Synthesis and reactivity of a ruthenium(III) bis(anilide) dimer by oxidative addition of an N,N′-disubstituted hydrazine

Article abstract of DOI:10.1021/om0700462

The Ru^III bis(anilide) dimer [Cp*RuCl(μ-NHPh)] ₂ (1a) is formed upon reaction of (Cp*RuCl)₄ with 1,2-diphenylhydrazine in benzene. An X-ray crystal structure shows a centrosymmetric (C_i) dimer with a planar Ru₂N₂ core. Reaction of (Cp*RuCl)₄ with a mixture of PhNHNHPh and TolNHNHTol gives only the homodimers la and [Cp*RuCl(μ-NHTol)] ₂ (Toi =p-tolyl). The lack of crossover indicates that cleavage of the hydrazine N - N bond is an intramolecular process. In polar solvents such as acetonitrile, the d dimer la isomerizes to the C_2i, isomer 1b, in which the anilido substituents are cis across the Ru₂N₂ core. Both isomers appear to be kinetic products of the synthesis, but 1b isomerizes to la in the benzene solvent. In the presence of la, 1,2-diphenylhydrazine disproportionates into azobenzene and aniline, and labeling studies show that this occurs without participation of the anilido ligands of la. Complex la shows slow exchange of the anilide ligands with toluidine (H₂NTol) by NMR spectroscopy and is unreactive toward methanol, triethylphosphine, styrene, and phenylacetylene. The addition of silver triflate and phenylacetylene to la leads to a new species, assigned as the acetylene complex [{Cp*Ru(μ-NHPh)}₂(μ-n ²:n²-PhCCH)](OTf)₂ (6a).

Full text of DOI:10.1021/om0700462

Organometallics 2007, 26, 3297-3305
3297
Synthesis and Reactivity of a Ruthenium(III) Bis(anilide) Dimer by
Oxidative Addition of an N,N′-Disubstituted Hydrazine
Jessica M. Hoover, Antonio DiPasquale,† James M. Mayer,* and Forrest E. Michael*
Department of Chemistry, Campus Box 351700, UniVersity of Washington,
Seattle, Washington 98195-1700
ReceiVed January 17, 2007
The RuIII bis(anilide) dimer [Cp*RuCl(µ-NHPh)]2 (1a) is formed upon reaction of (Cp*RuCl)4 with
1,2-diphenylhydrazine in benzene. An X-ray crystal structure shows a centrosymmetric (Ci) dimer with
a planar Ru2N2 core. Reaction of (Cp*RuCl)4 with a mixture of PhNHNHPh and TolNHNHTol gives
only the homodimers 1a and [Cp*RuCl(µ-NHTol)]2 (Tol ) p-tolyl). The lack of crossover indicates that
cleavage of the hydrazine N-N bond is an intramolecular process. In polar solvents such as acetonitrile,
the Ci dimer 1a isomerizes to the C2V isomer 1b, in which the anilido substituents are cis across the
Ru2N2 core. Both isomers appear to be kinetic products of the synthesis, but 1b isomerizes to 1a in the
benzene solvent. In the presence of 1a, 1,2-diphenylhydrazine disproportionates into azobenzene and
aniline, and labeling studies show that this occurs without participation of the anilido ligands of 1a.
Complex 1a shows slow exchange of the anilide ligands with toluidine (H2NTol) by NMR spectroscopy
and is unreactive toward methanol, triethylphosphine, styrene, and phenylacetylene. The addition of silver
triflate and phenylacetylene to 1a leads to a new species, assigned as the acetylene complex [{Cp*Ru-
(µ-NHPh)}2(µ-η2:η2-PhCtCH)](OTf)2 (6a).
addition of an amine N-H bond to an olefin gives a substituted
amine, without a change in the oxidation state of the substrate.8
Oxidative amination, with a stoichiometric oxidant, can yield
enamines, imines,9 or nitrogen heterocycles.10
Diamination reactions of alkenes and alkynes are also
oxidative processes.11 Early reports of vicinal diamination
reactions involve a stoichiometric transition-metal promoter,
such as the palladium-promoted process described by Ba¨ckvall12
and the stoichiometric addition of two tBuNH groups to alkenes
by osmium,13 among others.14 Recently, palladium-catalyzed
diamination reactions with sacrificial oxidants have been
Introduction
The development of new C-N bond forming reactions has
attracted much attention. Most interest lies in the catalytic
hydroamination and diamination of unsaturated hydrocarbons,
since these methods could provide efficient and atom-economic
routes to a variety of amines.1 The hydroamination of alkynes,
allenes, and alkenes catalyzed by early-transition-metal systems
have been studied in detail.2 Late metals are also known to
catalyze intra-3 and intermolecular4 hydroamination reactions,
including rhodium,5 iridium,6 and ruthenium complexes.7 The
* To whom correspondence should be addressed. E-mail:
mayer@chem.washington.edu (J.M.M.); michael@chem.washington.edu
(F.E.M.).
(5) Burling, S.; Field, L. D.; Messerle, B. A. Organometallics 2000, 19,
87-90. Coulson, D. R. Tetrahedron Lett. 1971, 12, 429-430.
(6) Casalnuovo, A. L.; Calabrese, J. C.; Milstein, D. J. Am. Chem. Soc.
1988, 110, 6738-6744.
† University of Washington X-ray Crystallography facility.
(1) Beller, M.; Breindl, C.; Eichberger, M.; Hartung, C. G.; Seayad, J.;
Thiel, O. R.; Tillack, A.; Trauthwein, H. Synlett 2002, 1579-1594.
(2) (a) Haak, E.; Bytschkov, I.; Doye, S. Angew. Chem., Int. Ed. 1999,
38, 3389-3391. (b) Pohlki, F.; Doye, S. Angew. Chem., Int. Ed. 2001, 40,
2305-2308. (c) Straub, B. F.; Bergman, R. G. Angew. Chem., Int. Ed. 2001,
40, 4632-4635. (d) Johnson, J. S.; Bergman, R. G. J. Am. Chem. Soc.
2001, 123, 2923-2924. (e) Cao, C.; Ciszewski, J. Y.; Odom, A. L.
Organometallics 2001, 20, 5011-5013. (f) Shi, Y.; Ciszewski, J. T.; Odom,
A. L. Organometallics 2001, 20, 3967-3969. (g) Shi, Y.; Hall, C.;
Ciszewski, J. T.; Cao, C.; Odom, A. L. Chem. Commun. 2003, 586-587.
(h) Thomson, R. K.; Bexrud, J. A.; Schafer, L. L Organometallics 2006,
25, 4069-4071. (i) Bytschkov, I.; Doye, S. Eur. J. Org. Chem. 2003, 68,
935-946. (j) Ackermann, L.; Bergman, R. G.; Loy, R. N. J. Am. Chem.
Soc. 2003, 125, 11956-11963.
(3) (a) Bajracharya, G. B.; Huo, Z.; Yamamoto, Y. J. Org. Chem. 2005,
70, 4883-4886. (b) Beccalli, E.; Broggini, G.; Martinelli, M.; Paladino,
G. Synlett 2006, 1, 73-76. (c) Siriwardana, A. I.; Kamada, M.; Nakamura,
I.; Yamamoto, Y. J. Org. Chem. 2005, 70, 5932-5937. (d) Krogstad, D.
A.; Cho, J.; DeBoer, A. J.; Klitzke, J. A.; Sanow, W. R.; Williams, H. A.;
Halfen, J. A. Inorg. Chim. Acta 2006, 359, 136-148. (e) Michael, F. E.;
Cochran, B. M. J. Am. Chem. Soc. 2006, 128, 4246-4247. (f) Mu¨ller, T.
E.; Pleier, A.-K. J. Chem. Soc., Dalton Trans. 1999, 583-587. (g) Campi,
E. M.; Jackson, W. R. J. Organomet. Chem. 1996, 523, 205-209.
(4) (a) Li, K.; Horton, P. N.; Hursthouse, M. B.; Hii, K. K. J. Organomet.
Chem. 2003, 665, 250-257. (b) Karshtedt, D.; Bell, A. T.; Tilley, T. D. J.
Am. Chem. Soc. 2005, 127, 12640-12646. (c) Kadota, I.; Shibuya, A.;
Lutete, L. M.; Yamamoto, Y. J. Org. Chem. 1999, 64, 4570-4571.
(7) (a) Tokunaga, M.; Eckert, M.; Wakatsuki, Y. Angew. Chem., Int.
Ed. 1999, 38, 3222-3225. (b) Klein, D. P.; Ellern, A.; Angelici, R. J.
Organometallics 2004, 23, 5662-5670. (c) Takaya, J.; Hartwig, J. F. J.
Am. Chem. Soc. 2005, 127, 5756-5757. (d) Kondo, T.; Okada, T.; Suzuki,
T.; Mitsudo, T. J. Organomet. Chem. 2001, 622, 149-154. (e) Tokunaga,
M.; Eckert, M.; Wakatsuki, Y. Angew. Chem., Int. Ed. 1999, 38, 3222-
3225.
(8) (a) Pohlki, F.; Doye, S. Chem. Soc. ReV. 2003, 32, 104-114. (b)
Beller, M.; Seayad, J.; Tillack, A.; Jiao, H. Angew. Chem., Int. Ed. 2004,
43, 3368-3398.
(9) (a) Beller, M.; Eichberger, M.; Trauthwein, H. Angew. Chem., Int.
Ed. Engl. 1997, 36, 2225-2227. (b) Brice, J. L.; Harang, J. E.; Timokhin,
V. I.; Anastasi, N. R.; Stahl, S. S. J. Am. Chem. Soc. 2005, 127, 2868-
2869. (c) Brunet, J. J.; Neibecker, D.; Philippot, K. Tetrahedron Lett. 1993,
34, 3877-3880.
(10) (a) Kondo, T.; Okada, T.; Mitsudo, T. J. Am. Chem. Soc. 2002,
124, 186-187. (b) Rogers, M. M.; Wendlandt, J. E.; Guzei, I. A.; Stahl, S.
S. Org. Lett. 2006, 8, 2257-2260. (c) Fix, S. R.; Brice, J. L.; Stahl, S. S.
Angew. Chem., Int. Ed. 2002, 41, 164-166.
(11) Lucet, D.; Le Gall, T.; Mioskowski, C. Angew. Chem., Int. Ed. 1998,
37, 2580-2627.
(12) Ba¨ckvall, J-E. Tetrahedron Lett. 1978, 19, 163-166.
(13) (a) Chong, A. O.; Oshima, K.; Sharpless, K. B. J. Am. Chem. Soc.
1977, 99, 3420-3426. (b) Corey, E. J.; Jardine, P. D.; Virgil, S.; Yuen,
P.-W.; Connell, R. D. J. Am. Chem. Soc. 1989, 111, 9243-9244.
(14) Zabawa, T. P.; Kasi, D.; Chemler, S. R. J. Am. Chem. Soc. 2005,
127, 11250-11251.
10.1021/om0700462 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/01/2007

3298 Organometallics, Vol. 26, No. 14, 2007
HooVer et al.
developed.15 A direct analogy to the hydroamination reaction
would be the direct addition of an N-N bond across a C-C
multiple bond. Such a process can be envisioned to occur by
oxidative addition of a hydrazine to a metal center to make an
oxidizing amide complex, followed by addition of the amido
ligands to an alkene with a two-electron reduction of the metal
center. An interesting example is the recently reported Pd-
catalyzed diamination of dienes with di-tert-butylaziridinone,
which may proceed through an oxidative addition pathway.16
Few studies have addressed the fundamental reactivity of
hydrazines with metal centers,17 except as models for the
cleavage of N-N bonds by nitrogenase enzymes.18 The reduc-
tive cleavage of hydrazines is accomplished by a number of
systems,19 and a few catalyze the disproportionation of hydrazine
into ammonia and dinitrogen.20 Schrock and co-workers have
proposed oxidative addition of a hydrazine to be on the pathway
to imido formation in their molybdenum and tungsten systems.19a
A recent publication reports the addition of 1,2-diphenylhydra-
zine to an iron(II) monomer to yield a dimeric iron(III) bis-
(imido) complex in a multistep process.21 To our knowledge,
there have been no direct observations of a simple oxidative
addition of a hydrazine N-N bond.
to Che’s [L2Ru(NHCMe2CMe2NH2)2]2+ complexes.26 The
Cp*Ru moiety has been shown to stabilize Ru(IV) species.27
Cp*Ru complexes are also known to react with C-C multiple
bonds,28 including a Cp*RuII-bis(amido) dimer which inserts
diphenylacetylene into a Ru-N bond29 and a Cp*RuIII-bis-
(thiolate) dimer which oxidizes alkenes to vicinal dithioethers.30
This paper reports the formation of the new ruthenium(III)-
bis(amido) complex [Cp*RuCl(µ-NHPh)]2 by oxidative addition
of 1,2-diphenylhydrazine to (Cp*RuIICl)4. The reactivity of this
complex toward hydrazines, amines, and terminal alkynes is
described.
Results
Ci-[Cp*RuCl(µ-NHPh)]2 (1a). The reaction of (Cp*RuIICl)4
with an excess of 1,2-diphenylhydrazine (PhNHNHPh) in C6H6
forms the anilide-bridged ruthenium dimer Ci-[Cp*RuIIICl(µ-
NHPh)]2 (1a; eq 1). After 3 days at room temperature followed
The Cp*Ru system (Cp* ) C5Me5) is a promising candidate
for hydrazine oxidative addition, since related oxidative addi-
tions are known for disulfides, alkyl halides,22 allyl halides,23
Si-H bonds,24 and others.25 Oxidative addition of a hydrazine
to a RuII center would form a RuIV bis(amido) species, similar
by 20 h at 50 °C, 1a was precipitated from solution with pentane
and isolated in 76% yield (see below). Complex 1a is also
formed on reaction of unsaturated Cp*RuIICl(PCy3)31 with
PhNHNHPh, with loss of PCy3, but it is not generated upon
reaction of [Cp*RuIIICl(µ-Cl)]2 with aniline.
The structure of 1a was established by single-crystal X-ray
diffraction to contain dimeric molecules in which the halves
are related by an inversion center (Figure 1, Tables 1 and 2).
The Ru-Ru distance of 2.7134(7) Å is typical of Ru-Ru single
(15) (a) Bar, G. L. J.; Lloyd-Jones, G. C.; Brooker-Milburn, K. I. J. Am.
Chem. Soc. 2005, 127, 7308-7309. (b) Steuff, J.; Ho¨velmann, C. H.; Nieger,
M.; Mun˜iz, K. J. Am. Chem. Soc. 2005, 127, 14586-14587.
(16) Du, H.; Zhao, B.; Shi, Y. J. Am. Chem. Soc. 2007, 129, 762-763.
(17) Barkley, J. V.; Heaton, B. T.; Jacob, C.; Mageswaran, R.; Sam-
panthar, J. T. J. Chem. Soc., Dalton Trans. 1998, 697-701.
(18) (a) Bernskoetter, W. H.; Pool, J. A.; Lobkovsky, E.; Chirik, P. J. J.
Am. Chem. Soc. 2005, 127, 7901-7911. (b) Bernskoetter, W. H.; Lobk-
ovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2005, 127, 14051-14061. (c)
Zhang, Q.-F.; Zheng, H.; Wong, W.-Y.; Wong, W.-T.; Leung, W.-H. Inorg.
Chem. 2000, 39, 5255-5264. (d) Fre´de´ric, B. Coord. Chem. ReV. 2003,
236, 71-89.
(19) (a) Schrock, R. R.; Glassman, T. E.; Vale, M. G. J. Am. Chem.
Soc. 1991, 113, 725-726. (b) Schrock, R. R.; Glassman, T. E.; Vale, M.
G.; Kol, M. J. Am. Chem. Soc. 1993, 115, 1760-1772. (c) Vale, M. G.;
Schrock, R. R. Inorg. Chem. 1993, 32, 2767-2772. (d) Prakash, R.;
Ramachandraiah, G. J. Mol. Catal. A: Chem. 2000, 151, 193-204. (e)
Nakajima, Y.; Suzuki, H. Organometallics 2003, 22, 959-969. (f) Nakajima,
Y.; Inagaki, A.; Suzuki, H. Organometallics 2004, 23, 4040-4046. (g)
Nakajima, Y.; Suzuki, H. Organometallics 2005, 24, 1860-1866. (h)
Shaver, M.; Fryzuk, M. D. J. Am. Chem. Soc. 2005, 127, 500-501. (i)
Henderson, R. A.; Leigh, G. J.; Pickett, C. J. J. Chem. Soc., Dalton Trans.
1989, 425-430.
(20) (a) Kuwata, S.; Mizobe, Y.; Hidai, M. Inorg. Chem. 1994, 33, 3619-
3620. (b) Hitchcock, P. B.; Hughes, D. L.; Maguire, M. J.; Marjani, K.;
Richards, R. L. J. Chem. Soc., Dalton Trans. 1997, 4747-4752. (c) Takei,
I.; Dohki, K.; Kobayashi, K.; Suzuki, T.; Hidai, M. Inorg. Chem. 2005, 44,
3768-3770.
(21) Ohki, Y.; Takikawa, Y.; Hatanaka, T.; Tatsumi, K. Organometallics
2006, 25, 3111-3113.
(26) Chiu, W.-H.; Peng, S.-M.; Che, C.-M. Inorg. Chem. 1996, 35, 3369-
3374.
(27) Arliguie, T.; Chaudret, B. Chem. Commun. 1986, 13, 985-986.
Nagashima, H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.-I.; Fukahori,
T.; Suzuki, H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organometallics 1990,
9, 799-807. Beach, N. B.; Jenkins, H. A.; Spivak, G. J. Organometallics
2003, 22, 5179-5181. Beach, N. J.; Williamson, A. E.; Spivak, G. J. J.
Organomet. Chem. 2005, 690, 4640-4647. Ferna´ndez, I.; Pregosin, P.
Organometallics 2006, 25, 4520-4529. Bruneau, C.; Renaud, J.-L.;
Demerseman, B. Chem. Eur. J. 2006, 12, 5178-5187.
(28) (a) Masuda, K.; Ohkita, H.; Kurumatani, S.; Itoh, K. Organometallics
1993, 12, 2221-2226. (b) de los R´ıos, I.; Tenorio, M. J.; Puerta, C. M.;
Valerga, P. J. Am. Chem. Soc. 1997, 119, 6529-6538. (c) De´rien, S.;
Dixeneuf, P. H. J. Organomet. Chem. 2004, 689, 1382-1392. (d) Koelle,
U.; Kang, B.-S.; Thewalt, U. Organometallics 1992, 11, 2893-2899. (e)
Carreno, R.; Chaudret, B.; Labroue, D.; Sabo-Etienne, S. Organometallics
1993, 12, 13-14. (f) Takemori, T.; Inagaki, A; Suzuki, H. J. Am. Chem.
Soc. 2001, 123, 1762-1763. (g) Tutusaus, O.; Delfosse, S.; Demonceau,
A.; Noels, A. F.; Nu´n˜ez, R.; Vin˜as, C.; Teixidor, F. Tetrahedron Lett. 2002,
43, 983-987. (h) Kawanami, Y.; Sonoda, Y.; Mori, T.; Yamamoto, K. Org.
Lett. 2002, 4, 2825-2827. (i) Oe, Y.; Ohta, T.; Ito, Y. Chem. Commun.
2004, 1620-1621. Fukuyama, T.; Yamaura, R.; Higashibeppu, Y.; Oka-
mura, T.; Ryu, I.; Kondo, T.; Mitsudo, T. Org. Lett. 2005, 26, 5781-5783.
(j) Inada, Y.; Yoshikawa, M.; Milton, M. D.; Nishibayashi, Y.; Uemura, S.
Eur. J. Org. Chem. 2006, 881-890. (k) Jia, G.; Lau, C. P. J. Organomet.
Chem. 1998, 565, 37-48. (l) Itoh, K.; Masuda, K.; Fukahori, T.; Nakano,
K.; Aoki, K.; Nagashima, H. Organometallics 1994, 13, 1020-1029. (m)
Yi, C. S.; Liu, N. J. Organomet. Chem. 1998, 553, 157-161.
(29) Takemoto, S.; Kobayashi, T.; Matsuzaka, H. J. Am. Chem. Soc.
2004, 126, 10802-10803.
(22) (a) Hubbard, J. L.; Morneau, A.; Burns, R. M.; Zoch, C. R. J. Am.
Chem. Soc. 1991, 113, 9176-9180. (b) Takahashi, A.; Mizobe, Y.;
Matsuzaka, H.; Dev, S.; Hidai, M. J. Organomet. Chem. 1993, 456, 243-
253.
(23) (a) Nagashima, H.; Mukai, K.; Itoh, K. Organometallics 1984, 3,
1314-1315. (b) Albers, M. O.; Liles, D. C.; Robinson, D. J.; Shaver, A.;
Singleton, E. Organometallics 1987, 6, 2347-2354. (c) Nagashijma, H.;
Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.; Fukahori, T.; Suzuki, H.;
Akita, M.; Moro-oka, Y.; Itoh, K. Organometallics 1990, 9, 799. (d) Kondo,
H.; Kageyama, A.; Yamaguchi, Y.; Haga, M.; Kirchner, K.; Nagashima,
H. Bull. Chem. Soc. Jpn. 2001, 74, 1927-1937.
(24) (a) Johnson, T. J.; Coan, P. S.; Caulton, K. G. Inorg. Chem. 1993,
32, 4594-4599. (b) Lemke, F. R.; Chaitheerapapkul, C. Polyhedron 1996,
15, 2559-2565.
(25) Kuhlman, R.; Folting, K.; Caulton, K. G. Organometallics 1995,
14, 3188-3195. Navarro Clemente, M. E.; Juarez Saavedra, P.; Cervantes
Vasquez, M.; Paz-Sandoval, M. A.; Arif, A. M.; Ernst, R. D. Organome-
tallics 2002, 21, 592-605.
(30) Kondo, T.; Uenoyama, S.; Fujita, K.; Mitsudo, T. J. Am. Chem.
Soc. 1999, 121, 482-483.
(31) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J. Chem. Soc., Chem.
Commun. 1998, 278-280. Arliguie, T.; Border, C.; Chaudret, B.; Devillers,
J.; Poilblanc, R. Organometallics 1989, 8, 1308-1314.

A Ruthenium(III) Bis(anilide) Dimer
Organometallics, Vol. 26, No. 14, 2007 3299
E ) S, 2.898(1)-2.9258(7) Å for E ) Se; R ) Me, Et, Ph.34,35
The Ru-N distances in 1a (2.072(4), 2.085(4) Å) are also
shorter than those in [Cp*RuII(µ-NHPh)]2 (2.101(8), 2.117(7)
Å). The anilido phenyl rings in 1a are oriented nearly
perpendicular to the Ru2N2 plane, with the torsional angle Ru1-
N1-C11-C16 ) 68.9(6)°. The rings are on opposite sides of
the Ru2N2 plane (anti), with the ipso carbons (C11) angled
35.04° out of the plane. In contrast, the thiolate-bridged dimers
most often have C2v structures with syn thiolate substituents.36
The amide hydrogens (H1, H1′) in 1a were located in the Fourier
difference map.
The 1H NMR spectrum of 1a shows a single Cp* resonance,
a single NH resonance, and five inequivalent aryl resonances.
Similarly, the 13C NMR spectrum shows one kind of Cp* and
six unique aryl resonances. The equivalence of the two Cp*
ligands and the two anilide ligands is consistent with the Ci
symmetry seen in the crystal structure. The spectra indicate that
1a is diamagnetic, again supporting the presence of a Ru-Ru
bond. The resonance at δ 11.0 was assigned as NH by its
1
disappearance in the H NMR spectrum of 1a-d2 made from
(Cp*RuCl)4 and PhNDNDPh. This assignment was confirmed
by H NMR analysis. The ESI-MS of 1a shows a parent ion
(m/z 693.3) and isotope distribution characteristic of dimeric
1a. Thus, the spectroscopy shows that 1a has the same structure
in solution as observed in the solid state.
Figure 1. ORTEP drawing of [Cp*RuCl(µ-NHPh)]2 (1a) showing
2
50% probability ellipsoids.
Table 1. Selected Bond Distances (Å) and Angles (deg) in 1a
Ru1-Ru1′
Ru1-N1
Ru1-N1′
2.7134(7)
2.072(4)
2.085(4)
Ru1-Cl1
C11-N1
2.4919(11)
1.429(6)
The 1H and 13C{1H} NMR spectra show that rotation of the
anilide phenyl rings is slow on the NMR time scale at room
temperature. The aryl resonances do not broaden upon heating
to 353 K. However, 2D EXSY experiments37 show exchange
cross-peaks between the two ortho resonances (δ 8.62, 7.33)
and give a rate constant for rotation about the Namido-Cphenyl
bond of 1.0 ( 0.2 s-1 at 298 K (∆Gq298 ) 17 ( 2 kcal mol-1).
An Eyring plot over a limited temperature range (T ) 285-
320 K) gives ∆Hq ) 10 ( 1 kcal mol-1 and ∆Sq ) -23 (
3 cal mol-1 K-1 (see the Supporting Information). The barrier
for this rotation is larger than the barriers to phenyl rotation in
related TpRuIIL2(NHPh) monomers: ∆Gq ) 12.8 kcal mol-1
at 0 °C for L ) PMe3, ∆Gq < 9.5 kcal/mol at -20 °C for L )
P(OMe)3.38 In the monomers, hindered rotation is in part due
to donation from the N lone pair into the phenyl π system.38 In
the case of 1a, however, the barrier results from steric factors,
since no nitrogen lone pair is available for donation into the
phenyl ring.
Ru1-N1-Ru1′
N1-Ru1-N1′
81.50(14)
98.50(14)
Ru1-N1-C11
Ru1′-N1-C11
128.0(3)
128.6(3)
Table 2. Crystallographic Data for 1a
formula
formula wt
space group
cryst syst
cryst color
cryst dimens (mm)
a (Å)
C32H42Cl2N2Ru2
727.72
P1h
triclinic
brown
0.24 × 0.07 × 0.07
9.361(5)
9.382(5)
10.278(5)
63.061(5)
82.784(5)
68.665(5)
748.7(7)
1
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
d
µ
calcd (Mg m-3
calc (mm-1
F(000)
)
1.614
1.211
370
To evaluate the scope of the hydrazine cleavage reaction,
(Cp*RuIICl)4 was reacted with several other hydrazines. 1,2-
Di-p-tolylhydrazine (TolNHNHTol) rapidly reacts with
(Cp*RuCl)4, forming the toluidide dimer [Cp*RuCl(µ-NHTol)]2
)
no. of unique rflns
no. of data used
no. of params refined
Ra
3554
3554
180
0.0537
0.1186
1.009
1
(2). Analogous to 1a, the H NMR spectrum of 2 shows one
b
Rw
Cp*, one NH, one tolyl methyl, and four aryl resonances. The
electron-deficient phenyl(trifluoroacetyl)hydrazine (PhNHNH-
COCF3) reacts more slowly with (Cp*RuCl)4, and cleavage of
the hydrazine N-N bond is not observed. Instead, [Cp*Ru(η6-
PhNHNHCOCF3)]Cl is formed by simple η6 coordination of
the arene ring, a very common reaction of (Cp*RuCl)4.59,39
Dimethyl hydrazine-1,2-dicarboxylate (MeO2CNHNHCO2Me),
GOFc
2
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w )
1/σ2(Fo). c GOF ) [∑w(|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
bonds32,35 and is significantly shorter than that found in the
divalent analogue [Cp*RuII(µ-NHPh)]2 (2.945(4) Å), which
lacks a Ru-Ru bond.33 The Ru-Ru distance in 1a is similar to
those in related thiolate- and selenolate-bridged Ru(III) dimers
[Cp*RuIIICl(µ-ER)]2: d(Ru-Ru) ) 2.8354(7)-2.847(1) Å for
(34) Nishibayashi, Y.; Imajima, H.; Onodera, G.; Inada, Y.; Hidai, M.;
Uemura, S. Organometallics 2004, 23, 5100-5103.
(35) Nishibayashi, Y.; Imajima, H.; Onodera, G.; Hidai, M.; Uemura,
S. Organometallics 2004, 23, 26-30.
(32) Ferrence, G. M.; Fanwich, P. E.; Kubiak, C. P.; Haines, R. J.
Polyhedron 1997, 16, 1453-1459. Kuncheria, J.; Mirza, H. A.; Jenkins,
H. A.; Vittal, J. J.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans. 1998,
285-290. Gao, Y.; Jennings, M. C.; Puddephatt, R. J. Organometallics
2001, 20, 3500-3509.
(36) Nishibayashi, Y.; Onodera, G.; Inada, Y.; Hidai, M.; Uemura, S.
Organometallics 2003, 22, 873-876.
(37) Perrin, C. L.; Dwyer, T. J. Chem. ReV. 1990, 90, 935-967.
(38) Conner, D.; Jayaprakash, K. N.; Gunnoe, T. B.; Boyle, P. D. Inorg.
Chem. 2002, 41, 3042-3049.
(33) Blake, R. E.; Heyn, R. H.; Tilley, T. D. Polyhedron 1992, 11, 709-
710.
(39) Arene coordination has been observed by 1H NMR and ESI-MS
and in some cases by X-ray crystallography.

3300 Organometallics, Vol. 26, No. 14, 2007
HooVer et al.
Figure 2. 1H NMR spectra of one sample of [Cp*RuCl(µ-NHPh)]2 in C6D6 (b) and with a C6Me6 internal standard ([): (a) the initial C2V
isomer 1b; (b) the Ci isomer 1a after isomerization.
1
which has no arene to coordinate, reacts so slowly with
(Cp*RuCl)4 in C6D6 solution that coordination of the benzene
solvent leads to precipitation of ([Cp*Ru(C6D6)]Cl) within 1
day. In CD2Cl2, MeO2CNHNHCO2Me converts (Cp*RuCl)4 to
a new Cp*-containing ruthenium species over the course of 5
days. This species has not yet been characterized but does not
appear to be [Cp*Ru(MeO2CNH)Cl]2, the bis(amido) product
analogous to 1a. The electron-rich, terminal 1,2-dimethylhy-
drazine reacts rapidly with (Cp*RuCl)4 to give new Cp*-
containing products that are not analogous to 1a and 2 and are
the subject of ongoing studies. Thus, it appears that the cleavage
of the N-N bond to form the bis(amido) dimer is specific to
1,2-diarylhydrazines.
In CD3CN, C6D6, or CD2Cl2, the H NMR resonances for
1b are distinct from those of 1a but show the same pattern: a
single Cp*, a single NH, and five inequivalent aryl resonances
(Figure 2). As with 1a, the 13C{1H} NMR spectrum of 1b in
CD3CN shows six unique aryl resonances consistent with
equivalent, nonrotating phenyl rings. The ESI-MS analysis of
1b shows an m/z value (693) and a fragmentation pattern
identical with that of 1a. When 1b is formed in CH3CN, isolated,
1
and then converted back to 1a by heating in C6D6, H NMR
spectra do not show any free CH3CN. This eliminates the
possibility that 1b could contain bound CH3CN. The data
indicate that complex 1b is an isomer of 1a with C2V symmetry
in which the Cp* ligands, the chloride ligands, and the anilido
substituents are all oriented cis with respect to the Ru2N2 plane.
Disproportionation of 1,2-Disubstituted Hydrazines by
[Cp*RuCl(µ-NHPh)]2. Monitoring the reaction of (Cp*RuCl)4
with excess PhNHNHPh (4 equiv) shows that the remaining 2
equiv of PhNHNHPh are slowly but completely converted into
azobenzene (PhNdNPh) and aniline (PhNH2). Similarly, the
addition of 2 equiv of PhNHNHPh to isolated 1a results in
complete disproportionation (eq 3). The time required for
C2W-[Cp*RuCl(µ-NHPh)]2 (1b). Monitoring the reaction of
(Cp*RuCl)4 with excess PhNHNHPh by 1H NMR spectroscopy
in C6D6 shows that the ruthenium starting material is completely
consumed within 3 min and at least three new Cp*-containing
species can be distinguished: 1a, 1b, and one or two reaction
intermediates. The reaction of Cp*RuCl(PCy3) with excess
PhNHNHPh shows the same set of 1H NMR resonances,
indicating formation of 1a, 1b, and the same intermediate(s) as
observed with (Cp*RuCl)4. After 70 min, the intermediate(s)
convert to 1a and 1b. After 5 h, 1b isomerizes to 1a.
Isomerization is observed in the other direction when isolated
1a is heated in CD3CN at 343 K for 21 h, quantitatively forming
2ArNHNHAr
9
1a8 ArNdNAr + 2ArNH2
(3)
disproportionation varies from sample to sample, in some cases
requiring 1 month at 50 °C. In larger scale preparations of 1a,
heating for 1 day at 50 °C is sufficient to ensure both the
conversion of 1b to 1a and complete disproportionation of
PhNHNHPh. This is done to avoid coprecipitation of the
hydrazine with 1a upon addition of pentane. The catalytic
disproportionation of hydrazines has been seen in several other
systems, all containing sulfur-ligated metal centers: [Cp*RuSR]2
1
1b (by H NMR integration, eq 2). Complex 1b is stable in
(R ) iPr, 2,6-Me2C6H3),20a [MoH(SC6H2 Pr3)3(PMePh2),20b and
several RuMo3 cubane clusters ([Cp*Mo]3(µ3-S)4RuH2(PR3)]-
i
[PF6]; R ) Ph, Cy).20c
To explore the disproportionation reaction, isolated 1a was
added to solutions of di-p-tolylhydrazine (3 equiv) in C6D6. This
reaction results in a similar complete hydrazine disproportion-
ation over 2 days to azotoluene (TolNdNTol) and toluidine
(TolNH2) in a 1:2 ratio. To our surprise, 1a remains unchanged
in this reaction, with no formation of either the toluamide dimer
2 or the mixed dimer [Cp*2Ru2Cl2(µ-NHPh)(µ-NHTol)] (3; see
below). PhNH2, PhNdNTol, and PhNdNPh were also not
observed by 1H NMR. Thus, the hydrazine is not being
CD3CN at 298 K and can be observed by 1H NMR spectroscopy
in C6D6 at 298 K. Complex 1b converts quantitatively back to
1a upon heating in C6D6 for 18 h at 343 K. Heating either 1a
or 1b in CD2Cl2 at 343 K for a day results in a 1:1 mixture of
the two isomers. Isomerization of 1b to 1a in the initial reaction
mixture (eq 1) appears to be faster than isomerization of isolated
1b in C6D6, perhaps indicating that interconversion is catalyzed
by a reaction intermediate in solution.

A Ruthenium(III) Bis(anilide) Dimer
Organometallics, Vol. 26, No. 14, 2007 3301
Scheme 1
incorporated into 1a and the anilide ligands of 1a do not appear
to be involved in the disproportionation.
an exchange process. Aniline and toluidine are present in the
reaction mixture from the disproportionation of the hydrazines
that is concurrent with formation of 1a and 2. Independent
experiments show that 1a is unreactive with toluidine (see
below), and 2 is unreactive with aniline under these room-
temperature conditions. Similarly, neither amine reacts with
(Cp*RuCl)4. Even though neither the starting material nor the
product reacts with arylamines, the reaction of (Cp*RuCl)4 with
5 equiv of PhNHNHPh in the presence of 18 equiv of toluidine
in C6D6 at room temperature does show incorporation of tolyl
substituents. Complexes 1a, 2, and 3 are observed after 25 h of
reaction, in a 1:1:0.7 ratio (by 1H NMR spectroscopy and
confirmed by ESI-MS). This surprising result indicates that there
is an intermediate that exchanges with ArNH2. This exchange
process is likely the origin of the small amount of 3 found in
the crossover experiment.
The lack of involvement of the anilide ligands raised the issue
of the role of 1a in the disproportionation reaction. A set of
reactions at 50 °C with 4.3 mM PhNHNHPh and different
concentrations of 1a (0.31, 1.04, 2.5, 5.2 mM) were monitored
by 1H NMR spectroscopy. All the reactions showed first-order
decay of the hydrazine with no apparent dependence on the
concentration of 1a (kobs ) 0.011 ( 0.002 s-1). When performed
in the presence of 2,6-di-tert-butyl-4-methylpyridine (2 equiv)
or 9,10-dihydroanthracene (1 equiv), the disproportionation
reaction proceeds without a reduction in rate. Similarly, the
radical initiator AIBN (0.4 equiv) does not promote the
disproportionation of PhNHNHPh in the absence or the presence
of 1a (0.2 equiv) at 75 °C over the course of 12 days. It appears
that the disproportionation reaction does not involve an acid-
promoted or a radical-initiated mechanism. Although 1a is a
necessary component in the disproportionation of PhNHNHPh,
its role is not yet understood. It is possible that an impurity in
1a is responsible for this reactivity, although isolated crystals
of 1a have also been shown to be catalytically active.
Reactivity of 1a. The anilide ligands in 1a do not exchange
with 8 equiv of toluidine (TolNH2) in C6D6 or CD3CN at room
temperature or after 1 day at 80 °C by 1H NMR. After days at
80 °C, however, a small amount of the mixed dimer 3 is seen
(1a:3 ) 1:0.16). The analogous addition of aniline (10 equiv)
to the bis(toluidide) complex 2 shows the presence of complexes
1a, 2, and 3, in a 1:0.14:0.46 ratio after 5 days at 80 °C.
Crossover Experiment. To determine whether both anilide
bridges of 1a and 1b arise from the same molecule of hydrazine,
a crossover experiment was performed using diphenyl- and di-
p-tolylhydrazines. (Cp*RuCl)4 was added to an equimolar
mixture of the hydrazines, both in excess, in C6D6. Monitoring
Complex 1a is unreactive with alkenes and alkynes, such as
norbornene, styrene, PhCtCPh and PhCtCH. Reactions were
run in C6D6 or CD3CN at room temperature with excess
1
1
by H NMR spectroscopy at room temperature over 1 day
substrate and were monitored by H NMR. The reactions in
showed predominant formation of the symmetric complexes 1a
(49%) and 2 (42%), with smaller amounts of the asymmetric
compound [Cp*2Ru2Cl2(µ-NHPh)(µ-NHTol)] (3; 9%) (Scheme
1). Compounds 1a, 2, and 3 were identified by their distinct
Cp* resonances (see below); the aryl resonances for 3 are the
same as those for 1a and 2. ESI/MS confirms the formation of
1a (m/z 693, [Cp*2Ru2(µ-NHPh)2Cl]+) and 2 (m/z 721, [Cp*2-
Ru2(µ-NHTol)2Cl]+) as the dominant species with small amounts
CD3CN showed only slow isomerization of 1a to 1b. Heating
a mixture of 1a with styrene (1.5 equiv), norbornene (12 equiv),
or phenylacetylene (20 equiv) in toluene-d8 at 100 °C for 3 days
gave no reaction. Complex 1a is also unreactive with trieth-
ylphosphine (50 equiv) over 1 day at 50 °C in either C6D6 or
in CD2Cl2 (by 1H NMR) and with 5 equiv of MeOH in C6D6 at
100 °C for 3 days.
Chloride Abstraction from 1a and Reaction with Terminal
Alkynes. Silver triflate reacts rapidly with 1a in C6D6 at room
temperature to remove the chloride ligands and form the bis-
1
of 3 (m/z 707, [Cp*2Ru2(µ-NHPh)(µ-NHTol)Cl]+). Both H
NMR spectroscopy and GC-MS analyses of the organic products
show both azobenzene and azotoluene, but the mixed PhNd
NTol was not observed.
1
(triflate) complex [Cp*Ru(µ-NHPh)(OTf)]2 (4). The H NMR
spectrum of 4 has a single Cp* resonance, a single NH
resonance, and five distinct aryl resonances, two of which are
overlapping. The 13C{1H} NMR spectrum shows six different
aryl carbons, indicating that the aryl rings are not rotating. The
19F NMR spectrum shows a single peak at -78.1 ppm in C6D6,
which indicates equivalent triflate anions covalently bonded to
the ruthenium.40 Addition of degassed water to a solution of 4
To confirm the identity and stability of the unsymmetric dimer
3, (Cp*RuCl)4 was reacted in C6D6 with a mixture of the three
symmetrical and unsymmetrical hydrazines: PhNHNHPh,
TolNHNHTol, and PhNHNHTol. The mixture of hydrazines
was made by reduction of a mixture of nitrobenzene and
1
nitrotoluene and shown by GC-MS and H NMR to have a
1
1:0.60:1.17 ratio of the PhPh, TolTol, and PhTol derivatives.
in C6D6 results in a shift of all resonances in the H NMR
Reaction with (Cp*RuCl)4 gives 1a, 2, and 3 in a 1:3.3:2.3 ratio,
spectrum, and after a few hours, complex 5 crystallized out of
solution. A single-crystal X-ray diffraction study was problem-
atic, because of low crystal quality and disorder, but suggested
that 5 is the monoaquo complex C2V-[Cp*Ru(µ-NHPh)2RuCp*-
(OH2)](OTf)2 (on the basis of this, 4 is assumed to also have
1
as determined by integration of the Cp* resonances of the H
NMR spectrum and confirmed by ESI-MS analysis. This
experiment not only serves as a control for the crossover
experiment but also shows that the more electron rich tolylhy-
drazines are more reactive with (Cp*RuCl)4.
The origin of the small amount of the mixed dimer 3 has
been explored, specifically whether it could be derived from
(40) Jones, V. A.; Sriprang, S.; Thronton-Pett, M.; Kee, T. P. J.
Organomet. Chem. 1998, 567, 199-218.

3302 Organometallics, Vol. 26, No. 14, 2007
HooVer et al.
Cl2.41 This shift is consistent with hydrogen bonding between
the triflate anion and the acetylenic hydrogen.42,43 The 19F NMR
of 6a shows one triflate resonance at -79.5 ppm, consistent
with noncoordinating counterions.40
Scheme 2
1
The H NMR spectra indicate dimeric molecules with Cs
symmetry, in which the mirror plane relates the two Cp*Ru
fragments and contains all of the other atoms. Three kinds of
structures are consistent with this data: a vinylidene complex,
a product from insertion of the alkyne into the Ru-N bond, or
an alkyne complex. The nature of the acetylene unit in 6a was
probed by preparing it with Ph13Ct13CH. The 13C{1H} NMR
spectrum of 6a-13C2 shows two acetylenic carbons (95.80 and
1
92.94 ppm) with a coupling constant of JCC ) 52 Hz. The
similarity of the 13C chemical shifts, only 3 ppm apart, argues
against a vinylidene complex or a structure in which PhCtCH
has coupled with an anilide ligand. A vinylidene complex can
also be eliminated, due to the absence of the characteristic
carbon resonance between 300 and 400 ppm.44
2D HMQC and HMBC experiments are consistent with an
alkyne-coordinated species (see the Supporting Information).
The 2D HMQC spectrum of 6a-13C2 confirms that the downfield
1
the cis structure). H NMR spectra of the mother liquor show
a single product with a single set of Cp* and anilido resonances,
indicating either that the material in solution is the diaquo
complex or that the unsymmetrical monoaquo seen in the crystal
is fluxional on the NMR time scale. The 19F NMR resonance
for 5 indicates ionic triflate (δ -79.2 in C6D6; δ -79.7 in CD2-
Cl2).
proton (9.3 ppm) is coupled to both acetylene carbons (1JHC
)
2
235 Hz, JHC ) 16 Hz). In addition, the HMBC experiment
shows coupling between the ortho protons of PhCtCH and Câ,
showing that the acetylene proton and the acetylene phenyl ring
remain on adjacent carbons, again eliminating a vinylidene
species as a possible structure. Coupling of a PhCtCH unit
with an anilide is unlikely, because the NH protons do not show
any coupling to 13C. Thus, the phenylacetylene is intact within
6a, and the C-C multiple bond has alkene character. In addition,
ESI/MS of 6a and 6b show fragmentation that involves loss of
the acetylene without loss of the anilide ligands, arguing against
the presence of a C-N bond.
Addition of an excess of phenylacetylene (PhCtCH) to 4
(generated in situ from 1a and 2 AgOTf) in C6D6 leads to
precipitation of a dark green solid, assigned as the acetylene
complex [{Cp*Ru(µ-NHPh)}2(µ-η2:η2-PhCtCH)](OTf)2 (6a)
-
(Scheme 2). The more easily isolated PF6 salt [{Cp*Ru(µ-
NHPh)}2(µ-η2:η2-PhCtCH)](PF6)2 (6b) was prepared similarly
from 1a, AgPF6, and PhCtCH in 51% yield. ESI-MS analyses
of both 6a and 6b show ions with one acetylene added to the
dimeric ruthenium unit, for instance [Cp*2Ru2(NHPh)2(PhCt
CH)OTf]+ from 6a (m/z 909). Isolating this m/z 909 ion in an
ion trap mass spectrometer and fragmenting it with helium atoms
proceeds with loss of HOTf ([Cp*2Ru2(NPh)(NHPh)(PhCt
CH)]+; m/z 759) and PhCtCH ([Cp*2Ru2(NPh)(NHPh)]+; m/z
657).
All of the data support the assignment of 6 as an alkyne
1
complex. The coupling constants (1JCC ) 52 Hz, JHC
)
235 Hz, JHC ) 16 Hz) suggest a µ-η2:η2-bound alkyne in 6a
2
because they are close to those observed for the µ-η2:η2 complex
1
[(CO)3Co(µ-η2:η2-HCtCH)Co(CO)3], which has JCC
)
55.9 Hz, JHC ) 209.8 Hz, and JHC ) 15.7 Hz.45 The
orientations of the substituents were determined by phase-
sensitive NOESY experiments (see the Supporting Information).
These show an NOE between the upfield NH resonance
(4.4 ppm) and the ortho protons of the rotating phenyl ring,
and an NOE between the downfield NH resonance (6.8 ppm)
and both ortho protons of the acetylene phenyl ring (Figure 3).
This indicates that the rotating phenyl ring and the acetylene
phenyl ring lie on opposite sides of the Ru-Ru bond. The data
taken together show that 6a and 6b are the µ-η2:η2-alkyne
complexes shown in Scheme 2.
1
2
The 1H NMR spectra of 6a and 6b in CD2Cl2 are only slightly
different, indicating the same basic structure in solution (the
values given are for 6a unless otherwise indicated). The H
1
NMR spectra show a single peak for two equivalent Cp* ligands
(30 H), which are also equivalent in the 13C{1H} NMR.
However, all of the other groups in the cation are inequivalent,
as there are two distinct NH protons (4.4 and 6.8 ppm for 6a)
and eight aryl resonances in the ratio 1:1:3:3:2:1:2:2, as well
as a characteristic downfield singlet (δ(CD2Cl2) 9.3). A 2D
COSY analysis indicates three distinct aryl rings, two of which
do not rotate on the NMR time scale, while the third does. The
more downfield of the nonrotating rings was assigned as the
phenyl of the acetylene, through the in situ synthesis of the
p-TolCtCH and p-tBuC6H4CtCH analogues. The assignment
of the NH resonances was confirmed by the synthesis of 6-(ND)2
from [Cp*RuCl(µ-NDPh)]2 (1a-d2), AgOTf, and PhCtCH. The
downfield singlet was similarly shown to originate from the
acetylene by the addition of PhCtCD to 1a and AgOTf to form
[{Cp*Ru(µ-NHPh)}2(µ-η2:η2-PhCtCD)](OTf)2 (6-PhCCD).
Derivatives of 6 with different counterions (from different silver
salts as reactants) show that this resonance shifts further
downfield with more hydrogen bonding counterions: δ 9.29
(OTf-), 9.02 (ClO4-), 8.83 (BF4-), and 8.45 (PF6-) in CD2-
Diphenylacetylene does not react with 4 under the same
conditions, perhaps due to unfavorable steric interactions. Steric
(41) Seppelt, K. Angew. Chem., Int. Ed. Engl. 1993, 32, 1025-1027.
(42) DeLaat, A. M.; Ault, B. S. J. Am. Chem. Soc. 1987, 109, 4232-
4236. Steiner, T. J. Mol. Struct. 1998, 443, 149-153. Scheiner, S.;
Grabowski, S. J.; Kar, T. J. Phys. Chem. A 2001, 105, 10607-10612.
Domagala, M.; Grabowski, S. J. J. Phys. Chem. A 2005, 109, 5683-5688.
Alkorta, I.; Zborowski, K.; Elguero, J. J. Phys. Chem. A 2006, 110, 10279-
10286.
(43) Sola`, J.; Riera, A.; Verdaguer, X.; Maestro, M. A. Organometallics
2006, 25, 5795-5799.
(44) Stu¨er, W.; Wolf, J.; Werner, H. J. Organomet. Chem. 2002, 203-
207. Pavlik, S.; Mereiter, K.; Puchberger, M.; Kirchner, K. J. Organomet.
Chem. 2005, 690, 5497-5507. Sun, Y.; Chan, H.-S.; Dixneuf, P.; Xie, Z.
Organometallics 2006, 25, 2719-2721. Kopf, H.; Pietraszuk, C.; Hu¨bner,
E.; Burzlaff, N. Organometallics 2006, 25, 2533-2546. Beach, N.; Walker,
J.; Jenkins, H.; Spivak, G. J. Organomet. Chem. 2006, 691, 4147-4152.
(45) Aime, S.; Osella, D.; Giamello, E.; Granozzi, G. J. Organomet.
Chem. 1984, 262, C1-4.

A Ruthenium(III) Bis(anilide) Dimer
Organometallics, Vol. 26, No. 14, 2007 3303
Formally, the anilido dimers 1 could be formed by direct
addition of PhNHNHPh to a diruthenium unit of the tetrameric
(Cp*RuCl)4. The trinuclear RuII hydride (Cp*Ru)3(µ2-H)(µ3-
H)2 has similarly been reported to add the monosubstituted
hydrazine RNHNH2 (R ) Me, Ph) to give the bis(imido)
complex (Cp*Ru)3(µ3-NR)(µ3-NH)(µ2-H).49 However, direct
formation of 1 from (Cp*RuCl)4 plus PhNHNHPh is ruled out
by the toluidine exchange experiments. TolNH2 is incorporated
into the product of PhNHNHPh + (Cp*RuCl)4, forming [Cp*2-
Ru2Cl2(µ-NHPh)x(µ-NHTol)2-x] (2, 3), but it does not exchange
with either (Cp*RuCl)4 or 1a under these conditions. This
requires that there be an intermediate along the pathway with
sufficient lifetime to undergo anilide exchange. In addition, 1
is also formed from PhNHNHPh and monomeric Cp*RuCl-
(PCy3), and the (Cp*RuCl)4, tetramer is known to be readily
cleaved into monomers.50,59 Thus, the reactions could also
proceed by oxidative addition of PhNHNHPh to a single metal
center to give a transient Ru(IV) bis(anilide) complex, which
could exchange with TolNH2 or be trapped by a source of
“Cp*RuCl”. Hydrazine oxidative addition to form a monomeric
bis(amido) metal complex has not yet, to our knowledge, been
reported. TolNH2 exchange could also occur in a dimeric
intermediate, similar to the reaction of [Cp*RuIIICl(µ-Cl)]2 with
a thiol to give [Cp*RuCl(µ2-SR)]2.36 However, the analogous
addition of aniline to [Cp*RuIIICl(µ-Cl)]2 does not form 1a or
1b. The crossover experiment showing that both anilide ligands
in 1 arise from the same hydrazine is consistent with either
mononuclear or binuclear oxidative addition mechanisms.
Similarly, either path could rationalize the formation of a
nonthermodynamic 1:1 ratio of Ci (1a) and C2V (1b) isomers
from PhNHNHPh plus (Cp*RuCl)4, which may simply reflect
the twisted hydrazine geometry.
Figure 3. Cationic fragment of 6, [{Cp*Ru(µ-NHPh)}2(µ-η2:η2-
PhCtCH)]2+, with key NOE interactions indicated by curved
arrows.
crowding in 6 is suggested by hindered rotation of two of the
phenyl rings.
Discussion
Anilide Dimers. [Cp*RuCl(µ-NHPh)]2 (1a and 1b) are
additions to the family of known Cp*Ru dimers. They are RuIII
analogues of the RuII-anilido dimer [Cp*RuII(µ-NHPh)]2 and
the more studied methoxide analogue [Cp*RuII(µ-OMe)]2 that
have been reported by Tilley and co-workers.33,46 Analogous
sulfide and selenide dimers [Cp*RuCl(µ-ER)]2 have also been
described.34-36 With these good bridging ligands, NHR and SR,
the dimers are diamagnetic with short RuIII-RuIII distances
(2.71-2.94 Å), implying metal-metal bonds and 18-electron
configurations. The analogous chloride dimer [Cp*RuIIICl(µ-
Cl)]2 is paramagnetic and crystallizes with two quite different
molecules in the unit cell, one with a Ru-Ru bond and one
without, d(RuIII-RuIII) ) 2.930(1), 3.752(1) Å,47 suggesting a
metal-metal interaction weaker than that found in 1a.
[Cp*RuIIICl(µ-X)]2 dimers have anti (Ci) or syn (C2V)
structures, depending on the distribution of the Cp* and Cl
groups about the central Ru2X2 unit. [Cp*RuIIICl(µ-Cl)]2, which
has the anti structure,47 is reported to react with 1-phenyle-
thanethiol to yield a 1:1 mixture of the syn and anti isomers of
[Cp*RuCl(µ-SCHPhMe)]2, which do not interconvert.48 Forma-
tion of these thiolate-bridged dimers by oxidative addition of
disulfides to (Cp*RuCl)4, however, yields only syn-[Cp*RuCl-
(µ-SR)]2.34-36 The anilide dimers in this work also exist in both
Ci (1a) and C2V (1b) forms, and slow isomerization between
the forms is observed. The isomers are close enough in energy
that the polarity of the solvent shifts the equilibrium position,
with the Ci isomer 1a that has no dipole moment favored in
nonpolar solvents such as benzene and the C2V isomer 1b favored
in the more polar acetonitrile solvent. In dichloromethane, a
solvent of intermediate polarity, an equimolar mixture of the
two isomers is observed.
Reactivity of 1a. Complex 1a is not very reactive, being inert
to alkenes and alkynes even upon heating. This is in contrast
to the analogous thiolate-bridged complexes which oxidize
alkenes to dithioethers.30 Substitution of the bridging NHPh
ligands by NHTol occurs only upon heating to 70 °C for 1 day.
No reaction is observed with methanol, even though a methoxy-
bridged dimer such as “[Cp*RuIIICl(µ-OMe)]2” would seem to
be a reasonable product.46 Triethylphosphine does not react with
1a at 50 °C, either to reduce it or to cleave the dimer into
monomeric complexes (which would be somewhat analogous
to Cp*RuIICl(py)(PCy3)).51 In general, the Ru2N2 core appears
to be quite stable both thermodynamically and kinetically.
Opening of the Ru2N2 ring is most likely involved in the
isomerization between 1a and 1b and in the slow exchange with
TolNH2, but the opened form is not easily trapped by other
reagents.
The propensity of the amido ligand to form strong bridges
presents a challenge in the pursuit of a reactive bis(amido)
monomer that will accomplish diamination. Oxidative addition
of a hydrazine requires an intermediate with an open coordina-
tion site, and such an unsaturated species could add to the bis-
(amido) desired product to form an amido-bridged compound.
Sterically bulky ligands could be used to prevent dimerization
but are also likely to inhibit reactivity with substrates. Electron-
deficient amide ligands could reduce the tendency to bridge and
Formation of 1. The addition of PhNHNHPh to (Cp*RuII-
Cl)4 to give 1 is a formal oxidative addition of the hydrazine
N-N bond. The reaction appears to be faster with the more
electron rich TolNHNHTol, while more electron-deficient
hydrazines such as PhNHNHCOCF3 and MeO2CNHNHCO2-
Me are unreactive. This pattern is opposite to what would be
expected from consideration of the hydrazine as an oxidant. It
may be that initial hydrazine coordination is playing an
important role.
(49) Nakajima, Y.; Suzuki, H. Organometallics 2003, 22, 959-969.
(50) Luo, L.; Nolan, S. P. Organometallics 1994, 13, 4781-4786. Hillier,
A. C.; Sommer, W. J.; Yong, B. S.; Petersen, J. L.; Cavallo, L.; Nolan, S.
P. Organometallics 2003, 22, 4322-4326. Cokoja, M.; Gemel, C.; Seinke,
T.; Schro¨der, F.; Fischer, R. A. Dalton Trans. 2005, 44-54.
(51) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J. Chem. Soc., Chem.
Commun. 1988, 278-280.
(46) Loren, S. D.; Campion, B. L.; Heyn, R. H.; Tilley, T. D.; Bursten,
B. E.; Luth, K. W. J. Am. Chem. Soc. 1989, 111, 4712-4718.
(47) Ko¨lle, U.; Kossakowski, J.; Klaff, N.; Wesemann, L.; Englert, U.;
Heberich, G. E. Angew. Chem., Int. Ed. 1991, 30, 690-691.
(48) Nishibayashi, Y.; Onodera, G.; Inada, Y.; Hidai. M.; Uemura, S.
Organometallics 2003, 22, 873-876.

3304 Organometallics, Vol. 26, No. 14, 2007
HooVer et al.
entific) and deuterio (Cambridge Isotope) solvents were dried before
use (pentane, THF, THF-d8, C6H6 using sodium/benzophenone;
C6D6, CD2Cl2, CH2Cl2 using CaH2; CD3CN using CaH2/P2O5/
CaH2). CH3OD was used as received. [Cp*RuCl2]2,58 (Cp*RuCl)4,59
1,2-di-p-tolylhydrazine,60 and phenyacetylene-d61 were prepared
according to literature methods. Pentamethylcyclopentadiene (Strem)
enhance reactivity with electrophiles such as alkenes, and these
will be a focus of future studies.
Chloride Abstraction and Subsequent Reaction with
PhCtCH. Removal of the chloride ligands from 1a with silver
salts generates reactive dinuclear complexes. Use of AgOTf
gives a triflate-coordinated dimer, according to 19F NMR spectra,
1
and RuCl3‚3H2O (Pressure Chemical) were used as received. H,
-
but the extent of anion coordination is not known for the PF6
,
13C, and 19F NMR spectra were recorded on Bruker Avance 300
(1H) and 500 MHz (1H, 13C, and 19F) spectrometers and referenced
to the residual solvent signal (1H and 13C) or an external CF3COOH
standard (-78.5 ppm);62 all coupling constants are reported in Hz.
Assignments of the 13C NMR resonances were made using 2D
HMQC and HMBC experiments. Mass spectra were recorded from
CH3CN solutions on a Bruker Esquire ion trap electrospray
ionization mass spectrometer. GC-MS analyses used a Hewlett-
Packard 5971A GC-MS with an Agilent DB-5MS column
(25 m × 200 µm i.d. × 0.33 µm phase thickness): 70 °C, 20 °C/
min, 210 °C. Elemental analyses were performed by Atlantic
Microlab, Inc.
BF4-, and ClO4- derivatives. Addition of PhCtCH gives a Cs-
symmetric dimer in which the acetylene is perpendicular to the
Ru-Ru bond. This binding mode is uncommon for ruthenium
dimers, which tend to incorporate a terminal alkyne either as a
vinylidene ligand52 or through insertion into the Ru-N bond,
such as in the [Cp*RuII(µ2-NHPh)]2 system.29,53 The thiolate
dimers [Cp*RuCl(µ-SR)]2 react with RCtCH and 1 equiv of
Ag+ to give vinylidene54 and allenylidene35,55 complexes.
Complex 1a, however, remains unreactive toward PhCtCH in
the presence of 1 equiv of AgOTf. A µ-η2:η2-bound acetylene
is found in the RuI-carbonyl dimer [Cp2Ru2(CO)2(µ-η2:η2-HCt
CH)],56 and this binding mode is common for other transition
metals.57
Ci-[Cp*RuCl(µ-NHPh)]2 (1a). A mixture of 1,2-diphenylhy-
drazine (700 mg, 3.8 mmol) and (Cp*RuCl)4 (1.196 g, 1.1 mmol)
was stirred in 50 mL of C6H6 for 3 days at room temperature and
then heated to 50 °C for ∼20 h. The volume was then reduced to
∼25 mL, and pentane (∼20 mL) was added to precipitate out a
dark brown solid. The mixture was filtered and the solid washed
with pentane (2 × 10 mL) to give 1.23 g of 1a (1.69 mmol, 77%).
1H NMR (C6D6, 500 MHz): δ 11.01 (s, 2H, NH), 8.62 (d, J )
7.5, 2H, o), 7.33 (d, J ) 6.5, 2H, o), 7.13 (2H, m), 7.01 (m, 4H, m,
p), 1.19 (s, 30H, Cp*). 13C{1H} NMR (C6D6): δ 130.62 (i), 130.27
(m), 128 (p), 126.22 (o), 123.48 (m), 122.62 (o), 94.11 (C5(CH3)5),
9.00 (C5(CH3)5). ESI/MS (CH3CN): m/z 693 ([Cp*2Ru2(NHPh)2-
Cl]+). Anal. Calcd for C32H42Cl2N2Ru2: C, 52.81; H, 5.82; N, 3.85.
Found: C, 52.59; H, 5.89; N, 3.96.
Conclusion
The RuIII-bis(amido) species [Cp*RuCl(µ-NHPh)]2 (1) is
easily accessed from the oxidative addition of 1,2-diphenylhy-
drazine to (Cp*RuCl)4. This complex shows solvent-dependent
interconversion between the Ci (1a) and C2V (1b) isomers and
promotes the disproportionation of PhNHNHPh into azobenzene
and aniline. Formation of these dimers involves oxidative
addition of the hydrazine N-N bond, which is a rare process.
Complex 1a has limited reactivity, in part because of the stability
of the Ru2(µ-NHPh)2 core. The strength of the bridging anilide
ligands inhibits the reactivity of 1a with unsaturated hydrocar-
bons. Abstraction of the chloride ligands gives a more reactive
species that adds phenylacetylene to give a complex with a µ-η2:
η2-PhCtCH ligand, an uncommon binding mode for a diru-
thenium compound. The disproportionation of hydrazine and
the propensity of the amido ligands to bridge may be some of
the challenges associated with the use of hydrazines in amination
reactions.
Ci-[Cp*RuCl(µ-NDPh)]2 (1a-d2). A J. Young tube was charged
with a solution of PhNDNDPh (96% 2H, prepared from exchange
with MeOD; 13 mg, 7 mmol) in C6D6. (Cp*RuCl)4 (2 mg,
2
1.8 mmol) was added, and after 3 days at room temperature, H
1
2
and H NMR show 94% H.
C2W-[Cp*RuCl(µ-NHPh)]2 (1b). A J. Young NMR tube was
charged with 1a (2 mg, 2.7 mmol) and CD3CN and the mixture
heated to 70 °C for 21 h. 1H NMR (CD3CN, 500 MHz): δ 9.85 (s,
2H, NH), 7.77 (d, J ) 7, 2H, o), 7.37 (m, 4H, m), 7.25 (t, 2H, p),
6.54 (d, J ) 6.5, 2H, o), 1.16 (s, 30H, Cp*). 13C{1H} NMR
(C6D6): δ 158.36 (i), 130.97 (m), 128.59 (m), 127.38 (o), 126.72
(p), 123.03 (o), 94.58 (C5(CH3)5), 8.40 (C5(CH3)5) ppm. ESI/MS
(CH3CN): m/z 693 ([Cp*2Ru2(NHPh)2Cl]+). Similar heating of 1a
in CD2Cl2 showed an equal mixture of 1a and 1b. 1H NMR of 1b
(CD2Cl2, 500 MHz): δ 9.66 (s, 1H, NH), 7.74 (d, 1H, o), 7.38 (m,
2H), 7.27 (m, 1H), 6.45 (d, 1H, o), 1.191 (s, 15H, Cp*).
[Cp*RuCl(µ-NH-p-tol)]2 (2). A C6D6 solution of di-p-tolylhy-
drazine (1 mg, 5 µmol) and (Cp*RuCl)4 (2 mg, 1.8 µmol) was
allowed to react for 2 days in a J. Young NMR tube. The solvent
was removed under vacuum, and the remaining brown solids were
washed with pentane and dried to give a dark brown solid. 1H NMR
(C6D6, 500 MHz): δ 11.09 (s, 1H, NH), 8.57 (d, J ) 8.5, 1H, o),
7.33 (d, J ) 8, 1H, o), 6.98 (d, J ) 8.5, 1H, m), 6.89 (d, J ) 7.5,
1H, o), 2.04 (s, 3H, p-methyl), 1.25 (s, 15H, Cp*). ESI/MS (CH3-
CN): m/z 721 ([Cp*2Ru2(NHTol)2Cl]+).
Experimental Section
General Considerations. All manipulations were performed
under N2 using standard high-vacuum-line or inert-atmosphere
glovebox techniques, unless otherwise noted. Protio (Fisher Sci-
(52) (a) Matsuzaka, H.; Takagi, Y.; Hidai, M. Organometallics 1994,
13, 13-15. (b) Takagi, Y.; Matsuzaka, H.; Ishii, Y.; Hidai, M. Organo-
metallics 1997, 16, 4445-4452. (c) Puerta, M. C.; Valerga, P. Coord. Chem.
ReV. 1999, 193-5, 977-1025. (d) Dragutan, V.; Dragutan, I. Platinum Met.
ReV. 2004, 48, 148-153.
(53) Insertion into Ru-N bonds: (a) Standfest-Hauser, C. M.; Mereiter,
K.; Schmid, R.; Kirchner, K. Dalton Trans. 2003, 2329-2334. (b) Busetto,
L.; Marchetti, F.; Zacchini, S.; Zanotti, V. J. Organomet. Chem. 2006, 291,
2424-2439. (c) Sun, Y.; Chan, H.-S.; Xie, Z. Organometallics 2006, 25,
3447-3453.
(54) Takagi, Y.; Matsuzaka, H.; Ishi, Y.; Hidai, M. Organometallics 1997,
16, 4445-4452.
(55) Nishibayashi, Y.; Waskiji, I.; Hidai, M. J. Am. Chem. Soc. 2000,
122, 11019-11020.
(56) Colborn, R. E.; Davies, D. L.; Dyke, A. F.; Knox, S. A. R.; Mead,
K. A.; Orpen, A. G. J. Chem. Soc., Dalton Trans. 1989, 1799-1805. Cooke,
M.; Davies, D. L.; Guerchais, J. E.; Knox, S. A. R.; Mead, K. A.; Roue´, J.;
Woodward, P. J. Chem. Soc., Chem. Commun. 1981, 862-864.
(57) (a) George, B. S. A.; McDonald, R.; Cowie, M. Can. J. Chem. 1996,
74, 2289-2303. (b) Zhang, Y.-H.; Lao, W.-J.; Liu, Y.-Q.; Yin, Y.-Q.; Wu,
J.-J.; Huanh, Z.-H. Polyhedron 2001, 20, 1108-1113. (c) Chen, X.-N.;
Zhang, J.; Yin, Y.-Q.; Huang, X.-Y. Organometallics 1999, 18, 3164-
3169.
Reaction of (Cp*RuCl)4 with Diphenylhydrazine and Di-p-
tolylhydrazine. (Cp*RuCl)4 (2.5 mg, 2.3 µmol) was added to a
(58) Koelle, U.; Kossakowski, J. Inorg. Synth. 1992, 29, 225-227.
(59) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc. 1989,
111, 1698-1719.
(60) Khurana, J. M.; Singh, S. J. Chem. Soc., Perkin Trans. 1 1999,
1893-1895.
(61) Gronheid, R.; Zuilhof, H.; Hellings, M. G.; Cornelisse, J. Lodder,
G. J. Org. Chem. 2003, 68, 3205-3215.
(62) Walstrom, A.; Pink, M.; Tsvetkov, N. P.; Fan, H.; Ingleson, M.;
Caulton, K. G. J. Am. Chem. Soc. 2005, 127, 16780-16781.

A Ruthenium(III) Bis(anilide) Dimer
Organometallics, Vol. 26, No. 14, 2007 3305
C6D6 solution of PhNHNHPh (1.5 mg, 8 µmol) and di-p-
tolylhydrazine (1.5 mg, 7 µmol) in a J. Young 1H NMR tube. The
H, 4.18; N, 2.70). The presence of some residual AgCl in
recrystallized 5 is indicated by solutions of this material becoming
cloudy with a gray-white solid overy time. Attempts to remove
the residual AgCl by filtration through Celite have been unsuc-
cessful.
1
reaction was monitored by H NMR spectroscopy. After ∼1 day
the reaction mixture was dried and washed with pentane. The
washings were analyzed by GC-MS and separated with retention
times of 18.2 min (m/z 182; PhNdNPh) and 21.9 min (m/z 210;
TolNdNTol). No PhNdNTol was observed.
[Cp*2Ru2(µ-NHPh)2(µ-η2:η2-PhCtCH)](OTf)2 (6a). An excess
(3.6 mg, 14.0 µmol) of AgOTF was added to a solution of 1a
(2.3 mg, 3.2 µmol) and PhCtCH (19 µmol) in C6D6 in a J. Young
NMR tube. The solution was decanted after the formation of dark
precipitates, which were then dried under vacuum. 1H NMR (CD2-
Cl2, 500 ΜΗz): δ 9.29 (s, 1H, PhCtCH), 8.20 (d, J ) 6, 1H,
o-PhCtCH), 8.02 (d, J ) 8, 1H, o-PhCtCH), 7.78 (t, J ) 6, 1H,
m-PhCtCH), 7.63 (m, 3H), 7.47 (m, 3H), 7.32 (m, 2H), 7.26 (t,
J ) 5, 1H, m-PhNH), 7.03 (d, J ) 5, 2H, o-PhNH), 6.77 (s, 1H,
NH), 6.71 (d, J ) 4, 1H, o-PhNH), 4.40 (s, 1H, NH), 1.53 (s, 15H,
Cp*). 13C NMR (CD2Cl2): δ 108.2 (Cp*), 95.8 (JCC ) 52.5,
Ph13Ct13CH), 92.9 (JCC ) 52.5, JHC ) 235, Ph13Ct13CH), 9.9
(Cp*). 19F NMR (CD2Cl2): δ -79.5 (CF3SO3). ESI/MS (CH3-
CN): m/z 909 ([Cp*2Ru2(NHPh)2(PhCCH)OTf]+).
[Cp*2Ru2(µ-NHPh)2(µ-η2:η2-PhCtCH)](PF6)2 (6b). To a solu-
tion of 1a (74.6 mg, 102.6 µmol) and AgPF6 (66 mg, 260 µmol) in
C6H6 (15 mL) was added an excess of phenylacetylene (40 µL,
363 µmol). The dark green precipitate was isolated by filtration,
extracted with CH2Cl2, reprecipitated with pentane, washed with
pentane, and dried to give 6 (60.3 mg, 52.4 µmol, 51%). 1H NMR
(CD2Cl2, 500 ΜΗz): δ 8.45 (s, 1H, PhCtCH), 7.92 (d, 1H,
o-PhCtCH), 7.79 (t, 1H, m-PhCtCH), 7.70 (m, 2H), 7.63 (m,
2H), 7.53 (t, 2H, m-PhNH), 7.41 (t, 1H, p-PhNH), 7.37 (t, 1H,
p-PhNH), 7.31 (t, 1H, m-PhNH), 7.21 (d, 1H, o-PhNH), 6.91 (d,
2H, o-PhNH), 6.78 (d, 1H, o-PhNH), 6.00 (s, br, 1H, NH), 4.70
(s, br, 1H, NH), 1.516 (s, 30H, Cp*). ESI/MS (CH3CN): m/z 905
([Cp*2Ru2(NHPh)2(PhCCH)PF6]+). Two independent samples were
analyzed. Anal. Found: C, 39.89; H, 3.83; N, 2.14. Found: C,
40.76; H, 4.24; N, 2.30; Cl, 0.55. These values are low for 6b (calcd
for C40H48F12N2P2Ru2: C, 45.8; H, 4.61; N, 2.67) but are consistent
with 6b‚AgCl (calcd for C40H48AgClF12N2P2Ru2: C, 40.30; H, 4.06;
N, 2.35; Cl, 2.97), except for the low Cl. Dissolving these samples
in C6H6 gave solutions that slowly deposited white solids, consistent
with AgCl as a contaminant.
Mixture of TolNHNHTol, p-TolNHNHPh, and PhNHNHPh.
This mixture was synthesized by following a modification of a
literature procedure.60 A solution of nitrobenzene (0.77 g,
6.3 mmol), nitrotoluene (2.765 g, 19.5 mmol), and aluminum
powder (1.4 g, 52 mmol) in methanol (14 mL) was treated with
KOH (8.3 g, 148 mmol). The mixture was stirred for 20 min, and
then aliquots of Al, KOH, and MeOH were added at 10 min
intervals until no azo compound was seen by TLC. The reaction
was quenched, and the product was extracted according to literature
procedures and recrystallized from hexanes. The 1H NMR spectrum
of the hydrazine mixture showed a 1:0.7 ratio of Ph and Tol groups,
but the unsymmetrical hydrazine could not be separately quantified
because its resonances are coincident with those of the symmetric
hydrazines. GC-MS analysis of the mixture (as an ether solution)
shows separate peaks for the corresponding azo compounds,
allowing for the indirect detection of the mixed hydrazine. The ratio
from GC-MS, 1.68:1:1.97 PhPh, TolTol, and PhTol (azo derivative
retention times 18.7, 21.7, and 20.2 min, respectively), is in
agreement with the Ph to Tol ratio obtained from integration of
1
the H NMR spectrum.
[Cp*Ru(µ-NHPh)(OTf)]2 (4) AgOTf (2.4 mg, 9 µmol) and 1a
(3.2 mg, 4.5 µmol) were dissolved in C6D6 in a J. Young tube.
The solution turned dark brown with the precipitation of AgCl. 1H
NMR (C6D6, 500 ΜΗz): δ 12.35 (s, 1H, NH), 8.01 (d, 1H, o),
7.07 (m, 1H, m), 6.93 (m, 2H, o, p), 6.43 (d, 1H, m), 0.976 (s,
15H, Cp*). 13C{1H} NMR (C6D6): δ 156.12 (i), 131.80, 130.16,
128.60, 126.23, 125.88, 121.864, 96.12 (C5(CH3)5), 8.48 (C5(CH3)5).
19F NMR (C6D6): δ -78.1.
[Cp*Ru(µ-NHPh)2RuCp*(H2O)](OTf)2 (5). AgOTf (50 mg,
0.349 mmol) and 1a (40 mg, 0.110 mmol) were combined in C6H6
(10 mL) and stirred for 30 min before filtration of the AgCl solids.
Degassed, wet C6H6 (2 mL) was added to the resulting solution,
and the mixture was stirred for 20 h. The resulting dark solids were
filtered, washed with C6H6 (1 mL) and pentane (2 × 1 mL), and
Acknowledgment. We are grateful to the University of
Washington and the National Science Foundation (Grant No.
CHE-0513023) for support of this work.
1
dried to give 28 mg (0.058 mmol, 53%). H NMR (C6D6, 200
ΜΗz): δ 11.77 (s, 1H, NH), 8.56 (d, J ) 7, 1H, o), 7.06 (t, J )
7, 1H), 6.82 (t, J ) 8, 1H), 6.66 (t, J ) 8, 1H), 5.91 (d, J ) 8, 1H,
o), 0.83 (s, 15H, Cp*). 19F NMR (C6D6): δ -79.2. 19F NMR (CD2-
Cl2): δ -79.1. The product was recrystalized from CH2Cl2/pentane
at -78 °C and analyzed. Anal. Found: C, 39.67; H, 4.27; N, 2.74.
These values are low for 5 (calcd for C68H86F12N4O13Ru4S4AgCl:
C, 41.97; H, 4.56; N, 2.88) but are consistent with a 1:1 mixture
of 5 and 4‚AgCl (calcd for C34H43AgClF12N4O13Ru4S4: C, 39.43;
Supporting Information Available: Figures giving an Eyring
plot for phenyl rotation in 1a, 2D HMQC and HMBC spectra of
1
6a-13C2, NOESY of 6a, and H NMR spectra of 2, 4, 5, and 6b
and a CIF file for 1a. This material is available free of charge via
the Internet at http://pubs.acs.org.
OM0700462