Diastereoselective insertion of isocyanide into the alkyl-metal bond of methylbenz[e]indenyl ansa-zirconocene complexes

Article abstract of DOI:10.1002/ejic.200400333

Alkylation of ansa-zirconocene [Zr{(η⁵-C₅H ₅)SiMe₂-(MBI)}Cl₂] (MBI = η⁵-Me- C₁₃H₇) with MgRCl gave the dimethyl complex [Zr{(η⁵-C₅H₅)S

Full text of DOI:10.1002/ejic.200400333

FULL PAPER
Diastereoselective Insertion of Isocyanide into the Alkyl؊Metal Bond of
Methylbenz[e]indenyl ansa-Zirconocene Complexes
[a]
[a]
[a]
´
´
Alfredo Sebastian, Pascual Royo,* Pilar Gomez-Sal, and
[b]
´
Carmen Ramırez de Arellano
Keywords: Metallocenes / Zirconium / Insertion / Isocyanides / Polymerization
Alkylation
of
ansa-zirconocene
[Zr{(η5-C5H5)SiMe2-
C5H5)SiMe2(MBI)}R{CR[η2-N-(2,6-xylyl)]}] (R = Me, CH2Ph,
CH2SiMe3). All of the new complexes were characterized by
(MBI)}Cl2] (MBI = η5-2-Me−C13H7) with MgRCl gave the di-
methyl complex [Zr{(η5-C5H5)SiMe2(MBI)}Me2], but unre- NMR spectroscopy and the X-ray molecular structures of the
solvable mixtures containing mono-alkylated compounds
were obtained when bulkier alkyls were used. However pure
dialkyl complexes [Zr{(η5-C5H5)SiMe2(MBI)}R2] (R = CH2Ph,
CH2SiMe3) were easily obtained using K(CH2Ph) and Li(CH-
dibenzyl and the imino-benzyl compounds were determined.
The catalytic activity for ethene polymerization and ethene/
1-hexene copolymerization of the dichloro zirconocenes
[Zr{(η5-C5H5)EMe2(MBI)}Cl2] (E = C, Si), activated with
2SiMe3) as alkylating agents. Diastereoselective insertion methylalumoxane (MAO), was measured.
into the MBI-unprotected Zr−R bond was observed when all
of these dialkyl complexes were treated with 2,6-xylyl isocy-
anide to give the iminoacyl compounds [Zr{(η5- Germany, 2004)
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Introduction
purpose. The isolation of the first group 4 metallocenes
containing this ligand has demonstrated high performance
in ethylene and propylene polymerization[11,12] as well as in
copolymerization processes using ethylene and octene[13] or
ethylene/polar monomers such as 10-undecene-1-ol and al-
lyl alcohol.[14,15]
Metal alkyl compounds are convenient models not only
for olefin polymerization but also for other insertion and
transmetallation reactions and as carbonϪcarbon bond for-
mation precursors.[16Ϫ18] Insertion of unsaturated substrates
into metalϪalkyl bonds are basic reactions for which many
synthetic, mechanistic and theoretical studies have been de-
veloped.[19] The migratory insertion of isocyanide has pro-
vided numerous iminoacyl complexes[20Ϫ24] and a solid
knowledge of the steric and electronic effects of the ligands
on the reactivity[25] and catalytic activity[9] of different sys-
tems.
We report herein the effect of the bulky MBI ligand on
the stereoselectivity of the migratory insertion of 2,6-di-
methylphenyl isocyanide into the metalϪalkyl bonds of new
dialkyl metallocenes prepared from the dichloro derivatives
reported recently.[26] We also report the results found from
our studies of catalytic activity of these dichloro-metallo-
cenes in the homopolymerization of ethylene and copoly-
merization of ethylene/1-hexene.
The rational design of different types of group 4 metal-
locenes to be used as olefin polymerization catalysts, after
activation with methylalumoxane (MAO), has been the ob-
jective of a great number of scientific contributions.[1Ϫ5]
Extensive studies have demonstrated the high degree of
electronic and steric control provided by sterically de-
manding cyclopentadienyl ligands, making them powerful
tools for producing convenient single-site catalysts for the
known broad range of precisely functionalized, tacticity-
controlled, branched and block polymers and
copolymers.[6Ϫ8] The main targets of many of the studies
have been the optimization of catalytic activity, stereospec-
ificity and the modulation of the molecular weight of the
resulting polymers.[9,10] It is well-known that the presence
of condensed benzene rings in the indenyl ligands of metal-
locene-type complexes induces a remarkable increase in
their catalytic activity, and the addition of a 2-methyl sub-
stituent in their Cp rings reduces the incidence of β-elimin-
ation processes, providing a significant increase in the mo-
lecular weight of the polymer. In this regard the 2-methyl-
benz[e]indenyl ligand (MBI) is an excellent choice for this
[a]
´
´
´
Departamento de Quımica Inorganica, Universidad de Alcala
´
Campus Universitario, 28871 Alcala de Henares, Spain
Fax: (internat.) ϩ 34-91-8854683
Results and Discussion
The dichloro ansa-zirconocenes [Zr{(η5-C5H5)EMe2(η5-
E-mail: pascual.royo@uah.es
[b]
´
´
Departamento de Quımica Organica, Facultad de Farmacia,
Universidad de Valencia
46100 Valencia, Spain
2-MeϪC13H7)}Me2] (E ϭ C: 1a, E ϭ Si: 1b) containing the
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400333
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Diastereoselective Insertion of Isocyanide
FULL PAPER
MBI ligand were isolated previously[26] by reaction in tolu- stable in CDCl3 under an inert atmosphere although they
ene of ZrCl4(THF)2 with the dilithium salts of the corre- are transformed into the dichloro complex 1b when heated
sponding ϪCMe2Ϫ and ϪSiMe2-bridged indenyl-cyclopen- at 110 °C in Teflon-valved NMR tubes.
tadienyl derivatives, as shown in Scheme 1.
The enantiotopic face of the MBI ligand makes these di-
alkyl compounds, 2Ϫ4, asymmetric molecules with two
1
nonequivalent alkyl groups. The H NMR spectrum of 2
shows two singlets for the Zr-methyl groups, one shifted
significantly highfield (δ ϭ Ϫ1.29) compared with the typi-
cal value (δ ϭ 0.09 ppm) observed for the other, which was
in the range found for related methyl zirconocenes.[30] NOE
experiments demonstrated that the highfield singlet is due
to the methyl group located under the benzene ring at-
tached to the indenyl moiety. Similar behavior was observed
for the four doublets due to the two diastereotopic methyl-
ene protons of the benzyl (3) and methylsilyl (4) ligands.
Two of the signals, corresponding to the alkyl group located
under the ring-fused benzene, are shifted highfield (δ ϭ 0.18
ppm and 0.28 ppm for 3; δ ϭ Ϫ2.20 ppm and Ϫ0.94 ppm
for 4) due to the anisotropic effect of the aromatic ring.
However this anisotropic contribution was not observed in
the 13C and gHMQC NMR spectra (see Exp. Sect.). In ad-
Scheme 1
The reaction of complex 1b with 2 equiv. of MgClMe
gave dimethyl zirconocene [Zr{(η5-C5H5)SiMe2(η5-2-
MeϪC13H7)}Me2] (2) in high yield. However this type of
dialkyl compound is not so easily accessible when bulky
substituents are located at the cyclopentadienyl β-carbon of
rigid ansa-metallocenes. The steric demands of the benzene
rings attached to the α and β positions of the η5-cyclopen-
tadienyl unit in the MBI ligand of complex 1b, make dialkyl-
ation difficult when bulky alkyl groups are used. In fact
alkylation of 1b with two equiv. of MgCl(CH2Ph) gave low
yields of the dibenzyl complex [Zr{(η5-C5H5)SiMe2(η5-2-
MeϪC13H7)}(CH2Ph)2] (3) which was always contaminated
by significant amounts of the monobenzyl compounds.
However complex 3 could be isolated in high yield as the
unique component when K(CH2Ph) was used as the alkyl-
ating agent. Similarly, MgCl(CH2SiMe3) has been exten-
sively used[27,28] to produce dialkyl derivatives of many me-
tallocenes with free cyclopentadienyl ligands, whereas re-
lated ansa-metallocenes usually yield the corresponding
monoalkyl compounds.[29] Consistently the dialkyl complex
[Zr{(η5-C5H5)SiMe2(η5-2-MeϪC13H7)}(CH2SiMe3)2] (4)
could not be isolated using the Grignard reagent but was
easily obtained in high yield with the lithium derivative
Li(CH2SiMe3). It is therefore evident that the steric hin-
drance due to the bulky MBI ligand may be overcome using
more appropriate nucleophilic alkylating agents, as shown
in Scheme 2. The air sensitive dialkyl compounds 2؊4 are
1
dition, the H NMR spectra of complexes 2Ϫ4 show the
expected singlet for the MBI-methyl group, two singlets for
SiϪMe, four multiplets for the C5H4 ring and one singlet
for the C5H(MBI) ring proton. All of the remaining MBI
nonequivalent protons give the set of signals corresponding
to two AB and ABCD spin systems.
Slow cooling at Ϫ30 °C of a toluene solution of the di-
benzyl complex 3 rendered appropriate crystals for X-ray
diffraction studies. The X-ray structure of 3 is shown in
Figure 1 with the atomic labeling scheme and selected bond
lengths and angles are listed in Table 1.
The coordination geometry of the zirconium atom is the
typical distorted tetrahedron formed by the two ring centro-
Figure 1. Ellipsoid plot of compound 3 (50% probability level);
hydrogen atoms have been omitted for clarity
Scheme 2
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A. Sebastian, P. Royo, P. G o mez-Sal, C. Ramırez de Arellano
FULL PAPER
˚
Table 1. Selected interatomic distances (A) and angles (°) for com-
plex 3 (Cp is the centroid of C(31)ϪC(32)ϪC(33)ϪC(34)ϪC(35)
ring; CpMBI is the centroid of C(41)ϪC(42)ϪC(43)ϪC(44)ϪC(45)
ring)
Zr(1)ϪCp
2.212
2.262
Zr(1)ϪC(33)
Zr(1)ϪC(34)
2.556(4)
2.559(5)
2.491(5)
2.515(4)
2.514(4)
2.578(4)
2.636(4)
2.582(4)
Zr(1)-CpMBI
Zr(1)ϪC(2)
Zr(1)ϪC(1)
C(1)ϪC(11)
C(2)ϪC(21)
Zr(1)ϪC(31)
Zr(1)ϪC(32)
C(2)ϪZr(1)ϪC(1)
2.308(4) Zr(1)ϪC(35)
2.315(6) Zr(1)ϪC(41)
1.478(8) Zr(1)ϪC(42)
1.481(6) Zr(1)ϪC(43)
2.491(5) Zr(1)ϪC(44)
2.487(5) Zr(1)ϪC(53)
97.4(2)
C(11)ϪC(1)ϪZr(1) 121.8(4)
C(21)ϪC(2)ϪZr(1) 125.5(3)
CpϪZr(1)ϪCpMBI 125.8
Scheme 3
ids and the carbon atoms of the benzyl ligands. The
These insertion reactions may lead to two diastereomers
Cp(centroid)ϪZrϪCpMBI(centroid) [125.8°] and the depending on which of the two nonequivalent alkyl groups
C(2)ϪZr(1)ϪC(1) [97.4(2)°] angles are similar to those ob- migrate to the isocyanide ligand. The 1H NMR spectra con-
served for related ansa-MBI compounds and the firm that one unique diastereoisomer is obtained in all of
˚
˚
Cp(centroid)ϪZr distances [Cp 2.212A and CpMBI 2.262A] these reactions, for which the signals due to the alkyl group
are in the range found in related indenyl zircono- located under the MBI system remain almost unmodified
cenes.[12,26,31,32]
[δ ϭ Ϫ1.20(s) (5), 0.27(d) and 0.56(d) (6), Ϫ1.86(d) and
The most remarkable difference is the orientation of the Ϫ2.97(d) (7)]. In contrast, signals due to the alkyl group
two nonequivalent benzyl ligands. One is located above the located far from the MBI system are significantly shifted
plane (torsion angle CpMBIϪZr(1)ϪC(1)ϪC(11) 62.6°) lowfield [δ ϭ 2.36(s) (5), δ 3.60(d) and 3.68(d) (6), 2.45(d)
while the other is located below (torsion angle and 2.63(d) (7)] as expected for the migrated C-bonded
CpMBIϪZr(1)ϪC(2)ϪC(21) 158.1°), with respect to the alkyl ligand. NOE experiments on the methyl derivative (5)
C(1)ϪZr(1)ϪC(2) plane. The benzyl ligand eclipsed by the demonstrate that the highfield shifted singlet corresponds
MBI system positions the methylene C(2) under the ben- to the methyl group located under the MBI system, which
zene ring condensed to the indenyl moiety with the phenyl is affected by the anisotropic effect of the aromatic ring.
ring oriented towards the other Cp system, whereas the
Similar behavior is also observed in the 13C NMR spectra
benzyl ring located on the open side, far away from the MBI which show significant lowfield shifts for all the signals due
system, has its phenyl ring directed towards the moiety with to the migrated alkyl group bound to the iminoacylic car-
the MBI system using the wide space. In spite of these dif- bon atom, appearing at δ ϭ 22.2, 44.6 and 22.7 for 5, 6 and
1
ferent orientations both benzyl ligands show ZrϪC dis- 7, respectively. All of the remaining H and 13C NMR sig-
˚
˚
tances [ZrϪC(1) 2.315(6) A and ZrϪC(2) 2.308(4) A] and nals show no significant changes.
ZrϪCϪC(Ph) angles [ZrϪC(1)ϪC(11) 121.8(4)° and
The 1H NMR spectrum of complex 7 represented in Fig-
ZrϪC(2)ϪC(21) 125.5(3)°] typical of σ-bonded benzyl ure 2 shows the typical pattern of signals observed for both
groups without benzallylic interactions [ZrϪC(11) 3.338 dialkyl and iminoacyl complexes.
˚
and ZrϪC(21) 3.389 A], and are similar to values
Therefore it is possible to conclude that the steric de-
found[31,33] for other benzyl zirconium compounds with mands of the bulky MBI system have a significant effect on
bulky Cp systems. the high diastereoselectivity of all of these insertion reac-
Reaction of diethyl ether solutions of the dialkyl com- tions, although the electronic contribution demonstrated for
plexes 2Ϫ4 with 1 equiv. of 2,6-xylyl isocyanide at room related [MBI]-silyl-η1-amido zirconium complexes (work
temperature gave the corresponding iminoacyl compounds still in progress),[34] for which electronic effects are signifi-
[Zr{(η5-C5H5)SiMe2(η5-2-MeϪC13H7)}R{CR[η2-N-(2,6- cantly important, cannot be discarded. However the spec-
xylyl)]}] (R ϭ Me: 5, CH2Ph: 6, CH2SiMe3: 7) as shown in troscopic data do not distinguish between the exo-N-coor-
Scheme 3, which were isolated as solids and characterized dinated iminoacyl formed under kinetic control and the
by elemental analysis and NMR spectroscopy. When moni- usually more favorable endo-N-coordinated iminoacyl iso-
1
toring the reactions by H NMR spectroscopy it was ob- mer formed under thermodynamic control. The endo-con-
served that insertion was easier for less bulky alkyl ligands figuration was confirmed for complex 6 by X-ray diffraction
following the order 5 Ͻ 6 Ͻ 7. The η2-coordination of the studies of its molecular structure.
isocyanide ligand is consistent with the IR [(Nujol): ν˜CϭN
Appropriate crystals of 6 were isolated by slow evapor-
ϭ 1600, 1585 and 1590 cmϪ1] and 13C NMR spectro- ation of a C6D6 solution. Figure 3 shows the X-ray molecu-
scopic data [δ ϭ 245.4 (4), 244.5 (5), 245.4 (6)]. Further lar structure of 6 with the atomic labeling scheme. Selected
reactions with an additional 1 equiv. or an excess of isocy- bond lengths and angles are collected in Table 2.
anide were not observed under any conditions, as was ex-
The pseudotetrahedral coordination of the zirconium
pected for these types of coordinately saturated 18e species. atom is defined by the Cp, the CpMBI, the benzyl methylene
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Diastereoselective Insertion of Isocyanide
FULL PAPER
1
Figure 2. H NMR for 7 in C6D6; the spectrum shows the normal pattern of signals for Zr(MBIϪSiMe2Cp)R2 complexes
˚
Table 2. Selected interatomic distances (A) and angles (°) for com-
plex 6
Cp is the centroid of C(31)ϪC(32)ϪC(33)ϪC(34)ϪC(35) ring.
CpMBI is the centroid of C(41)ϪC(42)ϪC(43)ϪC(44)ϪC(45) ring.
ZrϪCpMBI
ZrϪCp
ZrϪN
ZrϪC(10)
ZrϪC(2)
C(1)ϪC(10)
C(2)ϪC(21)
NϪC(10)
2.311
2.246
ZrϪC(32)
ZrϪC(33)
ZrϪC(34)
ZrϪC(35)
ZrϪC(41)
ZrϪC(42)
ZrϪC(43)
ZrϪC(44)
2.547(2)
2.605(2)
2.564(2)
2.492(2)
2.548(2)
2.530(2)
2.607(2)
2.708(2)
2.649(2)
2.287(2)
2.231(2)
2.372(2)
1.513(3)
1.468(3)
1.281(3)
2.532(2)
ZrϪC(31)
ZrϪC(53)
CpMBIϪZrϪCp
C(10)ϪZrϪN
C(10)ϪZrϪC(2)
NϪZrϪC(2)
C(1)ϪC(10)ϪZr
124.3
C(21)ϪC(2)ϪZr
C(10)ϪNϪZr
C(61)ϪNϪZr
NϪC(10)ϪC(1)
NϪC(10)ϪZr
123.24(13)
71.12(12)
161.83(13)
124.31(19)
75.96(12)
32.92(6)
116.43(7)
84.18(6)
Figure 3. Ellipsoid plot of compound 6 (50% probability level);
hydrogen atoms have been omitted for clarity
159.54(15)
carbon and the midpoint of the iminoacyl CϪN bond.
Both, the CpϪZr and CpMBIϪZr lines are almost perpen- tadienyl moiety [C(2)ϪZrϪC(44)ϪC(45) torsion angle
dicular to the corresponding C(31)ϪC(35) and 16.4(2)°]. The phenyl group of the benzyl ligand
C(41)ϪC(53) cyclopentadienyl main planes (87.3 and 85.0°, [C(21)ϪC(26)] is anti to the MBI system with respect to
respectively). The CpϪZrϪCpMBI bond angle [124.3°] is the ZrϪC(2) bond [C(21)ϪC(2)ϪZrϪCpMBI torsion angle
closer than that observed for complex 3 indicating the 178.0°]. Thus, the benzyl group adopts a geometry similar
larger bite of the cyclopentadienyl rings. The structure to that observed for the eclipsed benzyl group in com-
shows η2-coordination of the iminoacyl ligand with the pound 3.
˚
CϪN bond almost perpendicular to the line going from the
Zr atom to the CϪN bond midpoint (87.4°). The im- to the sp methylene benzyl ligand is 0.06A longer than that
The zirconium-carbon bond length [ZrϪC(2) 2.372(2) A]
3
˚
inoacylic-N adopts an endo-configuration, with
a
observed in complex 3 and longer than the distance to the
C(2)ϪZrϪC(10)ϪN torsion angle of 12.6(1)°, giving rise to sp2 iminoacyl carbon atom[35] [ZrϪC(10) 2.231(2) A], which
˚
˚
a very open C(2)ϪZrϪC(10) angle [116.44(7)°]. The benzyl is in the range [2.164Ϫ2.363A] observed for related im-
ligand is eclipsed by the MBI system, locating the methyl- inoacyl zirconium compounds.[21,36] However the zir-
˚
ene C(2) under the benzene ring condensed to the cyclopen- conium-nitrogen bond length [ZrϪN 2.2872(16) A] is
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FULL PAPER
slightly longer than those found in related zirconium im- higher molecular weight, similar to that observed for
[37,38]
˚
inoacyl compounds in the range 2.148Ϫ2.250A.
The [ZrCp2Cl2], although their polydispersities are similar. Un-
double bond character of the iminoacyl C(10)ϪN bond is der similar conditions (entries 3, 9) complex 1b is signifi-
˚
confirmed by the 1.281(3) A distance, which is longer than cantly more active than [ZrCp2Cl2] and almost 10 times
usual for related zirconium iminoacyl compounds and close more active than [Zr(SiMe2Cp2)Cl2]. Increasing Al/Zr ra-
[35]
˚
to that known for organic CϭN bonds [1.28A].
All of tios (entries 3, 4 and 5, 6) produce higher activities which
these elongated bonds are consistent with the steric hin- were only slightly dependent on the catalyst concentration.
drance due to the bulky MBI ring and the benzyl and 2,6-
xylyl substituents.
Both metallocenes show higher catalytic activities (entries
1, 2 and 4, 7, 8) in the presence of the comonomer 1-hexene
Both the iminoacyl N and the C(10) sp2 atoms show a as a consequence of the known ‘‘comonomer effect’’.[39] In
profoundly distorted trigonal planar disposition, although all cases incorporation of 1-hexene to the polymer chain is
the sum of their angles is 360°. The distortion is mainly seen rather high for both catalysts, and is significantly higher
in the close C(10)ϪNϪZr [71.13(12)°] and NϪC(10)ϪZr (6.69%) for the methylene-bridged complex 1a with its more
[75.95(12)°] angles and together with the small angle at the open bite compared to the silyl-bridged complex 1b. The
zirconium center [C(10)ϪZrϪN 32.92(6)°] are a conse- process was always accompanied by a very significant de-
quence of the η2-coordination of the iminoacyl ligand.
crease in molecular weight due to the favored β elimination
˚
The ZrϪCp distance [2.246A] is shorter than the produced by the presence of terminal 1-hexene inserted
˚
ZrϪCpMBI distance [2.311A]. Consistently the distances units.
from zirconium to the Cp ring carbon atoms
[2.492(2)Ϫ2.605(2) A] are slightly shorter than the corre- value expected for ‘‘single site’’ catalysts, although oc-
In most cases the polydispersity is close to the typical
˚
sponding distances to the MBI carbon atoms casional values higher than 3.0 are observed.
˚
[2.530(2)Ϫ2.708(2) A], the ZrϪC(44) and ZrϪC(53) bond
˚
lengths being unusually long [2.708(2) and 2.649(2) A,
respectively].
Experimental Section
General Considerations: All manipulations were performed under
argon using Schlenk and high-vacuum line techniques or a glove
box model HE-63. The solvents were pre-dried over sodium wire
prior to purification by distillation under argon using the appropri-
ate drying/deoxygenated agent: toluene, hexane and pentane (so-
dium-potassium alloy) and diethyl ether, THF (sodium-benzo-
Olefin Polymerization Results
The dichlorozirconocenes 1a and 1b, activated with a
large excess methylalumoxane (MAO), were used as catalyst
precursors for the polymerization of ethylene and copoly-
merization of ethylene/1-hexene. All experiments were car-
ried out at 70 °C in heptane for 15 min, under 4.0 bar of phenone). After being collected, the dried solvent was stored under
˚
argon in an ampoule over potassium mirrors or 4 A molecular
sieves (THF). Deuterated solvents from Scharlau were dried, de-
gassed and stored over molecular sieves. C, H and N microanalyses
ethylene in a Büchi autoclave, with variable amounts of
catalyst and a 10% toluene solution of MAO.
The reaction conditions, measured activities and proper-
ties of the resulting polymers are summarized in Table 3
and compared with data for [ZrCp2Cl2] and [Zr(Si-
Me2Cp2)Cl2] used as references.
Both catalysts 1a and 1b polymerize ethylene to give lin-
ear polyethylene with high activities. Complex 1b shows a
catalytic activity four times higher than that observed for
were performed on
a PerkinϪElmer 240B and/or Heraeus
CHNϪO-Rapid microanalyzer. IR spectra were performed in nujol
mulls on a PerkinϪElmer 883 spectrophotometer. NMR spectra,
measured at 25 °C, were recorded on a Varian Unity FT-300 (1H
NMR at 300 MHz, 13C NMR at 75 MHz) or FT-500 (1H NMR at
500 MHz, 13C NMR at 125 MHz) spectrometer and chemical shifts
were referenced to the residual protons or carbons of the deuter-
complex 1a (entries 1, 6) leading to a polymer of much ated solvents. MgMeCl and (2,6-xylyl)isocyanide were purchased
Table 3. Ethylene polymerization and ethylene/1-hexene copolymerization with 1a and 1b/MAO
Polymerization
Entry
Polymer
% C6
[a]
[c]
µmol Zr
Al/Zr
% C6 M
g PE
Activity[b]
Mw[d]
Mw/Mn
1a
1b
1
2
3
4
5
6
7
8
9
10
5.0
5.0
0.8
0.4
0.8
5.0
0.4
0.4
0.8
0.8
1500
1500
10000
10000
5000
Ϫ
39
Ϫ
Ϫ
Ϫ
Ϫ
24
39
Ϫ
Ϫ
10.7
21.9
14.47
4.33
4.57
13.83
4.44
8.1
2.14·106
4.38·106
1.81·107
1.08·107
5.71·106
8.33·106
1.11·107
2.03·107
1.05·107
1.06·106
Ϫ
6.69
Ϫ
Ϫ
Ϫ
95100
22600
284600
Ϫ
3.8
1.8
Ϫ
3.1
Ϫ
3.1
2.3
1.9
2.0
2.2
Ϫ
1500
Ϫ
289800
154000
101800
270000
35000
10000
10000
10000
10000
2.22
3.64
Ϫ
A[e]
B[e]
8.42
0.9
Ϫ
[a]
[b]
[c]
% mol of comonomer.
g PE/mol Zr·h·bar. % molar in the polymer. Determined by 13C NMR.[d] Mw measured by GPC.[e]
A
Cp2ZrCl2. B (Me2SiCp2)ZrCl2.
3818
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 3814Ϫ3821

Diastereoselective Insertion of Isocyanide
FULL PAPER
from Aldrich and used without further purification. [Zr{(η5-2-
Ϫ1.5 (SiMe), Ϫ0.5 (SiMe), 2.6 (SiMe3), 3.5 (SiMe3), 18.3 (CMe),
MeC13H8)(η5-C5H4)EMe2}Cl2] (E ϭ C, Si)[26], Li(CH2SiMe3)[40] 47.7 (CH2), 49.4 (CH2), 88.4 (Cipso, SiC), 103.8 (Cipso, SiC), 111.8,
and K(CH2C6H5)[41] were prepared following the literature meth-
ods.
112.6, 112.9, 116.6, 119.7, 123.1, 123.8, 125.9, 126.2, 127.5, 128.9;
(CH.), 125.3, 126.7, 130.4, 130.8, 132.2 (Cipso) ppm. C29H42Si3Zr
(566.12): calcd. C 61.53, H 7.48; found C 61.38, H 7.34.
Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}Me2] (2): A
THF solution of ClMgMe (3.0 , 0.5 mL, 1.52 mmol) was added Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}{Me}{η5-
to a stirred suspension of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}Cl2]
(1b) (0.35 g, 0.75 mmol) in diethyl ether (50 mL) at Ϫ78 °C. The ture of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}Me2] (2) (0.4 g,
C(Me)N(2,6-xylyl)}] (5): Diethyl ether (50 mL) was added to a mix-
mixture was allowed to warm to room temperature and stirred for
a further 12 h. The solvent was removed under reduced pressure
and the mixture was extracted into hexane. The supernatant solu-
0.95 mmol) and CN(2,6-xylyl) (0.12 g, 0.95 mmol) and the resulting
suspension was stirred for a further 5 h. The solvent was completely
removed under vacuum and the product was washed with cool pen-
tion was then filtered through celite from the MgCl2 residue, con- tane (10 mL) to give a pale yellow powder characterized as 5. Yield
centrated (10 mL) and cooled to -35 °C to give 2 as a pale yellow
powder. Yield 0.27 g, 84%. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ
Ϫ1.29 (s, 3 H, ZrMe), 0.09 (s, 3 H, ZrMe), 0.41 (s, 3 H, SiMe),
0.49 g, 89%. IR (Nujol): ν˜ ϭ 1585 (νCϭN) cmϪ1 1H NMR
.
(300 MHz, C6D6, 25 °C): δ ϭ Ϫ1.20 (s, 3 H, ZrMe), 0.67 (s, 3 H,
SiMe), 0.71 (s, 3 H, SiMe), 1.65 (s, 3 H, CMe), 1.94 (s, 3 H, CMe),
0.53 (s, 3 H, SiMe), 1.95 (s, 3 H, CMe), 5.43 (m, 1 H, C5H4), 5.52 1.97 (s, 3 H, CMe), 2.36 (3 H, ZrCMe), 5.18 (m, 1 H, C5H4), 5.72
(m, 1 H, C5H4), 6.50 (m, 1 H, C5H4), 6.59 (m, 1 H, C5H4), 7.1Ϫ7.2 (m, 1 H, C5H4), 5.91 (m, 1 H, C6H3), 5.94 (m, 1 H, C5H4), 5.99
(m, 3 H, C13H7), 7.27 (m, 1 H, C13H7), 7.39 (m, 1 H, C13H7), 7.67 (m, 1 H, C5H4), 6.80 (m, 2 H, C6H3), 6.82 (s, 1 H, C13H7), 7.21
(m, 1 H, C13H7), 8.05 (m, 1 H, C13H7) ppm. 13C{1H} NMR
(m, 2 H, C13H7), 7.30(m, 1 H, C13H7), 7.45(m, 1 H, C13H7), 7.68(m,
(75 MHz, CDCl3, 25 °C): δ ϭ Ϫ1.2 (SiMe), Ϫ0.8 (SiMe), 18.0 1 H, C13H7), 7.74 (m, 1 H, C13H7) ppm. 13C{1H} NMR (75 MHz,
(CMe), 31.0 (ZrMe), 35.5 (ZrMe), 86.2 (Cipso, SiC), 100.2 (Cipso
SiC), 110.2, 113.0, 113.6, 120.3, 120.6, 122.1, 123.7, 125.4, 125.9,
127.3, 128.9; (CH, C5H4, C13H7), 128.5, 129.2, 131.2, 131.5, 131.7;
,
CDCl3, 25 °C): δ ϭ Ϫ0.9 (SiMe), Ϫ0.1 (SiMe), 19.2 (CMe), 19.4
(CMe), 19.6 (CMe), 22.2 (ZrCMe), 32.2 (ZrMe), 92.3 (Cipso, SiC),
105.0(Cipso, SiC), 106.2, 106.3, 106.4, 114.3, 118.6, 123.2, 123.7,
(Cipso, C5H4, C13H7) ppm. C23H26SiZr (421.76): calcd. C 65.60, H 124.6, 125.0, 125.5, 126.2, 128.5, 128.9, 129.7 (CH, C13H7, C6H3),
6.21; found C 65.81, H 6.28.
119.8, 126.0, 127.8, 128.1, 129.4, 130.5, 132.6, 144.9; (Cipso, C13H7,
C6H3) 245.4 (CϭN) ppm. C34H39NSiZr (580.99): calcd. C 70.29,
N 2.41, N 6.77; found C 70.41, N 2.52, H 6.82.
Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}(CH2C6H5)2]
(3): Diethyl ether (50 mL) at Ϫ78 °C was added to a mixture of
[Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}Cl2] (1b) (0.4 g, 0.86 mmol) Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}{CH2C6H5}
and K(CH2C6H5) (0.22 g, 1.72 mmol) and the resulting suspension
was allowed to warm to room temperature and stirred for a further
12 h. The supernatant solution was then filtered through celite from
the KCl residue, concentrated under reduced pressure (10 mL) and
cooled to -35 °C to give 3 as an orange solid. Recrystallization
from toluene/hexane gave 3 as a microcrystalline solid. Yield 0.38 g,
78%. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ Ϫ0.18 (d, 1 H,
{η5-C(CH2C6H5)N(2,6-xylyl)}] (6): In a procedure analogous to
that described above for 5 a mixture of [Zr{(η5-2-MeC13H7)(η5-
C5H4)SiMe2}(CH2C6H5)2] (3) (0.5 g, 0.87 mmol) and CN(2,6-xylyl)
(0.11 g, 0.87 mmol) were reacted in diethyl ether (50 mL) to yield
an orange powder characterized as 6. Recrystallization from tolu-
ene/hexane gave 6 as a microcrystalline solid. Yield 0.56 g, 91%. IR
(Nujol): ν˜ ϭ 1600 (νCϭN) cmϪ1 1H NMR (300 MHz, C6D6, 25
.
ZrCH2, 11 Hz), 0.28 (d, 1 H, ZrCH2, 11 Hz), 0.34 (s,3 H, SiMe), °C): δ ϭ 0.27 (d, 1 H, ZrCH2, 9 Hz), 0.56 (d, 1 H, ZrCH2, 9 Hz),
0.46 (s, 3 H, SiMe), 1.75 (s, 3 H, CMe), 1.95 (d, 1 H, ZrCH2,
11 Hz), 2.13 (d, 1 H, ZrCH2, 11 Hz), 5.20 (m, 1 H, C5H4), 5.29 (m,
0.54 (s, 3 H, SiMe), 0.67 (s, 9 H, SiMe3), 1.32 (s, 3 H, CMe), 1.96
(s, 3 H, CMe), 2.29 (s, 3 H, CMe), 3.60 (d, 1 H, CCH2, 9 Hz), 3.68
1 H, C5H4), 5.80 (m, 1 H, C5H4), 6.31 (m, 1 H, C5H4), 6.52 (m, 2 (d, 1 H, CCH2, 9 Hz), 5.24 (m, 1 H, C5H4), 5.28 (m, 1 H, C5H4),
H, C6H5), 7.17Ϫ7.13 (m, 6 H, C6H5), 6.93 (s, 1 H, C13H7), 6.78 5.82 (m, 1 H, C5H4), 6.00 (m, 1 H, C5H4), 6.15 (m, 1 H, C6Hn),
(m, 1 H, C13H7), 7.21(m, 1 H, C13H7), 7.22(m, 1 H, C13H7), 7.33(m, 6.41 (m, 2 H, C6Hn), 6.66 (m, 1 H, C6Hn), 6.8Ϫ7.10 (m, 10 H,
2 H, C6H5), 7.41(m, 1 H, C13H7), 7.53(m, 1 H, C13H7), 7.89(m, 1 C6Hn), 6.84 (s, 1 H, C13H7), 7.18 (m, 1 H, C13H7), 7.29 (m, 1 H,
H, C13H7) ppm. 13C{1H} NMR (75 MHz, CDCl3, 25 °C): δ ϭ C13H7), 7.37 (m, 1 H, C13H7), 7.44 (m, 1 H, C13H7), 7.57 (m, 1 H,
Ϫ0.7 (SiMe), Ϫ1.3 (SiMe), 17.2 (CMe), 61.4 (CH2), 68.4 (CH2),
85.7 (Cipso, SiC), 100.7 (Cipso, SiC), 111.6, 113.6, 116.1, 121.1, 121.3,
C13H7), 7.71 (m, 1 H, C13H7) ppm. 13C{1H} NMR (75 MHz,
CDCl3, 25 °C): δ ϭ Ϫ0.4 (SiMe), Ϫ0.8 (SiMe), 19.5 (CMe), 19.7
122.5, 124.0, 124.0, 124.3, 125.3, 125.3, 126.3, 126.4, 126.4, 126.6, (CMe), 20.6 (CMe), 44.6 (CCH2), 47.0 (ZrCH2), 94.9 (Cipso, SiC),
127.6, 128.5, 128.7, 128.7, 128.9, 129.3; (CH.), 125.0, 128.8, 130.3, 106.3(Cipso, SiC), 106.8, 108.9, 109.3, 118.4, 118.8, 119.4, 123.1,
131.0, 132.3, 153.4, 154.6 (Cipso) ppm. C35H34SiZr (573.95): calcd.
C 73.24, H 5.97; found C 73.02, H 5.76.
124.0, 125.4, 125.5, 125.5, 125.8, 125.8, 125.9, 126.9, 127.2, 127.2,
128.3, 128.6, 128.7, 128.7, 129.0, 130.1, 130.1; (C13H7, C6Hn),
122.9, 124.9, 125.7, 129.2, 129.3, 131.4, 136.2, 145.2, 155.9; (Ci,
C13H7, C6Hn), 244.5 (CϭN; n ϭ 3, 5) ppm. C44H43NSiZr (705.13):
calcd. C 74.95, N 1.99, H 6.15; found C 75.22, N 2.05, H 6.28.
Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}(CH2SiMe3)2]
(4): In a procedure analogous to that described above for 3 a mix-
ture of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}Cl2] (1b) (0.35 g,
0.75 mmol) and Li(CH2SiMe3) (0.14 g, 1.52 mmol) were reacted in
diethyl ether (50 mL) to yield a pale yellow powder characterized
Preparation of [Zr{(η5-2-MeC13H7)(η5-C5H4)SiMe2}{CH2SiMe3}
{η5-C(CH2SiMe3)N(2,6-xylyl)}] (7): In a procedure analogous to
as 4. Yield 0.29 g, 68%. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ that described above for 5 a mixture of [Zr{(η5-2-MeC13H7)(η5-
Ϫ2.20 (d, 1 H, ZrCH2, 11 Hz), Ϫ0.94 (d, 1 H, ZrCH2, 11 Hz), C5H4)SiMe2}(CH2SiMe3)2] (4) (0.35 g, 0.62 mmol) and CN(2,6-xy-
Ϫ0.07 (d, 1 H, ZrCH2, 11 Hz), Ϫ0.21 (s, 9 H, SiMe3), 0.24 (s, 9 H, lyl) (0.08 g, 0.62 mmol) were reacted in diethyl ether (50 mL) to
SiMe3), 0.25 (d, 1 H, ZrCH2, 11 Hz), 0.42 (s, 3 H, SiMe), 0.49 (s,
yield an orange powder characterized as 7. Recrystallization from
3 H, SiMe), 2.07 (s, 3 H, CMe), 5.58 (m, 1 H, C5H4), 5.66 (m, 1 toluene/hexane gave 7 as a microcrystalline solid. Yield 0.37 g, 87%.
H, C5H4), 6.68 (m, 1 H, C5H4), 6.79 (m, 1 H, C5H4), 7.15 (s, 1 H, IR (Nujol): ν˜ ϭ 1590 (νCϭN) cmϪ1. 1H NMR (300 MHz, C6D6, 25
C13H7), 7.17Ϫ7.4 (m, 5 H, C13H7), 7.60 (m, 1 H, C13H7), 8.07 (m, °C): δ ϭ Ϫ2.97 (d, 1 H, ZrCH2, 12 Hz), Ϫ1.86 (d, 1 H, ZrCH2,
1 H, C13H7) ppm. 13C{1H} NMR (75 MHz, CDCl3, 25 °C): δ ϭ 12 Hz), Ϫ0.12 (s, 9 H, SiMe3), Ϫ0.01 (s, 9 H, SiMe3), 0.68 (s, 3 H,
Eur. J. Inorg. Chem. 2004, 3814Ϫ3821
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3819

´
´
´
A. Sebastian, P. Royo, P. G o mez-Sal, C. Ramırez de Arellano
FULL PAPER
SiMe), 0.70 (s, 3 H, SiMe), 1.83 (s, 3 H, CMe), 1.90 (s, 3 H, CMe), SHELXL-97.[42] Hydrogen atoms were included using rigid methyl
2.45 (d, 1 H, CCH2, 12 Hz), 2.57 (s, 3 H, CMe), 2.63 (d, 1 H,
CCH2, 12 Hz), 5.55 (m, 1 H, C6H3), 6.07 (m, 1 H, C5H4), 6.19 (m,
1 H, C5H4), 6.21 (m, 1 H, C5H4), 6.66 (m, 1 H, C5H4), 6.79 (m, 3
H, C13H7), 7.29 (m, 3 H, C13H7, C6H3), 7.47 (m, 1 H, C13H7), 7.67
(m, 2 H, C13H7) ppm. 13C{1H} NMR (75 MHz, CDCl3, 25 °C):
δ ϭ Ϫ0.43 (SiMe), Ϫ0.40 (SiMe), 0.9 (SiMe3), 3.9 (SiMe3), 19.6
(CMe), 20.4 (CMe), 20.6 (CMe), 22.7 (CCH2), 32.3 (ZrCH2), 96.5
(Cipso, SiC), 106.2(Cipso, SiC), 107.6, 107.7, 112.9, 115.6, 123.5,
124.2, 124.8, 125.3, 125.6, 127.8, 128.2, 128.5, 128.7, 128.8; (C13H7,
C6H3), 124.6, 125.5, 129.6, 129.7, 130.6, 133.3, 134.8, 145.7; (Ci,
C13H7, C6H3), 245.4 (CϭN) ppm. C38H51NSi3Zr (697.30): calcd. C
65.45, N 2.01, H 7.37; found C 65.79, N 2.16, H 7.52.
groups or a riding model.
CCDC-236220 (for 3) and -236644 (for 6) contains the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
[or from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ44-1223-336-
033; E-mail: deposit@ccdc.cam.ac.uk].
Polymerization Procedures
Ethylene Polymerizations: Polymerizations were carried out in a
Büchi autoclave equipped with a heating bath, mechanical stirrer
and connection to argon-vacuum lines. The reactor was evacuated,
flushed several times with argon and then charged at 25 °C with
600 mL of freshly distilled heptane and variable amounts of a 10%
toluene solution of MAO. The solution was saturated and pressur-
ized with ethylene at 4.0 bar and the thermostat set at 70 °C. Poly-
merization was started by injection of variable volumes of a pre-
viously prepared toluene solution of the zirconocene catalyst. The
reaction was stopped by addition of 5 mL of acidified methanol
(HCl/methanol, 1:1). Polymers were recovered by filtration, washed
with methanol and dried under vacuum at 80 °C for 1 day. The
molecular weight of the resulting polyethylene was evaluated by
GPC.
X-ray Structure Determination for Complex 3: Orange crystals of
compound 3 were obtained by cooling a concentrated toluene solu-
tion and a suitable sized crystal was mounted in a Lindemann tube
and mounted on an EnrafϪNonius CAD 4 automatic four-circle
diffractometer with graphite monochromated Mo-Kα radiation
˚
(λ ϭ 0.71073A). Crystallographic and experimental details are
summarized in Table 4. Data were collected at room temperature.
Intensities were corrected for Lorentz and polarization effects in
the usual manner. No absorption or extinction corrections were
made. The structure was solved by direct methods and refined by
least-squares against F2 (SHELXL 97).[42] All non-hydrogen atoms
were refined anisotropically, and the hydrogen atoms were intro-
duced from geometrical calculations and refined using a riding
model with the exception of the hydrogens of the CH2 groups which
were found in the difference Fourier map. The hydrogen atoms of
the disorder toluene molecule were not included.
Ethylene/1-Hexene Polymerizations: The same procedure described
above was followed for copolymerization experiments, the appro-
priate volume of 1-hexene being initially charged into the reactor
X-ray Structure Determination for Complex 6: Data were recorded
˚
using Mo-Kα radiation (λ ϭ 0.71073 A), graphite monochromator together with the solvent. The resulting copolymer was charac-
and ω scans on a Nonius Kappa CCD diffractometer (see Table 4).
The structure was refined anisotropically using the program
terized by 13C NMR spectroscopy in C6D3Cl3 to evaluate the ethyl-
ene/1-hexene ratio by reported methods.[43]
Table 4. Summary of X-ray data for compounds 3 and 6
3
6
Empirical formula
Color
C35H35SiZr·1/2C7H8
C44H43NSiZr
pale yellow
705.10
orange
621.40
block
9.611(2)
18.532(4)
17.891(4)
104.63(3)
3083.3(12)
4
Molecular mass
Crystal habit
prism
˚
a (A)
17.2139(10)
12.1819(9)
16.4343(10)
93.884(9)
3438.3(4)
4
˚
b (A)
˚
c (A)
β (°)
3
˚
V (A )
Z
T (K)
293(2)
1.336
monoclinic
P21/n
1292
150(2)
1.362
monoclinic
P21/c
1472
Dcalcd. (g·cmϪ3
Crystal system
Space group
F(000)
)
Crystal size (mm)
0.35 ϫ 0.30 ϫ 0.25
0.421
0.28 ϫ 0.26 ϫ 0.10
0.388
µ (mmϪ1
)
2θ (max.)
52.02
6357/5986
Ϫ11/0, 0/22, Ϫ21/22
5986/0/370
0.0746
54.96
26898/7873
Ϫ22/22, Ϫ15/15, Ϫ21/21
7873/381/429
0.0501
Total/indep. reflns.
Limiting indices (h, k, l)
Data/restraints/parameters
Rint
Goodness of fit F2
R int. [all data]
1.083
1.026
R1 ϭ 0.1000, wR2 ϭ 0.1649
R1 ϭ 0.0567, wR2 ϭ 0.1463
0.723 and Ϫ1.179
R1 ϭ 0.0585, wR2 ϭ 0.0817
R1 ϭ 0.0344, wR2 ϭ 0.0742
0.312 and Ϫ0.494
Final R int [I Ͼ 2σ(I)]
Largest diff. peak and hole [e·A
Ϫ3
˚
]
3820
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 3814Ϫ3821

Diastereoselective Insertion of Isocyanide
FULL PAPER
´
Gomez-Sal, A. Manzanero, P. Royo, J. Organomet. Chem.
1997, 542, 247Ϫ253.
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Financial support of our work by MCyT (project MAT2001Ϫ1309)
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fellowship (A. S.) and for the polymerization measurements.
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Early View Article
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Eur. J. Inorg. Chem. 2004, 3814Ϫ3821
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