Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands

Article abstract of DOI:10.1021/ja021146w

This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR₃)(Cl)₂Ru=CHR′, which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)₂(Cl)₂Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H₂IMes)(IMes)(Cl)₂Ru=CHPh, and the other of (PCy₃)(Cl)(CO)Ru[η²-(CH₂- C₆H₂Me₂)(N₂ C₃H₄)(C₆H₂Me₃)], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydridocarbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBu^t. We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.

Full text of DOI:10.1021/ja021146w

Published on Web 02/12/2003
Synthesis and Activity of Ruthenium Alkylidene Complexes
Coordinated with Phosphine and N-Heterocyclic Carbene
Ligands
Tina M. Trnka, John P. Morgan, Melanie S. Sanford, Thomas E. Wilhelm,
Matthias Scholl, Tae-Lim Choi, Sheng Ding, Michael W. Day, and
Robert H. Grubbs*
Contribution from the Arnold and Mabel Beckman Laboratory of Chemical Synthesis,
DiVision of Chemistry and Chemical Engineering, California Institute of Technology,
Pasadena, California 91125
Received September 4, 2002 ; E-mail: rhg@its.caltech.edu
Abstract: This paper reports the synthesis and characterization of a variety of ruthenium complexes
coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several
alkylidene derivatives of the general formula (NHC)(PR3)(Cl)2RudCHR′, which are highly active olefin
metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine)
ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs
NHC-alcohol or -chloroform adducts as “protected” forms of the NHC ligands. This route is advantageous
because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate
that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor
(NHC)(py)2(Cl)2RudCHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of
the mixed bis(NHC) derivative (H2IMes)(IMes)(Cl)2RudCHPh, and the other of (PCy3)(Cl)(CO)Ru[η2-(CH2-
C6H2Me2)(N2C3H4)(C6H2Me3)], the product of ortho methyl C-H bond activation. Other side reactions
encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydrido-
carbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium
vinylcarbene ligands by KOBut. We also evaluate the olefin metathesis activity of NHC-coordinated
complexes in representative RCM and ROMP reactions.
in (NHC)(PCy3)(Cl)2RudCHPh.4 These catalysts have enabled
Introduction
the widespread application of olefin metathesis in many areas
Since the discovery that well-defined ruthenium alkylidene
complexes could catalyze the ring-opening metathesis polym-
erization reaction,1 we2 and others3 have devoted considerable
effort to developing derivatives with improved properties,
especially enhanced activity, product selectivity, and stability.
The most successful modifications to date have involved
tricyclohexylphosphine (PCy3) ligands, as in (PCy3)2(Cl)2-
RudCHPh,2l-o and N-heterocyclic carbene (NHC) ligands, as
of synthetic chemistry.5
The emphasis of recent studies has been on ruthenium
(1) Nguyen, S. T.; Johnson, L. K.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem.
Soc. 1992, 114, 3974-3975.
(3) Representative homogeneous examples: (a) Stu¨er, W.; Wolf, J.; Werner,
H. J. Organomet. Chem. 2002, 641, 203-207. (b) Buchowicz, W.; Ingold,
F.; Mol, J. C.; Lutz, M.; Spek, A. L. Chem.-Eur. J. 2001, 7, 2842-2847.
(c) Coalter, J. N.; Caulton, K. G. New J. Chem. 2001, 25, 679-684. (d)
Nieczypor, P.; van Leeuwen, P. W. N. M.; Mol, J. C.; Lutz, M.; Spek, A.
L. J. Organomet. Chem. 2001, 625, 58-66. (e) Fu¨rstner, A.; Guth, O.;
Du¨ffels, Seidel, G.; Liebl, M.; Gabor, B.; Mynott, R. Chem.-Eur. J. 2001,
7, 4811-4820. (f) Amoroso, D.; Fogg, D. E. Macromolecules 2000, 33,
2815-2818. (g) Werner, H.; Jung, S.; Gonza´lez-Herrero, P.; Ilg, K.; Wolf,
J. Eur. J. Inorg. Chem. 2001, 1957-1961. (h) Leung, W.-H.; Lau, K.-K.;
Zhang, Q.-F.; Wong, W.-T.; Tang, B. Organometallics 2000, 19, 2084-
2089. (i) Katayama, H.; Urushima, H.; Ozawa, F. J. Organomet. Chem.
2000, 606, 16-25. (j) Saoud, M.; Romerosa, A.; Peruzzini, M. Organo-
metallics 2000, 19, 4005-4007. (k) van der Schaaf, P. A.; Kolly, R.; Kirner,
H.-J.; Rime, F.; Mu¨hlebach, A.; Hafner, A. J. Organomet. Chem. 2000,
606, 65-74. (l) Hansen, S. M.; Volland, M. A. O.; Rominger, F.;
Eisentra¨ger, F.; Hofmann, P. Angew. Chem., Int. Ed. 1999, 38, 1273-
1276. (m) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda,
A. H. J. Am. Chem. Soc. 1999, 121, 791-799. (n) Katayama, H.; Yoshida,
T.; Ozawa, F. J. Organomet. Chem. 1998, 562, 203-206.
(2) (a) Ro¨lle, T.; Grubbs, R. H. Chem. Commun. 2002, 1070-1071. (b) Trnka,
T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18-29. (c) Sanford, M.
S.; Henling, L. M.; Day, M. W.; Grubbs, R. H. Angew. Chem., Int. Ed.
2000, 39, 3451-3453. (d) Bielawski, C. W.; Louie, J.; Grubbs, R. H. J.
Am. Chem. Soc. 2000, 122, 12872-12873. (e) Ulman, M.; Belderrain, T.
R.; Grubbs, R. H. Tetrahedron Lett. 2000, 41, 4689-4693. (f) Lynn, D.
M.; Mohr, B.; Grubbs, R. H.; Henling, L. M.; Day, M. W. J. Am. Chem.
Soc. 2000, 122, 6601-6609. (g) Dias, E. L.; Grubbs, R. H. Organometallics
1998, 17, 2758-2767. (h) Sanford, M. S.; Henling, L. M.; Grubbs, R. H.
Organometallics 1998, 17, 5384-5389. (i) Chang, S.; Jones, L.; Wang,
C.; Henling, L. M.; Grubbs, R. H. Organometallics 1998, 17, 3460-3465.
(j) Dias, E. L.; Nguyen, S. T.; Grubbs, R. H. J. Am. Chem. Soc. 1997, 119,
3887-3897. (k) Wilhelm, T. E.; Belderrain, T. R.; Brown, S. N.; Grubbs,
R. H. Organometallics 1997, 16, 3867-3869. (l) Schwab, P.; Grubbs, R.
H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100-110. (m) Wu, Z.;
Nguyen, S. T. Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1995, 117,
5503-5511. (n) Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H.
Angew. Chem., Int. Ed. Engl. 1995, 34, 2039-2041. (o) Nguyen, S. T.;
Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1993, 115, 9858-9859.
9
2546
J. AM. CHEM. SOC. 2003, 125, 2546-2558
10.1021/ja021146w CCC: $25.00 © 2003 American Chemical Society

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
alkylidene complexes coordinated with NHC ligands, which
parallels the current use of NHCs in many other catalytic
systems, such as Heck and Suzuki couplings, aryl amination,
hydrogenation, and hydroformylation.6,7 The synthesis of NHC-
coordinated complexes for these applications can be achieved
in several ways.8 One of the most widely used methods,
pioneered by Lappert and co-workers in the 1970s and 80s,9 is
the thermal cleavage of enetetramines in the presence of metal
species. Unfortunately, this route is not compatible with the
synthesis of ruthenium alkylidene complexes because the high
temperatures required for enetetramine cleavage (g100 °C) lead
to the decomposition of alkylidene-containing precursors.
Another popular approach is the reaction of free NHCs with a
variety of metal species,8 which became possible after Arduengo
and co-workers successfully isolated the first free NHC in the
early 1990s.10 This route has been the method of choice for the
synthesis of NHC-containing ruthenium alkylidene complexes
because the substitution of a phosphine ligand with a free NHC
in bis(phosphine) precursors such as (PCy3)2(Cl)2RudCHPh is
a generally clean and straightforward reaction.4 In our experi-
ence, however, the isolation of novel free carbenes is often not
trivial due to difficulties with their synthesis or with decomposi-
tion, and we find the need to handle free NHCs under air-free
conditions inconvenient for large-scale preparations.
For these reasons, one of our goals has been the development
of improved ways to synthesize metal complexes with NHC
ligands. In this report, we describe an approach that employs
NHC adducts as “protected” forms of the free carbenes. These
adducts contain alkoxide or trichloromethyl groups, for instance,
and, as illustrated in eq 1, they can eliminate alcohol or
chloroform to unmask the carbene, which then coordinates to
the metal center.11
(4) (a) Love, J. A.; Morgan, J. P.; Trnka, T. M.; Grubbs, R. H. Angew. Chem.,
Int. Ed. 2002, 41, 4035-4037. (b) Wakamatsu, H.; Blechert, S. Angew.
Chem., Int. Ed. 2002, 41, 2403-2405. (c) Sanford, M. S.; Love, J. A.;
Grubbs, R. H. Organometallics 2001, 20, 5314-5318. (d) Seiders, T. J.;
Ward, D. W.; Grubbs, R. H. Org. Lett. 2001, 3, 3225-3228. (e) 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. (f) Fu¨rstner,
A.; Krause, H.; Ackermann, L.; Lehmann, C. W. Chem. Commun. 2001,
2240-2241. (g) Jafarpour, L.; Nolan, S. P. J. Organomet. Chem. 2001,
617-618, 17-27. (h) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.; Hoveyda,
A. H. J. Am. Chem. Soc. 2000, 122, 8168-8179. (i) Katayama, H.;
Urushima, H.; Nishioka, T.; Wada, C.; Nagao, M.; Ozawa, F. Angew.
Chem., Int. Ed. 2000, 39, 4513-4515. (j) Jafarpour, L.; Stevens, E. D.;
Nolan, S. P. J. Organomet. Chem. 2000, 606, 49-54. (k) Weskamp, T.;
Kohl, F. J.; Hieringer, W.; Gleich, D.; Herrmann, W. A. Angew. Chem.,
Int. Ed. 1999, 38, 2416-2419. (l) Huang, J.; Stevens, E. D.; Nolan, S. P.;
Petersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674-2678. (m) Weskamp,
T.; Kohl, F. J.; Herrmann, W. A. J. Organomet. Chem. 1999, 582, 362-
365. (n) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999,
1, 953-956. (o) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H.
Tetrahedron Lett. 1999, 40, 2247-2250. (p) Schanz, H.-J.; Jafarpour, L.;
Stevens, E. D.; Nolan, S. P. Organometallics 1999, 18, 5187-5190. (q)
Weskamp, T.; Schattenmann, W. C.; Spiegler, M.; Herrmann, W. A. Angew.
Chem., Int. Ed. 1998, 37, 2490-2493; Angew. Chem., Int. Ed. 1999, 38,
262.
(5) Recent reviews of olefin metathesis applications: (a) Mecking, S.; Held,
A.; Bauers, F. M. Angew. Chem., Int. Ed. 2002, 41, 544-561. (b) Coates,
G. W. J. Chem. Soc., Dalton Trans. 2002, 467-475. (c) Fu¨rstner, A. Angew.
Chem., Int. Ed. 2000, 39, 3013-3043. (d) Tsuji, J. Transition Metal
Reagents and Catalysts: InnoVations in Organic Synthesis; Wiley: Chich-
ester, 2000; Chapter 8. (e) Maier, M. E. Angew. Chem., Int. Ed. 2000, 39,
2073-2077. (f) Roy, R.; Das, S. K. Chem. Commun. 2000, 519-529. (g)
Jørgensen, M.; Hadwiger, P.; Madsen, R.; Stu¨tz, A. E.; Wrodnigg, T. M.
Curr. Org. Chem. 2000, 4, 565-588. (h) Yet, L. Chem. ReV. 2000, 100,
2963-3007. (i) Cook, G. R. Curr. Org. Chem. 2000, 4, 869-885. (j)
Buchmeiser, M. R. Chem. ReV. 2000, 100, 1565-1604. (k) Grubbs, R. H.;
Khosravi, E.; Davidson, T. A.; Wagener, K. B. In Synthesis of Polymers:
A Volume of the Materials Science and Technology Series; Schlu¨ter, A.-
D., Cahn, R. W., Haasen, P., Kramer, E. J., Eds.; Wiley-VCH: Weinheim,
1999; Chapter 3, pp 65-104 and Chapter 4, pp 105-122. (l) Zaragoza
Do¨rwald, F. Metal Carbenes in Organic Synthesis; Wiley-VCH: Weinheim,
1999. Phillips, A. J.; Abell, A. D. Aldrichimica Acta 1999, 32, 75-89.
(m) Wright, D. L. Curr. Org. Chem. 1999, 3, 211-240. (n) Kingsbury, C.
L.; Mehrman, S. J.; Takacs, J. M. Curr. Org. Chem. 1999, 3, 497-555.
(6) Reviews: (a) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290-
1309. (b) Jafarpour, L.; Nolan, S. P. AdV. Organomet. Chem. 2001, 46,
181-222. (c) Herrmann, W. A.; Weskamp, T.; Bo¨hm, V. P. AdV.
Organomet. Chem. 2001, 48, 1-69. (d) Herrmann, W. A.; Ko¨cher, C.
Angew. Chem., Int. Ed. 1998, 36, 22163-2187.
(7) Representative examples: (a) Jackstell, R.; Andreau, M. G.; Frisch, A.;
Selvakumar, K.; Zapf, A.; Klein, H.; Spannenberg, A.; Ro¨ttger, D.; Briel,
O.; Karch, R.; Beller, M. Angew. Chem., Int. Ed. 2002, 41, 986-989. (b)
Tan, K. L.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2002, 124,
3202-3203. (c) Albrecht, M.; Crabtree, R. H.; Mata, J.; Peris, E. Chem.
Commun. 2002, 32-33. (d) Batey, R. A.; Shen, M.; Lough, A. J. Org.
Lett. 2002, 4, 1411-1414. (e) Peris, E.; Loch, J. A.; Mata, J.; Crabtree, R.
H. Chem. Commun. 2001, 201-202. (f) Mathews, C. J.; Smith, P. J.;
Welton, T.; White, A. J. P.; Williams, D. J. Organometallics 2001, 20,
3848-3850. (g) Powell, M. T.; Hou, D.-R.; Perry, M. C.; Cui, X.; Burgess,
K. J. Am. Chem. Soc. 2001, 123, 8878-8879. (h) Tulloch, A. D.;
Danopoulos, A. A.; Tooze, R. P.; Cafferkey, S. M.; Kleinhenz, S.;
Hursthouse, M. B. Chem. Commun. 2000, 1247-1248. (i) McGuinness,
D. S.; Cavell, K. J. Organometallics 2000, 19, 741-748. (j) Chen, J. C.
C.; Lin, I. J. B. Organometallics 2000, 19, 5113-5121. (k) Gardiner, M.
G.; Herrmann, W. A.; Reisinger, C.-P.; Schwarz, J.; Spiegler, M. J.
Organomet. Chem. 1999, 572, 239-247. (l) Weskamp, T.; Bo¨hm, V. P.
W.; Herrmann, W. A. J. Organomet. Chem. 1999, 585, 348-352. (m)
McGuinness, D. S.; Green, M. J.; Cavell, K. J.; Skelton, B. W.; White, A.
H. J. Organomet. Chem. 1998, 565, 165-178. (n) Lappert, M. F.; Maskell,
R. K. J. Organomet. Chem. 1984, 264, 217-228. (o) Hill, J. E.; Nile, T.
A. Transition Met. Chem. 1978, 3, 315-316.
The direct use of an isolated NHC-alcohol adduct in the
synthesis of a metal complex was unprecedented at the time
we initiated our studies, although Lappert and co-workers had
used NHC-chloroform and -amine adducts to make (NHC)-
(PEt3)(Cl)2Pt and (NHC)2(Cl)2Pt complexes.12 However, in the
case of this particular chloroform adduct, 1,3-diphenyl-2-
(trichloromethyl)imidazolidine, it is not clear whether the
released NHC reacts directly with the platinum precursor or
whether 2 equiv first dimerize to form the enetetramine in situ
(Scheme 1).13 This ambiguity exists because the free carbene
has a strong tendency to dimerize14 and the enetetramine is
(9) (a) Lappert, M. F. J. Organomet. Chem. 1988, 358, 185-214. (b) Hitchcock,
P. B.; Lappert, M. F.; Pye, P. L. J. Chem. Soc., Dalton Trans. 1978, 826-
836. (c) Lappert, M. F.; Pye, P. L. J. Chem. Soc., Dalton Trans. 1978,
837-844. (d) Lappert, M. F.; Pye, P. L. J. Chem. Soc., Dalton Trans. 1977,
2172-2180. (e) Lappert, M. F. J. Organomet. Chem. 1975, 100, 139-
159. (f) C¸ etinkaya, B.; Dixneuf, P.; Lappert, M. F. J. Chem. Soc., Dalton
Trans. 1974, 1827-1833.
(10) (a) Arduengo, A. J.; Davidson, F.; Dias, H. V. R.; Goerlich, J. R.; Khasnis,
D.; Marshall, W. J.; Prakasha, T. K. J. Am. Chem. Soc. 1997, 119, 12742-
12749. (b) Arduengo, A. J.; Goerlich, J. R.; Marshall, W. J. J. Am. Chem.
Soc. 1995, 117, 11027-11028. (c) Arduengo, A. J.; Harlow, R. L.; Kline,
M. J. Am. Chem. Soc. 1991, 113, 361-363.
(11) The mechanism of this process has not been studied, but we believe that
some free carbene is released from the adduct in solution. Coordination of
the free NHC to the metal center would then drive the adduct-carbene
equilibrium toward more free carbene. This mechanism is supported by
the observation that free carbenes are obtained when the adducts are heated
under vacuum to remove the alcohol or chloroform byproduct (ref 17).
However, a metal-facilitated adduct deprotection or ligand substitution
mechanism cannot be discounted at this time.
(12) (a) Cardin, D. J.; C¸ etinkaya, B.; C¸ etinkaya, E.; Lappert, M. F. J. Chem.
Soc., Dalton Trans. 1973, 514-522. (b) Chamizo, J. A.; Lappert, M. F. In
AdVances in Metal Carbene Chemistry; Schubert, U., Ed.; Kluwer Academic
Publishers: Norwell, MA, 1989; pp 47-58.
(8) Other methods include the reduction of thiones, nucleophilic addition to
coordinated isocyanide ligands, and carbene transfer from one metal center
to another. Reviews: (a) Raubenheimer, H. G.; Cronje, S. J. Organomet.
Chem. 2001, 617-618, 170-181. (b) Weskamp, T.; Bo¨hm, V. P. W.;
Herrmann, W. A. J. Organomet. Chem. 2000, 600, 12-22. (c) Bourissou,
D.; Guerret, O.; Gabba¨ı, F. P.; Bertrand, G. Chem. ReV. 2000, 100, 39-
91. (d) Liu, S.-T.; Reddy, K. R. Chem. Soc. ReV. 1999, 28, 315-322.
(13) (a) C¸ etinkaya, B.; C¸ etinkaya, E.; Chamizo, J. A.; Hitchcock, P. B.; Jasim,
H. A.; Ku¨c¸u¨kbay, H.; Lappert, M. F. J. Chem. Soc., Perkin Trans. 1 1998,
2047-2054. (b) C¸ etinkaya, E.; Hitchcock, P. B.; Jasim, H. A.; Lappert,
M. F.; Kostas, S. J. Chem. Soc., Perkin Trans. 1 1992, 561-567. (c)
Wanzlick, H. W. Angew. Chem., Int. Ed. Engl. 1962, 1, 75-80.
(14) Hitchcock, P. B. J. Chem. Soc., Dalton Trans. 1979, 1314-1317.
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2547

A R T I C L E S
Trnka et al.
provide (Ph3Tri)(PCy3)(Cl)2RudCHPh (1a).18 Complete conver-
sion is achieved quickly by briefly heating the reaction mixture,
and then 1a is separated from the tricyclohexylphosphine and
methanol byproducts by precipitation from pentane. Complex
1a is a mixture of two conformational isomers, in which only
the orientations of the triazolylidene ligand and/or the alkylidene
Scheme 1
1
moiety are different. By H NMR, two doublet resonances for
the alkylidene R-protons occur at δ 19.56 [3JHP ) 8 Hz] and
19.37 [3JHP ) 6.5 Hz] in a 60:40 ratio. Likewise, 31P NMR
shows one singlet resonance for each of the isomers, at δ 24.14
and 23.04. The identity of the product is further supported by
high-resolution mass spectrometry data, which reveal only one
product molecular ion peak.
As illustrated in Scheme 2, complex 1a also can be obtained
by in situ deprotonation of the triazolium salt with NaH followed
by addition of (PCy3)2(Cl)2RudCHPh, or by direct reaction of
(PCy3)2(Cl)2RudCHPh with the isolated free carbene.19 How-
ever, we have found the air-stable Ph3Tri(H)(OMe) adduct most
convenient to isolate and handle, and this route provides 1a in
59% yield on a half-gram scale with minimal purification.
The dimethylvinyl alkylidene derivative (Ph3Tri)(PCy3)(Cl)2-
RudCHCHdCMe2 (1b) can be synthesized by the analogous
reaction between Ph3Tri(H)(OMe) and the bis(phosphine)
precursor (PCy3)2(Cl)2RudCHCHdCMe2. Like 1a, this product
is a mixture of conformational isomers characterized by two
doublets of doublets in the 1H NMR spectrum at δ 19.56 (3JHP
) 5.5 Hz, 3JHH ) 11 Hz) and 19.37 (3JHP ) 2.5 Hz, 3JHH ) 11
Hz) for the alkylidene R-protons, two doublets with 3JHH ) 11
Hz at δ 7.85 and 7.71 for the vinyl protons, and two 31P NMR
singlet resonances at δ 28.11 and 26.43.
Unfortunately, both 1a and 1b are unstable in solution. After
several hours in C6D6 or CD2Cl2 at room temperature under an
N2 atmosphere, significant decomposition is visible by NMR.
Included among the decomposition products are the [Ph3Tri-
(H)]+ salt and the bis(phosphine) ruthenium derivative (PCy3)2-
(Cl)2RudCHR, which suggests that the Ph3Tri ligand dissociates
from the metal center and phosphine reassociates to yield the
more stable (PCy3)2(Cl)2RudCHR complex.20 Because this
decomposition pathway is accelerated at elevated temperatures
and under catalytic turnover conditions, 1a and 1b are not ideal
olefin metathesis catalysts. Nevertheless, the synthesis of 1a
and 1b from the methanol adduct Ph3Tri(H)(OMe) established
that NHC adducts could provide a viable new route to the
ruthenium alkylidene complexes of interest.
known to react with [(PEt3)Pt(Cl)(µ-Cl)]2 to provide (NHC)-
(PEt3)Pt(Cl)2.12a In other related carbene adduct chemistry,
diazirines and oxadiazolines have been used to generate free
alkoxy-, amino-, and thiocarbenes by thermal elimination of
dinitrogen and/or ketones,15 and various carbene adducts have
been proposed as reaction intermediates.13,16
As demonstrated in this work, the application of NHC adducts
to the synthesis of metal complexes is a general, facile, and
reliable approach, especially for the important class of ruthenium
alkylidene complexes. We provide several examples of this
methodology using two different NHC-alcohol adducts and one
NHC-chloroform adduct, and we also describe a variety of
unexpected ruthenium byproducts encountered during the
development of this chemistry. In addition, the olefin metathesis
activity of these new NHC-coordinated complexes is compared
to that of previously reported catalysts in representative ring-
closing metathesis (RCM) and ring-opening metathesis polym-
erization (ROMP) reactions.
Results and Discussion
Preparation of (Ph3Tri)(PCy3)(Cl)2RudCHR (Ph3Tri )
1,3,4-Triphenyl-4,5-dihydro-1H-triazol-5-ylidene, R ) Ph
and CHdCMe2). We began our study with the triazole-based
methanol adduct Ph3Tri(H)(OMe), previously isolated by Enders
and co-workers from the reaction of the triazolium salt [Ph3-
Tri(H)][ClO4] with sodium methoxide (Scheme 2).17 To avoid
the perchlorate salt, the tetrafluoroborate derivative can be made
by refluxing N-phenylbenzamide phenylhydrazone with am-
monium tetrafluoroborate in triethyl orthoformate, or the tosylate
salt can be obtained in a similar reaction with p-toluenesulfonic
acid monohydrate and triethylorthoformate under azeotropic
distillation conditions. Alternatively, the methanol adduct can
be synthesized directly from N-phenylbenzamide phenylhydra-
zone in a one-pot procedure.
Preparation and Side Reactions of (H2IMes)(PCy3)-
(Cl)2RudCHPh (H2IMes ) 1,3-Dimesityl-imidazolidine-2-
ylidene). We next extended this adduct methodology to NHCs
with saturated C-C backbones.21 For example, the reaction of
KOBut with [H2IMes(H)][X] yields the tert-butyl alcohol adduct
The isolated Ph3Tri(H)(OMe) adduct reacts cleanly with the
ruthenium benzylidene precursor (PCy3)2(Cl)2RudCHPh to
1
H2IMes(H)(OBut) (eq 2). It is characterized by a H NMR
resonance at δ 5.61 for the C(2) proton, and a 13C NMR
resonance at δ 95.4 for the C(2) carbon. In comparison, the
C(2) of the free H2IMes carbene appears much further downfield
(15) (a) Moss, R. A. Acc. Chem. Res. 1999, 32, 969-974. (b) Ross, J. P.;
Couture, P.; Warkentin, J. Can. J. Chem. 1997, 75, 1331-1335. (c) Couture,
P.; Warkentin, J. Can. J. Chem. 1997, 75, 1281-1294. (d) Couture, P.;
Terlouw, J. K.; Warkentin, J. J. Am. Chem. Soc. 1996, 118, 4214-4215.
(e) Rigby, J. H.; Cavezza, A.; Ahmed, G. J. Am. Chem. Soc. 1996, 118,
12848-12849.
(16) (a) Lappert, M. F.; Pye, P. L. J. Less-Common Met. 1997, 54, 191-207.
(b) Hocker, J.; Merten, R. Angew. Chem., Int. Ed. Engl. 1972, 11, 964-
973. (c) Hoffmann, R. W. Angew. Chem., Int. Ed. Engl. 1968, 7, 754-
765. (d) Wiberg, N. Angew. Chem., Int. Ed. Engl. 1968, 7, 766-779.
(17) (a) Teles, J. H.; Melder, J.-P.; Ebel, K.; Schneider, R.; Gehrer, E.; Harder,
W.; Brode, S.; Enders, D.; Breuer, K.; Raabe, G. HelV. Chim. Acta 1996,
79, 61-83. (b) Enders, D.; Breuer, K.; Raabe, G.; Runsink, J.; Teles, J.
H.; Melder, J.-P.; Ebel, K.; Brode, S. Angew. Chem., Int. Ed. Engl. 1995,
34, 1021-1023.
(18) For preliminary results, see: Grubbs, R. H.; Trnka, T. M. U.S. Patent 6,-
426,419 B1, 2002.
(19) The synthesis of (Ph3Tri)(PCy3)(Cl)2RudCHPh from the free Ph3Tri carbene
also has been reported by Fu¨rstner and co-workers. See ref 4e.
(20) Although ortho metallation of the Ph3Tri ligand occurs in some metal
complexes (Enders, D.; Gielen, H.; Raabe, G.; Runsink, J.; Teles, J. H.
Chem. Ber. 1997, 130, 1253-1260), we have not observed this reaction in
the (Ph3Tri)(PCy3)(Cl)2RudCHR system.
(21) For preliminary results, see ref 4n and Grubbs, R. H.; Scholl, M. PCT Int.
Appl. WO 0071554, 2000.
9
2548 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
Scheme 2
at δ 244.22 As in the H2IMes-chloroform derivative,40 the protons
on the top and bottom faces of the CH2CH2 backbone and the
ortho and meta mesityl ring positions are inequivalent. Notably,
adduct formation does not occur with the imidazolium salt
[IMes(H)][X] (IMes ) 1,3-dimesityl-imidazoline-2-ylidene),
which differs from [H2IMes(H)][X] by an unsaturated CdC
backbone. Reaction with KOBut instead results in direct and
rapid deprotonation to the free NHC (eq 3).23
the ruthenium benzylidene precursor (PCy3)2(Cl)2RudCHPh
(Scheme 3, top pathway).4n However, we subsequently found
that crude samples of 2 from this preparation often retained
excess [H2IMes(H)][BF4] and the reaction byproducts KBF4 and
PCy3, all of which decrease the catalytic activity of 2.24 To
obtain cleaner product, the workup procedure can be modified
to include filtration through Celite to remove residual salts,
followed by multiple washings with methanol and pentane.
However, the use of methanol as a wash solvent leads
to contamination with a small amount of metal-hydride im-
purity. This yellow species was isolated and identified as the
hydrido-carbonyl-chloride complex (H2IMes)(PCy3)(CO)(H)-
(Cl)Ru (3a). The presence of the hydride is indicated by the
(29) Jafarpour, L.; Nolan, S. P. Organometallics 2000, 19, 2055-2057.
(30) Jafarpour, L.; Hillier, A. C.; Nolan, S. P. Organometallics 2002, 21, 442-
444.
(31) Huang, J.; Stevens, E. D.; Nolan, S. P. Organometallics 2000, 19, 1194-
1197.
(32) Jazzar, R. F. R.; Macgregor, S. A.; Mahon, M. F.; Richards, S. P.;
Whittlesey, M. K. J. Am. Chem. Soc. 2002, 124, 4944-4945.
(33) Representative 13C NMR resonances for the NHC carbon in related
compounds: (a) δ 219.6 for (H2IMes)(PPh3)(Cl)2RudCHPh, δ 222.5 for
(H2IMes)(PCy3)(Cl)2RudCH2, δ 219.1 for (H2IMes)(py)2(Cl)2RudCHPh,
Sanford, M. S.; Love, J. A.; Grubbs, R. H. J. Am. Chem. Soc. 2001, 123,
6543-6554. (b) δ 217.2 for (H2IMes)(PCy3)(Cl)2RudCF2, Trnka, T. M.;
Day, M. W.; Grubbs, R. H. Angew. Chem., Int. Ed. 2001, 40, 3441-3444.
(c) δ 216.2 for (H2IMes)(Cl)2Ru[η3-(CHPh)(CPh)(CPh)], Trnka, T. M.; Day,
M. W.; Grubbs, R. H. Organometallics 2001, 20, 3845-3847. (d) δ 220.7
for (H2IMes)(PCy3)(Cl)2RudCH(OEt), ref 26a.
H2IMes(H)(OBut) can be isolated as a semisolid, but because
it decomposes by elimination of tert-butyl alcohol at room
temperature, we find it most convenient to use when generated
in situ. Our first reported preparation of (H2IMes)(PCy3)(Cl)2-
RudCHPh (2) involved this protocol followed by reaction with
(22) Arduengo, A. J.; Krafczyk, R.; Schmutzler, R.; Craig, H. A.; Goerlich, J.
R.; Marshall, W. J.; Unverzagt, M. Tetrahedron 1999, 55, 14523-14534.
(23) Arduengo, A. J.; Dias, H. V. R.; Harlow, R. L.; Kline, M. J. Am. Chem.
Soc. 1992, 114, 5530-5534.
(24) Morgan, J. P.; Goldberg, S. D.; Grubbs, R. H. 2001, unpublished results.
(25) (a) Gill, D. F.; Shaw, B. L. Inorg. Chim. Acta 1979, 32, 19-23. (b)
Esteruelas, M. A.; Werner, H. J. Organomet. Chem. 1986, 303, 221-231.
(c) Moers, F. G.; Langhout, J. P. Recueil 1972, 91, 591-600. (d) James,
B. R.; Preece, M.; Robinson, S. D. In Catalytic Aspects of Metal Phosphine
Complexes; Alyea, E. C., Meek, D. W., Eds.; American Chemical
Society: Washington, DC, 1982; pp 145-161.
(26) (a) In addition, 3b has been obtained as a thermal decomposition product
from (PCy3)2(Cl)2RudCH(OEt). Louie, J.; Grubbs, R. H. Organometallics
2002, 21, 2153-2164. (b) Formation of 3b can be a problem in the
preparation of Ru(H)(Cl)(PCy3)2(dCOC3H6) as well. Coalter, J. N.; Caulton,
K. G. New J. Chem. 2001, 25, 679-684.
(34) Representative 13C NMR resonances for the carbonyl ligand in related
compounds: (a) δ 201.9 for (PCy3)2(Cl)(CO)(H)Ru, Yi, C. S.; Lee, D.
W.; Chen, Y. Organometallics 1999, 18, 2043-2045. (b) δ 202.4 for
[PBut2(CH2CH2OPh)]2(Cl)(CO)(H)Ru, Jung, S.; Ilg, K.; Brandt, C. D.; Wolf,
J.; Werner, H. J. Chem. Soc., Dalton Trans. 2002, 318-327. (c) δ 205.6
for (PPri3)2(Cl)(CO)(Ph)Ru, Coalter, J. N.; Huffmann, J. C.; Caulton, K.
G. Organometallics 2000, 19, 3569-3578. (d) δ 197.7 for (PPri2Ph)2(Cl)-
(CO)(H)Ru, Werner, H.; Stu¨er, W.; Weberndo¨rfer, B.; Wolf, J. Eur. J. Inorg.
Chem. 1999, 1707-1713.
(35) Representative νCO values: (a) 1896 cm-1 for (PCy3)(IMes)(Cl)(CO)(H)-
Ru, Lee, H. M.; Smith, D. C.; He, Z.; Stevens, E. D.; Yi, C. S.; Nolan, S.
P. Organometallics 2001, 20, 794-797. (b) 1902 (Nujol) or 1905 (C6H6)
cm-1 for (PCy3)2(Cl)(CO)(H)Ru, ref 25c and d. (c) 1905 cm-1 for (PPri3)2-
(Cl)(CO)(Ph)Ru, ref 34c. (d) 1906 cm-1 for [PBut2(CH2CH2OPh)]2(Cl)-
(CO)(H)Ru, ref 34b. (e) 1910 cm-1 for (PPri3)2(Cl)(CO)(H)Ru, Esteruelas,
M. A.; Werner, H. J. Organomet. Chem. 1986, 303, 221-231.
(36) This geometry was confirmed in the crystal structure of 5. Sanford, M. S.
Ph.D. Thesis, California Institute of Technology, Pasadena, CA, 2001.
(37) Yi, C. S.; Lee, D. W.; Chen, Y. Organometallics 1999, 18, 2043-2045.
(38) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Zeier, B.
Organometallics 1994, 13, 4258-4265.
(27) Carbonyl/chloride disorder is common and occurs in many related
molecules. For example: (a) (PCy3)2(Cl)(CO)(H)Os, Moers, F. G.; Noordik,
J. H.; Beurskens, P. T. Cryst. Struct. Commun. 1981, 10, 1149-1152. (b)
(PPri3)2(Cl)(CO)(H)Ru, Huang, D.; Streib, W. E.; Bollinger, J. C.; Caulton,
K. G.; Winter, R. F.; Scheiring, T. J. Am. Chem. Soc. 1999, 121, 8087-
8097. (c) (PPh3)2(Cl)(CO)Rh, Dunbar, K. R.; Haefner, S. C. Inorg. Chem.
1992, 31, 36776-3679. (d) (PPh3)2(Cl)(CO)Ir, Churchill, M. R.; Fettinger,
J. C.; Buttrey, L. A.; Barkan, M. D.; Thompson, J. S. J. Organomet. Chem.
1988, 340, 257-266.
(39) Harlow, K. J.; Hill, A. F.; Welton, T. J. Chem. Soc., Dalton Trans. 1999,
1911-1912.
(40) Arduengo, A. J.; Calabrese, J. C.; Davidson, F.; Dias, H. V. R.; Goerlich,
J. R.; Krafczyk, R.; Marshall, W. J.; Tamm, M.; Schmutzler, R. HelV. Chim.
Acta 1999, 82, 2348-2364.
(28) This test is part of the International Union of Crystallography CIF checking
program. Hirshfeld, F. L. Acta Crystallogr. 1976, A32, 239-244.
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2549

A R T I C L E S
Trnka et al.
Scheme 3
(phosphine)-ruthenium(IV) complex.”4e However, it appears that
this structure has been solved incorrectly and the compound is
almost surely (PCy3)2(CO)(H)(Cl)Ru (3b) instead. We base this
Scheme 4
1
evaluation on (i) the distinctive H NMR resonance (δ -24.4,
2
t, JHP ) 17 Hz) and IR νCO (1905 cm-1) that match the data
for 3b,25c (ii) the fact that “(PCy3)2(Cl)2(H)2Ru” was obtained
as a byproduct from a preparation of (L)(PCy3)(Cl)2RudCHPh
[L ) 1,3-di(2,6-diisopropylphenyl)-imidazolidine-2-ylidene] that
included methanol, which accounts for the origin of 3b, and
(iii) the unit cell parameters that match those of 3b. The
crystallographic evidence suggests that carbonyl/chloride dis-
order is a significant problem in this structure.27 For example,
the Cl displacement ellipsoids of “(PCy3)2(Cl)2(H)2Ru” are
anomalously large and elongated along the Cl-Ru-Cl bond
axis, and the Hirshfeld rigid-bond test gives extremely poor
results (a remarkably high 110 s.u.).28
To develop a synthesis of 2 that avoids salt contamination
and hydride formation, we adapted the one-pot preparation
reported by Nolan and co-workers for the synthesis of the related
complex (IMes)(PCy3)(Cl)2RudCHPh.29 In our procedure for
2, the ruthenium benzylidene precursor (PCy3)2(Cl)2RudCHPh,
the imidazolinium salt [H2IMes(H)][Cl], and KOBut are refluxed
in hexanes for 1 day. Although it visually appears as though
these sparingly soluble reactants remain suspended in the
hexanes, the soluble H2IMes(H)(OBut) adduct forms in situ and
reacts with the bis(phosphine) precursor (Scheme 3). Once all
the (PCy3)2(Cl)2RudCHPh is converted to 2, a 2-propanol/water
mixture is added to extract unreacted salts and phosphine oxide.
Complex 2 remains largely insoluble in this solvent system and
can be isolated as analytically pure material in good yield
(∼75%) simply by filtration, even on multigram scales. It is
unnecessary to use Nolan’s substitution of potassium tert-
amylate for KOBut,30 particularly because KOBut is less
expensive and more readily available.
distinctive upfield 1H NMR resonance at δ -24.90 split into a
doublet with 2JHP ) 21 Hz, which is characteristic of a hydride
situated trans to an empty coordination site and cis to a
phosphine. This resonance in the closely related (IMes)(PCy3)-
2
(CO)(H)(Cl)Ru derivative is similar (δ -24.83, d, JHP ) 21
Hz).35a The transformation of ruthenium alkylidene complexes
to hydrido-carbonyl-chloride derivatives was confirmed by direct
reaction with methanol to provide (H2IMes)(PCy3)(CO)(H)(Cl)-
Ru (3a), (PCy3)2(CO)(H)(Cl)Ru (3b), and (IMes)(PCy3)(CO)-
(H)(Cl)Ru (3c) (Scheme 4). Although the decarbonylation of
primary alcohols by group 8 metal precursors is a general route
to hydrido-carbonyl complexes,25 the mechanism of this process
is unknown, and it is not clear what happens to the benzylidene
fragment in the case of (L)(PCy3)(Cl)2RudCHPh.
We have also observed 3a or 3b under conditions where (H2-
IMes)(PCy3)(Cl)2RudCHPh (2) or (PCy3)2(Cl)2RudCHPh is
heated for prolonged periods in the presence of oxygen-
containing substrates, such as ethyl vinyl ether.26 Because of
this decomposition reaction, we have accidentally obtained
crystals of (PCy3)2(CO)(H)(Cl)Ru (3b) and redetermined its
structure (the crystal structures of 3b and 3c have been reported
previously),35a and we refer the interested reader to the Sup-
porting Information for these details. In this context, we also
note that Fu¨rstner and co-workers have reported a crystal
structure of “(PCy3)2(Cl)2(H)2Ru”, which they claim as, “the
second known crystal structure of a dihydro-dichloro-bis-
In this preparation, the chloride salt [H2IMes(H)][Cl] provides
better results than the tetrafluoroborate salt [H2IMes(H)][BF4].
When the reaction is monitored by 1H NMR spectroscopy, we
observe that substantially more (ButO)2(PCy3)RudCHPh forms
with the tetrafluoroborate salt. (ButO)2(PCy3)RudCHPh is the
product from direct reaction of (PCy3)2(Cl)2RudCHPh with
KOBut, and it is identified by the downfield resonances of the
alkylidene proton (δ 15.5, d, 3JHP ) 4.4 Hz) and the phosphorus
9
2550 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
(Cl)2RudCHCHdCMe2 is deprotonated by KOBut and other
bases to furnish a partially characterized ruthenium species with
a vinylvinyl unit, that is, [(PCy3)2(Cl)2Ru-CHdCHCMedCH2]
1
(eq 4). The H NMR spectrum for this product contains two
characteristic doublets at δ 8.93 and 6.27 (both 3JHH ) 13 Hz)
for the vinylic protons. Although this vinylvinyl species is
unstable in solution and could not be isolated, the related
vinylvinyl-carbonyl complex (PPri3)2(Cl)(CO)Ru-CHdCHCMed
CH2 (5) was obtained cleanly by the analogous reaction of
(PPri3)2(Cl)2(CO)RudCHCHdCMe2 with KOBut (eq 5). The
1H NMR spectrum of 5 likewise contains doublets at δ 7.96
3
and 5.80 (both JHH ) 16 Hz) for the vinylic protons, and the
coupling constant indicates a trans olefin geometry.36 The PCy3-
substituted derivative of 5 has been synthesized by Yi and co-
workers in a similar fashion by deprotonation of [(PCy3)2(Cl)-
(CO)RudCH-CHdCMe2][BF4] with triethylamine.37 The related
cyclohexyl vinylvinyl compound (PPri3)2(Cl)(CO)Ru-CHdCH-
[CdCH(CH2)4] has been reported as well,38 and both of these
Figure 1. Structure of 4 ‚ 1/2CH2Cl2. For clarity, solvent and all hydrogen
atoms have been omitted. Displacement ellipsoids are drawn at 50%
probability. Selected bond distances [Å] and angles [deg]: Ru-C(1) 1.811-
(3), Ru-C(2) 2.037(3), Ru-C(22) 2.097(2), Ru-P 2.402(1), Ru-Cl 2.435-
(1), C(1)-O 1.126(3), C(2)-N(1) 1.343(3), C(2)-N(2) 1.350(3), C(3)-
N(1) 1.468(3), C(4)-N(2) 1.481(3), C(5)-N(1) 1.445(3), C(3)-C(4)
1.523(4), C(14)-C(19) 1.408(3), C(14)-N(2) 1.436(3), C(19)-C(22) 1.487-
(3), C(1)-Ru-C(2) 93.7(1), C(2)-Ru-P 174.14(7), C(1)-Ru-Cl 165.73-
(8), O-C(1)-Ru 178.2(2), N(1)-C(2)-N(2) 108.2(2), C(19)-C(22)-Ru
108.1(2).
1
examples exhibit H NMR and IR data similar to those of 5.
As expected, addition of HCl to 5 regenerates the starting
material (PPri3)2(Cl)2(CO)RudCHCHdCMe2 (eq 5). Similar
transformations, such as from (PPh3)2(Cl)(MeCN)2Ru-CHd
CHCPh2OH to (PPh3)2(Cl)2RudCHCHdCPh2 upon addition of
HCl, have been observed by Hill and Welton.39
nucleus (δ 83.5).2c There are several possible explanations for
this counterion effect, such as differences in salt solubility or
the influence of chloride ion coordination to the C(2) proton in
[H2IMes(H)][Cl], but these are speculative.
It is necessary to carry out this preparation of 2 under a
moderately rigorous inert atmosphere. In instances when we
used a round-bottom flask with condenser and a slow argon
flow rather than a sealed Schlenk flask, we isolated a red-orange
powder that proved to be the alkyl-carbonyl-chloride complex
(PCy3)(Cl)(CO)Ru[η2-(CH2-C6H2Me2)(N2C3H4)(C6H2Me3)] (4)
instead of 2 (Scheme 4). This product is the result of C-H
bond activation of one ortho methyl of the mesityl group, and
both Nolan31 and Whittlesey32 have observed similar activation
processes in rhodium- and ruthenium-NHC complexes. Com-
pound 4 is characterized by 13C NMR resonances at δ 220.3
Access to catalyst 2 is also provided by the chloroform adduct
H2IMes(H)(CCl3), previously isolated by Arduengo and co-
workers as the product of slow chloroform C-H activation by
the H2IMes free carbene.40 As illustrated in Scheme 3, we have
developed an improved synthesis of H2IMes(H)(CCl3) directly
from the imidazolinium salt [H2IMes(H)][Cl] plus sodium
hydroxide and chloroform, which is advantageous because it
avoids the free carbene and is amenable to large-scale prepara-
tions. Furthermore, the H2IMes(H)(CCl3) adduct is significantly
more thermally stable than the tert-butyl alcohol derivative
H2IMes(H)(OBut), is easily isolated and purified by column
chromatography, and is a free-flowing, solid material instead
of the tacky H2IMes(H)(OBut) semisolid. As with other NHC
adducts, the reaction of H2IMes(H)(CCl3) with (PCy3)2(Cl)2-
RudCHPh is straightforward and provides 2 in good yield
(84%) upon heating at 60 °C for 90 min (Scheme 3).
(2JCP ) 90 Hz) for the NHC carbon33 and at δ 203.0 (2JCP
)
15 Hz) for the carbonyl ligand,34 as well as the IR carbonyl
stretching frequency at 1899 cm-1, which is within the range
for similar compounds (1896-1910 cm-1).35 Not surprisingly,
4 is air-stable both in solution and in the solid state.
The crystal structure of 4 is shown in Figure 1. Compared to
the structure of the closely related complex (PPh3)2(CO)(H)-
Ru[η2-(CH2-C6H2Me2)(N2C3H2)(C6H2Me3)],32 there is a sig-
nificant 0.14(1) Å contraction in the Ru-CH2 bond length of
4, presumably due to the absence of any ligand trans to the
CH2 linkage. There is also some shortening of the Ru-CN2,
Ru-CO, and CtO bonds by 0.03(1)-0.06(1) Å, which can be
attributed to differences between the 18-electron ruthenium
center in (PPh3)2(CO)(H)Ru[η2-(CH2-C6H2Me2)(N2C3H2)-
(C6H2Me3)] and the 16-electron one in 4.
The spontaneous decomposition exhibited by the Ph3Tri-
coordinated complexes 1a and 1b is not shared by 2 or its IMes
derivative, both of which have excellent thermal stability. Even
in the presence of excess PCy3, neither 2 nor related mono-
(NHC) derivatives4k generate any detectable (PCy3)2(Cl)2Rud
CHPh. This difference may be due to the ortho methyl groups
on the mesityl substituents, which favor a perpendicular
arrangement of the mesityl and imidazole rings by limiting
N-Mes rotation, or other stabilizing effects.
Because the bis(phosphine) dimethylvinyl alkylidene complex
(PCy3)2(Cl)2RudCHCHdCMe2 is readily accessible,2k we
hoped to use it to make the dimethylvinyl alkylidene derivative
of 2, (H2IMes)(PCy3)(Cl)2RudCHCHdCMe2. However, (PCy3)2-
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2551

A R T I C L E S
Trnka et al.
Scheme 5
temperature, the 1H NMR spectra of 6a and 6b each contain a
sharp alkylidene R-proton resonance at low field, but the rest
of the resonances appear broadened due to hindered rotation of
the H2IMes, IMes, and/or benzylidene ligands. At lower
temperature (-15 °C), these resonances sharpen into distinct
peaks for each set of inequivalent protons.
Scheme 6
Preparation of (H2IMes)(L)(Cl)2RudCHPh (L ) IMes or
H2IMes). In each synthesis of catalysts 1 and 2, the mono-
(substituted) (NHC)(PCy3)(Cl)2RudCHR product is observed
exclusively, even if a large excess of NHC is present. In theory,
the bis(substituted) product could also form, that is, (NHC)2-
(Cl)2RudCHR, as observed when the NHC is 1,3-dicyclohexyl-
imidazoline-2-ylidene.4q However, the origin of this effect is
not entirely steric congestion, as originally believed, especially
because examples of bis(IMes) metal complexes have been
synthesized.31 As illustrated in Scheme 5, the phosphine
exchange rate decreases dramatically when one of the PCy3
ligands in (PCy3)2(Cl)2RudCHPh is replaced by an H2IMes
ligand.41 This slow phosphine exchange rate in 2 may effectively
prevent further PCy3 substitution by the accepted dissociative
ligand substitution pathway. According to Scheme 6, this
The crystal structure of 6a is shown in Figure 2, and the
metrical data are presented in Table 2 along with compari-
sons to the mono(phosphine) derivatives (H2IMes)(PCy3)(Cl)2-
RudCHPh and (IMes)(PCy3)(Cl)2RudCHPh. Both of the
Ru-NHC distances in 6a are longer than those in either of the
corresponding mono(NHC) complexes, which surely reflects the
greater steric congestion in 6a and possibly also a more electron-
rich ruthenium center. Unfortunately, further comparisons of
the internal NHC bond lengths and angles have little meaning
because of disorder between the H2IMes and IMes ligands in
this structure.
Olefin Metathesis Activity. With several new NHC-co-
ordinated ruthenium alkylidene complexes in hand, we evaluated
their catalytic activity in representative RCM and ROMP
reactions. The cyclization of 4,4-dicarboethoxy-2-methyl-1,6-
heptadiene to the corresponding 4,4-dicarboethoxy-1-methyl-
cyclopentene product and the polymerization of 1,5-cyclooc-
tadiene were chosen as test cases because these transformations
corresponds to a situation where k1(NHC) is less than k1(PCy )
,
3
which is already slow. In addition, there may be a contribution
from the reverse rates if k-1(NHC) is less than k-1(PCy ), although
3
we cannot confirm this relationship because values of k-1(PCy )
1
3
are moderately challenging and easily monitored by H NMR
have been experimentally inaccessible.41
spectroscopy. The krel values for various catalyst derivatives are
Nevertheless, bis-substitution can be achieved by using
derivatives of 2 with more labile ligands in place of the tri-
cyclohexylphosphine, such as the pyridine complex (H2IMes)-
(py)2(Cl)2RudCHPh.4c For example, addition of the free IMes
carbene to (H2IMes)(py)2(Cl)2RudCHPh cleanly provides the
mixed H2IMes-IMes complex (H2IMes)(IMes)(Cl)2RudCHPh
(6a) (Scheme 5). Similarly, the reaction of (H2IMes)(py)2-
(Cl)2RudCHPh with the chloroform adduct H2IMes(H)(CCl3)
provides the bis(H2IMes) complex (H2IMes)2(Cl)2RudCHPh
(6b) (Scheme 5). These products are highly stable and can be
purified by column chromatography on silica gel.42 At room
collected in Table 3.
There is a great deal of variation in the overall activity of
different catalyst derivatives. The general activity trend is
(PCy3)2(Cl)2RudCH-CHdCMe2 ≈ (PCy3)2(Cl)2RudCHPh
<
(Cl2IMes)(PCy3)(Cl)2RudCHPh < (IMes)(PCy3)(Cl)2-
RudCHPh < (H2IMes)(PCy3)(Cl)2RudCHPh (2). This ordering
is consistent with results determined by Fu¨rstner and co-workers
for a variety of substrates by IR-thermography [(Ph3Tri)-
(PCy3)(Cl)2RudCHPh ≈ (PCy3)2(Cl)2RudCHPh < (Cl2IMes)-
(42) Other ruthenium alkylidene complexes (including 2) also can be purified
in this way. (a) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.;
Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791-799. (b) Tallarico, J.
A.; Bonitatebus, P. J.; Snapper, M. L. J. Am. Chem. Soc. 1997, 119, 7157-
7158.
(41) (a) Sanford, M. S.; Ulman, M.; Grubbs, R. H. J. Am. Chem. Soc. 2001,
123, 749-750. (b) Sanford, M. S.; Love, J. A.; Grubbs, R. H. J. Am. Chem.
Soc. 2001, 123, 6543-6554.
9
2552 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
Table 1. Crystal and Structure Refinement Data for
(PCy3)(Cl)(CO)Ru[η2-(CH2-C6H2Me2)(N2C3H4)(C6H2Me3)] (4) and
(H2IMes)(IMes)(Cl)2RudCHPh (6a)
parameters
4
6a
empirical formula
C40H58ClN2OPRu‚
1/2 CH2Cl2
792.84
CH2Cl2
tabular
C49H56Cl2N4Ru
formula weight
crystallization solvent
crystal habit
crystal color
crystal size (mm3)
a (Å)
872.95
CH2Cl2
plate
brown
0.25 × 0.16 × 0.04
11.663(3)
14.676(4)
25.176(7)
94.523(5)
95.698(4)
90.666(5)
4274(2)
orange
0.26 × 0.19 × 0.07
10.276(1)
13.039(1)
14.723(1)
92.336(2)
103.428(1)
91.814(1)
1915.5(3)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
4
crystal system
space group
θ range for data
collection (deg)
absorption coefficient
triclinic
P1h (No. 2)
2.0-28.4
triclinic
P1h (No. 2)
1.4-28.6
0.624
0.531
(Mo KR) (mm-1
)
reflections collected
28 236
101 139
independent reflections
8728
20 088
[Rint ) 0.0917]
447
[Rint ) 0.1006]
1457
no. parameters
final R1, wR2 indices
0.0383, 0.0807
0.0421, 0.0629
[I > 2σ(I)]
R1, wR2 indices (all data)
GOF on F 2
0.0503, 0.0832
1.187
0.0857, 0.0696
1.026
largest diff. peak
and hole (e Å-3
1.03 and -0.72
0.70 and -0.65
)
Figure 2. Structure of 6a. Side (a) and top (b) views. For clarity, only one
molecule in the asymmetric unit is shown, and most of the hydrogen atoms
have been omitted. Displacement ellipsoids are drawn at 50% probability;
hydrogens atoms are drawn at arbitrary scale.
easy access to in situ-generated (Ph3Tri)(PPh3)(Cl)2RudCHPh
(1c). Upon mixing at room temperature, (PPh3)2(Cl)2RudCHPh
and 1 equiv of Ph3Tri(H)(OMe) form 1c, which then catalyzes
the ROMP of COD at a fast rate (Table 3). This protocol is
also effective for the ROMP of bulk dicyclopentadiene. The
RCM reaction is less successful and goes to only 15%
conversion, probably because of catalyst decomposition. In
comparison, the bis(triphenylphosphine) starting material
(PPh3)2(Cl)2RudCHPh is completely inactive toward either of
these substrates. A related in situ preparation of catalyst 2
consisting of (PCy3)2(Cl)2RudCHPh + [H2IMes(H)][BF4] +
KOBut + phosphine scavenger has been described.48
We were particularly interested in the olefin metathesis
activity of the bis(NHC) complexes 6a and 6b because,
according to our mechanistic model, one NHC ligand would
have to dissociate from the ruthenium center for the catalyst to
initiate.41 (H2IMes)2(Cl)2RudCHPh (6b) shows slight activity
for RCM at 40 °C and no ROMP activity at 25 °C, but
respectable turnover for both reactions can be achieved at 80
°C (100% after 12 h). However, 6b does not react with ethylene
to form the corresponding methylidene derivative [Ru]dCH2
at any temperature. Although the latter result is consistent with
no observable catalyst initiation, the fact that 6b displays any
RCM or ROMP activity at all suggests that some initiation can
occur, at least at elevated temperatures.
(PCy3)(Cl)2RudCHPh
≈
(IMes)(PCy3)(Cl)2RudCHPh ,
(H2IMes)(PCy3)(Cl)2RudCHPh (2)],4e as well as with measure-
ments by Mol and co-workers for the metathesis of methyl oleate
[(PCy3)2(Cl)2RudCH-CHdCPh2 < (PCy3)2(Cl)2RudCHPh ,
(H2IMes)(PCy3)(Cl)2RudCHPh (2)].45 The larger variation in
krel values for RCM as compared to those of ROMP is partly
due to the higher temperature (40 °C for RCM vs 25 °C for
ROMP)46 because the NHC-coordinated catalysts initiate much
more efficiently at elevated temperatures.41 (PCy3)2(Cl)2Rud
CH-CHdCMe2 has a slightly lower krel than (PCy3)2(Cl)2Rud
CHPh because of its slightly lower initiation rate, but both
catalysts provide the same propagating species once they initiate.
We emphasize the remarkable differences in reaction rates when
the backbone of the NHC is varied from saturated (H2IMes) to
unsaturated (IMes) to chloro-substituted (Cl2IMes) (Table 3).
The greater overall activity of (H2IMes)(PCy3)(Cl)2RudCHPh
as compared to that of (IMes)(PCy3)(Cl)2RudCHPh has been
noted previously.4n,47
Although the Ph3Tri-coordinated catalysts 1a and 1b are
unstable in solution, the NHC adduct Ph3Tri(H)(OMe) provides
(43) Love, J. A.; Sanford, M. S.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc.
2003, 125, in press.
To test for NHC dissociation, (H2IMes)2(Cl)2RudCHPh (6b)
was heated in the presence of excess PCy3 to trap any of the
(44) Huang, J.; Stevens, E. D.; Nolan, S. P.; Petersen, J. L. J. Am. Chem. Soc.
1999, 121, 2674-2678.
(45) Mol, J. C. Green Chem. 2002, 4, 5-13.
(46) The ROMP of COD was not carried out at 40 °C because the reaction is
too fast to be monitored by 1H NMR with some of these catalysts. Likewise,
the RCM of 4,4-dicarboethoxy-2-methyl-1,6-heptadiene was not carried
out at 25 °C because the reaction is too slow to be conveniently monitored
by 1H NMR.
(47) (a) Schramm, M. P.; Reddy, D. S.; Kozmin, S. A. Angew. Chem., Int. Ed.
2001, 40, 4274-4277. (b) Bielawski, C. W.; Grubbs, R. H. Angew. Chem.,
Int. Ed. 2000, 39, 2903-2906.
(48) Morgan, J. P.; Grubbs, R. H. Org. Lett. 2000, 2, 3153-3155.
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2553

A R T I C L E S
Trnka et al.
Table 2. Structural Comparison of 6a, (H2IMes)(PCy3)(Cl)2RudCHPh, and (IMes)(PCy3)(Cl)2RudCHPh (in cases where there is more than
one chemically equivalent bond length or angle, the values have been averaged)
bond distances (Å)
and angles (deg)
(H IMes)(IMes)(Cl)2RudCHPh
(H IMes)(PCy3)(Cl)2RudCHPh
(IMes)(PCy3)(Cl)2RudCHPh
2
2
(6a, this work)
(ref 43)
(ref 44)
Ru-CN2 (IMes)
Ru-CN2 (H2IMes)
Ru-Cl
2.093(3)a
2.125(3)a
2.381(1)
1.819(3)
1.472(4)
1.421(5)a
1.382(5)a
1.364(3)a
1.359(3)a
1.435(3)a
1.434(3)a
166.11(3)
164.9(1)
136.1(2)
104.7(2)a
104.3(2)a
2.07(1)
2.085(2)
2.395(1)
1.835(2)
1.470(3)
1.515(3)
2.388(3)
1.84(1)
1.40(2)
RudC
RuC-Ph
CH2-CH2 backbone
CHdCH backbone
C-N (IMes)
1.30(1)
1.36(1)
C-N (H2IMes)
N-Mes (IMes)
N-Mes (H2IMes)
Cl-Ru-Cl
N2C-Ru-L
RudC-Ph
1.348(2)
1.46(1)
1.436(2)
167.71(2)
163.73(6)
140.0(2)
168.6(1)
163.2(3)
141(1)
N-C-N (IMes)
N-C-N (H2IMes)
101.0(8)
107.3(2)
a These bond lengths and angles are compromised because of disorder between the H2IMes and IMes ligands.
provides a small amount of the 14-electron species [(IPri)(Cl)2-
RudCHPh] that carries out catalysis. Interestingly, Herrmann
and co-workers also have reported that the reaction between
(PCy3)2(Cl)2RudCHPh and (ICy)2(Cl)2RudCHPh (ICy ) 1,3-
dicyclohexyl-imidazoline-2-ylidene) provides (ICy)(PCy3)(Cl)2-
RudCHPh in 15% yield after 12 h, which they attribute to a
bimolecular NHC transfer mechanism.4m Thus, although one
of the most widely cited features of NHC ligands is their strong
bonding to metal centers,6 there is a growing list of examples
that exhibit facile NHC dissociation and NHC transfer.8d,49 We
caution that predictions about the lability of NHC ligands in
new organometallic complexes should be made with care.
Table 3. krel Values for Various Ruthenium Catalysts in
Representative RCM and ROMP Reactions; Kinetics Measured by
1H NMR Spectroscopy
a
b
catalyst
k
rel for RCM
krel for ROMP
(PPh3)2(Cl)2RudCHPh
0
0
0.8
1
0
3
8
27
66
(PCy3)2(Cl)2RudCH-CHdCMe2
(PCy3)2(Cl)2RudCHPh
0.8
1
(H2IMes)2(Cl)2RudCHPh (6b)
(Cl2IMes)(PCy3)(Cl)2RudCHPhd
(IMes)(PCy3)(Cl)2RudCHPh
(H2IMes)(PCy3)(Cl)2RudCHPh (2)
(PPh3)2(Cl)2RudCHPh + 1 equiv
of Ph3Tri(H)(OMe)
c
19
53
138
c
a RCM conditions: 5 mM catalyst and 100 mM 4,4-dicarboethoxy-2-
methyl-1,6-heptadiene in C6D6 at 40 °C. b ROMP conditions: 5 mM catalyst
and 1500 mM 1,5-cyclooctadiene in CD2Cl2 at 25 °C. c The reaction did
not reach completion under these conditions. d Cl2IMes ) 1,3-dimesityl-
4,5-dichloro-imidazoline-2-ylidene; see ref 4e.
Conclusions
Our primary aim has been to demonstrate that NHC adducts
can be used to prepare ruthenium alkylidene complexes with
NHC ligands. We have presented several examples of this
methodology, including three routes to the synthetically impor-
tant olefin metathesis catalyst (H2IMes)(PCy3)(Cl)2RudCHPh
(2). Several properties of NHC adducts make them highly
desirable reagents: (i) they are easy to synthesize and use in
either isolated form, such as Ph3Tri(H)(OMe) and H2IMes(H)-
(CCl3), or when generated in situ, as in the case of H2IMes-
(H)(OBut), (ii) they are air-stable and thus easier to handle than
their free carbene counterparts, and (iii) the latent carbene is
readily released in solution. Unlike the introductory example
in Scheme 1, there is no evidence for dimer formation with the
Ph3Tri or H2IMes ligands, and therefore the adducts of these
NHCs provide direct access to metal-NHC complexes.
14-electron intermediate [(H2IMes)(Cl)2RudCHR] as the 16-
electron phosphine complex (H2IMes)(PCy3)(Cl)2RudCHPh (2).
As illustrated in eq 6, significant quantities of 2 form during
the course of the reaction: after 36 h, complex 2 is present in
a 6.3:1.0 ratio as compared to 6b. The reaction of 6b with 1
equiv of (PCy3)2(Cl)2RudCHPh also generates 2, but this
reaction is not as clean. This evidence strongly suggests that
6b is metathesis active because H2IMes dissociation at elevated
temperatures provides the necessary initiation pathway. The
resulting 14-electron species [(H2IMes)(Cl)2RudCHR] is ex-
traordinarily active, and a very small amount is capable of
producing the observed catalysis.41
For these reasons, NHC adducts have broad potential ap-
plications in the synthesis of countless other metal-NHC
complexes. This methodology has been used recently by
Herrmann and co-workers in the synthesis of (COD)M(Cl)(L)
(L ) NHC; M ) Rh, Ir) complexes,50 by Blechert and
co-workers to prepare polymer-supported (H2IMes)(PCy3)(Cl)2-
RudCHPh,51 and by Fu¨rstner and co-workers to prepare various
It is reasonable to expect that NHC dissociation occurs in
other (NHC)2(Cl)2RudCHPh complexes, such as those reported
by Herrmann and co-workers in 1998.4q The (IPri)2(Cl)2Rud
CHPh derivative (IPri ) 1,3-diisopropyl-imidazoline-2-ylidene),
for example, exhibits ROMP activity that is comparable to that
of (PCy3)2(Cl)2RudCHPh. This activity may be attributed to
dissociation of one IPri ligand from (IPri)2(Cl)2RudCHPh, which
(49) (a) Simms, R. W.; Drewitt, M. J.; Baird, M. C. Organometallics 2002, 21,
2958-2963. (b) Titcomb, L. R.; Caddick, S.; Cloke, F. G. N.; Wilson, D.
J.; McKerrecher, D. Chem. Commun. 2001, 1388-1389.
(50) Denk, K.; Sirsch, P.; Herrmann, W. A. J. Organomet. Chem. 2002, 649,
219-224.
(51) Schu¨rer, S. C.; Gessler, S.; Buschmann, N.; Blechert, S. Angew. Chem.,
Int. Ed. 2000, 39, 3898-3901.
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2554 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
ruthenium alkylidene complexes.4e In addition, we have found
that the reactions of Ph3Tri(H)(OMe) or H2IMes(H)(OBut) with
molybdenum hexacarbonyl afford the pentacarbonyl derivatives
(CO)5Mo(Ph3Tri) and (CO)5Mo(H2IMes), respectively.52
En route, we have described some interesting organometallic
reactions encountered during the development of this chemistry.
These results highlight the diverse reactivity patterns of
ruthenium carbene complexes and, in the case of NHC dis-
sociation, provide leading evidence for how bis(NHC) olefin
metathesis catalysts enter the catalytic cycle. By testing a variety
of catalyst derivatives in representative olefin metathesis reac-
tions, we also have found that small changes in catalyst
architecture have a large impact on the stability and activity of
these complexes, and current studies are directed toward un-
derstanding the subtle steric and electronic factors that determine
these properties.
brown semisolid. This material was triturated in pentane to yield 0.18
g of the desired product as a white powder (100%). The characterization
data of this compound are similar to those of [Ph3Tri(H)][ClO4].17
One-Pot Synthesis of Ph3Tri(H)(OMe). A suspension of N-
phenylbenzamide phenylhydrazone (0.20 g, 0.7 mmol) and ammonium
tetrafluoroborate (0.073 g, 0.7 mmol) in triethylorthoformate (1.5 mL,
excess) was refluxed for 4 h. The reaction mixture was cooled to room
temperature and pumped down under vacuum to an orange solid.
Methanol (4 mL) was added to the flask, followed by a solution of
sodium methoxide (0.045 g, 0.84 mmol) in methanol (3 mL). This
solution was stirred at room temperature for 15 min. The reaction
mixture was pumped down under vacuum to a reddish-brown solid,
which was extracted with pentane (3 × 10 mL). The combined extracts
were stripped of solvent, and the resulting brown material was
recrystallized from methanol to provide 0.095 g of the desired product
as a yellowish solid (43%).
Synthesis and Characterization of (Ph3Tri)(PCy3)(Cl)2RudCHR
(1a, R ) Ph). A Schlenk flask was charged with 0.500 g (0.608 mmol)
of (PCy3)2(Cl)2RudCHPh, 0.195 g (0.592 mmol) of Ph3Tri(H)(OMe),
and 17 mL of toluene. The reaction was stirred first at room temperature
for 20 min and then at 80 °C for 10-20 min. The resulting brown
solution was pumped down under vacuum. Next 100 mL pentane was
added to the residue and gently warmed to dissolve most of the material.
Upon being cooled to -78 °C, a tan-colored precipitate formed. The
supernatant was filtered off by cannula, and the solid was dried under
vacuum to yield 0.293 g of the desired product as a brown solid (59%).
1H NMR (CD2Cl2, 499.9 MHz): δ 19.56 [d, 3JHP ) 8, RudCH, major
isomer (∼60%)], 19.37 [d, 3JHP ) 6.5, RudCH, minor isomer (∼40%)],
8.21 [d, J ) 7.5, CHaryl], 7.85 [br d, J ) 6.5, CHaryl], 7.71 [t, J ) 7.5,
CHaryl], 7.58 [m, CHaryl], 7.44 [t, J ) 7.5, CHaryl], 7.40 [m, CHaryl],
7.31 [m, CHaryl], 7.21 [t, J ) 8, CHaryl], 7.11-6.99 [m, CHaryl], 6.88
[br, CHaryl], 2.11 [q, J ) 11.5, PCy3], 1.59 [br m, PCy3], 1.31-1.01
[m, PCy3]. 13C{1H} NMR (CD2Cl2, 125.7 MHz): δ 308.24 [m,
Experimental Section
General Considerations. All manipulations involving organome-
tallic complexes were performed using a combination of glovebox, high
vacuum, and Schlenk techniques under a nitrogen atmosphere, unless
otherwise specified. Solvents were dried and degassed by standard
procedures. NMR spectra were measured on Varian Inova 500, Varian
Mercury 300, and JEOL JNM-GX400 spectrometers. 1H NMR chemical
shifts are reported in ppm relative to SiMe4 (δ ) 0) and referenced
internally with respect to the protio solvent impurity. 13C NMR spectra
were referenced internally with respect to the solvent resonance. 31P
NMR spectra were referenced using H3PO4 (δ ) 0) as an external
standard. Coupling constants are in hertz. IR spectra were recorded on
a Perkin-Elmer Paragon 1000 spectrophotometer; the data are reported
in reciprocal centimeters. Elemental analyses were measured by
Midwest Microlab, Indianapolis, IN. Mass spectral analysis was
performed at the Southern California Mass Spectrometry Facility
(University of California at Riverside). Silica gel used for the
purification of organometallic complexes was obtained from TSI
Scientific, Cambridge, MA (60 Å, pH 6.5-7.0). N-Phenylbenzamide
phenylhydrazone, [Ph3Tri(H)][ClO4], and Ph3Tri(H)(OMe) were pre-
pared by the methods of Enders and co-workers.17 Although no
problems were encountered during the preparation and use of the
perchlorate salt, suitable care and precautions should be taken when
handling this potentially hazardous material.53 (H2IMes)(py)2(Cl)2-
RudCHPh,4c IMes free carbene,23 and 4,4-dicarboethoxy-2-methyl-1,6-
heptadiene54 were synthesized according to literature procedures.
(PCy3)2(Cl)2RudCHPh, (PCy3)2(Cl)2RudCHCHdCMe2, and all other
chemicals were obtained from commercial sources.
Synthesis of [Ph3Tri(H)][BF4]. A suspension of N-phenylbenzamide
phenylhydrazone (0.38 g, 1.3 mmol) and ammonium tetrafluoroborate
(0.14 g, 1.3 mmol) in triethylorthoformate (1.2 mL, excess) was refluxed
for 4 h. The reaction mixture was cooled to room temperature, and the
yellowish-brown product was isolated by filtration. This crude material
was recrystallized from boiling ethanol to yield 0.35 g of the product
as a dark brown solid (72%). The characterization data of this compound
are similar to those of [Ph3Tri(H)][ClO4].17
Synthesis of [Ph3Tri(H)][OTs]. A suspension of N-phenylbenzamide
phenylhydrazone (0.10 g, 0.35 mmol), p-toluenesulfonic acid mono-
hydrate (0.08 g, 0.42 mmol), triethylorthoformate (0.3 mL, 2.0 mmol),
and benzene (7 mL) was refluxed under azeotropic distillation condi-
tions with a Dean-Stark apparatus. After 5 h, the reaction mixture
was cooled to room temperature and concentrated under vacuum to a
2
RudC], 304.91 [m, RudC], 192.79 [d, JCP ) 89, Ru-CN2], 191.22
[d, 2JCP ) 92, Ru-CN2], 154.88 [d, 3JCP ) 3, ipso-CHPh], 154.02 [d,
3JCP ) 4, ipso-CHPh], 151.23 [s, Ph3Tri], 151.09 [s, Ph3Tri], 141.84
[s, Ph3Tri], 140.31 [s, Ph3Tri], 136.83 [s, Ph3Tri], 135.95 [s, Ph3Tri],
131.18 [br], 130.88 [s], 130.77 [br], 130.70 [s], 130.59 [s], 130.56 [s],
130.36 [br], 130.16 [br], 130.13 [s], 130.11 [s], 129.75 [s], 129.68 [s],
129.61 [s], 129.49 [s], 129.02 [s], 128.99 [s], 128.97 [s], 128.77 [s],
128.65 [s], 128.62 [s], 128.57 [s], 128.51 [s], 126.81 [s], 126.78 [s],
125.14 [s], 125.77 [s], 33.17 [d, JCP ) 16, PCy3], 33.08 [d, JCP ) 16,
PCy3], 28.23 [d, JCP ) 10, PCy3], 28.18 [d, JCP ) 10, PCy3], 26.81 [s,
PCy3], 26.78 [s, PCy3]. 31P{1H} NMR (C6D6, 161.9 MHz): δ 24.14
[s, minor isomer], 23.04 [s, major isomer]. HRMS analysis (FAB)
m/z: calcd [M+] 839.2476, found 839.2450. Anal. Calcd for C45H54N3-
Cl2PRu: C, 64.35; H, 6.48; N, 5.00. Found: C, 64.64; H, 6.31; N,
5.04.
(Ph3Tri)(PCy3)(Cl)2RudCHR (1b, R ) CHdCMe2). This was
synthesized analogously to 1a but starting with (PCy3)2(Cl)2Rud
1
3
CHCHdCMe2. H NMR (CD2Cl2, 499.9 MHz): δ 19.56 [dd, JHP
)
)
3
3
5.5, JHH ) 11, RudCH, major isomer (∼60%)], 19.37 [dd, JHP
2.5, 2JHH ) 11, RudCH, minor isomer (∼40%)], 8.63 [d, J ) 8, CHaryl],
3
8.00 [d, J ) 8, CHaryl], 7.97 [d, J ) 8, CHaryl], 7.85 [d, JHH ) 11,
3
RuCH-CH, (major isomer)], 7.71 [d, JHH ) 11, RuCH-CH, minor
isomer], 7.35 [t, J ) 7.5, CHaryl], 7.29 [br d, J ) 7.5, CHaryl], 7.13 [m,
CHaryl], 7.00 [m, CHaryl], 6.85-6.66 [m, CHaryl], 2.44 [q, J ) 11.5,
PCy3], 1.89 [m, PCy3], 1.70 [m, PCy3], 1.63 [m, PCy3], 1.42 [m, PCy3],
1.23 [m, PCy3], 1.01 [s, Me2vinyl, major isomer], 0.98 [s, Me2vinyl,
minor isomer], 0.80 [s, Me2vinyl, major isomer], 0.78 [s, Me2vinyl,
minor isomer]. 13C{1H} NMR (CD2Cl2, 125.7 MHz): δ 297.72 [m,
2
RudC], 294.33 [m, RudC], 194.90 [d, JCP ) 81, Ru-CN2, minor
(52) Trnka, T. M.; Grubbs, R. H. 1999, unpublished work.
2
isomer], 193.51 [d, JCP ) 85, Ru-CN2, major isomer], 155.09 [d,
(53) (a) Wolsey, W. C. J. Chem. Educ. 1973, 50, A335-A337. (b) Muse, L. A.
J. Chem. Educ. 1972, 49, A463-A466. (c) Everett, K.; Graf, F. A. In CRC
Handbook of Laboratory Safety, 2nd ed.; Steere, N. V., Ed.; CRC Press:
Boca Raton, FL, 1971; pp 265-276.
3
3JCP ) 2, RuCHCH, minor isomer], 153.83 [d, JCP ) 3, RuCHCH,
major isomer], 146.89, 146.80, 141.09, 140.91, 136.98, 136.28, 135.69,
134.71, 133.11, 132.17, 132.03, 131.39, 130.90, 130.85, 130.78, 130.74,
(54) Kirkland, T. A.; Grubbs, R. H. J. Org. Chem. 1997, 62, 7310-7318.
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2555

A R T I C L E S
Trnka et al.
130.70, 130.37, 130.23, 130.07, 130.01, 129.89, 129.84, 129.71, 129.64,
129.58, 129.39, 128.98, 128.85, 127.46, 126.70, 126.58 [br s], 126.14,
125.66, 122.72, 121.35 [br s], 32.92 [d, JCP ) 17, PCy3], 32.81 [d, JCP
) 16, PCy3], 29.29 [s, PCy3], 29.27 [s, PCy3], 28.25 [d, JCP ) 10.5,
PCy3], 27.82 [s, CH3, major isomer], 27.80 [s, CH3, minor isomer],
26.88 [s, PCy3], 20.96 [s, CH3, minor isomer], 20.90 [s, CH3, major
isomer]. 31P{1H} NMR (C6D6, 161.9 MHz): δ 28.11 [s, minor isomer],
26.43 [s, major isomer]. HRMS analysis (FAB) m/z: calcd [M+]
817.2632, found 817.2645.
with methanol (4 × 50 mL) and pentane (3 × 25 mL), and then dry it
under high vacuum to obtain (H2IMes)(PCy3)Cl2RudCHPh in 45%
yield (0.05 g).
Method 2. Charge a 750 mL Schlenk flask with dry [H2IMes(H)]-
[Cl] (6.60 g, 19.2 mmol), KOBut (2.46 g, 21.9 mmol), (PCy3)2(Cl)2-
RudCHPh (9.06 g, 11.0 mmol), and anhydrous hexanes (100 mL,
Aldrich SureSeal bottle). Attach the flask to a vacuum line, and degas
the solution by pulling vacuum for a few minutes. Leave the flask under
vacuum, wire down the septum, and heat the reaction at 60 °C for 24
h with very vigorous stirring. The suspension changes color from purple
to orange-brown during the reaction time. Allow the reaction to cool
to room temperature, open the flask to air, and add 1:1 2-propanol:
water (250 mL). Stir this mixture rapidly in air for 30 min. Collect the
peach-pink solid on a medium porosity frit, and wash it thoroughly
with the 2-propanol:water (3 × 100 mL) and with hexane (3 × 100
mL). Dry the solid under vacuum overnight to obtain (H2IMes)-
(PCy3)(Cl)2RudCHPh in 75% yield (6.9 g). Anal. Calcd for
C46H65N2Cl2PRu: C, 64.92; H, 7.94; N, 3.29. Found: C, 64.82; H,
7.74; N, 3.31.
Formation of (Ph3Tri)(PPh3)(Cl)2RudCHPh (1c). A screw cap
NMR tube was charged with 0.010 g (0.013 mmol) of (PPh3)2(Cl)2-
RudCHPh, 0.004 g (0.012 mmol) of Ph3Tri(H)(OMe), and 0.6 mL of
C6D6. The solution remained green in color throughout the reaction.
1
1H and 31P NMR spectra were recorded after 7 h at 40 °C. H NMR
3
(299.9 MHz): δ 19.37 [d, JHP ) 16, RudCH, major isomer], 19.28
3
[d, JHP ) 12, RudCH, minor isomer], 8.68 [d, J ) 7.5], 8.05 [m],
7.88 [d, J ) 7.5], 7.76-7.58 [several m], 7.39 [m], 7.20-6.68 [several
m], 6.43 [m]. 31P{1H} NMR (161.9 MHz): δ 31.26 [s], 30.90 [s].
Synthesis of H2IMes(H)(CCl3) from [H2IMes(H)][Cl]. First 8.2
mL of dry, degassed toluene was added to a flame-dried, 50 mL round-
bottomed flask equipped with stir bar and reflux condenser. A large
excess of powdered potassium hydroxide (>10 mmol, ground in a
mortar) was added to the flask, and the resulting suspension was stirred
rapidly. Chloroform (77 µL, 0.96 mmol) was then added to the
suspension by microsyringe. After 10 min at room temperature, 0.10 g
(0.29 mmol) of [H2IMes(H)][Cl] was added, and the reaction mixture
was heated at 60 °C for 75 min. The mixture was allowed to cool to
room temperature and filtered. The supernatant was concentrated under
vacuum to a yellowish-white solid. This crude product was purified
first through a silica gel plug (9:1 hexanes:ethyl acetate) and then by
recrystallization from boiling hexanes to yield 0.110 g of H2IMes(H)-
(CCl3) as a white solid (88%). 1H and 13C NMR match the data reported
in ref 40.
Synthesis and Characterization of H2IMes(H)(OBut): Method
1. A flame-dried Schlenk flask was charged with a solution of
[H2IMes(H)][BF4] (0.100 g, 0.30 mmol) in dry THF (3 mL). Next 0.028
g (0.25 mmol) of solid KOBut was added to this solution. The initially
colorless reaction mixture was stirred under a nitrogen atmosphere for
10 min, during which time a persistent yellowish color developed. The
solution was pumped down under vacuum to a yellowish solid, which
was washed with dry diethyl ether (5 mL) to yield 0.050 g of the desired
product as a colorless semisolid (50%). This material decomposes by
extrusion of HOBut at room temperature.
Method 3. A flame-dried, 50 mL Schlenk flask was charged with
0.165 g of (PCy3)2(Cl)2RudCHPh (0.20 mmol), 0.188 g of H2IMes-
(H)(CCl3) (0.44 mmol), and 5 mL of toluene. The reaction mixture
was heated at 60 °C for 90 min under a nitrogen atmosphere. After the
reaction cooled to room temperature, the solvent was removed under
vacuum. The resulting brownish-pink semisolid was washed with
methanol (2 × 5 mL) and pentane (3 × 10 mL), and was then dried
under vacuum for 12 h to provide 0.140 g of 2 as a reddish solid (84%).
Alternative Purification. (H2IMes)(PCy3)(Cl)2RudCHPh can be
further purified by column chromatography on TSI-brand silica gel with
gradient elution (7:1 hexanes:diethyl ether to 100% diethyl ether).
Formation of (PCy3)(L)(CO)(Cl)(H)Ru (3). In a glovebox, a vial
was charged with 0.020 g of (L)(PCy3)(Cl)2RudCHPh, ∼2 mL of
MeOH, and 5 drops of CH2Cl2. This mixture was stirred at room
temperature for 12 h. The yellow-orange supernatant was then decanted
into a Schlenk flask and pumped down under vacuum. In all cases, 1H
and 31P NMR showed partial conversion to the (PCy3)(L)(CO)(Cl)-
(H)Ru product, unreacted ruthenium benzylidene starting material, and
other unidentified side products. (H2IMes)(PCy3)(CO)(Cl)(H)Ru (3a),
1
2
characteristic H NMR (C6D6, 299.9 MHz): δ -24.90 [d, JHP ) 21,
Ru-H], 6.86 [s, m-H on Mes], 6.81 [s, m-H on Mes], 2.67 [s, Me],
2.13 [s, Me]. 31P{1H} NMR (C6D6, 121.4 MHz): δ 47.12 [s]. (PCy3)2-
(CO)(Cl)(H)Ru (3b) and (IMes)(PCy3)(CO)(Cl)(H)Ru (3c): 1H and 31
P
NMR data match those reported in refs 35a and 55.
Method 2. A J. Young NMR tube was charged with 0.040 g (0.101
mmol) of [H2IMes(H)][BF4], 0.011 g (0.101 mmol) of KOBut, and 1
mL of THF-d8. 1H and 13C NMR were recorded after 6 h at room
temperature. 1H NMR (399.9 MHz): δ 6.82 [s, 2H, m-CHMes], 6.81 [s,
2H, m-CHMes], 5.61 [s, 1H, CH], 3.74 [m, 2H, CH2CH2], 3.27 [m, 2H,
CH2CH2], 2.46 [s, 6H, CH3 of Mes], 2.34 [s, 6H, CH3 of Mes], 2.20
[s, 6H, CH3 of Mes], 1.11 [s, 9H, OBut]. 13C{1H} NMR (100.5 MHz):
δ 139.69, 138.76, 137.83, and 134.96 [o-CMes, ipso-CMes, and p-CMes],
129.19 [CHMes], 128.50 [CHMes], 95.40 [N2C], 70.81 [OCMe3], 48.58
[CH2CH2], 28.03 [CH3 on OBut], 20.06 [CH3 on Mes], 19.02 [CH3 on
Mes], 18.08 [CH3 on Mes]. This solution was also subjected to HRMS
analysis (EI) m/z: calcd for C25H36N2O [M+] 380.2828, found 380.2831.
Synthesis of (H2IMes)(PCy3)(Cl)2RudCHPh (2): Revised Method
1. The workup procedure described in ref 4n can be modified to produce
a cleaner product. Combine [H2IMes(H)][BF4] (0.90 g, 2.7 mmol),
KOBut (0.30 mg, 2.7 mmol), and THF (20 mL) in an oven-dried
Schlenk flask. Stir the resulting yellow suspension for 1 h, and then
add a solution of (PCy3)2(Cl)2RudCHPh (1.1 g, 1.3 mmol) in benzene
(20 mL). Heat the reaction mixture at 80 °C for 30 min. Remove the
volatiles under vacuum, and dry the solid thoroughly to ensure that all
of the THF is gone. Suspend the solid in benzene (25 mL), and filter
through dry Celite. Concentrate the resulting solution to ∼2 mL, and
precipitate the product with methanol (50 mL). Wash the pink solid
Characterization of (PCy3)(Cl)(CO)Ru[η2-(CH2-C6H2Me2)-
(N2C3H4)(C6H2Me3)] (4). H NMR (C6D6, 299.9 MHz): δ 7.02 [s,
1
1H, m-CHMes], 6.94 [s, 1H, m-CHMes], 6.83 [s, 1H, m-CHMes], 6.80 [s,
1H, m-CHMes], 3.87 [dt, J ) 5 and 9, 1H, NCH2CH2N], 3.44 [d, J )
9, RuCH2], 3.30 [d, J ) 11, RuCH2], 3.28 [m, 1H, NCH2CH2N], 3.04
[q, J ) 10, 1H, NCH2CH2N], 2.97 [dd, J ) 7 and 9, 1H, NCH2CH2N],
2.49 [s, 3H, CH3], 2.44 [s, 3H, CH3], 2.40-2.28 [br m, 3H, PCy3],
2.30 [s, 3H, CH3], 2.18 [s, 3H, CH3], 2.15 [s, 3H, CH3], 2.10-2.02 [br
m, 3H, PCy3], 1.84-1.50 [br m, 15H, PCy3], 1.40-1.16 [br m, 12H,
2
PCy3]. 13C{1H} NMR (CDCl3, 74.5 MHz): δ 220.3 [d, JCP ) 90,
2
RuCN2], 203.0 [d, JCP ) 15, CO], 144.0 [Caryl], 138.8 [Caryl], 137.9
[Caryl], 137.1 [Caryl], 136.9 [Caryl], 136.6 [Caryl], 134.4 [Caryl], 130.5 [Caryl],
130.3 [CHaryl], 129.5 [CHaryl], 129.2 [CHaryl], 125.9 [CHaryl], 52.6 [d,
4
1
4JCP ) 3, NCH2CH2N], 50.2 [d, JCP ) 3, NCH2CH2N], 34.2 [d, JCP
) 15, PCy3], 31.0 [d, JCP ) 2, PCy3], 29.9 [PCy3], 28.0 [d, JCP ) 3,
PCy3], 27.9 [PCy3], 26.7 [PCy3], 21.3 [CH3], 21.0 [CH3], 20.5 [CH3],
19.8 [CH3], 18.9 [CH3], 7.4 [d, 2JCP ) 4, RuCH2]. 31P{1H} NMR (C6D6,
121.4 MHz): δ 33.31 [s]. IR (KBr pellet): 2924 [s], 2849 [s], 2362
[w], 2346 [w], 2016 [w], 1899 [s, νCO], 1855 [w], 1617 [w], 1576 [w],
1472 [s], 1446 [s], 1424 [s], 1387 [m], 1380 [m], 1321 [m], 1298 [m],
(55) Moers, F. G.; Ten Hoedt, R. W. M.; Langhout, J. P. J. Inorg. Nucl. Chem.
1974, 36, 2279-2282.
9
2556 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003

Synthesis of Ruthenium Alkylidene Complexes
A R T I C L E S
1264 [s], 1174 [m], 1106 [w]. Anal. Calcd for C40H58N2ClPORu: C,
64.02; H, 7.79; N, 3.73. Found: C, 63.96; H, 7.87; N, 3.74. Crystals
for X-ray analysis were obtained by slow evaporation of a dichlo-
romethane solution.
1417 [m], 1379 [w], 1266 [s], 1239 [m], 1176 [w], 1035 [w], 896
[w], 849 [w], 738 [w], 686 [w], 642 [w], 577 [w]. Anal. Calcd for
C49H58N4Cl2Ru: C, 67.26; H, 6.68; N, 6.40. Found: C, 67.24; H, 6.71;
N, 6.21.
Reaction of (PCy3)2(Cl)2RudCHCHdCMe2 with KOBut. A screw
cap NMR tube was charged with 0.010 g (0.012 mmol) of (PCy3)2(Cl)2-
RudCHCHdCMe2, 0.001 g (0.011 mmol) of KOBut, and 0.6 mL of
C6D6. An immediate color change from purple to deep red occurred.
1H and 31P NMR spectra were recorded after 15 min at room
Reaction of (H2IMes)2(Cl)2RudCHPh with PCy3. A screw cap
NMR tube was charged with 0.015 g of 6b, 0.015 g of PCy3, and 0.8
mL of C6D6. This solution was heated in an 80 °C oil bath and
1
periodically monitored by H and 31P NMR. The results are shown in
eq 6.
1
Reaction of 6b with (PCy3)2(Cl)2RudCHPh. A screw cap NMR
tube was charged with 0.008 g of 6b, 0.008 g of (PCy3)2(Cl)2Rud
CHPh, and 0.8 mL of C6D6. This solution was heated in a 70 °C oil
temperature. H NMR (299.9 MHz): δ 8.93 [d, JHH ) 13, Ru-CH],
6.27 [d, JHH ) 13, RuCHdCH], 4.75 [s, CdCH2], 4.58 [s, CdCH2],
2.58-1.17 [multiple peaks, CH3 and PCy3]. 31P{1H} NMR (121.4
MHz): δ 23.55 [s]. A second unidentified product, which contained a
CdCH2 group and a ruthenium-hydride ligand, was also present. Full
conversion to this product occurred upon addition of more KOBut. 1H
NMR (299.9 MHz): δ 5.25 [s, CdCH2], 5.00 [s, CdCH2], 2.58-1.17
[multiple peaks], -27.52 [br t, J ) 14, RuH]. 31P{1H} NMR (121.4
MHz): δ 48.64 [s].
1
bath and periodically monitored by H and 31P NMR. After 23 h, the
(PCy3)2(Cl)2RudCHPh:6b:2 ratio was 0.5:1.0:0.2; after 47 h, the ratio
was 0.0:1.0:0.8.
Reaction of (H2IMes)2(Cl)2RudCHPh with Ethylene. A J. Young
NMR tube was charged with ∼0.015 g of 6b and 0.8 mL of C6D6. The
headspace in the tube was replaced with 1 atm of ethylene. This solution
was heated in a 60 °C oil bath for 24 h. No reaction was observed by
1H or 31P NMR.
RCM Reactions. An NMR tube with septum cap was charged with
0.60 mL of a catalyst stock solution (5 mM in C6D6, 0.003 mmol of
catalyst per run) in the glovebox. The tube was equilibrated at 40 °C
in the NMR probe. Next 15 µL of 4,4-dicarboethoxy-2-methyl-1,6-
heptadiene (100 mM) was injected into the tube. The reaction was
monitored by measuring the decreasing 1H NMR signals of the starting
material over at least three half-lives. The data were fit to a first-order
exponential with Varian kinetics software.56
ROMP Reactions. An NMR tube with septum cap was charged
with 0.60 mL of a catalyst stock solution (5 mM in CD2Cl2, 0.003
mmol catalyst per run) in the glovebox. The tube was equilibrated at
25 °C in the NMR probe. Next 110 µL of COD (0.90 mmol, 1500
mM) was injected into the tube. The reaction was monitored by
measuring the increasing 1H NMR signals of the product over at least
three half-lives. The data were fit to a first-order exponential with Varian
kinetics software.56
Synthesis and Characterization of (PPri3)2(Cl)(CO)Ru-CHd
CHCMedCH2 (5). A Schlenk flask was charged with 0.150 g (0.260
mmol) of (PPri3)2(Cl)2(CO)RudCHCHdCMe2, 0.057 g (0.510 mmol)
of KOBut, and 15 mL of benzene. The reaction was stirred at room
temperature for 30 min, during which time it changed color from orange
to pink. The resulting suspension was filtered by cannula. The solvent
was lyophilized to yield 0.11 g of the desired product as a pale pink
1
powder (78%). H NMR (CD2Cl2, 399.8 MHz): δ 7.96 [d, JHH ) 16,
1H, Ru-CH], 5.80 [d, JHH ) 16, 1H, RuCHdCH], 4.30 [s, 1H,
CdCH2], 4.16 [s, 1H, CdCH2], 2.71 [m, 6H, CH of PPri3], 1.70 [s,
3H, CH3], 1.28 [m, 36H, CH3 of PPri3]. 13C{1H} NMR (CD2Cl2, 100.5
MHz): δ 199.84 [t, JCP ) 14, Ru-CO], 146.78 [t, JCP ) 9, Ru-C],
138.64 [s, RuCHdCH], 134.92 [s, CH-C(Me)dCH2], 101.02 [s,
CdCH2], 21.20 [vt, JCP ) 9, CH of PPri3], 16.49 [s, Me of PPri3], 16.21
[m, Me of PPri3], 15.85 [s, CH3]. 31P{1H} NMR (C6D6, 161.9 MHz):
δ 38.45 [s]. IR (CH2Cl2 thin film): 1549 [νCdC), 1910 [νCO]. Anal.
Calcd for C24H49ClOP2Ru: C, 52.21; H, 8.95. Found: C, 52.17; H,
8.88.
Crystal Structure Determination of 4 and 6a. Crystal, intensity
collection, and refinement details are presented in Table 1. Data were
collected on a Bruker SMART 1000 area detector running SMART.57
The diffractometer was equipped with a Crystal Logic CL24 low-
temperature device, and the data sets were collected at low temperature
(98 K) using graphite-monochromated Mo KR radiation with λ )
0.71073 Å. The crystals were mounted on glass fibers with Paratone-N
oil. Data were collected as ω-scans with the detector 5 cm (nominal)
distant at a θ of -28°. The data were processed with SAINT.57
SHELXTL57 was used to solve (Patterson method) and to refine both
structures using full-matrix least-squares. No absorption or decay
corrections were applied.
The asymmetric unit of compound 4 consists of one molecule of 4
and one-half of a dichloromethane molecule disordered about a center
of symmetry. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were placed at calculated positions with Uiso values
based on the Ueq of the attached atom.
There are two crystallographically independent molecules in the
asymmetric unit of 6a. All non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were refined isotropically. Unfortunately,
the H2IMes and IMes ligands are disordered with one another, in
approximately a 60:40 ratio in each molecule. Consequently, the refined
geometry is a mixture of the H2IMes and IMes ligands.
The graphics were prepared with the Diamond and SHELXTL
programs.57
Crystallographic data (excluding structure factors) for the structures
in this paper have been deposited with the Cambridge Crystallographic
Synthesis and Characterization of (H2IMes)2(Cl)2RudCHPh (6b).
A small ampule was charged with 0.175 g (0.270 mmol) of (H2IMes)-
(py)2(Cl)2RudCHPh, 0.173 g (0.406 mmol) of H2IMes(H)(CCl3), and
8 mL of benzene. The reaction mixture was heated at 80 °C for 20 h.
The solution was then concentrated to ∼1.5 mL and purified by column
chromatography in air (silica gel, 5:1 pentane/THF). The brown fraction
was stripped of solvent, and the resulting material was redissolved in
a minimum amount of benzene and lyophilized to yield 0.125 g (0.143
mmol) of the desired product as a fluffy, pale brown solid (53%).
Crystals for X-ray analysis were obtained by slow evaporation of a
1
dichloromethane solution. H NMR (CD2Cl2, 25 °C, 499.9 MHz): δ
18.95 [s, 1H, RudCH], 8.81 [d, J ) 8, 1H, Ph], 7.18 [tt, J ) 1 and 7,
1H, Ph], 6.94 [dt, J ) 1 and 7, 1H, Ph], 6.81 [br s, 4H, m-CHMes], 6.74
[dt, J ) 1 and 7, 1H, Ph], 6.55 [br s, 2H, m-CHMes], 5.97 [d, J ) 7.5,
1H, Ph], 5.58 [br s, 2H, m-CHMes], 3.56 [br s, 6H, CH2CH2], 3.42 [br
s, 2H, CH2CH2], 2.48 [br s, 6H, Me], 2.21 [br m, 18H, Me], 1.90 [br
1
s, 6H, Me], 1.82 [br s, 6H, Me]. H NMR (CD2Cl2, -15 °C, 499.9
MHz): δ 18.81 [s, 1H, RudCH], 8.74 [d, J ) 8, 1H, Ph], 7.16 [tt, J
) 1 and 7, 1H, Ph], 6.93 [dt, J ) 1 and 7, 1H, Ph], 6.80 [s, 4H,
m-CHMes], 6.73 [dt, J ) 1 and 7, 1H, Ph], 6.52 [s, 2H, m-CHMes],
5.91 [d, J ) 8, 1H, Ph], 5.52 [s, 2H, m-CHMes], 3.55 [m, 6H,
CH2CH2], 3.39 [m, 2H, CH2CH2], 2.46 [s, 6H, Me], 2.21 [s, 6H,
Me], 2.17 [s, 6H, Me], 2.11 [s, 6H, Me], 1.87 [s, 6H, Me], 1.78 [s, 6H,
Me]. 13C{1H} NMR (CD2Cl2, 125.7 MHz): δ 296.32 and 296.04
[RudC], 221.19 [RuCN2], 150.79 and 150.77 [ipso-CPh], 138.26
[br], 137.60 [br], 137.19 [br], 136.41 [br], 136.40, 131.61 and 131.59,
130.49 [br], 129.77 and 129.75 [CHMes], 129.16 [br], 127.12 [CHMes],
126.79 [CHMes], 126.55 [CHMes], 53.56 [br, NCH2CH2N], 52.34 [br,
NCH2CH2N], 21.50 [br m, CH3], 19.29 [br m, CH3]. IR (KBr pellet):
2937 [w], 2914 [m], 2954 [w], 1609 [w], 1478 [m, νCN], 1441 [w],
(56) VNMR 6.1B Software; Varian Associates, Inc.
(57) (a) Bruker 1999 SMART, SAINT, and SHELXTL. Bruker AXS Inc.,
Madison, WI. (b) Diamond 2.1. 2000 Crystal Impact GbR, Bonn, Germany.
9
J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003 2557

A R T I C L E S
Trnka et al.
Data Centre as supplementary publication numbers 166803 (for 4) and
167135 (for 6a). These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12
Union Road, Cambridge CB2 1EZ, U.K.; fax: +44 1223 336033;
e-mail: deposit@ccdc.cam.ac.uk). Structure factors are available from
the authors by e-mail: xray@caltech.edu.
Henling (Caltech) for contributions to the crystallography and
Dr. Sharad P. Hajela (Materia) for helpful discussions.
Supporting Information Available: Crystal structure deter-
mination of (PCy3)2(Cl)(CO)(H)Ru (3b) and comparison with
other determinations, tables of crystallographic data for 4 and
6a, and synthetic details for (PPri3)2(Cl)2(CO)RudCHCHd
CMe2 and [H2IMes(H)][Cl] (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This research was supported by the U.S.
National Science Foundation and the National Institutes of
Health. T.M.T. acknowledges the U.S. Department of Defense
for a NDSEG graduate fellowship. We thank Lawrence M.
JA021146W
9
2558 J. AM. CHEM. SOC. VOL. 125, NO. 9, 2003