Bis(η5-cyclopentadienyl)- and bis(η5-indenyl)metallacycles of titanium and zirconium from methylenecyclopropanes by oxidative coupling

Article abstract of DOI:10.1016/S0022-328X(02)01472-9

Methylenecyclopropane (1a) reacts with bis(trimethylphosphane)titanocene (8) and (η²-1-butene)(trimethylphosphane)zirconocene (12a) via olefin complexes; e.g. 9, in a [2 + 2] cycloaddition to afford the metallacyclopentane derivates 10, 13 and

Full text of DOI:10.1016/S0022-328X(02)01472-9

Journal of Organometallic Chemistry 656 (2002) 288ꢁ298
/
www.elsevier.com/locate/jorganchem
Bis(h5-cyclopentadienyl)- and bis(h5-indenyl)metallacycles of
titanium and zirconium from methylenecyclopropanes by oxidative
coupling
Paul Binger *, Patrik Muller, Stefan Podubrin, Stefan Albus, Carl Kruger
¨
¨
Max Planck-lnstitut fur Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mulheim a.d. Ruhr, Germany
¨ ¨
Received 5 February 2002; accepted 12 April 2002
Dedicated to Professor Francois Mathey on occasion of his 60th birthday
¸
Abstract
Methylenecyclopropane (1a) reacts with bis(trimethylphosphane)titanocene (8) and (h2-1-butene)(trimethylphosphane)zircono-
cene (12a) via olefin complexes; e.g. 9, in a [2ꢀ2] cycloaddition to afford the metallacyclopentane derivates 10, 13 and 14. In
contrast, a [3ꢀ
2] cycloaddition reaction is observed with bis(h5-lndenyl)(h2-1-butene)(trimethylphosphane)zirconium (12b) to
/
/
furnish the 1-zircona-4-methylenecyclohexane 15. Similarly, reactions of the complexes 8 and 12a with benzylidenecyclopropane (1c)
give the olefin complexes 9c and 20, while a direct reaction between the indenyl complex 12b with 1c occurs to furnish the 1-zircona-
2-benzylidenecyclobutane complex 21b which was characterised by X-ray crystallography. # 2002 Elsevier Science B.V. All rights
reserved.
Keywords: Methylenecyclopropane; Titanocene(II) and zirconocene(II) complexes; Bis(h5-indenyl)zirconium complexes; [2ꢀ
Cycloadditions
/
2] and [3ꢀ2]
/
1. Introduction
the catalyst used. Consequently, the targeted (regiose-
lective) synthesis of methylenecyclopentanes with differ-
ing substitution patterns is possible (Scheme 1).
Some time ago, we developed a method with which
methylenecyclopentane derivatives can be prepared
directly from methylenecyclopropanes (1) and alkenes
Even now, the exact mechanisms of the two reaction
routes are not completely understood. However, from
the products obtained it is apparent that with a Pd(0)
catalyst the distal bond and with a Ni(0) catalyst the
proximal bond of the three-membered ring is cleaved.
Two possibilities have been discussed for the proximal
bond cleavage. Noyori et al. proposed a direct attack of
the nickel catalyst at this bond with a 2-methylene-1-
nickelacyclobutane complex 3a as an intermediate of the
catalysis [5]. The observation in cyclodimerisations and
cyclotrimerisations of methylenecyclopropanes that cy-
clobutane and cyclopentane derivatives are formed led
to the suggestion that both products are formed from a
common intermediate. Accordingly, the primary pro-
duct is the metallacyclopentane derivative 4a or 4b that
can rearrange to the metallacyclohexane derivative 5a or
5b. The reaction products then arise via reductive
eliminations from 4a, 4b and 5a, 5b (Scheme 2) [6,7].
via a transition metal-catalysed [3ꢀ2] cycloaddition [1].
/
Suitable catalysts for this process are, above all,
nickel(0) and palladium(0) complexes. Since methylene-
cyclopropane itself [2] as well as its derivatives sub-
stituted on the ring [3] or the double bond [4] are readily
accessible on a multi-gram scale and because numerous,
variously substituted alkenes can be employed, this
method is excellently suitable for the synthesis of very
differently substituted mono- and bicyclic methylenecy-
clopentanes. In addition, these cycloadditions can
proceed by different reaction pathways depending on
* Corresponding author. Present address: Fachbereich Chemie der
Universitat
Kaiserslautern,
Kaiserslautern, Germany. Fax: ꢀ
E-mail address: regitz@rhrk.uni-kl.de (P. Binger).
Erwin-Schrodinger-Strasse,
67663
¨
¨
/
49-631-205-3921.
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 4 7 2 - 9

P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ
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298
289
Scheme 1. Ni(0)- and Pd(0)-catalysed [2ꢀ
/
2] and [3ꢀ2] cycloadditions with methylenecyclopropane (1a).
/
This proposal is supported by the isolation and char-
acterisation of model compounds such as 2a and 4a
nium to afford the corresponding titanacyclopentane
derivatives 6a,b which, upon heating to 200 8C, under-
went preferential rearrangement to the 1,3-dienes 7a and
7b (Eq. 1) [10].
[L2ꢂa,a?-bipyridyl, 1,2-bis(dicyclohexylphosphanyl)-
/
ethane, 1,2-bis(dimethylphosphanyl)ethane] from which
the observed products can be obtained in a second
reaction step [8].
We now report on the reactivity of 1a and benzylide-
necyclopropane (1c) towards readily accessible metallo-
cene(II) complexes such as Cp2Ti(PMe3)2 [11],
Cp2Zr(PMe3)(h2-butene) [11] and analogous bis(h5-
indenyl)zirconium complexes [12]. We found that 1
can react with the tested metallocene derivatives to
furnish h2-olefin complexes, metallacyclopentane deri-
vatives and, via proximal cleavage of the three-mem-
bered ring, metallacyclobutane derivatives. By
combination of p-complex formation and ring opening
processes a direct route to metallacyclohexane deriva-
tives became available.
It is known that metallocene derivatives of titaniu-
m(II) and zirconium(II) readily participate in oxidative
coupling reactions with alkenes and alkynes to afford
metallacyclopentane, metallacyclopentene and metalla-
cyclopentadiene derivatives [9]. Thus, it seemed reason-
able to examine the behaviour of methylenecyclo-
propanes with this class of compounds in more detail.
Previous work had shown that methylenecyclopropane
(1a) and 2-phenylmethylenecyclopropane (1b) reacted
with bis(h5-pentamethylcyclopentadienyl)(ethene)tita-
ð1Þ

290
P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ298
/
Scheme 2. Ni(0)-catalysed [2ꢀ
/
2] and [3ꢀ
/
2] cycloadditions with methylenecyclopropane (1a): possible reaction paths.
2. Results and discussion
In contrast, reactions of 8 with the substituted methy-
lenecyclopropanes 1c and 1d stop at the stage of the
Bis(h5-cyclopentadienyl)bis(trimethylphosphane)tita-
nium(II) (8) [11,13] and bis(h5-cyclopentadienyl)-
trimethylphosphane(h2-1-butene)zirconium (12) [11,13]
proved to be the most suitable starting materials for the
preparation of olefin complexes and coupling products
of methylenecyclopropanes with metallocenes of tita-
nium and zirconium. The reaction of 8 with an
equimolar amount of 1a at 0 8C affords the olefin
complex 9a as a red powder in 78% yield. Use of excess
1a under otherwise identical reaction conditions leads
regioselectively to the titanacyclopentane derivative 10.
olefin complexes 9c and 9d [14]. The latter are obtained
as red powders in yields of 76 and 64%, respectively.
Upon longer standing in solution product 9d undergoes
rearrangement to the biscarbene complex 11 [14]
(Scheme 3).
A decisive influence of the structures of the two
cyclopentadienyl units on the course of the reactions
with the methylenecyclopropanes 1a and 1c is observed
when the bis(h5-cyclopentadienyl)(butene)zirconium
complex 12a and the respective bis(h5-indenyl)zirco-
nium complex 12b are used as starting materials. In

P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ
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298
291
Scheme 3. Reactions of Cp2Ti(PMe3)2 (8) methylenecyclopropane 1a, 1c and 1d.
analogy to the behaviour of the titanium complex 8, the
reaction of 1a with the zirconium complex 12a affords
the coupling product from two molecules of 1a with the
Cp2Zr fragment; however, this reaction is no longer
regioselective. Together with the zirconacyclopentane
derivative 13 the zirconacyclopentane derivative 14 is
formed in a ratio of 2:1 (combined yield 98%). Although
the h2-methylenecyclopropane complex initially formed
by expulsion of 1-butene can be detected by spectro-
scopy (NMR) it cannot be isolated in pure form also not
when one equivalent of 1a is used. Surprisingly, on the
other hand, the reaction of 1a with the bis(h5-inde-
nyl)zirconium complex 12b leads directly to the zirco-
nacyclohexane complex 15. No intermediates, such as a
(h2-methylenecyclopropane)zirconium complex or a
zirconacyclopentane complex analogous to 13, can be
detected. This, like the observation that complex 13
cannot be transformed into a complex analogous to 15
on heating, suggests that 15 is formed directly through
proximal ring opening of 1a in the course of an oxidative
[3ꢀ
2] cycloaddition with a (h2-methylenecyclopropa-
ne)zirconium complex (Scheme 4).
/
Two further examples for the differing behaviour of
1a in coupling reactions with alkyne or alkene com-
plexes of zirconocene and bis(h5-indenyl)zirconium are
provided by the reaction of the (h2-ethene)bis(h5-
indenyl)zirconium complex 16 with 1a and those be-
tween the (alkyne)zirconium complexes 18a,b and 1a. In
the first case, bis(h5-indenyl)-l-zircona-4-methylenecy-
clohexane (17) is formed exclusively via proximal ring
opening of 1a while, in the second case, the 1-zircona-
cyclopentene derivatives 19a and 19b are formed, also
regioselectively, with the spiro-three-membered ring
being in the vicinity of the metal (Scheme 5).
A comparable differentiation in reactivity is also
found in the reactions of the benzylidenecyclopropane
1c with 12a and 12b. On reaction with 1c at room
temperature, 12a affords the benzylidenecyclopropane
complex 20 which, upon warming at 60 8C for 18 h,
rearranges to the 1-zircona-2-benzylidenecyclobutane
complex 21a. In contrast, the bis(h5-indenyl)zirconium

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/
Scheme 4. Reactions of zirconium complexes 12a,b with methylenecyclopropane 1a.
complex analogous to 20 can neither be isolated nor
detected spectroscopically. An attempt to insert 3-
hexyne into one of the two metalla carbon-5-bonds of
21b to afford a 1-zirconabenzylidenecyclohexene analo-
gous to 17 failed. Although a reaction was observed at
80 8C, 1c was recovered and 3-hexyne reacted as
previously observed to afford the known 1-zirconacy-
clopentadiene complex 22 [12] (Scheme 6).
The titanium and zirconium complexes described here
for the first time possessed the calculated sum formulae,
however, their molecular masses could rarely be deter-
mined by mass spectrometry. Even so the spectra did
show characteristic fragmentation patterns. The struc-
tures were deduced from analyses of the NMR spectra.
Thus, the 1H- and 13C-NMR spectra of the p-complexes
9a, 9c and 20 which are measured at low temperature to
avoid rotation of the methylenecyclopropanes exhibit
signals characteristic for a complexed double bond [15].
For example, the co-ordination shifts d(complex)ꢁ
d(pure olefin) for 10a amount to ꢃ
5.12 (1H) and ꢃ
75ꢁ
90 ppm (13C). In contrast to the free olefin, the
/
Scheme 5. Different courses of the codimerisation of 1a with the
zirconium-complexes 16 and 18a,b.
/
/
/
complex 12b, prepared in situ from (lnd)2ZrCl2, two
equivalents of butyllithium and trimethylphosphane,
also reacts with 1c at room temperature but only to
furnish the corresponding 1-zircona-2-benzylidenecyclo-
butane complex 21b; intermediates such as, e.g. an olefin
1J(C,H) coupling constants especially are appreciably
reduced. As in the corresponding 1-alkene complexes of
titanium and zirconium [11], the ligands are in a
pseudotetrahedral arrangement about the metal. The
methylenecyclopropanes lie in the plane defined by the

P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ
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298
293
Scheme 6. Reactions of zirconium complexes 12a,b with benzylidenecyclopropane 1c.
MÃ
/
PMe3 bond and the olefin p-co-ordination axis. In
a high field shift typical for a metalla-four-membered
ring(1.3ꢁ12.7 ppm) [18]. The values for the CÄC double
contrast to the 1-alkene complexes, however, only one
rotamer is formed in which the three-membered ring
points in the opposite direction to the PMe3 group. This
is demonstrated by the differing coupling constants
J(P,C1) and J(P,C4) (13C), as well as the nuclear
Overhauser difference spectrum [16] (e.g. saturation of
the olefinic protons at C4 shows the adjacency to the
PMe3 group).
The 1-zircona-2-benzylidenecyclobutanes 21a and 21b
were identified by comparison of their NMR spectra
with those of 1-titana-2-methylenecyclobutanes [17].
The signals of the carbon atoms C(2) and C(4) directly
/
/
bond are practically unchanged and only one set of
signals is observed for the C and H atoms of the
cyclopentadienyl or indenyl units. The 1H- and 13C-
NMR data for the two zirconacyclohexane derivatives
15 and 17 are in accord with the proposed structures (see
Section 3) and are thus not discussed in detail here.
H,H-COSY experiments support the assignments of the
six multiplets of complex 15.
The structure of complex 21b in the solid state was
additionally confirmed by X-ray crystallography. The
results demonstrate a pseudotetrahedral arrangement
with the indenyl ligands possessing a eclipsed syn-
conformation. The angle between the metal and the
bonded to the metal with ca. 210 and 43ꢁ
experience a shift to low field, while that for C(3) shows
/59 ppm

294
P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ298
/
midpoints of the two indenyl five-membered rings
amounts to 136.58, the zircona-four-membered ring is
3. Experimental
˚
planar which deviation at C2 of 0.03 A, the benzylidene
The reactions were performed under argon in pre-
viously evacuated and baked-out Schlenk vessels. The
solvents used were dried with NaÃ
C4 carbon atom is also in this plane while ipso-C atom
of the phenyl ring cis to the zirconium in the four-
˚
membered ring is found to about 0.26 A above this
/K alloy (pentane,
hexane, toluene, [D8]-THF) and MgH2 (diethyl ether,
THF) prior to distillation and stored under argon.
Melting points were determined on a Gallenkamp
apparatus. 1H-, 13C- and 31P-NMR spectra were re-
corded on Bruker AC 200 FT and Bruker WH 400 FT
instruments with TMS as internal standard or 85%
H3PO4 as external standard. Mass spectra were recorded
with MAT 311 APF and Finntgan MAT 95 spectro-
meters. Chemicals: n-butyllithium in hexane (1.6 M)
(Deutsche Metallgesellschaft), titanocene dichloride (Al-
drich) and zirconocene dichloride (Fluka) were used
without further purification. Methylenecyclopropane 1a
[2a], Benzylidenecyclopropane 1c [4], trimethylpho-
sphane [20] Bis(trimethylphosphane)titanocene 8 [11a],
(h2-1-Butene) (trimethylphosphane) zirconocene [11a]
were prepared by published procedures.
plane. Not only the length of the CÄ
/
C double bond
˚
[1.35(1) A] [17a] but also those of the C,C and Zr,C
separations (see Fig. 1) are within the expected ranges
[19]. As a result of the small size of the ring, C2 with a
˚
value of 2.59(1) A has about the same bonding separa-
tion to zirconium as the C atoms in the indenyl five-
membered rings.
In the present work, we have shown that although
methylenecyclopropanes such as 1a or 1c preferentially
participate in h2-complexes over the CÄ
/C double bond
with transition metal complexes, under certain circum-
stances-probably triggered by steric hindrance-they can
also react through proximal opening of the three-
membered ring. This leads to isolable 1-metalla-2-
methylenecyclobutane derivatives such as the complexes
21a,b. These compounds apparently do not occur during
3.1. (h2-Methylenecyclopropane)
(trimethylphosphane)titanocene (9a)
dimerisation reactions, instead a [3ꢀ2] cycloaddition
/
with a h2-bound unsaturated system takes place.
Indications for this can be taken from the syntheses of
the metallacyclohexane derivatives 15 and 17 in which
there are no signs for the intermediate occurrence of a 1-
metallacyclobutane. Furthermore, no further ring ex-
pansion of the isolated 1-metalla-2-methylenecyclobu-
tanes by insertion of an unsaturated system can be
achieved.
To a solution of complex 8 (1.02 g, 3.1 mmol) in
pentane (20 ml) is added at 0 8C a 0.32 M solution of 1a
in diethyl ether (9.62 ml, 3.1 mmol). After stirring for 1 h
the solvent is evaporated (0.5 mbar, 20 8C) and the
residue is washed once with pentane (5 ml). Compound
9a is obtained as a red powder; yield 0.72 g (78%); m.p.
(dec.) 103 8C. 1H-NMR (400 MHz, [D8]-THF, ꢃ
80 8C): dꢂ0.23 (m, 2H, JP,H 11.0 Hz, ÄCH2); 0.88
and 0.96 (m, 4H, ring-H); 1.32 (d, 9H, JP,H 5.8 Hz,
/
/
ꢂ
/
/
ꢂ
/
PMe3); 4.90 (d, 10H, JP,H
(75.5 MHz, [D8]-THF, ꢃ110 8C): dꢂ
128, JP,C
ring-C); 27.8 (dt, JC,Hꢂ
CH2); 40.5 (d, JP,C 7.5 Hz, ring-C); 101.4 (d,
1JC,H 171 Hz, Cp). 31P-NMR (121.5 MHz, [D8]-
THF, ꢃ110 8C): dꢂ26.5. MS (70 eV): m/z (%)ꢂ
PMe3], 178 (100)
ꢂ
/
2.4 Hz, Cp). 13C-NMR
/
/
16.9 (dq, 1JC,H
ꢂ
156 Hz,
/
1
ꢂ
/
15.0 Hz, PMe3); 20.7 (t, JC,H
ꢂ
/
1
/
150 Hz, JC,P
ꢂ
/
20.6 Hz, Ä
/
ꢂ
/
ꢂ
/
/
/
/
[Mꢀ] not observed, 232 (2) [Mꢀ Ã
/
[Cp2Tiꢀ], 152 (8), 113 (21), 76 (14) [PMe3ꢀ], 61 (23)
C17H25PTi (308.2) Calc. C, 66.24; H, 8.18; P, 10.05; Ti,
15.53; Found: C, 66.24; H, 8.14; P, 10.11; Ti, 15.33%.
3.2. (h2-Benzylidenecyclopropane)(trimethyl-
phosphane)titanocene (9c)
To a solution of complex 8 (0.98 g, 3 mmol) in diethyl
ether (25 ml) is added dropwise a solution of 1c (0.85 g,
6.5 mmol) in ether (10 ml) at room temperature (r.t.).
˚
Fig. 1. Molecular structure of 21b; selected bond lengths (A) and
The solution turns red and during 1 h stirring a reddishꢁ
/
angles (8); ZrÃ
2.48(1), ZrÃC13 2.49(1), ZrÃ
1.57(2), C3ÃC4 1.35(1); C1ÃZrÃ
C2ÃC3 114.3(8), C2ÃC3ÃZr 85.5(6).
/
C1 2.18(1), ZrÃ
C14 2.58(1), C1Ã
C3 74.1(4), C2Ã
/
C3 2.19(1), ZrÃ
/
C2 2.59(1), ZrÃ
C2 1.56(1), C2Ã
C1ÃZr 86.1(6),C1Ã
/
C12
brown solid precipitates which is filtered off, washed
twice with pentane (3 ml) and dried under vacuum (0.5
mbar); yield 0.96 g (76%), m.p. (dec.) 129 8C. 1H-NMR
/
/
/
/
C3
/
/
/
/
/
/
/
/
/

P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ
/
298
295
(400 MHz, [D8]-THF, ꢃ
5.3 Hz, PMe3); [0.83, 1.16, 1.21, 1.45 (m, 4H, ring-H)];
1.28 (d, 3H, JP,H 6.6 Hz, PMe3); 1.59 (d, 3H, JP,H
6.2 Hz, PMe3); 1.79 (d, 1 H, JP,H 8.8 Hz); [4.94 (d, 5H,
JP,H 2.4Hz, Cp); 5.10 (d, 5H, JP,H 2.2 Hz, Cp)];
/
80 8C): dꢂ
/
0.47 (d, 3H, JP,H
ꢂ
/
removed in vacuum (0.5 mbar) and the oily residue
redissolved in diethyl ether (20 ml). After 3 days at ꢃ
20 8C, unreacted 20 has precipitated as a yellow solid,
which is filtered off. The volume of the mother liquid is
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
reduced to 10 ml. After 10 days at ꢃ20 8C, orange
/
[6.47, 7.57 (2H, o-phenyl)]; [6.59, 7.32 (2H, m-pheny)];
6.88 (1H, p-phenyl). 13C-NMR (75.5 MHz, [D8]-THF,
crystals have been precipitated which are filtered off and
dried in vacuum to leave 21a; yield 2.3 g (70%), m.p.
1
1
ꢃ
/
80 8C): dꢂ
/
14.3 (dq, JC,H
ꢂ
/
128 Hz, JP,C
18.9 Hz, PMe3);
8.8 Hz, PMe3); [21.3 (t,
156 Hz), C-ring]; 48.6
15.2 Hz, ÄCH); 48.8 (d,
C); 103.8 and 104.1 (d, JC,H
ꢂ
/
14.6 Hz,
(dec.) 125 8C. H-NMR (200 MHz, [D8]-THF, 25 8C):
PMe3); 16.7 (dq, 1JC,H
ꢂ
/
128 Hz, JP,C
ꢂ
/
dꢂ
Cp); 7.52 (m, 1H, 5-H); 7.0ꢁ
NMR (50.3 MHz, [D8]-THF, 25 8C): dꢂ
/
0.99 (m, 2H, 3-H); 1.80 (m, 2H, 4-H); 5.94 (s, 10H,
7.4 (m, 5H, phenyl). 13C-
1.3 (t, 1JC,H
137 Hz, C-4); 108.7 (d,
1
18.5 (dq, JC,H
1JC,H
ꢂ
/
124 Hz, JP,C
ꢂ
ꢂ
/
/
1
ꢂ
/
156 Hz); 22.1 (t, JC,H
/
/
ꢂ
/
1
1
(dd, JC,H
JP,C 9.6 Hz, ꢀ
Hz, Cp); 119.7 (d, JC,H
1JC,H
156 Hz, o-phenyl), 129.0 (d, JC,H
phenyl); 127.5 and 127.7 (d, JC,H
154.5 (d, JP,C
3.4 Hz, ipso-phenyl). 31P-NMR (121.5
MHz, [D8]-THF, ꢃ80 8C): dꢂ20.8. C23H29PTi (383.2)
ꢂ
/
145 Hz, JP,C
ꢂ
/
/
137 Hz, C-3); 43.4 (t, JC,H
1JC,H
170 Hz, Cp); 126.0 (d, JC,H
phenyl); 126.4 (d, JC,H
1JC,H
158 Hz, m-phenyl); 143.1 (s, ipso-phenyl); 137.2
(d, 1JC,H
145 Hz, C-5); 212.2 (s, C-2). MS (70 eV): m/z
(%)ꢂ
ꢂ
/
1
1
ꢂ
/
/
CÄ
/
ꢂ
/
171
ꢂ
/
ꢂ
/160 Hz, p-
1
1
ꢂ/158 Hz, p-phenyl); 123.5 (d,
ꢂ
/
157 Hz, o-phenyl); 128.5 (d,
1
ꢂ
/
ꢂ/153 Hz, o-
ꢂ
/
1
ꢂ/154 Hz, m-phenyl);
ꢂ
/
/
350 (6.6) [Mꢀ], 322 (13.3) [Mꢀꢃ
28], 220 (100)
/
ꢂ
/
[Cp2Zrꢀ]. C20H20Zr (351.6) Calc. C, 68.32; H, 5.73;
Found: C, 68.26; H, 5.84%.
/
/
Calc. C, 71.80; H, 7.55; P, 8.06; Ti, 12.47; Found: C,
71.69; H, 7.59; P, 8.26; Ti, 12.26%.
3.3. (h2-Benzylidenecyclopropane)(trimethylphosphane)
zirconocene (20)
3.5. Bis(h5-indenynl)-1-zircona-2-
benzylidenecyclobutane (21b)
To a solution of complex 12a (0.91 g, 2.23 mmol) in
diethyl ether (25 ml) at r.t. is added dropwise a solution
of 1c (0.64 g, 4.9 mmol) in diethyl ether (10 ml). During
the addition of 1c, 20 begins to precipitate as a yellow,
microcrystalline solid. After additional 1 h stirring, the
solid is filtered, washed three times with pentane (3 ml)
and dried at 0.5 mbar to leave 20; yield 0.87 g (91%),
m.p. 133 8C (decomp.). 1H-NMR (400 MHz, [D8]-
At ꢃ78 8C a 1.6 M solution of n-butyllithium in
/
hexane (4.9 ml, 7.9 mmol) is added dropwise to a
suspension of bis(h5-indenyl)zirconium dichloride (1.5
g, 3.9 mmol) in THF (80 ml). After stirring for 1 h 1c
(0.8 ml, 6.1 mmol) and trimethylphosphane (0.5 ml, 4.8
mmol) are added and the whole mixture is slowly
warmed to r.t. After stirring for another 15 h the solvent
is removed at 0.5 mbar and the residue extracted over
celite with toluene (25 ml). The toluene is evaporated at
0.5 mbar per 25 8C and the residue dissolved in diethyl
THF,
PMe3); 1.44 (d, 1H, JP,H
5H, JP,C 1.5Hz); 5.43 (d, 5H, JP,C
(1 H, p-phenyl); 6.46 and 6.78 (o-phenyl), 6.92 and 6.78
ꢃ
/
80 8C): dꢂ
/
1.14 (d, 9H, JP,H
5.3 Hz, ÄCHPh); [5.28 (d,
1.4 Hz), Cp]; 6.43
ꢂ
/
6.1 Hz,
ꢂ
/
/
ꢂ
/
ꢂ
/
ether. After cooling at ꢃ78 8C for 2 days a yellow
/
(m-phenyl). 13C-NMR (75.5 MHz, [D8]-THF, ꢃ
/
80 8C):
microcrystalline solid has precipitated, which is filtered
and dried in vacuum (0.5 mbar) to leave pure 21b as a
yellow powder; yield 1.1 g (63%). Crystals suitable for
an X-ray analysis were obtained by recrystallisation
1
15.6 (bm, PMe3); 20.0 (t, JC,H
dꢂ
/
ꢂ
/
155 Hz, three-
1
membered ring); 23.3 (t, JC,H
ꢂ
/
156 Hz, three-mem-
8.4 Hz, ÈCÄCHPh); 42.4
CHPh); 104.5
bered ring); 36.1 (d, JP,C
(dd, JC,H 140 Hz, JP,C
and 105.4 (d, 1JC,H
ꢂ
/
/
from diethyl etherꢁ
/
THF (3:1). 1H-NMR (200 MHz,
0.98 (m, 2H, 4-H); 0.31 (m,
2H, 3-H); 6.00 (t, 2H, JH,H 2.7 Hz, indenyl); 6.24 (d,
4H, 3JH,H
2.7 Hz, indenyl); 6.96 (m, 4H, indenyl); 7.30
(m, 4H, indenyl); 7.0ꢁ7.2 (m, 5H, phenyl); 7,41 (m, 1 H,
5-H). 13C-NMR (50.3 MHz, [D8]-THF, 25 8C): dꢂ
12.7
139 Hz, C-4);
147 Hz, C-5); 210.5 (s, C-2); [95.5 (d,
ꢂ
/
ꢂ
/
10.5 Hz, ÈCÄ
/
170 Hz, Cp); 117.7 (d, 1JC,H
ꢂ158
/
[D8]-THF, 25 8C): dꢂ
/
ꢃ
/
ꢂ
/
3
1
ꢂ
/
Hz, p-phenyl); 122.7 and 126.9 (d, JC,H
ꢂ153 Hz, o-
/
1
ꢂ
/
phenyl); 127.4 and 127.6 (d, JC,H
156.6 (d, JP,C
2.6 Hz, ipso-phenyl). 31P-NMR (121.5
MHz, [D8]-THF, ꢃ80 8C): dꢂ3.3. MS (70 eV): m/z
(%)ꢂ PMe3], 220
ꢂ
/
154 Hz, m-phenyl);
/
ꢂ
/
/
/
/
1
1
[Mꢀ] not observed, 350 (8) [Mꢀ Ã
/
(t, JC,H
ꢂ
/
137 Hz, C-3); 59.5 (t, JC,H
ꢂ
/
/
1
(100) [Cp2Zr4], 194 (10), 76 (16) [PMe3ꢀ], 61 (23).
C23H29PZr (427.7) Calc. C, 64.59; H, 6.83; P, 7.24; Zr,
21.33; Found: C, 64.51; H, 6.85; P, 7.29; Zr, 21.31%.
136.4 (d, JC,H
1JC,H
174 Hz); 99.3 (d, JC,H
1JC,H
ꢂ169 Hz); 123.7 (s); 123.8 (s); 124.1 (d); 124.4 (d);
ꢂ
/
1
ꢂ
/
ꢂ176 Hz); 111.8 (d,
/
/
125.5 (d), indenyl]; 126.3 (d, 1JC,H
ꢂ150 Hz, m-phenyl);
/
1
127.0 (d, JC,H
1
146 Hz, p-phenyl); 128.9 (d, JC,H
3.4. Bis(h5-cyclopentadienynl-1-zircona-2-
benzylidenecyclobutane (21a)
ꢂ
/
ꢂ
/
158 Hz, o-phenyl); 143.0 (s, ipso-phenyl). MS (70 eV):
450 (0.7) [Mꢀ], 422 (4.2) [Mꢀꢃ
28], 320 (100)
m/z (%)ꢂ
/
/
A solution of complex 20 (4.0 g, 9.3 mmol) in THF
(30 ml) is heated at 60 8C for 18 h. The solvent is
[indenyl2Zrꢀ]. C28H24Zr (451.7) Calc. C, 74.45; H, 5.36;
Found: C, 74.28; H, 5.39%.

296
P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ298
/
3.6. Bis(h5-cyclopentadienynl-4-
titanadispiro[2.2.2.1]nonane (10)
C18H22Zr (329.6) Calc. C, 65.59; H, 6.67; Zr, 27.68;
Found: C, 65.39; H, 6.75; Zr, 27.96%.
Complex 9a (0.7 g, 2.27 mmol) is suspended in
pentane (10 ml) and diethyl ether (30 ml) at 0 8C and
1a (0.25 g, 4.5 mmol) added. After 1 h stirring, a clear
red solution is obtained. After warming to r.t., the
solvent is evaporated and the residue resolved in
3.8. Bis(h5-indenyl)-4-zircona-7-
methylenespiro[2.5]octane (15)
To a suspension of bis(h5-indenyl)zirconium dichlor-
ide (0.97 g, 2.47 mmol) in THF (70 ml) at ꢃ78 8C is
/
pentaneꢁ
/
ether (20 ml, 1:1). Some impurities are filtered
added a 1.6 M solution of butyllithium in hexane (3.2
ml, 5.12 mmol). After 1 h stirring, trimethylphosphane
(0.5 ml, 4.8 mmol) and 1a (1 ml, 11 mmol) are added.
The reaction mixture is warmed to r.t. and stirred at this
temperature for 12 h. All volatile materials are removed
at 0.5 mbar and the oily residue is taken up in toluene
(20 ml). Insoluble material is removed by filtration over
celite and the solvent distilled off. The residue is taken
up in ether (2 ml) and pentane (10 ml) added. The
hereby formed colourless precipitate is filtered off and
over celite and the red filtrate is cooled to ꢃ
/
20 8C.
After 5 days red crystals are obtained which are filtered
and dried in vacuum (0.5 mbar); yield 0.36 g (56%) 10;
m.p. (dec.) 76 8C. 1H-NMR (200 MHz, [D8]-THF,
3
0.08 (ddd, JH,H
25 8C): dꢂ
/
ꢃ
/
ꢂ9.3 and 4.9 Hz,
/
2JH,H
9.1 and 5.5 Hz, JH,H
ꢂ
/
ꢃ
/
3.3 Hz, 2?-H and 3?-H); 0.02 (ddd, JH,H
ꢂ
/
3
2
ꢂ
/
ꢃ3.4 Hz, 7?-H and 8?-H); 0.12
/
(ddd, 7-H and 8-H); 0.20 (ddd, 2-H and 3-H); 0.98 (s, 9-
H); 1.34 (s, 5-H); 6.23 (s, Cp). 13C-NMR (75.5 MHz,
1
[D8]-THF, ꢃ
and C-8); 19.8 (t, 1JC,H
C-6); 49.6 (s, C-1); 52.6 (t, 1JC,H
1JC,H 128 Hz, C-5); 115.7 (d, 1JC,H
/
30 8C): dꢂ
/
15.8 (t, JC,H
ꢂ
/
158 Hz, C-7
the filtrate cooled to ꢃ78 8C. After 1 month, an ochre-
/
ꢂ
/
154 Hz, C-2 and C-3); 24.9 (s,
124 Hz, C-9); 59.4 (t,
173 Hz, Cp). MS
[Mꢀ] not observed, 178 (100)
coloured powder has precipitated, which is filtered and
dried in vacuum to afford 15; yield 1.06 g (58%), m.p.
ꢂ
/
1
ꢂ
/
ꢂ
/
(dec.) 157 8C. H-NMR (200 MHz, [D8]-THF, 25 8C):
(70 eV): m/z (%)ꢂ
/
dꢂ
/
ꢃ1.25 (m, 2H, 5-H); 0.09 and 0.59 (m, 4H, 2-H and
/
[Cp2Tiꢀ], 113 (10). Ci8H22Ti (286.3) calcd. C 75.51, H
7.75, Ti 16.72; Found: C, 74.98; H, 8.02; Ti, 16.59%.
3-H); 1.82 (s, 2H, 8-H); 2.46 (m, 2H, 6-H); 4.15 (m, 2H,
9-H); [5.68 (m, 2H); 6.02 (m, 2H); 6.21 (m, 2H); 7.1 1 (m,
4H); 7.26 (m, 2H); 7.60 (m, 2H); indenyl]. 13C-NMR
3.7. Bis(h5-cyclopentadienyl)-4-
zirconadispiro[2.2.2.1]nonane (13) and Bis(h5-
cyclopenta-dienyl)-4-zirconadispiro[2.1.2.2]nonane (14)
(50.3 MHz, [D8]-THF, 25 8C): dꢂ
/
ꢂ157
/
1
17.6 (t, JC,H
1
Hz, C-2 and C-3); 41.6 (t, JC,H
ꢂ
/
ꢂ122 Hz, C-6); 45.0
/
1
1
(s, C-1); 55.8 (t, JC,H
ꢂ
/
123 Hz, C-8); 60.0 (t, JC,H
154 Hz, C-9); 155.0 (s, C-
173 Hz); 104.0 (d, 1JC,H
173 Hz);
170 Hz); 125.0 (d); 125.3 (d); 125.5 (d);
ꢂ
/
120 Hz, C-5); 107.2 (t, 1JC,H
7); [100.9 (d, 1JC,H
118.7 (d, 1JC,H
ꢂ
/
To a solution of complex 12a (1.55 g, 4.4 mmol) in
diethyl ether (25 ml) is added dropwise a solution of 1a
(1.18 g, 22 mmol) in diethyl ether (20 ml) at 0 8C. After
stirring at 0 8C for 1 h the solution is warmed to r.t.
Small impurities are removed by filtration over celite
and the filtrate is evaporated to dryness. This leaves a
mixture of the complexes 13 and 14 in a ratio of 2:1
(determined by integration of 1H-NMR Cp signals) as a
yellow powder; yield 1.43 g (98%). The following NMR
data were determined from the 2:1 mixture of 13/14. 13:
ꢂ
/
ꢂ
/
ꢂ
/
125.8 (s); indenyl]. C26H26Zr (429.7) Calc. C, 72.67; H,
6.10; Found: C, 72.65; H, 6.08%.
3.9. Bis(h5-indenyl)-1-zircona-4-methylenecyclohexane
(17)
To a suspension of complex 16 (0.49 g, 1.15 mmol) in
THF (10 ml) is added at ꢃ78 8C a 1.87 M solution of
/
1H-NMR (200 MHz, C6D6, 25 8C): dꢂ
/
0.38 (ddd,
2.9 Hz, 2?-H, 3?-H
1a (0.62 ml, 1.16 mmol) in diethyl ether (10 ml). The
reaction mixture is warmed to r.t. and stirred at this
temperature for 6 h whereby a green solution is formed.
The solvents are removed at 0.5 mbar and the oily
residue is taken up in diethyl ether (2.5 ml). After 2
2
8.6 and 4.7 Hz, JH,H
3JH,H
ꢂ
/
ꢂ
/
ꢃ
/
and 8?-H); 0.45 (ddd, 2-H and 3-H); 1.05 (s, 9-H); 1.12(s,
5-H); 5.89 (s, Cp). 13C-NMR (75.5 MHz, [D8]-THF,
1
17.1 (t, JC,H
158 Hz, C-7 and C-8); 20.4 (s, C-6); 35.4 (s,
25 8C): dꢂ
/
ꢂ159 Hz, C-2 and C-3); 18.0
/
1
(t, JC,H
ꢂ
/
weeks a yellowꢁgreen solid has precipitated from which
/
1
C-1); 45.9 (t, JC,H
1
124 Hz, C-9); 50.6 (t, JC,H
ꢂ
/
ꢂ
/
124
the solvent is decanted. After drying at 0.5 mbar 17 is
obtained as a powder; yield 0.32 g (70%), m.p. (dec.)
1
Hz, C-5); 112.6 (d, JC,H
1
172 Hz, Cp). 14: H-NMR
ꢂ
/
1
(200 MHz, C6D6, 25 8C): dꢂ
/
0.38 (ddd, 3JH,H
ꢂ/8.6 and
73 8C. H-NMR (200 MHz, [D8]-THF, 25 8C): dꢂ
/
ꢃ
/
2
4.7 Hz, JH,H
ꢂ
/
ꢃ
/
2.9 Hz, 2?-H, 3?-H, 6?-H and 7?-H);
0.6 (m, 4H, 2-H and 6-H); 2.4 (m, 4H, 3-H and 5-H); 4.1
3
0.46 (ddd, 2-H, 3-H, 6-H and 7-H); 1.36 (m, 8-H and 9-
H); 5.84 (s, Cp). 13C-NMR (75.5 MHz, [D8]-THF,
25 8C): 5ꢂ
(s, 2H, exo-CH2); [5.9 (t, 2H, JH,H
4H); 7.1 (m, 4H); 7.3 (m, 4H); indenyl]. 13C-NMR (50.3
MHz, [D8]-THF, 25 C): dꢂ 125 Hz, C-3
41.4 (t, 1JC,H
and C-4); 55.7 (t, 1JC,H
119 Hz, C-2 and C-6); 107.6 (t,
1JC,H
153 Hz, exo-CH2); 157.2 (s, C-4); [101.1 (d,
1JC,H
ꢂ
/
3.3 Hz); 6.0 (d,
1
18.6 (t, JC,H
/
ꢂ
/
157 Hz, C-2, C-3, C-6 and
/
ꢂ
/
1
C-7), 35.4 (s, C-1 and C-5), 41.7 (t, JC,H
and C-9), 113.7 (d, 1JC,H
173 Hz, Cp). MS (70 eV): m/
z (%)ꢂ
[Mꢀ] not observed, 220 (100) [Cp2Zrꢀ], 194 (8).
ꢂ
/
126Hz, C-8
ꢂ
/
ꢂ
/
ꢂ
/
1
/
ꢂ
/
174 Hz); 117.9 (d, JC,H
ꢂ170 Hz); 124.9 (s);
/

P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ
/
298
297
1
1
170 Hz); 125.3 (d, JC,H
125.0 (d, JC,Hꢂ
/
ꢂ
/
160 Hz);
[Rint
tion 5152, of which 3647 were considered, observed with
I ꢀ2s(T). Structure solution and refinement: the struc-
ture was solved using direct methods (SHELX-86 [21] and
refined with the full-matrix least-squares procedure
against F2 (SHELX-93) [22], the anisotropic refinement
ꢂ
/
0.0420] independent reflections, collected reflec-
indenyl]. MS (70 eV): m/z (%)ꢂ
/
402 (1.6) [Mꢀ], 320
(100) [Ind2Zrꢀ]. C24H24Zr (403.7) calcd. C 71.41, H
5.99; Found: C, 71.55; H, 6.03%.
/
3.10. Bis(h5-cyclopentadienyl)-5,6-diphenyl-4-
zirconaspino [2,4]hept-5ene (19a)
converged at R1ꢂ
/
0.082 and Rwꢂ0.155.
/
To a solution of complex 18a (0.52 g, 1.1 mmol) im
THF (5 ml) is added at 0 8C 1a (0.26 g, 5 mmol). After 1
h stirring at r.t. THF is removed at 0.5 mbar and the
yellow solid residue suspended in pentane (15 ml),
filtered and dried at 0.5 mbar to yield 0.35 g (68%) of
4. Supplementary material
Crystallographic data (excluding structure factors) for
21b have been deposited with the Cambridge Crystal-
lographic Data centre as supplementary publication no.
CCDC-177976. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK [Fax: ꢀ44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www; http://
www.ccdc.cam.ac.uk)
1
complex 19a; m.p. (dec.) 152 8C. H-NMR (200 MHz,
[D8]-toluene, 25 8C): dꢂ/0.47 (m, 2H;JH,H
ꢂ3.1, 8.0
/
4,9, 8.8, trans 2-H and 3-H); 0.62 (m, 2H, cis 2-H and 3-
H); 2.29 (s, 2H, 7-H); 5.89 (s,10H,Cp), 6.58(m, 4H,
phenyl); 7.0 (m, 6H, penyl). 13C-NMR (75.5 MHz, [D8]-
/
THF, ꢃ
3); 40.5 (s, C-1); 49.8 (t, JC,H
/
30 8C) dꢂ
/
19.3 (t, 1JC,H
ꢂ
ꢂ
/
156 HZ, (C-2 and C-
124 HZ; 113.5 (d,
1
/
1JC,H
(s), 150.9(s), 127.3(d), 127.8(d), 122.9(d), 125,7(d),
128.3(d), 129.6(d) phenyl). MS(70 eV): m/z (%)ꢂ
452(8) [Mꢀ], 220(100)[Cp2Zrꢀ]. C28H26Zr(453.7)
ꢂ/172Hz Cp); 144,2 (s, C-6); 186.1 (s, C-5); [145,1
References
/
ꢃ
/
[1] (a) B.M. Trost, Angew. Chem. 98 (1986) 1; Angew. Chem. Int.
Ed. 25 (1986) 1;
(b) P. Binger, H.M. Buch, Top. Curr. Chem. 135 (1987) 77;
¨
Calc. C, 74.12; H, 5.78; Zr, 20.10; Found: C, 74.14; H,
5.78; Zr, 20.25%.
(c) D.M.T. Chan, in: B.M. Trost (Ed.), Comprehensive Organic
3.11. Bis(h5-indenyl)-5,6-diphenyl-4-
zirconaspiro[2.4]hept-5-ene (19b)
Synthesis, vol. 5, Pergamon Press, 1991, pp. 271ꢁ314;
/
(d) M. Lautens, W. Klute, W. Tam, Chem. Rev. 96 (1996) 49;
(e) P. Binger, T. Schmidt, in: A. de Meijere (Ed.), Houben-Weyl
1997, E17c, pp. 2217
To a solution of complex 18b (0.62 g, 1.08 mmol) in
[2] (a) R. Koster, S. Arora, P. Binger, Liebigs Ann. Chem. (1973)
¨
1619;
toluene (6 ml) is added at ꢃ40 8C an excess of 1a (1 ml,
/
(b) P. Binger, (Studienges. Kohle MbH) Ger. Offen. DE 4, 333,
1995, 491; Chem. Abstr. 122 (1995) 264949y.
[3] (a) S. Arora, P. Binger, Synthesis (1974) 801;
(b) E.W. Thomas, Tetrahedron Lett. 24 (1983) 1467;
(c) E. Sternberg, P. Binger, Tetrahedron Lett. 26 (1985) 301.
[4] K. Utimoto, M. Tamura, K. Sisido, Tetrahedron 29 (1973) 1169.
[5] (a) R. Noyori, T. Odagi, H. Takaya, J. Am. Chem. Soc. 92 (1970)
5780;
7 mmol). The yellow solution is warmed to r.t., stirred
for 4 days in a closed vessel, then the solvent is
evaporated at 0.5 mbar. The oily residue is taken up in
pentane (8 ml) and stirred for some hours whereby 19
precipitates as a yellow powder which is filtered off and
dried in vacuum (0.5 mbar); yield 0.47 g (79%), m.p.
1
(dec.) 110 8C. H-NMR (200 MHz, [D8]-THF, 25 8C):
(b) R. Noyori, Y. Kumagai, I. Umeda, H. Takaya, J. Am. Chem.
Soc. 94 (1972) 4018.
dꢂ/0.29 (m, 2H, trans 2-H and 3-H); 0.70 (m, 2H, cis 2-
H and 3-H); 2.05 (s, 2H, 7-H); 6.03 (m, 4H, indenyl);
3
6.10 (t, JH,H
[6] (a) P. Binger, Angew. Chem. 84 (1972) 352; Angew. Chem. Int.
Ed. 11 (1972) 309;
(b) P. Binger, Synthesis (1973) 427
ꢂ
/
3.6 Hz, indenyl); 6.3ꢁ7.4 (m, 18H,
/
phenyl). 13C-NMR (50.3 MHz, [D8]-THF, 25 8C): dꢂ
/
[7] (a) P. Binger, A. Brinkmann, P. Wedemann, Chem. Ber. 116
(1983) 2920;
20.6 (t, C-2 and C-3); 43.7 (s, C-1); 51.8 (t, C-7); 145.6 (s,
C-6); 188.2 (s, C-5); [103.1 (d); 104.3 (d); 121.7 (d);
indenyl]. C36H30Zr (553.8) Calc. C, 78.07; H, 5.46; Zr,
16.47; Found: C, 77.89; H, 5.48; Zr, 15.75%.
(b) P. Binger, P. Wedemann, Tetrahedron Lett. 26 (1985) 1045.
[8] (a) P. Binger, M.J. Doyle, R. Benn, Chem. Ber. 116 (1983) 1;
(b) H.M. Buch, P. Binger, in: R.B. King, J.J. Eisch (Eds.),
¨
Organometallic Synthesis, vol. 4, Elsevier, 1988, pp. 330ꢁ341.
/
Crystal structure analysis of 21b; crystal data:
451.71 g molꢃ1, orthorhombic space
[9] (a) S.L. Buchwald, B. Nielson, Chem. Rev. 88 (1988) 1047;
(b) E.-I. Negishi, Chem. Sr. 25 (1989) 457.
C28H24Zr,Mrꢂ
/
group Pbca (no. 61), aꢂ
/
14.632(3), bꢂ
/
6.636.4709(3),
[10] (a) K. Mashima, H. Takaya, Organometallics 4 (1985) 1464;
(b) K. Mashima, N. Sakai, H. Takaya, Bull. Chem. Soc. Jpn. 64
(1991) 2475.
3
˚
˚
cꢂ
/
16.989(2) A, Vꢂ
/
4135.4(1) A , Zꢂ
/8, dcalcd 1.451
ꢂ
/
Mg mꢃ3 Data Collection; data were collected with an
Enraf Nonius CAD-4 diffractometer at 100 K. Crystal
[11] (a) P. Binger, P. Muller, R. Benn, A. Rufinska, B. Gabor, C.
¨
Kruger, P. Betz, Chem. Ber. 122 (1989) 1035;
¨
size 0.9ꢄ
2.21Bu B
monochromator), 0B
/
0.28ꢄ
/
0.21 mm, range for data collection
(b) T. Takahashi, M. Murakami, M. Kunishige, M. Saburi, Y.
Uchida, K. Kozawa, T. Uchida, D.R. Swanson, E.-I. Negishi,
Chem. Lett. (1989) 761.
˚
/
/
28.068, lꢂ
/
0.71069 A, Moꢁ
/
Ka (graphite
/
h B18.0B22.0Bl B
/
/
/
/21, 4631

298
P. Binger et al. / Journal of Organometallic Chemistry 656 (2002) 288ꢁ298
/
[12] S. Podubrin, Dissertation, Universitat Kaiserslautern, 1993.
¨
(b) S.L. Buchwald, R.H. Grubbs, J. Am. Chem. Soc. 105 (1983)
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