Diastereospecific and diastereoselective syntheses of ruthenium(II) complexes using N,N′ bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N and their oxidation to imine ligands

Article abstract of DOI:10.1021/ic051590a

Coordination of N,N′ bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH₂-2-C₅H₄N 1 (Ar = 4-CH ₃-C₆H₄, 1a; 4-CH₃O-C ₆H₄, 1b; 2,6-(CH₃)₂-C ₆H₃, 1c; 4-CF₃-C₆H₄, 1d) to the moieties [Ru(bipy)₂]²⁺, [Ru(η⁵- C₅H₅)L]⁺ (L = CH₃CN, CO), or [Ru(η⁶-arene)Cl]²⁺ (arene = benzene, p-cymene) occurs under diastereoselective or diastereospecific conditions. Detailed stereochemical analysis of the new complexes is included. The coordination of these secondary amine ligands activates their oxidation to imines by molecular oxygen in a base-catalyzed reaction and hydrogen peroxide was detected as byproduct. The amine-to-imine oxidation was also observed under the experimental conditions of cyclic voltammetry measurements. Deprotonation of the coordinated amine ligands afforded isolatable amido complexes only for the ligand (1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine, 1e, which doesn't contain hydrogen atoms in a β position relative to the N-H bond. The structures of [Ru(2,2′-bipyridine)₂(1b)](PF₆)₂, 2b; [Ru(2,2′-bipyridine)₂(1c)](PF₆)₂, 2c; trans-[RuCl₂(COD)(1a)], 3; and [RuCl₂(η⁶- C₆H₆)(1a)]PF₆, 4a, have been confirmed by X-ray diffraction studies.

Full text of DOI:10.1021/ic051590a

Inorg. Chem. 2006, 45, 2483−2493
Diastereospecific and Diastereoselective Syntheses of Ruthenium(II)
Complexes Using N,N Bidentate Ligands Aryl-pyridin-2-ylmethyl-amine
ArNH-CH2-2-C5H4N and Their Oxidation to Imine Ligands
′
Javier Go´mez,† Gabriel Garc´ıa-Herbosa,*,† Jose´ V. Cuevas,† Ana Arna´iz,† Arancha Carbayo,†
Asuncio´n Mun˜oz,† Larry Falvello,‡ and Phillip E. Fanwick§
Departamento de Qu´ımica, Facultad de Ciencias, UniVersidad de Burgos, 09001 Burgos, Spain,
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, UniVersidad de Zaragoza, Zaragoza,
Spain, and Department of Chemistry, Purdue UniVersity, West Lafayette, Indiana 47907-1393
Received September 16, 2005
Coordination of N,N
′
bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N 1 (Ar
)
4-CH3-C6H4, 1a;
4-CH3O-C6H4, 1b; 2,6-(CH3)2-C6H3, 1c; 4-CF3-C6H4, 1d) to the moieties [Ru(bipy)2]2+, [Ru(
η
5-C5H5)L]+ (L
)
CH3CN,
+
CO), or [Ru(
η
6-arene)Cl]2 (arene
)
benzene, p-cymene) occurs under diastereoselective or diastereospecific
conditions. Detailed stereochemical analysis of the new complexes is included. The coordination of these secondary
amine ligands activates their oxidation to imines by molecular oxygen in a base-catalyzed reaction and hydrogen
peroxide was detected as byproduct. The amine-to-imine oxidation was also observed under the experimental
conditions of cyclic voltammetry measurements. Deprotonation of the coordinated amine ligands afforded isolatable
amido complexes only for the ligand (1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine, 1e, which doesn’t contain hydrogen
atoms in a
â
position relative to the N
−
H bond. The structures of [Ru(2,2
′
-bipyridine)2(1b)](PF6)2, 2b; [Ru(2,2
′-
bipyridine)2(1c)](PF6)2, 2c; trans-[RuCl2(COD)(1a)], 3; and [RuCl2(
η
6-C6H6)(1a)]PF6, 4a, have been confirmed by
X-ray diffraction studies.
Chart 1
Introduction
The state of the art in stereoselective synthesis in
coordination chemistry was reviewed by Knof and von
Zelewsky in 1999.1 They pointed out its relevance to such
important subjects as enantioselective catalysis, supramo-
lecular chemistry, and bioinorganic chemistry. To achieve
stereoselectivity at the metal center, one must modify the
ligands to introduce an element of chirality. Thus, for
instance, diastereospecificity has been reported, and qualified
as surprising, for 5,5′-(L-valine) amino acid substituted 2,2′-
bipyridyl ligands in the tris-chelated octahedral complexes
[M(NN)3]2+ (M ) FeII and CoII) with ∆ and Λ helical
structures.2 Diastereoselectivity has also been reported in the
reaction of the octahedral complexes (∆,Λ)-[Ru(2,2′-
bipyridine)2Cl2] with (R)-(+)-methyl-p-tolylsulfoxide to give
[Ru(2,2′-bipyridine)2(methyl-p-tolylsulfoxide)Cl]+, in which
the ∆,R isomer formed with a diastereomeric excess of nearly
50% over the Λ,R isomer.3,4 This represented the first process
by which a ligand occupying only a single coordination site
has had such an important influence on the stereochemical
outcome of ruthenium bis(bipyridine) complex formation.
In the foregoing examples, stereoselectivity was achieved
by using enantiomerically pure ligands. The results reported
here show that diastereoselectivity and diastereospecificity
can be observed using ligands 1 (see Chart 1). Once
* To whom correspondence should be addressed. Fax: 34 947 258 831.
Tel: 34 947 258 822. E-mail: gherbosa@ubu.es.
† Universidad de Burgos.
‡ Universidad de Zaragoza.
§ Purdue University.
(1) Knof, U.; von Zelewsky, A. Angew. Chem., Int. Ed. 1999, 38, 303-
322.
(2) Telfer, S. G.; Bernardinelli, G.; Williams, A. F. Chem. Commun. 2001,
1498-1499.
10.1021/ic051590a CCC: $33.50
Published on Web 02/16/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 6, 2006 2483

Go´mez et al.
coordinated to a metal in a chelating fashion, this kind of
ligand has two sources of chirality. One is the amine nitrogen
atom that is bonded to four different substituents (i.e., R or
S configuration) and the other is the δ,λ conformation of
the nonplanar five-membered chelate ring formed upon
coordination. Although facile inversion at the amino nitrogen
atom precludes separation of the enantiomers of the ligands,
the coordination to the octahedral or tetrahedral ruthenium(II)
metal complexes turned out to be diastereospecific or
diastereoselective as discussed below.
Dehydrogenation of secondary amines to imines,5-11 along
with the reverse process,12 is a subject of current interest.13,14
Herein we report that the amino complexes we have prepared
can be oxidized to imines by molecular oxygen in a base-
catalyzed reaction. This could be relevant to the subject of
oxidation of amines under green and sustainable chemistry
conditions and supports the mechanism proposed for the
oxidation of primary amines to imines and further to nitriles
in the presence of molecular oxygen.15,16 This mechanism
supplies an alternative pathway to that proposed by Keene
for the oxidative dehydrogenation of coordinated amines.17
explored as a means of obtaining amido complexes. Stable
amido complexes of ruthenium(II) have been obtained only
when â hydrogen atoms were avoided.
Experimental Section
Unless otherwise stated, all manipulations were carried out under
nitrogen using standard Schlenk techniques. Solvents were dried
and stored under nitrogen. Amine ligands 1a-d and dehydrogenated
imines (1-H2)a-d were prepared as described elsewhere.22
The starting compounds cis-[Ru(2,2′-bipyridine)2Cl2]‚2H2O,23
[RuCl2(η4-1,5-cyclooctadiene)]n,24 [RuCl2(CH3CN)(η6-C6H6)],25
[RuCl2(η6-C6H6)]2,26 [RuCl2(η6-p-cymene)]2,26 [Ru(η5-C5H5)(CH3-
CN)3]PF6,27 and [Ru(η5-C5H5)(CO)(CH3CN)2]PF627 were prepared
according to the literature. All other starting reagents were used as
commercially obtained.
1H NMR spectra were recorded on Varian VXR200S, Bruker
ARX 300, and Varian Unity Inova-400 spectrometers. Chemicals
shifts are in ppm relative to SiMe4 (TMS) as the external standard.
The IR spectra were recorded as KBr disks on a Nicolet Impact
410, and elemental analyses were made on a Leco CHNS 932.
Cyclic voltammetry was carried out using an EG&G VersaStat
potentiostat in conjunction with a three-electrode cell using 0.1 M
n
[NBu4 ][PF6] solutions in CH2Cl2, a Pt bead electrode, and the
As previously reported,18 amido complexes are intermedi-
ate in the oxidation of metal-coordinated amines to imines.
The amino-amido conversion is of great importance in the
catalyzed hydrogen-transfer reactions through the ruthenium-
nitrogen ligand bifunctional mechanism in which â hydrogen
atoms are present in the N-donor ligand and the use of chiral
amine effects asymmetric transformations.19,20 Nevertheless,
stable ruthenium complexes with terminal (nonbridging)
amido ligands containing â hydrogen atoms are not very
common.21 Deprotonation of amine complexes has been
saturated calomel electrode (SCE) as reference. Under the conditions
used, E0′ for the one-electron oxidation of [Fe(η5-C5H5)2], added
to the test solutions as an internal calibrant, is 0.47 V.
Syntheses
(1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine (1e). A 250 mL
flask equipped with a stir bar and Dean-Stark glassware was
charged with 2-acetylpyridine (5.7 g, 43.7 mmol), p-toluidine (p-
methylaniline; 4.68 g, 43.7 mmol), and a catalytic amount of
p-toluenesulfonic acid in toluene (125 mL). It was refluxed for 3
h. The solution was evaporated to dryness. The precipitate was
recrystallized in hexane and dried in vacuo, yielding a white solid
product identified as the product of condensation, (1-pyridin-2-yl-
ethylidene)-p-tolyl-amine28 (9.0 g, 98%). 1H NMR (CDCl3): δ 8.66
(1 H, m, py), 8.27 (1 H, dd, py H5), 7.76 (1 H, tt, py H4), 7.34 (1
H, m, py), 7.18 (2 H, d, Ar), 6.74 (2 H, d, Ar), 2.37 (6 H, s, Meim
+ MeAr). Anal. Calcd. for C14H14N2: C, 79.97; H, 6.71; N, 13.32.
Found: C, 80.12; H, 6.65; N, 13.09.
(3) Pezet, F.; Daran, J. C.; Sasaki, I.; Ait-Haddou, H.; Balavoine, G. G.
A. Organometallics 2000, 19, 4008-4015.
(4) Hesek, D.; Inoue, Y.; Everitt, S. R. L.; Ishida, H.; Kunieda, M.; Drew,
M. G. B. Inorg. Chem. 2000, 39, 317-324.
(5) Gu, X. Q.; Chen, W.; Morales-Morales, D.; Jensen, C. M. J. Mol.
Catal. A: Chem. 2002, 189, 119-124.
(6) Aidyn, A.; Medzhidov, A. A.; Fatullaeva, P. A.; Tashchioglu, S.;
Yalchin, B.; Saiyn, S. Russ. J. Coord. Chem. 2001, 27, 486-492.
(7) Coalter, J. N.; Huffman, J. C.; Caulton, K. G. Organometallics 2000,
19, 3569-3578.
To a stirred and cooled (at -50 °C) solution of (1-pyridin-2-
yl-ethylidene)-p-tolyl-amine (2.0 g, 9,52 mmol) in tetrahydrofuran
(10 mL) was slowly added 20 mL of a solution of 1.4 M LiMe (28
mmol). The solution was then stirred for 36 h at -50 °C and, after
warming to room temperature, water (15 mL) was added. The
tetrahydrofuran was removed in a rota-vapor. The organic residue
was extracted with diethyl ether (3 × 20 mL) and dried over
anhydrous MgSO4. The filtered solution was evaporated to dryness.
(8) El-Hendawy, A. M.; Alqaradawi, S. Y.; Al-Madfa, H. A. Transition
Met. Chem. 2000, 25, 572-578.
(9) Ell, A. H.; Samec, J. S. M.; Brasse, C.; Backvall, J. E. Chem. Commun.
2002, 1144-1145.
(10) Weeks, C. L.; Turner, P.; Fenton, R. R.; Lay, P. A. J. Chem. Soc.,
Dalton Trans. 2002, 931-940.
(11) Mukaiyama, T.; Kawana, A.; Fukuda, Y.; Matsuo, J. Chem. Lett. 2001,
390-391.
(12) Samec, J. S. M.; Backvall, J. E. Chem.sEur. J. 2002, 8, 2955-2961.
(13) Kamiguchi, S.; Nakamura, A.; Suzuki, A.; Kodomari, M.; Nomura,
M.; Iwasawa, Y.; Chihara, T. J. Catal. 2005, 230, 204-213.
(14) Cabort, A.; Therrien, B.; Stoeckli-Evans, H.; Bernauer, K.; Suss-Fink,
G. Inorg. Chem. Commun. 2002, 5, 787-790.
1
The residue was distilled in vacuo. Yield: 2.65 g, 85%. H NMR
(200 MHz, CDCl3): δ 8.61 (m, 1H, py H6), 7.59 (m, 2H, py H3-5),
7.13 (m, 1H, H4), 6.55 (m, 4H, Ar), 2.17 (s, 3H, Me-Ar), 1.67 (s,
(15) Mori, K.; Yamaguchi, K.; Mizugaki, T.; Ebitani, K.; Kaneda, K. Chem.
Commun. 2001, 461-462.
(22) Cuevas, J. V.; Garcia-Herbosa, G.; Munoz, A.; Garcia-Granda, S.;
Miguel, D. Organometallics 1997, 16, 2220-2222.
(23) Sullivan, B. P.; Salmon, D. J.; Meyer, T. J. Inorg. Chem. 1978, 17,
3334-3341.
(24) Albers, M. O.; Ashworth, T. V.; Oosthuisen, H. E.; Singleton, E. Inorg.
Synth. 1989, 26, 69.
(25) Takahashi, H.; Kobayashi, K.; Osawa, M. 2000, 16, 777-779.
(26) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974, 233-
241.
(27) Gill, T. P.; Mann, K. R. Organometallics 1982, 1, 485-488.
(28) Dieck, H. T.; Bruder, H.; Kuhl, E.; Junghans, D.; Hellfeldt, K. New
J. Chem. 1989, 13, 259-268.
(16) Yamaguchi, K.; Mizuno, N. Angew. Chem., Int. Ed. 2003, 42, 1480-
1483.
(17) Keene, F. R. Coord. Chem. ReV. 1999, 187, 121-149.
(18) Gunnoe, T. B.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc. 1996,
118, 6916-6923.
(19) Yamakawa, M.; Ito, H.; Noyori, R. J. Am. Chem. Soc. 2000, 122,
1466-1478.
(20) Abbel, R.; Abdur-Rashid, K.; Faatz, M.; Hadzovic, A.; Lough, A. J.;
Morris, R. H. J. Am. Chem. Soc. 2005, 127, 1870-1882.
(21) Gao, J. X.; Wan, H. L.; Wong, W. K.; Tse, M. C.; Wong, W. T.
Polyhedron 1996, 15, 1241-1251.
2484 Inorganic Chemistry, Vol. 45, No. 6, 2006

Synthesis of Ruthenium(II) Complexes Using ArNH-CH2-2-C5H4N
3
2
6H, Me2-C). Anal. Calcd for C15H18N2: C, 79.61; H, 8.02; N, 12.38.
Found: C, 79.21; H, 7.86; N, 12.24.
Hz, JHa-NH ) 4.3 Hz, N-H), 5.64 (dd, 1H, JHb-Ha ) 15.5 Hz,
3JHb-NH ) 11.9 Hz, CHaHb), 4.42 (m, 1H, -CH-cod), 4.66 (m,
2
3
1H, -CH-cod), 4.38 (dd, 1H, JHb-Ha ) 15.5 Hz, JHa-NH ) 4.3
Hz, CHaHb), 3.92 (m, 1H, -CH-cod), 3.59 (m, 1H, -CH-cod),
2.80 (m, 1H, -CH2(exo)-cod), 2.69 (m, 1H, -CH2(exo)-cod), 2.50
(m, 1H, -CH2(exo)-cod), 2.34 (m, 1H, -CH2(exo)-cod), 2.29 (s, 1H,
Me), 2.21 (m, 1H, -CH2(endo)-cod), 2.07 (m, 1H, -CH2(endo)-cod),
1.93 (m, 1H, -CH2(endo)-cod), 1.74 (m, 1H, -CH2(endo)-cod). 13C
NMR (100 MHz, CDCl3): δ 160.4, 149.8, 142.6, 137.9, 135.9,
129.9, 124.4, 122.2, 120.1, 92.2, 91.8, 88.1, 87.9, 60.1, 59.2, 30.3,
29.2, 28.6, 21.1. Anal. Calcd for C21H26Cl2N2Ru: C, 52.72; H, 5.48;
N, 5.86. Found: C, 52.51; H, 5.38; N, 5.49.
[Ru(2,2′-bipyridine)2(1)](PF6)2 (2). Compounds 2a-c were
prepared in the same way. The procedure for the synthesis of 2a is
described here. To a solution of cis-[Ru(2,2′-bipyridine)2Cl2]‚2H2O
(0.1 g, 0.22 mmol) in ethanol (20 mL) was added 1a (44 mg, 0.22
mmol). The mixture was refluxed for 4 h. After the solution was
cooled to room temperature, glacial acetic acid (three drops) and
NH4PF6 (300 mg, 1.84 mmol) dissolved in water (10 mL) were
added. The solution was boiled and partially concentrated. The
solution was cooled overnight in the fridge. The precipitate was
collected, washed with ether (10 mL), and dried in vacuo. The
product was dissolved in acetone (10 mL), and hexane (10 mL)
was added to induce precipitation. Yield: 170 mg, 85%. 1H NMR
(400 MHz, acetone-d6): δ 9.77 (d,1H), 8.87 (d, 1H), 8.76 (d, 1H),
8.54 (d, 1H), 8.44 (d, 1H), 8.33 (td, 2H), 8.06 (td, 2H), 7.99 (td,
2H), 7.96-7.83 (m, 5H), 7.79 (d, 1H), 7.75 (m, 1H), 7.58 (d, 1H),
7.40 (m, 1H), 7.32 (m, 2H), 6.44 (m, 4H, Ar), 5.04 (dd, 1H, 2JHa-Hb
[Ru(η6-C6H6)(1)Cl]PF6 (4). Compounds 4a-e were prepared
in the same way. The synthesis of 4a is described here. To a
suspension of [RuCl2(η6-C6H6)]2 (145 mg, 0.29 mmol) in aceto-
nitrile (10 mL) was added 1a (115 mg, 0.58 mmol). The mixture
was stirred at room temperature for 1 h. The mixture was evaporated
to dryness, and the solid was treated with ethanol (5 mL) and NaPF6
(164 mg, 1 mmol). The addition of water (10 mL) led to a yellow
solid that was collected by filtration, washed with water followed
by diethyl ether, and dried in vacuo. Yield: 232 mg, 72%. 1H NMR
(200 MHz, acetone-d6): δ 9.22 (m, 1H, py H6), 8.11 (td, 1H, py),
7.78 (m, 1H, py), 7.63 (m, 1H, py), 7.51 (m, 4H, Ar), 6.47 (br,
3
2
) 15.1 Hz, JHa-NH ) 5.0 Hz, CHaHb), 4.95 (dd, 1H, JHa-Hb
)
15.1 Hz, JHb-NH ) 6.0 Hz, CHaHb), 2.08 (s, 3H, Me).13C NMR
(100 MHz, acetone-d6): δ 162.7, 158.7, 158.6 157.8, 157.7, 152.8,
152.5, 152.3, 152.1, 150.9, 141.4, 138.3 138.1, 137.9, 137.3, 136.9,
134.9, 129.4, 128.3, 128.0, 127.5, 126.8, 125.6, 124.9, 124.8, 124.2,
123.7, 123.2, 118.2, 56.1, 19.9. IR (KBr, cm-1): 3287 (ν(NH)), 856-
828 (ν(P-F)). Anal. Calcd for C33H30F12N6P2Ru: C, 43.96; H, 3.35;
N, 9.32. Found: C, 43.74; H, 3.31; N, 9.21.
3
2
1H, NH), 5.70 (s, 6H, C6H6), 5.47 (dd, 1H, JHb-Ha ) 15.1 Hz,
2
3JHb-NH ) 10.6 Hz, CHaHb), 4.70 (dd, 1H, JHb-Ha ) 15.1 Hz,
3JHa-NH ) 3.2 Hz, CHaHb), 2.41 (s, 3H, Me). IR (KBr, cm-1):
3184 (ν(NH)), 850 (ν(P-F)). Anal. Calcd for C19H20ClN2PF6Ru: C,
40.91; H, 3.61; N, 5.02. Found: C, 41.29; H, 3.80; N, 4.92.
1
2b. Yield: 89%. H NMR (400 MHz, acetone-d6): δ 9.69 (d,
1H), 8.85 (d, 1H), 8.73 (d, 1H), 8.54 (d, 1H), 8.46 (d, 1H), 8.31
(td, 1H), 8.22 (m, 2H), 8.04 (td, 1H), 7.97 (td, 1H), 7.91-7.72 (m,
6H), 7.56 (d, 1H), 7.38 (tc, 1H), 7.30 (tc, 1H), 6.34 (m, 4H, Ar),
4.99 (dd, 1H, 2JHa-Hb ) 16.4 Hz, 3JHa-NH ) 8.3 Hz CHaHb), 4.91
1
4b. Yield: 82%. H NMR (200 MHz, acetone-d6): δ 9.22 (m,
1H, py H6), 8.11 (td, 1H, py), 7.78 (m, 1H, py), 7.67 (m, 1H, py),
7.52 (m, 4H, Ar), 6.43 (br, 1H, NH), 5.72 (s, 6H, C6H6), 5.45 (dd,
2
3
2
3
1H, JHb-Ha ) 14.8 Hz, JHb-NH ) 11.2 Hz, CHaHb), 4.69 (dd,
1H, 2JHb-Ha ) 14.8 Hz, 3JHa-NH ) 11.2 Hz, CHaHb), 3.88 (s, 3H,
MeO). IR (KBr, cm-1): 3182 (ν(NH)), 849 (ν(P-F)). Anal. Calcd for
C19H20ClN2OPF6Ru: C, 39.76; H, 3.52; N, 4.88. Found: C, 39.20;
H, 3.30; N, 4.90.
(dd, 1H, JHa-Hb ) 16.4 Hz, JHb-NH ) 5.7 Hz CHaHb), 3.61 (s,
3H, CH3). 13C NMR (100 MHz, acetone-d6): δ 162.6, 158.6, 158.5,
157.9, 157.7, 157.1, 152.8, 152.3, 152.2, 152.1, 150.9, 138.3, 138.0,
137.9, 137.2, 136.9, 136.7, 128.3, 128.0, 127.5, 126.8, 125.6, 124.9,
124.8, 124.2, 123.6, 123.2, 119.4, 114.1, 56.4, 55.2. IR (KBr, cm-1):
3294 (ν(NH)), 846-842 (ν(P-F)). Anal. Calcd for C33H30F12N6-
OP2Ru: C, 43.19; H: 3.29; N, 9.16. Found: C, 42.85; H, 3.12; N,
9.21.
1
4c. Yield: 80%. H NMR (200 MHz, acetone-d6): δ 9.62 (m,
1H, py H6), 8.12 (td, 1H, py), 7.64 (m, 1H, py), 7.29 (m, 1H, py),
7.20 (m, 4H, Ar), 6.74 (br, 1H, NH), 5.79 (s, 6H, C6H6), 4.95 (dd,
2
3
1
1H, JHb-Ha ) 19 Hz, JHb-NH ) 9.6 Hz, CHaHb), 4.62 (dd, 1H,
2c. Yield: 90%. H NMR (400 MHz, acetone-d6): δ: 9.62 (d,
2JHb-Ha ) 19 Hz, JHa-NH ) 3.8 Hz, CHaHb), 2.64 (s, 3H, Me),
3
1H), 8.76 (d, 1H), 8.68 (d, 1H), 8.58 (d, 1H), 8.25 (m, 2H), 8.16
(d, 1H), 8.01 (t, 2H), 7.94-7.84 (m, 3H), 7.80 (d, 1H), 7.64 (d,
1H), 7.59 (t, 1H), 7.51 (d, 1H), 7.45 (d, 1H), 7.36 (t, 2H), 7.25
(dd, 1H, NH), 7.04 (d, 1H), 6.69 (t, 1H), 6.54 (d, 1H), 6.37 (d, 1H),
5.62 (dd, 1H, 2JHa-Hb ) 19.6 Hz, 3JHa-NH ) 9.6 Hz, CHaHb), 5.19
2.31 (s, 3H, Me). IR (KBr, cm-1): 3184 (ν(NH)), 849 (ν(P-F)). Anal.
Calcd for C20H22ClN2PF6Ru: C, 42.00; H, 3.88; N, 4.90. Found:
C, 41.75; H, 3.67; N, 5.15.
1
4d. Yield: 76%. H NMR (200 MHz, acetone-d6): δ 9.22 (m,
1H, py H6), 8.12 (td, 1H, py), 7.93 (m, 4H, Ar), 7.80 (m, 1H, py),
7.65 (m, 1H, py), 6.72 (br, 1H, NH), 5.76 (s, 6H, C6H6), 5.57 (dd,
2
3
(dd, 1H, JHa-Hb ) 19.6 Hz, JHb-NH ) 2.5 Hz, CHaHb), 1.72 (s,
3H, CH3), 1.69 (s, 3H, CH3). 13C NMR (100 MHz, acetone-d6): δ
165.3, 158.7, 158.5, 158.1, 157.9, 153.4, 152.9, 152.7, 152.4, 151.1,
142.1, 138.6, 138.2, 138.0, 137.7, 137.5, 132.0, 129.2, 128.7, 128.5,
127.8, 127.3, 127.2, 126.7, 125.9, 125.5, 125.0, 124.8, 123.9, 123.5,
122.2, 58.1, 23.1, 16.8. IR (KBr, cm-1): 3330 (ν(NH)), 853-830
(ν(P-F)). Anal. Calcd for C34H32F12N6P2Ru: C, 44.60; H: 3.52; N,
9.18. Found: C, 44.37; H, 3.51; N, 9.21.
2
3
1H, JHb-Ha ) 15.0 Hz, JHb-NH ) 11.4 Hz, CHaHb), 4.77 (dd,
1H, 2JHb-Ha ) 15.0 Hz, 3JHa-NH ) 3.0 Hz, CHaHb). IR (KBr, cm-1):
3186, (ν(NH)), 852 (ν(P-F)). Anal. Calcd for C19H17ClN2PF9Ru: C,
37.30; H, 2.80; N, 4.58. Found: C, 36.70; H, 2.61; N, 4.63.
1
4e. Yield: 78%. H NMR (200 MHz, acetone-d6): δ 9.35 (d,
1H, py H6), 8.17 (t, 1H, py), 7.76 (d, 1H, py), 7.64 (t, 1H, py),
7.41 (s, 4H, Ar), 6.02 (s, 6H, C6H6), 5.56 (br, 1H, NH), 2.43 (s,
3H, Me-Ar), 1.95 (s, 3H, Me), 1.59 (s, 3H, Me). IR (KBr, cm-1):
3169 (ν(NH)), 846 (ν(P-F)). Anal. Calcd for C21H23ClN2PF6Ru: C,
43.05; H, 4.13; N, 4.88. Found: C, 43.27; H, 3.99; N, 5.01.
[Ru(η6-p-cymene)(1)Cl]PF6 (5). Compounds 5d,e were prepared
in the same way. The procedure for the synthesis of 5d is described
here. To a solution of [RuCl2(η6-p-cymene)]2 (100 mg, 0.163 mmol)
in dichloromethane (10 mL) was added 1d (89 mg, 0.35 mmol).
After being stirred for 1.5 h at room temperature, the mixture was
evaporated to dryness. Ethanol (5 mL) was added to the residue,
trans-[Ru(1,5-cyclooctadiene)(1a)Cl2] (3). To a suspension of
[RuCl2(η4-1,5-cyclooctadiene)]n (201.7 mg, 0.72 mmol) in ethanol
(20 mL) was added 1a (150 mg, 0.72 mmol). The mixture was
refluxed for 1 h. After being cooled overnight at -20 °C, the yellow
solid was collected and washed with ethanol (10 mL) and diethyl
ether (10 mL). The product was dissolved in chloroform (10 mL).
The addition of n-hexane and concentration to induce precipitation
afforded the complex (245 mg, 72%). 1H NMR (400 MHz,
CDCl3): δ 7.89 (m, 1H, py H6), 7.74 (td, 1H, py), 7.27 (t, 1H, py),
7.26 (m, 4H, Ar), 7.17 (m, 1H, py), 6.83 (dd, 1H, 3JHb-NH ) 11.9
Inorganic Chemistry, Vol. 45, No. 6, 2006 2485

Go´mez et al.
and the solution was treated with NaPF6 (200 mg, 1.2 mmol) and
water (30 mL). The solid was collected and dried in vacuo. Yield:
138 mg, 76%. H NMR (200 MHz, acetone-d6): δ 9.18 (m, 1H,
3H, C(MeMe)), 1.58 (s, 3H, C(MeMe)). IR (KBr, cm-1): 1975
(ν(CO)), 844 (ν(P-F)). Anal. Calcd for C21H23N2OPF6Ru: C, 44.61;
H, 4.10; N, 4.95. Found: C, 44.51; H, 3.89; N, 4.75.
[Ru(2,2′-bipyridine)2(1-H2)](PF6)2 (8). (a) Imine derivatives
8a-d were prepared as described for amine-related compounds 2
but using the imine ligands (1-H2)a-d.
1
py H6), 8.16 (td, 1H, py), 7.94 (m, 4H, Ar), 7.84 (m, 1H, py), 7.71
(m, 1H, py), 6.59 (br, 1H, NH), 5.74 (m, 2H, Ar p-cymene), 5.52
(dd, 1H, 2JHb-Ha ) 15.0 Hz, 3JHb-NH ) 12.0 Hz, CHaHb), 5.33 (d,
1H, Ar p-cymene), 5.12 (d, 1H, Ar p-cymene), 4.77 (dd, 1H, 2JHb-Ha
) 15.0 Hz, 3JHa-NH ) 3.0 Hz, CHaHb), 2.69 (hept, 1H, CH(Me)2),
2.00 (s, 3H, p-Me cymene), 1.15 (d, 3H, CH-MeMe), 1.01 (d, 3H,
CH-MeMe). IR (KBr, cm-1): 3285 (ν(NH)), 846 (ν(P-F)). Anal. Calcd
for C22H26ClN2PF6Ru: C, 40.35; H, 3.69; N, 4.28. Found: C, 40.70;
H, 3.49; N, 4.37.
5e. Yield: 71%.1H NMR (200 MHz, acetone-d6): δ 9.30 (m,
1H, py H6), 8.21 (m, 1H, py), 7.98 (m, 1H, Ar), 7.79 (d, 1H, py),
7.70 (m, 1H, py), 7.52 (m, 1H, Ar), 7.28 (m, 1H, Ar), 7.05 (m,
1H, Ar), 6.37 (m, 1H, Ar p-cymene), 6.03 (m, 1H, Ar p-cymene),
5.82 (m, 1H, Ar p-cymene), 5.48 (br, 1H, NH), 5.04 (m, 1H, Ar
p-cymene), 2.81 (hept, 1H, CH(Me)2), 2.42 (s, 3H, p-Me Ar), 2.04
(s, 3H, Me p-cymene), 2.00 (s, 3H, N-CMeMe), 1.95 (d, 3H, CH-
MeMe), 1.59 (s, 3H, N-CMeMe), 1.13 (d, 3H, CH-MeMe.) IR
(KBr, cm-1): 3285 (ν(NH)), 846 (ν(P-F)). Anal. Calcd for C22H26-
ClN2PF6Ru: C, 40.35; H, 3.69; N, 4.28. Found: C, 40.70; H, 3.49;
N, 4.37.
1
8a. Yield: 82%. H NMR (400 MHz, acetone-d6): δ 9.36 (s,
1H, HCdN), 8.88 (dc, 1H), 8.84 (m, 2H), 8.54 (m, 2H), 8.34 (dd,
1H), 8.30-8.18 (m, 4H), 8.12 (d, 1H), 8.06 (dc, 1H), 7.99 (dc,
1H), 7.96-7.91 (m, 2H), 7.74 (tc, 1H), 7.69 (tc, 1H), 7.63 (tc, 1H),
7.55 (tc, 1H), 7.40 (tc, 1H), 6.78 (m, 4H, Ar), 2.16 (s, 3H, Me).
13C NMR: δ 168.7, 157.7, 157.3, 157.2, 157.1, 156.9, 153.4, 152.4,
152.3, 152.1, 152.0, 147.0, 138.8, 138.6, 138.5, 138.4, 138.1, 137.9,
130.8, 129.7, 129.2, 128.4, 128.3, 128.0, 127.6, 124.8, 124.7, 123.9,
123.7, 121.4, 20.2. IR (KBr, cm-1): 846-842 (ν(P-F)). Anal. Calcd
for C33H28F12N6P2Ru: C, 43.89; H, 3.17; N, 9.09. Found: C, 44.01;
H, 3.24; N, 9.23.
Salt 8a was the resulting product when the reaction used to
prepare 2a was carried out in air. Yield: 78%.
1
8b. Yield: 85%. H NMR (400 MHz, acetone-d6): δ 9.32 (s,
1H, HCdN), 8.87-8.80 (m, 3H), 8.52 (dd, 2H), 8.36 (m, 1H), 8.26
(td, 1H), 8.20 (m, 3H), 8.09 (d, 1H), 8.06 (d, 1H), 7.98-7.93 (m,
3H), 7.72 (tt, 1H), 7.67 (tt, 1H), 7.61 (tt, 1H), 7.41 (tt, 1H), 6.68
(m, 4H, Ar), 3.67 (s, 3H, OMe). 13C NMR (100 MHz, acetone-d6):
δ 167.9, 160.0, 157.7, 157.3, 157.2, 157.1, 157.0, 153.4, 152.3,
152.2, 152.1, 151.9, 142.5, 138.6, 138.5, 138.0, 137.9, 130.6, 129.0,
128.4, 128.3, 128.0, 127.6, 124.8, 124.7, 123.8, 123.7, 123.0, 114.4,
55.3. IR (KBr, cm-1): 854-830 (ν(P-F)). Anal. Calcd for C33H28F12N6-
OP2Ru: C, 43.28; H, 3.08; N, 9.18. Found: C, 43.05; H, 3.10; N,
9.26.
[Ru(η5-C5H5)(1a)(CH3CN)]PF6 (6). To a solution of [Ru(η5-
C5H5)(CH3CN)3]PF6 (45 mg, 0.104 mmol) in dichloromethane (10
mL) was added 1a (22 mg, 0.111 mmol). After being stirred for 2
h at room temperature, the mixture was evaporated to dryness.
Diethyl ether (5 mL) was added to the residue, and the solid was
collected and dried in vacuo. Yield: 25.6 mg, 45%. 1H NMR (400
MHz, acetone-d6, major diastereomer): δ 9.36 (d, 1H, py), 9.25
(d, 1H, py), 8.55 (br, 1H, py), 7.98 (t, 1H, py), 7.33 (m, 4H, Ar),
4.45-4.97 (m, 2H, CH2), 3.88 (s, 5H, Cp), 2.32 (s, 3H, MeCN),
1
8c. Yield: 88%. H NMR (400 MHz, acetone-d6): δ 9.33 (s,
1H, HCdN), 8.82-8.76 (m, 3H), 8.82 (dc, 1H), 8.56 (dc, 1H),
8.46 (d, 1H), 8.43 (d, 1H), 8.30-8.20 (m, 3H), 8.15 (m, 3H), 7.92
(dc, 1H), 7.88 (td, 1H), 7.73 (tc, 1H), 7.67-7.60 (m, 2H), 7.48 (tc,
1H), 7.35 (tc, 1H), 6.90 (t, 1H), 6.82 (d, 1H), 6.63 (d, 1H), 2.22 (s,
3H, Me), 1.17 (s, 3H, Me). 13C NMR (100 MHz, acetone-d6): δ
172.7, 158.2, 157.4, 157.3, 156.4, 154.3, 152.9, 152.6, 152.0, 151.5,
146.9, 139.2, 138.8, 138.4, 138.2, 138.0, 131.4, 130.6, 129.6, 129.5,
129.0, 128.6, 128.3, 127.8, 127.7, 127.1, 126.6, 124.7, 124.6, 124.3,
122.7, 20.9, 16.5. IR (KBr, cm-1): 854-827 (νP-F). Anal. Calcd
for C34H28F15N6P2Ru: C, 41.56; H, 2.64; N, 8.81. Found: C, 41.32;
H, 2.72; N, 8.69.
1
2.28 (s, 3H, Me). H NMR (400 MHz, acetone-d6, minor diaste-
reomer): 9.36 (d, 1H, py), 9.25 (d, 1H, py), 8.55 (br, 1H, py),
7.98 (t, 1H, py), 7.33 (m, 4H, Ar), 4.45-4.97 (m, 2H, CH2), 4.26
(s, 5H, Cp), 2.46 (s, 3H, MeCN), 2.08 (s, 3H, Me). Anal. Calcd
for C20H18N3PF6Ru: C, 43.96; H, 3.32; N, 7.69. Found: C, 43.70;
H, 3.49; N, 7.37.
[Ru(η5-C5H5)(1)(CO)]PF6 (7). Compounds 7a,e were prepared
in the same way. The synthesis of 7a is described here. To a solution
of [Ru(η5-C5H5)(CO)(CH3CN)2]PF6 (40 mg, 0.095 mmol) in
dichloromethane (20 mL) was added 1a (20 mg, 0.1 mmol). After
being refluxed for 6 h, the mixture was evaporated to dryness.
Yield: 40 mg, 80%. 1H NMR (400 MHz, acetone-d6, major
diastereomer): δ 9.24 (m, 1H, py H6), 8.98 (m, 1H, py), 8.06 (m,
1H, py), 7.43 (t, 1H, py), 7.12 (m, 4H, Ar), 5.18 (s, 5H, Cp), 4.75
(dd, 1H, 2JHa-Hb ) 16.0 Hz, 3JHb-NH ) 7.4 Hz, CHaHb), 4.61 (dd,
1
8d. Yield: 80%. H NMR (400 MHz, acetone-d6): δ 9.48 (s,
1H, HCdN), 8.94 (d, 1H), 8.83 (c, 2H), 8.59 (d, 1H), 8.55 (d, 1H),
8.35-8.17 (m, 6H), 8.05 (c, 2H), 7.92 (m, 2H), 7.76-7.65 (m,
3H), 7.56 (t, 1H), 7.40 (t, 1H), 7.25 (m, 4H, Ar). 13C NMR (100
MHz, acetone-d6): δ 170.9, 157.3, 157.1, 157.0, 156.8, 153.4,
152.7, 152.5, 152.2, 152.1, 151.9, 138.9, 138.7, 138.6, 138.2, 137.9,
131.6, 129.7, 128.7, 128.4, 128.1, 127.9, 126.5, 126.4, 124.9, 124.8,
124.0, 123.7, 122.6. IR (KBr, cm-1): 854-827 (νP-F). Anal. Calcd
for C33H33F12N6P2Ru: C, 44.70; H, 3.31; N, 9.20. Found: C, 44.34;
H, 3.41; N, 9.33.
trans-[Ru(1,5-cyclooctadiene)(1a-H2)Cl2] (9). Complex 9 was
prepared as described above for complex 3 but using the imine
ligand (1a-H2). Yield: 75%. 1H NMR (400 MHz, CDCl3): δ 8.38
(s, 1H, HCdN), 8.20 (d, 1H, py H6), 7.92 (m, 2H, py), 7.51 (m,
1H, py), 7.23 (m, 4H, Ar), 4.70 (m, 2H, -CH-cod), 4.12 (m, 2H,
-CH-cod), 2.62 (m, 4H, -CH2(exo)-cod), 2.34 (s, 3H, Me), 2.13
(m, 2H, -CH2(endo)-cod), 1.99 (m, 2H, -CH2(endo)-cod). 13C NMR
(400 MHz, CDCl3): δ 168.2, 156.9, 147.3, 140.8, 138.3, 137.9,
129.7, 129.2, 128.0, 120.8, 92.5, 92.1, 29.9, 29.4, 21.3. Anal. Calcd
for C21H24Cl2N2Ru: C, 52.94; H, 5.08; N, 5.88. Found: C, 52.48;
H, 4.89; N, 5.70.
2
1H, JHa-Hb ) 16.0 Hz,3JHa-NH ) 4.4 Hz, CHaHb), 2.25 (s, 3H,
Me). 1H NMR (400 MHz, acetone-d6, minor diastereomer): δ 9.24
1
(m, H, py H6), 8.98 (m, 1H, py), 8.06 (m, 1H, py), 7.43 (t, 1H,
2
py), 7.12 (m, 4H, Ar), 4.85 (s, 5H, Cp), 4.95 (dd, 1H, JHa-Hb
)
15.3 Hz, 3JHb-NH ) 6.3 Hz, CHaHb), 4.46 (dd, 1H, 2JHa-Hb ) 15.3
Hz,3JHa-NH ) 4.0 Hz, CHaHb), 2.25 (s, 3H, Me). IR (KBr, cm-1):
3294 and 3270 (ν(NH)), 1969 (ν(CO)), 846 (ν(P-F)). Anal. Calcd for
C19H19N2OPF6Ru: C, 42.47; H, 3.56; N, 5.21. Found: C, 42.21;
H, 3.39; N, 5.46.
7e. Yield: 71%. 1H NMR (400 MHz, acetone-d6, major
diastereomer): δ 9.13 (m, 1H, py H6), 8.20 (m, 1H, py), 7.74 (m,
1H, py), 7.54 (t, 1H, py), 7.14 (m, 4H, Ar), 5.00 (s, 5H, Cp), 2.25
1
(s, 3H, Me), 1.75 (s, 3H, C(MeMe)), 1.75 (s, 3H, C(MeMe). H
NMR (400 MHz, acetone-d6, minor diastereomer): δ 9.13 (m, 1H,
py H6), 8.20 (m, 1H, py), 7.74 (m, 1H, py), 7.54 (t, 1H, py), 7.14
(m, 4H, Ar), 4.97 and 4.87 (s, 5H, Cp), 2.25 (s, 3H, Me), 1.68 (d,
2486 Inorganic Chemistry, Vol. 45, No. 6, 2006

Synthesis of Ruthenium(II) Complexes Using ArNH-CH2-2-C5H4N
Table 1. Crystal Data for Compounds 2b·CH2Cl2, 2c·2CH2Cl2, 3, and 4a·Me2CdO
2b‚CH2Cl2
2c‚2CH2Cl2
3
4a‚Me2CdO
formula
fw
a (Å)
b (Å)
c (Å)
C34H32Cl2F12N6OP2Ru
1002.57
18.573(4)
13.703(18)
16.916(6)
90
102.80(2)
90
4198.4(15)
P21/c (No. 14)
4
1.586
26(2)
0.71073
0.666
R1 ) 0.1418
wR2 ) 0.3421
R1 ) 0.4112
wR2 ) 0.4649
1.032
C36H36Cl4F12N6P2Ru
1085.52
14.2588(3)
21.5216(9)
28.1859(8)
90
C21H26Cl2N2Ru
478.41
9.052(6)
22.714(4)
9.890(6)
90
105.81(6)
90
1956.5(18)
P21/n (No. 14)
4
C22H26ClF6N2OPRu
615.94
8.3919(16)
11.6702(14)
13.5049(12)
80.353(10)
82.684(9)
72.537(10)
1239.6(3)
P1h (No. 2)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
space group
Z
90
90
8649.5(15)
Pbca (No. 61)
8
1.667
-100(2)
Dcalcd (g cm-3
T (°C)
λ (Å)
)
1.624
-123(1)
1.650
-10(1)
µ (mm-1
)
0.772
1.082
0.868
R values [I > 2σ(I)]a,b
R values (all data)a,b
quality-of-fitc
R1 ) 0.0714
wR2 ) 0.1758
R1 ) 0.0838
wR2 ) 0.1834
1.061
R1 ) 0.0624
wR2 ) 0.1410
R1 ) 0.1081
wR2 ) 0.1631
1.039
R1 ) 0.0496
wR2 ) 0.1182
R1 ) 0.0657
wR2 ) 0.1286
1.016
a R1 ) ∑||Fobs| - |Fcalcd||/∑|Fobs|. b wR2 ) [∑w(Fobs - Fcalcd2)2/∑w(Fobs2)2]1/2
.
c Quality-of-fit ) [∑w(Fobs - Fcalcd2)2/(Nobs - Nparam)]1/2
.
2
2
[Ru(η6-C6H6)(1-H2)Cl]PF6 (10). Salts 10a-d were prepared as
described above for salts 4 but using the imine ligands (1-H2).
10a. Yield: 87%. 1H NMR (200 MHz, acetone-d6): δ 9.70 (m,
1H, py H6), 8.84 (s, 1H, HCdN), 8.35 (m, 2H, py), 7.89 (m, 1H,
py), 7.56 (m, 4H, Ar), 6.04 (s, 6H, C6H6), 2.47 (s, 3H, Me). IR
(KBr, cm-1): 849 (ν(P-F)). Anal. Calcd for C19H18ClN2PF6Ru: C,
41.05; H, 3.26; N, 5.04. Found: C, 41.10; H, 3.04; N, 5.28.
10b. Yield: 85%. 1H NMR (200 MHz, acetone-d6): δ 9.68 (m,
1H, py H6), 8.82 (s, 1H, HCdN), 8.33 (m, 2H, py), 7.89 (m, 1H,
py), 7.50 (m, 4H, Ar), 6.05 (s, 6H, C6H6), 3.93 (s, 3H, MeO). IR
(KBr, cm-1): 852 (ν(P-F)). Anal. Calcd for C19H18ClN2OPF6Ru:
C, 39.91; H, 3.17; N, 4.90. Found: C, 40.10; H, 3.07; N, 5.10.
9.14 (s, 1H, HCdN), 8.49 (d, 1H, py), 8.34 (t, 1H, py), 7.76 (t, 1H,
py), 7.54 (m, 4H, Ar), 5.32 (s, 5H, Cp), 2.43 (s, 3H, Me). IR (KBr,
cm-1): 1982 (νCO), 850 (νP-F). Anal. Calcd for C19H17N2OPF6Ru:
C, 42.63; H, 3.20; N, 5.23. Found: C, 42.70; H, 3.39; N, 5.37.
[Ru(η6-p-C6H6)(1e-H)]PF6 (14). A suspension of 4e (50 mg,
0.085 mmol) in tetrahydrofuran (10 mL) was treated with a solution
0.5 M sodium methoxide (0.18 mL, 0.09 mmol) in methanol. The
mixture was evaporated to dryness. The solid was dissolved in
tetrahydrofuran (10 mL), and the resulting solution was filtered
1
and evaporated to dryness to afford a red solid. Yield: 87%. H
NMR (200 MHz, acetone-d6): δ 9.89 (d, 1H, py H6), 8.14 (t, 1H,
py), 7.82 (d, 1H, py), 7.68 (t, 1H, py), 7.28 (s, 4H, Ar), 5.81(s, 6H,
C6H6), 2.43 (s, 3H, Me-Ar), 1.42 (s, 6H, Me2). IR (KBr, cm-1):
842 (ν(P-F)). Anal. Calcd for C21H23N2PF6Ru: C, 45.91; H, 4.22;
N, 5.10. Found: C, 45.67; H, 4.09; N, 5.31.
1
10c. Yield: 87% H NMR (200 MHz, acetone-d6): δ 9.71 (m,
1H, py H6), 8.67 (s, 1H, HCdN), 8.34 (m, 2H, py), 7.90 (m, 1H,
py), 7.31 (m, 3H, Ar), 5.98 (s, 6H, C6H6), 2.44 (s, 3H, Me), 2.29
(s, 3H, Me). IR (KBr, cm-1): 849 (ν(P-F)). Anal. Calcd for C20H20-
ClN2PF6Ru: C, 42.15; H, 3.54; N, 4.92. Found: C, 42.10; H, 3.44;
N, 5.08.
[Ru(η6-p-cymene)(1e-H)]PF6 (15). A suspension of 5e (60 mg,
0.094 mmol) in tetrahydrofuran (10 mL) was treated with a solution
0.63 M sodium methoxide (0.15 mL, 0.095 mmol) in methanol.
The mixture was evaporated to dryness. The solid was dissolved
in tetrahydrofuran (10 mL), and the resulting solution was filtered
10d. Yield: 85% 1H NMR (200 MHz, acetone-d6): δ 9.73 (m,
1H, py H6), 8.97 (s, 1H, HCdN), 8.40 (m, 2H, py), 8.36 (m, 1H,
py), 8.04 (m, 4H, Ar), 6.08 (s, 6H, C6H6). IR (KBr, cm-1): 852
(ν(P-F)). Anal. Calcd for C19H14ClN2PF9Ru: C, 37.42; H, 2.48; N,
4.59. Found: C, 37.22; H, 2.38; N, 4.67.
[Ru(η6-p-cymene)(1d-H2)Cl]PF6 (11). Salt 11 was prepared as
described above for salt 5 but using the imine ligand (1d-H2).
Yield: 78%. 1H NMR (400 MHz, acetone-d6): δ 9.58 (d, 1H, py H6),
8.96 (s, 1H, HCdN), 8.30 (m, 2H, py), 7.99 (m, 4H, Ar), 7.89 (d,
1H, py), 6.09 (d, 1H, Ar p-cymene), 5.77 (m, 1H, Ar p-cymene),
1
and evaporated to dryness to afford a red solid. Yield: 87%. H
NMR (200 MHz, acetone-d6): δ 9.89 (d, 1H, py H6), 8.15 (t, 1H,
py), 7.83 (d, 1H, py), 7.71 (m, 1H, py), 7.28 (m, 4H, Ar), 5.84 (m,
1H, Ar p-cymene), 5.73 (m, 1H, Ar p-cymene), 5.41 (m, 2H, Ar
p-cymene), 2.81 (hept, 1H, CHMe2), 2.45 (s, 3H, Me-Ar), 2.29 (s,
3H, Me p-cymene), 1.40 (s, 6H, N-CMe2), 1.32 (d, 6H, CHMe2).
IR (KBr, cm-1): 3168 (νN-H), 843 (ν(P-F)). Anal. Calcd for
C25H31N2PF6Ru: C, 49.59; H, 5.16; N, 4.63. Found: C, 49.67; H,
5.04; N, 4.73.
5.71 (d, 1H, Ar p-cymene), 5.56 (d, 1H, Ar p-cymene), 2.47 (hept,
1H, CH(Me)2), 2.14 (s, 3H, p-Me cymene), 0.95 (d, 6H, CH(Me)2).
IR (KBr, cm-1): 848 (νP-F). Anal. Calcd for C23H22 ClN2PF9Ru:
C, 41.48; H, 3.48; N, 4.2. Found: C, 41.70; H, 3.49; N, 4.37.
[Ru(η5-C5H5)(1a-H2)(CH3CN)]PF6 (12). Salt 12 was prepared
as described above for salt 6 but using the imine ligand (1a-H2).
Molecular Mechanics Calculations. Quantum chemical calcula-
tions were performed using the MacSpartan Pro 1.0.2 program suite
implemented on an Apple Macintosh G4 1.25 GHz dual.29 Non-
geometrical restrictions were imposed. The calculations were carried
out at the semiempirical model PM3.30
X-ray Crystallography. General crystallographic data and
refinement indicators are presented in Table 1 for the structures of
2b‚CH2Cl2, 2c‚2CH2Cl2, 3, and 4a‚Me2CdO. Crystals were grown
from dichloromethane/diethyl ether (2b and 2c), from acetone/
1
Yield: 77%. H NMR (400 MHz, acetone-d6): δ 9.66 (d, 1H, py
H6), 9.08 (s, 1H, HCdN), 8.29 (m, 1H, py), 8.15 (td, 1H, py), 7.70
(m, 1H, py), 7.60 (m, 4H, Ar), 4.46 (s, 5H, Cp), 2.45 (s, 3H,
MeCN), 2.37 (s, 3H, Me). Anal. Calcd for C20H20N3PF6Ru: C,
43.80; H, 3.68; N, 7.66. Found: C, 43.70; H, 3.49; N, 7.47.
[Ru(η5-C5H5)(1a-H2)(CO)]PF6 (13). Salt 13 was prepared as
described above for salts 7 but using the imine ligand (1a-H2).
Yield: 79%. 1H NMR (400 MHz, acetone-d6): δ 9.35 (d, 1H, py H6),
(29) WaVefunction, version 1.0.2; Wavefunction, Inc.: Irvine, CA, 1999-
2000.
(30) Stewart, J. J. P. J. Comput. Chem. 1989, 10, 209-220.
Inorganic Chemistry, Vol. 45, No. 6, 2006 2487

Go´mez et al.
Scheme 1
diethyl ether (4a), and from chloroform/ethanol (3). X-ray diffrac-
tion data were measured using a Nonius KappaCCD diffractometer
with a rotating anode source for 2c and with a Nonius CAD-4
equipped with a sealed tube for the other structures.31 Multiscan
absorption corrections were used in all cases (with absorption data
obtained in the case of the CAD-4 by ψ-scans of a group of
scattering vectors spanning a wide range of Eulerian-equivalent ø
values in their respective bisecting positions). The structures were
solved by direct methods and refined to F2 using full-matrix least
32
squares.
Non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms were included at cal-
culated positions (derived from a local difference Fourier map for
methyl groups) with isotropic U constrained to values of 1.2× the
equivalent isotropic displacement parameters of their respective
parent atoms. The one exception was the H atom bonded to N2 in
the structure of 4a; this hydrogen atom is a H-bond donor to the
neighboring chlorine atom and was refined freely. For 2b, a total
of 1 formula equiv of CH2Cl2 was included in the model and
distributed over two sites, one of which was disordered. No
Scheme 2
-
hydrogen atoms were included for this moiety. The PF6 groups
Scheme 3
in 2b, 2c, and 4a showed signs of varying degrees of disorder;
similarity restraints were used where deemed appropriate.
Crystals of 2b‚CH2Cl2 presented special problems, which are
reflected in the poor quality of the results obtained from them. The
crystals diffracted very weakly at room temperature, but the
diffraction pattern became entirely unobservable when the temper-
ature was lowered to any value that might have been expected to
produce an improvement in the diffraction, e.g., -100 °C, probably
as the result of a first-order structural transformation. The results
that we report, obtained at room temperature, establish the con-
nectivity and general structural features, especially the relative
stereochemistries of the three possible sources of chirality (see
Results and Discussion); but we would advise against using bond
distances and angles from this structure determination in an analysis
of fine structural features or in a comparative geometrical study.
Crystallographic data in the form of a crystallographic informa-
tion file are included in the Supporting Information.
1d (under the same conditions as those indicated for 1a, 1b,
or 1c) afforded 8d. The acidity of the N-H bond after the
coordination of ligands 1 to ruthenium seems to control the
oxidation reaction as discussed below. The CF3 group in the
para position induces the strongest acidity, and compound
2d is elusive.
Synthesis of trans-[Ru(1,5-cyclooctadiene)(1a)Cl2] (3).
Complex 3 was prepared by the reaction of [RuCl2(1,5-
cyclooctadiene)]n with ligand 1a. The reaction conditions
were the same as those for compounds 2; the formation of
the imine derivative 9 was not observed (Scheme 2). Thus,
in addition to the substituents in the para position mentioned
for compounds 2, the nature of the ancillary ligands
coordinated to ruthenium also affects the oxidation reaction
of amine to imine.
Synthesis of [Ru(η6-arene)(1)Cl]PF6 (arene ) C6H6, 4;
p-cymene, 5). Salts 4a, 4b, 4c, 4d, and 4e were prepared by
the reaction of [RuCl2(CH3CN)(η6-C6H6)] with the appropri-
ate ligand 1a-e. Salts 5d,e were prepared by the reaction
of [RuCl2(η6-p-cymene)]2 with corresponding ligand 1d or
1e. As indicated for compounds 2, small amounts of imine
derivatives 10 were formed (Scheme 3) if oxygen was not
rigorously excluded from the reaction in the synthesis of salts
4a-d. However, compound 5d was synthesized under the
Results and Discussion
Synthesis of [Ru(2,2′-bipyridine)2(1)](PF6)2 (2). Com-
pounds 2a, 2b, and 2c were prepared by the reaction of
(∆,Λ)-cis-[Ru(2,2′-bipyridine)2Cl2] with amine ligands 1a,
1b, or 1c under nitrogen. The presence of small amounts of
adventitious oxygen led to small amounts of the oxidized
imine compounds 8a, 8b, and 8c following the reaction
shown in Scheme 1. Such â-oxidation reactions are known
to take place on amines coordinated to ruthenium upon
reaction with O2,33-35 and a possible mechanism has been
proposed.15,16 We failed to prepare compound 2d. The
reaction of (∆,Λ)-cis-[Ru(2,2′-bipyridine)2Cl2] with ligand
(31) (a) KappaCCD, COLLECT; Nonius BV: Delft, The Netherlands, 1999.
(b) DENZO, see: Otwinowski, Z.; Minor, W. In Methods in Enzymol-
ogy, Vol. 276A: Macromolecular Crystallography; Carter, C. W.,
Sweet, R. M., Eds.; Academic Press: New York, 1997; pp 307-326.
(c) SORTAV, see: Blessing, R. H. Acta Crystallogr., Sect. A, 1995,
51, 33-38. (d) CAD-4: Instrument Control, CAD4/PC, version 2.0;
Nonius BV: Delft, The Netherlands, 1996. (e) Harms, K. University
of Marburg, Germany. Private communication on data reduction using
XCAD4B, 1996. (f) SHELXTL, release 5.05/VMS; Siemens Analytical
X-ray Instruments, Inc.: Madison, WI, 1996.
(32) (a) Sheldrick, G. M. SHELXS-97: Fortran Program for Crystal
Structure Solution; University of Go¨ttingen: Go¨ttingen, Germany,
1997. Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467. (b)
Sheldrick, G. M. SHELXL-97: Fortran Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
2488 Inorganic Chemistry, Vol. 45, No. 6, 2006

Synthesis of Ruthenium(II) Complexes Using ArNH-CH2-2-C5H4N
Scheme 4
Chart 2
(η6-p-cymene)(1e-H)]PF6 (15). Our interest in amido com-
plexes led us to explore deprotonation reactions of the amine
complexes containing ligands 1a-d (NaOMe, KOBut, and
K-Selectride were used as deprotonating agents). We were
unable to characterize any amido complexes in these reac-
tions, and imine complexes were the only identified products.
The synthesis of ligand 1e (without â hydrogen atoms, see
Scheme 1) allowed for preparation of compounds 4e and
5e. We also attempted to prepare 2e but did not succeed,
likely because of the higher steric requirements of the
[Ru(bipy)2] moiety compared with those of [Ru(arene)Cl].
Amido complexes 14 and 15 were prepared by simple
deprotonation of amine complexes 4e or 5e with a stoichio-
metric amount of NaOMe.
Base-Catalyzed Oxidative Dehydrogenation of Amine
to Imine Complexes. The results described above indicate
that amido complexes, although elusive, play an important
role in the oxidation of the coordinated amine ligand to the
corresponding imine by air. In fact, the results presented here
suggest that the oxidation of amine complexes to imine
complexes takes place only if the amido complex is formed
in situ by deprotonation of the precursor amine complex.
The highest concentration of amido complex in solution
should lead to the fastest oxidation to imine complex. This
is strongly supported by our failure in attempting to prepare
2d, which should be the more acidic of complexes 2 thus
leading to the highest concentrations of amido complex in
solution. Complexes 2 and 4 were suspended or dissolved
in tetrahydrofuran and treated with different amounts of base
(NaMeO in MeOH) in air at room temperature. The
formation of imine derivatives 8 or 10 was monitored by 1H
NMR. The best yields of imine derivatives (yields greater
than 75% after 5 h at room temperature) were obtained when
10% of the amount of NaMeO required for a 1:1 base:Ru
molar ratio was used. This shows that the oxidation of amine
complex to imine complex is base-catalyzed. Thus, small
amounts of base made the oxidation reaction to imine faster,
whereas an excess of base led to lower yields and less-clean
reactions, likely because of the further reaction of imine
complexes with the excess of base. The presence of H2O2 in
the reaction (>10 mg L-1) was unequivocally proved in a
peroxide test (Quantofix test stick; detection range ) 0.5-
25 mg L-1 H2O2). Further oxidation of the imine ligand to
amide, as described for the reaction of [Ru(II)(diimine)2Cl2]
complexes with H2O2,36 was not observed. Whereas hydrogen
peroxide is an end product of the amine oxidation in
biological systems and the mechanism of the dioxygen
activation by oxidase enzymes is of current interest,37 this
is, to the best of our knowledge, the first report of hydrogen
same conditions without the formation (Scheme 3) of the
imine derivative 11. This indicates that the electronic effects
induced by substituents on the η6-arene ligands account for
the different behavior toward molecular oxygen. The syn-
thesis and characterization of stable compounds 4d and 5d
(we mentioned above that attempts to prepare 2d failed) again
support the notion that the oxidation of amine complexes to
imine complexes by molecular oxygen is strongly dependent
on the ancillary ligands coordinated to ruthenium.
Synthesis of [RuCp(L)(1)]PF6 (L) CH3CN, 6; CO, 7).
Salt 6 was prepared as a mixture of diastereomers (3:2, d.e.
20%) by the reaction of [Ru(η5-C5H5)(CH3CN)3]PF6 with 1a.
This mixture is very sensitive in solution to molecular
oxygen, leading to the imine derivative 12 (Scheme 4). Salts
7a,e were also prepared as mixtures of diastereomers (2:1,
d.e. 33%) by simple substitution reactions of [Ru(η5-
C5H5)(CO)(CH3CN)2]PF6 with the appropriate amine ligand
1a or 1e. In contrast to compound 6, compound 7a is stable
to air in solution (Scheme 4). The difference in the donor-
acceptor properties of ligands CO and CH3CN accounts for
such a different behavior.
Synthesis of Derivatives with Imine Ligands 1-H2. The
imine derivatives 8-13 were prepared for comparison
purposes. They are the products of oxidation of amine
derivatives 2-7 and differ only by one molecule of hydrogen.
As already indicated, they appear occasionally as impurities
if molecular oxygen is present in the experimental procedures
to synthesize the amine derivatives. In all cases, the synthetic
procedures consisted of the reaction of the appropriate
precursor with the corresponding imine ligand under the same
conditions as those used for the preparation of the amine
derivatives. Imine derivative 8a was also prepared in high
yield by the reaction of (∆,Λ)-cis-[Ru(2,2′-bipyridine)2Cl2]
with amine ligand 1a in air; the reaction required 4 h in
refluxing methanol.
Deprotonation of Amine Complexes. Synthesis of
Amido Complexes [Ru(η6-C6H6)(1e-H)]PF6 (14) and [Ru-
(33) Bailey, A. J.; James, B. R. Chem. Commun. 1996, 2343-2344.
(34) Naota, T.; Takaya, H.; Murahashi, S. I. Chem. ReV. 1998, 98, 2599-
2660.
(35) Gemel, C.; Folting, K.; Caulton, K. G. Inorg. Chem. 2000, 39, 1593-
(36) Menon, M.; Pramanik, A.; Chakravorty, A. Inorg. Chem. 1995, 34,
3310-3316.
1597.
Inorganic Chemistry, Vol. 45, No. 6, 2006 2489

Go´mez et al.
Scheme 5. Proposed Steps for the Oxidation of Ruthenium(II) Amine
Complexes with Air
Figure 1. Four possible geometrical isomers of the octahedral complex
3. Chelating 1,5-cyclooctadiene ligands have been omitted for clarity.
peroxide formation in the reaction between a coordination
compound and dioxygen. This could be used as a model to
understand the more complicated biological systems.
Mechanism for Amine Oxidation. Scheme 5 shows the
proposed mechanism for the oxidation of ruthenium(II) amine
complexes on the basis of the experimental results reported
above. The first step explains that a higher concentration of
amido complex leads to a faster oxidation reaction to imine.
A higher N-H bond acidity leads to an easier (faster)
oxidation to imine. Electron-withdrawing substituents, such
as CF3 on the aryl group, increase the acidity, and oxidation
becomes easier. This explains our failure in trying to prepare
complex 2d. However, the electronic effect of the ancillary
ligands on the acidity of the N-H bond is less evident,
although good π-acceptor ligands such as CO make oxidation
more difficult (compare the behaviors of 6 and 7a as shown
in Scheme 4). Step B is a one-electron transfer reaction and
the rate-determining step. Step D is in partial agreement with
the proposed mechanism for the ruthenium-catalyzed aerobic
oxidation (by molecular oxygen) of amines.15,16,38 However,
our results do not support the notion that the formation of
Ru-H species is always required. Thus, for instance, in the
case of the coordinatively saturated tris-chelate cationic
complexes 22+, we would have to accept seven-coordinated
Ru(II) or decoordination of a chelate ligand to create a vacant
coordination site for the hydrido ligand. Furthermore, direct
hydride removal from the methylene unit of a coordinatively
saturated tungsten benzylamido complex under oxidizing
conditions has been reported.18 Attempts to detect radicals
by the ESR spin-trap technique using 5,5-dimethyl-1-
pyrroline-N-oxide (DMPO) failed.
Figure 2. Crystal structure of 3. Hydrogen atoms have been omitted for
clarity. Selected bond distances (Å) and angles (deg): Ru1-N1, 2.102(6);
Ru1-N2, 2.169(8); Ru1-Cl1, 2.404(3); Ru1-Cl2, 2.438(3); Ru1-C1,
2.187(8); Ru1-C2, 2.196(8); Ru1-C5, 2.212(7); Ru1-C6, 2.212(7); Cl1-
Ru1-Cl2, 159.42(9); N1-Ru1-N2, 78.0(3); N1-Ru1-Cl1, 82.52(18);
N2-Ru1-Cl1, 85.0(4); N1-Ru1-Cl2, 81.34(18); N2-Ru1-Cl2, 79.3(4).
with the chloro ligand, a rapid equilibrium exchange between
both diastereomers cannot be ruled out. The energy barrier
for the λ,δ conversion is, in general, expected to be very
low, in the range 2-4 kcal mol-1. Quantum chemical
calculations performed at the PM3 level indicate that the
more stable conformation is (λ,R) or (δ,S). At this level of
theory, the other diastereomer (λ,S) or (δ,R) is not a minimum
in the potential energy surface. 1H NMR variable temperature
experiments in the range 193-300 K in d6-acetone showed
no signals of dynamic behavior.
The anisotropic displacement parameters of atom N(2) in
the structure of complex 3 (see Figure 2) reveal what appears
to be disorder of this atom in a direction roughly perpen-
dicular to the plane of the other four atoms of the five-
membered chelate ring. Given that the diffraction data were
less than ideal in this case, we cannot rule out the possibility
that the anomalous elongation of the ellipsoid for N(2) is an
artifact of the refinement. However, the elongation also has
a plausible chemical and structural interpretation, which is
supported by the finer numerical analysis of the displacement
parameters of N(2) and the atoms around it. (Details of this
analysis are available from the authors.) Taking into account
that the complex has two origins of chirality (the asymmetric
N(2), which can have either an R- or S-configuration, and
the five-membered chelate ring, which can be in either the
λ or δ conformation), and noting also that N(2) is the “flap”
atom of the envelope formed by the chelate ring, we can
consider two possibilities for explaining such disorder. First,
fluxionality based on the movement of N(2) in the direction
Stereochemical Considerations and Structural Char-
acterization of Complexes in Solid and in Solution.
Complex 3 has two sources of chirality. The stereogenic
amino nitrogen of the coordinated ligand 1a could have either
R or S configuration, and the puckered nonplanar five-
membered chelate ring of coordinated ligands 1 is also a
chiral entity identified as δ or λ.39 Two diastereomers can
be anticipated for complex 3 (see Figure 1). Although the
1H NMR could be assigned to the isomer (λ,R) and its
enantiomer (δ,S), which allow a hydrogen bond interaction
(37) Prabhakar, R.; Siegbahn, P. E. M.; Minaev, B. F. Biochim. Biophys.
Acta 2003, 1647, 173-178.
(38) Diamond, S. E.; Mares, F. J. Organomet. Chem. 1977, 142, c55.
(39) Petra, D. G. I.; Reek, J. N. H.; Handgraaf, J. W.; Meijer, E. J.; Dierkes,
P.; Kamer, P. C. J.; Brussee, J.; Schoemaker, H. E.; van Leeuwen, P.
Chem.sEur. J. 2000, 6, 2818-2829.
2490 Inorganic Chemistry, Vol. 45, No. 6, 2006

Synthesis of Ruthenium(II) Complexes Using ArNH-CH2-2-C5H4N
Figure 4. Crystal structure of Λ,λ,R-[2b]2+. Hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles (deg): Ru1-
N1, 2.01(3); Ru1-N2, 2.08(2); Ru1-N3, 2.06(2); Ru1-N4, 2.03(2); Ru1-
N5, 2.08(2); Ru1-N6, 2.09(3); N1-Ru1-N5, 173.8(11); N2-Ru1-N4,
172.9(10); N3-Ru1-N6, 172.3(9). These values are provided as a general
guide to the coordination geometry; see the Experimental Section for a
caveat regarding the quality of this structure determination.
Figure 3. Top: π-interaction allowed, diastereomer is formed. Down:
π-interaction is not allowed, diastereomer is not formed.
indicated by the displacement ellipsoid would give rise to
two diastereomers, for example, (δ,S) and (λ,S). This would
mean that the hydrogen bond N(2)-H(2A)‚‚‚Cl(1) favored
in diastereomer (δ,S) would be a longer contact after
fluxional motion to (λ,S). Second, a static model on the basis
of configurational disorder about N(2)-R/S, with hydrogen
pointing toward either Cl(1) or Cl(2) and with concomitant
stabilization of one five-membered ring conformation or the
other, would yield a disorder of the enantiomers (δ,S) and
(λ,R) and would lead to the same results from the structure
analysis. In either case, the crystal is racemic on the whole,
as the centric space group indicates, although either of the
models considered could give rise to local deviations from
stereochemical parity. Because the shape and topology of
the molecule are such that neither the conformation of the
chelate ring nor the stereochemistry about N(2) is expected
to influence crystal packing significantly, it is possible that
both conformational fluxionality and configurational disorder
about N(2) are in play.
Figure 5. Crystal structure of ∆,δ,S-[2c]2+. Hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles (deg): Ru-
N1, 2.079(5); Ru-N2, 2.200(5); Ru-N3, 2.075(5); Ru-N4, 2.039(5); Ru-
N5, 2.054(5); Ru-N6, 2.062(6); N1-Ru-N5, 174.9(2); N2-Ru-N4,
173.1(2); N3-Ru-N6, 172.2(2).
complex 3 that allows the aryl group to be arranged in a
less-crowded equatorial position in the five-membered che-
late ring (see Figure 1). The diastereomer Λ,λ,R allows
π-interactions between one of the 2,2′-bipyridine rings and
the aryl group (see Figure 3). NOE 1D experiments carried
out for compound 2a showed interaction between the
o-hydrogens of the aryl group and the hydrogen atoms H4,
H5, and H6 of one of the bipyridine rings. For compound
2c, NOE interactions were observed between the hydrogen
atoms of the 2,6-dimethyl groups and the hydrogen atoms
H,4 H5, and H6 of one of the bipyridine rings. Also in
compound 2c, anisotropic shifts were observed for the 2,6-
dimethyl groups that appear nonequivalent below 2 ppm in
the spectrum, indicating that free rotation of the aryl group
is not allowed.
The solid-state structure determination of 2b (Figure 4)
confirms that both enantiomers Λ,λ,R and ∆,δ,S are present
in the unit cell. The angle between the planes of the rings
that allow π-interactions is 31.4(10)° and the distance
between centroids is 4.12 Å, so although it no doubt
contributes to the stability of the molecule, this interaction
is significantly “slipped.”
The cationic complexes 22+, 4+, 5+, 6+, and 7+ have three
sources of chirality. In addition to those described for
complex 3, cationic complexes 22+ have helical structures
with ∆ and Λ descriptors for a right or left helix.1 The
cationic complexes 4+-7+ have instead RRu, SRu configura-
tions for the stereogenic ruthenium-metal center (RN and SN
refer to the configuration of the chiral nitrogen atom). Eight
geometrical isomers (four chiral diastereomers and their four
enantiomers) can be anticipated for complexes with three
sources of chirality.
1
The H NMR spectra of compounds 2 again show that
only one diastereomer is specifically formed. Molecular
models indicate that only the combination Λ,λ,R (or its
enantiomer ∆,δ,S) is sterically acceptable. It is interesting
to note that the combination is the same as that found in
A thermal ellipsoid plot of 2c is shown in Figure 5.
The cation is a six-coordinate Ru(II) tris chelato complex
containing two 2,2′-bipyridine ligands and the chelating
amine-pyridine ligand 2,6-(CH3)2C6H3NH-CH2-2-C5H4N.
Inorganic Chemistry, Vol. 45, No. 6, 2006 2491

Go´mez et al.
Table 2. Anodic Peak and Half-Wave Potentialsa
2a
2b
2cb
8a
8b
8c
8d
E
E
pk (V)
1/2 (V)
1.32
1.46
1.31
1.45
1.28
1.42
1.47
1.48
1.46
1.51
a Scan rate ) 100 mV s-1. Potentials vs SCE; Pt bead electrode; in
dichloromethane and tetrabutylammonium hexafluorophosphate as the
supporting electrolyte. b In the reverse scan, a new reversible wave appears
at E1/2 ) +0.8 V.
that extend in the z-direction. The maximal radius of the
columns, or thickness of the extended slabs, is roughly 6.5
Å; and the space between them, which is occupied by the
anions and interstitial solvent, is about 4.3 Å thick. The bond
distances and angles in the structures of 2b,c fall into the
expected ranges of values for the bond types involved.
The geometry of cationic complexes 4+ could lead to eight
different geometric isomers, as shown in Figure 7. Once
again, only one diastereoisomer (as an enantiomeric pair) is
specifically formed in solution.
The 1H NMR spectra for compounds 4 and 5 are assigned
to the diastereomer RRu,δ,SN and its enantiomer SRu,λ,RN, the
only stereochemistry that allows intramolecular hydrogen
bonding between the N-H bond and the chloro ligand. This
assignment is in agreement with the X-ray structural
characterization of 4a (See Figure 8), in which the distance
N(2)-H‚‚‚Cl(1) is 2.603 Å, which is in the accepted range
for such interactions.19,40 The stereochemical analysis of the
crystal structure of 4a unequivocally shows that both
enantiomers are present in the unit cell and form a nonco-
valent dimer through intermolecular hydrogen bonding with
an N-H‚‚‚Cl distance of 2.629 Å. As already mentioned
for compounds 3, 2b, and 2c, the chelating ligand 1a arranges
in 4a in such a way as to permit the aryl group to occupy an
equatorial position of the chelate ring.
In contrast to compounds 4 and 5, compounds 6 and 7,
which allow the same stereochemical analysis shown in
Figure 7, were synthesized as mixtures of two diastereomers.
As the main difference is the change of the chloro ligand in
4 and 5 for a neutral (CO or CH3CN) ligand in 6 and 7, we
suggest that the driving force for the diastereospecificity in
the synthesis of complexes 4 and 5 is the possibility of form-
ing a hydrogen bond. In the absence of this stabilizing factor,
two diastereoisomers appeared for 6 and 7 (likely those two
containing the aryl group in the equatorial position).
Electrochemistry. Cyclic voltammetry of compounds 2
in dichloromethane shows two anodic peaks and a cathodic
Figure 6. Perspective drawing of the extended structure of 2c showing
the columnar stacking arrangement. Hydrogen atoms have been omitted
for clarity.
The asymmetric unit of the crystal structure comprises a
single cation of [2c]2+, along with PF6- anions and interstitial
solvent sites; because the space group (Pbca) is centric, both
enantiomers Λ,λ,R and ∆,δ,S of the ruthenium complex are
present in equal numbers in the unit cell. The aryl (2,6-di-
methylphenyl) ring of the amine-pyridine moiety is oriented
so as to be nearly parallel to, and partially eclipsed with,
the plane of a coordinated bipyridine (atoms C(30)-C(34)
and N(6)) of the same molecule. The intramolecular distance
between the rings is 3.43 Å, calculated as the distance be-
tween the two ring centroids, projected onto the cell edge a.
The two rings are not quite parallel to each other, with a di-
hedral angle of 14.91 (17)°. The same aryl ring is also nearly
eclipsed with a symmetrically equivalent bipyridine entity
(also C(30)-C(34) and N(6)) of the neighboring molecule,
a mirror image of the first, at (0.5 + x, y, 0.5 - z), to give
an unbounded ring-stacking pattern propagated in a direction
parallel to the crystallographic x-axis. The intermolecular
distance between the rings, calculated as before, is 3.70 Å,
and the dihedral angle is 13.57(17)°. The stacking gives an
overall columnar appearance to the extended crystal structure
when viewed along the crystallographic c-axis, as shown in
Figure 6. In fact, the columns are further packed into slabs
Figure 7. Eight possible geometric isomers for cationic complexes 4+ and 5+. Only the framed couple of enantiomers RRu, δ, SN and SRu, λ, RN is actually
formed.
2492 Inorganic Chemistry, Vol. 45, No. 6, 2006

Synthesis of Ruthenium(II) Complexes Using ArNH-CH2-2-C5H4N
The additional wave shown by 2c can be attributed to a
chemical reaction on the para position of the aryl ring, as
reported in complexes containing such arylamino groups.43,44
Conclusions
Coordination of chiral N, N′ bidentate ligands 2-(arylami-
nomethyl)pyridine ArNH-CH2-2-C5H4N 1 (Ar ) 4-CH3-
C6H4, 1a; 4-CH3O-C6H4, 1b; 2,6-(CH3)2-C6H4, 1c; 4-CF3-
C6H4, 1d) to the moieties [Ru(bipy)2]2+, [RuCl2(COD)],
(COD ) 1,5-cyclooctadiene), [Ru(η5-C5H5)L]+ (L ) CH3CN,
CO), or [Ru(η6-arene)Cl]2+ (arene ) benzene, p-cymene)
occurs under diastereoselective or diastereospecific condi-
tions. Coordination of these secondary amine ligands acti-
vates their oxidation to imines by molecular oxygen, which
is reduced to hydrogen peroxide. The oxidation of amine
complexes to imine complexes by molecular oxygen is
strongly dependent not only on the ancillary ligands coor-
dinated to ruthenium but also on the substituents of the aryl
group. Electrochemical oxidation of the amine complexes,
under cyclic voltammetric conditions, resulted in the forma-
tion of imine complexes. Deprotonation of the coordinated
amine ligands afforded isolatable amido complexes only
when the â hydrogen atoms were excluded. The structures
of complexes [Ru(2,2′-bipyridine)2(1b)](PF6)2, 2b; [Ru(2,2′-
bipyridine)2(1c)](PF6)2, 2c; trans-[RuCl2(COD)(1a)], 3; and
[RuCl2(η6-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray
diffraction studies.
Figure 8. Left: Crystal structure of SRu,λ,RN-4a. Right: Assembly of pairs
of enantiomers RRu,δ,SN and SRu,λ,RN. Hydrogen atoms have been omitted
for clarity (hydrogen atoms involved in hydrogen bonding interactions are
shown). Selected bond distances (Å) and angles (deg): Ru1-Cl1, 2.403(14);
Ru1-N1, 2.093(5); Ru1-N2, 2.139(4); Ru1-C14, 2.182(6); Ru1-C15,
2.166(6); Ru1-C16, 2.159(6); Ru1-C17, 2.175(7); Ru1-C18, 2.192(6);
Ru1-C19, 2.168(6); N1-Ru1-Cl1, 84.83(12); N2-Ru1-Cl1, 83.34(13);
N1-Ru1-N2, 76.86(16).
Acknowledgment. The authors gratefully acknowledge
the European Commission (LIFE05 ENV/E/000333), the
Spanish Ministerio de Educacio´n y Ciencia (BQ2002-01039
and CTQ2005-03141), and the Junta de Castilla y Leo´n
(BU14/03) for financial support. We also acknowledge the
Servicios Centrales de Apoyo a la Investigacio´n (SCAI) de
la Universidad de Burgos for technical support. Valuable help
from the editor regarding Scheme 5 is deeply acknowledged.
This paper is dedicated to Professor D. Victor Riera Gonza´lez
on the occasion of his 70th birthday.
Figure 9. Cyclic voltammograms of 2a (a) and 8a (b). In dichloromethane,
n
0.1 M [NBu4 ][PF6] at a Pt bead electrode. Scan rate ) 100 mV s-1
.
peak as shown in Figure 9a for 2a. In the reverse scan, 2c
shows an additional small wave at E1/2 ) +0.8 V that is
apparently reversible under successive scans. Imine deriva-
tives show a reversible wave, as shown in Figure 9b for 8a.
The data are collected in Table 2.
Similar voltammograms have been reported for related
cationic complexes [Ru(bipy)2{2-(aminomethyl)pyridine}]2+,41
[Ru(bipy)2(R-iminoacidato)]+, and [Ru(bipy)2(R-iminoaci-
dato)]+.42 By analogy with previous reported data, the
irreversible anodic peak is considered to be a one-electron
oxidation of 2 to 2+. The apparently reversible couple in
the voltammograms of salts 2 is attributed to the transforma-
tion of 2+ into 8. The reversible couple was unequivocally
assigned by recording the cyclic voltammograms of 8, as
shown in Figure 9b for 8a.
Supporting Information Available: Supplementary X-ray
data submitted in CIF format for complexes 2b,c, 3, and 4a.
This material is available free of charge via the Internet at
http://pubs.acs.org.
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(42) Yamaguchi, M.; Machiguchi, K.; Mori, T.; Kikuchi, K.; Ikemoto, I.;
Yamagishi, T. Inorg. Chem. 1996, 35, 143-148.
(43) Espinet, P.; Alonso, M. Y.; Garc´ıa-Herbosa, G.; Ramos, J. M.; Jeannin,
Y.; Philochelevisalles, M. Inorg. Chem. 1992, 31, 2501-2507.
(44) Albeniz, A. C.; Calle, V.; Espinet, P.; Gomez, S. Chem. Commun.
2002, 610-611.
(40) Soleimannejad, J.; Sisson, A.; White, C. Inorg. Chim. Acta 2003, 352,
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(41) Ridd, M. J.; Keene, F. R. J. Am. Chem. Soc. 1981, 103, 5733-5740.
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