New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

Article abstract of DOI:10.1016/j.jorganchem.2007.04.007

New bimetallic complex [Cp₂ZrH₂ · ClAlEt₂]₂ (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp₂ZrH₂ · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene ≤ (+)-camphene < α-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.

Full text of DOI:10.1016/j.jorganchem.2007.04.007

Journal of Organometallic Chemistry 692 (2007) 3424–3429
www.elsevier.com/locate/jorganchem
New effective reagent [Cp2ZrH2 Æ ClAlEt2]2 for alkene hydrometallation
*
Lyudmila V. Parfenova , Rushana F. Vil’danova, Svetlana V. Pechatkina,
Leonard M. Khalilov, Usein M. Dzhemilev
Institute of Petrochemistry and Catalysis, Russian Academy of Sciences, 450075 Ufa, Prospect Oktyabrya 141, Russian Federation
Received 9 February 2007; received in revised form 26 March 2007; accepted 10 April 2007
Available online 14 April 2007
Abstract
New bimetallic complex [Cp2ZrH2 Æ ClAlEt2]2 (1) was synthesized, and its reactivity in hydrometallation reaction with the following
alkenes was studied: hept-1-ene, okt-1-ene, a-methylstyrene, (1S)-b-pinene, (+)-camphene. Complex 1 shows the highest reactivity
among the other known Al,Zr-bimetallic complexes: [Cp2ZrH2 Æ ClAlBui2]2 (2), [Cp2ZrH2 Æ AlEt3]2 (3), [Cp2ZrH2 Æ AlBui3]2 (4) and
[Cp2ZrH2 Æ HAlBu2i ] (5) as well as organoaluminium compounds (OAC): iBu2AlH, iBu3Al and iBu2AlCl in presence of Zr catalysts. Chlo-
rine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-b-
pinene 6 (+)-camphene < a-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-b-pinene and its subsequent oxidation
with I2 run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation
is less than that for (1S)-b-pinene, and the reaction gives predominately endo-camphanol.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Hydrometallation; Al,Zr-complexes; Organoaluminium compounds; Organozirconium compounds; trans-Myrtanol; endo-Camphanol
1. Introduction
Cp2ZrHCl generally attaches to the less hindered side of
the alkene.
More than 30 years passed since the moment when the
first zirconium hydrides: Cp2ZrHCl and Cp2ZrH2 were
synthesized by Wailes et al. [1]. The hydrozirconation
reagent Cp2ZrHCl, or Schwartz reagent, has been widely
used in laboratory practice. Under the mild conditions
the reagent hydrometallates alkenes of different structure
to obtain functional derivatives. According to Schwartz
[2], the relative rates of the alkenes hydrozirconation are
a-alkene > cis-alkene > trans-alkene > exocyclic alkene >
cyclic alkene > trisubstituted alkene. The last three alkenes
react with Cp2ZrHCl at temperature higher than 40 ꢁC.
Among the bicyclic hydrocarbons with various double
bond screening degrees the hydrozirconation rates are: nor-
bonene > sabinene > camphene > b-pinene [3]; moreover,
Unlike Schwartz reagent, Cp2ZrH2 did not become use-
ful in synthesis because of instability of dialkyl zircono-
cenes which are formed during the reactions with alkenes.
The dialkyl zirconocenes are disposed to the disproportion-
ation to give zirconocene ‘‘Cp2Zr’’ and a mixture of alkane
and alkene in mole ratio 1:1 [4a]. Furthermore, the reaction
of Cp2ZrH2 with acetylenes provides zirconocyclopentadi-
enes [4b].
Along with the mentioned above zirconium hydrides,
the isobutylalanes (HAlBui2, ClAlBu2i , AlBu3i ) are widely
used for the alkene reduction in the presence of Zr
catalysts.
We recently established the formation of hydride Al,Zr-
complexes during mechanism studies for the alkenes
hydroalumination by HAlBui2, ClAlBu2i and AlBu3i in the
presence of Cp2ZrCl2 catalyst [5]. As a result, new complex
[Cp2ZrH2 Æ ClAlBui2]2 (2) was found and shown to be a key
intermediate of the reaction (Scheme 1).
*
Corresponding author. Tel.: +7 3472 313527; fax: +7 3472 312750.
E-mail addresses: luda_parfenova@yahoo.com, ink@anrb.ru (L.V.
Parfenova).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.04.007

L.V. Parfenova et al. / Journal of Organometallic Chemistry 692 (2007) 3424–3429
3425
2 HAlBui2
i
+ HAlBu2
- ClAlBui2
i
- HAlBu2
Cp
Zr
Cp
Zr
i
H
AlBu 2
3 ClAlBui2
-2 Cl2AlBui
-2 C4H8
i
H
H
Cl
H
+ 2 ClAlBu2
- Cl2AlBui
- C4H8
Cl
H
i
i
Cl
Cp2Zr
H
Cp2ZrCl2
2 AlBui3
AlBu 2
1/2 Bu2Al
i
H
AlBu 2
Cp
Cp
+ AlBui3
- C4H8
6
2
-2 C4H8
H
- ClAlBui2
R
i
AlBu2
Cp2Zr
Cl
Cl
+
H
Cp2Zr
R
i
AlBu2
R
i
Al(Cl)Bu
i
+ HAlBu2
i
+Cl2AlBu
i
- ClAlBui2
AlBu2
+ ClAlBui2
Cl
R
- Cp2ZrCl
2
Cp2Zr
i
H
+ AlBu3
- C4H8
Scheme 1.
The structure of complex 2 was established by the means
of both NMR spectroscopy and encounter synthesis from
[Cp2ZrH2]2 and ClAlBui2. Moreover, the dimeric structure
of the complex was confirmed by cryoscopy. Further, com-
plex 2 can transform into trihydride complex Cp2ZrH2 Æ
ClAlBui2 ÆHAlBui2 (6), which does not react with alkenes.
However, complex 6 reduces carbonyl compounds [6] and
acetylenes [7]. Moreover, complex 2 coordinates the alkene
to form alkyl complex Cp2ZrCl(CH2CH2R) and HAlBui2,
which further rapidly transmetallates zirconocene alkyl-
chloride and gives both diisobulytalkylaluminium and
Cp2ZrHCl. Independently from the nature of initial
OAC, Cp2ZrHCl immediately transforms into complex 2,
thus closing the hydrometallation catalytic cycle.
Furthermore, during the study of the hydroalumination
mechanism we synthesized bimetallic hydride complexes 3
[8], 4 [5], 5 [9] by the encounter synthesis as represented
on Scheme 2. It was shown that all these complexes react
with alkenes and form alkylalanes [5].
In this paper we present novel complex [Cp2ZrH2 Æ ClA-
lEt2]2 (1), which is related to complex 2. The aims of the work
are the following: study of alkene hydroalumination with
new bimetallic complex 1 and complexes 2–5; comparison
of their reactivity; analysis of stereoselectivity of both (1S)-
b-pinene and (+)-camphene hydrometallation by complex 1.
2. Results and discussion
2.1. Synthesis and structure of [Cp2ZrH2 Æ ClAlEt2]2 (1)
Complex 1 was synthesized by treating the [Cp2ZrH2]2
with 2 equiv. of ClAlEt2 in C6H6 at room temperature
analogous to that of complex 2 [5].
Cp
Cp
Zr
Cp
Cp
Zr
Cl
H
H
H
H
H
H
AlEt2
Et2Al
Zr
Cp
+
2 ClAlEt2
H
H
Zr
Cl
Cp
Cp
Cp
1
1
NMR H spectrum of complex 1 is very similar to that
reported for complex 2 [5]. Complex 1 exhibits widened
triplet signal of the bridge Zr–H–Zr hydrogen at
2
ꢀ2.68 ppm with J = 4.2 Hz. The signal of the bridge Zr–
H–Al hydrogen is located at ꢀ0.91 ppm. It is wider than
that in Zr–H–Zr fragment, and it is not splitted into the
multiplet. On the other hand, both complexes 3 and 4 (type
[Cp2ZrH2 Æ AlR03]2) exhibit two sharp triplets for the both
bridge hydrogens [5]. Broadening of the signals of hydride
atoms in complexes 1 and 2 can be explained both by the
increase in the rate of intramolecular exchange between
bridge and terminal hydrides and by the shift of the equilib-
rium from the dimeric to monomeric form of the com-
plexes. The temperature behavior of the both dynamic
processes is similar to that in [Cp2ZrH2]2 [10]. The study
of the molecular weight of complex 1 by cryoscopy in ben-
Cp
Cp
Zr
H
H
AlR3
H
AlR3
R3Al
H
Zr
Cp
Cp
Cp
Cp
Zr
R= Et (3), Bui (4)
H
H
H
H
Zr
Cp
Cp
H
HAlBui2
i
AlBu 2
H
H
5
Cp2Zr
Scheme 2.

3426
L.V. Parfenova et al. / Journal of Organometallic Chemistry 692 (2007) 3424–3429
zene confirmed the dimeric structure of this compound.
The experimental value of the molecular weight was
640 g molꢀ1, while the theoretical weight is equal to 688 g
molꢀ1
.
2.2. Reactivity of complexes 1–5 in reactions with a-alkenes
Complexes 1–5 were evaluated in the reactions with a-
alkenes (hept-1-ene (7a), oct-1-ene (7b)) in C6H6 at room
temperature and different mole ratios of complex to alkene:
1:2 and 1:4. The NMR observation of the reactions shows
that the hydrometallation products: zirconocene alkylchlo-
rides 8a,b and alkylalanes 9a,b are formed in mole ratio 1:1.
The NMR spectra of 8a,b and 9a,b correlate with the data
presented in Ref. [5].
Cp
Cp
Zr
Fig. 1. The yield of heptane (10a) in hydrometallation of 7a with
complexes 1–5 at mole ratio of complex to alkene 1:2, vs. time (20 ꢁC,
C6H6).
Cl
H
H
H
R
Cl
Cl
H
H3O+
+
Cp2Zr
R'2Al
AlR'2
R'2Al
Zr
Cp
R
R
R
Cp
8a,b
R= n-C H11 (a), n-C6H13(b)
9a,b
10a,b
R'= Et ( ), Bui(2)
1
According to Fig. 1 the reactivity of Al,Zr-hydride com-
plexes 1–5 rises in the series 4 6 3 < 5 < 2 < 1. Therefore,
complexes 1 and 2 are the most active among the bimetallic
Al,Zr-hydride complexes studied by us. Probably, com-
pared to trialkylalanes AlR03, the chlorine containing
OACs ClAlR02 increase the rate of the intramolecular
exchange between bridge and terminal hydrides in dimer
[Cp2ZrH2]2 and, consequently, shift the equilibrium
between the dimeric and monomeric forms. This ‘‘shaking’’
of dimer [Cp2ZrH2]2 under the action of ClAlR02 eases the
process of alkene introduction into Zr–H bond.
Moreover, the reactivity of complexes 1 and 2 is higher
than that of Schwartz reagent. For example, the yield of
10a in the reaction of 7a with Cp2ZrHCl for 6 h in C6H6
at 20 ꢁC was 70%, whereas for complexes 1 and 2 the cor-
responding alkane yield of 87% was achieved after only 1 h.
We link the reason of this higher reactivity with the both
high solubility of the studied complexes in hydrocarbon
solvents and additional activation of [Cp2ZrH2]2 due to
the complex formation in reaction with ClAlR02.
5
However, the hydrometallation of alkenes with com-
plexes 3 and 4 proceeds more complex than that with com-
plexes 1 and 2 (Scheme 3). For example, at the mole ratio
1:2 we observed formation of alkylalanes 9a,b and alkylhy-
dride complexes 3a and 4a, which are similar to the com-
plexes described in the Schwartz work [11].
The increase of the alkene concentration to the mole
ratio of 1:4 leads to the broadening of the Cp-rings signals
in the NMR spectra. Analysis of the gaseous products
which appear in this reaction shows that for complex 3
the isolation of ethane and for complex 4 the formation
of isobutane is observed. Probably, the presence of an addi-
tional quantity of alkene accelerates the well-known process
of zirconocene alkylhydrides (3a and 4a) decomposition
into both ‘‘Cp2Zr’’ and alkanes R0H [11]. The interaction
of complex 5 with alkenes is similar to that for complexes
3 and 4.
Further, the influence of complex 1 to alkene 7a,b mole
ratio on the yields of alkanes 10a,b was studied. It was
Comparison of complexes 1–5 reactivity was carried out
in the reaction with alkene 7a at the mole ratio 1:2 (Fig. 1).
R'2Al
R
Cp
Cp
Cp
Zr
H
R
R
9a,b
H
H
AlR'2
Zr
Cp
H
AlR'3
R'3Al
H
Zr
R'
Cp
Cp
H
Cp
Cp
H
H
Cp2Zr
Zr R'
Cp
R' Zr
Cp
R'
R'= Et (3 ), Bui (4)
3a, 4a
R
R
+
Cp2Zr
R'H
"Cp2Zr"
R'
-
R
Scheme 3.

L.V. Parfenova et al. / Journal of Organometallic Chemistry 692 (2007) 3424–3429
3427
shown that the yield of 10a,b during the first 20 min of the
reaction at the mole ratio of 1:2 is two times higher than
that at the mole ratio of 1:4. After that, the dependence
of the alkane yield vs. the reaction time for both ratios
becomes equal. Therefore, it could be concluded that all
four hydride atoms in complex 1 participate in the hydro-
metallation process.
60 ꢁC for 12 h after hydrolysis gave pinane at the yield of
69%.
As follows from Table 1, the studied alkenes reactivity
in hydrometallation by complexes 1 and 2 is (1S)-b-pine-
ne 6 (+)-camphene < a-methylstyrene < oct-1-ene < hept-
1-ene.
2.4. Stereoselectivity of Bicyclic Olefin Hydrometallation by
Complex 1
2.3. Reactivity of alkenes in the reactions with complexes 1
and 2
In order to study the stereoselectivity of complex 1 reac-
tion with both (+)-camphene and (1S)-b-pinene we
obtained alcohols 11d and 11e by oxidation with dried oxy-
gen and consequent hydrolysis of the hydrometallation
products 8d,e and 9d,e. In these reactions the yield of alco-
hols was fairly low; for example, the formation of trans-
and cis-mirtanols (11e) proceeds with the yield of about
57%. Further, the yield of the alcohols was increased after
carrying out the additional transmetallation stage of 8d,e
by ClAlR02 as shown in Scheme 4 without isolation of
the organozirconium compound from the mixture. During
this reaction we observed formation of Cp2ZrCl2 and
OACs 9d or 9e. The oxidation of 9d or 9e and the subse-
quent hydrolysis provided compounds 11e and 11d at the
yields of 82% and 71% accordingly.
Further we studied the interactions of complexes 1 and 2
in C6H6 at room temperature with the following alkenes: a-
methylstyrene (7c), (+)-camphene (7d), (1S)-b-pinene (7e).
It was shown that complexes 1 and 2 react with 7c–e simi-
larly to that with a- alkenes 7a,b; as a result of the reaction,
zirconocene alkylchlorides 8c–e and alkylalanes 9c–e are
formed in mole ratio 1:1 (Scheme 4).
Hydrolysis of the hydrometallation products gives alk-
anes 10c–e, whose yields vs. both the initial reagents ratio
and the reaction time are presented in Table 1. Under the
optimal conditions at the mole ratio of 1:2 the maximal
yield of the products 10a,b is close to 87% after 1 h of
the reaction, whereas the isopropylbenzene (10c), cam-
phane (10d) and pinane (10e) yields of 86%, 78% and
84% were observed after 1.5, 2.0 and 2.5 h, correspond-
ingly. It is interesting that catalytic hydroalumination of
b-pinene by HAlBui2 in the presence of ZrCl4 [12] at
The correlation between the obtained alcohol stereoiso-
mers was established by both the technique of optical rota-
1
tion angle [a]D measurement and the means of H and 13C
Cl
AlR'2
H3O+
ZrCp2
1 or 2
+
7c
R'= Et or Bui
8c
9c
10c
H3O+
Cl
10d
1 or 2
AlR'2
ZrCp2
+
O2, H3O+
OH
OH
+
7d
9d
8d
[(3S)-exo]-11d
[(3R)- endo]-11d
ClAl R'2
(20%)
(80%)
-Cp2ZrCl2
Cl
ZrCp2
H3O+
AlR'2
1 or 2
OH
OH
+
10e
O2, H3O+
7e
8e
9e
+
ClAlR'
[(2S)- trans]-11e [(2
R)-cis]-11e
-Cp2ZrCl2
(3%)
(97%)
Scheme 4.

3428
L.V. Parfenova et al. / Journal of Organometallic Chemistry 692 (2007) 3424–3429
Table 1
H2PtCl6 catalyzed hydrosilylation of b-pinene using HSi-
MeCl2 or HSiMe2Cl gives trans-isomers [17], whereas no dia-
stereoselectivity was observed in the reaction with camphene
[14a].
Yield of hydrometallation products vs. complex nature, reagents concen-
tration and reaction time (C6H6, 20 ꢁC)
Complex Alkene
Mole
ratio
Time Hydrolysis
Yield
(%)
(h)
products
In our case the high diastereoselectivity of the bicyclic
alkenes reaction with complex 1 under the mild conditions
is probably caused by the structure of the complex, and,
therefore, the bicyclic alkene hydrometallation proceeds
at the most hindered exo-side with formation of thermody-
namically stable endo-isomers.
1
Hept-1-ene
(7a)
Oct-1-ene (7b) 1:2
1:2
0.25
1
0.25
1
0.25
3
0.25
1.5
Heptane (10a)
79
87
76
82
31
80
Octane (10b)
1:4
a-
1:2
Isopropylbenzene 64
(10c) 86
Methylstyrene
(7c)
3. Conclusion
(+)-
Camphene
(7d)
1:2
1:4
2
2
Camphane (10d) 78
Finally, a new bimetallic complex [Cp2ZrH2 Æ ClAlEt2]2
(1) was synthesized, and its reactivity in the reaction of alk-
enes hydrometallation was studied. Results of the alkenes
hydrometallation by hydride Al,Zr-complexes 1–5 show
that chlorine containing complexes 1 and 2 are the most
active among the complexes studied by us. In these reac-
tions a-alkenes exhibit the highest reactivity. The 1,10-
substituted alkenes (e.g. a-methyl styrene) are less active.
The bicyclic alkenes (e.g. camphene and b-pinene) due to
electronic and steric factors show the lowest activity in the
series of the alkenes examined. Because of the complexes
1 and 2 structure, the hydrometallation of (1S)-b-pinene
and (+)-camphene runs with high diastereoselectivity and
provides trans- and endo-alcohols, correspondingly. The
new reagent 1 opens the way to the synthesis of not only dia-
stereomerically pure bicyclic alcohols, but also optically
active OACs, for example, 9d,e, which are promising for
the purposes of organic and organometallic synthesis.
71
(1S)-b-pinene
(7e)
1:2
0.25
2.5
Pinane (10e)
34
83
2
7a
7b
7c
1:2
1:2
1:2
0.25
1
0.25
1
0.25
1.5
2
10a
10b
10c
78
83
74
80
61
84
81
7e
7a
7a
7a
1:2
1:2
1:2
1:2
10e
10a
10a
10a
3
4
5
1
1
1
19
17
43
NMR spectroscopy [13,14]. It was found that the hydro-
metallation of (1S)-b-pinene by complex 1 runs with high
diastereoselectivity and mainly provides trans-isomer 11e
(trans/cis ratio 97:3). However, the diastereoselectivity of
(+)-camphene hydrometallation is less than that of (1S)-
b-pinene, and the reaction and subsequent oxidation with
I2 give endo-camphanol (endo/exo ratio: 80:20).
4. Experimental
4.1. General
By the beginning of our studies the literature data con-
tained contradictory information concerning the stereose-
lectivity of the bicyclic alkenes reducing. However, an
opinion that the attachment of small molecules (BH3, HAl-
Bui2) to bicyclic alkenes proceeds at the least sterically hin-
dered side of the double bond was common for literature
sources. For example, in Ref. [15] devoted to oxidative
camphene hydroboration with BH3 a mixture of diastereo-
mers with predomination of endo-camphanol (endo/exo
ratio 80:20) was obtained. The same reaction with
b- pinene produces cis-mirtanol at high yield [16].
The camphene hydrozirconation by Schwartz reagent at
80 ꢁC and further oxidation of the reaction products also
provides endo-camphanol (endo/exo ratio 97:3) [3]. The
b- pinene hydrozirconation provides the excess of cis-isomer
(trans/cis ratio 13:87). The endo-isomers formation the
authors explained by the isomerization of zirconium r-com-
plex with the exo- configuration of substitutes which was ini-
tially formed in the steric control conditions. Furthermore,
boron- [15a,16] and organoaluminium [13] exo-isomers were
shown to be able to transform into more thermodynamically
stable endo-isomers after heating. It is interesting that
All operations were carried out under argon using
Schlenk techniques. Solvents were dried by refluxing over
either LiAlH4 or i-Bu2AlH and freshly distilled prior to
use. (+)-Camphene (7d) (Aldrich; 80%) was purchased and
used after double recrystallization. (1S)-(ꢀ)-b-Pinene
(Aldrich 99+%) was used without purification. Commer-
cially available 91.8% AlEt3, 90% ClAlEt2, 95% ClAlBui2,
91% AlBui3 and 74% HAlBui2were involved into the reac-
tions. Cp2ZrCl2 was prepared from ZrCl4(Aldrich, 99.5 %)
according to the procedure in Ref. [18]. The Cp2ZrH2 and
complexes 2–5 were prepared as described previously in
1
Ref. [5]. The NMR spectra H and 13C were recorded at
25 ꢁC on spectrometers JEOL FX-90Q (90 MHz 1H,
22.5 MHz 13C) and BRUKER AM-300 (300 MHz 1H,
75 MHz 13C). d6-Benzene and d-chloroform were used as
internal standard. Optical rotation angles [a]D were deter-
mined on spectropolarimeter Perkin–Elmer-341. The hydro-
lysis products of reaction mixture were analyzed on
chromatograph ‘‘Chrom-5’’ (flame-ionizating detector, col-
umn 2 m · 3 mm 15% ‘‘Peg-6000’’ or 5% ‘‘SE-30’’ on
Chromaton N-AW, 50–190 ꢁC). Mass spectra were obtained

L.V. Parfenova et al. / Journal of Organometallic Chemistry 692 (2007) 3424–3429
3429
on a Finnigan 4021 GLC-mass spectrometer. The yields of
Acknowledgements
the both alkanes and alcohols were calculated with respect
to the initial alkene amount.
The authors thank the Foundation of the President of
Russian Federation (Program for Support of Leading Sci-
entific Schools, U.M. Dzhemilev, Grant NSh-7470.2006.3,
Program for Support of Young Ph.D. Scientists, L.V. Par-
fenova, Grant MK-4526.2007.3, S.V. Pechatkina, Grant
MK-4977.2007.3) and the Russian Science Support Foun-
dation (Grant for Young Ph.D. Scientists, Parfenova
L.V.) for financial support.
4.2. Synthesis of [Cp2ZrH2 Æ ClAlEt2]2 (1)
A flask equipped with a magnetic stirrer and filled with
argon was loaded with Cp2ZrH2 (0.6 mmol, 134 mg) and
benzene (1.5 ml). ClAlEt2 (0.6 mmol, 0.11 ml) was added
dropwise until the precipitate was dissolved. Finally the
formation of complex 1 was observed.
1H NMR (C6D6) d 5.78 (20H, Cp); ꢀ0.91 (s, 2H,
References
2
ZrHAl); ꢀ2.68 (br.t, 2H, ZrHZr, JHH = 4.2 Hz); 1,46 (t,
12H, CH3, J = 8.3 Hz); 0.43 (q, 8H, CH2, J = 8.3 Hz).
13C NMR (C6D6) d 106.35 (Cp), 1.15 (t, C1), 9.83 (q,
C2). Molecular weight (cryoscopy in benzene): found
[1] (a) B. Kautzner, P.C. Wailes, H. Weigold, J. Chem. Soc., Chem.
Commun. D19 (1969) 1105;
(b) P.C. Wailes, H. Weigold, J. Organomet. Chem. 24 (1970)
405.
[2] (a) D.W. Hart, J. Schwartz, J. Am. Chem. Soc. 96 (1974) 8115;
(b) J. Schwartz, J.A. Labinger, Angew. Chem. Int. Ed. Engl. 15
(1976) 333.
640 g molꢀ1; calc. 688 g molꢀ1
.
4.3. Alkenes 7a–e hydrometallation with complexes 1–5
[3] M.S. Miftakhov, N.N. Sidorov, G.A. Tolstikov, Bull. Acad. Sci.
USSR, Div. Chem. Sci. 28 (1979).
[4] (a) P.C. Wailes, H. Welgold, A.P. Bell, J. Organomet. Chem. 43
(1972) 32;
(b) P.C. Wailes, H. Welgold, A.P. Bell, J. Organomet. Chem. 27
(1971) 373.
[5] L.V. Parfenova, S.V. Pechatkina, L.M. Khalilov, U.M. Dzhemilev,
Russ. Chem. Bull. 54 (2005) 316.
[6] L.I. Shoer, J. Schwartz, J. Am. Chem. Soc. 99 (1977) 5831.
[7] B.D. Carr, J. Schwartz, J. Am. Chem. Soc. 101 (1979) 3521.
[8] P.C. Wailes, H. Weigold, A.P. Bell, J. Organomet. Chem. 43 (1972)
29.
[9] L.I. Shoer, K.I. Gell, J. Schwartz, J. Organomet. Chem. 136 (1977)
19.
[10] P.G. Bickley, N. Hao, P. Bougeard, B.G. Sayrr, R. Burns, M. Burns,
M.J. McGlinchey, J. Organomet. Chem. 246 (1983) 257.
[11] (a) K.I. Gell, J. Schwartz, J. Am. Chem. Soc. 100 (1978) 3246;
(b) K.I. Gell, B. Posin, J. Schwartz, G.M. Williams, J. Am. Chem.
Soc. 104 (1982) 1846.
A flask equipped with a magnetic stirrer and filled with
argon was loaded with Cp2ZrH2 (0.6 mmol, 134 mg) and
benzene (0.5 ml). The OACs (0.6 mmol) were added drop-
wise until the precipitate was completely dissolved. Forma-
tion of complexes 1–5 were obtained. Then, either 0.6 or
1.2 mmol of alkenes 7a–e were added to reaction mixture.
The mixture was stirred for 2 h and the formation of mix-
ture of 8a–e and 9a–e at mole ratio 1:1 was observed. For
the kinetic study, the samples (0.2 ml) were syringed into
tubes filled with argon, and the samples were decomposed
with 10% HCl at 0 ꢁC. The decomposition products were
extracted with benzene; further, the organic layer was dried
over Na2SO4 and analyzed by GLC. The products yields
are presented in Table 1.
4.4. Oxidation of 9d,e with O2
[12] G.A. Tolstikov, U.M. Dzhemilev, O.S. Vostrikova, A.G. Tolstikov,
Izv. AN SSSR. Ser. Khim. (1982) 669.
An excess of ClAlEt2 or ClAlBui2 (0.6 mmol) was added
under vigorous stirring to either 8d,e or 9d,e mixture, which
was prepared as described in Section 4.3. The mixture was
stirred for 1 h at r.t. The solution of 9d,e was blown by dry
O2 and decomposed by 10% HCl at 0 ꢁC. The products were
extracted by benzene (3 · 5 ml); the combined organic
extracts were dried over Na2SO4 and the solvents removed
in vacuum. The products were recrystallized from CHCl3.
The yield of [(3R)-endo]- and [(3S)-exo]-1R,4S-2,2-dim-
ethylbicyclo[2.2.1]heptan-3-yl-methanol (11d) was 71%
(endo/exo ratio 80:20). The yield of [(2S)-trans]- and [(2R)-
cis]-1S,5S-6,6-dimethylbicyclo[3.1.1]heptan-2-yl-methanol
(11e)was 82% (trans/cis ratio97:3). 1H and13C NMR spectra
were identical to those of authentic sample [14a,14b,14c].
[13] trans-Myrtanol: H. Benn, J. Brandt, G. Wilke, Liebigs Ann. Chem.
(1974) 189.
[14] (a) Camphanol: J. Beckmann, D. Dakternieks, A. Duthie, S.L.
Floate, R.C. Foitzik, C.H. Schiesser, J. Organomet. Chem. 689
(2004) 909;
(b) myrtanol: M. Miyazawa, Y. Suzuki, H. Kameoka, Phytochem-
istry 45 (1997) 935;
(c) myrtanol: K.-Y. Kim, S.-G. Lee, Magn. Reson. Chem. 35 (1997)
451.
[15] (a) R. Dulou, J. Chretien-Bessiere, Bull. Soc. Chim. France (1959)
1362;
(b) J. Lhomme, G. Ourisson, Tetrahedron 24 (1968) 3201.
[16] (a) J.C. Braun, G.S. Fisher, Tetrahedron Lett. 21 (1960) 9;
(b) G. Zweifel, H.C. Brown, J. Am. Chem. Soc. 86 (1964) 393.
[17] D. Wang, T.H. Chan, Tetrahedron Lett. 24 (1983) 1573.
[18] R.Kh. Freidlina, E.M. Brainina, A.N. Nesmeyanov, Dokl. Acad.
Nauk SSSR 138 (1969) 1369.