Synthesis and characterization of dibromo-containing ruthenium(IV) η3-allyl and ruthenium(IV) η4-diene complexes. Formation of [Ru(η5-C5Me5)Br3]- and [Ru(η5-C5Me5)Br3]2

Article abstract of DOI:10.1021/om950662a

The reaction of Br₂ with Ru(η⁵-C₅H₅)(η⁴-diene)Br (diene = 1,3-butadiene (1a), 2-methyl-1,3-butadiene (1b), 1,3-hexadiene (1c)), Ru(η⁵-C₅Me₅)(η⁴-diene)Br (diene = 1,3-butadiene (2a), 2-methyl-1,3-butadiene (2b), 3-methyl-1,3-pentadiene (2c), 1,3-hexadiene (2d), 1-methoxy-1,3-butadiene (2e), 2,4-hexadiene (2f), phenyl-1,3-pentadiene (2g), diphenyl-1,3-butadiene (2h), 1,3-cyclohexadiene (2i), 2,3-dimethoxy-1,3-butadiene (2j), 2,3-dimethyl-1,3-butadiene (2k), 1,2-dimethylenecyclohexane (2l)), and Ru(η⁵-C₅Me₄Et)(η⁴-diene)Br (diene = 2,4-hexadiene (3)) has been studied. 1,3-Butadiene and mono-, and 1,2-disubstituted-1,3-butadiene complexes afford bromo-substituted Ru(IV) anti η³-allyl complexes in high yields. This process involves addition of bromine on the exo face of the diene ligand taking place regioselectively at the terminal carbon bearing no substituent. Unexpectedly, bromination of 2d yields the dibromoruthenium(IV) η-(1-3)-hexa-1,4-dien-3-yl complex (6). In the course of this process HBr is liberated involving the intermediacy of bromo-substituted Ru(IV) η³-allyl complexes. The molecular structure of 6 has been determined. 1,4-Disubstituted-1,3-butadiene complexes 2f-h and 3 react with Br₂ to form bromo-substituted Ru(IV) η³-allyl complexes 10a-c and 11 adopting exclusively the syn configuration. These compounds are not stable in solution and decompose to give either a dibromoruthenium(IV) η-(1-3)-hexa-1,4-dien-3-yl complex, as a result of HBr elimination, or the dimeric Ru(IV) complexes [Ru-(η⁵-C₅Me₅)Br₃]₂ (13) and [Ru(η⁵-C₅Me₄Et)Br₃]₂ (14), respectively. In order to explain the observed stereochemistry and reactivity of complexes 10a-c and 11 a weak three-center 4e^- C-Br?Ru interaction is proposed. In case of 2i, bromination leads to the formation of the complex salt [Ru(η⁵-C₅Me₅)(η⁶-C ₆H₆)][Ru(η⁵-C₅Me ₅)Br₃] (15) and of the dimeric Ru(III) complex [Ru(η⁵-C₅Me₅)Br₂]₂. 15 features a novel monomeric 17e^- half-sandwich Ru(III) complex as counteranion. The molecular structure of 15 has been determined. By contrast, bromination of 2,3-disubstituted-1,3-butadiene complexes 2j,k affords the novel cationic Ru(IV) η⁴-diene complexes [Ru(η⁵-C₅Me₅)(η ⁴-diene)Br₂]Br (diene = 2,3-dimethoxy-1,3-butadiene (16a), 2,3-dimethyl-1,3-butadiene (16b)). Complexes 16a,b are not stable in solution in the presence of Br^-. On replacement of the bromide counterion by CF₃SO₃^- the stable complexes 17a,b are obtained. The molecular structures of both 16a and 17a have been determined. Complexes 16 and 17 appear to be the first late transition-metal complexes approaching a σ²,π-metallacyclopentene structure.

Full text of DOI:10.1021/om950662a

532
Organometallics 1996, 15, 532-542
Syn th esis a n d Ch a r a cter iza tion of Dibr om o-Con ta in in g
Ru th en iu m (IV) η3-Allyl a n d Ru th en iu m (IV) η4-Dien e
Com p lexes. F or m a tion of [Ru (η5-C5Me5)Br 3]- a n d
[Ru (η5-C5Me5)Br 3]2
Christian Gemel,1a Kurt Mereiter,1b Roland Schmid,1a and Karl Kirchner*,1a
Institute of Inorganic Chemistry and Institute of Mineralogy, Crystallography, and Structural
Chemistry, Technical University of Vienna, Getreidemarkt 9, A-1060 Vienna, Austria
Received August 23, 1995X
The reaction of Br2 with Ru(η5-C5H5)(η4-diene)Br (diene ) 1,3-butadiene (1a ), 2-methyl-
1,3-butadiene (1b), 1,3-hexadiene (1c)), Ru(η5-C5Me5)(η4-diene)Br (diene ) 1,3-butadiene (2a ),
2-methyl-1,3-butadiene (2b), 3-methyl-1,3-pentadiene (2c), 1,3-hexadiene (2d ), 1-methoxy-
1,3-butadiene (2e), 2,4-hexadiene (2f), phenyl-1,3-pentadiene (2g), diphenyl-1,3-butadiene
(2h ), 1,3-cyclohexadiene (2i), 2,3-dimethoxy-1,3-butadiene (2j), 2,3-dimethyl-1,3-butadiene
(2k ), 1,2-dimethylenecyclohexane (2l)), and Ru(η5-C5Me4Et)(η4-diene)Br (diene ) 2,4-
hexadiene (3)) has been studied. 1,3-Butadiene and mono-, and 1,2-disubstituted-1,3-
butadiene complexes afford bromo-substituted Ru(IV) anti η3-allyl complexes in high yields.
This process involves addition of bromine on the exo face of the diene ligand taking place
regioselectively at the terminal carbon bearing no substituent. Unexpectedly, bromination
of 2d yields the dibromoruthenium(IV) η-(1-3)-hexa-1,4-dien-3-yl complex (6). In the course
of this process HBr is liberated involving the intermediacy of bromo-substituted Ru(IV) η3-
allyl complexes. The molecular structure of 6 has been determined. 1,4-Disubstituted-1,3-
butadiene complexes 2f-h and 3 react with Br2 to form bromo-substituted Ru(IV) η3-allyl
complexes 10a -c and 11 adopting exclusively the syn configuration. These compounds are
not stable in solution and decompose to give either a dibromoruthenium(IV) η-(1-3)-hexa-
1,4-dien-3-yl complex, as a result of HBr elimination, or the dimeric Ru(IV) complexes [Ru-
(η5-C5Me5)Br3]2 (13) and [Ru(η5-C5Me4Et)Br3]2 (14), respectively. In order to explain the
observed stereochemistry and reactivity of complexes 10a -c and 11 a weak three-center
4e- C-Br‚‚‚Ru interaction is proposed. In case of 2i, bromination leads to the formation of
the complex salt [Ru(η5-C5Me5)(η6-C6H6)][Ru(η5-C5Me5)Br3] (15) and of the dimeric Ru(III)
complex [Ru(η5-C5Me5)Br2]2. 15 features a novel monomeric 17e- half-sandwich Ru(III)
complex as counteranion. The molecular structure of 15 has been determined. By contrast,
bromination of 2,3-disubstituted-1,3-butadiene complexes 2j,k affords the novel cationic
Ru(IV) η4-diene complexes [Ru(η5-C5Me5)(η4-diene)Br2]Br (diene ) 2,3-dimethoxy-1,3-buta-
diene (16a ), 2,3-dimethyl-1,3-butadiene (16b)). Complexes 16a ,b are not stable in solution
in the presence of Br-. On replacement of the bromide counterion by CF3SO3 the stable
-
complexes 17a ,b are obtained. The molecular structures of both 16a and 17a have been
determined. Complexes 16 and 17 appear to be the first late transition-metal complexes
approaching a σ2,π-metallacyclopentene structure.
In tr od u ction
gated diene and acetylene3 and stoichiometric and
catalytic dimerization reactions of 1,3-dienes with Ru-
(η5-C5R5)(η4-diene) (R ) H, Me; diene ) 1,3-butadiene,
2-methyl-1,3-butadiene).4
As part of our current interest in the chemistry of
ruthenium diene complexes we have previously re-
ported5,6 on the oxidative addition of Br2 to complexes
of the type Ru(η5-C5Me5)(η4-diene)Br. The products of
Transition metal complexes containing conjugated
dienes are numerous and constitute an important class
of organometallic compounds. There is considerable
current interest in such complexes due to their applica-
tions in organic synthesis.2 Quite elaborate is the
organic chemistry of iron complexes of conjugated
dienes.2 The chemistry of ruthenium diene complexes,
however, has developed only recently including ruthe-
nium-mediated [2 + 4] cycloadditions between a conju-
(3) Masuda, K.; Ohkita, H.; Kurumatini, S.; Itoh, K. Organometallics
1993, 12, 2221.
(4) Itoh, K.; Masuda, K.; Fukahori, T.; Nakano, K.; Aoki, K.;
Nagashima, H. Organometallics 1994, 13, 1020.
(5) (a) Kirchner, K.; Mereiter, K.; Schmid, R. J . Chem. Soc., Chem.
Commun. 1994, 161. (b) Kirchner, K.; Mereiter, K.; Umfahrer, A.;
Schmid, R. Organometallics 1994, 13, 1886. (c) Mauthner, K.; Mereiter,
K.; Schmid, R.; Kirchner, K. Organometallics 1994, 13, 5054.
(6) Gemel, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometal-
lics 1995, 14, 1405.
X Abstract published in Advance ACS Abstracts, December 1, 1995.
(1) (a) Institute of Inorganic Chemistry. (b) Institute of Mineralogy,
Crystallography, and Structural Chemistry.
(2) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G. In
Principles and Applications of Organotransitionmetal Chemistry, 2nd
ed.; University Science Books: Mill Valley, CA, 1987.
0276-7333/96/2315-0532$12.00/0 © 1996 American Chemical Society

Ru(IV) η3-Allyl and Ru(IV) η4-Diene Complexes
Organometallics, Vol. 15, No. 2, 1996 533
Yield: 75%. Anal. Calcd for C10H13Br3Ru: C, 25.34; H, 2.76;
Br, 50.57. Found: C, 25.43; H, 2.72; Br, 50.39. 1H NMR (δ,
CD2Cl2, 20 °C): 5.96 (s, 5H), 5.21 (m, 1H), 4.67 (s, 1H), 4.09
(dd, 1H, J ) 9.1 Hz, J ) 3.6 Hz), 4.0 (d, 1H, J ) 1.7 Hz), 3.60
(dd, 1H, J ) 12.8 Hz, J ) 9.1 Hz), 2.26 (s, 3H). 13C{1H} NMR
(δ, CD2Cl2, 20 °C): 108.7, 96.0 (C5H5), 76.9, 57.3, 36.8 (CH2-
Br), 21.2 (Me).
(η5-Cyclop en ta d ien yl)d ibr om o(η-(2-4)-1-br om o-2-h ex-
en -4-yl)r u th en iu m (IV) (4c). This complex was synthesized
analogously to 4a with 1c as starting material. Yield: 83%.
Anal. Calcd for C11H15Br3Ru: C, 27.07; H, 3.10; Br, 49.12.
Found: C, 27.03; H, 3.01; Br, 49.23. 1H NMR (δ, CD2Cl2, 20
°C): 5.69 (s, 5H), 5.50 (m, 1H), 5.00 (m, 1H), 4.61 (dd, 1H, J )
6.8 Hz, J ) 11.6 Hz), 3.78 (dd, 1H, J ) 11.9 Hz, J ) 6.8 Hz),
3.40 (dd, 1H, J ) 11.6 Hz, J ) 11.9 Hz), 2.32-2.25 (m, 2H),
1.06 (t, 3H).
this reaction vary with the substituents of the diene
moiety. In the case of 2,4-cyclopentadienone, 1,3-
butadiene, and 2-methyl-1,3-butadiene neutral dibro-
moruthenium(IV) η3-allyl complexes are readily formed.
For 2,3-dimethyl-1,3-butadiene, in contrast, a novel
cationic dibromoruthenium(IV) η4-diene complex is ob-
tained being the first group 8 transition metal diene
complex approaching a metallacyclopentene structure.
In view of these findings, and to aid the interpretation
of these results, we have extended our studies and
report on the oxidative addition of Br2 to a variety of
Ru(η5-C5R5)(η4-diene)Br (R ) H, Me) complexes where
diene is
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(1-3)-4-
br om o-1-bu ten -3-yl)r u th en iu m (IV) (5a ). This complex was
synthesized analogously to 4a with 2a as starting material.
Yield: 330 mg (92%). Anal. Calcd for C14H21Br3Ru: C, 31.72;
H, 3.99; Br, 45.22. Found: C, 31.79; H, 4.02; Br, 45.32. 1H
NMR (δ, CDCl3, 20 °C): 5.90-5.60 (m, 1H), 5.48-5.35 (m, 1H),
4.38 (m, 1H), 3.59 (m, 1H), 2.98-2.86 (m, 2H), 1.57 (s, 15H).
X-ray structures of representative complexes and de-
composition products are given.
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(1-3)-4-
br om o-2-m et h yl-1-bu t en -3-yl)r u t h en iu m (IV) (5b ). This
complex was synthesized analogously to 4a with 2b as starting
material. Yield: 96%. Anal. Calcd for C15H23Br3Ru: C, 33.11;
H, 4.26; Br, 44.05. Found: C, 32.96; H, 4.17; Br, 44.06. 1H
Exp er im en ta l Section
Gen er a l In for m a tion . Manipulations were performed
under an inert atmosphere of purified nitrogen by using
standard Schlenk techniques and/or a glovebox. All chemicals
were standard reagent grade and used without further puri-
fication. The solvents were purified according to standard
procedures.7 The deuterated solvents were purchased from
Aldrich and dried over 4 Å molecular sieves. 1H and 13C{1H}
NMR spectra were recorded on a Bruker AC 250 spectrometer
operating at 250.13 and 62.86 MHz, respectively, and were
referenced to residual solvent protons. Microanalyses were
done by the Microanalytical Laboratories, University of Vi-
enna. Ru(η5-C5H5)(η4-diene)Br (diene ) 1,3-butadiene (1a ),
2-methyl-1,3-butadiene (1b) 1,3-hexadiene (1c)),8 Ru(η5-C5-
Me5)(η4-diene)Br (diene ) 1,3-butadiene (2a ), 2-methyl-1,3-
butadiene (2b), 3-methyl-1,3-pentadiene (2c), 1,3-hexadiene
(2d ), 1-methoxy-1,3-butadiene (2e), 2,4-hexadiene (2f), phenyl-
1,3-pentadiene (2g), diphenyl-1,3-butadiene (2h ), 1,3-cyclo-
hexadiene (2i), 2,3-dimethoxy-1,3-butadiene (2j), 2,3-dimethyl-
1,3-butadiene (2k ), 1,2-dimethylene-cyclohexane (2l)),9 and
Ru(η5-C5Me4Et)(η4-diene)Br (diene ) 2,4-hexadiene (3))9 have
been synthesized according to literature methods.
3
NMR (δ, CD2Cl2, 20 °C): 5.07 (ddd, 1H, H3, J 35 ) 12.9 Hz,
4
4
J 34 ) 3.8 Hz, J 23 ) 1.9 Hz), 3.79 (d, 1H, H2, J 23 ) 1.9 Hz),
3
3.73 (dd, 1H, H4, J 45 ) 8.5 Hz, J 34 ) 3.8 Hz), 3.01 (dd, 1H,
2
3
H5, J 35 ) 12.9 Hz, J 45 ) 8.5 Hz), 2.97 (s, 1H, H1), 2.40 (s,
3H), 1.74 (s, 15H). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 108.2,
105.5 (C5Me5), 71.4, 56.4, 35.3 (CH2Br), 22.4 (Me), 11.1 (C5Me5).
3
2
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(2-4)-1-
br om o-3-m eth yl-2-p en ten -4-yl)r u th en iu m (IV) (5c). This
complex was synthesized analogously to 4a with 2c as starting
material. Yield: 97%. Anal. Calcd for C16H25Br3Ru: C, 34.43;
H, 4.51; Br, 42.95. Found: C, 34.51; H, 4.55; Br, 42.73. 1H
NMR (δ, CDCl3, 20 °C): 5.38 (dd, 1H, J ) 4.1 Hz, J ) 13.1
Hz), 3.72 (dd, 1H, J ) 3.9 Hz, J ) 8.7 Hz), 3.56 (m, 1H), 3.01
(dd, 1H, J ) 8.7 Hz, J ) 13.1 Hz), 2.36 (s, 3H), 1.75 (s, 15H),
1.66 (d, 3H, J ) 6.4 Hz).
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o([2,3-E,4,5-
Z]-η-(1-3)-h exa -1,4-d ien -3-yl)r u t h en iu m (IV) (6). To a
stirred solution of 2d (450 mg, 1.135 mmol), 1 g of Na2SO4,
and 1 g of NaHCO3 in CH2Cl2 (20 mL) at -60 °C, Br2 (1 equiv),
in CH2Cl2 (5 mL), was added dropwise within a period of 30
min. The mixture was then warmed to room temperature.
Solid materials were removed by filtration, and the volatiles
were removed under vacuum. The remaining red solid was
washed with anhydrous diethyl ether and dried under vacuum.
Yield: 406 mg (75%). Anal. Calcd for C16H24Br2Ru: C, 40.27;
H, 5.07; Br, 33.49. Found: C, 40.22; H, 5.11; Br, 33.41. 1H
Syn th esis. (η5-Cyclop en ta d ien yl)d ibr om o(η-(1-3)-4-
br om o-1-bu ten -3-yl)r u th en iu m (IV) (4a ). To a stirred solu-
tion of 1a (250 mg, 0.833 mmol) in CH2Cl2 (20 mL) at -60 °C,
Br2 (1 equiv), in CH2Cl2 (5 mL), was added dropwise within a
period of 30 min. The volatiles were then removed under
vacuum. The remaining red solid was washed with anhydrous
diethyl ether and dried under vacuum. Yield: 300 mg (78%).
Anal. Calcd for C9H11Br3Ru: C, 23.50; H, 2.41; Br, 52.11.
Found: C, 23.45; H, 2.48; Br, 52.03. 1H NMR (δ, acetone-d6/
dmso-d6 (9:1), 20 °C): 5.93 (s, 5H), 5.80-5.68 (m, 1H, H3),
4.84-4.77 (m, 1H, H4), 4.59 (d, 1H, J ) 11.3 Hz), 4.44 (dd,
1H, J ) 6.6 Hz, J ) 1.6 Hz), 4.05 (dd, 1H, J ) 9.3 Hz, J ) 3.7
Hz), 3.57 (dd, 1H, J ) 12.8 Hz, J ) 9.3 Hz). 13C{1H} NMR (δ,
acetone-d6/dmso-d6 9:1, 20 °C): 95.5 (C5H5), 95.5, 80.8, 59.4,
32.6 (CH2Br).
3
NMR (δ, CDCl3, 20 °C): 6.28 (ddd, 1H, H5, J 56 ) 11.2 Hz,
4
3J 45 ) 11.0 Hz, J ) 1.7 Hz), 6.12 (m, 1H, H6), 5.18 (ddd, 1H,
3
3
3
H3, J 23 ) 6.0 Hz, J 34 ) 10.5 Hz, J 13 ) 9.6 Hz), 4.27 (d, 1H,
3
3
3
H2, J 23 ) 6.0 Hz), 3.67 (dd, 1H, H4, J 34 ) 10.5 Hz, J 45
)
11.0 Hz), 2.18 (d, 1H, H1, J 13 ) 9.6 Hz), 1.64 (s, 15H), 1.61
3
(dd, 3H, J ) 1.7 Hz, J ) 6.7 Hz). 13C{1H} NMR (δ, CDCl3,
20 °C): 131.6, 131.3, 103.3 (C5Me5), 93.8, 83.7, 60.9, 14.8, 10.2
(C5Me5).
4
3
(η5-Cyclopen tadien yl)dibr om o(η-(1-3)-4-br om o-2-m eth -
yl-1-bu ten -3-yl)r u th en iu m (IV) (4b). This complex was
synthesized analogously to 4a with 1b as starting material.
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(2-4)-1-
oxo-2-bu ten -4-yl)r u th en iu m (IV) (7). This complex was
synthesized analogously to 4a with 2e as starting material.
Yield: 94%. Anal. Calcd for C14H20Br2ORu: C, 36.15; H, 4.33;
Br, 34.35. Found: C, 36.08; H, 4.34; Br, 34.22. 1H NMR (δ,
(7) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: New York, 1988.
(8) Albers, M. O.; Robinson, D. J .; Shaver, A.; Singleton, E. Orga-
nometallics 1986, 5, 2199.
(9) Fagan, P. J .; Mahoney, W. S.; Calabrese, J . C.; Williams, I. D.
Organometallics 1990, 9, 1843.
3
CDCl3, 20 °C): 8.55 (d, 1H, H5, J 34 ) 7.3 Hz), 5.87 (ddd, 1H,
3
3
3
H3, J 34 ) 6.6 Hz, J 23 ) 6.8 Hz, J 13 ) 10.6 Hz), 5.39 (ddd,

534 Organometallics, Vol. 15, No. 2, 1996
Gemel et al.
3
3
4
1H, H4, J 34 ) 6.6 Hz, J 45 ) 7.3 Hz, J 24 ) 1.7 Hz), 4.56 (dd,
analogous procedure as for 10a with 3 as starting material
resulted in a mixture of 11 and 14. No attempts were made
to separate these complexes. 1H NMR (δ, CDCl3, 20 °C): 5.51
(m, 1H), 5.11 (t, 1H, J ) 9.7 Hz), 2.73 (m, 2H), 1.92 (q, 2H),
1.73 (s, 6H), 1.71 (s, 6H), 1.69 (d, 6H, J ) 4.4 Hz), 1.18 (t, 3H).
(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o([E,E]-η-(1-
3)-h exa -1,4-d ien -3-yl)r u th en iu m (IV) (12). 10a (122 mg,
0.219 mmol) was dissolved in 10 mL of CH2Cl2. AgCF3SO3
(56 mg, 0.218 mmol) was added, and the mixture was stirred
for 1 h. The resulting precipitate of AgBr was removed by
filtration. On addition of diethyl ether a red precipitate was
formed which was collected on a glass frit, washed with diethyl
ether and dried under vacuum. Yield: 76 mg (73%). Anal.
Calcd for C16H24Br2Ru: C, 40.27; H, 5.07; Br, 33.49. Found:
C, 40.13; H, 5.19; Br, 33.35. 1H NMR (δ, CD3CN, 20 °C): 6.41-
6.32 (m, 1H, H6), 6.00 (ddd, 1H, H5, 3J 56 ) 14.5 Hz, 3J 45 ) 10.4
3
4
3
1H, H2, J 23 ) 6.8 Hz, J 24 ) 1.7 Hz), 3.22 (d, 1H, H1, J 13
)
10.6 Hz), 1.79 (s, 15H). 13C{1H} NMR (δ, CDCl3, 20 °C): 196.6,
107.1 (C5Me5), 99.3, 74.0, 60.0, 10.7 (C5Me5).
[(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(1-3)-4-
(t r ie t h yla m m on io)-2-m e t h yl-1-b u t e n -3-yl)r u t h e n iu m -
(IV)] Br om id e (8). To a solution of 5b (250 mg, 0.472 mmol)
in CH2Cl2 (10 mL), triethylamine (97 µL, 0.538 mmol) was
added, and the mixture was stirred for 30 min. On addition
of diethyl ether a red precipitate was formed, which was
collected on a glass frit, washed with diethyl ether, and dried
under vacuum. Yield: 240 mg (79%). Anal. Calcd for C21H38
-
Br3NRu: C, 39.09; H, 5.94; N, 2.17; Br, 37.15. Found: C,
38.99; H, 5.92; N, 2.12; Br, 37.02. 1H NMR (δ, CD3NO2, 20
°C): 4.67 (d, 1H, J ) 12.3 Hz), 3.84 (s, 1H), 3.50 (q, 6H), 3.25
(dd, 1H, J ) 13.8 Hz, J ) 2.6 Hz), 3.20 (s, 1H), 2.66 (t, 1H, J
) 13.8 Hz, J ) 12.3 Hz), 2.56 (s, 3H), 1.86 (s, 15H), 1.38 (t,
9H). 13C{1H} NMR (δ, CD3NO2, 20 °C): 110.8, 108.6 (C5Me5),
60.3, 58.6, 54.6, 47.3, 22.6 (Me), 11.5 (C5Me5), 7.6.
4
3
3
Hz, J ) 1.6 Hz), 5.29 (ddd, 1H, H3, J 23 ) 6.3 Hz, J 34 ) 10.6
3
2
Hz, J 13 ) 10.2 Hz), 4.46 (d, 1H, H2, J 23 ) 6.3 Hz), 3.93 (dd,
1H, H4, 3J 45 ) 10.4 Hz, 3J 34 ) 10.6 Hz), 2.50 (d, 1H, H1, 3J 13
)
10.2 Hz), 1.70 (dd, 3H, 4J ) 1.6 Hz, 3J ) 6.8 Hz), 1.64 (s, 15H).
13C{1H} NMR (δ, CD2Cl2, 20 °C): 140.5, 130.9, 106.3 (C5Me5),
95.2, 92.4, 66.1, 19.6 (Me), 9.8 (C5Me5).
[(η5-P en ta m eth ylcyclop en ta d ien yl)d ibr om o(η-(1,2,3)-
4-pyr idin iu m yl-2-m eth yl-1-bu ten -3-yl)r u th en iu m (IV)] Br o-
m id e (9). This complex was synthesized analogously to 8 but
with pyridine as the nucleophile. Yield: 99%. Anal. Calcd
for C20H28Br3NRu: C, 38.54; H, 4.53; N, 2.25; Br, 38.46.
Found: C, 38.49; H, 4.45; N, 2.17; Br, 38.18. 1H NMR (δ, CD3-
CN, 20 °C): 8.89 (d, 2H), 8.54 (t, 1H), 8.07 (t, 2H), 4.75 (d,
1H, J ) 13.3 Hz), 4.64 (d, 1H, J ) 12.6 Hz), 3.89 (t, 1H, J )
12.6 Hz), 3.89 (s, 1H), 3.36 (s, 1H), 2.23 (s, 3H), 1.86 (s, 15H).
13C{1H} NMR (δ, CD3NO2/dmso-d6, 20 °C): 146.2, 144.8, 128.5,
107.4, 106.7 (C5Me5), 66.5, 58.7, 54.6, 21.6 (Me), 10.7 (C5Me5).
(η5-P en t a m et h ylcyclop en t a d ien yl)d ib r om o([3,4-E]-η-
(2-4)-5-br om o-2-h exen -4-yl)r u th en iu m (IV) (10a ). This
complex was synthesized analogously to 4a with 2f as starting
material. Yield: 78%. Anal. Calcd for C16H25Br3Ru: C, 34.43;
H, 4.51; Br, 42.95. Found: C, 34.35; H, 4.49; Br, 43.15. 1H
Bis(µ-b r om o)b is[(η5-p en t a m et h ylcyclop en t a d ien yl)-
d ibr om or u th en iu m (IV)] (13). Meth od a . 13 was prepared
by following a published procedure.10 Meth od b. A solution
of either 10b or 10c in CH2Cl2 was set aside for crystallization
by vapor diffusion with diethyl ether. After 1 day a dark red
precipitate was formed, which was collected on a glass frit,
washed with diethyl ether, and dried under vacuum. Yield:
75%. Anal. Calcd for C20H30Br6Ru2: C, 25.23; H, 3.18; Br,
50.36. Found: C, 25.99; H, 3.21; Br, 50.73. 1H NMR (δ, dmso-
d6, 20 °C): 1.47 (s, 15H).
Bis(µ-br om o)bis[(η5-tetr am eth yleth ylcyclopen tadien yl)-
d ibr om or u th en iu m (IV)] (14). Meth od a . 14 was prepared
according to the literature but with [Ru(η5-C5Me4Et)Br2]2 as
starting material.10 Yield: 93%. Meth od b. A solution of 11
in CH2Cl2 was set aside for crystallization by vapor diffusion
with diethyl ether. Within 1 day dark red crystals were formed
which were suitable for an X-ray diffraction study. Yield: 89%.
Anal. Calcd for C22H34Br6Ru2: C, 26.96; H, 3.50; Br, 48.92.
Found: C, 26.87; H, 3.36; Br, 49.24. 1H NMR (δ, dmso-d6, 20
°C): 1.86 (q, 2H), 1.61 (s, 6H), 1.57 (s, 6H), 1.13 (t, 3H).
Rea ction of Br 2 w ith [η5-P en ta m eth ylcyclop en ta d i-
en yl)br om o(η4-2,4-cycloh exa d ien e)r u th en iu m (II). F or -
m ation of (η5-P en tam eth ylcyclopen tadien yl)(η6-ben zen e)-
r u th en iu m (II) (η5-P en ta m eth ylcyclop en ta d ien yl)tr ibr o-
m or u th en a te(III) (15). Using an analogous procedure as for
4a with 2i as starting material resulted in the formation of
NMR (δ, CD2Cl2, 20 °C): 5.48 (m, 1H, H1, J ) 6.7 Hz, J 12
)
3
3
10.1 Hz), 5.07 (t, 1H, H3, J 34 ) 9.6 Hz, J 23 ) 9.9 Hz), 2.70 (t,
3
3
3
3
3
1H, H2, J 12 ) 10.1 Hz, J 23 ) 9.9 Hz), 2.68 (m, 1H, H4, J 34
)
3
3
3
9.6 Hz, J ) 6.1 Hz), 1.72 (d, 3H, J ) 6.5 Hz), 1.71 (d, 3H, J
) 6.1 Hz), 1.65 (s, 15H). 13C{1H} NMR (δ, CD3CN, 20 °C):
104.5 (C5Me5), 98.3, 82.6, 81.6, 57.1, 26.2 (Me), 19.0 (Me), 10.2
(C5Me5).
(η5-P en t a m et h ylcyclop en t a d ien yl)d ib r om o([3,4-E]-η-
(2-4)-1-b r om o-1-p h e n yl-2-p e n t e n -4-yl)r u t h e n iu m (IV)
(10b). Using an analogous procedure as for 10a with 2g as
starting material resulted in the formation of a mixture of 10b
(ca. 60-80%) and 13. Attempts to recrystallize 10b from CH2-
Cl2 led to the quantitative formation of 13. 1H NMR (δ, CD2-
Cl2, 20 °C): 7.66 (dd, 2H), 7.43-7.29 (m, 3H), 6.89 (d, H1, H1,
J ) 11.2 Hz), 5.29 (t, 1H, H3, J ) 10.5 Hz), 3.19 (t, 1H, H2, J
) 10.5 Hz, J ) 11.2 Hz), 2.71-2.60 (m, 1H, H4), 1.71 (d, 3H,
J ) 6.4 Hz), 1.27 (s, 15H).
11
15 and [Ru(η5-C5Me5)Br2]2 in a ratio of about 1:1. 1H NMR
(δ, CDCl3, 20 °C): 7.43 (s, 6H); 2.40 (s, 15H), 1.89 (s, 30H). A
solution containing 15 and [Ru(η5-C5Me5)Br2]2 in CH2Cl2 was
set aside for crystallization by vapor diffusion with diethyl
ether. Within 1 day dark red crystals of morphologically
different appearance were formed. They were separated
manually and crystallographically analyzed.
1
The decomposition of 10b was also monitored by H NMR
spectroscopy. A 5-mm NMR tube was charged with the crude
product and was capped with a septum. CD2Cl2 (0.5 mL) was
added by syringe, and the sample was transferred to a NMR
probe. 1H NMR spectra were recorded showing the quantita-
tive formation of phenyl-1,3-pentadiene.
(η5-P en t a m et h ylcyclop en t a d ien yl)d ib r om o([3,4-E]-η-
(2-4)-1-b r om o-1,4-d ip h en yl-2-p en t en -4-yl)r u t h en iu m -
(IV) (10c). Using an analogous procedure as for 10a with 2h
as starting material resulted in the formation of a mixture of
10c (ca. 60-80%) and 13. Attempts to recrystallize 10c from
CH2Cl2 resulted in complete decomposition to give 13. 1H
NMR (δ, CD2Cl2, 20 °C): 7.62 (d, 4H), 7.36-7.26 (m, 6H), 6.95
(d, 1H, H1, J ) 9.8 Hz), 5.75 (dd, 1H, H3, J ) 10.8 Hz, J ) 9.3
Hz), 3.78 (d, 1H, J ) 10.8 Hz), 3.31 (dd, 1H, J ) 9.3 Hz, J )
9.8 Hz), 1.27 (s, 15H).
[(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)d ib r om o(η4-2,3-
dim eth oxybu tadien e)r u th en iu m (IV)] Br om ide (16a). This
complex was synthesized analogously to 4a with 2j as starting
material. Yield: 98%. Anal. Calcd for C16H25Br3O2Ru: C,
32.56; H, 4.27; Br, 40.62. Found: C, 32.65; H, 4.29; Br, 40.55.
1H NMR (δ, CD3CN, 20 °C): 4.24 (s, 6H), 3.92 (d, 2H, 2J ) 6.1
2
Hz), 2.61 (d, 2H, J ) 6.1 Hz), 1.97 (s, 15H).
[(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)d ib r om o(η4-2,3-
d im eth ylbu ta d ien e)r u th en iu m (IV)] Br om id e (16b). This
complex was synthesized analogously to 4a with 2k as starting
material.6 Yield: 93%. Anal. Calcd for C16H25Br3Ru: C,
(10) Oshima, N.; Suzuki, H.; Moro-oka, Y. J . Organomet. Chem.
1986, 314, C46.
(11) (a) Tilley, T. D.; Grubbs, R. H.; Bercaw, J . E. Organometallics
1984, 3, 274. (b) Oshima, N.; Suzuki, H.; Moro-oka, Y. Chem. Lett. 1984,
1161. (c) Koelle, U.; Kossakowski, J . J . Organomet. Chem. 1989, 362,
383.
1
The decomposition of 10c was also monitored by H NMR
spectroscopy showing the liberation of diphenyl-1,3-butadiene.
(η5-Tetr a m eth yleth ylcyclop en ta d ien yl)d ibr om o(η-(2-
4)-5-br om o-2-h exen -4-yl)r u th en iu m (IV) (11). Using an

Ru(IV) η3-Allyl and Ru(IV) η4-Diene Complexes
Organometallics, Vol. 15, No. 2, 1996 535
Ta ble 1. Cr ysta llogr a p h ic Da ta a
6
14
15
16a ‚CH2Cl2
C17H27Br3Cl2O2Ru C17H25Br2F3O5RuS
675.09 659.32
17a
formula
fw
C16H24Br2Ru
477.24
C11H17Br3Ru
490.05
C26H36Br3Ru2
790.42
cryst size, mm
space group
a, Å
b, Å
c, Å
0.11 × 0.18 × 0.20 0.06 × 0.15 × 0.35 0.17 × 0.19 × 0.80 0.06 × 0.11 × 0.18 0.06 × 0.28 × 0.56
P212121 (No. 19)
17.459(4)
P21/n (No. 14)
8.544(3)
13.003(5)
12.756(4)
93.44(1)
1414.6(9)
4
Pnma (No. 62)
19.511(5)
Pnma (No. 62)
13.810(3)
P21/c (No. 14)
9.562(3)
8.328(3)
29.120(9)
94.22(1)
2312.6(13)
4
13.624(4)
12.732(3)
10.128(2)
7.383(2)
11.512(3)
17.065(4)
â, deg
V, Å3
Z
1756.1(8)
4
2859.7(12)
4
2386.8(9)
4
F
calc, g cm-3
T, K
1.805
2.301
1.836
1.879
1.894
300
299
295
295
294
µ(Mo KR), mm-1
abs corr
5.43
9.55
5.26
5.91
4.27
analytical
0.47/0.60
25
empirical
0.86/1.16
24
empirical
0.93/1.13
25
analytical
0.53/0.72
24
analytical
0.32/0.78
25
transm fact., min/max
θ
max, deg
index ranges
-20 e h e 20
0 e k e 16
0 e l e 8
3358
0 e h e 9
0 e k e 14
-10 e l e 10
2241
0 e h e 23
0 e k e 15
0 e l e 13
3619
0 e h e 15
0 e k e 11
0 e l e 19
2171
0 e h e 11
0 e k e 9
-34 e l e 34
4675
no. reflns measd
no. of unique reflns
no. of reflns > 4σ(F)
no. of params
3102
1986
2641
1999
4113
2265
1327
1691
1194
2861
183
137
156
127
270
R(F) (F > 4σ(F))a
R(F) (all data)
0.048
0.043
0.041
0.034
0.049
0.084
0.085
0.085
0.092
0.083
wR(F2) (all data)b
0.078
0.074
0.087
0.084
0.134
diff Four. peaks min/max, eÅ-3 -0.35/0.44
-0.53/0.45
-0.57/0.69
-0.65/0.62
-0.70/0.72
a
b
2
4 0.5
R(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR(F2) ) [w(Fo - Fc2)2/∑wFo
] .
Ta ble 2. Atom ic P osition a l a n d Isotr op ic
Disp la cem en t P a r a m eter s (Å2 × 103) for
Ru (η5-C5Me5)(η3-CH2CHCHCHdCHCH3)Br 2 (6)
34.43; H, 4.51; Br, 42.95. Found: C, 34.45; H, 4.48; Br, 42.78.
1H NMR (δ, acetone-d6, 20 °C): 3.97 (d, 2H, 2J ) 4.5 Hz), 3.12
2
(d, 2H, J ) 4.5 Hz), 2.07 (s, 6H), 1.82 (s, 15H).
a
x
y
z
Ueq
[(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)d ib r om o(η4-2,3-
d im eth oxybu ta d ien e)r u th en iu m (IV)] Tr iflu or om eth a n e-
su lfon a te (17a ). 16a (330 mg, 0.559 mmol) was dissolved in
10 mL of CH2Cl2. AgCF3SO3 (144 mg, 0.560 mmol) was added,
and the mixture was stirred for 1 h. The resulting precipitate
of AgBr was removed by filtration. On addition of diethyl ether
a red precipitate was formed, which was collected on a glass
frit, washed with diethyl ether, and dried under vacuum.
Yield: 350 mg (95%). Anal. Calcd for C17H25Br2F3O5RuS: C,
30.97; H, 3.82; Br, 24.24. Found: C, 31.05; H, 3.84; Br, 24.15.
1H NMR (δ, CD3CN, 20 °C): 4.23 (s, 6H), 3.86 (d, 2H, 2J ) 6.1
Hz), 2.03 (d, 2H, 2J ) 6.1 Hz), 1.93 (s, 15H). 13C{1H} NMR (δ,
CD3CN, 20 °C): 153.5, 114.9 (C5Me5), 62.6 (OMe), 51.3, 11.7
(C5Me5).
Ru
0.05749(4)
-0.06609(6)
0.11887(7)
0.0966(5)
0.1491(4)
0.1109(5)
0.0334(5)
0.0245(5)
0.1165(5)
0.2339(4)
0.1435(5)
-0.0239(5)
-0.0490(5)
-0.00092(5)
0.435(6)
0.16107(4)
0.07104(6)
0.02673(7)
0.2500(6)
0.1706(6)
0.0823(6)
0.1049(6)
0.2099(6)
0.3562(5)
0.1808(6)
-0.00186(6)
0.0343(6)
0.2638(6)
0.2831(6)
0.2522(6)
0.2708(6)
0.2462(9)
0.2975(10)
0.3884(10)
0.30774(8)
0.22554(14)
0.11610(14)
0.5374(9)
40(1)
77(1)
76(1)
38(2)
46(2)
44(2)
48(2)
51(2)
62(2)
64(3)
74(3)
82(3)
75(3)
54(2)
57(3)
63(3)
87(3)
101(4)
138(5)
Br(1)
Br(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0.5115(10)
0.5526(10)
0.5938(11)
0.5796(11)
0.5498(10)
0.4810(12)
0.5632(12)
0.6595(13)
0.6269(12)
0.1964(13)
0.0749(11)
0.1158(11)
0.00060(15)
-0.0007(16)
0.0998(17)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
0.1205(6)
0.1866(7)
0.2518(7)
0.2661(7)
[(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)d ib r om o(η4-2,3-
d im eth ylbu ta d ien e)r u th en iu m (IV)] Tr iflu or om eth a n e-
su lfon a te (17b). This complex was synthesized analogously
to 17a with 16b as starting material.6 Yield: 74%. Anal.
Calcd for C17H25Br2F3O3RuS: C, 32.55; H, 4.02; Br, 25.47.
Found: C, 32.46; H, 4.08; Br, 26.78. 1H NMR (δ, acetone-d6,
a
Ueq
)
1/3∑i∑jUijai*aj*(a ia j).
solved by direct methods.12 All non-hydrogen atoms were
refined anisotropically, and hydrogen atoms were included in
idealized positions.13 The structures were refined against F2.
Final positional parameters are given in Tables 2-6.
2
20 °C): 3.65 (d, 2H, J ) 1.7 Hz), 2.72 (s, 6H, Me), 2.53 ppm
2
(d, 2H, J ) 1.7 Hz), 2.16 (s, 15H). 13C{1H} NMR (δ, CD2Cl2,
20 °C): 140.7, 116.0 (C5Me5), 72.0, 22.2 (Me), 12.4 (C5Me5).
Rea ction of Br 2 w ith [(η5-P en ta m eth ylcyclop en ta d i-
en yl)br om o(η4-d im eth ylen ecycloh exa n e)r u th en iu m (II)
(2l). Following the protocol for 17a , bromination of 2l led only
to the formation of several intractable materials.
Resu lts a n d Discu ssion
1,3-Bu ta d ien e a n d Mon osu bstitu ted - a n d 1,2-
Disu bstitu ted -1,3-Bu ta d ien e Com p lexes. As shown
in Scheme 1, new bromo-substituted Ru(IV) η3-allyl
complexes 4a -c and 5a -c can be synthesized in high
yields by reacting 1a -c and 2a -c with stoichiometric
X-r a y Str u ctu r e Deter m in a tion for 6, 14, 15, 16a ‚-
CH2Cl2, a n d 17a . Crystal data and experimental details are
given in Table 1. X-ray data were collected on a Philips
PW1100 four-circle diffractometer using graphite-monochro-
mated Mo KR (λ ) 0.716 09 Å) radiation, and the θ-2θ scan
technique (6, 14, 15, 16a ‚CH2Cl2) or the ω-scan technique
(17a ). Three representative reference reflections were mea-
sured every 120 min and used to correct for crystal decay and
system instability. Corrections for Lorentz and polarization
effects and for absorption were applied. The structures were
(12) Hall, S. R.; Flack, H. D.; Stewart, J . M. XTAL3.2. Integrated
system of computer programs for crystal structure determination,
Universities of Western Australia (Australia), Geneva (Switzerland),
and Maryland (USA), 1992.
(13) Sheldrick, G. M. SHELXL93 Program for crystal structure
refinement, University of Go¨ttingen, Germany, 1993.

536 Organometallics, Vol. 15, No. 2, 1996
Gemel et al.
Ta ble 3. Atom ic P osition a l a n d Isotr op ic
Disp la cem en t P a r a m eter s (Å2 × 103) for
[Ru (η5-C5Me5)Br 3]2 (14)
Ta ble 6. Atom ic P osition a l a n d Isotr op ic
Disp la cem en t P a r a m eter s (Å2 × 103) for
[Ru (η5-C5Me5)(η4-CH2COMeCOMeCH2)Br 2]CF 3SO3
(17a )
a
x
y
z
Ueq
a
x
y
z
Ueq
Ru(1)
Br(1)
Br(2)
Br(3)
C(1)
0.59066(8)
0.66900(9)
0.79534(14)
0.43857(14)
0.5861(11)
0.5100(9)
0.48101(5)
0.50845(7)
0.61888(8)
0.59730(8)
0.3153(5)
0.3395(6)
0.3810(5)
0.3803(6)
0.3408(7)
0.2547(6)
0.3151(8)
0.4075(7)
0.4041(7)
0.3182(8)
0.1384(7)
0.35983(5)
0.55360(7)
0.34214(8)
0.23109(8)
0.3808(6)
0.2798(7)
0.2160(6)
0.2755(6)
0.3744(6)
0.4669(7)
0.2435(8)
0.1021(6)
0.2356(7)
0.4553(7)
0.4474(8)
34(1)
52(1)
77(1)
82(1)
41(2)
39(2)
33(2)
39(2)
47(2)
91(4)
84(4)
61(3)
64(3)
89(4)
138(6)
Ru
0.27943(5)
0.29483(9)
0.29393(9)
0.5113(7)
0.4584(8)
0.3795(8)
0.3842(8)
0.4649(7)
0.6129(8)
0.5008(11)
0.3231(11)
0.3352(10)
0.5103(10)
0.1247(7)
0.0384(7)
0.0351(8)
0.1166(7)
-0.0287(6)
-0.0336(6)
0.44750(7)
0.38929(11)
0.73639(10)
0.4408(10)
0.5162(10)
0.4006(10)
0.2540(9)
0.2784(10)
0.5144(13)
0.6746(11)
0.4176(13)
0.0949(10)
0.1504(11)
0.2539(10)
0.3770(11)
0.5262(12)
0.5351(12)
0.3698(7)
0.1517(2)
0.23676(3)
0.17876(3)
0.1516(3)
0.1092(3)
0.0835(3)
0.1084(3)
0.1507(2)
0.1876(3)
0.0920(4)
0.0344(3)
0.0900(3)
0.1837(3)
0.1475(3)
0.1642(3)
0.1409(3)
0.1017(3)
0.2017(2)
0.1601(3)
0.2234(4)
0.1333(5)
0.0666(1)
0.1097(3)
0.0429(4)
0.0616(6)
0.0288(4)
-0.0138(3)
0.0464(5)
0.0288(4)
43(1)
63(1)
66(1)
55(2)
61(2)
57(2)
55(2)
54(2)
89(3)
90(3)
94(3)
84(3)
84(3)
63(2)
61(2)
66(2)
72(2)
Br(1)
Br(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
O(1)
O(2)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
0.6224(9)
0.7683(10)
0.7454(11)
0.5145(14)
0.3445(10)
0.6073(11)
0.9250(9)
C(10)
C(11)
0.8770(12)
0.5372(18)
a
Ueq
)
1/3∑i∑jUijai*aj*(a ia j).
Ta ble 4. Atom ic P osition a l a n d Isotr op ic
Disp la cem en t P a r a m eter s (Å2 × 103) for
[Ru (η5-C5Me5)(η6-C6H6][Ru (η5-C5Me5)Br 3] (15)
76(2)
92(2)
0.6425(8)
C(15) -0.0456(11)
0.2152(13)
0.7902(14)
0.2370(5)
0.1623(18)
0.2511(24)
0.3818(16)
0.1474(38)
0.1579(15)
0.1122(23)
101(3)
136(5)
118(1)
200(6)
256(9)
290(11)
220(13)
207(5)
325(10)
259(8)
a
C(16) -0.0628(11)
x
y
z
Ueq
S
0.7653(4)
Ru(1)
C(1)
0.46009(3)
0.5618(4)
0.5261(3)
0.4674(3)
0.6286(4)
0.5457(4)
0.4180(3)
0.4670(4)
0.4174(5)
0.3636(4)
0.33163(3)
0.45599(5)
0.35274(5)
0.2198(4)
0.2476(3)
0.2928(3)
0.1685(5)
0.2291(4)
0.3289(3)
0.75
0.75
0.6605(5)
0.6948(4)
0.25
0.5460(5)
0.6250(6)
0.6986(6)
0.6435(6)
0.6933(7)
0.25
0.25
0.10766(6)
0.25
0.1584(5)
0.1932(4)
0.25
0.0473(6)
0.1257(5)
0.15402(5)
0.2303(6)
0.2690(4)
0.3331(4)
0.1652(7)
0.2508(6)
0.3959(6)
-0.0288(5)
0.0238(6)
0.0817(6)
0.27514(5)
0.33877(10)
0.12659(6)
0.2951(7)
0.3511(5)
0.4410(4)
0.1977(9)
0.3293(6)
0.5261(5)
49(1)
55(2)
58(2)
56(1)
90(3)
88(2)
101(3)
91(2)
96(3)
110(4)
55(1)
108(1)
108(1)
74(3)
64(2)
54(1)
146(6)
102(3)
81(2)
O(3)
O(4)
O(5)
C(17)
F(1)
F(2)
F(3)
0.7825(12)
0.6239(10)
0.8208(22)
0.8496(16)
0.8214(12)
0.9747(12)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
0.7925(19) -0.0345(13)
a
Ueq
)
1/3∑i∑jUij ai*aj*(a ia j).
Sch em e 1
Ru(2)
Br(1)
Br(2)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
a
Ueq
)
1/3∑i∑jUijai*aj*(a ia j).
Ta ble 5. Atom ic P osition a l a n d Isotr op ic
Disp la cem en t P a r a m eter s (Å2 × 103) for
[Ru (η5-C5Me5)(η4-CH2COMeCOMeCH2)Br 2]Br ‚CH2Cl2
(16a ‚CH2Cl2)
a
x
y
z
Ueq
internal substituent (1b, 2b,c) occurs such that the
substituent ends up on the central allyl carbon atom.
Under these reaction conditions, the addition is kineti-
cally controlled resulting in the sole formation of anti
η3-allyl isomers (as drawn). At elevated temperatures,
however, isomerization to the thermodynamically fa-
vored syn products takes place.14 All complexes are
stable to air in the solid state and also for extended
periods in solution. 4a -c and 5a -c have been fully
characterized by elemental analyses and 1H NMR
spectroscopy. Where solubility has permitted (4a ,b, 5b)
13C{1H} NMR spectra have also been recorded. The 1H
NMR spectra of 4a -c and 5a -c all show the expected
singlet resonances for the C5H5 and C5Me5 rings ap-
pearing in the ranges 5.69-5.96 ppm and 1.74-1.80
ppm, respectively, while characteristic multiplet reso-
nances assignable to the allyl ligands are observed in
the expected ranges. The signals of the CH2Br protons
are observed in the range 4.0-3.5 ppm. The 13C{1H}
Ru
0.40973(5)
0.30434(5)
0.55103(8)
0.5111(6)
0.5332(4)
0.5670(4)
0.4859(7)
0.5355(4)
0.6103(4)
0.3930(4)
0.3012(4)
0.2151(3)
0.2097(5)
0.1576(8)
0.2778(3)
0.0789(4)
0.25
0.41371(8)
0.25
0.32048(4)
0.24827(4)
0.59907(6)
0.2203(5)
0.2668(4)
0.3409(3)
0.1352(5)
0.2397(4)
0.4021(3)
0.4208(3)
0.4229(3)
0.4182(2)
0.4310(4)
0.6661(8)
0.6386(3)
0.5877(2)
39(1)
62(1)
63(1)
42(2)
43(2)
40(2)
57(3)
54(2)
49(2)
47(2)
48(2)
55(1)
81(3)
102(5)
128(2)
152(2)
Br(1)
Br(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
O
0.25
0.3641(6)
0.3212(6)
0.25
0.5041(7)
0.4062(7)
0.3818(7)
0.3194(7)
0.3781(5)
0.5184(8)
0.25
C(9)
C(10)
Cl(1)
Cl(2)
0.25
0.25
a
Ueq
)
1/3∑i∑jUijai*aj*(a ia j).
amounts of Br2 at -60 °C in CH2Cl2. The reactions
involve addition of bromine on the face of the cisoid η4-
diene group opposite to the metal center and regiose-
lectively at the terminal carbon atom bearing no sub-
stituent. Addition on η4-diene complexes with an
(14) Masuda, K.; Saitoh, M.; Aoki, K.; Itoh, K. J . Organomet. Chem.
1994, 473, 285.

Ru(IV) η3-Allyl and Ru(IV) η4-Diene Complexes
Organometallics, Vol. 15, No. 2, 1996 537
Sch em e 2
F igu r e 1. ORTEP drawing of Ru(η5-C5Me5)(η3-CH2-
CHCHCHdCHCH3)Br2 (6). Selected bond lengths (Å) and
angles (deg): Ru-Br(1) 2.555(1), Ru-Br(2) 2.550(1), Ru-
C(1-5)av 2.241(8), Ru-C(11) 2.190(7), Ru-C(12) 2.135(8),
Ru-C(13) 2.335(9), C(11)-C(12) 1.352(11), C(12)-C(13)
1.401(12), C(13)-C(14) 1.450(13), C(14)-C(15) 1.338(15);
Br(1)-Ru-Br(2) 83.02(4), C(11)-C(12)-C(13) 117.0(8).
NMR spectra of 4a ,b and 5b contain no surprising
features with the resonance of the sp3 carbon atom
bearing the bromide substituent observed in the range
of 32.6-36.8 ppm. Proof of the stereospecific exo addi-
tion was reached from X-ray crystallography as shown
previously.6
Sch em e 3
Bromination of 2d ,e gave, on workup, complexes 6
and 7 in 75 and 94% yield (Scheme 2). In the course of
this process HBr and MeBr, respectively, are liberated
involving apparently the intermediacy of a bromo-
substituted Ru(IV) η3-allyl complex where bromine
attack had taken place at the substituted terminal
carbon atom of the η4-diene ligand. Moreover, the
elimination of HBr is accompanied by isomerization to
the more stable syn product (as drawn in Scheme 2).
The rest of the ligand adopts cis stereochemistry.
1
Complexes 6 and 7 have been characterized by H and
1
13C{1H}NMR spectroscopy. In the H NMR spectrum
of 6, a sharp singlet at 1.64 ppm is observed for the C5-
Me5 ring; the resonance for the central allyl proton
appears as a double double doublet centered at 5.18 ppm
(η3-CH2CHCHCHdCHCH3)(η5-C5H5)(CO) both with all-
trans-type C6 chains.15,16
3
3
(3J 34 ) 10.5 Hz, J 13 ) 9.6 Hz, J 23 ) 6.0 Hz). The
Rea ction s of 5b w ith NEt3 a n d P yr id in e. Pre-
liminary studies on the reactivity of bromo-substituted
Ru(IV) η3-allyl complexes show that the halide of the
allyl moiety is readily replaced by other nucleophiles.
To illustrate the procedure, complex 5b has been
subjected to the action of the bases pyridine and NEt3.
5b is cleanly converted to new complexes readily identi-
fied by 1H and 13C{1H} NMR spectroscopy as the
cationic pyridinium- and triethylammonium-substituted
Ru(IV) anti η3-allyl complexes 8 and 9, respectively.
During substitution the sp3 carbon atom configuration
appears to be retained consistent with the occurrence
of a SN1 type of mechanism. A similar complex, the
cationic pyridinium-substituted Ru(IV) η3-cyclopen-
tenoyl complex [Ru(η5-C5H5)(η3-C5H4ONC5H5)Br2]Br has
been reported previously.4
3
proton coupling constant J 34 ) 10.5 Hz suggests that
the geometry around the C3-C4 bond has syn configu-
ration. The stereochemistry of the olefin part of the
3
ligand is apparent from the coupling constant J 56
)
11.2 Hz consistent with a cis arrangement. The 1H
NMR spectrum of 7 agrees with the postulated struc-
ture. The central allyl proton is found as a double
double doublet centered at 5.87 ppm (3J 13 ) 10.6 Hz,
3J 23 ) 6.8 Hz, J 34 ) 6.6 Hz). However, the coupling
3
constant of 3J 34 ) 6.6 Hz unequivocally places the CHO
substituent anti with respect to the allyl moiety.
The structure of 6 has been confirmed by X-ray
crystallography as depicted in Figure 1. Positional
parameters are given in Table 2 with important bond
distances and angles reported in the caption. The olefin
substitutent takes the syn position. The enyl function
of the allyl ligand is bonded asymmetrically to the metal
with the Ru-C bonds to the unsubstituted terminal and
central allyl carbon atoms C(11) and C(12) (2.190(7) and
2.135(8) Å, respectively) being distinctly shorter than
Ru-C bond to the third allyl carbon atom C(13) (2.335(9)
Å). The Ru-Br(1) and Ru-Br(2) bond distances are
nearly identical being 2.555(1) and 2.550(1) Å, respec-
tively. The asymmetric bonding of the allyl moiety to
the metal center is in good agreement with observations
on the related µ-(1-3)-hexa-1,4-dien-3-yl complexes of
Mo(η3-CH2CHCHCHdCHCH3)(CH3CN)2(CO)2Br and Fe-
1,4-Disu b st it u t ed -1,3-Bu t a d ien e
Com p lexes.
Treatment of complexes 2f-h and 3 with Br2 leads to
the formation of Ru(IV) η3-allyl complexes 10a -c and
11, where, surprisingly, all adopt the syn configuration
(Scheme 3). With the exception of 10a , unfortunately,
none of these complexes could be obtained in pure form.
10a has been characterized by elemental analysis, and
1H and 13C{1H} NMR spectroscopy. Inability to obtain
(15) Paz-Sandoval, M. A.; Saaredra, P. J .; Pomposo, G. D.; J oseph-
Nathan, P.; Powell, P. J . Organomet. Chem. 1990, 387, 265.
(16) Lee, G.-H.; Peng, S.-M.; Lush, S.-F.; Liao, M.-Y.; Liu, R.-S.
Organometallics 1987, 6, 2094.

538 Organometallics, Vol. 15, No. 2, 1996
Gemel et al.
Sch em e 4
a pure sample of 10b,c and 11 precluded suitable
microanalyses, and characterization was only by 1H
NMR spectroscopy. Structural evidence will, thus, be
discussed mainly with reference to 10a . The assign-
ments of the proton resonances were aided by detailed
double resonance experiments.
The 1H NMR spectrum of 10a resembles that for
3a -c and 4a -c with the major difference being a
substantial downfield shift for the aliphatic proton H1
3
3
resonating at 5.48 (m, 1H, J 12 ) 10.1 Hz, J ) 6.7 Hz)
(cf. the respective proton resonances of 3a -c and 4a -
c, which appear in the range 3.5-4.0 ppm, and thus,
the deshielding of H1 cannot be explained merely by the
-I effect of the bromine substituent). A sharp singlet
at 1.65 ppm is observed for the C5Me5 ligand while the
remaining allylic protons resonate at 5.07 (t, 1H, H3,
3J 23 ) 9.9Hz, 3J 34 ) 9.6 Hz), 2.70 (t, 1H, H2, 3J 12 ) 10.1
Hz, 3J 23 ) 9.9 Hz), and 2.68 ppm (m, 1H, H4, 3J 34 ) 9.6
10a -c and 11 a weak C1-Br‚‚‚Ru interaction is pro-
posed leading to structure III where the allyl adopts a
syn conformation.
3
Hz, J ) 6.1 Hz), respectively. The resonances of the
methyl groups are observed as two doublets centered
3
3
at 1.72 (d, 3H, J ) 6.5 Hz) and 1.71 ppm (d, 3H, J )
6.1 Hz). The proton coupling constant of 3J 23 ) 9.9 Hz
unequivocally proves that the 1-bromoethyl moiety
takes the syn configuration around the C2-C3 bond. The
downfield shift of H1 is even more pronounced for 10b,c,
where the proton resonances are observed at 6.89 and
6.95 ppm, respectively. Bromine attack in 10b took
place exclusively at the carbon atom adjacent to the
phenyl substituent. The 13C{1H} NMR spectrum of 10a
exhibits the characteristic three-signal pattern of the
enyl fragment appearing at 98.3, 82.6, and 57.1 ppm,
while resonances of C5Me5 ring and the methyl substit-
uents of the allyl ligand are found in the usual ranges.
Surprisingly, however, the resonance of the carbon atom
C1 is drastically shifted downfield to 81.6 ppm (cf. 4a ,b
and 5b exhibit the resonance of C1 between 32.6 and
36.8 ppm).
The formation of III may proceed via an anti syn
isomerization of the initially formed complex I being
presumably the kinetic product of the bromination of
2f-h and 3. The underlying mechanism may be the
dissociation of the terminus bearing the bromoalkyl
substituent to give an η1-allyl intermediate followed by
rotation around the C2-C3 and C1-C2 bonds. This
transformation leads to a vacant coordination site on
the metal which can be occupied by the bromide sub-
stituent of the sp3 carbon atom leading to a weak 4e-
three-center C1-Br‚‚‚Ru bond. Due to this interaction
charge is removed from both C1 and H1 which conse-
quently attain higher positive partial charges.10a -c
and 11, therefore, may be envisioned as “arrested”
intermediates along the two observed decomposition
pathways. The formation of the dimeric complexes 13
and 14, however, appears to be favored. It is possible
to speculate that 10a -c and 11 are not 20e- intermedi-
ates, if the shift of electron density from the C3-C2‚‚‚C1
interaction to a C1-Br‚‚‚Ru interaction is concerted.
The dimeric nature of 14 has been established by
X-ray crystallography (Figure 2). Positional parameters
are given in Table 3 with important bond distances and
angles reported in the caption. 14 consists of two
symmetry-equivalent ruthenium cations in half-sand-
wich four-legged piano stool environments which are
linked via a shared Br(1)-Br(1) edge. The overall
architecture of this molecule is novel. With regard to
the ruthenium coordination, however, 14 is similar to
the monomeric anion [Ru(η5-C5Me5)Br4]- described
recently.6 Mean bond distances and bond angles in 14
compare well with those found in the monomeric
complex.
10a -c and 11 are unstable in solution releasing free
diene (as monitored by 1H NMR spectroscopy) and
forming the dimeric complexes 13 and 14, respectively.
13 and 14 are poorly soluble in all common solvents and
are deposited as microcrystalline precipitates in high
yield. The synthesis of 13 by reacting [Ru(η5-C5-
11
Me5)Br2]2 with Br2 (1 equiv) in CH2Cl2 has been
reported previously10 but has been formulated as poly-
meric [Ru(η5-C5Me5)Br3]n. 14 can be prepared in analo-
17
gous fashion with [Ru(η5-C5Me4Et)Br2]2 as the pre-
cursor. While 10b,c and 11 are converted to 13 and 14
within a matter of minutes, 10a persists in solution for
a few hours and eventually yields, in addition to 13 as
the major decomposition product, complex 12 in about
20% yield as the result of HBr elimination. More
conveniently, however, 12 can be obtained in 73% yield
by treatment of 10a with 1 equiv of Ag+, introduced as
-
the CF3SO3 salt, in CH2Cl2 at room temperature.
The reasons for depicting the intermediate products
10a -c and 11 as done in Scheme 3 are as follows. The
structure to be assumed should accommodate the NMR
spectroscopic results and allow concurrent conversion
to 13 and 14 as well as 12. Neither the Ru(IV) anti
η3-allyl nor the Ru(IV) syn η3-allyl formulations I and
II conform to the strong deshielding of H1 and C1. Thus,
for an adequate description of the bonding situation in
Treatment of 2i with Br2 (1 equiv) in CH2Cl2 at -60
°C affords, on workup, a mixture of complex salt 15
together with the known dimeric Ru(III) complex [Ru-
(η5-C5Me5)Br2]2 (Scheme 5).17 15 contains the cationic
(17) Koelle, U.; Kossakowski, J .; Klaff, N.; Wesemann, L.; Englert,
U.; Herberich, G. E. Angew. Chem. 1991, 103, 732.

Ru(IV) η3-Allyl and Ru(IV) η4-Diene Complexes
Organometallics, Vol. 15, No. 2, 1996 539
F igu r e 3. ORTEP drawing of [Ru(η5-C5Me5)(η6-C6H6)]-
[Ru(η5-C5Me5)Br3] (15). Selected bond lengths (Å) and
angles (deg): Ru(1)-C(1-3)av ) 2.174(6), Ru(1)-C(7-9)av
) 2.192(6), Ru(2)-Br(1) 2.535(1), Ru(2)-Br(2) 2.526(1),
Ru(2)-C(11-13)av 2.189(6); Br(1)-Ru(2)-Br(2) 92.27(3),
Br(2)-Ru(2)-Br(2′) 91.71(4).
F igu r e 2. ORTEP drawing of [Ru(η5-C5Me4Et)Br3]2 (14).
Selected bond lengths (Å) and angles (deg): Ru-Br(1)
2.547(1), Ru-Br(2) 2.524(1), Ru-Br(3) 2.533(1), Ru-C(1-
5)av 2.243(8); Br(1)-Ru-Br(1′) 75.88(4), Br(1)-Ru-Br(2)
81.03(4), Br(2)-Ru-Br(3) 81.33(5), Br(1)-Ru-Br(3′)
79.76(4), Br(1)-Ru-Br(3) 129.81(4), Br(2)-Ru-Br(1′)
128.93(4).
Sch em e 6
Sch em e 5
eters are given in Table 4 with important bond distances
and angles given in the caption. 15 consists of the
cationic sandwich complex [Ru(η5-C5Me5)(η6-C6H6)]+ and
the anionic half-sandwich complex [Ru(η5-C5Me5)Br3]-
both with crystallographic mirror symmetry. The struc-
ture of the tribromo complex corresponds well to a
trigonal pyramid with C5Me5 at the apex and the three
bromide atoms at the base. The Ru-Br distances are
in the expected range (Ru(2)-Br(1) ) 2.535(1) Å, Ru(2)-
Br(2) ) 2.526(1) Å). These values are comparable to
the Ru-Br(terminal) distances in the Ru(III) complex
[Ru(η5-C5Me5)Br2]2 being 2.543(2) Å (cf. the bond dis-
tance of the Ru-Br(bridging) bond is 2.479(2) Å).17,19
2,3-Disu bstitu ted -1,3-Bu ta d ien e Com p lexes. Re-
action of Br2 with 2j,k does not lead to η3-allyl com-
pounds but instead gives the novel Ru(IV) η4-diene
complexes 16a ,b in 98 and 93% isolated yield, respec-
tively (Scheme 6). This formulation is based on elemen-
sandwich [Ru(η5-C5Me5)(η6-C6H6)]+ 18 and the novel
anionic Ru(III) complex [Ru(η5-C5Me5)Br3]- as the coun-
terion.
This latter ion could not be characterized by NMR
spectroscopy because of the paramagnetic nature of this
17e- molecule. The proton resonances of the diamag-
netic cationic part of 15, slightly broadened and some-
what downfield shifted, appear as singlets at 7.43 (s,
1
tal analysis, H NMR spectroscopic data, and an X-ray
structure determination of 16a . By contrast, 2l gave
only a mixture of intractable materials.
1
6H) and 2.40 ppm (s, 15H) (cf. the H NMR spectrum
18
of [Ru(η5-C5Me5)(η6-C6H6)]PF6 exhibits two sharp sin-
The 13C{1H} NMR spectrum was not available due
to both the poor solubility and instability of 16a ,b in
solution. The 1H NMR spectra of 16a ,b in CD3CN
display the characteristic resonances of the diene ligand.
The syn and anti protons of 16a give rise to two doublets
centered at 3.92 (2H) and 2.61 ppm (2H), respectively.
The geminal coupling constant of the CH2 protons is 6.1
Hz, respectively. This is indicative of an enhanced sp3
character of the terminal carbon atoms and points to a
metallacyclopentene resonance structure rather than
that of a classical diene otherwise typical for late
glets at 6.18 and 2.20 ppm). The second product was
1
identified as [Ru(η5-C5Me5)Br2]2 by H NMR spectros-
copy and X-ray crystallography.17,19 The dimer exhibits
a singlet resonance at 1.89 ppm and is in line with
literature-reported values.17 The formation of 15 along
with [Ru(η5-C5Me5)Br2]2 in the same reaction may be
due to an equilibrium [Ru(η5-C5Me5)Br2]2 + 2Br-
T
2[Ru(η5-C5Me5)Br3]- shifted to the right in the presence
of the large cation [Ru(η5-C5Me5)(η6-C6H6)]+.
A structural view of 15, as determined by X-ray
diffraction, is depicted in Figure 3. Positional param-
1
transition-metal η4-diene complexes.9 20 The H NMR
(18) Chaudret, B.; J alon, F. A. J . Chem. Soc., Chem. Commun. 1988,
spectrum of 16b is similar to that of 16a and is not
discussed here.6 For comparison, the geminal coupling
constants for terminal CH2 of Zr(η5-C5H5)2(η4-CH2-
CMeCMeCH2) and Ta(η5-C5Me5)2(η4-CH2CMeCMeCH2)-
Cl2 are equal 10.0 and 7.2 Hz, respectively.20b,e As noted
711.
(19) A structure determination of (Ru(η5-C5Me5) Br2) carried out
2
by us on crystals of the byproduct according to Scheme 4 gave the same
structure as reported in ref 17, except for a larger discrepancy in unit
cell dimensions for which we found space group P21/c, a ) 8.412(3) Å,
b ) 15.666(5) Å, c ) 28.148(6) Å, â ) 92.19(1)°, and V ) 3707(2) Å3.
Our values for a-c are large by about 0.9% than those in ref 17.
1
previously,6 the solution H NMR spectra of 16a ,b are

540 Organometallics, Vol. 15, No. 2, 1996
Gemel et al.
F igu r e 4. ORTEP drawing of [Ru(η5-C5Me5)(η4-CH2-
COMeCOMeCH2)Br2]Br‚CH2Cl2 (16a‚CH2Cl2). Selected bond
lengths (Å) and angles (deg): Ru-Br(1) 2.527(1), Ru-C(1-
5)av 2.259(7), Ru-C(7) 2.182(6), Ru-C(8) 2.408(6), C(7)-
C(8) 1.417(8), C(8)-C(8′) 1.406(13), C(8)-O 1.332(7), O-C(9)
1.439(8); Br(1)-Ru-Br(1′) 82.01(4).
F igu r e 5. ORTEP drawing of [Ru(η5-C5Me5)(η4-CH2-
COMeCOMeCH2)Br2]CF3SO3 (17a ). Selected bond lengths
(Å) and angles (deg): Ru-Br(1) 2.521(1), Ru-Br(2) 2.533(1),
Ru-C(1-3)av 2.271(7), Ru-C(11) 2.186(7), Ru-C(12)
2.433(7), Ru-C(13) 2.424(8), Ru-C(14) 2.175(7), C(11)-
C(12) 1.424(11), C(12)-C(13) 1.416(12), C(13)-C(14)
1.431(11), C(12)-O(1) 1.308(9), C(13)-O(2) 1.318(10), O(1)-
C(15) 1.448(11), O(2)-C(16) 1.473(12); Br(1)-Ru-Br(2)
82.95(4).
solvent dependent tentatively interpreted as an ion-
pairing phenomenon. While in low dielectric solvents,
such as CDCl3, ion-pairing between the cationic part of
16a and the counterion is favored, in the moderate
dielectric solvents CD3CN and C2D5OD the complexes
16a ,b are largely dissociated. Most solvent sensitive
are the resonances of the anti protons. For example,
the resonances of the anti protons of 16a appear as
expected, in the solid state structure of 17a (Figure 5),
which will be discussed in a following paragraph, no
direct interaction between the metal center and the
CF3SO3- counterion is observed. The shortest distances
are 4.971 Å to O(5) and 4.934 Å to F(2). The 13C{1H}
NMR spectrum of 17a shows singlets at 153.5 (internal
diene C atoms), 114.9 (C5Me5), 62.6 (OMe), 51.3 (ter-
minal diene C atoms), and 11.7 ppm (C5Me5), respec-
tively. The 13C{1H} NMR spectrum of 17b is very
similar to that of 17a and is not discussed here. The
marked downfield chemical shifts are indicative of the
high oxidation state of the ruthenium center.
The structures of 16a (in the form of 16a ‚CH2Cl2) and
17a have been confirmed by X-ray crystallography (see
Figures 4 and 5). Positional parameters are given in
Tables 5 and 6 with important bond distances and
angles given in the captions. The overall geometric
features of the two 2,3-dimethoxy-1,3-butadiene com-
plexes are very similar. Transition-metal s-cis η4-diene
complexes are generally described as resonance hybrids
of the limiting forms a and b. While the bonding of
2
doublets centered at 3.87 (2H, J ) 6.1 Hz), 2.61 (2H,
2J ) 6.1 Hz), and 2.66 ppm (2H, 2J ) 5.2 Hz) in CDCl3,
CD3CN, and C2D5OD, respectively, while the resonances
of the remaining protons are hardly affected. The solid
state structure of 16a ‚CH2Cl2, which will be discussed
in a following paragraph, reveals no significant direct
interaction between the metal center and the counter-
ion. The distance between ruthenium and the free Br-
anion is 5.139 Å.
-
The bromide counterion is readily replaced by CF3SO3
upon addition of AgCF3SO3 (1 equiv) in CH2Cl2 giving
the stable cationic complexes 17a ,b in 95 and 74%
isolated yield. Characterization of 17a ,b was by el-
1
emental analysis, H and 13C{1H} NMR spectroscopy,
and an X-ray diffraction study. The structure of 17b
has been reported earlier.6
1
The H NMR spectra of 17a ,b closely resemble those
of 16a ,b which, by contrast, are not very sensitive to
solvent. For instance, the resonances of the anti protons
2
of 17a appear as doublets centered at 2.71 (2H, J )
2
2
5.9 Hz), 2.44 (2H, J ) 6.0 Hz), 2.05 (2H, J ) 6.1 Hz),
and 2.26 ppm (2H, 2J ) 6.1 Hz) in CDCl3, CD2Cl2, CD3-
CN, and C2D5OD, respectively. This is not unexpected
since CF3SO3- is only a weakly coordinating ligand. As
dienes to early transition metals is normally more
accurately represented by the σ2,π-metallacylopentene
structure a , the vast majority of complexes containing
middle and late transition metals adopt the η4-s-cis-1,3-
diene structure b. Noteworthily, metallacyclopentene
complexes of late transition metals have been postulated
as intermediates; e.g., the interconversion of the diene
ligand in Co(η5-C5H5)(η4-diene) complexes can be ex-
plained only by an “envelope-flip” process involving a
metallacyclopentene intermediate.21 Complexes 16 and
(20) (a) Yamamoto, H.; Yasuda, H.; Tatsumi, K.; Lee, K.; Nakamura,
A.; Chen, J .; Kai, Y.; Kasai, N. Organometallics 1989, 8, 105. (b)
Kru¨ger, C.; Mu¨ller, G.; Erker, G.; Dorf, U.; Engel, K. Organometallics
1985, 4, 215. (c) Blenkers, J .; Hessen, B.; van Bolhuis, F.; Wagner, A.
J .; Teuben, J . H. Organometallics 1987, 6, 459. (d) Diamond, G. M.;
Green, M. L. H.; Walker, N. M.; Howard, J . A. K.; Mason, S. A. J .
Chem. Soc., Dalton Trans. 1992, 2641. (e) Yasuda, H.; Tatsumi, K.;
Okamoto, T.; Mashima, K.; Lee, K.; Nakamura, A.; Kai, Y.; Kanehisa,
N.; Kasai, N. J . Am. Chem. Soc. 1985, 107, 2410. (f) Hunter, A. D.;
Legzdins, P.; Einstein, F. W. B.; Willis, A. C.; Bursten, B. E.; Gatter,
M. G. J . Am. Chem. Soc. 1986, 108, 3843. (g) Davidson, J . L.; Davidson,
K.; Lindesll, W. E.; Murall, N. W.; Welch, A. J . J . Chem. Soc., Dalton
Trans. 1986, 1677. (h) Mereiter, K.; Kirchner, K. Unpublished results.
(i) Fru¨hauf, H.-W.; Wolmersha¨user, G. Chem. Ber. 1982, 115, 1070. (j)
Hogarth, G.; Arthurs, M.; Bickerton, J . C.; Daly, L.; Piper, C.; Ralfe,
D.; Morton-Blake, D. A. J . Organomet. Chem. 1994, 467, 145.
(21) Eaton, B.; King, J . A., J r.; Vollhardt, K. P. C. J . Am. Chem.
Soc. 1986, 108, 1359.

Ru(IV) η3-Allyl and Ru(IV) η4-Diene Complexes
Organometallics, Vol. 15, No. 2, 1996 541
Ta ble 7. Com p a r ison of Bon d Dista n ces (Å) in η4-Dien e Com p lexes
compd
M-C1,4
M-C2,3
C1,3-C2,4
C2-C3
ref
Ti(η5-C5Me5)(B)Cl2
2.183(10)
2.300(3)
2.267(5)
2.276(10)
2.303(3)
2.257(12)
2.220(3)
2.233(4)
2.182(6)
2.180(7)
2.190(7)
2.222(4)
2.222(3)
2.116(2)
2.125(5)
2.152(5)
2.284(9)
2.597(3)
2.641(5)
2.480(10)
2.478(3)
2.417(12)
2.338(2)
2.319(4)
2.408(6)
2.428(8)
2.352(7)
2.204(4)
2.155(3)
2.062(2)
2.123(4)
1.417(14)
1.451(4)
1.472(5)
1.503(14)
1.463(4)
1.455(16)
1.410(4)
1.409(6)
1.417(8)
1.427(11)
1.396(9)
1.393(5)
1.404(5)
1.409(3)
1.430(6)
1.518(7)
1.400(13)
1.398(4)
1.378(8)
1.384(15)
1.401(3)
1.375(16)
1.414(6)
1.364(7)
1.406(13)
1.416(12)
1.431(15)
1.433(5)
1.430(5)
1.423(3)
1.433(5)
1.513(8)
20a
20b
20b
20c
20d
20e
20f
20g
this work
this work
6
20h
9
a
Zr(η5-C5H5)2(DB)b
Hf(η5-C5H5)2(DB)
Hf(η5-C5Me5)(DB)(py)Cl2
Hf(PMe3)2(B)Cl2
Ta(η5-C5H5)(B)Cl2
Mo(η5-C5H5)(NO)(B)
Mo(η5-C5H5)(B)Cl2
[Ru(η5-C5Me5)(DOB)Br2]+ (16a )c
[Ru(η5-C5Me5)(DOB)Br2]+ (17a )
[Ru(η5-C5Me5)(DB)Br2]+ (17b)
[Ru(η5-C5Me5)(MB)(CH3CN)]+ d
Ru(η5-C5Me5)(B)I
Fe(C8H16N2)(CO)(DB)e
Rh(η5-C5H4Cl)(DOB)
20i
20j
22
Ru(η6-C6Me6)(PPhMe2)(C4H8)f
-
a
d
B ) 1,3-butadiene. b DB ) 2,3-dimethyl-1,3-butadiene. c DOB ) 2,3-dimethoxy-1,3-butadiene. MB ) 2-methyl-1,3-butadiene. e C8H16N2
) glyoxal bis(isopropylimine). f Ruthenacyclopentane:
Sch em e 7
17 appear to be the first examples of late transition-
metal complexes which approach the σ2,π structural
limit a . This is evident from the highly asymmetric
bonding of the diene, with metal-carbon bonds to the
diene termini being shorter by up to 0.248 Å (17a ) than
those to the internal carbon atoms (cf. in Zr(η5-C5H5)2(η4-
CH2CMeCMeCH2) the respective difference in metal-
carbon bond distances is 0.297 Å20b). The ruthenium-
carbon bonds to the terminal carbon atoms, on average,
are about 2.181 Å while the one to the internal carbon
atoms are 2.416 Å. For comparison, in the ruthenacy-
clopentane complex Ru(η6-C6Me6)(PPhMe2)(C4H8) the
ruthenium-carbon σ bond distance is 2.152(5) Å.21 In
the extreme σ2,π case an inversion of the carbon-carbon
distance sequence from that in the free diene is pre-
dicted; i.e., coordinated dienes are expected to exhibit
a long-short-long rather than a short-long-short
pattern of carbon-carbon bond distances. The struc-
tures of 16a and 17a reveal within the experimental
error no significant differences in carbon-carbon dis-
tances of the diene moieties (cf. in 17b 6 the internal
bond of the diene ligand is only slightly longer (C(8)-
C(8′) ) 1.431(15) Å) than the terminal bonds (C(7)-C(8)
) 1.396(9) Å) but the standard deviations are also
comparatively high). Thus, on the basis of both NMR
spectroscopy and X-ray crystallography the geometry
and bonding situation in 16 and 17 is best described as
an intermediate case between the two extremes a and
b. A summary of structural data of some representative
η4-diene complexes is given in Table 7.
due to unfavorable metal-diene orbital interactions
remains unclear, but it does seem likely that the driving
force of minimizing repulsions between the substituents
of the diene ligand and the C5Me5 moiety plays an
important role. It has been shown recently that the
structurally related Ru(II) η4-2,3-diphenyl-1,3-butadiene
complex Ru(η5-C5Me5)(η4-CH2CPhCPhCH2)Cl is un-
stable due to repulsive interactions between the phenyl
groups of the diene ligand and the C5Me5 ring.9 The
lifetime of B should, thus, be shortest in case of 2,3-
disubstituted-1,3-butadienes so that Br- cannot attack
before rotation of the diene ligand gives the sterically
more favorable endo isomer C. In case of parent 1,3-
butadiene and monosubstituted- and 1,2-disubstituted-
1,3-butadienes, the lifetime of B appears to be high
enough so that Br- can attack to give Ru(IV) anti η3-
allyl complexes D. This is in accordance with the fact
that cationic η4-diene complexes are typically the most
reactive of substrates toward nucleophilic attack un-
dergoing preferential attack at the terminal position.23
The activation is, at least partly, a consequence of the
Mech a n istic Con sid er a tion s. Scheme 7 presents
a mechanistic proposal of the formation of bromo-
substituted Ru(IV) η3-allyl and Ru(IV) η4-diene com-
plexes. As the first step, the oxidative addition of Br2
to the neutral Ru(II) η4-diene complex A leads to the
cationic Ru(IV) η4-diene intermediate B. The diene
moiety of the precursor A is exo oriented with respect
to the bromide ligand (as shown by X-ray crys-
tallography4,6,9,20h), and although intermediate B cannot
be isolated, it is reasonable to assume that B also adopts
the exo configuration. Whether its instability is partly
(23) (a) Davies, S. G.; Green, M. L. H.; Mingos, D. M. P. Tetrahedron
1978, 34, 3047. (b) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke,
R. G. Principles and Applications of Organotransitionmetal Chemistry,
2nd ed.; University Science Books: Mill Valley, CA, 1987.
(22) Barabotti, P.; Diversi, P.; Ingrosso, G.; Lucherini, A.; Marchetti,
F.; Sagramora, L.; Adovasio, V.; Nardelli, M. J . Chem. Soc., Dalton
Trans. 1990, 179.

542 Organometallics, Vol. 15, No. 2, 1996
Gemel et al.
strong electron-withdrawing effect of the Ru(IV) metal
center which dominates at the terminal carbon atoms
(cf. Davies-Green-Mingos rules).23 The diene ligand
in C, however, is not reactive toward nucleophilic attack,
and it is likely that species does not lie on the pathway
to D; i.e., C is no intermediate of D. Conversion of C
to D has not been observed even in the presence of
excess Br-. In fact, we have shown previously3 that 16b
reacts with either Br- or I- by loss of the diene ligand
involving nucleophilic attack at the metal center. Pre-
liminary density functional calculations24 show that in
C the frontier orbitals relevant for nucleophilic attack
are the pz orbitals of the internal carbon atoms contrib-
uting more strongly to the LUMO (lowest unoccupied
molecular orbital) rather than the terminal carbon
orbitals as one would expect (see LUMO of A).23 This
result further supports the observation that the diene
ligand in C is not particularly active toward nucleophilic
attack. Density functional calculations on a variety of
Ru(II) and Ru(IV) diene complexes are in progress and
will be the subject of a forthcoming paper.
Ack n ow led gm en t. Financial support by the “Fonds
zur Fo¨rderung der wissenschaftlichen Forschung” is
gratefully acknowledged (Project No. 9825).
Su p p or tin g In for m a tion Ava ila ble: Listings of hydrogen
atomic coordinates and U values, anisotropic temperature
factors, complete bond lengths and angles, and least-squares
planes for complexes 6, 14, 15, 16a ‚CH2Cl2, and 17a (33 pages).
Ordering information is given on any current masthead page.
(24) Hofer, M.; Gemel, C.; Margl, P.; Schwarz, K.; Schmid, R.;
Kirchner, K. To be published.
OM950662A