD/Labs).
(33) Hall, H. K., Jr. J. Am. Chem. Soc. 1957, 79, 5439-41.
(34) Birchall, J. M.; Haszeldine, R. N. J. Chem. Soc. 1959, 3653.
(35) Han, J.; Deming, R. L.; Tao, F.-M. J. Phys. Chem. A 2005, 109,
1159-1167.
(36) Galva´n-Arzate, S.; Santamar´ıa, A. Toxicol. Lett. 1998, 99, 1-13.

1944 Organometallics, Vol. 25, No. 8, 2006
Monfette and Fogg
5 min. Stirring was continued for 20 min, after which the product
was collected by filtration, washed with diethyl ether (10 mL), and
dried in vacuo. Yield: 1.61 g (91%).
4JHH ) 1.6 Hz, 2H, py, o-CH), 7.45 (t of t, 3JHH ) 7.8 Hz, 4JHH
)
3
1.6 Hz, 1H, py, p-CH), 7.28 (d, JHH ) 7.0 Hz, 2H, Ph, o-CH),
3
7.17 (t, JHH ) 7.5 Hz, 1H, Ph, p-CH), 7.08 (s, 2H, IMes dCH),
Ru[K2-OSO2-2-O-C6H2(3,5-Cl2)](IMes)(py)(dCHPh), 5. A so-
lution of 2 (299 mg, 0.41 mmol) in 5 mL of benzene was added to
a rapidly stirred suspension of [C6H2(3,5-Cl2)(2-OTl)(SO3Na)] (193
mg, 0.41 mmol) in 5 mL of H2O. The mixture was stirred vigorously
for 2 h, over which time a green-blue suspension formed. This
material was filtered off and washed with ether (10 mL), then
redissolved in 10 mL of THF and filtered through Celite to remove
TlCl. Concentration, addition of hexanes, and cooling to -35 °C
precipitated a blue-green powder, which was filtered off and dried
under vacuum. Yield: 242 mg (72%). 1H NMR (C6D6, 298 K): δ
17.68 (s, 1H, RudCH), 8.46 (d, 3JHH ) 5 Hz, 2H, py o-CH), 8.14
(d, 4JHH ) 3 Hz, 1H, Ar, aryloxide CH), 7.83 (d, 3JHH ) 7 Hz, 2H,
6.96-6.85 (m, 6H, Ph, m-CH; py, m-CH; Ar, Mes CH), 6.71 (d of
d, 3JHH ) 7.0 Hz, 4JHH ) 2.0 Hz, 1H, Ar, catechol o-CH), 6.70 (d
3
4
of d, JHH ) 7.0, JHH) 2.0 Hz, 1H, Ar, catechol o-CH), 6.58 (br
3
4
s, 2H, Mes CH), 6.49 (t of d, JHH ) 7.0 Hz, JHH ) 2.0 Hz, 1H,
3
4
Ar, catechol m-CH), 6.36 (t of d, JHH ) 7.0 Hz, JHH ) 2.0 Hz,
1H, Ar, catechol m-CH), 2.22 (s, 6H, Mes p-CH3), 2.16 (s, 6H,
Mes o-CH3), 1.88 (s, 6H, Mes o-CH3). 13C{1H} NMR (CDCl3, 298
K): δ 287.42 (RudCH), 189.60 (IMes NCN), 164.09 (Ar, catechol
O-C), 160.51 (Ar, catechol O-C), 154.68 (py, o-CH), 152.56 (Ph
Ci), 138.99 (Ar, Mes p-CMe), 136.58 (Ar, Mes o-CMe), 135.62
(Ar, Mes o-CMe), 135.14 (Ar, Mes Ci), 134.03 (py p-CH), 129.13
(Ar, Mes m-CH), 128.00 (Ph m-CH), 127.73 (Ph o-CH), 126.48
(Ph p-CH), 124.02 (IMes dCH), 123.70 (py, m-CH), 116.13 (Ar,
catechol CH), 114.77 (Ar, catechol CH), 114.17 (Ar, catechol CH),
113.76 (Ar, catechol CH), 21.06 (Mes p-CCH3), 17.82 (Mes
o-CCH3), 17.69 (Mes o-CCH3). Anal. Calcd for C39H39N3O2Ru:
C, 68.60; H, 5.76; N, 6.15. Found C, 69.03; H, 5.38; N, 6.14.
MALDI-TOF MS, m/z: calcd for [M - py]+• 604.2; found, 604.1.
General Procedure for Ring-Closing Metathesis. In a typical
experiment, 6 (10 mg, 14.6 µmol) and diethyl diallylmalonate (38.5
mg, 0.16 mmol) were weighed into separate vials. The catalyst was
dissolved in 1.00 mL of CDCl3, and 54.7 µL of this stock solution
was added to a solution of the substrate in 1.6 mL of solvent (final
[S] ) 100 mM). The reaction was divided between two sealed vials
and heated to reflux in a pierced aluminum block. Each experiment
was carried out in duplicate (total 4 runs), measuring conversions
by GC and NMR analysis.
4
Ph, o-CH), 7.53 (d, JHH ) 3 Hz, 1H, Ar, aryloxide CH), 7.23 (t,
3JHH ) 7 Hz, 1H, Ph, p-CH), 6.99 (t, 3JHH ) 8 Hz, 2H, Ph, m-CH),
6.77 (s, 2H, Ar, Mes CH), 6.60 (s, 2H, Ar, Mes CH), 6.49 (t, 3JHH
) 8 Hz, 1H, py, p-CH), 6.12 (t, 3JHH ) 7 Hz, 2H, py, m-CH), 6.06
(s, 2H, IMes dCH), 2.13 (s, 6H, Mes p-CH3), 1.99 (s, 6H, Mes
o-CH3), 1.66 (s, 6H, Mes o-CH3). 13C NMR signals could not be
directly observed, as the solubility of the complex in C6D6 is very
low, but the majority of the signals could be located via HMQC
and HMBC experiments (see text). 13C NMR (C6D6, 298 K): δ
320.9 (RudCH), 182.0 (IMes NCN), 154.0 (py, o-CH), 152.5 (Ph
Ci), 139.4 (Ar, Mes p-CMe), 136.0 (Ar, Mes Ci), 135.0 (py, p-CH),
132.5 (Ar, aryloxide CH) 130.9 (Ph o-CH), 129.6 (Ar, Mes CH),
129.3 (Ar, Mes CH), 128.3 (Ph, m-CH), 128.1 (Ph, p-CH), 126.0
(Ar, phenoxide CH), 124.6 (Ar, IMes dCH), 123.9 (py, m-CH),
20.8 (Mes, o-CH3), 17.8 (Mes, p-CH3). Anal. Calcd for C39H37-
Cl2N3O4RuS: C, 57.42; H, 4.57; N, 5.15. Found C, 57.77; H, 4.17;
N, 4.92. IR (KBr): ν(SdO) 1262 cm-1. MALDI-TOF MS, m/z:
calcd for [M - py]+• 736.1; found, 736.2.
Acknowledgment. This work was supported by the Natural
Sciences and Engineering Research Council of Canada, the
Canada Foundation for Innovation, the Ontario Innovation Trust,
and the Ontario Research and Development Corporation. Dr.
Melanie Eelman is thanked for carrying out the inert-atmosphere
MALDI MS analyses.
Ru(K2-O2C6H4)(IMes)(py)(dCHPh), 6. A solution of 2 (300
mg, 0.41 mmol) in 20 mL of benzene was treated with solid Tl2-
(o-O2C6H4) (216 mg, 0.42 mmol) and stirred vigorously for 2 h,
over which time it turned brown from green. The mixture was then
filtered through Celite to remove TlCl, and the filtrate was stripped
off to give a green solid, which was taken up in hexanes. The
suspension was chilled at -35 °C, and the solid was collected by
filtration, washed with diethyl ether (10 mL) and hexanes (5 × 10
mL), then dried in vacuo. Yield: 218 mg (77%). 1H NMR (CDCl3,
Supporting Information Available: 1H, 1H-13C HMQC, and
1
1H-13C HMBC NMR spectra for 5; H and 13C NMR spectra of
6. This material is available free of charge via the Internet at
http://pubs.acs.org.
3
298 K): δ 16.99 (s, 1H, RudCH), 8.36 (d of d, JHH ) 6.6 Hz,
OM050952J