Ruthenium complexes bearing bulky pentasubstituted cyclopentadienyl ligands and evaluation of [Ru(η5-C5Me4R)(MeCN) 3][PF6] precatalysts in nucleophilic allylic substitution reactions

Article abstract of DOI:10.1002/ejic.200800295

[Ru(η⁵-C₅Me₄R)(MeCN) ₃][PF₆] (R = CH₂ tBu, iPr, tBu, and CF ₃; 2-5) complexes were synthesized in two steps starting from the appropriate cyclopentadienes and RuCl₃·3H₂O. The fully substituted ruthenocenes [Ru(C₅Me₅)(C ₅Me₄R*)], [Ru(C₅Me₅)(C ₅nPr₄R*)] {R* = (1R,5S)-6,6-dimethylbicyclo- [3.1.1]hept-2-en-2-yl} and [Ru(C₅Me₅)(C ₅nPr₅)] were obtained by treating [Ru(C₅Me ₅)Cl]₄ with the corresponding cyclopentadienyllithium salts. Complexes 2-5 were evaluated as catalyst precursors for nucleophilic allylic substitution reactions, and the results were compared to those obtained with the [Ru(C₅Me₅)(MeCN)₃][PF₆] (1) precatalyst. The etherification of p-methoxyphenol with the typical aliphatic chlorohexene allylic substrate shows that the introduction of the bulky tert-butyl and trifluoromethyl groups into the tetramethylcyclopentadienyl ring results in a valuable enhancement in regioselectivity in favour of the branched allyl aryl ether. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800295

FULL PAPER
DOI: 10.1002/ejic.200800295
Ruthenium Complexes Bearing Bulky Pentasubstituted Cyclopentadienyl
Ligands and Evaluation of [Ru(η5-C5Me4R)(MeCN)3][PF6] Precatalysts in
Nucleophilic Allylic Substitution Reactions
Hui-Jun Zhang,[a,b] Bernard Demerseman,[b] Zhenfeng Xi,*[a] and Christian Bruneau*[b]
Keywords: Allylation / Cyclopentadienyl ligands / Homogeneous catalysis / Regioselectivity / Ruthenium / Metallocenes
[Ru(η5-C5Me4R)(MeCN)3][PF6] (R = CH2tBu, iPr, tBu, and
CF3; 2–5) complexes were synthesized in two steps starting
from the appropriate cyclopentadienes and RuCl3·3H2O. The
fully substituted ruthenocenes [Ru(C5Me5)(C5Me4R*)],
[Ru(C5Me5)(C5nPr4R*)] {R* = (1R,5S)-6,6-dimethylbicyclo-
[3.1.1]hept-2-en-2-yl} and [Ru(C5Me5)(C5nPr5)] were ob-
tained by treating [Ru(C5Me5)Cl]4 with the corresponding cy-
clopentadienyllithium salts. Complexes 2–5 were evaluated
with the [Ru(C5Me5)(MeCN)3][PF6] (1) precatalyst. The
etherification of p-methoxyphenol with the typical aliphatic
chlorohexene allylic substrate shows that the introduction of
the bulky tert-butyl and trifluoromethyl groups into the tet-
ramethylcyclopentadienyl ring results in a valuable enhance-
ment in regioselectivity in favour of the branched allyl aryl
ether.
as catalyst precursors for nucleophilic allylic substitution re- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
actions, and the results were compared to those obtained
Germany, 2008)
diate without the involvement of toxic thallium.[6] Recently,
the synthesis of the [Ru(η5-C5H5)(η6-naphthalene)][PF6]
alternate intermediate allowed the UV-irradiation step to be
avoided and thus provided a more efficient procedure.[7]
This required, however, the sacrifice of one cyclopen-
tadienyl ligand from ruthenocene, under drastic conditions.
Furthermore, the selective coordination of only one cy-
clopentadienyl ring was easily reached when pentamethylcy-
clopentadiene was treated with RuCl3·3H2O.[8–10] The sub-
sequent reduction of the resulting [Ru(η5-C5Me5)Cl2]2 ru-
thenium(III) dimer with Li[BHEt3] or zinc and coordina-
tion of acetonitrile afforded the desired cation, which was
conveniently isolated as its [Ru(η5-C5Me5)(MeCN)3][PF6]
(1) salt.[10–12] We report herein the synthesis of the analo-
gous [Ru(η5-C5Me4R)(MeCN)3][PF6] (R = CH2tBu, iPr,
tBu or CF3) complexes and of the new ruthenocene-type
Introduction
As a result of the lability of their acetonitrile ligands, the
cyclopentadienyltris(acetonitrile)ruthenium cations con-
tinue to provide a popular entry to a rich coordination
chemistry. To hinder the undesired formation of rutheno-
cene, their access was based on the removal, under UV-irra-
diation conditions in acetonitrile, of the benzene ligand
from [Ru(η5-cyclopentadienyl)(η6-benzene)]+ intermedi-
ates.[1–3] Such a procedure has also been successful for cy-
clopentadienyl ligands bearing a coordinating phosphane
or pyridine side arm.[4] Depending on the nature of the cy-
clopentadiene, the synthesis of the intermediates requires
the treatment of [(η6-benzene)RuCl2]2 with cyclopentadien-
ylthallium derivatives,[1,2,4] although a “one-pot” procedure
starting from RuCl3·3H2O, cyclopentadiene, benzene and
zinc as a reducing reagent was efficient in the cases of tri-
fluoromethyltetramethylcyclopentadiene and pentamethyl-
cyclopentadiene.[3,5] For the simple [Ru(η5-C5H5)(Me-
CN)3]+ cation, efforts have been made to prepare the corre-
sponding [Ru(η5-cyclopentadienyl)(η6-benzene)]+ interme-
complexes
[Ru(η5-C5Me5)(η5-C5nPr5)]
and
[Ru(η5-
C5Me5)(η5-C5R4R*)] {R = Me or nPr, R* = (1R,5S)-6,6-
dimethylbicyclo[3.1.1]hept-2-en-2-yl} arising from very
bulky substituted cyclopentadienes. The [Ru(η5-C5Me4R)-
(MeCN)3][PF6] cationic ruthenium derivatives were sub-
sequently evaluated as new catalyst precursors for allylation
[a] Beijing National Laboratory for Molecular Sciences (BNLMS),
Key Laboratory of Bioorganic Chemistry and Molecular Engi- reactions favouring the formation of branched products.
neering of Ministry of Education, College of Chemistry, Peking
Thus, the influence of the steric and electronic modifica-
University,
tions at the cyclopentadienyl ring on regioselectivity was
specified.
Beijing 100871, China
Fax: +86-10-62751708
E-mail: zfxi@pku.edu.cn
[b] Sciences Chimiques de Rennes, UMR 6226 CNRS-Université
de Rennes 1, Catalyse et Organométalliques, Université de
Rennes 1,
Results and Discussion
35042 Rennes Cedex, France
Synthetic work stimulated by an increasing need for
pentamethylcyclopentadiene has also provided two conve-
Fax: +33-2-23236939
E-mail: christian.bruneau@univ-rennes1.fr
3212
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Ruthenium Complexes as Precatalysts in Nucleophilic Allylic Substitutions
nient routes to 1-alkyl-2,3,4,5-tetramethylcyclopentadienes 1H and 13C NMR spectroscopy and elemental analysis. The
on the basis of (i) the reaction between two molecules of 2- 1H NMR spectra exhibited two resonances corresponding
lithio-2-butene with an ethyl ester RCO2Et and (ii) the ad- to the methyl groups, besides the resonances arising from
dition of an alkyllithium RLi to 2,3,4,5-tetramethylcy- the protons of the alkyl substituent. The 13C NMR spectra
clopent-2-en-1-one.[13,14] Thus, trifluoromethyl-,[15] isoprop- were also in agreement with the proposed structure.
yl-[16] and tert-butyl-tetramethylcyclopentadienes[17] were
Highly sterically demanding and electron-donating
readily available. We have similarly prepared neopentyltet- cyclopentadienyl-type ligands continue to stimulate interest
ramethylcyclopentadiene as a yellow oil obtained in a 60% to modify the reactivity of metal centres.[22,23] Under
yield by treating neopentyllithium with 2,3,4,5-tetrameth- similar conditions, attempts to obtain ruthenium(III)
ylcyclopent-2-en-1-one. Available according to a distinct intermediates starting from cyclopentadienes featuring n-
procedure allowing the introduction of the R alkyl substitu- propyl and (1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl
ent from the aldehyde RCHO,[18] (1R,5S)-2-(2,3,4,5-tetra- groups failed.
methylcyclopentadien-1-yl)-6,6-dimethylbicyclo[3.1.1]hept-
However, the reaction of the cyclopentadienyllithium
2-ene, (1R,5S)-2-(2,3,4,5-tetra-n-propylcyclopentadien-1-yl)- salts with [Ru(η5-C5Me5)Cl]4 afforded the corresponding
6,6-dimethylbicyclo[3.1.1]hept-2-ene and 1,2,3,4,5-penta- neutral ruthenocenes (Scheme 2) and provided evidence for
n-propylcyclopentadiene were also involved in this study. the ability of these bulky ligands to coordinate a ruthenium
The (1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl group centre. New ruthenocenes 6–8 were obtained in good yields
was conveniently introduced from commercially available (53–69%) as colourless crystallized solids, and they were
1
(–)-myrtenal as the aldehyde.
characterized by H and 13C NMR spectroscopy and ele-
The reaction of 1-alkyl-2,3,4,5-tetramethylcyclopentadi- mental analysis. The 1H and 13C NMR spectra of 6 showed
enes bearing a neopentyl, isopropyl or tert-butyl group with both singlet resonances indicating the presence of five
RuCl3·3H2O in ethanol (R = CH2tBu) or methanol (R = equivalent Me groups from the C5Me5 ring. Concerning the
iPr, tBu) at reflux yielded purple-brown crystalline precipi- second ring, the observation of four distinct methyl groups
tates reasonably assumed to be [Ru(C5Me4R)Cl2]2 dimers, resulted from the presence of the optically pure (1R,5S)-
1
as such a structure was determined when R = Me,[19] Et[20] 6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl group. The H and
and for the similarly prepared [Ru(C5Me4CF3)Cl2]2 di- 13C NMR spectra of 7 led to similar observations, whereas
1
mer.[21] Such chlorine-bridged ruthenium dimers might ex- the H and 13C NMR spectra of 8 were both consistent
hibit a bond-stretch isomerism,[22] as shown by previous with the presence of five equivalent n-propyl groups besides
structural, EPR and variable-temperature NMR spectro- the five equivalent methyl groups from the pentamethylcy-
scopic studies.[20,23c] These ruthenium(III) intermediates clopentadienyl ring.
were subsequently reduced with zinc in acetonitrile to gen-
erate the [Ru(C5Me4R)(MeCN)3]+ cations. The addition of
KPF6 to supply the [PF6]– anion afforded [Ru(C5Me4R)-
(MeCN)3][PF6] complexes 2–5 (Scheme 1).
Scheme 2. Synthesis of the new fully substituted ruthenocenes 6–8.
Starting from cyclopentadienes involving n-propyl
groups, a minor product arose from the presence of
nPrCH=C(nPr)–C(nPr)=CHnPr as an impurity coming
with the cyclopentadienes since identified and characterized
as the diene–ruthenium derivative [Ru(C5Me5){η4-
Scheme 1. Synthesis of [Ru(η5-C5Me4R)(MeCN)3][PF6] complexes
2–5.
Complexes 2–5 were obtained in good yields (58–69% nPrCH=C(nPr)–C(nPr)=CHnPr}Cl] (see Experimental
after recrystallization) as orange to orange-brown crystals, Section).
and they were moderately sensitive to air in the solid state.
The easy formation of ruthenocenes 6–8 contrasts with
Complex 5 was previously synthesized by UV irradiation of the failure to obtain ruthenium(III) dimers when the
the [Ru(C5Me4CF3)(C6H6)][PF6] intermediate in acetoni- reaction of the corresponding cyclopentadienes with
trile as solvent.[3] New complexes 2–4 were characterized by RuCl3·3H2O in alcohols was attempted.
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H.-J. Zhang, B. Demerseman, Z. Xi, C. Bruneau
FULL PAPER
Ruthenium-Catalyzed Allylic Substitution Reactions
The pentamethylcyclopentadienyl complex [Ru(C5Me5)-
(MeCN)3][PF6] (1) and the related Ru(C5Me5) cationic de-
rivatives have received considerable attention as catalyst
precursors for regioselective allylation reactions favouring
the formation of branched products.[24] However, little is
known concerning the influence of the cyclopentadienyl li-
gand itself on the fate of the catalytic process. Therefore,
complexes 2–5 were involved in selected allylic substitution
reactions. As a classical test, the reaction between allylic
carbonates and sodiodimethylmalonate [Equation (1)] al-
lowed the catalytic activity of complexes 2–5 to be com-
pared with that of 1.
(2)
The results given in Table 1 show the favoured formation
of the branched isomer of allylic ethers 11. A reaction time
of 18 h largely ensured completion of the reaction: the con-
version of the substrate (as determined by GC analysis)
reached 82 and 92% after reaction times of 1 and 2 h,
respectively, when complex 3 was used as catalyst precursor
(Table 1, Entries 3, 4). No isomerization took place, as the
observed regioselectivities were the same after 1, 2 and 18 h
of reaction (Table 1, Entries 3–5). Furthermore, the regiose-
lectivity was significantly improved by using 4 and 5 instead
of 1 as catalyst precursor. Thus, the substitution of one Me
group in the C5Me5 ligand by a bulkier tBu or CF3 group
resulted in a significant enhancement in the B/L ratio from
61:39 (Table 1, Entry 1) to 72:28 (Table 1, Entries 6, 7).
(1)
Table 1. Ruthenium-catalyzed formation of allyl aryl ethers 11.[a]
Thus, the addition of sodiodimethylmalonate (1.2 equiv.)
to a solution of ethyl cinnamyl carbonate (0.5 mmol) in
THF (4.0 mL) in the presence of 2–5 (3 mol-%) at ambient
temperature for 18 h to ensure complete conversion led to
monosubstituted dimethyl malonates 9 as a mixture of
branched (B) and linear (L) isomers, the ratio of which was
determined by 1H NMR spectroscopy. Excellent regioselec-
tivities in favour of the branched product (94:6 B/L ratio)
were reached by using 2–4 as catalyst precursors, that is, a
similar regioselectivity as observed when 1 was used as cata-
lyst precursor.[24c] The involvement of 5 in this catalytic pro-
cess was less satisfactory, as a moderate 82:18 B/L ratio was
obtained. On the contrary, starting from ethyl 2-(E)-hexen-
1-yl carbonate as the allylic substrate leading to monosub-
Entry Catalyst Reaction time [h] Conversion[b] [%] B/L[b]
1
2
3
4
5
6
7
1
2
3
3
3
4
5
18
18
1
100
100
82
61:39
66:34
68:32
68:32
68:32
72:28
72:28
2
92
18
18
18
100
100
100
[a] Experimental conditions: Catalyst (3 mol-%), MeCN as solvent,
room temperature. [b] Conversion and B/L ratio as determined by
1H NMR spectroscopy and GC analysis.
These regioselectivities compete with the best results
stituted dimethyl malonates 10 [Equation (1)], the linear (L) obtained from the same substrates in the presence of [Ru-
allylic derivative was produced as the major compound un- (C5Me5)(Ph2POMe)(MeCN)2][PF6] as catalyst precursor.[25]
der similar conditions. A modest 26:74 B/L ratio was However, although the substitution of one methyl group in
reached when 1, 2 and 5 were used as catalyst precursors, the pentamethylcyclopentadienyl ligand by a tert-butyl
whereas the use of 3 and 4 resulted in a B/L ratio of 35:65. group preserves the high reactivity of cyclopentadienyltris-
These results mainly emphasized again that the favoured (acetonitrile)ruthenium cations, the substitution of one ace-
formation of branched products remains a challenging tonitrile ligand in 1 by the bulky methyl diphenylphosphin-
problem with ruthenium catalysts when starting from ali- ite resulted in markedly reduced reactivity.[25] Moreover,
phatic allylic substrates.[25]
there is no additional constraint to prepare complex 4 rela-
Recently, we reported the synthesis of allyl aryl ethers tive to 1, as the syntheses of the corresponding cyclopenta-
from allylic chlorides and phenols in the presence of K2CO3 dienes are very similar.
and complex 1 as catalyst precursor.[26] Only modest regio-
The C5Me4CF3 ligand was described as equivalent to a
selectivities in favour of the branched products were ob- C5H5 one at the electronic point of view and to a C5Me5
tained when starting from aliphatic allylic substrates, and a one at the steric point of view.[15,21b] In contrast, recent
further enhancement in the regioselectivity is needed. As a studies have shown that complex 1 is a much more reactive
typical reaction, the etherification of p-methoxyphenol with and selective catalyst for allylic substitution than the cyclo-
chlorohexene, as a 4:1 mixture of 1-chloro-2-hexene and 3- pentadienyl [Ru(C5H5)(MeCN)3][PF6] complex.[24c,28] Our
chloro-1-hexene arising from the reaction of PCl3 with com- results provide straightforward evidence of the main influ-
mercial 3-(E)-hexen-1-ol,[27] allowed complexes 2–5 to be ence of steric effects resulting from the modification of the
compared to 1 as catalyst precursors [Equation (2)].
cyclopentadienyl ring with respect to regioselectivity, as the
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Eur. J. Inorg. Chem. 2008, 3212–3217

Ruthenium Complexes as Precatalysts in Nucleophilic Allylic Substitutions
RuCl3·3H2O (4.03 g, 15.4 mmol), and the mixture was heated at
catalytic behaviour of complex 5 is much more connected
to that of complexes 1–4 than to that of [Ru(C5H5)-
(MeCN)3][PF6].
reflux for 2.5 h to afford a dark-brown solution that was then co-
oled in a refrigerator. The resulting crystalline purple-brown pre-
cipitate of [Ru(C5Me4CH2tBu)Cl2]2 was collected by filtration,
washed with cold ethanol (20 mL) and dried under vacuum. Yield:
3.78 g, 67%. C28H46Cl4Ru2 (728.64): calcd. C 46.28, H 6.38; found
C 45.97, H 6.45. The intermediates [Ru(C5Me4iPr)Cl2]2 and [Ru-
(C5Me4tBu)Cl2]2 were conveniently obtained by using methanol in-
stead of ethanol in 52 and 67% yield, respectively. For [Ru-
(C5Me4tBu)Cl2]2, C26H42Cl4Ru2 (700.59): calcd. C 44.70, H 6.06;
found C 45.36, H 6.18. The [Ru(C5Me4CF3)Cl2]2 intermediate was
prepared as reported in the literature.[21]
Conclusions
The cationic [Ru(η5-C5Me4R)(MeCN)3][PF6] (R
=
CH2tBu, iPr, tBu, and CF3) complexes bearing three labile
acetonitrile ligands were conveniently prepared like the par-
ent [Ru(C5Me5)(MeCN)3][PF6] ruthenium derivative. Cy-
clopentadienes featuring one (1R,5S)-6,6-dimethylbicyclo-
[3.1.1]hept-2-en-2-yl or several n-propyl groups were appro-
priate for the synthesis of fully substituted bulky rutheno-
cenes. The involvement of the cationic [Ru(η5-C5Me4R)-
(MeCN)3][PF6] complexes, wherein R is a tert-butyl or a
trifluoromethyl group, as catalyst precursors for regioselec-
tive allylation reactions allowed a significant enhancement
in the regioselectivity in favour of branched allyl aryl ethers.
Synthesis of [Ru(C5Me4R)(MeCN)3][PF6] Complexes 2–5
2: As
a typical procedure, a mixture consisting of [Ru-
(C5Me4CH2tBu)Cl2]2 (1.05 g, 1.44 mmol), granular zinc (0.9 g, ex-
cess) and acetonitrile (30 mL) was stirred for 2 h. KPF6 (0.53 g,
2.88 mmol) was then added, and the mixture was stirred overnight.
The solvent was removed under vacuum, and the residue was ex-
tracted with dichloromethane (30 mL). The solution was filtered,
and the orange filtrate was evaporated to leave the crude product,
which was recrystallized from hot methanol (20 mL) containing
acetonitrile (0.5 mL) to afford orange-brown crystals of 2. Yield:
1
1.04 g, 64%. H NMR (200 MHz, CD2Cl2): δ = 0.93 (s, 9 H, tBu),
Experimental Section
1.66 (s, 6 H, 2 Me), 1.67 (s, 6 H, 2 Me), 2.08 (s, 2 H, tBuCH2),
2.32 (br., 9 H, MeCN) ppm. 13C NMR (50 MHz, CD2Cl2): δ = 4.0
(MeCN), 9.8 (2 Me), 11.9 (2 Me), 30.2 (CMe3), 34.0 (CMe3), 39.1
(tBuC), 80.4 (2 CMe), 84.2 (CCH2), 82.7 (2 CMe) ppm; no MeCN
resonance was detected due to coalescence. C20H32F6N3PRu
(560.53): calcd. C 42.86, H 5.75, N 7.50; found C 42.63, H 5.75, N
7.30.
General Considerations: The reactions were carried out under an
inert atmosphere of argon according to Schlenk techniques. THF,
diethyl ether and dichloromethane were distilled after drying ac-
cording to conventional methods, whereas HPLC-grade acetoni-
trile, methanol and ethanol were straightforwardly used. 1H and
13C NMR spectra were recorded at 297 K with AC 200 FT Bruker
instrument and referenced internally to the solvent peak. Elemental
analyses were performed at the “Service Central de Microanalyse
du CNRS” (Vernaison) or at the “Centre Régional de Mesures
Physiques de l’Ouest” (Rennes).
3: Prepared as above. Orange crystals, 58% yield. 1H NMR
3
(200 MHz, CD3CN): δ = 1.26 (d, J = 7.2 Hz, 6 H, CHMe2), 1.62
(s, 6 H, 2 Me), 1.65 (s, 6 H, 2 Me), 1.99 (s, 9 H, free MeCN), 2.53
(sept, 3J = 7.1 Hz, 1 H, CHMe2) ppm. 13C NMR (50 MHz,
CD3CN): δ = 9.1 (2 Me), 10.0 (2 Me), 22.3 (CHMe2), 25.6
(CHMe2), 78.7 (2 CMe), 83.2 (iPrC), 84.9 (2 CMe) ppm.
C18H28F6N3PRu (532.47): calcd. C 40.60, H 5.30, N 7.89; found C
39.41, H 5.08, N 7.12; the low carbon and nitrogen values likely
resulted from a residual presence of mineral salt.
Synthesis of Cyclopentadienes: The C5HMe4R 1-alkyl-2,3,4,5-tet-
ramethylcyclopentadienes, R = CF3,[15] iPr,[16] tBu,[17] were pre-
pared as reported previously. The C5HMe4CH2tBu neopentyl cy-
clopentadiene was prepared as detailed for the tert-butyl one[17] by
using tBuCH2Li[29] instead of a commercial solution of tBuLi. The
resulting crude yellow oil (b.p. 48 °C/Ͻ1 Torr), which was expected
to consist of several isomers, was used without further characteriza-
tion. The synthesis of (1R,5S)-2-(2,3,4,5-tetramethylcyclopenta-
dien-1-yl)-6,6-dimethylbicyclo[3.1.1]hept-2-ene, (1R,5S)-2-(2,3,4,5-
tetra-n-propylcyclopentadien-1-yl)-6,6-dimethylbicyclo[3.1.1]hept-
2-ene, and 1,2,3,4,5-penta-n-propylcyclopentadiene transiently in-
1
4: Prepared as above. Orange-brown crystals, 60% yield. H NMR
(200 MHz, CD2Cl2): δ = 1.34 (s, 9 H, tBu), 1.63 (s, 6 H, 2 Me),
1.75 (s, 6 H, 2 Me), 2.37 (s, 9 H, MeCN) ppm. 13C NMR (50 MHz,
CD2Cl2): δ = 4.3 (MeCN), 10.4 (2 Me), 13.8 (2 Me), 32.7 (CMe3),
33.7 (CMe3), 80.3 (2 CMe), 84.2 (tBuC), 86.7 (2 CMe), 123.9
(MeCN) ppm. C19H30F6N3PRu (546.50): calcd. C 41.76, H 5.53,
N 7.69; found C 41.37, H 5.50, N 7.27.
volved the in situ formation of
a zirconacyclopentadiene
[ZrC4R4(η5-C5H5)2] from 2-butyne (R = Me) or 4-octyne (R = nPr)
followed by the addition of the appropriate myrtenal or butyral-
dehyde and AlCl3. A detailed procedure is given elsewhere.[18] The
crude oils isolated after hydrolysis and chromatographic workup
were used without further characterization. The subsequent synthe-
sis of ruthenium complexes accounts for the nature of the desired
cyclopentadienes. The products involving n-propyl groups retained
a variable amount of nPrCH=C(nPr)–C(nPr)=CHnPr arising from
hydrolysis of the [ZrC4nPr4(η5-C5H5)2] intermediate. This was de-
tected by the formation of the [Ru(C5Me5){η4-nPrCH=C(nPr)
C(nPr)=CHnPr}Cl] diene–ruthenium complex as a byproduct.
5: Prepared as above. Orange crystals, 69% yield. 1H NMR spectro-
scopic data as reported previously.[3]
Synthesis of Ruthenocenes 6–8
[Ru(η5-C5Me5)(η5-C5Me4R*)] {R*
= (1R,5S)-6,6-Dimethylbicy-
clo[3.1.1]hept-2-en-2-yl} (6): To a solution of C5HMe4{(1R,5S)-6,6-
dimethylbicyclo[3.1.1]hept-2-en-2-yl} (0.24 g, 1.00 mmol) in THF
(10 mL) was added nBuLi (1.6  in hexane, 0.63 mL, 1.01 mmol).
The solution was stirred at room temperature for 0.5 h and
[10b]
[Ru(C5Me5)Cl]4
(0.27 g, 0.25 mmol) was added. The mixture
Synthesis of [Ru(C5Me4R)Cl2]2 Intermediates: As a typical pro-
cedure, the cyclopentadiene C5HMe4CH2tBu (5.90 g, 30.7 mmol)
and ethanol (50 mL, ethanol was required because this cyclopenta-
diene was not soluble in methanol) were added whilst stirring to
was heated at reflux overnight and then evaporated under vacuum.
The residue was extracted with hot heptane (20 mL), and the solu-
tion was chromatographed on an alumina column (10 cm, hep-
tane). A yellow fraction was collected, and removal of the solvent
Eur. J. Inorg. Chem. 2008, 3212–3217
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H.-J. Zhang, B. Demerseman, Z. Xi, C. Bruneau
FULL PAPER
under reduced pressure followed by addition of ethanol and cooling
Acknowledgments
in a refrigerator afforded 6 as a white microcrystalline solid. Yield:
1
0.28 g, 59%. H NMR (200.13 MHz, CDCl3): δ = 0.99 (s, 3 H, 1
H. J. Z. is grateful to the Ambassade de France in China and to
the International Program of the Natural Science Foundation of
China for Ph.D. financial support.
Me, CMe2), 1.29 (m, 1 H, from R*), 1.34 (s, 3 H, 1 Me, CMe2),
1.66 (s, 6 H, 2 Me, C5Me4), 1.68 (s, 3 H, Me, C5Me4), 1.70 (s, 15
H, C5Me5), 1.71 (s, 3 H, Me, C5Me4), 2.13 (m, 1 H, CH in R), 2.36–
2.50 (m, 4 H, R*), 5.42 (s, 1 H, CH=) ppm. 13C NMR (50.32 MHz,
CDCl3): δ = 10.4 (C5Me4R*), 10.4 (C5Me4R*), 10.8 (C5Me5), 11.5
(C5Me4R*), 11.8 (C5Me4R*), 22.1 (Me, R*), 26.76 (Me, R*), 32.4
(CH2, R*), 33.0 (CH2, R*), 38.3 (CMe2, R*), 40.9 (CH, R*), 48.2
(CH, R*), 82.1 (C5Me4R*), 82.2 (C5Me4R*), 83.7 (C5Me4R*), 83.8
(C5Me4R*), 83.8 (C5Me5), 93.6 (C5 Me4R*), 122.1 (CH=, R*),
143.7 (C=, R*) ppm. C28H40Ru (477.70): calcd. C 70.40, H 8.44;
found C 70.60, H 8.50.
[1] T. P. Gill, K. R. Mann, Organometallics 1982, 1, 485–488.
[2] a) Y. Matsushima, H. Kikuchi, M. Uno, S. Takahashi, Bull.
Chem. Soc. Jpn. 1999, 72, 2475–2482; b) G. P. McGlacken,
C. T. O’Brien, A. C. Whitwood, I. J. S. Fairlamb, Organometal-
lics 2007, 26, 3722–3728.
[3] J. K. Evju, K. R. Mann, Organometallics 2002, 21, 993–996.
[4] N. Dodo, Y. Matsushima, M. Uno, K. Onitsuka, S. Takahashi,
J. Chem. Soc., Dalton Trans. 2000, 35–41.
[5] A. Schmid, H. Piotrowski, T. Lindel, Eur. J. Inorg. Chem. 2003,
2255–2263, and references cited therein.
[6] B. M. Trost, C. M. Older, Organometallics 2002, 21, 2544–2546.
[7] E. P. Kündig, F. R. Monnier, Adv. Synth. Catal. 2004, 346, 901–
904.
[Ru(η5-C5Me5)(η5-C5nPr4R*)] {R*
= (1R,5S)-6,6-Dimethylbicy-
clo[3.1.1]hept-2-en-2-yl} (7): According to a similar procedure, ru-
thenocene 7 was isolated as colourless crystals starting from
C5HnPr4{(1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl}. Yield:
53%. A red-brown fraction was subsequently obtained by eluting
the column with diethyl ether to afford [Ru(η5-C5Me5)(η4-
C4H2nPr4)Cl] as an orange brown solid. Yield 11%. 1H NMR
[8] N. Oshima, H. Suzuki, Y. Moro-oka, Chem. Lett. 1984, 1161–
1164.
[9] T. D. Tilley, R. H. Grubbs, J. E. Bercaw, Organometallics 1984,
3, 274–278.
[10] a) P. J. Fagan, M. D. Ward, J. V. Caspar, J. C. Calabrese, P. J.
Krusic, J. Am. Chem. Soc. 1988, 110, 2981–2983; b) P. J. Fagan,
M. D. Ward, J. C. Calabrese, J. Am. Chem. Soc. 1989, 111,
1698–1719; c) P. G. Gassman, C. H. Winter, J. Am. Chem. Soc.
1988, 110, 6130–6135.
[11] a) W.-K. Wong, Y. Chen, W.-T. Wong, Polyhedron 1996, 15,
1575–1577; b) W.-K. Wong, Y. Chen, W.-T. Wong, Polyhedron
1997, 16, 433–439.
[12] a) B. Steinmetz, W. A. Schenk, Organometallics 1999, 18, 943–
946; b) J. L. Schrenk, A. M. McNair, F. B. McCormick, K. R.
Mann, Inorg. Chem. 1986, 25, 3501–3504.
3
(200.13 MHz, CD2Cl2): δ = 0.92 (t, JH,H = 7.2 Hz, 6 H, 2 Me,
3
nPr), 1.00 (t, JH,H = 7.8 Hz, 6 H, 2 Me, nPr), 1.03 (s, 3 H, 1 Me,
CMe2), 1.27 (m, 1 H, R*), 1.35 (s, 3 H, 1 Me, CMe2), 1.25–1.53
(m, 8 H, CH2Me), 1.69 (s, 15 H, C5Me5), 1.83–2.10 (m, 8 H,
CH2CH2Me), 2.10 (m, 1 H, R*), 2.34–2.52 (m, 4 H, R*), 5.51 (s,
1 H, CH=) ppm. 13C{1H} NMR (50.32 MHz, CD2Cl2): δ = 10.8
(C5Me5), 15.0 (Me, nPr), 15.1 (Me, nPr), 15.3 (2 Me, nPr), 21.7
(Me, R*), 25.9 (CH2, nPr), 26.3 (CH2, nPr), 26.4 (CH2, nPr), 26.5
(Me, R*, and CH2, nPr), 29.3 (2 CH2, nPr), 29.4 (CH2, nPr), 29.6
(CH2, nPr), 32.2 (CH2, R*), 32.8 (CH2, R*), 38.3 (CMe2, R*), 41.0
(CH, R*), 49.4 (CH, R*), 83.7 (C5Me5), 87.2 (C5nPr4), 87.4
(C5nPr4), 87.6 (C5nPr4), 88.1 (C5nPr4), 95.7 (C5R*), 123.5 (CH=,
R*), 143.5 (C=, R*) ppm. C36H56Ru (589.91): calcd. C 73.30, H
9.57; found C 73.20, H 9.64.
[13] R. S. Threlkel, J. E. Bercaw, J. Organomet. Chem. 1977, 136, 1–
5.
[14] a) C. M. Fendrick, L. D. Schertz, V. W. Day, T. J. Marks, Orga-
nometallics 1988, 7, 1828–1838; b) F. X. Kohl, P. Jutzi, J. Or-
ganomet. Chem. 1983, 243, 119–121.
[Ru(η5-C5Me5)(η5-C5nPr5)] (8): Starting from C5HnPr5, a similar
procedure led to ruthenocene 8 as colourless crystals and to
[RuCl(η5-C5Me5)(η4-C4H2nPr4)] as a minor product. Yields: 69 and
15%, respectively. 1H NMR (200.13 MHz, CD2Cl2): δ = 0.99 (t,
3JH,H = 7.2 Hz, 15 H, Me, nPr), 1.35–1.45 (m, 10 H, CH2Me), 1.65
(s, 15 H, C5Me5), 1.91–1.99 (m, 10 H, CH2CH2Me) ppm. 13C
NMR (50.32 MHz, CD2Cl2): δ = 10.8 (C5Me5), 15.6 (Me, nPr),
26.8 (CH2), 29.8 (CH2), 83.5 (C5Me5), 88.4 (C5nPr5) ppm.
C30H50Ru (511.80): calcd. C 70.40, H 9.85; found C 70.06, H 9.76.
[15]
P. G. Gassman, J. W. Mickelson, J. R. Sowa, J. Am. Chem. Soc.
1992, 114, 6942–6944.
[16] H. Schumann, M. R. Keitsch, J. Winterfeld, S. Mühle, G. A.
Molander, J. Organomet. Chem. 1998, 559, 181–190.
[17] H. Schumann, K. Zietzke, F. Erbstein, R. Weimann, J. Or-
ganomet. Chem. 1996, 520, 265–268.
[18] C. Zhao, P. Li, X. Cao, Z. Xi, Chem. Eur. J. 2002, 8, 4292–
4298.
[19] U. Kœlle, J. Kossakowski, N. Klaff, L. Wesemann, U. Englert,
G. E. Herberich, Angew. Chem. Int. Ed. Engl. 1991, 30, 690–
691.
[20] U. Kœlle, H. Lueken, K. Handrick, H. Schilder, J. K. Burdett,
S. Balleza, Inorg. Chem. 1995, 34, 6273–6278.
[21] a) O. V. Gusev, M. A. Ievlev, K. A. Lyssenko, P. V. Petrovskii,
N. A. Ustynyuk, P. M. Maitlis, Inorg. Chim. Acta 1998, 280,
249–256; b) O. V. Gusev, M. A. Ievlev, T. A. Peganova, M. G.
Peterleitner, P. V. Petrovskii, Y. F. Oprunenko, N. A. Ustynyuk,
J. Organomet. Chem. 1998, 551, 93–100.
[22] J. E. McGrady, Angew. Chem. Int. Ed. 2000, 39, 3077–3079.
[23] a) P. Bazinet, K. A. Tupper, T. Don Tilley, Organometallics
2006, 25, 4286–4291; b) S. Gauthier, E. Solari, R. Scopelliti, B.
Dutta, K. Severin, Chem. Commun. 2007, 1837–1839; c) B.
Dutta, E. Solari, S. Gauthier, R. Scopelliti, K. Severin, Organo-
metallics 2007, 26, 4791–4799; d) B. Dutta, R. Scopelliti, K.
Severin, Organometallics 2008, 27, 423–429.
Characterization of [Ru(η5-C5Me5)(η4-C4H2nPr4)Cl]: Orange-
brown crystals of [Ru(η5-C5Me5)(η4-C4H2nPr4)Cl] were obtained
upon cooling a saturated solution in diethyl ether. 1H NMR
3
(200.13 MHz, CDCl3): δ = 0.93 (t, JH,H = 7.3 Hz, 6 H, 2 Me,
3
nPr), 1.07 (t, JH,H = 7.4 Hz, 6 H, 2 Me, nPr), 1.44–2.25 (m, 18 H,
CH2CH2Me and RuCH), 1.55 (s, 15 H, C5Me5) ppm. 13C NMR
(50.32 MHz, CDCl3): δ = 10.3 (C5Me5), 15.6 (Me, nPr), 16.0 (Me,
nPr), 24.6 (CH2), 25.6 (CH2), 31.5 (CH2), 33.0 (CH2), 72.1
(nPrCH), 94.8 (C5Me5), 101.4 (nPrC) ppm. C26H45ClRu (494.17):
calcd. C 63.19, H 9.18; found C 63.17, H 9.26.
Catalytic Experiments: In a typical catalytic experiment, a sample
of p-methoxyphenol (0.5 mmol, 1 equiv.) was added to a stirred
mixture consisting of hexenyl chloride (0.5 mmol, 1 equiv.), catalyst
precursor (0.015 mmol, 3 mol-%), K2CO3 (1 equiv.) and acetoni-
trile (4.0 mL). After stirring for 18 h at room temperature, the
slurry was filtered (for GC analysis) then concentrated under vac-
[24] a) C. Bruneau, J.-L. Renaud, B. Demerseman, Chem. Eur. J.
2006, 12, 5178–5187; b) J.-L. Renaud, B. Demerseman, M. D.
Mbaye, C. Bruneau, Curr. Org. Chem. 2006, 10, 115–133; c)
B. M. Trost, P. L. Fraisse, Z. T. Ball, Angew. Chem. Int. Ed.
1
uum (for H NMR spectroscopy analysis).
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 3212–3217

Ruthenium Complexes as Precatalysts in Nucleophilic Allylic Substitutions
2002, 41, 1059–1061; d) T. Kondo, T. Mitsudo, Curr. Org.
Chem. 2002, 6, 1163–1179.
[25] B. Demerseman, J.-L. Renaud, L. Toupet, C. Hubert, C. Bru-
neau, Eur. J. Inorg. Chem. 2006, 1371–1380.
[26] M. D. Mbaye, B. Demerseman, J.-L. Renaud, L. Toupet, C.
Bruneau, Adv. Synth. Catal. 2004, 346, 835–841.
[27] C. D. Hurd, R. W. McNamee, J. Am. Chem. Soc. 1932, 54,
1648–1651.
[28] R. Hermatschweiler, I. Fernández, P. S. Pregosin, F. Breher, Or-
ganometallics 2006, 25, 1440–1447.
[29] R. R. Schrock, J. D. Fellmann, J. Am. Chem. Soc. 1978, 100,
3359–3370.
Received: March 20, 2008
Published Online: June 4, 2008
Eur. J. Inorg. Chem. 2008, 3212–3217
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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