Simple Route to Bis(3-indenyl)methanes and the Synthesis, Characterization, and Polymerization Performance of Selected racemic-Dichloro[methylenebis(Rn-1-indenyl)]-zirconium Complexes

Article abstract of DOI:10.1021/om990211g

A large range of bis(R_n-3-indenyl)methanes were obtained in good to fair yields with the base-catalyzed condensation between formaldehyde and (substituted) indenes. For example, bis(indenyl)methane and bis(4,7-dimethylindenyl)methane have been synthesized in 70percent and 50percent yield, respectively, from the corresponding indenes. Typical reaction conditions are as follows: indene in DMF or DMSO, 0.5 equiv of CH₂O, 0.2-0.5 equiv of EtONa, room temperature. This process provides an inexpensive and atom-efficient protocol for the synthesis of methylene-bridged ligands, providing a facile entry into methylene-bridged ansa-zirconocenes: MAO-activated C₂-symmetric rac-dichloro[methylenebis(η⁵-1-indenyl)]zirconium (1) and rac-dichloro[methylenebis(4,7-dimethyl-η⁵-1-indenyl)]zirconium (2) polymerize ethylene to low molecular weight, vinyl-terminated linear polyethylene, and liquid propylene to low molecular weight, low isotacticity polypropylene. The microstructure, molecular weight, and end-group structure of these isotactic polypropylenes (i-PP) are compared to those from rac-[isopropylidenebis(1-indenyl)]ZrCl₂ (3), rac-[ethylenebis(1-indenyl)]ZrCl₂ (4), rac-[ethylenebis(4,7-dimethyl-1-indenyl)]ZrCl₂ (5), and the silicon-bridged rac-[dimethylsilylbis(1-indenyl)]ZrCl₂ (6). The molecular structures of 1 and 2 have been determined and compared to those of 3-6. In liquid monomer at 50°C, the amount of secondary insertions increases on going from the more open to the more hindered systems. At the same time, there is an increase of the fraction of secondary units undergoing isomerization from the normal 2,1 unit to the 3,1 unit (tetramethylene sequence).

Full text of DOI:10.1021/om990211g

Organometallics 1999, 18, 3781-3791
3781
Articles
Sim p le Rou te to Bis(3-in d en yl)m eth a n es a n d th e Syn th esis,
Ch a r a cter iza tion , a n d P olym er iza tion P er for m a n ce of
Selected r a cem ic-Dich lor o[m eth ylen ebis(R -1-in d en yl)]-
n
zir con iu m Com p lexes
‡
‡
§
§
Vu Anh Dang, Lin-Chen Yu, Davide Balboni, Tiziano Dall’Occo,
,
§
#
#
#
Luigi Resconi,* Pierluigi Mercandelli, Massimo Moret, and Angelo Sironi
Montell Polyolefins, Research & Development Center, 912 Appleton Road,
Elkton, Maryland 21921, Centro Ricerche G. Natta, P.le G. Donegani 12, 44100 Ferrara, Italy,
and Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universit a` di Milano,
Via Venezian 21, 20133 Milano, Italy
Received March 25, 1999
n
A large range of bis(R -3-indenyl)methanes were obtained in good to fair yields with the
base-catalyzed condensation between formaldehyde and (substituted) indenes. For example,
bis(indenyl)methane and bis(4,7-dimethylindenyl)methane have been synthesized in 70%
and 50% yield, respectively, from the corresponding indenes. Typical reaction conditions
are as follows: indene in DMF or DMSO, 0.5 equiv of CH O, 0.2-0.5 equiv of EtONa, room
2
temperature. This process provides an inexpensive and atom-efficient protocol for the
synthesis of methylene-bridged ligands, providing a facile entry into methylene-bridged ansa-
5
zirconocenes: MAO-activated C
2
-symmetric rac-dichloro[methylenebis(η -1-indenyl)]zirco-
5
nium (1) and rac-dichloro[methylenebis(4,7-dimethyl-η -1-indenyl)]zirconium (2) polymerize
ethylene to low molecular weight, vinyl-terminated linear polyethylene, and liquid propylene
to low molecular weight, low isotacticity polypropylene. The microstructure, molecular weight,
and end-group structure of these isotactic polypropylenes (i-PP) are compared to those from
rac-[isopropylidenebis(1-indenyl)]ZrCl
enebis(4,7-dimethyl-1-indenyl)]ZrCl (5), and the silicon-bridged rac-[dimethylsilylbis(1-
indenyl)]ZrCl (6). The molecular structures of 1 and 2 have been determined and compared
2 2
(3), rac-[ethylenebis(1-indenyl)]ZrCl (4), rac-[ethyl-
2
2
to those of 3-6. In liquid monomer at 50 °C, the amount of secondary insertions increases
on going from the more open to the more hindered systems. At the same time, there is an
increase of the fraction of secondary units undergoing isomerization from the normal 2,1
unit to the 3,1 unit (tetramethylene sequence).
In tr od u ction
and acetone in DME, which gives 2,2-bis(3-indenyl)-
propane in up to 70% yield:
3
ansa-Metallocene ligands with a single carbon bridge
have been obtained via reaction of cyclopentadienyl or
1
indenyl anions with CH2Br2 or CH2I2 or by reaction of
a fulvene (or benzofulvene) with cyclopentadienyl, in-
2
denyl, or fluorenyl anions. In the case of bisindenyl
ligands, the above reactions are scarcely efficient.
3
4
Recently, Nifant’ev and co-workers, and later J ensen,
This reaction is highly convenient, since all reagents
are inexpensive, it does not require air- and moisture-
free conditions, and it is atom-efficient, since in prin-
ciple the only byproduct is water. It can however lead
to formation of bridged benzofulvenes, which are dif-
disclosed a simple, one-pot procedure for the syntheses
of bis(cyclopentadienyl)propane and bis(indenyl)pro-
pane. The simplest case is the condensation of indene
5
‡
Montell Polyolefins.
Centro Ricerche G. Natta.
Universit a` di Milano.
§
(3) Nifant’ev, I. E.; Butakov, K. A.; Aliev, Z. G.; Urazowski, I. F.
Metalloorg. Khim. 1991, 4, 1265. Nifant’ev, I. E.; Ivchenko, P. V.;
Borzov, M. V. J . Chem. Res., Synop. 1992, 162. Nifant’ev, I. E.; Borzov,
M. V.; Ivchenko, P. V.; Yarnikh, V. L.; Ustynyuk, Yu. A. Organome-
tallics 1992, 11, 3462. Nifant’ev, I. E.; Ivchenko, P. V.; Kuz’mina, L.
G.; Luzikov, Yu. N.; Sitnikov, A. A.; Sizan, O. E. Synthesis 1997, 469.
(4) Yang, Q.; Shuguang, S.; Hoffman, M. R.; J ensen, M. D. 212th
ACS National Meeting, 1996, ORGN 008.
#
(
1) (a) Schaltegger, H.; Neuenschwander, M.; Meuche, D. Helv.
Chim. Acta 1965, 48, 955. (b) Ewen, J .; Elder, M.; J ones, R.; Hasp-
eslagh, L.; Atwood, J .; Bott, S.; Robinson, K. Makromol. Chem.,
Macromol. Symp. 1991, 48/ 49, 253.
2) See for example ref 1b, and: Hafner, K.; Thiele, G. Tetrahedron
Lett. 1984, 25, 1445. Green, M. L. H.; Ishihara, N. J . Chem. Soc., Dalton
Trans. 1994, 657.
(
(5) Rouhi, A. M. Chem. Eng. News 1995, J une 19, 32.
1
0.1021/om990211g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 08/18/1999

3
782 Organometallics, Vol. 18, No. 19, 1999
Ta ble 1. Syn th esis of Bis(in d en yl)m eth a n es
Dang et al.
indenyl derivative
indene
CH
2
O
solvent/base
temp (°C)/time (h)
yield (%)
formalin
formalin
formalin
DMF/NaOEt
DMF/NaOEt
DMSO/NaOEt
DMSO/NaOEt
DME/NaOEt
DMF/NaOEt
DMSO/t-BuOK
DMF/NaOEt
25/12
70
48
50
33
0
79
82
34
4
4
4
4
3
3
,7-dimethylindene
,7-dimethylindene
,7-dimethylindene
,7-dimethylindene
-phenyl-4,6-dimethylindene
-tert-butylindene
25/12; 80/4
25/12; 80/4
25/12; 65/8
25/12
paraformaldehyde
paraformaldehyde
formalin
25/12
paraformaldehyde
paraformaldehyde
25/12
fluorene
25/12
Ta ble 2. Con d en sa tion of
-P h en yl-4,6-d im eth yl-1-in d en e w ith
F or m a ld eh yd e a n d Aceton e
ficult to remove from the reaction mixture, and in
addition is limited to indenes without substituents in
the 7 position. This reaction, in fact, cannot be applied
to 4,7-dimethylindene, even under more severe condi-
tions (DMSO/t-BuOK, 110 °C, 10 h). To overcome these
limitations, we have sought the synthesis of methylene-
bridged bis(substituted)indenyl ligands using formal-
dehyde, with the aim to expand the range of achievable
ligands for chiral zirconocene catalysts and to make
them simpler. Our first attempt, using DME as a
solvent, was unsuccessful.
3
aldehyde or ketone
solvent/base
temp (°C)/time (h) yield (%)
formalin
DMF/NaOEt
DMF/KOH
DMF/NaOEt
DME/KOH
DMF/NaOEt
DME/KOH
25/12
25/12
25/12
25/12
80/6
79
formalin
58
paraformaldehyde
formalin
54
traces
65
formalin
acetone
80/48
63
indicate that a strong base in a highly polar aprotic
solvent is preferred for the preparation of bis(4,7-
dimethyl-3-indenyl)methane:
We report here the synthesis of methylene-bridged
bisindenyl ligands via the base-catalyzed condensation
of indenes with formaldehyde in more polar solvents,
which in turn allows a facile entry to a large variety of
6
C2-symmetric, isospecific zirconocenes. This new method
is more convenient than those via fulvene or CH2X2 and
a recently published method that uses chloromethylpiv-
alate.7
Resu lts a n d Discu ssion
This methodology is also applicable to highly substi-
tuted indenes, allowing the synthesis of sterically
crowded ligands, such as bis(fluorenyl)methane: the
reaction of fluorene and paraformaldehyde in the pres-
ence of a base in dimethyl sulfoxide afforded bis-
Syn th esis of th e Liga n d s. The base-catalyzed con-
densation between formaldehyde and (substituted) in-
denes is a new, simple, inexpensive, and atom-efficient
protocol for the synthesis of a wide variety of bis-
(fluorenyl)methane in 34% yield (eq 1). A two-step
(
substituted)indenylmethanes, providing a facile entry
procedure (eq 2) through dibenzofulvene (7) yielded
into methylene-bridged ansa-zirconocenes. For example,
bis(indenyl)methane and bis(4,7-dimethylindenyl)meth-
ane have been synthesized in 70% and 50% yield,
respectively, from the corresponding indenes in DMF
or DMSO as solvents (Table 1). The reaction is catalyzed
by bases such as KOH, NaOH, t-BuOK, or EtONa, with
base/indene ratios as low as 0.2. In some cases, the
temperature of the reaction must be kept below 50 °C
to avoid isomerization to the conjugated 1-(3-indenylvi-
nylidenyl)indane.
(1)
As is the case for Nifant’ev’s acetone/indene conden-
sation, the appeal of using formaldehyde rather than
other bridging moieties is multifold: the main advan-
tages are that moisture- and air-free procedures are no
longer required and the higher atom-efficiency of the
process. In addition, we discovered that the base can
be catalytic, that benzofulvene byproducts are not
observed in the final product, and that neither the
indenes nor the solvents need distillation before use.
The downside is the sometimes unavoidable formation
of higher condensation products and the lower than
quantitative yields obtained in practice. All things
considered, comparing bisindenyl ligands with different
bridges, the present process is more convenient when
cheap indenes are used. If the methylene-bridged ligands
are the target, then the present process is the most
convenient presently available. The formaldehyde can
be either in polymeric form or in aqueous solution.
Various conditions for the synthesis of bis(4,7-dimethyl-
(2)
similar results. This demonstrates the efficiency of this
one-pot procedure. The reaction of 3-tert-butylindene
with paraformaldehyde in DMSO/t-BuOK yielded bis-
(1-tert-butyl-3-indenyl)methane in 82% yield. The reac-
tion of formaldehyde with 3-phenyl-4,6-dimethylindene,
using different bases and solvents, yielded bis(1-phenyl-
5,7-dimethyl-3-indenyl)methane in good yields (Table 2).
Since the proton of this indene is more acidic than that
of 4,7-dimethylindene, yields for these reactions were
higher as compared to 4,7-dimethylindene. Again, the
(
6) After this work was finished, a similar process for the synthesis
of methylene-bridged ligands was described in the patent literature:
K u¨ ber, F.; Riedel, M.; Schiemenz, B. Eur. Pat. Appl. 832,866 A2 to
Targor, 1998.
3
-indenyl)methane are shown in Table 1. The results

Simple Route to Bis(3-indenyl)methanes
Organometallics, Vol. 18, No. 19, 1999 3783
reaction with a strong base and a polar aprotic solvent
afforded the highest yield.
of 1-(phenylmethylidine)indene as a result of equilibri-
um, as shown in eq 6.
In contrast to 4,7-dimethylindene, 3-phenyl-4,6-di-
methylindene also reacted with acetone in KOH and
DME to afford 2,2-bis(1-phenyl-5,7-dimethyl-3-indenyl)-
propane in 63% yield (Table 2).
Rea ction Mech a n ism .We rationalize the failure of
4
,7-methylindene to undergo coupling with acetone as
follows. The reaction of indenyl anion (8, R ) H) and
acetone yields a fulvene intermediate (10, R ) H). The
intermediate has been isolated in many cases (see
below) and subjected to the same reaction conditions to
yield the coupling product. We also discovered that the
failure of 4,7-dimethylindene to produce 2,2-bis(4,7-
dimethyl-3-indenyl)propane (11, R ) CH3) results from
the inability to produce intermediates 9 (R ) CH3) and
(6)
1
0 (R ) CH3) because of the equilibrium between 8 (R
CH3) and 9 (R ) CH3).
)
Syn th esis of th e Zir con ocen es. The synthesis of
the zirconocenes is straightforward. Both the dipotas-
8
sium ligand salt in THF and the dilithium ligand salt
9
in Et2O/pentane can be conveniently used. The syn-
thesis of two representative zirconocenes, that is, rac-
CH2(Ind)2ZrCl2 (1) and rac-CH2(4,7-Me2-Ind)2ZrCl2 (2),
are reported in the Experimental Section. Although
yields were somewhat low (for example, 1 and 2 were
obtained in 9% and 23.2% yield, respectively, after
crystallization), all metallocenes were obtained in high
chemical and diastereomeric purity: only the racemic
isomers were isolated (Chart 1).
(3)
Cr ysta l a n d Molecu la r Str u ctu r es of r a c-Dich lo-
Employing a strong oxygen-affinitive magnesium as
5
r o[m eth ylen ebis(η -1-in d en yl)]zir con iu m (1), r a c-
a countercation of 9 shifts the equilibrium of indenyl
anion 8 (R ) CH3) and alkoxy anion 9 (R ) CH3) toward
the latter (eq 4). The trap of alkoxyanion 9 (R ) CH3)
leads to the isolation of the fulvene 10 (eq 5), which was
converted to 11, albeit in low yield.
5
Dich lor o[m eth ylen ebis(4,7-dim eth yl-η -1-in den yl)]-
zir con iu m (2), an d r a c-Dich lor o[isopr opyliden ebis-
5
(
η -1-in d en yl)]zir con iu m (3). The racemic nature of
compounds 1, 2, and 3 has been confirmed by X-ray
analysis. Figures 1, 2, and 3 show (each) two different
ORTEP views of 1, 2, and 3, respectively. Tables 3
(lengths) and 4 (angles) contain the most relevant
bonding parameters for the three compounds. Table 5
collects the angles between some relevant least-squares
planes, a few slip-fold indicators, and the geometrical
parameters described in Figure 4, for compounds 1-6.
Compounds 1-3 are isomorphous and crystallize in
the monoclinic space group I2/c (Table 6) with a crys-
tallographically imposed 2-fold symmetry (the molecules
lying about the Wycoff position 4e). Differences in cell
parameters and volume can be easily explained consid-
ering the additional steric demand of the methyl sub-
stituents in 2 and 3, with respect to 1.
(
4)
(
5)
The zirconium atoms are pseudo-tetrahedrally coor-
dinated by the two cyclopentadienyl groups of the
bisindenyl moiety and by two chloro ligands. As usual
for bent metallocenes, the overall coordination environ-
ment is best described by the set of parameters reported
in Figure 4, which can be related to zirconium acces-
sibility. In particular, the smaller the “bite angle” θ and
the bigger the cp-Zr-cp′ æ one, the more the metal is
tucked in the metal envelope.
Since a primary alkoxy anion is less basic and more
stable than a tertiary alkoxy anion, substituting form-
aldehyde for acetone (in eq 3) makes conversion of 4,7-
dimethylindene into bis(4,7-dimethyl-3-indenyl)methane
possible even under milder reaction conditions.
In an effort to prove the mechanism of the reaction,
we successfully isolated the intermediate, 4,7-dimethyl-
1
-(phenylmethylidine)indene, in 86% yield in the reac-
tion of 4,7-dimethylindene with benzaldehyde. This
fulvene intermediate was further treated with indenyl
anion to yield (indenyl)(phenyl)(4,7-dimethyl-1-indenyl)-
methane 12 in 63% yield together with a small amount
(
7) Luttikhedde, H. J . G.; Leino, R.; Wil e´ n, C.-E.; Laine, E.; Sillan-
p a¨ a¨ , R.; N a¨ sman, J . H. J . Organomet. Chem. 1997, 547, 129.
8) Grossman, R.; Doyle, R. A.; Buchwald, S. Organometallics 1991,
10, 1501.
(

3
784 Organometallics, Vol. 18, No. 19, 1999
Dang et al.
Ch a r t 1.a
a
Only the R,R enantiomer is shown for each racemic mixture.
Ta ble 3. Bon d Len gth s (Å)a
Ta ble 4. Selected Bon d An gles (d eg)a
1
2
3
1
2
3
Zr(1)-cp(1)
Zr(1)-Cl(1)
Zr(1)-C(1)
Zr(1)-C(2)
Zr(1)-C(3)
Zr(1)-C(3a)
Zr(1)-C(7a)
C(1)-C(2)
C(1)-C(7a)
C(1)-C(8)
C(2)-C(3)
C(3)-C(3a)
C(3a)-C(4)
C(3a)-C(7a)
C(4)-C(5)
C(4)-C(9)
C(5)-C(6)
C(6)-C(7)
C(7)-C(7a)
C(7)-C(10)
C(8)-C(9)
2.2123(18)
2.4215(6)
2.4357(18)
2.4618(18)
2.5624(19)
2.6259(18)
2.5186(17)
1.418(3)
1.435(3)
1.509(3)
1.400(3)
1.415(3)
2.216(2)
2.4184(7)
2.447(2)
2.434(2)
2.538(2)
2.631(2)
2.562(2)
1.415(3)
1.430(4)
1.516(3)
1.397(3)
1.411(3)
1.427(4)
1.442(4)
1.351(5)
1.494(5)
1.409(6)
1.367(5)
1.447(4)
1.501(5)
2.2069(17)
2.4241(5)
2.4347(17)
2.4508(18)
2.5483(18)
2.6142(17)
2.5332(17)
1.422(3)
1.443(2)
1.533(2)
1.397(3)
1.407(3)
cp(1)-Zr(1)-Cl(1)
cp(1)-Zr(1)-cp(1′)
cp(1)-Zr(1)-Cl(1′)
Cl(1)-Zr(1)-Cl(1′)
C(2)-C(1)-C(7a)
C(2)-C(1)-C(8)
C(7a)-C(1)-C(8)
C(1)-C(2)-C(3)
C(2)-C(3)-C(3a)
C(3)-C(3a)-C(4)
C(3)-C(3a)-C(7a)
C(4)-C(3a)-C(7a)
C(3a)-C(4)-C(5)
C(3a)-C(4)-C(9)
C(5)-C(4)-C(9)
C(4)-C(5)-C(6)
C(5)-C(6)-C(7)
C(6)-C(7)-C(7a)
C(6)-C(7)-C(10)
C(7a)-C(7)-C(10)
C(1)-C(7a)-C(3a)
C(1)-C(7a)-C(7)
C(3a)-C(7a)-C(7)
C(1)-C(8)-C(9)
C(1)-C(8)-C(1′)
C(1)-C(8)-C(9′)
C(9)-C(8)-C(9′)
109.23(2)
117.38(3)
110.15(2)
99.18(3)
106.67(18)
124.74(18)
125.87(16)
109.79(19)
108.48(19)
133.20(19)
107.19(18)
119.61(18)
119.1(2)
108.69(2)
117.07(3)
111.05(2)
98.77(4)
106.6(2)
121.9(2)
128.8(2)
110.3(2)
107.6(2)
129.5(3)
108.0(2)
122.5(2)
115.9(3)
119.8(3)
124.2(3)
122.8(3)
124.1(3)
115.9(3)
121.6(3)
122.4(4)
107.5(2)
133.7(3)
118.8(3)
108.72(2)
118.06(3)
109.98(2)
99.85(3)
105.87(16)
123.43(15)
128.34(14)
110.46(17)
108.09(16)
131.78(18)
107.91(16)
120.31(18)
119.05(19)
1.416(3)
1.447(3)
1.359(3)
1.424(3)
1.446(2)
1.345(3)
121.7(2)
121.4(2)
119.45(19)
121.25(19)
121.90(19)
119.57(18)
1.412(3)
1.355(3)
1.425(3)
1.421(3)
1.352(3)
1.428(2)
1.531(3)
107.82(17)
133.45(19)
118.73(19)
107.63(16)
134.46(17)
117.91(16)
113.59(11)
99.73(19)
111.41(12)
107.2(3)
a
cp refers to the centroid of the five-member ring of the organic
ligand.
101.4(2)
101.8(3)
As can be seen from the values reported in Table 5,
these parameters are very sensitive to differences in the
number and type of the ansa atoms, while the presence
of substituents on the ligand moiety leads to minor
changes in the local stereochemistry of the metal atom.
As a consequence, the only noticeable difference between
parameters for compounds 1-3 consists of a slightly
more open angle R (hence a more open θ one) for
methylene-bridged molecules (1 and 2) with respect to
the isopropylidene-bridged one (3).
a
Primes address symmetry-equivalent atoms (-x, y, 1/2 - z).
namely C(7a), which normally suffers from the indenyl
ring slippage, is bound to be closer to the zirconium
atom.
The presence of methyl substituents at the benzene
rings or at the ansa atom in 2 and 3 gives rise to some
additional molecular strain, and to relieve unfavorable
steric interactions, the indenyl ligands bend away from
the bridging moiety by means of a lengthening of the
Zr-C(3a) and Zr-C(7a) bonds (and a parallel shorten-
ing of the Zr-C(2) and Zr-C(3) ones), together with an
increased deviation from planarity (see the al-bz and
Ω values in Table 5).
On comparing the present ansa-1C molecules to the
related ansa-2C one, we notice that the presence of a
shorter bridge affects the spread of the Zr-C interac-
tions (which display a 1 > 2 > 2 pattern instead of a 2
>
2 > 1 one) since one of the two bridgehead atoms,

Simple Route to Bis(3-indenyl)methanes
Organometallics, Vol. 18, No. 19, 1999 3785
Ta ble 5. Releva n t Geom etr ica l P a r a m eter sa
1
2
3
4
5
6
R
101.4 101.8 99.7
94.6
84.8
16.3
61.8
â
84.8
14.5
72.4
84.5
14.9
71.5
85.0
14.4
70.9
84.6
62.1
85.8
59.9
γ
θ
æ
117.4 117.1 118.1 126.9 125.3 127.8
al-bz
ZrCl2-cp
2.2
5.1
2.4
5.4
31.1
5.7
30.1
3.4
31.0
36.2
35.8
35.5
bh-cp-cp′-bh′ 150.8 150.6 149.2 138.1 143.7 147.7
Ω
∆
1.3
1.6
1.9
2.3
0.21
1.5
0.16
1.7
0.20
0.20
0.21
0.19
a
All quantities in degrees, apart from ∆ (Å). The angles R, â,
γ, θ, and æ are defined in Figure 4. al, bz, cp, and ZrCl2 refer to
the least-squares planes defined by the allylic moiety [C(1), C(2),
C(3)], the aromatic six-member ring, the five-member ring, and
the ZrCl2 atoms, respectively. bh refers to the centroid of the
bridgehead atoms [C(3a) and C(7a)]. Ω is the angle between the
plane defined by the allylic moiety and the least-squares plane
defined by the atoms C(1), C(7a), C(3a), and C(3); ∆ is the distance
between the perpendicular projection of the heavy atom on the
ring least-squares plane and the ring centroid.
F igu r e 2. Top (a) and front (b) ORTEP views of 2.
Displacement ellipsoids are drawn at the 30% probability
level. Hydrogen atoms are given arbitrary radii.
1
20.3° vs 117.9° in 3). At variance, in 1 these angles
(133.4° vs 133.2° and 119.6° vs 118.7°) are more similar.
According to an adaptation by Schlogl of the Cahn-
Ingold-Prelog rules, the stereoisomers represented in
Figures 1, 2, and 3 have an S,S configuration at C(1)
and C(1′), respectively. However, both in solution and
in the solid state, as they crystallize in a centrosym-
metric space group, their R,R enantiomers are also
present.
P olym er iza tion s
F igu r e 1. Top (a) and front (b) ORTEP views of 1.
Displacement ellipsoids are drawn at the 30% probability
level. Hydrogen atoms are given arbitrary radii.
As representative examples of methylene-bridged
zirconocenes, we tested rac-CH2(Ind)2ZrCl2 (1) and rac-
CH2(4,7-Me2-Ind)2ZrCl2 (2), in both ethylene and pro-
pylene polymerization, and compared them to the
available isopropylidene-, ethylene-, and dimethylsi-
lylene-bridged analogues.
Moreover, in 2 and 3 the steric demand of the methyl
substituents determines a marked distortion of the
indenyl moiety within its average plane, recognizable
by comparing “equivalent” bond angles at the bridge-
head carbon atoms: C(3)-C(3a)-C(4) vs C(1)-C(7a)-
C(7) and C(4)-C(3a)-C(7a) vs C(3a)-C(7a)-C(7) (129.5°
vs 133.7° and 122.5° vs 118.8° in 2; 131.8° vs 134.5° and
Eth ylen e P olym er iza tion
The results are reported in Table 7. Both polymeri-
zation activities and PE molecular weights depend on

3
786 Organometallics, Vol. 18, No. 19, 1999
Dang et al.
series, the average viscosity molecular weight increases
5
-fold on going from 1 to 6, following the same order of
1
decreasing θ. End-group analysis by H NMR of PE from
-3 shows the presence of vinyl end groups, indicating
1
â-H transfer, likely to the monomer, and a minor
amount of vinylidene in the case of 1 and 2, very likely
arising from reinsertion of an ethylene macromer into
a growing polyethylene chain (Scheme 1). The proton
spectrum of the olefin region of the PE sample from rac-
CH2(4,7-Me2-Ind2ZrCl2 is shown in Figure 5, and the
relative composition of end groups in Table 8.
This mechanism has been invoked to explain long-
chain-branching formation in PE from both the Ti-
“
constrained geometry” catalyst and metallocene cata-
1
2
lysts and observed with a mixed catalyst system.
Traces of vinylenes are also present. These are
assigned to an internal vinylene structure, possibly
arising from â-H transfer after a secondary insertion of
1
3
the vinyl-terminated ethylene macromer. Assuming
that â-H transfer is the main chain transfer reaction
for all zirconocene catalysts investigated here, the
decrease of molecular weight for larger values of θ can
be rationalized in terms of a decrease in nonbonded
interactions in the conformation of the growing chain
leading to â-H transfer.
The same trend observed for 4 and 1 can be seen by
comparing 5 and 2: on going from the ethylene to the
methylene bridge, we obtain lower molecular weight and
lower catalyst activity. The second factor that affects
catalyst activity and PE molecular weight is indenyl
substitution. By increasing the number of substituents,
catalyst activity increases in the order 1 < 2 (the same
happens in the case of 4 vs 5), while molecular weight
is only marginally influenced. This important aspect will
be further investigated on a larger set of catalysts and
reaction conditions. The results of thermal analysis are
consistent with the molecular weight data: in particu-
lar, increasing molecular weights causes a slight in-
crease in the melting temperature and a decrease in the
F igu r e 3. Top (a) and front (b) ORTEP views of 3.
Displacement ellipsoids are drawn at the 30% probability
level. Hydrogen atoms are given arbitrary radii.
1
4
heat of fusion (crystallinity).
P r op ylen e P olym er iza tion
Selected results of propylene polymerization with 1
and 2, in comparison to zirconocenes with different
bridges, are shown in Table 9. These methylene-bridged
C2-symmetric, isospecific zirconocenes show a significant
variation in propylene polymerization performance with
F igu r e 4. Schematic representation of an ansa-zir-
conocene molecule detailing the angles listed in Table 5. R
is the angle C(1)-E-C(1′); â is the angle between the Zr-
cp vector and the cp least-squares plane; γ is the angle
between the C(1)-E vector and the cp least-squares plane;
θ is the angle between the least-squares planes of the two
cyclopentadienyl ligands; and æ is the angle cp-Zr-cp′.
(10) Flory, P. J . Principles of Polymer Chemistry; Cornell University
Press: Ithaca, NY, 1953.
(11) Bochmann, M.; Lancaster, S. J . J . Organomet. Chem. 1995, 497,
5. Haselwander, T.; Beck, S.; Brintzinger, H.-H. In Ziegler Catalysts;
5
Fink, G., M u¨ lhaupt, R., Brintzinger, H.-H., Eds.; Springer-Verlag:
Berlin, 1995; p 181. Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1994, 116, 10015.
both the type of bridge and the substitution on the
indenyl groups. We first analyze the series of the four
unsubstituted bisindenyl complexes with CH2 (1), Me2C
(12) Swogger, K. W. In Catalyst Design for Taylor-Made Polyolefins,
Studies in Surface Science Catalysis; Soga, K., Terano, M., Eds.;
Kodansha-Elsevier: Tokyo, 1994; Vol. 89, p 285. Soga, K.; Uozumi,
T.; Nakamura, S.; Toneri, T.; Teranishi, T.; Sano, T.; Arai, T. Macromol.
Chem. Phys. 1996, 197, 4237. Malmberg, A.; Kokko, E.; Lehmus, P.
L o¨ fgren, B.; Sepp a¨ l a¨ , J . V. Macromolecules 1998, 31, 8448. Barnhart,
R. W.; Bazan, G. C.; Mourey, T. J . Am. Chem. Soc. 1998, 120, 1082.
(13) Karol, F. J .; Kao, S.; Wasserman, E. P.; Brady, R. C. New J .
Chem. 1997, 21, 797. Wasserman, E.; Hsi, E.; Young, W.-T. Polym.
Prepr. Am. Chem. Soc., Div. Polym. Chem. 1998, 39 (2), 425.
(3), C2H4 (4), and Me2Si (6) bridges, for which we can
compare the structural parameters (see Table 5). Activi-
ties increase, within an order of magnitude, in the order
1
< 3 < 4 < 6, following the decrease in the value of
the “bite angle”, θ. We can rationalize this effect by
assuming that a smaller bite angle reduces the forma-
1
1
tion of deactivated bimetallic species. For the same
(14) (a) van der Ven, S. In Study in Polymer Science 7, Polypropylene
and other Polyolefins, Polymerization and Characterization; Elsevier:
Amsterdam, 1990; p 470. (b) Mandelkern, L. Acc. Chem. Res. 1990,
23, 380.
(
9) Resconi, L.; J ones, R. L.; Rheingold, A. L.; Yap, G. P. A.
Organometallics 1996, 15, 998.

Simple Route to Bis(3-indenyl)methanes
Organometallics, Vol. 18, No. 19, 1999 3787
Ta ble 6. Su m m a r y of Cr ysta l Da ta , Da ta Collection , a n d Str u ctu r e Refin em en t P a r a m eter s
1
2
3
Crystal Data
formula
fw
C19H14Cl2Zr
404.42
C23H22Cl2Zr
460.53
C21H18Cl2Zr
432.47
crystal system
space group
a (Å)
b (Å)
c (Å)
monoclinic
I2/c (No. 15)
11.632(3)
9.988(1)
14.162(3)
103.00(1)
1603.2(5)
4
monoclinic
I2/c (No. 15)
11.913(3)
11.984(2)
13.919(2)
99.57(2)
1959.5(7)
4
monoclinic
I2/c (No. 15)
11.506(1)
11.128(1)
13.969(1)
103.31(1)
1740.5(3)
4
â (deg)
3
V (Å )
Z
F(000)
808
1.676
1.011
red prism
0.26 × 0.14 × 0.12
936
1.561
0.838
872
1.650
0.937
orange block
0.20 × 0.18 × 0.16
density (g cm-3)
absorption coeff (mm-1)
crystal description
crystal size (mm)
orange block
0.20 × 0.16 × 0.16
Data Collection
diffractometer
scan mode
θ range (deg)
index ranges
Siemens SMART
ω
2.5 e θ e 26.8
-13 e h e 14
Enraf-Nonius CAD-4
ω
3.4 e θ e 25.0
-14 e h e 13
0 e k e 14
0 e l e 16
none
Enraf-Nonius CAD-4
ω
3.6 e θ e 27.0
-14 e h e 14
0 e k e 14
0 e l e 17
none
-
7 e k e 12
17 e l e 15
-
intensity decay (%)
absorption correction
transmission factors
none
SADABS
0.672, 0.886
ψ scan
0.833, 0.874
ψ scan
0.832, 0.861
(min, max)
no. of measured reflns
no. of ind reflns
Rint, Rσ
4068
1545
0.0156, 0.0246
1373
1716
1716
-, 0.0239
1445
1982
1902
0.0104, 0.0167
1666
R
no. of reflns with
I > 2σ(I)
Refinement
no. of data/restraints/
params
1545/0/101
1445/0/121
1666/0/111
weights (a, b)b
0.026, 0
0.910
0.0185
0.027, 1.26
1.082
0.0213
0.034, 0.56
1.134
0.0199
2
c
goodness-of-fit S(F )
d
R(F), I > 2σ(I)
2
e
wR(F ), all data
0.0432
0.0509
0.0538
largest diff peak,
0.251, -0.317
0.196, -0.175
0.236, -0.381
-
3
hole (e Å
)
a
Rint ) ∑|Fo - Fmean |/∑|Fo |; Rσ ) ∑|σ(Fo )|/∑|Fo |. w ) 1/[σ (Fo ) + (aP) + bP], where P ) (Fo + 2Fc )/3. c S ) [∑w(Fo - Fc ) /(n -
2
2
2
2
2
b
2
2
2
2
2
2
2 2
1
/2
d
e
2
2
p)] , where n is the number of reflections and p is the number of refined parameters. R(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR(F ) ) [∑w(Fo
-
2
2
4 1/2
Fc ) /∑wFo ]
.
Ta ble 7. P olym er iza tion of Eth ylen ea
Sch em e 1. F or m a tion of Vin ylid en es in
P olyeth ylen e
activity
b
c
d
Zr
(kgPE
/
[η]
Mh
v
T
4
m
∆H
-
zirconocene (racemic)
(µmol) (mmolZr h)) (dL/g) × 10 (°C) (J /g)
1
2
3
4
5
6
CH
CH
Me
2
2
(Ind)
(4,7-Me
2
ZrCl
2
0.25
0.43
0.34
0.24
0.21
0.22
6.9
22.8
10.0
53.8
67.5
62.0
0.9
1.1
1.36
2.0
2.6
3.0
4.5 130 206
5.9 131 191
8.0 131 190
13.6 137 152
19.5 138 178
23.7 138 175
2
2 2
-Ind) ZrCl
2
C(Ind)
2
ZrCl
ZrCl
(4,7-Me -Ind)
ZrCl
2
C
C
2
H
H
4
(Ind)
2
2
2
4
2
2 2
ZrCl
e
Me
2
Si(Ind)
2
2
a
Hexane, Tp ) 80 °C, 4.2 bar ethylene, 10 min; MAO cocatalyst,
Al/Zr ) 1000 mol/mol. MAO was dried in vacuo to a free-flowing
b
c
powder. Measured in THN at 135 °C. Obtained from [η] )
R
-4
9
d
K(Mv) with K ) 3.8 × 10 and R ) 0.725.
Peak melting
e
temperature of the second melting (heating rate 10 °C/min). 5
min, Tp ) 75 °C.
respect to their ethylene- (4, 5), isopropylidene- (3), or
dimethylsilylene-bridged (6) congeners. In fact, both
structural feature results in a lower isotacticity of i-PP
(Table 9). Regioselectivity does not seem to be influenced
in the series of complexes with unsubstituted indenes,
while 2 is more regiospecific than 5, reflecting a minor
nonbonded interaction between the incoming propylene
molecule and the 4-methyl group. At the same time, as
in the case of ethylene polymerization, 1 and 2 produce
polypropylenes with lower molecular weights than 3-6.
The end-group analysis of i-PP samples from 1-6 is
1
/MAO and 2/MAO produce isotactic polypropylenes,
which have both lower molecular weight and lower
isotacticity than those obtained from 3-6/MAO. 1/MAO
and 2/MAO, for example, produce waxy materials with
degree of oligomerization ∼70 and Tm ∼110-120 °C.
The X-ray analysis of 1 and 2 has shown that their
molecular structures are more open (larger θ, smaller
æ angles) than their analogues with other bridges. This

3
788 Organometallics, Vol. 18, No. 19, 1999
Dang et al.
F igu r e 5. 1H NMR spectra of the olefin region of HDPE from 2/MAO. g peak due to residual C
ppm) and f solvent impurity.
2
4
HDCl (reference at 5.95
Ta ble 8. Molecu la r Weigh t Da ta a n d Un sa tu r a ted En d Gr ou p Com p osition of P olyeth ylen es fr om Ra cem ic
Zir con ocen e/MAO Ca ta lysts: Dep en d en ce on Str u ctu r a l P a r a m eter s
a
From intrinsic viscosity, assuming Mh v ) Mh w ) 2 Mh n. b From 1H NMR, assuming one double bond per chain and no transfer to Al.
Ta ble 9. P olym er iza tion of P r op ylen ea
ton spectra of the olefin region of the i-PP samples from
1-5 are compared in Figure 6. In Table 10 we report
also the relative frequency of the 2-butenyl and vi-
nylidene end groups (end group per inserted propylene
unit).
activity
b
zirconocene
Al/Zr
(kgPP
/
mmmm 2,1 [η]
(%)
T
m
∆H
(
racemic) µmol (M) (mmolZr h))
(%) (dL/g) (°C) (J /g)
1
2
3
4
5
6
1.2
2.5
2.3
0.5
2.1
4000
2000
3000
8000
2000
62.0
23.5
65.8
152.0
71.8
198.0
71.4 0.5 ∼0.1 110 68
85.8 0.8 <0.1 122 81
80.7 0.4 ∼0.2 127 77
87.3 0.6 0.44 134 80
92.3 1.9 ∼0.1 131 88
90.3 0.5 0.63 144 84
We observe a correlation between Ph n and both θ and
æ, showing the direct influence of the bite angle on the
facility of â-H transfer reactions: the four members in
the series of the simple bisindenyl complexes 1, 3, 4,
and 6 show a decrease of both the relative rate of
secondary and primary â-H transfer reactions, with
decreasing values of θ.
0.2 38000
a
Liquid propylene, Tp ) 50 °C, 1 h, MAO cocatalyst. 2,1 is the
total secondary insertions in the chain (end groups not included).
Measured in THN at 135 °C.
b
reported in Table 10, together with the average degree
of polymerization, Ph n, estimated from the unsaturated
end groups, in the hypothesis of one double bond per
chain and no chain transfer to Al. Since the most
important unsaturated end groups are 2-butenyl and
vinylidene, the two relevant chain-transfer reactions are
primary and secondary â-hydride transfers.15 The pro-
Con clu sion s
We have described an inexpensive and atom-efficient
protocol for the synthesis of bis(indenyl)methanes, via
the base-catalyzed condensation between formaldehyde
and (substituted) indenes in polar solvents such as DMF
or DMSO. This method can be applied to alkylated
indenes, and even to fluorene, providing a facile entry
(15) Resconi, L.; Camurati, I.; Sudmeijer, O. Top. Catal. 1999, 7 (1-
4
), 145.

Simple Route to Bis(3-indenyl)methanes
Organometallics, Vol. 18, No. 19, 1999 3789
Ta ble 10. Un sa tu r a ted En d Gr ou p Com p osition a n d F r equ en cy of Ch a in -Tr a n sfer Rea ction s in
P olyp r op ylen es fr om Ra cem ic Zir con ocen e/MAO Ca ta lysts: Dep en d en ce on Str u ctu r a l P a r a m eter s
a
From 1H NMR, assuming one double bond per chain and no transfer to Al, and not considering the internal vinylidene. Frequencies
are defined as end groups per monomer unit. Average values. c 9.7% triplet at 5.2 ppm. d 5.5% triplet at 5.2 ppm, ca. 2% peaks at 4.9-
.1 ppm.
b
5
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were performed under
nitrogen. Anhydrous solvents (Aldrich) were used without
further purification. 1H NMR spectra were recorded on a
Varian Unity 300 instrument. Chemical shifts (δ) are in ppm
downfield from tetramethylsilane as internal standard. Mass
spectra were recorded at 70 eV on a Hewlett-Packard 5890
GC/MSD instrument. Preparations of the zirconocenes were
performed under nitrogen by using conventional Schlenk-line
techniques. Solvents were distilled from blue Na-benzophe-
none ketyl (THF, Et
carbons) and stored under nitrogen. KH, MeLi, and BuLi
Aldrich) were used as received. All NMR solvents were dried
over LiAlH or CaH and distilled before use. Polymerization
2 2 2 2 3
O), CaH (CH Cl ), or Al(i-Bu) (hydro-
(
4
2
grade ethylene and propylene were received directly from the
Montell Ferrara plant. MAO (Witco, 10% w/w in toluene) was
1
6
used as received. The zirconocenes rac-Me
2
C(Ind)
2
ZrCl
2
,
rac-
and rac-Me
were prepared according to literature proce-
1
7
18
C
2
H
4
(Ind)
2
ZrCl
2
,
rac-C
2
H
4
(4,7-Me
2
-Ind)
2
ZrCl
2
,
2
-
1
9
Si(Ind)
2
ZrCl
2
dures. All were characterized as reported in the literature and
gave satisfactorily elemental analyses.
Bis(4,7-d im eth yl-3-in d en yl)m eth a n e. Formalin (37% so-
lution, 0.28 g, 3.47 mmol) was added to a mixture of 4,7-
dimethylindene (1.0 g, 6.94 mmol) and sodium ethoxide (0.15
g, 2.20 mmol) in dimethyl sulfoxide (10 mL). The reaction
mixture was stirred at room temperature for 12 h and then at
8
0 °C for another 4 h and cooled to room temperature; then
HCl (1 M, 10 mL) was added. The mixture was extracted with
CH Cl
(2 × 50 mL). The organic phases were combined,
washed with brine and then with water, dried (MgSO ), and
2
2
4
F igu r e 6. 1H NMR spectra of the olefin region of i-PP
samples from (a) 5/MAO, (b) 2/MAO, (c) 4/MAO, (d) 3/MAO,
and (e) 1/MAO.
concentrated to yield a brown solid. A yellow solid was obtained
after washing with MeOH (0.52 g, 50%). The yield of a similar
reaction in DMF was 48%.
Analogously, paraformaldehyde (2.08 g, 69.4 mmol) was
added to a mixture of 4,7-dimethylindene (25.0 g, 174 mmol)
and sodium ethoxide (5.9 g, 87 mmol) in dimethyl sulfoxide
into methylene-bridged ansa-zirconocenes. The meth-
ylene-bridged chiral zirconocenes, investigated in this
work, produce vinyl-terminated low molecular weight
polyethylenes, and polypropylene waxes with lower
molecular weights and lower isotacticities than their
closer analogues. In fact, both 1/MAO and 2/MAO
produce isotactic oligopropylenes, which have both lower
molecular weight and lower isotacticity than those
obtained from rac-C2H4(Ind)2ZrCl2/MAO and rac-C2H4-
(200 mL). After stirring at room temperature for 12 h, the
reaction mixture was heated at 65 °C for another 8 h. It was
then cooled to room temperature. Hydrochloric acid (1 M, 400
mL) was added. The mixture was extracted with CH Cl (400
2 2
(
16) Spaleck, W.; Antberg, M.; Dolle, V.; Klein, R.; Rohrmann, J .;
Winter, A. New J . Chem. 1990, 14, 499.
17) Wild, F.; Wasiucionek, M.; Huttner, G.; Brintzinger, H. H. J .
Organomet. Chem. 1985, 288, 63.
18) Resconi, L.; Piemontesi, F.; Camurati, I.; Balboni, D.; Sironi,
A.; Moret, M.; Rychlicki, H.; Zeigler, R. Organometallics 1996, 15, 5046.
19) Spaleck, W.; Antberg, M.; Rohrmann, J .; Winter, A.; Bachmann,
(
(
(4,7-Me2Ind)2ZrCl2/MAO. 2/MAO, for example, produces
(
i-PP with degree of oligomerization ∼70. The products
B.; Kiprof, P.; Behm, J .; Hermann, W. Angew. Chem., Int. Ed. Engl.
1992, 31, 1347.
are waxy materials with Tm ≈ 110-120 °C.

3
790 Organometallics, Vol. 18, No. 19, 1999
Dang et al.
mL). All organic layers were combined, washed with brine and
then with water, dried (MgSO ), and concentrated to yield a
viscous brown liquid. GC analysis showed only product and
starting material. No fulvene derivative was detected. Pre-
cipitation occurred when the brown liquid was added into
pentane (100 mL). Bis(4,7-dimethyl-3-indenyl)methane (6.8 g,
equipped with a magnetically driven stirrer and a 35 mL
stainless steel vial, connected to a thermostat for temperature
control, previously purified by washing with a TIBA solution
in hexanes, and dried at 50 °C in a stream of propylene. The
autoclave was then thermostated at 48 °C. A toluene solution
containing the catalyst/cocatalyst mixture was injected in the
autoclave by means of nitrogen pressure through the stainless
steel vial, the temperature rapidly raised to 50 °C, and the
polymerization carried out at constant temperature for 1 h.
After venting the unreacted monomer and cooling the reactor
to room temperature, the polymer was dried under reduced
pressure at 60 °C. The i-PP samples were purposely not treated
with acidic methanol to avoid isomerization of the vinylidene
end groups.
P olym er iza tion s of Eth ylen e. A 90 mL sample of hexane
was introduced at room temperature in a 200 mL glass
autoclave, previously purified and purged with ethylene at 35
°C and equipped with magnetic stirrer, temperature indicator,
and feeding line for the ethylene. The catalytic system was
prepared separately in 10 mL of hexane, by introducing a
toluene solution obtained by contacting for 5 min under
stirring the metallocene and MAO. The solution was then
introduced into the autoclave under ethylene flow, the reactor
was closed, and the temperature was increased to 80 °C and
the pressure to 4.6 bar g. The total pressure was kept constant
by feeding ethylene. After 10 min, the polymerization was
stopped by cooling, degassing the reactor, and introducing 1
mL of methanol. The polymer was washed with acidic metha-
nol, then with methanol, and dried in an oven at 60 °C under
vacuum.
4
3
3% yield) was obtained as a yellow solid after filtering and
1
washing with pentane and EtOH successfully. H NMR
(
3
CDCl ): δ 6.85-7.05 (m, 4 H), 6.35 (s, 2 H), 4.20 (s, 2 H), 3.2
(s, 4 H), 2.55 (s, 6 H), 2.35 (s, 6 H).
Similar procedures were employed for the other compounds.
The pure compounds were obtained by precipitation from
methanol.
1
Bis(3-in d en yl)m eth a n e. H NMR (CDCl
3
, δ, ppm): 7.10-
7
.60 (m, 8 H), 6.25 (s, 2 H), 3.85 (s, 2 H), 3.40 (s, 4 H).
1
Bis(1-ter t-bu tyl-3-in d en yl)m eth a n e. H NMR (CDCl
3
, δ,
ppm): 7.7-7.1 (m, 8 H), 6.2 (s, 2 H), 3.8 (s, 2 H), 3.2 (s, 2 H),
.0 (s, 18 H).
Bis(1-p h en yl-5,7-d im eth yl-3-in d en yl)m eth a n e. H NMR
CDCl
1
1
(
3
3
, δ, ppm): 6.7-7.2 (m, 14 H), 6.25 (s, 2 H), 4.5 (s, 2 H),
.8 (s, 2 H), 2.35 (s, 6 H), 2.0 (s, 6 H).
Bis(flu or en yl)m eth a n e. 1H NMR (CDCl
, δ, ppm) 7.2-
3
7
.8 (m, 16 H), 4.4 (t, 2 H, J ) 7.6 Hz), 2.2 (t, 2 H, J ) 7.6 Hz).
r a c-CH (1-In d ) Zr Cl (1). A 2.135 g sample of bis(1-
2
2
2
indenyl)methane (8.75 mmol) was dissolved in 30 mL of THF
and slowly added to a stirred suspension of 0.8 g of KH (19.5
mmol) in 50 mL of THF in a 100 mL Schlenk tube. Evolution
of H
solution was separated from excess KH. This solution and a
solution of ZrCl (THF) (3.3 g, 8.75 mmol) in THF (80 mL) were
2
ceases after 1 h 30 min, and the resulting brownish
4
2
both added dropwise via dropping funnels to a 250 mL flask
containing rapidly stirring THF (20 mL) over 5.5 h. At the
end of the addition the mixture was stirred overnight at room
temperature. A yellow-orange solution and a precipitate
formed. After concentrating the suspension under reduced
X-r a y Diffr a ction Str u ctu r a l An a lysis. (a ) Collection
a n d Red u ction of X-r a y Diffr a ction Da ta . Suitable crystals
of 1, 2, and 3 were mounted in air on a glass fiber tip onto a
goniometer head. Single-crystal X-ray diffraction data were
collected on a Siemens SMART CCD area detector diffracto-
meter for 1 and on an Enraf-Nonius CAD-4 diffractometer for
2 and 3, using graphite-monochromatized Mo KR radiation (λ
) 0.71073 Å) at room temperature. The structure of 3 has been
previously reported by others.24 The two determinations are
in agreement, within the experimental error.
For 1, unit cell parameters were initially obtained from 37
reflections (5° < θ < 20°) taken from 45 frames collected in
three different ω regions and eventually refined against 3611
reflections; while for 2 and 3 the setting angles of 25 randomly
distributed intense reflections with 10° < θ < 14° were
processed by least-squares fitting.
For 1, more than one hemisphere of reciprocal space was
scanned by 0.3° ω steps, collecting 1270 frames each at 40 s
exposure. The detector was kept at 5.50(2) cm from the sample.
Intensity decay was monitored by re-collecting the initial 50
frames at the end of data collection and analyzing the duplicate
reflections. The collected frames were processed for integration;
an empirical absorption correction was made on the basis of
3665 symmetry-equivalent reflection intensities (average re-
dundancy: 2.59).20
For 2 and 3 data collection was performed by the ω scan
method with variable scan speed (maximum time per reflection
75 and 60 s for 2 and 3, respectively) and variable scan range
(1.00 + 0.35 tan θ°). Crystal stability under diffraction was
checked by monitoring three standard reflections every 180
pressure to about 10 mL, 10 mL of Et
suspension was filtered, and the residue was dried in vacuo
and extracted with refluxing CH Cl until the washing was
colorless (2 h). The CH Cl solution (part of the product
precipitated during extraction) was concentrated to yield 2.135
g of red solid. This was washed with Et
O (3 × 5 mL), 2 mL
CH Cl , and again Et O, to give 1.06 g of the target compound
with some organic impurities. Crystallization from toluene
yielded 0.32 g (9.0%) of red-orange rac-CH (1-Ind) ZrCl free
, δ, ppm): s, 4.87, 2 H,
; d, 6.02-6.04, 2 H; d, 6.59-6.61, 2 H; three m, 7.1-7.7,
2
O were added, the
2
2
2
2
2
2
2
2
2
2
2
1
of its meso isomer. H NMR (CD
CH
2 2
Cl
2
8
5
H). Anal. Calcd for C19
6.9; H, 3.6.
H
14Cl
2
Zr: C, 56.4; H, 3.5. Found: C,
r a c-CH
2
(4,7-Me
2
-1-In d )
2
Zr Cl (2). A suspension of bis(4,7-
2
dimethyl-indenyl)methane (2 g, 6.7 mmol) in THF (30 mL) was
added via cannula to a stirred suspension of KH (0.6 g, 15
mmol) in THF (35 mL). After hydrogen evolution had ceased
(
2 h) the resulting brownish solution was separated from
excess KH. This solution and a solution of ZrCl (THF) (2.5 g,
.7 mmol) in THF (65 mL) were both added dropwise via
dropping funnels to a flask containing rapidly stirring THF
30 mL) over 4 h. At the end of the addition the mixture was
4
2
6
(
stirred overnight. A brick-red solution and a precipitate
formed. After concentrating in vacuo to about 4 mL, 10 mL of
Et
was dried in vacuo (brown powder) and was extracted with
refluxing CH Cl until the washing was colorless. The CH Cl
2
2
O was added, the suspension was filtered, and the residue
2
2
2
(
20) Sheldrick, G. M. Sadabs: program for empirical absorption
solution was concentrated to 7 mL and cooled to -20 °C
correction; University of G o¨ ttingen: G o¨ ttingen, 1996.
(21) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.,
Sect. A 1968, 24, 351.
1
overnight. A red solid (0.715 g) was isolated by filtration. H
NMR showed the formation of the pure racemic isomer of
(22) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
1
methylenebis(4,7-dimethylindenyl)ZrCl
2
. H NMR (CDCl
3
, δ,
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
ppm): 6.99 (d, 2 H), 6. 76 (d, 2 H), 6.65 (d, 2 H), 5.88 (d, 2 H),
.09 (s, 2 H), 2.76 (s, 6 H), 2.30 (s, 6 H). Anal. Calcd for C23
Cl Zr: C, 60.0; H, 4.8. Found: C, 60.4; H, 4.9.
P olym er iza tion s of P r op ylen e. A 200 g sample of pro-
pylene was charged in a 1 L jacketed stainless steel autoclave,
435.
(
23) Sheldrick, G. M. SHELX97: program for crystal structure
refinement; University of G o¨ ttingen: G o¨ ttingen, 1997.
24) Voskoboynikov, A. Z.; Agarkov, A. Yu.; Chernyshev, E. A.;
5
22
H -
2
(
Beletskaya, I. P.; Churakov, A. V.; Kuz’mina, L. G. J . Organomet.
Chem. 1997, 530, 75.

Simple Route to Bis(3-indenyl)methanes
Organometallics, Vol. 18, No. 19, 1999 3791
min. An emprical absorption correction was applied using ψ
scans of three suitable reflections having ø values close to 90°.21
with an isotropic displacement parameter 1.2 times that of the
pertinent carbon atom. The final difference electron density
map showed no features of chemical significance, with the
largest peaks lying close to the metal atoms. Final conventional
agreement indexes and other structure refinement parameters
are listed in Table 6.
The measured intensities were corrected for Lorentz, polariza-
2
tion, and background effects and reduced to F
o
. Crystal data
and data collection parameters are summarized in Table 6.
b) Str u ctu r e Solu tion a n d Refin em en t. The structures
(
2
2
were solved by direct methods and subsequent Fourier
synthesis; they were refined by full-matrix least-squares on
F (SHELX97) using all reflections for 1, and reflections with
I > 2σ(I) for 2 and 3. Scattering factors for neutral atoms and
anomalous dispersion corrections were taken from the internal
library of SHELX97. Weights were assigned to individual
observations according to the formula w ) 1/[σ (F
bP], where P ) (F
a flat analysis of variance in terms of F
Ack n ow led gm en t. We thank I. E. Nifant’ev for
many useful discussions, S. Tartarini and F. Pazzi for
the polymerization experiments, and I. Camurati, M.
Colonnesi, H. Rychlicki, and F. Piemontesi for NMR
analysis of the zirconocenes and the polymers.
2
23
2
2
) + (aP)2
o
2
2
+
o
+ 2F
c
)/3; a and b were chosen to give
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
diffraction data, final atomic coordinates, and full bond
distances and angles for 1-3. This material is available free
of charge via the Internet at http://pubs.acs.org.
2
o
. Anisotropic displace-
ment parameters were assigned to all non-hydrogen atoms.
Hydrogen atoms were placed in idealized position (dC-H ) 0.93,
0
.96, and 0.97 Å for aromatic, methylene, and methyl hydrogen
atoms, respectively) and refined riding on their parent atom
OM990211G