[Ru(η5-C5Me5)(Me2NCH 2CH2NMe2)]+, a stable 16-eleetron complex. Reaction with dioxygen and formation of a monomeric hydroxoruthenium tetramethylfulvene complex

Article abstract of DOI:10.1021/om9706774

NaBAr′₄ (Ar′ = 3,5-C₆H₃(CF₃)₂) abstracts chloride from Ru(η⁵-C₅Me₅)(Me₂NCH ₂CH₂NMe₂)Cl (1) in Et₂O to give the stable cationic 16e complex [Ru(η⁵-C₅Me₅)(Me₂NCH ₂CH₂NMe₂)]BAr′₄ (2). Exposure of a Et₂O solution of 2 to air at room temperature yields the novel monomeric hydroxotetramethylfulvene complex [Ru(η⁶-C₅Me₄CH₂)(Me ₂NCH₂CH₂NMe₂)(OH)]BAr′ ₄ (4).

Full text of DOI:10.1021/om9706774

Organometallics 1997, 16, 5601-5603
5601
[Ru (η5-C5Me5)(Me2NCH2CH2NMe2)]+, a Sta ble 16-Electr on
Com p lex. Rea ction w ith Dioxygen a n d F or m a tion of a
Mon om er ic Hyd r oxor u th en iu m Tetr a m eth ylfu lven e
Com p lex
Christian Gemel,† Kurt Mereiter,‡ Roland Schmid,† and Karl Kirchner*,†,§
Institute of Inorganic Chemistry and Institute of Mineralogy, Crystallography, and Structural
Chemistry, Technical University of Vienna, Getreidemarkt 9, A-1060 Vienna, Austria
Received August 4, 1997X
Summary: NaBAr′4 (Ar′ ) 3,5-C6H3(CF3)2) abstracts
chloride from Ru(η5-C5Me5)(Me2NCH2CH2NMe2)Cl (1)
in Et2O to give the stable cationic 16e complex [Ru(η5-
C5Me5)(Me2NCH2CH2NMe2)]BAr′4 (2). Exposure of a
Et2O solution of 2 to air at room temperature yields the
novel monomeric hydroxotetramethylfulvene complex
[Ru(η6-C5Me4CH2)(Me2NCH2CH2NMe2)(OH)]BAr′4 (4).
Coordinatively unsaturated half-sandwich ruthenium
complexes that are not stabilized by heteroatomic
anionic ligands through metal-ligand multiple bonds,
e.g., alkoxides or halides,1 appear to be very reactive
and to date have not been isolated or structurally
characterized. Thus, compounds of the type [Ru(η5-C5-
Me5)(P-P)]+ (P-P ) tertiary bisphosphines) are pre-
pared in situ and react readily with dioxygen to give
stable peroxo Ru(IV) complexes [Ru(η5-C5Me5)(P-P)(η2-
O2)]+.2 The related complex [Ru(η5-C5Me5)(Ph2PCH2-
CH2NMe2)]+ smoothly undergoes N-methyl â-hydrogen
elimination to give a cyclometallated complex.3 If the
P-P or P-N coligand is replaced with a diamine, N-N,
group, a remarkably stable unsaturated complex is
obtained. Herein we report the first cationic 16e
ruthenium complex [Ru(η5-C5Me5)(Me2NCH2CH2NMe2)]+,
adding to the recently described isostructural iron
F igu r e 1. Structural view of [Ru(η5-C5Me5)(Me2NCH2CH2-
NMe2)]BAr′4 (2). Selected bond lengths (Å) and angles
(deg): Ru-C(1-5)av, 2.124(7); Ru-N(1), 2.183(7); Ru-N(2),
2.180(6); N(1)-Ru-N(2), 80.3(3).
Et2O affords the blue cationic 16e complex [Ru(η5-C5-
Me5)(Me2NCH2CH2NMe2)]BAr′4 (2) in 92% isolated
yield.9,10,11 Characterization of 2 was achieved by
elemental analysis, and 1H and 13C{1H} NMR spec-
troscopies.9 The complex is characterized by the pres-
1
ence of single resonances in the H NMR spectrum for
4a
variants [Fe(η5-C5Me5)(Ph2PCH2CH2PPh2)]PF6 and
the NMe2 and NCH2CH2N protons. The simplicity of
the spectrum is indicative of a cationic complex that has
C2v symmetry. This is also supported by the 13C{1H}
NMR data and unequivocally confirmed by X-ray crys-
tallography (see Figure 1).12 The angle between the
planes defined by the C5Me5 ring and the atoms N(1),
Ru, and N(2) is 89.3(3)°, indicating no pyramidalization
[Fe(η5-C5Me5)(Pri PCH2CH2PPri )]BPh4,4b and also de-
2
2
lineate some reactivities. It may be noted that the solid
Ru(η5-C5Me5)(acac) purported to be a 16e complex5
turned out to be a dimer.6
Halide abstraction from Ru(η5-C5Me5)(Me2NCH2CH2-
NMe2)Cl (1)7 with NaBAr′4 (Ar′ ) 3,5-C6H3(CF3)2)8 in
† Institute of Inorganic Chemistry.
(9) Preparation and data for 2: A solution of 1 (86 mg, 0.222 mmol)
in Et2O (4 mL) was treated with NaBAr′4 (196 mg, 0.222 mmol) and
stirred for 5 min at room temperature. After removal of the solvent,
the residue was dissolved in Et2O (0.5 mL), insoluble materials were
removed by filtration, and the blue product was precipitated by
‡ Institute of Mineralogy, Crystallography, and Structural Chem-
istry.
§ E-mail: kkirch@fbch.tuwien.ac.at.
X Abstract published in Advance ACS Abstracts, November 15, 1997.
(1) J ohnson, T. J .; Folting, K.; Strib, W. E.; Martin, J . D.; Huffman,
J . C.; J ackson, S. A.; Eisenstein, O.; Caulton, K. G. Inorg. Chem. 1995,
34, 488.
addition of n-hexane. Yield: 248 mg (92%). Anal. calcd. for C48H43
-
BF24N2Ru: C, 47.42; H, 3.57; N, 2.30. Found: C, 47.77; H, 3.83; N,
2.04. 1H NMR (δ, CD2Cl2, -40 °C): 7.76 (m, 8H), 7.61 (s, 4H), 2.88 (s,
12H, NMe2), 1.80 (s, 4H, NCH2CH2N), 1.45 (s, 15H, C5Me5). 13C{1H}
NMR (δ, CD2Cl2, -40 °C): 160.3 (q, J BC ) 49.6 Hz), 133.3, 127.4 (q,
J CF ) 31.5 Hz), 123.1 (q, J CF ) 272.3 Hz), 115.9, 69.3 (C5Me5), 57.1,
48.3, 8.5 (C5Me5).
(10) If NaBPh4 is used for halide abstraction, not 2 but the sandwich
complex Ru(η5-C5Me5)(η6-C6H5BPh3) is quantitatively formed.
(11) For related 16e ruthenium complexes, see: Campion, B. K.;
Heyn, R. H.; Tilley, D. D. J . Chem. Soc., Chem. Commun. 1988, 278.
Lindner, E.; Haustein, M.; Mayer, H. A.; Gierling, K.; Fawzi, R.;
Steinmann, M. Organometallics 1995, 14, 2246. Sutter, J .-P.; J ames,
S. L.; Steenwinkel, P.; Karlen, T.; Grove, D. M.; Veldman, N.; Smeets,
W. J . J .; Spek, A. L.; van Koten, G. Organometallics 1996, 15, 941.
Mashima, K.; Kaneyoshi, H.; Kaneko, S.; Mikami, A. Tani, K.;
Nakamura, A. Organometallics 1997, 16, 1016.
(2) (a) Kirchner, K.; Mauthner, K.; Mereiter, K.; Schmid, R. J . Chem.
Soc., Chem. Commun. 1993, 892. (b) Lindner, E.; Haustein, M.; Fawzi,
R.; Steimann, M.; Wegner, P. Organometallics 1994, 13, 5021. (c) de
los Rios, I.; J imenez Tenorio, M.; Padilla, J .; Puerta, M. C.; Valerga,
P. J . Chem. Soc., Dalton Trans. 1996, 377.
(3) Mauthner, K.; Slugovc, C.; Mereiter, K.; Schmid, R.; Kirchner,
K. Organometallics 1997, 16, 1956.
(4) (a) Hamon, P.; Toupet, L.; Hamon, J .-R.; Lapinte, C. Organo-
metallics 1996, 15, 10. (b) de la J ara Leal, A.; Tenorio, M. J .; Puerta,
M. C.; Valerga, P. Organometallics 1995, 14, 3839.
(5) Ko¨lle, U.; Kossakowski, J .; Raabe, G. Angew. Chem., Int. Ed.
Engl. 1990, 29, 773.
(6) Ko¨lle, U.; Rietmann, C.; Raabe, G. Organometallics 1997, 16,
3273.
(7) Wang, M. H.; Englert, U.; Ko¨lle, U. J . Organomet. Chem. 1993,
453, 127.
(8) Brookhart, M.; Grant, B.; Volpe, J . Organometallics 1992, 11,
3920.
(12) Crystal data of 2: monoclinic space group P21/c (no. 14), a )
12.968(5) Å, b ) 19.841(8) Å, c ) 21.505(8) Å, â ) 104.91(1)°, V ) 5347-
(4) Å3, Z ) 4, R1 ) 0.065 (I g 2σ(I)), R1 ) 0.089 (all data), wR2 ) 0.192
(all data), no. of reflections 6880, no. of refined parameters 677.
S0276-7333(97)00677-8 CCC: $14.00 © 1997 American Chemical Society

5602 Organometallics, Vol. 16, No. 26, 1997
Communications
Sch em e 1
at the metal center. A planar ground-state structure
has indeed been predicted on the basis of MO calcula-
tions for diamagetic d6 complexes of the types CpML2
and CpMLL′ when L and L′ are pure or predominant
σ-donor ligands.1,13 The shortest distance between the
ruthenium center and the carbon and hydrogen atoms
of the NMe2 groups is 2.97 and 3.05 Å, respectively,
excluding agostic interactions. Compound 2 is remark-
ably stable for a 16e complex and does not react with
H2, HSiEt3, or MeBr. However, treatment of 2 with Br2
(0.5 equiv) affords the monobromo Ru(III) complex
[Ru(η5-C5Me5)(Me2NCH2CH2NMe2)Br]+ (3) instead of
the expected dibromo Ru(IV).2a
Exposure of a Et2O solution of 2 to air at room
temperature yields the novel monomeric hydroxotet-
ramethylfulvene complex [Ru(η6-C5Me4CH2)(Me2NCH2-
CH2NMe2)(OH)]BAr′4 (4) in 86% yield (Scheme 1). This
reaction involves methyl C-H bond cleavage of the C5-
Me5 ligand. 1H and 13C{1H} NMR spectra of 4 showed
the characteristic resonances of the coligands.14 The
X-ray analysis of crystals of 4 revealed15 its monomeric
nature (see Figure 2). The coordination about the Ru-
(II) is approximately octahedral, three sites being taken
up by an η6-tetramethylfulvene, the remaining three by
one terminal OH group and the Me2NCH2CH2NMe2
ligand. The methylenic dCH2 is bent toward the metal
by about 0.87 Å from the C5 plane, corresponding to an
angle of about 39.2°. Dioxygen-induced methyl C-H
activations of transition metal coordinated C5Me5 and
C6Me6 ligands, which may be related to this process,
have been reported previously.16 The formation of a
hydroxo species could involve prior dioxygen coordina-
tion at ruthenium. Indeed, if the reaction of 2 with O2
is carried out at -50 °C in Et2O, a diamagnetic complex,
tentatively formulated as [Ru(η5-C5Me5)(Me2NCH2CH2-
NMe2)(O2)]+ (5), but contaminated with 4 (ca. 10%), is
isolated and characterized by 1H and 13C{1H} NMR
F igu r e 2. Structural view of [Ru(η6-C5Me4CH2)(Me2NCH2-
CH2NMe2)(OH)]BAr′4 (4). Selected bond lengths (Å) and
angles (deg): Ru-N(1), 2.213(5); Ru-N(2), 2.238(5); Ru-
O, 1.990(3); Ru-C(1), 2.074(6); Ru-C(2), 2.158(6); Ru-
C(3), 2.184(7); Ru-C(4), 2.218(7); Ru-C(5), 2.186(6); Ru-
C(6), 2.430(11); N(1)-Ru-N(2), 80.3(2).
spectroscopies.17 In the 13C{1H} NMR spectrum, reso-
nances of the ring carbon atoms of the C5Me5 ligand are
low-field-shifted from 69.3 ppm in 2 to 106.2 ppm in 5,
indicative of an oxidation state of ruthenium >+II. On
warming an anaerobic acetone-d6 solution of 5 (con-
taminated with 4) from -50 to 0 °C, 4 is formed
quantitatively as monitored by 1H NMR spectroscopy.17
This conversion is also achieved even at low tempera-
ture upon addition of PPh3 (1 equiv), giving 4 and
OdPPh3 in a ratio of 1:1. This result is evidence of 5
containing coordinated dioxygen. It is not clear at
present whether a d5 Ru(III) superoxo or a d4 Ru(IV)
peroxo complex is dealt with. The diamagnetic behavior
of 5 would be consistent with both descriptions since in
the first case magnetic coupling between the metal (S
1
1
) /2) and the superoxide ligand (S ) /2) may occur,
resulting in a ground state with S ) 0.18 Unfortunately,
IR measurements are hampered due to the intensive
-
bands of the BAr′4 anion overlapping with the O-O
stretching frequencies of coordinated dioxygen (O2
-
1200-1070 cm-1, O22- 930-740 cm-1).18 The formula-
tion of a superoxo Ru(III) compound is conjectural but
is in line with the finding that no Ru(η5-C5Me5) complex
in conjunction with N-donor ligands in the oxidation
state +IV is known. It should also be noted that 5 does
not react with Me2CdCMe2 to give an epoxide.
In summary, we have shown that the Ru(η5-C5Me5)
fragment bearing a hard σ-donor N-N coligand actually
forms a remarkably stable 16e complex, while in the
(13) Ward, T. R.; Schafer, O.; Daul, C.; Hofmann, P. Organometallics
1997, 16, 3207.
(16) For related ruthenium fulvene complexes, see: Fan, L.; Turner,
M. L.; Hursthouse, M. B.; Malik, K. M. A.; Gusev, O. V.; Maitlis, P. M.
J . Am. Chem. Soc. 1994, 116, 385. Fan, L.; Wei, C.; Aigbirhio, F. I.;
Turner, M. L.; Gusev, O. V.; Morozova, L. N.; Knowles, D. R. T.; Maitlis,
P. M. Organometallics 1996, 15, 98. Li, C.; Luo, L.; Nolan, S. P.;
Marshall, W.; Fagan, P. J . Organometallics 1996, 15, 3456. Ko¨lle, U.;
Kang, B.-S. J . Organomet. Chem. 1990, 386, 267. For ruthenium-
hydroxo systems, see: Burn, M. J .; Fickes, M. G.; Hartwig, J . F.;
Hollander, F. J .; Bergman, R. G. J . Am. Chem. Soc. 1993, 115, 5875.
(17) NMR data for 5: 1H NMR (δ, acetone-d6, -50 °C): 7.80 (m, 8H),
7.68 (s, 4H), 3.12-2.70 (m, 4H), 2.87 (s, 6H), 2.70 (s, 6H), 1.56 (s, 15H,
C5Me5). 13C{1H} NMR (δ, acetone-d6, -50 °C): 163.1 (q, J BC ) 49.6
Hz), 135.8, 130.3 (q, J CF ) 32.0 Hz), 125.6 (q, J CF ) 271.8 Hz), 119.1,
106.2 (C5Me5), 64.7, 56.5, 52.4, 9.7 (C5Me5).
(14) Preparation and data for 4: A solution of 2 (123 mg, 0.101 mmol)
in Et2O (4 mL) was stirred at room temperature in the presence of air
for 3 min. After removal of the solvent, the residue was dissolved in
Et2O (0.5 mL), insoluble materials were removed by filtration, and the
product was precipitated by adding n-hexane. Yield: 107 mg (86%).
Anal. Calcd for C48H43BF24N2ORu: C, 46.81; H, 3.52; N, 2.27. Found:
C, 46.72; H, 3.68; N, 2.14. 1H NMR (δ, acetone-d6, -50 °C): 7.80 (m,
8H), 7.69 (s, 4H), 4.47 (s, 2H, dCH2), 3.07-2.96 (m, 2H), 2.89 (s, 6H),
2.74-2.62 (m, 2H), 2.55 (s, 6H), 1.74 (s, 6H), 1.72 (s, 6H). 13C{1H} NMR
(δ, acetone-d6, -50 °C): 163.0 (q, J BC ) 50.1 Hz), 135.9, 130.4 (q, J CF
) 32.0 Hz), 125.8 (q, J CF ) 271.8 Hz), 119.1, 103.2, 95.4, 70.3, 66.7,
62.0, 56.2, 51.0, 9.1, 8.9.
(15) Crystal data of 4: triclinic space group P1h (no. 2), a ) 12.400-
(4) Å, b ) 13.176(4) Å, c ) 17.276(5) Å, R ) 96.63(1)°, â ) 96.52(1)°, γ
) 95.38(1)°, V ) 2769(2) Å3, Z ) 2, R1 ) 0.054 (I g 2σ(I)), R1 ) 0.079
(all data), wR2 ) 0.163 (all data), no. of reflections 9699, no. of refined
parameters 919.
(18) (a) Zhang, X.; Loppnow, G. R.; McDonald, R.; Takats, J . J . Am.
Chem. Soc. 1995, 117, 7828. (b) Fujisawa, K.; Tanaka, M.; Moro-oka,
Y.; Kitajima, N. J . Am. Chem. Soc. 1994, 116, 12079. (c) Egan, J . W.;
Haggerty, B. S.; Rheingold, A. L.; Sendlinger, S. C.; Theopold, K. H.
J . Am. Chem. Soc. 1990, 112, 2445.

Communications
Organometallics, Vol. 16, No. 26, 1997 5603
case of the Ph2PCH2CH2NMe2 coligand oxidative addi-
tion of the methyl C-H bond takes place. For the Me2-
NCH2CH2NMe2 ligand, not even any agostic interaction
between the ruthenium center and the N-methyl C-H
bond could be observed. Further, in situ prepared 16e
complexes with a bisphosphine coligand are reactive
toward H2, Br2, or O2 undergoing oxidative addition to
form Ru(IV) complexes. In contrast with the N-N
coligand, such 2e changes do not appear to be realized,
but instead a Ru(III) complex is favored. From this
point of view, coordination of dioxygen should lead to a
superoxo rather than a peroxo compound. This inter-
mediate eventually activates a methyl C-H bond of the
C5Me5 ligand, giving rise to the hydroxoruthenium
tetramethylfulvene complex.
Ack n ow led gm en t. Financial support by the “Fonds
zur Fo¨rderung der wissenschaftlichen Forschung” is
gratefully acknowledged (Project No. 11896).
Su p p or tin g In for m a tion Ava ila ble: Text giving full
experimental details and analytical data for complex 3 and
tables of X-ray structural data, including data collection
parameters, positional and thermal parameters, and bond
distances and angles for complexes 2 and 4 (32 pages).
Ordering information is given on any current masthead page.
OM9706774